• Title, Summary, Keyword: Mechanical Failure

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Failure Probability of Corrosion Pipeline with Varying Boundary Condition

  • Lee, Ouk-Sub;Pyun, Jang-Sik
    • Journal of Mechanical Science and Technology
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    • v.16 no.7
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    • pp.889-895
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    • 2002
  • This paper presents the effect of external corrosion, material properties, operation condition and design thickness in pipeline on failure prediction using a failure probability model. The predicted failure assessment for the simulated corrosion defects discovered in corroded pipeline is compared with that determined by ANSI/ASME B31G code and a modified B31G method. The effects of environmental, operational, and random design variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress and pipe thickness on the failure probability are systematically studied using a failure probability model for the corrosion pipeline.

Effect of Boundary Conditions of Failure Pressure Models on Reliability Estimation of Buried Pipelines

  • Lee, Ouk-Sub;Pyun, Jang-Sik;Kim, Dong-Hyeok
    • International Journal of Precision Engineering and Manufacturing
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    • v.4 no.6
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    • pp.12-19
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    • 2003
  • This paper presents the effect of boundary conditions in various failure pressure models published for the estimation of failure pressure. Furthermore, this approach is extended to the failure prediction with the aid of a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with each corrosion defect in buried pipelines for long exposure period with unit of years. A failure probability model based on the von-Mises failure criterion is adapted. The log-normal and standard normal probability functions for varying random variables are adapted. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically investigated for the corrosion pipeline by using an adapted failure probability model and varying failure pressure model.

Reliability Estimation of Buried Gas Pipelines in terms of Various Types of Random Variable Distribution

  • Lee Ouk Sub;Kim Dong Hyeok
    • Journal of Mechanical Science and Technology
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    • v.19 no.6
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    • pp.1280-1289
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    • 2005
  • This paper presents the effects of corrosion environments of failure pressure model for buried pipelines on failure prediction by using a failure probability. The FORM (first order reliability method) is used in order to estimate the failure probability in the buried pipelines with corrosion defects. The effects of varying distribution types of random variables such as normal, lognormal and Weibull distributions on the failure probability of buried pipelines are systematically investigated. It is found that the failure probability for the MB31G model is larger than that for the B31G model. And the failure probability is estimated as the largest for the Weibull distribution and the smallest for the normal distribution. The effect of data scattering in corrosion environments on failure probability is also investigated and it is recognized that the scattering of wall thickness and yield strength of pipeline affects the failure probability significantly. The normalized margin is defined and estimated. Furthermore, the normalized margin is used to predict the failure probability using the fitting lines between failure probability and normalized margin.

Failure Strength of the Composite Mechanical Joint according to the Stacking Angle (적층각 변화에 따른 복합재료 기계적 체결부의 파손강도)

  • Jo, Dae-Hyeon;Kim, Cheol-Hwan;Choi, Jin-Ho
    • Composites Research
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    • v.30 no.4
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    • pp.229-234
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    • 2017
  • Generally, joints are the weakest part in the composite structures. Composite joints can be classified into adhesive joints and mechanical joints, and mechanical joints are mainly used in areas less sensitive to environmental conditions. In this paper, the failure loads of composite mechanical joints with five different stacking angles are tested and predicted. Finite element analysis of mechanical joints were performed and failure loads were predicted by the FAI(Failure Area Index) method using Tsai-Wu and Yamada-Sun failure criteria, and the predicted failure loads were compared with experimental results. From the experiment and analysis, the failure loads of the mechanical joints were decreased as the ratio of 0 degree layer was low and they could be predicted within 13.03% using the FAI method and Yamada-Sun failure criteria.

Failure Pressure Prediction of Composite Cylinders for Hydrogen Storage Using Thermo-mechanical Analysis and Neural Network

  • Hu, J.;Sundararaman, S.;Menta, V.G.K.;Chandrashekhara, K.;Chernicoff, William
    • Advanced Composite Materials
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    • v.18 no.3
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    • pp.233-249
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    • 2009
  • Safe installation and operation of high-pressure composite cylinders for hydrogen storage are of primary concern. It is unavoidable for the cylinders to experience temperature variation and significant thermal input during service. The maximum failure pressure that the cylinder can sustain is affected due to the dependence of composite material properties on temperature and complexity of cylinder design. Most of the analysis reported for high-pressure composite cylinders is based on simplifying assumptions and does not account for complexities like thermo-mechanical behavior and temperature dependent material properties. In the present work, a comprehensive finite element simulation tool for the design of hydrogen storage cylinder system is developed. The structural response of the cylinder is analyzed using laminated shell theory accounting for transverse shear deformation and geometric nonlinearity. A composite failure model is used to evaluate the failure pressure under various thermo-mechanical loadings. A back-propagation neural network (NNk) model is developed to predict the maximum failure pressure using the analysis results. The failure pressures predicted from NNk model are compared with those from test cases. The developed NNk model is capable of predicting the failure pressure for any given loading condition.

The Effects of Elbow Joint Angle on the Mechanical Properties of the Common Extensor Tendon of the Humeral Epicondyle

  • Han, Jung-Soo
    • Journal of Mechanical Science and Technology
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    • v.18 no.4
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    • pp.582-591
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    • 2004
  • The purpose of this study was to determine the effects of elbow joint angle on mechanical properties, as represented by ultimate load, failure strain and elastic modulus, of bone-tendon specimens of common extensor tendon of the humeral epicondyle. Eight pairs of specimens were equally divided into two groups of 8 each, which selected arbitrarily from left or right side of each pair, positioned at 45$^{\circ}$ and 90$^{\circ}$ of elbow flexion and subjected to tension to failure in the physiological direction of the common extensor tendon. For comparison of the differences in the failure and elastic modulus between tendon and the bone-junction, data for both were evaluated individually. Significant reduction in ultimate load of bone-tendon specimens was shown to occur at 45$^{\circ}$. The values obtained from the bone-tendon junctions with regard to the failure strain were significant higher than those from tendon in both loading directions, but the largest failure strain at the bone-tendon junction was found at 45$^{\circ}$. The elastic modulus was found to decrease significantly at the bone-tendon junction when the loading direction switched from 90$^{\circ}$ to 45$^{\circ}$. Histological observation, after mechanical tensile tests, in both loading directions showed that failure occurred at the interface between tendon and uncalcified fibrocartilage in the thinnest fibrocartilage zone of the bone-tendon junction. We concluded that differences in measured mechanical properties are a consequence of varying the loading direction of the tendon across the bone-tendon specimen.

Magnetically Controlled Growing Rods: The Experience of Mechanical Failure from a Single Center Consecutive Series of 28 Children with a Minimum Follow-up of 2 Years

  • Beaven, Alastair;Gardner, Adrian C.;Marks, David S.;Mehta, Jwalant S.;Newton-Ede, Matthew;Spilsbury, Jonathan B.
    • Asian Spine Journal
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    • v.12 no.5
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    • pp.794-802
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    • 2018
  • Study Design: Retrospective observational study of a continuous series of 28 children. Purpose: To determine the mechanical failure rate in our cohort of children treated with magnetically controlled growth rods (MCGRs). Overview of Literature: Previous studies report a MCGR mechanical failure rate of 0%-75%. Methods: All patients with MCGR implantation between 2012 and 2015 were examined and followed up for a minimum of 2 years. A retrospective evaluation of contemporaneously documented clinical findings was conducted, and radiographs were retrospectively examined for mechanical failure. The external remote controller (ERC)-specified length achieved in the clinic was compared to the length measured on subsequent radiographs. Results: Fourteen mechanical failures were identified in 28 children (50%) across a total of 52 rods (24 pairs and four single constructs). Mechanical failures were due to: failure to lengthen under general anesthesia (seven children), actuator pin fracture (four), rod fracture (one), foundation screw failure (one), and ran out of rod length (one). Of the 14 mechanical failures, six were treated with final fusion operations (reflecting limited further growth potential), and eight patients were treated with the intention for further lengthening. We therefore consider these eight patients to represent the true incidence of mechanical failure in our cohort (29%). The difference between the ERC length and radiographic length was found to be identical in 11% cases; 35% were overestimates, and 54% were underestimates. The median underestimate was 2.45 mm whereas the median overestimate was 3.1 mm per distraction episode. In total, 95% of all ERC distractions were within ${\pm}10mm$ of the radiographic length achieved over a median of nine distraction episodes. Conclusions: Our series is the most comprehensive MCGR series published to date, and we present a mechanical failure rate of 29%. Clinicians should be mindful of the discrepancies between ERC length and radiographic measurements of rod length; other modalities may be more helpful in this regard.

Fault diagnosis of walking beam roller bearing by FTA (FTA(Fault Tree Analysis)기법을 이용한 이송용 대부하 베어링 고장 진단)

  • Bae, Y.H.;Lee, H.K.;Lee, S.J.
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.5
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    • pp.110-123
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    • 1994
  • The development of automatic production systems have required inteligent diagnostic and monitoring function to repair system failure and reduce production loss by the failure. In order to perform accurate functions of intelligent system, inferencing about total system failure and fault analysis due to each mechanical component failures are required. Also the solution about repair and maintenance can be suggested from these analysis results. As an essential component of mechanical system, a bearing system is investigated to define the failure behavior. The bearing failure is caused by lubricant system failure, metallurgical defficiency, mechanical condition(vibration, overloading, misalignment) and environmental effect. This study described roller bearing fault train due to stress variation and metallurgical defficiency from lubricant failure by using FTA.

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Optimum Design of Co-cured Steel-Composite Tubular Single Lap Joints (동시경화 강철-복합재료 원형 단일 겹치기 조인트의 최적설계)

  • Jo, Deok-Hyeon;Lee, Dae-Gil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.5
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    • pp.1203-1214
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    • 2000
  • In this paper, a failure model for co-cured steel-composite tubular single lap joints has been proposed incorporating the nonlinear mechanical behavior of steel adherends and different failure mode s such as steel adherend failure and composite adherend failure. The characteristics of the co-cured steel-composite tubular single lap joint were investigated with respect to the test temperature, the stacking sequence of composite adherend, the thickness ratio of steel adherend to composite adherend, and the scarf ratio of steel adherend. Thus, the optimum design method for the co-cured steel-composite tubular single lap joint was suggested.

Reliability Analysis of Slab Transfer Equipment in Hot Rolling Furnace (열간압연 가열로 슬라브 이송장치 신뢰도 해석)

  • Bae, Young-Hwan
    • Journal of the Korean Society of Safety
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    • v.21 no.1
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    • pp.6-14
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    • 2006
  • The development of automatic production systems have required intelligent diagnostic and monitoring functions to overcome system failure and reduce production loss by the failure. In order to perform accurate operations of the intelligent system, implication about total system failure and fault analysis due to each mechanical component failures are required. Also solutions for repair and maintenance can be suggested from these analysis results. As an essential component of a mechanical system, a bearing system is investigated to define the failure behavior. The bearing failure is caused by lubricant system failure, metallurgical deficiency, mechanical condition(vibration, overloading, misalignment) and environmental effects. This study described slab transfer equipment fault train due to stress variation and metallurgical deficiency from lubricant failure by using FTA.