Explicit coupled thermo‐mechanical finite element model of steel solidification

Abstract

SUMMARYThe explicit finite element method is applied in this work to simulate the coupled and highly non-linear thermo-mechanical phenomena that occur during steel solidification in continuous casting processes. Variable mass scaling is used to efficiently model these processes in their natural time scale using a Lagrangian formulation. An efficient and robust local-global viscoplastic integration scheme (Int. J. Numer. Meth. Engng 2006; 66:1955-1989) to solve the highly temperature-and rate-dependent elasticviscoplastic constitutive equations of solidifying steel has been implemented into the commercial software ABAQUS/Explicit (ABAQUS User Manuals v6.7. Simulia Inc., 2007) using a VUMAT subroutine. The model is first verified with a known semi-analytical solution from Weiner and Boley (J. Mech. Phys. Solids 1963; 11:145-154). It is then applied to simulate temperature and stress development in solidifying shell sections in continuous casting molds using realistic temperature-dependent properties and including the effects of ferrostatic pressure, narrow face taper, and mechanical contact. Example simulations include a fully coupled thermo-mechanical analysis of a billet-casting and thin-slab casting in a funnel mold. Explicit temperature and stress results are compared with the results of an implicit formulation and computing times are benchmarked for different problem sizes and different numbers of processor cores. The explicit formulation exhibits significant advantages for this class of contact-solidification problems, especially with large domains on the latest parallel computing platforms.

On the introduction of adaptive mass scaling in a finite element model of Ti6Al4V orthogonal cutting

“…Indeed, although many integration steps are necessary in the explicit resolution, it is often much faster than the implicit one. The absence of iterations and tangent stiffness matrix are the main reasons [35]. The contact management and thermal coupling are taken into account more easily and quickly in explicit [35].…”

Measuring Mechanical Behavior of Steel During Solidification: Modeling the SSCC Test

“…The validity of using this method is found elsewhere. [73] The effectiveness of using separate constitutive model for austenite and delta-ferrite to predict the tensile behavior of the Wray [14,15] and Suzuki et al [20] experiments has been shown elsewhere as well. [77] Figure 4 [77] shows that the constitutive models for delta-ferrite and austenite match well with tensile data from Wray for samples strained to 5 pct.…”

“…[64,65] Computational modeling evolved to more complex behavior including coupling the heat conduction and mechanical equilibrium equations with creep [66,67] and elasticviscoplastic behavior. [16,[68][69][70][71][72] Koric and Thomas and coauthors implemented the Kozlowski III model for austenite [13] and the Zhu model for delta-ferrite [68] into both implicit [16] and explicit [73] integration schemes to model the high-temperature behavior of steel. These models have been applied to predict crack formation during continuous casting.…”

High-efficiency coupled solidification-thermal stress simulation of casting based on explicit finite element method

“…できる技術を開発することが重要である． 鋳造の凝固・熱応力問題は非線形性が極めて強い現象であることから， 数値解析で取り扱おうとすれば，収束解を得るまでに莫大な計算コストを要してしまうことが多々ある．このよ うな非線形性の強い熱変形問題に対しては，陽解法有限要素法（FEM）に Mass Scaling 法を適用する手法が計算 時間を短縮する上で有効であるとされており，鋼の連続鋳造 (Koric, et al, 2009a(Koric, et al, , 2009b)，溶接時の熱変形(麻, 梅津, 2008)や熱間鍛造時における温度依存の変形抵抗を扱う問題 に適用してその効果を示した研 究例がある．しかし，上記の連続鋳造を対象とした研究例では，解析対象の一部のみを計算するにとどまってお り，その他の研究例では数分程度と短い現象時間を対象としたものがほとんどである．一方，大型鋼塊の鋳造問 題に対しては， 鋳塊の凝固挙動や凝固中の溶湯流動， さらには成分のマクロ偏析の解析に関する研究 (Schneider and Beckermann, 1995，Gu and Beckermann, 1999，Pickering, 2013 …”