ansys basic concepts for ansys structural analysis
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
ANSYSBasic Concepts for ANSYS Structural Analysis
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Contents1 Disciplines and Element Types2 Analysis Types3 Linear Analysis and Nonlinear
Analysis4. Material Models5. Failure Criteria of Materials
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• Structural Analysis• Thermal Analysis• Fluid Dynamic Analysis• Electric Field Analysis• Magnetic Field Analysis• Coupled-field Analysis
Disciplines and Element Types
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• Example 1: Thermal Stress Analysis• Example 2: Structure-Fluid Interactions• Example 3: Thermal Actuator
Examples
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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
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Analysis Types
• 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.
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Transient Analysis
• Inertia forces• Damping forces• Elastic forces• External forces
FKDDCDM
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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.
FKD
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Modal Analysis
• Modal analysis is to analysis a structure under free vibration.
• The solutions typically include– Vibration frequencies (or periods)– Vibration modes
0KDDCDM
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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
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Linear Analysis and Nonlinear Analysis
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Linear Analysis
• Small deformation• Hooke’s law appies• No status or
topological changes, eg., contacts
Loads
Responses
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Nonlinear Analysis
• Geometric nonlinearity• Material nonlinearity• Status nonlineaity
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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.
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Elastic vs. Plastic
Elastic materials(a) Nonlinear elastic(b) Hysteresis elastic(c) Linear Elastic
Stress
Strain
(a)
Stress
Strain
(b)
(c)
Stres
s
Strain
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Elastic vs. Plastic
Plastic materials
Strain
Stress
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Viscous vs. Nonviscous
Nonvisousmaterials
Time
Stress
TimeS
train
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Viscous vs. Nonviscous
Visousmaterials
Stress
Strain
Time
Time
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Viscous vs. Nonviscous
Creeping
Time
Stress
Time
Strain
Time
Strain
Time
Stress
Stress Relaxation
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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.
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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.
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Isotropic, Anisotropic, and Othothropic Materials
G
G
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Dσε
zx
zxzx
yz
yzyz
xy
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y
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x
xzx
z
zz
x
xyx
z
zyz
y
yy
z
zxz
y
yxy
x
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G
G
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Hooke’s Law for Isotropic Material
Hooke’s Law for Anisotropic
Material
Hooke’s Law for Orthotropic
Material
z
zx
x
xz
z
zy
y
yz
y
yx
x
xy
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Failure Criteria of Materis
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Ductile vs. Brittle
Ductile Material
Strain
Stress
Strain
Stress
Brittle Material
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Failure Criteria for Brittle Materials
Maximum Principal Stress Failure Criteria:• Fracture will occur when tensile stress is
greater than ultimate tensile strength, i.e.,
u 1
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Failure Criteria for Ductile Materials
Tresca Failure Criteria:• Yielding will occur when shear stress is
greater than shear yield strength, i.e.,
2231 y
y 31
or
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Failure Criteria for Ductile Materials
von Mises Failure Criteria:• Yielding will occur when the von Mises
stress is greater than yield strength, i.e.,
ye 213
232
2212
1