Simple stress, strain, elongation relationship question

In summary, the conversation revolves around a question regarding the normal stress, normal strain, and elongation of a circular bar subjected to an axial load. The material is assumed to be steel with an Elastic Modulus of 200GPa. The answer is provided as 159 MPa for normal stress and 795*10^-6 for normal strain. However, there is confusion about how to solve for the elongation, with the correct answer being 0.8mm by multiplying the strain with the original length. The conversation ends with an admission of oversight and a need for more practice with the metric system.
  • #1
Iclaudius
36
0
Howdy ya'll,

a relatively simple question,

A circular bar 20mm in diameter and 1m long is subjected to an axial load of 50kN. Determine:

(i) The normal stress.
(ii) The normal strain.
(iii) The elongation.

Assume the material is steel with an Elastic Modulus of 200GPa.

ok so i got normal stress = 159 MPa, normal strain = 795*10^-6,
but here is my problem - solving for elongation why can i not just plug in the strain amount and solve for the change in length i.e strain * original length = change in length?
by the way elongation = 0.8mm which is not what i get using the aforementioned method.

(sorry for no math symbols)
Thanks in advance,
Claudius
 
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  • #2
795 x 10-6 multiplied by 1 m is not approximately 0.8 mm?
 
  • #3
oh snap, don't know what i was thinking lol, thanks for pointing out my oversight, guess i need more practice with the metric system :(
 

1. What is simple stress and strain?

Simple stress and strain refer to the relationship between the force applied to an object and the resulting deformation or elongation of that object. It is a measure of how much a material can stretch or compress under a given amount of force.

2. How is stress calculated?

Stress is calculated by dividing the force applied to an object by its cross-sectional area. The unit of stress is typically measured in Newtons per square meter (N/m^2) or Pascals (Pa).

3. What is the difference between tensile and compressive stress?

Tensile stress is the force that stretches or elongates an object, while compressive stress is the force that compresses or shortens an object. They are both types of simple stress, but act in opposite directions.

4. What is the relationship between stress and strain?

The relationship between stress and strain can be represented by a graph called a stress-strain curve. It shows that as stress increases, strain also increases, but at a decreasing rate. The slope of the curve represents the material's stiffness or elasticity.

5. How does temperature affect the stress-strain relationship?

Temperature can affect the stress-strain relationship by changing the material's stiffness and its ability to withstand stress. High temperatures can cause a material to become more ductile and have a higher strain at failure, while low temperatures can make a material more brittle and have a lower strain at failure.

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