Hejun Wang

Micromold-Based Laser Shock Embossing of Metallic Foil: Fabrication of Large-Area Three-Dimensional Microchannel Networks

Micromold-based laser shock embossing is a new three-dimensional (3D) forming technique, which utilizes laser-generated shock wave to shape the workpiece. In this article, the microchannel networks mold was produced by micro-wire electrical discharge machining (Micro-WEDM). Large-area three-dimensional microchannel networks were successfully fabricated on metallic foil surface using laser-generated shock wave. The investigation reveals that 3D microchannel networks have a high spatial resolution at the micron level. The fracture in the forming experiment was also detected. The fabrication cost is independent of the microstructures complexity. Therefore, micromold-based laser shock embossing holds promise for achieving precise, well-controlled, low-cost, high efficiency of 3D metallic microstructures.

Numerical simulation and experimentation of a novel laser indirect shock forming

A novel laser indirect shock forming is presented, which uses laser-driven flyer to load the workpiece. Experiments were performed by allowing the laser-driven flyer to impact a stationary workpiece. The flyer can protect the workpiece from thermal effects so that pure mechanical effects are induced. The experimental results show that laser indirect shock forming is possible and the workpiece have a high spatial resolution at the micron level. In addition, the forming technology can effectively prevent wrinkling. The effect of laser energies on the deformation mechanism was investigated experimentally, and experimental data obtained were then used to validate the corresponding simulation model. The results show that the finite element analysis can predict the final shape of workpiece properly.

The effect of point defect on mechanical properties of MoSi2

The effect of point defect on mechanical properties of MoSi2 has been investigated by the first-principles. The elastic constants, mechanical modulus, hardness and thermodynamic properties of MoSi2 with four different single point defects have been calculated. By comparing with the defect-free MoSi2, it is found that the bulk modulus/shear modulus ratio (B/G) of MoSi2 with a single point defect increases slightly while the Debye temperature decreases drastically, which indicates that MoSi2 with some point defects have relatively good ductility. The calculated three-dimensional (3D) contours of elastic modulus and these projections on the (001) and (010) planes show that the directionality of Young’s modulus and shear modulus is unapparent for MoSi2 with a point defect (VMo and MoSi) but it is relatively obvious for MoSi2 with VSi and SiMo. It suggests that VSi and SiMo can strengthen the anisotropy in elasticity. The electronic properties of C11b MoSi2 with different single point defects have been studied to reveal further the influencing mechanism of point defect on mechanical properties. This work should help reveal the interrelation between intrinsic defects and service performance of MoSi2.

Finite Element Simulation of a Novel Laser High Speed Punching

A novel laser high speed punching is presented. The laser induced shock wave acts as a punch. The forming speed can be controlled by adjustment of the laser energy. The previously-reported experimental results show that laser high speed punching is possible. This paper reports an investigation into the laser high speed punching process through finite element simulation. The Johnson-Cook model shear damage model is used as the fracture criterion for laser high speed punching. The finite element method was applied through the use of ANSYS/LS-DYNA code.