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Mechanical System Failure
Published in Seong-woo Woo, Design of Mechanical Systems Based on Statistics, 2021
Deformation includes any changes in the shape of an object because of an acted force. Strain is a physical deformation response of a material to stress. A result of stresses in the vertical axis is the corresponding strains along the horizontal axis. When an external load is applied, it will cause deforms on the body of product. Once the load is eliminated, the body will regain its original shape without permanent deformation in the member. We call this ‘elastic deformation’. This pattern of deformation includes stretching of the atomic bonds.
Concept of stress and strain
Published in M.L. Jeremic, Ground Mechanics in Hard Rock Mining, 2020
On the basis of ideal, linearly elastic bodies, the classical theory of elasticity shows that stress is directly proportional to strain. This relationship has subsequently been proven experimentally. It is known as Hooke’s law.
Properties of materials
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
A material subject to external forces which stretch it is said to be in tension, when subject to forces which squeeze to be in compression. In discussing the application of forces to materials the concern is the force applied per unit area, this being termed the stress. Stress is measured in pascals (Pa), with 1 Pa being a force of 1 newton per square metre, i.e. 1 Pa = 1 N/m2. When a material is subject to tensile or compressive forces, it changes in length, and the term strain, symbol ε, is used for the change in length divided by the original length. Since strain is a ratio of two lengths it has no units. However, strain is frequently expressed as a percentage, i.e. the percentage change in length.
Real-time monitoring of railroad track tension using a fiber Bragg grating-based strain sensor
Published in Instrumentation Science & Technology, 2018
Strain can be positive (tensile) or negative (compressive). When the material is compressed in one direction, it tends to expand in the other two directions, and this is known as the Poisson effect. Poisson’s ratio (v) is a measurement of this effect, and it is defined as the negative ratio in the cross direction of strain. Together with the fact that it is unitless, strain can sometimes be indicated in units such as inch/inch or mm/mm. The magnitude of the strain measured in practice is very small. Thus, it is generally indicated in microstrains (µε).