Effects of Interface Bonding on the Residual Stresses in Cold-Sprayed Al-6061: A Numerical Investigation

Abstract

A contact model that accounts for interfacial cohesion and thermal conduction is developed to investigate the influence of bonding on the final residual stresses build-up in cold spray. The residual stress evolution in the cold-sprayed Al-6061 coating on an Al-6061 substrate is investigated via three-dimensional single-particle and multi-particle impact simulations. It is shown that the interface bonding mainly affects the local residual stress distribution near the interfaces. The residual stresses are largely due to the kinetic peening and bonding effects. The thermal cooling has negligible influence. In general, this work finds that peening introduces compressive stress, while bonding causes relaxation. The balance between the peening and the bonding effects, which depends strongly on the local bonding environment, determines the final residual stress in the system. This work suggests that the interface bonding should be considered as one of the essential factors in numerical modeling of the residual stresses evolution in cold spray.

Appendix

The proposed surface contact model (Fig. 3) is implemented in ABAQUS/Explicit through a user subroutine VUINTERACTION. To verify the implementation, the separation-traction history for the contact pair between south pole of the particle and center point of the substrate in the cohesive region (δ_n > 0) is monitored throughout the single-particle impact simulation, as shown in Fig. S1. Each black circle in Fig. S1 represents the separation-traction relationship at the monitored simulation time step. It is clearly seen that the traction follows the assumed bilinear cohesive behaviors with δ_n, as expected. The values of the monitored cohesive stiffness k_coh = 10¹¹ MPa/mm, cohesive strength σ₀ = 325 MPa and cohesive damage energy G = 1.0 J/m² are exactly the same as those that are input to the code (listed in Table 1). In Fig. S1, it is also seen that after the onset of cohesive damage ($\sigma_{t}^{n} > \sigma_{0}$ or δ_n > δ_nc), the traction follows the degraded k_coh to load and unloading with δ_n until its final failure.