Mechanical testing

Mechanical testing covers a wide range of tests, which can be divided broadly into two types:

1. those that aim to determine a material's mechanical properties, independent of geometry.
2. those that determine the response of a structure to a given action, e.g. testing of composite beams, aircraft structures to destruction, etc.

Mechanical testing of materials

Tensile test. A standard specimen is subjected to a gradually increasing load (force) until failure occurs. The resultant load-displacement behaviour is used to determine a stress–strain curve, from which a number of mechanical properties can be measured.

There exists a large number of tests, many of which are standardized, to determine the various mechanical properties of materials. In general, such tests set out to obtain geometry-independent properties; i.e. those intrinsic to the bulk material. In practice this is not always feasible, since even in tensile tests, certain properties can be influenced by specimen size and/or geometry. Here is a listing of some of the most common tests:

• Hardness Testing
  • Vickers hardness test (HV), which has one of the widest scales
  • Brinell hardness test (HB)
  • Knoop hardness test (HK), for measurement over small areas
  • Janka hardness test, for wood
  • Meyer hardness test
  • Rockwell hardness test (HR), principally used in the USA
  • Shore durometer hardness, used for polymers
  • Barcol hardness test, for composite materials
• Tensile testing, used to obtain the stress-strain curve for a material, and from there, properties such as Young modulus, yield (or proof) stress, tensile stress and % elongation to failure.
• Impact testing
  • Izod test
  • Charpy test
• Fracture toughness testing
  • Linear-elastic (K_Ic)
  • K–R curve
  • Elastic plastic (J_Ic, CTOD)
• Creep Testing, for the mechanical behaviour of materials at high temperatures (relative to their melting point)
• Fatigue Testing, for the behaviour of materials under cyclic loading
  • Load-controlled smooth specimen tests
  • Strain-controlled smooth specimen tests
  • Fatigue crack growth testing
• Non-Destructive Testing