The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
H G Georgiadis - One of the best experts on this subject based on the ideXlab platform.
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Tangential Displacement effects in the wedge indentation of an elastic half space an integral equation approach
Computational Mechanics, 1998Co-Authors: H G GeorgiadisAbstract:The idea of considering Tangential-Displacement effects in a classical elastostatic contact problem is explored in this paper. The problem involves the static frictionless indentation of a linearly elastic half-plane by a rigid wedge, and its present formulation implies that the Tangential surface Displacements are not negligible and should thus be coupled with the normal surface Displacements in imposing the contact zone boundary conditions. L.M. Brock introduced this idea some years ago in treating self-similar elastodynamic contact problems, and his studies indicated that such a formulation strongly influences the contact-stress behavior at half-plane points making contact with geometrical discontinuities of the indentor. The present work again demonstrates, by studying an even more classical problem, that the aforementioned considerations eliminate contact-stress singularities and therefore yield a more natural solution behavior. In particular, the familiar wedge-apex logarithmic stress-singularity encountered within the standard formulation of the problem (i.e. by avoiding the Tangential Displacement in the contact boundary condition) disappears within the proposed formulation. The contact stress beneath the wedge apex takes now a finite value depending on the wedge inclination angle and the material constants. By utilizing pertinent integral relations for the Displacement/stress field in the half-plane, an unusual mixed boundary-value problem results whose solution is obtained through integral equations.
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dynamic indentation of an elastic half plane by a rigid wedge frictional and Tangential Displacement effects
International Journal of Solids and Structures, 1995Co-Authors: H G Georgiadis, L M Brock, A P RigatosAbstract:Abstract A dynamical contact problem is studied in this paper. It involves an elastic half-plane which is indented by a rigid wedge-shaped body. In an effort to depart from the classical formulation of this problem, we consider frictional and Tangential-Displacement effects. More specifically, it is assumed that Coulomb friction develops between the contacting bodies and also that the Tangential surface Displacements are not negligible and should thus be coupled with the normal surface Displacements in imposing the contact-zone boundary conditions. Certainly, the foregoing considerations model the dynamic indentation of an elastic half-plane in a more realistic way than the usual frictionless and uncoupled formulation. The contact region is assumed to extend at a constant sub-Rayleigh speed (this situation can be achieved by conveniently specifying the indentor kinetics), whereas, due to symmetry, friction may act in opposing directions on opposite sides of the indentor. The study exploits the problem's self-similarity by utilizing homogeneous-function techniques along with the Riemann-Hilbert problem analysis. As the present exact analysis shows, both the sign reversal of the Tangential traction and the coupling of the Displacement components along the contact length strongly influence the contact-stress behavior at the wedge-apex station. In particular, friction tends to create a power-type singularity at the changeover point of boundary conditions (due to symmetry, this point here is the point where the wedge apex makes contact with the half-plane surface), whereas the Tangential-Displacement effect tends to eliminate singular behavior there. Representative numerical results are given for the normal stress and Tangential Displacement along the contact zone, and the relation between the contact-zone expansion velocity and the indentor velocity.
Joris Degroote - One of the best experts on this subject based on the ideXlab platform.
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dynamic load and stress analysis of a large horizontal axis wind turbine using full scale fluid structure interaction simulation
Renewable Energy, 2019Co-Authors: Gilberto Santo, Mathijs Peeters, W Van Paepegem, Joris DegrooteAbstract:Abstract A dynamic load and stress analysis of a wind turbine is carried out using transient fluid-structure interaction simulations. On the structural side, the three 50 m long commercial glass-fiber epoxy blades are modelled using shell elements, accurately including the properties of the composite materials. On the fluid side, a hexahedral mesh is obtained for every blade and for the hub of the machine. These meshes are then overlaid to a structured background mesh through an overset technique. The Displacements prescribed by the structural solver are imposed on top of the rigid rotation of the turbine. The atmospheric boundary layer (ABL) is included using the k-epsilon turbulence model. The computational fluid dynamics (CFD) and computational solid mechanics (CSM) solvers are strongly coupled using an in-house code. The transient evolution of loads, stresses and Displacements on each blade is monitored throughout the simulated time. The ABL induces oscillating axial Displacements in the outboard region of the blade. Furthermore, the influence of gravity on the structure is accounted for and investigated, showing that it largely affects the Tangential Displacement of the blade. The oscillating deformations lead to sensible differences in the torque provided by each blade during its rotation.
A P Rigatos - One of the best experts on this subject based on the ideXlab platform.
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dynamic indentation of an elastic half plane by a rigid wedge frictional and Tangential Displacement effects
International Journal of Solids and Structures, 1995Co-Authors: H G Georgiadis, L M Brock, A P RigatosAbstract:Abstract A dynamical contact problem is studied in this paper. It involves an elastic half-plane which is indented by a rigid wedge-shaped body. In an effort to depart from the classical formulation of this problem, we consider frictional and Tangential-Displacement effects. More specifically, it is assumed that Coulomb friction develops between the contacting bodies and also that the Tangential surface Displacements are not negligible and should thus be coupled with the normal surface Displacements in imposing the contact-zone boundary conditions. Certainly, the foregoing considerations model the dynamic indentation of an elastic half-plane in a more realistic way than the usual frictionless and uncoupled formulation. The contact region is assumed to extend at a constant sub-Rayleigh speed (this situation can be achieved by conveniently specifying the indentor kinetics), whereas, due to symmetry, friction may act in opposing directions on opposite sides of the indentor. The study exploits the problem's self-similarity by utilizing homogeneous-function techniques along with the Riemann-Hilbert problem analysis. As the present exact analysis shows, both the sign reversal of the Tangential traction and the coupling of the Displacement components along the contact length strongly influence the contact-stress behavior at the wedge-apex station. In particular, friction tends to create a power-type singularity at the changeover point of boundary conditions (due to symmetry, this point here is the point where the wedge apex makes contact with the half-plane surface), whereas the Tangential-Displacement effect tends to eliminate singular behavior there. Representative numerical results are given for the normal stress and Tangential Displacement along the contact zone, and the relation between the contact-zone expansion velocity and the indentor velocity.
Gunnar Bjoourkman - One of the best experts on this subject based on the ideXlab platform.
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solution of large Displacement contact problems with friction using newton s method for generalized equations
International Journal for Numerical Methods in Engineering, 1992Co-Authors: Anders Klarbring, Gunnar BjoourkmanAbstract:This work is concerned with the formulation and numerical realization of large Displacement contact problems with friction. A restricted class of contact problems is treated, where the deformation of one of the contacting bodies is prescribed. The formulation utilizes a particular convected co-ordinate chart to define, firstly, Tangential components for all potential contact points and, secondly, the notion of incremental Tangential Displacement. By writing the discretized problem as a generalized equation in the sense of Robinson it is made clear how Newton's method may be extended to this kind of non-differentiable problems. The proposed algorithm is verified by several numerical examples.
Alfredo Taboada - One of the best experts on this subject based on the ideXlab platform.
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stress and strain from striated pebbles theoretical analysis of striations on a rigid spherical body linked to a symmetrical tensor
Journal of Structural Geology, 1993Co-Authors: Alfredo TaboadaAbstract:Striations on a pebble are interpreted as resulting from slip due to either a homogeneous stress state or a small homogeneous coaxial deformation in the matrix. In terms of stress, striations are assumed to be parallel to the applied shear stress. In terms of strain, striations are considered to be parallel to the relative Tangential Displacement between the pebble and adjacent matrix particles. Slip on the surface of a spherical rigid body enclosed in a deformable matrix (brittle or ductile) is theoretically analysed for different stress and strain regimes. The analysis predicts the topology of the resulting striations and singularity distribution on the sphere. Both in terms of stress and strain, the Tangential vector field on the sphere's surface derives from a potential function proportional to the magnitude of the normal vector field. Tangential and normal vectors represent either shear and normal stresses, or Displacement components (in terms of strain). The plot of continuous curves parallel to striations (integral curves) and of equipotential curves on the sphere, allows simultaneously the magnitude and orientation of the Tangential and normal vector fields to be visualized. Close to singular points, the integral curves correspond to power laws and the equipotentials correspond to conic sections. This theoretical analysis allows graphical method for estimating the stress ratio (σ2 − σ3)(σ1 − σ3) from striated faults to be proposed, once the orientations of the principal stress directions are known (i.e. by means of other graphical methods).
