To Determine Yield Strength & Tensile Strength of a Steel Bar 

Advertisements

Apparatus:UTM, Test Specimen, Vernier Calipers, Ruler etc.
A machine designed to perform tensile, compression, bend and shear tests, is called UTM,. It mainly consists of two parts.
Procedure:


Gauge length = 8 inch Determine the yield strength by the following methods.
To determine the yield strength by the this method, it is necessary to secure data (autographic or numerical) from which a stressstrain diagram with a distinct modulus characteristic of the material being tested may be drawn. Then on the stressstrain diagram, lay off om equal to the specified value of the offset (i.e. yield strength ~0.2%), draw mn parallel to OA, and thus locate r, the intersection of mn with the stressstrain curve corresponding to load R, which is the yield strength load. In recording values of yield strength obtained by this method, the value of offset specified or used, or both, shall be stated in parentheses after the term yield strength. Figure  Stressstrain diagram for the determination of yield strength by the offset method. Secant MethodThis method is also referred as the tangent, secant or chord modulus for the line drawn from the shear stressshear strain curve at 5% (1/20) and 33% (1/3) of the maximum compressive shear stress. This region usually lies well within reasonably linear part of the curve. Lower part of the curve, representing a straight region being associated with closing up the interfaces between mortar and units is ignored, as they normally close up due to self weight in real structures. Calculations for Ec are as follows. Ec = ∆ Shear Stress / ∆Shear Strain ∆ Shear Stress = (Shear stress corresponding to 1/3 of the compressive strength)  (Shear stress corresponding to 1/20 of the compressive strength) ∆ Shear Strain = Difference of the Shear strain at corresponding values of Shear stress. ASTM Standards
Elongation = 9.8 – 8 = 1.9


Related Articles  
Bend Test on Steel Bar Reaction in Simply Supported Beam Deflection in Overhanging Beam 