• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4647-4658
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• 2023

In this paper, elastic-plastic fracture mechanics analysis is performed to determine the critical crack sizes of the multipurpose canister (MPC) manufactured using austenitic stainless steel under dynamic loading conditions that simulate drop accidents. Firstly, dynamic finite element (FE) analysis is performed using Abaqus v.2018 with the KORAD (Korea Radioactive Waste Agency)-21 model under two drop accident conditions. Through the FE analysis, critical locations and through-thickness stress distributions in the MPC are identified, where the maximum plastic strain occurs during impact loadings. Then, the evaluation using the failure assessment diagram (FAD) is performed by postulating an external surface crack at the critical location to determine the critical crack depth. It is found that, for the drop cases considered in this paper, the principal failure mechanism for the circumferential surface crack is found to be the plastic collapse due to dominant high bending axial stress in the thickness. For axial cracks, the plastic collapse is also the dominant failure mechanism due to high membrane hoop stress, followed by the ductile tearing analysis. When incorporating the strain rate effect on yield strength and fracture toughness, the critical crack depth increases from 10 to 20%.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.45-55
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• 2004

In the past it has been often observed that the shear stresses at failure are much smaller than the shear strength obtained from traditional laboratory tests and conventional analysis technique is inadequate in stiff soil, such as cemented sand. Many researchers have brought attention to the fact that the presence of flaws i.e. fissures, cracks, joints have a great effect on the strength and overall stress-strain behavior of such materials. They have thought that fracture mechanics may appropriately be adopted as a good tool for analysis of these materials. However, the use of fracture mechanics concept especially for cemented sands is faced with difficulties in obtaining relevant parameters, because fracture parameters and predictions are highly dependent on the material constituents and the size of specimens as well as the size of particles. This paper addresses the effects of sizes which include specimen and aggregate on fracture properties of cemented sand. The results of laboratory tests show that the sizes of specimens and particle have a great effect on the fracture properties such as nominal strength of cemented sand.

• Coupled systems mechanics
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• v.6 no.1
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• pp.97-111
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• 2017

The present paper reports an analytical study of delamination fracture in the Mixed Mode Flexure (MMF) functionally graded beam with considering the material non-linearity. The mechanical behavior of MMF beam is modeled by using a non-linear stress-strain relation. It is assumed that the material is functionally graded along the beam height. Fracture behavior is analyzed by the J-integral approach. Non-linear analytical solution is derived of the J-integral for a delamination located arbitrary along the beam height. The J-integral solution derived is verified by analyzing the strain energy release rate with considering the non-linear material behavior. The effects of material gradient, crack location along the beam height and material non-linearity on the fracture are evaluated. It is found that the J-integral value decreases with increasing the upper crack arm thickness. Concerning the influence of material gradient on the non-linear fracture, the analysis reveals that the J-integral value decreases with increasing the ratio of modulus of elasticity in the lower and upper edge of the beam. It is found also that non-linear material behavior leads to increase of the J-integral value. The present study contributes for the understanding of fracture in functionally graded beams that exhibit material non-linearity.

• Interaction and multiscale mechanics
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• v.2 no.3
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• pp.277-293
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• 2009

The Enriched Free Mesh Method (EFMM) is a patch-wise procedure in which both a displacement field on an element and a stress/strain field on a cluster of elements connected to a node can be defined. On the other hand, the Superconvergent Patch Recovery (SPR) is known to be an efficient post-processing procedure of the finite element method to estimate the error norm at a node. In this paper, we discuss the relationship between solutions of the EFMM and those of the SPR through several convergence studies. In addition, in order to solve the demerit of the smoothing effect on the fracture mechanics fields, we implement a singular stress field to a local patch in the EFMM, and its effectiveness is investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.231-234
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• 2009

Based on combined continuum-fracture mechanics, fracture criterion was utilized to predict impact performance of advanced high-strength steel sheets: 340R and TWIP940. The macro-crack propagation behavior at high stress triaxiality was characterized by V-notch tests while deformation behavior at high strain rate was characterized by simple tension tests with various cross head speeds. The characterized mechanical properties were incorporated into the FE program ABAQUS/Explicit to simulate the charpy impact tests, which showed good agreement with experiments.

• Coupled systems mechanics
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• v.9 no.4
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• pp.381-396
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• 2020

Analytical investigation of the fracture of inhomogeneous beam with two parallel lengthwise cracks is performed. The thickness of the beam varies continuously along the beam length. The beam is loaded in three-point bending. Two beam configurations with different lengths of the cracks are analyzed. The two cracks are located arbitrary along the thickness of the beam. Solutions to the strain energy release rate are derived assuming that the material has non-linear elastic mechanical behavior. Besides, the beam exhibits continuous material inhomogeneity along its thickness. The balance of the energy is analyzed in order to derive the strain energy release rate. Verifications of the solutions are carried-out by considering the complementary strain energy stored in the beam configurations. The influence of the continuous variation of the thickness along the beam length on the lengthwise fracture behavior is investigated. The dependence of the lengthwise fracture on the lengths of the two parallel cracks is also studied.

• Journal of the Korean Society of Safety
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• v.17 no.1
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• pp.18-24
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• 2002

This study verified the relationship between fracture mechanics parameters(${\Delta}K,\;K_{max}$) and X-ray parameters ($(\sigma}_r,;B$) for G365 steel at elevated temperature up to $300{\circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to crack length direction was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase in low ${\Delta}K$ region, reach to a maximum value at a certain value of $K_{max}$ or ${\Delta}K$ and then decrease. Residual stress was independent on stress ratio by arrangement of ${\Delta}K$ and half value breadth was independent by the arrangement of $K_{max}$. The equation of ${\sigma}_r-{\Delta}K$ was established by the experimental data. Therefore, fracture mechanics parameters could be estimated by the measurement of X-ray parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.667-670
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• 2001

For major structural components periodic inspections and integrity assessments are needed for the safety. However, many flaws are undetectable because sampling inspection is carried out during in-service inspection. Probabilistic integrity assessment is applied to take into consideration of uncertainty and variance of input parameters arise due to material properties and undetectable cracks. This paper describes a Probabilistic Fracture Mechanics(PEM) analysis based on the Monte Carlo(MC) algorithms. Taking a number of sampling data of probabilistic variables such as fracture toughness value, crack depth and aspect ratio of an initial surface crack, a MC simulation of failure judgement of samples is performed. For the verification of this analysis, a comparison study of th PFM analysis using a commercial code, mathematical method is carried out and a good agreement was observed between those results.

• Smart Structures and Systems
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• v.23 no.4
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• pp.373-385
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• 2019

A study concerning the strength of brittle materials is presented in this paper. The failure behavior was investigated examining the plane of the crack after the failure and comparing the results obtained with those deriving from the fracture mechanics theory. Although the proposed methods are valid in general for brittle materials, the experiment was performed on glass because the results are more significant for this. Glass elements of various sizes and different edge finishes were subjected to bending tests until collapsing. The bending results were studied in terms of failure load and energy dissipation, and the fracture surfaces were examined by means of microscopic analysis, in which the depth of the flaw and the mirror radius of the fracture were measured and the strength was calculated. These results agreed with those obtained from the fracture mechanics analysis.

• Computers and Concrete
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• v.33 no.2
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• pp.147-162
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• 2024

This study presents a random-aggregate mesoscale model integrating the random distribution of the coarse aggerates and the damage mechanics of the mortar and interfacial transition zone (ITZ). This mesoscale model can generate the random distribution of the coarse aggregates according to the prescribed particle size distribution which enables the automation of the current methodology with different coarse aggregates' distribution. The main innovation of this work is to propose the "correction factor" to eliminate the dimensionally dependent mesh sensitivity of the concrete damaged plasticity (CDP) model. After implementing the correction factor through the user-defined subroutine in the randomly meshed mesoscale model, the predicted fracture resistance is in good agreement with the average experimental results of a series of geometrically similar single-edge-notched beams (SENB) concrete specimens. The simulated cracking pattern is also more realistic than the conventional concrete material models. The proposed random-aggregate mesoscale model hence demonstrates its validity in the application of concrete fracture failure and statistical size effect analysis.