EXPERIMENT # 3 Instructor: M.Yaqub TENSILE TEST EXPERIMENT # 3 Instructor: M.Yaqub

TENSILE TEST The purpose of TENSILE TEST is to check the strength of any metal. Before understanding the test, following definition are required to know. Engineering Stress: Ratio of the applied force to the initial area.

Where F is the applied force in newton or in pound. is the cross section area of the test piece in m2 or in inch2. The unit for the Engineering Stress is pascals(N/m2) or PSI (lb/ inch2)

Engineering Strain: Ratio of the change in length (elongation) to the original length. Where Change in length because of the force applied. Where is the original length.

TENSILE TEST SPECIMEN

GRAPH FROM TENSILE TEST

Zone I Relation between stress and stain is linear and the curve is a straight line. Where E is proportionality constant and called YOUNG’S MODULUS. Deformation is Elastic in this zone, means No permanent deformation.

Zone II Deformation is permanent. Stress and Strain are not linear. This zone starts from end of the first zone and ends at the highest point of the curve which is called NECKING POINT. This point corresponds to the maximum force applied during the test. The deformation in this zone is called PLASTIC DEFORMATION.

Zone III After necking point, the area of the specimen decreases and hence load carrying capacity of the sample also decreases. Load decreases in the zone and after some time sample fail (fracture) from necking point.

Yield Strength (sy): Stress corresponds to the Elastic Limit (up to where, the curve is linear, called yield point). If two limits, Lower will be yield point.

Yield Strength at 0.2% (offset yield strength

ULTIMATE TENSILE STRENGTH (su) Also called Tensile Strength (TS), or Engineering Tensile Strength (suts). Stress at highest point of the curve or at necking point.

ENGINEERING FRACTURE STRENGTH (sF) Stress at the last point of the curve. This point is the fracture point.

DUCTILITY Ability of a material to deform plastically without fracture. Measure in two terms. Percentage Elongation (%EL) Percentage Reduction in Area (%RA)

RESILIENCE & MODULUS OF RESILIENCE (UR) The ability of a material to absorb energy when deformed elastically and to return it when unloaded is called resilience. Modulus of Resilience is the energy per unit volume stored in the specimen while deform elastically. It is area under the curve up to elastic region and can be obtain from

TOUGHNESS & MODULUS OF TOUGHNESS (UT) Ability of the material to absorb energy in elastic region. This is the energy stored in the specimen during the test and can be expressed in energy per unit volume. It is the area under the hole curve and can be approximated by For ductile material For brittle material

TRUE STRESS (st) Ratio of the instantaneous load and instantaneous (actual) Area. Area conserved during the test up to necking point.