Applied Mechanics and Materials Vols. 10-12

Abstract: Resistance spot welding (RSW) is widely employed in sheet metal fabrication, in particular in automotive bodies and structures. Manufacturers are increasingly demanding reduced design periods with improved safety requirements, which could potentially be achieved through computational simulations. This paper presents an integrated approach combining simulation of the welding process, materials characterisation and mechanical modelling to study the effect of welding parameters on the strength of spot-welded joints. The welding process was simulated and the dimensional attributes were used to build the mechanical models for strength analysis. The constitutive material properties of the base, nugget and the heat-affected-zone (HAZ) were determined by an inverse FE modelling approach using indentation test data. The predicted deformation of spot-welded joints of a typical automotive steel under tensile-shear load showed a good agreement with experimental results. The validated models were further used to predict effects of welding parameters on the strength and failure behaviour of weld joints. Potential uses of the approach in optimising welding parameters for strength were also discussed.

Abstract: Aiming at the influence law of indenter tip radius to indentation hardness, testing on the hardness of single-crystal silicon was carried out based on nanoindentation technique. Two kinds of Berkovich indenter with radius 40nm and 60nm separately were used in this experiment. According to the load-depth curve, the hardness of single-crystal silicon was achieved by Oliver-Pharr method. Experimental results are presented which show that indenter tip radius influence the hardness, the hardness value increases and the indentation size effect becomes obvious with the increasing of tip radius under same indentation depth.

Abstract: In this paper, the temperature distribution is analyzed during ceramic sintering process and the temperature difference variation is compared under the linear sintering curves with different slopes. Then the changes of temperature difference curve are analyzed under both linear sintering curves and step sintering curves with different slopes. The results indicate that: there are overlap area and platform area in all the temperature difference curves; all the temperature difference curve change from overlap area to platform area; the max temperature difference can not be reduced effectively by applying the heat preservation process at any time; the max temperature difference can be reduced effectively when the heat preservation process is applied at the time of the curve being at the overlap area; the reduction of max temperature difference is small when the temperature difference curve approaches the platform area.

Abstract: In order to realize general management of PCBN tool multimedia information, this paper set up multimedia cutting database of PCBN tool on the platform of Visual Basic, mainly applied database interface technology of Visual Basic and database management system of Microsoft SQL Server 2000. Aimed at the characteristic of large video data, handling relative path was brought forward as a method. Practice proved that handling relative path could realize all functions the database needed, and increase system running speed, general management of PCBN tool information under different machining conditions was realized.

Abstract: This article focuses on a case study, described in the following description, concerning a novel design for a hardening shop for universal mill heavy rail. The case offers a comparison between traditional un-structured creativity methods and the systematic process offered by CAI software. And it also described a structured approach for manufacture process equipment innovation.

Abstract: Most mechanical parts like bearings, gears, and shafts are produced by finishing processes such as hard turning, grinding and/or honing. The durability and reliability of these precision products are directly influenced by mechanical behavior of material. If those parts are in micro nano scale such as micro interconnector, micro valve, micro actuator, and micro switch in that case micro nano mechanical properties is an important factor for better performance. This present paper discusses the low energy ECR ion beam irradiation effects on mechanical property of material in micronano scale. To complete this research ion beams were irradiated for different accelerating energy to Si surface. Nano indentations were done for hardness and elasticity measurement. AFM was used for roughness and depth measurement. From data analysis It shows accelerating energy is an important factor to control mechanical property of material during nano scale fabrication by ion beam.

Abstract: This study investigated the model and simulation of dynamic cutting forces for high speed end mills, performed frequency spectrum analysis of dynamic cutting forces, and propounded the model and failure criterion of high speed end mills with indexable inserts. According to results of modal analysis and stress field analysis, the safety prediction and experiment of high speed end mills for machining aluminum alloy were done. Results indicate that more teeth of cutter and greater cutting contact angle make the energy more dispersible, higher cutting speed and greater rake of cutter can depress dynamic cutting forces. The rigidity failure rotational speed is higher the strength failure rotational speed, the connection strength between cutter body and screw bolt affects directly the safety of cutter. The model of high speed end mills based on spectrum simulation for dynamic cutting forces, and the safety prediction based on finite element analysis should be applied to the development of high speed end mills as an effective means.

Abstract: Machining hardened steels has become an important manufacturing process, particularly in the automotive and bearing industries. Hardened steel GCr15 with its harness between HRC50 and HRC65 is one kind of more difficult machining material. Abrasive processes such as grinding have typically been required to machine hardened steels, but advances in machine tools and a new cutting material of polycrystalline cubic boron nitride (PCBN) have allowed hard turning on modern lathes to seems to gain an ever increasing industrial acceptance as an economically and environmentally friendly alternative to many grinding applications. In this paper, based on large deformation theory and updated Lagrangian procedure, a coupled thermo-mechanical plane strain orthogonal precision cutting model with general finite element analysis software is developed to the influence of cutting edge preparation on the cutting of GCr15 with PCBN tool, such as cutting forces, shear angle, and cutting temperature. The three major designs of cutting edge preparation are used on most commercial cutting inserts: a) sharp edge, b) honed edge, and c) chamfer edge. The friction between the tool and the chip is assumed to follow a shear model and the local adaptive remeshing technique is used for the formation of chip. The calculated principle cutting forces are compared with published data and found to be in good agreement. The simulation results can be used as a practical tool both by researchers and toolmakers to design new tools with rational tool edge and to optimize the cutting process.

Abstract: The nickel-based superalloy GH4169 is a typical difficult-to-cut material, but it has been used in a good many kinds of aeronautical key structures because of its high yield stress and anti-fatigue performance at the temperature below 650°C. In this paper, finite element method (FEM) was introduced to study the saw-tooth chip forming process in detail when machining nickel-based superalloy GH4169. By the way of Lagrangian visco-elastic plastic approach, adiabatic shear band (ASB) was simulated in high speed machining condition by general commercial finite element code, and the mechanism of the adiabatic shearing phenomenon at primary shear zone was analyzed with the help of finite element analysis (FEA). The comprehensive comparisons of saw-tooth chip morphology under a wide range of cutting speed were also presented.

Abstract: This paper introduces the characteristics and general laws of cutting complex curved surface by Wire-cut Electric Discharge Machining (WEDM) system. Taking the three-axle and double-rotating linkage system as an example, the universal mathematical model of polar coordinates is derived. Moreover, the simulation of WEDM system is introduced, which utilizing language Visual C++ and the three dimensional graph software OpenGL.This simulation method is helpful in improving machining quality and productivity of complex curved surfaces, and is fundation for establishing CAD/CAPP/CAM technology in WEDM.