![Compressive strip](https://upload.wikimedia.org/wikipedia/commons/5/52/Compressive_strip.jpg)
The plane strain compression test is a specialized test used on some materials ranging from metals to soils.
Metals
One variation of the test is also known as the ''Watts-Ford test''. It is an
engineering
Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...
test, and is a particularly specialized way of determining some of the material characteristics of the
metal
A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...
being tested, and its specialization can be summarized by this quote:
The test is useful when the sheet pieces are too small for a tensile test of a balanced biaxial test. It can give stress-strain curves up to considerably higher strains than tensile tests.
Plane-strain compression testing is typically used for measuring mechanical properties and for exploring microstructure development in the course of thermomechanical treatment.
During the test the specimen is placed between the punches and the constrain plates. When the upper punch is pushed down during the material test, the specimen is extended to horizontal directions. Friction between the tool and the specimen can be reduced by applying lubricants, such as graphite, MoS2, glass or PTFE(Teflon).
The testing essentially consists of a thin metal bar being compressed by two equally wide compressive strips, which are located of opposite sides of the thin bar. Then, over a range of increasing loads on the bar, the compressive forces lead to the thickness of the metal bar being reduced. This change of thickness is then measured sequentially after each loading, and after some mathematics a
stress-strain curve can be plotted.
The advantages of the Watts-Ford test are that it is convenient for testing thin sheets or strips, it is similar to a rolling process (in manufacturing analyses), frictional effects may be minimized, there is no 'barrelling' as would occur in a cylindrical compression test, and the plane strain deformation eases the analysis.
Stress-strain curve
The stress-strain curve is the relationship between the
stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
(force per unit area) and
strain
Strain may refer to:
Science and technology
* Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes
* Strain (chemistry), a chemical stress of a molecule
* Strain (injury), an injury to a mu ...
(resulting compression/stretching, known as deformation) that a particular material displays;
stress–strain curves of various materials differ widely, and different tensile tests conducted on the same material yield different results depending upon the temperature of the specimen and the speed of the loading.
When performing Watts-Ford tests, temperatures of the metal specimens will vary from 800-1100 °C and strain rates of (0.01- 10 s-1).
Pressure
The average pressure on a unit of area of the contact surface between the punch and the specimen is expressed as: P= F/(wb), where F is force, w is the punch width, b is the specimen width.
[Drozd, K., Horsinka, J., KLIBER, J., ČERNÝ, M., OSTROUSHKO, D., & MAMUZIC, I. (January 2011). Study of development of strain in plane strain compression test. In ''Metal 2011''.]
See also
*
Compression (physics)
In mechanics, compression is the application of balanced inward ("pushing") forces to different points on a material or structure, that is, forces with no net sum or torque directed so as to reduce its size in one or more directions.Ferdinand ...
*
Compressive strength
In mechanics, compressive strength or compression strength is the capacity of a material or structure to withstand loads tending to reduce size (as opposed to tensile strength which withstands loads tending to elongate). In other words, compre ...
*
Shear stress
Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the ot ...
Citations
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Continuum mechanics
Materials testing