摩擦攪拌點銲U型試片之應力強度因子分析

林燁偉(Lin-yeh-wei)

指導教授 ： 林派臣

國立中正大學/工學院/機械工程學系/碩士(2015年)

摘要

本論文採用理論及數值方法探討摩擦攪拌點銲U型試片的應力強度因子。由於摩擦攪拌銲點具有階層狀結構，無法以文獻中電阻點銲的理論解替代，故本研究採用理論方法推導出理論解，再利用有限元素法進行數值分析。研究內容可分成兩個部份，第一部分根據Kirchoff板理論及彈性力學，推導出階層模型受拉力的結構應力理論解，再將結構應力理論解分別代入適用於異種材質及不同厚度試片的應力強度因子公式，取得應力強度因子的理論解。第二部分以摩擦攪拌點銲之圓杯型試片模型為基礎，使用有限元素分析取得應力強度因子的數值解。最後將兩組結構應力及應力強度因子解進行比較及分析，提供未來的疲勞分析需求。

關鍵字

應力強度因子 ； U型試片 ； 摩擦攪拌點銲

並列摘要

In this paper, the stress intensity factor (SIF) solutions of friction stir spot welds (FSSWs) in U-shape specimens were studied by theoretical and numerical approaches. The upper sheets of FSSWs have step structure with complex geometries; therefore, the SIF solutions for resistance spot welds cannot be used. In this study, both theoretical and finite element methods were used for the derivation of SIF solutions. In the first part, the structural stress solutions of FSSWs under counter bending, opening, and cross counter bending loading conditions were obtained by the plate theory and the section method. The SIF solutions for FSSWs were then obtained from the structural stress solutions. In the second part, the numerical SIF solutions were obtained based on the 3D finite element model of the FSSW U-shape specimen as well. Finally, the analytical and numerical solutions of structural stresses and SIFs were compared and discussed.

並列關鍵字

U-shape specimens ； Friction stir spot welds (FSSWs) ； Stress intensity factor

參考文獻

[3] J. Bannantine, Fundamentals of Metal Fatigue Analysis, Prentice Hall, 1990.

[4] P. C. Paris, F. Erdogan, A critical analysis of crack propagation laws, Journal of Fluids Engineering 1963; 85(4): 528-534.

[5] Timoshenko, Stephen,W.K. Sergius, Theory of plates and shells, Vol. 2. New York: McGraw-hill, 1959.

[6] J. R. Rice, A path independent integral and the approximate analysis of strain concentration by notches and cracks, Journal of applied mechanics 1968; 35(2): 379-386.

[9] K.C. Chung, C.M. Wang, Optimal design of stepped circular plates with allowance for the effect of transverse shear deformation, International Journal of Fracture 2002; 44: 1163-1177.