Ansys Tips

An XANSYS forum poster pointed out an interesting thesis on load path index U*. There was a brute force method of a solution for every single node shown in Figure 8. Alternately, there is a  U* Toolkit  found in Nastran which appears to really speed the calculations. The brute force method was used here in this Ansys Classic input file :  link Figure 1: Load Path Index U*

Torsional springs can come in handy when inertia plays a large role in the dynamic response. Fortunately a simple snippet converts a typical linear spring into a torsional spring. Workbench uses COMBIN14 springs by default. keyopt , _sid, 3, 1    ! rotational DOF about spring axis r , _sid, 0.01        ! rotational stiffness Torsional Mode due to Torsional Spring One could also specify the radial stiffness of the spring above by specifying the direction. Note that KEYOPT(2)=1. keyopt , _sid, 2, 1 ! UX direction about global axis r , _sid, 1e5            ! Translation stiffness Same goes for off-axis rotational DOF via KEYOPT(2)=4. keyopt , _sid, 2, 4 ! ROTX direction about global axis r , _sid, 1e5            ! Rotation stiffness The Workbench (v18.2) Archived File: LINK

Motivation Perhaps one of the biggest curse to any engineering analyst is the the lack of key parameters to make a good estimate. For adhesive modeling, what parameters should one use? One can try to look up typical values online or from research papers but they are often not exactly what's being used immediately.  To overcome this difficulty, you could create an experimental test for your adhesive to extract the information you need as described in the  paper  by Dastjerdi et al [1]. The rest of the blog post details how to interpret the test data. Next, by using extracted parameters, replicate the test in Ansys to get similar results (as expected).   How to Extract CZM Parameters From Test Data? A few years ago, I was pulled in to do some adhesive modeling. The project leaders later decided against using adhesives but it peaked my interest on how to simulate adhesives using Cohesive Zone Modeling  (CZM). Mode I Peel direction failure was a concern and gl...

Sorting * The *MOPER command has a sort which can be quite convenient. Here's an example of sorting the matrix of different columns consecutively. /PREP7 ! Creates Matrix *dim , mymatrix, array, 5, 3 mymatrix(1, 1) = 4 mymatrix(2, 1) = 7 mymatrix(3, 1) = 4 mymatrix(4, 1) = 1 mymatrix(5, 1) = 4 mymatrix(1, 2) = 42 mymatrix(2, 2) = 78 mymatrix(3, 2) = 42 mymatrix(4, 2) = 16 mymatrix(5, 2) = 22 mymatrix(1, 3) = 3 mymatrix(2, 3) = 8 mymatrix(3, 3) = 2 mymatrix(4, 3) = 6 mymatrix(5, 3) = 5 ! Writes Original Matrix *cfopen , origmatrix, txt  *vwrite , mymatrix(1,1), mymatrix(1,2), mymatrix(1,3) (E20.5, ' ', E20.5, ' ', E20.5) *cfclos The original "mymatrix" is: 4 42 3 7 78 8 4 42 2 1 16 6 4 22 5 ! Reorder Matrix by first column, then second, then third *dim , ordering,,5 ! Ordering index array *moper , ordering(1), mymatrix(1,1), sort, , 1,2,3 ! ordering column ! Writes Sorted Matrix *cfopen , newmatrix, txt  *vwr...

Happy Holidays! Hope everyone has a Merry Christmas and a Happy New Year! PS:  Way cooler animation by EpsilonFEA: http://www.epsilonfea.com/happy-holidays-17/ PPS: Archived V18.2 file: Link

Figure 1: Equivalent Stress of White Paper Model There are many software out there now that does weld analysis. Among others... For fatigue type analysis, there are: FE-Safe  (Verity Method) &  Ncode  (Volvo Method) For static type analysis, there are: FEWeld & EDRMedeso A good reference classic book is Blodgett's  Design of Welded Structures  (1966). This book is a real gem even though it's quite old.  Here is a short write-up by the same author et al with similar material: Welded Connections . White Paper Figure 2: Weaver's White Paper Comparing  FEA to Hand Calculations I came across this really good white paper by Weaver Engineering that had a worked example comparing both hand calculation to their software along with in depth discussions. The example was detailed enough to be replicated. This is a great stepping stone when following the  crawl-walk-run philosophy. The rest of the post seeks to replicate the results ...

Where should the accelerometers be placed? - Test Person Test People are tough to work with! I was one before so I would know. Have a bit of sympathy for them though as they could be frantically troubleshooting equipment in the middle of no-where or spend countless hours rolling-and-unrolling cables. Goal of Measurement Points Selection OK, we have a model with natural frequencies and mode shapes. If your company is well endowed, this is a simple question with pretest software like  FEMtools  or some other software that optimizes the MAC matrix . This would also help with correlation later. Generally speaking, the software will maximize the diagonal matrix while minimize the off diagonal matrix values. Loosely defined, this means the modes are relatively unique (mathematically speaking) for the chosen measurement locations. Poor Man's Method for Picking Measurement Locations Alternately, we can pick measurement locations by hand based on past experience and liberal use...