Advanced Materials Research Vols. 197-198

Abstract: GCr15 bearing steel was turned with PCBN cutting tools in a manner of hard and dry cutting, and the characteristics and morphology of rake and flank face of PCBN cutting tools were observed, the element distribution of different regions of rake and flank face of PCBN cutting tools were tested and analyzed by use of EDS, and finally the wear mechanisms of PCBN cutting tools were discussed. The results showed that the wear areas of rake and flank face of PCBN cutting tools were small and mostly concentrated near the tip and sub-chamfering, and the reason was mechanical, oxidation, chemical and phase transition wear, which resulted in the joint action of tool wear.

Abstract: The material characterization and mechanical behaviors of aluminum alloy (6063) were investigated using flat specimens and the butterfly specimens with a modified Arcan fixture. The butterfly specimens were tensile-loaded at various stress triaxiality by changing the loading angles of the Arcan fixture. The flat specimens were tensile-loaded at various strain rates. The results of tensile tests at various stress triaxiality showed that the curves of engineering stress-engineering strain are obviously different. The results of different strain rates tensile tests showed that the yield stress and fracture stress increased slightly with strain rates increasing, however the fracture strain decreased obviously with strain rates increasing, and the ultimate strength almost remained constant. The Johnson-cook constitutive model could be used to describe the dynamic axial crashing behavior of thin-walled 6063 aluminum alloy tubes under impact loading. The material constants of the Johnson-cook constitutive model and failure model were acquired to be used for FEM simulation through material characterization.

Abstract: Due to the complexity of service environment of thermal protection system on the aerocraft, the thermal shock resistance (TSR) of ultra-high-temperature ceramics (UHTCs), which are used as thermal protection materials, is no longer the material itself’s. Based on the restrictions of current experiments and the lack of theories, hafnium diboride (HfB2) is used to study the effects of the external constraint conditions and different thermal environment on the TSR of the UHTC in detail. The effects of different initial temperature, different external constraint conditions, and temperature rising rate on the TSR of the UHTCs through numerical simulation are discussed in detail in this study. This study can provide a more intuitively visual understanding of the evolution of the TSR of UHTCs during actual causative conditions.

Abstract: This study evaluates the filtration efficiency of a cabin filter and according filter media for fine particle (PM2.5) through laboratory tests and on road tests. Two testing system for the filter media test and filter tests were designed according to the international standard (EN1822 and ISO 11155).On road tests were completed on the real roadway conditions. In cabin particle concentration and ambient particle concentration was gotten by DustTrak(TSI). And then the filter efficiency was calculated according to the I/O ratio. The results showed the filter media’s efficiency was highest, compared the lowest efficiency of filter total efficiency. The real particle removal total efficiency on road was higher than the laboratory test result. According to the experiment data, the on road testing results (particle reductions) are approximately equal to geometrical mean of filter media efficiency and filter total efficiency.

Abstract: In this paper, microstructure and impact properties of borated stainless steel type 304B6-GradeB were investigated, which was used as raw materials of high-density storage racks in some nuclear power plants. Microscopic examinations reveal that a large amount of particles are heterogeneously distributed on austenitic matrix which displayed different shapes in the rolling and thickness directions, the results of XRD and EDS prove that the secondary particle is (Fe,Cr)₂B and boron is distributed only in the particles while not in the matrix, fracture analysis all indicates that this borated stainless steel type 304B6-GradeB obviously exhibits features of brittle fracture.

Abstract: The effects of heat treatment process on the microstructure and mechanical properties of TC4 alloy were investigated. The double shear and tensile tests were carried out by using the 12mm diameter standard specimens after solution treatment at 520°С for 1.5h and water quenching, followed by aging at 480-540°С for 8h. The microstructure and facture surface were analyzed using the equipment of metallurgical microscope and scanning electron microscopy. The results show that TC4 alloy show the best comprehensive performances after solution treatment at 940°С for 1.5h, aging at 520°С for 8h; the tensile specimens display a typical ductile fracture with oval dimples of various sizes; the microstructures with clear grain boundary and obvious lamellar structure are observed at room temperature. It indicates that the excellent comprehensive properties can be obtained by controlling the grain size of primary α phase and the morphology structure and amount of the secondary α phase at optimized aging temperature.

Abstract: Uni-tension test and torsion test with specimens of A3 steel are completed, and deformation rate, the spin of Euler configuration to Lagrange configuration and generalized Jaumann rate of Kirchhoff stress in torsion problem are given. Large strain constitutive relationship with generalized Jaumann stress rate is studied based on torsion test. The simple shear problem is discussed by using the constitutive model given in this paper. The result indicates that the hardening coefficient of constitutive model with generalized Jaumann rate may be given by the same expression as that of constitutive model with Jaumann objective rate when determining by using torsion tests and the shear stress response curve in simple shear problem obtained by using the constitutive model in this paper is similar to the shear stress-strain curve given in solid circular shaft torsion tests.

Abstract: Glass fiber reinforced polymer composites were prepared by dispersing zinc oxide (ZnO) whiskers in resin matrix. Static and dynamic tensile tests of the as-prepared composites were performed by means of a universal testing machine and the split hopkinson tensile bar (SHTB), respectively. Good tensile properties, which can be affected by the strain rates, of the composites are obtained. The fracture section morphology of the composites was investigated by scanning electron microscope (SEM). The different failure of the composites under static and dynamic tension is found. The tensile properties of the composites are dominated by pull-out and fracture of fiber bundles. The influence of ZnO whiskers on the performance of composites has been discussed. ZnO whiskers, which have unique three-dimensional structures and corresponding stress transfer, contribute to the tensile properties of the composites.

Abstract: The properties of gravity casting AZ91D-0.4Ca-0.3Sr alloy with Gd and Y in metal mould were studied by controlling the total strain amplitude ranged from 0.05mm to 0.25mm.under the conditions of the stress of ratio R equal to –1. In addition, the microstructure, phases, chemical constitute, fracture and low cycle fatigue behaviors of the magnesium alloy were primarily researched by means of SEM, EDAX and XRD and so on. The results showed that 3.0wt%Gd and 3.0wt%Y introduced the AZ91D-0.4Ca-0.3Sr alloy can refine α-Mg, and that Gd cooperating with Y can significantly improve the low cycle fatigue life. The low cycle fatigue times can be up to approximately 9874.

Abstract: Quasi-crystals is not only a new structure of solids but also a new class of functional and structural materials. With the research and development of quasi-crystals, the mechanical properties of quasi-crystals get more and more attention. In the paper, quasi-Hamilton principle of quasi-crystals beam is established in non-conservative systems. And applying the quasi-Hamilton principle, all the equations of non-conservative quasi-crystals beam problem are obtained in the phonon field and the phason field respectively.