Applied Mechanics and Materials Vols. 670-671

Abstract: In order to study the physical phenomena and mechanical properties of cutters when cutting rock, a test apparatus for cutting performance of cutters of large excavation equipment is established. The test apparatus is composed of a vertical loading system, a rotary loading system, a control system and a test system. Tests of different cut penetrations and spacings were carried out using the test apparatus. Meanwhile, the real-time images of the cutting process and forces acting on the cutters were obtained. The result shows that the test apparatus has good practicality and reliability, and it provides a laboratory test method to study the cutter-rock coupling mechanism and cutting performance of cutters.

Abstract: Flatness of the face milled surface usually changes within a time of resignation after released from the fixture; and machining parameters have significance influence on the flatness of the milling surface. This paper studies the different machining parameters’ effects on the time-dependent flatness. The experiment was designed by Taguchi method. The experiment results reveal that the time-dependent flatness is influenced by machining parameter.

Abstract: Model of the film-substrate interface of diamond coatings is built with the method of molecular dynamic, and the molecular dynamic simulation is applied to study the mechanical property of the model based on the Morse potential function and Tersoff potential function with temperature ranging from 0K to 800K. The results show that the adhesive strength of the interface between the diamond coatings and the cemented carbide substrate behaves a downward trend when the temperature rises from 0K to 800K and the downward trend is sharp when the temperature increases from 0K to 300K and the downward trend is smooth when the temperature rises from 300K to 800K. Meanwhile, the varying trend of the energy with the temperature is similar to the adhesive strength.

Abstract: This paper presents an experimental investigation into microfabrication of nickel template by femtosecond laser in air at atmospheric pressure. The laser pulses used for the study are 800 nm in wavelength, 100fs in pulse duration, and the repetition rate used is 1KHz. Micro-hole ablation experiments are carried out in air by focusing the femtosecond laser beam on the nickel target surface at normal incidence with the long-focus objective lens of enlargement factor 50 and NA=0.7. Dependence of the diameter, depth and depth-to-diameter ratio of the fabricated holes on the laser power and number of pulses are revealed experimentally. Microgrooves with good uniformity are fabricated on nickel template with femtosecond laser by optimizing the process parameters.

Abstract: WC–5TiC–10Co cemented carbides inserts were prepared and used for the cutting tool for HT250 gray cast iron. The objective was to investigate the wear mechanism when machining HT250 gray cast iron with WC–5TiC–10Co cemented carbides inserts. WC–10Co cemented carbides with the same sintering technology and grain size were prepared for comparison. wear mechanism was examined at the same cutting parameters. The cutting tests were performed at a speed of 120 m/min with feed rate of 0.2 mm/rev and a constant depth of cut of 0.2 mm under dry conditions. Tool wear mechanism is analyzed by SEM and EDS. Adhesive and built-up-edge were found to be the predominant tool wear for WC–5TiC–10Co cemented carbides inserts. However, Attrition was the main wear mechanisms observed in WC–10Co cutting tools. The results obtained indicated that WC–5TiC–10Co cutting tools performed better than WC–10Co cutting tools, in terms of tool wear with current parameters.

Abstract: Thermal barrier coatings (TBCs) provide a good protection to high temperature corrosion of superalloy substrate in gas turbine. However, the lateral growth of the thermally grown oxide (TGO) and the thermal expansion misfit between underlying bond coat (BC) and TGO may induce internal stresses. In this work, the distortion occurring near a groove on a heat-resistant Fecralloy substrate was analyzed due to subjected to thermal and thermo-mechanical cycling. Experimental result shows that the distortion of the groove strongly effected by mechanical load.

Abstract: Mirror grinding mainly depends on the precision of the machine tool, cutting and grinding amount and wheel selection and dressing. This paper mainly studies the MG1432 high-precision universal cylindrical grinder, exploring the impact on the workpiece roughness through selection and design of various process parameters in grinding, such as changing work table speed in dressing the grinding wheel and grinding, workpiece linear velocity and excessive feeding. The experimental conditions were: Using resin binder white corundum graphite grinding wheels, workpiece: GCr15 (HRC60); dressing tool: sharp single particle diamond correction pen, and ultimately achieving mirror grinding process results.

Abstract: This paper introduces conductive heat turning method using the high manganese steel as experimental materials.An experimental platform has been established, and vibration signal collected through continuous wavelet transform. By comparing and analyzing different processing parameters and working conditions,the effectiveness of conductive heating turning method’s reducing the vibration in the process of turning the size has been proved.

Abstract: The surface of a porous silica ceramic substrate was coated with water impermeable lithium aluminosilicate glass-ceramic layer by sintering a slurry consisted of fine glass powder. The coating was 600~800 microns thick. It is demonstrated that the glass-ceramic coating consists of β-Li₂Al₂Si₃O₁₀ crystallites. The coated sample has an excellent water proof performance. After the coating, both the dielectric constant and loss increase. The coating protected the substrate from ablation under 1700°C.

Abstract: Stress, strain and residual energy of the thermal barrier coatings under high temperature shock were simulated by using ABAQUS software. The results show that cooling rate has certain effects on the residual stress. With the increase of cooling rate, the interface stress between the coating and substrate increased. Rapid cooling resulted in the phase transition and larger residual stress in the coating. With increasing of thermal cycles, the residual stress accumulated gradually. And the residual stress of the fourth thermal cycling increased by half compared with the first time. Moreover, the strain presented an increasing tendency with the increase of thermal cycling times and reached to 23.1097×10-3 μm after the fourth thermal cycling. The residual energy increased to 15.5 J after four thermal cycling and increased 1.2 J compared to the first time.