Optimization of Extreme Environment Cyclic Testing : Analysis of thermal cycle load cases on a plastic cab component through simulation and testing

Sammanfattning: The purpose of this Master thesis was to deepen the knowledge and understanding regarding control parameters for the Extreme Environment Cyclic Testing (EECT) on interior and exterior cab components. The investigated parameters were temperature gradient, length of the warm and cold sections and number of cycles. These parameters were investigated since they control the settings of the Extreme Environment Cyclic Testing. In addition, temperature data was also gathered in order to be analysed along with a simplified case of sun radiation. The method consisted of three parts, where the first part was to perform a literature survey to gather relative data and knowledge. The second part was to perform simulations in COMSOL Multiphysics and the third part consisted of physical testing at Scania and at SP in Borås. To gather temperature data a simulation of a field test was performed in a wind tunnel at Scania. The results displayed a difference of the thermal image of the component when a simplified sun case was compared to a case without applied sun light. Regarding temperatures and temperature gradients it was found that a temperature gradient, based on testing from South Africa, can be up to 2.91°C/min in nature. The temperature results displayed a clear difference between obtained temperatures in a cab compared to results from a car. The angle of the windscreen and the volume difference are believed to be parts of the explanation. The simulations showed that an increase of the temperature gradient to 2°C/min from 1°C/min can be done without changing the time that the temperature of the material is heated respectively cooled significantly. These results were supported from the component testing at Scania which displayed that the difference in strain range when the temperature gradient was changed between 1°C/min to 2°C/min was below 1.2 %, which corresponds to less than 1E-4. The testing at Scania also displayed that the change in maximum strain for different length configurations, 3 h cold 6 h warm, 4 h cold 8 h warm and 6 h cold 12 h warm, could be neglected. The deviation in strain range between the 3h6h and 4h8h configuration was found to be below 1 %, which in absolute terms was 5E-5. It was also showed that the variance of the strain range did not change significant after six cycles. The maximum deviation in strain range between six and ten cycles was 0.15 %. The testing at SP with deformation scans with structural light scans displayed fluctuation in the deformation for the first cycles and a consistent decrease of maximum deformation after 8 cycles. The conclusions from the sun light simulations in COMSOL Multiphysics were that the difference between a simplified sun radiation case with a homogenous ambient temperature and the more realistic one with a set temperature on one surface of the component in combination with a homogenous ambient temperature could be neglected for components with a height up to 0.01 m. This was only valid if the temperature difference was below 10°C. For a larger temperature difference it was found valid for a height up to 0.001 m. Based on the results the author recommends that the control parameters of the Extreme Environment Cyclic Testing are set accordingly to obtain a more efficient testing method:  The number of cycles in the EECT should be 8, since more cycles will not make a significant change on the results  The time should be 3 h in the cold section and 6 h in the warm section  The increase of temperature should be 2°C/min to improve testing efficiency Also, an additional suggestion is to investigate the possibility of a pre-thermal heating phase in the EECT.