Release Note. Version 5.0r323

Transcription

1 Release Note Version 5.0r323 March 3, 2016

2 Before addressing the new version of AMLS, FastFRS and Delivery Data Base (DDB), CDH will make a number of recommendations based on over 45 years of experience with Nastran and 15 years of working with AMLS and FastFRS. These recommendations and suggestions lead to more accurate results as well as cause fewer problems in the solutions. 1. Nastran Parameter Settings: param, k6rot, 0.0 param, snorm, 45.0 param, coupmass, 1 Please note that these values were also recommended by Dr. Richard MacNeal and Bob Harder, the original developers of the k6rot and snorm capability. 2. Use of strain gage or display shell elements: Strain gage elements are usually used as a coating on the surface of solid elements. The display elements are usually connected to some rigid elements, e.g., displaying the tire surface connected to a spindle point with RBE2. In these cases, the shell elements properties, PSHELL, should only have an MID1 definition, meaning they will behave as membrane elements only. Thus a typical PSHELL should be, for example: PSHELL ID MID NOT!! PSHELL ID MID MID2 1. MID3 In the latest release of the DDB the parameters K6ROT and SNORM will automatically be set to 0.0 and 45.0, respectively! Likewise, if the user specifies QRMETH=5, the following System Cells for MSC and NX Nastran will be automatically set to: NASTRAN system(601)=2 $ MSC NASTRAN system(589)=2 $ NX This implies that: The drilling degrees-of-freedom are deactivated for those QUADR or TRIAR which have membrane stiffness only (MID2 and MID3 are blank on the PSHELL entry) 2

3 Differences between 5.0.r257 and 5.0.r323: A. AMLS The issues/errors from r257 will be described in some detail so that users will have a better understanding of the differences between r257 and r323. Most of the errors described occur very rarely for unusual models. New Features: 1. Support for using ODS with the generic interface has been added. In addition, the ODS procedure has been streamlined by the use of the executable, fastfrs_ods, which takes the place of FastFRS in an ODS run. 2. Support for running multiple jobs in the same directory with NASTRAN has been added. This support includes changes in both the scripts and the executables. Improvement: The error handling for when a write fails has been augmented. An example of the new error message is: **********************Error in Phase 4a********************** Error: Write failed to complete entire block This may be due to insufficient disk space File name: /some/directory/cdh.12345/v1_data Path for file: /some/directory/cdh Size of partition: GB Free space: MB Attempted write size: MB Function: binary_file::put() File: /home/muller/v1_data ************************************************************** Called by: write_v1_col Called by: form_v1 Called by: subspace_iteration Called by: phase4a Called by: fork function for AMLS Phase4a Called by: main amls driver Issue 1: A particular ungracefully fails in phase3, due to being unable to find space in a workspace. This is caused by the model possessing three needed properties: 3

4 1. Phase3 is given less than the min amount of memory to run for this model, so it ups the memory usage to the minimum. 2. The memory high water for this model in phase3 is processing the last ss. 3. This model has mechanisms outside of the last ss, which are moved by phase3 to the last ss. This version increases the phase3 memory estimate for the last substructure, in case some nodes are moved to the last ss due to mechanisms. Issue 2: The auxiliary vectors (aka the area matrix) were being handled improperly in cases where phase3 changed the substructure tree due to moving nodes into the last substructure. This issue only affects models with the following characteristics: 1. They have an area matrix 2. Some nodes are moved to the root substructure by phase3 due to rigid body like behavior encountered outside of the root ss. 3. The moving of these nodes caused a substructure to no longer be coupled to its parent, thus causing phase3 to both reorganize and renumber the substructure tree and miscommunicate the information to phase5. Phase3 has been fixed to properly communicate substructure area matrix information to phase5. 4

5 B. FastFRS: New Features: 1. Support for using ODS with the generic interface has been added. In addition, the ODS procedure has been streamlined by the use of the executable, FastFRS_ods, which takes the place of FastFRS in an ODS run. 2. Support for running multiple jobs in the same directory with NASTRAN has been added. This support includes changes in both the scripts and the executables. 3. The "max normalization" feature has been added. This feature is used when a user scales the eigenvectors so that the maximum entry in a column is one. (Typically, the eigenvectors are mass normalized.) The max norm feature works by un-doing the scaling - making the modal mass matrix identity again. The feature only works when the mass matrix is diagonal and the entries are larger than zero. Issue 1: In the FastFRS_state file, this info was reported: Memory available: GB Memory limit specified: 348 GB Memory required: GB Error: More memory required to run job. Memory was not initialized correctly. Issue 2: A memory error was found in the translator. A user has never reported this memory error; its occurrence is very rare. The memory error is fixed. Issue 3: When the amount of memory specified by the command line argument is less than zero, FastFRS failed. 5

6 Now, when the amount of memory specified is less than zero, FastFRS uses the default memory (half of the machine's memory). Issue 4: When using param, g, an ungraceful error is produced when ω 2 equals an entry in the stiffness matrix. Now, the frequencies and the complex stiffness matrix are examined and exits gracefully with a helpful error message. Issue 5: The FastFRS_state file was not echoed into the user output - i.e., the NASTRAN *.log file. Changed the FastFRS script (fr_mod2) to echo the FastFRS_state file, and also changed it to delete the FastFRS state and report files after they have been echoed. Issue 6: The routine which checks if λ = ω 2 incorrectly determined that there was a problem. The routine now has been corrected. Issue 7: When using ODS with a generic interface, a number of shortcomings were reported when ODS are calculated for both structure and fluid. These problems have now been resolved. 6

7 C. Nastran Solver Interface MSC and NX Delivery Data Bases (DDB): For this release the DDB for the following versions of Nastran will be available: MSC: , , , , and NX: 10 and 10.2 If there is a special need for an older DDB version, please contact: support@cdh-ag.com. Please note that every new release of AMLS DDBs are stamped with the creation date, which can be seen in the f06 files. So for this version the following can be found in the f06 file: ******************************************************** ******************************************************** ** ** ** COPYRIGHT 2007 ** ** THIS DMAP PROGRAM HAS BEEN DEVELOPED BY CDH AG ** ** ALL RIGHTS RESERVED. ** ** CREATION DATE: ** ** ** ******************************************************** ******************************************************** The following items were new or changed in both MSC and NX DDBs. 1. New method of specifying residual vectors in MSC/Nastran. One typical use of residual vectors it to apply a set of loads equal and opposite, across a CDAMP, CBUSH and other such one-dimensional elements. Presently, this is done in MSC Nastran via specifying corresponding DAREA, RLOADi for each desired element and these loads are not requested in Case Control. In NX/Nastran there is a more convenient method of doing this by simply creating a data record in the Bulk Data Deck, e.g., RVEL, ELtype, ID1, ID2, ID3, thru, ID4 and NX Nastran internally creates equal and opposite residual loads across the elements listed in RVEL. 7

8 This feature is not available in MSC/Nastran and CDH has created a similar alternative that achieves the same goal. In the Case Control Deck, the user must specify a desired set of elements, e.g., SET Id = ID1, ID2, ID3, thru, ID4 and in the Bulk Data Deck the following parameter must be defined, e.g., param, rvel, Id which refers to the SET Id in Case Control. From now on, param, resvec should not be used in Bulk Data Deck, but rather, use the RESVEC command in Case Control. The user is remained that if RESVEC is not specified in Case Control, the default is that residual loads are applied for all possible cases (see MSC and NX QRG). Since the release of the previous Data Base, the restriction on the use of RESVEC(DAMP) was removed, so that now, the DDB is in full compliance with the standard DDB (SSS). Therefore, if the user wishes to apply residual loads across damping elements such as hydromounts or shock absorbers, the best approach is to use the new capability in MSC (set definition + param, rvel) or NX (Bulk Data RVEL). In Case Control, always specify RESVEC(NODAMP), because if this is not done, the residual loads will be applied across ALL damping elements, including damping elements that represent the modal critical damping in modal tire models. Doing this is simply wrong and it can lead to potential numerical difficulties. 2. CDH has also developed a new technique for computation with frequency dependent elements (recommend only CBUSH!) and is included in the latest DDB. This technique is computationally very efficient, but it is of specialized nature, therefore, if any one is interested, please contact support@cdh-ag.com. 3. In the previous release of FastFRS and DDB, the user had the ability to specify which algorithm would be used by FastFRS via the Bulk Data parameter, k4meth. This parameter still exists, however, an new parameter, decide, has been introduced: 8

9 param, decide [yes, no] the default being yes, which means that FastFRS itself will choose the optimal algorithm. To revert to the previous method simply input param, decide, no and param, k4meth, x. 4. As has already mention at the beginning of this release note, the new DDB will automatically set the values of these three parameters to: param, k6rot, 0. param, snorm, 45.0 param, qr6rot, 2 The following messages will be found in the *.f06 file in case the user did not specify k6rot=0. and snorm=45.0: ^^^=============================================== ^^^WARNING MESSAGE: PARAMETER SNORM RESET TO 45.0 ^^^=============================================== ^^^=============================================== ^^^WARNING MESSAGE: PARAMETER K6ROT RESET TO 0.0 ^^^=============================================== Consequently, the results may slightly change for a well defined model, but it is the opinion of CDH that these defaults should always be used. So, it is better to do it sooner than later. However, if some users are adamant about using the old defaults, there is a way to obtain those defaults, but it will not be described in this document, rather contact support@cdh-ag.com. 5. At present, AMLS and FastFRS, are used for most dynamic response calculations by many companies. There is one particular application that needs some further explanation for the most effective use of FastFRS and it involves the modal frequency response analysis of powertrains. In a typical powertrain analysis observed by CDH, most users define multiple load cases, each case with its own RPM definition and a corresponding unique FREQ definition. For example, there may be as any as 61 subcases with RPMs ranging from 1000 to 7000 in steps of 100. This means that the FastFRS will be called by Nastran 61 times. If there is any structural damping present in 9

10 the model (which is typically the case) then the optimal selection of FastFRS parameters in the Bulk Data Deck is: param, decide, no param, k4meth, 0. For technical support and assistance to CDH/AMLS and CDH/FastFRS application, please contact 10