Recently, a student asked how to implement variable cross-section beam element definition in ANSYS Workbench. Shuige will explain the common methods here.
Since ANSYS Mechanical’s GUI has very limited support for variable cross-section beams, there are generally two methods to simulate them:
1. Divide the variable cross-section area into multiple segments, then use constant cross-section methods to approximate the simulation. The accuracy of this method depends on the number of divisions, and it involves establishing multiple cross-section dimensions, making the operation cumbersome. Shuige does not recommend this approach in practice.
2. Insert commands through APDL. The commands used include secdata and sectype. By manually inserting command streams later and modifying element cross-section properties to achieve this, this is the most suitable and highest precision method. Shuige recommends using this approach.
As shown below is a simple triangular roof truss, width 2000, bottom column height 1000. The columns use variable cross-section circular ring sections 60*5~120*5, and other member cross-section dimensions are all 60*5.
Below, this article briefly demonstrates the APDL insertion operation.
1. Draw the geometry in SC, specify it as beam elements, and set a uniform cross-section size of 60*5.
2. Enter Mechanical, and define NS components for the areas that need variable cross-section definition respectively. Note that the NS component type must be elements.
3. Insert commands, use Secadata and sectype commands to define variable cross-sections. Note that to avoid conflicts between the defined variable cross-section numbers and existing variable cross-section numbers, parameterized numbering should be implemented for each parameter.
/prep7
allsel,all
*get,secmax,secp,num,num,max
sectype,secmax+1,ctube
secdata,30,25
sectype,secmax+2,ctube
secdata,60,55
sectype,secmax+3,taper
secdata,secmax+1,0,1000
secdata,secmax+2,0,0
cmsel,s,bj1
emodif,all,secn,secmax+3
allsel,all
4. Modify the solution output to output the beam element section force to facilitate verification.
5. After solution, check the section force and deformation.
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