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Recent content by davidmandis

  1. davidmandis

    Bilinear isotropic material property

    Hi, I am trying to model a composite tube with bilinear isotropic material property in ANSYS WB which gets crushed under impact using. After I run the simulation the material tends to act as a spring. Wanted to know if this is the way it is supposed to behave? and how can I make the tube...
  2. davidmandis

    Changing the slope of spring in ANSYS Workbench

    Hi Doug, I used the same method you mentioned here but am having a lot of convergence issues. This is the command being inserted under the spring, et,_sid,COMBIN39,0,0,1,0,,1 r,_sid,0.0, 0.0, 0.001016, 2224, 0.002032, 4448, rmore, 0.003048, 6672, 0.004064, 8896, 0.00508, 11120...
  3. davidmandis

    Response to impact pulse

    Hi, Sorry for the late reply. I forgot to mention that I got the same results from ANSYS for this simulation. So Pete's approach and code is right! Thanks, David
  4. davidmandis

    Changing the slope of spring in ANSYS Workbench

    Hi All, I am working on a simulation where I am using a spring in ANSYS Workbench 11.0, and would like to change the slope of the spring when the force in the spring exceeds a certain value. I do not know how to extract the force in the spring. Is there any way I can do this in ANSYS WB 11.0...
  5. davidmandis

    Implicit Dynamic Analysis (Drop Test) ANSYS Workbench

    Hey guys I am currently working on a impact simulation problem in ANSYS WB. The problem is that I am using an educational version which does not have the LS DYNA solver, so I wanted to ask if you guys using a LS DYNA solver? If not where did you learn to carry out drop tests in ANSYS WB...
  6. davidmandis

    Finding Stress-Strain Curve from Load-Deflection Data

    Yes you are right but I want the stress strain curve for the geometry only and don't want to characterize the material. The load-deflection curve was obtained from a reference standard handbook so even though there must have been some bowing, I do not know the values of the out of...
  7. davidmandis

    Finding Stress-Strain Curve from Load-Deflection Data

    Thanks for the reply & sorry for not providing details. This is a composite tube with a quasi-static compressive force applied to it, so I guess it would be the parts overall length that is used for calculating strain. The load-deflection curve is highly non-linear so no constant Young's...
  8. davidmandis

    Finding Stress-Strain Curve from Load-Deflection Data

    Hi, I have the load-deflection data for a composite tube and would like to find the stress-strain curve. I know the dimensions of the tube. Is it just calculating stress=force/area & strain = change in length/original length at each point from the load-deflection curve or do I have to take...
  9. davidmandis

    Finding Equivalent Isotropic Properties for Composite Material

    Thank you guys! That helped. Thanks again, David
  10. davidmandis

    Download proe wildfire model of bolt (5/16"-18x11/4")

    Hi, Like the subject line says, I am looking for a pro/engineer cad model of a 5/16" grade 18 bolt which is 1 1/4" long. Anyone know of any resources or have the model themselves? Thanks, David
  11. davidmandis

    Finding Equivalent Isotropic Properties for Composite Material

    Hi, I am trying to model a Carbon/Epoxy structure in a finite element software but the software does not have the capability to analyze composite materials at this point. So, I wanted to find the equivalent Young's modulus and Poissons ratio so that it can be treated as an isotropic material...
  12. davidmandis

    Response to impact pulse

    hmmmm that is what i am trying to figure out....i.e. if I can pre-program an acceleration, disp, vel profile in ANSYS. will let you know as soon i figure it out. Thanks, David
  13. davidmandis

    Response to impact pulse

    I have attached the reference used to get the acceleration crash pulse and time period data. Fig. 1 (a) on page 3 shows the crash pulse and also the change in velocity to be 42...
  14. davidmandis

    Response to impact pulse

    I just noticed a change in velocity, deltaV = 42 ft/sec....which is equal to ((48G's*32.2*0.054sec)/2) corresponding to the triangular acceleration crash pulse also given in the specifications, but will this change in velocity be the same as initial velocity? I am trying to verify my answer...
  15. davidmandis

    Response to impact pulse

    Ok I take that back.........applying an initial velocity will also require a transient analysis since the spring is nonlinear........but will applying an intial velocity to the mass be same as applying the acceleration crash pulse to the fixed support? David
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