Interaction analysis between strain concentration and strain localization in cracked body

Abstract

The appearance of strain localization (SL) in front of the crack tip is a factor that promotes transition toward the fatigue crack extension mode. Therefore, to predict fatigue crack extension behavior in case multiple modes occur, it is necessary to evaluate the degree of SL. In this study, the following simulations were performed on a single-crystal twinning-induced plasticity (TWIP) steel:(a) SL characterization by crystal plasticity finite element method (CPFEM) analysis of a smooth specimen under tension, (b) strain concentration (SC) characterization by EP-FEM analysis of a cracked specimen under tension, and (c) characterization of interaction results between SC and SL of a cracked specimen under tension by CPFEM analysis. A comparison of the above results found that the interaction between SC and SL was large for long cracks and a significant strain field, different from the Hutchinson, Rice, Rosengren (HRR) singular field, was formed in front of the crack tip. Therefore, a parameter was proposed to quantify the SL properties in a smooth specimen.Subsequently, a fracture-mechanics-like method was proposed in which the results of (b) and the introduced parameters control the results of (c).

Material index for strain localization susceptibility in cracked bodies: Examination of single‐crystal Cu using crystal plasticity finite element method

“…Since the symmetry constraints are met, a quarter of the model is used, as shown in Figure 2B, to reduce the solving cost. 20 The total number of elements in this model is 256,000. Moreover, this specimen is the same type as the 2D smooth specimen.…”

“…A ratio to indicate the strain localization behavior during tensile loading was proposed by Li et al 20 Strain localization means the local strain is higher than in other areas. The necking area is the area with the highest strain localization.…”

“…where ε max and ε yy are the maximum normal strain and average normal strain in the tensile direction along the necking plane, respectively, for smooth plane specimen under tensile loading (Figure 1B). Li et al 20 gave the variation figure of the M as the average normal strain ε yy increase. The figure shows M will increase firstly and then become a constant value as ε yy increase.…”

“…To quantify this term, we proposed a new parameter that can indicate the SLS of a material in our previous study. 20 In the previous paper, we showed that the interactions among material behavior, strain localization, mechanical behavior, and strain concentration led to the formation of a strain field in a cracked single crystal subjected to remote tensile stress that was quite different from the HRR singularity introduced in the homogeneous continuum. 21 However, the availability of a material index for SLS was not verified.…”

Deterministic approach on microstructurally small crack definition based on a crystalline plasticity finite element method incorporating strain localization

“…[16][17][18] Recently, Verma et al 19 and Suzuki et al 20 found that strain distribution around the crack tip, fatigue limit, and crack extension mode for the metals susceptible to strain localization differs from those of the metals that are unsusceptible to strain localization. Li et al 21 proposed a new strain localization parameter to quantify the susceptibility of strain localization for the metal. Therefore, strain localization should be considered a material property of the metal.…”