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non-linear analysis options 1
- Thread starter rob768
- Start date
Hi,
The Model | Load | Nonlinear menu is used to define all the types of Nonlinear Analysis.
Nonlinear behavior can be modeled using many different methods. In some structures, the kinematic relationship is nonlinear and displacements and rotations can be large. This behavior is known as geometric nonlinear or large displacement behavior. For this behavior, equilibrium is satisfied in the deformed configuration.
A related effect to geometric nonlinear analysis is follower force effects. A follower force changes its orientation as the structure deforms, whereas a small displacement analysis (for example, Linear Statics), the force always maintains its initial orientation. Large displacement effects are set as a parameter using the Analysis Set Manager (Model | Analysis), by selecting the Large Displacement (LGDISP) check-box in the NASTRAN Bulk Data Options dialog box .
A more obvious nonlinear effect is due to material nonlinearity, where there is no longer a linear relationship between forces and displacements. The material stiffness can change during the analysis and the material may yield, perhaps resulting in plastic deformation. NX Nastran for FEMAP can represent materials that exhibit nonlinear elastic and plastic behavior. Material Nonlinearity can be set-up using the Model | Material menu and choosing the Nonlinear button. Elastic-plastic materials can be modeled using either Von-Mises or Tresca Yield Criteria, while other materials can take advantage of the extended Material Model which includes formats for Mohr-Coulomb and Drucker-Prager material definitions.
Time dependent effects of long term load application can be taken into account using a material with creep properties defined using an Empirical Model or a Tabular Model. Creep is a time dependent phenomenon where strain changes under constant stress. It is a material relaxation whose rate is both load and/or temperature dependent.
Representing materials like rubber require the consideration of element strains that are nonlinear functions of element deformation and possibly large strains. NX Nastran for FEMAP can model this type of material behavior using hyperelastic materials.
To learn more go to the Femap Help...
The Model | Load | Nonlinear menu is used to define all the types of Nonlinear Analysis.
Nonlinear behavior can be modeled using many different methods. In some structures, the kinematic relationship is nonlinear and displacements and rotations can be large. This behavior is known as geometric nonlinear or large displacement behavior. For this behavior, equilibrium is satisfied in the deformed configuration.
A related effect to geometric nonlinear analysis is follower force effects. A follower force changes its orientation as the structure deforms, whereas a small displacement analysis (for example, Linear Statics), the force always maintains its initial orientation. Large displacement effects are set as a parameter using the Analysis Set Manager (Model | Analysis), by selecting the Large Displacement (LGDISP) check-box in the NASTRAN Bulk Data Options dialog box .
A more obvious nonlinear effect is due to material nonlinearity, where there is no longer a linear relationship between forces and displacements. The material stiffness can change during the analysis and the material may yield, perhaps resulting in plastic deformation. NX Nastran for FEMAP can represent materials that exhibit nonlinear elastic and plastic behavior. Material Nonlinearity can be set-up using the Model | Material menu and choosing the Nonlinear button. Elastic-plastic materials can be modeled using either Von-Mises or Tresca Yield Criteria, while other materials can take advantage of the extended Material Model which includes formats for Mohr-Coulomb and Drucker-Prager material definitions.
Time dependent effects of long term load application can be taken into account using a material with creep properties defined using an Empirical Model or a Tabular Model. Creep is a time dependent phenomenon where strain changes under constant stress. It is a material relaxation whose rate is both load and/or temperature dependent.
Representing materials like rubber require the consideration of element strains that are nonlinear functions of element deformation and possibly large strains. NX Nastran for FEMAP can model this type of material behavior using hyperelastic materials.
To learn more go to the Femap Help...
- Thread starter
- #3
I just re-read my onwn post and admit i am not very clear. What i want is to model contact between two bodies using contact elements, and use axis-symmetric elements for the circular shaped bodies. I want to calculate the amount of plastic stress , but can't get it work. The stress calculation appears to be lineair and i was wondering if this was related to the use of axisymmetric AND contact elements.
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1
- #4
BlasMolero
Mechanical
Dear Rob,
NX NASTRAN v8.5 Edge-to-Edge Contact between the edges of axisymmetric, plane stress, and plane strain elements is only supported by :
• Solution 101 and consecutive solutions 103, 105, 111, and 112 for elements in the XZ or XY plane
• Solution 601 for elements in the XZ plane only
For NX NASTRAN Basic Nonlinear Analysis (SOL106) you can use 3-D Slide Line Contact Analysis and node-to-node CGAP elements:
Slide line contact lets you model interactions between two deformable bodies. One of the deformable bodies is called the master and the other is called the slave. The modeling of interaction requires that you define contact regions in terms of slide lines. You may specify as many slide lines as you need.
A slide line contact region consists of a master line and a slave line. A master line is a list of grid points in the topological order on the master body. A slave line is a list of grid points in the topological order on the slave body. The grid points on the master line are called the master nodes, and on the slave line are called the slave nodes. A line segment joining two consecutive master nodes is called a master segment. Thus a master line, in general, consists of number of master segments. A minimum of one master segment consisting of two master nodes are required for the master line. Similar to master line, a slave line, in general, consist of a number of slave segments. However, a slave line may not have any slave segments; it may have just one slave node. Check NX NASTRAN manuals, everything is there.
Best regards,
Blas.
~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director
IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:
NX NASTRAN v8.5 Edge-to-Edge Contact between the edges of axisymmetric, plane stress, and plane strain elements is only supported by :
• Solution 101 and consecutive solutions 103, 105, 111, and 112 for elements in the XZ or XY plane
• Solution 601 for elements in the XZ plane only
For NX NASTRAN Basic Nonlinear Analysis (SOL106) you can use 3-D Slide Line Contact Analysis and node-to-node CGAP elements:
Slide line contact lets you model interactions between two deformable bodies. One of the deformable bodies is called the master and the other is called the slave. The modeling of interaction requires that you define contact regions in terms of slide lines. You may specify as many slide lines as you need.
A slide line contact region consists of a master line and a slave line. A master line is a list of grid points in the topological order on the master body. A slave line is a list of grid points in the topological order on the slave body. The grid points on the master line are called the master nodes, and on the slave line are called the slave nodes. A line segment joining two consecutive master nodes is called a master segment. Thus a master line, in general, consists of number of master segments. A minimum of one master segment consisting of two master nodes are required for the master line. Similar to master line, a slave line, in general, consist of a number of slave segments. However, a slave line may not have any slave segments; it may have just one slave node. Check NX NASTRAN manuals, everything is there.
Best regards,
Blas.
~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director
IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:
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