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Stress in a material body may be due to multiple physical causes, including external influences and internal physical processes. Some of these agents (like gravity, changes in temperature and phase , and electromagnetic fields) act on the bulk of the material, varying continuously with position and time.
Fracture strength, also known as breaking strength, is the stress at which a specimen fails via fracture. [2] This is usually determined for a given specimen by a tensile test, which charts the stress–strain curve (see image). The final recorded point is the fracture strength.
The ultimate tensile strength of a material is an intensive property; therefore its value does not depend on the size of the test specimen.However, depending on the material, it may be dependent on other factors, such as the preparation of the specimen, the presence or otherwise of surface defects, and the temperature of the test environment and material.
The stress needed to fracture bulk glass is around 100 MPa (15,000 psi). The theoretical stress needed for breaking atomic bonds of glass is approximately 10,000 MPa (1,500,000 psi). A theory was needed to reconcile these conflicting observations.
When a part is subjected to a cyclic stress, also known as stress range (Sr), it has been observed that the failure of the part occurs after a number of stress reversals (N) even if the magnitude of the stress range is below the material's yield strength. Generally, higher the range stress, the fewer the number of reversals needed for failure.
In physics, Hooke's law is an empirical law which states that the force (F) needed to extend or compress a spring by some distance (x) scales linearly with respect to that distance—that is, F s = kx, where k is a constant factor characteristic of the spring (i.e., its stiffness), and x is small compared to the total possible deformation of the spring.
Physical insight into strains can be gained by observing that a given strain can be decomposed into normal and shear components. The amount of stretch or compression along material line elements or fibers is the normal strain , and the amount of distortion associated with the sliding of plane layers over each other is the shear strain , within ...
Nine men pull on a rope. The rope in the photo extends into a drawn illustration showing adjacent segments of the rope. One segment is duplicated in a free body diagram showing a pair of action-reaction forces of magnitude T pulling the segment in opposite directions, where T is transmitted axially and is called the tension force.