Advanced Materials Research Vols. 941-944

Abstract: It is a difficult problem to fabricate deep and micro holes on the difficult-to-cut metals in the field of aviation manufacturing. The experimental research of electrochemical drilling technology with high-speed micro electrode for fabricating deep micro holes is carried out. The influences of rotary speed on machining precision and stability are studied. The holes, which the diameter is about 400μm, the aspect ratio is more than 10, and have steep wall and sharp edges were fabricated successfully on the nickelbase superalloys on self-developed high-precision micro-electrochemical machining system. It is proved that the high-speed electrochemical drilling process for fabricating deep and micro holes has a huge potential and broad application prospects.

Abstract: The surface fatigue layers made of Cr12 were machined by the handheld high velocity arc machining equipment, the machined surface was observed by SEM, and the material removal mechanisms was studied. The results show that the material removal mechanisms of handheld high velocity arc machining is based on lots of the pulse discharge processes, and every pulse discharge process contains five sub-processes, which is similar with the material removal mechanisms of EDM. However, the discharge gap for handheld high velocity arc machining is at the range of arc discharge gap, which is longer than that of EDM.

Abstract: Titanium alloy Ti-1023 is difficult to machine because of its high strength, chemical reactivity and low thermal conductivity. And it have tool wear and chipping due to its poor machinability. The relationship between milling force, tool life and milling parameters by adopting single-factor experimentation method is studied, The optimized milling parameters are selected, and processing efficiency is improved. The result shows: The appropriate cutting parameters of Titanium alloy Ti1023 are cutting speed Vc=15~20m/min, feed per tooth fz=0.12~0.18mm, depth of cut (DOC) ap=4~7mm; Besides, when the unit positive pressure of the cutting edge surpasses 320N, chipping is likely to happen on the blade.

Abstract: There are a number of problems with the traditional way of machining Nomex composite materials, Ultrasonic vibration cutting as a new method can overcome most of the problems. This paper presents the machining process characteristics of ultrasonic cutting honeycomb structures of Nomex composite materials using two kinds of specials tools, and has a research on Ultrasonic machining tools posture control strategy, then proposed calculation method of generating the cutter location date. The main system was developed to meet the automatic generation cutting path of Nomex composite materials based on VS2008 and UG commercial software. The result of experiment shows this system can automatic generate rational machining path and correct NC date.

Abstract: An investigation was carried out to find out the influence of process parameters on surface roughness (SR) and material removal rate (MRR) in electric discharge machine of Al-7%Si-4%Mg with 20% of red mud Metal Matrix Composites since electric discharge machining is a thermo-electric machining process, an electronic die sinking electric discharge machine was used to drill holes in the composite work piece, copper is used as tool material. Experiment was carried out to find surface roughness, material removal rate and tool wear rate by varying the peak current, flushing pressure of dielectric fluid and pulse on time. It was found that the surface roughness of composite metal increases with the increase peak current ,pulse on time and flushing pressure due larger and deeper craters on the drilled surface. It was also found that there was increase in metal removal rate with the increase in peak current and flushing pressure and slightly decreases with the increase in pulse on time due carbon deposits on the electrodes. Experimental analysis is carried using Taguchi’s Design of Experiment method with various parameters like peak current, flushing pressure of dielectric fluid and pulse on time to identify the key factors that influence the surface roughness, material removal rate and tool wear rate. It was found that the peak current was the most significant parameter that influences surface roughness, material removal rate and tool wear rate. The Taguchi experiments results confirm the actual results obtained from the numerical calculation.

Abstract: Spring residual stress is a great influence on the overall performance of springs. In this paper, a flat spiral spring is taken as the research object, based on ABAQUS, the finite element model of residual stress during cold working of flat spiral springs is built. The magnitude and distribution of residual stress in cold working of flat spiral springs are simulated under different parameters. The effect of residual stress on the use performance of flat spiral springs is investigated. Optimization of process parameters is acquired. A reasonable processing technology is formulated, which provides theoretical basis for the cold working process.

Abstract: A kind of elastic coated abrasives used for polishing large mould surface, such as automobile panel mould, is investigated in this research. Many polishing experiments were finished by using elastic coated abrasives in order to study the effects of grit and workpiece material on surface roughness and machining efficiency. It is concluded that surface roughness is minimum and polishing efficiency is the highest when using 120^# abrasives at the same condition, surface roughness is the lowest and polishing efficiency is the highest for AISI 1045 steel in three materials. The difficulty of material removal is different if the textures prior to polishing are different in workpiece surface. Surface texture prior to polishing has effects on surface roughness and polishing efficiency. The research results provide foundation for process planning to achieve good surface roughness and high efficiency in the future research.

Abstract: Titanium alloy (Ti-6Al-4V) has a wide range of application in various fields of engineering. Titanium is mainly used to manufacture aerospace components like landing gear, fuselage, wings, engines etc. and biomedical components like hip joint, knee joint, dental implants etc. Titanium has outstanding material properties such as corrosion resistance, fatigue strength, tensile strength and a very good biocompatibility which makes this material very alluring for biomedical applications. Contrary, the machinability of the material is problematic because of the phase transformations and thus, titanium alloy is a challenge for machining operation. This research is a comparative analysis between the implants manufactured by traditional method of casting and machining. The femoral stem of the hip joint replacement is designed and the component is machined using a five-axis CNC machine. The machined component was subjected to surface roughness testing, tensile testing and bulk hardness testing. The values were compared with the values of titanium implants manufactured by casting.

Abstract: Remanufacture is an important way for green manufacture. To materialize the field processing of surface fatigue layers for some bulky and heavy waste productions, the processing principle and some key technologies such as discharge gap control, conductive wheel design for handheld high velocity arc machining equipment are introduced in this paper. The new machining technology and equipment is very fit to the remove of surface fatigue layers for some bulky and heavy parts under field conditions for its small volume, low costs and high efficiency.

Abstract: Spray quenching process is nitrogen, water mixture as the cooling medium of the new quenching process. The research shows that the flow of water and nitrogen pressure can be controlled to achieve the purpose of cooling rate. T10 steel as a cylindrical test object, the different ratio of water flow, nitrogen pressure as different quenching conditions, it cooled from 780 °C to 10 °C time ranging from 48 to 270 seconds, and the surface of the core after quenching hardness changes in operating conditions as occurred with the change.