알루미늄합금(Al 2024-T3)의 疲勞 派壞에 미치는 Shear lip의 影響

梁光永,尹聖雲 조선대학교 동력자원연구소 1992 動力資源硏究所誌 Vol.14 No.2

After marking fatique in loading constant cycling load in order to analyze the fatique fracture behavior of High Strength Aluminum Alloy Material (AL2024-T3), the main conclusions obtained are as follows : 1. The ratio K_op/K_nax between stress intensity fator and crack opening point depends on stress ratio R according to the measuring position, but, in case of using the load of crack opening point measure in crack mouse, it is shown that the effect of stress ratio R could be ignorent. 2. It is shown that the effect of stress ratio R on fatique crack propagation behavior is high at stress intensity factor range ΔK_lh on THRESHOLD section. 3. It is possible that fatique crack behavior along the dimensions of shear lip could accurately be analyze by controlling efftive stress intensity range ΔK_eff among efftive stress intensity range ΔK_eff, stress intensity factor K_max and stress intensity factor range ΔK.

R-Curve에 의한 SUS 410 鋼의 波壤靭成 評價

양광영,이상호 조선대학교 생산기술연구소 1988 生産技術硏究 Vol.10 No.1

The Irwin's R-Curve Method shows the function of stress intensity factor K_(RC) anti Crack extension △α. The R-Curve was plotted with contains both stable crack growth and unstable crack growth, and it is applied only when plastic behavior happen around crack tip. It is known that the R-Curve is not influenced byload control, specimen shape and initial crack length etc, but by specionen thickness and temperature. In this paper, we intend to classify the plates of SUS 410 steel as welding material and non welding material, find out fracture Toughness with the R-Curve method define the characteristics of each part of a welding specimen and investigate the influence of initial crack length. The main conclusions are as follows. (1) In non-welding material and welding material, the values of K_(RC) in welding metal part. H.A.Z part and Base metal part were 160~170, 175~200. 180~200㎏/㎜◁수식삽입▷ (원문을 참조하세요) (2) R-Curve and critical stress intensity factor K_(RC) are not influenced by the change of initial crack length with a constant thickness. (3) The curve of compliance with EB2V₁/P and α/w shows a steep positive slope.

충격하중의 함수 근사식을 이용한 평판의 충격응력해석

양광영,이상호 조선대학교 동력자원연구소 1992 動力資源硏究所誌 Vol.14 No.2

In the study, it was analized impact stresses to generate at the impact loading point of the fragile material, glass plate In the analysis of impulsive response of plates, the famous Lagrange's theory of the classical plate theory and Reissner's theory including the influence of shear deformation and Mindlin's theory including the influence of rotary inertia and shear deformation are generally used. But it is difficult to obtain good accurary in case of the application of the theoretical analysis on thick plates or local deformations by concentrated load, impact load, etc. Specifically, the impulsive stress directly underneath the concentrated impact point cannot be analyzed because the solution fails to convege. In the paper, therfore, an attempt is made to analyze the implusive stresses directly underneath the concentrated impact point of for a supported square glass plate by using the three dimensional dynamic theory of elasticity and the potential theory of displacement on the suposition that the impact load acted on the central part of it. Especially, it was suggested for the new method to approximate impact load to the analyzable function to be able analyze implusive stresses underneath over all impact range to determine the range of impact load factor.

자유단 층간분리를 갖는 복합재 적층판의 최종 파괴강도

양광영,윤성운,김재열,김인권 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.2

This paper presents experimental and analytical studies of ultimate strength of [30_2/-30_2/90]_s carbon/epoxy laminates with free-edge delamination under uniaxial tension. We performed tensile test for laminates with Telflon inserted on interfaces to simulate initial free-edge delamination. The experiment reveals that extensional stiffness of the laminate decreases by the initiation of the delamination, and that strength of the laminate without delamination is smaller than that of the laminated with delamination. Generalized quasi-three dimentional finite element analysis, which employs energy release rate and maximum stress criteria, predicts the ultimate strength of the laminates with sufficient accuracy.

알루미늄합금(7075-T6)의 疲勞龜裂進展과 龜裂開口擧動에 關한 硏究

양광영,박삼균 조선대학교 동력자원연구소 1992 動力資源硏究所誌 Vol.14 No.1

After considering the influence of crack opening ratio reaching to fatigue crack propagation behavior in an Aluminum Alloy, the fatigue test is performed by the stress ratio and the variable of openinig measuring position. The main conclusions obtained are as follows: 1. In fatigue crack propagation, da/dN equal as the stress ratio in range of ΔK is increasing, the da/dN is higher, In case of relating to the ΔK_eff of crack opening ratio, the same value is showed regardless of stress ratio in all domain. 2. In case of using the effective stress intensity factor range, ΔK_eff considering the crack opening ratio to crack propagation estimation, it is reasonable that the measuring position of crack opening point ignoring various factor is measured at a distant from crack tip. 3. The variable ratio of effective stress intensity factor can be showem by the only R fo stress ratio in AI alloy (7075-T6) material.

인장하중을 받는 의사등방성 복합재 적층판의 피로손상

양광영,임경택,이동하,김택현,김인권 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.1

The purpose of this work is to investigate fatigue damage of quasi-isotropic laminates under tensile loading in different directions. Low cycle fatigue tests of [O/-60/+60]s laminates and [+30/-30/90]s laminates were carried out. Materials systems used are AS4/Epoxy and AS4/PEEK. The fatigue damage of [+30/-30/90]s is very different from that of [O/-60/+60]s. The position of delamination generated at AS4/Epoxy and AS4/PEEK laminates were differentiated by the matrix difference that is, we suppose, the value of both G (critical energy release rate of mode-I) and G (critical energy release rate of mode-Ⅲ) difference. The experimental results are compared with the result obtained from the method of determining strain energy release rate components proposed by the authors.

金屬材 및 非金屬材 齒車의 이뿌리부에서의 굽힘 疲勞强度에 關한 硏究

丁太權,梁光永,梁仁榮,金澤鉉,羅基大,鄭洛奎,李相鎬 조선대학교 동력자원연구소 1990 動力資源硏究所誌 Vol.12 No.1

This stydy carried out to determine the bending fatigue strength of spur geaftooth root part of SCM4 according to the four kind heat treatment, and it was considered the influence of residual stress and surface hardness from the heat treaments. The main conclusions obtained are as fallows 1. The residual stress to initiate in the heat treatment redistributed for the cyclid constant load and over load, and it was increased the fatigue limit. The initiation of slip band and crack was clearly confirmed accofding to the change of residual stress. 2. The case to load the over load during the constant load amplitude was decreased the fatigue limit of 30~60% about the case to load the constant load amplitude. 3. The analytical result and experimental result was clearly approxomate, and heat treatment effect was becomed the order of normalzing, annealing and carburizing, normalizing and carburizing. 4. Because of the effect of surface hardness to rise for the heat treatment, the softening behavior was the more humiliating than the hardening behavior in the case of normalizing and carburizing, annealing and carburizing. The case of normalizing was becomed the fracture to be hardenig of the innertia of tooth root part.

비파괴 초음파 측정법을 이용한 탄소/탄소 브레이크 디스크의 특성평가

허욱,양광영,양인여 朝鮮大學校 機械技術硏究所 2006 機械技術硏究 Vol.9 No.1

탄소/탄소 브레이크 디스크는 탄소 메트릭스에 함침된 탄소섬유로 구성된 기존재료들에 비해 분명한 이점이 있다. 탄소/탄소 브레이크는 우주항공과 자동차 응용분야에 사용되어왔다. 게다가, 탄소/탄소 복합재료는 저밀도, 고온전도도, 훌륭한 기계적 성질 등을 가지고 있다. 이러한 성질들은 항공기와 자동차 브레이크 디스크에 이상적인 재료이다. 하지만,다단 계의 공정에 의해 제작된 탄소/탄소 복합재료는 미세기공,불균질성 등이 존재한다. 이러한 것들을 검사하기위해 비파괴 검사가 필수적이라 생각한다. 많은 비파괴 평가 방법 중 몇가지 초음파 평가법을 수행하였다. 물과 같은 스며드는 접촉매질 때문에, 재료의 성질과 부품 의 균질성을 평가하기위해 비접촉 비파괴 평가 방법을 시도하였다. 이번 연구에서, 탄소/탄소 복합재료는 자동 인식 스캐너 사용하여 비접촉과 접촉 초음파 측정방법으로 평가하였다. 특히, 탄소/탄소 복합재료에 대한 초음파 이미지와 속도는 비첩촉 및 접촉식 초음파 측 정방법이 일치됨을 알 수 있었다. 초음파 펄스의 amplitude와 비행시간을 기초로한 저주파수 투과법 스캔은 재료의 특성 중 불균질성을 도식하는데 사용되었다. 드라이커플링 초음파 측정법, 수침속에서의 투과법, 피크지연측정법을 통해 획득된 결과를 비교하였다. 결론적으로, 피크지연측정법을 사용한 결과는 펄스 오버랩방법의 초음파 속도와 잘 일치하였다. 초음파 측정법은 결함발견 뿐만아니라 재료의 특성평가에도 유용하다. Carbon/carbonft(C/C) brake disks have obvious advantages in comparison with conventional materials, which are consisting of carbon fibers embedded in a carbon matrix. The C/C brake disks have become to be utilized as parts of aerospace and automotive application. In addition, C/C composites feature low density, high thermal conductivity, excellent mechanical properties and so on. These characteristics make ideal materials for aircraft and automotive brake disks. However, We consider that C/c composites material may be micro void, inhomogeneity, and so on because of C/C composites included many manufacturing process. For evaluating these. We think that nondestructive evaluation(NDT) is necessary under manufacturing processes. We performed several ultrasonic testings of many NDT. Because of permeation of coupling medium such as water, we try to perform contact-less nondestructive evaluation to assess material properties and part homogeneity. In this work, a C/C composite material was evaluated both non-contact and contact ultrasonic methods using automated acquisition scanner. Especially, ultrasonic images and velocities for C/C composite brake disk was measured and found to be consistent to some degree with the non-contact and contact ultrasonic measurement methods. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the inhomogeneity of material properties. Measured results were compared with those obtained by the system with using dry-coupling ultrasonics measurement method, through-transmission method in immersion and peak-delay measurement method. Finally. results using a proposed peak-delay measurement method well corresponded to ultrasonic velocities of the pulse overlap method. Ultrasonic testing is very useful in detecting the defect as well as evaluating characteristic of materials.

ESPI를 이용한 충격손상을 받은 복합재료 내부결함의 정량평가

김경석,양광영,장호섭,지창준,윤홍석 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

Electronic Speckle Pattern Interferometry for quantitative evaluation of a impact defect inside of composite material plate are described. The impact on composite material makes inside delamination which is difficult to detect visual inspection and ultrasonic testing due to non-homeogenous structure. This paper proposes the quantitative evaluation technique of defects under real impact. Artificial defects are designed inside of composite plate for development of inspection technique and real defects under impact are inspected and compared with results of visual inspection.

경사충돌이 탄소섬유강화 적층쉘의 특성에 미치는 영향

김영남,조영재,양광영 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

최근 탄소섬유 강화 플라스틱(이하CFRP)는 금속재료에 비해 비강도 및 비강성이 우수하여 우주항공분야에서 널리 사용되고 있다. 본 연구에서는 복합재 적층웰의 곡률과 적층방향에 따른 관통특성을 고찰하고자 한다. 또한, 경사충돌을 적용하여 복합재 적층웰의 관통특성을 연구하였다. 시험편의 적층구성은 [0₃/90₃)_(s), [90₃/0₃]_(s) 와 [0₂/90₃/0]_(s), [90₂/0₃/90]_(s) 2계면구조와 4계면 구조로 적층하였으며 다양한 곡률반경 (R= 100, 150, 200mm 와 ∞)을 적용하였다. 실험 방법으로는 강구를 시험편에 횡방향으로 관통시켰으며, 두 개의 ballistics-screen에서 강구가 통과한 시간의 전 · 후를 측정한 후 속도를 계산하였다. 그 결과 임계관통 에너지는 계면의 수가 적고 충격면의 경사각도가 커질수록 증가하였다. 또한. [0₃/90₃]_(s) 와 [0₂/90₃/0]_(s) 시험편이 [90₃/0₃]_(s) 와 [90₂/0₃/90]_(s) 시험편보다 임계관통에너지가 더 높게 나왔다. Currently, carbon-fiber reinforced plastics(CFRP) are widely used in both space and civil aircraft due to their superior stiffness and strength to weight ratios compared to conventional metallic materials. This paper is to study the effects of curvature and stacking sequence on the penetration characteristics of composite laminated shell. And were performed to investigate the penetration characteristics of composite laminated shells by the oblique impact. They are stacked to [0₃/90₃]_(s), [90₃/0₃]_(s) and [0₂/90₃/0)_(s), [90₂/0₂/90)S their interlaminar number two and fore. They are manufactured to varied curvature radius (R= 100.150,200mm and ∞). When the specimen is subjected to transverse impact by steel ball. the velocity of the steel ball was measured both before and after impact by determining the time for it to pass two ballistics-screen sensor located a known distance apart. In general, the critical penetration energy interface decrease and slope angle on the impact surface increased. [0₃/90₃]s and [0₂/90₃]_(s) specimens higher than [90₃/0₃]_(s) and [90₂/0₃/90]_(s) specimens.