Week - 4 - crash box simulation

TITLE: CRASH BOX SIMULATION USING LSDYNA

OBJECTIVE: TO CREATE A RIGID WALL AND PERFORM A CRASH BOX SIMULATION USING LS DYNA.

• At first I opened the mesed model of box in LS prepost and then look for part card and rename ita s box.
• Then I create a rigid wall using create option then rigid and 1+N option from the box.

• After creating wall,now I assign material and section to the box part.
• Material used here is matwise linear plastic(024) and properties of steel are used.
• Section Shell is created with ELFORM2.

• After creating section and shell,Its time to define them in part id.
• After assigning them in part ID,Boundary card is used to create boundary condition where initial velocity is applied to the box as 50kmph i.e 13.889mm/ms.

• After defining the boundary condition its time to define the contact.As the box will collide and bounce back therefore automatic single surface contact is given in contact defination.

• Now as contacts are also defined.I look for defining the control cards.
• Here three control cards are given,those are termination,hourglass and energy.
• All the default statndard values are used for in the control card.
• Control termination time is used is 3ms.

• Now I define the final output cards, as section force is needed in the middle of the therefore I need to define the set of nodes and elements to define the cross section card.
• The define the set of nodes and elements create option is used there set is used.

• Now I define the data base cards.
• Those are ASCII,D3PLOT,CROSS SECTION FORCE
• In ASCII card glsat,sleout,rcforc and sec force is defined.

RESULTS:

1. FOR T = 1.2mm

• Stress contour

Stress = 1.44e-1

• Strain contour

Strain = 4.27e-09

• SECTIONAL FORCE ALONG LENGTH (T = 1.2mm)

In this curve it seen the curve is very noise after 2ms when the box section collide with the wall.Where as maximum force is seen to happen around 2.1ms.

• Energy plots.

Here the plot justifies the crash situation,as internal engergy increases then kinetic energy decreases .

Total energy increases after crash in 2ms.

There is sudden rise in the hourglass energy seen after 2ms.

Sliding energy seems to be flat in this experiment.

• DIRECTINONAL STRESS

Here is seen to ncreasing gradually from begining and the after 2.1ms it goes decreasing

After 2ms its flucuating.

After 2.2ms its flucuating.

2) T = 1.5mm

• Energy plot

• SECTION FORCE

Here the graph is flucuating after 2ms of time i.e after 2ms the box crashes to the wall.

• Enegry plots

ALL THE GRAPHS OF ENERGIES ARE SIMILAR TO THE ABOVE VALUES i.e T= 1.2mm.

COMPARING THE GRAPHS OF T= 1.2mm and T = 1.5mm

1. ACCELERATION(T=1.2mm)

Here after 2ms graphs is decreased in -6 and the peak value is around 2.4ms.

• ACCELERATION(T= 1.5mm)

Here after 2ms graphs shows small peak then it go down aand the peak is around 2.9ms.

2. STRESS/STRAIN PLOT

• T = 1.2mm

Here the peak is around 2.6ms.

After 2.1ms its shows smooth line.

• T= 1.5mm

Here the peak is around 2.3ms

Here the peak is around 2.1 and then smooth line.

Table to compare the results.

Maximum values

Acceleration(mm/ms2) time(ms) Stress(Mpa) time(ms) strain(mm)(e-3) time(ms)

T= 1.2mm 2.9 e+3 2.4 250 2.6 0.68 2.1

T= 1.5mm 2.1 e+3 2.9 250 2.3 0.58 2.1

CONCLUSION:

• Two different simulations are performed using different shell thickneses.
• Results are compared and found useful.
• Graphs are plotted sucessfully.