Advances in Materials and Processing Technologies XV

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Authors: Chun Ho Liu, A. Cheng Wang, Kuo Zoo Liang
Abstract: To develop a generalized numerical model by the elasto-plastic formulation coupling with dynamic finite element method for the shot peening process of metal alloys is the main goal of this paper. The analysis code is based on the finite deformation theory; the optimum numerical technique and the relevant parameters of forming process. In this study, the simulations of single and multi shot forming process were performed. The effects of impact velocity and strain rate, size of workpiece, and the residual stress were observed and discussed in details. After comparing with the corresponding papers, the universal model for metal shot peening analyses will be developed completely. The most significant advantage of this paper is the development of the precise analysis technology to suit for the future necessity of the manufacturing processes. The suggested models and techniques are helpful in solving of impact problems or metal forming processes.
Authors: Fardin Nematzadeh, Sayed Khatiboleslam Sadrnezhaad, A.H. Kokabi, M. Razani, A.H. Mohagheghi
Abstract: Stent placement has been a main approach to treat gastrointestinal diseases during past decade. Nitinol superelastic stents have been considered as a solution to such difficulties as restenosis after implantation, low twisting ability, inadequate radial mechanical strength and inappropriate dynamic behaviors associated with the ducts. In this paper, effects of Af temperatures on mechanical performance of z-shaped Nitinol wire stent under crimping test for clinical applications are investigated by finite element simulation. Having 60% crimping and high radial resistive strength, favorable superelastic behaviors are attained at Af temperature of 22°C. The performance of the stent is seen to be drastically different with a mere change of 1° in the segments angle.
Authors: Stefan Kleditzsch, Michael Lätzer, Birgit Awiszus, Erhard Leidich
Abstract: Faced with increasing cost pressures, manufacturers need to find new solutions for shaft-hub connections. One example is the knurled interference fit, where a shaft with knurls and interference is pressed in a soft hub with a cylindrical bore. At present the potential of the knurled interference fit is not fully used, because there are no general standards available for the design and for the joining process. But the joining process in particular has an important impact on the join strength. A predominantly forming joining process offers some advantages compared to cutting. Forming allows a clearly higher contact pressure over the groove because of the displacement of the hub material, which leads to greater axial reliability. Also, the natural material structure is preserved by the forming, and this, in combination with the hardening of the hub, should allow a higher transmittable torque. The Finite Element Method is used for detailed investigation of the joining process and the transmission behavior in the axial direction. With this method, the local loads, for example the hardening of the hub over the groove due to the formed join, are investigated as well as further parameter variations (e.g., chamfer angle, interference). Hence, an analytical approach for the determination of the necessary joining force was derived.
Authors: M.K.A. Ariffin, Rohaya Kamaluddin, S.H. Tang, Saiful Bahri Mohamed
Abstract: The paper presents the work of analysis of Automated G-clip Paperclip machine of using Solidworks Simulation and a comparison between results of each analysis in cutting process using design of experiment (DOE) and followed by design verification of simulating the cutting process after design changes. It emphasizes on the analysis of process and additional substation process to overcomes current machining problem. The current problem is occurred at the cutting station, which lead to poor quality product. There is two-design stage, which is preliminary of design of experiments conducted in order to fulfill the design validity and design verification. Application of longitudinal cyclic transfer system in feeding with pre-straightener substation is implied for comprehensive feeding of the wire with 1.3 mm diameter in 2 second. Forming dies with stepper motor controller give the precise positioning and repeatability of movement since good stepper motors have an accuracy between 3 5% of a step and this error is non-cumulative from one step to the next. By incorporating the new station in simulation procedure for this machine, it shows that the product quality is improved.
Authors: Yin Gang Liu, Miao Quan Li
Abstract: The 300M steel was isothermally compressed on a Gleeble-3500 simulator at the deformation temperatures ranging from 1123 K to 1473 K, the strain rates ranging from 0.1 s-1 to 25.0 s-1 and a strain of 0.51. The morphology of austenite grains in the isothermally compressed 300M steel was observed using an OLYMPUS PMG3 microscope. The experimental results show that the deformation temperature and strain rate have an interaction effect on austenite grains in the isothermally compressed 300M steel. Dynamic recrystallization occurs more easily at high deformation temperature and low strain rate. Dynamic recrystallization occurs completely and the coarse grains occur at the deformation temperature above 1413 K. The austenite grain size increases as the deformation temperature increases while it decreases as the strain rate increases.
Authors: Andreas Krause, Hanns Kache, Georg Ullmann
Abstract: The early detection of defects in forged parts offers economical advantages due to the possibility of sorting them out of the process chain betimes. Hence, no further production costs are occurred by those parts. However, the detection of defects during forging processes is not state of the art. Usually defects of forged parts which are often not obvious and therefore cannot be identified by the press operator are detected by measurements after cooling or later by the customer. In both cases costs occur. Due to the rough conditions in forging shop floors (e. g. high temperatures and forces) the integration of sensors monitoring the forging process is hardly viable. Within the presented research project an in-situ forging process monitoring system is developed which works without sensors in the forging tool and shows results on the process quality directly after forging. A system consisting of two independent concepts (defect-identification and filling-identification) is developed to detect typical forging process failures. On the one hand the defect-identification is able to detect e.g. wrong press energy or insert-position. On the other hand the filling-identification aims to detect, if the cavity is completely filled by the work-piece. Both concepts work in real-time with the help of a computer and a screen visualising the results. One the one hand this paper presents the results of forging trials using the defect-identification and evaluates its capability. On the other hand the concept for the filling identification is presented.
Authors: Shane Giskaas, Preston Wolfram, Kip O. Findley, Bernard S. Levy, Chester J. Van Tyne
Abstract: One mode that limits the usefulness of hot forging die steels is localized plastic deformation in regions of high pressure. To understand this behavior the yield strength of the steel needs to be measured at working temperatures in order to determine the likelihood of localized plasticity. One of the issues in using die steels for hot forging applications is that they are initially tempered to a hardness value when put into service. As the die is used to produce forged components, the contact with the hot forging causes the die to continue to temper and hence soften with continued used. To explore these issues three different die steels were obtained and tested experimentally. Experimental compressive yield strengths were determined for the three die steels (FX, 2714 and WF). The die steels were tempered to various hardness values prior to compression testing. The five room-temperature hardness values after tempering ranged from 20 to 38 HRC. The five temperatures for compression testing ranged from 593 to 704 °C (1100 to 1300 oF). From these tests a good characterization of the high temperature plastic behavior of each steel was obtained. It was found that the WF steel which had the highest alloy content was the strongest of the three steels under all test conditions. The FX and 2714, which had similar alloy contents (with FX having slightly less carbon, nickel and vanadium), had yield strengths that were close to each other at the intermediate temperatures, but at the high and low end of the testing range for temperature the FX was stronger than the 2714. Hence, to obtain the greatest resistance to localized plastic deformation during operations the choice of die steel should be WF, followed by FX and then 2714.
Authors: Dyi Cheng Chen, Wen Jong Chen, Tai Lin Hong, Sheng Han Chen, Yi Xiang Lin, Ming Jer Tsai
Abstract: Forging is a simple and low-cost mass production process. Metallic materials can be processed using plastic deformation. This research analyzes an innovative forging mold design for the highway bicycle pedal. A series of simulation analyses in which the variables depend on various temperatures of forging billet and mold, friction factors, and forging speed show effective stress, effective strain, and die radial load distribution for a forging process and mold design of a highway bicycle pedal. Finally, we identify the results of simulation analyses with the design of an experimental forging mold to lower deformation behavior of a highway bicycle pedal. The analysis results provide highway bicycle pedal forming mold references to identify whether it is suitable with the finite element results for high-strength mold design.
Authors: Abdulrahman Aljabri, Zheng Yi Jiang, Dong Bin Wei, Xiao Dong Wang, Hasan Tibar
Abstract: Controlling cold strip profile is a difficult and significant problem has been found in industry during thin strip rolling. At present choosing the new type of strip rolling mill is the one of main methods to control the strip shape quality in cold rolling. The influences of rolling process parameters such as the work roll cross angle and work roll shifting on the strip shape and profile of thin strip are recognised throughout this study. The results show that the roll crossing and shifting is efficient way to control the strip shape. The increase of the work roll crossing angle would lead to improve the strip profile significantly by decreasing the exit strip crown and edge drop. The strip profile would be enhanced if the axial roll shifting was increased. Moreover, the total rolling force was analysed in detail by changing the roll cross angle and axial shifting roll.

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