scholarly journals Effects of Heterogeneous Microstructures on the Strain Hardening Behaviors of Ferrite-Martensite Dual Phase Steel

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 824 ◽  
Author(s):  
Chuang Ren ◽  
Wenjiao Dan ◽  
Yongsheng Xu ◽  
Weigang Zhang
Keyword(s):  
Flow Stress ◽  
Strain Hardening ◽  
Shape Factor ◽  
Grain Shape ◽  
Strain Curve ◽  
Martensite Phase ◽  
Dual Phase ◽  
Stress Strain ◽  
Dp Steel ◽  
Heterogeneous Microstructures

The complex strain hardening behaviors of dual phase (DP) steel are subjected to the heterogeneous microstructures. The current work aims to predict the strain hardening behaviors of ferrite-martensite DP steel, focusing on the effects of heterogeneous microstructure on mechanical properties. The flow stress of material was calculated based on the dislocation-based work-hardening model with considering the multi-boundaries hardening. The ferrite-martensite phase boundary percent and grain shape factor were selected as the heterogeneous feature parameters, which were introduced into the new proposed model. The theoretical calculated stress-strain responses were verified with experimental results using the tensile test. The model with the boundary strengthening consideration has more accurate results. The parameter effects of ferrite-ferrite boundary (FFB) spacing, ferrite-martensite boundary (FMB) percent, and grain shape factor on the flow stress-strain curve were researched.

Determination of Stress-Strain Curve of Dual Phase Steel by Nanoindentation Technique

2015 ◽  
Vol 658 ◽  
pp. 195-201 ◽  
Author(s):  
Suttirat Punyamueang ◽  
Vitoon Uthaisangsuk
Keyword(s):  
Strain Curve ◽  
High Strength ◽  
Dual Phase ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Dp Steel ◽  
Multiphase Microstructure ◽  
Indentation Tests ◽  
Novel Material ◽  
Parallel Finite Element

The advanced high strength (AHS) steels, for example, dual phase (DP) steels, transformation induced plasticity (TRIP) steels and complex (CP) steels principally exhibit multiphase microstructure features. Thus, mechanical behavior of the constituent phases significantly affects the resulting overall properties of such AHS steels. Novel material characterization techniques on micro- and nano-scale have become greatly more important. In this work, stress-strain response of the DP steel grade 1000 was determined by using the Nanoindentation testing. The DP steel showed the microstructure containing finely distributed martensite islands of about 50% phase fraction in the ferritic matrix. The nano-hardness measurements were firstly performed on each individual phase of the examined steel. In parallel, finite element (FE) simulations of the corresponding nano-indentation tests were carried out. Flow curves of the single ferritic and martensitic phases were defined according to a dislocation based theory. Afterwards, the load and penetration depth curves resulted from the experiments and simulations were compared. By this manner, the proper stress-strain responses of both phases were identified and verified. Finally, the effective stress-strain curve of the investigated DP steel could be determined by using 2D representative volume element (RVE) model.

Fracture Assessment of Pipes Having Multiple Flaws Based on Ramberg–Osgood-Type Stress–Strain Relationships

2011 ◽  
Author(s):  
Hideo Machida ◽  
Tetsuya Hamanaka ◽  
Yoshiaki Takahashi ◽  
Katsumasa Miyazaki ◽  
Fuminori Iwamatsu ◽  
...  
Keyword(s):  
Flow Stress ◽  
Stress Concentration ◽  
Fracture Strength ◽  
Strain Curve ◽  
Assessment Method ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Relationship ◽  
Fracture Assessment

This paper describes a fracture assessment method for a pipe having multiple circumferential flaws. According to Fitness-for-Service (FFS) codes for nuclear facilities published by the Japanese Society of Mechanical Engineers (JSME), the fracture strength of a high-ductility pipe having a circumferential flaw is evaluated using the limit load assessment method assuming the elastic–perfectly-plastic stress–strain relationship. In this assessment, flow stress is used as a proportional stress. However, previous experimental results [1, 2, 3] show that a crack penetrates before the entire flawed pipe section reaches the flow stress. Therefore, stress concentration at a flaw was evaluated on the basis of the Dugdale model [4], and the fracture strength of the crack-ligament was evaluated. This model can predict test results with high accuracy when the ligament fracture strength is assumed to be tensile strength. Based on this examination, a fracture assessment method for pipes having multiple flaws was developed considering the stress concentration in the crack-ligament by using the realistic stress–strain relationship (Ramberg–Osgood-type stress–strain curve). The fracture strength of a multiple-flawed pipe estimated by the developed method was compared with previous experimental results. When the stress concentration in the crack-ligament was taken into consideration, the fracture strength estimated using the Ramberg–Osgood-type stress–strain curve was in good agreement with experimental results, confirming the validity of the proposed method.

A General Autofrettage Model of a Thick-Walled Cylinder Based on Tensile-Compressive Stress-Strain Curve of a Material

2005 ◽  
Vol 40 (6) ◽  
pp. 599-607 ◽  
Author(s):  
X. P Huang
Keyword(s):  
Strain Hardening ◽  
Compressive Stress ◽  
Bauschinger Effect ◽  
Strain Curve ◽  
Accurate Prediction ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Perfectly Plastic ◽  
Hardening Models ◽  
Elastic Perfectly Plastic

The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage models are based on different simplified material strain-hardening models, which assume linear strain-hardening or power strain-hardening or a combination of these strain-hardening models. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material is proposed. The model incorporates the von Mises yield criterion, an incompressible material, and the plane strain condition. Analytic expressions for the residual stress distribution have been derived. Experimental results show that the present model has a stronger curve-fitting ability and gives a more accurate prediction. Several other models are shown to be special cases of the general model presented in this paper. The parameters needed in the model are determined by fitting the actual tensile-compressive curve of the material, and the maximum strain of this curve should closely represent the maximum equivalent strain at the inner surface of the cylinder under maximum autofrettage pressure.

Strain-hardening parameters determined from the stress-strain curve

1977 ◽  
Vol 9 (6) ◽  
pp. 704-707 ◽  
Author(s):  
V. K. Babich ◽  
V. A. Pirogov ◽  
I. A. Vakulenko
Keyword(s):  
Strain Hardening ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain

Evaluation of Anisotropic Pipe Steel Stress-Strain Relationships Influence on Strain Demand

2012 ◽  
Author(s):  
James D. Hart ◽  
Nasir Zulfiqar ◽  
Joe Zhou
Keyword(s):  
Strain Hardening ◽  
Pipe Steel ◽  
High Strain ◽  
Strain Curve ◽  
High Strength ◽  
Strain Response ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Hardening Modulus ◽  
Strain Relationship

Buried pipelines can be exposed to displacement-controlled environmental loadings (such as landslides, earthquake fault movements, etc.) which impose deformation demands on the pipeline. When analyzing pipelines for these load scenarios, the deformation demands are typically characterized based on the curvature and/or the longitudinal tension and compression strain response of the pipe. The term “strain demand” is used herein to characterize the calculated longitudinal strain response of a pipeline subject to environmentally-induced deformation demands. The shape of the pipe steel stress-strain relationship can have a significant effect on the pipe strain demands computed using pipeline deformation analyses for displacement-controlled loading conditions. In general, with sufficient levels of imposed deformation demand, a pipe steel stress-strain curve with a relatively abrupt or “sharp” elastic-to-plastic transition will tend to lead to larger strain demands than a stress-strain curve with a relatively rounded elastic-to-plastic transition. Similarly, a stress-strain curve with relatively low strain hardening modulus characteristics will tend to lead to larger strain demands than a stress-strain curve with relatively high strain hardening modulus characteristics. High strength UOE pipe can exhibit significant levels of anisotropy (i.e., the shapes of the stress-strain relationships in the longitudinal tension/compression and hoop tension/compression directions can be significantly different). To the extent that the stress-strain curves in the different directions can have unfavorable shape characteristics, it follows that anisotropy can also play an important role in pipeline strain demand evaluations. This paper summarizes a pipeline industry research project aimed at evaluation of the effects of anisotropy and the shape of pipe steel stress-strain relationships on pipeline strain demand for X80 and X100 UOE pipe. The research included: a review of pipeline industry literature on the subject matter; a discussion of pipe steel plasticity concepts for UOE pipe; characterization of the anisotropy and stress-strain curve shapes for both conventional and high strain pipe steels; development of representative analytical X80 and X100 stress-strain relationships; and evaluation of a large matrix of ground-movement induced pipeline deformation scenarios to evaluate key pipe stress-strain relationship shape and anisotropy parameters. The main conclusion from this work is that pipe steel specifications for high strength UOE pipe for strain-based design applications should be supplemented to consider shape-characterizing parameters such as the plastic complementary energy.

scholarly journals Constitutive Model of 30CrMoA Steel with Strain Correction

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1214
Author(s):  
Song Zhang ◽  
Xuedao Shu ◽  
Jitai Wang ◽  
Yingxiang Xia
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
High Speed ◽  
Strain Curve ◽  
Material Constant ◽  
Test Machine ◽  
Experimental Stress ◽  
High Speed Train ◽  
Stress Strain Curve ◽  
Stress Strain

It is necessary to establish a constitutive model of 30CrMoA steel to optimize the forming shape and mechanical properties of high-speed train axles. The experimental stress–strain curve of 30CrMoA steel was obtained by an isothermal compression test on a Gleeble-3500 thermal simulation test machine under temperature of 1273~1423 K and strain rate of 0.01~10 s−1. Considering the effect of strain on the material constant, an empirical constitutive model was proposed with strain correction for 30CrMoA steel. In addition, the material constant in the constitutive model is determined by linear regression analysis of the experimental stress–strain curve. Comparing the theoretical value and experimental value of flow stress, the correlation R is 0.9828 and the average relative error (ARRE) is 4.652%. The constitutive model of 30CrMoA steel with strain correction can reasonably predict the flow stress under various conditions. The results provide an effective numerical tool for further study on accurate near-net forming of high-speed train axles.

Modelling of the Strain Hardening Behaviour of Die-Cast Magnesium-Aluminium-Rare Earth Alloy

2020 ◽  
Vol 35 ◽  
pp. 1-8
Author(s):  
Hua Qian Ang
Keyword(s):  
Strain Hardening ◽  
Tensile Deformation ◽  
Deformation Behaviour ◽  
Strain Curve ◽  
Deformation Mode ◽  
Prismatic Slip ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Die Cast ◽  
Cast Magnesium

The tensile deformation behaviour of magnesium alloy AE44 (Mg-4Al-4RE) under strain rates ranging from 10-6 to 10-1 s-1 has been investigated. Present study shows that the deformation mode begins with the activation of elastic (Stage 1), followed by <a> basal slip and twinning (Stage 2), <a> prismatic slip (Stage 3) and finally to <c+a> pyramidal slip (Stage 4). The commencement of these deformation mechanisms results in four distinct stages of strain hardening in the stress-strain curve. In this work, the four stages of deformation behaviour are modelled, and an empirical equation is proposed to predict the entire stress-strain curve. Overall, the model predictions are in good agreement with the experimental data. This study on the decomposition of stress-strain curve into four stages provides insights into the contribution of individual deformation mechanism to the overall deformation behaviour and opens a new way to assess mechanical properties of die-cast magnesium alloys.

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