Method Development and Analysis of Tensile Stresses in Windscreens : A study on the dynamic stresses on windscreens subjected to random vibrations.

Sammanfattning: The thesis work deals with the study and determination of static and dynamic stresses acting on windscreen structures during transportation from the manufacturing site to the production plant. To simulate the stress distribution affected by the transportation, a finite element model of the windscreen is development of the structure and tested. The evaluated results from the stress analysis are then verified against results from literature and by own experimental results. The constructed FE model is simulated for modal response, and the response is validated against data from the experimental modal analysis. The data from the experiment is also used to calibrate the material card in an effort to get the most realistic dynamic response. The dynamic stress experiment was carried out at RISE Borås in accordance to ASTM D4169-16 DC3. Strain gauges were mounted at areas of interest. The readings obtained from the strain gauges used in the analytical calculation of stress, which were used to verify the finite element stress results. The fundamental aim of both experiments was to evaluate the dynamic behaviour and validate the numerical model. The pre-processing software ANSA was used to construct the finite element model and MSC Nastran was used as the FE- solver to simulate static and dynamic stresses on the structure. Transport loads were simulated using the random vibration load case, where a input load is in form of Power Spectral Density (PSD) data which describes the distribution of power into frequency components for a given time series. The input PSD was also in accordance with ASTM D4169-16 DC3, which is used to simulate the same response as in the experiment. During the numerical analysis, the glass and the intermediate PVB layer is assumed to be linear and isotropic. A validation of the numerical model was carried out against the experimental results to evaluate the predictive capability of the developed numerical model. The finite element model leads to good correlation of natural frequencies and their corresponding mode shapes at the lower range of frequencies valid till 100 Hz. This study is thus intended to construct and develop a FE model in order to predict the dynamic response and stress states experienced during transportation. It is further extended to predict the critical areas on the windscreen and help optimize the packaging of windscreens. During the course of study, it was found that, windscreens in the current transport arrangement experienced high stresses at areas close to the supports. The simulated stress values near the top right spacer (holding area) were close to the elastic limit of glass. This therefore, presented a high chance of damage to the windscreen when subjected to the random vibration.