Information about Tensile Strength
Tensile strength 
, or 
measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks.
There are three typical definitions of tensile strength:
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.
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.
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.
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.
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.
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.
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 is not a strictly correct use of the term.
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.
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".)
(Source: A.M. Howatson, P.G. Lund and J.D. Todd, "Engineering Tables and Data" p41)
Fiber or fibre[1] is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.
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, or 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.There are three typical definitions of tensile strength:
- Yield strength: The stress at which material strain changes from elastic deformation to plastic deformation, causing it to deform permanently.
- Ultimate strength: The maximum stress a material can withstand.
- Breaking strength: The stress coordinate on the stress-strain curve at the point of rupture.
Concept
The various definitions of tensile strength are shown in the following stress-strain graph for low-carbon steel:)
Stress vs. Strain curve typical of structural steel
1. Ultimate Strength
2. Yield Strength
3. Rupture
4. Strain hardening region
5. Necking region.
1. Ultimate Strength
2. Yield Strength
3. Rupture
4. Strain hardening region
5. Necking region.
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.
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.
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.
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.
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.
)
Stress vs. Strain curve of a very untypical brittle material
1. Ultimate Strength
2. Rupture.
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.
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 is not a strictly correct use of the term.
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.
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".)
Typical tensile strengths
Some typical tensile strengths of some materials:| Material | Yield strength (MPa) |
Ultimate strength (MPa) |
Density (g/cm³) | ||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Structural steel ASTM A36 steel | 250 | 400 | 7.8 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steel, API 5L X65 (Fikret Mert Veral) | 448 | 531 | 7.8 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steel, high strength alloy ASTM A514 | 690 | 760 | 7.8 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steel, prestressing strands | 1650 | 1860 | 7.8 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steel Wire | 7.8 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steel (AISI 1060 0.6% carbon) Piano wire | 2200-2482 MPa[1] | 7.8 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| High density polyethylene (HDPE) | 26-33 | 37 | 0.95 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Polypropylene | 12-43 | 19.7-80 | 0.91 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Stainless steel AISI 302 - Cold-rolled | 520 | 860 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cast iron 4.5% C, ASTM A-48 | 276 (??) | 200 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Titanium Alloy (6% Al, 4% V) | 830 | 900 | 4.51 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Aluminum Alloy 2014-T6 | 400 | 455 | 2.7 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Copper 99.9% Cu | 70 | 220 | 8.92 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cupronickel 10% Ni, 1.6% Fe, 1% Mn, balance Cu | 130 | 350 | 8.94 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Brass | approx. 200+ | 550 | 5.3 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Tungsten | 1510 | 19.25 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Glass | 50 (in compression) | 2.53 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| E-Glass | N/A | 3450 | 2.57 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| S-Glass | N/A | 4710 | 2.48 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Basalt fiber | N/A | 4840 | 2.7 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Marble | N/A | 15 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Concrete | N/A | 3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Carbon Fiber | N/A | 5650 | 1.75 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Spider silk | 1150 (??) | 1200 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Silkworm silk | 500 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Aramid (Kevlar or Twaron) | 3620 | 1.44 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| UHMWPE | 23 | 46 | 0.97 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| UHMWPE fibers[2][3] (Dyneema or Spectra) | 2300-3500 | 0.97 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Vectran | 2850-3340 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Pine Wood (parallel to grain) | 40 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Bone (limb) | 130 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Nylon, type 6/6 | 45 | 75 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Rubber | - | 15 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Boron | N/A | 3100 | 2.46 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Silicon, monocrystalline (m-Si) | N/A | 7000 | 2.33 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Silicon carbide (SiC) | N/A | 3440 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Sapphire (Al2O3) | N/A | 1900 | 3.9-4.1 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Carbon nanotube (see note above) | N/A | 62000 | 1.34 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Elements in the annealed state | Young's Modulus (GPa) |
Proof or yield stress (MPa) |
Ultimate strength (MPa) |
|---|---|---|---|
| Aluminium | 70 | 15-20 | 40-50 |
| Copper | 130 | 33 | 210 |
| Gold | 79 | 100 | |
| Iron | 211 | 80-100 | 350 |
| Lead | 16 | 12 | |
| Nickel | 170 | 14-35 | 140-195 |
| Silicon | 107 | 5000-9000 | |
| Silver | 83 | 170 | |
| Tantalum | 186 | 180 | 200 |
| Tin | 47 | 9-14 | 15-200 |
| Titanium | 120 | 100-225 | 240-370 |
| Tungsten | 411 | 550 | 550-620 |
| Zinc (wrought) | 105 | 110-200 | |
Sources
- A.M. Howatson, P.G. Lund and J.D. Todd, "Engineering Tables and Data"
- Giancoli, Douglas. Physics for Scientists & Engineers Third Edition. Upper Saddle River: Prentice Hall, 2000.
- Köhler, T. and F. Vollrath. 1995. Thread biomechanics in the two orb-weaving spiders Araneus diadematus (Araneae, Araneidae) and Uloboris walckenaerius (Araneae, Uloboridae). Journal of Experimental Zoology 271:1-17.
- Edwards, Bradly C. "The Space Elevator: A Brief Overview" http://www.liftport.com/files/521Edwards.pdf
- T Follett "Life without metals"
- Min-Feng Yu et. al (2000), Strength and Breaking Mechanism of Multiwalled Carbon Nanotubes Under Tensile Load, Science 287, 637-640
See also
- Tension (mechanics)
- Toughness
- Deformation
- Tensile structure
- Universal Testing Machine
- Specific Strength
References
External links
- Tensile Strength Test
- January 2003 sci.physics thread on water tensile strength and trees
- Theory re the discrepancy in static vs dynamic measurements of water's tensile strength
- Engineering Stress-strain Curve
- Tensile Strength Testing
Tensile stress (or tension) is the stress state leading to expansion; that is, the tensile stress may be increased until the reach of tensile strength, namely the limit state of stress.
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Engineering is the applied science of acquiring and applying knowledge to design, analysis, and/or construction of works for practical purposes. The American Engineers' Council for Professional Development, also known as ECPD,[1] (later ABET [2]
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Materials science or materials engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. This science investigates the relationship between the structure of materials and their properties.
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Mechanical Engineering is an engineering discipline that involves the application of principles of physics for analysis, design, manufacturing, and maintenance of mechanical systems.
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Structural engineering is a field of engineering that deals with the design of a structural system(s) with the purpose of supporting and resisting various loads. Though other disciplines touch on this field, a physical object or system is truly considered a part of structural
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yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to plastically deform. Prior to the yield point the material will deform elastically and will return to its original shape when the applied
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Steel is an alloy consisting mostly of iron, with a carbon content between 0.02% and 1.7 or 2.04% by weight (C:1000–10,8.67Fe), depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese and
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dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of real materials. The theory was originally developed by Vito Volterra in 1905.
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Work hardening, or strain hardening, is an increase in the strength of a material due to plastic deformation. In metallic solids permanent change of shape is usually carried out on a microscopic scale by defects called dislocations which are created by stress and rearrange
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In engineering mechanics, deformation is a change in shape due to an applied force. This can be a result of tensile (pulling) forces, compressive (pushing) forces, shear, bending or torsion (twisting). Deformation is often described in terms of strain.
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Ductility is the mechanical property of being capable of sustaining large plastic deformations due to tensile stress without fracture (in metals, such as being drawn into a wire). It is characterized by the material flowing under shear stress. It is contrasted with brittleness.
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The Macro Expansion Template Attribute Language complements TAL, providing macros which allow the reuse of code across template files. Both were created for Zope but are used in other Python projects as well.
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Work hardening, or strain hardening, is an increase in the strength of a material due to plastic deformation. In metallic solids permanent change of shape is usually carried out on a microscopic scale by defects called dislocations which are created by stress and rearrange
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In materials or mechanical engineering, necking is a mode of ductile flow of a material in tension. This is visible when applied stress passes a material’s ultimate strength.
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brittle if it is liable to fracture when subjected to stress. That is, it has little tendency to deform (or strain) before fracture. This fracture absorbs relatively little energy, even in materials of high strength, and usually makes a snapping sound.
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Concrete is a construction material that consists of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel limestone or granite, plus a fine aggregate such as sand or
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Carbon fibre or carbon fiber can refer to carbon filament thread, or to felt or woven cloth made from those carbon filaments. By extension, the term is also used informally to mean any composite material made with carbon filament, such as carbon fiber reinforced plastic.
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In physics, force is an action or agency that causes a body of mass m to accelerate. It may be experienced as a lift, a push, or a pull. The acceleration of the body is proportional to the vector sum of all forces acting on it (known as net force or resultant force).
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Area is a physical quantity expressing the size of a part of a surface. The term Surface area is the summation of the areas of the exposed sides of an object.
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Units
Units for measuring surface area include:- square metre = SI derived unit
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Si, si, or SI may refer to (all SI unless otherwise stated):
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In language:
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The newton (symbol: N) is the SI derived unit of force, named after Sir Isaac Newton in recognition of his work on classical mechanics.
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square metre (also spelled meter, see spelling differences) is the SI derived unit of area, with symbol m². It is defined as the area of a square whose sides measure exactly one metre.
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The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Young's modulus and tensile strength). It is a measure of perpendicular force per unit area i.e. equivalent to one newton per square meter or one Joule per cubic meter.
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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.
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pound per square inch or, more accurately, pound-force per square inch (symbol: psi or lbf/sq in) is a unit of pressure or of stress based on avoirdupois units.
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rope (IPA: /rəʊp/) is a length of fibers, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength (i.e.
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Stress Intensity Factor, K, is used in fracture mechanics to more accurately predict the stress state ("stress intensity") near the tip of a crack caused by a remote load or residual stresses. It is a theoretical construct applicable to a homogeneous elastic material.
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Fiber or fibre[1] is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.
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Liquid is one of the four principal states of matter. A liquid is a fluid that can freely form a distinct surface at the boundaries of its bulk material.
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tree is a perennial woody plant. It is sometimes defined as a woody plant that attains diameter of 10 cm (30 cm girth) or more at breast height (130 cm above ground).
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