Papers by Keyword: 3D FEA

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Authors: L. Zheng, J.M. Luo, Bang Cheng Yang, Ji Yong Chen, Xing Dong Zhang
Abstract: Stress shielding, which occurred always around traditional one part implant applied for prosthetic artificial lower limb attachment, would cause osteoporosis and thus result in the loose and extrusion, and then the malfunction of the implant. To improve the structure of the implant, a new type of implant—multi-part implant was developed in this article. Based on CT data and under the maximal load during a normal walking cycle, 3D finite element analysis (FEA) was carried out to analyze the stress of bone around the new implant in three cases of distally truncated femur at high position、middle-position and low-position. Results reveal that stress shielding and stress concentration under the new type of implant reduced effectively compared with the traditional one-part implant, and the stress distribution is much close to the natural bone. Application for distally truncated femur at middle-position and low-position was much better, while stress concentration was marked at high-position. Meanwhile, the stability in vivo can also be maintained with the multi-part implant. The new implant is promising applied for prosthetic limb.
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Authors: Thomas Henke, Markus Bambach, Gerhard Hirt
Abstract: Gearing components are an example for widely used machining parts in engines. Nowadays the development and optimization of materials and process chains are driven towards a concurrent improvement of final product properties and production efficiency. Excellent mechanical properties needed for gearing components e.g. high load capacity and high fatigue resistance depend on a fine homogeneous microstructure in the final product. Efficiency in gear manufacturing can be optimized by increasing the temperature during processing, which allows for lower forging loads and lower die stresses, thus improving die life in terms of mechanical fatigue. Additionally, increasing the temperature during case hardening reduces the process duration significantly. Hence process efficiency also increases. To meet the need of a fine homogenous microstructure, dynamic recrystallization has to be initiated during hot forging and grain growth has to be avoided during dwell times and case hardening. This grain size control can be achieved by applying micro-alloying concepts. Recently, an Nb-Ti-based alloying concept for case hardening steels was introduced, which increases fine grain stability and therefore potentially allows for higher forging and case hardening temperatures, leading to improved process efficiency [1]. In this paper a 25MoCr4-Nb-Ti steel grade is characterized in terms of flow resistance and microstructure evolution by hot compression tests and annealing experiments. The processing limits of this material in terms of abnormal grain growth are determined and a JMAK-based microstructure model considering these limits is presented and implemented in the FE-Software DEFORM 3dTM. The model is used in a case study to design a laboratory scale forging process for lowest possible die stresses and finest possible grain sizes. Experimentally measured grain sizes and forging loads from forgings at the laboratory scale are used to evaluate the process design. It is shown that considering microstructure evolution in process design is absolutely necessary to jointly optimize for process efficiency and final properties. The application of the Nb-Ti-based micro-alloying concepts allows for lower die stresses and thus seems to reduce mechanical fatigue of the dies compared to conventional case-hardening steels. [1] S. Konovalov et. al.: Testcase gearing component. In: G. J. Schmitz, U. Prahl (Ed.): Integrative Computational Materials Engineering, Wiley-VCH Verlag GmbH & Co. KGaA, 2012, ISBN 978-3-527-33081-2
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