Forging new generations of engineers. Tensile Testing. The following MATERIAL PROPERTIES can be evaluated / determined by TENSILE TESTING: STRENGTH DUCTILITY ELASTICITY STIFFNESS. Material Properties. STRENGTH - the greatest stress that the material can withstand prior to failure.
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STRENGTH - the greatest stress that the material can withstand prior to failure.
DUCTILITY - a material property that allows it to undergo considerable plastic deformation under a load before failure.
ELASTICITY - a material property that allows it to retain its original dimensions after removal of a deforming load.
STIFFNESS - a material property that allows a material to withstand high stress without great strain.
A machine which applies a tensile force (a force applied in opposite directions) to the specimen, and then measures that force and also the elongation:
This machine usually uses a hydraulic cylinder to create the force. The applied force is determined by system pressure, which can be accurately measured.
AppliedForce is hydraulic pressure times the area of the cylinder’s piston.
F = PRESSURE x AREA
= 0.6N/mm2 x 1962.25mm2
Data Acquisition Unit
A precision punch with two points exactly 2.000” apart is used to mark the sample in the tested region.
This establishes the original length.
This device, called an EXTENSOMETER, measures the distance between the two prongs very precisely while the test is in progress.
Necking: The localized decrease in diameter in a specimen near the rupture point.
Elastic Deformation Region: The area of a stress - strain curve where the specimen will deform under load, yet return to its original shape when the load is removed.
Plastic Deformation: Deformation that occurs once the object has been stressed past its elastic limit. The deformation is no longer reversible.
“Necking” occurs as the sample leaves the elastic deformation region and begins to deform plastically.
The classic cup & cone shape of a fairly ductile tensile fracture is visible here.
Upon completion of the test, the sample is reassembled and final measurements for total elongation and minimum diameter are made using a vernier caliper.
For maximum precision, the points of the vernier caliper must be placed exactly at the center of the marks made by the punch prior to the test.
All three failed under tension
ELASTIC DEFORMATION REGION
The point of departure from the elastic deformation region is known as the “yield point.”
In the elastic region, the slope of this line is the material’s Modulus of Elasticity.