Key Engineering Materials Vols. 579-580

Abstract: To overcome the problems resulting from weldment trimming and assemble errors, thermal deformation, arc blow, etc., a set of new tracking system of fillet seam for automatic corrugated plate welding was put forward based on machine vision technology. The tracking system included two cameras: the precursor was set in front of the welding torch (a corrugation cycle far away), for capturing the linear laser projected on the side plate and the base plate; the another one was installed over the melting pool for capturing the image of welding torch tip and the seam. The processed image information from the precursor camera was used to track the fillet seam three-dimensional trajectory and the seam width, according to the information the welding motion controller and the welding power made preplanning; the processed torch tip and seam image information was sent to the motion controller and the welding power so that they could make real-time motion and welding parameter adjustment. Computer simulation proved that this new tracking system could work efficiently.

Abstract: Disposable mechanical elements are widely used in many fields such as aerospace and military industries. It is known for their extremely short work time which is quite different from general mechanical elements. The stress level of disposable mechanical elements is much higher than general mechanical elements. In this situation, the traditional fatigue fracture failure will be replaced by fatigue elastic failure used in the design of disposable mechanical elements. The fatigue elastic failure is closely related to the ratcheting properties of materials. Therefore, this paper focuses on the ratcheting properties of typical cyclic softening materials steel 45 and 42 CrMo. The fatigue elastic failure phenomenen of these two materials are shown through the stress control tests.

Abstract: Based on the experiment of two-way plane grinding-hardening machine, this paper studied the influence of workpieces height size and grinding parameter on the microstructure, micro-hardness and hardening depth of grinding-hardened layer. The results show that under this experimental condition, workpieces height size has no substantial influence on grinding-hardening, but while the height size increased, the micro-hardness and hardening depths average value of completely hardened zone presents trend of "saddle type". The workpieces quality of grinding-hardening can be improved by adopting reasonable workpieces height size.

Abstract: Titanium alloy is a kind of materials difficult to be machined. In this paper, the author performed the wear experiment of polycrystalline diamond (PCD) tool in precision cutting of titanium alloy material Ti-6A1-4V, and carried out test for morphology and composition of the wear area of tool using scanning electron microscopy and energy dispersive analyzer. The results showed that the hard particles wear and adhesive wear were main reason for cutting tool wear, and main wear form is flank wear.

Abstract: In this paper,the laser transmission joint strength is studied with semiconductor laser based on the surface pitting of 304 stainless steel and PA66.Unevenly distributed pits are formed on the surface of 304 stainless steel with 10% ferric chloride solution for two hours, which have certain morphology, depth and size. Different laser power, welding speed and welding pressure are used in laser transmission joining 304 stainless steel and PA66,which 304 stainless steel contains pitting corrosion before and after. The tensile strength test of joined samples shows that: the joint strength of pitted 304 stainless steel and PA66 with laser transmission joining is improved at least 135%; the riveted structure formed at the joining interface improve the joint strength.

Abstract: In order to study the finishing mechanism of abrasive flow machining (AFM), the model of material removal and solving method of surface roughness during material deformation have developed based on axial force and radial force. However, the axial force and radial force have been respectively measured by two pressure transducers fixed in the fixture. Both the material removal weight and surface roughness of workpiece have been calculated and measured during AFM experiments. The conclusions arrived by the analysis about the results of theoretical calculation are in agreement with the experimental AFM in some extent.

Abstract: Volumetric error has large effect on machine tool accuracy; improving CNC machine tool accuracy through error compensation has received significant attention recently. This paper intends to represent volumetric error measurement based on laser tracker. The volumetric error is modeled by homogenous transformation matrix with each coordinate corresponding to each motion axis. Based on parts of spatial points volumetric error, the geometric errors which affect volumetric positioning error are verified through particle swarm optimization with the L₂ parameters as the target function. The chebyshev orthogonal polynomials are applied to approximate geometric errors.

Abstract: Based on the iso-scallop 5-axis NC machining theory, analyses the convexity and concavity of the missile radome, then research on the processing strategy while using cylindrical grinding wheel and wheeled grinding wheel. At last, discrete the bus of the gyro-rotor and find out the most reasonable grinding parameters according to the radius of curvature of the whole processing bus. So the grinding precision can be increased and controlled.

Abstract: A three-dimensional coupled thermal structural model for micro electrical discharge is presented in this paper. Temperature field and thermal stress field of a single spark discharge process are analysed using this model by indirect coupling method. Temperature field is firstly solved which acts as the foundation of solving thermal stress field. To make the simulation results more reliable, these important elements are also taken into account, such as temperature-dependent properties of material, the phenomenon of plasma channel radius expanding, the percentage of discharge energy transferred to the workpiece and Gaussian distribution of heat flux. The results can explain the formation of cracks around the discharge crater. The thickness of the white layer and residual stresses can be predicated using this model.

Abstract: This paper presents a laser transmission joining (LTJ) experiment between thermoplastic Polycarbonate (PC) and glass reinforced nylon (PA66GF) using diode laser equipment. Laser transmission joining experimental design and experiment are carried out according to a single process parameters window. Response surface methodology (RSM) in Design-Expert v7 software is employed to develop mathematical models between LTJ process parameters and joint strength. The interaction effects of joining process parameters (line energy, spot diameter, clamp pressure) on the joint strength are investigated using analysis-of-variance (ANOVA), the result shows that the interaction effect of line energy and spot diameter has maximum influence on the joint quality. Finally, the predicted values from mathematical models developed by RSM are compared with the experimental values and it is found that they are nearly agreed with each other. The purpose of predicting joint strength based on reasonable process parameters is achieved.