Advanced Materials Research Vol. 820

Abstract: For solving the crack in crankshaft, laser cladding remanufacturing was involved. There were three key points about laser cladding remanufacturing discussed in this paper.The three key points included process flow , process environment and laser cladding materials selection . Using the ANSYS analysis software, the simulated analysis of the temperature field , stress field and the residual stress of the three kinds of cladding layer have been carried on, the best cladding materials for single-throw crankshaft crack of base material 45# is determined by studying the repaired results about Iron-based,Cobalt-based,Nickel-based self-fluxing alloy powder cladding materials.

Abstract: This paper introduces a kind of electric hot milling method for superalloy and analyses its feasibility. Fe-based superalloy GH2132 is selected as experimental object. An experiment platform is established. In the machining process, vibration signals are collected by a set of signal acquisition system. Afterward, these signals are processed by using wavelet transform, compared and analyzed in different machining parameters and working conditions. The results of the study indicate that compared with dry milling, electric hot milling can reduce vibration in machining process and machining superalloy more effectively. It also improves the cutting tool durablity.

Abstract: This paper mainly focus on the researches of tool wear mechanisms in turning Ni-based superalloy GH706 with PCBN insert. First, the process of flank face wear and rake face wear are studied by observing the pictures of tool wear. There are notch wear and flank wear on the flank face, and there are built-up-edge and micro-chipping on the rake face. Secondly, tool wear mechanisms are researched by combining the tribology and chemistry. A phenomenon called furrow effect cause flank face wear, and there are some chemical reactions on the rake face in cutting process. Lastly, in order to make sure a tool wear value which may be as a standard of PCBN tool in turning GH706, the relationships of cutting forces and flank face wear V_B are showed by drawing the curves of cutting force values along V_B, which indicate cutting forces turn up at the point where V_B =180μm.

Abstract: The deep drawing progressive forming process was analyzed by introducing the drawing progressive die design of shell parts. The drawing progressive design, layout design and mold structure was described detailedly.

Abstract: In this paper, a novel model combining the microstructure prediction model and a modified constitutive model of the Johnson-Cook (JC) model was developed and embedded into FEM software via the user subroutine. The chip formation and microstructure evolution in high speed cutting of Ti-6Al-4V alloy were simulated. The results indicated that dynamic recrystallization mainly happened in adiabatic shear bands (ASBs), where the grain size had a big decline. Then FEM simulations were carried out to investigate the effect of cutting velocity, uncut chip thickness, and the rake angle on the ASBs width of the serrated chips. It can be concluded that the width of ASB increases with the increasing of cutting depth and cutting velocity, and decreases with the increasing of rake angle of the tool.

Abstract: corrosions on gathering and long-distance pipelines in high sour gas field are often found on the HAZ, coarse grained region is the weakest region in the HAZ. We got L415 Pipelines coarse grained region of different heat inputs and post-treatments by welding thermal simulation, researched microstructures, hardness, impact energy and fracture, the result showed that, when the heat input is 25KJ/Cm, followed by annealing treatment with temperature 700°C for 1 hour, we can get good mechanical properties of coarse grained region.

Abstract: Two dimensional ultrasonic vibration assisted grinding (TDUVG) is analyzed based on theoretical analysis of the cutting trace of a grain in the finished surface, and it gives the kinematical model of single grit during TDUVG, and the condition of the separate cutting is established, so two dimensional ultrasonic vibration are introduced into the system, which helps to form good machining way. Then TDUVG is applied in the ultra-precise machining of nanoZrO₂ ceramics, and grinding experiments on surface quality of nanoZrO₂ ceramics were carried out using diamond grinding both with and without ultrasonic vibration. Experimental results show that the surface quality after two dimensional ultrasonic assisted grinding is superior to that of diamond grinding. As a result, it is suitable for the ultra-precise machining of ceramics.

Abstract: To improve voltage-gradient and to reduce the sintering temperature of ZnO varistors, high voltage-gradient ZnO varistors were synthesized with a conventional solid state reaction route. By means of SEM and DC parameter instrument for varistor, the influence of different technological parameters on microstructure, voltage-gradient and leakage current of ZnO varistors was investigated. The experimental results show that by using the process that presintering the additives at 850°C, the density is improved, the voltage-gradient is increased, and the leakage current is decreased. The optimum voltage-gradient and leakage current are 371V/mm and 3μA, respectively.

Abstract: According to dislocation dynamics, a distribution equation of mobile dislocations during the deformation of monolithic component was established. Slip deformation was solved through dislocation density and Burgers vector, and then the mathematical relationship between slippage and plastic deformation was established. Thus the mathematical relation model between dislocations and the machining distortion of monolithic component was established by plastic deformation as intermediate variable. It is shown that the machining distortion of monolithic component is upward embossment, and its maximum deformation occurs near the middle of the beam. The amount of machining distortion is directly proportional to the stress field at different depths of the surface layer, proliferation strength of dislocation and the length of the work piece, and inversely proportional to the thickness of the work piece.

Abstract: The dynamical model of laser cladding width is identified by the method of step response experiments. Mathematical models between the cladding width and the laser power, the scanning speed, or the powder flowrate are established respectively according to corresponding experimental results. Simulating experiment results verify the validity of these models. The dynamical identification lays foundation for the closed loop control in laser shaping process so as to improve the quality of the laser formed parts.