Materials Science Forum Vols. 532-533

Abstract: The utilization of ceramics materials for structural components has been widespread because of their excellent properties. But the ceramic components require high precision and integrity of surface. The grinding is the main productive technique for finishing the ceramic components in the manufacturing industry, but it is prone to surface and sub-surface damage. Consequently the induced damage will reduce the life of the component, even leads to failure. So, to improve grinding quality and reduce grinding damage, it is important to understand the damage mechanisms and process for ceramic materials. In this paper, attempts are made to build a damage model and to compute damage variable D. The damage variable will be used in the further computation. The research effort made may be the foundation of the ceramic components design and the optimization and control of ceramic grinding process.

Abstract: Diamond wire sawing has been used for many applications in stone industries and civil engineering several decades ago. The wear of bead is a major factor that affects wire-sawing performance in machining process. In this paper, seven diamond wires with different matrix system and different structures are taken from the factory. The diameters in the front, middle and end of bead along the moving direction of diamond wire, are measured respectively. The wear of diamond grits is also observed using a digital video microscope system. It is show that the wear of bead varies along the moving direction of diamond wire. The wear in the front of bead is greater than the others. The diameter gaps are associated with the type of matrix and the wear of diamond grits. The diameter gaps keep constant in the smooth sawing process.

Abstract: In this study, the finite element method was used to analyze comprehensively the effects of punch shape on forming the forging recess. Then, the polynomial network and genetic algorithm were combined to construct the predicted and designed system. Through this approach, we can predict the forging results formed from arbitrary shaped punches, and design the optimal punch shape for forging recess. Through the interactive verifies of modeling repeatedly, the errors resulted from modeling analysis, network prediction and genetic algorithm optimal design are extremely limited. Consequently, the predicted and designed approach of optimal punched shape for forming recess in this study could be extended to the design of more complicated and difficult formed forging die.

Abstract: The wrought nickel-based superalloy has been the indispensable material for aviation manufacturing industry, but it is also one of extremely difficult-to-cut materials. Now many researches were focused on the machinability of wrought nickel-based superalloy, and many useful and favorable results can be collected. But most of these researches studied on single kind of wrought nickel-based superalloy, the general and integrated study is absent. In this paper, six typical wrought nickel-based superalloys (GH80A, GH738, GH3030, GH3044, GH4033 and GH4169) were studied. By means of studies on tool wear rate, cutting forces, cutting vibration and tool wear mechanism, the comprehensive comparison of the machinability of wrought nickel-based superalloys was showed. The influences of major elements on the machinability were investigated. The machinability of the six kinds of wrought nickel-based superalloys queues from easiness to difficulty as follows: GH3030, GH3044, GH4033 and GH80A, GH4169, GH738. Finally the comprehensive comparisons of tool failure modes and wear mechanism of these wrought nickel-based superalloys were also presented. Experiment results are comprehensive and have great practical significance to the high efficient machining of wrought superalloys.

Abstract: The rolling technic of involute spline has many advantages. This method can increase the production efficiency, has no cutting, can improve the metal structure of machining surface to increase the quality of surface and prolong the life of product, so the technic is used extensively in the industry of automobile and tractor. The design model of spline outline is built according to the formative theory of equidistant spiral surface by means of meshing principle of involute spline, roller is manufactured and machining spline is test according to the model. The correction of spline outline is accounted by means of measuring the outline of spline in three-coordinates measuring machine and comparing the measuring data and the data of ideal involute spline. The spline is remachined in corrected roller and ideal spline shape is gotten.

Abstract: In the field of the mold-curved free surface polishing, how to control the removing depth of the polishing surface exactly is one of the important problems to be solved. In this paper, a mould automatic polishing system that is developed on Motoman-NL20 robot is used to make theoretical analysis and experimental research on the removing depth of the polishing surface based on a novel Spinning-Inflated-ballonet Polishing tool for curved surface of mould. Firstly, FEM (finite element analysis) software is used to emulate three kinds of situation in the process of polishing, then the model of surface removing depth of SBCT polishing is established. At last, through the analysis and comparison, the result of emulation and experiment has a remarkable consistency which accords with the model established by formal theory. This indicates the correctness of the model.

Abstract: To achieve the desired dynamic impedance and the smooth chamfer contour, some adaptive controls and intelligent control schemes are incorporated in the impedance control for uncertain constrained robot systems. Most of them still result in an uneven chamfer for its characteristics in nature as the burrs vary highly. In this paper, an intelligent force controller based on impedance control with a neural network compensator is proposed for the robotic deburring process. The compensator is used to deal with the various burrs by modifying the input command according to the contact force and reference position. The performance of the intelligent force controller is compared with the conventional impedance control. The effectiveness of the proposed approach is testified by simulation experiments of the robotic deburring process.

Abstract: To improve low lapping efficiency of silicon nitride balls in conventional lapping process, fixed abrasive lapping technology for ceramic balls is investigated in this paper. Diamond abrasives and photosensitive resin are used to fabricate the fixed abrasive plate. The lapped ball surface is observed with microscopy to identify the dominant wear mechanism. The results show that the material removal rate of the fixed abrasive lapping is about 20 times of that of conventional free abrasive lapping process, and the roughness is close to the conventional one. The experimental results indicate that the fixed abrasive lapping technology is a promising process to instead of conventional free abrasive lapping process for ceramic balls in rough and semi-finishing process.

Abstract: We investigated the residual stress in diamond films grown on molybdenum substrates as a function of different places in the same large sample. The diamond film wafers of Ф60 mm diameter were deposited at 900°C by high power DC arc plasma jet CVD method using a gas mixture of methane (1.8% vol.) and hydrogen ( 90% vol.). The grain sizes, obtained from the top view scanning electron microscopy (SEM) images, were found to become larger from center to the border in the same sample, and the x-ray diffraction indicated that the intensity of characteristic spectroscopy in same diamond film was changed from (220) to (111) with the increases of (311). Profile curves presented the appreciable difference of surface texture from center to edge. The film had 4.3GPa of residual compressive stress. Examination of the Raman spectra of the film revealed that residual stress in the film of up to approximately 0.70GPa, and the Raman spectroscopy shifts from 1332.99cm-1 at the center to 1331.17cm-1 at the border, which means the stress mode changed from compressive to tensile. These demonstrated a significant inhomogeneity of stress in diamond films. The differences have been attributed partly to high temperature inhomogeneity arc jet during growth and morphological aspects of the film growth. The relationships between stress and methane concentration, and substrate temperature are discussed in detail.

Abstract: In this paper, an experimental study was carried out to fabricate a new kind of ultra-fine abrasive polishing pad by means of gel technology. The polishing pad was then used to polish silicon wafer on a nano-polishing machine. Optical microscope and ZYGO 3D surface analyzer were applied to observe the surface morphologies of the silicon wafer. Meanwhile, surface morphology of ultra-fine abrasive polishing pad was observed by ESEM. No obvious gathering of ultra-fine grains were found on the ultra-fine abrasive pad. The surface roughness (Ra) of the silicon wafer was reduced to 0.3nm after being polished by the abrasives with average grain size of 10μm. Mirror surface can be realized after being polished with the polishing pad.