Hello all,
I did a tensile test for a deformed steel bar with diameter of 10 mm using using UH-X Universal Hydraulic Test Machine (SHIMADZU-300kN ). The Gauge length of the steel bar (Lo) is 200mm and the speed of the test was 10mm/min. In addition to the time (Sec), the outputs of the machine was as followed
1- Strike (mm)
2- Force (N)
3- Strain (%)
The force was converted to stress (F/A) in order to draw the stress strain curve. The maximum yielding stress at was roughly about 600 MPa which is logic, but when i calculated the slop (E) of the curve (engineering stress-strain) at the elastic zone it was found to be much much lower than 200 GPa as shown in the attached photos.
Thank you all
Dear Hamdi Alsofi
Did you use "Extensometer" for determining changing length of the sample during the test time?
Dear Farshad Nazari ,
Thanks for your reply. I did not use any Extensometer to measure the change in length. I used the strike (mm) produced by the Tensile Machine during the testing and i divide this strike (elongation)/ The gauge length (Lo) to produce the strain. But i am not sure whether this way is correct or no, any advice is highly appreciated Mr. Farshad Nazari
Thanks alot
Dear Hamdi Alsofi ,
Your procedure is correct for determining Yield and Ultimate stress, and elongation and fracture length, but for determining elastic modulus (Young's modulus), you should use Extensometer to record the strain accuracy. Because of in start the process that the strains are very small, recording the strain without Extensometer is not accurate enough.
If you don't have an Extensometer, for determining the Elastic modulus you can use a strain gauge for recording the strain during the test accurately.
Best regards,
Okey very clear Mr. Farshad Nazari .
What if i use Strain Gauge and i stick to the steel bar, is this way will give accurate results the same as Extensometer. The main reason behind this is that i am out of Extensomter but i have strain gauge (10 mm Size) as in the attached photo
Thanks again Farshad Nazari
Yes, this method is accurate and common in the scientific works. The type of strain gouge that is attached is true but you should select a correct model of it according to your sample parameters such as thickness, material and etc.
It is better that study a user guide about using strain gauge in the tensile test.
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