NDN
UNIST/Mechanical Engineering
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Posted:
7 years ago
2017年8月17日 GMT-4 02:24
It maybe useful for u
https://www.youtube.com/watch?v=k-4bjO1Cq-4&list=PLC7C49A0F0814EF1E
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Posted:
7 years ago
2017年8月17日 GMT-4 02:58
These videos are based on resonant frequency. But I need to find the bending of cantilever beam due to a tip mass.
These videos are based on resonant frequency. But I need to find the bending of cantilever beam due to a tip mass.
Ivar KJELBERG
COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted:
7 years ago
2017年8月17日 GMT-4 07:47
Updated:
7 years ago
2017年8月17日 GMT-4 07:48
Hi
I assume you mean under gravity load ?
In such a case your tip mass will always bend a little, so you should probably state tip not to bend more than ...
That is an typically an optimisation problem: you define the beam shape width and length, the material, the tip mass value and then you set as parameter the beam thickness and measure the tip motion and loop back to optimise the thickness until you reach the tip bending limit value you want.
A simpler way is just to do a parametric sweep of the same model, with the beam thickness as parameter, you define a start stop, step range and you monitor the tip deviation by i.e. a point integration of one of the tip points. Once plotted out you can easily read out the thickness value for a given deflection.
There are also some other "engineering" rule of thumb ways (rough approximation, but often quite OK), as for a simple tip loaded beam the first eigenfrequency f0 is roughly :
2*pi*f0 = sqrt(k/m) = sqrt(g_const/Dz)
where k[N/m] is the beam stiffness, m[kg] the tip load mass (assumed to be greater than the beam mass) g_const is the gravity constant 9.18[m/s^2] and Dz is the maximum tip displacement in [m]
Then one can optimise the first eigenfrequency to be above this limit deduced by the formula above
--
Good luck
Ivar
Hi
I assume you mean under gravity load ?
In such a case your tip mass will always bend a little, so you should probably state tip not to bend more than ...
That is an typically an optimisation problem: you define the beam shape width and length, the material, the tip mass value and then you set as parameter the beam thickness and measure the tip motion and loop back to optimise the thickness until you reach the tip bending limit value you want.
A simpler way is just to do a parametric sweep of the same model, with the beam thickness as parameter, you define a start stop, step range and you monitor the tip deviation by i.e. a point integration of one of the tip points. Once plotted out you can easily read out the thickness value for a given deflection.
There are also some other "engineering" rule of thumb ways (rough approximation, but often quite OK), as for a simple tip loaded beam the first eigenfrequency f0 is roughly :
2*pi*f0 = sqrt(k/m) = sqrt(g_const/Dz)
where k[N/m] is the beam stiffness, m[kg] the tip load mass (assumed to be greater than the beam mass) g_const is the gravity constant 9.18[m/s^2] and Dz is the maximum tip displacement in [m]
Then one can optimise the first eigenfrequency to be above this limit deduced by the formula above
--
Good luck
Ivar
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Posted:
7 years ago
2017年8月23日 GMT-4 05:36
As am not familiar with the steps kindly send me the .mph file for the same. Thanks in advance.
As am not familiar with the steps kindly send me the .mph file for the same. Thanks in advance.
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Posted:
7 years ago
2017年9月12日 GMT-4 07:18
Hi I dint know how to start .can you please send me the file with these steps(optimization). So that i can proceed. Thanks.
Hi I dint know how to start .can you please send me the file with these steps(optimization). So that i can proceed. Thanks.
