Hi,
I'm currently working on a university project and I'm designing a tube straightener machine for an specific application. Here is a drawing of the machine.
Hoping you can see, the tube (slightly bent) comes into the rollers/wheels and once it makes contact with them, the rollers drags it by friction until the tube passes through. I've been searching info about the stresses occurred on the contact tube-roller and for the specific case I couldn't find it. So I was wondering if Simulation Mechanical has a tool to calculate contact stresses for this particular case (Normal force and tangential force (friction) on Point Contact surface).
Thank you in advance
Ignacio.
Hi Ignacio,
You could perform an MES analysis on the rollers and tubes to calculate the stresses. It would probably take a week to setup and get an answer (depending on what simplifications you want to make. For example, how important is the friction compared to the normal contact.) I would begin with a non-moving tube and bring the non-spinning wheels into contact.
The other simulation products like Nastran In-CAD and Fusion 360 can also do a similar type of analysis if some simplifications are permissible.
Ignacio,
I have had good luck with simulating Hertz contact and friction loading and stresses with deflections with Simulation Mechanical. I have also had good luck with the use of a free software package called HertzWin by an engineering firm named Vink (Netherlands) for very local linear Hertz contact stress analysis. Trying the model the Hertz contact behavior with the required, very small element sizes does not leave much processing capacity for modeling the global behavior. So, I recommend the following approach:
Thank you both for your guidance!
John: As you suggested me, I'm trying to calculate the case with no movement, just the normal force between wheel and tube. To start I'm focusing on the case of a cylinder (wheel) on a flat surface (tube) and comparing the stresses with theory results (or the ones from the program Keith mentioned). I have a couple of questions:
Since the tube is expected to suffer a full plastic deformation (due to straightening) should I use a static linear model or a static nonlinear one? Here's a picture of the model.
Keith: The machine is meant to straightening copper tubes of 1,3 inch outside diameter and they will be mechanically introduced between the wheels. At the end they will fall by gravity into a chute.
About HertzWin, I've been trying to use it, basically to compare the results with those from Simulation Mechanicals and see if I'm heading to the right place. At this point I'm not having good results, so I assume I'm doing something wrong in my FEA model or in HertzWin. Here's what I'm doing.
I'm not sure about what is the Maximum Stress value and the Length value. I assume the first one is the yield tensile strength and the second is the width of the bodies in line contact (length of line of contact). I also have a doubt about the force, it is a normal point force or it is applied as a distributed load along the line contact area pre deformation?
Thanks you again.
Ignacio
Ignacio,
Some quick notes that may help:
I have also developed an open-source web app
https://foadsf.github.io/OpenHertz/
that pretty much does the job. You may read more about it here on Reddit.