Difference between Optistruct and Nastran ?

Altair Forum User

Can anybody help me to understand difference between Optistruct and Nastran .? (As a solver and modeling )

Any document is also very helpful....

 

Thanks in advance....

 

Rahul Rajan_21763

Hi,

Using Altair Hyperworks you would have access to Optistruct (Linear & Non linear finite element solver,Optimization).

Cards used in most of the analysis type is similar for Optistruct & Nastran.Refer Optistruct user guide for detailed information.

Let us know if want to know any specific information about any analysis.

Regards

Rahul R

Rahul_P1

Altair® OptiStruct® is an industry proven, modern structural analysis solver for linear and nonlinear structural problems under static and dynamic loadings. It is the market-leading solution for structural design and optimization. Based on finite element and multi-body dynamics technology, and through advanced analysis and optimization algorithms, OptiStruct helps designers and engineers rapidly develop innovative, lightweight and structurally efficient designs. OptiStruct is used by thousands of companies worldwide to analyze and Optimize structures for their strength, durability and NVH (noise, vibration and harshness) characteristics. Refer to Features for a list of solutions available in OptiStruct.

Finite element solutions via OptiStruct include:

•Linear static analysis

•Nonlinear implicit quasi-static analysis

•Linear buckling analysis

•Normal modes analysis

•Complex eigenvalue analysis

•Frequency response analysis

•Random response analysis

•Linear transient response analysis

•Geometric nonlinear explicit and implicit analysis

•Linear fluid-structure coupled (acoustic) analysis

•Linear steady-state heat transfer analysis

•Coupled thermal-structural analysis

•Nonlinear steady-state heat transfer analysis

•Linear transient heat transfer analysis

•Contact-based thermal analysis

•Inertia relief analysis with static, nonlinear contact, modal frequency response, and modal transient response analyses

•Component Mode Synthesis (CMS) for the generation of flexible bodies for multi-body dynamics analysis

•Reduced matrix generation

•One-step (inverse) sheet metal stamping analysis

•Fatigue analysis

A typical set of finite elements including shell, solid, bar, scalar, and rigid elements as well as loads and materials are available for modeling complex events.

Multi-body dynamics solutions integrated via OptiStruct for rigid and flexible bodies include:

•Kinematics analysis

•Dynamics analysis

•Static and quasi-static analysis

•Linearization

All typical types of constraints like joints, gears, couplers, user-defined constraints, and high-pair joints can be defined. High pair joints include point-to-curve, point-to-surface, curve-to-curve, curve-to-surface, and surface-to-surface constraints. They can connect rigid bodies, flexible bodies, or rigid and flexible bodies. For this multi-body dynamics solution, the power of Altair MotionSolve has been integrated with OptiStruct.

 

Structural Design and Optimization

Structural design tools include topology, topography, and free-size optimization. Sizing, shape and free-shape optimization are available for structural optimization.

In the formulation of design and optimization problems, the following responses can be applied as the objective or as constraints:  compliance, frequency, volume, mass, moment of inertia, center of gravity, displacement, velocity, acceleration, buckling factor, stress, strain, composite failure, force, synthetic response, and external (user-defined) functions. Static, inertia relief, nonlinear quasi-static (contact), normal modes, buckling, and frequency response solutions can be included in a multi-disciplinary optimization setup.

Topology, topography, size, and shape optimization can be combined in a general problem formulation.

 

Topology Optimization

Topology optimization generates an optimized material distribution for a set of loads and constraints within a given design space. The design space can be defined using shell or solid elements, or both. The classical topology optimization set up solving the minimum compliance problem, as well as the dual formulation with multiple constraints are available. Constraints on von Mises stress and buckling factor are available with limitations. Manufacturing constraints can be imposed using a minimum member size constraint, draw direction constraints, extrusion constraints, symmetry planes, pattern grouping, and pattern repetition. A conceptual design can be imported in a CAD system using an iso-surface generated with OSSmooth, which is part of the OptiStruct package.

Free-size optimization is available for shell design spaces. The shell thickness or composite ply-thickness of each element is the design variable.

 

Topography Optimization

Topography optimization generates an optimized distribution of shape based reinforcements such as stamped beads in shell structures. The problem set up is simply done by defining the design region, the maximum bead depth and the draw angle. OptiStruct automatically provides the design variable creation and optimization control. Manufacturing constraints can be imposed using symmetry planes, pattern grouping, and pattern repetition.

 

Size and Shape Optimization

General size and shape optimization problems can be solved. Variables can be assigned to perturbation vectors, which control the shape of the model. Variables can also be assigned to properties, which control the thickness, area, moments of inertia, stiffness, and non-structural mass of elements in the model. All of the variables supported by OptiStruct can be assigned using HyperMesh. Shape perturbation vectors can be created using HyperMorph.

The reduction of local stress can be accomplished easily using free-shape optimization. Shape perturbations are automatically determined by OptiStruct (based on the stress levels in the design) when using this technique.

The layout of laminated shells can be improved by modifying the ply thickness and ply angle of these materials.

 

Multi-body Dynamics Analysis

Different solution sequences for the analysis of mechanical systems are available; these include Kinematics, Dynamics, Static, and Quasi-static solutions.

Flexible bodies can be derived from any finite element model defined in OptiStruct.

Altair Forum User

 

HELLO,

when converting the (.nas) file and (.fem ) file into hypermesh there was a problem in the optimization card, that of the varriable. Can anybody help me to understand Where does this problem come from? and how can I solve it?

 

Regards,

 

HAJAR

Altair Forum User

HELLO,

when converting the (.nas) file and (.fem ) file into hypermesh there was a problem in the optimization card, that of the varriable. 

normally when converting ilo you have to change DTPL by the command TOPVAR !!/emoticons/default_mellow.png' title=':mellow:' />

Can anybody help me to understand Where does this problem come from? and how can I solve it?

 

Regards,

 

HAJAR

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<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi,

 

Not all parameters/cards are supported. Few cards may not be supported in OptiStruct which are used in NASTRAN.

 

Please create missing cards in OptiStruct and try again.