Yeou-Yih Lin

The effects of various ceramic-metal on wear performance of clad layer

Abstract This work deals with the wear performance of clad layers, which clad WC and TiC powders on medium carbon steel by gas tungsten arc welding (GTAW) method. Various metal powders with equal percentage by weight were added to the base powder (WC, TiC) to prepare the cladding materials, which were used to study the effects of various ceramic–metal cladding materials on clad surface wear resistance ability. A rotating type tribometer was used to evaluate the wear behaviors of different cladding specimens under dry sliding conditions. According to the experimental results, the specimen clad by WC-based powder contains certain Ti metal powders which had the best wear performance in all WC clad specimens. In all TiC cladding specimens, the TiC with W clad layer had superior wear performance to the other cladding specimens under low sliding speed condition. On the contrary, the TiC with Cu clad layer was superior to the other cladding specimens under high sliding speed condition. In addition, oxide films influence the wear behaviors of different specimens during wear testing, and at some conditions oxidation wear would dominate the wear behaviors of clad layer.

Finite element modeling for chemical mechanical polishing process under different back pressures

Abstract In this paper, the revolutions of wafer and pad were considered the same and the force forms including the pressure exerted on the top of wafer surface and the carrier back pressure were axisymmetric distributed, a 2D axisymmetric quasi-static model for chemical mechanical polishing process (CMP) was first established. Based on the principle of minimum total potential energy, a 2D axisymmetric quasi-static finite element model with a carrier back pressure compensation for CMP was then established. In this model, the four-layer structures including wafer carrier, carrier film, wafer and pad are involved. The effect of a given carrier back pressure on the stress components and von Mises stress on wafer surface was analyzed and the effect of different carrier back pressures on the von Mises stress and nonuniformity on wafer surface was investigated. The findings indicated that the axial stress was the dominant factor to the von Mises stress distribution on wafer surface. Because that the back pressure had the maximum affect on the axial stress and it made the axial stress increased along the − z direction. Thus, while applying a back pressure, the von Mises stress distribution increased. In addition, the changes of back pressure had the trend to be proportional to the von Mises stress variation and to be inversely proportional to the nonuniformity variation. The result showed obviously that during the CMP process, it could achieve the purpose to improve the planarization of wafer surface by compensating the different carrier back pressures.

A study on the wear behavior of hardened medium carbon steel

Abstract It is well known that the mechanical properties such as strength and hardness of structural steel are usually enhanced by the martensite-phase transformation method. In many industrial applications, hardness has always been used as an index to reflect the wear-resistance performance. As a result, steel is quenched to a large extent in order to increase the hardness and wear-resistance performance. In general, from the wear mechanism, no exact relationship between the hardness and wear resistance of materials can be formulated. Also there are few conclusive studies on the effects of running procedures on wear-resistance performance. Therefore, the friction behavior of S45C carbon steel with and without a quenching process was evaluated by a rotating tribometer under various test conditions. The experimental results show that the running conditions cause a great influence on the wear-resistance performance of the materials. Under low speed and light apparent pressure conditions, the quenched specimens have high wear-resistance performance. Contrarily, at high speed and heavy loading, the wear-resistance performance of hardened specimens decreases due to tempering effects at the rubbing surface when the contact temperature becomes increased. Therefore, this causes more severe wear to the hardened specimens than to the unhardened specimens.

A study of oblique cutting for different low cutting speeds

Abstract In this paper, the finite deformation theory and an updated Lagrangian formulation (ULF) were used to describe the oblique cutting process. Either the tool geometrical location condition or the strain energy density constant was combined with the twin node processing method to be adopted as the chip separation criterion. An equation for 3D tool face geometrical limitation was established to inspect and correct the relation between the chip node and tool face. In addition, a 3D finite difference equation for heat transfer was derived. Based on this approach, a coupled thermo-elastic–plastic large deformation finite element model for oblique cutting was established, for which mild steel was used as the workpiece material and P20 as the tool. Under the different cutting speed conditions, the chip deformation process and the effect of different cutting speeds on the chip flow angle, cutting force and specific cutting energy were first explored. Then, the effect of different cutting speeds on the separation location of the chip node and the geometrical phenomenon at the instant of chip separation from the tool face, and on both stress and temperature distributions on the chip surface, were analyzed. Finally, the effect of different cutting speeds on the residual stress, displacement and temperature distributions on the machined surface after cutting were investigated to understand the relation between the cutting speeds and the integrity of the machined surface. During the chip deformation process, the simulated chip flow angles under the different low cutting speed conditions approximately matched with the designated tool inclination angle, which complied with the geometrical requirements of Stabler’s criterion. Further, the simulated specific cutting energy under a given low cutting speed condition was compared with the experimental data, the result of which was within an acceptable range, and the trend of specific cutting energies under the different low cutting speed conditions were the same as the experimental trends. It is obvious from the above findings that the model presented in this paper is consistent with the geometrical and mechanics requirements, which verifies that the proposed model is acceptable.

An investigation of sticking behavior on the chip–tool interface using thermo-elastic–plastic finite element method

Abstract This paper presents a high-speed orthogonal cutting model and also establishes a finite element method to analyze the mechanics of steady state in the high-speed orthogonal precision cutting process of oxygen-free high conductivity copper. The paper proposes a variant pseudo-friction coefficient concept to modify the large-deformation finite element formulation and to develop a stress analysis model of the chip–tool interface to solve the problems of the shear stress, normal stress and variant pseudo-friction coefficient on the chip–tool interface. In spite of the high-speed micro-cutting, the effect of high strain rate and high temperature will produce the sticking phenomenon on the rake face of the tool. Not only will the sticking phenomenon shorten tool life, but also will have an effect on the machining accuracy in precision diamond cutting. Therefore, the results in this study can be considered as acceptable consideration during the procedure of high-speed precision cutting.

A study of an oblique cutting model

Abstract The finite deformation theory and the updated Lagrangian formulation (ULF) were used to describe the oblique cutting process in an attempt to develop an oblique cutting elastic–plastic finite-element analytical model. In this paper, an elastic–plastic stiffness matrix equation was first derived. The geometrical non-linear quality of the material was also taken into consideration to infer the appropriate geometrical stiffness matrix. Under the condition of balanced variation rate of the surface force before and after deformation, the load corrective matrix was derived. At the same time, the friction force on the chip–tool interface was transformed into a friction corrective matrix based on the Coulomb friction law. The above matrices were combined into an elastic–plastic finite-element governing equation. With either the strain energy density constant or the geometrical condition as the chip-separation criterion, an equation of 3-D tool face geometrical limitation was established to examine and correct the chip node. Based on this approach, the tool advancement was achieved in displacement increments step-by-step from the initial tool contact with the workpiece until the formation of a steady cutting force. Mild steel was used as the workpiece in this study and P20 as the tool. The cutting simulation was conducted under a lower cutting speed of 274.8 mm s −1 and a constant temperature of 25°C to analyze the variation of the physical properties of workpiece. During the deformation process, the chip flow angle along the chip node flow direction approximately matched the tool inclination angle, which satisfied Stabler’s criterion and proved the accuracy of the chip geometrical shape of the present model. At the same time, the multiplication of cutting speed and cutting force obtained by the coordinate transformation of the force component on the chip was used to establish the specific cutting power on the basis of the unmachined workpiece cross-section. This simulated value also matched experimental findings, which further verified the feasibility of the present model.

Influence of a Retaining Ring on Strain and Stress in the Chemical Mechanical Polishing Process

In this article, a two-dimensional axisymmetric quasi-static finite element wafer scale model for chemical mechanical polishing (CMP) process involved in the wafer carrier, the carrier film, the wafer, the pad, and the retaining ring was developed to investigate the effect of a retaining ring surrounding the wafer carrier to the strain, stress, and nonuniformity of the wafer surface for the purpose of improving edge exclusion of wafer and preventing the wafer sliding from the carrier while grinding. Considering the same revolutions of the wafer and the pad and the axisymmetric distributed force forms of the wafer carrier and the retaining ring, and applying the principle of minimum potential energy, a two-dimensional axisymmetric quasi-static finite element model for CMP process was established. Following the developed model, the effects of the retaining ring on the strain components, the stress components, the von Mises stress, and the wafers nonuniformity were investigated. The findings indicated that a retaining ring installed in the conventional CMP mechanism could reduce the variation of the von Mises stress distribution to reach the lower wafers nonuniformity effectively, improve the over-grinding phenomenon and prevent the wafer sliding from the carrier while grinding.

Modeling of chemical mechanical polishing process using FEM and abductive network

In this paper, modeling of a two-dimensional axisymmetric quasic-static finite element model in conjunction with an abductive network for chemical-mechanical polishing process (CMP) was established. Three prediction models can be achieved, i.e., model for von Mises stress at wafer center, model for maximum von Mises stress and model for nonuniformity on wafer surface under various combinations of process parameters. The data of von Mises stress and nonuniformity on wafer surface can be first achieved under different conditions of the carrier load, pads elastic modulus and thickness by using the developed finite element model for CMP. Next, an abductive network was applied to synthesize the data sets from the FE simulation. It is a self-organizing adaptive modeling tool that establishes the mathematical relationship between input and output variables based on abductive modeling technique and it can automatically synthesize the optimal network structure, including the optimal network structure, the number of layers and the form of functional nodes. Finally, the results from the three developed abductive networks with test data are compared with those from FE simulation to confirm the feasibility of this approach. The findings verified that the results confirm the feasibility and the proposed prediction models for CMP are acceptable.

APPLICATION OF ABDUCTIVE POLYNOMIAL NETWORK AND GREY THEORY TO DRILL FLANK WEAR PREDICTION

An abductive polynomial network for drill flank wear prediction was established, in which grey relational analysis was incorporated to explore the effect of various drilling parameters on flank wear. An abductive polynomial network usually includes multiple layers, each of which contains different polynomial functional nodes. It can automatically synthesize the optimal network structure, including the optimal number of layers and the optimal form of functional nodes. The correlation between the drilling input parameters, including the average thrust force, torque, cutting speed, feed and drill diameter, and drill flank wear can be achieved through this network model. Based on experimental data, the developed network of this paper attained better accuracy in predicting drill flank wear, given the CPM of 0.1. The findings prove that the network is feasible and accurate in predicting flank wear. In addition, grey relational analysis was used in this paper to investigate the effect of the aforementioned five drilling parameters on flank wear. According to the analytical results, the most influential factor on flank wear is drill diameter, followed by the average thrust force.

Relationship between the Punch–Die Clearance and Shearing Quality of Progressive Shearing Die

This study performed experiments for the progressive shearing die of thin phosphorous bronze sheet to investigate effects of punch materials, punch–die clearance, sheared angle, and number of shearing strokes on burnish band of a sheared surface and burr width of shearing corner. It also analyzed the relationship between height of the burnish band and gravimetric wear rate. The concept of manufacturing tolerance was applied to establish an analytical model of the dimensional tolerance between punch and punch base. It was concluded that after assembling the punch and punch base under the worst conditions, the possible offset of the punch center and the punch–die clearance can be analyzed, and the burr width of the shearing corner can be accessed. Based on the experimental data, four linear predictive models elucidating the characteristics of shearing qualities such as punch–die clearance, punch gravimetric wear rate, and height of the burnish band of a sheared surface can be deduced. Besides, a predictive model of burr width was built by using the least-square method, exponential method, and polynomial regressive method. The result is highly referential to the assessment of sheared products as well as the prediction of tool life.