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Showing papers on "Strain hardening exponent published in 2012"


Journal ArticleDOI
TL;DR: In this article, the properties of a refractory multi-component alloy, Ta20Nb20Hf20Zr20Ti20, were determined in the temperature range of 296-1473 K and strain rate range of 10−1-10−5 s−1.
Abstract: Compression properties of a refractory multi-component alloy, Ta20Nb20Hf20Zr20Ti20, were determined in the temperature range of 296–1473 K and strain rate range of 10−1–10−5 s−1. The properties were correlated with the microstructure developed during compression testing. The alloy was produced by vacuum arc melting, and it was hot isostatically pressed (HIPd) and homogenized at 1473 K for 24 h prior to testing. It had a single-phase body-centered cubic structure with the lattice parameter a = 340.4 pm. The grain size was in the range of 100–200 μm. During compression at a strain rate of έ = 10−3 s−1, the alloy had the yield strength of 929 MPa at 296 K, 790 MPa at 673 K, 675 MPa at 873 K, 535 MPa at 1073 K, 295 MPa at 1273 K and 92 MPa at 1473 K. Continuous strain hardening and good ductility (e ≥ 50%) were observed in the temperature range from 296 to 873 K. Deformation at T = 1073 K and έ ≥ 10−3 s−1 was accompanied by intergranular cracking and cavitation, which was explained by insufficient dislocation and diffusion mobility to accommodate grain boundary sliding activated at this temperature. The intergranular cracking and cavitation disappeared with an increase in the deformation temperature to 1273 and 1473 K or a decrease in the strain rate to ~10−5 s−1. At these high temperatures and/or low-strain rates the alloy deformed homogeneously and showed steady-state flow at a nearly constant flow stress. Partial dynamic recrystallization, leading to formation of fine equiaxed grains near grain boundaries, was observed in the specimens deformed at 1073 and 1273 K and completed dynamic recrystallization was observed at 1473 K.

547 citations


Journal ArticleDOI
TL;DR: In this article, the effects of blending fibers on the tensile behavior of Ultra High Performance Hybrid Fiber Reinforced Concrete (UHP-HFRC) are investigated and four types of steel macro-fibers (of differing length or geometry) and one type of steel micro-fiber are considered.
Abstract: The effects of blending fibers on the tensile behavior of Ultra High Performance Hybrid Fiber Reinforced Concrete (UHP-HFRC) are investigated. Four types of steel macro-fibers (of differing length or geometry) and one type of steel micro-fiber are considered. In producing the specimens, the volume content of the macro-fiber was held at 1.0%, whereas the volume content of the micro-fiber varied from 0.0% to 1.5%. The overall shape of tensile stress–strain curves of UHP-HFRC is primarily dependent upon the type of macro-fiber, although the addition of micro-fibers favorably affects the strain hardening and multiple cracking behaviors. UHP-HFRC produced from macro-fibers with twisted geometry provides the best performance with respect to post cracking strength, strain capacity and multiple micro-cracking behavior, whereas UHP-HFRC produced with long, smooth macro-fibers exhibits the worst performance.

502 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the kinetics of the deformation structure evolution and its contribution to the strain hardening of a Fe 30.5Mn-2.1Al-1.2C (wt.%) steel during tensile deformation by means of transmission electron microscopy and electron channeling contrast imaging combined with electron backscatter diffraction.

396 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reported the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (NWs), including Young's modulus, yield strength, and ultimate tensile strength.
Abstract: This paper reports the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (NWs), including Young's modulus, yield strength, and ultimate tensile strength. In-situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a scanning electron microscope (SEM). Young's modulus, yield strength, and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the $\ensuremath{\langle}110\ensuremath{\rangle}$ orientation. The size effect in the yield strength is mainly due to the stiffening size effect in the Young's modulus. Yield strain scales reasonably well with the NW surface area, which reveals that yielding of Ag NWs is due to dislocation nucleation from surface sources. Pronounced strain hardening was observed for most NWs in our study. The strain hardening, which has not previously been reported for NWs, is mainly attributed to the presence of internal twin boundaries.

268 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of grain size on the strain hardening of two Fe −22Mn −0.6C (wt.%) twinning-induced plasticity steels with average grain sizes of 3 and 50μm, respectively, was investigated.

224 citations


Journal ArticleDOI
Bo Song1, Renlong Xin1, Gang Chen1, Xiyan Zhang1, Qing Liu1 
TL;DR: In this paper, the tensile and compressive properties of AZ31 plates were dramatically enhanced by pre-rolling with small thickness reduction along the transverse direction, attributed to the subdivision of grains by introducing extension twin boundaries.

201 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigate hardening mechanisms in pure magnesium and apply a dislocation-based formalism to model anisotropy, showing that pure magnesium under large strains develops substantial multivariant twinning and multifold twinning.

197 citations


01 Jan 2012
TL;DR: The continuous strength method (CSM) as mentioned in this paper replaces the concept of crosssection classification with a cross-section deformation capacity and replaces the assumed elastic, perfectly plastic material model with one that allows for strain hardening.
Abstract: Current stainless steel design standards are based on elastic, perfectly plastic material behaviour providing consistency with carbon steel design expressions, but often leading to overly conservative results, particularly in the case of stocky elements. More economic design rules in accordance with the actual material response of stainless steel, which shows a rounded stress–strain curve with significant strain hardening, are required. Hence, the continuous strength method (CSM) was developed. The CSM replaces the concept of cross-section classification with a cross-section deformation capacity and replaces the assumed elastic, perfectly plastic material model with one that allows for strain hardening. This paper summarises the evolution of the method and describes its recent simplified form, which is now suitable for code inclusion. Comparison of the predicted capacities with over 140 collected test results shows that the CSM offers improved accuracy and reduced scatter relative to the current design methods. The reliability of the approach has been demonstrated by statistical analyses and the CSM is currently under consideration for inclusion in European and North American design standards for stainless steel structures.

189 citations


Journal ArticleDOI
TL;DR: In this article, a Finite Element (FE) based modeling using Representative Volume Elements (RVEs) approach was proposed for predicting overall stress-strain behavior of the investigated dual phase (DP) steels.

184 citations


Journal ArticleDOI
TL;DR: In this paper, a magnesium alloy AZ91 plate was mechanically tested in five different test orientations in the solution-treated, underaged, peak-aged and overaged conditions and the critical resolved shear stresses for activation of basal slip, prismatic slip and twinning were then estimated for each of the ageing conditions.

179 citations


Journal ArticleDOI
TL;DR: In this article, the effect of initial texture on the mechanical properties and strain hardening behavior of AZ31 magnesium alloy has been investigated, and the results indicate that the yield strength and the strain-hardening rate are highly anisotropic with respect to the initial texture.
Abstract: The effect of initial texture on the mechanical properties and strain hardening behavior of AZ31 magnesium alloy has been investigated. Cylindrical specimens of extruded and hot rolled AZ31 are compressed along different directions, with the compression axis (C) perpendicular or parallel to the extrusion direction (ED) or the sheet normal direction (ND), referred to as C⊥ED, C//ED, C⊥ND and C//ND specimen, respectively. The compression tests are conducted at room temperature with a strain rate of 0.01 s−1. The results indicate that the yield strength and the strain hardening rate are highly anisotropic with respect to the initial texture. The significant yield behavior can be induced by only a small volume of twins. When the initial grain orientations are unfavorable for { 10 1 ¯ 2 } twinning, the strain hardening rate decreases gradually. When the initial grain orientations are favorable for { 10 1 ¯ 2 } twinning, the strain hardening behavior exhibits three distinct stages. The main contribution to increasing strain hardening rate (corresponding to the stage II) results from texture strengthening, which rotates grain orientations into hard orientations by the { 10 1 ¯ 2 } twinning. The length of the stage II is predominantly related to the volume fraction of grains which are favorable for { 10 1 ¯ 2 } twinning.

Journal ArticleDOI
TL;DR: In this paper, a theoretical model focusing on the behaviour of nano/microcracks was proposed to optimize the mechanical properties of bimodal metals, by tuning the constituent fractions and the size of the microstructures.

Journal ArticleDOI
TL;DR: In this article, the deformation induced crystal-crystal transition of polybutene-1 (PB-1) from forms II to I at different temperatures was studied with in situ synchrotron radiation wide-angle X-ray scattering (WAXS).
Abstract: Deformation induced crystal–crystal transition of polybutene-1 (PB-1) from forms II to I at different temperatures is studied with in situ synchrotron radiation wide-angle X-ray scattering (WAXS). Analyses on the evolution of crystallinity and orientations of forms II and I during tensile deformation show that stretch accelerates the transformation from forms II to I, which is interpreted based on either a direct crystal–crystal transition or an indirect approach via an intermediate state of melt, namely a melting recrystallization process. A three-stage mechanical deformation including linear deformation, stress plateau, and strain hardening is observed in the engineering stress–strain curves, which corresponds to a process of incubation, nucleation, and gelation of form I crystals. It establishes a nice correlation between phase transition and mechanical behavior in this study.

Journal ArticleDOI
TL;DR: In this article, discrete dislocation dynamics (DDDDDD) has been used to model the deformation of nickel-based single crystal superalloys with a high volume fraction of precipitates at high temperature.

Journal ArticleDOI
TL;DR: Theoretical and empirical solutions for burst pressure prediction are evaluated in this paper relative to a burst pressure database comprising more than 100 tests covering a variety of pipeline steel grades and pipe sizes.

Journal ArticleDOI
TL;DR: In this paper, the deformation behavior of incoherent Cu/Zr multilayers was studied in uniaxial compression experiments using micropillars with individual layer thicknesses (h) ranging from 5 to 100nm.

Journal ArticleDOI
TL;DR: The plastic deformation of an extruded Mg-Al-Mn (AM30) magnesium alloy in the extrusion direction by compression can be characterized by three distinct stages as discussed by the authors.

Journal ArticleDOI
TL;DR: In this paper, the deformation behavior of wrought α-uranium was studied using electron backscattered diffraction and crystal plasticity modeling, and the authors reported stress-strain response and texture evolution for 12 different cases corresponding to tension and compression tests performed on three different initial textures: straight-rolled, clock-rolled and swaged.

Journal ArticleDOI
TL;DR: In this article, the tensile behavior of Strain-hardening cement-based composites (SHCC) subjected to elevated temperatures and different strain rates and to combinations of these parameters was investigated.

Journal ArticleDOI
TL;DR: In situ neutron diffraction experiments were performed to measure the tensile deformation behavior of high manganese austenitic steels with different Al contents (0, 1.5, 2.0, 3.0), and significant variations of peak shift, broadening and asymmetry of the diffraction peaks were observed in the plastic region with the measurement as discussed by the authors.

Journal ArticleDOI
TL;DR: In this paper, the mechanisms of and different theoretical approaches dedicated to the strain hardening of twinning-induced plasticity steels are presented and discussed using results available in the literature.

Journal ArticleDOI
TL;DR: In this paper, a constitutive model based on anisotropic hardening was used in the finite element (FE) simulations of springback and its performance was compared with that of conventional hardening laws.

Journal ArticleDOI
TL;DR: In this paper, the tensile performance of Cementitious composites is evaluated at the level of a single crack, and the performance is evaluated in terms of tensile stress-crack opening behavior.

Journal ArticleDOI
TL;DR: In this article, the effect of tool rotation rate and traverse speed on strain hardening behavior of friction stir welded (FSWed) copper joints was investigated using hardening capacity and strain hardness exponent concepts.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the tensile properties and strain hardening behavior of a friction stir welded (FSWed) thick AA2219 aluminum alloy under optimized welding parameters and varying cooling conditions (air cooling and water cooling) with three slices through the plate thickness.
Abstract: Microstructures, tensile properties and strain hardening behavior of a friction stir welded (FSWed) thick AA2219 aluminum alloy under optimized welding parameters and varying cooling conditions (air cooling and water cooling) were investigated with three slices (top, middle and bottom) through the plate thickness. While the yield strength was lower in the FSWed joints than in the base metal, the ultimate tensile strength of the FSWed joints with water cooling reached nearly that of the base metal. In particular, FSW resulted in a significant improvement in the ductility of the alloy due to the presence of recrystallized fine grains with fragmented and uniformly dispersed second-phase particles in the weld nugget zone. Water cooling resulted in both higher strength and ductility, but lower strain hardening capacity than that with air cooling during FSW. Compared with the middle and bottom slices, the top slice had a higher strength, but lower ductility and strain hardening capacity. While stages III and IV hardening occurred after yielding in both base metal and FSWed samples, the FSW led to higher hardening capacity and strain hardening rate and exponent mainly in the middle and bottom slices. The fracture surfaces after FSW exhibited more obvious ductile fracture characteristics with dimples and tearing ridges along with micropores.

Journal ArticleDOI
TL;DR: In this paper, a near Ni-Ni-free, Mn-N bearing duplex stainless steel (D-SS) was developed, which exhibited an excellent strength-ductility combination over 1000 MPa tensile strength and 50% elongation.
Abstract: A near-Ni-free, Mn–N bearing duplex stainless steel (D-SS) that shows transformation induced plasticity was developed. The present D-SS exhibited an excellent strength–ductility combination over 1000 MPa tensile strength and 50% elongation. An analysis of the element partitioning during annealing revealed that the stacking fault energy of austenite was low enough for a strain induced martensite (SIM) transformation to occur. The strain hardening rate began to increase at ∼10% strain with the same manner of SIM fraction. The TEM and EBSD analyses showed that not only the ɛ martensite band intersections but the austenite grain boundaries acted as the SIM nucleation sites. The SIM transformation was saturated because of the austenite grain refinement and the corresponding austenite stabilization. The austenite grain refinement was caused by the mutual impingement of growing SIM and as a result by the engulfment of remaining austenite by SIM. The deformation behavior of the present D-SS was characterized by analyzing the kernel average misorientation (KAM) of the constituent phases with strain. The KAM distribution of austenite, ferrite and SIM exhibited different characteristics. The average KAM of austenite and ferrite increased as the strain increased, but its increasing rate of austenite was higher than that of ferrite. These KAM characteristics were discussed along with the dislocation glide modes of austenite and ferrite. By contrast, the average KAM of SIM was insensitive to strain and higher than that of the other two phases.

Journal ArticleDOI
Guo-zheng Quan1, Yuan-ping Mao1, Gui-sheng Li1, Wen-quan Lv1, Yang Wang1, Jie Zhou1 
TL;DR: In this article, a series of isothermal experiments with height reduction of 60% were performed at the temperatures of 573, K, 623,K, 673 K and 723 K, and the strain rates of 0.058556 (Z/A ) 0.00702 respectively.

Journal ArticleDOI
TL;DR: Fascial strain hardening does not seem to rely on cellular contraction, but rather on this super-compensation phenomenon, characterised by matrix hydration higher than initial levels and increases in tissue stiffness.

Journal ArticleDOI
TL;DR: In this paper, a multi-scale micro-mechanical model was proposed to predict the cyclic behavior of dual-phase steels and a simplified dislocation density model was incorporated into the crystal plasticity finite element method (CP-FEM) to reproduce the transient hardening behavior during load reversal.
Abstract: A multi-scale micro-mechanical model was proposed to predict the cyclic behavior of dual-phase steels The approach proposed in this study incorporates a simplified dislocation density model into the crystal plasticity finite element method (CP-FEM) The back stress resulting from dislocation pileups was used to reproduce the transient hardening behavior during load reversal The simulations conducted using representative volume elements for the dual-phase steels lead to the following conclusions: (1) the large Bauschinger effect (BE) and permanent softening in dual-phase steels originate primarily from the inhomogeneity due to the soft and hard phases; (2) the elastic incompatibility due to the grain orientation distribution generates some BE, but is not sufficient to explain the measured stress–strain curve; and (3) the inclusion of the back stress produced by the dislocation pileup can explain the strain hardening stagnation during reverse loading

Journal ArticleDOI
TL;DR: In this paper, a multidisciplinary field and laboratory study performed on a Cretaceous carbonate grainstone to investigate the microprocesses associated to deformation banding in this rock.