• 소성∙가공
• /
• 제26권5호
• /
• pp.293-299
• /
• 2017

In this paper, finite element stamping analysis was carried out for the front lower arm to examine the applicability of solid element with damage theory to predict shear fracture phenomena induced by sheared edge as well as deformation mechanisms. Mechanical properties related to deformation and damage theory were determined from tensile test. Shear fracture was predicted by normalized Cockcroft-Latham model with initial imposition of the damage value along the sheared edge. Simulation results illustrated that the analysis with solid element and damage theory predicted edge profile, strain distribution, and forming load more accurately than the analysis with shell element. Simulation with solid element can also predict the shear fracture more exactly comparing to analysis with shell element and forming limit curve.

• 한국구조물진단유지관리공학회 논문집
• /
• 제6권4호
• /
• pp.129-137
• /
• 2002

In this study, mixed-mode fracture behavior is simulated effectively through the numerical method using the axial defomation link elements which can predict the behavior of quasi-brittle material. The behavior of quasi-brittle material is modeled numerically using the exponential tension softening constitutive equation and verified by comparing with the result of published experimental result. In order to verify the mixed-mode fracture behavior through the developed numerical method, analysis of mode I is formulated and the result is compared with those of FEM first, and then mixed-mode analysis is analyzed and compared with existing theories and experimental data. Also the characteristics of fracture behavior is examined through the analysis of crack generation with respect to various mode mixity.

• Safety and Health at Work
• /
• 제12권4호
• /
• pp.544-545
• /
• 2021

The article by Tae-Gu Kim et al. conducted elastic FE modeling, which was inappropriate for fracture of elastic-plastic chain material (11.3% of elongation). FE analysis results and the findings in the fracto-graphic analysis did not tally but contradicted each other. The article identified "incorrect installation"/bending forces as the root cause while FE results of the chain under bending forces showed very low stresses at fracture locations but the highest stress in the middle of shank of the chain. The article's "step-like topographies indicating the fracture due to bending moment rather than uniaxial tension" lacked scientific support. The load value carried by each chain section under bending/incorrect installation was only half of that under tension, thus the article using same load value in FE simulation comparison for bending and tension was incorrect. The real cause of the chain fracture was likely improper checking the lifted load or/and using the wrong chain with much lower safety working load.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.160-163
• /
• 2004

The hub hole in a wheel of vehicles usually formed with hole expansion process. Formability of material, especially the hole expansion ratio, is important to produce a fine hub hole. The hub hole expansion process is different from general forming process or bore expansion process in the viewpoint of forming a thick plate. In the hole expansion process of the plate with a hole, as the hole being expanded, the crack is occurred to outward direction at the boundary of a hole. Therefore, it is need to apply the fracture criterion in the hub hole expansion process. In this paper, the hub hole expansion process is simulated with commercial elasto-plastic finite element code, LS-DYNA3D considering some ductile fracture criteria. Fracture mode and hole expansion ratio is compared with respect to the fracture criteria. Analysis results demonstrate that only the effective plastic strain is not adequate to predict the fracture mode in the hub hole. And the analysis results also indicate that the ductile fracture criteria properly predict the fracture mode but hole expansion ratio is different with the result of each other because of their different characteristics.

• 지질공학
• /
• 제8권1호
• /
• pp.1-12
• /
• 1998

단열의 기하학적 인자 중에서 단역크기는 지반공학적 및 수리지질학적으로 중요한 인자임에도 불구하고 측정과 분석단계에서 불확실성이 가장 크게 작용한는 요소이다. 본 연구는 단열크기 추정을 위한 연구동향을 소개하고, 최근 제시된 순산 모델링(forword modeling) 기법을 이용한 추정방법에 대하여 조가 단면적과 단열 단면적과의 차이에 따른 쿄차확률관계 및 단열조와 조사면이 이루는 방향에 따른 교차확률의 변화에 대하여 모사적 검증을 시도하였다. 검증 결과 순산 모델링 기법을 이용한 단열크기 추정방법은 동굴 벽면이나 시추공,노두면에서 단열조별로 확률을 알고, 단열길이의 확률분포특성을 근사하게 추정할 수 있다면 실제 단열크기를 알아 낼 수 있는 방법으로 적용 가능하다고 인정된다.

• Restorative Dentistry and Endodontics
• /
• 제17권1호
• /
• pp.153-165
• /
• 1992

Dental composite resin is a kind of the particle - reinforced composite material, and is widely used in recent dental restoration of anterior and posterior tooth region. The purpose of this study was to investigate the fracture behaviour according to volume fractions and external findings of the filler particles for better interpretation of the fracture characteristics of posterior dental composite resins by analytic method of fracture mechanics. The plane strain fracture toughness($K_{IC}$) and Acoustic Emission were determined with three - point bending test using the single edge notch specimen according to the ASTM - E399, and its analyzed data was compared with filler volume fractions derived from the standard ashing test and scanning electron fractographs of each specimen including the unfilled experimental resin as a control. The results were that the value of fracture toughness of the composite resin material was in the range from 0.85 MPa$\sqrt{m}$ to 1.60 MPa$\sqrt{m}$ and was higher than the value of the unfilled experimental resin, and the fracture behaviours dervied from Acoustic Emission analysis show prominent differences according to the volume fraction and the size of filler particles used in each composite resin. The degree of resistance against crack propagation seems to be increase and the fractographs demonstrate the high degree of surface roughness and irregularity according with the increase of fracture toughness value.

• 대한기계학회논문집A
• /
• 제29권1호
• /
• pp.107-114
• /
• 2005

In order to analyze the elastic-plastic fracture behavior of a structure, the fracture resistance curve of the material should be known first. The standard CT specimen was used to obtain the fracture resistance curves of a piping system. However, it is known that the fracture resistance curve by the standard CT specimen is very conservative to evaluate the integrity of a structure. Also the fracture resistance curve is effected by the specimen geometry and the dimensions because of the constraint effect. The objective of this paper is to be certain the conservativeness of the fracture resistance curve by the standard CT specimen and to provide an additional safety margin. For these, the fracture tests using a real pipe specimen and the standard CT specimen test were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method was used to measure the crack extension and the length for the pipe test. Also finite element analyses were performed with a CT specimen and a pipe in order to prove the additional safety margin. From the result of tests and analyses of the pipe and the standard CT specimen, it was observed that the fracture analysis with the standard CT specimen is conservative and the additional safety margin was proved.

• 한국기계가공학회지
• /
• 제20권1호
• /
• pp.95-102
• /
• 2021

Analysis of the fracture surface is one of the most important methods for determining the cause of equipment structural failure. Whether structural failure is caused by impact or fatigue is necessary information in industrial fields. For ferrous and non-ferrous metal materials, two fracture phenomena are generated on the fracture surface: ductile and brittle fractures. In this study, machine learning predicts whether the fracture is based on ductile or brittle when structurural failure is caused by impact. The K-means algorithm calculates this ratio by clustering the brittle and ductile fracture data from a photograph of the impact fracture surface, unlike the existing method, which calculates the fracture surface ratio by comparison with the grid type or the reference fracture surface shape.

• 한국해양공학회지
• /
• 제19권5호
• /
• pp.65-70
• /
• 2005

Fracture behavior and pipe strength are very important to the integrity of energy plants, ocean structures, and so forth. The pipes of energy plants and ocean structures are subject to local wall thinning, resulting from severe erosion-corrosion damage. Recently, the effects of local wall thinning on fracture strength and fracture behavior of piping systems have been the focus of many studies. In this paper, the elasto-plastic analysis is performed by FE code ANSYS on straight pipes with wall thinning. We evaluated the failure mode, fracture strength and fracture behavior, using FE analysis. Also, the effect of the axial strain on deformations and failure modes was estimated by FE analysis.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1358-1361
• /
• 2003

In this study, intrinsic static/dynamic fracture toughness of Al 7175-T74 are evaluated from the apparent static/dynamic toughness of notched specimen. The notch/crack critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The notch/crack critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, critical notch root radius can be predicted by notch/crack critical average stress fracture model.