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Everything posted by Rahul Ponginan

These eBooks discuss the FEA and CAE theory in detail and involves extensive discussions.

We have books on this and other tools and topics, you can download them for free here  https://altairuniversity.com/freeebooks2/

The equation of motion for a static analysis is as below: [K] {X} = {F}  (1) [K] > Global Stiffness Matrix {X} > Unknown Displacement {F} > External Force Applied. For the body to be in static equilibrium, the net force acting at every node must be zero. Therefore, the basic statement of static equilibrium is that the internal forces, I, and the external forces, F, must balance each other: [K] {X} is nothing but internal force 'I' Equation (1) now becomes, ==> I = F or I  F = 0 (2) In Dynamic Analysis, the imbalance between the external and internal forces results in an acceleration: F  I = M a. F > External Forces I > Internal Force M*a > Inertial Forces (mass times acceleration) In linear static analysis the stiffness matrix is constant and shall not change/update throughout the analysis. There are many check need to be performed once you have linear static results for well conditioned problems. The equation (1) is decomposed one time to find the unknown displacement. [K] {X} ={F} After decomposition, a singularity may lead to an incorrect solution. In static analysis to obtain {X} (displacements). Using these displacements, One can calculate a “residual” loading vector as follows: [K] {X} {F} =δ F This residual vector should theoretically be null (equation 2) but may not be null due to numeric roundoff. In Nonlinear static analysis, The stiffness matrix changes in each and every iteration since the stiffness matrix is dependent on the external load. The external load in Nonlinear static analysis is applied in increments and time here has no physical meaning. Time is just a convenient way to apply full load in nonlinear static analysis. In Optistruct the incremental load is controlled by 'NINC' field in the NLPARM card for NLSTAT load steps, this is a fixed load increment method. If you add the PARAM,EXPERTNL,YES to the deck, the time increment method becomes automatic in which case, the increment (load) is increased or cut back based on the convergence rate. NLGEOM loadstep has automatic time step by default. In NLGEOM loadstep the RAMP load curve can be defined using TABLED1 card and then refer this in NLOAD1 card. In nonlinear static analysis, OptiStruct uses the NewtonRaphson method to obtain solutions for nonlinear problems to maintain the residuals close to zero (equation 2) In a nonlinear analysis the solution usually cannot be calculated by solving a single system of equations, as would be done in a linear problem. Instead, the solution is found by applying the specified loads gradually and incrementally working toward the final solution. Therefore, OptiStruct breaks the simulation into a number of load increments (NINC) and finds the approximate equilibrium configuration at the end of each load increment. It is important that you clearly understand the difference between an analysis step (NLSTAT / NLGEOM), a load increment (NINC of NLPARM card), and an iteration (MAXITER of NLPARM card) The load history for a simulation consists of one or more steps. Within a step you will have many no of increments (NINC), within increment there can be many no. of iteration (MAXITER). OptiStruct checks the equilibrium equation ( equation 2) for each and every iteration. If the solution from an iteration is not converged, OptiStruct performs another iteration to try to bring the internal and external forces into balance. An increment is part of a step. An iteration is an attempt at finding an equilibrium solution in an increment when solving with an implicit method. If the model is not in equilibrium at the end of the iteration, OptiStruct tries another iteration. With every iteration the solution OptiStruct obtains should be closer to equilibrium; sometimes OptiStruct may need many iterations to obtain an equilibrium solution. When an equilibrium solution has been obtained, the increment is complete.

Click here for Optistruct tips and tricks

setup of a composite simulation
Rahul Ponginan replied to Rahul Ponginan's topic in Altair OptiStruct

Learn more about this from the FEA eBook http://www.altairuniversity.com/freeebooks2/freeebookpracticalaspectsoffiniteelementsimulationastudyguide/

Essential Steps To Start With Nonlinear FEA
Rahul Ponginan replied to Rahul Ponginan's topic in Altair OptiStruct
Learn more about this from the FEA eBook http://www.altairuniversity.com/freeebooks2/freeebookpracticalaspectsoffiniteelementsimulationastudyguide/ 
Essential Steps To Start With Nonlinear FEA
Rahul Ponginan replied to Rahul Ponginan's topic in Altair OptiStruct
Essential Steps To Start With Nonlinear FEA • Learn first how the software works on a simple model before you use a nonlinear feature which you haven’t used. Also guess how your structural component will behave, i.e. check for available studies, reports and benchmarks . • Try to understand the software’s supporting documentation, its output and warnings. • Know what you are looking for. Prepare a list of questions you think your analysis should be able to answer. Design the analysis, including the model, material model, and boundary conditions, in order to answer the questions you have in mind. • Keep the final model as simple as possible. A linear analysis done first can provide a lot of information such as where are the high stresses in the model, where the initial contact may occur, and what level of load will introduce plasticity in the model. The results of the linear analysis may even point out that there is no need for a nonlinear analysis. Examples of such a situation include the yield limit not being reached, there is no contact, and the displacements are small. • Verify and validate the results of the nonlinear FEA solution. Verification means that “the model is computed correctly” from the numerical point of view. Wrong discretization with respect to the mesh size and time stepping are common errors. Validation asks the questions if “the correct model” is computed e.g. the geometry, material, boundary conditions, interactions etc coincide with the one acting in reality. • Try to look into the assumptions made with respect to the structural component, its geometry behavior with respect to large strain (On/Off), look into different material models if the earlier model is unable to give you a result you expect (sometimes software only make some models compatible with commonly used elements and in this case you might look into a possibility of changing the element formulation). Essential Steps To Start With Nonlinear FEA • Learn first how the software works on a simple model before you use a nonlinear feature which you haven’t used. Also guess how your structural component will behave, i.e. check for available studies, reports and benchmarks . • Try to understand the software’s supporting documentation, its output and warnings. • Know what you are looking for. Prepare a list of questions you think your analysis should be able to answer. Design the analysis, including the model, material model, and boundary conditions, in order to answer the questions you have in mind. • Keep the final model as simple as possible. A linear analysis done first can provide a lot of information such as where are the high stresses in the model, where the initial contact may occur, and what level of load will introduce plasticity in the model. The results of the linear analysis may even point out that there is no need for a nonlinear analysis. Examples of such a situation include the yield limit not being reached, there is no contact, and the displacements are small. • Verify and validate the results of the nonlinear FEA solution. Verification means that “the model is computed correctly” from the numerical point of view. Wrong discretization with respect to the mesh size and time stepping are common errors. Validation asks the questions if “the correct model” is computed e.g. the geometry, material, boundary conditions, interactions etc coincide with the one acting in reality. • Try to look into the assumptions made with respect to the structural component, its geometry behavior with respect to large strain (On/Off), look into different material models if the earlier model is unable to give you a result you expect (sometimes software only make some models compatible with commonly used elements and in this case you might look into a possibility of changing the element formulation). 
AcuSolve Introduction Training webinar recording. The recording is useful for any new user to get an overview of AcuSolve workflow. http://www.altairuniversity.com/gettingstarted/learnacusolvetrainingwebinars/

Learn more about this from the FEA eBook http://www.altairuniversity.com/freeebooks2/freeebookpracticalaspectsoffiniteelementsimulationastudyguide/

New Feature in HW 2017 – Collision Detection Tool
Rahul Ponginan replied to Rahul Ponginan's topic in Altair RADIOSS
New Feature in HW 2017 – Collision Detection Tool (Click Here) A new feature called ‘Collision Detection ‘is introduced from HyperMesh 2017, which will check components or groups for element penetrations and intersections and we can fix those manually or automatically. Please note that the Collision Detection tool is only available in the RADIOSS and LSDYNA user profiles. Penetration is defined as the overlap of the material thickness of shell elements, while Intersection is defined as elements that actually pass completely through one another: Any penetrations or intersections in the model can lead to weird model behavior and may also result in run termination. So, it is important and always recommended to fix the penetrations or intersections in the model. 
Radioss 2017 Reference Manual Documents, User Guide and Tutorials
Rahul Ponginan replied to a topic in Altair RADIOSS
Hello All, Users can download RADIOSS 2017 Reference Guide , RADIOSS 2017 User Guide and RADIOSS 2017 Tutorial files from here. The model files for Student Edition users – accompaniment to the tutorials in Help can be downloaded from: http://www.altairuniversity.com/modelfilesforstudenteditionusersaccompanimenttothetutorialsinhelp/ RADIOSS_2017_Reference_Guide.pdf RADIOSS_2017_Tutorials_and_Examples.pdf RADIOSS_2017_User_Guide.pdf 
Altair HyperCrash is a CAE preprocessor developed to support RADIOSS, Altair's nonlinear finite element solver. HyperCrash provides a comprehensive environment to study occupant simulations and other requirements of the crashsafety domain. Fully supporting RADIOSS and LSDYNA solvers, combining the power of an intuitive GUI with an automated set of proven crash and safety modeling procedures, HyperCrash enables users to realize unprecedented time savings while achieving highquality, accurate results. Learn about the Latest Features on HyperCrash 2017 from http://www.altairuniversity.com/learninglibrary/hypercrashnewfeatures/ Also, watch Winter Directed Learning Webinar Series – Crash Analysis with RADIOSS at http://www.altairuniversity.com/learninglibrary/2017winterdirectedlearningwebinarseriescrashanalysiswithradioss/ You can also download the HyperCrash 2017 user guide from here: HyperCrash_2017_user_guide.pdf

Essential Steps To Start With Nonlinear FEA
Rahul Ponginan replied to Rahul Ponginan's topic in Altair OptiStruct
Essential Steps To Start With Nonlinear FEA • Learn first how the software works on a simple model before you use a nonlinear feature which you haven’t used. Also guess how your structural component will behave, i.e. check for available studies, reports and benchmarks . • Try to understand the software’s supporting documentation, its output and warnings. • Know what you are looking for. Prepare a list of questions you think your analysis should be able to answer. Design the analysis, including the model, material model, and boundary conditions, in order to answer the questions you have in mind. • Keep the final model as simple as possible. A linear analysis done first can provide a lot of information such as where are the high stresses in the model, where the initial contact may occur, and what level of load will introduce plasticity in the model. The results of the linear analysis may even point out that there is no need for a nonlinear analysis. Examples of such a situation include the yield limit not being reached, there is no contact, and the displacements are small. • Verify and validate the results of the nonlinear FEA solution. Verification means that “the model is computed correctly” from the numerical point of view. Wrong discretization with respect to the mesh size and time stepping are common errors. Validation asks the questions if “the correct model” is computed e.g. the geometry, material, boundary conditions, interactions etc coincide with the one acting in reality. • Try to look into the assumptions made with respect to the structural component, its geometry behavior with respect to large strain (On/Off), look into different material models if the earlier model is unable to give you a result you expect (sometimes software only make some models compatible with commonly used elements and in this case you might look into a possibility of changing the element formulation). 
Learn more about this from the FEA eBook http://www.altairuniversity.com/freeebooks2/freeebookpracticalaspectsoffiniteelementsimulationastudyguide/

The equation of motion for a static analysis is as below: [K] {X} = {F}  (1) [K] > Global Stiffness Matrix {X} > Unknown Displacement {F} > External Force Applied. For the body to be in static equilibrium, the net force acting at every node must be zero. Therefore, the basic statement of static equilibrium is that the internal forces, I, and the external forces, F, must balance each other: [K] {X} is nothing but internal force 'I' Equation (1) now becomes, ==> I = F or I  F = 0 (2) In Dynamic Analysis, the imbalance between the external and internal forces results in an acceleration: F  I = M a. F > External Forces I > Internal Force M*a > Inertial Forces (mass times acceleration) In linear static analysis the stiffness matrix is constant and shall not change/update throughout the analysis. There are many check need to be performed once you have linear static results for well conditioned problems. The equation (1) is decomposed one time to find the unknown displacement. [K] {X} ={F} After decomposition, a singularity may lead to an incorrect solution. In static analysis to obtain {X} (displacements). Using these displacements, One can calculate a “residual” loading vector as follows: [K] {X} {F} =δ F This residual vector should theoretically be null (equation 2) but may not be null due to numeric roundoff. In Nonlinear static analysis, The stiffness matrix changes in each and every iteration since the stiffness matrix is dependent on the external load. The external load in Nonlinear static analysis is applied in increments and time here has no physical meaning. Time is just a convenient way to apply full load in nonlinear static analysis. In Optistruct the incremental load is controlled by 'NINC' field in the NLPARM card for NLSTAT load steps, this is a fixed load increment method. If you add the PARAM,EXPERTNL,YES to the deck, the time increment method becomes automatic in which case, the increment (load) is increased or cut back based on the convergence rate. NLGEOM loadstep has automatic time step by default. In NLGEOM loadstep the RAMP load curve can be defined using TABLED1 card and then refer this in NLOAD1 card. In nonlinear static analysis, OptiStruct uses the NewtonRaphson method to obtain solutions for nonlinear problems to maintain the residuals close to zero (equation 2) In a nonlinear analysis the solution usually cannot be calculated by solving a single system of equations, as would be done in a linear problem. Instead, the solution is found by applying the specified loads gradually and incrementally working toward the final solution. Therefore, OptiStruct breaks the simulation into a number of load increments (NINC) and finds the approximate equilibrium configuration at the end of each load increment. It is important that you clearly understand the difference between an analysis step (NLSTAT / NLGEOM), a load increment (NINC of NLPARM card), and an iteration (MAXITER of NLPARM card) The load history for a simulation consists of one or more steps. Within a step you will have many no of increments (NINC), within increment there can be many no. of iteration (MAXITER). OptiStruct checks the equilibrium equation ( equation 2) for each and every iteration. If the solution from an iteration is not converged, OptiStruct performs another iteration to try to bring the internal and external forces into balance. An increment is part of a step. An iteration is an attempt at finding an equilibrium solution in an increment when solving with an implicit method. If the model is not in equilibrium at the end of the iteration, OptiStruct tries another iteration. With every iteration the solution OptiStruct obtains should be closer to equilibrium; sometimes OptiStruct may need many iterations to obtain an equilibrium solution. When an equilibrium solution has been obtained, the increment is complete.

Are any HyperWorks Applications slow during start up?
Rahul Ponginan replied to Rahul Ponginan's topic in Begin Here
You can fix this by closing all HW Applications and then searching/deleting the following folders: C:\ProgramData\xformation %USERPROFILE%\AppData\Local\VirtualStore\ProgramData\xformation\ss.<userID>.lock (if present) %USERPROFILE%\AppData\Local\xformation\ %USERPROFILE%AppData\Local\Temp\xformation C:\Windows\Temp\xformation Once these folders are deleted, reinvoke the product. You should see it open immediately. 
Anomalies with the browsers, the user interface layout (tab locations, command window, panel location, toolbars,) keyboard preferences, import/export settings etc certain malfunctions with errors and crashes can generally be resolved by deleting the settings files. The following problems in HyperMesh have been successfully fixed by deleting the settings files. Entities missing Radio buttons missing in panel area Buttons missing in panel area Toolbar icons missing Utility menu is blank, browser has icons missing Status bar is missing Errors Can’t set hm framework minibar Segmentation error when user starts hm Fatal menu system error hmmenu.set has one or more fatal errors Menu system corrupted : menu itemgroup : get pointer “Only a single create/edit window supported at a time, do you want to close current window before proceeding” “Node command is out of sequence" while importing .fem file "Nodes already exist in the model" while converting Trias to tetras selection Unable to select lines and points from the graphics area, Unable to select elements, Entities do not change colour on being selected While selecting a node adjacent node gets selected. Unable to choose coincident nodes in the model. When user tries to choose one of the nodes at a particular location it does not show the option of picking one of the two or more nodes. crashes HyperMesh 11.0 crashes when he tries to translate a component operations The mesh is not seeded all along the edges of a model and not taking the element size specified When user tries to organize elements using organize option, elements are not moved and tool hangs graphics Panel area is resized User is not able to get White background JPEG if the Check box is marked for Blank background under options panel. While using automesh option, if user does a reject/abort, then all masked elements will be unmasked. i.e. If User masks some of the elements of the same and locally remeshes remaining elements with F12 and aborts the operation then masked elements will appear on the screen without doing unmask elements. Components are not being displayed in the graphics area, though they are active in the model browser and are not masked. Masked Temporary Nodes appear while selecting by window. Find attached elements will select all the elements including those in undisplayed components. The colour of the component does not match between that in the model browser and the graphics area. Creates a material and tries to update a card image but, it goes blank without displaying any options

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Before you ask a query in the forum here ....
Rahul Ponginan replied to Rahul Ponginan's topic in Begin Here
Search the Support forum  The support forum is an extensive database of queries from HyperWorks  FEA users worldwide, it is likely that your question has been asked and answered before, use the search option in the top right hand corner to search for your question. Search Help documentation  The full HyperWorks HTML documentation (part of your installation) provides a thorough, searchable resource to find detailed information about HyperWorks, including an extensive set of tutorials HyperWorks offers comprehensive documentation in the online help.The Help can be accessed through the menu bar or the use of the “h” , keyboard (help documentation is “intelligent”, opening in the section representing the panel that the user is actively in) Help also contains detailed tutorials on many advanced HyperMesh functions. Search and go through the Free EBooks  Design of Experiments with HyperStudy – A Study Guide Practical Aspects of Finite Element Simulation (A Study Guide) Practical Aspects of Structural Optimization (A Study Guide) Practical Aspects of MultiBody Simulation with HyperWorks Crash Analysis With RADIOSS – A Study Guide 有限元仿真实践原理 Search and explore the Learning Library  An extensive collection of interactive training videos (with audio) covering the most essentials about interacting with the graphical user interface, basics of geometry cleanup, introduction in 2D meshing, analysis, debugging, topology optimization, and postprocessing (visit the Learning Library for more information) Search and explore Tips and Tricks 
Learn more about this from the FEA eBook http://www.altairuniversity.com/freeebooks2/freeebookpracticalaspectsoffiniteelementsimulationastudyguide/