Strengt Testing

6 Pages 1621 Words

Compressive & Tensile

Strength Testing

OBJECTIVE

Our purpose to determine some mechanical properties (compressive and tensile strength) of steel bar and concrete.

1- TENSILE STRENGTH TESTING

INTRODUCTION

There is as yet no standard test for directly determining tensile strength. However there are two common methods for estimating tensile strength through indirect tensile tests. The first, is the splitting test carried out on a standard cylinder specimen by applying a line load along the vertical diameter. It is not practical to apply the a true line load to the cylinder because the side are not smooth enough and because it would induced high compressive stresses at the surface. Therefore, a narrow loading strip made of soft material is used.
Another way of estimating tensile strength is the flexural test. A specimen beam 6 x 6 x 20 inches is molds in two equal layers each rodded 60 times, once for each 2 in2 of top surface area. The beam may be vibrated and should be cured in the standard way. This test tends to overestimate the true tensile strength by about 50%. This can be explained by the fact that the simple flexural formula used is based on a linear stress-strain distribution whereas concrete has a nonlinear distribution. This is an important test because it model how a concrete beam is normally loaded.

EXPERIMENTAL WORK

Specimen : Steel Bar
Apparatus : Venier compass
Steel type meter
Testing machine for tensile strength




EVAULATION

Required :

a)Tensile Stress of Steel Bar, ċ (max) = ? MPa
b)Yield Stress of Steel Bar, ċ (yield) = ? MPa

a) ċ(max) = Pmax / Area ;

Pmax = 76.89 kN
ƒÖ = 14 mm Area = 0.000154 m2

ċ(max) = 76.89 / 0.000154 = 499300 kN/m2 (MPa)

b) ċ(yield)=Pyield/ Area ;

...