회귀분석법에 의한 복합재료 적층판의 인장 파손특성 분석

이명건(Myoung Keon Lee),오광근(Kwang Keun Oh),김재훈(Jae Hoon Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

Failure theory that is widely used in composit structure is first ply failure. It regards failure of a ply as laminate failure. This theory predicts correct failure by using strength characteristic of lamina. but, It is leading to conservative results because laminate can endure force when failing a lamina. Recently, advanced airline uses laminate failure theory that estimate strain of composit structure for airplanes. It is important to get value of mechanical fracture characteristic for the entire range of applicable layups (percentage of 0°, +/-45° and 90° plies) before appling laminate failure theory. This paper contains the results of tensile failure characteristics developed by using regression analysis method. The regression analysis is performed with the response variable being the laminate ultimate fracture strength and the regressor variables being two ply orientation(0° and ±45°) variables. Composit material is a 350°F(177°C) cured, carbon fiber reinforced plastic(CFRP) composite material system that incorporates an epoxy resin. The specimens used in this paper is designed with plies oriented only in four standard orientation of 0°, +45°, -45° and 90°. All specimens contain a minimum of 10% plies in each of the 0°, +45°, -45° and 90° orientations, thus ensuring that all test experienced a fiber failure mode without significant non-linearities in the load-strain response. A total of 149 tension tests were conducted on specimens from 14 distinct laminates and 3 material batches. ASTM-D-3039 was used for test method

복합 정수장 구조물의 유한요소해석을 통한 내진성능 평가

조한민,허종완 한국복합신소재구조학회 2018 복합신소재구조학회 학술발표회 Vol.2018 No.04

In this study, finite element (FE) analysis was performed to evaluate the seismic performance of the water treatment plant, which is a major state of the art water treatment plant, to predict tensile cracks and compressive failure. The FE model simulation for two facilities of the water purification plant was made considering the initial conditions, boundary conditions and water effect. For the nonlinear dynamic analysis, seismic analysis was performed using ground acceleration. Tensile cracks and compressive failure are analyzed and the effects on the structures are analyzed. As a result of the analysis, tensile cracks can be predicted to occur in the main structure.

음향방출을 이용한 일방향 탄소섬유강화 플라스틱의 손상평가에 관한 연구

이장규,박성완,김봉각,우창기 한국공작기계학회 2005 한국생산제조학회지 Vol.14 No.1

This study is to investigate a damage estimation of single edge notched tensile specimens as a function of acoustic emission(AE) according to the uni-directionally oriented carbon fiber/epoxy composites, CFRP. In fiber reinforced composite materials, AE signals due to several types of failure mechanisms are typically observed. These are due to fiber breakage, fiber pull-out, matrix cracking, delamination, and splitting or fiber bundle breaking. And these are usually discriminated on the basis of amplitude distribution, event counts, and energy related parameters. In this case, AE signals were analyzed and classified 3 regions by AE event counts, energy and amplitude for corresponding applied load. Bath-tub curve shows 3 distinct periods during the lifetime of a single-edge-notch(SEN) specimen. The characterization of AE generated from CFRP during SEN tensile test is becoming an useful tool for the prediction of damage failure or/and failure mode analysis.

Flexural and tensile properties of a glass fiber-reinforced ultra-high-strength concrete: an experimental, micromechanical and numerical study

M. Jason Roth,Thomas R. Slawson,Omar G. Flores 사단법인 한국계산역학회 2010 Computers and Concrete, An International Journal Vol.7 No.2

The focus of this research effort was characterization of the flexural and tensile properties of a specific ultra-high-strength, fiber-reinforced concrete material. The material exhibited a mean unconfined compressive strength of approximately 140 MPa and was reinforced with short, randomly distributed alkali resistant glass fibers. As a part of the study, coupled experimental, analytical and numerical investigations were performed. Flexural and direct tension tests were first conducted to experimentally characterize material behavior. Following experimentation, a micromechanically-based analytical model was utilized to calculate the material’s tensile failure response, which was compared to the experimental results. Lastly, to investigate the relationship between the tensile failure and flexural response, a numerical analysis of the flexural experiments was performed utilizing the experimentally developed tensile failure function. Results of the experimental, analytical and numerical investigations are presented herein.

Comparison of Nail Tensile Force by Feed Back Analysis rind Measurements

Jeon, Seong-Kon 한국지반공학회 2002 지반 : 한국지반공학회지 Vol.18 No.3

쏘일네일링 공법은 굴착이나 사면안정을 위해 가시설이나 영구용으로 국내에서 널리 이용되고 있다. 특히, 도심지 근접 굴착시 쏘일네일링 공법 적용시 고려사항은 벽체변위와 네일의 인장등 이다. 본 연구는 국내 여러 암반층을 포함하는 다층토 지반의 11개 쏘일네일링 현장에서 굴착단계별 네일의 인장력 거동을 계측자료와 역해석을 통하여 고찰하였다. 역해석 결과 네일의 최대인장력은 계측값의 50% 정도로 낮게 나타났고, 벽면에서 가상 파괴활동면까지의 거리를 주동영역거리라 할때 CLOUTERRE 보고서와 Cartier & Gigan이 각각 제안한 최종굴착 깊이(H$_{f}$ )의 0.3$H_f$,0.5$H_f$,에 비해 계측결과는 크게 나타났으며, 역해석은 이들이 제안한 범위내에 포함되었다. Soil nailing type of retaining structures has been widely used in Korea far the purpose of the temporary and permanent support in excavations and slope stability. The important factors in application of soil nailing systems in urban excavation site nearby the existing structures are the displacement of the wall and tensile farce of the nails, etc. In this paper, the fled back analyses are carried out at 11 excavation sites to investigate the behavior of tensile farce of nails at stepwise excavation in the multi-layered strata including various rock layers. The results of the fled back analysis are less than about 50% of the measured ones. The distance of active zone by measurements are shown almost larger than that of fled back analysis when the distance of active Bone is defined from the surface of wall to the potential failure surface. And the results of fled back analysis are within the range proposed by the project CLOUTERRE and Cartier & Gigan (1983) which were 0.3$H_f$, and 0.5$H_f$, of the final excavation depth ($H_f$,) respectively, but the values of the measurement were larger than these values.

첨단복합재료 적층판의 인장 파손특성 시험적 평가

이명건(Myoung Keon Lee),이정원(Jeong Won Lee),윤동현(Dong Hyun Yoon),김재훈(Jae Hoon Kim) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.10

최근 선진항공사에서는 항공기 복합재 구조의 변형률을 평가할 때 적층판 파손이론을 사용한다. 적층판 파손이론은 복합재 구조평가에 적층판의 파손변형률을 사용한다. 본 논문은 적층판 인장파손특성의 시험적 평가 절차를 보여준다. 시험적 평가는 회귀분석법(regression analysis method)을 사용하였다. 회귀분석은 적층판의 파손변형률을 응답변수로 하고 적층판 내 0°, ±45°층의 비율을 회귀변수로 하는 방법이다. 본 논문에 사용된 복합재료는 177°C(350°F)에서 경화되는 Carbon/Epoxy UD Tape 프리프레그이다. 시편은 0°, +45°, -45° 및 90°층으로 적층된 14 종류의 노치없는 적층판으로 총149개 시편으로 구성하였다. 시험방법은 ASTM-D-3039 규정을 사용하였다. In recent years, major airplane manufacturers have been using the laminate failure theory to estimate the strain of composite structures for airplanes. The laminate failure theory uses the failure strain of the laminate to analyze composite structures. This paper describes a procedure for the experimental assessment of laminate tensile failure characteristics. Regression analysis was used as the experimental assessment method. The regression analysis was performed with the response variable being the laminate failure strain and with the regressor variables being two-ply orientation (0° and ±45°) variables. The composite material in this study is a carbon/epoxy unidirectional (UD) tape that was cured as a pre-preg at 177°C(350°F). A total of 149 tension tests were conducted on specimens from 14 distinct laminates that were laid up at standard angle layers (0°, 45°, -45°, and 90°). The ASTM-D-3039 standard was used as the test method.

Seismic Stability of 3D Tunnel Face considering Tensile Strength Cut-Off

Chuan-Tan Hou,Xiao-li Yang 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.7

Classical Mohr-Coulomb (M-C) criteria is typically applied to assess the soil strength in the analysis of tunnel face stability, in which the tensile strength is expressed as the extension of the compressive portion. However, the actual tensile strength of soils is quite unreliable. Therefore,the classical Mohr-Coulomb criterion is modified by involving the concept of tension cut-off, in which a nonlinear portion is introduced to express the tensile strength. Based on this, this paper presents a kinematic approach of limit analysis to estimate the face stability of tunnels with tensile strength cut-off subject to seismic excitations. An effective 3D rotational failure mechanism with consideration of tension cut-off is established. Based on the 3D failure mechanism, an explicit expression of the critical face pressure can be deduced by equating the external work rate and internal energy dissipated rate. The most critical face pressure is sought through an optimization program. A comparison between the existing researches and this work is made to verify the proposed approach. A parameter analysis and a series of design charts are presented. The results show that considering the presence of soil cohesion has a beneficial effect on the stability of the tunnel face and the presence of tension cut-off results in a more conservative outcome. The influence of tension cut-off increases with the increase of soil cohesion and is more noticeable at a small tensile strength cut-off coefficient. In some cases, the tunnel face stability may be mis-evaluated without considering tension cut-off, threatening engineering safety. In addition, the presence of seismic force will reduce the impact of tension cut-off on the analysis of tunnel face stability. This work provides a useful method to assess the face stability of 3D seismic tunnels under the impact of tensile strength cut-off, and the findings can serve as a reference tool in the seismic design of tunnel engineering.

Modelling of Mechanical Behavior of Porous Sintered Low Alloy Steels

Khorsand H.,Alizadeh M. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

The mechanical properties of sintered low alloy steels were analysed using Finite Element Methods (FEM), in which the powder is modelled as an elastic-plastic continuum material. A quantitative analysis of microstructure was correlated with tensile and fatigue behavior to understand the influence of pore size, shape, and distribution on mechanical behavior. Tensile strength, Young’s modulus, strain-to-failure, and fatigue strength all increased with a decrease in porosity. The decrease in Young’s modulus with increasing porosity was predicted by analytical modeling. Two-dimensional microstructure-based finite element modeling showed that the enhanced tensile and fatigue behavior of the denser steels could be attributed to smaller, more homogeneous, and more spherical porosity which resulted in more homogeneous deformation and decreased strain localization in the material. The relationship between relative density of P/M steels and mechanical behavior is also obtained from FEA and compared with the experimenta data. Good agreement between the experimental and FEA results is observed, which demonstrates that FEA can capture the major features of the P/M steels behaviour during loading. The implications of pore size, morphology, and distribution on the mechanical behavior and fracture of P/M steels are discussed. It is therefore demonstrated that FEA can predict the possible mechanism of failure during loading.

철도차량 차축 재료의 파괴특성 적외선열화상 모니터링

김정국(Jeongguk Kim) 한국비파괴검사학회 2010 한국비파괴검사학회지 Vol.30 No.2

차축과 차륜으로 구성되는 철도차량 윤축은 차량의 운행과 관련하여 안전과 직결되는 중요한 철도 부품의 하나이다. 본 연구에서는 철도차량의 차축 재료의 인장파괴거동에 대한 특성을 분석하였다. 20년 이상 운행된 전기기관차 및 디젤전기기관차의 차축 시편에 대하여 연장시험을 수행하였다. 인장시험 동안 시편의 파괴특성을 모니터링하기 위해 고속 적외선카메라가 사용되었는데, 인장시험 동안의 시편 표변의 온도 변화를 모니터링하여 온도 분포로부터 인장파괴거동을 설명하고 파괴모드를 규명하고자 하였다. The wheelset, an assembly of wheel and axle, is one of important parts in railway bogie, directly related with the running safety of railway rolling stock. In this investigation, the tensile failure behavior of railway axle materials was investigated. The tensile coupons were prepared from the actual rolling stock parts, which were operated over 20 years. The tensile testing was performed according to the KS guideline. During tensile testing, an infrared camera was employed to monitor temperature changes in specimen as well as demonstrate temperature contour in terms of infrared thermographic images. The thermographic images of tensile specimens showed comparable results with mechanical behavior of tensile materials. In this paper, the failure mode and behavior of railway axle materials were provided with the aid of infrared thermography technique.

Numerical study on tensioned membrane structures under impact load

Yingying Zhang,Yushuai Zhao,Mingyue Zhang,Yi Zhou,Qilin Zhang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.2

This paper presents the numerical simulation of membrane structure under impact load. Firstly, the numericalsimulation model is validated by comparing with the test in Hao’s research. Then, the effects of the shape of the projectile, themembrane prestress and the initial impact speed, are investigated for studying the dynamic response and failure mechanism, basedon the membrane displacement, projectile acceleration and kinetic energy. Finally, the results show that the initial speed and thepunch shape are related with the loss of kinetic energy of projectiles. Meanwhile, the membrane prestress is an important factor thataffects the energy dissipation capacity and the impact resistance of membrane structures.