2030 – 06 – Types of Strength
Strength describes a material’s ability to resist stress. There are three basic types of stress that materials can withstand: shear, compression and tensile stress.
Shear stress occurs when the material slides against itself. Shear strength resists this sliding. Torsion stress is a type of shear stress: It adds rotation motion to one end of the metal, twisting the material. Shear strength is tested with a torsion test. Materials with high shear strength typically have high tensile strength as well.
Compression stress describes how well a material resists squeezing. It’s tested by putting a part under a load and assessing how much weight the part can handle. Brittle metals perform poorly on this test, but stronger metals will swell without fracturing.
Tensile stress is exerted when materials are pulled apart. Tensile strength describes how well a material can resist the pulling. It’s tested by pulling a sample piece of material from each end. As the material is pulled, its diameter gets smaller and the total length gets longer until the piece breaks. The term “necking” describes this reduction in diameter.