General Mechanical

Initial Velocity

Subscriber

What is difference between two velocity options in explicit dynamics . One is initial velocity in initial condition section (T=0) other is in analysis setting. I observed that If I am using T=0 velocity then object is bouncing back with some velocity and if i am using velocity in analysis setting then it deforms the object continuously.

• peteroznewman
Subscriber

If you throw a ball upward with an initial velocity of 1 m/s and gravity is pulling it down, it gradually slows down until it stops going up and starts falling.  The 1 m/s was the Initial Condition for Velocity.

If you put that ball in a car and drive the car at 1 m/s, that is a boundary condition. The ball will always travel at that velocity.

Subscriber

Thank you sir ,

Very nicely explained. If some particles released from a nozzle at some velocity and particles travels (small distance) to strike on a plate at different strike angles  then which velocity is suitable for this case. I am using T=0 Velocity format (case 1) , What is your recommendation.

I have one more question to you that how to calculate the mass of a plate if there is some erosion (some element loss) . I am using "massall" expression but result is not satisfactory because mass shown in geometry and mass calculated through massall expression are not matched even there is no element loss or erosion.

Thanking You

• peteroznewman
Subscriber

The particles should have a velocity set under the Initial Conditions folder because after they travel a small distance and hit the plate, you want them to have a different velocity after making contact with the plate.

If you had a punch tool that was much stiffer/stronger than a soft material, you could use a velocity boundary condition on the punch tool to push it through the soft material.

I inserted your images below because ANSYS staff are not permitted to open attachments.  I haven't used the MASSALL() command, so I don't know what it does. Since the number is larger than the plate, does it include the mass of the particles?  What does workbench show as the total mass of the model?

Subscriber

Thank you sir

Defining velocity to a body is now clear.

Yes , mass of particles are included with plate.

I have to calculate the  mass loss of the material (say plate) after the impact of the striking of some object (say balls) . here target material is flexible and striking object is consider as rigid body. Using the erosion expression in user defined result I am able to calculate the element loss but not getting the way to calculate the loss of material due to the impact of the particle.

Erosion= mass of plate before the impact- mass of plate after the impact

With Regards