DRESP1

For further information about the various internal responses, refer to Internal Responses in the User Guide.

Format

Examples

Definitions

Comments

1. VOLFRAC is equivalent to MATFRAC in previous versions of OptiStruct. MATFRAC is still supported.
2. Responses of the same RTYPE with the same region identifier are grouped together into the same region. If the region identifier is blank, elements identified by an ATTi field (when PTYPE = ELEM) are grouped together into the same region, but for properties or materials, each property or material identified by an ATTi field will form its own region. Refer to Constraint Screening in the User Guide for a more detailed explanation.

   For composite responses (RTYPE = CSTRESS, CSTRAIN, CFAILURE; PTYPE = PCOMP, PCOMPG), each ply is given its own region. However, if a region identifier is defined explicitly for the entire lay-up (ATTB=ALL), this region identifier applies to all plies. It is not recommended to do this.

3. DRESP1 entries must have unique identification numbers with respect to DRESP2 and DRESP3 entries.
4. In normal modes analysis, the frequencies are in Hz (cycles/time).
5. The total displacement can be requested using ATTA=7; the total rotation using ATTA=8.
6. PTYPE = PCOMP, PCOMPG can be selected for RTYPE = STRESS or RTYPE = STRAIN, in which case homogenized stresses or strains are used. RTYPE = CSTRESS or RTYPE = CSTRAIN should be used instead for composite responses.
7. Stresses are element stresses. For CBAR, CBEAM, stresses are normal (axial) stresses for the element.
8. VOLFRAC and MASSFRAC can only be applied to topology design domains. OptiStruct will terminate with an error if this is not the case.
9. MASS, MASSFRAC, COG and INERTIA responses are not available for PBUSH, PDAMP, PELAS, PGAP, PVISC, and PWELD.
10. VOLUME and VOLFRAC responses are not available for CONM2, PDAMP, PELAS, PGAP, PMASS, and PVISC.
11. The VOLUME of a single CWELD element is 1.0. The response then is the number of welds.
12. WCOMP, WFREQ, COMB require the definition of WEIGHT and/or MODEWEIGHT Subcase commands. if WEIGHT or MODEWEIGHT are not defined, the following defaults apply:

    RTYPE	Applicable Subcase Commands	Default
    WCOMP	WEIGHT in static subcases	WEIGHT = 1.0 for all static subcases.
    WFREQ	MODEWEIGHT in normal modes subcase	MODEWEIGHT (1) = 1.0 in most cases for topology optimization. MODEWEIGHT (7) = 1.0 if no SPC is defined for the subcase, EIGRL does not define a V1 > 0.0, and it is solving for more than 6 modes or all modes below an upper bound.
    COMB	WEIGHT in static subcases MODEWEIGHT in normal modes subcase	WEIGHT = 1.0 for all static subcases.

13. CSTRESS, CSTRAIN, and CFAILURE are only available for PCOMP, PCOMPG.

    ATTB = # refers to a ply on a PCOMP.

    Example: DRESP1, 12, PLY23, CSTRESS, PCOMP, SMAP, 23, 43.

    ATTB = G# refers to a global ply on a PCOMPG.

    Example: DRESP1, 12, GLOBAL11, CFAILURE, PCOMPG, HILL, G11, 17.

    ATTB must be blank for PLY response type.

    CSTRESS, CSTRAIN, and CFAILURE responses can be requested at the middle, top, bottom, or both (top and bottom) locations of the ply. See DRESP1 - Static Stress/Strain Item Codes for Composites and DRESP1 - Static Failure Item Codes for Composites for more information.

14. STRAIN responses not applicable for CELAS.
15. Composite Stress/Strain item codes S1Z and S2Z for Shear-1Z and Shear-2Z are for CSTRESS only, these are not available for CSTRAIN.
16. Lower bound constraints are not allowed on von Mises stress.
17. LABEL must begin with an alphabetical character.
18. Responses that do not exist are ignored, and a warning is issued.
19. EXCL only applies to RTYPE = STRESS, STRAIN, FORCE, CSTRESS, CSTRAIN, CFAILURE, FRSTRS, FRSTRN, and FRFORC response types.
20. For RTYPE = MASS, MASSFRAC, VOLUME, VOLFRAC, COG, INERTIA, BEADFRAC, and COMP; ATTi can only be blank if PTYPE is also blank. ATTi blank means that all relevant entities are included. They all belong to the same region for constraint screening.
21. For RTYPE=STRESS, STRAIN, FORCE, FRSTRS, FRSTRN, FRFORC, CSTRESS, CSTRAIN, and CFAILURE; ATTi can only be blank if PTYPE is a property type (not allowed when PTYPE is ELEM). ATTi blank means that all entities of the defined PTYPE are selected.
22. For RTYPE = MASS, MASSFRAC, MBMASS, VOLUME, VOLFRAC, COG, MBCOG, INERTIA, MBINER, COMP, and BEADFRAC; ATTB = COMB results in the creation of a single response for the combination of all ATTi entities.
23. For RTYPE=MASS, MBMASS, VOLUME, MBCOG, MBINER, COMP, MASSFRAC, and VOLFRAC; ATTB=SUM is the same as ATTB=COMB.
24. For RTYPE = FRDISP, FRVELO, FRACCL, FRSTRS, FRSTRN, FRFORC, FRERP, PSDDISP, PSDVELO, PSDACCL, and PSDPRES the following functions can be applied through the character input on ATTB. The formulas are applied across all loading frequencies. The use of MAX can be very inefficient computationally and it is better to leave ATTB blank and let constraint screening take care of it.

    Function	Description	Formula
    SUM	Sum of arguments	$\mathit{SUM}(y_1,y_2\dots y_m)=\sum _{j=1}^m{y}_j$
    AVG	Average of arguments	$\mathit{AVG}(y_1,y_2,\dots y_m)=\left[\sum _{j=1}^m{y}_j\right]/m$
    SSQ	Sum of square of arguments	$\mathit{SSQ}(y_1,y_2\dots y_m)=\sum _{j=1}^m{y}_j^2$
    RSS	Square root of sum of squares of arguments	$\mathit{RSS}(y_1,y_2\dots y_m)=\sqrt{\sum _{j=1}^m{y}_j^2}$
    MAX	Maximum of arguments	$MAX(y_1,y_2\mathrm{...}{y}_m)=y_i$
    MIN	Minimum of arguments	$MIN(y_1,y_2\mathrm{...}{y}_m)=y_i$
    SUMABS	Sum of absolute value of arguments	$\mathit{SUM}(y_1,y_2\dots y_m)=\sum _{j=1}^m\left|y_j\right|$
    AVGABS	Average of absolute value of arguments	$\mathit{AVG}(y_1,y_2\dots y_m)=\left[\sum _{j=1}^m\left|y_j\right|\right]/m$
    MAXABS	Maximum of absolute value of arguments	$MAXABS(y_1,y_2\mathrm{...}{y}_m)=MAX\left[\left|y_i\right|\right],i=1,2,\mathrm{...}m$
    MINABS	Minimum of absolute value of arguments	$MINABS(y_1,y_2\mathrm{...}{y}_m)=MIN\left[\left|y_i\right|\right],i=1,2,\mathrm{...}m$
    RMS	Root Mean Square value of arguments.	$\mathit{RMS}(y_1,y_2,\mathrm{...},y_m)=\sqrt{\frac{1}{m}\left(\sum _{i=1}^m{y}_i^2\right)}$

25. For RTYPE = INERTIA, the Moment of Inertia is with reference to the center of gravity. The Moment of Inertia of the whole model is referred to the center of gravity of the whole model. The Moment of Inertia of each property or material is referred to the center of gravity of that property or material.
26. For acoustic optimization, pressure responses are defined using RTYPE=FRPRES; however, it is acceptable to define a pressure response on a fluid grid as RTYPE=FRDISP with ATTA as one of M-TX, R-TX or I-TX, internally it will be converted to FRPRES (with M-TX/R-TX/I-TX interpreted as M-PRES/R-PRES/I-PRES). Likewise, RTYPE=PSDDISP or RMSDISP are accepted in place of PSDPRES or RMSPRES, respectively.
27. For RTYPE = MBDIS, MBVEL, MBACC, or MBFRC, the PTYPE must be MBREQM. These four response types must be defined using MARKERs, and requested by MBREQM. For RTYPE = MBEXPR, the PTYPE must be MBREQE. The response must be requested by MBREQE. For RTYPE = MBMASS, MBCOG, or MBINER, the PTYPE must be PFBODY.
28. MBREQE referenced in DRESP1 must have single expression although MBREQE allows up to 6 expressions for analysis output.
29. MBD system level responses must be scalar quantities. Thus, the ATTB field must have one of the following - MAX, MIN, MAXABS, or MINABS so that time dependent vectors can be converted to scalar quantities.
30. Legacy data with RANDPS ID defined on the PTYPE or ATTB entry is also supported.
31. A blank field for RANDID on the EXTN extended attributes entry indicates that all RANDPS cards in the input file will be used.
32. For Static Stress responses for homogeneous materials, the ATTB field on the DRESP1 entry can be used to define the "Cluster Size" which may help avoid stress concentrations or gradients. "Cluster Size" affects each of the elements defined via PID or EID on the ATTi field for a particular stress response. Cluster Size represents the number of elements around the specified element whose stress contributions are included in the calculation of the individual element's stress contribution. The contributions of the elements in the cluster are weighted based on their distance to the center of the cluster (Available for Shell and Solid elements). Weighting element stress contributions using Cluster Size is generally useful in models with stress gradients or stress concentrations in the design space. If the stress distribution within the selected element cluster is uniform, there may not be any significant difference in the stress response. A separate result type Element Stress Cluster is available in the _s#.h3d file and stress results based on element cluster response(s) can be viewed in HyperView by selecting Element Stresses Cluster in the Result type: drop-down menu.
33. The Resultant Section Force and Resultant Section Moment can be specified as responses via RTYPE=RESFORCE. The ATTA field specifies whether Resultant Section Force components (1,2,3) or Resultant Section Moment components (4,5,6) are selected. The ATTi fields should reference the Identification Numbers of the SECTION Bulk Data Entry that define the cross-section.
    The SECTION entry can be used to define a face of the cross-section on which the forces/moments are calculated as a response in optimization runs via RTYPE=RESFORCE (on the DRESP1 entry). In such cases, Grid Point Forces or Moments are added at each GRID specified within the grid set (GSID). The effect of all elements on the grid points (GSID) is considered in the calculation of the response except the elements specified via ESID. The section is determined through a set of Grid points and the particular face is specified by a set of elements. The face is interpreted as the side of the Grid point set NOT containing the specified elements (refer to SECTION). This is similarly applicable to Rigid Element sets through RSID.

    
    
    Figure 1. Defining the SECTION for the RESFORCE Response

    
    
    Figure 2. Selecting the GSID Set

    
    
    Figure 3. Selecting the Corresponding ESID

    The default GID is the geometric center of the cross-section. For example, in a shell model, if the cross-section is tapered (Figure 4), the geometric center is automatically updated (if the GID field is blank).

    
    
    Figure 4. Geometric Center via GID=Default

34. 1. Extended options are available for Frequency-based response definitions via the LOWFQ, HIGHFQ, SCALE, and OCTAVE fields on the EXTN continuation line.

       LOWFQ and HIGHFQ: Defines the Frequency Range within which the responses are determined. Additionally, the ATTB field can be used to specify functions to calculate combined responses over the frequency range.

       SCALE: This field can be used to Scale and/or Weight the responses in the frequency range. (In the case of sound pressure, weighting is applied to measured (or calculated) sound levels to account for the relative loudness perceived by the human ear, which is less sensitive to low and high frequencies).

       • LIN (default) - The Linear Response function is output without any applied weighting or scaling.(1)
         $${\mathit{RESP}}_{\mathit{LIN}}=P_{\mathit{cal}}$$

         Where, ${\mathit{RESP}}_{\mathit{LIN}}$ is the linear response function calculated for the SCALE=LIN option, $P_{\mathit{cal}}$ is the calculated Frequency Response output.

       • LOG - The logarithmic response function is output directly without any applied weighting.(2)
         $${\mathit{RESP}}_{\mathit{LOG}}=20{\text{log}}_{10}\left(\frac{P_{\mathit{cal}}}{P_{\mathit{ref}}}\right)$$

         Where, ${\mathit{RESP}}_{\mathit{LOG}}$ is the Logarithmic response function calculated for the SCALE=LOG option, $P_{\mathit{cal}}$ is the calculated Frequency Response output, and $P_{\mathit{ref}}$ is the Reference Response defined by PARAM, SPLREFDB (Default = 1.0) or the UNITS I/O Options Entry.

       • DBA A-Weighting is applied to the responses within the frequency range.(3)
         $$W_A(f)=\frac{{12200}^2{f}^4}{\left(f^2+{20.6}^2\right)\sqrt{\left(f^2+{107.7}^2\right)\left(f^2+{737.9}^2\right)}\left(f^2+{12200}^2\right)}$$
         (4)
         $${\mathit{RESP}}_A(f)=2.0+20{\text{log}}_{10}{W}_A(f)+20{\text{log}}_{10}\left(\frac{P_{\mathit{cal}}}{P_{\mathit{ref}}}\right)$$

         Where, ${\mathit{RESP}}_A(f)$ is the A-Weighted frequency response output at a frequency $(f)$ , $W_A(f)$ is A-Weighting factor at frequency $(f)$ , $P_{\mathit{cal}}$ is the calculated Frequency Response output, and $P_{\mathit{ref}}$ is the Reference Response defined by PARAM, SPLREFDB (Default = 1.0) or the UNITS I/O Options Entry.

       • DBB B-Weighting is applied to the responses within the frequency range.(5)
         $$W_B(f)=\frac{{12200}^2{f}^3}{\left(f^2+{20.6}^2\right)\sqrt{\left(f^2+{158.5}^2\right)}\left(f^2+{12200}^2\right)}$$
         (6)
         $${\mathit{RESP}}_B(f)=0.17+20{\text{log}}_{10}{W}_B(f)+20{\text{log}}_{10}\left(\frac{P_{\mathit{cal}}}{P_{\mathit{ref}}}\right)$$

         Where, ${\mathit{RESP}}_B(f)$ is the B-Weighted Frequency Response output at a frequency $(f)$ , $W_B(f)$ is B-Weighting factor at frequency $(f)$ , $P_{\mathit{cal}}$ is the calculated Frequency Response output, and $P_{\mathit{ref}}$ is the Reference Response defined by PARAM, SPLREFDB (Default = 1.0) or the UNITS I/O Options Entry.

       • DBC C-Weighting is applied to the responses within the frequency range.(7)
         $$W_C(f)=\frac{{12200}^2{f}^2}{\left(f^2+{20.6}^2\right)\left(f^2+{12200}^2\right)}$$
         (8)
         $${\mathit{RESP}}_C(f)=0.06+20{\text{log}}_{10}{W}_C(f)+20{\text{log}}_{10}\left(\frac{P_{\mathit{cal}}}{P_{\mathit{ref}}}\right)$$

         Where, ${\mathit{RESP}}_C(f)$ is the C-Weighted Frequency response output at a frequency $(f)$ , $W_C(f)$ is C-Weighting factor at frequency $(f)$ , $P_{\mathit{cal}}$ is the calculated Frequency Response output, and $P_{\mathit{ref}}$ is the Reference Response defined by PARAM, SPLREFDB (Default = 1.0) or the UNITS I/O Options Entry.

         The reference response is dependent on the units specified on the UNITS I/O Options Entry. If the units are SI, the value is set as 2.0E-5 Pa. If they are CGS, it is set as 2.0E-4 barye. If they are MPa, it is set as 2.0E-11 MPa. If they are BG or EE, then it is set as 4.17E-7 lbf/ft². If no UNITS data is present, the default value is 1.0.

       OCTAVE: This field can be used to specify the Octave Band types for Response calculation. Sound spectrum is usually represented in Octave or 1/3 Octave Frequency bands instead of narrow Frequency Bands. This representation is linked to the perception of sound by the human ear and it allows for compression of information across similar responses within frequency bands. Responses are accumulated for all the frequencies within the Octave band using the function specified on the OCTOPT field (see below). Full Octave, 1/3 Octave, and 1/8 Octave bands are commonly used in NVH analysis and are available (other bands are also available, if required). Weighting is also taken into account (depending on the SCALE field) prior to Response accumulation over Octave bands.

       • Full Octave - OCTAVE = 1
       • 1/3 Octave - OCTAVE = 3
       • 1/8 Octave - OCTAVE = 8

       Other Octave bands are also available and can be requested similarly.

       The OCTOPT field can be set to INT, SUM, or AVG. INT, the default, calculates the value under the weighted response-frequency curve for each octave band. SUM is simply the sum of the response values in each octave band. AVG is the average response in each octave band.

       The ATTB field is ignored, if the OCTAVE field is specified.

       Note: The Decibel scale generally uses 10 for power quantities and 20 for field quantities. Therefore, 10 for ERP and 20 for other responses (like sound pressure) is used. So in this case, for LOG, DBA, DBB, DBC, we use 20*log(<values>) as evidenced by the corresponding formulae above.
35. RTYPE=VOLUME and ATTA=ENCLOSED can be used to create an enclosed volume response for Shape, Free-Shape, and Topography optimization. The ENCLOSED option indicates that this response is an enclosed volume defined by a closed 2D mesh (free-edges are not supported). For this enclosed volume response type, ATTI field(s) should be set to PID.
36. The ATTB field can be set to RMS or ZCF for RMS responses. ATTB=RMS represents the RMS response, ATTB=ZCF represents the Zero Crossing Frequency response based on the corresponding RMS response (see Random Response Analysis in the User Guide for further information regarding Zero Crossing).
37. Surface stress responses can be defined for solid elements by using RTYPE=STRESS and using one or more of the Surface stress response Item Codes (SVMS, SMPS, and SMIPS).
38. Allowable Stress for Static Failure response (RTYPE=FAILURE) are retrieved from the MAT1 or MATT1 entry. The ST field (tension) is used for MISES and MAJOR, the SC field (compression) is used for MINOR, and the SS field (shear) is used for TRESCA. Multiple failure criteria can be used with different allowables. For shells, there are no specific item codes for Z1 and Z2, instead, both responses are generated, and the critical response is retained and printed.
39. Coordinate systems for DRESP1 are currently supported for the following responses.

    Grid-based Responses: DISP, SPCFORCE, and GPFORCE (CID specifies a coordinate system ID, or BASIC for the basic coordinate system).

    Element-based Responses: STRESS, STRAIN, and FORCE for shell elements (CID specifies a coordinate system, BASIC for the basic coordinate system, ELEM for the elemental coordinate system, or LOCAL for the local coordinate system).

40. Neuber stress/strain response is not supported in topology or free-size optimization.
41. This card is represented as an optimization response in HyperMesh.