Applied Mechanics and Materials Vols. 446-447

Abstract: The impact shear response of crystallized polypropylene under combined compression and shear loading was studied by using an inclined gas gun and electro-magnetic particle velocity gauges. The experimental results show that the transverse wave velocity increases nonlinearly with the impact velocity, indicating its shear behavior is strongly related to the hydrostatic pressure. Remarkable shear wave attenuation occurs near the impact surface when the impact velocity and inclination angle reach the critical value. The micro-observation of recovered samples with a polarized optical microscope reveals that there exists a melting layer of about 2-3μm thick, i.e. adiabatic shear failure layer, very near the impact surface (about 5μm) which causes the shear wave attenuation.

Abstract: Multi-arc ion plating technique was used to fabricate TiN film on the surface of high speed steel (HSS) to improve its wear resistance. The structure and morphology of TiN film were analyzed by XRD and SEM,and the bonding strength between the film and substrate was studied by the scratch tester. The results show that the thin film formed on the surface of the substrate consists of compact TiN. There are some white spots and black spots on the surface of the film. The bonding strength between the film and the substrate reaches 43 N/mm², which correlates to formation of a pseudo diffusion layer. The tribological experimental results show that plating TiN film can greatly improve wear resistance of HSS.

Abstract: Aluminium doped zinc oxide (AZO) thin films were prepared by magnetron-sputtering. The optical and structural properties of the films were investigated by optical transmission spectra and X-ray diffraction (XRD) measurements, respectively. The results indicate that the AZO films have hexagonal wurtzite structure with highly c-axis preferred orientation. The optical and structural properties of the films are observed to be subjected to the argon pressure. The AZO film prepared at the argon pressure of 0.5 Pa exhibits the largest crystallite size and the highest average visible transmittance. Also, the refractive index and optical energy-gap of the films were determined by optical characterization methods. The dispersion behavior of the refractive index was studied using the Sellmeier’s dispersion model.

Abstract: Fused Deposition Modeling (FDM) is one of the relatively more successful Additive Manufacturing (AM) techniques and is more widely applied in the recent past. Apart from finding alternative materials targeting specific industrial application, FDM is also researched for medical applications with biopolymers and composites. While commercial FDM uses flat layer slicing of CAD models as the basic approach for the process, alternative slicing and deposition schemes such as curved layer FDM evolved specifically for thin shell-like parts. Curved layer FDM was shown to be effective in imparting better surface quality as well as mechanical strength of parts produced. Past research also established that raster angle plays a significant role on the mechanical characteristics of FDM parts. The current research attempts to bring the two approaches together and establish the effects of varying raster angles on the performance of parts produced by curved layer FDM. Mathematical algorithms used for curved layer slicing are reviewed and experimental results based on curved layer samples printed with varying raster angels are discussed.

Abstract: The impact of friction factor, thickness of the cold extrusion, semi-cone angle and other factors on cold extrusion was analyzed. Various process parameters were set and optimized. Cold extrusion process of hollow pieces was simulated by DEFORM-3D software. Through the simulation of the virtual velocity field, strain field, stress field, load - stroke curve and metal deformation process, the flow velocity of the metal and the deformation of the workpiece were studied. The metal flow routes and the parts that are easy to wear in die were gained. The above research results provide valuable references for the processing of hollow pieces.

Abstract: The high speed milling of silicon carbide was discussed by using flat end-mill 2 mm in diameter diamond coated tool. Ultra-precision high speed spindle attachment was used to achieve cutting tool rotation speed as high as 50,000 rpm. Special fixture was designed to minimize the chatter on work-piece surface during the machining process. Three cutting parameters were selected as independent variables of the experiments. They were spindle speed, depth of cut and feed rate. The arithmetic mean value of roughness (Ra) was measured on the work-piece surface as the response of the experiment. Result of the experiment shows that the value of surface roughness can be achieved as low as 0.150 μm. Statistical analysis was provided to study the significant of the model, interaction among the cutting parameters and their effects to the surface roughness value.

Abstract: In order to optimize the hot stamping process of an A-pillar and speed up getting the product to the market, we separately simulate forming and heat transfer to get a better tooling design. In the analysis of forming, the thinning rate is under 30%, we judge that there is no crack issue. In the analysis of heat transfer, the cooling curve is out of bainite and ferrite in CCT diagram, so the cooling design can meet the requirements of quenching. Finally, we bring simulation to tooling and test variables to get a better process parameter.

Abstract: This paper has established a viscoelasticplastic constitutive model for A7N01T6 alloy welding, which is temperature and deformation history dependent. The model uses elasticmixed hardening plastic and creep equation to describe the strain hardening at low temperatures and strain softening at high temperatures, respectively. Then it is applied for finite element numerical simulation of the welding process. By comparison with the conventional temperature dependent elasticperfectly plastic model, the overall longitudinal residual compressive plastic strain and the maximum deformation of welding sheet are larger. This is because that the plastic strain is mostly produced in high temperature range. Strain softening has great influence on the evolution of plastic strain. The compressive plastic strain during heating is larger than the tensile plastic strain during cooling. Strain hardening effect on welding residual strain and stress is almost negligible. Using the established constitutive model, welding residual stress and strain are in good agreement with the theoretical results.

Abstract: The precipitation characterization of SUS 310S weld metal was investigated by TG/DSC and metallography technique. SMAW was selected for this study and then cut with water jet avoiding thermal effect. Austenitic is the main microstructure of weld metal because of high Cr_eqv./Ni_eqv. Precipitation launched higher both %mass change and heat consumed as well as the precipitation temperature was around 800 degree Celsius.

Abstract: This study presents experimental result of surface roughness and chip-tool interface temperature developed during turning of AISI 316 austenitic stainless steels using TiAlSiN coated cemented carbide insert. TiAlSiN coating is deposited by Cathodic Arc Evaporation (PVD) technique. The work-tool thermocouple calibration set-up was developed. The air heater was used as a heating element at the work-tool junction. The experiments were conducted at cutting speeds in the range of 140 to 320 m/min, feed in the range of 0.08 to 0.26 mm/rev keeping depth of cut constant at 1 mm. The influence of cutting parameters and tool coating were investigated on the average chip-tool interface temperature and surface roughness. Experimentally interface temperature 979°C was observed at 260 m/min cutting speed and 0.14 mm/rev feed. The interface temperature in turning is strongly dependent on the cutting speed followed by feed and exactly reverse case was observed in case of surface roughness. TiAlSiN coating shows better performance and can be considered as a prominent candidate for the machining of AISI 316 work material.