Characteristics of ultrasonic spot welding of Cu/Ni dissimilar metals

Abstract

With increasing clamping pressure, the bond density increases, the effective thickness decreases, and the plastic deformation at the Cu side near the welding interface regions below the sonotrode tip peak and valley increases; the maximum lap shear tensile load is obtained at the clamping pressure of 0.5 MPa. In the case of the Cu/Ni joint prepared at the clamping pressure of 0.5 MPa, evident mutual diffusion and nanoscale wave-like pattern appear in the Cu/Ni interfacial area, bonding between Cu and Ni sheets is formed by the interdiffusion of the parent elements. Plastic strain distribution and temperature on weld cross-section were simulated employing finite element analysis.

Numerical analysis of ultrasonic spot welding of metal sheets: A review

“…Resulting in complex deformation at the faying interface between the two sheets and the formation of a wave-like shape instead of a flat outline. Similar results are reported by Ni et al [10], Li et al [8], Jedrasiak and Shercliff [36] and Chen et al [31]. It is beneficial to enhance the joint strength, as demonstrated by Prangnell et al [63].…”

“…The highest plastic deformation is at the peak and valley of the indentation, here the stress is the maximum (Figure 13(a)). Similar results were reported by Ni et al [10], Li et al [19] and Du et al [25]. It can be observed that in the vibration direction, the compressive plastic strain is generated on the side of the peak, where the knurl is moving whereas the tensile is on the opposite side (Figure 13(b)).…”

“…However, in the experiment carried out by Cai et al [2], the maximum limits of the normal load and sliding frequency provided by the friction tester are 100 N and 10 Hz, respectively. They are much lower than the actual welding clamping force used by Ni et al [10], Li et al [8] and the high vibration frequency (20 kHz) in a typical ultrasonic spot welding process. This means that the obtained friction coefficient may not accurately reflect the behaviour at the interface between two metal sheets.…”

“…The modelling issues in ultrasonic spot welding mentioned above are summarised as below: (1) The latter stages of welding is not be considered in the models. In this stage, the heat generation and plastic deformation are critical to the microstructure evolution, effective thickness and bond density [10]. Thus, it can influence the joint strength and microstructure.…”