Week - 5 - Modelling Spotwelds
Objective:
The aim of the challenge is to study about spot weld for the given assembly of the part and run a crash test using ls dyna.
Also compare the results for spot weld made by beam elements and solid elements.And unit system followed by these assignment is gm mm ms.
Procedure for Beam elements.
1. Keyword file is imported in ls propost.
2.Create a set file for shell elements.
where ,One end of the shell element is fixed at all the directions.
Prescribed motion set is created by displacements and load curves.
3.Create section to both shell and beam
ELFORM for shell as 16
ELFORM for spotweld as 9
4.Create a material properties for both shell and beam elements.
5.Create a contact for Automatic single surface here slave and master can be define as same ,
where we can use SSID = 1,SSTYP=2,
6.Create a contact for Tied_Shell_Edge_To_Surface contact is used
where Slave nodes as spotweld,
Master nodes as shell elements.
7.Create a Control termination as 10ms
8.Create Database Binary d3plots, Ascii files.
9.Create database history nodes for plot a graph
10.Create a Rigid wall with 10 mm away from shell elements.
11.Apply initial velocity of 13.88 ms towards the rigid wall.
12.Run the stimulation in Ls program manager
13.Plot the axial and shear force for compared beam elements.
create the section id for the material by clicking section in keyword manager and select the element as beam with thickness 3mm.
create the section id for the material by clicking section in keyword manager and select the element as shell with thickness 1.5mm.
Assign the material id for the beam in the model, as MAT_SPOTWELD, where RO= 7800000, E 2.100e+05, PR=0.3
Assign the material id for the parts in the model, MAT_ELASTIC as RO= 7800000, E 2.100e+05, PR=0.3
Assign a curve by keyword manager >define>curve
create the part in keyword manager and assign the section id and mat card what we create before
create the output file by clicking the database and select the binary d3 plot and also create outfile by clicking Database>ASCII_option>select the glstat and MATSUM,NODOUT,SECFORC,SLEOUT.
Next in control card select the termination for animation time for the model
Create a contact for Automatic single surface here slave and master can be define as same ,
where we can use SSID = 1,SSTYP=2
Create a contact for Tied_Shell_Edge_To_Surface contact is used
where Slave nodes as spotweld,Master nodes as shell elements
After defining the sections , open the part tab in the key-word manager assingining rigid_wall in front of shell elements with 10mm away.
Creating the intial velocity click keyword manager and select the velocity now give the velocity for the shell elements. create the node set id for which the elements to be in velocity,in the negative x direction with 13.88mm/ms,so it get crash on the rigid wall.
After assigning every thing save as.k file.
Open ls manager>solver>browse the k.file>run. results are in the notepad files.
Post processing Results:
Maximum vonmises peak is 3.131e+04 at node 100982
Minimum value is 0.000E+00 at node 110011.
Where the shell elements move towards rigidwall at some perticular velocity 13.88ms,when it hits the wall it attain a max peak values of 3.131e+04 at a node point of 100982.
Plot the axial and shear force for compared beam elements.
Plot thegraph of kinetic energy, internal energy, total energy and sliding energy with respect to time.
From the above graph its shows that the level of internal ,kinetic ,total and sliding energy,here internal energy and total energy is keep on increasing ,were as kinetic energy is increased to some perticular level and sliding energy keep on decreasing certain levels
Procedure for Solid elements:
1. Keyword file is imported in ls propost.
2.Create a set file for shell elements.
where ,One end of the shell element is fixed at all the directions.
Prescribed motion set is created by displacements and load curves.
3.Create section to both shell and beam
ELFORM for Solid as 1
ELFORM for spotweld as 9
4.Create a material properties for both shell and beam elements.
5. Create a Part id by assign the material and section ids
6.Create a contact for Automatic single surface here slave and master can be define as same ,
where we can use SSID = 1,SSTYP=3,
7.Create a contact for Tied_Shell_Edge_To_Surface contact is used
where Slave nodes as spotweld,
Master nodes as shell elements.
7.Create a Control termination as10ms
8.Create Database Binary d3plots, Ascii files.
9.Create database history nodes for plot a graph
10.Create a Rigid wall with 10 mm away from shell elements.
11.Apply initial velocity of 13.88 ms towards the rigid wall.
12.Run the stimulation in Ls program manager
13.Plot the axial and shear force for compared beam elements.
Maximum vonmises peak is 1.291E+03
Minimum value is 0.000E+00
The shell elements hitting the rigid wall to some certain velocity of 13.88ms ,its gets some defelection to max point 1.291E+03 .
Plot the axial and shear force for compared solid elements.
According to above graphs axial and shear forces when the shell elements hit the rigid wall the at 4ms , the axial force is defelected to various level of solid spot weld,
and Shear force is decreasing to some certain levels
Plot thegraph of kinetic energy, internal energy, total energy and sliding energy with respect to time.
From the above graph its shows that when model crashes the rigid wall
Therefore the kinetic energy of the system increase at some point and internal energy gained in these model.and the total energy gets gained.
Conculsion:
The Solid spotweld fails :
hex spot weld element ID 110017 failed at time at time 2.4008E-01
hex spot weld element ID 110018 failed at time at time 2.4040E-01
hex spot weld element ID 110019 failed at time at time 2.7279E-01
hex spot weld element ID 110020 failed at time at time 3.5080E-01
Problem time = 1.0000E+01
Problem cycle = 17832
Total CPU time = 410 seconds ( 0 hours 6 minutes 50 seconds)
CPU time per zone cycle = 2289.965 nanoseconds
Clock time per zone cycle= 2287.911 nanoseconds
The Beam elements fails:
beam element 110011 failed at time 6.0002E+00
Problem time = 1.0000E+01
Problem cycle = 19145
Total CPU time = 361 seconds ( 0 hours 6 minutes 1 seconds)
CPU time per zone cycle = 1877.195 nanoseconds
Clock time per zone cycle= 1881.101 nanoseconds
For beam elements the spot weld constrained fails
Spot weld constraint failed between nodes 508489 & 502736
: Time = 1.15039E-03 : Plastic str = 0.00000E+00
: Axial = -1.27922E+02 : Shear = 7.18091E+03
Spot weld constraint failed between nodes 501074 & 505896
: Time = 1.15039E-03 : Plastic str = 0.00000E+00
: Axial = 1.30660E+02 : Shear = 7.15503E+03
Spot weld constraint failed between nodes 502573 & 508489
: Time = 1.72455E-03 : Plastic str = 0.00000E+00
: Axial = -1.70437E+02 : Shear = 9.33517E+03
Spot weld constraint failed between nodes 509814 & 501074
: Time = 1.72455E-03 : Plastic str = 0.00000E+00
: Axial = 1.70074E+02 : Shear = 9.31418E+03
Spot weld constraint failed between nodes 508477 & 502573
: Time = 2.29815E-03 : Plastic str = 0.00000E+00
: Axial = -2.19513E+02 : Shear = 1.20211E+04
Spot weld constraint failed between nodes 504455 & 509814
: Time = 2.29815E-03 : Plastic str = 0.00000E+00
: Axial = 2.19008E+02 : Shear = 1.19939E+04
Spot weld constraint failed between nodes 501985 & 508477
: Time = 2.87141E-03 : Plastic str = 0.00000E+00
: Axial = -2.77499E+02 : Shear = 1.43090E+04
Spot weld constraint failed between nodes 507929 & 504455
: Time = 2.87141E-03 : Plastic str = 0.00000E+00
: Axial = 2.60602E+02 : Shear = 1.42708E+04
Spot weld constraint failed between nodes 507929 & 501985
: Time = 3.44442E-03 : Plastic str = 0.00000E+00
: Axial = -2.93898E+02 : Shear = 1.60949E+04
In these Assignments ,we have used spotweld technique for both beam and solid elements in details with an crash stimulation using the assembly in LSdyna.
From these above results we can come to conclude that beam elements receives more effective stresss while compare to the solid elements.