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The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman
The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman
Theses and Dissertations
As part of a joint AFRL/DAGSI turbine blade research effort, a computer program has been developed that uses a von Karman large-deflection two-dimensional finite element approximation to determine stress levels and patterns in isotropic thin plates. The dynamic loading of various plates has been carried out in order to model a high cycle fatigue situation. The research considered the various effects of mode shapes, resident frequency, non-linear cyclic effect, endurance limits, and stress variations within a high cycle fatigue environment. Two main initiatives were taken. First, a transient analysis tool was developed that calculates stress and displacement patterns over a …
Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha
Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha
Theses and Dissertations
Most advanced composite materials have nonlinear stress versus strain curves--grossly so in the laminas shear direction. If linear approximations are used, overly conservative design will result. This thesis expands the usefulness of the Automated Structural Optimization System (ASTROS) finite element (FE) program by incorporating a newly developed capability to include material nonlinearities. By dividing a FE problem into several intervals, and incorporating the changing nature of the nonlinear material properties within each element, a good approximation of the laminate's actual stresses and strains can be obtained without the undue experimentation involved in testing every individual configuration. Each material property is …
The Non-Linear Dynamics Of Composite Cylindrical Shells, James M. Greer Jr.
The Non-Linear Dynamics Of Composite Cylindrical Shells, James M. Greer Jr.
Theses and Dissertations
The non-linear dynamic behavior of suddenly loaded composite shells is the subject of this research. The objective of research is two-fold: (1) to characterize the apparently random physical behavior sometimes observed in the finite element analysis as either numerical instability, chaotic behavior, or both; and (2) to develop criteria for choosing time steps for the finite element model, referred to as DSHELL. This displacement based finite element code is capable of dynamic analysis of plates, arches, and cylindrical shells undergoing large displacements and moderately large rotations during deformation. DSHELL uses a 36-DOF isoparametric shell element to obtain numerical results. A …