Grain Size Measurement of Copper Spot Welding Caps Via Ultrasonic Attenuation and Scattering Experiments

Abstract

Duringultrasonic testing of resistance spot welds in real time the probe sends the sound waves through the thickness of the copper electrode cap into the materials being welded. Characteristics of the reflected waves from the weld interfaces allow a reliable decision to be made on the quality of the joint. Transmission of high frequency sound waves through the relatively thick copper welding cap cause the signal to be greatly attenuated due to grain scattering. For this reason, close monitoring of the copper cap properties prior to installation is essential for adequate performance. Finding copper alloys with a small average grain sizes is essential to minimize the attenuating effects. The conducted backscatter and attenuation experiments indicate correlation between the ultrasonically measured parameters and the optically found copper grain size. This correlation suggests that the attenuation or backscatter technique could be used alone in order to validate the proper copper alloy to be used in spot weld probes. Using non-destructive testing techniques for this purpose greatly reduces the time and cost involved compared to optical techniques.

Uncovering microstructural heterogeneities in binder jet printed SS316L through ultrasonic testing and X-ray computed tomography

“…Through theoretical and experimental studies, the interaction of ultrasonic (i.e., elastic) waves with solid media can be quantitatively linked to internal features. Past studies in polycrystalline materials have investigated the effect of pores [14][15][16], grain size [17] and morphology [18], texture [19][20][21], residual stress [22,23], and elastic constants [24]. For several decades, these studies have focused on metals generated using traditional manufacturing techniques.…”

Appraising scattering theories for polycrystals of any symmetry using finite elements

“…The scattering of elastic waves by the anisotropic grains of polycrystals is a classical problem of great practical importance in various fields, such as seismology [1,2] and non-destructive evaluation [3,4]. Studying this problem enables us to inform the grain structure of a polycrystal from scattering behaviours [5][6][7][8] and better discern the features of interest (e.g. fractures and voids) in a polycrystal by eliminating the influence of grain scattering [9,10].…”

Characterization of Grain Size in 316L Stainless Steel Using the Attenuation of Rayleigh Wave Measured by Air-Coupled Transducer

“…Meanwhile, the immersed ultrasonic technique is generally used with focus transducers to enhance the backscatter signals, which is limited by the large size, as well as immovability and service status of the workpiece in industrial applications. At present, the scattering model is established to associate the grain size with the longitudinal wave attenuation, which makes one may achieve quantitative results of grain size with precise attenuation (longitudinal or shear) measurements [ 14 , 15 , 16 ]. However, the longitudinal wave attenuation in a low frequency range is too small in fine-grain materials to recognize the variation of the grain size, and multiple reflections, well surface condition and necessary thickness are needed to accurately determination [ 17 ].…”