• Title, Summary, Keyword: Combined Loading

Search Result 526, Processing Time 0.042 seconds

Nondestructive Evaluation of Temporarily Repaired CFRP Laminates Subjected to Delaminations due to Localized Heating and Cyclic Loading Combined

  • Han, Tae-Young;Kwon, Oh-Yang
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.27 no.3
    • /
    • pp.268-279
    • /
    • 2007
  • The reliability of cold-bonding repair technique of carbon-fiber reinforced plastics (CFRP) laminates, often used as a temporary repair for the airplane maintenance, has been evaluated during cyclic loading and localized heating by nondestructive methods. Major concern was given to the evolution of damage after repair in the form of delaminations due to localized heating and cyclic loading combined. An area of interest both on the specimen repaired by cold-bonding and the specimen without repair where delaminations were induced by localized heating and cyclic loading was monitored by acoustic emission (AE) testing and further examined by pitch-catch low-frequency bond testing, and pulse-echo high-frequency ultrasonic testing. The results showed that the reliability of cold-bonding repair would be significantly reduced by the localized heating and cyclic loading combined rather than by the cyclic loading only. AE monitoring appeared to be an effective and reliable tool to monitor the integrity of temporarily repaired CFRP laminates in terms of the structural health monitoring (SHM) philosophy.

Behavior of a combined piled raft foundation in a multi-layered soil subjected to vertical loading

  • Bandyopadhyay, Srijit;Sengupta, Aniruddha;Parulekar, Y.M.
    • Geomechanics and Engineering
    • /
    • v.21 no.4
    • /
    • pp.379-390
    • /
    • 2020
  • The behavior of a piled raft system in multi-layered soil subjected to vertical loading has been studied numerically using 3D finite element analysis. Initially, the 3D finite element model has been validated by analytically simulating the field experiments conducted on vertically loaded instrumented piled raft. Subsequently, a comprehensive parametric study has been conducted to assess the performance of a combined piled raft system in terms of optimum pile spacing and settlement of raft and piles, in multi-layered soil stratum subjected to vertical loading. It has been found that a combined pile raft system can significantly reduce the total settlement as well as the differential settlement of the raft in comparison to the raft alone. Two different arrangements below the piled raft with the same pile numbers show a significant amount of increase of load transfer of piled raft system, which is in line with the load transfer mechanism of a piled raft. A methodology for the factor of safety assessment of a combined pile raft foundation has been presented to improve the performance of piled raft based on its serviceability requirements. The findings of this study could be used as guidelines for achieving economical design for combined piled raft systems.

Damage Evaluation of Bi-directionally Prestressed Concrete Panels under Blast-fire Combined Loading (폭발 후 화재하중 시나리오에 따른 2방향 프리스트레스트 콘크리트 패널부재의 손상도 평가)

  • Choi, Ji-Hun;Choi, Seung-Jai;Kim, Tae-Kyun;Kim, Jang-Ho Jay
    • Journal of the Korea Concrete Institute
    • /
    • v.29 no.3
    • /
    • pp.237-248
    • /
    • 2017
  • Frequent terror or military attack by explosion, impact, fire accidents have occurred recently. These attacks and incidents raised public concerns and anxiety of potential terrorist attacks on important infrastructures. However, structural behavioral researches on prestressed concrete (PSC) infrastructures such as Prestressed Concrete Containment Vessel (PCCV) and Liquefied Natural Gas (LNG) storage tanks under extreme loading are significantly lacking at this time. Also, researches on possible secondary fire scenarios after terror and bomb explosion has not been performed yet. Therefore, a study on PSC structural behavior from an blast-induced fire scenario was undertaken. To evaluate the blast-fire combined resistance capacity and its protective performance of bi-directional unbonded PSC member, blast-fire tests were carried out on $1,400mm{\times}1,000mm{\times}300mm$ PSC specimens. Blast loading tests were performed by the detonation of 25 kg ANFO explosive charge at 1.0 m standoff distance. Also, fire and blast-fire combined loading were tested using RABT fire loading curve. The test results are discussed in detail in the paper. The results can be used as basic research references for related research areas, which include protective design simulation under blast-fire combined loading.

Fracture Behaviors of Alumina Tubes under Combined Tension/Torsion (알루미나 튜브의 인장/비틀림 조합하중하의 파괴거동)

  • Kim, K.T.;Suh, J.;Cho, Y.H.
    • Journal of the Korean Ceramic Society
    • /
    • v.28 no.1
    • /
    • pp.20-28
    • /
    • 1991
  • Fracture of Al2O3 tubes for different loading path under combined tension/torsion was investigated. Macroscopic directions of crack propagation agreed well with the maximum principal stress criterion, independent of the loading path. However, fracture strength from the proportional loading test($\tau$/$\sigma$= constant) showed either strengthening or weakening compared to that from uniaxial tension, depending on the ratio $\tau$/$\sigma$. The Weibull theory was capable to predict the strengthening of fracture strength in pure torsion, but not the weakening in the proportional loading condition. The strengthening or weakening of fracture strength in the proportional loading condition was explained by the effect of shear stresses in the plane of randomly oriented microdefects. Finally, a new empirical fracture criterion was proposed. This criterion is based on a mixed mode fracture criterion and experimental data for fracture of Al2O3 tubes under combined tension/torsion. The proposed fracture criterion agreed well with experimental data for both macroscopic directions of crack propagation and fracture strengths.

  • PDF

Photocatalytic and Sonophotocatalytic degradation of alachlor using different photocatalyst

  • Bagal, Manisha V.;Gogate, Parag R.
    • Advances in environmental research
    • /
    • v.2 no.4
    • /
    • pp.261-277
    • /
    • 2013
  • The degradation of alachlor has been investigated using sonolysis (US), photocatalysis (UV) and sonophotocatalysis (US/UV) using three photocatalyst viz. $TiO_2$ (mixture of anatase and rutile), $TiO_2$ (anatase) and ZnO. The effect of photocatalyst loading on the extent of degradation of alachlor has been investigated by varying $TiO_2$ (both types) loading over the range of 0.01 g/L to 0.1 g/L and ZnO loading over the range of 0.05 g/L to 0.3 g/L. The optimum loading of the catalyst was found to be dependent on the type of operation i.e., photocatalysis alone or the combined operation of sonolysis and photocatalysis. All the combined processes gave complete degradation of alachlor with maximum rate of degradation being obtained in the case of sonophotocatalytic process also showing synergistic effect at optimized loading of photocatalyst. About 50% to 60% reduction in TOC has been obtained using the combined process of sonophotocatalysis depending on the operating conditions. The alachlor degradation fitted first order kinetics for all the processes under investigation. It has been observed that the $TiO_2$ (mixtrure of anatase and rutile) is the most active photocatalyst among the three photocatalysts studied in the current work. The effect of addition of radical enhancers and scavengers on sonophotocatalytic degradation of alachlor has been investigated in order to decipher the controlling mechanism. The alachlor degradation products have been identified using LC-MS method.

Determination of Chaboche Cyclic Combined Hardening Model for Cracked Component Analysis Using Tensile and Cyclic C(T) Test Data (표준 인장시험과 반복하중 C(T) 시험을 이용한 균열해석에서의 Chaboche 복합경화 모델 결정법)

  • Hwang, Jin Ha;Kim, Hune Tae;Ryu, Ho Wan;Kim, Yun Jae;Kim, Jin Weon;Kweon, Hyeong Do
    • Transactions of the Korean Society of Pressure Vessels and Piping
    • /
    • v.15 no.2
    • /
    • pp.31-39
    • /
    • 2019
  • Cracked component analysis is needed for structural integrity analysis under seismic loading. Under large amplitude cyclic loading conditions, the change in material properties can be complex, depending on the magnitude of plastic strain. Therefore the cracked component analysis under cyclic loading should consider appropriate cyclic hardening model. This study introduces a procedure for determining an appropriate cyclic hardening model for cracked component analysis. The test material was nuclear-grade TP316 stainless steel. The material cyclic hardening was simulated using the Chaboche combined hardening model. The kinematic hardening model was determined from standard tensile test to cover the high and wide strain range. The isotropic hardening model was determined by simulating C(T) test under cyclic loading using ABAQUS debonding analysis. The suitability of the material hardening model was verified by comparing load-displacement curves of cyclic C(T) tests under different load ratios.

Development of Assessment Methodology for Locally Wall-Thinned Pipe Under Combined Loading (복합하중이 작용하는 국부감육배관 평가법 개발)

  • Shim Do-Jun;Kim Yun-Jae;Kim Young-Jin;Park Chi-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.29 no.10
    • /
    • pp.1399-1406
    • /
    • 2005
  • Recently authors have proposed a new method to estimate failure strength of a pipe with local wall thinning subject to either internal pressure or global bending. The proposed method was based on the equivalent stress averaged over the minimum ligament in the locally wall thinned region, and the simple scheme to estimate the equivalent stress in the minimum ligament was proposed, based on the reference stress concept. This paper extends the new method to combined internal pressure and global bending. The proposed method is validated against FE results for various geometries of local wall thinning under combined loading. The effect of internal pressure is also investigated in the present study. Comparison of maximum moments, predicted according to the proposed method, with published full-scale pipe test data fur locally wall-thinned pipes under combined internal pressure and global bending, shows good agreement.

Behaviour of open beam-to-tubular column angle connections under combined loading conditions

  • Liu, Yanzhi;Malaga-Chuquitaype, Christian;Elghazouli, Ahmed Y.
    • Steel and Composite Structures
    • /
    • v.16 no.2
    • /
    • pp.157-185
    • /
    • 2014
  • This paper examines the behaviour of two types of practical open beam-to-tubular column connection details subjected to combined moment, axial and/or shear loads. Detailed continuum finite element models are developed and validated against available experimental results, and extended to deal with flexural, axial and shear load interactions. A numerical investigation is then carried out on the behaviour of selected connections with different stiffness and strength characteristics under various load combination scenarios. The influence of applied levels of axial tensile or compressive loads on the bending stiffness and capacity is examined and discussed. Additionally, the interaction effects between shear forces and co-existing bending and axial loads are examined and shown to be comparatively insignificant in terms of stiffness and capacity in most cases. It is also shown that the range of connections considered in this paper can provide rotational ductility levels in excess of those required under typical design scenarios. Based on these findings, a simplified component-based representation is proposed and described, and its ability to represent the connection response under combined loading is verified using results from detailed numerical simulations.

Effect of Compressive Stress on Multiaxial Loading Fracture of Alumina Tubes (알루미나 튜브의 복합하중 파괴에 미치는 압축응력의 영향)

  • Kim, K.T.;Suh, J.
    • Journal of the Korean Ceramic Society
    • /
    • v.28 no.10
    • /
    • pp.810-818
    • /
    • 1991
  • Fracture responses of Al2O3 tubes were investigated for various loading paths under combined tension/torsion. The fracture criterion did not depend on loading paths. Fracture angles agreed well with the maximum tensile stress criterion. As the loading condition approaches a shear dominant state, the tensile principal stress at fracture increases compared to the uniaxial fracture strength. By using the Weibull modulus obtained from tension and torsion tests, the Weibull statistical fracture strengths were compared with experimental data. This comparison suggests that fracture may occur at the surface of the specimen when tensile stress is dominant, but within the volume of the specimen when shear stress is dominant. The Weibull fracture strength increased as the loading conition approached a shear dominant state, but underestimated compared to experimental data. Finally, a new fracture criterion was proposed by including the effect of compressive principal stress. The proposed criterion agreed well with experimental data of Al2O3 tubes not only at combined tension/torsion but also at balanced biaxial tension.

  • PDF

An experimental-computational investigation of fracture in brittle materials

  • De Proft, K.;Wells, G.N.;Sluys, L.J.;De Wilde, W.P.
    • Computers and Concrete
    • /
    • v.1 no.3
    • /
    • pp.227-248
    • /
    • 2004
  • A combined experimental-computational study of a double edge-notched stone specimen subjected to tensile loading is presented. In the experimental part, the load-deformation response and the displacement field around the crack tip are recorded. An Electronic Speckle Pattern Interferometer (ESPI) is used to obtain the local displacement field. The experimental results are used to validate a numerical model for the description of fracture using finite elements. The numerical model uses displacement discontinuities to model cracks. At the discontinuity, a plasticity-based cohesive zone model is applied for monotonic loading and a combined damage-plasticity cohesive zone model is used for cyclic loading. Both local and global results from the numerical simulations are compared with experimental data. It is shown that local measurements add important information for the validation of the numerical model. Consequently, the numerical models are enhanced in order to correctly capture the experimentally observed behaviour.