Computational Studies for the Yield-Point Phenomenon of Metals
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REVIEW
Computational Studies for the Yield‑Point Phenomenon of Metals Jaehyun Kim1 · Do‑Nyun Kim2,3,4 Received: 28 April 2020 / Revised: 28 April 2020 / Accepted: 15 July 2020 © Korean Multi-Scale Mechanics (KMSM) 2020
Abstract The yield-point phenomenon (YPP) is an accustomed topic in sheet metal forming fields. Over hundred and fifty years since the first observation of the YPP, many research efforts have been continued to understand and describe it. Recent spotlights for the YPP studies are focusing on high-degree numerical methods with the support of increasing computing performance. Here, we review the representative computational studies on YPP to share the latest progress and remaining challenges to obtain better mechanical insights into it. After the duality of the YPP is addressed in terms of avoiding and utilizing it, the constitutive material models for the YPP as well as bake hardening models are discussed for a continuum level FE simulations, and the features of the discussed YPP models are compared. Microscopic and multiscale schemes are also briefly handled. It is expected that more advanced computational work can be initiated from this review. Keywords Yield-point phenomenon · Lüders band · Finite element analysis · Bake hardening
Introduction Strongly related to the well-known Cottrell atmosphere, the yield-point phenomenon (YPP) is an intriguing yielding behavior often observed in some alloys and metals such as an annealed or aged low carbon steel. Generally, in a uniaxial tensile test, prominently heightened yielding point and subsequent stress tumble with fluctuation can epitomize this phenomenon. These characteristics are illustrated in Fig. 1. As described in Fig. 1b with the specimen schematics, the sharply increased yielding stress typically occurs at the end of the reduced section. This can be an elastic limit which
* Do‑Nyun Kim [email protected] Jaehyun Kim [email protected] 1
Materials Forming Research Group, POSCO, 100 Songdo Gwahak‑ro, Yeonsu‑gu, Incheon 21985, Republic of Korea
2
Department of Mechanical Engineering, Seoul National University, 1 Gwanak‑ro, Gwanak‑gu, Seoul 08826, Republic of Korea
3
Institute of Advanced Machines and Design, Seoul National University, 1 Gwanak‑ro, Gwanak‑gu, Seoul 08826, Republic of Korea
4
Institute of Engineering Research, Seoul National University, 1 Gwanak‑ro, Gwanak‑gu, Seoul 08826, Republic of Korea
also can be called the upper yield point. The lower yielding fluctuation after the subsequent stress drop results from the local plastic deformation consisting of Lüders bands nucleation and propagation. If the material does not have the YPP, homogeneous plastic deformation is commonly observed in the reduced section of the specimen as the last schematic of Fig. 1b. Piobert et al. [1] found superficial markings on an iron plate against which artillery projectiles were fired in their experiments. Although these markings were not described explicitly with inherent material characteristics in their study [2], they have been regar
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