Multiaxial low cycle fatigue of five kinds of solders
Yamamoto Takaei; Sakane Masao; Ohnami Masateru; Yamashita Mitsuo; Shiokawa Kunio
Abstract:This paper describes the multiaxial low cycle fatigue (LCF) of 63Sn37Pb, 40Sn60Pb, 93.5Pb5Sn1.5Ag, 91.5Sn8.5Sb and 90Sn7.5Bi2Ag0.5Cu solders. Push-pull and reversed torsion LCF tests were carried out using the hollow tube specimens of the five kinds of solders at 313 K. 63Sn37Pb and 40Sn60Pb solders had the largest LCF life compared at the same Mises' strain among the five solders. 90Sn7.5Bi2Ag0.5Cu had the smallest LCF life far smaller than the other solders. 93.5Pb5Sn1.5Ag and 91.5Sn8.5Sb solders had the intermediate LCF life. The Mises' strain was a suitable strain parameter for correlating the push-pull and reversed torsion lives but an energy parameter defined by the multiplication of stress and strain ranges gave a better correlation with the LCF life than Mises' strain. Many small cracks whose length was less than 100 mm were initiated and propagated in the maximm shear direction in the push-pull and reversed torsion tests for all the solders excepting 90Sn7.5Bi2Ag0.5Cu. Main cracks whose length was around 10 mm were found in the push-pull and reversed torsion tests for 93.5Pb5Sn1.5Ag, 91.5Sn8.5Sb and 90Sn7.5Bi2Ag0.5Cu. For 63Sn37Pb and 40Sn60Pb, main cracks were observed in the push-pull test, though no main crack was clearly found in the reversed torsion test. Variation of stress range with respect to number of cycles corresponded to the cracking behavior. A rapid drop in variation of stress range with respect to number of cycles was observed for the materials in which macroscopic crack propagation was found, but a gradual drop for the materials in which no macroscopic crack propagation was detected. Key Words:five kinds of solders, multiaxial low cycle fatigue, Mises' strain, strain energy, crack propagation, cyclic constitutive relation