In this experiment we were introduced to the test is a basic mechanical test you can perform on material. Tensile tests are simple, relatively inexpensive, and fully standardized. By pulling on something, we will be able to determine how a material reacts when forces being applied in tension. As the material is being pulled, we will find its strength along with how much it will elongate. The tests are conducted by placing the specimen into the test apparatus and then applying a force to the specimen by separating the testing machine crossheads. And by using our equations:-
σ = F / Ao
ϵ = ΔL / Lo
σT = F / Ao = (F / Ao) * ( Ao / A) = σ ( Ao / A) = σ (ΔL / L) = σ ( 1 + ϵ ).
Where (F) is the forced applied, (Ao) is origin cross-section, (ΔL) is for the difference in length and Lo is the original length between the two marked points.
During this lab, the tension test was used to determine the material properties of A36 steel and cast iron. We used “button head round bar” specimens to conduct the test. This is a basic test that provides very valuable information about the material being tested, including elastic modulus, strength, and ductility.
Before we started the test, we put two reference marks (called gage points) on each specimen two inches apart. The initial gage length, L0, and initial diameter, D0, of each specimen was measured. After making sure the universal testing frame was properly calibrated, we placed the first sample in the machine. The extensometer was attached to measure the elongation of the specimen. The specimen was placed under a gradually higher load until it fractured, at which point the second material was tested. After fracture, the final gage length was measured between the two reference points as well as the final diameter at the point of fracture.
The data from the tension test was then used to create a stress-strain curve of the A-36 steel. This graph can be used to determine the aforementioned material properties.
1) It doesn’t make sense to calculate true stress and true strain using the equations given in the lab notes after the maximum load is reached because at that point necking has began taking place. Once the material begins necking the volume of the sample at the point of necking becomes inconsistent and therefore true stress and true