Tensile Strength Testing
One of the most common mechanical testing methods, tensile testing, is used to determine the behavior of a sample while an axial stretching load is applied. These types of tests may be performed under ambient or controlled (heating or cooling) conditions to determine the tensile properties of a material.
Tensile testing is performed on a variety of materials including metals, plastics, elastomers, paper, composites, rubbers, fabrics, adhesives, films, etc.
Tensile testing is commonly used to determine the maximum load (tensile strength) that a material or a product can withstand. Tensile testing may be based on a load value or elongation value.
Common tensile testing results include:
- Maximum Load
- Deflection of Maximum Load
- Work at Maximum Load
- Load at Break
- Deflection at Break
- Work at Break
- Chord Slope
- Young’s Modulus: This method of testing is used to determine a sample’s behavior under an axial stretching load. Common tensile test results include elastic limit, tensile strength, yield point, yield strength, elongation, and Young’s Modulus. Young’s Modulus is reported commonly as N/mm2 (lbs/in2), MPA (psi).
Ductility testing involves determining the extent by which a material can withstand deformation without rupture.
Bend test for ductility provides a simple way to evaluate the quality of materials by their ability to resist cracking or other surface irregularities during one continuous bend. With a ductile fracture, there is a considerable amount of plastic deformation prior to failure. In metals, for example, the fracture shows a typical cone and cup formation and the fracture surface appears rough and fibrous. Ductile materials show a measured amount of plastic deformation prior to fracture.
The increase in a sample’s gauge length measured after a rupture or break divided by the sample’s original gauge length is referred to as elongation. The greater the elongation, the higher the ductility or elasticity of the material.
Elongation cannot be used to predict the behavior of materials subjected to sudden or repeated loading. Some non-rigid materials like rubber and some plastics have very high elongations prior to break. Cross-head travel can be used to measure elongation of specimens with uniform width dimensions. If the specimen is in a dog-bone or dumb-bell shape with a reduced cross-sectional region called gage length, an extensometer will be required to measure elongation within the gage length region by attaching it directly to the specimen and tracking movement as the material is stretched to failure.