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Jeom Kee Paik - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional thermo elastic plastic finite element method modeling for predicting weld induced residual stresses and distortions in steel stiffened plate structures
    World Journal of Engineering and Technology, 2018
    Co-Authors: Chung Min Hyun, Jeom Kee Paik
    Abstract:

    The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced Initial Deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced Initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.

  • a semi analytical method for the elastic plastic large Deflection analysis of stiffened panels under combined biaxial compression tension biaxial in plane bending edge shear and lateral pressure loads
    Thin-walled Structures, 2005
    Co-Authors: Jeom Kee Paik, Man Seung Lee
    Abstract:

    Abstract In the earlier publications [Paik JK, Thayamballi AK, Lee SK, Kang SJ. A semi-analytical method for the elastic-plastic large Deflection analysis of welded steel or aluminium plating under combined in-plane and lateral pressure loads. Thin-Walled Struct 2001;39;125–52; Paik JK, Thayamballi AK. Ultimate limit state design of steel-plated structures. Chichester: Wiley; January 2003], the author presented a semi-analytical method for the elastic–plastic large Deflection analysis of unstiffened plates under biaxial loads, edge shear, biaxial in-plane bending and out-of-plane (lateral) pressure loads until the ultimate strength is reached. In the present paper, a similar method is applied to stiffened panels subjected to the same type of loading. The effect of Initial imperfections in the form of Initial Deflection and welding residual stresses is accounted for in the calculations. The validity of the developed method is demonstrated by comparing with existing theoretical and numerical results where relevant. The present theory can be useful for ultimate strength analysis of plates and stiffened panels made of steel or aluminium alloys.

  • effect of Initial Deflection shape on the ultimate strength behavior of welded steel plates under biaxial compressive loads
    Journal of Ship Research, 2004
    Co-Authors: Jeom Kee Paik, Anil Kumar Thayamballi, Jaemyung Lee
    Abstract:

    The shape of weld-induced Initial distortion in steel plates bounded by support members is normally very complex. It must be recognized that it is not only the magnitude of Initial distortion, but also its shape that can significantly affect the plate collapse behavior. In this paper, some typical plate Initial Deflection shapes are selected from measurements for merchant ship plating between stiffeners. The influence of such Initial Deflection shapes on the ultimate strength behavior of steel plates subjected to biaxial compression as well as uniaxial thrust is then investigated applying nonlinear finite element analyses. It is confirmed that an Initial Deflection shape that approximates the buckling mode, with its maximum amplitude selected to be the same as the measured maximum Initial Deflection, is a good representation for the purposes of somewhat pessimistic evaluation of the ultimate strength of plating between stiffeners under biaxial compression as well as under uniaxial compression. Also, it appears that the influence of Initial Deflection shape on the plate collapse behavior under predominantly transverse axial compression or biaxial compression can be quite different from that under predominantly longitudinal axial compression. As another contribution, the ultimate strength interaction relationship of plating under biaxial compressive loads is presented. The results and insights developed from the present study are summarized.

  • ultimate strength formulations for stiffened panels under combined axial load in plane bending and lateral pressure a benchmark study
    Thin-walled Structures, 2002
    Co-Authors: Jeom Kee Paik
    Abstract:

    This paper develops advanced, yet design-oriented ultimate strength expressions for stiffened panels subject to combined axial load, in-plane bending and lateral pressure. The collapse patterns of a stiffened panel are classified into six groups. It is considered that the collapse of the stiffened panel occurs at the lowest value among the various ultimate loads calculated for each of the collapse patterns. The panel ultimate strengths for all potential collapse modes are calculated separately, and are then compared to find the minimum value which is then taken to correspond to the real panel ultimate strength. The post-weld Initial imperfections (Initial Deflection and residual stress) are included in the developed panel ultimate strength formulations as parameters of influence. The validity of the developed formula is confirmed by comparing with the mechanical collapse tests and nonlinear FEA. A comparison of the present method is also made with theoretical solutions from the Det Norske Veritas classification society design guideline. Important insights developed are summarized.

  • a semi analytical method for the elastic plastic large Deflection analysis of welded steel or aluminum plating under combined in plane and lateral pressure loads
    Thin-walled Structures, 2001
    Co-Authors: Jeom Kee Paik, Anil Kumar Thayamballi, Sang Kon Lee, Sung Jun Kang
    Abstract:

    Abstract The aim of the present paper is to develop a semi-analytical method which can quickly and accurately compute the elastic–plastic large Deflection response of welded steel or aluminum plating under a combination of biaxial compression/tension, biaxial in-plane bending, edge shear and lateral pressure loads, until the ultimate limit state is reached. The post-weld Initial imperfections (i.e. Initial Deflection and residual stresses) are included in the method as parameters of influence. It is assumed that the plating is simply supported at all (four) edges which are kept straight. A unique feature of the developed method is that geometric nonlinearity associated with large Deflection response of plating under combined loads is treated by analytically solving the nonlinear governing differential equations of the elastic large Deflection plate theory, while material nonlinearity due to plasticity is dealt with implicitly by a numerical procedure. This approach reduces the magnitude of numerical computations, resulting in a saving of modeling effort and computing time. As another contribution, this paper investigates and discusses the ultimate strength characteristics of plating, by varying the plate properties and load combinations, based on elastic–plastic large Deflection analysis using the developed method.

O. A. Volokhovskaya - One of the best experts on this subject based on the ideXlab platform.

  • Bearing type influence on vibration activity at coasting of bent double-span rotor with skew-symmetric residual unbalance
    'JVE International Ltd.', 2019
    Co-Authors: O. A. Volokhovskaya
    Abstract:

    The paper is dedicated to study the dependence of vibration activity at coasting of high-temperature segment of turbine unit (TU), which includes high pressure and medium-low pressure rotors (HPR-MLPR system) with skew-symmetric residual unbalance of each rotor, from frequently used types of bearings. Six-block segmental and elliptical bearings are considered. The study takes into account the presence of unrecoverable Initial Deflection of the shaft. Calculations are performed for turbine model K-300-23.5. Detailed analysis of results is performed

  • Evaluation of the influence of the Initial Deflection curve shape of a two-span rotor with residual imbalance on its vibroactivity during rundown
    Journal of Machinery Manufacture and Reliability, 2017
    Co-Authors: O. A. Volokhovskaya, O. V. Barmina
    Abstract:

    This work is devoted to the evaluation of the influence of the curve shape of the ineradicable Initial Deflection of a two-span rotor with the residual imbalance on the transition vibration amplitudes at low critical speeds under the rundown. The model corresponds to a high-pressure rotor–combined mid-low-pressure rotor (HPR–MLPR) system of a turbine unit. It is assumed that rotors are connected by a rigid coupling and installed on anisotropic elastic damper supports. It is supposed that the resulting Deflection (bend) of this system is formed as a result of the fact that a high-pressure rotor acquires the Initial Deflection during the operation or because of abnormal launch conditions, the curve shape of which for a load-free rotor is known. The influence of the mutual arrangement of the residual imbalances of rotors and the imbalances caused by the resulting Deflection of shafting in a system on the amplitudes of its transition vibration under the rundown of a turbine unit has been studied for two shapes of the Initial rotor Deflection curve that have the highest and lowest values of the shape parameter. The values of the Initial rotor bending Deflection and the residual imbalance of both rotors have been set equal to the maximum acceptable values for the operation of a turbine unit. Amplitude calculations have been performed for rotors of a K-300-23.5 Leningrad Mechanical plant (LMZ) turbine.

  • Vibration activity evaluation of double-span rotor at rundown caused by its Initial curvature and residual unbalance
    Thermal Engineering, 2017
    Co-Authors: A. G. Kostyuk, O. A. Volokhovskaya
    Abstract:

    The work is dedicated to the study of vibration activity of double-span rotor of turbine unit (TU) consisting of a high-pressure rotor and a rotor of medium-low pressure rotor combined with it (HPR—MLPR system) at the lowest critical rotational frequencies at rundown. When using the design model of the system, it was assumed that the rotors were installed on anisotropic elastic-damper supports, tied among themselves by a rigid clutch, and having the Initial curvature (nonremovable Initial Deflection) and the residual unbalances in both spans. Two types of bearings were considered–elliptical and six-shoe segmental bearings. It was believed that the Initial Deflection during operation or as a result of noncompliance of start-up conditions Initially gets only HPR and the axis shape of unloaded HPR is known and it is a flat curve. The resultant curve of nonremovable Deflection of the HPR–MLPR system occurring after installing the shafting into the bearings was also considered flat and located in the same plane as the Initial Deflection of HPR. The cases of additional presence with the rotors of concentrated residual unbalances in the middle of each span are considered. The case of availability with both rotors of the shafting antisymmetric point unbalances on each of the spans was not considered in this work. The values of each of the factors of vibration activity (of the Initial Deflection of HPR and residual unbalances of both rotors) were chosen to be equal to the maximum permissible established by the active in the practice of TU operation limitations on the maximum values of the Initial Deflection of thermally unstable rotor and its residual unbalances. The influence of location of residual unbalances in relation to the Initial Deflection curve of HPR–MLPR system on the total amplitudes of transient vibrations caused by both excitation factors in the reference points of the system at TU rundown was investigated. It was established that, at the unfavorable relations between directions of curvature of the rotors of HPR–MLPR system and their residual unbalances with segmental bearings, touching in the diaphragm seals in the middle of HPR span is possible.

Nannong Huang - One of the best experts on this subject based on the ideXlab platform.

  • creep Deflection of viscoelastic laminated cylindrical panels with Initial Deflection under axial compression
    Composites Part B-engineering, 1999
    Co-Authors: Nannong Huang
    Abstract:

    Abstract The viscoelastic behaviors of symmetric cross-ply and antisymmetric angle-ply cylindrical panels under axial compression are examined. The laminates considered are simply supported and have various amplitudes of Initial imperfection. The analysis is based on the geometrically nonlinear viscoelastic approach. The stress function is obtained by solving the compatibility equation using the Laplace transform and a numerical integration scheme. Deflections are calculated by employing the generalized Galerkin method in conjunction with the numerical integration. The characteristics of creep Deflection behaviors are illustrated, and a numerical procedure for tracing the post-snapping paths is provided. Effects of Initial imperfection and the magnitude of loading on the creep buckling are studied. Numerical results for Deflection histories and critical time for glass reinforced epoxy and glass reinforced vinyl ester laminates are presented. Solutions based on the quasi-elastic approach are also presented for comparison.

  • viscoelastic analysis of creep response for uniaxially compressed laminates with Initial Deflection including the effect of physical aging
    International Journal of Solids and Structures, 1998
    Co-Authors: Nannong Huang
    Abstract:

    The viscoelastic behavior of simply-supported, cross-ply and angle-ply laminated plates with a physical aging phenomenon is examined. The laminates considered are under uniaxial inplane compression and have various amplitudes of Initial imperfection. The analysis is based on a geometrically nonlinear viscoelastic formulation. The effective time theory is employed to construct the stress-strain relations. By assuming every component of relaxation moduli in each lamina has the same aging shift rate, the analysis is conducted on the effective time scale. The stress function is obtained by solving the compatibility equation by the use of the Laplace transform and a numerical integration scheme. Deflection is calculated from the moment equation by the Galerkin method in conjunction with the numerical integration. Numerical results for Deflection history and edge shortening for the glass-reinforced vinyl ester laminates are presented. The effects of the physical aging, the pre-loading aging time, the amplitude of imperfection, the magnitude of loading, and the coupling relaxation moduli on the creep responses are illustrated in the numerical examples. Solutions based on the quasi-elastic approach are also presented for comparison.

  • viscoelastic analysis of von karman laminated plates under in plane compression with Initial Deflection
    International Journal of Non-linear Mechanics, 1997
    Co-Authors: Nannong Huang
    Abstract:

    The creep responses of simply-supported cross-ply and angle-ply viscoelastic laminates, having various magnitudes of imperfections, under in-plane compression are examined. The non-linear strain-displacement relation is based on the von Karman assumption. The stress function is obtained by solving the compatibility equation by the use of the Laplace transform, and the Deflection is calculated from the moment equation by the Galerkin method and a numerical integration scheme. The numerical results of Deflection history and edge shortening for the glass/epoxy laminates are presented for illustrating the effect of imperfections and viscoelastic properties on the creep behavior. The solutions based on the quasi-elastic approach are also presented for comparison.

  • thermoviscoelastic response of fiber reinforced plastic laminates with Initial Deflection imperfection
    Journal of Thermal Stresses, 1997
    Co-Authors: Nannong Huang
    Abstract:

    Abstract The viscoelastic behaviors of simply supported cross-ply and angle-ply laminates, having various magnitudes of imperfections, and, subject to instantaneous temperature rise, are examined. Each viscoelastic lamina is taken to be a thermorheologically simple material. The analysis is based on the von Karman assumption and the first-order shear deformation theory. The stress function and the angles of rotation are obtained separately from the compatibility equation and from the moment equilibrium equations using the Laplace transform. Deflection is calculated from the transverse force equilibrium equation using the Galerkin method and a numerical integration scheme. Numerical results for Deflection and stress resultant histories for Glass / Epoxy laminates are presented. Solutions based on the classical laminate theory are also presented for comparison.

Xiaojun Wang - One of the best experts on this subject based on the ideXlab platform.

  • post buckling analysis of a thin stiffened plate with uncertain Initial Deflection via interval analysis
    International Journal of Non-linear Mechanics, 2009
    Co-Authors: Zhiping Qiu, Xiaojun Wang
    Abstract:

    Abstract The post-buckling behavior of the thin stiffened plates with uncertain Initial Deflection under uni-direction compression load is investigated based on Von-Karman large Deflection theory. The uncertain Initial Deflections are considered to be unknown except that they belong to a given set in the interval range. Interval analysis model for computing the bounds of curves of the post-buckling Deflection versus load of the plate is presented. Interval analysis model is compared with the stochastic model, which is taken as the benchmarks of accuracy for judgment. The results indicate that the non-probabilistic and stochastic methods will produce similar results for a large deviation of uncertainty. If the probabilistic information is unavailable, one should not propose the probabilistic method based on an arbitrary assumption on the distribution of the Deflection coefficients. Rather, one should use the non-probabilistic method to uncertainty.

Deyu Wang - One of the best experts on this subject based on the ideXlab platform.

  • ultimate torsional strength of cracked stiffened box girders with a large deck opening
    International Journal of Naval Architecture and Ocean Engineering, 2016
    Co-Authors: Lei Ao, Deyu Wang
    Abstract:

    The present paper studies the ultimate torsional strength of stiffened box girders with large deck opening due to the influence of cracks. Three types of hull girders with different spans are provided for comparison. Potential parameters which may have effects on the torsional strength including the mesh refinement, Initial Deflection, material strain hardening, geometric properties of crack and stiffener are discussed. Two new concepts that play an significant role in the ultimate strength research of damaged box girders are introduced, one of which is the effective residual section (ERS), the other is the Initial damage of the failure zone (IDFZ) for intact structures. New simple formulas for predicting the residual ultimate torsional strength of cracked stiffened box girders are derived on the basis of the two new concepts.

  • residual torsional strength of cracked stiffened girders with a large deck opening
    ASME 2016 35th International Conference on Ocean Offshore and Arctic Engineering, 2016
    Co-Authors: Lei Ao, Deyu Wang
    Abstract:

    This paper studies the residual torsional strength of stiffened girders with large deck openings by using the software ABAQUS. The influence of cracks is considered. Potential parameters which may have effects on the torsional strength including the mesh refinement, Initial Deflection, geometric properties of crack are discussed. Two new concepts that play significant roles in the ultimate strength research of damaged box girders are introduced, one of which is the effective residual section (ERS), the other is the Initial damage of the failure zone (IDFZ) for intact structures. New simple formulas for predicting the residual ultimate torsional strength of cracked stiffened girders are derived on the basis of the two new concepts. The formulas are verified to be reasonable which can be used as an reference.Copyright © 2016 by ASME