Materials Science Forum Vols. 471-472

Abstract: An investigation was carried out to predict the wear performance of diamond sawblade segments by using a Levenberg-Marquardt backpropagation (BP) neural network. The wear of the diamond segments were measured in circular sawing of natural gray granite in order to train the network and examine its validation. Since the depth of cut and workpiece speed are two main variables in the sawing of a specific granite material with a fixed diamond sawblade, a 2-5-1 structure of BP network was found to be capable of predicting the wear performance. In spite of the limited experimental data, the average value of relative errors between the simulated and measured results was found to be around 10%. Since experimentally measuring of segment wear is a time-consuming job, the trained network was also used to predict the wear performance under a very wide range of operating parameters, which can provide a useful guideline for the optimization of stone sawing.

Abstract: In this paper, some molding process parameters such as injection time, packing time, packing pressure and process temperature etc. were optimized by the Computer Aided Engineering (CAE) simulation (Moldex 3D) for injection molding of a plastic lens. Some experimental trials were carried out for verifying of the CAE simulation results with checking of the lens shrinkage and birefringence etc. as well. The results showed that, the recommended molding process parameters from CAE simulation and the actual experiments were almost the same, hence the CAE is a established tool based on the scientific approach to reduce experimental works, to identify critical parameters and to save substantial costs. Lately, a perfect plastic lens was gained by the Injection–Compression Molding process with the optimized process parameters by a CAE simulation.

Abstract: The frequency of piezoelectric transducer requires high stability and can also be continuously changed. The voltage requires smooth and stable sine wave. To the two problems, a high precision power supply for vibration cutting is designed. It divides the whole frequency band into several small bands. By means of CPLD, the sine wave is digitally fitted individually at each small band. So the sine wave can be always suitable at a wide frequency band. At the power output, OCL power amplifier is adopted. The output sine voltage becomes smooth and stable by adding voltage negative feedback to the power amplifier. The experiment results show its feasibility.

Abstract: A definition of forming limit is given with minimum centerline radius min R before wrinkling for NC bending process of thin-walled tube. Based on the developed FEM wrinkling prediction system TBWS-3D, an effective searching algorithm of wrinkling limit is proposed and forming limit can be obtained conveniently. Thus influence laws of main forming parameters on wrinkling limit are investigated and revealed. Measures to improve forming limit is put forward consequently. The achievements may help to both practice of thin-walled precise tube bending and research of plastic wrinkling.

Abstract: This document explains and demonstrates an experimental method to determine principal plastic strains in industrially stamped sheet panels. The principal strains distribution after a given stamping process can be obtained using computer aided grid experimental method. In contrast with FLD (Forming Limit Diagram) obtained by the material testing, the measured results of strain distribution can be used to determine the sheet metal’s formability allowing to determine at which point the sheet metal cracks or uneven stretch occurs and other forming defects. The main principle and related theory of this approach are discussed. One automobile panel stamped part as a practical case was studied, the strain distribution of the part after a given stamping process was measured and calculated, a demonstration of how to deal with the results in comparison with FLD to determine and solve forming problems is analyzed.

Abstract: Reverse engineering of free-form surfaces is one of the most challenging technologies in advanced manufacturing. With the development of industry more and more sculptured surfaces, such as molds and turbine blades, are required to measure quickly and accurately. Optical non-contact probes possess many advantages, such as high speed, no measuring force, in comparison with contact ones. The ability of stereovision probe with CCD cameras in gathering a large amount of information simultaneously makes it the most popularly used one in sculptured surface measurements. So based on the laser triangular principle, a measuring and testing device with two CCD cameras was designed, and its accuracy was analyzed. With a virtual 3D target in form of a grid plate, all the intrinsic and extrinsic parameters of CCD camera including the uncertainty of image scale factor and optical center of camera can be readily calibrated. In order to obtain all the required data with high accuracy in a short time, the curvature-based adaptive sampling strategy is presented. Due to huge amount of arbitrary scattered points, the Delaunay triangular division and Bezier interpolation and NURBS interpolation are applied to get a continuous surface.

Abstract: This paper studies the NC grinding process for Isometric Polygonal Profiles (IPP) with self-made machine tools accessories, and establishes the time series model of the grinding process by means of measuring and analyzing the vibratory signal in the grinding process. The grinding experiment indicates that the surface formative motions of IPP can be achieved with the step-motor-driven accessories and it is reasonable to design the grinding machine for IPP according to the principle. This method solves the technical problems in IPP NC processing and can act as an important elicitation and illustration for NC processing other polygonal profiles.

Abstract: Hard turning has been recognized as a substitute for abrasive-based processes not only due to its flexibility, economic benefit and environmental consciousness, but also its determinate surface integrity (surface roughness, micro hardness and residual stress), which is superior and more consistent than ground surfaces. Residual stress is of considerable industrial importance because they can affect failure by fatigue, creep or cracking. It is believed that compressive residual stresses are more favorable for fatigue life than tensile residual stresses. Hard turning generally generates compressive residual stress, which is the dominant role in determining both the variance and average value of fatigue life. This paper focus on the published data, especially C.R.Liu’s research, which address the residual stresses by hard turning in terms of experimental approaches， theoretical modeling，numerical simulation by Finite Element Analysis (FEA) and the correlation with its fatigue life and performance. The potential trends and key technologies for residual stresses are predicated and discussed so as to capture the most effective approach to investigate residual stress by hard turning.

Abstract: A PID controller based on Back-propagation neural networks is presented and used to the pneumatic proportional positioning system in this paper. A proportional valve-cylinder without rod system for buffering and positioning, which is controlled by microcomputer, is designed and completed in this paper. The experimental results show that the system gains self-adaptability because of the application of this control method. And the buffering and positioning of the cylinder can be implemented under different working conditions.