Week - 3 Drop test Challenge

Week 3 Phone drop test

Objective

• Perform a phone drop test using initial velocity card in LS -PrePost
• Given – Meshed model of a phone and plate
• Drive Link - https://drive.google.com/file/d/1v1LN4SZkEaV2SYmdwVWTWlj_nPhYVQe1/view?usp=sharing

Explanation

• Phone is dropped from a height of approximately 20 mm in the model, considering a person mostly has the phone in his hand or a table the drop height will be around 4 feet (1219mm).Hence the velocity of the model has to be calculated to meet the 4ft drop.
• Most often drop test are done to find out the energy absorbed by the model. From the law of conservation of energy PE = KE
• mgh = ½ (mv2) , velocity of drop is independent of mass
• v = sqrt(2*g*h) = ( 2*9.806*1e-3*1219) = 4.889 mm/ms

In this model units system used is [g mm ms Mpa N-mm)

Procedure

• Assign sections and material properties to the parts – which are phone and shell plate.
• Materials – MAT020 is assigned to the shell plate and MAT024 piecewise linear plasticity is assigned. For the phone material used is aluminium

• Section for the solid phone is defined using element formulation 2 and for the rigid plate same is formulation with thickness 2mm

• Assign the material and sections to the parts.
• Boundary SPC is created for the rigid plate with all DOF constrained

• Contact is created using automatic surface to surface with phone as slave and plate as master. Set needs to be created for master and slave sets.

• Initial velocity card is used to apply velocity of a free fall to the phone. Node set needs to be created for the load application.

• In this case gravity is defined using a define curve. And then load body z card.

• Database cards – GLSTAT , MATSUM, RCFORC, SLEOUT ; binary d3plot are created
• Control cards – termination (time = 5ms ) and energy card for hourglass and contact energy are created
• Save the file as K file to the desired location.

Results

• Open the d3plot, we can observe a maximum of 27.28 MPa of stress is observed in the phone.
• Another observation is shock as the impact forces travels through the phone

• Verification of the global energies , we can observe that the hourglass energy are within the limits of less than 5% .
• As the phone impacts the plate we can observe the rise in internal energy and drop in KE , later we can observe the rise KE as the phone bounces of the plate.

• Rigid wall forces of the magnitude of 4.93e4 N is absorbed by the phone.

Conclusion

- Creation of solver deck and post processing of a drop test for phone was performed.