Abstract A detailed study has been made of the effects of hydrostatic pressures in the range 0.1–600 MPa on the tensile fracture strain of an α-brass. Fracture strain has been found to increase linearly with pressure up to 350 MPa, to decrease between pressures of 350 and 375 MPa and to then increase to a constant value at pressures greater than 450 MPa. The abrupt change from linearity of the fracture strain-pressure relationship at a pressure of 350 MPa was found to coincide with the suppression of large scale void development. At pressures below 350 MPa, fracture was found to occur by the conventional mechanism involving void coalescence whereas at higher pressures fracture occurred entirely by a shear process. Calculations of the increase of the resultant triaxial stress component in the necked region of specimens with strain have shown that, at pressures up to 350 MPa, fracture occurs when this stress reaches a critical value of about 325 MPa.
Last. C.W. Weaver(Australian Department of Defence)H-Index: 2
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Abstract The effects of hydrostatic pressures in the range 0.1 to 600 MPa on the tensile fracture of a free machining brass have been studied. In agreement with the results of earlier workers, the natural strain to fracture was found to increase rapidly with pressure for pressures up to 300 MPa, but to increase less rapidly at the higher pressures. The rapid increase in ductility under confining pressures up to 300 MPa is shown to be due to the suppression of void development, by the pressure, u...
For specimens under ultra-low-cycle fatigue loading, cyclic plasticity and negative stress triaxialities are two main differences from monotonic loading cases. In this chapter, a crack initiation rule by adding a damage accumulation rule under negative stress triaxialities is proposed, where no damage accumulation is assumed for stress triaxialities below −1/3. This rule is based on previous experimental results. This chapter is mainly focused on the crack initiation rule of ductile metal under ...
#1Philip J. Noell(SNL: Sandia National Laboratories)H-Index: 7
#2Jay Carroll(SNL: Sandia National Laboratories)H-Index: 18
Last. Brad L. Boyce(SNL: Sandia National Laboratories)H-Index: 42
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Abstract One of the most confounding controversies in the ductile fracture community is the large discrepancy between predicted and experimentally observed strain-to-failure values during shear-dominant loading. Currently proposed solutions focus on better accounting for how the deviatoric stress state influences void growth or on measuring strain at the microscale rather than the macroscale. While these approaches are useful, they do not address a significant aspect of the problem: the only rup...
Shape memory alloys present a unique ability to undergo a solid-to-solid, diffusionless, reversible phase transformation. The forward phase transformation is commonly associated with transforming from the austenitic phase to the martensitic phase, while the reverse transformation is defined by going from the martensitic phase to the austenitic phase. In thermal actuation loading paths, forward transformation is generally associated with cooling, while reverse transformation is commonly associate...
A limiting factor of high pressure die cast (HPDC) Mg alloys is the presence of porosity, which has a detrimental effect on the mechanical strength and gives rise to a large variability in the ductility. The application of hydrostatic pressure after casting is known to be beneficial to improve the mechanical response of HPDC Mg alloys. In this study, a combined experimental and simulation approach has been developed in order to investigate the influence of pressurization on the 3D porosity distr...
Abstract This paper aims to predict ductile fracture of mild steel under cyclic large strain loading (CLSL) using only tensile coupon test results. A micromechanics-based fracture model which adopts void growth model and Miner's rule in incremental form is proposed, where fracture is assumed to occur when a damage index reaches unit. Damage is postulated not to accumulate when stress triaxiality is less than a threshold. To calibrate the fracture model, cyclic experimental and numerical studies ...
It has been shown that the plastic response of many materials, including some metallic alloys, depends on the stress state. Based on plasticity analysis of three metal alloys, a series of new plasticity models with stress state effect is proposed. The effect of stress state on plasticity and the general forms of the yield function and flow potential for isotropic materials are assumed to be functions of the first invariant of the stress tensor (I1) and the second and third invariants of the devi...
We start by generalizing the one dimensional Considere condition to a maximum power condition for arbitrary three dimensional loadings. In particular, proportional loadings with arbitrary confining pressures and Lode angles are considered. It is shown that the maximum power localization criterion for J2 material does not agree with experimental observations. The constitutive relationship of damage plastic solids is then introduced to the maximum power condition for the diffused necking. We show ...
#1Yingbin Bao(MIT: Massachusetts Institute of Technology)H-Index: 6
#2Tomasz Wierzbicki(MIT: Massachusetts Institute of Technology)H-Index: 65
Abstract Although yield condition of metals does not strongly depend on it, mean stress plays an important role in fracture of metals. A cut-off value of the stress triaxiality equal to −1/3, below which fracture never occurs, was derived analytically from the fracture locus in the principal strain space experimentally reported from upsetting tests. It was found that this result is consistent with tensile tests under hydrostatic pressure (Bridgman tests). Numerical simulations performed in this ...