Influence of material inhomogeneity on the mechanical response of a tempered martensite steel

2017 ◽  
Vol 231 (1-2) ◽  
pp. 14-22 ◽  
Author(s):  
M Li ◽  
FW Sun ◽  
RA Barrett ◽  
E Meade ◽  
DF Li ◽  
...  
Keyword(s):  
Heat Affected Zone ◽  
Mechanical Response ◽  
Voronoi Tessellation ◽  
Void Formation ◽  
Material Point ◽  
Contributory Factor ◽  
Tempered Martensite ◽  
Material Inhomogeneity ◽  
Rate Dependent ◽  
Intercritical Region

Failure in steel weldments operating at high temperatures often occurs in the heat-affected zone adjacent to the weld. Such failures can be a result of material inhomogeneity within the heat-affected zone and in the case of tempered martensite steels have been linked with regions of untransformed α (ferrite) phase or over-tempered martensite within the intercritical region of the heat-affected zone. In this work, two-dimensional Voronoi tessellation is used to construct polygonal Voronoi cells to represent the microstructure of the heat-affected zone of a weld in a tempered martensite steel. The Voronoi construction is treated as a representative volume element of the material and is discretised by 8-node linear brick elements, with periodic boundary conditions. The lattice orientation at each material point is specified by three Euler angles, which are assumed to be randomly distributed, to represent the initial lack of texture in the intercritical region of the heat-affected zone. The constitutive response is represented by a nonlinear, rate-dependent, finite-strain crystal plasticity model. The results indicate that small amounts of ferrite can induce significant enhancements in stress and inelastic deformation at the interface of the ferrite and martensite grains. This localisation of stress and strain may be critical for microcrack and/or void formation and may be a contributory factor to Type IV cracking.

Microstructural Modelling of P91 Martensitic Steel Under Uniaxial Loading Conditions

2013 ◽  
Author(s):  
Brian Golden ◽  
Dongfeng Li ◽  
Noel O’Dowd
Keyword(s):  
Power Plant ◽  
Mechanical Response ◽  
Electron Backscatter Diffraction ◽  
Voronoi Tessellation ◽  
Peak Stress ◽  
Grain Structure ◽  
Plant Materials ◽  
Deformation And Failure ◽  
Rate Dependent ◽  
Modelling Studies

The changing face of power generation requires an improved understanding of the deformation and failure response of power plant materials. Important insights can be obtained through microstructurally motivated modelling studies. This paper deals with the comparisons of predictions of the mechanical response of a power plant steel (P91), obtained from a model with a measured microstructure with those obtained from a numerically simulated microstructure. Electron backscatter diffraction (EBSD) is employed to obtain the orientation of the martensitic grain structure of the steel. This information is incorporated within a representative volume element (RVE) to represent the material microstructure. A non-linear, rate dependent, finite strain crystal plasticity model is used to represent the deformation of the material, with the orientation of each finite-element integration point determined from the EBSD analysis. The deformation under uniaxial tension is analysed. Due to the inhomogeneous microstructure strong strain gradients are generated within the RVE even under remote homogenous strain states. It is seen that peak stress/strain states are associated with particular features of the microstructure. The results taken from the model are compared with those obtained with an equiaxed microstructure generated using the Voronoi tessellation method.

Shear banding in elasto-plastic slumping process on a GPU: mechanical and hydromechanical MPM solver

2021 ◽  
Author(s):  
Michel Jaboyedoff ◽  
Emmanuel Wyser ◽  
Yury Podladchikov
Keyword(s):  
Liquid Phase ◽  
High Resolution ◽  
Strain Localization ◽  
Mechanical Response ◽  
Shear Banding ◽  
Shear Bands ◽  
Material Point ◽  
Future Perspective ◽  
Deformation Problem ◽  
Rate Dependent

<p>Strain localization plays an important role in the mechanical response of a slumping mass and defines the overall behaviour of such process. We study strain localization with the help of the Material Point Method (MPM), which is well-suited to simulate large deformation problem.</p><p>We implemented both mechanical and hydromechanical (i.e., we assume fully saturated conditions of the material) MPM-based solvers within a rate-dependent formulation framework under a GPU architecture. We selected an explicit MPM formulation enriched with the Generalized Interpolation Material Point (GIMP) variant, which fixes a major flaw of MPM, i.e., the cell-crossing error. To avoid spurious oscillation of the pressure field (due to the use of low-order elements) for both solid and liquid phase, we used an element-based averaging technique. This minimizes volumetric locking problems. This numerical framework allows to study high-resolution two-dimensional elasto-plastic (i.e., Mohr-Coulomb plasticity) problems in an affordable amount of time. The solvers were written in a CUDA C environment on a single Nvidia GPU. We report a speed-up factor of 500 compared to a similar MATLAB implementation.</p><p>Our results showcase a contribution of pore water pressures over shear banding. In particular, we report a significant influence of the liquid phase over the steady thickness of the shear bands and their location. Pore pressures add a viscous contribution to the elasto-plastic rheological model we choose, i.e., Mohr-Coulomb.</p><p>As a future perspective, even high resolution could be achieved considering the extension of the actual implementation toward a multi-GPU solver using MPI.</p>

scholarly journals A nonlinear strain-rate dependent constitutive model for uncured rubber materials under large deformation

2020 ◽  
Vol 37 ◽  
pp. 118-125
Author(s):  
Weihua Zhou ◽  
Changqing Fang ◽  
Huifeng Tan ◽  
Huiyu Sun
Keyword(s):  
Constitutive Model ◽  
Large Deformation ◽  
Mechanical Response ◽  
Uniaxial Tensile ◽  
Hysteresis Phenomenon ◽  
Mechanical Behaviors ◽  
Nonlinear Constitutive Model ◽  
Rate Dependent ◽  
Parallel Networks ◽  
Non Gaussian

Abstract Uncured rubber possesses remarkable hyperelastic and viscoelastic properties while it undergoes large deformation; therefore, it has wide application prospects and attracts great research interests from academia and industry. In this paper, a nonlinear constitutive model with two parallel networks is developed to describe the mechanical response of uncured rubber. The constitutive model is incorporated with the Eying model to describe the hysteresis phenomenon and viscous flow criterion, and the hyperelastic properties under large deformation are captured by a non-Gaussian chain molecular network model. Based on the model, the mechanical behaviors of hyperelasticity, viscoelasticity and hysteresis under different strain rates are investigated. Furthermore, the constitutive model is employed to estimate uniaxial tensile, cyclic loading–unloading and multistep tensile relaxation mechanical behaviors of uncured rubber, and the prediction results show good agreement with the test data. The nonlinear mechanical constitutive model provides an efficient method for predicting the mechanical response of uncured rubber materials.

Strain rate dependent dynamic mechanical response of bainitic multiphase steels

2019 ◽  
Vol 745 ◽  
pp. 279-290 ◽  
Author(s):  
Behnam Shakerifard ◽  
Jesus Galan Lopez ◽  
Mari Carmen Taboada Legaza ◽  
Patricia Verleysen ◽  
Leo A.I. Kestens
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Dynamic Mechanical ◽  
Rate Dependent ◽  
Multiphase Steels

Osmo-inelastic response of the intervertebral disc annulus fibrosus tissue

2020 ◽  
Vol 234 (9) ◽  
pp. 1000-1010
Author(s):  
Amil Derrouiche ◽  
Ameni Zaouali ◽  
Fahmi Zaïri ◽  
Jewan Ismail ◽  
Zhengwei Qu ◽  
...  
Keyword(s):  
Intervertebral Disc ◽  
Annulus Fibrosus ◽  
Mechanical Response ◽  
Rate Sensitivity ◽  
Image Correlation ◽  
Inelastic Response ◽  
Full Field ◽  
Osmotic Effect ◽  
Rate Dependent ◽  
Optical Strain

The aim of this article is to provide some insights on the osmo-inelastic response under stretching of annulus fibrosus of the intervertebral disc. Circumferentially oriented specimens of square cross section, extracted from different regions of bovine cervical discs (ventral-lateral and dorsal-lateral), are tested under different strain-rates and saline concentrations within normal range of strains. An accurate optical strain measuring technique, based upon digital image correlation, is used in order to determine the full-field displacements in the lamellae and fibers planes of the layered soft tissue. Annulus stress–stretch relationships are measured along with full-field transversal strains in the two planes. The mechanical response is found hysteretic, rate-dependent and osmolarity-dependent with a Poisson’s ratio higher than 0.5 in the fibers plane and negative (auxeticity) in the lamellae plane. While the stiffness presents a regional-dependency due to variations in collagen fibers content/orientation, the strain-rate sensitivity of the response is found independent on the region. A significant osmotic effect is found on both the auxetic response in the lamellae plane and the stiffness rate-sensitivity. These local experimental observations will result in more accurate chemo-mechanical modeling of the disc annulus and a clearer multi-scale understanding of the disc intervertebral function.

scholarly journals A finite dissipative theory of temporary interfibrillar bridges in the extracellular matrix of ligaments and tendons

2008 ◽  
Vol 6 (39) ◽  
pp. 909-924 ◽  
Author(s):  
P. Ciarletta ◽  
M. Ben Amar
Keyword(s):  
Extracellular Matrix ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Collagen Type I ◽  
State Theory ◽  
Ground Substance ◽  
Type I ◽  
Dissipative Effects ◽  
Rate Dependent

The structural integrity and the biomechanical characteristics of ligaments and tendons result from the interactions between collagenous and non-collagenous proteins (e.g. proteoglycans, PGs) in the extracellular matrix. In this paper, a dissipative theory of temporary interfibrillar bridges in the anisotropic network of collagen type I, embedded in a ground substance, is derived. The glycosaminoglycan chains of decorin are assumed to mediate interactions between fibrils, behaving as viscous structures that transmit deformations outside the collagen molecules. This approach takes into account the dissipative effects of the unfolding preceding fibrillar elongation, together with the slippage of entire fibrils and the strain-rate-dependent damage evolution of the interfibrillar bridges. Thermodynamic consistency is used to derive the constitutive equations, and the transition state theory is applied to model the rearranging properties of the interfibrillar bridges. The constitutive theory is applied to reproduce the hysteretic spectrum of the tissues, demonstrating how PGs determine damage evolution, softening and non-recoverable strains in their cyclic mechanical response. The theoretical predictions are compared with the experimental response of ligaments and tendons from referenced studies. The relevance of the proposed model in mechanobiology research is discussed, together with several applications from medical practice to bioengineering science.

scholarly journals Inelastic Behavior in Repeated Shearing of Bovine White Matter

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Taylor S. Cohen ◽  
Andrew W. Smith ◽  
Panagiotis G. Massouros ◽  
Philip V. Bayly ◽  
Amy Q. Shen ◽  
...  
Keyword(s):  
White Matter ◽  
Strain Rate ◽  
Critical Strain ◽  
Mechanical Response ◽  
Tissue Mechanics ◽  
Strain Rates ◽  
Inelastic Behavior ◽  
Fiber Breakage ◽  
Rate Dependent ◽  
Strain Threshold

Understanding the brain’s response to multiple loadings requires knowledge of how straining changes the mechanical response of brain tissue. We studied the inelastic behavior of bovine white matter and found that when this tissue is stretched beyond a critical strain threshold, its reloading stiffness drops. An upper bound for this strain threshold was characterized, and was found to be strain rate dependent at low strain rates and strain rate independent at higher strain rates. Results suggest that permanent changes to tissue mechanics can occur at strains below those believed to cause physiological disruption or rupture of axons. Such behavior is characteristic of disentanglement in fibrous-networked solids, in which strain-induced mechanical changes may result from fiber realignment rather than fiber breakage.

scholarly journals A new methodology to simulate subglacial deformation of water saturated granular material

2015 ◽  
Vol 9 (4) ◽  
pp. 3617-3660 ◽  
Author(s):  
A. Damsgaard ◽  
D. L. Egholm ◽  
J. A. Piotrowski ◽  
S. Tulaczyk ◽  
N. K. Larsen ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Fluid Pressure ◽  
Fluid Phase ◽  
Large Degree ◽  
Numerical Approach ◽  
Unconsolidated Sediments ◽  
Close Monitoring ◽  
Stick Slip ◽  
Rate Dependent ◽  
Water Saturated

Abstract. The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions. The rheology of a water-saturated granular bed may include both plastic and rate-dependent dilatant hardening or weakening components, depending on the rate of deformation, the material state, clay mineral content, and the hydrological properties of the material. The influence of the fluid phase is negligible when relatively permeable sediment is deformed. However, by reducing the local permeability, fast deformation can cause variations in the pore-fluid pressure. The pressure variations weaken or strengthen the granular phase, and in turn influence the distribution of shear strain with depth. In permeable sediments the strain distribution is governed by the grain-size distribution and effective normal stress and is typically on the order of tens of centimeters. Significant dilatant strengthening in impermeable sediments causes deformation to focus at the hydrologically more stable ice–bed interface, and results in a very shallow cm-to-mm deformational depth. The amount of strengthening felt by the glacier depends on the hydraulic conductivity at the ice–bed interface. Grain-fluid feedbacks can cause complex material properties that vary over time, and which may be of importance for glacier stick-slip behavior.

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