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Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781722458737 Category : Languages : en Pages : 34
Book Description
Crack propagation and closure behavior of thin, and thick middle crack tension specimens under constant amplitude loading were investigated using a three dimensional elastic plastic finite element analysis of fatigue crack propagation and closure. In the thin specimens the crack front closed first on the exterior (free) surface and closed last in the interior during the unloading portion of cyclic loading; a load reduced displacement technique was used to determine crack opening stresses at specified locations in the plate from the displacements calculated after the seven cycle. All the locations were on the plate external surface and were located near the crack tip, behind the crack tip, at the centerline of the crack. With this technique, the opening stresses at the specified points were found to be 0.52, 0.42, and 0.39 times the maximum applied stress. Chermahini, R. G. and Blom, Anders F. Unspecified Center NAG1-529...
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781722458737 Category : Languages : en Pages : 34
Book Description
Crack propagation and closure behavior of thin, and thick middle crack tension specimens under constant amplitude loading were investigated using a three dimensional elastic plastic finite element analysis of fatigue crack propagation and closure. In the thin specimens the crack front closed first on the exterior (free) surface and closed last in the interior during the unloading portion of cyclic loading; a load reduced displacement technique was used to determine crack opening stresses at specified locations in the plate from the displacements calculated after the seven cycle. All the locations were on the plate external surface and were located near the crack tip, behind the crack tip, at the centerline of the crack. With this technique, the opening stresses at the specified points were found to be 0.52, 0.42, and 0.39 times the maximum applied stress. Chermahini, R. G. and Blom, Anders F. Unspecified Center NAG1-529...
Author: Zhuang He Publisher: ISBN: Category : Elastic plates and shells Languages : en Pages : 165
Book Description
Theoretical, numerical and experimental studies involving elastic plate components, weakened by through-the-thickness cracks and subjected to loading parallel to the plane of the plate, are often based on plane stress or plane strain simplifications. These simplifications essentially reduce the dimensionality of the physical three-dimensional problem and enable the achievement of effective analytical and numerical solutions for many important practical problems. The influence of various three-dimensional effects, such as the variation of stresses across the plate thickness, effects of the three-dimensional corner (vertex) singularities and coupling of fracture modes II and III, on the deformation and stresses near the crack front are at present largely ignored or viewed as negligible for all practical purposes. As a result of this view, the outcomes of experimental studies and fracture tests are also commonly analysed within the framework of the plane theories of elasticity. Nevertheless, a number of theoretical and experimental studies over the past two decades have demonstrated that the predictions made within these theories can be unsatisfactory and the effect of three-dimensional stress states at the crack front on deformation, fatigue and fracture of plate components can be significant. This thesis aims to elucidate the role of three-dimensional stress states in the deformation, fracture and fatigue phenomena further. The main outcomes of this thesis are: (1) the development and validation of a simplified method for the evaluation of the fatigue crack front shapes and their effect on the steady-state fatigue crack growth rates in plate components; (2) investigation of the effect of three-dimensional corner (vertex) singularities on the stress intensities and displacement field near the crack front; and (3) development and validation of a new experimental approach for the evaluation of mode I and mode II stress intensity factors from the measurement of the out-of-plane displacements in the near crack tip region, which are affected by three-dimensional effects, and, in particular, by the 3D corner (vertex) singularity. This new research is important in many engineering contexts. For example, the new theoretical model, which takes into account the actual shape of the crack front, can be utilised in advanced fatigue life calculations, as well as in failure investigations. The latter is possible as the shape of the fatigue crack front can now be related to the parameters of fatigue loading. The new experimental approach developed in this thesis can be useful in fracture characterisation of thick plate components with through-cracks. This approach specifically addresses the situation when the Kdominance zone, or William's solution convergence domain, are relatively small. In this case, the data extraction region can be affected by the three-dimensional stress states leading to significant errors in the evaluation of the stress intensity factors when using traditional approaches. This thesis is presented in the form of a compendium of published papers that are the summation of the research undertaken by the author. The five articles which form the main body of the thesis are united by a common theme, which is the investigation of three-dimensional effects near the crack front on stresses and displacements, fracture and fatigue phenomena. Two appendices are also included; they represent a compilation of the candidate's publications related to the main topic of the thesis.
Author: L. Yingzhi Publisher: ISBN: Category : Eigenfunction expansion Languages : en Pages : 14
Book Description
This paper deals with fracture analyses in three-dimensional bodies containing a surface crack. A general solution of stress-strain fields at the crack tip is proposed. Based on the stress-strain fields obtained, a high-order, three-dimensional special element is established to calculate the stress-intensity factors in a plate with surface crack. The variation of stress-intensity factors with geometric parameters is investigated.
Author: G. C. Sih Publisher: ISBN: Category : Languages : en Pages : 62
Book Description
Finite element procedures are used to solve two- and three-dimensional problems of cracks in elastic bodies. The two-dimensional, plane strain analysis is concerned with the effect of a crack approaching a free edge at right angles. The strain energy density fracture criterion is used to determine the direction of fracture for various distances from the crack tip to thr free edge. These results provide a possible mechanism for the creation of the shear lip region in a plate of finite thickness. The three-dimensional isoparametric finite element procedure is specialized for application to crack problems by the introduction of elements which model the crack edge singularity. The finite element approach is used to study the problem of a through crack in a finite thickness plate subject to symmetric loading. Variations of the stress intensity factor, near field stress components, and strain energy density through the plate thickness are reported.
Author: Emmanuel Gdoutos Publisher: Springer Nature ISBN: 3030478831 Category : Technology & Engineering Languages : en Pages : 345
Book Description
This book presents the proceedings of the 3rd edition of the International Conference on Theoretical, Applied and Experimental Mechanics. The papers focus on all aspects of theoretical, applied and experimental mechanics, including biomechanics, composite materials, computational mechanics, constitutive modeling of materials, dynamics, elasticity, experimental mechanics, fracture mechanics, mechanical properties of materials, micromechanics, nanomechanics, plasticity, stress analysis, structures, wave propagation.
Author: National Aeronautics and Space Administration (NASA)
Author: National Aeronautics and Space Administration (NASA)
Author: J. C. Newman
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Author: Zhuang He
Author: 
Author: L. Yingzhi
Author: G. C. Sih
Author: 
Author: 
Author: Emmanuel Gdoutos