The ship hull can be considered as a thin – walled box gider constituted by stiffened panels. In order to research the ship ultimate strength, the ultimate strength of stiffened panel must be considered. Stiffened plates are typical... more
The ship hull can be considered as a thin – walled box gider constituted by stiffened panels. In order to research the ship ultimate strength, the ultimate strength of stiffened panel must be considered. Stiffened plates are typical structure of ship. Ultimate strength analysis of stiffened plate for the analysis of ships' structures. In present paper, the nonlinear finite element method is employed to predict the ultimate strength of stiffened plate model under longitudinal compression, transverse compression, lateral pressure.
In this work, nonlocal nonlinear finite element analysis of laminated composite plates using Reddy's third-order shear deformation theory (TSDT) [1] and Eringen's nonlocality [2] is presented. The governing equations of third order shear... more
In this work, nonlocal nonlinear finite element analysis of laminated composite plates using Reddy's third-order shear deformation theory (TSDT) [1] and Eringen's nonlocality [2] is presented. The governing equations of third order shear deformation theory with the von Kármán strains are derived employing the Eringen's [2] stress-gradient constitu-tive model. The principle of virtual displacement is used to derive the weak forms, and the displacement finite element models are developed using the weak forms. Four-noded rectangular conforming element with 8 degrees of freedom per node has been used. The coefficients of stiffness matrix and tangent stiffness matrix are presented along with non-local force vector. The developed finite element model can be employed to capture the small scale deviations from local continuum models caused by material inhomogeneity and the inter atomic and inter molecular forces. Numerical examples are presented to illustrate the effects of nonlocality, anisotropy, and the von Kármán type nonlinearity on the bending behaviour of laminated composite plates.
This paper presents the life estimation of the diffuser structure. Literature shows that the welds are the source of failure in case of welded structure; hence the estimation of its life is very critical. There are two kinds of methods... more
This paper presents the life estimation of the diffuser structure. Literature shows that the welds are the source of failure in case of welded structure; hence the estimation of its life is very critical. There are two kinds of methods for life estimation stress life approach and strain life approach which have been validated for simple problems. Stress life approach was identified as appropriate for life estimation of the variable diffuser. There are papers indicating the methodology for life estimation using commercial software for life prediction. Here, Optistruct-Hyper-Works for pre-processing and solver and Hyper-View-Hyper-Works for post processing has been used for the indeterminate structure, complex loading and boundary condition. The mathematical model subjected to the variable pressure contours for a particular Mach No., with the gimbal joint boundary condition at the test section end and the roller support at the other end. In this paper stress and fatigue analysis of the variable diffuser has been carried out and life of the variable diffuser has been estimated. Keywords —fatigue analysis; finite element method; fatigue life. I. INTRODUCTION Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. Mechanical components and structures used in day today life contain notches and geometrical discontinuities in them. For example, shafts have keyways in them and pressure vessels contain openings for the operational requirements. These notches, holes, keyways produce stress concentrations in the structure. Notches and keyways can be the region where crack initiation takes place which leads to crack propagation and finally failure of the structure when the stresses higher than the nominal value. Therefore predicting fatigue strength of the component is relevant considering design and safety of the component. Hence fatigue crack initiation life can be estimated based on local stress-strain approach. Wind tunnel is used for aerodynamic flow simulation around the scaled models for force and moment measurements. Wind tunnel testing is indispensible in the design phase of any vehicle flying (subsonic to supersonic) for its aerodynamic characterisation. There are two types of wind tunnels open circuit and closed circuit wind tunnels. In open circuit tunnels the high pressure air stored in the reservoir is forced on to the model through a nozzle to get the required Mach no and then is let out to the atmosphere with the aid of a diffuser. Whereas in case of close circuit tunnel the high pressure compressed air is recalculated in a close circuit. Variable diffuser is one of the components in the wind tunnel circuit. The CSIR-NAL trisonic wind tunnel is more than 50 years old. The diffuser of the wind tunnel needs to be analyzed for fatigue life. The literature reviews show that the linear static analysis has to be carried out for the given loads and then wind tunnel runs are to be used for cyclic loading case for fatigue.
This paper presents the life estimation of the diffuser structure. Literature shows that the welds are the source of failure in case of welded structure; hence the estimation of its life is very critical. There are two kinds of methods... more
This paper presents the life estimation of the diffuser structure. Literature shows that the welds are the source of failure in case of welded structure; hence the estimation of its life is very critical. There are two kinds of methods for life estimation stress life approach and strain life approach which have been validated for simple problems. Stress life approach was identified as appropriate for life estimation of the variable diffuser. There are papers indicating the methodology for life estimation using commercial software for life prediction. Here, OptistructHyper-Works for pre-processing and solver and Hyper-ViewHyper-Works for post processing has been used for the indeterminate structure, complex loading and boundary condition. The mathematical model subjected to the variable pressure contours for a particular Mach No., with the gimbal joint boundary condition at the test section end and the roller support at the other end. In this paper stress and fatigue analysis of the ...
