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Axisymmetric Hertz's Contact Model
Posted 13 mar 2017, 21:40 GMT-4 Materials, Structural Mechanics Version 5.2a 2 Replies
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Hi All,
I have a quite simple 2D axisymmetric system: indentation (0.75 um) of a spherical probe (5 um diameter) into a relatively large and soft linear elastic sample (40 um height, E=1 kPa, Poisson's ratio=0.48). However, I'm constantly getting reaction force about 20% lower than predicted by Hertz's theory, with different meshes and step sizes. I think the problem could be in the high Poisson's ratio, but I see no difference in solution with and without "nearly incompressible material" selection. For lower Poison's ratio the solution is closer to the theory, and when I'm using the hyperelastic Mooney–Rivlin material too. But I need a linear elastic material for my future studies and want to find the reason for such difference. Any advice?
Thanks,
Yuri
I have a quite simple 2D axisymmetric system: indentation (0.75 um) of a spherical probe (5 um diameter) into a relatively large and soft linear elastic sample (40 um height, E=1 kPa, Poisson's ratio=0.48). However, I'm constantly getting reaction force about 20% lower than predicted by Hertz's theory, with different meshes and step sizes. I think the problem could be in the high Poisson's ratio, but I see no difference in solution with and without "nearly incompressible material" selection. For lower Poison's ratio the solution is closer to the theory, and when I'm using the hyperelastic Mooney–Rivlin material too. But I need a linear elastic material for my future studies and want to find the reason for such difference. Any advice?
Thanks,
Yuri
2 Replies Last Post 14 mar 2017, 10:04 GMT-4
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Posted:
8 years ago
Hi,
You could try the "Force linear strains" check box. When running contact analysis you always get a geometrically nonlinear formulation. The Hertz's theory is however based on linear strain assumptions.
Making this change will not give a more correct solution, but probably one that is more close to the theory, including its limitations.
Regards,
Henrik
You could try the "Force linear strains" check box. When running contact analysis you always get a geometrically nonlinear formulation. The Hertz's theory is however based on linear strain assumptions.
Making this change will not give a more correct solution, but probably one that is more close to the theory, including its limitations.
Regards,
Henrik
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Posted:
8 years ago
Henrik,
Thank you, this indeed worked well. With the "Force linear strains" selection difference between theory and solution is below 3%. I had to deselect the "nearly incompressible material" box, because then they're selected together there is no convergence.
Yuri
Thank you, this indeed worked well. With the "Force linear strains" selection difference between theory and solution is below 3%. I had to deselect the "nearly incompressible material" box, because then they're selected together there is no convergence.
Yuri