A new working style assisted with various computer technologies is reviewed in this article for improving the planing stage and manufacturing stage in welding and joining engineering. A new production system fully supported with some computer systems are introduced at the first section, and specified each relevant systems to planning and the manufacturing stages, separately. The systems have been developed with many computer simulation codes, co-simulation tools, AI tools, and many types of sensing and capturing tools of the welding state data, which can be used in the high current fields. Finally, some typical research results relating to this CAWS are summarized to show the current state of researches including recurrent model of Neural networks, hybrid simulation, and an example of professional skill database.

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This report describes the observation result of joining phenomena in the friction stage, and an improvement of the conventional friction welding method with similar materials. The materials used were carbon steels and a brake type (direct drive) friction welding machine was used for joining. As the improving friction welding method, relative speed was instantaneously rendered to zero at the end of each friction time. The wear of both surfaces started at periphery portion (outer surface) of the joint and moved to center portion (center axis). Seizure and joining began at center portion and then extended toward periphery portion. The friction torque reached to initial peak torque when the welded interface was joined completely and upsetting of both substrates started. It was determined that friction welded joints with 100% joint efficiency and good bend ductility could be obtained by using only the friction stage up to initial peak torque and without the need for the forging (upsetting) stage. As a conclusion, friction welded joints made without using the forging stage has the same mechanical properties as those welded by the conventional friction welding process including that stage. The friction welding method without forging stage has the advantages of less burn-off (axial shortening) and less burr.

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The possibility of joining composite materials, conventional steel and lighter aluminum alloys, is tested using friction welding that preserves the natural environment greatly. The friction welding of aluminum alloy, Al-Mg (A5056), and carbon steel (S45C) are done under various experimental conditions and the friction welding characteristics are examined. The mechanical property (tensile strength) of the welded specimen has enough strength under the friction welding conditions of 1000 rpm, the friction pressure of above 20MPa, the friction time of less than 1 second and a quite high upset pressure near the plastic flow pressure of A5056. The macroscopic and microscopic interface structures are also examined in relation to the friction welding conditions in order to clarify the joining mechanism of the interface between different materials by the friction welding. Moreover, the heat quantity during friction welding that relates closely to the generation of the inter-metallic compound and the joining mechanism is also examined. The amount of upset that relates closely to the mechanical properties of the welded specimen is also examined.

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Friction-stir welding of 6061,2024,2219,and 7075 aluminum alloys to themselves as well as dissimilar systems of 6061/2024 and 2219/7075 aluminum alloys are studied to produce sound welds, and to characterize the microstructure, material flow, and properties of their butt joints. The material flow patterns are clearly revealed by the flow visualization marked with a copper-powder tracer technique in the welds of 6061 aluminum alloy. The copper powder is placed at the whole, the top, the middle, and the bottom third of the faying surface along the welding direction. Although all the nugget zones are composed of fine equiaxed grain, structures, significant differences in the plastic deformation and flow patterns have been observed throughout the same and dissimilar friction-stir welds. A significant hardness loss at the thermomechanical affected zone (TMAZ) and the heat affected zone (HAZ) is found throughout all the welds as compared to the nugget zones and the parent metals, The dissimilar metal welds exhibit complex alternative lamellae that produce distinct hardness fluctuations in the nugget zone. At the top surface of the weld, the material transport occurs due to the action of the rotating tool shoulder. The inward return flow in the interior of the nugget zone appears much stronger than the outward surface flow along the weld surface. Dissimilar metal Welds are successfully performed to further characterize the degree of material mixing and interdiffusion, the thickness of the deformed aluminum lamellae.

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Braze Pressure Welding (B. P. W.) with high frequency induction heating has been invented as the new joining method for bonding general steel pipes for piping. The piping with B. P. W. has many merits as follows : small deformation at joint, less influence by heating around the joint, the fillets formed on the steps at the edge of joint. Especially the fillet relaxes the stress concentration, and makes the tensile strength of piping comparable to that of base metal. B. P. W. requires less skill for joining, so tensile strength of piping has less variation by welders. It has high work efficiency, and high portability without large equipments. The less potential danger of fire enables on-site B. P. W.' application even for indoor piping and repairing.

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TIG arc welding and laser welding are used widely in the world. However, these wilding processes have some advantages and problems respectively. In order to improve problems and make use of advantages of the arc welding and the laser welding processes, hybrid welding process combined the TIG arc with the YAG laser was studied. Especially, the suitable welding conditions for thin steel plate welding were investigated to obtain sound weld with beautiful surface and back beads but without weld defects. As a result, it was confirmed that the shot position of the laser beam is very important to obtain sound welds in hybrid welding. Therefore, a new intelligent system to monitor the welding area using vision sensor is constructed. Furthermore, control system to shot the laser beam to a selected position in molten pool, which is formed by TIG arc, is constructed. As a result of welding experiments using these systems, it is confirmed that the hybrid welding process and the control system are effective on the stable welding of thin stainless steel plates.

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Microstructure and strength properties of Sn-0.39∿3.9mass%Ag-0.5mass%Cu solder ball bonded by the reflow have been examined for the information of the influence of the cooling rate (5-200K/min) and the Ag addition. The primary Sn grain size has been finer with the faster cooling rate of the reflow. Ag3Sn dispersion precipitate in the primary Sn phase has coarsened with the slower cooling rate. The interface structure of the ball with under 1.21mass% has the flat Cu6Sn5 reaction layer. The column shape Cu6Sn5 layer is observed at the cooling rate over 100K/min. The hardness of the ball bonded at the faster cooling rate increases since the Sn grain size and Ag3Sn dispersion precipitate are finer.

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A pure aluminum and pure silicon were anodic-bonded to a borosilicate glass. The anodic bonds were studied by cross-sectional TEM. For al/glass, sodium was not completely depleted from a sodium-depleted region of glass. Diffusion paths of aluminum tended to grow into the sodium-depleted region from the metal. The paths were of γ-Al_2O_3. At a higher temperature, the paths grew longer and branched more. The aluminum diffusion accounted for the Al/glass bond formation. For Si/glass, sodium was almost completely depleted from the sodium-depleted region. Several regions that were not well understand existed in the glass near the Si/glass interface. Oxygen was likely to diffuse into silicon from glass, which resulted an amorphous SiO_2 region. It was then concluded that anodic material played key roles in ion-diffusion processes near metal/glass interface during anodic bonding.

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Porous ceramics have many attractive properties, and they are often used as joint structures. Subsequently, the stress and fracture analysis at the interface is a matter of concern. Recent stress analysis by finite element method (FEM) for such heterogeneous materials is going toward the multi-scale analysis considering the microstructures and the micro-macro coupling effect. To model the very complex microstructures, the homogenization theory has been considered to be effective and accurate with the help of FEM. In the former part of this paper, 3D micro-macro coupled analysis by this theory is presented with digital image-based modeling technique. Because the homogenization theory assumes the periodic array of a unit microstructure model, however, the interface stress of joint structure can't be analyzed. Hence, a novel multi-scale method named finite element mesh superposition method is proposed. A demonstrative example of a porous ceramics joint with interface crack is presented to show the accuracy and the effectiveness of the proposed method.

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In order to obtain sound welded joints in the welding of horizontal fixed pipes, it is important to control the back bead width in the first pass. However, it is difficult to obtain optimum back bead width, because the proper welding conditions change with welding position. In this paper, in order to fully automatize the welding of fixed pipes, a new method is developed to control the back bead width with monitoring the shape and dimensions of the molten pool from the reverse side by autonomous mobile robot system. This robot has spherical shape so as to move in a complex route including curved pipe, elbow joint and so on. It has also a camera to observe inner surface of pipe and recognize a route in which the robot moves. The robot moves to welding point in the pipe, and monitor the reverse side shape of molten pool during welding. The host computer processes the images of molten pool acquired by the robot vision system, and calculates the optimum welding conditions to realize adaptive control of welding. As a result of the welding control experiments, the effectiveness of this system for the penetration control of fixed pipes is demonstrated.

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A theoretical analytical model for cold-and-hot PV wrapping bond rolling of unbounded double-layers sheet is derived to explore the stress field at the roll gap by using the direct formulation without Runge Kutta numerical method. Constant shear friction between the rolls and the double-layers sheet and different roll speeds are assumed. In this study, the neutral points between the rolls are moved toward the exit and entrance respectively by controlling front tension, back tension and roll speed ratio; this situation is called as PV rolling. If the component layer of double-layers sheet is wrapped along the roll at the entrance, then called as wrapping. Besides the double-layers sheet is not bonded at the entrance, therefore, this study is more complicated. The rolling pressure distribution along the contact interface between the rolls and the double-layers sheet, the horizontal stresses in the component layers of the double-layers sheet, the rolling force, and the rolling torque etc., can be easily and rapidly calculated by using this analytical model. In addition, it is important to obtain the bonding point at the interface and the thickness ratio of double-layers sheet at the exit from this study. Moreover, the bonding conditions for the double-layers sheet are found to offer useful knowledge in performing the bond rolling so as to avoid the bond failure.

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This paper reviews modern meaning, mechanics, and applications of various joining and complex formation especially by plasticity technology. Recently they have come to be recognized as an effective mean for adding value to products as well as a structure-controlled deforming process. As the methods are suited to systems for small-lot production of varied items, they are likely to become even more important for the realization of new multifunctional elements and other purposes. A bond must be sufficiently strong while in use, but the members should be disassembled after use is completed. Modern ideal bonding or complex formation should stand the four essential points; performance of the complex member, simplicity of the bonding method, high bonding strength, and possibility of disassembly.

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End-user-driven product customization and continued demands for cost and time saving have generated a renewed interest in agile manufacturing based on improvements on Rapid Prototyping (RP) technologies. However, a shift from "prototyping" to "manufacturing" necessitates several improvements including a greater flexibility in choice of materials. This paper presents the development of a novel extrusion-based system, for fused deposition modeling (FDM) technology, which will broaden the range of material selection. It has been observed that in FDM the main obstacle for the use of new materials often comes from a need of an intermediate material form such as a filament. The novel system discussed in this paper, consisting of a mini-extruder mounted on a high-precision positioning system, is fed with bulk material in granulated form. This configuration opens up opportunities for the use of wider range of materials, making the FDM to become a viable alternative manufacturing process for specialty products.

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Large-scale geometries such as turbine blades, gears, precision ball bearing surfaces, injection molds and automotive bodies can be measured with relative ease and high accuracy using today's technologies. However, for small-scale geometries (i. e. microelectromechanical systems (MEMS)) such a technology does not exist. Accordingly, a non-dimensional comparison makes current tolerances of MEMS products comparable to tolerances achievable in 18_<th> century. The small size of MEMS products either makes them inaccessible for existing metrology instruments or makes the use of such instruments inefficient. This paper presents coordinate metrology results for micro-systems. In particular, the paper focuses on standardized algorithms developed for metrology in general, and then implements those algorithms for use in measuring small components. The algorithms are based on a least squares approach to data fitting. Both primitive geometric element analyses as well as point cloud to CAD model registration are discussed. initial results of micro-measurements are presented in the paper.

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The Authors report development of manufacturing-knowledge-database that deals the manufacturing stream and connection between knowledge of different manufacturing processes. Manufacturing knowledge databases tend to be developed independently in each process categories. However, the production is usually performed by multiple different processes as a stream from a raw material to a final product, and there is a problem that the former processes effect on the later process. Especially, it often takes important role in the improvement of the production and development of new technologies. It has been carried out in some huge enterprises to share the information between divisions dedicated to different manufacturing processes in a form to solve the problem, however, it is sometimes difficult for small and medium enterprises (SMEs) dedicated to a few manufacturing processes. The authors intend to develop the database components and its open applications for SMEs, that can connect each other across the manufacturing process categories and enable the collaboration of knowledge of database components. The authors investigate the point of the connection in change of internal state of materials and geometric effect and quality such as dimensions, roughness and structure of surface. The data is classified on each small topic including the above points to perform database component. The component is gathered manually and automatically at the presentation layer on web page and application software. The components are established with JAVA, HTML and XML on the network. The database is being developed on the IT-MT Unification Enterprise, one of enterprises of Digital Meister Projects of Small and Medium Enterprise Agency of METI..

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The main objective of this research is the development of machining strategy for sculptured surfaces in both rough finish cutting, In this study, the contour map strategy with three tool path patterns will be employed for the rough cutting. Here, Methods of optimal tool size selection and cutting layer determination will be suggested for rough cutting in the finish cutting, a modified CC (Cutter Contact)-variable algorithm will be used to determine the cutter contact points effect. In the finish cutting, the offset strategy will be used because the accuracy of the machined workpiece in the finish cutting is a more important issue than that in the rough cutting. The optical lens, a sculptured surface, is used as an industrial example through the research to show the effectiveness and efficiency of the developed CNC tool path generation strategy and database construction.

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The practical laser-guided deep-hole boring tool of 110mm diameter is produced for application and higher performance on the basis of the experimental results of the prototype tool. The practical tool consists of a counter-boring head, piezoelectric actuators for its attitude control, an active rotation stopper and a laser system for detecting its attitude. Experiments are conducted to examine the performance of this tool in detail using a duralumin (A2017-T4) workpiece with a prebored 108-mm diameter hole. To improve guiding accuracy, a guiding axis is optically arranged to bring in line with a desired one. Rolling of the tool is restricted by a rolling proof apparatus for detecting and controlling its attitude precisely. Results show that the practical tool can be guided to go straight through along the desired axis. The tool can be practically used to bore a precise hole using a rolling proof apparatus.

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In this paper, we adopt a 2D re-parameterization procedure to regenerate boundary-conformed toolpaths. Three methods for the 2D re-parameterization of trimmed boundaries in parametric space are examined and compared. They are the Coons method, the Laplace method, and a newly developed boundary blending method. Complete algorithms for surface re-parameterization and toolpath generation are developed and implemented. The results showed that compared with the other methods, the newly developed boundary blending method has advantages in both the computational efficiency and parameterization robustness, in addition, it alleviates the uneven distribution problem appeared in the Laplace results.

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Failure of thermal barrier coating (TBC) layer, especially spalling-off of ceramic coating layer, results not only in degradation of thermal barrier properties. but also in crucial damage to turbine components. The spalling of ceramic coating layer will follow the crack initiation on propagation along the interface between ceramic top-layer and metal bonding layer. In the present study fatigue crack growth tests of TBC with various porosity were carried out at room and elevated temperatures. It is found that the interface crack induced by a pre-introduced notch propagates along the interface under mixed mode condition, and its growth behavior can be well characterized by using the parameter [numerical formula]. which corresponds to the change of energy release rate. It is also found that the crack propagation resistance decreases with the increase of the porosity of the top ceramic coating. The crack propagation resistance also becomes weaker under the elevated temperature than under room temperature.

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This study focuses on the assessment of the surface quality of ground unidirectional carbon fibrereinforced plastics (CFRP) under different grinding conditions including the effect of fibre orientation. The mechanisms of surface defect formation were characterized by SEM, optical microscope and quantitative evaluation of surface roughness. It was found that the surface damage occurred mostly as micro cracking in matrix, fibre fracturing and fibre-matric debonding. The results showed that fibre orientation and grinding depth had a strong influence on surface integrity achievable. The wheel and table speeds also affected the ground surface quality under certain fibre orientation. Howerver, there existed an optimal group of grinding parameters under which the subsurface damage could be minimized.

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A Plasma display panel (PDP) is a type of flat panel display (FPD) utilizing the light emission that is produced by a discharge of gas. In this paper, a new type of PDP barrier ribs manufacturing process assisted by micro tooling technology was described and evaluated. The master pattern was made using the silicon wafer dicing process and then is transferred to a silicone rubber mold. Finally, the PDP barrier ribs were formed with the mold. This simple process is able to produce the high quality barrier ribs at a low cost.

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Selective Laser Sintering is one of the rapid prototyping technologies in the market. It was attracted much attention and interest since the introduction of metal object fabrication by metal layer sintering. The success of this technology mainly lies on its ability to fabricate complicated shape object in shorter time and cheaper cost. However the complexity of new metal object design has reached to a level that some special shape objects could not be fabricated without post infiltration joining works due to its process limitation. This paper has studied the feasibility of using brazing process in joining the sintered parts fabricated by selective laser sintering method. Suitable brazing metal were chosen by wettability test and the application example of the new model heat exchanger fabrication was discussed in this paper.

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The present paper describes the application of Kansei Engineering to physical design of engineering products as well as its realization by laser sintering. We have investigated information that might be included in three-dimensional objects such as ceramic bowl for tea ceremony. First, X-ray CT apparatus is utilized to retrieve surface data from the teabowl, and then frequency analysis is carried out after noise is filtered. The surface fluctuation is characterized by the power spectrum that is in inverse proportion to the wave number f in circumference. Second, we consider how to realize the surface with a 1/f fluctuation on a computer screen using a 3D CAD model. The fluctuation is applied to a reference shape assuming that the outer surface has a spiral flow line on which unevenness is superimposed. Finally, the selective laser sintering method has been applied to the fabrication of 1/f fluctuation objects. Nylon powder is sintered layer by layer using CO_2 laser to form an artificial teabowl with complicated surface patterns.

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Laser Based Additive Manufacturing (LBAM, laser metal powder deposition) is a promising manufacturing technology that can be widely applied to part reparation, surface modification, and Solid Freeform Fabrication (SFF). The thermal behavior of the molten pool is one of the key factors that influences the laser deposition performances such as geometrical accuracy and material properties. In this paper, the infrared image sensing of the molten pool is studied for the closed-loop control of the LBAM process. A high frame-rate (up to 800frame/s) camera with a near infrared (NIR) filter is installed coaxially at the top of the laser-nozzle setup. The camera setup provides a full view of the NIR image of the molten pool and its omnidirectional to the scanning directions. The high frame-rate camera with the NIR filter is calibrated by a black body. The edge of the molten pool in the NIR image is verified by the normal image acquired by an additional high shutter-speed camera installed beside the laser head. The calibrated NIR camera can measure the temperature and geometrical features of the molten poll accurately, and provide a quantitative prediction of the cooling rate. The laser output power is controlled according to the size of the molten pool. The experimental results show that the closed-loop control achieves a great performance improvement for the laser deposition process.

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In order to fully characterize the metal flow of an aluminum billet during the extrusion process, several modeling and simulation techniques can be employed. Material flow and strain distribution may be studied by a visioplasticity technique using modeling materials. Laboratory scale extrusion tests on engineering materials can be performed to determine the influence of processing parameters. The microstructural response of the material to processing variables may be obtained from a thermal mechanical simultor, which accurately reproduces thermal cycles of extrusion. The crystallographic evolution of grains during thermal-mechanical treatment including the effect of die design and surface deformation conditions can be investigated via Electron Backscatter Diffraction (EBSD). Finally, the stress and temperature gradients can be calculated with Finite Element Modeling (FEM). The combination of these techniques, all applied to different aspects of the extrusion process, can give a full account of how extrusion press conditions affect material flow and microstructure evolution.

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This paper deals with the complexly-shaped hat channel product, which combines a straight part with a curved part in the longitudinal direction. Twist in the longitudinal direction is the most typical and serious of all dimensional inacuracies in the product. Influencing factors in twisting can be classified into residual stress and residual moment. At first by varying forming conditions, such as blank holding force and cushion force, the influence of the residual stress generated on shrink and stretch flange on twist are investigated. Contrary to our expectation, the residual stress had almost no twist. Subsequently, by cutting flanges and side wall to release the residual moment, the influence of the residual moment on twist was investigated. It was observed that the residual moment plays an important role on twist. Based on the above, some parts of die radius are varied to control residual moment. As a result, it is experimentally found that twist decreased.

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In sheet metal forming, spring-back phenomenon is important issue and microscopic evaluation of materials is required. In this study, In order to clarify relationship between the changes of material structure or material properties and the plastic strain, analysis and experiment were performed. First, the changes of through-thickness distribution for mild-steel sheets were measured by analyzing the cross-sectional microphotographs of material structure. And next, the relationship between Young's modulus or hardness and the plastic strain was investigated by cyclic nano-indentation testing by which micro regional material properties can be obtained. Consequently, the distributions of grain oblateness and its changes caused by V-bending were quantitatively obtained by analyzing the microphotographs. Moreover by cyclic nano-indentation testing, hardness was decreased by increasing plastic strain. Though the quantitative evaluation of Young's modulus was tough work and we couldn't find peculiar tendency, stable value of it could be measured where maximum indentation load was larger than 1000μN.

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An innovative and relatively recent development in sheet metal products is the use of laminated metal as the workpiece. The application of a polymer/adhesive between two metal sheets yields clear acoustic advantages over conventional sheet stock. Product manufacturing with polymer laminated steels, however, presents difficulties associated with forming and bending operations, mainly in predicting and compensating for springback. This paper describes a research program focused on bending operations applied to laminated steel products. It si shown that the springbcak factor decreases with decreasing punch/die clearance and die radius as well as increasing punch depth, but that sidewall curl occurs regularly in these materials.

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This study experimentally examines the effects of changes in flow velocity at the die cavity during extrusion and investigates the mechanism of their occurrence. Dies have two cavities of different diameters. One of the cavity serves as the velocity standard cavity and has a fixed diameter (D_1=6mm), while the other cavity serves as the velocity comparison cavity and had different diameter (D_2=7.3mm, 8.5mm, 10.4mm). Flow velocity at die cavities during extrusion is evaluated by the average flow velocity (D_1; V_1,D_2; V_2) calculaed by the extrusion time and the extruded profile length for every 10mm of ram stroke. And changes in flow velocity are evaluated by flow velocity ratio (V_2/V_1 The flow velocity ratio changes during extrusion, and the following tendencies can be seen upon dividing the extrusion cycle into the initial extrusion period (flow velocity ratio R_I), the mid-extrusion period (flow velocity ratio R_M), and the end extrusion period (flow velocity ratio R_E). ・ During the initial and mid-extrusion periods, the flow velocity ratio is R_I>R_M>1,but during the end extrusion period, a rapid change in flow velocity occurs, where R_E<1. ・ The flow veloity ratio in the mid-extrusion period shows stable conditions in respect to changes in ram stroke.

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6xxx series aluminium alloys are mainly used in door- and window- frame manufacturing. Commonly the raw material is recycled aluminium with the correct Mg and Si additive content. The aluminium profile beams extrusion process presents several failure defects, which are obviously associated with various forming parameters such as die geometry and material mechanical properties affected by its chemical constitution. In the present paper, several aluminium alloys were subjected to an experimental procedure in order to estimate the way the above-mentioned parameters affect the extrusion load. Various aluminium alloys were used with Si rating between 0.2% and 0.6% p. w. and Mg rating between 0.5% and 1.3% p. w. This procedure also focused on semi-angle die cone effect, as well as temperature conditions. The most significant result concerns the decrease in the extrusion load observed in aluminium alloys with Mg rate over 0.9% p. w. and Si rate between 0.2% and 0.3% p. w. Extruded through small semi-angle cone die, maintaining improved mechanical characteristics.

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In magnesium alloy extrusion it is well known that the surface cracks usually occurred at the vertical direction to the extrusion prohibit the productivity and surface quality. The die with the taper brake bearing have investigated. Then it became clear that the die with the taper brake bearing is effective for improving the occurring of the surface cracks. So, we adopted the method at the practical industrial scale using the new magnesium alloy with low aluminum and zinc contents. Then on the magnesium extrusion, by using the method it became clear that we can extrude on the extremely high speed.

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Glass entrapment and rheology have a major impact on surface quality during hot extrusion of steel using flat dies. This paper outlines this relationship between glass properties, its behavior and the process conditions. It presents a glass rheological model which extends the previous work of Baque to unsteady conditions during extrusion. Then it included elements of an upper bound model for glass entrapment in single port extrusion. The integrated model which includes both glass rheology and entrapment is applied to the published results of hot extrusion. It is shown that the glass entrapment and flow model adequately explains the formation of the glass film and its breakdown.

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Extrusion tests of mixed wood powders of cryptomeria with Japanese cypress are carried out at various temperatures in order to confirm the possibility of near net shape forming of wood powders. Effects of the extrusion temperature, extrusion ratio, and the moisture content and particle size of the mixed wood powders on the flow characteristics, bending strength, hardness and bulk density of extruded products are discussed. The experimental results show that the fluidity of the mixed powders and the bending strength and bulk density of extruded products increase with increasing temperature and moisture content of powders. However, when the extrusion temperature is too high, the bending strength and bulk density of extruded products tend to decrease due to bubbles generated in the extruded product.

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An optimal multi-stage cold forging process is one that allows for the most product throughput for an acceptable batch size while limiting the cost associated with producing quality parts. The goal of this research was to address this issue and start to establish a basis that manufacturing engineers can use when they design the progression of any multi-stage forging operation. The research methodology employed utilized basic forging science principles applied in the form of a numerical forging simulator. The usage of this simulator was coupled with a customized optimization sequence to iteratively determine the most effective multi-stage forging sequence for selected classes of products. As a result of this research endeavor, it was shown that this comprehensive science-based optimization approach can lead to the significant enhancement of multi-stage forging processes.

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The presentation in the literature of analyses of the riveting process by upset forging is not new. However, based on the results that have been published to date, it is not easy to produce guidelines for the optimum design of the punch shape because each of these analyses was carried out using models of different sizes. In this paper, the riveting process by upset forging using five types of punches under a constant rivet head volume are investigated. This paper presents experimental findings as well as the results of rigid plastic finite element simulations. The results include the relationship between the upset force and the punch stroke as well as a clarification of the deformation characteristics of rivet heads. Moreover, the distributions of the compressive stress on the riveted plate in relation to joint strength were analysed.

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In this investigation we suggest the new process for micro forming by forging (micro forging). It is reported that processing performance is improved by making a tool or material vibrate in the high frequency by ultra sound waves in case of metal processing, because of the reduction of the load and the decrease in resistance to deformation. In this investigation, a processing tool is made to vibrate at high speed by the ultrasound vibration in micro forging and the characteristics have been investigated. Moreover, in micro forging the flow stress of the material was decreased by heating the specimen to the high temperature. As a result, the processing characteristics of micro forging could be improved. And the processing characteristics was investigated by the changing of the temperature conditions and the lubrication condition in this manufacturing process.

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Accompanying increasing demands for lightweight, thin and small products, the drawing technology for fine wires is making a rapid progress. However, there are number of problems to be overcome in the field of superfine wire drawing, such as wire breaks during the drawing process that lead to low productivity and high production cost. This study analyzed wire breaks by means of the finite element analysis (FEA) that occurred in the drawing fine copper wires containing flaw on the wire surface, inclusion and void. The deformation behavior of an inclusion was examined in which the inclusion's location is assumed of the center axis of wire and the cause of wire breaks and their prevention method were clarified. The authors also clarified that drawing stress rapidly increases as a large inclusion passes through a die, inducing a wire break. It was estimated that an inclusion diameter/wire diameter ratio of 0.4 or higher increases the likelihood of wire break. When the inclusion is not in the center of wire, it was also found that necking and wire breaks appear more frequently. In addition, date obtained from actual manufacturing processes in plants was compared with the analytical results. From the simulation of the multi-pass wire drawing, the void in the wire rod were confirmed through the density measurement of experimental drawn wires. FEA showed that a flaw grew in the every processing, when small circumferential flaw is placed on the wire rod surface, and eventually becomes a surface defect, which is called a check mark in practice.

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Super alloys present a real challenge to near-net shape rolling because of their high strength at elevated temperature, limited ductility, and narrow forming temperature range. Currently, the simulation of shape rolling requires application of time-consuming 3D finite element techniques. It is necessary to know the most important characteristics of the material behavior during processing in a small fraction of time taken by a finite element analysis in order to reduce the design and analysis cycle time. The upper bound elemental technique (UBET) is a rapid load estimating technique that has the potential to produce the results in a short time. Therefore, this paper presents an UBET-based simulation tool for modeling shape rolling of high-temperature aerospace materials. Simulation results have been compared with industrial data obtained for high-temperature alloys such as IN718 and TI-6AL-4V.

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Axles are one of the most important components in railway vehicle with regard to safety, since a fail-safe design in not available. The problems of fretting fatigue crack initiation in a press-fitted axle have not been completely solved even though up-to-date fatigue design methods are employed. The objective of the present paper is to clarify the effect of under stress on fretting fatigue crack initiation behavior in the press-fitted axle. Most of the stress amplitude given to the axle in service is less than the fretting fatigue limit based on the stress to initiate cracks under a constant load σ_<wfl>. Rotating bending fatigue tests were performed using a 40 mm-diameter press-fitted axle assembly. Two-step variable stresses consisting of σ_<wfl> and half or one-third of σ_<wfl> were used in the experiment. Crack initiation life was defined as the number of cycles when a fretting fatigue crack longer than 30 μm was found using a metallurgical microscope. Fretting fatigue cracks were initiated even when the variable stress did not contain the stress above the fretting fatigue crack initiation limit. The crack initiation life varied from 4.0×(10)^7 to 1.2×(10)^8 depending on the stress frequency ratio nL/nH. The sum of the number of cycles of higher stress at crack initiation N_H was much smaller than the number of cycles to initiate cracks estimated from modified Miner's rule. The value of the modified Miner's damage ranged from 0.013 to 0.190. To clarify the effect of variable amplitude on the fretting fatigue crack initiation. a comprehensive investigation related to relative slip. tangential force and fretting wear is necessary.

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Research on fatigue behavior in the ultra high cycle regime has been recently focused since the fatigue mechanism and S-N behavior different from those observed less than (10)^7 cycles have been observed. It is also of importance from the viewpoint of the long-term service use of structures and machines. Limited research works have been available on fretting fatigue in the ultra high cycle regime, while lots of studies have been done on plain fatigue even in this regime. In the present study, a new machine for ultra high cycle fatigue test has been developed with an electro-magnetic vibrator. It was confirmed that fretting fatigue strength, lives, frictional force and relative slip amplitude were not significantly influenced by the cyclic loading rate up to 300 Hz, which was the present test condition for ultra high cycle fretting fatigue. The fretting fatigue strengths defined at (10)^7 cycles were effective up to (10)^8 and (10)^9 cycles for titanium alloy and aluminum alloy. The fretting fatigue crack initiated at the end region of fretting contact area even in the ultra high cycle regime, which indicated that the fatigue mechanism would not change even in the ultra high cycle regime. This might result from the singular stress field near the contact edge in fretting fatigue.

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Plain fatigue and fretting fatigue tests of cast and forged aluminum alloys were carried out in air and calcium chloride solution. Although plain fatigue strength of the cast alloy was significantly low compared to that of forged one, fretting fatigue strength of cast alloy was almost equal to that of forged one in air. Fretting fatigue strengths of both alloys in calcium chloride (CaCl_2) solution were lower than those in air. Measurement of tangential force coefficient and SEM observations of surface were also carried out to discuss the effect of environment on fretting fatigue characteristics. Tangential force coefficient of both alloys in the environment was nearly equal to that in air. Though all of the fretting fatigue cracks for cast aluminum alloy initiated near the edge of the contact region, some fretting fatigue cracks for forged aluminum alloy in CaCl_2 solution were not fretting part in this study. In the cast aluminum alloy, the casting defect seemed to have no significant influence on the initiation of fretting fatigue cracks and the sensitivity of fretting and corrosion in the low stress amplitude regime is small in comparison with that for the forged aluminum alloy.

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Compressive residual stress is qualitatively known to have a strong effect of deceleration of crack propagation rate and hence improvement of fatigue strength. In fretting fatigue a fatigue crack generally initiates in the very early stage of fatigue life, which is therefore mainly dominated by the fatigue crack propagation life. This paper investigated the quantitative effects of residual stress on fretting fatigue crack propagation and fretting fatigue strength using aluminum alloy specimens with and without WPC treatment, which can induce residual stress in the specimen surface layer. It was found that the compressive residual stress in the surface layer decelerates the crack propagation rate, while it has no obvious effect on the crack initiation. A simple quantitative method for evaluating the effect of residual stress on crack propagation has been proposed. It was found that both the effects of residual stress on fretting fatigue crack propagation and fatigue life could be quantitatively evaluated according to the proposed method. Moreover, based on the method proposed, the estimation of the increase of fretting fatigue strength due to residual stress agrees well with the experimental results.

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Rolling contact fatigue tests were carried out with two cylindrical specimens of sintered alloy. Damage of the specimen was detected by using acceleration sensor before occurrence of final failure. In order to study the behavior of damage process in contact fatigue behavior of sintered alloy, surface and cross section of the specimens were observed after the contact fatigue test. Damage on the specimen surface such as pitting mode of failure was not significantly observed. Contact fatigue damage was observed as subsurface crack initiation and propagation. Subsurface crack growth behavior was evaluated by an interrupted test. Crack length increased with increasing number of cycles. Crack initiation and propagation in the subsurface of specimen induced a spalling mode of fracture. Stress distribution of subsurface was estimated by FEM (Finite Element Method) analysis. The location of the maximum shear stress by FEM analysis coincided with the depth of crack initiation point observed in experiments. The position of the maximum shear stress approached to the specimen surface with increase in the tangential force at the contact surface. Subsurface crack growth behavior was dominated by shear stress amplitude.

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Base on the real-time observation of the workpiece surface in a series of compression-sliding experiment, it is found that the contact area is much greater than that evaluated by the existing theorems such as the junction-growth theorem. With the aid of finite element analysis, it is verified that the tool sliding motion along with the minute elastic deformation of tool surface around the asperity peaks increase the asperity contact area significantly as the sliding motion continues. The existence of shear stress on the asperity peak also encourages the growth of contact area. An incremental model has been developed to predict the evolution of contact area with the relative sliding distance between tool and workpiece. The effect of the tool deformation on the variation of contact area is a function of the tool Young's modulus, the shear strength of workpiece, the current contact area, and the mean interface pressure.

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Scratch tests were carried out on TiC and TiN coatings formed by PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition) techniques. The critical load L_c detected by both AE signal and frictional force curve coincided with that at which the local delamination of coating was observed on the scratch track. In order to study damage process of coating during scratch test, scratch track were observed. Hair cracks parallel to the scratch track were observed before local delamination occurs. Other cracks perpendicular to the scratch direction were observed in the scratch track at L_c. Local delamination also occurred at the edge of scratch track at L_c. Shear stress at the interface between coating and substrate induced this local delamination. Stress distribution at the interface was estimated by FEM (Finite Element Method) analysis. Shear stress at the interface depended on the tangential force. Critical load L_c decreased with decreasing of tangential force due to increase of frictional coefficient. Indentation test without tangential force was also carried out. The critical load was high in indentation test compared to that in scratch test. However, the critical shear stresses at the interface for both scratch and indentation tests coincided each other. It is concluded that the critical shear stress at the interface can be the criterion for the cohesive strength between coating and substrate.

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The present paper describes cracking behavior of brittle materials in sphere indentation experiment. Fused silica glass plates were used for the specimen. An electro-mechanical testing apparatus was applied for the experiment. A silicon nitride sphere was penetrated with various cross head speed in air at room temperature. Au coating was applied on the testing surface to avoid the effect of corrosion. The cracking behavior was observed continuously during the test by installing a CCD camera with a lens assembly behind the specimen and was recorded with a digital memory. Acoustic emission (AE) measurement was also connected for the evaluation. The indentation strength based on an elastic contact theory was calculated. Reliability of the fracture load determination by AE measurement and the effect of cross head speed on the cracking behavior were evaluated. Obtained results revealed that the controlling the cross head speed was important for the indentation strength measurement.

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This work clarifies the origin of anomalous surface deformation reflected by peculiar surface patterns around indentation impressions on various crystallographic planes of sapphire. The three-dimensional finite element simulation (3D-FEM) of nanoindentation in Al_2O_3 crystal allowed the authors to localize the regions in which various kinds of twinning and slip are most prone to be activated. The work provides a novel approach to the "hardness anisotropy", which was modeled so far using a modified uniaxial-stress approximation of this essentially 3D, non-isotropic contact problem. The calculated results enabled the authors to unravel the unexpected surface deformation detected by the high-resolution microscopy, which remained a dilemma for the nanoindentation of sapphire, and cannot be explained by simple crystallographic consideration

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