Tensile strength

 isthe measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. 

Explanation

The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before failure. The definition of failure can vary according to material type and design methodology. This is an important concept in engineering, especially in the fields of material science, mechanical engineering and structural engineering. 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. ... Engineering is the design, analysis, and/or construction of works for practical purposes. ... Materials science includes those parts of chemistry and physics that deal with the properties of materials. ... Mechanical engineering is an engineering discipline that involves the application of principles of physics for analysis, design, manufacturing, and maintenance of mechanical systems. ... Taipei 101, the worlds tallest building as of 2004. ...

There are three typical definitions of tensile strength:

a. Yield strength]

 The stress at which material strain changes from elastic deformation to plastic deformation, causing it to deform permanently. 

b. Ultimate strength:

 The maximum stress a material can withstand. 

c. Breaking strength:

 The stress coordinate on the stress-strain curve at the point of rupture. 

A stress-strain curve is a graph derived from measuring load (stress - σ) versus extension (strain - ε) for a sample of a material. ...

Concept

The various definitions of tensile strength are shown in the following stress-strain graph for low-carbon steel:

Image:Stress v strain Strain curve typical of structural steel
1. Ultimate Strength
2. Yield Strength
3. Rupture
4. Strain hardening region
5. Necking region.]] The steel cable of a colliery winding tower. ... Yield strength, or the yield point, is defined in engineering and materials science as the stress at which a material begins to plastically deform. ... Cold Work is a quality imparted on a material as a result of plastic deformation. ... In materials or mechanical engineering, necking is a mode of ductile flow of a material in tension. ...

Metals including steel have a linear stress-strain relationship up to the yield point, as shown in the figure. In some steels the stress falls after the yield point. This is due to the interaction of carbon atoms and dislocations in the stressed steel. Cold worked and alloy steels do not show this effect. For most metals yield point is not sharply defined. Below the yield strength all deformation is recoverable, and the material will return to its initial shape when the load is removed. For stresses above the yield point the deformation is not recoverable, and the material will not return to its initial shape. This unrecoverable deformation is known as plastic deformation. For many applications plastic deformation is unacceptable, and the yield strength is used as the design limitation. Yield strength, or the yield point, is defined in engineering and materials science as the stress at which a material begins to plastically deform. ... In materials science, a dislocation is a crystallographic defect, or irregularity, within a crystal structure. ... Cold Work is a quality imparted on a material as a result of plastic deformation. ... In physics and materials science, plasticity is a property of a material to undergo a non-reversible change of shape in response to an applied force. ...

After the yield point, steel and many other ductile metals will undergo a period of strain hardening, in which the stress increases again with increasing strain up to the ultimate strength. If the material is unloaded at this point, the stress-strain curve will be parallel to that portion of the curve between the origin and the yield point. If it is re-loaded it will follow the unloading curve up again to the ultimate strength, which has become the new yield strength. Ductility is the physical property of being capable of sustaining large plastic deformations without fracture (in metals, such as being drawn into a wire). ... For alternative meanings see metal (disambiguation). ... Cold Work is a quality imparted on a material as a result of plastic deformation. ...

After a metal has been loaded to its yield strength it begins to "neck" as the cross-sectional area of the specimen decreases due to plastic flow. When necking becomes substantial, it may cause a reversal of the engineering stress-strain curve, where decreasing stress correlates to increasing strain because of geometric effects. This is because the engineering stress and engineering strain are calculated assuming the original cross-sectional area before necking. If the graph is plotted in terms of true stress and true strain the curve will always slope upwards and never reverse, as true stress is corrected for the decrease in cross-sectional area. Necking is not observed for materials loaded in compression. The peak stress on the engineering stress-strain curve is known the ultimate tensile strength. After a period of necking, the material will rupture and the stored elastic energy is released as noise and heat. The stress on the material at the time of rupture is known as the breaking stress. In materials or mechanical engineering, necking is a mode of ductile flow of a material in tension. ...

Ductile metals do not have a well defined yield point. The yield strength is typically defined by the "0.2% offset strain". The yield strength at 0.2% offset is determined by finding the intersection of the stress-strain curve with a line parallel to the initial slope of the curve and which intercepts the abscissa at 0.002. A stress-strain curve typical of aluminum along with the 0.2% offset line is shown in the figure below.

Stress vs. Strain curve typical of aluminum
1. Ultimate Strength
2. Yield strength
3. Proportional Limit Stress
4. Rupture
5. Offset Strain (typically 0.002).

Brittle materials such as concrete and carbon fiber do not have a yield point, and do not strain-harden which means that the ultimate strength and breaking strength are the same. A most unusual stress-strain curve is shown in the figure below. Typical brittle materials do not show any plastic deformation but fail while the deformation is elastic. One of the characteristics of a brittle failure is that the two broken parts can be reassembled to produce the same shape as the original component. A typical stress strain curve for a brittle material will be linear. Testing of several identical specimens will result in different failure stresses. The curve shown below would be typical of a brittle polymer tested at very slow strain rates at a temperature above its glass transition temperature. Some engineering ceramics show a small amount of ductile behaviour at stresses just below that causing failure but the initial part of the curve is a linear. Image File history File links Stress_v_strain_Aluminum_2. ... Image File history File links Stress_v_strain_Aluminum_2. ... Yield strength, or the yield point, is defined in engineering as the amount of strain that a material can undergo before moving from elastic deformation into plastic deformation. ... A material is brittle if it is subject to fracture when subjected to stress i. ... Concrete being poured, raked and vibrated into place in residential construction in Toronto, Ontario, Canada. ... Carbon fiber composite is a strong, light and very expensive material. ...

Stress vs. Strain curve of a very untypical brittle material
1. Ultimate Strength
2. Rupture.

Tensile strength is measured in units of force per unit area. In the SI system, the units are newtons per square metre (N/m²) or pascals (Pa), with prefixes as appropriate. The non-metric units are pounds-force per square inch (lbf/in² or PSI). Engineers in North America usually use units of ksi which is a thousand psi. Image File history File links Stress_v_strain_brittle_2. ... Image File history File links Stress_v_strain_brittle_2. ... In physics, force is an influence that may cause an object to accelerate. ... Area is a physical quantity expressing the size of a part of a surface. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... The newton (symbol: N) is the SI unit of force. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... Pounds-force per square inch (lbf/in²) is a non-SI unit of pressure. ...

The breaking strength of a rope is specified in units of force, such as newtons, without specifying the cross-sectional area of the rope. This is often loosely called tensile strength, but this not a strictly correct use of the term. Coils of rope used for long-line fishing A rope (IPA: ) is a length of fibers, twisted or braided together to improve strength for pulling and connecting. ... The newton (symbol: N) is the SI unit of force. ...

In brittle materials such as rock, concrete, cast iron, or soil, tensile strength is negligible compared to the compressive strength and it is assumed zero for many engineering applications. Glass fibers have a tensile strength stronger than steel[1], but bulk glass usually does not. This is due to the Stress Intensity Factor associated with defects in the material. As the size of the sample gets larger, the size of defects also grows. In general, the tensile strength of a rope is always less than the tensile strength of its individual fibers. Concrete being poured, raked and vibrated into place in residential construction in Toronto, Ontario, Canada. ... Stress Intensity Factor, K, is used in fracture mechanics to more accurately predict the stress state (stress intensity) near the tip of a crack (crack tip) caused by a remote load or residual stresses. ... Coils of rope used for long-line fishing A rope (IPA: ) is a length of fibers, twisted or braided together to improve strength for pulling and connecting. ... Fiber or fibre[1] is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. ...

Tensile strength can be defined for liquids as well as solids. For example, when a tree draws water from its roots to its upper leaves by transpiration, the column of water is pulled upwards from the top by capillary action, and this force is transmitted down the column by its tensile strength. Air pressure from below also plays a small part in a tree's ability to draw up water, but this alone would only be sufficient to push the column of water to a height of about ten metres, and trees can grow much higher than that. (See also cavitation, which can be thought of as the consequence of water being "pulled too hard".) A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... The coniferous Coast Redwood, the tallest tree species on earth. ... Transpiration is the evaporation of excess water from aerial parts and of plants, especially leaves but also stems, flowers and fruits. ... Capillary action, capillarity, or capillary motion is the ability of a substance (the standard reference is to a tube in plants but can be seen readily with porous paper) to draw a substance up against gravity. ... This article or section does not cite any references or sources. ...