Papers by Author: Cheng Dong Wang

Abstract: Machined surface quality is the deciding factor when evaluating the machinability of CFRP. This present work concerns the influence of fiber orientation on the machined surface quality of the machined surface in terms of surface morphology and surface roughness during milling of unidirectional T800/X850 CFRP laminates. Four group milling tests are conducted under the fiber orientation angle of 0°, 45°, 90° and 135°, respectively. For the fiber orientation angle of 0°, the machined defects are mainly fiber pull-out and fiber brittle fracture owing to interfacial debonding between the fibers and matrix resin. For the fiber orientation angle of 45°, the machined defects are mainly resin cavities and the surface morphology is rough and presents wavy fractures. For the fiber orientation angle of 90°, smooth or neat surface is observed except for the surface as the cutting tool cutting in the workpiece on which severe cracks are observed. For the fiber orientation angle of 135°, the surface is smooth with less fibers pull-out. Evaluation profile and surface roughness of the machined surfaces were measured as well. Dramatically fluctuate of the evaluation profile is observed for the fiber orientation angle of 45° with a high surface roughness Ra. Verification tests were also conducted on the multidirectional CFRP (cross-ply) laminates. It is indicated that the presence of the fiber orientation angle of 45° is the main factor leading to the decline of the machined surface quality.

Abstract: In this paper, experiment investigation is conducted on the machinability when ball milling A880 gas turbine blade profile. Cutting force spectrum acquired online is used to optimize the cutting parameters. The results indicate that cutting force signal in time domain and frequency domain can reveal the cutting stability, which provides an experimental guideline for gas turbine blades manufacturing.

Abstract: Reasonable tool condition has crucial importance to prevent tool malfunction such as abnormal wear, chipping and cutting teech breakage when broaching expensive components i.e. gas turbine engines disks. This paper proposes a broaching simulation test method of using customized single tooth groove tools with a variety of rake angle and clearance angle to simulate broaching processing at shaper machine under different cutting depth. The effects of tool condition and cutting depth on cutting forces, surface roughness analyzed by Response Surface Methodology and surface morphology of machined surface were discussed, which revealed that the changes of cutting depth play a dominate role in processing quality, followed by tool rake angle, and tool clearance is subordinate. Good tool edge strength should be assured from prevent shock and vibration during the selection of tool condition.

Abstract: In this paper, effects of milling parameters on cutting force and surface roughness during symmetrical face dry milling process of super high strength steel 30CrMnSiNi2A were presented. Multiple linear regression model and orthogonal rotary quadratic regression model were established to analyze cutting force and surface roughness, respectively. Their adequacy was estimated by variance analysis and experimental data comparison. Parameters optimization for maximum metal removal rate and minimum surface roughness were also discussed.

Abstract: In order to enhance mechanical property and restrain crack growth of 6061-T6 aluminum alloy, laser shot peening (LSP) was employed to induce compressive residual stress and plastic deformation on the surface of metal. The FEA code ABAQUS and MSC. Fatigue were used to simulate crack growth of Compact tension (CT) specimens treated by LSP. The numerical simulation results showed that LSP can effectively inhibit the crack growth, decrease the crack growth rate as well as increase the final crack size, and as a consequence, fatigue life was extended. Adding peening times could get deeper compressive residual stress field which strengthen material surface and restrain crack growth, but the fatigue stress intensity factor threshold decreases.

Abstract: . Progressive dies are widely used for the mass production of sheet metal components due to the high productivity, high precision and low cost, but the design of progressive die is a complex and highly specialized procedure. In this paper, a design method of progressive die based on component was presented. Based on the technology of component object module, a number of key techniques in the design of progressive die design were addressed, the knowledge-based design frame system was developed, and the assembling model under UG environment was established. Finally, a practical design process for progressive die of complex panel was demonstrated, and the 3D integrated mould was realized.

Abstract: A numerical analytical model for both-side laser shot peening (LSP) of specimen with center-hole was established, the influence of the center-hole on peening effect was investigated, and the 3D residual stress distributions of ZK60 specimen after one-side and both-side LSP were analyzed. The results showed that compressive residual stresses were obtained at the both sides of specimen after both-side LSP, with a stress value of -179.41MPa on the bottom surface, much larger than that of one-side LSP. The typical experiment of LSP for ZK60 specimen was carried out and the experimental data were well correlated with the simulated results.

Abstract: Typical specimens of AZ31B Magnesium alloy were processed by single point and continuous laser shock peening (LSP). The selected laser energy was 25 J, spot diameter was 8 mm, peening spacing was 8 mm and peening times were 2. The obtained value of residual compressive stresses were -144.3 MPa and -230 MPa for single and continuous LSP respectively, and the magnitude of residual stress was in direct proportion to the depth of deformation in definite micro-deformation range. The average surface micro-hardness in the laser spot zone was 92.42 HV, which increased by 26% as compared to 73.2 HV of substrate, the depth of hardened layer was about 0.3 mm, and the maximum micro-hardness was about 109.86 HV beneath surface of 0.05~0.075 mm. Large amount of crystal chunks appeared at the crystal grain boundaries and inside the grains, and the average grain size decreased from the untreated 7 μm to the peened 4 μm. The results show that the nucleation of fatigue crack can be retarded and the mechanical properties of AZ31B magnesium alloy sheet can be improved greatly with LSP process.