Construction method of thermal damage performance test conditions for vehicle parts and comprehensive determination method of the impact of thermal damage on vehicle service life

Abstract

A method for constructing a thermal damage performance test condition for vehicle parts and a method for comprehensively determining the degree of influence of thermal damage on the service life of a vehicle, the method comprising the following steps: step S1, establishing four sets of fitting equations according to the ambient temperature and relative humidity of the following four test conditions respectively; the four test conditions are respectively: a low-speed climbing condition, a high-speed climbing condition, a high-speed driving condition and an urban driving condition; step S2, calculating the relative humidity corresponding to each condition according to the highest ambient temperature of the meteorological big data corresponding to the four test conditions and the fitting equation, and then determining the environmental conditions for the four test conditions in an environmental chamber in combination with the intensity of solar radiation; step S3, testing the vehicles to be tested in the environmental chamber respectively under the environmental conditions of the four test conditions, selecting conditions that are consistent with road tests, and constructing a thermal damage performance test method for vehicle parts under the four test conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal damage to vehicle parts, and in particular to a method for constructing a thermal damage performance test condition for vehicle parts and a method for comprehensively determining the degree of influence of thermal damage on the service life of a vehicle. Background Art

[0002] The vehicle component thermal damage test conditions accurately reflect vehicle usage in China, and the component thermal damage prediction results provide comprehensive feedback on the impact of thermal damage on component life under vehicle usage conditions in China. For example, if a vehicle's designed service life is 300,000 kilometers and thermal damage testing of vehicle components in an environmental chamber is conducted to verify the component's test results, it is found that the test results of a certain component do not meet the long-term temperature resistance limit requirements. Using the vehicle thermal damage test results, analysis can be performed using prediction methods to determine that the impact of component thermal damage on the component's service life is reduced by 10,000 kilometers, resulting in a total vehicle service life of 290,000 kilometers.

[0003] Components within the vehicle's engine compartment and around the chassis exhaust system, such as batteries, wiring harnesses, rubber mounts, generators, compressors, fuel pipes, brake pipes, fuel tanks, and headlights, all have operating temperature requirements. Suppliers generally provide two temperature limits: short-term and long-term. The definitions of these temperature limits are as follows:

[0004] a) Short-term temperature resistance limit is defined as the temperature at which a component will melt, crack, fail, or experience performance degradation within a certain period of time (varies between different components, but is generally within 30 minutes), directly affecting the safety and normal use of the vehicle.

[0005] b) The definition of long-term temperature resistance limit is that the components can ensure the designed service life when working at this temperature. When the temperature is exceeded, there will be no problems such as melting, cracking, and functional failure, but only the service life or aging problems will be affected. For example, the battery limit is 80℃. When the temperature is exceeded during use, it will only affect the battery life. If the temperature is not exceeded, the battery can be used for 4 years, and if it is exceeded, it may only be used for 2 years.

[0006] According to the definition of the temperature resistance limit of components, the short-term temperature resistance limit is not allowed to be exceeded during the product development and verification process, but the long-term temperature resistance limit can be exceeded. Current passenger cars, especially hybrid passenger cars, have many components in the engine compartment, and the layout is complex and tight. The cabin ventilation is relatively poor, and it is easy for the temperature of individual components to exceed the long-term temperature resistance limit in the heat damage test results. In the work of solving the problem of component heat damage, it is necessary to improve the design, increase insulation measures or replace the component materials and models, which will incur huge costs. Figure 1As shown in the figure, when the over-temperature duration of a component is very short and the over-temperature range is not large, if the impact of the over-temperature on the component life can be predicted, and the problem is controllable, the problem of the component whose life is affected by heat damage can be solved in after-sales service by checking and replacing the component at an appropriate time according to the prediction results, this can not only reduce the difficulty of product development, but also greatly save the cost of the entire vehicle.

[0007] Currently, most automakers in the industry require that the results of thermal damage tests on vehicle components during product development must be lower than the corresponding short-term and long-term temperature resistance limits. This is the sole basis for OTS approval of product component development. Although such a determination can ensure the service life of all components, many efforts to resolve thermal damage issues are ineffective.

[0008] Prior art Patent document CN111523176A published on August 11, 2020, discloses a method and system for constructing thermal damage test conditions for passenger cars. The technical solution recorded therein first collects the road conditions of roads in characteristic areas, and determines the test route based on the collection results; based on the determined test route, conducts a field driving test of the vehicle, and collects the vehicle driving conditions and the status of the entire vehicle during the test; analyzes the vehicle driving conditions and extracts the vehicle's characteristic conditions, which include vehicle climbing conditions, vehicle uniform speed driving conditions, and vehicle traffic jam conditions; according to the characteristic conditions and vehicle status of the vehicle in different sections in different test routes, the section where the vehicle load exceeds a preset threshold during the vehicle field driving test is selected as the passenger car thermal damage test condition; and simulates the test of the passenger car thermal damage test condition on the rotating hub. This type of test condition only takes into account road conditions, but does not take into account environmental factors. Environmental factors also have a great impact on the thermal damage of automotive parts. The main role of environmental factors in the vehicle bench thermal damage test is to significantly increase the temperature in the cab, increase the load on the air-conditioning system, and thus increase the load on the air-conditioning compressor and the heat dissipation of the air-conditioning system condenser. The power of the air-conditioning compressor comes from the engine. When the compressor load increases, the overall load of the engine increases, resulting in increased heat generation. When the heat dissipation of the condenser increases, the air inlet temperature in the engine compartment increases, which is not conducive to the heat dissipation of the cabin. The above two aspects directly lead to an increase in the degree of thermal damage to the parts in the engine compartment. Therefore, the measured data obtained under the working conditions constructed by this technical solution cannot truly reflect the actual road test conditions. Summary of the Invention

[0009] The present invention solves the problem that the thermal damage test of vehicle parts in the prior art has poor effect in solving the problem of parts.

[0010] The method for constructing a thermal damage performance test condition for vehicle components according to the present invention comprises the following steps:

[0011] Step S1, establishing four sets of fitting equations according to the ambient temperature and relative humidity of the following four test conditions; the four test conditions are: low-speed climbing condition, high-speed climbing condition, high-speed driving condition, and urban driving condition;

[0012] Step S2: Calculate the relative humidity corresponding to each test condition based on the maximum ambient temperature of the meteorological big data corresponding to the four test conditions and the fitting equation, and then determine the environmental conditions in the environmental chamber for the four test conditions in combination with the solar radiation intensity;

[0013] Step S3: The vehicle to be tested is tested in the environmental chamber under the environmental conditions of the four test conditions respectively, and conditions that are consistent with the road test are selected to construct a thermal damage performance test method for vehicle parts under the four test conditions.

[0014] Furthermore, in one embodiment of the present invention, in step S1, the fitting equation corresponding to the low-speed climbing condition is: y=-4.731x+206, where x is the ambient temperature in °C, and y is the relative humidity in %.

[0015] The fitting equation corresponding to the high-speed climbing condition is: y = -4.107x + 182.3;

[0016] The fitting equation corresponding to the high-speed driving condition is: y=-1.0499x+54.8;

[0017] The fitting equation corresponding to the urban driving condition is: y=-3.756x+179.8.

[0018] Furthermore, in one embodiment of the present invention, in step S3, the conditions for selecting the conditions that comply with the road test are:

[0019] Under the environmental conditions of the low-speed hill climbing test condition in the environmental chamber, simulate driving on slopes of 7%, 9%, and 12%, and obtain the heat values ​​transferred from the engine to the exhaust system of the test vehicle under the three slopes. The heat value that is closest to the heat value transferred from the engine to the exhaust system of the vehicle under road driving state is selected, and the slope corresponding to this heat value is used as the slope condition for the low-speed hill climbing test condition;

[0020] Under the environmental conditions of the high-speed climbing test condition in the environmental chamber, driving on slopes of 5.5%, 6%, and 6.5% is simulated respectively, and the heat values ​​transferred from the engine of the test vehicle to the exhaust system at the three slopes are obtained. The heat value closest to the heat value transferred from the engine to the exhaust system of the vehicle under road driving conditions is selected, and the slope corresponding to this heat value is used as the slope condition for the high-speed climbing test condition.

[0021] Furthermore, in one embodiment of the present invention, the heat value transferred from the engine to the exhaust system is calculated according to the formula:

[0022] Obtained, where Qw is the heat transferred from the engine to the exhaust system, in kJ / s; A is the ratio of heat transferred from the engine to the exhaust system, which is taken as 30%; ge is the engine fuel consumption rate, in kg / kw-h; Ne is the engine power, in kw; hn is the lower calorific value of the fuel, in kJ / kg.

[0023] Furthermore, in one embodiment of the present invention, in step S3, the vehicle to be tested is subjected to a low-speed climbing condition test in an environmental chamber, wherein the vehicle is driven for 30 minutes at 40 km / h and a slope of 9%, and then immediately stopped and turned off for 15 minutes, and then idled for 30 minutes, which is consistent with the road test.

[0024] The vehicle to be tested is subjected to a high-speed climbing test in an environmental chamber, with the conditions being selected to be consistent with the road test, namely, driving at 90 km / h and a slope of 5.5% for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes;

[0025] The vehicle to be tested is subjected to a high-speed driving condition test in an environmental chamber, with the condition of 140 km / h being selected to meet the road test requirements. The vehicle is driven for 30 minutes, immediately stopped and turned off for 15 minutes, and then idled for 30 minutes.

[0026] The vehicle to be tested is subjected to an urban driving condition test in an environmental chamber, and the vehicle is selected to be in compliance with the road test condition by driving according to an urban driving condition curve.

[0027] The method for comprehensively determining the degree of impact of thermal damage on the service life of a vehicle according to the present invention is implemented based on the test conditions constructed by the method for constructing a thermal damage performance test condition for vehicle components described above, and comprises the following steps:

[0028] The vehicle to be tested is subjected to four test conditions: low-speed climbing condition, high-speed climbing condition, high-speed driving condition, and urban driving condition, to obtain the thermal damage performance of the vehicle components under the four test conditions;

[0029] Step S4, calculating the over-temperature mileage of the vehicle under the four test conditions by combining the thermal damage performance of the vehicle components under the four test conditions with the mileage of the vehicle under test in the two stages;

[0030] Step S5, the calculated over-temperature mileage of the vehicle to be tested under the four test conditions is combined with the vehicle life mileage distribution of the four test conditions of low-speed climbing condition, high-speed climbing condition, high-speed driving condition and urban driving condition to calculate the total over-temperature mileage, and the degree of influence of heat damage on the service life of vehicle components is judged based on the total over-temperature mileage result.

[0031] Furthermore, in one embodiment of the present invention, in step S4, the two driving phases of the vehicle to be tested are a driving phase and a parking phase.

[0032] Furthermore, in one embodiment of the present invention, in step S4, the calculation formula for the over-temperature mileage of the vehicle to be tested under the four test conditions is:

[0033] L m =L1+L2, where L m is the over-temperature mileage of the components under their respective operating conditions, L1 is the mileage during the driving phase where the over-temperature of the components affects the lifespan, and L2 is the mileage during the parking phase where the over-temperature of the components affects the lifespan;

[0034] The mileage L2 of the impact of component overheating during the parking phase on life is the average vehicle speed under each operating condition × the actual overheating time.

[0035] Furthermore, in one embodiment of the present invention, in step S5, the vehicle life mileage proportion of the low-speed climbing condition is allocated to 0.4%;

[0036] The high-speed climbing condition accounts for 1.5% of the vehicle's design life mileage;

[0037] The high-speed driving condition accounts for 48% of the vehicle's design life mileage;

[0038] The proportion of vehicle design life mileage in urban driving conditions is 50.4%.

[0039] Furthermore, in one embodiment of the present invention, in step S5, the calculation formula for the total over-temperature mileage of the vehicle to be tested under the four test conditions is:

[0040] L x =L m ×n, where L x is the total over-temperature mileage of components under their respective working conditions, L m is the over-temperature mileage of the component under each working condition, and n is the number of cycles of each working condition.

[0041] This invention solves the problem of poor performance in thermal damage testing of vehicle components in the prior art. In the process of constructing the test conditions, road and environmental factors are fully considered, making the constructed conditions closer to the actual operating state of the vehicle. The test under the constructed conditions can obtain data that can reflect the actual operating state of the vehicle. Specific beneficial effects include:

[0042] 1. The method for constructing the test conditions described in the present invention fully considers road and environmental factors during the construction process. Moreover, the environmental factors are constructed based on the actual environmental characteristics of my country. Therefore, when conducting tests under the conditions constructed by the present invention, experimental data can be obtained that is closer to the conditions of driving on Chinese roads, and can more realistically reflect the thermal damage performance of vehicle components.

[0043] 2. The comprehensive determination method for the extent of the impact of thermal damage on the service life of a vehicle described in the present invention is used to verify whether the thermal damage performance of components within the engine compartment and around the chassis exhaust system of the vehicle meets the allowable operating temperature limit requirements of the components. If the test results of a component do not meet the long-term temperature resistance limit requirements of the component, the method predicts the extent of the impact of thermal damage on the service life of the vehicle based on the vehicle thermal damage test results. Therefore, this determination method plays a very important role in guiding design improvements, solution determination, and project decision-making during the product development stage. The comprehensive determination method solves the problem of poor performance of existing vehicle component thermal damage tests in solving problem components. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0045] Figure 1 This is a diagram showing the results of a high-speed driving heat damage test as described in the background art.

[0046] Figure 2 This is a diagram showing the relationship between ambient temperature and humidity in Chongqing urban area as described in the second embodiment.

[0047] Figure 3 It is a temperature and humidity diagram of the test environment for each working condition described in the second embodiment.

[0048] Figure 4 This is a diagram showing the thermal test results of the exhaust system under the low-speed climbing condition described in the third embodiment.

[0049] Figure 5 This is a diagram showing the thermal test results of the exhaust system under high-speed climbing conditions described in the third embodiment.

[0050] Figure 6 This is the urban driving curve diagram described in the third embodiment.

[0051] Figure 7 This is a working condition diagram of the thermal damage performance test of vehicle parts described in the third embodiment.

[0052] Figure 8 This is a flowchart of vehicle driving condition analysis according to the fourth embodiment.

[0053] Figure 9 It is the kinematic segment eigenvalue graph described in the fourth embodiment.

[0054] Figure 10 This is the original data array diagram described in the fourth embodiment.

[0055] Figure 11 It is a comprehensive characteristic value diagram of various kinematic segments described in the fourth embodiment.

[0056] Figure 12 This is a vehicle operation status classification diagram described in the fourth embodiment.

[0057] Figure 13 It is a mileage distribution diagram of the whole vehicle design life corresponding to the whole vehicle thermal damage test conditions described in Implementation Method Seven.

[0058] Figure 14 4 is a graph showing the results of a thermal damage test on the front bushing of the left front lower control arm according to the ninth embodiment.

[0059] Figure 15 This is a curve diagram of the low-speed climbing test process at an ambient temperature of 35°C as described in the ninth embodiment.

[0060] Figure 16 This is a curve diagram of the high-speed climbing test process at an ambient temperature of 35°C as described in the ninth embodiment.

[0061] Figure 17 This is a curve chart of the urban operating condition test process at an ambient temperature of 43°C as described in the ninth embodiment.

[0062] Figure 18 This is the over-temperature mileage distribution diagram of the left front lower control arm front bushing component described in the ninth embodiment. DETAILED DESCRIPTION

[0063] The following will clearly and completely describe various embodiments of the present invention in conjunction with the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0064] Implementation method 1: The method for constructing the vehicle component thermal damage performance test conditions described in this implementation method includes the following steps:

[0065] Step S1, establishing four sets of fitting equations according to the ambient temperature and relative humidity of the following four test conditions; the four test conditions are: low-speed climbing condition, high-speed climbing condition, high-speed driving condition, and urban driving condition;

[0066] Step S2: Calculate the relative humidity corresponding to each test condition based on the maximum ambient temperature of the meteorological big data corresponding to the four test conditions and the fitting equation, and then determine the environmental conditions in the environmental chamber for the four test conditions in combination with the solar radiation intensity;

[0067] Step S3: The vehicle to be tested is tested in the environmental chamber under the environmental conditions of the four test conditions respectively, and conditions that are consistent with the road test are selected to construct a thermal damage performance test method for vehicle parts under the four test conditions.

[0068] In this embodiment, the thermal damage performance test of vehicle components mainly assesses the operating temperature of components in the engine compartment and components around the chassis exhaust system. The heat sources of these parts all come from the heat generated by the operation of the engine and are closely related to environmental conditions. Thermal damage problems of components are more likely to occur in hot summer weather.

[0069] The test environment conditions are derived from the actual environmental characteristics of China, and the engine heat conditions are mainly derived from the road characteristics of the vehicle deployment area. Therefore, it is necessary to select and formulate corresponding operating conditions based on the engine's heat conditions. The engine's heat generation is directly related to the engine's operating load. The vehicle driving conditions for passenger car engines running at high loads are mainly mountainous driving conditions and high-speed driving conditions. The vehicle driving conditions for engines running at small and medium loads are mainly urban and suburban driving conditions.

[0070] Through online resource research, Google Maps, and vehicle GPS data, a big data analysis of over 20 typical mountain roads in typical tropical regions across China was conducted. Representative roads were selected, including the Gangou Mountain Highway in Turpan, the Jinfoshan Highway in Chongqing, the Yuanmo Expressway, and the Wuzhi Mountain Highway. Actual road weather, road condition information, and vehicle data were collected through actual vehicle testing, ultimately creating simulated mountain driving test conditions. High-speed driving conditions adhered to national regulations requiring a 120 km / h speed limit, with an overspeed of 10%. The test was conducted at a constant speed of 140 km / h. Urban and suburban driving conditions were conducted in accordance with the WLTC conditions specified in the national standard "GB18352.6 Light-Duty Vehicle Pollutant Emission Limits and Measurement Methods."

[0071] Implementation 2: This implementation further limits the method for constructing the vehicle component thermal damage performance test condition described in Implementation 1. In this implementation, the fitting equation corresponding to the low-speed climbing condition is: y = -4.731x + 206, where x is the ambient temperature in ° C, and y is the relative humidity in %.

[0072] The fitting equation corresponding to the high-speed climbing condition is: y = -4.107x + 182.3;

[0073] The fitting equation corresponding to the high-speed driving condition is: y=-1.0499x+54.8;

[0074] The fitting equation corresponding to the urban driving condition is: y=-3.756x+179.8.

[0075] In this embodiment, there is a correlation between ambient temperature and relative humidity. Taking the urban driving conditions as an example, Chongqing was selected as the basis for the design. Since higher ambient temperatures result in more demanding tests, the measurement environment was chosen during the hottest days of the year. During July and August, from 9:00 AM to 4:00 PM (sun exposure period), the ambient temperature and relative humidity at a point one meter above the urban test road were measured hourly. Because only 55 sets of environmental condition data were collected, they could not be directly used to define the environmental conditions for the test conditions. Therefore, the collected test data was compared with meteorological bureau statistics from the same period (1980-2012) to determine the final test environmental conditions.

[0076] The collected ambient temperature and relative humidity were compared with the statistical data of the Meteorological Bureau. Since high temperature has a harsh effect on the test results, the statistical data of the Meteorological Bureau is based on the relative humidity corresponding to the highest ambient temperature of each day in July and August each year, totaling 1984 sets of data. The two sets of measured and statistical data were linearly fitted, as shown in the following example: Figure 2 shown.

[0077] Figure 2 It can be seen that the linear curves fitted by the two sets of data tend to be parallel and have basically the same slope, indicating that regardless of actual measurement or the forecast of the Meteorological Bureau, the corresponding change relationship between the ambient temperature and relative humidity in Chongqing urban area is certain. Therefore, as long as the ambient temperature is determined, the relative humidity can be directly calculated by the fitting formula.

[0078] y=-3.756x+179.83

[0079] Where y is relative humidity, unit is %; x is ambient temperature, unit is ℃

[0080] According to 1984 sets of data on the maximum daily ambient temperature in Chongqing city during July and August, the highest ambient temperature was 43°C. According to the formula, the relative humidity at this temperature was 18.3%.

[0081] The above-mentioned method for determining the ambient temperature and humidity conditions of urban working conditions, the ambient temperature and humidity conditions of low-speed climbing, high-speed climbing and high-speed working conditions all first determine the temperature based on the big data of the Meteorological Bureau, and then calculate the relative humidity through big data fitting.

[0082] The low-speed climbing condition mainly refers to the Wuzhi Mountain Highway in Hainan, the high-speed climbing condition mainly refers to the Yuanjiang-Mojiang section of the Yunnan Expressway, and the high-speed condition mainly refers to the Turpan area of ​​Xinjiang Expressway. The above method is used to comprehensively determine the ambient temperature and humidity conditions of these four conditions, such as Figure 3 As shown, the fitting equation for the low-speed climbing condition is y=-4.731x+206; the fitting equation for the high-speed climbing condition is y=-4.107x+182.3; the fitting equation for the high-speed driving condition is y=-1.0499x+54.8; and the fitting equation for the urban driving condition is y=-3.756x+179.8.

[0083] In July and August, when the temperature in urban areas was around 25°C, it was raining, so the calculated relative humidity reached above 85%. Since the sunlight simulation equipment needed to be turned on during the test, the maximum average solar radiation intensity that could be achieved under the test conditions was 1000w / m 2 Therefore, the relative humidity limit in urban working conditions at 25℃ is 50%.

[0084] Implementation method 3: This implementation method further limits the method for constructing the vehicle component thermal damage performance test conditions described in implementation method 1. In this implementation method, in step S3, the conditions for selecting the conditions that comply with the road test are:

[0085] Under the environmental conditions of the low-speed hill climbing test condition in the environmental chamber, simulate driving on slopes of 7%, 9%, and 12%, and obtain the heat values ​​transferred from the engine to the exhaust system of the test vehicle under the three slopes. The heat value that is closest to the heat value transferred from the engine to the exhaust system of the vehicle under road driving state is selected, and the slope corresponding to this heat value is used as the slope condition for the low-speed hill climbing test condition;

[0086] Under the environmental conditions of the high-speed climbing test condition in the environmental chamber, driving on slopes of 5.5%, 6%, and 6.5% is simulated respectively, and the heat values ​​transferred from the engine of the test vehicle to the exhaust system at the three slopes are obtained. The heat value closest to the heat value transferred from the engine to the exhaust system of the vehicle under road driving conditions is selected, and the slope corresponding to this heat value is used as the slope condition for the high-speed climbing test condition.

[0087] The calculation formula for the heat value transferred from the engine to the exhaust system is:

[0088] Get, where Q w is the heat transferred from the engine to the exhaust system, in kJ / s; A is the ratio of heat transferred from the engine to the exhaust system, which is 30%; g e is the engine fuel consumption rate, unit is kg / kw﹒h; N e is the engine power, unit is kw; h n It is the lower calorific value of fuel, unit is KJ / Kg;

[0089] The vehicle to be tested is subjected to a low-speed climbing condition test in an environmental chamber, with the conditions being selected to be consistent with the road test, namely, driving at 40 km / h and a slope of 9% for 30 minutes, immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes;

[0090] The vehicle to be tested is subjected to a high-speed climbing test in an environmental chamber, with the conditions being selected to be consistent with the road test, namely, driving at 90 km / h and a slope of 5.5% for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes;

[0091] The vehicle to be tested is subjected to a high-speed driving condition test in an environmental chamber, with the condition of 140 km / h being selected to meet the road test requirements. The vehicle is driven for 30 minutes, immediately stopped and turned off for 15 minutes, and then idled for 30 minutes.

[0092] The vehicle to be tested is subjected to an urban driving condition test in an environmental chamber, and the vehicle is selected to be in compliance with the road test condition by driving according to an urban driving condition curve.

[0093] In this embodiment, the main parameters that need to be known in order to simulate the vehicle operation information of the climbing condition in the laboratory are: driving speed, slope and driving time / distance. How to accurately simulate the road conditions requires considering the equivalence between the laboratory and the road. The thermal damage test method for vehicle parts is formulated. The only heat source for the engine compartment and the surrounding parts of the exhaust system is the exhaust system of the engine. The heating of the parts is also a process of heat accumulation. The amount of heat generated by the engine is transferred to the exhaust system in a certain proportion (about 30%). Therefore, it is necessary to compare the cumulative value of the heat generated by the engine under the vehicle driving conditions. The cumulative value of the engine heat generated by the bench simulation will be slightly higher than the actual measurement on the road. The cumulative heat value is calculated according to the following formula

[0094]

[0095] Where Q wis the heat transferred from the engine to the exhaust system, in kJ / s; A is the ratio of heat transferred from the engine to the exhaust system, here it is 30%; g e is the engine fuel consumption rate, unit is kg / kw·h; N e is the engine power, unit is kw; h n It is the lower calorific value of fuel, unit is KJ / Kg.

[0096] According to the above formula, the total heat of the exhaust system during the entire test can be calculated cumulatively, and the bench simulation test conditions can be determined by comparing the total heat.

[0097] The low-speed climbing condition mainly refers to the 224 National Highway Milestone 213km to Milestone 188km between Tongshi and Maoyang in Atuoling, Wuzhishan District, Hainan Province, with a total length of 24.07km and an altitude of 780m. The effective test section is 17.9km long. The maximum slope of this section is 12%, the average slope is 7.1%, and the average test speed is about 40km / h. Based on this road condition information, the laboratory test condition is planned to be a speed of 40km / h, with slope simulations of 12%, 7% and 9%, and a test time of 30min. The actual road test was carried out by the test vehicle and the test was completed in the laboratory according to the proposed conditions. The test results are as follows Figure 4 .

[0098] from Figure 4 It can be seen that the cumulative heat transferred to the exhaust system in the road test is 22406kJ. In the simulation test, only when the slope is set to 9%, the test result of 23902 is slightly higher than the road test result, meeting the requirements. Therefore, the low-speed climbing condition information is a vehicle speed of 40km / h, a slope simulation of 9%, and a test time of 30min.

[0099] The high-speed climbing condition is mainly based on the Yunnan Yuanmo Expressway, where the long slope section from the Honghe Bridge to the Dafengyakou Tunnel is 27 kilometers long. The longitudinal slope of many sections along the entire line is as high as 6%, which is a typical high-speed vehicle climbing section and has experimental value. Based on this road condition information, the laboratory test condition is planned to be a vehicle speed of 90km / h, and the slopes of 5.5%, 6% and 6.5% are simulated on the bench in the environmental chamber. The test time is 30 minutes. The actual road test is carried out by the test vehicle and the test is completed in the laboratory according to the proposed conditions. The test results are as follows: Figure 5 shown.

[0100] from Figure 5 It can be seen that the cumulative heat transferred to the exhaust system in the road test is 43271kJ. In the simulation test, only when the slope is set to 5.5%, the test result of 44706 is slightly higher than the road test result, meeting the requirements. Therefore, the high-speed climbing condition information is a vehicle speed of 90km / h, a slope simulation of 5.5%, and a test time of 30min.

[0101] The vehicle high-speed driving condition setting is implemented in accordance with the regulatory requirements. Current regulations require that the speed limit on highways is 120km / h, and 10% overspeed is allowed, which is 132km / h. Therefore, the test condition is determined to be 140km / h, and the driving time is 30 minutes.

[0102] The urban driving condition refers to the CA.1 low-speed driving condition curve and CA.2 medium-speed driving condition curve in the national standard "GB 18352.6-2016 Light-duty Vehicle Pollutant Emission Limits and Measurement Methods (China Phase VI)". According to the actual driving measurement of the vehicle on the road, it can be determined that the temperature of the engine compartment and the surrounding components of the exhaust system will reach stability after the vehicle has been driving for about 40 minutes. Therefore, the urban condition is set as a combination of driving and idling, with a cumulative time of 3000s. The driving condition is a combination of 3 CA.1 curves and 2 CA.2 curves. The specific conditions are as follows: Figure 6 shown.

[0103] Based on the above environmental conditions and vehicle operation information, the final vehicle component thermal damage performance test conditions are as follows: Figure 7 As shown, the low-speed climbing condition and high-speed climbing condition select the time period with the highest local ambient temperature in the environmental chamber according to Figure 3 Thermal damage performance tests of vehicle components are carried out under various working conditions, and the maximum temperature of the components during the test is selected as the test result.

[0104] In summary, under low-speed climbing conditions, the ambient temperature is 35°C, the relative humidity is 40%, and the sunlight intensity is 1000W / m 2 , driving at 40km / h and 9% slope for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes; high-speed climbing conditions, ambient temperature 35℃, relative humidity 40%, and sunlight intensity 1000W / m 2 , driving at 90km / h and 5.5% slope for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes; high-speed driving condition 1, ambient temperature 43℃, relative humidity 9%, sunlight intensity 1000W / m 2 , driving at 140km / h for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes; High-speed driving condition 2, ambient temperature 35℃, relative humidity 20%, sunlight intensity 1000W / m 2 , driving at 140km / h for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes; High-speed driving condition 3, ambient temperature 25℃, relative humidity 30%, sunlight intensity 1000W / m 2, driving at 140km / h for 30 minutes, then immediately stopping and turning off the engine for 15 minutes, followed by idling for 30 minutes; Urban driving condition 1, ambient temperature 43°C, relative humidity 20%, sunlight intensity 1000W / m 2 , driving according to the urban driving condition curve; urban driving condition 2, ambient temperature 35℃, relative humidity 50%, sunlight intensity 1000W / m 2 , driving according to the urban operating condition curve; urban driving condition 3, ambient temperature 25℃, relative humidity 50%, sunlight intensity 1000W / m 2 , drive according to the urban operating curve.

[0105] Implementation method 4: A comprehensive determination method for the degree of impact of thermal damage on the service life of a vehicle according to this implementation method is implemented based on the test conditions constructed by the method for constructing the vehicle component thermal damage performance test conditions described in implementation method 1. The method includes the following steps:

[0106] The vehicle to be tested is subjected to four test conditions: low-speed climbing condition, high-speed climbing condition, high-speed driving condition, and urban driving condition, to obtain the thermal damage performance of the vehicle components under the four test conditions;

[0107] Step S4, calculating the over-temperature mileage of the vehicle under the four test conditions by combining the thermal damage performance of the vehicle components under the four test conditions with the mileage of the vehicle under test in the two stages;

[0108] Step S5, the calculated over-temperature mileage of the vehicle to be tested under the four test conditions is combined with the vehicle life mileage distribution of the four test conditions of low-speed climbing condition, high-speed climbing condition, high-speed driving condition and urban driving condition to calculate the total over-temperature mileage, and the degree of influence of heat damage on the service life of vehicle components is judged based on the total over-temperature mileage result.

[0109] In this implementation, a big data platform system is used to obtain one year of driving data for all vehicles of a certain brand in China. Based on the vehicle operation information, characteristic parameter values ​​of the driving curve are statistically calculated. Then, multi-parameter statistical theories such as principal component analysis and cluster analysis are applied to study and classify kinematic segments (the movement of a vehicle from one idle start to the next idle start is defined as a kinematic segment). When comparing different driving condition curves horizontally, characteristic parameters that can represent their characteristics are used as evaluation criteria. Figure 4 The characteristic parameters of the kinematic segments are listed, which are also the main basis for the analysis of vehicle operation status. The analysis process is as follows: Figure 8 shown.

[0110] 1. Kinematic segment eigenvalues

[0111] Some characteristic parameters that can represent the characteristics of kinematic segments are used as evaluation criteria, such as Figure 9 As shown in Figure 2, these characteristic parameters are also the basic characteristic values ​​for constructing the vehicle driving cycle operating curve.

[0112] 1) Short stroke (kinematic segment): The movement of a vehicle from one idle start to the next idle start, usually consisting of an idle part and a driving part, but if the duration of this driving process is less than 3 minutes, it will not be considered.

[0113] 2) Acceleration: The vehicle acceleration value is greater than or equal to 0.2m / s 2 continuous process;

[0114] 3) Deceleration: The vehicle acceleration value is less than or equal to 0.2m / s 2 continuous process;

[0115] 4) Uniform speed: The absolute value of the vehicle acceleration is less than 0.2m / s 2 And the continuous process of vehicle speed is not 0;

[0116] 5) Idle: The continuous process in which the car engine is running but the vehicle speed is 0.

[0117] 2. Principal Component Analysis

[0118] A vehicle's actual driving conditions (transient conditions) consist of several short trips from one idle state to the next. During the development of actual vehicle driving conditions, these short trips need to be categorized based on traffic characteristics, specifically short trip characteristic values ​​(such as maximum speed and average speed).

[0119] If one or two short-trip eigenvalues ​​are used as classification indicators, some information may be lost; if more eigenvalues ​​are used to classify short trips, too many variables increase the complexity of the calculation and also bring difficulties to the reasonable analysis and explanation of the problem; secondly, although each variable provides certain information, some variables have a certain correlation, that is, the variables are not independent of each other.

[0120] Let X1, X2, ..., X p Let X be the p random variables involved in a practical problem, and let X = (X1, X2, ..., X p ) T , its covariance matrix is:

[0121] ∑=(σ i,j ) p×p =E[(XE(X))(XE(X)) T ]

[0122] It is a p-order non-negative definite matrix. Let l i=(l i1 , l i2 ,…,l ip ) T (i=1, 2, ..., p) is a p constant vector, and the following linear combination is considered:

[0123]

[0124] It is easy to know that:

[0125]

[0126]

[0127] If Y1 is used to replace the original p variables X1, X2, ..., X p , which requires Y1 to reflect the information of the original p variables as much as possible. Here, "information" is measured by the variance of Y1, that is, reaches the maximum. But for any constant k, if we take but Therefore, l1 must be restricted, otherwise Var(Y1) is unbounded. The most convenient restriction is to require l1 to have unit length, that is, under the constraint Under this condition, find l1 to maximize Var(Y1), and the random variable determined by l1 is Let X1, X2, ..., X p The first principal component of .

[0128] If the first principal component Y1 is not sufficient to reflect the information of the original variable, further calculate Y2. In order to make the information reflected by Y1 and Y2 of the original variable not overlap, it is required that Y1 and Y2 are uncorrelated, that is,

[0129] Cov(Y1,Y2)=l1 T ∑l2=0

[0130] So, under the constraints and Under this condition, find l2 to maximize Var(Y2), and the random variable determined by l2 is Let X1, X2, ..., X p The second principal component of .

[0131] Generally, under the constraints and Next, find l i Make Var(Y i ) reaches its maximum, so l i The random variable Y is determined i =l i T X is called X1, X2, ..., Xp The i-th principal component of .

[0132] 3. Cluster analysis

[0133] The basic idea of ​​cluster analysis is to define distances between samples and similarity coefficients between variables. Distances or similarity coefficients represent the degree of similarity between samples or variables. Samples are categorized one by one based on the degree of similarity. Closely related clusters are clustered into small units, which are then gradually expanded to larger units with more distant relationships. This continues until all samples or variables are clustered, forming a pedigree diagram that represents the closeness of the relationships. Samples or variables are then categorized according to certain requirements.

[0134] We choose the fast sample clustering method for cluster statistical analysis. Its advantages are small memory usage, small amount of calculation, and fast processing speed. It is particularly suitable for cluster analysis of large samples. The algorithm of the fast sample clustering method is as follows:

[0135] Suppose there are n samples, and each sample has p indicators (variables) measured. The original data array is as follows: Figure 10 As shown. ij (i=1,L,n;j=1,L,p) is the observed data of the jth indicator of the i-th sample. i is described by the i-th row of the matrix X, so any two samples X k With X l The similarity between them can be characterized by the similarity between the kth row and the lth row in the matrix X.

[0136] The distance we use for cluster analysis is Euclidean distance, that is,

[0137] d(x i , x j )=||x i -x j ||=[(x i -x j ) T (x i -x j )] 1 / 2

[0138] Suppose the set of k initial cluster points is:

[0139] L (0) ={x1 (0) , x2 (0) ,…,x k (0)}

[0140] Use the following principles to achieve initial classification, remember:

[0141] Gi (0) ={x:d(x,x i (0) )≤d(x,x j (0) ),j=1,2,…,k,j≠i},i=1,2,…,k

[0142] In this way, the samples are divided into k disjoint categories. The principle of the above initial classification is that each sample is classified according to the closest initial cluster point. According to the above calculation, an initial classification is obtained.

[0143] G (0) ={G1 (0) , G2 (0) ,…,G k (0)}

[0144] From G (0) Start calculating the new cluster point set L (1) , with G i (0) The center of gravity is used as the new gathering point:

[0145]

[0146] where n i It is class G i (0) The number of samples in x l It's G i (0) In this way, we get a new set of cluster points:

[0147] L (1) ={x1 (1) , x2 (1) ,…,x k (1)}

[0148] From L (1) Set out and classify the samples into new categories.

[0149] G i (1) ={x:d(x,x i (1) )≤d(x,x j (1) ),j=1,2,…,k,j≠i},i=1,2,…,k

[0150] Get classification G (1) ={G1 (1) , G2 (1) ,…,G k (1)}In this way, the calculation is repeated in sequence.

[0151] Suppose that the classification G is obtained in the mth step (m) ={G1 (m) , G2 (m) ,…,G k (m)}

[0152] In the above recursive calculation process, x i (m) It is class G i (m-1) The center of gravity, x i (m) Not necessarily a sample, and generally not G i (m) As m increases, the classification becomes stable. i (m) It will be approximately G i (m) The center of gravity of x i (m+1) ≈x i (m) , G i (m+1) ≈G i (m) , the algorithm ends. In actual calculation, starting from a certain step m, when the classification

[0153] G (m+1) ={G1 (m+1) , G2 (m+1) ,…,G k (m+1)} and G (m) ={G1 (m) , G2 (m) ,…,G k (m)} is exactly the same, and the calculation is complete.

[0154] 4. Mileage Allocation

[0155] A total of 52,030 valid kinematic fragments were obtained using the big data platform. The overall kinematic fragment samples were divided into three categories through cluster analysis. Figure 11It is an average statistic based on traffic characteristics for each type of kinematic segment and the overall sample. Analysis of the 15 average statistics for the three types of kinematic segments shows that the first type of kinematic segment has more frequent acceleration and deceleration, with larger acceleration and deceleration rates and higher average speeds, typical of non-urban roads. The first type of kinematic segment has fewer kinematic segments, reflecting the driving characteristics of typical mountain roads. The second type of kinematic segment has more time spent at a constant speed and an average speed exceeding 100 km / h, typical of highway driving. The third type of kinematic segment has more time spent idling and an average speed of 21.5 km / h, with relatively frequent acceleration and deceleration, typical of urban road driving.

[0156] After the classification is completed, the classification is mainly based on the average speed, and the specific classification is based on the area, date, slope, etc. of each vehicle operation. Figure 12 shown.

[0157] Implementation method five: This implementation method further limits the comprehensive determination method of the degree of influence of thermal damage on the service life of the vehicle described in implementation method four. In this implementation method, in step S4, the two driving phases of the vehicle to be tested are the driving phase and the parking phase.

[0158] In this embodiment, there are driving phases and parking (engine shutoff or idling) phases in low-speed climbing, high-speed climbing, high-speed, and urban conditions.

[0159] Embodiment 6: This embodiment further limits the comprehensive determination method for the degree of impact of thermal damage on the service life of the vehicle described in Embodiment 4. In this embodiment, the calculation formula for the over-temperature mileage of the vehicle to be tested under the four test conditions in step S4 is:

[0160] L m =L1+L2, where L m is the over-temperature mileage of the components under their respective operating conditions, L1 is the mileage during the driving phase where the over-temperature of the components affects the lifespan, and L2 is the mileage during the parking phase where the over-temperature of the components affects the lifespan;

[0161] The mileage L2 of the impact of component overheating during the parking phase on life is the average vehicle speed under each operating condition × the actual overheating time.

[0162] In this embodiment, the test results of the two stages are processed as follows:

[0163] Over-temperature conditions occur during driving: the mileage (L1) affected by component over-temperature on life is the actual over-temperature mileage;

[0164] If there is over-temperature during parking, the mileage (L2) affected by the over-temperature of the component life is the average vehicle speed under this condition multiplied by the actual over-temperature time.

[0165] After the environmental simulation test is completed under each working condition, calculate the over-temperature mileage L of the component under each test condition according to the above method. m =L1+L2.

[0166] Embodiment 7: This embodiment further limits the comprehensive determination method of the degree of influence of heat damage on the service life of the vehicle described in embodiment 4. In this embodiment, in step S3, the proportion of the vehicle life mileage in the low-speed climbing condition is allocated to 0.4%;

[0167] The proportion of the vehicle's design life mileage under the high-speed climbing condition is 1.5%;

[0168] The proportion of the vehicle's design life mileage under high-speed driving conditions is 48%;

[0169] The proportion of the vehicle's design life mileage under urban driving conditions is 50.4%.

[0170] In this embodiment, the classification situation is combined with Figure 11 Combined with the working conditions, according to the number of kinematic segments, the mileage distribution of the vehicle design life is completed, and the mileage ratio corresponding to each verification working condition is determined. The specific results are shown in Figure 13 As shown in the figure, the low-speed and high-speed climbing conditions are harsh conditions under the vehicle's operating conditions. The cumulative mileage accounts for 1.9% of the total mileage, the cumulative mileage of urban driving conditions accounts for 50.4%, and the cumulative mileage of high-speed driving conditions accounts for 48%, which is basically consistent with the actual usage of users.

[0171] Embodiment 8: This embodiment further defines the comprehensive determination method for the degree of impact of heat damage on the service life of a vehicle described in Embodiment 4. In this embodiment, in step S5, the calculation formula for the total over-temperature mileage of the vehicle under test under the four test conditions is:

[0172] L x =L m ×n, where L x is the total over-temperature mileage of components under their respective working conditions, L m is the over-temperature mileage of the component under each working condition, and n is the number of cycles of each working condition.

[0173] In this embodiment, the total over-temperature mileage L of each test condition is x =L m ×n, n is Figure 8 The number of cycles of each working condition, L of each working condition x The cumulative total is the total mileage of the final impact of heat damage on life.

[0174] Implementation method 9: This implementation method is based on the comprehensive determination method of the degree of influence of heat damage on the service life of the vehicle described in the present invention, and provides a practical implementation method in combination with specific objects:

[0175] In this embodiment, a certain vehicle model product development conducted a component heat damage test according to this patented method. Among them, the front bushing component of the left front lower control arm had a heat damage overtemperature problem. The maximum allowable temperature of this component is 70°C. The specific test results are as follows Figure 14 As shown in the figure, the test process curve of over-temperature condition is as follows Figure 15 、 16 and 17.

[0176] The overtemperature test curves show that components overheat during both the driving and parking phases in both low-speed and high-speed climbing conditions, and overheating in the latter part of urban conditions. The overtemperature mileage under each condition was calculated using the calculation method.

[0177] 1) Calculation of over-temperature mileage under low-speed climbing conditions at an ambient temperature of 35°C

[0178] The over-temperature mileage during the driving phase is the actual mileage. Through test measurements, it can be seen that the over-temperature mileage is 15.5km;

[0179] The over-temperature mileage during the parking phase is calculated as follows: the average vehicle speed during the entire operating period is 21.5 km / h, the total over-temperature duration during the parking phase is 405 seconds, and the calculated over-temperature mileage is 21.5×405÷3600=2.4 (km);

[0180] The cumulative over-temperature mileage of the front bushing components of the left front lower control arm under low-speed climbing conditions is 17.9km.

[0181] 2) Calculation of over-temperature mileage under high-speed climbing conditions at an ambient temperature of 35°C

[0182] The over-temperature mileage during the driving phase is the actual mileage. Through test measurements, it can be seen that the over-temperature mileage is 27.8km;

[0183] The over-temperature mileage during the parking phase is calculated as follows: the average vehicle speed during the entire operating period is 48.2 km / h, the total over-temperature duration during the parking phase is 451 seconds, and the calculated over-temperature mileage is 48.2 × 451 ÷ 3600 = 6 (km);

[0184] The cumulative over-temperature mileage of the front bushing components of the left front lower control arm under low-speed climbing conditions is 33.8km.

[0185] 3) Calculation of over-temperature mileage in urban conditions at an ambient temperature of 43°C

[0186] The over-temperature mileage during the driving phase is the actual mileage. Through test measurements, it can be seen that the over-temperature mileage is 6.9km;

[0187] The over-temperature mileage during the parking phase is calculated as follows: the average vehicle speed during the entire operating period is 22.5 km / h, the total over-temperature duration during the parking phase is 400 seconds, and the calculated over-temperature mileage is 22.5 × 400 ÷ 3600 = 2.5 (km);

[0188] The cumulative over-temperature mileage of the front bushing components of the left front lower control arm under low-speed climbing conditions is 9.4km.

[0189] 4) Overheating affects the life and mileage of the vehicle

[0190] The left front lower control arm front bushing test results and over-temperature calculation mileage distribution are as follows Figure 18 As shown in the figure, the front bushing of the left front lower control arm has a lifespan of 300,000 km, and the mileage due to heat damage is 25,012 km, accounting for 8.3% of the total mileage.

[0191] According to the test results, the improvement plan is as follows:

[0192] 1) Replace the front bushing of the left front lower control arm with one with higher temperature resistance. According to the heat damage test, the temperature resistance limit needs to be increased from the current 70°C to 80°C.

[0193] 2) Maintain the current plan and inspect the left front lower control arm front bushing components during vehicle use and maintenance. Replace them in advance if any damage is found, or directly replace with new components when the vehicle has traveled 250,000 kilometers.

Claims

1. A method for constructing a thermal damage performance test condition for vehicle parts, characterized in that: The following steps are involved: Step S1, establishing four sets of fitting equations according to the ambient temperature and relative humidity of the following four test conditions; the four test conditions are: low-speed climbing condition, high-speed climbing condition, high-speed driving condition and urban driving condition; Step S2, calculating the relative humidity corresponding to each working condition according to the maximum ambient temperature of the meteorological big data corresponding to the four test working conditions and the fitting equation, and then determining the environmental conditions for the four test working conditions in the environmental chamber in combination with the solar radiation intensity; Step S3, the vehicle to be tested is tested in the environmental chamber under the environmental conditions of the four test conditions respectively, and the conditions that are consistent with the road test are selected to construct the thermal damage performance test method of the vehicle parts under the four test conditions; In step S3, the conditions for selecting the conditions that meet the road test are: Under the environmental conditions of the low-speed climbing test condition in the environmental chamber, driving on slopes of 7%, 9% and 12% is simulated respectively, and the heat values ​​of the engine of the vehicle to be tested transferred to the exhaust system under the three slopes are obtained, and a heat value closest to the heat value of the engine of the vehicle to be tested transferred to the exhaust system under the road driving state is selected, and the slope corresponding to the heat value is used as the slope condition of the low-speed climbing test condition; Under the environmental conditions of the high-speed climbing test condition in the environmental chamber, driving on slopes of 5.5%, 6% and 6.5% is simulated respectively, and the heat values ​​of the engine of the vehicle to be tested transferred to the exhaust system under the three slopes are obtained. The heat value closest to the heat value transferred to the exhaust system by the vehicle engine under road driving state is selected, and the slope corresponding to the heat value is used as the slope condition of the high-speed climbing test condition.

2. The method for constructing a vehicle component thermal damage performance test condition according to claim 1, characterized in that: In the step S1, the fitting equation corresponding to the low-speed climbing condition is: y=-4.731x+206, where x is the ambient temperature, in units of °C, and y is the relative humidity, in units of %; The fitting equation corresponding to the high-speed climbing condition is: y=-4.107x+182.3, where x is the ambient temperature, in °C, and y is the relative humidity, in %. The fitting equation corresponding to the high-speed driving condition is: y=-1.0499x+54.8, where x is the ambient temperature, in °C, and y is the relative humidity, in %. The fitting equation corresponding to the urban driving condition is: y=-3.756x+179.8, where x is the ambient temperature, in units of °C, and y is the relative humidity, in units of %.

3. The method for constructing a vehicle component thermal damage performance test condition according to claim 1, characterized in that: The heat value transferred from the engine to the exhaust system is based on the formula: Get, where Q w is the heat transferred from the engine to the exhaust system, in kJ / s; A is the heat ratio transferred from the engine to the exhaust system, which is 30%; g e is the engine fuel consumption rate, unit is kg / kw.h; N e is the engine power, in kw; h n It is the lower calorific value of fuel, unit is KJ / Kg.

4. The method for constructing a vehicle component thermal damage performance test condition according to claim 1, characterized in that: In step S3, the vehicle to be tested is subjected to a low-speed climbing condition test in the environmental chamber, and the conditions that meet the road test are selected as 40 km / h and a slope of 9% for 30 minutes, and then the vehicle is immediately stopped and turned off for 15 minutes, and then idled for 30 minutes; The vehicle to be tested is subjected to a high-speed climbing test in an environmental chamber, and the conditions that meet the road test are selected as 90km / h and a slope of 5.5% for 30 minutes, and then the vehicle is immediately stopped and turned off for 15 minutes, and then idled for 30 minutes; The vehicle to be tested is subjected to a high-speed driving condition test in an environmental chamber, and the conditions that meet the road test are selected to be 140 km / h, driving for 30 minutes, immediately stopping and turning off the engine for 15 minutes, and then idling for 30 minutes; The vehicle to be tested is subjected to an urban driving condition test in an environmental chamber, and the condition that meets the road test is selected to be driving according to an urban driving condition curve.

5. A comprehensive determination method for the degree of influence of heat damage on the service life of a vehicle, characterized in that the method is implemented based on the test conditions constructed by the method for constructing the test conditions for heat damage performance of vehicle parts according to claim 1, and the method comprises the following steps: The vehicle to be tested is subjected to four test conditions: low-speed climbing condition, high-speed climbing condition, high-speed driving condition and urban driving condition, to obtain the thermal damage performance of vehicle parts under four test conditions; Step S4, the over-temperature mileage of the vehicle under the four test conditions is calculated by combining the thermal damage performance of the vehicle parts under the four test conditions with the mileage of the vehicle under the two stages; Step S5, the calculated over-temperature mileage of the vehicle to be tested under the four test conditions is combined with the vehicle life mileage distribution of the four test conditions: low-speed climbing condition, high-speed climbing condition, high-speed driving condition and urban driving condition, to calculate the total over-temperature mileage, and the degree of influence of heat damage on the service life of vehicle parts is judged according to the total over-temperature mileage result.

6. The comprehensive determination method of the degree of influence of heat damage on the service life of a vehicle according to claim 5 is characterized in that: In the step S4, the two driving phases of the vehicle to be tested are the driving phase and the parking phase.

7. The comprehensive determination method of the influence of heat damage on the service life of a vehicle according to claim 5 is characterized in that: In step S4, the calculation formula for the over-temperature mileage of the vehicle to be tested under the four test conditions is: L m =L1+L2, where L m is the over-temperature mileage of the components under their respective working conditions, L1 is the mileage of the impact of over-temperature on the service life of the components during the driving stage, and L2 is the mileage of the impact of over-temperature on the service life of the components during the parking stage; The mileage L2 of the impact of component overheating on life during the parking phase is the average vehicle speed under the respective operating conditions × the actual overheating time.

8. The comprehensive determination method of the influence of heat damage on the service life of a vehicle according to claim 5 is characterized in that: In step S5, the vehicle life mileage proportion of the low-speed climbing condition is allocated to 0.4%; The vehicle design life mileage proportion of the high-speed climbing condition is 1.5%; The vehicle design life mileage proportion of the high-speed driving condition is 48%; The vehicle design life mileage proportion of the urban driving condition is 50.4%.

9. The comprehensive determination method of the influence of heat damage on the service life of a vehicle according to claim 5, characterized in that: In step S5, the calculation formula for the total over-temperature mileage of the vehicle to be tested under the four test conditions is: L x =L m ×n, where L x is the total over-temperature mileage of the components under their respective working conditions, L m is the over-temperature mileage of the component under each working condition, and n is the number of cycles of each working condition.

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