Mechanical Impact Experiments: Analyzing Speed & Energy

[Michael777]

Hello there,
I got this little project I am working on, it maybe simple to you , but I have a hard time getting some useful results.
I have an assembly, it looks like a square box(section) 6 inches long, with a cylinder attached to one end.
On the end I have the possibility to attach a sleeve made of a rubbery material (I use relatively soft , Shore 80 A Santoprene) . The measured weight of the assembly is 3.77 lbs.
In my experiment I attached this assembly to an arm (67 inch long), which can swing like a pendulum.
The arm is rotating on a pin with a bearing on it
I bring the arm horizontally, and let the assembly swing in the gravity field, initial speed 0.
At 90 degree (arm vertical) the assembly impacts a concrete wall and bounces back.
The impact area of the assembly is the ream of the sleeve.
In reality, the contact is not a cylindrical ring because the contact is not always centric.
I have instances when the contact is a segment of a ring, since the initial wall-ring contact is an edge of the ring ; under impact forces the edge deforms and at times folds (changing the area of contact) and changing the bounce speed of the assembly.
To complicate the things, I have some small masses attached to the assembly through some miniature connectors.
The fashion these masses are attached to the assembly is in such a way that the inertial forces generated at impact pulls them out of the connectors, overcoming the retaining forces. The connecting pins are parallel with the impact force vector.
I did my homework and I’ve drawn my conclusions regarding this experiment (I don’t mind sharing my thinking about how to solve this problem with any of you).
Below, I will formulated the questions I want answered as a reality check:

I need to find out;
1/ the impact speed of the assembly
2./ the max deceleration at impact
3./ the maximum kinetic energy developed along the trajectory.

TIA,
Michael

 

[zmike]

Hi Michael,
It sounds like you have an interesting project that you are working on. It seems like a difficult problem to solve, but I'm sure you can find some useful results with the right approach.
To answer your questions, you will need to consider the forces at play when your assembly impacts the wall. You should take into account the weight of the assembly, the mass of the additional masses attached to it, and the acceleration due to gravity. With this information, you can calculate the initial velocity and the deceleration at impact. You can also calculate the maximum kinetic energy developed along the trajectory.
Hopefully this helps in your project. Good luck!

 

[ravenprp]

Hello Michael,

Thank you for sharing your project with me. It sounds like you have a very interesting and complex experiment on your hands. Mechanical impact experiments can be challenging, but also very rewarding. I would be happy to offer some suggestions and insights to help you achieve your desired results.

First, let's address your questions. To find the impact speed of the assembly, you can use a high-speed camera to capture the motion of the assembly as it swings towards the wall and bounces back. By analyzing the footage, you can measure the time it takes for the assembly to reach the wall and then return to its original position. From there, you can use the distance and time measurements to calculate the speed of the assembly.

To determine the maximum deceleration at impact, you can attach an accelerometer to the assembly. This device will measure the acceleration of the assembly as it impacts the wall. From the acceleration data, you can calculate the deceleration using the formula a = Δv/Δt, where a is acceleration, Δv is the change in velocity, and Δt is the change in time.

Lastly, to find the maximum kinetic energy developed along the trajectory, you can use the formula KE = 1/2mv^2, where KE is kinetic energy, m is the mass of the assembly, and v is the velocity of the assembly. You can use the results from the high-speed camera and accelerometer to calculate the velocity and mass of the assembly at impact.

Now, regarding the complexities of your experiment, I would suggest carefully considering the design and setup of your assembly and arm. It is important to ensure that the arm is stable and consistent in its swing, and that the assembly is securely attached to the arm. Any deviations or inconsistencies in the setup could affect your results.

Additionally, for a more accurate and precise measurement of the impact, you may want to consider using a more advanced instrument such as a force plate or a load cell. These devices can provide more detailed information about the forces and energy involved in the impact.

I hope this helps and I wish you the best of luck with your experiment. If you have any further questions or would like to discuss your project further, please don't hesitate to reach out.