Mechanical Engineering
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Browsing Mechanical Engineering by Author "Nassar, Sayed"
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Item LOAD DISTRIBUTIONS IN BOLTED SINGLE LAP JOINTS UNDER NON-CENTRAL TENSILE SHEAR LOADING(2021-11-16) Sinthusiri, Chaiwat; Nassar, Sayed; Shillor, Meir; Yang, Xianjie; Wu, ZhijunThis study uses a numerically calibrated beam theory-based model to investigate the bolt load distributions in a preloaded two-bolt single lap joint under non-central tensile shear loading. The linear spring-based modeling is used for the two preloaded bolts and substrates. The bolt stiffnesses were derived from the bolt flexibilities influence by the bending deformation, the shear deformation, the bolt, and plate contact deformations. Due to the non-uniform load distribution along the bolt shank, the 3D finite element analysis was used to determine the correlation factors of each influence factors. Non central loading may be due to geometric tolerances that would cause additional moment loading on the joint. Thus, the load would not be equally distributed among all bolts in the joint. The effect of various joint parameters, bolt preload and off-center location of the tensile shear loading is investigated and discussed.Item PROCESS OPTIMIZATION OF AUTOCLAVE BONDED LIGHT-WEIGHT MATERIAL JOINTS(2022-04-01) Jagatap, Shraddha Ratnakar; Nassar, Sayed; Shillor, Meir; Yang, LianXiang; Wu, ZhijunThis dissertation research fills a gap in the existing open literature regarding the significance of autoclave cure process variables and their interactions on the static strength of lightweight material single lap joints under tensile-shear loading. Specifically, the research investigates the dependence between the degree of cure of the epoxy adhesive and the mechanical performance of the single lap joint boded with same epoxy adhesive. Lightweight material system includes polycarbonate, Aluminum 6061 and glass reinforced plastics (GFRP) extren 500. A commercially available polyurethane film adhesive PE399 was selected to bond Polycarbonate single lap joints (SLJ) while epoxy film adhesive AF163-2K was selected to bond aluminum and GFRP joints. Studied variables include cure temperature, cure pressure and their respective rates as well as the duration of cure time. Dynamic Mechanical Analysis (DMA) is used to quantify glass transition temperature of AF163-2K cured with different combinations of autoclave process variables. The relative significance of variables and variable combinations are investigated for their effect on the bond strength. Experimental test data shows interaction between autoclave variable cure temperature in combination with cure time, temp ramp rate and pressure ramp rate have significant effect on glass transition temperature, bond strength and failure mode. Changes in joint static load transfer capacity (LTC) was investigated after cyclic temperature profile fluctuates between 20° C and 85° C at a constant relative humidity (RH) level of 85 %.