Simcenter 3D Response Dynamics

Simcenter 3D Response Dynamics is a Pre/Post solution process for use with Simcenter Nastran. It allows you to evaluate the static or dynamic responses of a structural model subjected to various loading conditions. The software calculates these responses using modal approaches.

Sample displacement and stress response functions and stress contour results

FE model and solution

You prepare the finite element model for analysis by defining the mesh, material properties, loads, and special boundary conditions called excitation locations. You can also use an assembly FEM containing a Mode Set, or FRF Set, to compute modal responses using Response Dynamics. You solve either the SOL 103 Real Eigenvalues or SOL 103 - Response Dynamics Simcenter Nastran solution to evaluate the dynamic response.

Modal model

Depending on the type of excitation (loading) and data recovery method you use, this solution generates the following types of mode shapes for the structure:

• Normal modes representing the deformed shapes (eigenvectors) of the structure at specific natural frequencies (eigenvalues).

• Attachment modes representing the static deformation shape due to a unit static load applied at the location where an excitation force will be applied. Attachment modes are necessary for using the Mode Acceleration data recovery method.

• Constraint modes representing the static deformation due to a unit static displacement of a boundary degree of freedom (DOF). Constraint modes are necessary for using the Enforced Motion excitation type.

• Distributed attachment modes representing the structural behavior due to a dynamic load. They are required for calculating mode acceleration responses to distributed dynamic excitations.

Note:

The SOL 103 Real Eigenvalues solution solves only for the normal modes.

The combination of the mode shapes, damping, and other modal information comprises the modal model.

You can apply excitation functions to the FE (physical) model to represent applied forces, enforced motions, or distributed loads.

The Functions and Graphing tools allow you to create, investigate, and manage excitation and response functions. In addition, a Function Toolkit is available in Response Dynamics to create, import, and manage excitation and response functions. For more information, see Response Dynamics Function Toolkit.

Analysis events

Your excitations and modal parameters are contained within one of the following types of analysis events.

Event type	Description
Transient	Calculates the dynamic response of a structure to a set of simultaneous excitations that vary over time. A transient excitation is either a point load (nodal force or enforced motion) applied to a nodal degree of freedom or a distributed load. The software calculates the response at each instant in time.Examples of transient excitations include the time history of driving an automobile over a test track or any event in which a mechanical device is exposed to an excitation over a period of time.
Frequency	Calculates the steady-state responses of a structure to a set of simultaneous oscillatory excitations. A frequency excitation can be either a point load applied to a nodal DOF or a distributed load.The software calculates the response at each frequency.Examples of frequency excitations include the effects on the driver's comfort in an automobile from an engine's rotation or wheel imbalance.
Random	Calculates the power spectral density (PSD), root mean square (RMS), and level-crossing rate (LCR) results of a structure to a one or more simultaneous random excitations. A random excitation can be a nodal force PSD function, an enforced motion PSD function (displacement, velocity, acceleration), or a distributed load.You can correlate two random excitations in the frequency domain by defining a phase relationship or time delay between them. PSD response at each frequency is calculated using the transfer functions between the sources of excitation and the requested response quantities, while the RMS of the random process is calculated for the PSD function.Examples of random excitations include jet engine noise, a profile of a road surface, and the effects of turbulence on an airplane.
Response Spectrum(also called shock response spectrum)	Calculates the peak response of a structure to a set of simultaneous base excitations defined by response spectrum functions. The peak response is calculated using modal approximation methods (such as Absolute Method, Square Root of the Sum of Squares, and others). This is the output expected at each mode frequency, and therefore the response of the whole model at one modal frequency, which then needs to be combined with any other mode frequencies in the range of the response spectrum.Examples of response spectrum shock excitations include aircraft landings, nuclear overpressure, drop testing, and seismic effects.
DDAM (Dynamic Design Analysis Method)	Calculates the dynamic response of a ship's components to shocks applied to the ship's hull, deck, or shell plating mountings.The Dynamic Design Analysis Method was developed by the United States Navy. You can apply DDAM excitations for surface ships or submarines, to the hull, deck, or shell plating mountings. You can apply these enforced motion excitations in vertical (Y), athwartship (Z), and fore/aft (X) directions. Available deformation types include Elastic and Elastic-Plastic. Response Dynamics uses U.S. Navy specification DDS-072-1.For confidentiality, the software allows you to enter the DDAM loading coefficients each time you perform the response evaluation. You can predefine the coefficients in a text file.
Quasi-Static	Calculates the static response of a structure to a set of simultaneous time-varying static excitations. To create a static excitation, you use a function to scale the load that was applied in the modal solution. The software calculates the response at each instant in time by linearly combining (superposing) the static results of all the loads with the specified time history scaling function.This event type is useful if you are only interested in static results and need faster solution performance than a full dynamic solution.
Random Base Excitation	Evaluates the dynamic response of a structure subjected to a random base acceleration power spectral density (PSD) function. This event leverages a standalone solver which uses multithreading as well as advanced integration and estimation algorithms for faster solution time. It computes peak results that correspond to a desired confidence level for a number of quantities, including failure indices, strength ratios and margins of safety. It also computes PSD XY functions and the number of positive zero crossings.Random base excitation testing is prevalent in the space, automotive and electronics industries.For more information, see Random Base Excitation.

Dynamic response calculations

Algorithms within this software calculate the dynamic responses of the structure to excitations. You can evaluate:

• Displacement, velocity, acceleration, and reaction force at a given node.

• Stress, strain, element force, beam element force, and shell stress resultant at a given element.

• Response results for the given loading history, strength, peak value, RMS, and Level Crossing Rate (LCR).For more information on random analysis response evaluations see Random vibration.

Post-processing tools

You can evaluate the responses using post-processing tools such as contour plots and XY graphs.

The Functions and Graphing tools within this software allow you to create, investigate, and manage excitation and response functions.

Teamcenter Integration support

You can also run Response Dynamics in Teamcenter Integration mode. You can reload a simulation from the Teamcenter database, including all associated excitation and response functions.

Quick links

Command reference

Pre/Post video examples

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Simcenter 3D Response Dynamics, Simcenter 3D 2021.1 Series

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