Thermal-Vibration Coupling Analysis And Accelerated Life Test Of LED Vehicle Headlamps

With the continuous innovation and development of the automobile industry,the driving speed increased gradually,so the safety has become the focus.As the car's eyes,the headlamps' importance is becoming more and more important.The manufacturers of automotive headlamps also increase the standard.The traditional headlamps light source has been unable to meet the market requirements.The new light source light-emitting diode(LED)as the fourth generation has many advantages.It has become the first and new choice of automotive lighting technology for its energy-efficiency,environmental protection,small size etc.In the upmarket,it has replaced the traditional lighting.But the development and application of the LED is limited by heat dissipation problem.When the vehicle is moving,the external environment such as vibration and shock is inevitable.The mechanical reliability of headlamps is vital for the security and high efficiency of the whole system.In addition,LED lighting standards and testing system are not perfect,the valuation method is not authoritative and scientific,an effective method for Life evaluation need to be established quickly.Based on the theory of finite element analysis,heat transfer,the finite element model of LED headlight was established.The thermal-vibration coupling analysis of LED headlight was done to get the temperature distribution and the structure variety condition by Ansys Workbench.In the meantime,the working characteristic with independent vibration was also investigated to achieve the stress and deformation of LED.By comparing the thermal-vibration situation and independent vibration situation,we can know the relevant changes trend and how reduce the stress generated by considering thermal mechanical situation.The coupled analysis maximum reduction is nealy 6.2% compared to the independent vibration situation.Structure optimization for LED headlamp is developed for getting low stress situation and temperature distribution.It implies a basis for high reliability design of LED automotive headlamp.For structural aspect,this paper focuses on the reasonable of overall design of the lamp and not considers the reliability of the chip only.An special jig for the car headlight is designed,which met the requirements by test.Modal test tools and software were used to test the dynamic property of the headlight.So the natural frequency and modal deformation were obtained.By comparing the natural frequency and modal deformation between test and simulation,the maximum difference 17.64% was obtained.And it belongs to the reasonable range,so the validity of the finite element model is proved.Considering the main influence factor of the lamp life,the temperature was selected as accelerated life stress.On the basis of the existing research and the the lamp' performance parameters,the constant temperature accelerated life test for test sample was performed.Based on the United States energy star LM-80 standard,the test time is shorted.The Weibull distribution is used to describe the life of the product distribution.The least squares and Arrhenius model were utilized to count data,so the life of the product under normal stress level was extrapolated.In short,in this thesis,the FEA analysis,dynamic property test and accelerated life testing were carried out to analyze the heat dissipation property,structural reliability and life evaluation method of automotive headlight.The results can offer good reference to the headlight optimization design and the guidance for the establishment of the life prediction model.