A Modified Johnson–Cook Model to Predict Stress-strain Curves of Boron Steel Sheets at Elevated and Cooling Temperatures

2012 ◽  
Vol 31 (1) ◽  
Author(s):  
Nguyen Duc-Toan ◽  
Banh Tien-Long ◽  
Jung Dong-Won ◽  
Yang Seung-Han ◽  
Kim Young-Suk
Keyword(s):  
Tensile Test ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Boron Steel ◽  
Isotropic Hardening ◽  
Air Cooling ◽  
Stress Strain ◽  
Material Parameters ◽  
Hardening Law ◽  
Simulation Results

AbstractIn order to predict correctly stress-strain curve for tensile tests at elevated and cooling temperatures, a modification of a Johnson–Cook (J-C) model and a new method to determine (J-C) material parameters are proposed. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick and Voce's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. An FEM tensile test simulation based on the isotropic hardening model for metal sheet at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code. The simulation results at elevated temperatures were firstly presented and then compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation. The modified (J-C) model showed the good comparability between the simulation results and the corresponding experiments.

scholarly journals The influence of rate of deformation on the tensile test with special reference to the yield point in iron and steel.

1938 ◽  
Vol 165 (923) ◽  
pp. 568-592 ◽  
Author(s):  
C. F. Elam ◽  
Henry Cort Harold Carpenter
Keyword(s):  
Tensile Test ◽  
Special Reference ◽  
Yield Point ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Iron And Steel ◽  
Plastic Distortion

The following experiments were carried out with two principal objects in view: (1) to investigate the deformation of those metals, particularly iron and steel, in which the stress-strain curve does not immediately rise at the onset of plastic distortion; (2) to determine the effect of rate of deformation on the yield and subsequent stress-strain curve. It is impossible to give an adequate summary of the literature which deals with this subject, but a bibliography is included in an appendix and some of the most important results are referred to briefly below.

Further Investigation of the Hydrostatic Bulge Test in a Plasticity Laboratory

2009 ◽  
Vol 37 (2) ◽  
pp. 159-174
Author(s):  
O. Ifedi ◽  
Q. M. Li ◽  
Y. B. Lu
Keyword(s):  
Tensile Test ◽  
Effective Stress ◽  
Strain Curve ◽  
Plasticity Theory ◽  
Loading Path ◽  
Uniaxial Tensile ◽  
Bulge Test ◽  
Uniaxial Tensile Test ◽  
Stress Strain Curve ◽  
Stress Strain

In plasticity theory, the effective stress–strain curve of a metal is independent of the loading path. The simplest loading path to obtain the effective stress–strain curve is a uniaxial tensile test. In order to demonstrate in a plasticity laboratory that the stress–strain curve is independent of the loading path, the hydrostatic bulge test has been used to provide a balanced biaxial tensile stress state. In our plasticity laboratory we compared several different theories for the hydrostatic bulge test for the determination of the effective stress–strain curve for two representative metals, brass and aluminium alloy. Finite element analysis (FEA) was performed based on the uniaxial tension test data. It was shown that the effective stress–strain curve obtained from the biaxial tensile test (hydrostatic bulge test) had a good correlation with that obtained in the uniaxial tensile test and agreed well with the analytical and FEA results. This paper may be used to support an experimental and numerical laboratory in teaching the concepts of effective stress and strain in plasticity theory.

Significance of Lu¨der’s Plateau on Pipeline Fault Crossing Assessment

2010 ◽  
Author(s):  
Lanre Odina ◽  
Robert J. Conder
Keyword(s):  
Finite Element ◽  
Compressive Strain ◽  
Strain Curve ◽  
Isotropic Hardening ◽  
Flow Rule ◽  
Pipe Material ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Integrity Assessment ◽  
Analytical Approaches

When subjected to permanent ground deformations, buried pipelines may fail by local buckling (wrinkling under compression) or by tensile rupture. The initial assessment of the effects of predicted seismic fault movements on the buried pipeline is performed using analytical approaches by Newmark-Hall and Kennedy et al, which is restricted to cases when the pipeline is put into tension. Further analysis is then undertaken using finite element methods to assess the elasto-plastic response of the pipeline response to the fault movements, particularly the compressive strain limits. The finite element model is set up to account for the geometric and material non-linear parameters. The pipe material behaviour is generally assumed to have a smooth strain hardening (roundhouse) post-yield behaviour and defined using the Ramberg-Osgood stressstrain curve definition with the plasticity modelled using incremental theory with a von Mises yield surface, associated flow rule and isotropic hardening. However, material tests on seamless pipes (X-grade) show that the stress-strain curve typically displays a Lu¨der’s plateau behaviour (yield point elongation) in the post-yield state. The Lu¨der’s plateau curve is considered conservative for pipeline design and could have a significant impact on strain-based integrity assessment. This paper compares the pipeline response from a roundhouse stress-strain curve with that obtained from a pipe material exhibiting Lu¨der’s plateau behaviour and also examines the implications of a Lu¨der’s plateau for pipeline structural integrity assessments.

Strain Localisation during a Tensile Test of Metallic Plates: Experimental and Numerical Results

2009 ◽  
Vol 417-418 ◽  
pp. 569-572
Author(s):  
D.A. Cendón ◽  
Jose M. Atienza ◽  
Manuel Elices Calafat
Keyword(s):  
Tensile Test ◽  
Strain Curve ◽  
Maximum Load ◽  
Surface Strain ◽  
Displacement Curve ◽  
Strain Localisation ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Fields ◽  
Developed Surface

The stress-strain curve of a material is usually obtained from the load-displacement curve measured in a tensile test, assuming no strain localisation up to maximum load. However, strain localisation and fracture phenomena are far from being completely understood. Failure and strain localisation on plane tensile specimens has been studied in this work. A deeply instrumented experimental benchmark on steel specimens has been developed. Surface strain fields have been recorded throughout the tests, using an optical extensometer. This allowed characterisation of the strain localisation and failure processes. Tests have been numerically modelled for a more detailed analysis. Preliminary results show a substantial influence of geometrical specimen defects on the strain localisation phenomena that may be critical on the stress-strain curves obtained and in the failure mechanisms.

scholarly journals Experimental and Theoretical Investigation on the Thermo-Mechanical Properties of Recycled Aggregate Concrete Containing Recycled Rubber

2021 ◽  
Vol 8 ◽  
Author(s):  
Yunchao Tang ◽  
Wanhui Feng ◽  
Zheng Chen ◽  
Yumei Nong ◽  
Minhui Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Microstructural Analysis ◽  
Strain Curve ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Recycled Rubber

The utilization of recycled aggregates made from construction wastes and recycled rubber made from waste tires is an effective method to realize the sustainable development. Thus, this study aims to determine the feasibility of using recycled aggregate concrete containing rubber, named rubberized recycled aggregate concrete (RRAC) as a new type of green-building material. The experimental carbon emissions test verified RRAC as a low-carbon material. In addition, the residual mechanical properties of RRAC were investigated under elevated temperatures. After exposure at 200, 400, and 600 C for 60 min, the stress−strain curve, compressive strength, energy absorption capacity, and spalling resistance of RRAC with recycled aggregate replacement ratios of 50 and 100%, rubber contents of 0, 5, 10, and 15% were explored with microstructural analysis. Moreover, empirical models were proposed to describe the effects of heated temperatures and rubber contents on the stress–strain relationship of RRAC. The results indicated that the rubber particles could reduce the spalling of specimens based on the vapor pressure theory. Therefore, this study provided scientific guidance for the design of structures made with RRAC for resisting high temperatures.

Deformational characteristics of thermally treated sandstone from an underground coalmine fire region, India

2021 ◽  
Author(s):  
Adarsh Tripathi ◽  
Noopur Gupta ◽  
Ashok Kumar Singh ◽  
Nachiketa Rai ◽  
Anindya Pain
Keyword(s):  
Large Scale ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Small Scale ◽  
Carbonaceous Shale ◽  
Deformation Pattern ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Thermomechanical Behaviour ◽  
Thermally Treated

<p>The Jharia region of lower Gondwana in India is one of the largest Underground Coalmine Fires (UCF) affected coalfield in the world. The UCF induced small scale as well as large-scale surface fracturing often creates the life-threatening conditions to coal miners and local surroundings. So, there is a need to understand the thermomechanical behaviour of coal measures rocks to predict the land disturbances in thermo-environmental conditions. It will provide an insight into the UCF induced subsidence mechanism and its preventive measures. The Jharia coal field predominantly consists of sandstone (75-80% by volume) and rest is composed of coal, shale and carbonaceous shale. The present study focuses on thermo-mechanical behaviour of Barakar sandstone (BS) under elevated temperatures. The cores of BS sample were prepared according to the ISRM standards. Further, samples were grouped and thermally treated in temperature range of 25°C, 100°C, 150°C, 300°C, 400°C, 500°C, 600 °C, 700°C and 800°C at a heating rate of 5°C/min for 24 hours in furnace.  Then, these thermally treated BS samples were subjected to laboratory test for stress-strain characteristics. In the process of deformational characteristics evaluation, effect of mineralogical changes and mode of fracture pattern were also studied at the mentioned elevated temperature. Based on the obtained results, the deformational behaviour of thermally treated BS specimens can be grouped into three zones, viz., zone 1 (25-300°C), zone 2 (300-500°C) and zone 3 (500-800°C). In zone 1, the characteristics of the stress-strain curve is similar to those under air dried sandstone specimen. However, small increment in stiffness were observed upto 300°C. The stress-strain curves in this zone shows dominantly brittle fracturing. The increment in stiffness may be related to evaporation of pore water that increases the cohesion between the mineral grains resulting higher stiffness value. In zone 2, the deformation pattern again shows brittle fracturing with continuous decrement in stiffness. The reduction in stiffness may be related to thermally induced porosity and increased microcrack density. In zone 3, the stress strain curve is observed to be concave upward. It indicates the pseudo-ductile behaviour of the thermally treated BS specimens. The observed results suggest a typical behaviour of deformation pattern under UCF induced rock fracturing which may be useful in predicting the land subsidence in UCF affected areas. Present research outcome may be used to design the support measures to reduce the associated hazards.</p>

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