Performance and Improvement Investigation of Accelerated Temperature Change Test.

Abstract: This thesis is focused on Accelerated Temperature Change Test (ATCT). This test is performed in order to deteriorate and age a product in a faster than natural way. The ATCTs are primarily controlled with four parameters: the temperature range (∆T), ramp rate (RR), dwell time (DT) and number of cycles in test ( . A comprehensive investigation was carried out to analyze the performance and functionality of the cabinet, used for performing ATCT. This was achieved by performing repeated measurements in the empty cabinet with different combinations of temperature range (∆T) and dwell time (DT). The test parameters are normally adjusted according to values given in the standards common in automotive environmental testing and also according to the thermal properties and size of the tested components. In this investigation, four different standards for accelerated testing were taken into consider. They are TB1900, ISO 16750-4:2010 (International Organization for Standardization), IEC 60068-2-14 (International Electrotechnical Commission) and The GMW3172: User Guide. From each standard, each parameter definitions are illustrated. Practical tests were executed on three different types of components and with different test conditions. A suitable experimental-setup was prepared to record the temperature measurements on/in the DUT (Device Under Test). This experimental-setup was designed using thermocouples (Type - K) and DEWESoft. The results from the test were used to analyze the deviation between the standards and practical testing. This comparison helps in understanding the required improvements in the test parameters values i.e. the cabinet parameter settings or the test conditions. The values assigned for each parameter before the test are called Cabinet Parameter Settings (CPS). The temperature readings from the DUT are recorded and plotted after ATCT. Based on these ATCT measurements, optimal values of the test parameter are estimated. These are called Estimated Parameter Values (EPV). A significant deviation is observed between CPS and EPV. From these EPV, an acceleration factor (AF) for each test is calculated using two different life prediction models i.e. (i) Coffin-Manson and (ii) Norris Landzberg. And using this AF, an evaluation of the “number of cycles in the field (Nf)” with certain “number of cycles in the test (Nt)” is made. This evaluation helps in understanding the effect of parameter values during the test on the acceleration conditions. A simple aluminum box (one of the test component) is replicated into a simple structure, to implement in COMSOL Multiphysics Simulations. When the simulation results show good agreement with practical results, then simulations are recommended to be used to find the proper test conditions and test parameter values. Further, the simulations are used to find the sensitive point in/on the component. These simulations take some reasonable efforts. Index Terms— Acceleration factor, Dwell time, Fatigue failure, Accelerated temperature change test, Stress level, Temperature range, Coefficient of Thermal Expansion.