Brinell hardness test simulation using Comsol Multiphysics

[@moderntechnologies9334]

Hi, Thank you. I need help regarding plastic strain, how can i measure plastic strain of this simulation? please

[@JafScience]

I thought of the following workaround: plastic strain= total strain (from results) - elastic strain. Elastic strain = yield stress divided young modulus.

[@moderntechnologies9334]

@@JafScience Thank you so much! I want to get plastic strain results like Von mises stress in results section. but i couldn't

[@JafScience]

@@moderntechnologies9334 Von mises stress is not strain. You can plot total von-Mises stress and if you subtract yield stress you will get plastic stress.

[@ibrahimfadilah9655]

I got error on convergence

[@bhargabbarua8700]

How to model die sinking EDM operation? Kindly make one video on that

[@etibarmikayilov4891]

Thanks for the video. But everytime that i m trying to do the same procedure there is an error: - Feature: Time-Dependent Solver 1 (sol1/t1) Undefined value found. - Detail: Undefined value found in the stiffness matrix. There are 3645 equations giving NaN/Inf in the matrix rows for the variable comp1.u. at coordinates: (0.0098,0.005), (0.00985,0.005), (0.0099,0.005), (0.00994422,0.00495086), (0.00992211,0.00497543), ... There are 3645 equations giving NaN/Inf in the matrix rows for the variable comp1.w. at coordinates: (0.0098,0.005), (0.00985,0.005), (0.0099,0.005), (0.00994422,0.00495086), (0.00992211,0.00497543), ... and similarly for the degrees of freedom, NaN/Inf in the matrix columns. I really do not understand the reasons.

[@JafScience]

It looks like there's rigid body motion. Is the geometry constrained properly? Did you follow all steps for the contacts/physics/solver?

[@etibarmikayilov4891]

Thanks for your answer. I followed the same steps you did for the boundary load, contact, and physics, but I used different materials. The indenter, with a 2 mm radius, is made of PLA (polylactic acid) with a density of 1240 kg/m³, Young's modulus of 1639 MPa, and Poisson's ratio of 0.35. The sample, which is 5 mm tall and 10 mm wide, is made of NBR (nitrile butadiene rubber) with a density of 1000 kg/m³, Young's modulus of 4 MPa, and Poisson's ratio of 0.5.@@JafScience

[@JafScience]

Could it it be that the force is too much for these materials?

[@etibarmikayilov4891]

In this test, I used a maximum of 100 Newtons. And again the same error occurred.@@JafScience

[@etibarmikayilov4891]

Should I set "t1" in the parameters as shown in the error? Because in the "Definitions" part -->"Boundary System 1" --> "Coordinate names" - t1 (first), to(second) and n(third) are mentioned. Maybe that's why the error occurs. - Feature: Time-Dependent Solver 1 (sol1/t1) Undefined value found. ....@@JafScience

[@davidndishu4457]

@Jafscience How do I obtain the saturation exponent of a material? Version 6.1 doesn't have the direct or solver search method in Physics module, which is the best to search method to use? Kindly share your email. Thank you.

[@JafScience]

Experimental data is needed to find the saturation exponent. Alternatively you could use a simple bilinear model as a starting point and then use curve fitting to estimate the saturation exponent. Which search methods appear in your version?

[@davidndishu4457]

@@JafScience heirachal Exhaustive Distance tracking

[@JafScience]

@@davidndishu4457 I'm not familiar with these methods unfortunately. But different methods only affect convergence in different applications. The final solution, if converged, should be the same regardless of the method used. So I would suggest to try them out and see which one works best in your model, i.e. convergence and least time to solve.

[@davidndishu4457]

@@JafScience I have decided to use ANSYS software. Thank you very much.

[@chordy3390]

Hi, thank you for great tutorials. How did you Calculate/fine sigma saturation for Aluminium?? is it always constant in the same model or can it also change with loadchanging??

[@JafScience]

Sigma saturation is the difference between the ultimate tensile strength and the initial yield stress. The ultimate strength is a material property and I got it from a journal paper. It doesn't change with loading, but the initial yield point changes once it is exceeded and the sample is unloaded. Therefore, the saturation flow stress will change accordingly.

[@chordy3390]

@@JafScience Thanks for the quick answer. I have used 86 MPa as sigma saturation and solved the model under the application a pressure of 145 MPa and it worked. But when I enter 72 MPa as pressure instead of 145 MPa in the same model, it does not work and Comsol can not solve the problem. It works only if I enter Sigma saturation lower, for example 40MPa. And 40 MPa (sigma saturation) doesnt work for a Pressure145 MPa

[@JafScience]

@@chordy3390 Are you ramping up the applied pressure gradually? For a given saturation flow stress, a lower applied pressure should make the model easier to solve. And for a given applied pressure, a lower saturation stress reduces numerical stability due to the higher non-linearity associated with the higher plastic strain.

[@chordy3390]

@@JafScience Tnx for your help. I could whit your help solve the problem in my thesis. :)

[@占星魔仙]

Thank you for your tutorials. Can you make a tutorial or example for nanoindentation test? All the tutorials I can find used ABAQUS.

[@JafScience]

I don't have experience with doing nano-scale simulations unfortunately.

[@karimmosli8637]

thank you sir for this video

[@davidndishu4457]

@karimmosli8637 How did you plot the results.

[@niranjanthorali4564]

Show a lot of error for the same settings as suggested

[@newmail3549]

thank you for great tutorials. any example with AC (coil) and DC (coil or magnet) magnetic sources together?

[@JafScience]

I'm thinking of a suitable application to show. Introducing a magnet in the time domain will induce unwanted large eddy currents for a very short time. This may cause problems depending on the application. Two time-dependent steps can be used to overcome this issue.

[@mohdazfar997]

Hallo sir, can you make a tutorial or example for 180 degree peel test ?

[@JafScience]

I don't have experience with modelling adhesives so I won't be making such a tutorial in the near future, sorry.

[@mohdazfar997]

@@JafScience ok, Thank you sir

[@ibrahimfadilah9655]

sirr,if can i know how long time needed to compute

[@JafScience]

Computational time depends on mesh size, number of iterations to converge, and your computer's speed. Thus, it's difficult to predict computational time.

[@davidndishu4457]

​@@JafScience How did you obtain the results? I am stuck here. You could have guided on steps of getting results and then bring the results without showing the simulation. You help will be appreciated.

[@muhammadiwan2323]

Comsol version?

[@JafScience]

5.6

[@muhammadiwan2323]

@@JafScience okay thanks

[@mestarmaroua1962]

Thank you

[@davidndishu4457]

@mestarmoroua1962 How did you get the results. I got lost on how and which results to plot.

[@JafScience]

Insert a 2D plot from results, insert surface plot, and define the quantities that you're interested in.

[@davidndishu4457]

@@JafScience Thank you.