Material characterization of 316L (original) (raw)
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Constitutive equations for time independent plasticity and creep of 316 stainless steel at 550°C
International Journal of Pressure Vessels and Piping, 2003
The paper concerns the development of constitutive equations for 316 stainless steel at 550 8C; it, firstly, considers time independent plastic straining at high temperature; and, secondly, describes how mechanisms-based creep constitutive equations have been formulated. It is shown how a power-law hardening model may be used to describe the effects of prior plastic pre-strain, by providing excellent comparisons with the results of experiments. The paper then develops constitutive equations for time dependent creep based on the theory of continuum damage mechanics. The corresponding state variable rate equations have been selected to include a description of strain hardening in primary creep, a major contributor to strain in this material, and also softening due to creep constrained cavity growth. Despite the paucity of data at lower stresses, corresponding to lifetimes in the region of 10 5 h, a model has been formulated which gives good predictions of experimental results over a wide stress range. The paper discusses how the time independent and time dependent models may be combined in a finite element analysis code to predict inelastic straining due to initial loading and to stress redistribution encountered in reheat cracking of welded pressure vessels.
Determination of materials parameters under dynamic loading
Computational Materials Science, 2010
In the combined experimental/numerical/optimization approach adopted in this work, the constants of material models are identified by optimizing the difference between the numerical and experimental profiles of specimen after deformation without using experimental stress-strain curve. Three materials including two low carbon steels and an aluminum alloy are used in this investigation. The constants of Johnson-Cook (J-C) model are identified from tension, compression and using optimization technique with different number of variables. The quasi-static related constants of the model are also determined from compressive quasi-static tests. The constants obtained in different ways nearly coincide and verify the approach adopted in this investigation. The constants of Zerilli-Armstrong (Z-A) and power law plasticity (P-L) models are also identified. The results indicate that J-C and Z-A models can accurately describe the behaviour of two of the materials used in this work but the power law model proves not to be an appropriate model for the two forgoing materials. This is thought to be due to the reason that the model cannot incorporate thermal effects in a thermo/mechanical stress analysis adopted in the present work. On the other hand, the power law model is found to be capable of describing the flow stress of materials which show temperature hardening/softening behaviour in tensile tests using least square method. The reason is that the model's constants could be defined in terms of temperature.
International Journal of Plasticity, 2005
Combination of physically based constitutive models for body centered cubic (bcc) and face centered cubic (fcc) metals developed recently by the authors [Voyiadjis, G.Z., Abed, F.H., 2005. Microstructural based models for bcc and fcc metals with temperature and strain rate dependency. Mech. Mater. 37, are used in modeling the plastic deformation of AL-6XN stainless steel over a wide range of strain rates between 0.001 and 8300 s À1 at temperatures from 77 to 1000 K. The concept of thermal activation analysis as well as the dislocation interaction mechanism is used in developing the plastic flow model for both the isothermal and adiabatic plastic deformation. In addition, the experimental observations of AL-6XN conducted by Nemat-Nasser et al. . Thermomechanical response of AL-6XN stainless steel over a wide range of strain rates and temperatures, J. Mech. Phys. Solids 49, 1823-1846] are utilized in understanding the underlying deformation mechanisms. The plastic flow is considered in the range of temperatures and strain rates where diffusion and creep are not dominant, i.e., the plastic deformation is attributed to the motion of dislocations only.
Nuclear Engineering and Design, 1989
This paper is concerned with the experimental behavior of a 316 stainless steel and a 2024 aluminium alloy at room temperature and under complex nonproportional strainings in tension-torsion. The basic features of this behavior are underlined and their interactions emphasized. It is observed that the response of these materials under general loading paths is a balance between hardening and softening occurring respectively when the nonproportionality of the straining path is increased or decreased.
Identification of the dynamic tensile properties of metals under moderate strain rates
Stainless steel 316L, titanium alloy grade 7, and alloy C22 are currently under consideration as candidate materials for use in various components associated with the spent nuclear fuel package, which must be designed to withstand structural deformation caused by static, thermal, and handling loads. In addition, it has to maintain its integrity in case of accidents, where it may be
Transactions of the Indian Institute of Metals, 2015
Significance of time independent and dependent constitutive modeling to analyze macroscopic material deformation behavior employing semi-implicit integration is studied in this work. A simplified expression for infinitesimal plastic strain increment is discussed. Investigation of cyclic hardening behavior of SS 316 L is carried out at various mean stresses under uniaxial cyclic mechanical loading. The corresponding results are aimed to differentiate the cyclic hardening/deformation behavior at room temperature and 550°C using time independent (Model-1) and time dependent (Model-2) constitutive models. Cyclic hardening phenomenon is characterized into Phases-I and-II representing rapid and slow hardening zones, respectively which further reveals the severity of damage during asymmetric cyclic loading for Models-1 and-2. Suitability of the constitutive models at different temperature and stressing rates is proposed depending on contribution of viscoplasticity/rate dependence. Present formulation is validated by comparing the results with previously published experimental data.
Key Engineering Materials, 2004
In this study, subsequent time-dependent deformation after cyclic preloading and a constitutive model is discussed. Stress-strain curves of 10 th and 30 th cycle of cyclic loading under the strain rate of 0.01%/sec with the strain amplitude of 0.5% using Type 304 stainless steel at room temperature are almost same. However, creep and stress relaxation after the two cyclic loading are different due to the number of cycle of the cyclic preloading. The experimental results are simulated by a unified constitutive model. The model is constructed referring to dislocation observations after 10 th and 30 th cycles of cyclic loading by using TEM (Transmission Electron Microscope). The constitutive model shows good agreements with the experimental results of the subsequent creep and the subsequent stress relaxation.
Aerospace Science and Technology, 2015
Stainless steels, especially ferritic ones, are used in heat-resistant devices, home appliances, construction materials due to their high corrosion resistance, high and low temperature availability, mechanical strength and long-time durability. In this study, it was aimed to identify the Johnson-Cook (JC) parameters of the AISI 430 ferritic stainless steel depending on the gage length variation. After preparing tensile samples with seven different gage lengths (0.5, 1, 2, 5, 10, 20 and 50 mm), the samples were subjected to tensile tests at the same deformation speed (2 mm/s). Here, the variation of the yield stress depending on the strain rate was investigated because the deformation speed was kept constant and the gage length was changed. The tensile tests at different strain rates were conducted on the same setup. The materials were also subjected to the tensile tests at different temperatures on reference strain rate to perceive the change of the yield stresses at elevated temperatures. As a result of these tests, the JC parameters of the material were determined. Finally, by using these parameters, the tensile test simulations of the material were performed in the finite element simulation package. When the obtained experimental and numerical data were compared, it was determined that there was a deviation of 3.17% between them and the validity of the JC parameters of the material was proved.
International Journal of Plasticity, 2010
A coupled isotropic-kinematic hardening material model was developed based on phenomenological observations of performed two stage experiments on a medium carbon steel -SAE 1144, where the first deformation is performed at elevated temperatures and the second deformation at room temperature. Above all, deformations with orthogonal loading at various temperatures were investigated in order to determine the influence of the loading direction as well as of the temperature. Bergström's theory of work hardening as well as the nonlinear kinematic hardening of an Armstrong-Frederick type were used as a basis for the model development. In the proposed model a relationship between material coefficients of the classical Bergström model and temperature was investigated. The aim of the new material model was to introduce the least possible amount of new parameters as well as to facilitate the mathematical determination of parameters during the fitting of the model with experimental data. The developed model was implemented in an in-house FE-Code in order to simulate the material behavior due to the dynamic strain aging and the hardening behavior after the dynamic strain aging process. Representative simulation results were compared with the experimental data in order to validate the efficiency and the application range of the model. models to describe the temperature, strain rate and the strain dependence of the flow stress . If a material with dynamic strain aging characteristics, like SAE 1144, is formed at a certain temperature, the strength after cooling to room temperature and reloading in the same direction is much higher than the strength of the undeformed material. However, if the loading direction of the second deformation is not the same e.g. perpendicular to the loading direction at elevated temperatures, the stress drop will increase prominently. These two types of deformations are modeled separately, where deformations without changing the loading direction are modeled with the isotropic hardening and deformations with different loading directions are modeled with the combined isotropic-kinematic hardening model as proposed in this paper. Besides temperature dependence, the dynamic strain aging effect depends on the material composition and especially on the free nitrogen and/or carbon concentration. It is well recognized that the effect of nitrogen on strain aging is more pronounced than one of carbon as it has a higher solubility and diffusion coefficient in steel. In the early work of Bergström, TEM (transmission electron microscopy) investigations were performed at room temperature to study dislocation structures in undeformed as well as in deformed materials. It is important to mention that those studies are very helpful to derive a relationship between dislocation density and deformation, but in some cases, e.g. at elevated temperatures, it is very difficult to conduct such studies and to make quantitative statements regarding physical phenomena.