Advanced Materials Research Vols. 76-78

Abstract: Miniature parts with high accuracy and precision are increasingly in demand for various industries. Microturning is a process for fabrication of such miniaturized parts with features that range from tens of micrometres to a few millimetres. In this present study commercially available Oxygen Free High Conductivity (OFHC) copper rods have been microturned using cermet inserts of 0.1mm nose radius. The effects of machining parameters on the surface generated have been discussed. Scanning electron microscope images of worn out inserts and machined surfaces are analysed to ascertain the wear mechanism and study the nature of the surface generated.

Abstract: With the technology advancement, crystal plasticity finite element modeling becomes more and more popular in the simulation of metal forming process. In order to obtain a better understanding of the difference between the Taylor model and finite element model during the simulation of metal forming process, an implicit time-integration procedure with the two polycrystal models is applied in the commercial finite element code ABAQUS to simulate the plane strain compression separately. FCC metal is used in this study. The simulation shows that the two polycrystal models both can predict the compression process approximately. The two modelling results of surface roughness show an agreement with that of the experimental results. However, the side profile calculated by the Taylor polycrystal model is much steeper and straighter than that of finite element polycrystal model. The experimental surface roughness curve shows a high frequency fluctuation. It is much steeper than those of the two models. The simulation results also show that the von Mises stress from the Taylor model is much higher than that of the finite element model.

Abstract: Surface roughness plays an important role in determining the tribological behaviour of mechanical components (e.g. gears and roller bearings etc.) under full-film and mixed (or partial) elastohydrodynamic lubrication conditions. This paper describes a detailed mechanics analysis of the surface roughness transformation of thin strip which has been cold rolled on an experimental mill. Low carbon steel strips were rolled at various speeds and reductions, and the effects of rolling parameters on surface roughness are studied. The results of surface roughness can provide important information to optimise the rolling schedule and to improve the rolled strip quality.

Abstract: During the cold rolling of thin strip on the 1220mm five-stand tandem cold mills, scratch marks occur on the surfaces of strip and work roll. The surface quality of strip is degraded and the roll wear increases, which resulting in significant economic loss. In this paper, the mechanics of strip scratch marks was studied by carrying out both field experiments and theoretical analysis. Slippage Factor (SF) and Scratch Mark Factor (SMF) were presented to indicate the conditions of strip scratch marks. Meanwhile, mathematical models and simulation code were developed to optimise the rolling schedules and to improve the scratch marks. The practical application of the developed models to the 1220 mm five-stand tandem cold mills verifies the effectiveness of the developed models. The mathematical models can be applied to other similar tandem cold mills.

Abstract: There are many defects on the surface of continuous casting slab, such as corner cracks, longitudinal cracks etc. To analyze the cracks and determine their locations, two-dimensional heat transfer mathematical model and thermal elasto-plastic stress model of slab casting were established in this paper. The process of solidification, temperature field, and thermal stress distribution on slab surface were analyzed using finite element method. The effect of thermal stress on the cracks on the slab surface was discussed. The location of the cracks caused by thermal stress can be predicted. This is useful for finding approaches to overcome these defects.

Abstract: Two-dimensional micro mix driven by electroosmotic flow was studied by finite element simulation and mixes speed of microchannels with unified zeta potential of the wall surface and the polar opposite one was contrasted. Relation between the section shape of the microchannels and the speed of mixing is cleared when the wall surface has the polar opposite zeta potential. The results show that section mixing speed of microchannel whose wall surface with unified zeta potential is lower than the one with polar opposite wall surface zeta potential. The ratio of width to height in microchannels of homolographic rectangle section and the height of microchannels with isosceles trapezoid section also have influence on mixing speed. When former increases or later decreases the mixing speed rapidly increases and then drops slowly. The mixing speed arrived at maximum value when the former and the later are 1.44 and 10μm, respectively.

Abstract: The present work is aimed at optimizing the parameters of micro Wire Electric Discharge Machining (µ-WEDM) process by considering the simultaneous effects of input parameters viz: gap voltage, capacitance and feed rate. Experiments were planned and conducted using DoE techniques. ANOVA was performed to find out the significance of each factor. Regression models were developed for the experimental results of surface roughness and overcut of the micro slots produced on aluminium. Then Genetic Algorithm (GA) was employed to determine the values of optimal process parameters for the desired output value of micro wire electric discharge machining characteristics.

Abstract: Micro WEDM is a versatile technique used to machine electrically conductive materials to make components for micro system technologies. This paper presents an attempt to develop an appropriate machining strategy for micro WEDM of titanium alloy using zinc coated copper wire of 70 µm diameter. Voltage, capacitance, feed, wire tension and wire speed were taken as input parameters. Surface finish is considered as the measure of process performance. Design of experiments was done using Taguchi L16 orthogonal array and optimization was carried out using Taguchi S/N ratio technique. The results obtained from the experiments were analyzed with ANOVA method to find the significance of each input factor on the surface quality. In addition ANN model was developed and trained.

Abstract: A micro-grooving method by ultrasonic machining with a lamination tool has been devised. Thin walls on the tip of an ultrasonic tool can fabricate many grooves on a workpiece by one ultrasonic-machining process. Thinner wall for fabricating micro grooves, however, poses the lack of the stiffness of the tool, resulting in the difficulty of the grooving. Then the walls are enfolded with a soft material such as a polymer plastic to supplement the lack of the stiffness. Since soft material absorbs the energy of the ultrasonic vibration, the damage by the impacts of the abrasive particle on the workpiece surface under the soft material is little. Therefore multiple micro-grooves can fabricate efficiently by using of a lamination tool in which thin hard-materials and thin soft-materials are laminated alternately. In this paper, the lamination tools were developed with a thin shim-sheet as the hard material and an epoxy adhesive as the soft material. The fabrication experiments of the parallel grooves on alumina ceramics were conducted. This paper investigates the influences of the parameters of ultrasonic machining such as the grain size of the abrasive particle, the static machining load or static normal stress applied to the tool-workpiece contact region and the grooving time upon the characteristics of the micro-grooves. The results show that the grooving efficiency depends on the grooving time and the static normal stress. Finally, some applications are shown.

Abstract: Industrial application of synthetic diamond ceramics is growing very fast due to their super hardness, superb wear resistance and long-life durability. In rock, concrete and metal cutting, drilling, mining and quarrying and dimension stone industries, cutting tools made of diamond composites or impregnated diamond composite segments are gradually replacing the more commonly used cemented tungsten carbide (WC) tools. Through its SMARTCUT research program, CSIRO in the past 15 years has developed harder and stronger thermally stable diamond composite (TSDC) drag picks to encourage and help manufacturing and mining industries improve their cutting performance by replacing these traditional WC cutting tools with the new revolutionary TSDC tools. This improvement process however is much more complex than a simple material or cutting tool replacement, since the mechanism and configuration of cutting are substantially different in the two cutter head systems and its successful implementation requires a better understanding of the basics of rock cutting. Some of the factors influencing the differences are: cutter wear, fracture toughness, compressive and tensile strength, thermal properties, geometrical shape, spacing, angle of attack, rake angle, sharpness and bluntness characteristics, lacing design and cutter arrangements. Besides, it is most important to understand the relation between the tool or tool force and the fragmentation of the rock, which is the main focus of this paper.