Abstract
In this study, the short fatigue crack behavior in a precipitation-strengthened CuNi2Si alloy was investigated using a replica technique under rotating bending loads with periodic overloads, an overload ratio of 1.5, and the stress ratio of both was R = −1. The results show that all the fatigue cracks originated from the surface of the specimen and displayed a trend of slow initiation and then rapid propagation. The introduction of overloads significantly reduced the fatigue crack initiation time and the fatigue life of the sample. The average life of the overloaded samples was only 31% that of the constant load samples. For overload specimens, multiple cracks grew at the same time and merged at different stages, causing the crack length to increase instantaneously after they merged, thereby considerably reducing the fatigue life. Fractographical analysis and observation of the surface-etched sample replica film showed that cracks in samples with and without overload both propagated along the grain boundaries.
Highlights
CuNi2 Si alloy is a precipitation-strengthened copper alloy that exhibits high strength [1,2], good electrical and thermal conductivity [3], and has good resistance to fatigue and corrosion [4]
It was found that both the monotonic tensile strength and the yield strength were significantly improved by using the cold-working, which changed the fracture mode under different atmospheric conditions
A scanning electron microscope was used to observe the fractures of the samples, and the photos of the constant load and overload samples are depicted in Figures 7 and 8, respectively
Summary
CuNi2 Si alloy is a precipitation-strengthened copper alloy that exhibits high strength [1,2], good electrical and thermal conductivity [3], and has good resistance to fatigue and corrosion [4]. It is used to manufacture electrical components, such as electrical connectors, circuit breakers, and relays [5,6] It is utilized for making the steady clamps in high-speed railway catenary systems [7]. Investigated the fatigue crack growth behavior of CuNi2 Si alloy under different loading modes and found that the crack of the sample under tensile-compression load propagates approximately an order of magnitude faster than that under rotating bending load. Purnowidodo et al [22] studied crack growth behavior behavior after after an an overload overload on on aa solid solid round round bar They found that the retardation retardation or or acceleration acceleration of growth growth depended depended on whether the residual stress state in front front of of the the crack crack tip tip was was compression compression or or tension.
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