scholarly journals A Plane Stress Failure Criterion for Inorganically-Bound Core Materials

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 247
Author(s):  
Philipp Lechner ◽  
Christoph Hartmann ◽  
Florian Ettemeyer ◽  
Wolfram Volk
Keyword(s):  
Finite Element ◽  
Plane Stress ◽  
Failure Criterion ◽  
Axial Stress ◽  
Material Model ◽  
Failure Criteria ◽  
Plane Stress State ◽  
Testing Methods ◽  
Coulomb Model ◽  
Core Materials

Inorganically-bound core materials are used in foundries in high quantities. However, there is no validated mechanical failure criterion, which allows performing finite-element calculations on the core geometries, yet. With finite-element simulations, the cores could be optimised for various production processes from robotic core handling to the decoring process after the casting. To identify a failure criterion, we propose testing methods, that enable us to investigate the fracture behaviour of inorganically-bound core materials. These novel testing methods induce multiple bi-axial stress states into the specimens and are developed for cohesive frictional materials in general and for sand cores in particular. This allows validating failure criteria in principal stress space. We found that a Mohr-Coulomb model describes the fracture of inorganic core materials in a plane stress state quite accurately and adapted it to a failure criterion, which combines the Mohr-Coulomb model with the Weakest-Link theory in one consistent mechanical material model. This novel material model has been successfully utilised to predict the fracture force of a Brazilian test. This prediction is based on the stress fields of a finite element method (FEM) calculation.

scholarly journals Behaviour of laminar RC structures subjected to cyclic loading

2019 ◽  
Author(s):  
Rajendra Varma ◽  
Joaquim A. O. Barros ◽  
José Sena-Cruz
Keyword(s):  
Cyclic Loading ◽  
Plane Stress ◽  
Axial Stress ◽  
Material Model ◽  
Plane Stress State ◽  
Biaxial Compression ◽  
Strength Increase ◽  
Concrete Element ◽  
Rc Structures ◽  
Finite Element Software

<p>When a concrete element is subjected to a multi-axial stress field, a suitable failure criterion is required to define the failure of concrete, e.g. Mohr-Columb, Drucker Prager, etc. This paper presents the modelling of laminar concrete structures like walls that can be considered as a plane stress problem, or 3D plane shells assumed as the assemblage of layers in plane stress state.</p><p>Some of the important aspects of the plane stress simulation are to address the following issues: the strength of concrete subjected to biaxial stresses; deviation in material properties before and after cracking; concrete cracking and, the crack propagation. As all these mechanical behaviours are critical to predict the behaviour of laminar structures, hence the issues are investigated by development of numerical model. Cyclic material constitutive laws were implemented in in-house finite element software – FEMIX. The material model matches the existing experimental evidence for the behaviour of reinforced concrete shear wall subjected to monotonic and cyclic loading. The implemented model does simulate the strength increase of concrete when submitted to biaxial compression, and the strength decrease when submitted to tension-compression and tension- tension, as was evidenced by experimental research.</p>

Improving failure sub-models in an orthotropic plasticity-based material model

2020 ◽  
pp. 002199832098265
Author(s):  
Loukham Shyamsunder ◽  
Bilal Khaled ◽  
Subramaniam D Rajan ◽  
Gunther Blankenhorn
Keyword(s):  
Finite Element ◽  
Failure Criterion ◽  
High Speed ◽  
Simulation Models ◽  
Material Model ◽  
Failure Criteria ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Explicit Finite Element Analysis ◽  
Static Tensile

Theoretical details of two failure criteria implemented in an orthotropic plasticity model are presented. Improvements to the well-known Puck Failure criterion and a recently developed Generalized Tabulated Failure criterion are used to illustrate how to link a failure sub-model to existing deformation and damage sub-models in the context of explicit finite element analysis. These models are implemented in LS-DYNA, a commercial transient dynamic finite element code. Two validation tests are used to evaluate the failure sub-model implementation and improvements - a stacked-ply test carried out at room temperature under quasi-static tensile and compressive loadings, and a high-speed, projectile impact test where there is significant damage and material failure of the impacted panel. Results indicate that developed procedures and improvements provide the analyst with a reasonable and systematic approach to building predictive impact simulation models.

scholarly journals Buckling of regular, chiral and hierarchical honeycombs under a general macroscopic stress state

2014 ◽  
Vol 470 (2167) ◽  
pp. 20130856 ◽  
Author(s):  
Babak Haghpanah ◽  
Jim Papadopoulos ◽  
Davood Mousanezhad ◽  
Hamid Nayeb-Hashemi ◽  
Ashkan Vaziri
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Closed Form ◽  
Plane Stress ◽  
Plane Stress State ◽  
Cellular Structures ◽  
Two Dimensional ◽  
Buckling Strength ◽  
Macroscopic Stress ◽  
Unit Cells

An approach to obtain analytical closed-form expressions for the macroscopic ‘buckling strength’ of various two-dimensional cellular structures is presented. The method is based on classical beam-column end-moment behaviour expressed in a matrix form. It is applied to sample honeycombs with square, triangular and hexagonal unit cells to determine their buckling strength under a general macroscopic in-plane stress state. The results were verified using finite-element Eigenvalue analysis.

Strength Simulation of Woven Fabric Composite Materials With Material Nonlinearity Using Micromechanics Based Model

2000 ◽  
Author(s):  
A. Tabiei ◽  
G. Song ◽  
Y. Jiang
Keyword(s):  
Finite Element ◽  
Shear Failure ◽  
Material Model ◽  
Failure Criteria ◽  
Woven Fabric ◽  
Woven Composites ◽  
Explicit Finite Element ◽  
Representative Cell ◽  
Pure Matrix ◽  
Transverse Failure

Abstract The objective of the current investigation is to predict failure strength of woven composites, which considers the two-dimensional extent of woven fabric, based on micro-mechanics. The formulation has an interface with nonlinear finite element codes. At each load increment, global stresses and strains are communicated to the representative cell and subsequently distributed to each subcell. Once stresses and strains are associated to a subcell they can be distributed to each constituent of the subcell (i.e. fill, warp, and resin). Consequently micro-failure criteria (MFC) are defined for each constituents of a subcell and the proper stiffness degradation is modeled. Different stages of failure such as warp transverse failure, fill transverse failure, failure of pure matrix in longitudinal and shear, shear failure in fill and warp, and fiber in fill and warp in longitudinal tension are considered. Good correlation is observed between the predicted and the experimental results presented in the published literature. This material model is suitable for implicit failure analysis under static loads and is being modified for explicit finite element codes to deal with problems such as crashworthiness and impact.

scholarly journals Failure criteria for C/SiC composites under plane stress state

2014 ◽  
Vol 4 (2) ◽  
pp. 021007 ◽  
Author(s):  
Chengpeng Yang ◽  
Guiqiong Jiao ◽  
Hongbao Guo
Keyword(s):  
Stress State ◽  
Plane Stress ◽  
Failure Criteria ◽  
Plane Stress State ◽  
Sic Composites

Strain-Based Failure Criteria for Sharp Part-Wall Defects in Pipelines

1998 ◽  
Author(s):  
Aaron S. Dinovitzer ◽  
Brian A. Graville ◽  
Alan G. Glover
Keyword(s):  
Finite Element ◽  
Failure Criterion ◽  
Local Strain ◽  
Failure Criteria ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Element Analysis ◽  
Acceptance Criterion ◽  
Linear Finite Element ◽  
Non Linear

Failure criteria in current engineering critical assessment procedures for defects in pipelines and welds are stress-based. For example, failure is presumed to occur when the net section average stress reaches some arbitrary flow stress. These approaches are unrealistic for defects of limited length where loading of the net section (ligament) is essentially strain controlled. In order to improve upon this, the authors developed a strain-based failure criterion for part wall pipe defects in terms of the maximum ligament plastic extension. While this criterion[l] provided a basis for assessing the criticality of blunt defects, with respect to plastic collapse, it did not address sharp or planar defects which promote fracture. As a defect becomes sharper, failure is determined more by local strain at the defect tip which is typically characterized by the crack tip opening displacement (CTOD). This paper describes the development of a sharp/planar defect strain-based failure criterion which relates the maximum ligament extension to the critical CTOD of the material. Two and three dimensional non-linear finite element analyses are used to determine local root extensions of circumferential defects which can be related to the loading, defect and pipe dimensions. The root extensions are calibrated to standard CTOD measurements through non-linear finite element analysis. The failure criterion development process considers various defect lengths, material work hardening rates and material models. The failure criterion is compared with analytical and experimental data to demonstrate its predictive capability. The end result of this work is the development of an alternative acceptance criterion for sharp weld defects permitting more effective repair decisions to be made based on a more uniform level of reliability.

A strain-based tensor polynomial failure criterion for anisotropic materials

1988 ◽  
Vol 23 (4) ◽  
pp. 179-186 ◽  
Author(s):  
W Zhang ◽  
K E Evans
Keyword(s):  
Epoxy Resin ◽  
Plane Stress ◽  
Failure Criterion ◽  
Maximum Stress ◽  
Failure Criteria ◽  
Anisotropic Materials ◽  
Maximum Strain ◽  
Stress Space ◽  
Failure Envelope ◽  
Stress Maximum

A strain-based tensor polynomial failure criterion for anisotropic materials is proposed with explicit derivations given in both strain and stress space. The physical distinction between this strain-based criterion and the current stress-based tensorial criterion of Tsai and Wu, is clarified. The viability of the proposed criterion is shown by its application to a graphite—epoxy resin lamina under plane stress. The allowed loadings and failure envelope of this lamina are predicted. Comparison is made with existing failure criteria (both stress-based and strain-based), in particular the maximum stress, maximum strain, and Tsai-Wu criteria.

scholarly journals Finite-element model of tread of stair with loadbearing bolts

2008 ◽  
Vol 56 (4) ◽  
pp. 143-150
Author(s):  
Radek Pospíšil ◽  
Zdeňka Havířová
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Failure Criterion ◽  
Static Load ◽  
Geometric Model ◽  
Limit State ◽  
Vertical Direction ◽  
Material Model ◽  
Element Model ◽  
Load Bearing

Stair with load bearing bolts is the special modern type of wooden staircase. This new type of staircase needs a basic verification by valuable standards for using in a different indoor using. Stair with load bearing bolts is combined wooden and metal materials and their mechanical properties in construction.The goal of this paper is to review wooden tread behaviour as consequence of static load defining by Eurocode 5, implemented in Czech standards. Static load is exactly defined in different load values and the loading places. The three different loading place dimensions are defined by Eurocode 5 too.The wooden tread mechanical behaviour is modelled by FEM software ANSYS 11.0. The numerical simulation offers the distribution of specific magnitudes in the numerical model. The analysis is broken into three parts: geometric model, material model and finite element model. The geometric mo­del is created via script by Ansys Parametric Design Language. This method allows using parametric creation. Material model is defined like linear elastic material model for nine independent values.The defined evaluative criteria begin to ultimative limit state and serviability limit state. The Euro­code 5 for this case defined the minimum load value and the maximum deflection value in vertical direction. The last selected is Hoffman’s failure criterion used to identify the possible crash places. Hoffman’s failure criterion is appropriate for orthotropic material like wood. The loading places must simulate the real constructional tread using.

On Systematic Errors of Two-Dimensional Finite Element Modeling of Right Circular Planar Flexure Hinges

2004 ◽  
Vol 127 (4) ◽  
pp. 782-787 ◽  
Author(s):  
B. Zettl ◽  
W. Szyszkowski ◽  
W. J. Zhang
Keyword(s):  
Finite Element ◽  
Plane Strain ◽  
Plane Stress ◽  
Compliant Mechanisms ◽  
Three Dimensional ◽  
Systematic Errors ◽  
Plane Stress State ◽  
3D Analysis ◽  
Two Dimensional ◽  
Flexure Hinges

This paper discusses the finite element method (FEM) based modeling of the behavior of typical right circular flexure hinges used in planar compliant mechanisms. Such hinges have traditionally been approximated either by simple beams in the analytical approach or very often by two-dimensional (2D) plane stress elements when using the FEM. The three-dimensional (3D) analysis presented examines these approximations, focusing on systematic errors due to 2D modeling. It is shown that the 2D models provide only the lower (assuming the plane stress state) or the upper (assuming the plane strain state) limits of the hinge’s stiffness. The error of modeling a particular hinge by 2D elements (with either the plane stress or the plane strain assumptions) depends mainly on its depth-to-height ratio and may reach up to about 12%. However, this error becomes negligible for hinges with sufficiently high or sufficiently low depth-to-height ratios, in which either the plane strain or stress states dominate respectively. It is also shown that the computationally intensive 3D elements can be replaced, without sacrificing accuracy, by numerically efficient 2D elements if the material properties are appropriately manipulated.

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