Truck wire harness aging test method realized based on simulation of severe working conditions

Abstract

The invention relates to the technical field of wire harness aging test, in particular to a truck wire harness aging test method based on simulation of severe working conditions, which comprises the following steps of: 1, calibrating working condition mapping reference parameters, then detecting various parameters of a wire harness in sequence, and establishing a wire harness performance reference parameter library with reference values of the parameters; 2, placing the wire harness in an environmental chamber, and carrying out a 60-hour composite environment aging cycle test; 3, carrying out hierarchical failure determination after each cycle; 4, when at least one parameter reaches the failure standard, the aging life of the truck wire harness is converted according to the corresponding relation between the preset cycle index and the actual use time. According to the invention, severe working conditions can be accurately simulated: complex actual working conditions of a truck mining area and a construction site are comprehensively considered, and various environmental stresses are comprehensively simulated in an aging test. Compared with a traditional single or simply combined test environment, the performance change and potential problems of the wire harness in a real scene can be more effectively detected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of harness aging test, and particularly relates to a truck harness aging test method based on simulation of harsh working conditions. BACKGROUND

[0002] As a key connecting component of the vehicle electrical system, the truck harness needs to withstand the combined effects of harsh working conditions for a long time, including high-frequency vibration in complex road conditions such as mine areas and mountainous areas, extreme temperature cycles of-30 DEG C to 120 DEG C, corrosion of corrosive media such as deicing agent, mud, and industrial waste gas, and electromagnetic and electrical stress impact of vehicle-mounted radar and engine starting current.

[0003] Therefore, the harness that responds to complex working conditions needs to be scientifically tested for aging resistance to ensure its reliability throughout its life cycle and avoid electrical failures caused by harness aging, which affects the safety of truck driving.

[0004] For example, in the patent with the patent application number 201821125851.9, a high-temperature aging test system is disclosed, which mainly performs cycle test by controlling temperature and vibration parameters.

[0005] In actual testing, the method involved in the above patent has the following problems: First, the above patent cannot simulate the aging effects of vehicle-mounted radar electromagnetic radiation and road vibration, engine compartment high temperature when the truck is driving in the mine area, which leads to insufficient aging evaluation of the electromagnetic sensitive parts and non-objective evaluation method in the test.

[0006] Second, the corrosion test of the above patent cannot match the solid pollutants such as coal dust and construction site silt commonly seen in the mine area, cannot simulate the actual corrosion scene of mud splashing and high-temperature drying alternation, and is prone to cause the evaluation of the sheath wear and corrosion effect to be missing, and is difficult to reflect the aging state of the harness in the complex pollution environment.

[0007] Therefore, it is necessary to design a truck harness aging test method based on simulation of harsh working conditions. SUMMARY

[0008] To solve one of the above technical problems, the technical solution adopted is: a truck harness aging test method based on simulation of harsh working conditions, comprising the following steps: step 1: first, perform working condition mapping reference parameter calibration under the environmental condition of 25 DEG C ± 2 DEG C, and then perform detection of each parameter of the harness in sequence: obtain all parameter detection results, and establish a harness performance reference parameter library with reference values of each parameter.

[0009] Step 2: place the harness in the environmental chamber for 60-hour composite environmental aging cycle test.

[0010] 0-20h: temperature cycle operation and synchronous environmental stress application.

[0011] 20-40h: alternating spray and ozone exposure, step tensile stress superimposed with torsion and timing pulse current application operation under set temperature and humidity.

[0012] 40-60h: bidirectional bending under high temperature, superimposed vibration, and timed measurement of insulation resistance operation.

[0013] Step 3: After each cycle, perform hierarchical failure determination, retest the parameters of step 1 and compare, if the conductivity decreases by more than 15%, the insulation resistance decreases by more than 30%, the mechanical performance is not up to standard, the temperature rise is more than 20℃, the joint defect amplitude increases more than 6dB or the sheath crack is greater than or equal to 3mm, it is judged to be failed.

[0014] Step 4: If the parameters of step 1 are not failed, return to step 2 to continue the composite environmental aging simulation test cycle; when at least one parameter reaches the failure standard, stop the test cycle, and calculate the aging life of the truck wire harness according to the preset correspondence between the cycle number and the actual use time.

[0015] The specific steps of the preset correspondence between the cycle number and the actual use time include: determining the design service life of the truck wire harness (for example, 8 years) and the average daily working hours of the truck under actual working conditions (for example, 10 hours), and calculating the total actual use time of the wire harness in the whole life cycle (the calculation formula is: design service life × 365 days × average daily working hours, that is, 8 years × 365 days × 10 hours = 29200 hours).

[0016] Select a sample of the same model and specification as the truck wire harness to be tested, and continuously test it in the laboratory according to the composite environmental aging simulation test conditions of step 2 until the sample reaches the failure standard specified in step 3, and record the total test cycle number at this time.

[0017] Divide the total actual use time calculated in step 1 by the total test cycle number recorded in step 2 to get the actual use time corresponding to a single test cycle, which is used as the preset correspondence between the cycle number and the actual use time (i.e. actual use time corresponding to a single cycle = total actual use time ÷ total test cycle number).

[0018] On the basis of any of the preceding technical solutions, further optimization is that: when detecting the parameters of the wire harness, the detection parameters include: conductivity of the conductor, insulation resistance, tensile strength and elongation at break of the sheath, Shore hardness is measured at three points of the joint, bending and straight section of the wire harness, and the average value is taken as the evaluation parameter of the mechanical property of the sheath; the ultrasonic probe scans the crimp joint and detects whether there is internal defect, whether there is scratch and bulge on the surface of the sheath, and records them; the infrared thermal imager records the temperature rise distribution of the wire harness under the rated current.

[0019] On the basis of any of the preceding technical solutions, further optimization is that: the specific steps of the temperature cycle operation and the synchronous application of environmental stress include: increasing to 120℃ at 10℃ / min and keeping for 5h, then decreasing to -30℃ at 8℃ / min and keeping for 5h, repeating 1 time; simultaneously applying 10-30Hz, acceleration 8-15g mine road spectrum vibration and 30-50Hz, acceleration 5-10g mine road spectrum vibration, frequency 24GHz and 77GHz, electric field intensity 80-100V / m electromagnetic radiation; The peak time deviation of the three is controlled to be less than or equal to 50ms.

[0020] On the basis of any of the preceding technical solutions, further optimization is that: the specific steps of the operation of alternating spraying and ozone exposure, step tensile stress and synchronous torsion, and timed pulse current application under the set temperature and humidity include: maintaining the temperature in the environmental chamber at 60℃ and the relative humidity at 95%, and alternately performing spraying operation and ozone exposure treatment every 2h, the spraying operation is 10 minutes long and the pressure is 0.8MPa.

[0021] On the basis of any of the preceding technical solutions, further optimization is that: subsequently, a tensile stress is applied to the wire harness, the stress starts from 50MPa and gradually increases to 200MPa according to an equal gradient, and the tensile stress is applied synchronously and the wire harness is twisted by 30 degrees at an angular velocity of 0.5 rad / s.

[0022] On the basis of any of the preceding technical solutions, further optimization is that: every 3 hours, a pulse current of 300A with a duration of 100ms is applied to the wire harness at 0.5 seconds after the tensile stress reaches the peak value.

[0023] In the liquid used for the spraying operation, the content of sodium chloride is 5% and the content of construction site silt is 10%, so as to simulate a liquid environment with certain corrosion and impurities.

[0024] During the ozone exposure treatment, the exposure treatment is performed for 50 minutes, and the exposure environment contains 0.01% of sulfur dioxide (SO2) by volume fraction and 50ppm of ozone by concentration.

[0025] On the basis of any of the technical solutions above, further optimization is that: the specific steps of the operation of high-temperature bidirectional bending, superimposed vibration, standing cooling and regular insulation resistance measurement include: under the condition that the ambient temperature is 80 DEG C, the wire harness is bent in two opposite directions with the length of 6 times the diameter of the wire harness as the bending radius, the wire harness completes 150 bending actions per minute, the bending direction is changed once every 1000 times of bending, while the bidirectional bending is performed, vibration with a frequency of 10 Hz and an acceleration of 5 g is superimposed, after the above operation, the wire harness is cooled by standing, and the insulation resistance of the wire harness is measured every 6 hours.

[0026] On the basis of any of the technical solutions above, further optimization is that: the specific steps of the level failure determination after each cycle are: environmental recovery and preparation: after the cycle test is completed, the temperature of the environmental chamber is adjusted to 25 DEG C ± 2 DEG C, and the temperature and humidity are stabilized for 30 minutes to ensure that the temperature and humidity are within the standard detection range, and a stable environment is provided for subsequent parameter re-measurement.

[0027] Parameter re-measurement: according to the method and process of line bundle parameter detection in step 1, the conductivity of the conductor, the insulation resistance, the tensile strength and the elongation at break of the sheath, the sheath hardness, the internal defects of the crimp joint, the surface condition of the sheath and the temperature rise distribution of the wire harness under the rated current are re-detected in sequence to ensure that the detection instrument is in normal state and the operation is standardized.

[0028] Data arrangement and analysis: the data obtained by re-measurement are summarized and arranged, and abnormal values are eliminated, and the average value and the standard deviation of each parameter under the current state are calculated according to the same method as establishing the performance benchmark parameter library in step 1.

[0029] Data comparison: the parameters calculated by re-measurement are compared with the initial benchmark values in step 1 respectively, and the change rate or deviation value of each parameter is calculated.

[0030] For example, the percentage decrease of conductivity, the percentage decrease of insulation resistance, etc.

[0031] Failure determination: according to the failure standards of each parameter in the industry specification, the failure of each parameter is judged one by one.

[0032] For example, if any of the following conditions occurs: the conductivity decreases by more than 15%, the insulation resistance decreases by more than 30%, the mechanical properties do not meet the standard (such as the tensile strength and elongation at break of the sheath being lower than the standard value), the temperature rise is more than 20 DEG C, the joint defect amplitude increases by more than 6 dB or the sheath crack is greater than or equal to 3 mm, the wire harness is determined to fail in this cycle test; if all parameters do not meet the failure standard, the wire harness is determined to be not failed.

[0033] Result record and archive: whether the result is failure or non-failure, the relevant information of this level failure judgment is recorded in detail, including judgment time, environmental conditions, retest data, comparison results, judgment conclusion, and the report is arranged and archived together with the previous test records for subsequent review and analysis.

[0034] On the basis of any of the above technical solutions, further optimization is that: when the infrared thermal imager records the temperature rise distribution of the wire harness under the rated current in step 1, the specific operation is as follows: before testing, the infrared thermal imager needs to be preheated in a 25℃±1℃ environment for 30 minutes to ensure that the temperature of the detector is stable.

[0035] The wire harness sample is fixed on the test table in the assembled state of the whole vehicle to avoid heat accumulation deviation caused by the installation method.

[0036] After applying the rated current, the thermal image is collected every 10 seconds for the first 5 minutes, and every 30 seconds for 5-30 minutes, and the sampling frequency is stabilized at 10Hz.

[0037] When analyzing the temperature rise distribution, select three characteristic regions of the wire harness joint, bending section and straight section, and take the average temperature rise of 5 measuring points in each region as the reference value of the region, and the joint area needs to cover the crimping and 10mm range of the insulating layer edge.

[0038] On the basis of any of the above technical solutions, further optimization is that: the specific parameters of the mine area pavement spectrum vibration are as follows: the X-axis vibration of the six-degree-of-freedom vibration table reproduces the vibration in the driving direction of the truck, the energy ratio of 10-20Hz frequency band is 40%, and the energy ratio of 20-30Hz is 30%; the Y-axis 10-20Hz is 20%, and the 20-30Hz is 25%; the Z-axis 10-20Hz is 30%, and the 20-30Hz is 45%, and the energy distribution of each frequency band is based on the fitting of the measured mine area pavement spectrum.

[0039] Among them, the vibration acceleration control adopts closed-loop feedback to ensure that the actual acceleration deviation from the set value is ≤±0.3g.

[0040] The vibration duration and temperature cycle are strictly synchronized. In the warming-up stage, the vibration intensity increases linearly with the temperature rise, and in the cooling-down stage, it decreases linearly with the temperature drop, simulating the correlation characteristics of vehicle speed and vibration intensity.

[0041] On the basis of any of the above technical solutions, further optimization is that: when performing the spraying operation, a double-nozzle spraying mode is adopted, the spraying pressure is controlled at 0.8MPa±0.05MPa, the flow rate is stabilized at 1.5-2.0L / min, the spraying liquid temperature is consistent with the temperature in the environmental chamber, and the thermal shock of the sheath caused by temperature difference is avoided.

[0042] On the basis of any one of the preceding technical solutions, further optimization is that: the specific steps of the wire harness twisting are that a servo motor is used to drive a twisting mechanism and a torque sensor is used to monitor the twisting force in real time.

[0043] When twisted clockwise, from the initial position, rotate at an angular velocity of 0.5 rad / s to the 30° position at a constant speed, keep for 10 s, then rotate counterclockwise at the same angular velocity to reset, and complete one twisting cycle.

[0044] After each twisting cycle, pause for 5 s before the next one, and synchronize with the tensile stress loading, that is, complete 5 twisting cycles during the holding phase of the tensile stress at a certain step value.

[0045] During the twisting process, the axial displacement of the wire harness is monitored by a displacement sensor to ensure that the displacement does not exceed 1% of the length of the wire harness, so as to avoid affecting the twisting test accuracy due to excessive stretching.

[0046] On the basis of any one of the preceding technical solutions, further optimization is that: during the static cooling process, the specific control mode is that the heating device matched with the environment chamber is closed, the temperature control system is started, and a target cooling curve is set, starting from 80℃, uniformly cooling at a rate of 5℃ / h, until it is reduced to 25℃±2℃.

[0047] During the cooling process, the temperature in the chamber and the surface temperature of the wire harness are recorded every hour, and the temperature difference between the two is controlled to be ≤3℃, so as to ensure uniform cooling.

[0048] In order to avoid stress in the wire harness, when the temperature is cooled to 50℃ and 30℃, two key nodes, respectively, pause for 1 h, so that the internal and external temperatures of the wire harness tend to be consistent.

[0049] During the cooling period, the environment chamber is kept naturally ventilated, the ventilation volume is 2 times / h of the volume of the chamber, so as to prevent the accumulation of humidity in the chamber, and the relative humidity is controlled to be between 40%-60%.

[0050] Compared with the prior art, the beneficial effects of the present application are as follows: 1、The present application can accurately simulate harsh working conditions: considering the complex actual working conditions of truck mining areas and construction sites, various environmental stresses are simulated comprehensively in the aging test. For example, when temperature cycling is performed, the temperature is raised and lowered at a certain rate and kept for a corresponding period of time, while the mine road spectrum vibration of different frequency bands and acceleration, the electromagnetic radiation of a certain frequency and electric field strength are simultaneously applied, and the peak time deviation of the three is accurately controlled to be ≤50 ms, which highly restores the comprehensive influence of actual harsh working conditions on the wire harness, and compared with the traditional single or simple combined test environment, the performance change and potential problems of the wire harness in the real scene can be more effectively detected.

[0051] 2、The application detects the wire harness in detail before testing, including conductor conductivity, insulation resistance, sheath mechanical properties (tensile strength, elongation at break, Shore hardness), internal defects of crimped joints, sheath surface condition and temperature rise distribution and other multi-dimensional parameters, and establishes a performance benchmark parameter library.

[0052] After each cycle test, these parameters are retested strictly according to the same method and compared with the benchmark value, realizing comprehensive and accurate monitoring of parameter changes in the test process, providing rich and reliable data basis for accurate determination of wire harness failure, and being able to capture the performance degradation of wire harness more carefully.

[0053] 3、Stage aging cycle test: different and targeted operations are performed in each stage of 0-20h, 20-40h and 40-60h. For example, in 20-40h, under specific temperature and humidity, spray with specific components and ozone exposure are alternately performed, while step tensile stress and synchronous twisting of the wire harness are applied, and pulse current is also applied at regular intervals, simulating the combined effect of multiple complex working conditions.

[0054] The phased test process can accelerate the aging of the wire harness more comprehensively and deeply, quickly expose its potential failure risk, and greatly improve the test efficiency and accuracy compared with the conventional single mode aging test. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. In all the drawings, similar elements or components are generally identified by similar reference numerals. In the drawings, each element or component is not necessarily drawn according to the actual proportion.

[0056] Figure 1 The workflow of the present application is shown in the figure. DETAILED DESCRIPTION

[0057] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application. The specific structure of the present application is shown in Figure 1 .

[0058] Embodiment 1: A truck wire harness aging test method based on simulation of harsh working conditions, comprising the following steps: Step 1: Under the environmental conditions of 25℃±2℃, first perform working condition mapping benchmark parameter calibration, and then sequentially perform wire harness parameter detection: obtain all parameter detection results, and establish a wire harness performance benchmark parameter library with parameter benchmark values.

[0059] In a stable and standard ambient temperature, through specific detection means and equipment, the key parameters of the wire harness are measured. The working condition mapping reference parameter calibration is to associate the subsequent simulated severe working conditions with the actual use scene, and to provide a reference standard for accurately evaluating the performance changes of the wire harness under different conditions. The detected parameters cover conductor conductivity, insulation resistance, sheath mechanical properties (tensile strength, elongation at break, Shore hardness), internal defects of crimp joints, sheath surface condition and temperature rise distribution, etc. These parameters comprehensively reflect the electrical, mechanical and physical properties of the wire harness.

[0060] The above steps ensure the accuracy and comparability of the subsequent test data. By establishing a reference parameter library, a clear comparison basis is provided for the performance changes of the wire harness during the aging test, so that the degradation of each parameter at different test stages can be accurately judged, thereby providing a data basis for evaluating the aging degree and life of the wire harness. That is, an initial and comprehensive wire harness performance database is constructed as the starting point and comparison reference for the entire aging test process. In subsequent tests, by comparing with the data in the reference library, the change trend of each performance of the wire harness under simulated severe working conditions can be intuitively understood, and then it can be judged whether the wire harness reaches the failure standard.

[0061] The reference parameter library established by the above steps can not only be used to judge the aging state of the current wire harness sample, but also can be used as a reference for evaluating the quality consistency of the same type and specification of wire harness products. If multiple wire harness samples show similar patterns in the degree of deviation from the reference parameter library under the same test conditions, it can be inferred that there may be common problems in this batch of products; if the deviation degree difference is large, further investigation of the discrete factors in the production process can help to improve the quality control level of the wire harness products from the source.

[0062] Step 2: The wire harness is placed in the environmental chamber for 60 hours of combined environmental aging cycle test.

[0063] 0-20h: temperature cycle operation and synchronous application of environmental stress are performed, including: increasing to 120℃ at 10℃ / min and maintaining for 5h, then decreasing to -30℃ at 8℃ / min and maintaining for 5h, repeating 1 time; simultaneously applying 10-30Hz, 8-15g acceleration of mine road spectrum vibration and 30-50Hz, 5-10g acceleration of mine road spectrum vibration, 24GHz and 77GHz frequency, 80-100V / m electric field intensity of electromagnetic radiation; controlling the peak time deviation of the three to be ≤50ms.

[0064] The temperature cycle operation simulates the scene of the truck running under different environmental temperatures. Rapid heating and cooling and long time high temperature and low temperature maintenance can cause internal stress changes of the wire harness material due to thermal expansion and contraction, accelerating the material aging.

[0065] Synchronous application of mine road surface spectrum vibration, through the combination of different frequency bands and acceleration, simulates the vibration generated by the truck driving on the complex road in the mine, which will cause mechanical fatigue to the wire harness.

[0066] At the same time, the electromagnetic radiation of a certain frequency and electric field intensity is applied, simulating the electromagnetic interference environment around the truck. In this electromagnetic environment, the internal electronic components and signal transmission of the wire harness may be affected.

[0067] By strictly controlling the peak time deviation of temperature cycle, vibration and electromagnetic radiation to be less than or equal to 50 ms, the actual situation of multiple harsh working conditions acting on the wire harness at the same time can be more realistically simulated.

[0068] This method of synchronous application of multiple stresses and precise control of time deviation is different from the traditional method, which can greatly improve the authenticity and effectiveness of the test. Compared with single stress test or simple superposition of different stresses, this method can more comprehensively reveal the potential failure risk of the wire harness under complex actual working conditions, shorten the test period, improve the test efficiency, and also more accurately evaluate the reliability of the wire harness. In addition, by simulating the combined action of multiple harsh environmental stresses, the aging process of the wire harness is accelerated, and the performance change data of the wire harness under the condition close to the actual complex working condition are obtained in a short time, which provides a basis for subsequent judgment of the life and reliability of the wire harness.

[0069] The complex stress environment simulated in the above test stage is of great significance for studying the performance of the wire harness under special working scenarios (such as mine, industrial area with strong electromagnetic interference, etc.). By analyzing the failure mode of the wire harness under such extreme conditions, targeted guidance can be provided for improving the design of the wire harness, selecting more suitable materials, and optimizing the manufacturing process, so that it can better adapt to special working environments and expand the application range of the wire harness product. This is obviously different from the conventional aging test which only focuses on life evaluation under general use scenarios.

[0070] 20-40h: alternating spray and ozone exposure under the set temperature and humidity, step tensile stress with synchronous torsion and timed pulse current application, the specific steps include: maintaining the temperature in the environmental chamber at 60℃ and the relative humidity at 95% environmental conditions, alternating every 2h spray operation with pressure of 0.8 megapascal for 10 minutes and ozone exposure treatment.

[0071] On the basis of any one of the technical solutions, further optimization is that subsequently applying a tensile stress to the wire harness, the stress starts from 50 MPa and gradually increases to 200 MPa according to an equal gradient, and the tensile stress is applied synchronously and the wire harness is twisted at an angular velocity of 0.5 rad / s for 30 degrees.

[0072] Further optimized on the basis of any of the above technical solutions is that every 3 hours, a pulse current of 300A with a duration of 100 milliseconds is applied to the wire harness at 0.5 seconds after the tensile stress reaches the peak value.

[0073] In the liquid used for the spraying operation, the content of sodium chloride is 5%, and the content of construction site sediment is 10%, so as to simulate a liquid environment with certain corrosiveness and impurities.

[0074] During the ozone exposure treatment, the exposure treatment is performed for 50 minutes, and the exposure environment contains 0.01% by volume of sulfur dioxide (SO2) and 50 ppm of ozone.

[0075] Under a certain temperature and humidity environment, spraying and ozone exposure are alternately performed to simulate the case that the truck drives in a humid environment with corrosive gas and liquid. Sodium chloride and construction site sediment contained in the spraying liquid simulate actual liquids with corrosiveness and impurities, which can cause corrosion and wear of the sheath of the wire harness. Sulfur dioxide and ozone in the ozone exposure environment have strong oxidizing properties and can accelerate the aging of the materials of the wire harness.

[0076] The step tensile stress is applied and synchronous torsion is applied to simulate the tensile and torsional forces that the wire harness may be subjected to during vehicle operation. As the stress gradually increases, the materials inside the wire harness will gradually produce fatigue damage. The application of the timing pulse current simulates the instantaneous large current impact that may occur in the vehicle electrical system. Such current impact may cause the wire harness to heat, locally overheat, or even be damaged.

[0077] This design comprehensively simulates the harsh environments and mechanical and electrical stresses that the truck may face in actual use through the combination of various complex working conditions, can quickly and effectively trigger the potential failure modes of the wire harness, and provides support for accurately evaluating the reliability and life of the wire harness under complex working conditions. The interaction between different stress factors can more realistically reflect the actual situation, and compared with single or simple combination test methods, can more effectively improve the accuracy and effectiveness of the test. In this phase, the aging process of the wire harness is further accelerated through the combination of simulation of various actual harsh working conditions, the failure mechanism of the wire harness under complex stress conditions is better analyzed, and at the same time, more data about the performance degradation of the wire harness is obtained to provide rich data support for judging whether the wire harness has reached the failure standard.

[0078] The benzene stage test method can be used to evaluate the applicability of the wire harness in special working environments (such as chemical transportation, construction sites, etc.). By analyzing the failure reasons of the wire harness in such high-corrosion and high-stress environments, protective measures or improvements can be developed to make the wire harness run reliably in these special environments. In addition, the data obtained during the test process can also be used to establish a more accurate wire harness life prediction model to provide a reference for preventive maintenance of vehicles, which is significantly different from the traditional aging test method that only focuses on life evaluation under general working conditions.

[0079] 40-60h: Perform high-temperature bidirectional bending, superimposed vibration, and static cooling, and measure insulation resistance at regular intervals. The specific steps include: under the condition of an environmental temperature of 80°C, bend the wire harness in two opposite directions with a bending radius of 6 times its own diameter, complete 150 bending actions per minute, and change the bending direction every 1000 times. While performing bidirectional bending, superimpose vibration with a frequency of 10 Hz and an acceleration of 5g. After completing the above operation, allow the wire harness to cool down, and measure the insulation resistance of the wire harness every 6 hours.

[0080] The bidirectional bending operation at high temperature simulates the repeated bending deformation of the wire harness due to component movement during vehicle operation. With a bending radius of 6 times its own diameter and specified bending frequency and number of times, the wire harness produces fatigue under specific stress conditions. The superimposed vibration further aggravates the mechanical stress of the wire harness, simulating the influence of the vibration environment on the wire harness in the bending state during vehicle travel.

[0081] The static cooling process after the operation controls the cooling rate and monitors temperature changes to avoid additional stress on the wire harness due to rapid temperature changes. Finally, by measuring the insulation resistance at regular intervals, the changes in insulation performance of the wire harness after undergoing the above complex operations can be monitored. A decrease in insulation resistance can indicate damage or aging of the wire harness insulation layer.

[0082] The above steps consider the effects of high temperature, bending, and vibration on the wire harness, simulate complex mechanical working conditions in actual use, and comprehensively investigate changes in the mechanical and insulation performance of the wire harness. This can more accurately evaluate the reliability and life of the wire harness in actual working environments, and compared to single-factor testing, it can more realistically reflect the failure of the wire harness in actual use. By measuring the insulation resistance, the final performance state of the wire harness after undergoing the above series of aging operations can be evaluated to provide a key basis for determining whether the wire harness has failed.

[0083] Step 3: After each cycle, perform a hierarchical failure determination. Re-measure the parameters of step 1 and compare them. If the conductivity drops by more than 15%, the insulation resistance drops by more than 30%, the mechanical properties do not meet the standards, the temperature rise exceeds 20°C, the joint defect amplitude increases by more than 6dB, or the sheath crack is ≥3mm, it is determined to be a failure.

[0084] Each parameter is evaluated individually. If even one parameter reaches the failure threshold, the harness is deemed to have failed in this cycle of testing. By comprehensively retesting all parameters and comparing them with baseline values, degradation in harness performance across various aspects can be promptly identified, providing a basis for accurately determining harness failure, avoiding subjective judgment errors, and improving the credibility of test results.

[0085] At the node of the aging test cycle, the performance status of the wiring harness is comprehensively evaluated to determine whether the wiring harness has reached the failure standard, providing a reference basis for deciding whether to continue the test cycle or terminate the test and convert the aging life.

[0086] Step 4: If all parameters in step 1 are not invalid, return to step 2 to continue the composite environment aging simulation test cycle; when at least one parameter reaches the failure standard, stop the test cycle and convert the aging life of the truck wiring harness according to the corresponding relationship between the preset number of cycles and the actual usage time.

[0087] The specific steps for the correspondence between the preset number of cycles and actual usage time include: determining the design service life of the truck wiring harness (taking 8 years as an example) and the average daily working hours of the truck under actual working conditions (taking 10 hours as an example), and then calculating the total actual usage time of the wiring harness over its entire life cycle (the calculation formula is: design service life × 365 days × average daily working hours, that is, 8 years × 365 days × 10 hours = 29,200 hours).

[0088] This calculation method is consistent with the conventional life planning and working mode setting of truck wiring harnesses in actual applications, providing reliable basic data for the establishment of subsequent corresponding relationships.

[0089] Select a sample of the same model and specification as the truck wiring harness to be tested, and continue testing in the laboratory according to the composite environmental aging simulation test conditions in step 2 until the sample reaches the failure standard specified in step 3. Record the total number of test cycles at this time.

[0090] Divide the total actual usage time calculated in step 1 by the total number of test cycles recorded in step 2 to obtain the actual usage time corresponding to a single test cycle. This is used as the correspondence between the preset number of cycles and the actual usage time (i.e., actual usage time corresponding to a single cycle = total actual usage time ÷ total number of test cycles).

[0091] The total actual use time is divided by the total test cycle number to determine the actual use time corresponding to a single test cycle, and the calculation logic makes the calculation method have clear physical meaning and mathematical rationality.

[0092] From the physical meaning, the total actual use time represents the expected working time of the wire harness in actual application, and the total test cycle number represents the cycle number experienced by the wire harness to reach the failure standard under the simulated conditions in the laboratory. The actual use time corresponding to a single cycle is obtained by dividing the two, which can closely associate the laboratory test results with the actual use.

[0093] In mathematical calculation, the method is based on explicit numerical relationship for operation, and the calculation process is simple and direct, without complex assumptions and ambiguous derivation, which ensures the accuracy and reliability of the calculation result, so that the corresponding relationship between the preset cycle number and the actual use time has scientific basis and practical value, and has good feasibility.

[0094] The corresponding relationship established by the scheme can accurately convert the cycle number obtained by the accelerated aging test in the laboratory into the use time of the wire harness under actual working conditions, providing an intuitive and quantitative index for evaluating the aging life of the wire harness.

[0095] Automobile manufacturers and maintenance enterprises can also determine the aging degree and remaining life of the wire harness according to the corresponding relationship and the cycle number recorded in the actual use process, so as to develop a reasonable maintenance plan and replacement strategy. The scheme can be closely combined with the actual application demand, and has significant practical guiding significance and application feasibility.

[0096] In specific operation, when the wire harness does not reach the failure standard after one aging cycle test, the next round of composite environment aging simulation test is continued, and the aging process of the wire harness is continuously accelerated through multiple cycles until it reaches the failure standard.

[0097] In determining the corresponding relationship between the preset cycle number and the actual use time, first, the total actual use time in the whole life cycle of the truck wire harness is calculated according to the designed use life and the average working time per day. Then, the same type and same specification samples are tested under the same conditions in the laboratory, and the total test cycle number when reaching the failure standard is recorded. Finally, the actual use time corresponding to a single test cycle is obtained by division operation, so as to establish the quantitative corresponding relationship between the cycle number and the actual use time, which is used to convert the aging life of the truck wire harness to be tested.

[0098] The above design can more accurately determine the aging life of the wire harness through continuous cycle testing, and avoid inaccurate life evaluation caused by insufficient test times. Meanwhile, by establishing a correspondence between the cycle number and the actual use time, the laboratory test results can better reflect the life of the wire harness in actual use, and improve the practicality and reliability of the test results.

[0099] On the basis of any of the technical solutions above, further optimization is that: when detecting various parameters of the wire harness, the detection parameters include: conductivity of the conductor, insulation resistance, tensile strength and breaking elongation of the sheath, Shore hardness at three points of the joint, bending and straight section of the wire harness is measured respectively, and the average value is taken as the evaluation parameter of the mechanical property of the sheath; the ultrasonic probe scans the crimp joint and detects whether there is an internal defect; the infrared thermal imager records the temperature rise distribution of the wire harness under the rated current.

[0100] When detecting various parameters of the wire harness, the working principle is based on various physical effects and detection technologies. For the conductivity detection of the conductor, according to the working mechanism of the conductivity detector, a known voltage is applied to the conductor under specific environmental conditions, and the current passing through the conductor is measured, so as to obtain the resistance value. Then, according to the inverse proportion relationship between conductivity and resistance, combined with the geometric size parameters such as the cross-sectional area and length of the conductor, the conductivity value of the conductor is obtained through accurate calculation. The value reflects the internal free electron mobility and density of the conductor material, and is a key indicator for measuring the current carrying capacity of the conductor. The insulation resistance measurement is to use an insulation resistance tester to apply a stable specific voltage to the insulation layer of the wire harness. At this time, since the insulation layer is not absolutely insulated, there will be very weak leakage current passing through. The leakage current is captured by a high-precision current measurement device, and then calculated according to Ohm's law to obtain the insulation resistance value. The insulation resistance value can effectively represent the ability of the insulation material to prevent current from passing through. By measuring it, it can be found whether the insulation layer has defects such as damage, moisture, etc. leading to insulation performance decline. The sheath tensile property detection uses the existing tensile testing machine equipment. After the sheath sample is clamped and fixed, the driving device of the equipment applies gradually increasing tensile force to the sample. Under the action of the tensile force, the sample will undergo elastic deformation until plastic deformation, and finally break. In this process, the sensor monitors the tensile force and the sample elongation in real time. When the sample breaks, the maximum tensile force per unit cross-sectional area is calculated, i.e. the tensile strength is obtained. The breaking elongation is obtained by calculating the percentage of the elongation of the sample at the time of breaking to the original length, so as to comprehensively evaluate the tensile property of the sheath material.

[0101] Shore hardness measurement is by means of a Shore hardness tester. The indenter of the hardness tester is vertically pressed into the surface of the sheath material under a specified pressure. According to the depth of indentation or the magnitude of the pressure, the Shore hardness value is converted by the internal conversion mechanism of the hardness tester. In order to more comprehensively evaluate the mechanical performance of the sheath, the measurements are taken at the joint, the bend and the straight section of the wire harness, and the average value is taken, so as to effectively reflect the hardness difference and the overall mechanical performance level of the sheath at different positions.

[0102] The internal defect detection of the crimped joint adopts the existing ultrasonic detection technology. The ultrasonic probe emits high-frequency ultrasonic waves to the crimped joint. If pores, cracks and other defects are encountered during the propagation of the ultrasonic waves in the joint, the propagation path and characteristics will change, resulting in reflection, refraction and scattering phenomena. The receiving probe captures these reflected ultrasonic wave signals and converts them into electrical signals. Through in-depth analysis of the strength, time and other characteristics of the echo signals by professional signal analysis software, it can accurately judge whether there are defects inside the joint, as well as the specific location and size of the defects.

[0103] The sheath surface condition inspection mainly relies on manual visual inspection, and optical magnification equipment is used when necessary to directly observe whether there are scratches, bulges and other abnormal conditions on the surface of the sheath. These surface defects not only affect the appearance quality of the sheath, but more importantly, they may damage the integrity of the protective structure of the sheath, affect its protective performance, and even become a potential hidden danger to accelerate the aging of the wire harness, so careful inspection and recording are required.

[0104] The infrared thermal imager records the temperature rise distribution of the wire harness under the rated current. Its working principle is based on the correspondence between the surface temperature of an object and the intensity of infrared radiation. When the wire harness is connected to the rated current, heat will be generated due to the existence of resistance in each part, and different temperature regions will emit different intensities of infrared radiation. The infrared thermal imager can capture and convert these invisible infrared radiation into visible thermal images. Through analysis and processing of the thermal images, the temperature distribution on the surface of the wire harness can be reflected in real time and intuitively, so as to monitor the heating state of the wire harness.

[0105] The above parameter detection scheme comprehensively includes the electrical performance (conductor conductivity, insulation resistance) of the wire harness, the mechanical performance (sheath tensile strength, elongation at break, Shore hardness), the structural integrity (internal defects of the crimped joint, surface condition of the sheath) and the thermal performance (temperature rise distribution). The initial performance state of the wire harness is detected from multiple parameters, avoiding the limitations of single parameter detection, and the initial performance state of the wire harness can be more accurately and comprehensively evaluated. The specific detection method and equipment for each detection parameter are specified, the operation is standardized, and the accuracy and repeatability of the detection results are guaranteed. At the same time, the targeted detection of key parts (joints, bends) fully considers the areas prone to problems in actual use of the wire harness, improving the effectiveness of the detection.

[0106] In addition, when the wire harness related failure occurs during the use of the vehicle, by comparing the detection parameters of the failed wire harness with the initial baseline parameters, the cause of the failure can be quickly located as a quality problem in the production link or aging or abnormal damage in the use process, providing strong evidence for quality responsibility definition and product improvement.

[0107] On the basis of any of the above technical solutions, further optimization is: the specific steps of level failure determination after each cycle are: environmental recovery and preparation: after the end of the cycle test, adjust the temperature of the environmental chamber to 25℃±2℃, wait for 30 minutes for environmental stability, ensure that the temperature and humidity are within the standard detection range, and provide a stable environment for subsequent parameter retesting.

[0108] Environmental factors have a significant impact on the accuracy of the detection results. Different temperature and humidity conditions can change the physical and electrical properties of the wire harness materials. High temperature can soften the insulation material, resulting in a decrease in insulation resistance; increased humidity can cause conductor oxidation or insulation layer dampness, affecting conductivity and insulation performance.

[0109] The temperature of the environmental chamber is adjusted to 25℃±2℃, because this temperature range is the standard environment for wire harness parameter detection, and the detection results under this condition have comparability and reliability. Stabilizing for 30 minutes ensures that the temperature and humidity in the environmental chamber are uniform and stable, eliminating the residual effects of environmental changes during the test cycle on the wire harness, ensuring that the wire harness is in a standard detection state, thereby ensuring the accuracy of the subsequent parameter retesting data.

[0110] Parameter retesting: according to the methods and procedures of wire harness parameter detection in step 1, the conductivity of the conductor, the insulation resistance, the tensile strength and elongation at break of the sheath, the sheath hardness, the internal defects of the crimp joint, the surface condition of the sheath, and the temperature rise distribution of the wire harness under the rated current are retested in sequence to ensure that the detection instrument is in normal condition and the operation is standardized.

[0111] According to the parameter detection standard method and procedure established in step 1, each parameter is re-measured using the existing corresponding detection instrument. By strictly following the established procedure and standard operation, the consistency and accuracy of the detection process are guaranteed.

[0112] Through retesting, the performance degradation or potential defects of the wire harness under simulated harsh conditions can be found in time, providing specific data support for subsequent failure determination.

[0113] In addition, the data generated by the parameter retest process can also be used to construct a performance degradation model of the wire harness component. By analyzing the changes in parameters after multiple cycle tests, the performance change trend of the wire harness during future use can be predicted, providing a scientific basis for preventive maintenance of the vehicle. In addition, for newly developed wire harness materials or processes, by comparing the parameter retest results of different batches of samples after the same test cycles, the stability and reliability of the new materials or processes can be evaluated, accelerating the development process of new products.

[0114] Data processing and analysis: The data obtained by retesting are summarized and arranged, and abnormal values are eliminated. The average value and standard deviation of each parameter under the current state are calculated in the same way as establishing the performance benchmark parameter library in step 1, such as the percentage decrease in conductivity, the percentage decrease in insulation resistance, etc.

[0115] Abnormal values may be caused by accidental errors, instrument malfunctions or operation errors during testing, which can interfere with the data analysis results, so they need to be eliminated. The average value and standard deviation are calculated in the same way as when establishing the benchmark parameter library. The average value reflects the central tendency of the data and can be used as a representative value of the parameter under the current state. The standard deviation measures the dispersion of the data and can reflect the stability and consistency of the data. Through this data processing method, representative and reliable statistical characteristics can be extracted from the retest data.

[0116] Data comparison: Compare each parameter calculated by retesting with the initial benchmark value in step 1, and calculate the change rate or deviation value of each parameter.

[0117] By calculating the change rate or deviation value, the change of each performance parameter of the wire harness relative to the initial state can be intuitively reflected. The formula for calculating the change rate is (initial value - retest value) / initial value x 100%, and the deviation value is the difference between the retest value and the initial value. These calculation results quantitatively show the degree of performance degradation of the wire harness during the cycle test, facilitating data analysis and comparison.

[0118] Determine the degree of change of each performance parameter of the wire harness after cycle testing to provide direct data basis for failure determination. By comparing the change rate or deviation value, it can be quickly determined which parameters have shown significant degradation, and whether the wire harness has reached the failure standard.

[0119] By comparing the parameter change rates after different cycle numbers, the acceleration or deceleration trend of the wire harness aging can be understood.

[0120] Failure determination: According to the failure standards of each parameter in the industry specifications, the failure of each parameter is judged one by one.

[0121] For example, if any of the following conditions occurs, such as a decrease in electrical conductivity of more than 15%, a decrease in insulation resistance of more than 30%, mechanical performance not meeting the standard (such as sheath tensile strength and elongation at break being lower than the standard value), temperature rise being more than 20°C, joint defect amplitude increasing more than 6dB, or sheath crack being greater than or equal to 3mm, it is determined that the wiring harness fails in the current cycle test; if all parameters do not meet the failure standard, it is determined that the wiring harness does not fail.

[0122] The standards in the industry specification can clearly define under what circumstances each parameter is considered to be in a failure state.

[0123] By comparing the data, the rate of change or deviation value of each parameter is compared with the failure standard one by one to determine whether the wiring harness meets the failure condition. As long as one parameter meets or exceeds the failure standard, it indicates that the wiring harness has serious performance degradation in the current cycle test and cannot meet the normal use requirements, i.e. it is determined to be failed. Based on the industry specification, the authority and fairness of the determination result are guaranteed. The clear and specific failure standard makes the determination process operable and deterministic, avoiding ambiguous judgment and human factors, and improving the credibility and consistency of the test results.

[0124] Results recording and archiving: whether the determination result is failure or non-failure, the relevant information of this level failure determination is recorded in detail, including determination time, environmental conditions, retest data, comparison results, determination conclusion, and it is arranged into a report and archived together with the previous test records for subsequent review and analysis. Arranging these information into a report and archiving it forms a complete test archive, which is convenient for review and analysis when needed.

[0125] On the basis of any one of the technical solutions above, further optimization is that: when the infrared thermal imager records the temperature rise distribution of the wiring harness under rated current in step 1, the specific operation is as follows: before testing, the infrared thermal imager needs to be preheated in a 25°C±1°C environment for 30 minutes to ensure that the temperature of the detector is stable.

[0126] The detector of the infrared thermal imager is sensitive to temperature, and its performance will fluctuate with the change of its own temperature. Preheating the instrument in a 25°C±1°C environment for 30 minutes is to make the detector reach a state of thermal equilibrium, stabilize the performance of its internal electronic components and the temperature measurement accuracy.

[0127] Without sufficient preheating, the detector may have temperature drift, resulting in inaccurate measurement of infrared radiation signals, which in turn affects the measurement results of the wiring harness temperature rise distribution. Through stable preheating environment and time control, the detector can output stable electrical signals to accurately convert the infrared radiation of different temperature regions on the surface of the wiring harness into corresponding temperature data.

[0128] The wire harness sample is fixed on the test bench in the assembled state of the whole vehicle to avoid heat accumulation deviation caused by installation method.

[0129] The installation method of the wire harness in the whole vehicle affects its heat dissipation condition and heat distribution. Fixing in the assembled state of the whole vehicle can maximize the restoration of the physical environment of the wire harness in actual use, including the contact condition with the surrounding components, air flow condition, etc. If the installation method is improper, it may cause the wire harness to be in close contact with the test bench or other fixing devices locally, affecting heat dissipation, causing local heat accumulation, and thus the measured temperature rise distribution cannot truly reflect the heating condition of the wire harness under actual working conditions. By simulating the actual installation state, the heat dissipation path and heat exchange condition of the wire harness can be ensured to be consistent with the actual situation, and accurate temperature rise data can be obtained.

[0130] After applying the rated current, the thermal image is collected every 10 seconds for the first 5 minutes, and every 30 seconds for 5-30 minutes, with a stable sampling frequency of 10 Hz.

[0131] In the initial stage of applying the rated current, the temperature change of the wire harness is relatively rapid, and the thermal image is collected every 10 seconds within the first 5 minutes, which can timely capture the change in the rapid temperature rise stage and obtain the dynamic change data of temperature with time.

[0132] As time goes on, the temperature of the wire harness gradually tends to be stable, and the thermal image is collected every 30 seconds during 5-30 minutes, which can not only ensure that enough data points are obtained to reflect the stable trend of temperature, but also avoid data redundancy caused by excessive collection.

[0133] The stable 10 Hz sampling frequency ensures the continuity and consistency of data collection, so that the collected thermal image can accurately reflect the temperature distribution state of the wire harness at different times, which is convenient for subsequent data analysis and temperature change trend research. By setting different data collection frequencies in stages, both the capture of the dynamic process of the temperature change of the wire harness and the data acquisition in the stable state are considered, which improves the efficiency and effectiveness of data collection.

[0134] When analyzing the temperature rise distribution, select the joint, bending section and straight section of the wire harness as three characteristic regions, and take the average temperature rise of 5 measuring points in each region as the reference value of that region. The joint region should cover the range of 10 mm around the crimping and insulation layer edge.

[0135] The joint, bending section and straight section of the wire harness are the key regions for thermal performance.

[0136] The joint has a large contact resistance due to the existence of crimping connection, which is prone to heat generation; the bending section may cause changes in the internal structure of the material during bending, affecting heat conduction; the straight section serves as a reference region to reflect the thermal performance of the main body of the wire harness.

[0137] In each area, 5 measuring points are selected to take the average value, which can reduce local measurement error and improve the representativeness of data.

[0138] The joint area covers the crimping and the edge of the insulation layer within a range of 10 mm, because these parts are the key positions of heat concentration and transmission, and measuring them can more accurately evaluate the thermal performance of the joint. By analyzing the temperature rise of these three characteristic areas, the overall temperature rise distribution of the wire harness can be comprehensively understood.

[0139] On the basis of any one of the technical solutions above, further optimization is that: the specific parameters of the mine area pavement spectrum vibration applied are that the X-axis vibration of the six-degree-of-freedom vibration table reproduces the vibration in the driving direction of the truck, the energy proportion in the 10-20 Hz frequency band is 40%, and the proportion in the 20-30 Hz frequency band is 30%; the Y-axis 10-20 Hz proportion is 20%, and the 20-30 Hz proportion is 25%; the Z-axis 10-20 Hz proportion is 30%, and the 20-30 Hz proportion is 45%, and the energy distribution in each frequency band is fitted based on the measured mine area pavement spectrum.

[0140] The six-degree-of-freedom vibration table simulates the vibration conditions in different directions of the truck driving on the mine area pavement by independently controlling the vibrations of the X, Y, and Z axes. The energy distribution in each frequency band is fitted based on the measured mine area pavement spectrum because the vibration energy in different frequency bands has different effects on the truck wire harness. The 10-30 Hz frequency band is the main energy concentration area of the mine area pavement vibration, and such a setting can accurately restore the actual pavement vibration characteristics.

[0141] The closed-loop feedback control acceleration compares the actual acceleration data of the vibration table collected by the sensor in real time with the set value, and when there is a deviation, the control system automatically adjusts the output of the vibration table to make the actual acceleration stable within the range of ±0.3g of the set value, thereby ensuring the accuracy of the vibration parameters.

[0142] The vibration duration is synchronized with the temperature cycle, and the vibration intensity changes linearly during the temperature rising and falling stages, which takes into account that the speed change during vehicle driving will cause the vibration intensity to change, and the temperature change will also affect the performance of the wire harness material. This setting can more realistically simulate the combined effects of temperature and vibration on the wire harness under vehicle driving conditions. The vibration application parameter setting in the method can be used to study the effects of different mine area pavement conditions on the wire harness. By adjusting the energy distribution ratio in each frequency band, the vibration characteristics of different types of mine area pavements can be simulated, and the failure modes of the wire harness under different vibration environments can be analyzed, thereby providing a basis for targeted improvement of the wire harness design.

[0143] The vibration acceleration control adopts closed-loop feedback to ensure that the actual acceleration deviation from the set value is ≤±0.3g.

[0144] The closed-loop feedback adopted by the vibration acceleration control is a system that works together with existing sensors, controllers, and actuators to achieve precise control, as follows: Real-time monitoring by sensors: High-precision acceleration sensors are installed on the six-degree-of-freedom vibration table, which can collect real-time acceleration data of the vibration table in X, Y, and Z axis directions. The sensors continuously and quickly perceive the acceleration changes of the vibration table and convert the physical quantities into processable data forms such as electrical signals, which are fed back to the control system.

[0145] Analysis and decision-making by the controller: The control system receives the actual acceleration data from the acceleration sensors and compares them with the pre-set acceleration values. When the deviation between the actual acceleration and the set value exceeds the allowed range (i.e., ±0.3g), the control system calculates the required adjustment parameters and direction, and generates corresponding adjustment instructions.

[0146] Output adjustment by the actuator: The driving device of the vibration table acts as an actuator, which receives the adjustment instructions from the control system and immediately adjusts the output of the vibration table. By changing the output power, frequency, and other parameters of the driving device, the vibration intensity and acceleration of the vibration table are changed, so that the actual acceleration changes towards the set value.

[0147] Cyclic feedback regulation: The acceleration sensor continues to monitor the adjusted actual acceleration in real time and feeds the data back to the control system again. The control system continuously compares, analyzes, and decides, and drives the actuator to continuously adjust, so that the process is repeated in a loop, forming a dynamic closed-loop regulation process. Until the actual acceleration stabilizes within the range of ±0.3g of the set value, ensuring that the vibration table runs stably according to the pre-set acceleration parameters throughout the test process.

[0148] Among them, the acceleration sensor: preferably 352C65 type acceleration sensor, suitable for vibration test scene; or 3701B series of acceleration sensor.

[0149] The controller is preferably a Siemens S7-1500 series PLC controller or a UNO series embedded controller.

[0150] The actuator is preferably a servo electric cylinder to achieve high-precision linear motion control and control the vibration intensity and acceleration of the vibration table.

[0151] The vibration duration and temperature cycle are strictly synchronized. During the temperature rise phase, the vibration intensity increases linearly with the temperature rise, and during the temperature drop phase, it decreases linearly with the temperature drop, simulating the correlation between vehicle speed and vibration intensity.

[0152] Temperature cycle and vibration control are coordinated and managed by the same control system. The temperature sensor monitors the temperature changes in the environmental chamber in real time and feeds the data back to the control system.

[0153] During the heating stage, as the temperature value fed back by the temperature sensor gradually rises, the driving power of the vibration table is gradually increased according to a linear relationship, thereby increasing the vibration intensity.

[0154] During the cooling stage, when the temperature drops, the control system reduces the vibration table driving power accordingly, causing the vibration intensity to decrease linearly.

[0155] At the same time, the start and stop times of the vibration table are strictly synchronized with the various stages of the temperature cycle to ensure that the vibration and temperature changes are closely related throughout the test process, accurately simulating the combined effects of vehicle speed changes (usually speed is related to engine power and driving resistance, which in turn affects vibration intensity) and ambient temperature changes on the wiring harness during driving.

[0156] This control design breaks the pattern of independent effects of temperature and vibration in traditional tests, and fully considers the intrinsic relationship between vehicle speed, temperature and vibration under actual working conditions.

[0157] Through linear increments and decrements and a synchronization mechanism, the test environment is closer to real-world scenarios, significantly improving the validity and credibility of test results. Compared to single-stage temperature or vibration stress testing, or simple combined testing methods, this design can more effectively stimulate potential failure modes of wiring harnesses under complex operating conditions, providing more comprehensive and accurate data for wiring harness reliability assessment.

[0158] Example 2: Compared with Example 1, this example is different in that it also includes the following technical features: Based on any of the above technical solutions, further optimization is: when performing the spraying operation, a double-nozzle spraying method is adopted, the spraying pressure is controlled at 0.8MPa±0.05MPa, the flow rate is stabilized at 1.5-2.0L / min, and the temperature of the spraying liquid is consistent with the temperature in the environmental chamber to avoid thermal shock of the sheath caused by temperature difference.

[0159] The dual-nozzle spraying method uses two nozzles to spray the spray liquid in a fan-shaped or cone-shaped mist. Compared with a single nozzle, it can cover the surface of the wire harness more evenly, ensuring that all parts of the wire harness are sprayed uniformly.

[0160] The pressure control system monitors the pressure in the spray pipeline in real time through a pressure sensor and compares it with the preset pressure value of 0.8MPa. When the pressure deviates from the range of ±0.05MPa, it automatically adjusts the speed of the water pump or the opening of the valve to maintain a stable spray pressure.

[0161] The matching flow control system monitors the spray liquid flow in real time through a flow meter. When the flow exceeds the range of 1.5-2.0L / min, the pipe diameter or water pump power is adjusted to ensure stable flow.

[0162] In terms of temperature control, the spray liquid is heated or cooled by a heat exchanger to keep the temperature of the spray liquid consistent with the temperature in the environmental cabin, so as to avoid thermal stress of the wire harness sheath material due to thermal expansion and contraction caused by temperature difference, and affect the test result.

[0163] On the basis of any one of the technical solutions above, the specific steps for twisting the wire harness are: a servo motor is used to drive the twisting mechanism, and a torque sensor is used to monitor the twisting force in real time.

[0164] When twisting clockwise, the wire harness is rotated at an angular velocity of 0.5 rad / s from the initial position to the 30° position, and then rotated counterclockwise at the same angular velocity to reset after 10 s, to complete one twisting cycle.

[0165] After each twisting cycle, the wire harness is stopped for 5 s before the next cycle, and the stretching stress is loaded synchronously, that is, 5 twisting cycles are completed during the holding stage of a certain step value of the stretching stress.

[0166] During the twisting process, the displacement sensor monitors the axial displacement of the wire harness to ensure that the displacement does not exceed 1% of the length of the wire harness, so as to avoid affecting the twisting test accuracy due to excessive stretching.

[0167] The servo motor serves as a driving source and can accurately control the rotation of the twisting mechanism according to the preset motion parameters.

[0168] During the twisting process, the torque sensor collects the twisting force data of the wire harness in real time and feeds it back to the existing control system, so that when the twisting force fluctuates abnormally, the control system can adjust the output of the servo motor in time to ensure the stability of the twisting force.

[0169] The pause after each cycle provides stress relaxation time for the wire harness material to avoid test errors caused by continuous twisting. Synchronous stretching stress loading is because in actual working conditions, the wire harness often bears stretching and twisting forces at the same time, and the twisting cycle is completed during the holding stage of the stretching stress step value, which more realistically simulates the complex stress state. The displacement sensor monitors the axial displacement of the wire harness in real time, and once the displacement exceeds 1% of the length of the wire harness, the control system intervenes to adjust the twisting mechanism or the stretching device to prevent excessive stretching from interfering with the test result. The twisting test environment simulates the actual complex stress working conditions for the wire harness On the basis of any one of the technical solutions above, the specific control method during the static cooling process is: the environmental cabin closes the matching heating device, opens the temperature control system, sets the target cooling curve, starts from 80℃, uniformly cools at a rate of 5℃ / h, and cools to 25℃±2℃.

[0170] During the cooling process, the temperature in the cabin and the wire harness surface temperature are recorded every hour, and the temperature difference between the two is controlled to be ≤3℃, to ensure uniform cooling.

[0171] To avoid stress inside the wire harness, at the two key nodes of cooling to 50℃ and 30℃, respectively, stop for 1h, so that the temperature inside and outside the wire harness tends to be consistent.

[0172] During the cooling period, the environment cabin is kept naturally ventilated, with a ventilation rate of 2 times / h of the cabin volume, to prevent humidity accumulation in the cabin, and the relative humidity is controlled between 40%-60%.

[0173] The multiple temperature sensors distributed in the cabin collect the environmental temperature in real time, while the infrared temperature meter or contact temperature probe monitors the wire harness surface temperature, and the data is fed back to the control system. When the temperature difference between the two exceeds 3℃, the control system automatically adjusts the air outlet position, air speed and other parameters of the refrigeration equipment to promote the convection of air in the cabin and ensure uniform temperature distribution.

[0174] At the time of cooling to 50℃ and 30℃, the cooling process is paused, and this time is used to allow the internal heat of the wire harness to be fully conducted to the surface, eliminating internal thermal stress caused by excessive cooling rate.

[0175] The natural ventilation system drives air flow by fan, replacing 2 times of cabin volume of air per hour, and cooperating with humidity sensor monitoring and dehumidification equipment linkage, to maintain the relative humidity at 40%-60%, avoiding the influence of humidity change on the performance of wire harness materials.

[0176] As can be seen from the above, the present application realizes the accuracy, efficiency and reliability of the test through multi-dimensional technical optimization. Before testing, a performance benchmark parameter library is established to provide a reference for subsequent evaluation; during the test process, various adverse working conditions such as temperature cycle, complex stress, humid corrosion and mechanical deformation are simulated in stages, and each link is closely coordinated.

[0177] Designs such as vibration and temperature cycle coordination, accurate control of spraying parameters, wire harness twisting and stretching synchronization, etc. truly restore the actual use environment of truck wire harness.

[0178] Precise regulation and control of the standing cooling link avoids introducing additional interference factors, and the hierarchical failure judgment is based on clear standards to ensure that the results are scientific and objective.

[0179] The whole method forms a complete closed loop from test condition simulation to result judgment, not only can accurately evaluate the aging life of truck wire harness, but also can be applied to other fields for its test method and control method, providing strong support for wire harness reliability test and related product quality improvement.

[0180] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application is described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; any alternative improvement or change made by those skilled in the art to the embodiments of the present application falls within the protection scope of the present application.

[0181] The parts not described in detail in the present application are known to those skilled in the art.

Claims

1. A truck wiring harness aging test method based on simulating harsh working conditions, characterized in that: The steps include: Step 1: Under the environmental conditions of 25℃±2℃, first calibrate the working condition mapping benchmark parameters, and then test the various parameters of the wiring harness in sequence: obtain all parameter test results and establish a wiring harness performance benchmark parameter library with the benchmark values ​​of each parameter; Step 2: Place the wiring harness in an environmental chamber for a 60-hour composite environmental aging cycle test: 0-20h: Perform temperature cycling and apply environmental stress simultaneously: 20-40h: Perform alternating spraying and ozone exposure, step tensile stress plus synchronous torsion, and timed pulse current application at set temperature and humidity; 40-60h: Perform bidirectional bending at high temperature, superimpose vibration, then let it cool down and measure the insulation resistance regularly; Step 3: After each cycle, perform a layer failure determination. Re-test the parameters in step 1 and compare them. If the conductivity drops by more than 15%, the insulation resistance drops by more than 30%, the mechanical properties do not meet the standards, the temperature rise exceeds 20°C, the joint defect amplitude increases by more than 6dB, or the sheath crack is ≥3mm, it is determined to be a failure. Step 4: If all parameters in step 1 are not invalid, return to step 2 to continue the composite environment aging simulation test cycle; when at least one parameter reaches the failure standard, stop the test cycle and convert the aging life of the truck wiring harness according to the corresponding relationship between the preset number of cycles and the actual usage time.

2. The testing method according to claim 1, wherein: When testing various parameters of the wiring harness, the test parameters include: the electrical conductivity of the conductor, the insulation resistance, the tensile strength and elongation at break of the sheath, and the Shore hardness is measured at three points: the joints, bends and straight sections of the wiring harness. The average value is taken as the evaluation parameter of the mechanical properties of the sheath; the ultrasonic probe scans the crimped joints and detects whether there are internal defects, observes and records the scratches and bulges on the surface of the sheath; and the infrared thermal imager records the temperature rise distribution of the wiring harness under rated current.

3. The testing method according to claim 2, wherein: The specific steps of performing the temperature cycling operation and synchronously applying the environmental stress include: increasing the temperature to 120°C at 10°C / min and holding for 5 hours, then decreasing the temperature to -30°C at 8°C / min and holding for 5 hours, repeating once; synchronously applying a mining road surface spectrum vibration of 10-30Hz, an acceleration of 8-15g, and a mining road surface spectrum vibration of 30-50Hz, an acceleration of 5-10g, and applying electromagnetic radiation with a frequency of 24GHz and 77GHz and an electric field strength of 80-100V / m; Control the time deviation of the three peaks to be ≤50ms.

4. The testing method according to claim 3, wherein: The specific steps of performing the operations of alternating spraying and ozone exposure, step tensile stress plus synchronous torsion, and timed pulse current application under set temperature and humidity include: Maintaining the environmental chamber at a temperature of 60°C and a relative humidity of 95%, alternately perform a 10-minute spray operation at a pressure of 0.8 MPa and an ozone exposure treatment every 2 hours. Then, a tensile stress is applied to the wire bundle, starting from 50 MPa and gradually increasing to 200 MPa according to a uniform gradient. At the same time, the tensile stress is applied and the wire bundle is twisted 30 degrees at an angular velocity of 0.5 radians per second. Every three hours, a pulse current of 300A with a duration of 100 milliseconds is applied to the wiring harness 0.5 seconds after the tensile stress reaches its peak.

5. The testing method according to claim 4, characterized in that: The specific steps of performing bidirectional bending at high temperature, superimposing vibration, standing still to cool down and measuring insulation resistance at regular intervals include: under an ambient temperature of 80°C, bending the wire harness in two opposite directions with a bending radius of 6 times its own diameter, completing 150 bending actions per minute, and changing the bending direction after completing 1,000 bending actions. While performing bidirectional bending, superimpose vibration with a frequency of 10 Hz and an acceleration of 5 g. After completing the above operations, standing still to cool down the wire harness, and measuring the insulation resistance of the wire harness once every 6 hours.

6. The method according to claim 5, characterized in that The specific steps for determining layer failure after each cycle are as follows: Environmental recovery and preparation: Parameter retest: Retest the wiring harness parameters according to the method and process in step 1; Data collation and analysis: Summarize and collate the retested data, remove outliers, and calculate the mean and standard deviation of each parameter under the current state using the same method as in step 1 to establish the performance benchmark parameter library. Data comparison: Compare each parameter obtained from the re-measurement calculation with the initial reference value in step 1, and calculate the change rate or deviation value of each parameter; Failure determination: Based on the failure criteria of each parameter in the industry specifications, the failure conditions of each parameter are determined one by one; Results are recorded and archived.

7. The method according to claim 6, characterized in that In step 1, when the infrared thermal imager records the temperature rise distribution of the wiring harness under rated current, the specific operations are as follows: Before testing, the infrared thermal imager needs to be preheated in an environment of 25℃±1℃ for 30 minutes; The wiring harness sample is fixed on the test bench according to the vehicle assembly state; After the rated current is applied, thermal images are collected every 10 seconds for the first 5 minutes and every 30 seconds for 5-30 minutes, with the sampling frequency stabilized at 10 Hz. When analyzing the temperature rise distribution, three characteristic areas are selected: the harness connector, the curved section, and the straight section. The average temperature rise of 5 measuring points in each area is taken as the reference value of the area. The connector area must cover the crimping point and the 10mm range of the insulation layer edge.

8. The method according to claim 7, characterized in that The specific parameters of the spectral vibration applied to the mining area road surface are: The six-degree-of-freedom vibration table's X-axis vibration replicates the truck's driving direction, with the 10-20Hz frequency band accounting for 40% of the energy and the 20-30Hz frequency band accounting for 30%. The Y-axis accounts for 20% of the energy and 25% of the energy. The Z-axis accounts for 30% of the energy and 45% of the energy. The energy distribution in each frequency band is based on the measured road surface spectrum in the mining area. The vibration duration is strictly synchronized with the temperature cycle. During the heating stage, the vibration intensity increases linearly with the temperature, and during the cooling stage, it decreases linearly with the temperature, simulating the correlation between vehicle speed and vibration intensity.

9. The method according to claim 8, characterized in that During the spraying operation, a double-nozzle spraying method is adopted, the spraying pressure is controlled at 0.8MPa±0.05MPa, the flow rate is stable at 1.5-2.0L / min, and the temperature of the spraying liquid is consistent with the temperature in the environmental chamber to avoid thermal shock of the sheath caused by temperature difference.

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