It was reported that the incremental sheet metal forming (ISMF) produces larger deformations as compared to the conventional forming processes. We developed a new ISMF method based on incremental punching. In this study, a theoretical method based on M-K analysis is presented to determine the forming limit curve (FLC) in this forming process and it has been integrated to our in-house FEM program. Also, a ductile fracture model is used for comparing of the forming limit of the process. A numerical example is then given and verified by experiments. The results indicate that the proposed method provides an available approach to determine the FLC of incremental punching process.
Currently, with the rapid improvement of CAD design technology, the design cycle and production cycle became shorter and shorter. Therefore, it is highly demanded to develop the dexterous machining tools, which are suitable for measuring and machining of small parts with complex shapes. In this research, a compact desktop machine tool with polar-coordinate is proposed. Based on its polar-coordinate configuration, two rotational axes and one linear axis, it provides a higher flexibility than the traditional 3-axis machine tools. By using a hotwire cutter as the cutting tools, it could rapidly machine a fine product from a CAD model. Furthermore, by changing the tools into a touch probe sensor, it could also precisely measure the shape of a 3D object. With the versatile CAD/CAM software, which was specially designed for this Polar-coordinate desktop machine tool (PDMT), this system could fulfill various tasks, such as measurement of 3D objects, reconstruction of 3D models, machining of 3D parts, and even duplication of 3D products.
Prediction of mechanical power losses of gear pairs requires elastohydrodynamic lubrication (EHL) analyses to be carried out at every discrete contact position. This makes gear efficiency models computationally demanding. As a remedy to this problem, a method is proposed in this study to derive EHL-based friction coefficient and rolling power loss formulae to be used in gear efficiency models. This method employs a large number of EHL analyses covering a full matrix of all key contact parameters, namely normal load, rolling and sliding velocities, radii of curvature, lubricant parameters and surface roughness amplitudes, within typical ranges dictated by gear contacts. Linear regression of the results of the EHL analyses yields friction coefficient and rolling power loss formulae suitable for gear efficiency models. In the EHL model, the hydrodynamic fluid and asperity contact zones are treated in a unified manner. The sliding friction is computed as the sum of the viscous shear within the lubricant and the boundary friction at the local asperity contact spots. The rolling power loss induced by fluid pressure gradient is formulated to include the entire contact zone instead of only the inlet region, since the pressure gradient is substantial within the contact for rough surface condition. The proposed method is demonstrated using an example turbine fluid. Typical measured gear surface roughness profiles are used in the analyses. At the end, the results from the regression formulae are compared to actual EHL predictions to assess their accuracy under various contact conditions.
This work presents an optimization model for planar four-bar motion and path generation. This model includes the four-bar linkage kinematic model by Suh and Radcliffe(13) as an objective function. This kinematic model allows for the direct minimization of the error between the prescribed and achieved coupler parameters while synthesizing the crank and follower links in a closed loop. Both order and branching conditions are included among the constraint equations.
According to diversified customer demands and global competition, introduction of mixed-model assembly lines becomes popular to realize the small-lot-multi-kinds production in a rational way. For recent years, we have been studying a sequencing problem of mixed-model assembly line that is operated under continuous and leveling production and includes a lot production line as its preceding process. By taking into account the difference of operation manners in both lines together, we have formulated the sequencing problems as a bi-objective optimization problem. It aims to prevent various line stoppages, and to reduce volume of WIP inventory simultaneously. Based on such formulation, this study concerns with the multi-objective analysis first. Then, we have proposed a two-stage multi-objective optimization method. It tries to apply multi-objective optimization method termed MOON2R relying on the foregoing multi-objective analysis. Finally, through numerical experiments performed by one of the author as virtual decision makers, we have validated effectiveness of the proposed approach.
In this paper, we report on the co-operative control of a 5-DOF controlled magnetically-levitated (maglev) local actuator (MLA) combined with a conventional electrical discharge machine, which we developed as a means to increasing the electrical discharge machining (EDM) speed for small deep holes. The MLA enables the electrode to be rotated as well as to be rapidly positioned. Compared to conventional EDM without electrode rotation, the machining speeds in machining φ0.5×4mm and φ1×4mm through holes were increased by 125% and 337%, respectively, using the EDM machine combined with the MLA without electrode rotation ; while with electrode rotation, the co-operatively controlled combination increased the machining speed by a maximum of 343% in machining φ0.5×4mm through holes at 800rpm and 433% in machining φ1×4mm through holes at 600rpm.
To avoid a longer settling time of an isolation table, switching of the feedforward controller which is used for the control of supplied air's disturbances, is needed after starting and prior to stopping the table. However, this switching also causes the fluctuation of the table. In order to suppress the fluctuation of the table caused by switching, this study uses a difference operator before the feedforward compensator and the combination of feedforward and feedback loops. The effectiveness of this method is experimentally demonstrated.
This paper presents a novel method based on the virtual sliders for constructing a deployable ball mechanism and reveals the geometric constraint of the 20-bar ball mechanism and the radially foldable linkage that were extracted from the Hoberman switch-pitch structure. This leads to the development of the chain structure equation to unravel the radial motion characteristics of the mechanism and to the construction of the 20-bar ball mechanism with simulation and rapid prototyping process. The paper further presents position analysis and Jacobian matrix of the mechanism and simulation and numerical analysis are used to illustrate the kinematic characteristics. The analysis corresponds to motion in both simulation and prototyped ball mechanism.
This paper presents vision-based measurement of two-dimensional positioning errors of machine tools. A pre-calibrated grid plate is used as an artefact. The position of a grid point is measured in an image captured by a charge coupled device (CCD) camera attached to a spindle. Unlike conventional two-dimensional digital scales, the vision-based measurement can target the artefact in any orientation, and thus can be also applied to error calibration of a rotary axis. A longer working distance between the lens and the target is also its potential advantage for safer measurement. The paper demonstrates experimental applications of the vision-based measurement to the measurement of 1) static and 2) dynamic error motions of 1) a linear axis and 2) a rotary axis of a machine tool.
Due to the increasing demand of high accuracy in printed electronics industry at a micrometer-level, it is necessary to have a precise control scheme for web velocity and tension in the presence of disturbances. In this paper, a generalized mathematical model of non-linear control system is proposed and a systematic procedure is presented to design a backstepping controller taking the modified backstepping approach. With application of the proposed theory, a precise control algorithm is developed for a nonlinear two-span roll-to-roll web control system based on the backstepping method. The design parameters are chosen optimally by using the modified genetic algorithm. The reliability of the proposed algorithm is validated through simulations in Matlab/Simulink and real experiments
A welded joint formed between stainless steel and a copper-base alloy is a combination of materials with high corrosion resistance and high mechanical strength and materials with high thermal conductivity. Such a combination is suitable for applications in heat exchangers and piping design among others. Forming a welded joint between stainless steel and a copper-base alloy is difficult because the physical properties of the two metals—such as thermal conductivity and melting point—are different, and they do not form an alloy. In this study, we propose a method for butt welding brass and stainless steel using a disk YAG laser by selecting appropriate bonding conditions, and evaluate the characteristics of the joint. The results indicate that a good weld can be obtained by shifting the laser irradiation position to the brass side.
In this study, to improve accuracy and reproducibility of knee laxity diagnosis, Orthopaedic physical examination assisting system was developed. The system enables the surgeon to monitor the force vector added by himself and the posture of the knee in real-time. The advantage of the developed system is to quantify the normal orthopaedic physical examination, without any modification, which is accustomed to general orthopaedic surgeons. The force vector added to the shank by a surgeon is measured with 3 axis force sensor and 6DOF magnetic tracker FASTRAK, and 6DOF knee joint motion of the patient is measured with two FASTRAK receivers which are attached on its thigh and shank. In this system, to describe the 6DOF knee motion, Femoral and tibial coordinate systems are defined with bony landmark which is easily palpated and are registered to the thigh or shank receiver coordinate system by homogeneous transformation matrix which is acquired by the special stylus. To evaluate the effectiveness of the system, the posterior drawer test with the system was done by 5 young healthy people. The evaluation parameters were knee posture, load magnitude and load position during the experiment. The result showed examination accuracy was significantly improved in all evaluation parameters.
Several insulating ceramic materials have been machined by electrical discharge machining (EDM) using the assisting electrode method that has been proposed by the authors' group. In this machining process, carbide products that are electrically conductive are made on the surface of workpiece. These products maintain the electrical conductivity of the workpiece surface during the machining process. The physical and mechanical characteristics of the layer were affected by the electrical machining conditions and by the physical characteristics of the workpiece. In this paper, three types of insulating ZrO2 ceramics were sintered and machined using sinking EDM in order to investigate the effects of different additive amounts on the machining properties of ZrO2-Y2O3 insulating ceramics. The material removal rate, wear ratio of the electrode, and the surface roughness were estimated. As the experimental factors, the ideal polarity of the electrode, setup discharge current, and Al2O3 additive amount were researched. The electrically conductive layer adhesion condition was recorded by SEM observation.
This work deals the creasing characteristics of coated paperboard. It was not clarified to estimate the deformation behavior of creased line from the first peak bending moment Mp1 and the initial gradient C1 of bending moment. In this study, a new prototype testing apparatus has been developed for seeking the bending moment and the side view picture of creased part during repeated folding motion. The permanent (residual) deformation angles, the variance of residual stiffness and the hysteresis characteristics of bending moment were analyzed for the nominal shear strain (the scoring depth) γ . The obtained results were as follows: (1) C1 was characterized with γ, while the second term gradient C2 was characterized with γ and the inverse of tracking angle Θ-1. (2) By introducing the area of closed curve of second term hysteresis ACC, it is revealed that the gradient of ACC was remarkably varied with Θ at near the peak point Mp1.
In this study, we have proposed a gelatin-based stone (gelatin stone) with a new polishing mechanism that can polish a free-form surface. To clarify the possibility of using a gelatin stone as a fine polishing tool, we experimentally examined its fundamental polishing performance. Two types of gelatin stones (jelly and gummy) were prepared. A convex glass and a pure aluminum plate were used as work materials. The main results obtained are as follows. Polishing the convex glass with the jelly-type gelatin stone improves the surface roughness while maintaining profile accuracy. The surface roughness of the pure aluminum plate can be improved by polishing with the gummy-type gelatin stone, although the polishing cannot yield a mirror-finished surface. The abrasive grains in the gelatin stones can be recovered by incineration at 600-650°C.