Grinding Trace Research Articles

Residual stress distribution of silicon wafers machined by rotational grinding based on molecular dynamics

Wafer rotational grinding is widely used to thin silicon wafers and the grinding-induced residual stress distribution is desired to be known. However, it is difficult to obtain it directly by measurement since the variation of residual stress values of different locations tends to be submerged in the fluctuations of measured values. In this study, molecular dynamics was employed to obtain the residual stress states of ground monocrystalline silicon of different crystal directions. The actual cutting directions of the abrasive grains were obtained as the tangential directions of the abrasive grain's traces on the silicon wafer surface relative to the crystal coordinate system. It was found that the actual cutting direction of an abrasive grain along a single grinding trace would change from the center to the edge of the silicon wafer since the grinding traces are curved lines. The residual stress state at a specific point on the wafer surface was obtained by mapping the residual stress values obtained by molecular dynamics to the actual cutting direction. The residual stress distribution map was obtained successfully and any point of the ground silicon wafer could be known. The location of maximum residual stress was found to deviate from the [1 1 0] crystalline direction on the ground wafer due to the change in the actual cutting direction relative to it.

Up/down processing modes effects on residual stress for belt grinding

ABSTRACT Belt grinding is increasingly being used to process complex parts because of its ability to achieve flexible, form-following machining. Although the choice between down-grinding or up-grinding is one of the most common issues in process decisions, the influences of the differences in material removal mechanisms remain unclear, especially on surface residual stresses (RS). Thus, this paper focuses on the different grinding direction’s influence on residual stress distribution, followed by a causal analysis of the abrasive cutting mechanism. The results suggest that the up-grinding surface is more prone to compressive RS of σ a due to the different material flow directions close to the machined surface, and has stronger stress amplitudes of σ t due to the increased belt wear caused by the grits entering from the hardened machined surfaces. For both down- and up-grinding, σ a along the grinding trace’s cross-section is symmetrically distributed in a peaked pattern, but σ t is closer to a uniform distribution. One possible reason is that the contact wheel dissipates heat more quickly on both sides than in the center. Besides, the consistency of the RS distribution is better for up-grinding both within the same grinding trace and among different grinding traces.

Effect of laser surface melting on bulk metallic glass: Investigation of microstructure, microhardness, friction and wear properties

10 × 3 × 80 mm3 fully dense crack-free plate-like Cu46Zr42Al7Y5 bulk metallic glass (BMG) samples were successfully prepared by a copper mold casting method in an argon atmosphere and subjected to surface laser surface melting (LSM) under different laser frequencies. X-ray diffraction patterns showed that the degree of crystallization is determined by the crystalline phase in the heat-affected zone and the welding fusion zone; the heat-affected zone is easier to crystallize than the welding fusion zone at the same laser frequency. The microhardness of the welding fusion zones reached a maximum of 508.2 Hv at a laser frequency of 16 Hz. However, the microhardness of the heat-affected zone declined drastically with increasing laser frequency. In addition, the average frictional coefficient dramatically increased and then decreased with an increase in sliding velocity, and the values reached a maximum at the sliding velocity of 500 mm/min. The property of wear resistance was moderately improved at laser frequencies of 12, 14, and 16 Hz. Moreover, the grinding trace widths slightly increased with increasing sliding velocity. The friction and wear mechanisms and morphological representations were completely different under different sliding velocities.

Research on Plane Grinding under Combined Movement of X-Y Axis

There are many parameters which can influence plane grinding. It is a situation in high workload and poor realizability to find the optimization parameters of the grinding by using experimental method. Taking x-y linkage plane grinding as the platform, research on different influence of grinding quality with 4 factors including initial diameter of the abrasive, initial phase angle, lapping plate & workpiece speed ratio and x-y linkage workbench though simulation. The results show that initial radius vector of the abrasive basically has no effect on grinding trace. When speed ratio between lapping plate with workpiece is decimal the grinding trace seems much better. The significant influence of grinding quality can made by straight and helical x-y linkage motion on workbench.

Tribological properties of wood as a cellular fiber-reinforced composite

The relationships among microstructural, viscoelasticity, micro-hardness, elasticity modulus and tribological properties of wood are important for the understanding and bio-mimicking of fiber-reinforced composite materials. The microstructural, viscoelasticity, micro-hardness, elasticity modulus of wood and the friction between steel ball and wood have been studied. Results revealed that normal load and sliding speed had little effect on the friction coefficient of a hard much fiber wenge (Millettia laurentii). By contrast, sliding speed significantly affected that of a soft porous tamarisk (Tamarix aphylla). The groove of wood surface could store wear debris. The tamarisk had more groove shape vascular cells than the wenge so that the tamarisk friction coefficient was smaller than that of the wenge. Furthermore, the viscoelasticity of the tamarisk was higher than that of the wenge. The tamarisk friction force which was derived from the deformation resistance was smaller than that of the wenge resulting in the tamarisk friction coefficients being smaller. The micro-hardness and elasticity modulus of the tamarisk were lower than that of the wenge resulting in the friction interface contact surface being larger than that of the wenge. The tamarisk grinding trace sizes were bigger than that of the wenge.

Research on friction and wear behavior of a bulk metallic glass under different sliding velocity

Linear reciprocating sliding friction and wear behavior in a Zr55Cu30Ni5Al10 bulk metallic glass (BMG) at different sliding velocities was investigated. The friction and wear tests nearly have not changed the amorphous structure and thermal stability of the BMG. The sliding velocity significantly affects the friction and wear behavior of the BMG. During the frictional and wear tests, the average frictional coefficient locates between 0.244 and 0.302 and increases gradually with increasing sliding velocity. The grinding trace width locates between 36μm and 227μm and descends gradually with increasing sliding velocity. The grinding traces exhibit smooth linear furrows, on both sides of which some heaping alloy scraps can be observed, while at the ends of which these accumulation extent of surface alloy scraps becomes more serious. The smaller the sliding velocity is, the more serious the wear extent is. At smaller sliding velocities, the wear mechanism inclines to the combined effects of continuous wear, occlusion or bite welding, adhesive wear and abrasive wear. With the increase of sliding velocity, the wear mechanism changes gradually to a combined result of slight bite or bite welding and continuous wear.

Wear analysis of the offset type preloaded ball–screw operating at high speed

In a high-speed ball–screw transmission system, a preload is always applied in the ball–screw to avoid vibration and backlash during all linear transmission periods. However, the sliding wear is the main reason why the applied preload decreases or vanishes. This study presents a new two body abrasion model combining the kinematic theory describing the variations in the axial wear depths with the operating strokes, which is related to the preload directly. The contact shape of the contact asperities is considered to be an elliptic area with a different ellipticity ratio to simulate the grinding trace of a raceway. The total wear depth of the axis direction is dominated by the wear depth of an asperity, the contact ratio between the plastic and normal contact areas, and the wear frequency due to the relative speed of the two contact surfaces. The axial wear depth increases with a raising operating stroke, an increasing rotational speed, and a small ellipticity ratio for the contact shape. Analysis of the results indicates that a high ellipticity ratio of contacting asperities on a raceway can effectively reduce the increasing rate of wear in an offset type preloaded ball–screw when operating in a high rotational speed.

Effect of Load on Linear Reciprocating Sliding Friction and Wear Behavior in Zr-Based Bulk Metallic Glass

The effect of load on linear reciprocating sliding friction and wear behavior in a Zr55Cu30Ni5Al10 bulk metallic glass was investigated. With increasing load, the average friction coefficient descends, while the grinding trace width increases. The grinding traces exhibit smooth linear furrows. The larger the load is, the more serious the wear extent exhibits. Under smaller loads, the wear mechanism inclines to a combined result of slight bite or bite welding and continuous wear. While with the increase of load, the wear mechanism changes gradually to the combined effects of continuous wear, occlusion or bite welding, adhesive wear and abrasive wear.

Effects of ion implantation on surface structures and properties for bulk metallic glass

A plate-like Zr 55Cu 30Ni 5Al 10 bulk metallic glass (BMG) was prepared and Co ion implantation was carried out. The effects of ion implantation on surface structures and properties of the BMG have been studied. The results showed, after Co ion implantation, the BMG specimen still maintained an amorphous structure on the whole. Ion implantation changed the thermodynamic parameters and enhanced the thermal stability of the amorphous alloy. Along the depth direction, cobalt element implanted basically existed in a metal state. The maximum enhancement of surface micro-hardness was about 103 Hv or 18%. The average friction coefficients before and after ion implantation were 0.331 and 0.168, respectively, and the corresponding grinding trace widths were 80.23 and 60.17 μm, respectively, i.e., the Co ion implantation has reduced the average friction coefficient and corresponding grinding trace width by about 52.3% and 32.68%, respectively. The reasons of efficient improving the surface performances by ion implantation surface modification in BMG were analyzed and discussed.

Geometrical Simulation of Surface Finish Improvement in Helical Scan Grinding Method by Means of 3D-CAD Model

Estimation of mechanism of surface finish improvement in helical scan grinding, a method in which a good surface finish is obtained besides keeping a high grinding efficiency, is performed based on the virtual grinding trace using a 3D-CAD model. In three grit models, (a) a single grit on a wheel, (b) plural grits arrangement on a helical line on the wheel circumference, and (c) multiple grit arrangement in a triangular pattern, virtual grinding traces and their unevenness or surface roughness are investigated. The virtual grinding trace in helical scan grinding is made by interference of grit trajectories, and the results of the analysis are very similar to experimental results.

Machining of micro aspherical mould inserts

Abstract This paper reports a parametric investigation and development of grinding technologies for micro aspherical mould inserts using parallel grinding method. The parametric investigation revealed that at nanometric scale the undeformed chip thickness has little influence on the surface finish of ground inserts. The grinding trace spacing has a slightly larger influence on the surface finish. A new technique was developed to true and dress the resin bonded micro wheels with mesh size of #3000, which produced a satisfactory wheel form accuracy and relatively high grain packing density. A form error compensation technique was also developed, with which mould inserts of submicron form accuracy were consistently produced. Using the developed technologies, micro aspherical inserts of diameters ranging from 200 μm to 1000 μm with surface finish of around 10 nm and form error of ∼0.2–0.4 μm were successfully fabricated.

Impact of grinder configurations on grinding rate, particle size, and trace element contamination of plant samples

Samples of varying abrasiveness, including rice hulls, rice straw, wheat grain, orange leaves, and filter paper, were ground to pass a 0.5‐mm screen in two cyclone mills (Tecator Cyclotec model 1093 and Newport Scientific model 6200) with original and modified internal components. The ground samples were then digested in nitric acid and analyzed for 12 elements by Inductive Coupled Plasma (ICP) spectroscopy. Analysis of aluminum (Al), copper (Cu), iron (Fe), and zinc (Zn) showed that the amount of metal contamination from each mill was related to the abrasiveness of the plant material and the metal composition of the internal components of the mill. Least contamination was achieved using the Newport Scientific 6200 mill fitted with a stainless steel impeller and an abrasive steel strap with industrial diamonds set in pure nickel. For abrasive samples such as rice hulls a stainless steel impeller was about six times more durable than an aluminum impeller. The Newport mill ground samples in less time and reduced plant dry matter to finer particles, but impeller wear caused more variation in the distribution of particle size, than the Cyclotec mill.