Calibration of ductile fracture criteria at negative stress triaxiality

Kubík, Petr; Šebek, František; Hůlka, Jiřı́; Petruška, Jindřich

doi:10.1016/j.ijmecsci.2016.02.001

Cited by 60 publications

(17 citation statements)

References 35 publications

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“…Over the last several years, researchers have developed a number of fracture models for determining the moment of fracture initiation. These models can be classified as follows [5][6][7][8]:…”

Section: Introductionmentioning

confidence: 99%

Rotary compression in tool cavity—a new ductile fracture calibration test

Pater

Tomczak

Bulzak

et al. 2020

Int J Adv Manuf Technol

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Ductile fracture is one of the most common failure modes in hot metal forming. It can be predicted by means of so-called damage functions that describe the relation between stress, deformation and fracture initiation. A practical use of these functions requires the knowledge of the critical damage value of the material that is determined by calibration tests based on compression, tension and torsion. For the prediction to be correct, one must ensure that the modelled and real stresses are in agreement. Previous studies did not offer any effective test for determining critical values of damage under changing load conditions that occur in cross and skew rolling processes, among others. To compensate for this knowledge gap, researchers at the Lublin University of Technology have developed a new test consisting in rotary compression of a test-piece in a cavity between the tools, which is described in this paper. In the proposed test, a cylindrical test-piece is rolled over a cavity (impression) created by grooves on two mating tools. The cavity height is smaller than the test-piece diameter. At the critical value of the forming length, the state of stress induced thereby in the test-piece axis causes fracture. Knowing the critical forming length, it is possible to determine the critical value of damage by numerical modelling. The practical application of the proposed test is illustrated through the case of C45 grade steel subjected to forming in the temperature range 950-1150°C. The analysis makes use of the normalized Cockcroft-Latham (NCL) criterion of ductile fracture.

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Section: Introductionmentioning

confidence: 99%

Rotary compression in tool cavity—a new ductile fracture calibration test

Pater

Tomczak

Bulzak

et al. 2020

Int J Adv Manuf Technol

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“…Churyumov et al investigated the change in stress triaxiality according to deformation, and attempted to determine the critical values of the modified Rice and Tracy criteria by considering the stress triaxiality at the moment of fracture under various temperature and strain-rate conditions [18]. Kubík et al investigated the ductile fracture criteria under low stress triaxialities for aluminum alloy 2024-T351 and AISI 1045 carbon steel, and implemented the calibrated ductile fracture criteria in the user subroutine VUMAT of the commercial finite element code Abaqus [19]. Kim and Kim formulated a damage-based fracture criteria incorporating the temperature and strain-rate effects and predicted the fracture behavior of magnesium alloy sheets [20].…”

Section: Introductionmentioning

confidence: 99%

A Study on the Effect of Process and Material Variables on the Hot Stamping Formability of Automotive Body Parts

You

Kim

2021

Metals

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Hot stamping is a method capable of manufacturing high-strength automotive body parts by inducing a martensitic phase transformation through forming and die quenching after heating a metal sheet into a high temperature austenite phase. However, it is not easy to solve various formability problems occurring in the hot stamping process due to the complexity of the process and material behavior during high temperature forming. In this study, fracture-related forming limits and martensite phase ratio were selected as criteria for evaluating hot stamping formability. First, a hot stamping test was performed on a T-type part that simplified the B-pillar, an automotive body part, and the fracture behavior according to the temperature and thickness of the sheet blank was investigated. Additionally, forming analysis was performed on the hot stamping process of mass-produced B-pillar parts by varying the temperature of the sheet blank, the thickness of the sheet blank, the die-blank friction coefficient, and the strain-rate sensitivity of material among various process and material variables. Based on the analysis results, the effect of each process and material variable on the hot stamping formability of B-pillar parts was quantitatively analyzed. By utilizing the results of this study, it will be possible to solve the formability problem that occurs in the mass-production hot stamping process for automotive body parts and improve the quality of parts in the future.

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“…Often, to enhance model shear predictive capability [18] or to reproduce the failure locus for shear-sensitive materials [19,20], dependence on the third deviatoric stress invariant effect is introduced phenomenologically. In most cases, these model adjustments are verified in the regime of low positive stress triaxialities, although ductile fracture in the negative stress triaxiality regime has been also investigated by more than a few authors [21][22][23].…”

Section: Introductionmentioning

confidence: 97%

modelling ductile fracture in third stress invariant sensitive materials: application to al2024-T351

Bonora

Testa

Ricci

et al. 2022

Preprint

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Triaxiality alone is not sufficient to account for the role of stress state on ductility in materials that exhibit shear effects on fracture strain. For these materials, it has been proposed that ductility also depends on the third invariant of the stress deviator. Recently, Bonora and Testa [N. Bonora, G. Testa, Plasticity damage self-consistent model incorporating stress triaxiality and shear-controlled fracture mechanisms – model formulation, Eng. Frac. Mech. 271, 108634 (2022).] derived a plasticity damage self-consistent (PDSC) model considering damage contributions due to intervoid necking, shearing, and sheeting for an arbitrary stress state. In this work, the PDSC model has been applied to Al2024-T351 considering the experimental results reported in the literature obtained on several different sample geometries and material batches. The ability of the model to predict the transition from cup-cone to slant fracture for different stress states is shown. In addition, the possibility to predict ductile fracture in the negative stress triaxiality range has been also demonstrated showing that it can occur for stress triaxiality even much less than -0.5 as long as there is a dominant shear deformation state.

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Calibration of ductile fracture criteria at negative stress triaxiality

Cited by 60 publications

References 35 publications

Rotary compression in tool cavity—a new ductile fracture calibration test

Rotary compression in tool cavity—a new ductile fracture calibration test

A Study on the Effect of Process and Material Variables on the Hot Stamping Formability of Automotive Body Parts

modelling ductile fracture in third stress invariant sensitive materials: application to al2024-T351

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