Product help with community knowledge

# Which Analysis to Use?

1. 1. Linear
2. 2. Nonlinear
3. 3. Thermal
4. 4. Fluid Flow
5. 5. Electrostatic
6. 6. Mass Transfer
7. 7. Multiphysics

Use the following guidelines to help choose the correct analysis type for your situation.

## Linear

Linear analyses follow these basic assumptions (unless otherwise noted):

• The change in direction of the loading due to deformation is small and can be neglected.
• The materials are linear within the elastic region on the stress-strain curve.
• The boundary conditions do not change.

Static Stress with Linear Material Models

• Calculate the displacements and stresses due to static loads.
• The magnitude or direction of the loading will not change over time.
• No inertial effects. The mass of the model is used to determine loads, such as gravity and centrifugal forces.
• Although contact is a nonlinear effect, it can be included in a static stress analysis. The solution becomes iterative.
• Examples: structures (buildings, car frames, truss systems), bodies (valve bodies, ship hulls, housings, support brackets, pressure vessels), press-fits.

Natural Frequency (Modal)

• Calculate the natural frequencies and mode shapes of the model due to purely geometric and material properties.
• Examples: structures (buildings, bridges, towers), shafts, bodies (housings, support brackets).

Natural Frequency (Modal) with Load Stiffening

• Calculate the natural frequencies and mode shapes of the model due to purely geometric and material properties.
• Axial compressive or tensile loads affect the frequency of the system.
• Examples: structures (buildings, bridges, towers), shafts, bodies (housings, support brackets).

Response Spectrum

• Calculate the maximum displacements and stresses due to a spectrum-type load.
• Examples: structures subjected to earthquakes, blast and shock loads, and so on.

Random Vibration

• Calculate the statistical response of a system (displacements and stresses) due to a random vibration, white noise, or a power spectrum density.
• Examples: suspension systems, aerospace components, fans, and pumps.

Frequency Response

• Calculate the steady state response (displacements and stresses) due to a harmonic or sinusoidal load or acceleration.
• Examples: structures with rotating imbalance, frequency sweeps, fans, and pumps

Transient Stress (Direct Integration or Modal Superposition)

• Calculate the displacements and stresses over time due to loads that will vary in a known fashion.
• Inertial effects are included.
• Examples: structures subjected to transient events (buildings, bridges, towers), bodies (housings, support brackets), rotating imbalance.

• Calculate the load that causes your model to buckle due to geometric instability.
• No inertial effects. (The mass of the model is used to determine loads, such as gravity and centrifugal forces.)
• Examples: column designs, structures (buildings, bridges, towers).

Dynamic Design Analysis Method (DDAM)

• Use when you want to calculate the maximum displacements and stresses due to a spectrum-type load.
• Use when designing naval equipment or vessels.
• Examples: exhaust uptakes, masts, propulsion shafts.

## Nonlinear

The assumptions listed for linear analyses are not limitations when doing a nonlinear analysis. Unless indicated otherwise, nonlinear permits the following:

• Rigid body motion and/or rotations are accounted for.
• The materials can be nonlinear, either elastic (such as rubber) or plastic (such as a metal that exceeds the yield strength).
• The boundary conditions can change over time in a known fashion.

MES (Mechanical Event Simulation) with Nonlinear Material Models

• Calculate the displacements, velocities, accelerations, and stresses over time due to dynamic loads.
• The loads can be constant, vary over time, or vary based on calculated results.
• Inertial effects are included.
• Examples: linkages and mechanisms, press-fit, snap-fits, multiple body contact and impact, forming and extruding processes, rubber and foam components (bellows, seats).

Static Stress with Nonlinear Material Models

• Calculate the displacements and stresses due to static loads.
• The loads can be constant, vary between time steps or load cases, or vary based on calculated results.
• Inertial effects are ignored. (The mass of the model is used to determine loads, such as gravity and centrifugal forces.)
• Examples: press-fit, multiple body contact and impact, forming and extruding processes, rubber and foam components (bellows, seats).

Natural Frequency (Modal) with Nonlinear Material Models

• Calculate the natural frequencies and mode shapes of the model.
• The change in frequency due to displacements or changing material properties is not included.
• Loads do not affect the frequencies.
• Boundary conditions are fixed.
• Examples: structures (buildings, bridges, towers), shafts, bodies (housings, support brackets).

MES Riks Analysis

• Calculate the displacements and stresses before and after the model has buckled or collapsed.
• Inertial effects are ignored.
• Examples: columns, components with snap-through behavior.

## Thermal

• Calculate temperature and heat fluxes after an infinite period (steady-state conditions).
• The thermal loads are constant over time.
• Examples: structures (furnaces, insulating wall), electrical components.

Transient Heat Transfer

• Calculate the temperature and heat fluxes over time due to the thermal loads.
• The thermal loads can be constant or change over time.
• The material can change states between a solid and liquid.
• Examples: structures (furnaces, insulating walls, brake systems), electrical components, annealing processes.

## Fluid Flow

• Calculate the velocity and pressure distribution due to the motion of a fluid.
• The fluid has reached a steady-state solution at each time step or load case.
• Inertial effects are ignored.
• Examples: valves, rotating equipment (fans, mixers), wind and drag force analysis, flow measuring devices.

• Calculate the velocity and pressure distribution due to the motion of a fluid.
• The fluid is undergoing an acceleration during the analysis or change over time.
• Inertial effects are included.
• Examples: valves, rotating equipment (fans, mixers), wind and drag force analysis, flow measuring devices.

Flow through Porous Media

• Calculate the velocity and pressure distribution of a fluid passing through a series of filtering layers.
• The flow is through (or dominated by) a fully saturated porous medium.
• The fluid has reached a steady-state solution after an infinite period.
• Inertial effects are ignored.
• Examples: Aquifers, catalyst beds, filters, sedimentary studies.

## Electrostatic

Electrostatic Current and Voltage

• Calculate the current and voltage distribution after an infinite period (steady-state conditions) due to induced voltages and current sources.
• Examples: electrical components (circuit breakers, circuit boards, batteries), piezoelectrics.

Electrostatic Field Strength and Voltage

• Calculate the electric field and voltage distribution after an infinite period (steady-state conditions) in an insulator due to induced voltages and charges.
• Examples: insulators, micro electro mechanical systems (MEMS).

## Mass Transfer

Transient Mass Transfer

• Calculate the concentration over time of multiple species.
• The transport of the species is due to random molecular motion.
• Examples: chemical species through a membrane (drug delivery).

## Multiphysics

Steady Coupled Fluid Flow and Thermal

• Calculate the temperatures, heat fluxes, velocities, and pressure distribution in a fluid or a model with fluid and solid parts.
• The fluid has reached a steady-state solution at each time step or load case.
• The thermal results have reached a steady-state solution at each time step or load case.
• Inertial effects are ignored.
• Examples: heat exchangers, circuit boards, cooling/heating system design, HVAC systems.

Transient Coupled Fluid Flow and Thermal

• Calculate the temperatures, heat fluxes, velocities, and pressure distribution in a fluid or a model with fluid and solid parts.
• All the results can vary over time.
• The fluid is undergoing an acceleration during the analysis or change over time.
• Inertial effects are included.
• The thermal loads can be constant or change over time.
• Examples: heat exchangers, circuit boards, cooling/heating system design, HVAC systems.