How to Calculate Strain and Dimensional Changes in Complex Loading Systems

[smiffy66]

I missed a day at college last week when i was off sick due to tonsilitis. I received some homework today and it is going to be similar to a test next week. I really need to know how to do this and the lecturer has not been very helpful either.


A) I have a rectangular cross-section bar that is, 100mm x 40mm square and 500mm long. This is subjected to an axial tensile load of 210kN.

From this information i need to determine.
1) The axial strain.
2) The lateral strain.
3) The changes in cross sectional dimensions.

The material has a modulus of elasticity 80GPa, and poissons ratio of 0.25.


B) A bar of circular cross-section is subjected to a tensile load of 210kN, which is within the elastic range. The bar is made from a steel with 80GPa and Poissons ration = 0.25, it has a diameter of 25mm and 0.8m long. Determine the extension of the bar and the decrease in diameter..



Please give me as much help as you can as i am finding this very confusing, all help is appreciated.

 

[LowlyPion]

Welcome to PF.

Try:

http://en.wikipedia.org/wiki/Elastic_modulus
http://en.wikipedia.org/wiki/Poisson's_ratio

 

[LowlyPion]

Also:

The lateral strain at any point in a bar is usually proportional to the axial strain at the same point if the material is linearly elastic, and the ratio of the lateral strain to the axial strain is known as Poisson's ratio (n).

http://www.me.cmu.edu/academics/courses/NSF_Edu_Proj/StrAnalysis_ANSYS/pb1_part1_8.html

 

[smiffy66]

Thanks for the help, i should be able to make an attempt now at least. :)