32 research outputs found
Experimental analysis and theoretical predictions of the limit strains of a hot-dip galvanized interstitial-free steel sheet
Full text link
A damage model for predicting ductile fracture with considering the dependency on stress triaxiality and Lode angle
Full text linkA methodology for determination of extended strain-based forming limit curve considering the effects of strain path and normal stress
No full textA large deformation constitutive model for plastic strain-induced phase transformation of stainless steels at cryogenic temperatures
Full text linkFINITE ELEMENT MODELING OF FATIGUE CRACK GROWTH IN CORRODED PIPELINE
No full textEnsuring the safety of pipelines in the oil and gas industry is important to
prevent financial losses and human injuries. One of the threats of pipelines is
corrosion effects and it may occur locally and by repeating changes in loading
and operation pressure conditions, it could lead to the phenomenon of fatigue
in corroded pipelines. In this research, the corrosion of the inner surface of
the API 5L Gr. x52 pipeline using ASME B31.G. and the finite element method was
studied and the obtained results along with experimental results were compared.
It was found that the effective area method of ASME B31.G. with a maximum error
of 3.83\% compared to the FEM had good compatibility with the FEM and the
laboratory method. Then, by taking into account the phenomenon of fatigue due
to working pressure changes, crack growth due to both fatigue and corrosion was
studied simultaneously by theoretical methods and extended finite element
method. The effect of various factors and conditions on the formation and crack
growth due to fatigue by considering the effects of corrosion on the inner
surface of the pipeline using XFEM was investigated. By the failure pressure of
corroded pipelines, the fatigue crack growth would be investigated and by
obtaining stress intensity factors using Paris law and XFEM, results would be
investigated in terms of important factors in the fatigue crack growth and the
significance and effect of depth and length of cracks on the stress intensity
factors will be detected by the results of XFEM. Using the results, the effects
of various factors such as corrosion area characteristics, crack geometry
including crack depth, crack length, and fluctuations in fluid working conditions including work pressure in fatigue crack growth were investigated. In the model 61\%, the first mode of the stress intensity factor of the theoretical method with an error of 0.43\% compared to the XFEM showed good agreement with the results of the theoretical methods and the XFEM in the field of fatigue crack growth
Analysis of Concrete Pressure Vessels in the Framework of Continuum Damage Mechanics
Full text link In this article, a constitutive model in the framework of continuum damage mechanics is proposed to simulate the elastic behavior of concrete in tension and compression states. We assume two parts for Gibbs potential energy function: elastic and damage parts. In order to obtain the elastic-damage constitutive relation with the internal variables, two damage thermodynamic release rates in tension and compression derived from the elastic part of Gibbs potential energy are introduced. Also, two anisotropic damage tensors (tension and compression) are defined which characterize the tensile and compressive behaviors of concrete. Furthermore, two different linear hardening rules for tension and compression states are adopted for characterizing the damage evolution. The spectral decomposition technique is used to resolve the stress tensor into tensile and compressive components. The accuracy and performance of the proposed model are validated by comparing the predicted results with different experimental data, such as monotonic uniaxial tension and compression tests, and monotonic biaxial compression test. As an application, an analytic closed-form solution for a concrete thick-walled cylinder is obtained. It is shown that two damages: tensile damage [Formula: see text] and shear damage [Formula: see text] propagate in the cylinder. These two damages introduce anisotropy in the elastic behavior of the concrete structure. The influence of these two damages is investigated on the stress field in the cylinder. It is found that effect of shear damage [Formula: see text] on radial and tangential stresses as well as the effect of tensile damage [Formula: see text] on radial stress are negligible, while the effect of tensile damage [Formula: see text] on the tangential stress in a concrete thick-walled cylinder is significant. </jats:p
NUMERICAL ANALYSIS OF GROWING THE DUCTILE DAMAGE IN STRUCTURES REINFORCED BY SMA USING CONTINUUM DAMAGE MECHANICS APPROACH
No full textIn general, materials include micro-cracks and small holes which is created during the manufacturing process. The growth of these micro-cracks leads to degradation of mechanical properties and resulting in deterioration of the materials. Continuum damage mechanics is the new field of failure criteria which survey the behavior and responses of weakened material during the complete process of deterioration of material. This method defines the damage growth with an internal variable and can be used to predict the failure behavior of many materials such as metals, composites, polymers, and so on. Shape memory alloys have unique features, such as, having memorable properties, being super elastic and being energy absorber, which led to new applications in science and engineering research. Super elastic property accompanies with a lot of energy absorption during creating a Hysteresis loop. In this research, we examine mechanical behavior of materials reinforced with smart alloy in the context of environmental damage mechanics. Simulation and experimental results were very close. The considered structure is a notched piece of aluminum which is reinforced by the smart alloy. This material is notched because when the smart alloy reaches to its maximum reversible strain, damage variable reaches to its critical value due to the stress concentration. Accordingly, in this case, the effect of existence of the smart alloy is studied to find how it reduces the growing of the damage. Simulation of the mentioned structure is performed with Finite Element Analysis, where the structure was modeled under longitudinal loading. UMAT code of Lemaiter model, was developed for behavioral properties with damaged aluminum, UMAT code of Brinson model was used for behavioral properties of shape memory alloy. Simulation results suggest that different behavioral aluminum with aluminum reinforced by SMA. Existence of smart alloy on the aluminum substrate reduces the damage evolution and the structure fails in higher loadings. Also, the simulation results showed that reinforcing materials such as aluminum with shape memory alloys, up to the failure, are suitable choices for cyclic loading
Experimental and numerical fatigue life study of cracked AL plates reinforced by glass/epoxy composite patches in different stress ratios
Full text linkThe strain gradient approach for determination of forming limit stress and strain diagrams
No full text
