- Tensile stress strain properties is the most common test the rubber industry for Quality Control .
- The principle is essentially a dumbell shaped , test pieces are strained at a constant rate of traverse , and force and corrresponding extensions recorded . The forces reading are expressed as stresses by reference to the original sectional area of the test piece .
- The following measurements can be be taken from a stress/strain curve for rubber :
- Tensile strength ( Stress at break ) - The maximum tensile stress reached in stretching tensile test piece to breaking point.
- Elongation at break ( Strain at break ) - Then tensile strain in the length at breaking point
Young's modulus : Ratio of stress to strain. The value can be obtained from the linear portion of the curve of the order of few percent.Determination of tear properties .
- In a tear test , the force is not applied evenly but concentrated on a deliberated flaw or sharp discontinuity and the force to continuously produce a new surface is measured.
- This force to start or maintain tearing will depend in rather a complex manner on the geometry of the test piece and on the nature of dicontinuity .
- The initiation and propagation of a tear is a real and very important factor in the failure of rubber products.
- Tear strength is calculated as Ts= F/d
, where Ts
is the tear strength in N/mm
is the force and d
is the thickness.