On the modelling of strain ageing in a metastable austenitic stainless steel

Larsson, Rikard; Nilsson, Larsgunnar

doi:10.1016/j.jmatprotec.2011.08.003

Cited by 11 publications

(6 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…De Almeida et al [47] reported that austenitic stainless steels are prone to timeindependency at 200°C-800°C. Models were developed to address isothermal and an-isothermal loading conditions and to introduce dynamic strain aging effect into the constitutive models [48][49][50][51][52][53]. Tests on 35CrMo and 25Cr2MoVA steel samples [54,55] at elevated temperature were conducted at various stress rates to assess ratcheting under asymmetric load cycles.…”

Section: The Influence Of Operating Temperaturementioning

confidence: 99%

Visco-Plastic Ratcheting Evaluation of Steel Alloys undergoing various Step-Loading Conditions by means of Isotropic-Kinematic Hardening Rules

Karvan¹

2022

Preprint

View full text Add to dashboard Cite

<p>The present thesis develops visco-plastic constitutive equations to assess ratcheting response of several steel alloys of 304, austenitic Z2CND18.12N, U71Mn, and 316 examined under various step-loading conditions through use of the Ohno-Wang (O-W) and Ahmadzadeh- Varvani (A-V) kinematic hardening rules. The framework of hardening rules was incorporated isotropic hardening rules of Lee and Zavrel (Iso-LZ), Chaboche (Iso-C), and Kang (Iso-K) to emulate expansion of yield surfaces. The unified visco-plastic flow rule was adapted to account for the effects of stress rate and time-dependency in ratcheting assessment of steel samples. Kang's function on dynamic strain aging was employed to further evaluate time-dependent ratcheting response at operating room and elevated temperatures. This function was integrated to the dynamic recovery terms leading to drop in ratcheting magnitude and rate resulting in plastic shakedown shortly after a few stress cycles over Low-High loading sequence. The effect of the presence of peak/valley holding time resulting in static recovery was introduced into the kinematic hardening rules through inclusion of a backstress-dependent function proposed earlier by Ding. This integration enabled hardening rules to predict the excess of ratcheting strain values generated by static loading at maximum and minimum stresses over each loading cycle. Visco-plastic ratcheting evaluation of various stainless steel samples were evaluated at various stress rate, stress levels, loading steps and sequences, operating temperatures and holding times through use of the O-W and A-V hardening rules. The predicted ratcheting curves and hysteresis loops by the O-W and A-V frameworks were compared with those obtained experimentally. The predicted ratcheting curves of steel samples tested at Low-High-Low and High-Low-High loading sequences and at room and elevated temperatures revealed that both frameworks elevated ratcheting strains over Low-High loading sequence and dropped them over High-Low loading sequence. Choices of material constants and number of segments taken from stress-strain curve based on the O-W model noticeably influenced ratcheting response of steel samples. The O-W model held more backstress components, and consequently more coefficients, requiring longer Central Processing Unit (CPU) time for ratcheting evaluation than the A-V model which possessed a less complex framework with a fewer number of coefficients.</p>

show abstract

Section: The Influence Of Operating Temperaturementioning

confidence: 99%

Visco-Plastic Ratcheting Evaluation of Steel Alloys undergoing various Step-Loading Conditions by means of Isotropic-Kinematic Hardening Rules

Karvan¹

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…One of the first ones was given by A.G. Cottrell [30] and explained the effect with a diffusion of solute atoms to dislocations and their "pinning" due to the interaction with the solute atoms [14,16]. It is worth mentioning that this point of view is shared by many researchers of the Portevin-Le Chatelier effect today (for example, [22,33,39,45,50,53,57,58,62,70] and longs lists of their references. B.M.…”

Section: The Portevin-le Chatelier Effectmentioning

confidence: 99%

Serrated Yielding: Physical Mechanisms, Experimental Data, Macrophenomenological Models

2018

PNRPU MB

View full text Add to dashboard Cite

Keywords:review, the Portevin-Le Chatelier effect, serrated yielding, physical mechanisms, strain aging, negative strain-rate sensitivity, instability, experimental studies, phenomenological models.Jump-like deformations as a phenomenon of plastic deformation instability is found for a wide range of ductile materials within certain temperature and strain rate ranges. It is known that temperature and strain rate are the most important parameters of inelastic deformation. For most polycrystals, in the absence of phase transitions, the increase of temperature and decrease of deformation speed leads to a reduction of stresses of inelastic deformation resistance. At the same time there is an inverse dependence of the flow stress for a great number of alloys in some ranges of temperatures and strain rates. Many researchers think that the main reason of this anomalous behaviour is a diffusion process and interaction of dislocations with solute atoms. The Portevin-Le Chatelier effect is one of the best known manifestations of the influence of diffusion processes on the behaviour of deformable materials. At the moment it is an urgent problem to identify ranges of actions, within which serrated yielding is implemented in order to exclude them from manufacturing modes of metal processing.It is preferable to use methods and approaches based on mathematical modelling for the analysis of serrated yielding, determination of optimal processing modes and design of new materials, as experimental methods are very resource intensive and applicable only for existing materials. It is not possible to build mathematical models of the studied processes with a required degree of sufficiency without a thorough study of available empirical data and establishment of leading physical mechanisms.In the first part of the review we consider the works devoted to the description of physical mechanisms and experimental studies of serrated yielding. The main mechanism is considered to be dislocations pinning with solute atoms during delays of motion of dislocations with barriers of different nature. Three main types of the Portevin-Le Chatelier effects have been allocated based on the experimental data of uniaxial loading, in real experiments, different combinations of these three types can be found. Different approaches and models (macrophenomenological, structural mechanical, physical) are used for the theoretical description of serrated yielding; only phenomenological models are analyzed in the present review. © PNRPU

show abstract

Section: The Portevin-le Chatelier Effectmentioning

confidence: 99%

“…The macrophenomenological model, which is a modification of the MacCormick model and focused on the description of the behaviour of metastable stainless steel of the austenitic class, was considered in [45]. In the equation of the yield surface, the flow stress depends on the terms responsible for dynamic and static strain aging, martensitic transformation of a part of the material and speed hardening, i.e.…”

Section: Macrophenomenological Modelsmentioning

confidence: 99%

A Set of Tests for Studying the Effect of the Stress State on Ultimate Metal Plasticity at High Temperature

2018

PNRPU MB

View full text Add to dashboard Cite

Smirnov S.V., Vichuzhanin D.I., Nesterenko A.V. A set of tests for studying the effect of the stress state on ultimate metal plasticity at high temperature.Keywords: ultimate plasticity, fracture locus, effect of the stress state, aluminium alloy.A set of tests that can be used tostudy the effect of the stress state on ultimate metal plasticity at high temperature is proposed. Ultimate plasticity can be characterized quantitatively by the strain accumulated to failure. Dimensionless invariant parameters, such as the triaxiality parameter k and the Lode-Nadai parameter µ σ , are used as a characteristic of the stress state. A set of the parameters k and µ σ unambiguously characterizes the stress state under plastic deformation. Being dimensionless, these parameters can be used to compare the stress state of materials with different levels of strength properties. The triaxiality parameter k characterizes the level of normal stresses. If k > 0, then normal tensile stresses dominate. If k < 0, then normal compressive stresses dominate. The Lode-Nadai parameter µ σ characterizes the type of the stress state. The value of µ σ = +1/-1 corresponds to the stress state of axisymmetric compression/tension, and µ σ = 0 under the plane stress state. The set of tests consists of conventional tension tests of cylindrical specimens, tension tests of notched cylindrical specimens, newly developed tests of "bell" specimens and tests of a thick-walled cup with a thinned bottom. This types of tests has allowed us to investigate ultimate plasticity under monotonic deformation in the range of parameters -1.2 < k < 1.2 and -1 < µ σ < +1 without applying high pressure technique. The stressstrain state under tests was evaluated by the results of mathematical simulation by means of the finite element method in ANSYS. The tests performed on 01570 aluminium alloy specimens. The test temperature was 360 °C. The shear strain rate was H = 0.1; 0.3; 0.5 s -1 . The fracture locus of the 01570 aluminium alloy has been obtained from the test results. The fracture locus can be used in damage mechanics models to predict alloy fracture under metal forming processes. © PNRPUStepanova L.V., Roslyakov P.S. Complete asymptotic expansion M. Williams near the crack tips of collinear cracks of equal lengths in an infinite plane medium.

show abstract

On the modelling of strain ageing in a metastable austenitic stainless steel

Cited by 11 publications

References 22 publications

Visco-Plastic Ratcheting Evaluation of Steel Alloys undergoing various Step-Loading Conditions by means of Isotropic-Kinematic Hardening Rules

Visco-Plastic Ratcheting Evaluation of Steel Alloys undergoing various Step-Loading Conditions by means of Isotropic-Kinematic Hardening Rules

Serrated Yielding: Physical Mechanisms, Experimental Data, Macrophenomenological Models

A Set of Tests for Studying the Effect of the Stress State on Ultimate Metal Plasticity at High Temperature

Contact Info

Product

Resources

About