A critical assessment of surface texturing for friction and wear improvement

The third comprehensive survey on scheduling problems with setup times/costs

Grain refinement of LY2 aluminum alloy induced by ultra-high plastic strain during multiple laser shock processing impacts

The laser shock peening (LSP) process using a Q-switched pulsed laser beam for surface modification has been reviewed. The development of the LSP technique and its numerous advantages over the conventional shot peening (SP) such as better surface finish, higher depths of residual stress and uniform distribution of intensity were discussed. Similar comparison with ultrasonic impact peening (UIP)/ultrasonic shot peening (USP) was incorporated, when possible. The generation of shock waves, processing parameters, and characterization of LSP treated specimens were described. Special attention was given to the influence of LSP process parameters on residual stress profiles, material properties and structures. Based on the studies so far, more fundamental understanding is still needed when selecting optimized LSP processing parameters and substrate conditions. A summary of the parametric studies of LSP on different materials has been presented. Furthermore, enhancements in the surface micro and nanohardness, elastic modulus, tensile yield strength and refinement of microstructure which translates to increased fatigue life, fretting fatigue life, stress corrosion cracking (SCC) and corrosion resistance were addressed. However, research gaps related to the inconsistencies in the literature were identified. Current status, developments and challenges of the LSP technique were discussed.

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Laser Peening Process and Its Impact on Materials Properties in Comparison with Shot Peening and Ultrasonic Impact Peening

The present disclosure provides three-dimensional (3D) objects, 3D printing processes, as well as methods, apparatuses and systems for the production of a 3D object. Methods, apparatuses and systems of the present disclosure may reduce or eliminate the need for auxiliary supports. The present disclosure provides three dimensional (3D) objects printed utilizing the printing processes, methods, apparatuses and systems described herein.

Apparatuses, systems and methods for three-dimensional printing

Laser shock processing is an innovative surface treatment technique similar to shot peening. It can impart compressive residual stresses in material for improving fatigue, corrosion and wear resistance of metals. FEM simulation is an effective method to predict mechanical effects induced in the material treated by laser shock processing. An analysis procedure including dynamic analysis performed by LS-DYNA and static analysis performed by ANSYS is presented in detail to attain the simulation of the single and multiple laser shock processing to predict the residual stress field and the surface deformation. History of the energies during dynamic analysis is analyzed and validated by the theoretical calculation. The predicted residual stress field for single laser shock processing is well correlated with the available experimental data and a homogeneous depression with little roughness modification in the action zone of the shock pressure is induced on the treated surface according to the simulation of surface deformation. Simulation of multiple laser shocks is also performed, which indicates that compressive residual stresses and plastically affected depth can be extensively increased and gradually reach the saturated state with the increase of laser shock number.

3-D FEM simulation of laser shock processing

Laser forming is a complex thermal–mechanical process. To reveal the mechanisms dominating the forming process is essential to control accurately the deformation of metal plate. Numerous efforts had been made to understand the mechanisms of laser forming. Proposed mechanisms mainly included temperature gradient mechanism, buckling mechanism and upsetting mechanism. However, in the investigation of laser forming, it is found that the above three mechanisms cannot depict fully the process of deformation. Based on the study of thermal transfer and elastic–plastic deformation, the above three mechanisms are further explained. In addition, a new mechanism, coupling mechanism, is proposed. To verify the validity of the mechanisms proposed, numerical simulations are carried out, and simulation results are consistent with analyses of mechanisms. Further analyses of forming mechanisms provide a theoretical basis for the scanning path and heating conditions as well as high-precision forming.

Research on the mechanisms of laser forming for the metal plate

Friction and wear performance of laser peen textured surface under starved lubrication

Material removal of optical glass BK7 during single and double scratch tests

Lower power lasers operating at higher frequencies, which are much more reliable and economical, have been explored for laser shock processing to improve fatigue and wearing resistance of metals. Laser shock processing with a Q-switched Nd:YAG pulsed laser was attained by the overlap of small laser spots for the treatment of AISI 1045 steel. The changes of mechanical properties of the specimen treated by different overlapping rates were investigated by both experiments and numerical simulation. Surface quality was essentially unaffected after treatment. Plastic affected depth was much shallower than that obtained with larger spot sizes, due to rapid attenuation of shock waves. Induced residual stress field was uniform on the top surface and was enhanced with the increase of overlapping rate. Surface micro-hardness reached a larger value than that reached on the untreated region and was also improved with the increase of overlapping rates. A plastically deformed martensite transformation zone was found in an extremely thin layer near the top surface due to the heat effect.

Zhenqiang Yao

Papers

3-D FEM simulation of laser shock processing

Research on the mechanisms of laser forming for the metal plate

Friction and wear performance of laser peen textured surface under starved lubrication

Material removal of optical glass BK7 during single and double scratch tests

Overlapping rate effect on laser shock processing of 1045 steel by small spots with Nd:YAG pulsed laser