Improving Mechanical Property and Microstucture Evolution of 7075 Aluminum Panel Formed by Unequal Alternate Double-sided Laser Shock Forming

With thrust weight ratio increasing, integral panel is an important component to reduce the aircraft weight, and it is a great challenges to ensure the forming accuracy and mechanical property in the lager-scale panel. Laser shock forming has a great development prospect in achieving integral panel forming and improving its mechanical properties. This work investigated unequal alternate double-sided laser shock forming, which can make 7075 aluminum panel form and induce harden layer in both panel sides. The improvement in mechanical properties and microstucture evolution of 7074 aluminum panel were analyzed after unequal alternate double-sided laser shock forming. The residual stress and microhardness in surface and subsurface were verified to be enhanced by the laser shock wave. The results of XRD and EBSD provided an evidence of grain refinement. The strengthening mechanism of unequal alternate double-sided laser shock forming was analyzed in this work. The grains are distorted and refined during high strain rate plastic deformation due to dislocation slip and accumulation. The mechanical properties were enhanced by unequal alternate double-sided laser shock forming for harden layers in both panel sides. The harden layers and grain refinement has a great significance in inhibiting the crack generation and growth.

Application of the method of dimensional analysis in laser-shock-wave processing of titanium alloys with shape memory

The processes of laser-shock-wave processing of NiTi alloys with shape memory effect are investigated by the methods of dimensional analysis and finite element modeling. The dependences of the depth of the plastic zone on the peak pressure in the shock wave and the duration of the laser pulse are obtained at different peak pressures. Keywords: shape memory alloys, laser-shock-wave processing, dimensional analysis, residual stresses, plastic zone depth. [email protected]

Repeated Laser Shock-Wave Adhesion Test for Metallic Coatings: Adhesion Durability and Its Mechanism Studied by Molecular Dynamics Simulation

We evaluated the adhesion of polycrystalline metallic coatings using the laser shock-wave adhesion test (LaSAT). This study used Cu plating on stainless steel as a coating model. The adhesion strength and toughness were successfully estimated using LaSAT and finite element method with cohesive zone model. Next, repeated LaSAT was conducted to apply cyclic loading to evaluate adhesion fatigue life, i.e., the number of loading cycles required for delamination. Furthermore, this study performed molecular dynamics (MD) simulations to elucidate the adhesion mechanism for the Cu/Fe interface. To verify our model, the interfacial fracture toughness was computed using the MD simulation and compared with the results of LaSAT. Next, cyclic loading was applied to the MD model to investigate crack initiation around the interface. We found that dislocations are generated from the internal grain and are accumulated at grain boundaries. This accumulation results in fatigue crack initiation due to stress concentration.

Application of laser"shock"wave treatment to increase crack resistance of materials

A finite element model is developed for predicting the appearance of new and the propagation of existing cracks during laser-shock-wave treatment (LSWT) of materials with linear and V-shaped cracks. The optimal modes of LSWT were determined for the maximum reduction in the rate of crack propagation. Keywords laser-shock-wave treatment, finite element method, residual stresses, stress intensity factor, crack growth rate, crack resistance. [email protected]