Key Engineering Materials Vol. 522

Abstract: Owing to the Poor Surface Quality of Workpiece Processed by SEAM, the Work Used the Design Method of Orthogonal Experiment to Search for the Rules between Process Factors and Surface Quality of Machining. through the Range Analysis of Test Results and the Establishment of Process Regression Equation to Find the Rules between the Surface Quality of Workpiece and Process Factors, the Paper Provided the Test and Theoretical Basis to Achieve the Purpose of Improving the Surface Quality of Workpiece of Short Electric Arc Machining Process.

Abstract: Laminated templates electro-deposition (LTE) is a new manufacturing technique aimed at a highly precise and low-cost fabrication of metallic structures through a number of planar template-patterned depositing. The ability to control deposit surface non-uniformity in each planar depositing has been proved a key to this technique. Correspondingly a 3D simulation for electrical field has been modeled using finite-element method in line with the real experimental conditions. The mapped contour of simulating proved the variedly distributed electrical field and basically match with experimental results. Three groups of LTE test by direct current, pulse and double-pulse current are introduced and assessed in term of their effect to improve uniformity. By comparison, pulse application, especially double-pulse offered a better deposit quality with optimized parameters including pulse width, frequency, working time and off time. A bulk of 10-15layers copper parts, section size 20mm×20mm and 4-6mm thick were produced using the modified parameters.

Abstract: Pre-stress Hard Cutting, known as a new machining technology, is the combination of hard cutting and pre-stress cutting. Some reports show pre-stress machining can improve residual stress state of machined surface and prolong fatigue life of mechanical part, such as drive shaft, bearing and engine vane etc. Based on the principle of this technology, this paper take aero-screw shaft machining as object, investigated the pre-stress loading method, experimental device and implementation process of pre-stress hard cutting. Experiment is carried out for aero-screw shaft with PCBN tool, cutting force, machined surface residual stress state and distribution are measured. The experimental results show that by using this method, residual compressive stress is got on machined surface and good surface finish is gained, hence it can control machined surface residual stress state actively and improve the fatigue life of aero-screw shaft..

Abstract: A finite element simulation study of cutting process and whole part deformation of a large thin-wall aluminum alloy part used in aerospace is carried out by ABAQUS. The geometry model, material model and heat conduction model are built. The friction conditions and boundary constraints are determined. The whole process of chip generation is simulated and the distribution of strain, stress, cutting temperature and are given. The chip formation and the cutting force are also predicted. Based on the prediction results, the deformation of whole part is predicted. This study establishes the foundation of selection and optimization of cutting parameters and deformation compensation for this kind of large thin-wall parts.

Abstract: The principle of laser welding of combined translucent thermoplastic and absorbance thermoplastics is that laser transmit through translucent material and shoot at laser absorptive material, where the material absorb energy and melt down to complete welding. This paper studied the applicability of basic law of laser transmission welding beam mechanism and light absorption process – Beer-Lamber Law to plastic materials. Numerical simulation model of melting depth was established. Single factor relevance curve and double factor relevance surface were drawn with MATLAB; Impact of laser power, distance between weld zone and lens and scanning speed to melting depth was quantitatively analyzed on melting depth, which provided effective reference for setting parameters in the experiment.

Abstract: The oxidation resistance of Ni-Si-Ti-C, Ni-Si-C-Nb in-situ reinforcement clad layers has been investigated by cyclic oxidation tests at the temperature 1100°C. The oxidation performance were characterized by Thermo-gravimetric (TG),scanning electron microscopy (SEM) and X-ray diffractometer (XRD),the TG date indicates good oxidation resistant was reached for the clad layers. The kinetic constant Kp and the micrograph of oxidized samples shown that NbC reinforce clad layers which oxide products including NiO, SiO2 and Nb2O5 has better oxidation resistant than TiC reinforce clad layers which oxide products including NiO, some SiO2 and TiO2.

Abstract: In order to research the influence property of pre-tightening force, centrifugal force and dynamic cutting force on cutter components, and reveal safety recession of the cutter components, this paper makes load analysis for high speed milling cutter, studies cutter deformation, joint surface crushing, ductile fracture and other damage characteristics, gets the safety recession order of cutter components by safety margin theory. By means of the grey correlation analysis for safety recession, acquires the safety recession model of cutter. The experiment results confirmed that screw component firstly occurs the safety recession, and the safety recession model has certain reliability.

Abstract: For vibration-wear characteristics of cutter in high speed ball-end milling hardened steel, established vibration-wear model of high speed milling cutter according to the principle of friction work, researched the influence of basic frequency and multiplication frequency of cutter vibration on its wear, and analyzed the interaction between cutter vibration and wear. By means of changing cutter extended length, rotation speed and cutting depth, made the change of cutter vibration, analyzed the influence of cutter vibration on its fretting and impact wear, explored the evolution process of composite vibration wear of cutter. Results show that the interaction between fretting fatigue wear and the impact wear make for cutter vibration-wear, lead to the increase of cutting force and vibration amplitude, and further increase the interaction strength of vibration and wear.

Abstract: On the basis of the surface grinding-hardening test, studied on the quality of grinding-hardening in 65Mn steel. The results show that grinding method has insignificant effect on the microstructure and the high hardness value of the completely hardened region at different locations alone the direction of length. The completely hardened region is composed of fine acicular martensites, residual austenites and a little carbides, and the high hardness value is between 760-820HV. As the changing of grinding method, the uniformity and depth of the hardened layer changed accordingly. The quality of grinding-hardening could be improved with big depth of cut, small table speed and combined with the grinding method of up-down grinding or down-up-down grinding which could effectively control the depth and uniformity of the hardened workpieces.

Abstract: Low-temperature deposition manufacturing (LDM) has been proven as an effective bone scaffold preparation process, but its further application has been seriously hindered by the existing material over-accumulation problem. In view of the over-accumulation problem of the traditional pneumatic extrusion material feeding way, designed and developed a feeding system based on pneumatic-extrusion and valve-control, which can achieve rapid pressure/relief, Combined with the inflation / deflation time calculation method of fixed volume container for analysis and calculation. A unified data management method of the material feeding device and a regulation scheme of the controller are given. Experimental results show that, by adjusting parameters, the feeding system based on pneumatic-extrusion and valve-control can achieve rapid gas pressure/relief, the flux has been well controlled, the over-accumulation on deposition path at the end has been eliminated, which lead to effective guarantee of scaffold forming quality.