Effect Of Stress Intensity Factor Research Articles

Mathematical modeling and prediction of pit to crack transition under cyclic thermal load using artificial neural network

The formation of pitting is a major problem in most metals, which is caused by extremely localized corrosion that creates small holes in metal and subsequently, it changes into cracks under mechanical load, thermo-mechanical stress, and corrosion process factors. This research aims to study pit to crack transition phenomenon of steel boiler heat tubes under cyclic thermal load, and mathematical modeling as well as Artificial Neural Networks (ANN) used to estimate the cycles takes to initiate a crack. In this study, the pit-to-crack transition model is developed mathematically, and the effects of stress intensity factor on the number of cycles to initiate crack and pit size are studied for steam tubes under thermal stress at 500℃. The ANN model is designed to predict the number of cycles required for the transition from pit to crack. The novelty of the approach lies in the use of ANN model for the complex behavior of materials under cyclic thermal loading. The stress intensity factor is a parameter that amplifies the magnitude of applied stress that includes the geometric parameter. In-pit-to-crack transition stage stress intensity factor-based approach and volumetric pit growth rate used. The fit regression of all R-values of the output pit size and number of cycles is 0.99195 and 0.9954 respectively showing good agreement for the obtained results using ANN. In addition, the comparison of mathematical model predicted results using equations and ANN predicted outputs using MATLAB® for pit size, and number of cycles shows good agreement in results. In addition, the comparison of mathematical model predicted results using equations and ANN predicted outputs using MATLAB® for pit size, and number of cycles shows good agreement in results. Hence, the formation of pitting problems in most of the metals can be effectively analyzed and reduced by using this research study.

Effect of the Fibers Orientation of the Different Types of Composite Plates Notched of U-Shape Repaired by Composite Patch

The main objective of this work is to repair a structure of composite materials by gluing composite patches with different fiber directions. The effects of stress distribution, damaged area ratio, stress intensity factor KIC and imposed stacking sequence were highlighted by a comprehensive study that contained two sides, an applied experimental side and a numerical model side. The composite materials plates studied in this work are 8-layer of graphite/epoxy, glass/epoxy and boron/epoxy, with different angles. The results obtained clearly show with respect to the experimental side that the orientation of the fibers affects the ultimate strength of failure and that the fibers oriented longitudinally in the direction of the tensile strength give us an ideal performance of the composite material. As for the model aspect of this study, the effects of stress intensity factor and the relationship between the damaged area and the fiber orientation on the performance of these patches were studied. We can conclude from this study that the orientation of the fibers has an important role in the performance of the composite material and its efficiency in repair.

Study of the interaction mechanism of oppositely propagating cracks by dynamic photoelasticity and numerical simulation

The interaction mechanism of oppositely propagating cracks is an important basis for the study of rock fracture under dynamic loading. In this article, the stress field superposition and crack tip stress evolution are deeply investigated during the interaction of oppositely propagating cracks by using dynamic photoelastic experiment method and numerical simulation analysis. Obtained results indicate that the cracks interaction process is accompanied by the deflection of the crack, and the deflection of the cracks is mainly affected by the shear stress field at the crack tip. According to the difference of the crack deflection characteristics, the interaction process of the oppositely propagating cracks can be divided into two stages. The Stage I: the non-interlaced stage and Stage II: the interaction stage after the mutual staggered. It includes the period of Stage I that the oppositely propagating cracks are not interlaced with each other; the Stage II is the interaction period after the oppositely propagating cracks are interlaced with each other. The effects of stress intensity factor K I, stress intensity factor K II and far-field T stress on crack propagation process should be comprehensively considered when predicting the crack growth trajectory. The interaction of the stress field between cracks is the main factor determining the crack propagation trajectory. In addition, the vertical spacing between cracks also has a significant effect on the fracture behavior of oppositely propagating cracks. When the vertical distance between the two cracks is large, the local stress fields at the crack tip cannot overlap and interfere with each other, and the oppositely propagating cracks will expand independently of each other.

Fatigue-Corrosion of High Strength Steels in Synthetic Seawater under Cathodic Protection

The paper is aimed to the study of the corrosion-fatigue behavior of high strength steels for offshore pipelines. Tests have been performed in order to study fatigue crack growth in synthetic seawater under cathodic protection. The tests have been carried out on three different steel grades from 65 to 85 ksi with tempered martensite and ferrite-bainite microstructures. The effect of stress intensity factor, cathodic protection potential and cyclic loading frequency is shown.

Customization of the coupled environment fracture model for predicting stress corrosion cracking in Alloy 600 in PWR environment

The coupled environment fracture model (CEFM) has been modified and calibrated to predict crack growth rate (CGR) in Alloy 600 under typical PWR primary coolant conditions. The customized CEFM provides quantitative predictions of the effects of stress intensity factor, hydrogen concentration, yield strength, and temperature on CGR in Alloy 600 in PWR primary coolant environments, as well as explaining the dominating mechanism of stress corrosion cracking (SCC) in this alloy. The importance of the mechanical properties, such as yield strength and stress intensity factor, as identified previously from Artificial Neural Network (ANN) analysis of CGR data in the literature, has been confirmed theoretically. The success in explaining the intergranular stress corrosion cracking (IGSCC) of Alloy 600, argues that the CEFM, which was originally developed to describe IGSCC in sensitized stainless steels, is equally applicable for describing IGSCC in Alloy 600.

Stress Intensity Factor (SIF) analysis on the Pressurized Base Weld Component (PBWC) Materials a Review

This paper presented comprehensive review of literature of past years research work already done in proposed field is presented. The work includes the research work published in various journals and conferences, articles, magazine, available in open literature. The literature review focus on Stress Intensity Factor (SIF) analysis in both surface and depth direction and residual stresses concentration of the Pressurized Base Weld Component (PBWC). Stress intensity is used in fracture mechanics to predict the stress intensity near the crack tip which is caused by residual stresses. In present investigation effect of stress intensity factor over the pressurized weld component has been done on the basis of LEFM, residual stresses and previous studies so far to predict the effect on the crack growth in a pressurized base weld component in any NPP as we know the property of the welded zone of a pipe differs from its parent metal. For a design engineer it is very important to ensure the safety of the nuclear reactor as large amount of energy is transferred when the nuclear reaction takes place. A failure in the piping can be hazardous not only to the environment but also to the human lives and money. Review work very useful to us find the research gap in the proposed field.

Evaluation of stress corrosion cracking susceptibility of forged 316 stainless steel in simulated primary water

The bolts for the reactor coolant pump are planned to be made of the forged 316 stainless steel. Prior to use, the stress corrosion cracking (SCC) resistance of the material requires investigation in simulated primary water at 320 °C. The crack growth rates (CGRs) of two duplicate compact tension (CT) specimens are measured using direct current potential drop method. The effects of stress intensity factor (K, changes from 21 to 41 MPa√m), dissolved oxygen (DO, changes from <10 to 2000 ppb) and dissolved hydrogen (DH, 2800 ppb) on CGRs are comprehensively examined. The results indicate that CGR increases with increasing K. The forged 316 stainless steel is sensitive to SCC in oxygenated water. Changing oxygenated water to hydrogenated water leads to more than one order of magnitude decreases of CGR. The fracture surface, crack path, and the influence of the crack branching on CGR are discussed.

Corrosion Fatigue Crack Growth Behavior of Alloy 690 in High-Temperature Pressurized Water

Corrosion fatigue crack growth behavior of Alloy 690 was investigated in air and high-temperature pressurized water environments. The stress intensity factor amplitude threshold (ΔKth) was obtained, and the effects of stress intensity factor (ΔK), cyclic frequency (f), loading ratio (R), and material orientation on the corrosion fatigue crack growth rates were studied. The observed environmental acceleration on corrosion fatigue crack growth was quantitatively analyzed, and an empirical formula and the Ford-Andresen model were utilized to describe and explain the corrosion fatigue behavior of Alloy 690.

STUDY OF MODE - I FRACTURE PARAMETERS IN HIGH PERFORMANCE CONCRETE

In this paper an experimental investigation was carried out to study the fracture behavior of plane high performance concrete beams subjected to three point bending. In this investigation to study the effect of stress intensity factor and Fracture energy of concrete beams of various sizes with constant notch depth ratios at center. It was found that the stress intensity factor and fracture energy increases with the increasing of beam sizes and decreasing the failure stresses with increasing the beam sizes.

EXPERIMENTAL STUDY OF MIXED MODE CRACK PARAMETERS IN HIGH PERFORMANCE CONCRETE

In this paper an experimental investigation was carried out to study the fracture behavior of plain high performance concrete beams subjected to three point bending. In this investigation to study the effect of stress intensity factor and Fracture energy of concrete beams of various sizes with constant position of notch from center of beam and notch depth ratios. It was found that the stress intensity factor and fracture energy increases with the increasing of beam sizes and decreasing the failure stresses with increasing the beam sizes.

Effects of Stress Intensity Factor on Electrochemical Corrosion Potential at Crack Tip of Nickel-Based Alloys in High Temperature Water Environments

Abstract Stress will enhance the local anodic dissolution rate of nickel-based alloys at crack tip and accelerate the crack propagation in high temperature water environments. The relationship between stress and corrosion was studied by the elastic plastic finite element method. The effects of stress intensity factor on the surface electrochemical corrosion potential (ECP) at the crack tip of alloys 600 with a 1T-CT specimen in simulated boiling water reactor environment were analyzed. The effects of plastic deformation and elastic deformation on the changes of the electro-chemical corrosion potential around the crack tip were also discussed. The results indicate that the effects of stress intensity factors on ECP changes of the crack tip surface have the maximum values in the front of the crock propagation, and they decrease gradually towards the sides of the crack. The values of ECP changes increase with the increase of stress intensity factor. The effect of plastic deformation is more obvious than that of elastic deformation.

Effect of Stress Intensity Factor On Fatigue Crack Morphology in High-Strength Steels in Sour Environments

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Deterministic Formulation of the Effect of Stress Intensity Factor on PWSCC of Ni-Base Alloys and Weld Metals

The fundamental correlations such as crack growth rate (CGR) versus K for primary water stress corrosion cracking (PWSCC) of nickel-base alloys in simulated pressurized water reactor environments are quantified with the theoretical model based on the combination of crack tip mechanics and oxidation kinetics. Materials reliability program (MRP) proposed a CGR disposition curve in a report MRP 55 for PWSCC of thick-section Alloy 600 materials. This deterministic CGR equation has been adopted by Section XI Nonmandatory Appendix O of the ASME Boiler and Pressure Code for flaw evaluation. MRP also proposed a CGR disposition curve in a report MRP 115 for PWSCC of Alloy 82/182/132 weld metals. Stress intensity factor (K), temperature and thermal activation energy are included in both MRP 55 and MRP 115 reports. Both MRP 55 and MRP 115 are engineering-based. The results of mechanism-based modeling are compared with the screened experimental data for typical PWSCC systems of nickel-base alloys and the consistence is observed.

On the effect of stress intensity factor in evaluating the fatigue crack growth rate of aluminum alloy under the influence of compressive stress cycles

To date, most of the studies conducted on fatigue life estimation of structural components have focused on the Constant Amplitude Loading (CAL) scenarios. However, very few structures in the real world experience such a loading condition, and most structural components undergo a Variable Amplitude Loading (VAL) during their service life. It is also observed that most of the available fatigue crack growth (FCG) models ignore the influence of the compressive stresses, despite the fact that recent studies have highlighted the detrimental effect of compressive stress cycles (CSCs) on the FCG of materials.In this paper, a VAL stress–time history is used to study the fatigue response of 6061-T651 aluminum alloy, with a focus on the compressive portion of the stress time history. An experimental investigation is conducted to assess the influence VAL, in particular, the influence of the CSC on FCG of the material. In the tests, the tensile portion of the stress–time history was kept unchanged, while the compressive portion of the stress–time history were varied by various scaling factors. The experimental results demonstrate that the compressive stress portion of the applied load has a significant influence on the overall fatigue life of the material. It is observed that even introducing a few number of small CSC into the stress–time history can significantly decrease the fatigue life of the material.In addition, the influence of the CSC is also examined by means of a microscopic evaluation of crack surfaces’ roughness.

Moisture effects of crack initiation in nanocrystalline silicon: a hybrid density-functional/molecular-dynamics study

ABSTRACTA hybrid quantum-mechanical/molecular-dynamics simulation is performed for a cracked-Si model under tension with multiple H2O molecules around the crack-front, to investigate possible effects of the environmental molecules on fracture initiation in Si. Electronic structures near the crack-front are calculated quantum-mechanically on the basis of the density-functional theory. The quantum-mechanical atoms are embedded in a system of classical atoms. The hybrid simulation results show significant effects of stress intensity factor on the reaction processed of the H2O molecules at the crack front.

Interference Effects of Stress Intensity Factor with Plural Edged Cracks Under Uniform Tension

Interference Effects of Stress Intensity Factor with Plural Edged Cracks Under Uniform Tension

Simulation of crack propagation in porous compacted specimens of aspirin

A model originally developed to simulate crack propagation in structural steel has been evaluated for porous compacted specimens of aspirin. The fracture mechanism is assumed to consist of hole growth and coalescence. The program allows both visualization of crack growth and the calculation of crack velocity. Simulations to investigate the effect of stress intensity factor indicate that the critical stress intensity factor for sustained growth for aspirin is of the order of 0.15 MPa m1/2 consistent with experimental findings. The program is easy to use enabling many simulations to be performed with minimum effort.

Simulation of crack propagation in tablet film coatings containing pigments

A model originally developed to stimulate crack propagation in structural steel has been evaluated for tablet film coatings containing pigments. The fracture mechanism is assumed to consist of hole formation around the pigment particles, growth and coalescence. The program allows both the visualisation of crack growth and the calculation of crack velocity. Simulations to investigate the effect of stress intensity factor indicate that the critical stress intensity factor for sustained crack growth in hydroxypropyl methylcellulose is of the order of 0.3 MPA m 1 2 consistent with experimental findings. Simulations to investigate the effect of the particle size of pigments indicate that the crack velocity is highest at small particle sizes but becomes independent of size above 1–2 μm. In general, agreement with experiment both qualitatively and quantitatively is extremely good.

Effect of stress field parameters on dynamic crack branching

A review of the existing crack branching criteria is made. Effect of stress intensity factor, crack velocity and remote stress acting parallel to the crack on the predictions of various criteria is investigated. A new criterion based on the strain energy method is proposed. This criterion predicts the influence of the stress field coefficients including the stress intensity factor and the remote stress acting parallel to the crack on the crack branching phenomenon. Experiments have been conducted to verify the predictions of the proposed criterion.