Random Output Requests dialog box

Modeling Object
Name	Sets the name for the random output requests modeling object.
Accelerations page
Accelerations	Computes nodal acceleration random results if the solution OP2 file contains displacement results.For more information, see Contours options and PSD XY Functions options.
Displacements page
Displacements	Computes nodal displacement random results if the solution OP2 file contains displacement results.For more information, see Contours options and PSD XY Functions options.
Element Forces page
Element Forces	Computes element force random results if the solution OP2 file contains element force results.For more information, see Contours options and PSD XY Functions options.
Failure Metrics page
Failure Metrics	Computes failure metrics for elements that reference homogeneous materials when the Random Base Excitation Event check box in the SOL 103 Response Dynamics Solution dialog box. Von Mises stresses are automatically generated, since they are required to compute the metrics.For more information, see Contours options for failure metrics and Output Location options.
Failure Metrics - Laminates page
Failure Metrics - Laminates	Computes failure metric results for elements that reference a laminate or solid laminate physical property when the Random Base Excitation Event check box in the SOL 103 Response Dynamics Solution dialog box.Note: The equations for failure index, strength ratio, and margin of safety depend on the failure theory that you defined in the Laminate Modeler or Solid Laminate Modeler dialog box.For more information, see Contours options for failure metrics and Output Location options.
Grid Point Forces page
Grid Point Forces	Computes nodal grid point force random results if the solution OP2 file contains grid point force results. The software can only compute peak results for this quantity.For more information, see Contours options.
MPC Forces page
MPC Forces	Computes nodal multipoint constraint (MPC) force random results if the solution OP2 file contains MPC force results.For more information, see Contours options and PSD XY Functions options.
SPC Forces page
SPC Forces	Computes nodal single-point constraint (SPC) force random results if the solution OP2 file contains SPC force results.For more information, see Contours options and PSD XY Functions options.
Strains page
Strains	Computes strain random results for both homogeneous and laminate elements if the solution OP2 file contains strain results. You can elect to compute principal strains using exact and faster approximate methods.Von Mises strain is automatically computed.Because Von Mises results do not follow Gaussian distributions, the random base excitation solver calculates the peak Von Mises strains using a proprietary approach.Note: The random base excitation solver computes random ply strain results at the same locations that are used for the ply results in the OP2 file. For 3D laminates, before solving your Nastran solution, you define the ply location from the Composite Solid Ply Output list on the Strain page in the Structural Output Requests dialog box.For more information, see Contours options, PSD XY Functions options, and Output Location options.
Stresses page
Stresses	Computes stress random results for both homogeneous and laminate elements if the solution OP2 file contains stress results. You can elect to compute principal stresses using exact and faster approximate methods.Von Mises stress is automatically computed.Because Von Mises results do not follow Gaussian distributions, the random base excitation solver calculates the peak Von Mises stresses using a proprietary approach.Note: The random base excitation solver computes random ply stress results at the same locations that are used for the ply results in the OP2 file. For 3D laminates, before solving your Nastran solution, you set the ply location from the Composite Solid Ply Output list on the Stress page in the Structural Output Requests dialog box.For more information, see Contours options, PSD XY Functions options, and Output Location options.
Velocities page
Velocities	Computes nodal velocity random results if the solution OP2 file contains displacement results.For more information, see Contours options and PSD XY Functions options.
PSD XY Functions page
Most of the following options specify frequency settings for the abscissa attributes for all PSD XY function requests that you specified on the other pages. These options affect only the format of the output XY plots. They do not have any relation to the excitation frequencies used by the integration algorithms, and therefore have little or no impact on performance. The plotting frequency options apply in the same way to both even and uneven functions.The functions are stored in the OP2 file generated by the random base excitation solver.
Maximum Number of PSD XY Functions per Request	Sets the maximum number of generated functions for each PSD XY function output request. The purpose of this setting is to avoid generating an unmanageable number of XY functions.Example: If you set 5,000 as the maximum number of functions per request, and you request XY functions for displacements and accelerations, the software generates at most 10,000 XY functions in the OP2 file: 5,000 for displacements and 5,000 for accelerations.You can control the default value for this box using the Maximum Number of PSD XY Functions per Request customer default.
Frequency Option	Specifies how the plotting frequencies are generated for the frequency range defined in the Edit Translational Nodal Excitation dialog box.Linear IncrementsGenerates the plotting frequencies linearly using the number of increments you set in the Number of Increments box.Logarithmic IncrementsGenerates the plotting frequencies logarithmically using the number of increments you set in the Number of Increments box.Between FrequenciesGenerates the plotting frequencies by specifying the number of excitation frequencies between two modal frequencies and the end points (lower and upper frequency bounds).
Interpolation Between Frequencies	Appears when Frequency Option is set to Between Frequencies.Specifies linear or logarithmic interpolation between frequencies.
Number of Excitation Frequencies	Appears when Frequency Option is set to Between Frequencies.Sets the number of excitation frequencies within each subrange including the end points. The first subrange is between the lower bound and the first modal frequency within the bounds. The second subrange is between first and second modal frequencies between the bounds. The last subrange is between the last modal frequency within the bounds and the upper bound.
Cluster	Appears when Frequency Option is set to Between Frequencies.Sets clustering of the excitation frequency near the end points of the range. The cluster value is used to obtain better resolution near the modal frequencies where the response varies the most. A value greater than 1.0 provides closer spacing of excitation frequencies towards both ends of the frequency range, while a value of less than 1.0 provides closer spacing towards the center of the frequency range.
Include Natural Frequencies	Appears when Frequency Option is set to Linear Increments or Logarithmic Increments.Includes the natural frequencies in the plotting frequencies.
Additional Plotting Frequencies	Specifies additional plotting frequencies to display in the graphs. Typically, add any frequency break points in your input power spectral density function.

Contours options

These options are available on all pages except Failure Metrics, Failure Metrics - Laminates, and PSD XY Functions.

The random base excitation solver writes the number of positive zero crossings and peak results to binary files. To instruct the solver to also write these results to text files, set the Text Output customer default.

Tip:

To find a customer default, choose File tab→Utilities→Customer Defaults, and click Find Default .

Contours
Peak	Enables the computation of peak values for the requested result set. The peak value is the maximum value that a quantity achieves for the specified confidence level. For a Gaussian distribution:peak value = RMS value x the number of standard deviationsFor more information, see Confidence level in peak results computation and Random results for zero-mean Gaussian process.The following quantities do not follow a Gaussian distribution: Von Mises strains and stresses, principal strains and stresses, some ply failure indices, ply strength ratios, and margins of safety. For more information, see Random results for non-Gaussian responses.Peak values account for the user-defined confidence level, typically 99.73% or 3-sigma. It is therefore not required to post-process the results, like you would for a heritage random event by multiplying root mean squared (RMS) results by 3.
Principal Strains****Principal Stresses	Appears only on the Strains or Stresses page.Specifies how the principal strains and stresses are computed. Because principal stresses and strains do not follow Gaussian distributions, the random base excitation solver calculates the exact peak minimum and maximum principal stresses and strains using a proprietary approach.NoDoes not compute principal strains or stresses.**Approximate (Faster)**Computes principal strains or stresses using an approximate approach, which uses looser convergence criteria for faster computation time.**Precise (Slower)**Computes principal strains or stresses using the precise approach, which uses tighter convergence criteria for more precise peak values.The peak maximum principal stress or strain is computed such that the probability P(max principal ≤ peakmaxp) = confidence level. For example, if the confidence level is 99.73% and the computed peakmaxp value is 300.0, the probability that the maximum principal stress is less than or equal to 300.0 is 99.73%.The peak minimum principal stress or strain is computed such that P(min principal ≥ peakminp) = confidence level. For example, if the confidence level is 99.73% and the computed peakminp value is -200.0, the probability that the minimum principal stress is greater than or equal to -200.0 is 99.73%. As a result, the reported peak values for the minimum principal stress or strain are often negative.
Positive Crossings	Not available for Grid Point Forces page.Enables the computation of the number of positive zero crossings for the requested result set. The number of positive zero crossings for a response power spectral density (PSD) function is computed as follows:where:N0 is the number of positive zero crossings.S(f) is the response PSD function.f is the frequency.∫S(f)df is the RMS value for the selected result set.					where:N0 is the number of positive zero crossings.S(f) is the response PSD function.f is the frequency.∫S(f)df is the RMS value for the selected result set.
				where:N0 is the number of positive zero crossings.S(f) is the response PSD function.f is the frequency.∫S(f)df is the RMS value for the selected result set.
Elements or Nodes	Specifies the entities on which the software computes the output results.AllComputes the requested results on all nodes or elements which have the corresponding results in the OP2 file generated by the solution.GroupComputes the requested results on the nodes or elements that are in the selected group. For more information, see Element or Node Selection options.

Contours options for failure metrics

These options are available for Failure Metrics and Failure Metrics - Laminates pages.

Von Mises stress and strain are automatically computed along the homogeneous element failure metrics. Because Von Mises results do not follow Gaussian distributions, the random base excitation solver calculates the peak Von Mises stresses and strains using a proprietary approach.

Contours
Failure Index	Enables the computation of ply failure indices and failure index results for homogenous elements.For homogenous elements, the following equation is used:where:F is the failure index.σVM is the peak Von Mises stress.σall is the ultimate or yield strength property of your material, which is stored in the solution OP2 file.For the computation of ply failure indices for the supported failure theories, see:Laminate failure analysisHill failure analysis (2D) and Hill failure analysis (3D)Hoffman failure analysis (2D) and Hoffman failure analysis (3D)Tsai-Wu failure analysis (2D) and Tsai-Wu failure analysis (3D)Maximum stress failure analysis (2D) and Maximum stress failure analysis (3D)Maximum strain failure analysis (2D) and Maximum strain failure analysis (3D)					where:F is the failure index.σVM is the peak Von Mises stress.σall is the ultimate or yield strength property of your material, which is stored in the solution OP2 file.
				where:F is the failure index.σVM is the peak Von Mises stress.σall is the ultimate or yield strength property of your material, which is stored in the solution OP2 file.
Strength Ratio	Appears only on the Failure Metrics - Laminates page.Enables the computation of strength ratio results for each ply. For more information, see Laminate failure analysis.
Margin of Safety	Enables the computation of margin of safety results for each ply, or for homogenous elements.For homogenous elements, the following equation is used:where:MS is the margin of safety.FS is the safety factor.For the computation of ply failure indices for the supported failure theories, see Laminate failure analysis.					where:MS is the margin of safety.FS is the safety factor.
				where:MS is the margin of safety.FS is the safety factor.
Failure Mode	Appears only on the Failure Metrics page.Specifies the homogeneous element failure mode which can be either Yield or Ultimate. The software uses the value of either yield strength or ultimate strength in the computation of the failure index and the margin of safety.
Safety Factor	Sets the safety factor value, which is used to compute the margin of safety.
Elements	Specifies the entities on which the software computes the output results.AllComputes the requested results on all the elements which have the corresponding results in the OP2 file generated by the solution.GroupComputes the requested results on the elements that are in the selected group. For more information, see Element or Node Selection options.

PSD XY Functions options

These options are available on all pages except Failure Metrics, Failure Metrics - Laminates, Grid Point Forces, and PSD XY Functions.

PSD XY Functions
Power Spectral Densities	Enables the generation of the power spectral density (PSD) functions for the requested result set in SORT2 format. This allows you to plot the functions from the XY Function Navigator.The software does not compute the XY functions for Von Mises stress results.For more information, see Random response for ply stress components.
Elements or Nodes	Specifies the entities on which the software computes the output results.AllComputes the requested results on all the nodes or elements which have the corresponding results in the OP2 file generated by the solution.GroupComputes the requested results on the nodes or elements that are in the selected group. For more information, see Element or Node Selection options.

Output Location options

These options are available on the Failure Metrics, Failure Metrics - Laminates, Strains, and Stresses pages.

Output Location
Output Location	Specifies the location at which the software computes the requested strain, stress, and failure metric results.CenterComputes the results only at the center of each element.Center and CornerComputes the results at the center and corners of each element. For example, for a parabolic hexahedral element, you get results at 9 different locations of each element.

Element or Node Selection options

Element Selection or Node Selection
Group Reference	Appears when Elements or Nodes is set to Group.Applies the requested results to the selected group. For more information, see Group Reference options.
Select Object	Appears when Elements or Nodes is set to Group.Lets you select elements or nodes to request the results on them.Excluded lets you remove individual entities from within your selected object.Note: The Element Selection Filtering options are available when the Type Filter list on the Top Border bar is set to Elements.
Stacked Smart Selector Methods	Opens the Smart Selector Methods dialog box where you can specify a progression of smart selection filters.For more information, see Smart Selector Methods dialog box.

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Random Output Requests dialog box, Simcenter 3D 2021.1 Series

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