Week - 5 - Modelling Spotwelds
AIM:The main aim of this week challenge is to model spotwelds for the given model. The spotwelds should be modeled in two different ways
1. with beam elements
2. with solid elements
The result for the two methods are then analysed and the appropriate failure modes are then calibrated.
PROCEDURE:
Modelling of spotwelds using beam elements:
STEP 1: Open the LS-DYNA pre post and import the basic file containing the nodes and element.
STEP 2:Now create material and section cards for the parts.
STEP 3:Open the keyword manager and check the all button.Under the MAT keyword select the MAT 24 PIECEWISE_LINEAR_PLASTICITY.
STEP 4:Open the keyword manager and check the all button.Under the SECTION keyword select the SHELL card for the parts.Now give the properties of shell as desired.
STEP 5: Now go to PART keyword and assign the part with the desired material and section cards.
STEP 6: Go to element generation and check the beam radio button and select the nodes between which you need to create beam elements. The position of the beam elements should be the similar to one asked in the question.
STEP 7:Open the keyword manager and check the all button.Under the MAT keyword select the MAT 100 SPOTWELDS.
STEP 8:Open the keyword manager and check the all button.Under the SECTION keyword select the BEAM card for the spotwelds.Now give the properties of shell as desired.
STEP 9:Now go to PART keyword and assign the spotwelds with the desired material and section cards.
STEP 10:Now go to the create entity tab and create a SPC constrained for set of nodes to be fixed in all direction.
STEP 11:Now define a curve in order to give the displacement boundary condition.
STEP 12:Open the keyword manager and check the all button.Under the DEFINE keyword select the CURVE.
STEP 13: Open the keyword manager and check the all button.Under the BOUNDARY keyword select the PRESCRIBED_MOTION_SET.
STEP 14:To create a contact first create a part ID set and node set for the master set and node set.
Open the keyword manager and check the all button.Under the CONTACT keyword and select AUTOMATIC_SINGLE_SURFACE.
Open the keyword manager and check the all button.Under the CONTACT keyword and select TIED_SHELL_EDGE_TO_SURFACE.
STEP 15: Open the keyword manager and check the all button.Under the CONTROL keyword and select TERMINATION.Now give the total time of the simulation.
STEP 16: Open the keyword manager and check the all button.Under the DATABASE keyword and select ASCII,D3PLOT and CROSS_SECTION_SET.
In order to capture the exact failure modes the simulation is run at two different failure model.
The failure is made at time 5 sec and 8.5 sec and the shear force, axial force and resultant moment are tabulated
| TIME | AXIAL FORCE | SHEAR FORCE |
| 5 | 908 | 894 |
| 8.5 | 1210 | 965 |
Thus the failure method has been changed in the spotweld material
Modelling of spotweld using solid elements:
STEP 17: Now create solid elements to replace the beam elements and give the appropriate section cards for it.
In order to capture the exact failure modes the simulation is run at two different failure model.
The failure is made at time 5 sec and 8.5 sec and the shear force, axial force and resultant moment are tabulated
| TIME | AXIAL FORCE | SHEAR FORCE | RESULTANT MOMENT |
| 5 | 780 | 1800 | 11000 |
| 8.5 | 821 | 1800 | 11000 |
OUTPUT REQUEST:
X-STRESS - BEAM ELEMENTS/SOLID ELEMENTS
Y-STRESS - BEAM ELEMENTS/SOLID ELEMENTS
X-STRAIN - BEAM ELEMENTS/SOLID ELEMENTS
Y-STRAIN - BEAM ELEMENTS/SOLID ELEMENTS
SECTION FORCE - BEAM ELEMENTS/SOLID ELEMENTS
SPOTWELD FORCE - BEAM ELEMENTS/SOLID ELEMENTS
ENERGIES - BEAM ELEMENTS/SOLID ELEMENTS
Conclusion:
Thus the two cases have been studied and their results have be recorded.
| BEAM ELEMENTS | SOLID ELEMENTS | |
| X-STRESS | 736.2 | 643.5 |
| Y-STRESS | 533.5 | 165.3 |
| X-STRAIN | 0.068 | 0.13 |
| Y-STRAIN | 0.103 | 0.105 |