scholarly journals Influence of Stress on Kinetics and Transformation Plasticity of Ferrite Transformation Based on Hysteresis Effects

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 73 ◽  
Author(s):  
Wenhong Ding ◽  
Yazheng Liu ◽  
Jianxin Xie ◽  
Li Sun ◽  
Tianwu Liu
Keyword(s):  
Residual Stresses ◽  
Micromechanical Model ◽  
Transformation Plasticity ◽  
Cooling Process ◽  
Mechanical Stabilization ◽  
Continuous Cooling ◽  
Ferrite Transformation ◽  
External Stresses ◽  
Transformation Hysteresis ◽  
Experimental Values

Transformation plasticity and kinetics play an essential role in the prediction of residual stresses resulting from transformation. This paper is devoted to the investigation of the influence of stress on the kinetics and transformation plasticity of ferrite for H420LA steel. It has been shown that under small external stresses, lower than the yield stress of the weaker phase, the ferrite transformation is inhibited at the beginning of the transformation in the continuous cooling process and the mechanical stabilization of austenite is observed, due to transformation hysteresis effects. This phenomenon affects the metallurgical and mechanical behaviors of the transformation progress. However, most existing models ignore these effects, leading to deviations in the description of transformation plasticity during the transformation progress. Considering the hysteresis effects, the micromechanical model for kinetics and transformation plasticity is reexamined. A general formulation of austenite decomposition kinetics accounting for these effects is developed to better describe the phase transformation under a continuous cooling process. In addition, the influence of hysteresis effects on the evolution of transformation plasticity is analyzed. Consideration of the hysteresis effects decreases the discrepancy between the calculated and experimental values. This will allow better prediction of residual stresses in the thermomechanically controlled processes.

The effects of thermal residual stresses and interfacial properties on the transverse behaviors of fiber composites with different microstructures

2017 ◽  
Vol 24 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Xiaojun Zhu ◽  
Xuefeng Chen ◽  
Zhi Zhai ◽  
Zhibo Yang ◽  
Qiang Chen
Keyword(s):  
Residual Stresses ◽  
Cohesive Zone Model ◽  
Micromechanical Model ◽  
Interfacial Properties ◽  
Zone Model ◽  
Computational Accuracy ◽  
Fiber Model ◽  
Thermal Residual Stresses ◽  
Generalized Method Of Cells ◽  
Experimental Values

AbstractThis study presents a new micromechanical model to investigate the effects of thermal residual stresses and interfacial properties on the transverse behaviors of SiC/Ti composites with different microstructures. In this model, the fiber-matrix interface is modeled by the bilinear cohesive zone model. The interface model is introduced into the generalized method of cells, which has the advantage of computational accuracy and efficiency. At the same time, the generalized method of cells is extended to consider thermal residual stresses within the fiber and matrix phases. Thermal residual stresses are found to have a significant influence on the transverse behaviors of the composites. Compared with the perfect interface, the transverse behaviors of the composites with weak interface bonding are much lower. Moreover, with the increase of fiber fraction, the stiffness of the composites increases before debonding occurs while the saturation stress decreases. The predicted results using the circular fiber model and considering thermal residual stresses are more consistent with the experimental values compared with the results using the square or elliptical fiber model. When the stress concentration factor is considered and the interface is weakly bonding, the strength predictions are much better than the results using the perfect bonding.

Short Crack Propagation Model Applied to Shot Peened Aluminium Alloys

2009 ◽  
Vol 65 ◽  
pp. 53-61 ◽  
Author(s):  
J. Solis ◽  
J. Oseguera-Peña ◽  
I. Betancourt
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Aluminium Alloys ◽  
Micromechanical Model ◽  
High Strength ◽  
Crack Arrest ◽  
Propagation Model ◽  
Safe Load ◽  
Compressive Residual Stresses

The Navarro-Rios micromechanical model was used to assess the bounds of two different damage zones: crack arrest region and crack propagation region of controlled shot peening (CSP) of high strength aluminium alloys. Performance of CSP in terms of fatigue resistance was investigated. This comparison indicated that CSP in terms of fatigue depends on the competition between its beneficial and detrimental products, i.e. surface roughness and compressive residual stresses respectively. The gathered information can be used for safe load determinations in design.

A New Micromechanical Model to Study Transformation Plasticity in High-Carbon Steels

2019 ◽  
Author(s):  
Rohit Voothaluru ◽  
Vikram Bedekar ◽  
Praveen Pauskar
Keyword(s):  
Finite Element ◽  
Micromechanical Model ◽  
Inelastic Strain ◽  
Material Model ◽  
Carbon Steels ◽  
Transformation Plasticity ◽  
Element Approach ◽  
In Situ Neutron Diffraction ◽  
Constitutive Formulation

Abstract Hardened steels in engineering applications tend to have gradient microstructures with varying amounts of retained austenite alongside harder phases such as martensite or bainite. However, the metastable austenite can transform into martensite under mechanical loads, resulting in an inelastic strain within the material from the volumetric mismatch between FCC austenite and BCT martensite. In this work, a new constitutive formulation based upon the critical driving force for austenite transformation is presented. The model was implemented into a crystal plasticity formulation, and empirical data from in-situ neutron diffraction was used to determine the local micro-plasticity and transformation plasticity parameters. The results from finite element modeling also show that using a homogenized finite element approach could help to establish a material model that can capture the transformation plasticity within these materials with good accuracy.

Simulating welding with shell elements

2004 ◽  
Vol 120 ◽  
pp. 347-354
Author(s):  
F. Faure ◽  
J.-M. Bergheau ◽  
J.-B. Leblond
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Shell Element ◽  
Thermal Calculation ◽  
Transformation Plasticity ◽  
Thin Structures ◽  
Shell Elements ◽  
Mechanical Calculation ◽  
Complex Interactions ◽  
Mechanical Phenomena

Finite element simulations can be used to evaluate residual stresses and distortions induced by welding. Such simulations must account for complex interactions between thermal, metallurgical and mechanical phenomena. “Local” simulations are often sufficient for satisfactory predictions of residual stresses in the heat-affected zone (HAZ), but 3D “global” simulations are often necessary to calculate distortions, which can be important even far from the HAZ. In order to avoid such heavy calculations, a special shell element is proposed for the simulation of welding of thin structures. The thermal calculation involves only one nodal degree of freedom but fully accounts for boundary conditions on the faces of the shell. The metallurgical and mechanical calculations are based on a “multi-layer” approach. Due account is taken of transformation plasticity in the mechanical calculation. Numerical results obtained with this approach are compared to those of experiments and some 3D simulation.

Continuous Cooling Phase Transformation Rule of 20CrMnTi Low-Carbon Alloy Steel

2019 ◽  
Vol 944 ◽  
pp. 303-312
Author(s):  
Li Zhang Li ◽  
He Wei ◽  
Lin Lin Liao ◽  
Yin Li Chen ◽  
Hai Feng Yan ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Cooling Rate ◽  
Vickers Hardness ◽  
Rolling Process ◽  
Transformation Rule ◽  
Low Carbon ◽  
Continuous Cooling ◽  
Starting Time ◽  
Ferrite Transformation ◽  
The Ideal

Gear steel is a ferritic steel. In the rolling process, the ideal structure is ferrite + pearlite, and bainite or martensite is not expected. However, due to the high alloy content, the hardenability is good, and the bainite or martensite structure is very likely to be generated upon cooling after rolling. In this paper, phase transformation rules during continuous cooling of 20CrMnTi with and without deformation were studied to guide the avoidance of the appearance of bainite or martensite in steel. A combined method of dilatometry and metallography was adopted in the experiments, and the dilatometer DIL805A and thermo-simulation Gleeble3500 were used. Both dynamic and static continuous cooling transformation (CCT) diagrams were drawn by using the software Origin. The causes of those changes in starting temperature, finishing temperature, starting time and transformation duration in ferrite-pearlite phase transformation were analyzed, and the change in Vickers hardness of samples with different cooling rate was discussed. The results indicate that with different cooling rate, there are three phase transformation zones: ferrite-pearlite, bainite and martensite. Deformation of austenite accelerates the occurrence of transformation obviously and moves CCT curve to left and up direction. When the cooling rate is lower than 1 °C/s, the phases in samples are mainly ferrite and pearlite, which is the ideal microstructure of experimental steel. As the cooling rate increases, starting temperature of ferrite transformation in steel decreases, starting time reduces, transformation duration gradually decreases, and the Vickers hardness of samples increases. Under the cooling rate of 0.5 °C/s, ferrite transformation in deformed sample starts at 751.67 °C, ferrite-pearlite phase transformation lasts 167.9 s, and Vickers hardness of sample is 183.4 HV.

Solidification Modeling of Bulk Amorphous Alloys

2003 ◽  
Vol 806 ◽  
Author(s):  
Sang Bok Lee ◽  
Nack J. Kim
Keyword(s):  
Heterogeneous Nucleation ◽  
Amorphous Alloys ◽  
Nucleation Theory ◽  
Cooling Rates ◽  
Continuous Cooling ◽  
Wide Range ◽  
Temperature Transformation ◽  
Transformation Diagrams ◽  
Experimental Values ◽  
Kinetics Of

ABSTRACTClassical heterogeneous nucleation theory coupled with DTA data has been used to closely estimate the crystallization behavior of continuously cooled bulk metallic glass (BMG) alloys. Continuous cooling transformation and time temperature transformation diagrams of three BMG alloys, Zr41.2Ti13.8Cu12.5Ni10Be22.5, Cu47Ti33Zr11Ni6Si1Sn2 and Mg65Cu25Y10 alloys, have been calculated. The critical cooling rates Rc of three alloys were calculated to be 1.7 K/s, 242 K/s and 36 K/s for Zr41.2Ti13.8Cu12.5Ni10Be22.5, Cu47Ti33Zr11Ni6Si1Sn2 and of Mg65Cu25Y10 alloys, respectively, which match well with the experimental values. We conclude that heterogeneous nucleation is more favorable than homogeneous nucleation for the formation of crystals during cooling of BMG alloy liquids. Our approach can be applied to the analyses of crystallization kinetics of BMG alloys with a wide range of critical cooling rates during continuous cooling as well as isothermal annealing.

scholarly journals Analytical and Experimental Study of Residual Stresses in CFRP

2013 ◽  
Vol 2013 ◽  
pp. 1-4
Author(s):  
Chia-Chin Chiang ◽  
Vu Van Thuyet ◽  
Shih-Han Wang ◽  
Liren Tsai
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Curing Process ◽  
Cooling Process ◽  
Element Analysis ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites ◽  
Good Environment

Fiber Bragg Grating sensors (FBGs) have been utilized in various engineering and photoelectric fields because of their good environment tolerance. In this research, residual stresses of carbon fiber reinforced polymer composites (CFRP) were studied using both experimental and analytical approach. The FBGs were embedded inside middle layers of CFRP to study the formation of residual stress during curing process. Finite element analysis was performed using ABAQUS software to simulate the CFRP curing process. Both experimental and simulation results showed that the residual stress appeared during cooling process and the residual stresses could be released when the CFRP was machined to a different shape.

Numerical Simulation on Temperature Distributions to Cold Store

2012 ◽  
Vol 217-219 ◽  
pp. 1460-1464 ◽  
Author(s):  
Jing Xie ◽  
Yi Tang ◽  
Jin Feng Wang ◽  
Chen Miao ◽  
Yong Yan Lin
Keyword(s):  
Numerical Simulation ◽  
Simple Algorithm ◽  
Simulation Method ◽  
Calculation Error ◽  
Cooling Process ◽  
Temperature Distributions ◽  
Cold Store ◽  
Simulation Results ◽  
Experimental Values ◽  
Simulation Condition

On the basis of previous work, the simulation condition of cold store was improved to reduce calculation error. The SIMPLE algorithm and Boussineq assumption were used and the turbulent intensity was also set. The numerical simulation results reflected that the temperature distribution was closer to the previous experimental results after using new method. The error between simulation values and experimental values was decreased. The simulation result showed that temperature of corner was highest in the cold store. The temperature change of the cold store in the cooling process could be better predicted by using modified simulation method and the accuracy of numerical simulation of cold store in the cooling process could also be validated.

Influence of Hot Leveling and Cooling Process on Residual Stresses of Steel Plates

2010 ◽  
Vol 168-170 ◽  
pp. 1130-1135 ◽  
Author(s):  
Ji Ping Chen ◽  
Jian Qing Qian ◽  
Sheng Zhi Li
Keyword(s):  
Residual Stress ◽  
Temperature Distribution ◽  
Residual Stresses ◽  
Initial Temperature ◽  
Steel Plate ◽  
Coupled Model ◽  
Distribution Patterns ◽  
Cooling Process ◽  
Initial Temperature Distribution ◽  
Actual Measurement

A three-dimensional thermo-mechanical coupled model of hot leveling and cooling processes of the steel plate has been conducted with MSC.Superform software. Four kinds of initial temperature distribution patterns have been determined according to literature. The effects of hot leveling and cooling processes on the transversal and longitudinal residual stresses of the steel plate have been analyzed. The results show that the initial temperature distribution patterns have significant influence on the residual stress of the plate. The more uniform temperature distribution patterns along the width of the plate, the smaller residual stress and also the smaller stress fluctuations. The cooling process has greater effect on the residual stress compared with the hot leveling process. The bigger the temperature gradient along the width of steel plate, the larger the residual stress and its fluctuation is. Through the FEM study, the value and direction of transversal and longitudinal residual stresses can be confirmed quantitatively at various positions along the width and length of plate, which can provide guidance to actual measurement of residual stress.

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