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In this study, the characteristics of the SKD61 material used for the stem of an extruder were analyzed through structural analysis, tensile testing, and fatigue testing. The extruder works by pushing a cylindrical billet into a die with a stem to reduce its cross-sectional area and increase its length, and it is currently used to extrude complex and diverse shapes of products in the field of plastic deformation processes. Finite element analysis was used to determine the maximum stress on the stem, which was found to be 1152 MPa, lower than the yield strength of 1325 MPa obtained from tensile testing. Fatigue testing was conducted using the stress–life (S–N) method, considering the characteristics of the stem, and statistical fatigue testing was employed to create an S–N curve. The predicted minimum fatigue life of the stem at room temperature was 424,998 cycles at the location with the highest stress, and the fatigue life decreased with increasing temperature. Overall, this study provides useful information for predicting the fatigue life of extruder stems and improving their durability.

A multi-stage cold forging process was developed and complemented with finite element analysis (FEA) to manufacture a high-strength one-body input shaft with a long length body and no separate parts. FEA showed that the one-body input shaft was manufactured without any defects or fractures. Experiments, such as tensile, hardness, torsion, and fatigue tests, and microstructural characterization, were performed to compare the properties of the input shaft produced by the proposed method with those produced using the machining process. The ultimate tensile strength showed a 50% increase and the torque showed a 100 Nm increase, confirming that the input shaft manufactured using the proposed process is superior to that processed using the machining process. Thus, this study provides a proof-of-concept for the design and development of a multi-stage cold forging process to manufacture a one-body input shaft with improved mechanical properties and material recovery rate.

Recently, mechanical joining processes have received much attention for joining multi-materials. In particular, these processes have a great demand in the automobile industry for weight reduction. The press-fitting process is a representative mechanical joining process. In this process, the shape of the interfacial serration on the joining plane is very important because it has a significant effect on the joining strength. In this study, the characteristics of the aluminum&ndash, steel press joining process were investigated according to the shape of the interfacial serration of the joining plane. The deformation of the material and the forming load were investigated by conducting finite element analysis. In addition, the unfilled height of the material, joining force, and torque were measured experimentally.

In the aluminum porthole extrusion process, excessive wear occurs on the surface of mandrel. This study evaluates the applicability of direct metal deposition (DMD), a 3D printing process, for repairing the hot aluminum extrusion die. The wear characteristics of three die repairing methods (parent-STD61, DMD-STD61, and welded-STD61) were compared through a high-temperature pin-on-disk wear test that considers the aluminum extrusion temperature. The results confirm that DMD results in superior wear characteristics when compared to overlay welding repair method. Further, the wear resistance of DMD-STD61 is similar to that of parent-STD61. The application of the DMD process is expected to yield a wear life similar to that of the parent STD61.

Manufacturing industries have become increasingly conscious of energy wastage and environmental emissions. The energy consumption and environmental effect of each manufacturing process is different. This study aims to compare the environmental effects of the hot forging process and machining process for manufacturing sprocket wheels. It is important to design a preform when forging a sprocket wheel. The sprocket wheel tooth section is the weak point in folding, and an unfilling defect may occur. Therefore, preform and flash stopper shapes are critical design factors in the hot forging process for manufacturing sprocket wheels. Finite element analysis was used to design the preform, and analyze the deformation and effect of flash stopper in the hot forging process. The energy consumption for an actual product and for a product based on the analysis were compared to analyze the environmental effects. The results showed that the material loss and energy consumption were reduced in the developed hot forging process; this process is a green process with comparatively higher energy saving than the machining process.

Densification behaviours of 17-4PH stainless steel powders (SUS17-4PH) of three different particle sizes during the sintering were investigated. The samples with different mean particle sizes of 3.17, 4.22 and 8.30 µm were prepared through powder-binder mixing, injection moulding, and solvent and thermal debindings. The in situ shrinkage data measured by dilatometry tests were treated to analyse the densification behaviour of each sample. In order to characterise the densification behaviour with a minimum set of experiments, the master sintering curve (MSC), as well-known and straight-forward approach, was employed. After constructing the MSCs for powders of different particle sizes, the effects of particle size on the densification were analysed in many respects including shrinkage, strain rate, apparent activation energy, and work of sintering.

In this study, a hot multi-point forming process was proposed. The hot multi-point forming die can form the various curved surface by controlling the height of each punch. In addition, the cooling system was installed inside each punch and can be selectively used as a punch or a cooling nozzle. Therefore, efficient hot forming and cooling of the thick plate is possible. However, in manufacturing plant, there has not been sufficient fundamental research on hot multi-point forming process with cooling system. In this study, the hot forming and cooing performance of the hot multi-point forming process according to punch arrangement and forming curvature conditions was evaluated through FE-analysis. As a result of FE-analysis, a punch arrangement design suitable for the target curvature is required in consideration of the shape error and the cooling rate.

The manufacturing process of long fiber thermoplastic is initiated by supplying reinforced fiber wound in a spool dispenser. If problems such as tangling or kinking occur in the apparatus used for supplying the reinforced fiber in the long-fiber thermoplastic direct process, the productivity of the long-fiber thermoplastic decreases. Therefore, it is important to enhance the supply stability of reinforced fiber. In general, the increase in supply stability can be achieved by maintaining a steady balloon shape that is controlled by the unwinding velocity or tensile force of the reinforced fiber. In this research, the range of suitable tensile force was determined under the assumption that the unwinding velocity remained constant. The reinforced fiber was assumed to be inextensible, homogeneous, and isotropic and to have uniform density. The transient-state unwinding equation of motion to analyze the unwinding motion of reinforced fiber can be derived by using Hamilton’s principle for an open system in which mass can change within a control volume. In the process of solving the transient-state unwinding equation of motion, the exact two-point boundary conditions are adopted for each time step.

Dynamic compressive properties of a Boryeong shale were evaluated by using a split Hopkinson pressure bar, and were compared with those of a Hwangdeung granite which is a typical hard rock. The results indicated that the dynamic compressive loading reduced the resistance to fracture. The dynamic compressive strength was lower in the shale than in the granite, and was raised with increasing strain rate by microcracking effect as well as strain rate strengthening effect. Since the number of microcracked fragments increased with increasing strain rate in the shale having laminated weakness planes, the shale showed the better fragmentation performance than the granite at high strain rates. The effect of transversely isotropic plane on compressive strength decreased with increasing strain rate, which was desirable for increasing the fragmentation performance. Thus, the shale can be more reliably applied to industrial areas requiring good fragmentation performance as the striking speed of drilling or hydraulic fracturing machines increased. The present dynamic compressive test effectively evaluated the fragmentation performance as well as compressive strength and strain energy density by controlling the air pressure, and provided an important idea on which rock was more readily fragmented under dynamically processing conditions such as high-speed drilling and blasting.

Design technologies of a cutting head attachment for mechanical excavation works are studied for improving grinding efficiency. Similar to a hydraulic breaker, a cutting head attachment is attached to the front of an excavator. However, unlike the hydraulic breaker, which breaks rocks via repeated mechanical knockings, a cutting head attachment grinds rocks via the rotational motion of a conical drum. Hence, generally the grinding efficiency and working speed of a cutting head attachment is higher than those of a hydraulic breaker. Further, the working noise is significantly low because of the same reasons. In the cutting head attachment, the grinding tools, named as pick cutters, are arranged, and they perform the role of breaking rocks by interacting with them. Hence, it is very important to arrange these tools for improving the grinding efficiency. In this study, arrangement design methodologies of several pick cutters are developed by multi-body dynamics analysis. Further, the grinding efficiency of the designed pick cutter arrangement is studied for sumping and shearing cutting works through excavator’s boom motions.

The directed energy deposition process has been mainly applied to re-work and the restoration of damaged steel. Differences in material properties between the base and the newly deposited materials are unavoidable, which may affect the mechanical properties and durability of the part. We investigated the effect of heat treatment on the characteristics of tool steel deposited by the DED process. We prepared general tool steel materials of H13 and D2 that were deposited onto heat-treated substrates of H13 and D2, respectively, using a direct metal tooling process. The hardness and microstructure of the deposited steel before and after heat treatment were investigated. The hardness of the deposited H13 steel was higher than that of wrought H13 steel substrate, while that of the deposited D2 was lower than that of wrought D2. The evolution of the microstructures by deposition and heat treatment varied depending on the materials. In particular, the microstructure of the deposited D2 steel after heat treatment consisted of fine carbides in tempered martensite and it is expected that the deposited D2 steel will have isotropic properties and high hardness after heat treatment.

High-strength steel sheets, which are considerably cheaper than aluminum alloy sheets, are useful in reducing the weight of automobiles. The superior mechanical properties of these steel sheets, however, make stamping operations more difficult by reducing formability and tool life. An ultra-high-strength steel sheet has an even higher surface hardness and yield strength than the highstrength sheets, that further increase the forming force, die wear/galling and springback, resulting in an even greater reduction in die life during stamping. Given the clear need for a more durable die material, in this study, we evaluate the wear and fatigue characteristics of a new die material that has been developed for stamping ultra-high-strength steel. Through pin-on-disk wear testing and rotating bending fatigue testing, it is found that both the wear and fatigue characteristics of the die are improved by using this new material. And die wear is evaluated by FE analysis and experiment for ultra-high-strength steel stamping.

Multi-pass shape drawing is very important to produce steel profiles in round samples. In the current study, a process design system is developed for a multi-pass shape drawing. In general, the number of passes for a multi-pass shape drawing is 2 to 3 when the reduction ratio, drawing stress, and productivity are considered. Therefore, calculating the drawing stress and designing the intermediated die shapes are very important. In order to calculate the drawing stress, a shape drawing load prediction method is proposed using a general axisymmetric drawing load prediction model. An intermediate die shape design method is proposed using the initial and the final product shapes. Based on this analysis, a process design system is developed for multi-pass shape drawing for steel profiles. The system works with AutoCAD. The system was applied to design a shape drawing of a spline.

Nebulizers are inhalers for treating respiratory problems by converting aqueous solutions into aerosols of respirable size (1–5 ¼m) in the lower respiratory tract. In this study, improvements in the spray performance of the baffle type pneumatic nebulizer are investigated. First, to determine the causes of spray performance degradation, the reverse engineering of two pneumatic nebulizers is carried out. As a result, it was found that the major cause of performance degradation is the significant distortion of the inner parts due to the post-deformation after injection molding. Therefore, in this study, design changes are made to reduce post-deformation. Subsequently, to verify the spray performance of the suggested model, an injection molding analysis, flow analysis, and physical experiment are conducted. The results confirm that the suggested design helps improve the spray performance of a pneumatic nebulizer.

The purpose of this study is to propose a method for reducing carbon emissions produced during the manufacture of output shafts by increasing productivity and reducing energy consumption. To this end, the existing machining process was redesigned as a multistage cold forging process, using a computer-aided engineering technique. The critical parameters considered for the redesigning were material deformation, metal flow, and load. Rigid plastic finite element analysis software DEFORM-2D3D was utilized to identify and analyze these parameters. The derived multi-stage cold forging process was designed on the basis of the test results. It was also verified that the new process substantially increased productivity. A carbon life cycle assessment (LCA) was performed to compare the amounts of carbon emission, material loss and energy consumption of the existing machining process and derived multistage cold forging processes. The comparison results indicated considerably lower carbon emissions, material loss and energy consumption in case of the latter.

To minimize social cost and to avoid existing obstacles (e.g., buildings, buried pipes, rivers, and ocean), cable and electricity tunnels are constructed mainly using trenchless technology. We have developed a new method for micro-tunnel excavation using a multihammer drilling machine and identified the optimum operating conditions of the system. A linear percussion testing system was constructed to acquire rock drilling data. The tests were conducted under various air pressures and RPMs consistent with field conditions. Three classes of rock specimens in terms of strength (i.e., hard, medium, and moderate rock) were tested. The test results yielded the optimum operating conditions of the multi-hammer drilling machine according to rock strength.

In this paper, the operating stiffness of a parallel robot used to handle heavy packages is optimized. Because the studied model, called a "pick and place robot," is applied for packaging logistics, it is important for the robot to be lightweight so that it may respond rapidly and have high stiffness to allow sufficient operating precision. However, these two requirements of low weight and high stiffness are mutually exclusive. Thus, the dynamic characteristics of the robot are analyzed through multibody dynamics analysis, and topology optimization is conducted to achieve this exclusive performance. Lastly, the reliability of the topology optimization is verified by applying the optimized design to the parallel robot.

Porthole extrusion is a useful process for manufacturing lightweight materials with complex cross-sectional shape. In porthole extrusion, the material flow is complex due to the complex structure of the die. Therefore, it is not easy to design an appropriate extrusion process. Magnesium alloy exhibits low deformability at temperatures below 200°C because of its hexagonal close-packed crystal structure. It also suffers from the problem of surface oxidation at temperatures above 400°C. Therefore, it is important to set the appropriate extrusion conditions. In this study, the porthole extrusion process for manufacturing automobile bumper back beams is designed. The influence of initial billet temperature, ram velocity, and nitrogen cooling system on the surface temperature of extruded magnesium alloy is investigated using FE analysis. First, the initiation temperature of surface oxidation is evaluated through extrusion test. Then, based on the FE analysis, the extrusion limit diagram is obtained considering the surface oxidation temperature and the extruder capacity. The effect of nitrogen cooling on surface temperature is investigated through coupled CFD and FE analysis. From the analyzed results and extrusion limit diagram, the initial billet temperature and ram velocity are determined. Finally, the effectiveness of the designed extrusion process is verified through an experiment.

A series of multiphase CFD (computational fluid dynamics) simulation was carried out in order to evaluate the design study of flushing device of rock reaming machine. The Star-CCM+ code was adopted for simulating rock particle discharge flow of flushing air during the rock reaming process. The input parameters for the flow simulation of rock particle were obtained from a previously performed in-situ drilling test results. After three design factors (degree of swash plate, radius of curvature of swash plate, and diameter of flushing channel) were determined, the experimental design method (response surface methodology) was applied to determine optimum value of each factor.

The drill bit, which directly transmits percussive forces and torque to the rock, is the core part of a rock drilling machine. For effective drilling, the button arrangement of a drill bit should be optimized because it is the most important design factor in determining drilling efficiency. Furthermore, a quantitative method is necessary to evaluate the button arrangement for the optimization of the drill bit button. Therefore, we propose a new method for the evaluation of the drill bit button arrangement using new evaluation indices, which include the overlapped impact area, blank area, and moment. Moreover, we verify the suitability of the proposed evaluation method by applying it to the conventional button arrangement.

In the powder metallurgy process, if the compact body has a non-uniform density distribution, it would be very difficult to achieve the desired dimensional accuracy because of the non-uniform shrinkage that occurs during the sintering process. In the case of the ceramic sub-mounts of a light-emitting diode (LED), produced from a porous ceramic powder tape, the fabrication involves punch-forming, warm isostatic pressing, and sintering. To ensure the proper functioning of the reflective surface of the LED package, the surface should be produced with the designed angle. In this study, the shape deformation of the final product was predicted using a numerical simulation. A simulation model that can describe the deformation of a porous body based on the plasticity theory. The model considers both the compaction and sintering that occurs during the continuous fabrication process, and was used in a finite element analysis for designing the fabrication process. The angle of the reflective surface of the sub-mount was calculated for various punch angles, and the reliability of the simulation model was verified by comparing its predictions with experimental results.

In order to prevent the surface defect in the magnesium alloy extrusion process, it is important to set an appropriate process condition. The extrusion limit diagram is very useful to achieve the maximum extrusion speed without surface defect. In this study, the extrusion limit diagram for the magnesium alloy extrusion is constructed by using extrusion experiment and finite element analysis. For finite element analysis hot compression test is carried out to obtain the effective stress and stain curves according to the various strain rates and temperatures. The effectiveness of the constructed extrusion limit diagram is verified through the porthole extrusion experiment for producing the magnesium alloy bumper beam.

Adapters are a component of the output system in the internally geared hub for a bicycle. Originally, adapter parts were produced by a machining process with low productivity and material usage rate. In this study, the metal powder injection molding (MIM) process has been applied as an alternative manufacturing method to the machining process. Microstructure analysis and mechanical property testing has been conducted in order to select the material for the adapter with changes in the nickel content. The geometrical precision of the adapter is measured by using three-dimensional scanner with various mixing ratios of the powder and the binder. The developed alternative process for the adapter results in increased productivity and material usage rate. Previously, this process was only used for small parts less than 10 mm in diameter. With this development, the MIM process may be used more widely than before.

Interior permanent magnet synchronous motors (IPMSMs) are frequently used in industrial applications because their efficiency and power density are both very high. The IPMSM also makes a very good choice for an electric vehicle or hybrid electric vehicle, because the range of operating speeds is wide enough for use in traction applications. Recently, however, as a result of concerns about there being insufficient supplies of rare earth permanent magnets as well as atmospheric pollution caused by the exhaust gases of automobiles, a need has arisen for motor technologies that require fewer magnets and which can offer a higher level of efficiency. In this paper, we propose a bridgeless IPMSM as a means of reducing the number of permanent magnets used in a motor while simultaneously increasing the power density. The bridge structure, which supports the centrifugal forces generated in a motor’s permanent magnets as the rotor core rotates, was eliminated. To provide support for the separated pole-pieces and permanent magnets, new supporting structures are proposed. As a result, although the air gap torque of the bridgeless IPMSM is almost the same as that of the conventional design, the mass of the permanent magnets can be reduced by 10%.

Green manufacturing is very important to reduce the environmental pollution and the material loss. Porthole extrusion is a useful process for producing a long aluminum cylinder tube. In this process, the initial billet is homogenized at a high temperature for a long time to improve the extrudability. The homogenization process is not only a high energy-consuming process but also a high pollution process. Therefore, an alternative process is needed for green manufacturing. In this study, a new porthole extrusion for green manufacturing was developed to reduce the energy consumption through the convergence of the homogenization heat treatment process and the billet pre-heating process. The flow stress of the initial billets with the conventional homogenization heat treatment process and the proposed converged process were obtained through the hot compression test. FE analysis was performed to assess the application of the proposed method. Through FE analysis the extrusion load, material flow, temperature, effective strain, and welding pressure were compared with each other. Finally the porthole extrusion experiment was carried out based on the result of FE analysis. As a result, it can be seen that the aluminum cylinder tube without defect can be produced by applying the proposed green extrusion process.

The manufacture of helical pinion gears has involved machining processes such as hobbing and shaving to achieve the required dimensional accuracy. However, these conventional processes have some disadvantages such as excessive material loss, low productivity, high-energy consumption, and high carbon emissions. To overcome these problems, a cold extrusion process is applied to the manufacture of helical gears. In this study, we analyze the environmental effects of the cold extrusion process, designed for the sustainable production of helical gears. We quantitatively analyze the environmental effects of the conventional machining and cold extrusion processes, using the Life Cycle Assessment technique in accordance with ISO 14000. This analysis includes the energy consumption and carbon emissions for a helical gear manufactured using the conventional machining processes and those of single- and double-type gears manufactured using the cold extrusion process. Moreover, the material properties of the extruded helical gears are compared with the conventionally machined gears. In conclusion, the extruded gears exhibited a higher strength while consuming less energy during their manufacture than the gears manufactured using the conventional machining processes. Further, this alternative process is more cost effective as it generates less waste and exhibits high productivity compared to the conventional machining processes.

To develop a green manufacturing process is very important to minimize material loss, energy consumption and so on. In this study, a shrink fitting process for producing die carring hook of stamping die set was developed through alternative process for sustainable production. Die carring hook is usually manufactured by machining process. Machining process is very common and easy process. However, this process has some disadvantages such as excessive material loss, low productivity, and relatively low mechanical properties. Especially, the excessive material loss and the low productivity are the most serious problems. In order to overcome these problem, the shrink fitting process was applied to manufacture die carring hook for achieving less material loss and higher productivity. In this study, after manufacturing the head ring and body of die carry hook, the two parts was tighten through shrink fitting process. In order to apply the shrink fitting process, the shrink fitting process was analyzed by using FEM. Through FE analysis, heating and cooling process of shrink fitting was analyzed. And after cooling process, the clamping force between head ring and body was predicted to evaluate the quality of die carring hook. The result of FE analysis was verified through experiment. As a result, when the shrink fitting process was applied, not only material utilization but also productivity can be improved approximately 32% and 40%, respectively.

In this research, a cold extrusion process that can replace conventional machining process is developed for sustainable production. The cold extrusion method requires an analytical design process to assure desired dimensional accuracy of the final product. Therefore, the design must consider the material flow during the process in order to avoid product defects such as folding and underfilling. The forming load and material flow were analyzed using a commercial finite element code, DEFORM3D. To improve the dimensional accuracy, the shape of die and initial billet were designed using minimum distance analysis via FE simulation. Also the developed process included ejection for improving dimensional accuracy, and it was verified by a gear accuracy test. Isothermal annealing and spheroidizing were applied for increasing the formability of high strength workpiece. Finally a helical pinion gear was manufactured using the developed process and the product was compared to the simulation results. In conclusion, the developed process is a scrap reducing and energy saving method for manufacturing extrusion product with high dimensional accuracy.

The cold tube drawing has been generally regarded as an effective technology because of its high productivity and low production costs. It has been used instead of the swaging process to form monobloc tube shafts (MTSs) with a constant outer diameter or hollow shafts without defects. MTSs are used nowadays to reduce the weight of shafts and to improve power transmission in the auto industry nowadays. The objective of this study was to design an optimal die that can prevent material fracture considering critical damage value in the tube drawing process. To achieve this objective, a finite element simulation and the flexible polyhedron search method are used. The drawing die shape is represented by the Bezier curve that is able to generate all the possible die shapes. The tube drawing experiments were carried out using the optimized tool. In the experiments, it was possible to produce sound products without fracture.

In this research, a multi-stage cold forging process for a spring guide pin of stamping die set is designed through alternative process for sustainable production. Highly energy and material consuming process needs to be converted to an energy saving process. Up to now, a spring guide pin for stamping die set is usually manufactured by machining process in order to achieve dimensional accuracy. However, machining process has some disadvantages such as excessive material loss, low productivity, and poor mechanical properties. In order to overcome these problems, a multi-stage cold forging process is applied to manufacturing spring guide pin for achieving less material loss and higher productivity. Multi-stage forging process requires careful design steps to prevent the defects of the final product. So, the design must consider the material flow during the whole process and the loading limit of the press in order to avoid product defects such as folding and underfilling. To develop multi-stage forging process for spring guide pin the forming load and material flow at each step is analyzed using a commercial finite element code, DEFORM. The guide pin is then manufactured by the developed multistage forging process, and is compared to the simulation results. Also the efficiency of the developed forging process is compared to the machining process. The developed process is a green manufacturing process minimizing material loss, which achieves cost reduction through improved material usage and productivity compared to the more widely used machining process.

In this paper, a unified model for describing compaction and sintering based on plasticity theory is presented. To explain both compaction and sintering within a single model, the sintering driving force is treated as hydrostatic pressure and added to the yield function for a general porous material. The constitutive equation is derived by applying the flow rule to the origin shifted yield function considering the sintering driving force, and the derived equation is then and verified by comparison to experimental results. Finite element analysis is performed using the verified model to predict the non-uniform density distribution due to compaction and the dimensional change of the final product due to sintering. Finally, the simulation results are compared to other experimental and simulation results to evaluate the reliability of the proposed model.

In a multi-pass wire drawing process, inhomogeneous deformation through the cross section of a wire, heat generation resulting from plastic deformation, and friction generate residual stress in the drawn wire. The tensile residual stress in the wire deteriorates the mechanical properties of the drawn wire, with the maximum tensile residual stress occurring on its surface. This paper proposes a prediction model for the maximum axial residual stress that considers the inhomogeneous deformation and heat generation in a high-carbon (0.82-wt% C) drawn wire. An elastoplastic finite element (FE) analysis that considered the flow stress at a high strain range was carried out. Based on the results of this FE analysis, a stress prediction model was established. In order to verify the effectiveness of the prediction model, a multi-pass wire drawing experiment was performed. After performing the drawing experiment, the axial surface residual stress in the drawn wire was measured by X-ray diffraction. From the results, a close agreement was observed between the predicted residual stress and the measured residual stress.

The shape drawing process is a very useful metalworking process that can produce an elongated component with a constant cross-sectional shape. The prediction of drawing load is critical for evaluating the potential of shape drawing. However, it is challenging to predict the drawing load of shape drawing because of the complex cross-sectional shape of the drawn material. In this study, a new theoretical method is proposed to predict the drawing load of shape drawing. The proposed method is based on the geometric division of the cross section and an axisymmetric drawing load prediction model. The drawing loads of square and hexagon shape drawings from round material are predicted by using the proposed method. The effectiveness of the proposed method is verified through finite element analysis and a shape drawing experiment.