Optimal free-form shapes for holes in flat plates under uniaxial and biaxial loading

Ratchetting behavior of SA-333 Gr. 6 carbon steel used as primary heat transport (PHT) piping material has been investigated with three constitutive models proposed by Armstrong-Frederick, Chaboche and Ohno-Wang involving different hardening rules. Performance of the above mentioned models have been evaluated for a broad set of uniaxial and biaxial loading histories. The uniaxial ratchetting simulations have been performed for a range of stress ratios (R) by imposing different stress amplitudes and mean stress conditions. Numerical simulations indicated significant ratchetting and opening of hysteresis loop for negative stress ratio with constant mean stress. Application of cyclic stress without mean stress (R = −1.0) has been observed to produce negligible ratchet-strain accumulation in the material. Simulation under the biaxial stress condition was based on modeling of an internally pressurized thin walled pipe subjected to cyclic bending load. Numerical results have been validated with the experiments as per simulation conditions. All three models have been found to predict the observed accumulation of circumferential strain with increasing number of cycles. However, the Armstrong Frederick (A-F) model was found to be inadequate in simulating the ratchetting response for both uniaxial as well as biaxial loading cases. The A-F model actually overpredicted the ratchetting strain in comparison with the experimental strain values. On the other hand, results obtained with the Chaboche and the Ohno-Wang models for both the uniaxial as well as biaxial loading histories have been observed to closely simulate the experimental results. The Ohno-Wang model resulted in better simulation for the presents sets of experimental results in comparison with the Chaboche model. It can be concluded that the Ohno-Wang model suited well compared to the Chaboche model for above sets of uniaxial and biaxial loading histories.

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Quantifying the Constraint of Three-Dimensional Biaxially Loaded Specimens Containing Semi-Elliptical Cracks Using the J-A2 Method

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2012-78404 ◽

2012 ◽

Cited By ~ 1

Author(s):

L. W. Sharpe ◽

Y. J. Chao

Keyword(s):

Fracture Toughness ◽

Structural Integrity ◽

Biaxial Loading ◽

Three Dimensional ◽

Flat Plates ◽

Constraint Effect ◽

Element Analysis ◽

Applied Loading ◽

Analysis Models ◽

Elliptical Cracks

Fracture toughness is an important material property used to assess the structural integrity of mechanical components containing cracks. Often, the fracture toughness depends upon the geometry of the component as well as the applied loading. This dependence is referred to as the constraint effect in fracture. The two parameter J-A2 method can be used to quantify the constraint effect. The J-A2 method is a more accurate representation of the stress fields near the crack compared to the classical HRR solution, as additional terms from the series solution are used. The subject of the current study is to apply the J-A2 method to published fracture toughness data of three-dimensional, flat plates containing semi-elliptical cracks and subjected to both uniaxial and biaxial loading to determine the constraint effect and also to determine if the method can be used to predict fracture. The J-A2 results of the flat plates are compared to those of 3PB specimens to determine if loss of constraint exists. Finite element analysis models were developed for each specimen to determine the constraint parameter A2 for each applied loading. The results of the current study reveal that both the uniaxial and biaxial loaded plates exhibit loss of constraint relative to the 3PB specimen and biaxial load increases the constraint of the uniaxially loaded specimen. Further, the J-A2 method shows potential as a tool to predict failure with different constraint level.

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Microstress distribution in graphite fibre/epoxy composites containing an elastomeric interphase: response to uniaxial and biaxial loading conditions

Composites ◽

10.1016/0010-4361(95)93670-f ◽

1995 ◽

Vol 26 (4) ◽

pp. 269-280 ◽

Cited By ~ 8

Author(s):

Steven D. Gardner ◽

Charles U. Pittman ◽

Tao C. Chang ◽

Boon Y. Low ◽

Robert M. Hackett

Keyword(s):

Biaxial Loading ◽

Epoxy Composites ◽

Loading Conditions ◽

Graphite Fibre ◽

Uniaxial And Biaxial Loading

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A hyper-elastic thermal aging constitutive model for rubber-like materials

Journal of Elastomers & Plastics ◽

10.1177/0095244319883405 ◽

2019 ◽

Vol 52 (8) ◽

pp. 677-700

Author(s):

Ahmed G Korba ◽

Abhishek Kumar ◽

Mark Barkey

Keyword(s):

Natural Rubber ◽

Thermal Aging ◽

Biaxial Loading ◽

Strain Curve ◽

Aging Effect ◽

Elastic Materials ◽

Stress Strain Curve ◽

Stress Strain ◽

Hyper Elastic ◽

Uniaxial And Biaxial Loading

Different phenomenological, empirical, and micromechanical constitutive models have been proposed to describe the behavior of incompressible isotropic hyper-elastic materials. Among these models, very few have accounted for the thermal aging effect on the model constants and parameters. This article introduces a new empirical constitutive hyper-elastic model for thermally aged hyper-elastic materials. The model named “the weight function based (WFB) model” considers the effect of aging temperature and time on its parameters. The WFB model formulation can facilitate fatigue analysis and lifetime prediction of rubber-like materials under aging conditions. The WFB model in this article defines all rubber-like material properties, such as fracture stretch, strength, and stiffness, by predicting the full stress–strain curve at any aging time and temperature. The WFB model was tested on natural rubber for uniaxial and biaxial loading conditions. More than 100 specimens were aged and tested uniaxially under various temperatures and aging times to extract the stress–strain behavior. The temperatures used in the test ranged from 76.7°C to 115.5°C, and the aging time ranged from 0 to 600 hours (hrs). A classical bulge test experiment was generated to extract the biaxial natural rubber material behavior. An ABAQUS finite element analysis model was created to simulate and verify the generated biaxial stress–strain curve. The proposed model represents the aging effect on the tested natural rubber under uniaxial and biaxial loading conditions with an acceptable error margin of less than 10% compared to experimental data.

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