Analysis of deformation of skin due to a probe
Analysis of deformation of skin due to a probe
(OP)
Hi,
I have problem of finding the deformation of skin using a probe. I have identified the different layers of skin and made the model accordingly along with a probe in contact with the top layer of skin. The model is basically 15x15mm model with extrudes of different thickness for each layer.
The layers are stratum corneum, viable epidermis, dermis, hypodermis and muscle respectively. Each layer has different mechanical properties and is given isotropic elasticity condition.
The force of 0.1N is given to the probe and the bottom and the sides of the skin model are given fixed support condition.
The deformation in the first four layers are acceptable but the muscle layer acts like a cube of immense stiffness in a sense that no stress, no deformation, no strain occurs in the muscle layer. I cannot seem to identify the cause of this problem and i need some HELP figuring this out!
PS: I have attached the picture of the model, the sectional view of the results and the material properties of each layer
The model was created on SOLIDWORKS 2015
The normal strain in y-axis

Material properties

Sectional view of deformation

Skin model with probe

Closeup of top 3 layers of the skin
I have problem of finding the deformation of skin using a probe. I have identified the different layers of skin and made the model accordingly along with a probe in contact with the top layer of skin. The model is basically 15x15mm model with extrudes of different thickness for each layer.
The layers are stratum corneum, viable epidermis, dermis, hypodermis and muscle respectively. Each layer has different mechanical properties and is given isotropic elasticity condition.
The force of 0.1N is given to the probe and the bottom and the sides of the skin model are given fixed support condition.
The deformation in the first four layers are acceptable but the muscle layer acts like a cube of immense stiffness in a sense that no stress, no deformation, no strain occurs in the muscle layer. I cannot seem to identify the cause of this problem and i need some HELP figuring this out!
PS: I have attached the picture of the model, the sectional view of the results and the material properties of each layer
The model was created on SOLIDWORKS 2015
The normal strain in y-axis

Material properties

Sectional view of deformation

Skin model with probe

Closeup of top 3 layers of the skin





RE: Analysis of deformation of skin due to a probe
Does your mesh have sufficient resolution?
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RE: Analysis of deformation of skin due to a probe
isn't it amazing what FEA is being used to solve these days ?
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RE: Analysis of deformation of skin due to a probe
Cheers
Greg Locock
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RE: Analysis of deformation of skin due to a probe
@greglocock the boundary conditions are that all sides of the model except for the top side is fixed and a force of 0.1N is applied to the top of the probe.
I had also assumed that because muscle is much more stiffer than the hypodermis, this problem happens. But my mentor says that something is wrong in the model and that this problem should not occur. So i tried redoing the entire thing again (many times) and the problem still persists.
From the above replies i don't know whether my problem is actually a problem or just a solution.
RE: Analysis of deformation of skin due to a probe
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Analysis of deformation of skin due to a probe
It may be so that from the perspective of the hypodermis the muscle is rigid. Try by making the hypodermis 100 times stiffer. Just to see what happens.
Thomas
RE: Analysis of deformation of skin due to a probe
Von mises stress
Normal stress (y axis)
Normal stress (z axis)
RE: Analysis of deformation of skin due to a probe
Deformation
Von mises stress
Normal stress(y axis)
Normal stress (z axis)
RE: Analysis of deformation of skin due to a probe
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Analysis of deformation of skin due to a probe
Deformation
Von mises
Normal stress (y axis)
Normal stress (z axis)
RE: Analysis of deformation of skin due to a probe
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Analysis of deformation of skin due to a probe
RE: Analysis of deformation of skin due to a probe
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Analysis of deformation of skin due to a probe
Every time i post the results i state the constraints i use.
The 1st set of results shown are when the x and the y coordinates are fixed (the sides and the bottom are given fixed support condition)
2nd set of results are also when the x and y coordinates are fixed (the sides and the bottom are given fixed support condition)
3rd set is when the x coordinate is fixed (bottom of the muscle layer (muscle layer is the last layer) is NOT fixed)
4th set is when the y coordinate is fixed (bottom of the muscle layer (muscle layer is last layer) is fixed).
The issue is that the muscle layer does not show any deformation or stress or strain. Even though i gave a fixed support condition to the bottom of the muscle layer, the interpretation for results shows that a fixed support condition is given to the bottom of the hypodermis layer (the layer prior to the muscle layer)
RE: Analysis of deformation of skin due to a probe
RE: Analysis of deformation of skin due to a probe
like I sauid before, I think that from the perspective of the hypodermis the muscle layer is "rigid". It is 125 times stiffer. I would make the hypodermis 100 times stiffer as a test.
If that doesn't work I would remake the entire model to reduce the the stiffness variation. Just to ensure that the probes action is reasonable. You can also try by reducing the Poissons ration to 0.4 or something. 0.49 can result in numerical issues.
Thomas
RE: Analysis of deformation of skin due to a probe
I assume you're modelling this as a flat "plate", not as a cylinder ??
another day in paradise, or is paradise one day closer ?