Matthew Joseph. Perricone

Shear Testing of Laser Spotwelds.

A shear test was used to investigate the effect of shielding gas (Argon, Nitrogen and air) on the mechanical properties of laser spot welds in Fe-28Ni-17Co alloy (Kovar). The load vs. displacement curves obtained, while superficially resembling those of a standard tensile test, were quite non-reproducible, and obscured the differences due to process conditions. Fractographic examination of the samples and analysis of the testing conditions led to significant conclusions about how to correctly interpret the shear test results, which in turn enabled a determination of the real effects of the change in shielding gas. Several different types of fracture morphology were noted, depending upon how the fracture surface developed relative to the original weld. This resulted in the disparate nature of the load-displacement curves. The results of the shear testing, fractography and metallography will be used to support interpretation of the differences found with respect to porosity formation, strength and work hardening behavior.A shear test was used to investigate the effect of shielding gas (Argon, Nitrogen and air) on the mechanical properties of laser spot welds in Fe-28Ni-17Co alloy (Kovar). The load vs. displacement curves obtained, while superficially resembling those of a standard tensile test, were quite non-reproducible, and obscured the differences due to process conditions. Fractographic examination of the samples and analysis of the testing conditions led to significant conclusions about how to correctly interpret the shear test results, which in turn enabled a determination of the real effects of the change in shielding gas. Several different types of fracture morphology were noted, depending upon how the fracture surface developed relative to the original weld. This resulted in the disparate nature of the load-displacement curves. The results of the shear testing, fractography and metallography will be used to support interpretation of the differences found with respect to porosity formation, strength and work hard...