Calculating Poisson's Ratio and Modulus of Elasticity for a Solid Cylinder

In summary: The normal stress is the stress after the object has been deformed, so you would calculate the initial stress and then divide that by the deformed size.
  • #1
bono141
3
1
Hi, I am new to this so bear with me,

I'm stuck on a question, basically, i need to work out the poissons ratio for a solid cylinder 140mm dia by 4.0m long to find out if it's steel or aluminium. I know the formula for poisson ratio is lateral strain / axial strain. The question states that there is a force acting on the cylinder but gives no values, how would I go about working out the poisson's ratio? Any help would be much appreciated.

Many Thanks
Scott.
 
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  • #2
Does the problem provide stresses or strains, and the elastic or bulk modulus?

One would need to know the axial and lateral strains, or a force/stress.

Please write the problem as given.
 
  • #3
the whole question

A circular cross section tie rod located in a structure has a diameter of 140mm and a length of 4.0m. If under load the length increases by 1.2mm and the diameter decreses by 0.11mm, identify the relationship between lateral and transverse strain and determine the value of poisson's ratio.

I have no idea how to go about completing this one. Any help would be greatly appreciated.
 
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Likes Morrai Waram
  • #4
What is the definition for strain? You have two things you need to calculate in order to calculate Poisson's Ratio, the axial strain and the lateral strain. You are given all of the pieces of the two parts. What two numbers will make up the axial strain? What two numbers will make up the lateral strain?
 
  • #5
continued...

the strain formula is: change divided by original

the 4.0m & 1.2mm increase is for the lateral strain and the 140mm and 0.11mm decrease is for the axial strain i beleive.
 
  • #6
Right. Now just make sure you are dealing with the same units for each number. Either m or mm, it doesn't matter, just make sure you use only one.
 
  • #7
Okay I know this thread is so old now, but I'm working a similar problem and its also asking for me to find the modulus of elasticity.

I know the basic formula for it is normal stress divided by the normal strain.

So I'm thinking the normal strain is the same as the axial strain?
Also when it says the normal stress does that mean I calculate the Initial stress with the undeformed diamter or do i calculate both of them and just use the difference of the two?
 

Related to Calculating Poisson's Ratio and Modulus of Elasticity for a Solid Cylinder

1. What is Poisson's ratio?

Poisson's ratio is a material property that measures the ratio of lateral strain to axial strain under tensile or compressive stress. It is denoted by the symbol ν (nu) and is typically between -1 and 0.5 for most materials.

2. How is Poisson's ratio calculated?

Poisson's ratio can be calculated by dividing the absolute value of the transverse strain (change in width) by the absolute value of the axial strain (change in length) in response to applied stress. This calculation can be done using experimental data or through mathematical modeling.

3. What factors affect the value of Poisson's ratio?

The value of Poisson's ratio is affected by various factors such as the type of material, its microstructure, temperature, and the magnitude of applied stress. It can also be influenced by the direction of stress and the rate at which the stress is applied.

4. Can Poisson's ratio be negative?

Yes, Poisson's ratio can be negative for certain materials such as auxetic materials, which exhibit a negative Poisson's ratio due to their unique microstructure. However, for most materials, the value of Poisson's ratio is positive.

5. What is the significance of Poisson's ratio?

Poisson's ratio is an important property to consider in material selection and design, as it affects the behavior of a material under stress. It can also provide information about the elasticity and stiffness of a material. In some cases, it can also be used to determine the presence of defects or damage in a material.

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