In this study; the weight of the modal accelerometer used in the Roving Hammer Impact Test Method was added in the finite element analysis (FEA) and the undamped modal analysis of the automotive rear lamp lenses were performed. Also, calculated new Elastic Modulus for Polymethylmethacrylate (PMMA) material with using natural frequency formula and this value was used in the ANSYS WB program and the undamped modal analysis was repeated. After that, frequency response functions (FRFs) of an automotive rear lamp lens were obtained by using Roving Hammer Impact Test Method. At the same time; dynamic characteristics of the structure, natural frequencies, damping ratios and mode shapes were obtained. Damping ratios were calculated from the FRF’s by using the Half Power Method. Finally, experimental modal analysis (EMA) and FEA results were compared.

In this study; first of all, finite element undamped modal analysis was performed on one of the automotive rear lamp lenses and were obtained natural frequencies and mode shapes. Then, Frequency Response Functions (FRF) of an automotive rear lamp lens, made of polymethyl methacrylate (PMMA) material, were obtained by using Impact Hammer Test Methods. At the same time; dynamic characteristics of the structure, natural frequencies, damping ratios and mode shapes were obtained. Damping ratios were calculated from the FRF’s by using the Half Power Method. Finite Element Analysis (FEA) results and test results were compared and the best test method was determined.

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Automotive lighting products, such as Head Lamps (HL), Fog Lamps (FL), Daytime Running Lamps (DRL), face with mechanical vibrations during service life which may coincide with the resonance frequencies of the light source. When excited at resonance frequencies, especially in the case of HL’s, light beam cut-offline may deteriorate and vibration of light beam occurs. This situation is also called light flickering. This state has disturbing effect on the driver’s visibility, which is valid for both the driver and the counter drivers. Most of the automotive manufacturers have developed test specifications for evaluation of flickering state under sinusoidal frequency sweep acceleration loading and they have introduced limits for flickering angle range or displacement range of the light beam with respect to frequency measured on a screen which is put on a prescribed distance from the light source. In this study a traditional way of light beam flickering angle deviation measurement method of HL is presented. Furthermore, application of precise & efficient way of measurement method by the use of quartz rotational accelerometer is inspected.

In this study, Random and Harmonic vibration durability test specifications for Automotive Lighting systems are compared according to their damage content. Harmonic and Random vibration durability test specifications which have different durations and Acceleration Power Spectrum Densities (PSD G) are plotted and compared according to damage accumulated on single degree of freedom (SDOF) system. Outcome of this study is the fast evaluation of fatigue strength of common or similar parts used on lighting systems which are dedicated to different customers, different car segments; and evaluation of the severity of new customer vibration durability test specifications and evaluation of special design precautions for new design projects. Shorter duration PSD G's and Harmonic sweep tests which have equivalent Fatigue Damage Spectrums (FDS) can be created and instant design improvements can be tested and evaluated. In addition, in this study, random test time reduction formula was validated with physical tests.