# Presentation: 103840

## V E R I D I A N                  E N G I N E E R I N G

- DELIVERING INFORMATION ON DEMAND

- V E R I D I A N                  E N G I N E E R I N G
-                    DIVISION
- Aeronautics Sector

- V E R I D I A N                  E N G I N E E R I N G
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**FEMCI Workshop 2001****	**
**Innovative FEM Solutions to Challenging Problems**
**NASA Goddard Space Flight Center**
***Jim Maltby****	**16 May 2001*
- _[james.maltby@veridian.com](mailto:james.maltby@veridian.com)_

**Practical External Utility Programs for Finite Element Modeling using SDRC I-DEAS Master Series**

## Discussion Topics

**Modeling Multiple Bolted Joints using I-DEAS FEM Assembly**
**One method for joining multiple FE parts of an assembly**** **
**Summarizing FEA Results in One Plot**
**Using Superposition to Show the Worse Stresses****   **
**Model Verification**
**Color Plots of Element Thickness**

**Mechanical Designs Courtesy of the Space Systems Laboratory at UMD **

## Modeling Multiple Bolted Joints using I-DEAS FEM Assembly

**Problem: Connect FE parts with multiple bolts into one assembly**
**Solutions:**
**Model bolt with a BEAM and tie interface together with an RBE2**
- Merge plate thickness together to form one plate
- Tie plates together with an RBE2
- Tie bolt pattern together with RBE3
- Model entire bolt with bolt hole, contact problem
**Pros/Cons:**
**Can simulate bolt preload with temperature**
**Can determine preloads and shear loads**
**Does not account for bolt bending, nut/washer stiffness, friction  **
**Local brick mesh will effect joint stiffness**
**Mesh is less complicated, one coordinate system is needed**
**Less time to create RBEs**

## Bolted Joint Test Case

**Bolted Joint Test Case**

**FE Model – Axial Load**

**Results**

**Bolt modeled as beam**

**Bolt fully modeled (Contact Model)**

**Restraints**

**Bolt with ********T**

**Beam with ********T**

## Bolted Joint Methodology

## Bolted Joint - Example

**Bolted Joint - Example**

**Assembles Model**

**Assembled FEMs**

**Bolt FEMs**

**RBEs**

**Beam**

**261 Bolts**

## Summarizing FEA Results in One Plot

**Problem: Showing the worse case stresses for each element in the model**
**Solution:**
**Run unit load cases, use superposition for each maneuver point (time), combine component stresses, create universal file,  and plot results**
**Pros/Cons:**
**Can quickly determine worse case load cases and locations**
**Beam element data assumes circular cross section and extracts highest loads independent of maneuver point **
**Can extract stresses for each load point for LCF analysis**
**Can add additional load cases, thermals, margin of safety criteria**

## Summarizing Results Methodology

## Summarizing Results - Example

**Input:**
**MANEUVER     ACC     ACC     ACC     ACC     ACC     ACC  SAFETY**
**  ****NUMBER     ATX     ATY     ATZ     RAX     RAY     RAZ  FACTOR**
**               ****G       G       G   R/S/S   R/S/S   R/S/S**
**----------------------------------------------------------------**
**     ****1.0  -0.103   2.073   2.726   0.012   0.041   0.016   2.000**
**     ****2.0  -0.103   2.073   2.726   0.012   0.041  -0.016   2.000**
**Output:**
**STRESSSUM.TXT**
**                                     ****STRESS SUMMARY **
**     ****ELE      MP    MAXP    MINP    VONM    MAXP    MINP    VONM**
**                     ****TOP     TOP     TOP     BOT     BOT     BOT**
**----------------------------------------------------------------**
**       ****1    295.   6170.      0.   5478.   5528.      0.   4800.**
**       ****2    282.   3103.   -241.   3231.   2815.      0.   2793.**** **
**STRESSSUM.UNV ****(Universal file for I-DEAS plate element post processing)**
**FORCESUM.TXT**
**                       ****FORCE SUMMARY (BEAM ONLY)**
**     ****ELE      MP    BEAM   AXIAL Y-SHEAR Z-SHEAR TORSION  Y-BEND  Z-BEND**
**                     ****END   FORCE   FORCE   FORCE  MOMENT  MOMENT  MOMENT**
**                             ****LBS     LBS     LBS  IN-LBS  IN-LBS  IN-LBS**
**------------------------------------------------------------------------**
**    ****2254           BEGIN   -397.   1096.    309.   1117.    233.      0.**
**    ****2254           END      397.  -1096.   -309.    171.    260.      0.**
**    ****2256           BEGIN   -650.    -91.    389.    -74.    176.      0.**
**    ****2256           END      650.     91.   -389.    -65.    588.      0.**
**FORCESUM.UNV ****(Universal file for I-DEAS beam element post processing)**

## Summarizing Results - Example

**FEA Model**

**Plate results**

**Beam results**

## Model Verification – Thickness Plot

**Problem:  Checking plate element thickness via color plot**
**Solution:**
**Export model to NASTRAN dataset, read CQUAD4/CTRIA3  and PSHELL cards, write Universal file  **
**Pros/Cons:**
**Can verify plate thickness graphically**
**Can verify plate thickness transitions**

## Thickness Plot - Example

**Graphical Thickness Plot  **

**Color Band Thickness Plot**