• Title/Summary/Keyword: Failure Analysis and Modeling

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Micromechanical failure analysis of composite materials subjected to biaxial and off-axis loading

  • Ahmadi, Isa
    • Structural Engineering and Mechanics
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    • v.62 no.1
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    • pp.43-54
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    • 2017
  • In this study, the failure behavior of composite material in the biaxial and off-axis loading is studied based on a computational micromechanical model. The model is developed so that the combination of mechanical and thermal loading conditions can be considered in the analysis. The modified generalized plane strain assumption of the theory of elasticity is used for formulation of the micromechanical modeling of the problem. A truly meshless method is employed to solve the governing equation and predict the distribution of micro-stresses in the selected RVE of composite. The fiber matrix interface is assumed to be perfect until the interface failure occurs. The biaxial and off-axis loading of the SiC/Ti and Kevlar/Epoxy composite is studied. The failure envelopes of SiC/Ti and Kevlar/Epoxy composite in off-axis loading, biaxial transverse-transverse and axial-transverse loading are predicted based on the micromechanical approach. Various failure criteria are considered for fiber, matrix and fiber-matrix interface. Comparison of results with the available results in the litreture shows excellent agreement with experimental studies.

Evaluation of dam strength by finite element analysis

  • Papaleontiou, Chryssis G.;Tassoulas, John L.
    • Earthquakes and Structures
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    • v.3 no.3_4
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    • pp.457-471
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    • 2012
  • Current code procedures for stress and stability analysis of new and existing concrete-gravity dams are primarily based on conventional methods of analysis. Such methods can be applied in a straightforward manner but there has been evidence that they may be inaccurate or, possibly, not conservative. This paper presents finite element modeling and analysis procedures and makes recommendations for local failure criteria at the dam-rock interface aimed at predicting more accurately the behavior of dams under hydraulic and anchoring loads.

The Failure Analysis of Paralleled Solar Array Regulator for Satellite Power System in Low Earth Orbit

  • Jang, Sung-Soo;Kim, Sung-Hoon;Lee, Sang-Ryool;Choi, Jae-Ho
    • Journal of Astronomy and Space Sciences
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    • v.28 no.2
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    • pp.133-141
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    • 2011
  • A satellite power system should generate and supply sufficient electric power to perform the satellite mission successfully during the satellite mission period, and it should be developed to be strong to the failure caused by the severe space environment. A satellite power system must have a high reliability with respect to failure. Since it cannot be repaired after launching, different from a ground system, the failures that may happen in space as well as the effect of the failures on the system should be considered in advance. However, it is difficult to use all the hardware to test the performance of the satellite power system to be developed in order to consider the failure mechanism of the electrical power system. Therefore, it is necessary to develop an accurate model for the main components of a power system and, based on that, to develop an accurate model for the entire power system. Through the power system modeling, the overall effect of failure on the main components of the power system can be considered and the protective design can be devised against the failure. In this study, to analyze the failure mode of the power system and the effects of the failure on the power system, we carried out modeling of the main power system components including the solar array regulator, and constituted the entire power system based on the modeling. Additionally, we investigated the effects of representative failures in the solar array regulator on the power system using the power system model.

Micro-mechanical Failure Prediction and Verification for Fiber Reinforced Composite Materials by Multi-scale Modeling Method (멀티스케일 모델링 기법을 이용한 섬유강화 복합재료의 미시역학적 파손예측 및 검증)

  • Kim, Myung-Jun;Park, Sung-Ho;Park, Jung-Sun;Lee, Woo-Il;Kim, Min-Sung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.1
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    • pp.17-24
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    • 2013
  • In this paper, a micro-mechanical failure prediction program is developed based on SIFT (Strain Invariant Failure Theory) by using the multi-scale modeling method for fiber-reinforced composite materials. And the failure analysis are performed for open-hole composite laminate specimen in order to verify the developed program. First of all, the critical strain invariants are obtained through the tensile tests for three types of specimens. Also, the matrices of strain amplification factors are determined through the finite element analysis for micro-mechanical model, RVE (Representative Volume Element). Finally, the microscopic failure analysis is performed for the open-hole composite laminate specimen model by applying a failure load obtained from tensile test, and the predicted failure indices are evaluated for verification of the developed program.

Development of Modeling Technique and Material Prediction Method Considering Structural Characteristics of Woven Composites (직조 복합재료의 구조적 특성을 고려한 모델링 기법 및 물성 예측 기법 개발)

  • Choi, Kyung-Hee;Hwang, Yeon-Taek;Kim, Hee-June;Kim, Hak-Sung
    • Composites Research
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    • v.32 no.5
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    • pp.206-210
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    • 2019
  • As the use of composite materials of woven structure has expanded to various fields such as automobile and aviation industry, there has been a need for reliability problems and prediction of mechanical properties of woven composites. In this study, finite element analysis for predicting the mechanical properties of composite materials with different weaving structures was conducted to verify similarity with experimental static properties and an effective modeling method was developed. To reflect the characteristics of the weave structure, the meso-scale representative volume element (RVE) was used in modeling. Three-dimensional modeling was carried out by separating the yarn and the pure matrix. Hashin's failure criterion was used to determine whether the element was failed, and the simulation model used a progressive failure model which was suitable for the composite material. Finally, the accordance of the modeling and simulation technique was verified by successfully predicting the mechanical properties of the composite material according to the weave structure.

An Improved SysML-Based Failure Model for Safety Verification By Simulation (시뮬레이션을 통해 안전성 검증을 위한 개선된 SysML 기반 고장 모델)

  • Kim, Chang-Won;Lee, Jae-Chon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.10
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    • pp.410-417
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    • 2018
  • System design errors are more likely to occur in modern systems because of their steadily increasing size and complexity. Failures due to system design errors can cause safety-related accidents in the system, resulting in extensive damage to people and property. Therefore, international standards organizations, such as the U.S. Department of Defense and the International Electrotechnical Commission, have established international safety standards to ensure system safety, and recommend that system design and safety activities should be integrated. Recently, the safety of a system has been verified by modeling through a model-based system design. On the other hand, system design and safety activities have not been integrated because the model for system design and the failure model for safety analysis and verification were developed using different modeling language platforms. Furthermore, studies using UML or SysML-based failure models for deriving safety requirements have shown that these models have limited applicability to safety analysis and verification. To solve this problem, it is essential to extend the existing methods for failure model implementation. First, an improved SysML-based failure model capable of integrating system design and safety verification activities should be produced. Next, this model should help verify whether the safety requirements derived via the failure model are reflected properly in the system design. Therefore, this paper presents the concept and method of developing a SysML-based failure model for an automotive system. In addition, the failure model was simulated to verify the safety of the automotive system. The results show that the improved SysML-based failure model can support the integration of system design and safety verification activities.

Modeling of unreinforced brick walls under in-plane shear & compression loading

  • Kalali, Arsalan;Kabir, Mohammad Zaman
    • Structural Engineering and Mechanics
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    • v.36 no.3
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    • pp.247-278
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    • 2010
  • The study of the seismic vulnerability of masonry buildings requires structural properties of walls such as stiffness, ultimate load capacity, etc. In this article, a method is suggested for modeling the masonry walls under in-plane loading. At the outset, a set of analytical equations was established for determining the elastic properties of an equivalent homogeneous material of masonry. The results for homogenized unreinforced brick walls through detailed modeling were compared in different manners such as solid and perforated walls, in-plane and out-of-plane loading, etc, and it was found that this method provides suitable accuracy in estimation of the wall linear properties. Furthermore, comparison of the results of proposed modeling with experimental out coming indicated that this model considers the non linear properties of the wall such as failure pattern, performance curve and ultimate strength, and would be appropriate to establish a parametric study on those prone factors. The proposed model is complicated; therefore, efforts need to be made in order to overcome the convergency problems which will be included in this study. The nonlinear model is basically semi-macro but through a series of actions, it can be simplified to a macro model.

Industry-University Cooperation Research Activities Through Idea Factory (Optimized Modeling in Butterfly Valve Disk by Creative Selection in Material) (Idea Factory를 통한 산학 협력 연구 활동 (소재의 적절한 선정을 통한 버터플라이 밸브 디스크의 최적화 모델링))

  • Kim, Yun-Hae;Park, Chang-Wook;Bae, Chang-Won;Kim, Han-Sol;Jung, Min-Kyo
    • Journal of Engineering Education Research
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    • v.19 no.6
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    • pp.44-48
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    • 2016
  • This research is one of the Industry-University cooperation in idea factory of Korea Maritime and Ocean University. Idea factory of Korea Maritime and Ocean University is trying to train creative talented students and discover ingenious ideas. The contents are consisted of the possibility for the replacement of a metal valve disk to composite valve disk in butterfly valve based on the diversification. Purpose in this study is to predict failure field by each fly by appling Tsai-Wu Failure Index.

Numerical simulation and countermeasure on upheaval generation in the road caused by sliding of a slope (사면활동으로 야기된 도로부 융기발생에 대한 수치해석 및 고찰)

  • Kim, Seung-Hee;Rhee, Jong-Hyun;Koo, Ho-Bon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.833-841
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    • 2008
  • Recently, the upheaval generation in the road which is under service had been reported. Due to the upheaval generation, total 4 lanes were forced to curtail to 3 lanes, and traffic was delayed. In normal situation of cut-slopes in korea, that condition is hard to detect since most cut-slopes contain discontinuous material, that is rock. Common collapses in rock-slopes is wedge failure, plane failure and toppling failure which is all individual mechanism of discontinuous rock mass. In contrast, such upheaval in the road in front of cut-slope can be generated only when circular movement is triggered within the cut-slope. In this sense, rock-slopes barely show any kind of movement in the road locates at the front of them. Numerical analysis is general method in simulation of slope displacement and evaluation of safety. However, numerical analysis programs which are related with rock-slopes are not able to simulate such upheaval movement because that programs are based on discontinuous modeling mechanism. In addition, although numerical analysis programs which are based on FEM/FDM and thus utilize continuous modeling mechanism are able to simulate circular movement and upheaval situation, they have weakness in reflecting discontinuities of rock-slope itself. In this study, detailed in-site investigation and numerical analysis based on in-site condition were performed in order to expect upheaval movement in the road. In this procedure, the FLAC program which uses continuous modeling method was utilized, and new approach reflecting discontinuity developed toward the road with a ubiquitous joint model was tried to derive reliable analysis result.

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An approach for failure analysis of composite bridge deck systems with openings

  • Zhao, Lei;Karbhari, Vistasp M.
    • Structural Engineering and Mechanics
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    • v.20 no.1
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    • pp.123-141
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    • 2005
  • Design details pertaining to the connection between some recently developed fiber reinforced polymer (FRP) composite deck systems and the supporting girders require openings through cells of the deck. This significantly changes the stress distribution in these components. As a result, the conventional assumptions that deck designs are controlled by their stiffness, and not strength, needs a closer examination. This paper proposes an analytical method to investigate the stress states and failure mechanisms using a type of "global-local" modeling perspective, incorporating classical lamination theory and first ply failure criterion with use of appropriate stress concentration factors around the cutouts. The use of a "smeared-stress" approach is presented as a potential means of simplifying certain FRP specific complexities, while still enabling prediction of overall failure.