Tensile test with solidworks

Simulation
1

Hello to you. 

I have to perform, for an exercise at my school, various tensile tests in solidworks by modifying the tightening of the mohrs. I have no knowledge about this software. I discovered it in September and it was with great difficulty that I drew my piece and applied constraints to it. However, I haven't found how to model the mohrs and above all, how to modify the tightening. I thought of drawing 4 other parts that will stick to the faces of my (flat) test tube to imitate the way you insert the test piece on a classic tensile machine. 

Do you have any advice or steps to give me? 

Thank you in advance.

2

Hello@stephan01

You have embarked on a hell of an adventure, especially for someone who, according to your words, is rather a beginner.

If you want to achieve results, you should already give up measuring the slip in the jaws according to a clamping.

  1. If you think about it, you'll see that the notion of tightening is just another way of saying that there is slippage. It is therefore more correct to say that we want to gradually increase the slip resistance by changing the coefficient.
  2. So it is only by pressing and changing the slip coefficient that you will achieve your goals.
  3. There is no point in simulating having the real jaws since only the contact areas are represented on the specimen. Simply replace the jaws with demarcated areas with the help of dividing line. Then to apply the measures that are going well and in the right direction.
  4. Another point to know is that the simulation only works in the elastic domain so you will not be able to simulate the maximum tensile force since you will have reached the MPa limit before the ruin criteria (understand the indefinable point of the moment of failure). This way, all the pulling forces on the jaws between the elastic area and the ruin will be unknown to you.

 To allow you to move forward, you must be able to correctly use the criterion of pressure and slip coefficient. The solidworks online help is very easy to understand in general.
If you are unsure of the understanding of the online help, you can always ask us more questions.

Kind regards

PS: when you say my school I assume that it is not the first grade and that you are not at polyclinic, but you give no details on your level of knowledge which would be very useful for those who will answer you and who have to adapt what they will have to say according to your supposed knowledge.

1 Like
3

Hello

I have a question: does the problem that your school is asking you to solve explicitly concern the interface between the jaws and the test tube? Or is it a question of checking the suitability of the model for a real tensile test?

I say this because tensile specimens are made to break in the middle and be independent of the means of traction. In this case, I would just put a fixed end face, another in tension (force and/or displacement), with enough distance between these faces and the area of constraint, so that this degraded modeling does not influence the result.

M.

4

To answer both posts at the same time, I drew my test tube and then gave it thickness. Then, as you probably said, I drew rectangles on the contact faces (4 in all) because by fiddling a little, I noticed that you could apply a force on a given area (and therefore simulate the pressure of the mohrs, I put a screen in PC). So I will only have to modify this force before "simulating a tensile test".

From what the teacher told me, it's just a simulation without dwelling on what happens in real life. I imagine that he did not ask for it because unfortunately we no longer have access to the machines since the lockdown.

Thank you.  


4.png
5

Hello@stephan01

Your image gives us absolutely nothing, we need at least two areas and here we only see one. In addition, you have to show us all the parameters if not very clever that will give you valid information.

From what I see, you are already missing at least one constraint that should perhaps be elastic.

Post your ASM using the "pack and GO" function, all in a zip

Kind regards

PS:  

@mgauroy
In my answer, I have tried to answer both points of the request

  1. Tensile tests in SOLIDWORKS by modifying the tightening of the Mohrs.
  2. I haven't found how to model the Mohrs and above all, how to modify the tightening.
  3.  My remark in my previous point 4, concerning the elastic domain remains valid in all cases  ;-)

 

6

@Zozo_mp: I didn't say that you didn't answer the statement. I just questioned the statement, it can be legitimate.

1 Like
7

Yes, but I reproduced what I inserted in PJ on the other 3 faces where theoretically will be placed. That's how I see it because, in the DUT, I was able to carry out tensile tests or, to tighten the samples, I used a kind of clamp that clamped the part. By applying a force on the 4 rectangles I have drawn, I think I can reproduce the effect of the mohrs on the sample, right? 

Regarding the force to be applied, I don't know which value to choose. I try to search the internet for values.

What does ASM mean? The question may sound silly and I apologize for it, but I'm just a beginner on Solidworks.

8

Hello Stefan01

Your choice of a strength is not the right parameter.

The force is only used when an object is attached and the workpiece is pressed somewhere to see how it will deform.

What to do instead

1°) these are the displacement parameters imposed by having a virtual wall or what would be better would be to use the other parts, the jaws and define the coefficient of friction.  The higher the coeff, the less it slides. (which the Egyptians understood with their heavy pebbles)

2°) Another solution to be tested would be elastic supports that allow you to modulate the pressure.

ASM and the abbreviation for Assembly. As you had spoken of a scaretaker stuck in bits, it implied that you had at least 5 parts (4 jaws and a test tube). These five pieces can only be in one assembly. If you have a single part with components, it's more complicated, if not impossible, if you're not multi-body.

If you publish your assembly, we may be able to help you. (To publish, use the Pack and GO function by selecting a ZIP output.

Kind regards

9

Hello 

Thank you for your advice. In theory, I'm starting to pretty much see what I should do. In practice, it's something else...  

Here is the test tube that I tried to model. 

Reading you, I'm understanding that I have to make 1 other piece that I'm going to place at the 4 corners of my test tube instead of the areas I had drawn. Am I wrong? 


piece.sldprt
10

Hello

As Zozo_mp told you in point n°1, you have to define your imposed movements (the static analyses of your part file do not have any). Finite element analysis considers your part as a set of points connected by springs. This is the network. To oversimplify, think of your test tube as one large spring. To study how it behaves, you can:

  • Either fix one end and pull the other over a certain distance, measuring the effort to do this;
  • Either fix one end and put an effort on the other side by measuring the resulting increase in distance

In the same way in the software, you must either block your test tube on one side and move the other side, or block one side by putting an effort on the other side. I personally advise you to simplify your problem first, then to make it more complex as you learn the tool (this was the meaning of my previous post).

In particular, I advise you first to learn how to put an imposed displacement (orange on the image) and an effort (easier to find a valid value like this; in purple on the image) on the two extreme sides:

Afterwards, you can try to apply your boundary conditions (imposed displacements & forces) on your virtual faces that you have defined with the separation lines (it's already not bad if you know how to do that):

Finally, you can tackle the more detailed models offered by Zozo_mp (elastic support, analysis within the specimen+jaw assembly, etc.) which will not lack interest for your training/knowledge. This will teach you to take a step back from what you are doing.

Don't hesitate to do a simulation by modeling, which will allow you to compare the results after the fact :

In the two simplified cases that I have proposed, I have been able to see that the stress in the fillet area of the specimen is almost identical in both cases (6.581 MPa & 6.575 MPa). If you try, however, you will see that the max stress increases, at the separation line in model 2, which does not seem to me to be very realistic.

PS: a good way to train is to use the tutorials integrated into solidworks by going to the menu "?/SOLIDWORS Simulation/Tutorials ":

Good luck

M.

1 Like
11

Great thanks, I'll try to see that!