Week - 3 Drop test Challenge

Objective: To Perform the Drop Test Simulation of Mobile Phone on the Floor using the Initial velocity Boundary entity.

Model:

The Model Consist of two parts the mobile phone and the Floor which is already been meshed

Material Models:

• The mobile phone, we are using Aluminum Material properties

Although many material models exist for metals, one of the most robust models is *MAT_024 or *MAT_PIECEWISE_LINEAR_PLASTICITY. This material model is the standard workhorse and is the recommended starting point for elastic-plastic simulation of metals and general plastics since it can also handle viscoelastic behavior (i.e., strain-rate dependency).

And for defining this material we are using MAT_024 (MAT_PIECEWISE_LINEAR_PLASTICITY) This is Material Type 24, which is an elasto-plastic material with arbitrary stress.

1. MID Material identification. A unique number or label not exceeding 8 Characters must be specified.
2. RO Mass density.
3. E Young’s modulus.
4. PR Poisson’s ratio.
5. SIGY Yield stress.
6. ETAN Tangent modulus, ignored if (LCSS.GT.0) is defined.

• Material for Floor

Since the Floor is UnDeformable Object in this Condition and we are going to Focus our result in area of Mobile Phone we can Use MAT_RIGID . By setting bodies (i.e., parts) to use *MAT_RIGID, where deformation and stresses are not of interest, significant CPU savings can be realized. In the background, LS-DYNA retains the surface mesh of the part for contact behavior and calculates an inertia matrix to simulate the dynamic behavior of the body. What is useful with this approach is that the body still retains its inertia and physical characteristics as it interacts with other bodies within the simulation but at a fraction of the numerical cost of dragging around a fully deformable body

The implementation of rigid bodies open doors to making your models run faster and allows you to focus on what is important and avoid getting distracted

1. MID Material identification. A unique number or label not exceeding 8 characters must be specified.
2. RO Mass density
3. E Young’s modulus. Reasonable values have to be chosen for contact analysis
4. PR Poisson’s ratio. Reasonable values have to be chosen for contact analysis

Section Creation

Section Creation Define the section Properties for different Element

• For Shell Element we use SECTION_SHELL
• For Solid Element we use SECTION_SOLID

The Mobile Phone Element are made of the solid element So we used SECTION_SOLID

1. SECID Section ID. SECID is referenced on the *PART card. A unique Number or label must be specified.
2. ELFORM Element formulation options.
3. ELFORM - 2 Fully integrated S/R solid intended for elements With poor aspect ratio, accurate formulation

The same Properties can be used For the Floor since even they are made of solid elements.

The Material and Section keyword is created now they have to be assigned to the respective Part.

Contact Creation

Since The Mobile phone is been dropped onto the floor the contact must be created between these parts or else the mobile phone will simple pass through the floor We are going to use two-way contact definition Two-way contacts - masters and slaves are reversed and contact checked both ways.

Contact Algorithms: Penalty based – use numerical springs to prevent penetration of nodes of one surface into segments of the other Transfers loads between two parts

CONTACT_AUTOMATIC_SURFACE_TO_SURFACE is defined between The Mobile Phone and Floor

Floor is set to be Master and Mobile Phone is set to be Salve and Master and Salve type is set to be Part ID

Static and dynamic coefficient of friction is set to be 0.2 and 0.1 respectively

Boundary Condition

• Boundary_SPC

SPC-Single point constraint is used on Floor to lock all the degree of freedom during the simulation So that Floor doesn’t move during the impact of the Mobile Phone.

Each DOF is set to 1, a value of zero means no Constraint and 1 means the DOF is locked

• Initial Velocity

The Initial Velocity is defined to the mobile phone

The initial velocity of 6 mm/ms in negative Z direction which is towards the Floor is added

Control Cards

• Control­_Termination is defined at what time the simulation ends or the end time of the simulation.It is set to 5 ms

• Control_Energy It Provides controls for energy dissipation options.

HGEN- Hourglass energy calculation option. Is set to 2 In Which hourglass energy is computed and included in the energy balance.

RWEN - Rigid wall energy dissipation option: Is set to 2 in Which energy dissipation is computed and included in the energy balance

SLNTEN - Sliding interface energy dissipation option Since the Contact is Defined it is set to 2 So That energy dissipation is computed and included in the energy balance

Database Creation

• BINARY_D3PLOT - It define the frequency at which the animation file is to be created and is set to 0.1ms
• ASCII_option keyword

The output request in ASCII format, The following keyword are Activated

1. ELOUT- Element Data
2. GLSTAT- Global Data
3. MATSUM- Material Energies and
4. SLEOUT – Sliding Interface Energies.

KeyWords :

Model Check:

Results :

Von Mises Stress:

Effective Strain :

Energy Graph

It shows how the kinetic energy of the mobile phone drops down as it hits the bottom plate and at the same time internal energy is gained by the mobile phone due to the impact. Total Energy is a Straight line with no deflection which means the hourglass energy and contact energy is very less compared to the internal and kinetic energy.

Sliding and Hourglass Energy:

It clearly shows sliding energy changed once the object comes in contact with the Floor.

Hourglass energy is very low as compared to internal energy. Hourglass energy should not exceed 15% of internal energy.

Conclusion :

Drop Test Simulation of Mobile Phone on the Floor using the Initial velocity Boundary Condition is Performed and the following output is derived

• Energy Output
• Von Mises Stress
• Effective Strain
• Hourglass and sliding Energy