Stress from impact loading

[njm789]

Hi all,

I am analyzing a scenario where a part impacts another part and wanted to find the stresses induced in the material (see attached picture). From what I have gathered I should use conservation of energy where the kinetic energy of the moving piston is transferred to cause deformation of the material (strain energy where dU = Pdx). The housing is fixed. The piston is made of weaker plastic and therefore I assume this will fail first. I am a little confused on how to apply the strain energy to this scenario as most the examples I have seen apply to a constant CSA part that hits a fixed boundary. Any help is appreciated. Thanks

 

[hydtools]

After equating strain energy to kinetic energy, use Young's modulus which relates strain to stress.

https://www-engineeringtoolbox-com.cdn.ampproject.org/v/s/

http://www.engineeringtoolbox.com/a...gineeringtoolbox.com/stress-strain-d_950.html

Ted

 

[hydtools]

The end of this attachment may help.


Ted

 

[njm789]

Ted, Thanks for the reply. That is the exact document I have been using. I'm not sure which volume to use...Would it be the csa of the piston that contacts the housing multiplied by the distance? In the example the whole rod is axially loaded so the entire volume of the rod is used.

 

[3DDave]

Picture how Jello of that shape would deform. Some places will deform large amounts, others not so much. The exact distribution is normally found using finite element analysis.

 

[njm789]

Thanks 3DDave. How would you determine the force due to impact as the distance the distance the work is dissipated over changes the force? Do you use a dynamic analysis or find a force and apply it in a static study?

 

[dvd]

I use the methodology from this note for impact factors -

 

[hydtools]

Maybe use a shape like the hatched volume. The angle is 45 degrees, shear stress angle.

Ted