Electric heating coil accelerated life test method and system
By combining screening and orthogonal experiments with the training of corrected parameters of the standard life model, the problem of large errors in the life test results of electric heating coils was solved, and the reliability and accuracy of the electric heating coil life test data were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-23
- Publication Date
- 2026-04-07
AI Technical Summary
The lack of unified parameter standards and standardized procedures in existing electric heating coil life tests leads to large errors in test results.
An accelerated life test method using electric heating coils was adopted. By screening samples and test parameters, orthogonal tests were conducted, and the standard life model was used to train the corrected parameters. Combined with stress loading unit, sample tooling unit and monitoring and acquisition unit, a complete test closed loop was formed.
This improves the reliability and accuracy of data from electric heating coil life tests, ensures consistency of test parameters, and enhances the accuracy and standardization of electric heating coil life assessment.
Smart Images
Figure CN121805751A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrical component testing technology, and in particular to a method and system for accelerated life testing of electric heating coils. Background Technology
[0002] Electric heating coils for injection molding machines are core components in plastic molding processes, and their service life directly affects production efficiency and product quality. Traditional electric heating coil life tests rely on natural aging to simulate the actual operating conditions of injection molding machines (rated voltage or temperature cycling), continuously running and periodically checking indicators such as temperature uniformity, power deviation, and insulation resistance until the sample fails, and recording the cumulative running time. In recent years, some personnel in the electric heating coil industry have conducted accelerated life tests by applying high voltage. Based on the principle of stress acceleration, 1.2 to 2 times the rated voltage is applied, and a test platform is built with a high-voltage power supply and data acquisition system. By increasing the voltage load, the aging of the heating wire or insulation layer is accelerated, and the failure time under high voltage is recorded and then converted to the normal operating condition life.
[0003] Regarding the aforementioned technologies, the application of high voltage to measure the lifespan of electric heating coils during life testing results in large errors due to the lack of unified parameter standards and standardized procedures. Summary of the Invention
[0004] In order to standardize test parameters and obtain the life of electric heating coils quickly, reliably and accurately, this invention provides an accelerated life test method and system for electric heating coils.
[0005] In a first aspect, the present invention provides a method for accelerating the life test of an electric heating coil, employing the following technical solution: A method for accelerated life testing of electric heating coils includes: Step S1: In response to a preset test signal, acquire the performance parameters of multiple initial samples; Step S2: Obtain initial samples and assign them random numbers to obtain initial sample numbers. Filter the initial samples according to performance parameters and preset filtering rules to obtain performance sample numbers. Step S3: Obtain the sample stress group based on performance parameters and screening rules. The sample stress group is a voltage-temperature dual stress coupling. Step S4: The electric heating coil corresponding to the control performance sample number is subjected to a preset orthogonal test according to the sample stress group to obtain the test results; Step S5: Input the test results into the preset standard lifetime model for training to obtain the corrected parameters; Step S6: Correct the standard lifetime model with the correction parameters to obtain the actual lifetime model, and output it.
[0006] By adopting the above technical solution, the electric heating coil samples and test parameters are screened, and the test results are obtained based on the test. These results are then substituted into the model to ensure that the relevant data in the model are accurate and complete. This avoids the problem of inaccurate test results caused by inconsistent test parameters, ensures that the test parameters are consistent during the test, and improves the reliability and accuracy of the data in the accelerated life test of the electric heating coil.
[0007] Optionally, the method for obtaining test results by conducting a pre-set orthogonal test on the electric heating coil corresponding to the control performance sample number according to the sample stress group includes: Step S40: Obtain the target high temperature and the target low temperature; Step S41: Control the power supply of the sample corresponding to the performance sample number, and at the same time acquire the sample temperature and sample status, and accumulate the power supply time. The sample status includes normal status and damaged status. Step S42: When the sample temperature reaches the target high temperature, the sample corresponding to the control performance sample number is powered off and the accumulation time is stopped to obtain the test duration; Step S43: When the sample temperature reaches the target low temperature, re-control the power-on of the sample corresponding to the performance sample number and continue to accumulate the power-on time based on the test duration; Step S44: When the sample status is damaged, the electric heating coil corresponding to the control performance sample number is de-energized and the test duration is counted to obtain the characteristic lifetime; Step S45: Use the characteristic lifetime and sample stress group as the test results.
[0008] By adopting the above technical solution, the electric heating coil is energized and de-energized according to the temperature, so that the electric heating coil can be kept in good condition during the test. The time obtained from multiple tests is statistically analyzed to obtain the characteristic life, avoiding inaccurate life measurement results caused by excessively long single energization time of the electric heating coil, and improving the accuracy and reliability of the electric heating coil life test results.
[0009] Optionally, methods for inputting experimental results into a pre-defined standard lifetime model for training to obtain corrected parameters include: Step S50: Perform a preset logarithmic calculation on the standard lifetime model to obtain a linear model; Step S51: Further simplify the linear model to obtain a simplified model; Step S52: Unify the simplified model to obtain the general formula model; Step S53: Convert the general formula model into a matrix to obtain the matrix model; Step S54: Obtain the correction parameters based on the experimental results, matrix model, and the preset least squares principle.
[0010] By adopting the above technical solution, the model for calculating the final constant parameters is obtained by performing corresponding operations on the standard life model, making the steps for calculating the characteristic constants simpler and providing strong data and formula support for subsequent calculations of the electric heating coil life.
[0011] Alternatively, the formula for the standard lifetime model is: Where L is the characteristic lifetime, T is the absolute temperature, U is the voltage stress, Ea is the activation energy, k is the Boltzmann constant, and C, α, A, and B are undetermined constants; Wherein, the absolute temperature T is obtained by adding the temperature stress to the preset absolute zero, and the activation energy Ea and the undetermined constants C, α, A and B are obtained from multiple sets of characteristic lifetimes L, absolute temperature T and voltage stress U according to the formula of the standard lifetime model. Calculated.
[0012] Optionally, the formulas for the linear model and the simplified model are: and In the formula for the linear model, lnL is the logarithm of the characteristic lifetime, lnC is the logarithm of the undetermined constant C, and lnT is the logarithm of the absolute temperature. In the simplified model formula, y is lnL, β0 is lnC, β1 is α, x1 is lnT, and β2 is E. a / k, x2 is 1 / T, β3 is A, β4 is B, x3 is U, and x4 is U / T.
[0013] Alternatively, the formula for the general model is: , where n is the total number of initial sample numbers for a stress group, i is the current stress group, j is the current initial sample number, {n(i-1)+j} is the j-th initial sample number for the i-th group, and ε is the residual.
[0014] Alternatively, the formula for the matrix model is: Where Y is y {n(i-1)+j} X is a matrix β is a parameter column vector of β0, β1, β2, β3, and β4.
[0015] Alternatively, the formula for the least squares principle is: and ; in, The vector of estimated values containing parameters β0 to β4, X T Let X be the transpose of X.
[0016] Secondly, the present invention provides an accelerated life testing system for electric heating coils, which adopts the following technical solution: An accelerated life testing system for an electric heating coil, applied to an accelerated life testing method for an electric heating coil as described above, includes a stress loading unit for maintaining constant test data, a sample tooling unit, a monitoring and acquisition unit for collecting electrical and temperature parameters, and a control and analysis unit for fitting a model and calculating the life.
[0017] By adopting the above technical solution, the stress loading unit, sample tooling unit, monitoring and acquisition unit, and control and analysis unit form a complete experimental closed loop with division of labor and cooperation. This accurately adapts to the entire process requirements of the aforementioned accelerated life test method, avoids problems such as inaccurate control of traditional test parameters, incomplete data acquisition, and low processing efficiency, ensures test standardization and data reliability, and improves the accuracy of electric heating coil life assessment.
[0018] Optionally, the sample fixture unit includes a metal support, a metal fixture body disposed on one side of the metal support for placing the sample, heat dissipation devices disposed on both sides of the metal fixture body for dissipating heat, and a temperature sensor disposed on the side of the metal fixture body away from the metal support to obtain temperature data.
[0019] By adopting the above technical solution, the metal bracket provides stable support for the overall structure, the metal tooling body realizes the standardized positioning and installation of the electric heating coil sample, the heat dissipation devices on both sides can regulate the temperature environment of the tooling and the sample, and the temperature sensor captures the sample temperature data in real time. This unit achieves integrated adaptation of sample installation, environmental control and data acquisition through structural design, ensuring the accuracy of test data.
[0020] In summary, the present invention has at least one of the following beneficial technical effects: By screening samples and experimental parameters, and then conducting experiments to obtain experimental results, the model is trained using the obtained experimental results to obtain accurate and unified relevant parameters. Finally, the lifespan of the electric heating coil is calculated using the trained model, thereby improving the accuracy of the calculated lifespan and the uniformity and reliability of the experimental data. By monitoring relevant data of the electric heating coil samples in real time, the power on and off of the electric heating coils can be controlled and the time can be counted, so that the electric heating coil samples can be tested in the best condition and the reliability of the test data can be guaranteed. Attached Figure Description
[0021] Figure 1 This is a flowchart of an accelerated life test method for an electric heating coil according to an embodiment of this application; Figure 2 This is a table showing the stress groups and corresponding characteristic lifetimes of an accelerated life test method for an electric heating coil according to an embodiment of this application; Figure 3 This is a table showing the test results of stress groups and corresponding characteristic lifetimes for an accelerated life test method for an electric heating coil according to an embodiment of this application. Figure 4 This is a block diagram of an electric heating coil accelerated life testing system according to an embodiment of this application; Figure 5 This is a structural diagram of the metal tooling according to an embodiment of this application.
[0022] The parts referred to by the numbers in the above attached figures are as follows: 1. Metal bracket; 2. Heat dissipation device; 3. Metal tooling body; 4. Temperature sensor. Detailed Implementation
[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0024] This invention discloses a method for accelerating the life test of an electric heating coil.
[0025] Reference Figure 1 and Figure 2 A method for accelerated life testing of electric heating coils, comprising: Step S1: In response to a preset test signal, acquire the performance parameters of multiple initial samples.
[0026] The test signal refers to the signal indicating that a life test will be performed on the electric heating coil. The response here is via an electrical signal button installed on the system; pressing it triggers the test.
[0027] Performance parameters refer to the test parameters used for initial testing of the samples. Here, initial testing refers to screening the electric heating coil samples against their performance parameters. These parameters are obtained by operators through input on the system's control panel, such as a physical button control panel or a touch-screen control panel. When the operator presses the test signal button, the performance parameters are input into the system via the control panel. Examples include temperatures of 230℃, 260℃, 290℃, 320℃, and 350℃, and voltages of 299V, 368V, 437V, 506V, and 575V.
[0028] Step S2: Obtain initial samples and assign them random numbers to obtain initial sample numbers. Filter the initial samples according to performance parameters and preset filtering rules to obtain performance sample numbers.
[0029] The initial sample number refers to the unique number of the sample requiring initial testing. This initial sample number is obtained by randomly selecting samples from the same batch of electric heating coils and then marking each coil with a unique identifier. The screening rules refer to the matching criteria between the selected samples and the test parameters. These rules involve testing the samples corresponding to the initial sample number to screen for samples corresponding to the performance sample number, while simultaneously identifying the relevant limiting parameters of the electric heating coil, including the dual stress coupling caused by voltage and temperature. These screening rules are obtained by those skilled in the art through multiple experiments to obtain relevant data on the electric heating coils, which is then input into the system. The performance sample number refers to the unique number of the electric heating coil sample that passes the initial test. This is obtained by the system performing initial tests on the electric heating coils corresponding to the initial sample number, screening, and recording the initial sample numbers that meet the screening rules as the performance sample numbers.
[0030] Step S3: Obtain the sample stress group based on performance parameters and screening rules.
[0031] A sample stress set refers to a combination of stresses selected from performance parameters that require subsequent testing. This is achieved by the system screening performance parameters, eliminating those limits that the electric heating coil sample cannot withstand, and obtaining the remaining parameter combinations as the sample stress set. Specifically, the sample stress set is a voltage-temperature dual-stress coupling. For example, five temperature stresses are selected: 230℃, 260℃, 290℃, 320℃, and 350℃; five voltage stresses are selected: 299V, 368V, 437V, 506V, and 575V. Starting from the upper limit of 575V, extreme voltage tests are conducted. It is ultimately found that the electric heating coil cannot undergo accelerated life testing at 575V. Therefore, the ultimate extreme voltage is selected as 506V, and the temperature stresses 230℃, 260℃, 290℃, 320℃, and 350℃ are combined with the voltage stresses 299V, 368V, 437V, and 506V to form the sample stress set. Figure 3 As shown.
[0032] Step S4: The electric heating coil corresponding to the control performance sample number is subjected to a preset orthogonal test according to the sample stress group to obtain the test results.
[0033] Orthogonal testing refers to a lifespan test of an electric heating coil. It is pre-set by professionals in the field based on their experience and relevant online resources. The test result is the lifespan obtained from testing the electric heating coil. Here, the method involves conducting an orthogonal test on electric heating coil samples according to the parameters of the sample stress group. Three samples are measured for each data group. First, the resistance of the three samples is measured. If any sample's resistance does not fall within the standard value, it is discarded and replaced. If the resistance of all three samples falls within the standard value, the average value is taken, and this average value is output and recorded as the test result. The standard resistance value here is the rated value set by the professional based on the electric heating coil at the factory and the allowable deviation range. The number of test results is the same as the number of parameter groups in the sample stress group. Figure 2 Based on the stress groups U1 and T1, the electric heating coil sample was tested, and the result L1 was obtained.
[0034] Step S5: Input the test results into the preset standard life model for training to obtain the corrected parameters.
[0035] The standard life model refers to the model used to measure the lifespan of an electric heating coil. Here, the standard life model is the generalized Eyring model, which will be explained in detail in the following steps and will not be repeated here. Correction parameters are constant parameters that help calculate the standard lifespan of the electric heating coil. These are obtained by inputting multiple sets of experimental results into the formula of the standard life model, then calculating the unknown constants in the formula, and using these unknown constants as correction parameters.
[0036] Step S6: Correct the standard lifetime model with the correction parameters to obtain the actual lifetime model, and output it.
[0037] The actual life model refers to a model capable of calculating the lifespan of an electric heating coil. Here, it is obtained by replacing the constants in the standard life model with corrected parameters to obtain a standard life model containing accurate constants, which serves as the actual life model.
[0038] The output here replaces the original standard life model in the system with the actual life model.
[0039] The method for obtaining test results by conducting a pre-set orthogonal test on the electric heating coil corresponding to the control performance sample number according to the sample stress group includes: Step S40: Obtain the target high temperature and the target low temperature.
[0040] The target high temperature refers to the critical temperature at which the electric heating coil is de-energized. The target low temperature refers to the critical temperature at which the electric heating coil is energized. Both the target high and target low temperatures are set by those skilled in the art based on experimental requirements.
[0041] Step S41: Power on the sample corresponding to the performance sample number, and simultaneously acquire the sample temperature and sample status, and accumulate the power-on time.
[0042] Sample temperature refers to the temperature of the electric heating coil used as the sample. This temperature is obtained by the system through temperature sensor 4. Sample status refers to the state of the electric heating coil undergoing accelerated life testing. This status is obtained by the system acquiring real-time data such as voltage, current, and power of the electric heating coil using existing monitoring devices. The sample status includes both normal and damaged states. Power-on time refers to the duration for which the electric heating coil is powered. This is accumulated by the system simultaneously controlling the sample to power on and using an existing timing device to record the time in real-time.
[0043] The normal state refers to the condition where the heating coil is undamaged and can continue the life test. The damaged state refers to the critical state at which the heating coil should be terminated from the life test. The normal state and the damaged state are determined by the system based on the real-time acquisition of relevant data such as voltage, current, and power of the heating coil by existing monitoring devices. When a breakdown open circuit occurs, or the power attenuation of the heating coil is greater than or equal to 10%, the sample state is defined as the damaged state. If there is no breakdown open circuit, or the power attenuation of the heating coil is greater than or equal to 10%, it is considered the normal state.
[0044] Step S42: When the sample temperature reaches the target high temperature, the sample corresponding to the control performance sample number is powered off and the cumulative time is stopped to obtain the test duration.
[0045] The test duration refers to the required lifespan for testing the electric heating coil. It is obtained by summing up the cumulative durations from multiple tests.
[0046] When the sample temperature reaches the target high temperature, it indicates that the electric heating coil used as the sample has been energized for a long time and is at a high temperature. Continuing to energize it may damage the electric heating coil, thus making the measurement life inaccurate. Therefore, the sample corresponding to the performance sample number is de-energized and the accumulation time is stopped to obtain the test duration.
[0047] Step S43: When the sample temperature reaches the target low temperature, re-control the power-on of the sample corresponding to the performance sample number and continue to accumulate the power-on time based on the test duration.
[0048] When the sample temperature reaches the target low temperature, it indicates that the electric heating coil used as the sample has cooled down and the test can continue. Therefore, the sample corresponding to the performance sample number is powered on again and the power-on time is accumulated based on the test duration.
[0049] Step S44: When the sample is in a damaged state, the electric heating coil corresponding to the control performance sample number is de-energized and the test duration is recorded to obtain the characteristic lifetime.
[0050] Characteristic lifetime refers to the failure time of an electric heating coil obtained through lifetime testing. Here, it is obtained by adding the test durations obtained during both energized and de-energized periods, and using the total duration as the characteristic lifetime.
[0051] When the sample is in a damaged state, it means that the electric heating coil has reached its life limit and can no longer be used. Therefore, the electric heating coil corresponding to the control performance sample number is powered off and the test duration is recorded to obtain the characteristic life.
[0052] Step S45: Use the characteristic lifetime and sample stress group as the test results.
[0053] The characteristic lifetime is mapped to the data set in the corresponding sample stress set, and this mapping is used as the experimental result.
[0054] The methods for inputting experimental results into a pre-defined standard lifespan model for training to obtain corrected parameters include: Step S50: Perform a preset logarithmic calculation on the standard lifetime model to obtain a linear model.
[0055] The logarithmic transformation scheme refers to the method of converting relevant data in the model into logarithmic form. A linear model, after transformation using the logarithmic transformation scheme, is a linear function model with stress-related variables as independent variables and the logarithm of life as the dependent variable. Here, it is obtained by taking the natural logarithm of both sides of the standard life model.
[0056] Step S51: Further simplify the linear model to obtain a simplified model.
[0057] A simplified model refers to a linear model that is simpler, easier to solve, and does not lose key fitting accuracy. Here, it is obtained by preserving the core stress influence laws of the linear model, eliminating secondary variables, merging relevant parameters, or simplifying the stress terms.
[0058] Step S52: Unify the simplified model to obtain the general formula model.
[0059] The general formula model refers to a standardized, universal linear expression that unifies a simplified model into one applicable to the life prediction of similar electric heating coils. This is achieved by defining unified symbols for independent variables, dependent variables, and parameter terms, eliminating numerical values specific to particular scenarios, and retaining the core linear structure.
[0060] Step S53: List the general formula model as a matrix to obtain the matrix model.
[0061] A matrix model is a mathematical model that transforms the linear expression of a general formula model into a matrix operation form. Here, it is obtained by integrating the dependent variable, independent variable, and parameter vectors into corresponding column matrices.
[0062] Step S54: Obtain the correction parameters based on the experimental results, matrix model, and the preset least squares principle.
[0063] The least squares principle is a mathematical optimization principle that minimizes the sum of squared errors between the actual observed values and the model's predicted values of the dependent variable in a matrix model by finding a set of parameter estimates. Here, the correction parameters are obtained by substituting the experimental results into the matrix model and calculating the relevant constant parameters according to the least squares principle formula. These constant parameters are then used as the correction parameters.
[0064] The formula for the standard lifetime model is as follows: Where L is the characteristic lifetime, T is the absolute temperature, U is the voltage stress, Ea is the activation energy, k is the Boltzmann constant, and C, α, A, and B are undetermined constants.
[0065] Wherein, the absolute temperature T is obtained by adding the temperature stress to the preset absolute zero, and the activation energy Ea and the undetermined constants C, α, A and B are obtained from multiple sets of characteristic lifetimes L, absolute temperature T and voltage stress U according to the formula of the standard lifetime model. The calculation yielded the characteristic life L, which is the experimental result described in step S4. The absolute temperature T is the sum of the temperature stress and absolute zero (-273.15℃). The Boltzmann constant k is 8.617 × 10⁻⁶. -5 eV / ℃.
[0066] The formulas for the linear model and the simplified model are as follows: and Among them, the formula for the linear model In this equation, lnL is the logarithm of the characteristic lifetime, lnC is the logarithm of the undetermined constant C, and lnT is the logarithm of the absolute temperature.
[0067] Among them, the simplified model formula In this context, y is lnL, β0 is lnC, β1 is α, x1 is lnT, and β2 is E. a / k, x2 is 1 / T, β3 is A, β4 is B, x3 is U, and x4 is U / T.
[0068] The formula of the standard life model Taking the natural logarithm of both sides yields the formula for the linear model. Then, the linear model is redefined as follows: y = lnL, β0 = lnC, β1 = α, x1 = lnT, and β2 = E.a The simplified model is obtained by simplifying k, x2 as 1 / T, β3 as A, β4 as B, x3 as U, and x4 as U / T. .
[0069] The formula for the general model is: , where n is the total number of initial sample numbers for a stress group, i is the current stress group, j is the current initial sample number, {n(i-1)+j} is the j-th initial sample number for the i-th group, and ε is the residual.
[0070] Assume the transformed data is y {n(i-1)+j}1 (dependent variable) and x {n(i-1)+j}1 x {n(i-1)+j}2 x {n(i-1)+j}3 x {n(i-1)+j}4 (Independent variable), thus obtaining the general formula model. Here, the data is labeled. The labeling method is as follows: let the total number of groups be m, the current group be i, the total number of items in each group be n, and the current number of items be j. Then, sort and label the data starting from the first item in the first group. Therefore, the labeling formula is {n(i-1)+j}. The labeling of the data in the first group only needs to be based on the number of items, so it is {n(1-1)+j}, that is, n multiplied by 0 and then j added to equal j (the number of items). Subsequent labels are labeled in the same way. For example, if there are 5 groups in total and 5 items in each group, then the 4th item in the 3rd group is calculated as {5(3-1)+4}, which is the 14th item. Here, the general model formula corresponds to the simplified formula, only the data labels are added.
[0071] The formula for the matrix model is as follows: Where Y is y {n(i-1)+j} X is a matrix β is a parameter column vector of β0, β1, β2, β3, and β4.
[0072] The matrix model here is obtained by fusing β0~β4 from the general model into β to obtain the vector β.
[0073] The formula for the least squares principle is: and .
[0074] in, The vector of estimated values containing parameters β0 to β4, X T Let X be the transpose of X.
[0075] Here This is the summation notation of the sum of squares of the residuals. For the sum of squared residuals, For the vector β(X) introduced above T X) -1 Let X be a matrix T The inverse matrix of X.
[0076] Based on the same inventive concept, embodiments of the present invention provide an accelerated life testing system for an electric heating coil.
[0077] Reference Figure 4 An accelerated life testing system for an electric heating coil is applied to an accelerated life testing method for an electric heating coil. The system includes a stress loading unit for maintaining constant test data, a sample tooling unit, a monitoring and acquisition unit for collecting electrical and temperature parameters, and a control and analysis unit for fitting a model and calculating the life.
[0078] The stress loading unit here includes a programmable thermostatic chamber with a temperature control accuracy of no more than 1°C above or below the set temperature. It also features an adjustable AC power supply with an operating range of 0~550V and a power output of ≥7kW. The monitoring and acquisition unit here can collect electrical parameters (voltage, current, power, sampling rate 1Hz) and temperature (using a type K thermocouple with an accuracy of no more than 0.5°C above or below the set temperature). The control and analysis unit here enables automatic stress loading, real-time data storage, lifetime model fitting, and lifetime prediction.
[0079] Reference Figure 5 The sample tooling unit includes a metal bracket 1, a metal tooling body 3, a heat dissipation device 2, and a temperature sensor 4.
[0080] The metal bracket 1 is fixedly connected to the metal fixture body 3 to support and fix the metal fixture body 3. The metal fixture body 3 is used to hold the electric heating coil sample. Two heat dissipation devices 2 are installed on both sides of the metal fixture body 3 to dissipate heat. A temperature sensor 4 is installed on the side of the metal fixture body 3 away from the metal bracket 1 to monitor the internal temperature of the metal fixture body 3 in real time.
[0081] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. A method for accelerated life testing of an electric heating coil, characterized in that, include: Step S1: In response to a preset test signal, acquire the performance parameters of multiple initial samples; Step S2: Obtain initial samples and assign them random numbers to obtain initial sample numbers. Filter the initial samples according to performance parameters and preset filtering rules to obtain performance sample numbers. Step S3: Obtain the sample stress group based on performance parameters and screening rules. The sample stress group is a voltage-temperature dual stress coupling. Step S4: The electric heating coil corresponding to the control performance sample number is subjected to a preset orthogonal test according to the sample stress group to obtain the test results; Step S5: Input the test results into the preset standard lifetime model for training to obtain the corrected parameters; Step S6: Correct the standard lifetime model with the correction parameters to obtain the actual lifetime model, and output it.
2. Among them, The method for obtaining test results by conducting a pre-set orthogonal test on the electric heating coil corresponding to the control performance sample number according to the sample stress group includes: Step S40: Obtain the target high temperature and the target low temperature; Step S41: Control the power supply of the sample corresponding to the performance sample number, and at the same time acquire the sample temperature and sample status, and accumulate the power supply time. The sample status includes normal status and damaged status. Step S42: When the sample temperature reaches the target high temperature, the sample corresponding to the control performance sample number is powered off and the accumulation time is stopped to obtain the test duration; Step S43: When the sample temperature reaches the target low temperature, re-control the power-on of the sample corresponding to the performance sample number and continue to accumulate the power-on time based on the test duration; Step S44: When the sample status is damaged, the electric heating coil corresponding to the control performance sample number is de-energized and the test duration is counted to obtain the characteristic lifetime; Step S45: Use the characteristic lifetime and sample stress group as the test results.
3. The accelerated life test method for an electric heating coil according to claim 1, characterized in that, Methods for inputting experimental results into a pre-defined standard lifetime model for training to obtain corrected parameters include: Step S50: Perform a preset logarithmic calculation on the standard lifetime model to obtain a linear model; Step S51: Further simplify the linear model to obtain a simplified model; Step S52: Unify the simplified model to obtain the general formula model; Step S53: Convert the general formula model into a matrix to obtain the matrix model; Step S54: Obtain the correction parameters based on the experimental results, matrix model, and the preset least squares principle.
4. The accelerated life test method for an electric heating coil according to claim 3, characterized in that, The formula for the standard lifetime model is: Where L is the characteristic lifetime, T is the absolute temperature, U is the voltage stress, Ea is the activation energy, k is the Boltzmann constant, and C, α, A, and B are undetermined constants; Wherein, the absolute temperature T is obtained by adding the temperature stress to the preset absolute zero, and the activation energy Ea and the undetermined constants C, α, A and B are obtained from multiple sets of characteristic lifetimes L, absolute temperature T and voltage stress U according to the formula of the standard lifetime model. Calculated.
5. The accelerated life test method for an electric heating coil according to claim 4, characterized in that, The formulas for the linear model and the simplified model are as follows: and In the formula for the linear model, lnL is the logarithm of the characteristic lifetime, lnC is the logarithm of the undetermined constant C, and lnT is the logarithm of the absolute temperature. In the simplified model formula, y is lnL, β0 is lnC, β1 is α, x1 is lnT, and β2 is E. a / k, x2 is 1 / T, β3 is A, β4 is B, x3 is U, and x4 is U / T.
6. The accelerated life test method for an electric heating coil according to claim 5, characterized in that, The formula for the general model is: , where n is the total number of initial sample numbers for a stress group, i is the current stress group, j is the current initial sample number, {n(i-1)+j} is the j-th initial sample number for the i-th group, and ε is the residual.
7. The accelerated life test method for an electric heating coil according to claim 6, characterized in that, The formula for the matrix model is: Where Y is y {n(i-1)+j} X is a matrix β is a parameter column vector of β0, β1, β2, β3, and β4.
8. The accelerated life test method for an electric heating coil according to claim 7, characterized in that, The formula for the least squares principle is: and ; in, The vector of estimated values containing parameters β0 to β4, X T Let X be the transpose of X.
9. An accelerated life testing system for an electric heating coil, applied to the accelerated life testing method for an electric heating coil as described in claim 8, characterized in that: It includes a stress loading unit for maintaining constant test data, a sample tooling unit, a monitoring and acquisition unit for collecting electrical and temperature parameters, and a control and analysis unit for fitting the model and calculating the lifetime.
10. The accelerated life testing system for an electric heating coil according to claim 9, characterized in that: The sample fixture unit includes a metal support (1), a metal fixture body (3) located on one side of the metal support (1) for placing the sample, a heat dissipation device (2) located on both sides of the metal fixture body (3) for dissipating heat, and a temperature sensor (4) located on the side of the metal fixture body (3) away from the metal support (1) to obtain temperature data.