• 소음진동
• /
• 제11권3호
• /
• pp.437-442
• /
• 2001

In this study, the fracture phenomena of optical disks are discussed by theoretical and experimental approaches and then some recommendations are presented to prevent the fracture. Linear equations of motion are discretized by using the Galerkin approximation. From the discretized equations, the dynamic responses are computed by the generalized- time integration method. As a fracture criterion for optical disks, the critical crack length is presented. From experimental methods, the fracture procedure is analyzed. The fracture occurs when disks have crack on the inner radius of the disks. Since the crack growth and the fracture result from the stress concentration on the tip of the crack, a measure should be taken to overcome the stress concentration. This problem can be resolved by the structural modification of a disk. This study proposes 3 types of improved optical disks.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집A
• /
• pp.339-344
• /
• 2000

In this study, the fracture phenomena of optical disks are discussed and then some recommendations are presented to prevent the fracture. The fracture occurs when disks have crack on the inner radius of the disks. Since the crack growth and the fracture result from the stress concentration on the tip of the crack, a measure should be taken to overcome the stress concentration. This problem can be resolved by the structural modification of a disk. This study proposes 3 types of improved optical disks, which are robust to the disk fracture due to the high spinning speed of a disk. The first type is a disk reinforced by wire rings, the second type is a disk added by texture fibers, and the third type is a rubber-coated disk.

• 한국추진공학회지
• /
• 제13권4호
• /
• pp.55-62
• /
• 2009

본 연구에서는 액체연료와 고체연료를 추진제로 사용하는 공기흡입식 추진기관의 세라믹 돔포트 커버의 파괴거동을 수행하였다. 파괴 특성은 충격파관을 이용하여 세라믹을 이용한 돔포트 커버 상사모델을 통하여 파괴시험 및 분석되었다. 파괴 거동은 압력센서를 통하여 파괴 압력을 측정하고 초고속 카메라를 이용하여 비산현상을 관찰하였다. 본 연구로부터 얻어진 결과는 공기흡입식 추진기관에서 돔포트커버 설계의 기초 자료로 이용될 수 있을 것이다.

• 대한기계학회논문집A
• /
• 제33권11호
• /
• pp.1274-1278
• /
• 2009

Fracture characteristics for plate and dome shapes of glass filled ceramics using shock tube were carried out. Glass filled ceramics have been considered as a promising candidate material for the dome port cover of air breathing engine. This part of the air breathing engine has an important role as separated membrane between combustion and external air, and needs the frangible characteristics that the particles of fractured glass filled ceramics should not affect the internal components of combustion. The objectives of this study are to evaluate the fracture pressures for various thicknesses and diameters of shock impact area. Also fracture phenomena of separated membrane using a shock tube compare with analytical method. The experimental apparatus consists of a driver, a driven section and a dump tank. The used material is glass filled ceramic made from Corning company. Specimens have the thickness of 3, 4.5 and 6mm. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
• /
• pp.171-177
• /
• 1995

Fracture mechanics does work for concrete, provided that one uses a proper, nonlinear form of fracture mechanics in which a finite nonlinear zone at fracture front is being considered. The fracture process zone is a region ahead of a traction-free crack, and the development of model of fracture process zone is most important to describe fracture phenomena in concrete. This paper is about fracture behavior of concrete cylinder under lateral pressure. Concrete cylinders were made of high strength normal connote, steel fiber reinforced concrete and steel fiber reinforced polymer-impregnated concrete and concrete and the fracture behavior such as cracking propagation and ultimate load are observed. The fracture process zone is modelled by a Dugdale-Barenblatt type model with linear tension-softening curve and are implemented to the boundary element technique for the fracture analyses of the cylinders. The experimental results are compared with analysis results and tension-softening curves for the steel fiber reinforced concrete and steel fiber reinforced polymer-impregnated concrete are obtained by back analyses.

• 대한기계학회논문집
• /
• 제5권2호
• /
• pp.110-121
• /
• 1981

In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1995년도 봄 학술발표회 논문집
• /
• pp.35-41
• /
• 1995

Fracture Mechanics does work for concrete, provided that a finite nonlinear zone at fracture front is being considered. The development of model for fracture process zone is most important to describe fracture phenomena in concrete. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important rules. The toughness due to bridging is dominant compared to toughness induced by microcracking, so that the bridging is dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrack with stresses transmitted by aggregates in concrete, is model led by a Dugdale-Barenblatt type model with linear tension-softening curve. Two finite element techniques are shown for the model of fracture process zone in concrete.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 1994년도 추계 학술발표 강연 및 논문 개요집
• /
• pp.6-6
• /
• 1994

• 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.

• 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.