• Title, Summary, Keyword: Failure Criteria

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A study on different failure criteria to predict damage in glass/polyester composite beams under low velocity impact

  • Aghaei, Manizheh;Forouzan, Mohammad R.;Nikforouz, Mehdi;Shahabi, Elham
    • Steel and Composite Structures
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    • v.18 no.5
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    • pp.1291-1303
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    • 2015
  • Damage caused by low velocity impact is so dangerous in composites because although in most cases it is not visible to the eye, it can greatly reduce the strength of the composite material. In this paper, damage development in U-section glass/polyester pultruded beams subjected to low velocity impact was considered. Different failure criteria such as Maximum stress, Maximum strain, Hou, Hashin and the combination of Maximum strain criteria for fiber failure and Hou criteria for matrix failure were programmed and implemented in ABAQUS software via a user subroutine VUMAT. A suitable degradation model was also considered for reducing material constants due to damage. Experimental tests, which performed to validate numerical results, showed that Hashin and Hou failure criteria have better accuracy in predicting force-time history than the other three criteria. However, maximum stress and Hashin failure criteria had the best prediction for damage area, in comparison with the other three criteria. Finally in order to compare numerical model with the experimental results in terms of extent of damage, bending test was performed after impact and the behavior of the beam was considered.

Premature failure Criteria of RC Beams Strengthened with FRP II (FRP보강 RC보의 조기파괴기준 II)

  • Kim, Tae-Woo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.141-144
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    • 2005
  • Rip-off failure and Debonding failure were commonly reported premature failure modes. The main reasons of premature failure in RC beams bonded with FRP were strengthening length and the reinforcement ratio. in this study, On the basis of premature failure mechanism in RC beams bonded with FRP, premature failure criteria were proposed. Also It was verified that Rip-off failure and Debonding failure occured according to premature failure criteria

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A Study on the Evaluation of Fiber and Matrix Failures for Laminated Composites using Hashin·Puck Failure Criteria (Hashin·Puck 파손기준 기반 적층 복합재료의 섬유 및 기지파손 평가에 관한 연구)

  • Lee, Chi-Seung;Lee, Jae-Myung
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.2
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    • pp.143-152
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    • 2015
  • In the present study, the fiber and matrix failure of composite laminates under arbitrary biaxial stresses were evaluated based on separate mode criteria such as Hasnin and Puck theories. There is a limitation to predict the fiber-dominant and/or matrix-dominant failures under arbitrary stress states using limit criteria (maximum stress and maximum strain theories) and interactive criteria (Tsai-Hill and Tsai-Wu theories). There is little literature for failure analysis of ships and offshore composite structures considering advanced failure theories such as Hashin and Puck theories. Furthermore, there is not enough practical commercial finite element analysis (FEA) code which is basically adopted the separate mode criteria. Hence, in the present study, the user-defined subroutine of commercial FEA code ABAQUS for evaluation of fiber and matrix failures of composite structures was developed based on Hashin and Puck failure criteria. And then, the proposed subroutine was validated by comparing with a series of experimental results of carbon- and glass-implemented composite laminates to guarantee the reliability and usefulness of the developed method.

A Study on Thermomechanical Failure Behavior of Granites for Radioactive Waste Repository (방사성폐기물 지층처분을 위한 화강암의 열역학적 파괴거동 연구)

  • 양형식;장명환
    • Tunnel and Underground Space
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    • v.6 no.1
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    • pp.69-74
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    • 1996
  • High temperature confined compressive tests for thermomechanical failure criteria were carried out for Iksan and Whandeung granites. Authors suggested new polynomial type failure coefficient functions by which conventional Hoek-Brown failure criteria was extended to thermomechanical one. Obtained results are as follow; 1) Failure coefficients, m and s of Hoek and Brown's empirical failure criteria were decreased as temperature increased. 2) Theoretically calculated values by suggested equations and experimented ones by confined compressive test were well coincided.

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An Estimative Model of Spot Weld Failure-1. Failure Criteria (점 용접점 파단의 정량적 모델-1. 파단조건식)

  • Lee, T.S.;Lee, H.Y.;Shin, S.J.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.40-52
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    • 1998
  • A good grasp of the failure mechanisms of resistance spot weld, widely used in joining the auto-panels, in essential to the structural/crashworthy analyses and integrity assessment of the whole auto-body. In this study, We provide an estimative model describing the failure behavior of resistance spotf weld, and apply the model to the finite element analysis of crashworthiness. First, in "Part 1-Failure Criteria", to be used for the finite element analysis of spot-welded structural panels of an auto-body, (i) a methodology for quantifying the spot weld failure and the accompanying failure criteria are presented, and (ii) the coefficients of the failure equation are determined by a munimum number of appropriate experimental tests. To achieve these, we derive the functional form of the failure envelop by limit analysis, and correlate it with the form in PAM-$CRASH^{TM}$ code, and also investigate the effect of the failure coefficients on the failure envelop form. An estimative model obtained in this Part1, as spot weld failure criteria is applied to the Macroscopic finite element analysis of autobody structural panels using PAM-$CRASH^{TM}$ code in Part 2.

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Validation of a Local Failure Criteria Using the Results of Wall-Thinned Pipe Failure Tests (감육배관 손상시험 결과를 이용한 국부손상기준 검증)

  • Kim, Jin-Weon;Lee, Sung-Ho;Park, Chi-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.12
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    • pp.1393-1400
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    • 2009
  • The objective of this study is to validate local failure criteria, which were proposed based on the notched-bar specimen tests combining with finite element (FE) simulations, using the results of real-scale pipe failure tests. This study conducted burst test using wall-thinned pipe specimens, which were made of 4 inch Sch.80 ASTM A106 Gr.B carbon steel pipe, under simple internal pressure at ambient temperature and performed associated FE simulations. Failure pressures were estimated by applying the failure criteria to the results of FE simulations and were compared with experimental failure pressures. It showed that the local stress based criterion, given as true ultimate tensile stress of material, accurately estimated the failure pressure of wall-thinned pipe specimens. However, the local strain based criterion, which is fracture strain of material as a function of stress tri-axiality, could not predict the failure pressure. It was confirmed that the local stress based criterion is reliably applicable to estimation of failure pressure of local wall-thinned piping components.

Definition and Diagnostic Criteria of Acute Kidney Injury (급성 신손상의 정의와 진단 기준)

  • NamGoong, Mee-Kyung
    • Childhood Kidney Diseases
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    • v.15 no.2
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    • pp.101-106
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    • 2011
  • Acute renal failure means that the word does not contain a mild kidney injury. In addition, the criteria for acute renal failure per researcher are different, and it is difficult in interpreting the results of research on acute renal failure. Therefore, rather than acute renal failure, a new term "acute kidney injury" meaning to include all the levels of injury is introduced. In 2002, to diagnose by means of serum creatinine, glomerular filtration rate and urine output, a detailed classification of acute kidney injury, the RIFLE criteria has been proposed. In 2007, the RIFLE criteria by transforming, AKIN criteria has been proposed. The pediatric RIFLE criteria for children has also been proposed. The author reviews here these criteria by comparing them.

Investigating the effects of confining pressure on graphite material failure modes and strength criteria

  • Yi, Yanan;Liu, Guangyan;Xing, Tongzhen;Lin, Guang;Sun, Libin;Shi, Li;Ma, Shaopeng
    • Nuclear Engineering and Technology
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    • v.52 no.7
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    • pp.1571-1578
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    • 2020
  • As a critical material in very/high-temperature gas-cooled reactors, graphite material directly affects the safety of the reactor core structures. Owing to the complex structures of graphite material in reactors, the material typically undergoes complex stress states. It is, therefore, necessary to study its mechanical properties, failure modes, and strength criteria under complex stress states so as to provide guidance for the core structure design. In this study, compressive failure tests were performed for graphite material under the condition of different confining pressures, and the effects of confining pressure on the triaxial compressive strength and Young's modulus of graphite material were studied. More specifically, graphite material based on the fracture surfaces and fracture angles, the graphite specimens were found to exhibit four types of failure modes, i.e., tension failure, shear-tension failure, tension-shear failure and shear failure, with increasing confining pressure. In addition, the Mohr strength envelope of the graphite material was obtained, and different strength criteria were compared. It showed that the parabolic Mohr-Coulomb criterion is more suitable for the strength evaluation for the graphite material.

Comparing the generalized Hoek-Brown and Mohr-Coulomb failure criteria for stress analysis on the rocks failure plane

  • Mohammadi, M.;Tavakoli, H.
    • Geomechanics and Engineering
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    • v.9 no.1
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    • pp.115-124
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    • 2015
  • Determination of mobilized shear strength parameters (that identify stresses on the failure plane) is required for analyzing the stability by limit equilibrium method. Generalized Hoek-Brown (GHB) and Mohr-Coulomb (MC) failure criteria are usually used for obtaining stresses on the plane of failure. In the present paper, the applicability of these criteria for determining the stresses on failure plane is investigated. The comparison is based on stresses on the real failure plane which are obtained from the Mohr stress circle. To do so, 18 sets of data (consist of principal stresses and angle of failure plane) presented in the literature are used. In addition, the values account for (VAF) and the root mean square error (RMSE) indices were calculated to check the determination performance of the obtained results. Values of VAF and RMSE for the normal stresses on the failure plane evaluated from MC are 49% and 31.5 where for GHB are 55% and 30.5, respectively. Also, for the shear stresses on failure plane, they are 74% and 36 for MC, 76% and 34.5 for GHB. Results show that the obtained stresses and angles of failure plane for each criterion differ from real ones, but GHB results are closer to the empirical results. Also, it is inferred that results are affected by the failure envelope not real failure plane. Therefore, obtained shear strength parameters are not mobilized. Finally, a multivariable regressed relation is presented for determining the stresses on the failure plane.

Multiple failure criteria-based fragility curves for structures equipped with SATMDs

  • Bakhshinezhad, Sina;Mohebbi, Mohtasham
    • Earthquakes and Structures
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    • v.17 no.5
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    • pp.463-475
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    • 2019
  • In this paper, a procedure to develop fragility curves of structures equipped with semi-active tuned mass dampers (SATMDs) considering multiple failure criteria has been presented while accounting for the uncertainties of the input excitation, structure and control device parameters. In this procedure, Latin hypercube sampling (LHS) method has been employed to generate 30 random SATMD-structure systems and nonlinear incremental dynamic analysis (IDA) has been conducted under 20 earthquakes to determine the structural responses, where failure probabilities in each intensity level have been evaluated using Monte Carlo simulation (MCS) method. For numerical analysis, an eight-story nonlinear shear building frame with bilinear hysteresis material behavior has been used. Fragility curves for the structure equipped with optimal SATMDs have been developed considering single and multiple failure criteria for different performance levels and compared with that of uncontrolled structure as well as structure controlled using passive tuned mass damper (TMD). Numerical analysis has shown the capability of SATMDs in significant enhancement of the seismic fragility of the nonlinear structure. Also, considering multiple failure criteria has led to increasing the fragility of the structure. Moreover, it is observed that the influence of the uncertainty of input excitation with respect to the other uncertainties is considerable.