Cyclic plasticity modelling of austenitic steels with complex behavior

Significance 

Structural components are susceptible to failure under different loading conditions. Therefore, it is important to understand the different causes of structural failures so as to enable the optimization and design of long-lasting structural components. Steel is the widely used material for various applications globally due to its excellent properties such as toughness, corrosion resistance and stiffness. Unfortunately, cyclic behavior prediction of structural materials is not fully explored.

Presently, several cyclic models have been developed to describe the cyclic behaviors of materials and structures. For instance, non-linear kinematic rules were proposed to enhance ratcheting effect description as well as extending it to cyclic plastic modelling analysis. Generally, austenitic steels are favorable for analysis of cyclic behavior under low cycle fatigue thus attracting interest among researchers. Cyclic modeling of 316L steels comprises of ratcheting response, hardening and strain range memory. For 316L steels, pre-hardening effect and the cyclic behavior have been investigated based on the microstructural analysis. Therefore, back stress is the main cause of strain memory effect, particularly during uniaxial cyclic loading. These stresses are associated with the interaction of the short-range and long-range dislocations. This calls for a great need for a better description of microstructural evolution during cyclic deformation.

A group of researchers at the University of Technology of Troyes: Dr. Jianqiang Zhou, Dr. Zhidan Sun, Dr. Pascale Kanouté and Prof. Delphine Retraint performed an experimental analysis and cyclic modeling of 316L austenitic stainless steels in the low cycle fatigue region. Their research work is published in the research journal, International Journal of Plasticity.

Briefly, the authors commenced their experimental work by performing low cyclic fatigue tests on two steel samples at room temperature and strain amplitudes in the range of ±0.3% to ±1.5%.

They then investigated the cyclic behavior and properties of the materials including Young’s modulus and yield point. The cyclic softening and hardening effects in the back stress were incorporated using the nonlinear kinematic hardening rules with an introduced multiplicative coefficient. The material parameters were identified based on the experimental results of the steel samples. Eventually, the simulation and experimental results were compared to validate the effectiveness of the model.

The research team observed that under low strain amplitudes, the two samples underwent hardening followed by long-range softening. However, for the 316L-B sample, secondary hardening was achieved under relatively high strain amplitudes. Additionally, the two steel samples showed strain range memory effect, particularly during cyclic loading. This was attributed to the back stress that influenced hardening, softening and strain range memory effect.

In a nutshell, University of Technology of Troyes scientists successfully developed and implemented a cyclic constitutive model to predict the cyclic behavior of steel samples throughout the entire cyclic loading. The accuracy and feasibility of the method were validated by the similarities in the experimental and simulations results of the austenitic 316L-A steel which also proved suitable for material analysis in the low cyclic fatigue regime. The method is versatile and thus can be extended to investigate other material features. This will advance the design of efficient structural materials for various applications.

Cyclic plasticity modelling of austenitic steels with complex behavior - Advances in Engineering

About the author

Dr. Jianqiang Zhou is an Assistant Professor in the school of mechanical engineering, Northwestern Polytechnical University (NPU), China. He received his Bachelor’s and Master’s degree in mechanical engineering from NPU in 2010 and 2013, respectively. Afterwards, he worked as a structure design engineer in AECC Commercial Aircraft Engine Co., Ltd (China). In 2014, he began PhD study in France, and received the PhD degree in mechanical engineering from Charles Delaunay Institute, University of Technology of Troyes (France), in 2018.

Dr. Zhou’s research interests currently focus on fatigue properties of materials in relation to the process history, the microstructure, and the loading forms in service, including cyclic plasticity, residual stress, damage mechanism, fatigue life.

About the author

Dr. Zhidan Sun received his Bachelor’s degree in Mechanical Engineering from Shanghai Maritime University (SMU) in 2002, Engineer’s degree in Mechanics from National Engineering Institute in Mechanics and Microtechnology (ENSMM) in 2004, and his Ph.D. in Materials Engineering from National Institute of Applied Sciences of Lyon (INSA-Lyon) in 2008. After spending several years as post-doctoral researcher in MINES-ParisTech and in University of Versailles Saint-Quentin-en-Yvelines (UVSQ), he is currently Assistant Professor in University of Technology of Troyes (UTT), France.

Dr. Sun’s research interests are focused on mechanical properties of materials in relation to microstructural and environmental parameters such as hydrogen embrittlement. The work contains characterization of fatigue properties from Low Cycle Fatigue (LCF) to Very High Cycle Fatigue (VHCF) under different loading modes, analysis of damage and fracture mechanisms, as well as numerical modelling and simulation using finite element method (FEM). He has participated in some major projects supported by French National Research Agency (ANR).

About the author

Pascale Kanoute received her PhD in Solids, Structures and Mechanical Systems (CERN fellowship) from the University Pierre et Marie Curie, Paris 6, in 1999. Since then, she has been working as a research scientist at ONERA, the French Aerospace Lab, in the department of Metallic Materials and Structures. She is currently the Head of the Metallic Material Mechanics Group (11 people and around 5 PhD students) and since 2009, she has been also a part-time associate professor at Charles Delaunay Institute, University of Technology of Troyes (France).

Her fields of expertise concern the modeling of the non-linear behavior of metallic materials submitted to cyclic thermo-mechanical loads, the development of multiscale approaches to describe the relationship between the microstructure and the mechanical behavior, the fatigue lifetime assessment (multiaxial fatigue, fatigue-creep or fatigue-creep-oxidation interaction).

About the author

Delphine Retraint received her engineering degree and Master Degree in Materials Science from the Institut National Polytechnique de Grenoble in 1992, and her PhD in Materials Science (Dassault Aviation Fellowship) from the Institut National Polytechnique de Grenoble (INPG – France) in 1995. She is Professor at Charles Delaunay Institute, University of Technology of Troyes (France), where she is currently the head of the Life Assessment of Structures, Materials, Mechanics and Integrated Systems (LASMIS) Lab (72 members).

Her field of expertise concerns the study of residual stresses, the parameter study and modelling of mechanical surface treatment processes (shot peening, laser peening, surface mechanical attrition treatment – SMAT), the analysis of the relationship between surface treatments and mechanical properties of materials, the generation of superficial nanostructures thanks to severe plastic deformation.

She has led/participated in different European and French research projects in the field of her expertise.

Reference

Zhou, J., Sun, Z., Kanouté, P., & Retraint, D. (2018). Experimental analysis and constitutive modelling of cyclic behavior of 316L steels including hardening/softening and strain range memory effect in LCF regime. International Journal of Plasticity, 107, 54-78.

Go To International Journal of Plasticity

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