Modeling of Twinning Based Plasticity Phenomenon in Austenite Dominated Steels Under Combined Loading

2014 ◽  
Author(s):  
Rashid Khan ◽  
Tasneem Pervez ◽  
Omar S. Al-Abri ◽  
Majid Al-Maharbi
Keyword(s):  
Finite Element ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
High Strength Steels ◽  
High Strength ◽  
Combined Loading ◽  
Plastic Behavior ◽  
Successful Implementation ◽  
Advanced High Strength Steels ◽  
Finite Element Software

Advanced high strength steels cover a vast range of applications more specifically in aerospace and oil industry where large deformation of a material is desired in order to attain a specified shape and geometry of the product. The main reason behind their successful implementation is having an optimum combination of strength and formability. Austenite based twinning induced plasticity steel lies in the second generation and has excellent strength-cum-formability combination among the group of advanced high strength steels. The stress assisted phase transformation from austenite to martensite, which is known as twinning, found to be principal reason behind an enhancement of these properties. This work is aimed to investigate an elastic-plastic behavior of an austenite dominated steel, which undergoes slip and mechanical twinning modes of deformation. Initially, a micromechanical model of twining induced plasticity phenomenon is developed using crystal plasticity theory. Then, the developed model is numerically implemented into finite element software ABAQUS through a user-defined material sub-routine. Finally, finite element simulations are done for single and poly-crystal austenite subjected to combined load. This replicates the complex loading condition which exists in material forming processes like pipe expansion, extrusion, rolling. The variation in stress-strain response, magnitude of shear strain, and volume fraction of twinned martensite are plotted and analyzed.

Study on Microstructure Transformation of High Strength Hot Rolled Steel by Using Finite Element Simulation

2020 ◽  
Vol 1009 ◽  
pp. 95-100
Author(s):  
Siam Thongnak ◽  
Tanongsak Yingnakorn ◽  
Loeslakkhana Sriklang ◽  
Sakhob Khumkoa
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Hot Rolling ◽  
Volume Fraction ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Deformation Degree ◽  
Advanced High Strength Steels ◽  
Element Simulation

Advanced High-strength steels (AHSS) has widely application in automotive due to their high tensile strength and remarkable ductility. These good mechanical performances are strongly influenced by the processing and final microstructure. This paper performed Deformation Dilatometer and finite element simulation to study the effect of hot rolling parameters such as strain, cooling rate, and holding time at constant temperature on the microstructure formation of Nb-V low carbon microalloyed steel grade. It found that increasing deformation degree increased the volume fraction of ferrite, both of deformation dilatometer and finite element simulation give a similar trend of effects of hot rolling parameters on evolution of volume fraction of ferrite. These results give an insight for industrial application.

scholarly journals Effects of Heat Affected Zone Softening Extent on the strength of Advanced High Strength Steels Resistance Spot Weld

2018 ◽  
Author(s):  
Hassan Rezayat ◽  
Hassan Ghassemi-Armaki ◽  
Sudarsanam Suresh Babu
Keyword(s):  
Finite Element ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Volume Fraction ◽  
Load Capacity ◽  
High Strength Steels ◽  
High Strength ◽  
Stress Strain ◽  
Resistance Spot ◽  
Advanced High Strength Steels

Resistance spot welds made from Advanced High Strength Steels (AHSS) exhibit Heat Affected Zone (HAZ) softening due to the tempering of pre-existing martensite phase and the consequent decomposition into a mixture of ferrite and cementite. Despite the high strength level for the base metal, the occurrence of HAZ softening may lead to inferior joint strength during Tension-Shear (TS) and Cross-Tension (CT) testing. In this work, we investigated the effects of the HAZ softening on the global loading response for AHSS steels with three different volume fractions of martensite. Microhardness mapping was used as a measure of martensite tempering and extent of softening. Based on the data, the softening was identified in the sub-critical heat affected zone. Hardness drop with the magnitude of 6%, 18%, and 42% was observed in steels with 16%, 52% and 100% of martensite volume fraction (MVF), respectively. In order to model the welded joint loading response using finite element methods (FEM), there is a need to represent the softening in terms of stress-strain relationships. In this work, local stress-strain curves for different weld zones were obtained by scaling the base metal constitutive properties with local hardness ratio. Finite element (FE) simulations of Tension-Shear tests showed that HAZ softening can affect the Tension-Shear load capacity of specimens more significantly when the base metal tensile strength is above 1000 MPa. The paper will discuss the validity of the above finite element approach for describing experimental results and future directions.

Influence of the contact with friction on the deformation behavior of advanced high strength steels in the Nakajima test

2021 ◽  
pp. 030932472110212
Author(s):  
Mohammad Mehdi Kasaei ◽  
Marta C Oliveira
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Strain Rate ◽  
Contact Pressure ◽  
Deformation Behaviour ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
Deformation Mechanics ◽  
Nakajima Test

This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the interaction between the friction conditions and the deformation behaviour of a dual phase steel. The methodology is based on the finite element analysis of the Nakajima test, considering different values of the classic Coulomb friction coefficient, including a pressure-dependent model. The validity of the finite element model is examined through a comparison with experimental data. The results show that friction affects the location and strain path of the necking point by changing the strain rate distribution in the specimen. The strain localization alters the contact status from slip to stick at a portion of the contact area from the pole to the necking zone. This leads to the sharp increase of the strain rate at the necking point, as the punch rises further. The influence of the pressure-dependent friction coefficient on the deformation behaviour is very small, due to the uniform distribution of the contact pressure in the Nakajima test. Moreover, the low contact pressure range attained cannot properly replicate real contact condition in sheet metal forming processes of advanced high strength steels.

Finite Element Simulation of Chain-Die Forming U Profiles with Variable Cross-Section

2017 ◽  
Vol 898 ◽  
pp. 1177-1182 ◽  
Author(s):  
Y.G. Li ◽  
Y. Sun ◽  
H.L. Huang ◽  
D.Y. Li ◽  
S.C. Ding
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Low Cost ◽  
High Strength Steels ◽  
High Strength ◽  
Variable Cross Section ◽  
Roll Forming ◽  
Variable Cross ◽  
Advanced High Strength Steels ◽  
Die Forming

Roll forming has been widely used to manufacture constant cross-section products because of high quality, efficiency and low cost. It is quite epidemic in producing automobile parts made of advanced high strength steels (AHSS) nowadays. However, with the development of the vehicle industry and diversity of the products, variable cross-section profiles have attracted more and more attention. The traditional roll forming technique is difficult to meet the requirements. Chain-die forming which was introduced in recent years makes it possible. Chain-die forming is an extension of roll forming and its key characteristic is enlarging the rotation radii of the moulds, by which the deformation zone is extended. The study focused on the finite element simulations of Chain-die forming U profiles with variable cross-section, including variable width and height. The feasibility of Chain-die forming producing variable cross-section products was verified by the perfect simulation results. The advantage of Chain-die forming was that there was no need to design the intermediate moulds except the finished-profile ones, which reduced the mould quantity immensely. Then the cost was lower.

scholarly journals Addressing Retained Austenite Stability in Advanced High Strength Steels

2013 ◽  
Vol 738-739 ◽  
pp. 212-216 ◽  
Author(s):  
Elena V. Pereloma ◽  
Azdiar A. Gazder ◽  
Ilana B. Timokhina
Keyword(s):  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
High Strength Steels ◽  
High Strength ◽  
Processing Parameters ◽  
Advanced High Strength Steels ◽  
Austenite Stability ◽  
Retained Austenite Stability ◽  
Size And Morphology

Advances in the development of new high strength steels have resulted in microstructures containing significant volume fractions of retained austenite. The transformation of retained austenite to martensite upon straining contributes towards improving the ductility. However, in order to gain from the above beneficial effect, the volume fraction, size, morphology and distribution of the retained austenite need to be controlled. In this regard, it is well known that carbon concentration in the retained austenite is responsible for its chemical stability, whereas its size and morphology determines its mechanical stability. Thus, to achieve the required mechanical properties, control of the processing parameters affecting the microstructure development is essential.

Finite Element Modeling of Spot Welding for Advanced High Strength Steels (AHSS)

2007 ◽  
Author(s):  
Sankaran Subramaniam ◽  
Ramakrishna Koganti ◽  
Armando Joaquin
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Spot Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Cost Effective ◽  
Advanced High Strength Steels ◽  
Safety Regulations ◽  
Effective Manner ◽  
Improved Accuracy

Weldability is a critical enabler for application of new grades of steel, which have found widespread applications in the auto industry to meet new safety regulations and reduce weight of vehicles. There are a wide variety of these grades of steel which are being used across the industry. Even within a OEM the number of material and gauge combinations becomes quite large. This requires a considerable amount of testing to prove out welding feasibility of these steels. This paper discusses the use of a finite element method (FEM) to model spot welding of DP600 and correlates the results with experiments. Improved accuracy and confidence in these tools can provide a way to better understand the physics of the process and improve the weldability of these steels in a cost effective manner.

scholarly journals The Effect of Mn and Si on the Properties of Advanced High Strength Steels Processed by Quenching and Partitioning

2010 ◽  
Vol 654-656 ◽  
pp. 94-97 ◽  
Author(s):  
Bohuslav Mašek ◽  
Hana Jirková ◽  
Daniela Hauserova ◽  
Ludmila Kučerová ◽  
Danuše Klauberová
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength Steels ◽  
High Strength ◽  
Microstructural Development ◽  
X Ray Diffraction ◽  
Quenching And Partitioning ◽  
Advanced High Strength Steels ◽  
High Ultimate Strength

The concepts new types of materials are, for economic reasons, focused mainly on low alloyed steels with a good combination of strength and ductility. Suitable heat and thermo-mechanical treatments play an important role for the utilization of these materials. Different alloying strategies are used to influence phase transformations. The quenching and partitioning process (Q-P Process) is one of the heat treatment methods which can result in a high ultimate strength as well as a good ductility. However, these good properties can be obtained only if a sufficient amount of retained austenite is stabilized. The influence of different contents of manganese, silicon and chromium on microstructural development and mechanical properties were experimentally tested. Alloying elements were used to stabilize the retained austenite in the final microstructure and also to strengthen the solid solution. Ultimate strengths of over 2000MPa with ductility over 10% were reached after the optimization of the Q-P Process. The microstructures were analyzed using several microscopic methods; mechanical properties were determined by a tensile test and the volume fraction of the retained austenite was established by X-ray diffraction phase analysis.

An Investigation of Springback in U-Channel Sheet Metal by Finite Element Analysis

2012 ◽  
Vol 548 ◽  
pp. 456-460 ◽  
Author(s):  
Gopi Alagappan ◽  
Syed H. Masood ◽  
Xuan Zhi Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
High Strength Steels ◽  
High Strength ◽  
Element Analysis ◽  
Advanced High Strength Steels ◽  
Forming Tools

In sheet metal forming, springback is defined as an elastic material recovery after unloading of the forming tools. Springback causes variations and inconsistencies of final part dimensions. Therefore prediction of springback is very important for production of precise products used in automobile and aerospace industries. There are various parameters involved in the process of sheet metal forming, including Young’s modulus, coefficient of friction, Poisson’s ratio, blank thickness, blank length, die radius, punch radius and blank holder force. The aim of this paper is to investigate the springback of a U-channel part by finite element analysis (FEA) and to identify the influences of important parameters on the springback of advanced high strength steels (AHSS) using numerical simulation.

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