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Strength of materials is materials science applied to the study of engineering materials and their mechanical behavior in general (such as stress, deformation, strain and stress-strain relations). Strength is considered in terms of compressive strength, tensile strength, and shear strength, namely the limit states of compressive stress, tensile stress and shear stress respectively. Strength can be simply defined as the ability of a material to resist the application of force. The effects of dynamic loading is probably the most important practical part of the strength of materials, especially the problem of fatigue. Repeated loading often initiates brittle cracks, which grow slowly until failure occurs. Image File history File links Broom_icon. ...
The Materials Science Tetrahedron, which often also includes Characterization at the center Materials science is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. ...
Stress is the internal distribution of force per unit area that balances and reacts to external loads applied to a body. ...
In engineering mechanics, deformation is a change in shape due to an applied force. ...
This article is about the deformation of materials. ...
Compressive strength is the capacity of a material to withstand axially directed pushing forces. ...
Tensile strength , or measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. ...
Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. ...
Compressive stress is the stress applied to materials resulting in their compaction (decrease of volume). ...
Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ...
Shear stress is a stress state where the stress is parallel or tangential to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. ...
In materials science, fatigue is the progressive, localised, and permanent structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that have maximum values less than (often much less than) the static yield strength of the material. ...
Definitions
Stress terms Stress is the ratio of the force and the cross-sectional area of the material on which the force is acting. - Compressive stress (or compression) is the stress state when the material (compression member) tends to compact. A simple case of compression is the uniaxial compression induced by the action of opposite, pushing forces. Compressive strength for materials is generally higher than that of tensile stress, but geometry is very important in the analysis, as compressive stress can lead to buckling.
- Tensile stress is a loading that tends to produce stretching of a material by the application of axially directed pulling forces. Any material which falls into the "elastic" category can generally tolerate mild tensile stresses while materials such as ceramics and brittle alloys are very succeptable to failure under the same conditions. If a material is stressed beyond its limits, it will fail. The failure mode, either ductile or brittle, is based mostly on the microstructure of the material. Some Steel alloys are examples of materials with high tensile strength.
- Shear stress is caused when a force is applied to produce a sliding failure of a material along a plane that is parallel to the direction of the applied force. An example is cutting paper with scissors.
Compressive stress is the stress applied to materials resulting in their compaction (decrease of volume). ...
Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ...
Columns Ionic column base A compression member is a general class of structural elements of which a column is the most common specific example. ...
In engineering, buckling is a failure mode characterised by a sudden failure of a structural member that is subjected to high compressive stresses where the actual compressive stresses at failure are smaller than the ultimate compressive stresses that the material is capable of withstanding. ...
Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ...
The steel cable of a colliery winding tower. ...
Shear stress is a stress state where the stress is parallel or tangential to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. ...
Different types of scissors - sewing, kitchen, paper Scissors are a tool used for cutting thin material which requires little force. ...
Strength terms Compressive strength is a limit state of compressive stress that leads to compressive failure in the manner of ductile failure (infinite theoretical yield) or in the manner of brittle failure (rupture as the result of crack propagation, or sliding along a weak plane - see shear strength). Compressive strength is the capacity of a material to withstand axially directed pushing forces. ...
Compressive stress is the stress applied to materials resulting in their compaction (decrease of volume). ...
Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. ...
Tensile strength is a limit state of tensile stress that leads to tensile failure in the manner of ductile failure (yield as the first stage of failure, some hardening in the second stage and break after a possible "neck" formation) or in the manner of brittle failure (sudden breaking in two or more pieces with a low stress state). Tensile strength , or measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. ...
Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ...
Fatigue strength is a measure of the strength of a component under repeated or cyclical loading, and is usually more important for structures than the two previous measures of strength. It is always lower than those values, and is critical in assessing safety factors, for example. When components fail, they always fracture in a brittle manner, irrespective of whether or not the material normally behaves in a brittle or ductile fashion. Fatigue failure occurs by growth of one or more brittle cracks from stress concentrations in the component. In materials science, fatigue is the progressive, localised, and permanent structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that have maximum values less than (often much less than) the static yield strength of the material. ...
A stress concentration is a phenomenon encounterered in mechanical engineering where an object under load has higher than average local stresses due to its shape. ...
Strain - deformation terms Deformation of the material is the change in geometry when stress is applied (in the form of force loading, gravitational field, acceleration, thermal expansion, etc.). Deformation is expressed by the displacement field of the material. In engineering mechanics, deformation is a change in shape due to an applied force. ...
Strain or reduced deformation is a mathematical term to express the trend of the deformation change among the material field. For uniaxial loading - displacements of a specimen (for example a bar element) it is expressed as the quotient of the displacement and the length of the specimen. For 3D displacement fields it is expressed as derivatives of displacement functions in terms of a second order tensor (with 6 independent elements). This article is about the deformation of materials. ...
In mathematics, a tensor is (in an informal sense) a generalized linear quantity or geometrical entity that can be expressed as a multi-dimensional array relative to a choice of basis; however, as an object in and of itself, a tensor is independent of any chosen frame of reference. ...
Deflection is a term to describe the magnitude to which a structural element bends under a load. This article or section does not cite any references or sources. ...
Stress-strain relations Elasticity is the ability of a material to return to its previous shape after stress is released. In many materials, the relation between applied stress and the resulting strain is directly proportional (up to a certain limit), and a graph representing those two quantities is a straight line. The slope of this line is known as Young's Modulus, or the "Modulus of Elasticity." The Modulus of Elasticity can be used to determine stress-strain relationships in the linear-elastic portion of the stress-strain curve. The linear-elastic region is taken to be between 0 and 0.2% strain, and is defined as the region of strain in which no yielding (permanent deformation) occurs. In engineering mechanics, deformation is a change in shape due to an applied force. ...
In solid mechanics, Youngs modulus (E) is a measure of the stiffness of a given material. ...
Plasticity or plastic deformation is the opposite of elastic deformation and is accepted as unrecoverable strain. Plastic deformation is retained even after the relaxation of the applied stress. Most materials in the linear-elastic category are usually capable of plastic deformation. Brittle materials, like ceramics, do not experience any plastic deformation and will fracture under relatively low stress. Materials such as metals usually experience a small amount of plastic deformation before failure while soft or ductile polymers will plasticly deform much more. For other uses, see Plasticity. ...
Consider the difference between a fresh carrot and chewed bubble gum. The carrot will stretch very little before breaking, but nevertheless will still stretch. The chewed bubble gum, on the other hand, will plasticly deform enormously before finally breaking.
Design terms Ultimate strength is an attribute directly related to a material, rather than just specific specimen of the material, and as such is quoted force per unit of cross section area (N/m²). For example, the ultimate tensile strength (UTS) of AISI 1018 Steel is 440 MN/m². In general, the SI unit of stress is the pascal, where 1 Pa = 1 N/m². In English units, the unit of stress is given as lbf/in² or pounds-force per square inch. This unit is often abbreviated as psi. One thousand psi is abbreviated ksi. In physics, the newton (symbol: N) is the SI unit of force, named after Sir Isaac Newton in recognition of his work on classical mechanics. ...
The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ...
Pounds-force per square inch (lbf/in²) is a non-SI unit of pressure. ...
Factor of safety is a design constraint that an engineered component or structure must achieve. FS = UTS / R, where FS: the Factor of Safety, R: The applied stress, and UTS: the Ultimate force (or stress). Factor of safety (FoS) can mean either the fraction of structural capability over that required, or a multiplier applied to the maximum expected load (force, torque, bending moment or a combination) to which a component or assembly will be subjected. ...
Margin of Safety is also sometimes used to as design constraint. It is defined MS=Factor of safety - 1
For example to achieve a factor of safety of 4, the allowable stress in an AISI 1018 steel component can be worked out as R = UTS / FS = 440/4 = 110 MPa, or R = 110×106 N/m².
Suggested reading - Mott, Robert L, "Applied Strength of Materials", 4th edition, Prentice-Hall, 2002, ISBN 0-13-088578-9
- Beer F.P., Johnston E.R., et al, Mechanics of Materials, 3rd edition, McGraw-Hill, 2001, ISBN 0-07-248673-2
- Timoshenko S., Strength of Materials, 3rd edition, Krieger Publishing Company, 1976, ISBN 0-88275-420-3
- Drucker D.C., Introduction to mechanics of deformable solids, McGraw-Hill, 1967.
- Shames I.H., Cozzarelli F.A., Elastic and inelastic stress analysis, Prentice-Hall, 1991, ISBN 1-56032-686-7
- Den Hartog, Jacob P., Strength of Materials, Dover Publications, Inc., 1961, ISBN 0-486-60755-0
- Popov, Egor P., Engineering Mechanics of Solids, Prentice Hall, Englewood Cliffs, N. J., 1990, ISBN 0-13-279258-3
- Groover, Mikell P., Fundamentals of Modern Manufacturing, John Wiley & Sons,Inc., 2002, 2nd Ed. ISBN 0-471-40051-3
- Lebedev, Leonid P. and Cloud, Michael.J., Approximating Perfection: A Mathematician's Journey into the World of Mechanics, Princeton University Press, 2004, ISBN 0-691-11726-8
- Alfirević, Ivo, Strength of Materials I, Tehnička knjiga, 1995, ISBN 953-172-010-X
- Alfirević, Ivo, Strength of Materials II, Tehnička knjiga, 1999, ISBN 953-6168-85-5
Stephen Timoshenko Stephen P. Timoshenko or Stepan Prokofyevich Timoshenko (Ukrainian: , Russian: , December 23, 1878 – May 29, 1972), is reputed to be the father of modern engineering mechanics. ...
Other fundamental engineering topics A resistive circuit is a circuit containing only resistors, ideal current sources, and ideal voltage sources. ...
In physics, dynamics is the branch of classical mechanics that is concerned with the effects of forces on the motion of objects. ...
Thermodynamics (from the Greek θεÏμη, therme, meaning heat and δυναμις, dunamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ...
Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ...
Engineering economics, previously known as engineering economy, is a subset of economics for application to engineering projects. ...
In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ...
The Materials Science Tetrahedron, which often also includes Characterization at the center Materials science is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. ...
Statics is the branch of physics concerned with physical systems in static equilibrium, that is, in a state where the relative positions of subsystems do not vary over time, or where components and structures are at rest under the action of external forces of equilibrium. ...
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