How to calculate sample stiffness

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In summary, to calculate the torsional stiffness of a sample, use the equation: 1/samplek= 1/totalk - 1/machinek. The machine k is given as 42800NM/radian. The total k is the slope of the line, which is y=658x. To find the shear modulus, use the given equation to find the sample stiffness and then calculate the shear modulus using the total stiffness.
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febbie22
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hi i need to calculate the torsional stiffness of a sample, the data is in the excel file.

To work it out it = 1/samplek= 1/totalk - 1/machinek

the machine k was given as 42800NM/radian

the total k is the slope of the line which comes to y=658x

what i don't get is what am i meant to do with y=658x,

cheers any help would be great
 

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I've done a question very similar to that, and if I remember correctly then the gradient was either one of the stiffnesses or the shear modulus. But it was a year ago and I've not done anything like that since so I'm a little rusty on torsion.

Edit: it's come back to me slightly. You have to find the shear modulus of the material, right? The slope is the total stiffness. Use the given equation to find out the sample stiffness and then you can easily calculate the shear modulus.
 
Last edited:

What is sample stiffness and why is it important to calculate?

Sample stiffness is a measure of the resistance of a material to deformation under an applied load. It is important to calculate because it can provide valuable information about the mechanical properties of the material, which can be useful in fields such as engineering, materials science, and biomechanics.

What is the equation for calculating sample stiffness?

The equation for calculating sample stiffness is stiffness = (applied load/change in displacement). It is typically measured in units of force per unit of displacement, such as N/m or lb/in.

How do you determine the applied load and change in displacement?

The applied load can be determined by using a force-measuring device, such as a load cell, to measure the force being applied to the sample. The change in displacement can be measured using a displacement sensor, such as a linear variable differential transformer (LVDT) or a strain gauge.

What are some common methods for calculating sample stiffness?

Some common methods for calculating sample stiffness include tensile testing, compression testing, and bending testing. These methods involve applying a known load to the sample and measuring the resulting displacement, then using the equation mentioned above to calculate stiffness.

Are there any limitations to calculating sample stiffness?

Yes, there are some limitations to calculating sample stiffness. The accuracy of the calculation can be affected by factors such as the size and shape of the sample, the type of loading applied, and the condition of the sample (e.g. if it is damaged or has imperfections). Additionally, the calculation may not accurately reflect the true stiffness of the material in real-world applications, as it is typically performed under controlled laboratory conditions.

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