TENSION AND COMPRESSION

STATIC STRESS-STRAIN PROPERTIES IN

(I)

Most engineers are primarily concerned with the development and design of machines, structures and products of various kinds. Since these constructions are usually subjected to internal for­ces and deformations called stresses and strains, the properties of materials under the action of these stresses and strains for various environments become an important engineering considera­tion. The macroscopic properties of materials when subjected to these stresses and strains are called the mechanical properties. The study of the macroscopic stress-strain properties of materi­als may be referred to as solid state mechanics in the same way as solid state physics refers to the atomic and molecular beha­viour of materials on the submicroscopic level. An understanding of the stress-strain properties of materials are important, since high values of stress and strain may result in the failure of a construction. Failures may lead to loss of life and costly damage when airliners or trains are wrecked or a bridge collapses. Sometimes failures do not lead to loss of life but involve need­less costly repairs, delays in operation, or replacement of parts.

Notes:

N 5

STATIC STRESS-STRAIN PROPERTIES

IN ТENSION AND COMPRESSION

(II)

A thorough knowledge of material stress-strain behavior is required by the engineer so that failures can be avoided. Such knowledge is also necessary in order to utilize materials most economically. Fоr example, if the stresses or strains in a component of a machine or structure are too low, the size of the part is larger than necessary and the material is not being used economically. The need for a careful consideration of material properties has also been made necessary in recent years by the increased scarcity of certain materials and the need for the use of substitute materials. Many new developments in the transpor­tation, power and other industries, for both domestic and milita­ry applications, have led to the development of new materials with improved properties. Materials with high resistance to ele­vated temperatures are needed for many modern constructions such as jet engines, rockets, missiles, high-speed aircraft, and nuclear reactors. Sometimes these applications require considera­tion of corrosion, impact and fatigue properties in addition to temperature properties.

Notes

N 6

Date: 2015-01-12; view: 668