Key Engineering Materials Vols. 622-623

Abstract: A theoretical and experimental analysis of heat induction bending for tubes used in the power industry is performed. First, the design of the heat induction bending process for tubes is described and industrial application areas for this technology are presented. Next, the main methods for tube bending with local induction heating are discussed and the effect of the technology on geometrical parameters of bends formed is presented. Then, the heat induction bending process for tubes is modeled using numerical techniques (FEM). The simulations are performed in a three-dimensional strain state, where thermal phenomena are taken into account, using the commercial software package Simufact Forming v. 11.0. In the simulations, the changes in workpiece geometry in the region of the bend being made (cross section ovalization, darkening and thickening of walls, neutral axis position) are examined. Also, potential phenomena that could limit the stability of the bending process and cause shape defects are predicted. The results of the numerical modeling are then compared to those obtained under industrial conditions.

Abstract: Micro parts like medical catheters or end effectors require micro rotary swaging to process forming or joining. Higher strength or sophisticated inner features can be achieved through micro rotary swaging which are difficult for the micro machining or grinding process. This work focuses on examining the formability of micro pipes of AISI 304 stainless steel with micro rotary plunge-swaging. Both as-received and vacuum-annealed pipes with both furnace-cooling and water-cooling were tested. The micro hardness and grain size of the as-received and vacuum-annealed pipes were measured. The result shows that the as-received micro pipes need be annealed to be suitable for the micro swaging process. Best swaging result was obtained when annealing with a holding time of 45 minutes and furnace-cooling were used. The G2 workpiece is better than the G1 and the G3 workpieces. This is because the G1 workpieces experience more deformation due to thicker walls, and insufficient grain layers were formed in the G3 workpiece during the annealing.

Abstract: Recently, special tubes for high efficiency heat exchangers, high functionality electrodes, and super-micro medical needles have attracted attention. In order to produce such special tubes, however, a special processing method or tool is required. In this study, fabrication of special tube by bunch drawing and fluid-mandrel drawing were attempted. And it was revealed that the fabrication of special tubes with a variety of cross-sectional shape is possible, when a bunch of tubes, or a tube of large diameter in which a number of fine tubes are inserted, is drawn. Presumption of cross-sectional shapes after bunch drawing was examined by FE analysis. Cross-sectional shapes and the distribution of Vickers hardness which has relation to equivalent strain were compared between tubes obtained virtually by FE analysis and fabricated actually in this study. It was found that they correspond very well and FE analysis is useful for the presumption of cross-sectional shapes after bunch drawing. Meanwhile, downsizing of medical needles and heat exchanger tubes has been required from the market. So it is necessary to fabricate an inner-grooved fine tube with thin wall-thickness, and at that time the inner grooved geometry must be homothetic. Hollow sinking was carried out to reduce the diameter of a tube. And cross-sectional shape, groove geometry, and the change of wall thickness after processing were examined. In hollow sinking, increase of wall-thickness, change of inner groove geometry, and poor inner surface quality were found. Therefore, newly-devised fluid-mandrel drawing was applied. And it was revealed that it is possible to obtain an inner grooved tube of which groove shape is nearly similar to that of pre-processed tube, even after the processing of diameter reduction. Also, it was clarified that the production of a medical painless needle of 0.2mm in diameter by fluid-mandrel drawing was possible.

Abstract: Tube hydroforming (THF) is one of metal forming technologies which has been widely used to manufacture complex hollow workpeices. In THF, a variety of failures may occur and one of them is wrinkling. But recent researches show that wrinkling may be used as a preforming process to improve the formability of tubes. In this paper, a new geometry-based wrinkling indicator is proposed to evaluate the wrinkling level in THF and the wrinkle evolution diagram (WED) based on the shape change of the wrinkles is presented to display the four-stage evolution of the useful wrinkles. The wrinkling levels in THF with axial feeding under various loading paths are predicted respectively via finite element simulation, the influence of loading paths on the wrinkling behavior is investigated, and the evolving stages of the useful wrinkles is revealed via the proposed WED. The results indicate that the proposed wrinkle indicator can distinctly evaluate the wrinkling level, the wrinkling level under pulsating loading path is higher than that under polygonal linear one and four-stage evolution of the useful wrinkles could be evidently demonstrated via the WED. Notation

Abstract: Application of sensitivity analysis in optimization of process parameters of production processes for innovative materials, e.g. dual phase steel, requires deterministic model of thermomechanical processes and large datasets that covers whole surface of results. Difficulties in optimization of process parameters correspond with large number of control variables, which should be considered in the technology design. Furthermore, conduction of such analysis takes the great computational cost. Presented work concerns possibility of application of regression trees, especially CART model, in preliminary analysis for sensitivity analysis. Use of data mining algorithms enables acquiring of preliminary, rough results: relationships among parameters of the hot rolling process of dual phase steel strips and rules of optimization of this process, it also does not require any apriori knowledge about thermomechanical processes.

Abstract: Aim of the paper is to solve the inverse problem in solidification of binary alloyby applying the Artificial Bee Colony algorithm. Considered inverse problem consists in recon-struction of the heat flux and the distribution of temperature in case when the temperaturemeasurements in selected points of the alloy are known and is mathematically modeled be meansof the heat conduction equation with the substitute thermal capacity and with the liquidus andsolidus temperatures varying in dependence on the concentration of the alloy component. Fordescribing the concentration the lever arm model is applied and for minimizing a functional,constituting the crucial part of the procedure, the ABC algorithm is used.

Abstract: The paper presents an application of Ant Colony Optimization algorithm as a partof procedure for solving the inverse solidification problem. Investigated task consists in recon-struction of the boundary condition (heat flux) on the basis of temperature measurements inselected points of the cast. First step of the method is based on the finite difference method withapplication of the generalized alternating phase truncation method and serves for solving theappropriate direct solidification problem. In the second step some functional representing thecrucial part of the procedure is minimized with the aid of Ant Colony Optimization algorithm.

Abstract: The success of sheet hydroforming process largely depends on the loading pressure path. Pressure path is one of the most important parameters in sheet hydroforming process. In this study, a combination of finite element simulation, artificial intelligence and simulated annealing optimization have been utilized to optimize the pressure path in producing cylindrical-spherical parts. In the beginning, the finite element model was verified based on laboratory experimental results. The experiments were designed and a radial basis neural network model was developed using data generated from verified finite element model to predict the thickness in the critical region of the product. Results indicated that the neural network model could be applied successfully to predict the sheet thickness in the critical region. In addition, the neural network model was used as a fitness function in simulated annealing algorithm to minimize the thickening in the above mentioned critical region. The final results showed that utilization of the optimized pressure path yields good thickness distribution of the part.

Abstract: With regard to the climate change as well as the shortage and increase in price of natural resources, efficient resource management becomes more and more important, also for production processes. More than half of the sheet metal used in the automotive industry is wasted. Considering the amount of energy and the added value associated to the discards, enormous savings are possible. The approach of this research work is to avoid waste during a forming process by means of a continuous process monitoring and a self-learning intelligent tool interacting with the servo press. The flexibility of the servo press, which is so far used to optimize the single press stroke, only, shall be exerted to respond on altering material properties of blank sheets and the thereby changing forming behaviour. The sample process includes a two-tiered bending process, in which a conventional punch performs the pre-bending in the first step and an independent servo axis the compensation-bending in the second step. If an inadmissible bending angle is measured after the second step, the servo press stops automatically and the additional servo axis performs a teaching-stroke to adjust the compensation angle. After that, the continuous process starts again. This paper presents the springback compensation strategy which uses flexible correction algorithms based on data of the on-line process monitoring as well as data of the previous bending steps. Finite Element Analyses are carried out to validate the strategy.

Abstract: Bicycle industry has been an international reputation as bicycle kingdom in Taiwan, but the problem of global warming green energy rise, the development of insulating object of hub dynamo and power output connector to bring new hope to bike industry. In this study connector power output to gather public opinion related to patent, basis of collected documents as basis for design, structural components in least drawn to power output with simple connector. The study objectives connector hoped at structure strongest, highest efficiency in output performance characteristics such as use computer-aided drawing software Solid works to establish power output connector parts of 3D model. A series of simulation analyses, in which the variables relied on Moldflow and ANSYS software forming, which were execution to investigate the effective stress, effective strain, weld line, injection time, injection pressure and filling state of insulating object plastic injection forming of insulating object of bicycle dynamo hub.