Key Engineering Materials Vol. 667

Abstract: Aluminum-polymer composite products have advantages of metals with high specific stiffness, specific strength and abrasion resistance as well as that of the polymers with easy forming and low cost. The aluminum-polymer parts with lightweight, high strength can be produced to meet the requirement and demand of market. The interface conditions between aluminum and polymer, especially the metal surface temperature has important effect on the strength of the molded products. On the basis of aluminum-polymer composite molding principle, the heat transfer process during the molding process is analyzed. First, the finite element model for the aluminum and the metal mold heat transfer is established, and the boundary conditions are analyzed and calculated. Then the temperature field of the aluminum and the metal mold after heating process are obtained by finite element method. Lastly, the simulation results are compared with the actual temperature test. It is showed that the simulation and test results are in good condition within error range. Results presented in this paper can be helpful to study the mechanism of aluminum-polymer composite molding process and improve their interface strength.

Abstract: Turning instead of grinding of the hardened steel is an environmentally cleaner production technology and green fabrication technique. Using the negative rake angle basic shape blades of Mountain of Sweden Sandvik Coromant PCBN7015 cut hardened bearing steel GCr15 and observe fine surface under microscopic condition.. Microscopic observation showed that there was side stream between hard turning two knife marks forming carinata. Side stream level aggravate on the fine surface with the enlargement of Tool Nose radius. The White layer of hard turning fine surface is divided into three areas. White-bright zone is made up of Cryptocrystalline martensite, Dark gray zone is made up of tempered martensite, Grayish zone is made up of the original martensite. This research will enrich theory of hard turning.

Abstract: . Based on orthogonal test, the forming accuracy and density of laser sintering eucalyptus/PES blend is studied in this paper. It mainly analysed the effect of the powder size and process parameters (such as laser power, layer thickness, preheating temperature, etc) on the forming precision and density of sintered eucalyptus/PES parts, also the correlation analysis of molding error caused by the powder’s physical properties and machine is performed. By measuring the parts’ dimensions, the results show that the laser power and powder size are two main factors influencing parts’ density, and variable density, layer thickness and preheating temperature jointly affect the dimensional accuracy. The optimized processing parameters are obtained. The powder size, laser power, scanning rate, layers thickness and preheating temperature are 300 mesh, 43W, 2000mm/s, 0.1mm, 60°C respectively.

Abstract: Laser shock processing is a new kind of technology to improve the physical and mechanical properties of the metal surface. It uses the high-amplitude stress wave produced by the interaction of short-pulse laser and material, to make the material produce the compressive residual stress and refinement internal structure, and lead to the improved hardness and strength of material. In this paper, the simulation of laser shocking process with square spot of Titanium alloy plate was carried out through ABAQUS. The influences of the shock time, laser energy, plate thickness and spot size on the strengthening are investigated from the view of residual stress. The results show that: There are the compression residual stress in the workpiece surface after laser shcok processing, and its amplitude is about 300-400Mpa. With the increase of shock time, the surface residual stress increases, the area and depth of strengthening zone also increase. The strengthening area becomes a circular, while the distribution of residual stress becomes unhomogeneous. The surface residual stress increases as the laser energy increasing, but the amplitude is smaller. The plate thickness does not affect the amplitude of the surface residual stress. When the shock pressure is constant, surface residual stress does not change with the spot size. However, if the laser energy is constant, due to the shock pressure will decrease with the increase of spot size. Therefore, there should be an optimized spot size when the strengthening effectiveness and efficiency are both considered.

Abstract: Magnesium alloy which is one of the least light density (about1.7g/cm³) composites material on the ground for trade business, this material has better strength ratio of room temperature, high strength and rigidity, with good vibration attenuation, better damping, and good heat conduction,resistant radiation, don’t produce spark when friction, good ductility, better cutting machine and formed possibility, may be welded, adhesives, and have good chemical stability to Alkali, kerosene, gasoline, mineral oil and dry atmosphere, With no magnetic and electromagnetic shielding properties, Magnesium alloy products easy to recycle and no pollution to environment etc. Known as in twenty-first century the "green engineering materials”, In order to improve the use range of alloy,it need for improved performance of AZ31 magnesium alloy, AZ31 magnesium alloy surface modification technology to solve the main problems is to reduce the cost and environmental issues of a single technology, There is a wide prospect for the application of compound modification.

Abstract: In view of the physical process of the wood powder/PES composite powder material selective laser sintering forming ,this article establishes the plane moving Gaussian heat source as the input laser heat source model .Based on selective laser sintering wood powder/PES composite powder sintering theory and combined with thermal conductivity of composite powder, specific heat, density and other related theoretical analytical models .It establishes three dimensional finite element model of selective laser sintering process of wood powder/PES composite powder transient temperature field .The laser sintering simulation experiment of wood powder/PES composite powder under different laser power obtains temperature field distribution law of the wood powder/PES composite powder forming under different laser power distribution, and the influence of the forming parts forming quality of wood powder/PES composite powder materials caused by the temperature field. The simulation results also provide certain theoretical basis for the choice of laser power in the subsequent laser sintering experiment.

Abstract: Because of the non-uniformity of the section shape of rail and complexity of its temperature changing, the degree of thermal expansion and contraction of section must be different which leads to the interior stress is produced inevitable in it. The residual stress in rail is elastic stress and its maximum value is elastic limit stress. They affect the dimension stability, mechanical property, deformation and etc. And it is the important factor of rail quality. This paper builds a finite element model of temperature field through the MSC.Marc software during the process of heating and cooling of 55Q rail, which simulates the rail stress field of air cooling and water cooling. Our paper conducts the experiments on the rails of same material and condition and also selects the temperature and stress of appointed nodes to analyze them. The results of experiments and simulations are very identical. Simulating the residual stress of air cooling and water cooling, the result is that residual stress of water cooling is bigger than that of air cooling. This consequence gives the reference for planning the suitable heat treatment and improving the service life.

Abstract: Carbon fiber-reinforced plastics (CFRP) are typical difficult-to-machine materials, which is easy to produce many defects such as burrs, dilacerations, layering in milling process. And selecting the appropriate cutting tool has become the key to machining CFRP with high quality and efficiency. In the paper, the machining principle of milling CFRP with new type end mill was analyzed. The diamond coating of general right-hand end mill, cross-flute router and fine-cross-nick router were used to cutting CFRP under the same cutting condition. Through the comparative analysis of the workpiece’s surface quality and tool wear, it concluded that: compared with right-hand diamond coated end mill, cross-flute diamond coated router or fine-cross-nick diamond coated router could effectively suppress the appearance of burrs and dilacerations; abnormal coating peeling appeared in the flank face of right-hand diamond coated end mill, forming the boundary wear, which accelerated wear failure; the flank wear of diamond coated cross-flute router and fine-cross-nick router were both abrasive wear. Due to having more cutting edge than cross-flute router in cutting process, the flank wear of fine-cross-nick router was slower, and the tool life was longer. So it was more suitable for cutting CFRP.

Abstract: The nickel-based superalloy GH4169 is widely used in the aerospace industry because of its excellent comprehensive mechanical properties under high temperature and corrosion condition. It is one of the most difficult-to-machine materials due to low thermal conductivity and hard particle. One method of solving the problem of maching difficult-to machine materials is using new material cutting tool. PCBN tool has excellent cutting property in maching nickel-based superalloy because of its great hardness, high wear resistance and good chemical stability. The cutting process of in-depth study of PCBN tool cutting nickel-based superalloy, shows the variation rule of cutting force and cutting temperature, can provide a theoretical basis for process specification high temperature alloy and efficient processing, has a very big practical significance. On the basis of reasonable hypothesis, this paper discusses in detail the transformation from actual turning to 2D orthogonal free cutting geometry model. Based on this,through the establishment of simulation model of PCBN turning the nickel-based superalloy GH4169, studying on the tool rake angle γo, back angle α_o, cutting speed v_c and feed f on cutting process of cutting force and cutting temperature effect.

Abstract: Powder metallurgy is a technology process that the powder is pressed and sintered to get the metal and composite products. The sintering temperature is one of the main technology parameters of pressing sintering. In significant measure, the sintering temperature determines the organization and geometry size of the material, which directly affects the performance of the material. This paper takes magnesium powder metallurgy sintering material as the research object, studying the transient thermal analysis with the ANSYS finite element software, systematic researching the sinter temperature field and thermal stress field of sintered body in the sintering process, and observing in the corresponding distribution of stress field and deformation under different sintering temperature distribution graph. Temperature field and thermal stress field are the main factors affecting the quality of the sintered body in sintering process. Uneven temperature distribution will cause larger thermal stress. When the thermal stress exceeds a certain limit, the sample will be deformed. With the temperature increases, the sintering temperature difference increases, the stress distribution in the constantly changes. The stress and deformation is not entirely visible for sintered body, the deformation and cracking will be side by side in the sintering process. Therefore, theory of temperature field and thermal stress distribution are studied and discussed in certain sintering processing, the sintering process optimization can be designed to provide quantitative basis of the theoretical analysis.