三種類のはんだの繰返しねじり低サイクル疲労試験におけるき裂の発生および伝ぱ挙動

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This paper studies the crack initiation and propagation behavior of three types of solders. Hollow cylinder tube specimens of Sn-37 Pb, Sn-93.5 Pb-1.5 Ag and Sn-7.5 Bi-2 Ag-0.5 Cu solders were torsionally fatigued at 313 K at a Mises strain rate of 0.5%/s. Crack initiation and propagation behavior was observed by a replication method. Cracks were initiated in the life ratio less than 0.05, so that the crack propagation was the main fatigue damage process. Main cracks propagated in the maximum shear direction for Sn-37 Pb and Sn-93.5 Pb-1.5 Ag but in the maximum principal direction for Sn-7.5 Bi-2 Ag-0.5 Cu. The main crack propagation was uniquely correlated with the life ratio, independent of the strain range and types of solders. Combining this correlation with Manson-Coffin rule, an equation that describes the relationship between crack length, plastic strain range and number of cycles was discussed. The equation evaluated the remaining life by knowing crack length and plastic strain range.
2003-08-25