NEi Nastran Linear Tips and Tricks
Contents
1. View 1 Untited Data Selection Category 0 Any Output G Cut Model Parallel Sections Type 0 Value or Magnitude D Wikis asiu T Data at Comers Program Analysis Type Set Value AN CASE 1 Z NEnastan Static o Tn Tyre D Value 7 7 Maximum 54758 1 271555 Mode 1 TOTAL TRANSLATION 4 Contour Transformation 55489 0 00797957 16509 o 775 SHELL MESH CONVERGENCE ERROR BOTTOM Trace Locations 776 SHELL MESH CONVERGENCE ERROR TOP 77 NVERCE Streamline Options IN PRINCIPAL STRESS BOTTOM TOF 5038 SHELL MAX MAX SHEAR STRESS BOTTOM TOP 16038 SHELL MAX VON MISES STRESS BOTTOM TOP 16043 SHELL FIBER DISTANCE TOP NEi Sensitive Proprietary Not releasable to other FEA ven www NEiSoftware com Mesh Convergence Error NEI NS Design Analysis and Simulation Output from LOG and RSF Files MAXIMUM QUAD ELEMENT PRINCIPAL STRESS 8 116895E amp 03 AT ELEMENT MINIMUM QUAD ELEMENT PRINCIPAL STRESS 8 116895E 03 AT ELEMENT MAXIMUM QUAD ELEMENT SHEAR STRESS 4 283409E 03 AT ELEMENT MAXIMUM QUAD ELEMENT VON MISES STRESS 8 350951E 03 AT ELEMENT Dane MAXIMUM SHELL ELEMENT NORMALIZED STRESS ERROR 7 650357E 02 AT GRID 6 MINIMUM SHELL ELEMENT NORMALIZED STRESS ERROR 0 000000E 00 AT GRID 18 SHELL ELEMENT RELATIVE STRESS ERROR 7 650357E 02 www NEiSoftware com itive Proprietary Not releasable to other FEA vendors Mesh Convergence Erro2. Element Type Options NEi Software Design Analysis and Simulation Parameter Description Type Default SHELLRNODE Shell element drill degree of freedom option When set to ON ON OFF OFF CQUAD4 and CTRIA3 entries will be converted to CQUADR and CTRIAR entries respectively www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA ver Nei YSitware Design Analysis and Simulation Improving Accuracy www NEiSoftware com NEi Sensitive Proprietary Not able to other FEA vendors Improving Accuracy NEi Design Analysis and Simulation e SKINGEN Model Parameter ENHCBARRSLT Model Parameter ENHCQUADRSLT Model Parameter www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN Model Parameter NE YSitware Design Analysis and Simulation What does it do Generates nonstructural surface skin elements over the exterior of the solid element part What are the options DISABLE SURFACE HYBRIDX HYBRIDM and HYBRIDA see Reference Manual for more information Which options do care about Default which is DISABLE and the SURFACE option When should use this parameter Anytime you have a solid model and are concerned about the coarseness of the mesh as it pertains to stress and strain accuracy www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN M
3. NEi Software Presents J une 2013 Nastran User Conference ae NEi Nastran Linear Tips and mi David Weinberg NEi Software NEI NS Design Analysis and Simulation A www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors NEi Design Analysis and Simulation NEi Nastran Basic Tips and Tricks www NEiSoftware com Topics NEi Design Analysis and Simulation e Selecting the Right System to Run On Element Type Options e Improving Accuracy e Assessing Accuracy Troubleshooting www NEiSoftware com NEi Design Analysis and Simulation Selecting the Right System to Run On www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Computer Recommendations NEI Design Analysis and Simulation Order of Importance when purchasing a computer 1 RAM 2 CPU 3 Storage www NEiSoftware com Computer Recommendations NE YSitware Design Analysis and Simulation RAM You must have sufficient memory to run the analysis otherwise it will slow down drastically Use the task manager and check the memory usage of the Nastran exe process to estimate memory usage Make sure you are running a et Abit OS to take advantage of higher memory limits www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Computer Recommendations ME SS Software Design Analysis
4. Display www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The ENHCBARRSLT Model Parameter NEi YSitware Design Analysis and Simulation Parameter Description Default ENHCBARRSLT Oplivn fur enhanced CBAR and CBEAM elemenl resulls When sel OFF to ON an improved method for calculating CBAR and CBEAM element stress results is used when a corresponding PBARL and PBEAML property type is specified Maximum direct and invariant stresses are determined using an automatically generated internal cross sectional mesh at each element end A separate finite element solution is performed on each mesh with direct and invariant results calculated at each mesh point and the maximum and minimum values reported www NEiSoftware com y No o other FEA vendors Design Analysis and Simulation Peak Stress MPa The ENHCQUADRSLT Model Parameter NEI NS Plate with Hole Filleted Plate LELEO CEECEE pesca MSC Nastran NEINastran Target Ei Peak Stress MPa 8 g gs 8 MSC Nastran m NEiNastran Target mo 1500 1 2 3 5 1 as 4 5 Mesh Refinement ial esata www NEiSoftware com NEi Sensitive Proprietary Not releasable to other FEA vendors The ENHCQUADRSLT Model Parameter NEi Software Design Analysis and Simulation Parameter Description ENHCQUAD
5. NDOF Sse rt eS uP www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Solution Error Measure Epsilon NEI NS Design Analysis and Simulation Output from LOG and RSF Files MAXIMUM DISPLACEMENT MAGNITUDE 4 340151E 02 AT GRID 2 MAXIMUM ROTATION MAGNITUDE 6 367040E 03 AT GRID 2 5 336379E SOLUTION TIME FOR 12 DEGREES OF FREEDOM 0 0 SECONDS MAXIMUM SINGLE POINT CONSTRAINT FORCE MAGNITUDE 1 005037E 03 AT GRID 1 MAXIMUM SINGLE POINT CONSTRAINT MOMENT MAGNITUDE 1 000050E 04 AT GRID 1 www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Vector Resultant Balance NEI NEi Design Analysis and Simulation Output from OUT File LOAD VECTOR RESULTANT SUBCASE T T2 3 RL R2 R3 ID 1 1 000000E 02 1 000000E 03 1 000000E 01 0 000000E 00 1 000000E 02 1 000000E 04 SINGLE POINT CONSTRAINT VECTOR RESULTANT SUBCASE T T2 3 RL R2 R3 ID 1 1 000000E 02 1 000000E 03 1 000000E 01 0 000000E 00 1 000000E 02 1 000000E 04 www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA Nei YSitware Design Analysis and Simulation Troubleshooting www NEiSoftware com NEi Sensitive Proprietary Not rel Typical Issues NE SGhtware Design Analysis and Simulation Bad epsilon greater that 108 Bad eigenvalue error measures greater than 10 2 Bad eigenvalue orthogonality losses gr
6. after multipoint constraints are applied before single point constraints are applied Perform checks after single point constraints are applied before static condensation 4 Perform checks after static condensation before decomposition 5 Perform checks 1 4 above 2 RBCHECKMODES Specifies the number of modes to solve for in an automated modal Integer rigid body check When set to a value greater than zero will perform an eigenvalue extraction analysis requesting that number of specified modes on the unconstrained model Displacements and strain energy are output Multipoint constraints requested in the first L subcase of the model will be included www NEiSoftware com to other FEA vendors NE NEi Design Analysis and Simulation ey www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Nei YSitware Design Analysis and Simulation a Questions www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors
7. degradation auto The AUTO setting default will use the ON setting for stiffness matrix and stress calculations for models less than DECOMPAUTOSIZE or nonlinear solutions For models greater than DECOMPAUTOSIZE and AUTO only the stiffness matrix assembly phase will use the ON setting The AUTO setting is recommended and provides optimal performance with accuracy QUADINODE Quad element internal node option When set to ON quad elements ON OFF AUTO will produce more accurate results with a small performance AUTO degradation The AUTO setting default will use the ON setting for stiffness matrix and stress calculations for models less than DECOMPAUTOSIZE models with composite shell elements or nonlinear solutions For models greater than DECOMPAUTOSIZE and AUTO only the stiffness matrix assembly phase will use the ON setting The AUTO setting provides optimal performance with accuracy TETINODE Tet element internal node option When set to ON parabolic tet ON OFF OFF elements will produce slightly more accurate results with a small AUTO performance degradation The AUTO setting default will use the ON setting for stiffness matrix and stress calculations for models less than DECOMPAUTOSIZE or nonlinear solutions For models greater than DECOMPAUTOSIZE and AUTO only the stiffness matrix assembly phase will use the ON setting www NEiSoftware com jeasable to other FEA vendors ary Not
8. 1632399E 12 41532399E 12 41632399212 0 000000E 00 0 000000E 00 4 632399E 12 4 632399E 12 AT ELEMENT 1 AT ELEMENT 1 AT ELEMENT 1 MAXIMUM BAR ELEMENT TOTAL STRESS MINIMUM BAR ELEMENT TOTAL STRESS MAXIMUM BAR ELEMENT VON MISES STRESS www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The ENHCBARRSLT Model Parameter NEi Software Design Analysis and Simulation 3000 BAR MOMENT END A Z PLANE 1 3001 BAR MOMENT END A Y PLANE 2 3002 BAR MOMENT END B Z PLANE 1 3004 BAR FORCE END A Y PLANE 1 3005 BAR FORCE END A Z PLANE 2 3006 8AR FORCE END B Y PLANE 1 3007 BAR FORCE END B Z PLANE 2 3008 BAR FORCE END AX g 3076 BAR STRESS END A POINT D 3077 BAR STRESS END A POINT E 3078 BAR STRESS END A POINT F 3083 8AR STRESS END B POINT C 3084 BAR STRESS END B POINT D 3085 8AR STRESS END B POINT E 3107 BAR STRESS END A AXIAL 3108 BAR STRESS END B AXIAL 5108 8AR STRESS END A MAX 3110 BAR STRESS END A MIN 3111 BAR STRESS END B MAX 3112 BAR STRESS END B MIN 53195 BAR VON MISES STRESS Section Gut Options e tio Parallel Sections Cut Model Multiple Sections Program Analysis Type Set value NENastran Value Maximum Minimum Maximum Minimum p Final Output Set Output Set Increment Contour Options Trace Locations Contour Vectors Streamline Options Ca Ereehody
9. RSLT Type Default Oplion for entianved CQUADR element resulls Wher sel lv ON an ON OFF OFF improved method for calculating CQUADR element stress results is used which gives better accuracy in regions with stress concentrations www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Nei YSitware Design Analysis and Simulation Assessing Accuracy www NEiSoftware com NEi Sensitive Proprietary Not able to other FEA vendors Results Quality Assessment NE YSitware Design Analysis and Simulation e Mesh Convergence Error Solution Error Measure Vector Resultant Balance www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Mesh Convergence Error Nei YSitware Design Analysis and Simulation Establishes an upper bound of the stress error associated with shell and solid elements mesh density Provides a normalized error based on von Mises stress at each solid or shell element grid point Useful in determining areas where mesh density should be increased or can be decreased Max Min grid point and overall model shell and solid element errors output in all structural oom ee solutions Humber o omen www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors NEI Mesh Convergence Error Software Design Analysis and Simulation Select PostProcessing Data
10. and Simulation CPU The clock speed has a direct relationship with analysis time Get the Intel Xeon processors as they perform better at the same clock speed vs the consumer i5 i7 processors www NEiSoftware coem NEI Sensitive Proprietary Not releasable to other FEA vendors Computer Recommendations NEi g Software Design Analysis and Simulation Storage e Using a solid state disk SSD can significantly increase the performance of large models that use a lot of temporary files www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors CPU Clock Speed vs Cores Nei YSitware Design Analysis and Simulation Ahighly scalable 1 3 Million DOF model was compared on 2 systems r System 1 Intel Xeon quad core 3 4GHz System 2 Dual Intel Xeon 8 core 2 6GHz 1 3 Million DOF Direct Frequency Response Model The goal is to find out if higher clock speeds are faster or if more cores are faster www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Computer Recommendations CPU NEI NEI are Clock Speed vs Cores Design Analysis and Simulation Most models such as linear static won t see as much scaling so in general the higher clock speed CPU will be faster for typical models If you do significant direct frequency response analysis the larger core count CPUs may be faster of cpus Sol
11. d dimensions Review vector resultants in OUT file www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Useful Parameters for Troubleshooting NEi Software Design Analysis and Simulation Parameter Description Type Default AUTOFIXELEMGEOM Option for automatically correcting elements that are singular due to ON OFF ON an incorrect ordering of the element grid points AUTOFIXRIGIDELEM When set to ON will automatically correct improperly defined RBES ON OFF ON elements by adding rotational degrees of freedom to averaging grid points as needed to prevent rigid body motion AUTOFIXRIGIDSPC When set to ON will automatically correct the following rigid element ON OFF OFF interpolation element and MPC equation issues by adding a near rigid spring at the dependent degrees of freedom A rigid element interpolation element or MPC equation dependent degree of freedom is constrained One or more rigid elements interpolation elements or MPC equations reference the same dependent degree of freedom A series of rigid elements interpolation elements and or MPC equations are connected in a continuous link An RBE2 element is defined with the independent grid point located at the origin of a cylindrical coordinate system and rigidity is desired only in the R or T component direction When AUTOFIXRIGIDSPC is set to OFF behavior will be that of a rigid element def
12. eater than 10 Singularity or non positive definite errors Element geometry warning messages More or less than expected number of rigid body modes Excessive mesh convergence error No convergence in the maximum number of iterations permitted Applied load and SPC vector resultants are not equal and opposite Unrealistic results sa WM RIES Ravana ork NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NE YSitware Design Analysis and Simulation Bad epsilon greater that 108 Typically caused by a lack of constraint where the displacements are unrealistically high often absurd An iterative solution was performed for the solution of displacements using the VIS or PCGLSS solver and convergence was not achieved or convergence tolerance too low SPARSEITERTOL model parameter There are unrealistically high or low values of stiffness sometimes both in the model Bad element geometry use the ELEMGEOMOUT model parameter and check the OUT file for a low or negative Jacobian www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NEI Shew Software Design Analysis and Simulation Bad epsilon greater that 108 Continued Bad material properties check the OUT file material output Check other warning messages and refer to User s Manual Error Messages section www NEiSoftware com NEI Sensitive Proprietary Not releasable to o
13. element volume it ELEMGEOMOUT is set to JACOBIAN2 then the sort will be in ascending order and only based on the minimum Jacobian determinant at each comer node normalized using adjacent element edge lengths www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA ver Useful Parameters for Troubleshooting NEi Software Design Analysis and Simulation Parameter Description Type Default PARTGEOMOUT Individual part geometry statistics output option When set to ON ON OFF OFF additional part statistical information will be output including Material Property type Bounding box dimensions Mass Volume e Number of grid points Number of elements PARTMASSOUT Individual part mass properties output option When set to ON ON OFF OFF additional part mass properties information will be output including Material e Property type e Mass e Location of center of gravity Mass moment of inertia www NEiSoftware com to other FEA vendors Useful Parameters for Troubleshooting NEi Software Design Analysis and Simulation Parameter Description Type Default NLKIAGAFACT Specifies the stiffness to be added to diagonal terms of the global Real 00 stiffness matrix Specifying a small positive value is useful in stabilizing a solution and preventing a non positive definite or singularity error In nonlinear static solutions
14. ement mesh surface There are HYBRIDX five options HYBRIDM 0 Automated surface skin generation is disabled HYRRINA 1 Surface skin elements and results are generated on the solid element mesh surface No changes are made to the connected solid element corner results 2 Surface skin elements and results are generated on the solid element mesh surface Connected solid element corner stress and strain values are replaced with corresponding skin element values regardless of magnitude 3 Surface skin elements and results are generated on the solid element mesh surface Connected solid element corner stress and strain values are replaced with corresponding skin element values if the magnitude of the skin element component is larger 4 Surface skin elements and results are generated on the solid element mesh surface Connected solid element corner stress and strain values are averaged with corresponding skin element values The character variables DISABLE SURFACE HYBRIDX HYBRIDM and HYBRIDA may be used in place of the numerical options 0 through 4 www NEiSoftware com NEI Sensitive Propr 2 to other FEA vendors The ENHCBARRSLT Model Parameter NE YSitware Design Analysis and Simulation Previous Limitations of Bar Element Results Load Load rO YO c Circular bar with vertical loading When the load is rotated the c Standard stress recovery points value changes Stress Mc l c 7071 rad
15. epending on the setting for QUADINODE The DKT and DKQ elements may be slightly more accurate than the SRI in very coarse meshes however the SRI element performs better in nonlinear and buckling solutions All three element types handle finite transverse shear stiffness The SRI and DKQ element types are supported in all solutions The DKT element type is supported in linear solutions only if QUADINODE is set to ON and the DKT element type is selected the bending element will be comprised of four DKT subelements and a center node If QUADINODE is set to OFF and the DKT element type is selected the bending element will be comprised of two overlapping DKT sub elements TRIELEMTYPE Tri element bending formulation option DKTISRI DKT DKT Discrete Kirchhoff Mindlin Triangle SRI Selective Reduced Order Integration The DKT element is typically more accurate than the SRI in coarse meshes and like the SRI element works well for both thick and thin plates Both element types handle finite transverse shear stiffness and are supported in all solutions www NEiSoftware com jeasable to other FEA vendors NEi Sensitive Pro ary Not Element Type Options NEi Software Design Analysis and Simulation Parameter Description Type Default HEXINODE Hex element internal node option When set to ON hex elements will ON OFF AUTO produce more accurate results with a small performance
16. ined in the Cartesian rectangular system which defined the specified cylindrical system When AUTOFIXRIGIDSPC is set to ON and a translational or rotational component is missing the local grid coordinate system at each independent grid point defines that dependent independent segment The spring element stiffness is defined by the KRIGIDELEM model parameter See KRIGIDELEM below www NEiSoftware com 10 other FEA vendors NEi Sensitive Pro Useful Parameters for Troubleshooting NEi Software Design Analysis and Simulation Parameter Description Type Default ELEMGEOMOUT Option to output individual element geometry statistics When ON OFF OFF ELEMGEOMOUT is set to ON the following statistics are output to ASPECTRATIO the Model Results Output File for each element SKEWANGLE Aspect ratio JACOBIANI JACOBIAN2 Taper ratio Skew angle Warping angle Normalized Jacobian The data is sorted based on normalized Jacobian determinant skew angle and aspect ratio in ascending order for each element type If ELEMGEOMOUT is set to ASPECTRATIO then the sort will be in descending order and only based on element aspect ratio If ELEMGEOMOUT is set to SKEWANGLE then the sort will be in descending order and only based on element skew angle If ELEMGEOMOUT is set to JACOBIANI then the sort will be in ascending order and only based on the total Jacobian determinant normalized using
17. ius now c radius Stress is predicted lower www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The ENHCBARRSLT Model Parameter NE YSitware Design Analysis and Simulation ENHCBARRSLT parameter addresses this Nastran limitation Small FEA model of bar is built automatically and run with loading from forces moments Peak stress values extracted Shear stresses and torques are included Requires PBARL or PBEAML www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The ENHCBARRSLT Model Parameter NEi SGhtware Design Analysis and Simulation Advantages No more stress recovery points needed Correct c value used Stresses now independent of recovery points Principal stresses reported which include full stress tensor www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The ENHCBARRSLT Model Parameter NE YSitware Design Analysis and Simulation New Output Vector Definition e SX C Maximum Stress X D Minimum Stress SX E Maximum Stress Magnitude e SX F Minimum Stress Magnitude usually zero unless SX D is positive SX MAX and SX MIN are simply the max and min of the others STRESSES IN BAR ELEMENTS ELENENT DISTANCE sx c 5x 0 SX E SX F AXIAL SX NAX SX MIN ID 1 0 0000 1 273344E 04 1 273344E 04 1 273344E 04 2 617484E 01 0 000000E 00 1 273344e 04 1 273344E 04 10000 4
18. le to other FEA vendors Typical Issues Nei YSitware Design Analysis and Simulation No convergence in the maximum number of iterations permitted Typically this only happens if the user has limited the number of iterations as a performance consideration Increasing the maximum number of iterations for the VIS and PCGLSS solvers use MAXSPARSEITER model parameter will fix this www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NE YSitware Design Analysis and Simulation Applied load and SPC vector resultants are not equal and opposite Often due to the PCGLSS convergence tolerance being too high Decreasing the convergence tolerance use SPARSEITERTOL model parameter will fix this Could also be due to bad RBE3 element definition invalid MPC equations or internal constraints due to bad materials excessively high stiffnesses non collocated CELASi elements etc www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NE YSitware Design Analysis and Simulation Unrealistic results Check for other issues by first reviewing warning messages Verify that previously discussed issues are not the cause Use RBCHECKLEVEL model parameter and or RBCHECKMODES Check the OUT file material output Check Grid Point Weight Generator output Use PARMASSOUT model parameter to verify individual part mass an
19. nd 256GB aleae eet and Hard Disk SSD for temp files P Note High write speed is critical at least 400MB sec is good Operating System Windows 7 Professional 64 bit or Windows 8 Professional 64 bit www NEiSoftware com Computer Recommendations NEi Software Design Analysis and Simulation Laptop Budget Laptop Intel Core i5 Dual or Quad Core High End Laptop Intel Core i7 Dual or Quad Core CPU at high clock speed at high clock speed Memory RAM 4GB 16GB Graphics Card 1 GB dedicated video card 2 GB NVIDIA or equivalent ATI i 1TB SATA 7200RPM 9120D OF TRIS Hard Disk Note High write speed is critical at least 400MB sec is good Operating System Windows 7 Professional 64 bit or Windows 8 Professional 64 bit NEI Sensitive Proprietary Not releasable to oi www NEiSoftware com er FEA vendors Nei YSitware Design Analysis and Simulation Element Type Options www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Element Type Options NEi Software Design Analysis and Simulation Parameter Description Type Default QUADELEMTYPE Quad element bending formulation option SRI DKO SRI DKT SRI Selective Reduced Order Integration DKQ Discrete Kirchhott Mindlin Quadrilateral DKT Discrete Kirchhoft Mindlin Triangle either two overlapping or four dissecting DKT elements d
20. ndors Typical Issues NE Sina Software Design Analysis and Simulation More or less than expected number of rigid body modes More means there is a lack of constraint or internal mechanisms Less means there are internal constraints either due to AUTOSPC by the solver or bad MPC equations invalid RBE3 elements or non collocated CELASi elements www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NE YSitware Design Analysis and Simulation Element geometry warning messages If the distortion is extreme such as a quad element that resembles a tri element or a tet element that is almost completely flat it can cause other issues and generate inaccurate results The ELEMGEOMOUT model parameter will sort elements by worst to best making it easy to verify Can use ALIGNEDGENODE model parameter if the issue is related to EPLR or EPAD The AUTOFIXELEMGEOM model parameter will fix obvious issues like wrong node numbering www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NEI Sina Software Design Analysis and Simulation Excessive mesh convergence error Often corrected by increasing the mesh density in that area if it is critical Switching the element type parabolic vs linear may help Can also force QUADINODE and HEXINODE model parameters to ON www NEiSoftware com NEI Sensitive Proprietary Not releasab
21. odel Parameter NEI NS Design Analysis and Simulation Automatic Surface Skin Generation ASSG Creates nonstructural membrane surface elements on all solid element types to enhance the accuracy of peak stress recovery Solid Mesh Membrane Mesh www NtEiSottware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN Model Parameter NEI YSitware Design Analysis and Simulation We look at 2 different meshes i e Ahex8 mesh and a tet10 mesh 1 element through the thickness Ann Cantilever beam with a bending load L Tet10 mesh Hex8 mesh www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN Model Parameter NE YSitware Design Analysis and Simulation Theoretical solution Z displacement P 6 5 inches 3EI Max bending stress o 28 8 KSI www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN Model Parameter NE SGftware Design Analysis and Simulation Actual solution Z displacement Tet10 6 3 2 error Hex8 6 4 1 error www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN Model Parameter NE YSitware Design Analysis and Simulation Actual solution Element e Max bending stress Tet10 28 3 28 3 1 error Hex8 30 7 30 7 10 error NEI Sensiti
22. r NE YSitware Design Analysis and Simulation Parameter Description Type Default STRESSERROR Controls the output of normalized grid point stress error mesh ON OFF ON convergence error When setto ON stress error at each grid point is calculated using i nooo 4 pe o Azbr a where Nis the number of shell or solid elements attached to the node Zi is the von Mises stress predicted by element n at grid point i is the mean von Mises stress at grid point i The normalized error output is generated using and a relative stress error based on element volume www NEiSoftware com NEI Sensitive 2 to other FEA vendors Solution Error Measure Epsilon NE YSitware Design Analysis and Simulation Measure of accuracy of the global displacement vector e Values less than 10 are generally considered acceptable The DELTASTRAINEGOUT model parameter can be used to output residual strain energy at each grid point Causes for unacceptably large epsilon values discussed in next section www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Solution Error Measure Epsilon Nei YSitware Design Analysis and Simulation The residual strain energy vector is calculated using E Ku P u where uis the global displacement vector P is the global load vector K is the global stiffness matrix The solution error measure epsilon is calculated using
23. the added stiffness is decreased at the completion of each increment so to reach the value defined by NLKDIAGMINAFACT at the completion of the last increment See also NLKDIAGCOMP and NLKDIAGMINAFACT SOLUTIONERROR When set to ON it directs the program to substitute the value of ON OFF OFF FACTDIAG default 1 0E 10 for the factored diagonal term when a singularity or non positive definite is detected if FACTDIAG is set to zero non positive definites are ignored while a singularity will result in program termination SOLUTIONERROR and FACTDIAG are ignored in eigenvalue solutions and when the sparse iterative solvers PCGLSS or VIS are used While this option is useful for modeling checkout it may lead to solutions of poor quality or fatal messages later in the run It is recommended that SOLUTIONERROR be set to OFF for production runs www NEiSoftware com tary Not releasable to other FEA vendors Useful Parameters for Troubleshooting NEi Software Design Analysis and Simulation Parameter Description Type Default RBCHECKLEVEL Stiffness matrix equilibrium checks option Equilibrium checks verity 0 lt Integer lt 5 0 whether an unrestrained model can undergo simple rigid body motion without generating intemal forces There are six options 0 Do not perform any checks 1 Perform checks after stiffness matrix assembly before multipoint constraints are applied Perform checks
24. ther FEA vendors Typical Issues NE YSitware Design Analysis and Simulation Bad eigenvalue error measures greater than 10 2 Causes and actions are similar to actions taken with a bad epsilon value There are unrealistically high or low values of stiffness sometimes both in the model Unrealistically high values of mass Check other warning messages and refer to User s Manual Error Messages section www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NEi i Software Design Analysis and Simulation Bad eigenvalue orthogonality losses greater than 10 2 Causes and actions are similar to bad eigenvalue error measures www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors Typical Issues NEi i Software Design Analysis and Simulation Singularity or non positive definite errors Typically due to a lack of constraint or an internal mechanism in a static solution Use the SOLUTIONERROR or NLKDIAGAFACT model parameters to help identify the source of the issue e Also can use RBCHECKLEVEL and RBCHECKMODES model parameters to identify the source e Negative stiffness can cause this so check the Grid Point Singularity Table and the OUT file material output Shell element drill DOF issues can cause this so try the SHELLRNODE model parameter www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA ve
25. ution Time Solution Time 16 Core 4 Core 16 Core Faster J 1479 223 a 884 129 a 713 86 zg 614 19 1g 7f s14 39 NEI Sensitive Proprietary No Performance of 1 3M DOF Direct Frequency Response 2500 A 2000 g Solution Time 4 Core a D 1500 E Solution Time 16 Core g Q 1000 3 oJ N 500 0 __ __ _ _ 0 4 8 12 16 Number of CPUs www NEiSoftware com releasable to other FEA vendors Computer Recommendations NEI NEI are SSD vs HDD Design Analysis and Simulation CPU Intel Core i7 2 8GHz RAM 8 GB HDD Western Digital Black 7 200RPM 1TB SSD Samsung 470 128GB Sequential Read Write Performance m Avg Read Speed MB s Avg Write Speed MB s With the SSD an average speedup of 27 was found for large models that use a lot of temporary files SSD Speedup E Modell Model2 Model3 Model Model5 Madel 6 www NEiSoftware com NEi Sensitive Proprietary Not releasable to other FEA vendors Computer Recommendations Workstation NEI Re were Design Analysis and Simulation Budget System High End System Intel Core i5 i7 Dual or Quad Dual Intel Xeon Quad core CPUs at high clock speed 3 5 GHZz or CPU Core at high clock speed single Xeon 8 core CPU at high clock speed 2 8 GHz Memory RAM 8 GB 32GB Graphics Card 1 GB dedicated video card oR Quadrolk2000 or 1TB SATA 7200RPM a
26. ve Proprietary Not releas Actual solution Skin Max bending stress Tet10 27 9 28 3 1 error Hex8 27 5 27 9 2 error www NEiSoftware com able to other FEA vendors The SKINGEN Model Parameter NE NE Design Analysis and Simulation More accurate outer fiber stress 7 OOOO Mesh Convergence Skin Stress vs Solid Stress 250 245 240 235 Solid Stress 230 225 m Skin Stress x Symmet Von Mises Stress mo Theoretical 215 210 o 1 2 3 4 5 6 7 Elements Through Thickness www NEiSoftware com NEI Sensitive Proprietary Not releasable to other FEA vendors The SKINGEN Model Parameter NEI NS Design Analysis and Simulation Solid element stress Shell skin element stress eaman a ena iate a ho vecis cefrmston _ Wansfarratan Te D ke io R 6336177 LIOTA TETON E z no a yO me rae estore Snerre cone ren aad www NEiSoftware com NEi Sensitive Proprietary Not rel le to other FEA vendors The SKINGEN Model Parameter Nei YSitware Design Analysis and Simulation Parameter Description Type Default SKINGEN Automated Surface Skin Generation ASSG Generates non O lt Integer 4 0 structural surface skin elements used in stress and fatigue analysis DISABLE A value between O and 4 defines the method used to calculate SURFACE element corner results on a solid el
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