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ptar May18-11 09:36 PM

Young's Modulus of Pressure Sensor
 
1. The problem statement, all variables and given/known data
Here's the question, verbatim;
We want to build a pressure using a block of elastic material, where the pressure applied to the top surface is measured by a strain gauge mounted on one of the side walls of the block. The gauge factor of the strain gauge is 2.5. When 1 mm Hg of pressure is applied to the top surface, we obtain a delta R/R of 0.01% on the strain gauge. The nominal resistance of the strain gauge is 1000 Ohm.
(a) What is Young's Modulus of Elasticity (E) for the elastic block?


2. Relevant equations
Young's Modulus= Stress/ Strain = (F/A) / (delta l/l)


3. The attempt at a solution
Here the strain can also be given by the formula ((1/F) x delt.R/R), where F is the gauge factor. Plugging numbers in here, I've worked out the strain to be 4 x 10^-5. However, I have no idea what to do next. I'm sure you need area to work out stress. Or would integrating the pressure work, as pressure is dF/dA? But then you would still be left with a variable in the stress result.

Please help! Thanks.

mathewmakil May19-11 02:27 AM

Re: Young's Modulus of Pressure Sensor
 
I have this same problem for my assignment and am stuck. i've found out the strain but no idea on working out the stress.
Quote:

Quote by ptar (Post 3310288)
1. The problem statement, all variables and given/known data
Here's the question, verbatim;
We want to build a pressure using a block of elastic material, where the pressure applied to the top surface is measured by a strain gauge mounted on one of the side walls of the block. The gauge factor of the strain gauge is 2.5. When 1 mm Hg of pressure is applied to the top surface, we obtain a delta R/R of 0.01% on the strain gauge. The nominal resistance of the strain gauge is 1000 Ohm.
(a) What is Young's Modulus of Elasticity (E) for the elastic block?


2. Relevant equations
Young's Modulus= Stress/ Strain = (F/A) / (delta l/l)


3. The attempt at a solution
Here the strain can also be given by the formula ((1/F) x delt.R/R), where F is the gauge factor. Plugging numbers in here, I've worked out the strain to be 4 x 10^-5. However, I have no idea what to do next. I'm sure you need area to work out stress. Or would integrating the pressure work, as pressure is dF/dA? But then you would still be left with a variable in the stress result.

Please help! Thanks.



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