• Title/Summary/Keyword: Failure Analysis and Modeling

Search Result 429, Processing Time 0.029 seconds

Reliability and Availability Modeling of the MIN (Multistage Interconnection Network) System (신뢰도를 고려한 다단계 스위치 망의 성능 분석)

  • 이강원
    • Korean Management Science Review
    • /
    • v.15 no.1
    • /
    • pp.63-76
    • /
    • 1998
  • Reliability evaluation methodologies of the multipath MIN system are reviewed and critically compared. Some guidelines are proposed to select efficient evaluation method for the system designers to use. Considering the switch failure and repair characteristics of the MIN system, three types of Markov models are proposed for the MIN system availability models. These models can be used for the MIN performance analysis. The performance of the MIN system are supposed to vary according to the failure state of the system.

  • PDF

Finite element modeling of corroded RC beams using cohesive surface bonding approach

  • Al-Osta, Mohammed A.;Al-Sakkaf, Hamdi A.;Sharif, Alfarabi M.;Ahmad, Shamsad;Baluch, Mohammad H.
    • Computers and Concrete
    • /
    • v.22 no.2
    • /
    • pp.167-182
    • /
    • 2018
  • The modeling of loss of bond between reinforcing bars (rebars) and concrete due to corrosion is useful in studying the behavior and prediction of residual load bearing capacity of corroded reinforced concrete (RC) members. In the present work, first the possibility of using different methods to simulate the rebars-concrete bonding, which is used in three-dimensional (3D) finite element (FE) modeling of corroded RC beams, was explored. The cohesive surface interaction method was found to be most suitable for simulating the bond between rebars and concrete. Secondly, using the cohesive surface interaction approach, the 3D FE modeling of the behavior of non-corroded and corroded RC beams was carried out in an ABAQUS environment. Experimental data, reported in literature, were used to validate the models. Then using the developed models, a parametric study was conducted to examine the effects of some parameters, such as degree and location of the corrosion, on the behavior and residual capacity of the corroded beams. The results obtained from the parametric analysis using the developed model showed that corrosion in top compression rebars has very small effect on the flexural behaviors of beams with small flexural reinforcement ratio that is less than the maximum ratio specified in ACI-318-14 (singly RC beam). In addition, the reduction of steel yield strength in tension reinforcement due to corrosion is the main source of reducing the load bearing capacity of corroded RC beams. The most critical corrosion-induced damage is the complete loss of bond between rebars and the concrete as it causes sudden failure and the beam acts as un-reinforced beam.

A Discrete Time Approximation Method using Bayesian Inference of Parameters of Weibull Distribution and Acceleration Parameters with Time-Varying Stresses (시변환 스트레스 조건에서의 와이블 분포의 모수 및 가속 모수에 대한 베이시안 추정을 사용하는 이산 시간 접근 방법)

  • Chung, In-Seung
    • Proceedings of the KSME Conference
    • /
    • 2008.11a
    • /
    • pp.1331-1336
    • /
    • 2008
  • This paper suggests a method using Bayesian inference to estimate the parameters of Weibull distribution and acceleration parameters under the condition that the stresses are time-dependent functions. A Bayesian model based on the discrete time approximation is formulated to infer the parameters of interest from the failure data of the virtual tests and a statistical analysis is considered to decide the most probable mean values of the parameters for reasoning of the failure data.

  • PDF

Numerical modeling and prediction of adhesion failure of adhesively bonded composite T-Joint structure

  • Panda, Subhransu K;Mishra, Pradeep K;Panda, Subrata K
    • Structural Engineering and Mechanics
    • /
    • v.74 no.6
    • /
    • pp.723-735
    • /
    • 2020
  • This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

Investigation of bond-slip modeling methods used in FE analysis of RC members

  • Demir, Serhat;Husem, Metin
    • Structural Engineering and Mechanics
    • /
    • v.56 no.2
    • /
    • pp.275-291
    • /
    • 2015
  • Adherence between reinforcement and the surrounding concrete is usually ignored in finite element analysis (FEA) of reinforced concrete (RC) members. However, load transition between the reinforcement and surrounding concrete effects RC members' behavior a great deal. In this study, the effects of bond-slip on the FEA of RC members are examined. In the analyses, three types of bond-slip modeling methods (perfect bond, contact elements and spring elements) and three types of reinforcement modeling methods (smeared, one dimensional line and three dimensional solid elements) were used. Bond-slip behavior between the reinforcement and surrounding concrete was simulated with cohesive zone materials (CZM) for the first time. The bond-slip relationship was identified experimentally using a beam bending test as suggested by RILEM. The results obtained from FEA were compared with the results of four RC beams that were tested experimentally. Results showed that, in FE analyses, because of the perfect bond occurrence between the reinforcement and surrounding concrete, unrealistic strains occurred in the longitudinal reinforcement. This situation greatly affected the load deflection relationship because the longitudinal reinforcements dominated the failure mode. In addition to the spring elements, the combination of a bonded contact option with CZM also gave closer results to the experimental models. However, modeling of the bond-slip relationship with a contact element was quite difficult and time consuming. Therefore bond-slip modeling is more suitable with spring elements.

Nonlinear finite element modeling of steel-sheathed cold-formed steel shear walls

  • Borzoo, Shahin;Ghaderi, Seyed Rasoul Mir;Mohebi, Saeed;Rahimzadeh, Ali
    • Steel and Composite Structures
    • /
    • v.22 no.1
    • /
    • pp.79-89
    • /
    • 2016
  • Cold formed steel shear panel is one of the main components to bearing lateral load in low and mid-rise cold formed steel structures. This paper uses finite element analysis to evaluate the stiffness, strength and failure mode at cold formed steel shear panels whit steel sheathing and nonlinear connections that are under monotonic loading. Two finite element models based on two experimental model whit different failure modes is constructed and verified. It includes analytical studies that investigate the effects of studs and steel sheathing thickness changes, fasteners spacing at panel edges, one or two sides steel sheathing and height-width ratio of wall on the lateral load capacity. Dominant failure modes include buckling of steel sheet, local buckling in boundary studs and sheet unzipping in the bottom half of the wall.

Analysis of the shear failure process of masonry by means of a meso-scopic mechanical modeling approach

  • Wang, Shuhong;Tang, Chun'an;Jia, Peng
    • Structural Engineering and Mechanics
    • /
    • v.24 no.2
    • /
    • pp.181-194
    • /
    • 2006
  • The masonry is a complex heterogeneous material and its shear deformation and fracture is associated with very complicated progressive failures in masonry structure, and is investigated in this paper using a mesoscopic mechanical modelling, Considering the heterogeneity of masonry material, based on the damage mechanics and elastic-brittle theory, the newly developed Material Failure Process Analysis (MFPA) system was brought out to simulate the cracking process of masonry, which was considered as a three-phase composite of the block phase, the mortar phase and the block-mortar interfaces. The crack propagation processes simulated with this model shows good agreement with those of experimental observations by other researchers. This finding indicates that the shear fracture of masonry observed at the macroscopic level is predominantly caused by tensile damage at the mesoscopic level. Some brittle materials are so weak in tension relative to shear that tensile rather than shear fractures are generated in pure shear loading.

A SOFTWARE RELIABILITY ESTIMATION METHOD TO NUCLEAR SAFETY SOFTWARE

  • Park, Gee-Yong;Jang, Seung Cheol
    • Nuclear Engineering and Technology
    • /
    • v.46 no.1
    • /
    • pp.55-62
    • /
    • 2014
  • A method for estimating software reliability for nuclear safety software is proposed in this paper. This method is based on the software reliability growth model (SRGM), where the behavior of software failure is assumed to follow a non-homogeneous Poisson process. Two types of modeling schemes based on a particular underlying method are proposed in order to more precisely estimate and predict the number of software defects based on very rare software failure data. The Bayesian statistical inference is employed to estimate the model parameters by incorporating software test cases as a covariate into the model. It was identified that these models are capable of reasonably estimating the remaining number of software defects which directly affects the reactor trip functions. The software reliability might be estimated from these modeling equations, and one approach of obtaining software reliability value is proposed in this paper.

Source Mechanism Analysis and Simplified Modeling for Rockburst (록버스트 발생기구 분석과 단순화 모델링)

  • Choi, Byung-Hee;Oh, Se-Wook;Kim, Hyunwoo;Jung, Yong-Bok
    • Explosives and Blasting
    • /
    • v.39 no.3
    • /
    • pp.1-14
    • /
    • 2021
  • Rockburst is a sudden and violent failure of rock. During the failure process, excess energy is liberated as seismic energy, which in turn causes the surrounding rock mass to vibrate. The level of the ground vibration can reach a magnitude of over 4.5 in the Richter local scale. Thus, a rockburst can cause not only injury to persons, but also damage to both underground workings and surface structures. In this paper the source mechanism of rockburst is analyzed based mainly on the two reports of the Canadian Rockburst Research Program (CRRP). A simplified LS-DYNA modeling is also performed to identify the tensile failure patterns occurring in the remaining rock mass right after blasting in mine stope. The configuration of the simplified model will probably be useful in small-scale laboratory tests for investigating the source mechanism of rockburst.

Simulation-based fatigue life assessment of a mercantile vessel

  • Ertas, Ahmet H.;Yilmaz, Ahmet F.
    • Structural Engineering and Mechanics
    • /
    • v.50 no.6
    • /
    • pp.835-852
    • /
    • 2014
  • Despite the availability of other transport methods such as land and air transportations, marine transportation is the most preferred and widely used transportation method in the world because of its economical advantages. In service, ships experience cyclic loading. Hence, it can be said that fatigue fracture, which occurs due to cyclic loading, is one of the most critical failure modes for vessels. Accordingly, this makes fatigue failure prevention an important design requirement in naval architecture. In general, a ship structure contains many structural components. Because of this, structural modeling typically relies on Finite Element Analysis (FEA) techniques. It is possible to increase fatigue performance of the ship structures by using FEA in computer aided engineering environment. Even if literature papers as well as rules of classification societies are available to assess effect of fatigue cracks onto the whole ship structure, analytical studies are relatively scarce because of the difficulties of modeling the whole structure and obtaining reliable fatigue life predictions. As a consequence, the objective of this study is to improve fatigue strength of a mercantile vessel against fatigue loads via analytical method. For this purpose, the fatigue life of the mercantile vessel has been investigated. Two different type of fatigue assessment models, namely Coffin-Manson and Morrow Mean stress approaches, were used and the results were compared. In order to accurately determine the fatigue life of the ship, a nonlinear finite element analysis was conducted considering plastic deformations and residual stresses. The results of this study will provide the designer with some guidelines in designing mercantile vessels.