<\/h1>\nHow You Use APDL Math<\/h1>\n
When using APDL math you should follow some basic steps.\u00a0 I\u2019m always a big proponent of the crawl-walk-run approach to anything, so I also recommend that you start with small, simple models to figure stuff out.<\/p>\n
First Step: Know the Math<\/h2>\n
Then makes sure that you understand the math in ANSYS, and that includes the files being used by ANSYS.\u00a0 A good place to look is in the Programmer\u2019s Manual, Chapter 1 lists the various files and what is in them.\u00a0 It might also not be a bad idea for you to crack open the theory manual\u00a0 We all know that ANSYS solve Kx = F, but how, and what matrices and vectors are used.\u00a0 Section 17.1 explains the static analysis approach used, with lots of links to more detailed explanations.<\/p>\n Since the whole point of using APDL math is to do stuff with Matrices\/Vectors, you need to start by creating them.\u00a0 Note that we are not doing anything with APDL Math yet.\u00a0 We are using APDL, ANSYS, or an external program to get our matrix\/vector so that we can then get it into APDL Math.. There are three types of sources you can get matrices\/vectors from:<\/p>\n Using *DMAT, *SMAT, and *VEC you convert the APDL array, ANSYS file, or external format file into a matrix or a vector.\u00a0 You can also use *INIT to make one from scratch, filling it with constants, zeros, random numbers or by setting the diagonal or anti-diagonal\u00a0 values.<\/p>\n In this step you can modify matrices in a lot of different ways.\u00a0 The simplest is to use *MULT or *AXPY to do math with several matrices\/vectors to get a new matrix\/vector.<\/p>\n Another simple way to change things is to simply refer to the entries in the matrix using APDL.\u00a0 As an example, to change the damping at I=4 and J =5 in a damping matrix called dmpmtrx just use dmpmtrx(4,5) \u2013 124.321e4.<\/p>\n You can take that one step further and use the APDL operators that work on arrays like *SET, *MOPER, *VGUN and whatever *DO loops you need.<\/p>\n If you can\u2019t do the modification you need in APDL or APDL Math, then you can use *EXPORT to write the matrices out and use an external tool like matlab or Mathematica to do your manipulation. Of course you then use *DMAT with an IMPORT argument to read the modified matrix\/vector back inside.<\/p>\n Now it is finally time to use your matrices\/vectors.\u00a0 The most common use is to bundle it up in a substructure matrix (*EXPORT,,SUB) and use it in a solve.\u00a0 What is great about this is that you can also (I know, we don\u2019t want to use the N-word) save the file as a NASTRAN substructure and give it to that annoying DMAP guru who insists that NASTRAN is the only structural analysis code in the world.\u00a0 He gets his file, and you get to use ANSYS.<\/p>\n You can also solve using APDL Math.\u00a0 This can require multiple steps depending on what you want to do. A typical solve involves using the *LSENGINE command to define how you want to solve, then factor your matrix with *LSFACTOR, then solve with *LSBAK.<\/p>\n There are also ways to continue a solve in ANSYS after changing the EMAT file.\u00a0 Unfortunately my plans to do an example of this have been thwarted and ANSYS did not provide one, so I\u2019m not 100% sure on the steps required.\u00a0 But a LSSOLVE that does not force ANSYS to recreate the matrices should work.\u00a0 Maybe a topic for a future posting.<\/p>\n There is a lot more too this, and the help is where you can learn more.\u00a0 But a few things everyone needs to be ware of are listed here.<\/p>\n A key area where people have problems is understanding how the DOF\u2019s in your matrix or vector are ordered. This is because ANSYS reorders things for efficiency of memory and solve.\u00a0 The nice thing is that ANSYS stores a map in the full file that you can use to convert back and forth using the *MULT command.<\/p>\n Please read section 4.4 ( \/\/ ANSYS Parametric Design Language Guide \/\/ 4. APDL Math \/\/ 4.4. Degree of Freedom Ordering) in the manual. They have a great description and some examples.<\/p>\n Just remember to remember to deal with DOF ordering.<\/p>\n This is still a new tool set and as users apply it to real world problems, they are adding functionality.\u00a0 Right now there are some limitations.<\/p>\n Most of the features in APDL math work with matrices that have imaginary terms in them. Be careful and read the help if you are using complex math, it can get tricky.\u00a0 Especially read 4.3 on how to specify a position in a matrix for real or imaginary numbers.<\/p>\n There are not a lot out there.\u00a0 The manual has some in section 4.7.\u00a0 Take a look at these before you do anything. If you can not find a specific example, contact your technical support provider and see if they have one, or if they can ask development for one.<\/p>\n This is a new feature, and a power user feature.\u00a0 So what is happening is some very smart people are doing some very cool things with it, and not sharing.\u00a0 It is very important that you share your effort with your Channel Partner or ANSYS, Inc so that they can not only see how people use this tool, but also modify the tool to do even more cool things.<\/p>\n It would also be cool if you posted what you do on XANSYS for the masses to see.\u00a0 Very cool.<\/p>\n","protected":false},"excerpt":{"rendered":" APDL Math.\u00a0 It is one of the most powerful, uber-user, deep down under the hood, wrapping your hands around the […]<\/p>\n","protected":false},"author":33,"featured_media":30855,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2323],"tags":[],"post-podcast":[],"_links":{"self":[{"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/posts\/25612"}],"collection":[{"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/users\/33"}],"replies":[{"embeddable":true,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/comments?post=25612"}],"version-history":[{"count":0,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/posts\/25612\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/media\/30855"}],"wp:attachment":[{"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/media?parent=25612"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/categories?post=25612"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/tags?post=25612"},{"taxonomy":"post-podcast","embeddable":true,"href":"https:\/\/www.padtinc.com\/wp-json\/wp\/v2\/post-podcast?post=25612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"image\"](\"https:\/\/www.padtinc.com\/wp-content\/uploads\/oldblog\/image_216.png\" "\\"image\\"")
<\/a>The first step, or maybe the zero\u2019th, is to understand your math.\u00a0 If you charge in and start grabbing the stiffness matrix from the .FULL file and changing values, who knows what you will end up with. Chart out the math you want to do on paper or in a tool like Mathematica.<\/p>\nSecond Step: Create your Matrices\/Vectors<\/h2>\n
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Third Step: Get the Matrices\/Vectors into APDL Math<\/h2>\n
Fourth Step: Manipulate the Matrices\/Vectors<\/h2>\n
Fifth Step: Use the Matrix<\/h2>\n
Other Stuff to Know About<\/h1>\n
DOF Order<\/h2>\n
Limitations<\/h2>\n
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<\/a>Real and Imaginary<\/h2>\nExamples<\/h2>\n
Give it a Shot, and Share<\/h1>\n