Creep-Fatigue Properties of Sn-37Pb Solder Material Evaluated by Room Temperature Testing under Various Strain Waveforms

Abstract

Isothermal axial-strain-controlled creep-fatigue tests of a eutectic alloy Sn-37Pb were carried out at room temperature. Four kinds of triangular strain waveforms, so-called fast-fast, fast-slow, slow-fast and slow-slow, were used. First, constant-amplitude fully-reversed creep-fatigue tests were performed in order to obtain the creep-fatigue properties of the material as the partitioned inelastic strain range versus life relationships; that is, Δ ε_ij-N_ij relationships (ij=pp, pc, cp, and cc). The obtained Δ ε_ij-N_ij relationships were compared with the literature data. Second, two-step variable-amplitude fully-reversed creep-fatigue tests, so-called low-high and high-low, were conducted under fast-fast and slow-fast straining conditions. The results were analyzed and discussed based on the creep-fatigue damage rule proposed by the author and his colleague in a previous study for other high-temperature materials. Finally, the effects of ratcheting strain on creep-fatigue life were studied by conducting creep-fatigue tests under the strain waveforms involving small tensile ratcheting strain.