The effect of stress triaxiality and strain-rate on the fracture characteristics of ductile metals

Mirza, M. Saeed; Barton, D.C.; Church, P.

doi:10.1007/bf01139164

Cited by 92 publications

(42 citation statements)

References 9 publications

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“…A simple exponential expression for the evolution of the equivalent strain with stress triaxiality was established by McClintock (1968) and Rice and Tracey (1969) based on the analysis of void growth under hydrostatic loads, which is usually referred to as the two-dimensional fracture loci. The work performed by Mirza et al (1996) on pure iron, mild steel, and aluminum alloy BS1474 over a wide range of strain rates confirmed the strong dependence of the equivalent strain to crack formation with the level of stress triaxiality.…”

Section: Constitutive Models For Ductile Failure Under High and Low Tsupporting

confidence: 67%

Ductile Failure Modelling: Stress Dependence, Nonlocality, and Damage to Fracture Transition

Pires

Andrade³

et al. 2013

Handbook of Damage Mechanics

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In this chapter, some recent developments and proposals for improvement of material models at the constitutive level to deal with ductile damage at large plastic strains are addressed. Numerical tests are carried out to test their performance on shear-dominated stress states where their main differences lie. Subsequently, aspects of the use of nonlocal models for the regularization of the numerical values associated with damage models, namely, discretization dependency, are reviewed. Different approaches on the choice of the regulation variable or variables are tested at different stress states characterized by different values of triaxiality and third invariant of the deviatoric stress tensor. Finally, a simple strategy on how to handle the transition from damage to fracture by means of the extended finite element method is described.

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Section: Constitutive Models For Ductile Failure Under High and Low Tsupporting

confidence: 67%

Ductile Failure Modelling: Stress Dependence, Nonlocality, and Damage to Fracture Transition

Pires

Andrade³

et al. 2013

Handbook of Damage Mechanics

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“…8, can be used to calculate the residual stress triaxiality (ratio of hydrostatic to von Mises stresses) at any location along the measurement line. This parameter can have a significant effect on crack initiation and opening behaviour in ductile materials [34] and on fracture [35][36][37]. The measurements show that exceptionally high stress triaxiality is present (approaching unity) in the region between 17 and 22 mm from the CT blank front face.…”

Section: Discussionmentioning

confidence: 82%

Measurement of the Residual Stress Tensor in a Compact Tension Weld Specimen

et al. 2012

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Neutron diffraction measurements have been performed to determine the full residual stress tensor along the expected crack path in an austenitic stainless steel (Esshete 1250) compact tension weld specimen. A destructive slitting method was then implemented on the same specimen to measure the stress intensity factor profile associated with the residual stress field as a function of crack length. Finally deformations of the cut surfaces were measured to determine a contour map of the residual stresses in the specimen prior to the cut. The distributions of transverse residual stress measured by the three techniques are in close agreement. A peak tensile stress in excess of 600 MPa was found to be associated with an electron beam weld used to attach an extension piece to the test sample, which had been extracted from a pipe manual metal arc butt weld. The neutron diffraction measurements show that exceptionally high residual stress triaxiality is present at crack depths likely to be used for creep crack growth testing and where a peak stress intensity factor of 35 MPa√m was measured (crack depth of 21 mm). The neutron diffraction measurements identified maximum values of shear stress in the order of 50 MPa and showed that the principal stress directions were aligned to within~20°of the specimen orthogonal axes. Furthermore it was confirmed that measurement of strains by neutron diffraction in just the three specimen orthogonal directions would have been sufficient to provide a reasonably accurate characterisation of the stress state in welded CT specimens.

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“…The results which are mentioned later relate to mild steel which is highly similar to S355J2G3 steel in terms of mechanical characteristics. Based on results of Mirza et al (1996), it is specified that fracture strain is highly dependent on triaxial stress of while it doesn't change considerably in different strain rates. Tests have been performed at room temperature.…”

Section: Continuous Damage Modelsmentioning

confidence: 99%

“…Based on work of Mirza et al (1996), the information obtained from numerical tests and simulations in different strain rate and different triaxial stress levels has been used for obtaining constants in Johnson -Cook damage model. To use this model, only limited number of constants is necessary while more constants are required for use of fracture models of soft metals, Seaman et al (1987) and Needleman and Tvergaard (1984).…”

Section: Continuous Damage Modelsmentioning

confidence: 99%

Studying energy absorption in tapered thick walled tubes

Tehrani

Ferestadeh

2015

Lat. Am. j. solids struct.

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In many engineering structures different energy absorption systems may be used to improve crashworthiness capability of the system and to control damages that may occur in a system during an accident. Therefore, extensive research has been done on the energy-absorbing cells. In this paper, energy absorption in tapered thick walled tubes has been investigated. As a practical case, studies have been focused on the crush element of Siemens ER24PC locomotive. To investigate performance of this part at collision time, it has been modeled in Abaqus software and its collision characteristics have been evaluated. Considering that the crash element is folded at time of collision, an analytical approach has been presented for calculation of instantaneous folding force under axial load. Basis of this method is definition and analysis of main folding mechanism and calculation of average folding force. This method has been used for validation of the results of numerical solution. Since sheet thickness of the crash element is high and may be ruptured at time of collision, some damage models have been used for numerical simulations. One of the three damage models used in this paper is available in the software and coding has been done for two other damage models and desirable damage model has been specified by comparing results of numerical solution with results of laboratory test. In addition, authenticity of the desirable damage model has been studied through ECE R 66 standard. To improve crashworthiness characteristic some attempts, such as use of metal foam and creation of trigger in suitable situations to reduce maximum force resulting from collision, have been performed. Finally though different simulation optimal crush element has been introduced and its performance and efficiency have been evaluated.

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The effect of stress triaxiality and strain-rate on the fracture characteristics of ductile metals

Cited by 92 publications

References 9 publications

Ductile Failure Modelling: Stress Dependence, Nonlocality, and Damage to Fracture Transition

Ductile Failure Modelling: Stress Dependence, Nonlocality, and Damage to Fracture Transition

Measurement of the Residual Stress Tensor in a Compact Tension Weld Specimen

Studying energy absorption in tapered thick walled tubes

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