Method of predicting fatigue lifetimes of metallic structures

Details Method of predicting fatigue lifetimes of metallic structures Method of predicting fatigue lifetimes of metallic structures

1988-03-15

1990-08-07

Lall, Parshotam S.

Boots, shoes, and leggings

364506, 340679, 340665, 73760, 73763, 73788, G01M 500

Patent

active

049473417

ABSTRACT:
The lifetime NF (number of cycles to failure) of a metallic structure such as a soldered joint or the like is determined by three simple, rapid tests. The first is to determine creep displacement rate vs. load (stress). Next, from the same data, the slope of the matrix creep displacement vs. load (stress) curve is determined. A third test is to obtain load (stress) relaxation over a short period of time from a load (stress) in the matrix creep displacement region. The matrix creep displacement per cycle (CPS) is then derived by plotting matrix creep displacement rate vs. time and integrating the area under this curve. The number of cycles to failure (NF) is then calculated using the formula: ##EQU1##

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M. C. Shine et al. "Fatigue of Solder Joints in Surface Mount Devices," Proc. ASTM Symp on Low Cycle Fatigue, Oct. 1985.

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