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ANSYS Basic Concepts for ANSYS Structural Analysis. Disciplines and Element Types Analysis Types Linear Analysis and Nonlinear Analysis Material Models Failure Criteria of Materials. Contents. Disciplines and Element Types. Structural Analysis Thermal Analysis Fluid Dynamic Analysis
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ANSYS Basic Concepts for ANSYS Structural Analysis
Disciplines and Element Types Analysis Types Linear Analysis and Nonlinear Analysis Material Models Failure Criteria of Materials Contents
Disciplines and Element Types • Structural Analysis • Thermal Analysis • Fluid Dynamic Analysis • Electric Field Analysis • Magnetic Field Analysis • Coupled-field Analysis
Examples • Example 1: Thermal Stress Analysis • Example 2: Structure-Fluid Interactions • Example 3: Thermal Actuator
Element Types • ANSYS elements are classified according to • Discipline • Dimensionality • Geometry • Order • Example • SOLID45: 3D hexahedral linear structural element • PLANE67: 2D quadralateral linear coupled thermal-electric element
Static Analysis Dynamic Analysis Transient Analysis Modal Analysis Harmonic Response Analysis etc. Buckling Analysis Structural Analysis Static, Transient, Modal, Harmonic, Buckling, etc. Thermal Analysis Steady-state, Transient Electric Field Analysis Static, Transient, Modal, Harmonic etc. Analysis Types
Transient Analysis • Inertia forces • Damping forces • Elastic forces • External forces
Static Analysis • When dynamic effects can be neglected, a problem can be solved statically. • Dynamic effects can be neglected only when the deformation velocity and acceleration are small. • Two cases: • Steady-state solution • approximation solution for a real-world problem.
Modal Analysis • Modal analysis is to analysis a structure under free vibration. • The solutions typically include • Vibration frequencies (or periods) • Vibration modes
Harmonic Response Analysis • Harmonic response analysis is to analysis a structure under periodic excitation of external forces. • The solutions typically include maximum responses under various frequencies of external forces
Responses Loads Linear Analysis • Small deformation • Hooke’s law appies • No status or topological changes, eg., contacts
Nonlinear Analysis • Geometric nonlinearity • Material nonlinearity • Status nonlineaity
Material Models • Material models are mathematically represented by a set of equations called constitutive equations. • The constitutive equations describe the relations between stresses and strains (or strain rates). • The parameters in the constitutive equations are called material parameters. • ANSYS provides many material models to be chosen from.
Elastic materials (a) Nonlinear elastic (b) Hysteresis elastic (c) Linear Elastic (a) Stress Strain (b) Stress Strain (c) Stress Strain Elastic vs. Plastic
Plastic materials Stress Strain Elastic vs. Plastic
Nonvisous materials Stress Time Strain Time Viscous vs. Nonviscous
Visous materials Time Time Viscous vs. Nonviscous Stress Strain
Creeping Stress Strain Time Time Strain Stress Time Time Viscous vs. Nonviscous Stress Relaxation
Homogeneous vs. Heterogeneous • A material body is said to be homogeneous if it has uniform material properties everywhere in the body. • Otherwise it is said to be heterogeneous. • Note that, homogeneousness does not necessarily imply isotropy.
Isotropic, Anisotropic, and Othothropic Materials • A material is said to be isotropic if it has the same material properties along any directions in the body. • Otherwise it is said to be anisotropic. • An anisotropic material is said to be orthotropic, if the planes of material symmetry are mutually orthogonal.
Isotropic, Anisotropic, and Othothropic Materials Hooke’s Law for Isotropic Material Hooke’s Law for Anisotropic Material Hooke’s Law for Orthotropic Material
Ductile Material Stress Stress Strain Strain Ductile vs. Brittle Brittle Material
Failure Criteria for Brittle Materials Maximum Principal Stress Failure Criteria: • Fracture will occur when tensile stress is greater than ultimate tensile strength, i.e.,
Failure Criteria for Ductile Materials Tresca Failure Criteria: • Yielding will occur when shear stress is greater than shear yield strength, i.e., or
Failure Criteria for Ductile Materials von Mises Failure Criteria: • Yielding will occur when the von Mises stress is greater than yield strength, i.e.,