Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or in notation) [1] is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate tensile strength is close to the yield point, whereas in ductile materials, the ultimate tensile strength can be higher.
The ultimate tensile strength is usually found by performing a tensile test and recording the engineering stress versus strain. The highest point of the stress–strain curve is the ultimate tensile strength and has units of stress. The equivalent point for the case of compression, instead of tension, is called the compressive strength.
Tensile strengths are rarely of any consequence in the design of ductile members, but they are important with brittle members. They are tabulated for common materials such as alloys, composite materials, ceramics, plastics, and wood.
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.
Some materials break very sharply, without plastic deformation, in what is called a brittle failure. Others, which are more ductile, including most metals, experience some plastic deformation and possibly necking before fracture.
Tensile strength is defined as a stress, which is measured as force per unit area. For some non-homogeneous materials (or for assembled components) it can be reported just as a force or as a force per unit width. In the International System of Units (SI), the unit is the pascal (Pa) (or a multiple thereof, often megapascals (MPa), using the SI prefix mega); or, equivalently to pascals, newtons per square metre (N/m2). A United States customary unit is pounds per square inch (lb/in2 or psi). Kilopounds per square inch (ksi, or sometimes kpsi) is equal to 1000 psi, and is commonly used in the United States, when measuring tensile strengths.
Many materials can display linear elastic behavior, defined by a linear stress–strain relationship, as shown in figure 1 up to point 3. The elastic behavior of materials often extends into a non-linear region, represented in figure 1 by point 2 (the "yield strength"), up to which deformations are completely recoverable upon removal of the load; that is, a specimen loaded elastically in tension will elongate, but will return to its original shape and size when unloaded. Beyond this elastic region, for ductile materials, such as steel, deformations are plastic. A plastically deformed specimen does not completely return to its original size and shape when unloaded. For many applications, plastic deformation is unacceptable, and is used as the design limitation.
After the yield point, ductile metals undergo a period of strain hardening, in which the stress increases again with increasing strain, and they begin to neck, as the cross-sectional area of the specimen decreases due to plastic flow. In a sufficiently ductile material, when necking becomes substantial, it causes a reversal of the engineering stress–strain curve (curve A, figure 2); this is because the engineering stress is calculated assuming the original cross-sectional area before necking. The reversal point is the maximum stress on the engineering stress–strain curve, and the engineering stress coordinate of this point is the ultimate tensile strength, given by point 1.
Ultimate tensile strength is not used in the design of ductile static members because design practices dictate the use of the yield stress. It is, however, used for quality control, because of the ease of testing. It is also used to roughly determine material types for unknown samples. [2]
The ultimate tensile strength is a common engineering parameter to design members made of brittle material because such materials have no yield point. [2]
Typically, the testing involves taking a small sample with a fixed cross-sectional area, and then pulling it with a tensometer at a constant strain (change in gauge length divided by initial gauge length) rate until the sample breaks.
When testing some metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers. [3] This practical correlation helps quality assurance in metalworking industries to extend well beyond the laboratory and universal testing machines.
Material | Yield strength (MPa) | Ultimate tensile strength (MPa) | Density (g/cm3) |
---|---|---|---|
Steel, structural ASTM A36 steel | 250 | 400–550 | 7.8 |
Steel, 1090 | 247 | 841 | 7.58 |
Chromium-vanadium steel AISI 6150 | 620 | 940 | 7.8 |
Steel, 2800 Maraging steel [4] | 2,617 | 2,693 | 8.00 |
Steel, AerMet 340 [5] | 2,160 | 2,430 | 7.86 |
Steel, Sandvik Sanicro 36Mo logging cable precision wire [6] | 1,758 | 2,070 | 8.00 |
Steel, AISI 4130, water quenched 855 °C (1,570 °F), 480 °C (900 °F) temper [7] | 951 | 1,110 | 7.85 |
Steel, API 5L X65 [8] | 448 | 531 | 7.8 |
Steel, high strength alloy ASTM A514 | 690 | 760 | 7.8 |
Acrylic, clear cast sheet (PMMA) [9] | 72 | 87 [10] | 1.16 |
Acrylonitrile butadiene styrene (ABS) [11] | 43 | 43 | 0.9–1.53 |
High-density polyethylene (HDPE) | 26–33 | 37 | 0.85 |
Polypropylene | 12–43 | 19.7–80 | 0.91 |
Steel, stainless AISI 302 [12] | 275 | 620 | 7.86 |
Cast iron 4.5% C, ASTM A-48 | 130 | 200 | 7.3 |
"Liquidmetal" alloy[ citation needed ] | 1,723 | 550–1,600 | 6.1 |
Beryllium [13] 99.9% Be | 345 | 448 | 1.84 |
Aluminium alloy [14] 2014-T6 | 414 | 483 | 2.8 |
Polyester resin (unreinforced) [15] | 55 | 55 | |
Polyester and chopped strand mat laminate 30% E-glass [15] | 100 | 100 | |
S-Glass epoxy composite [16] | 2,358 | 2,358 | |
Aluminium alloy 6061-T6 | 241 | 300 | 2.7 |
Copper 99.9% Cu | 70 | 220[ citation needed ] | 8.92 |
Cupronickel 10% Ni, 1.6% Fe, 1% Mn, balance Cu | 130 | 350 | 8.94 |
Brass | 200 + | 500 | 8.73 |
Tungsten | 941 | 1,510 | 19.25 |
Glass | 33 [17] | 2.53 | |
E-Glass | — | 1,500 for laminates, 3,450 for fibers alone | 2.57 |
S-Glass | — | 4,710 | 2.48 |
Basalt fiber [18] | — | 4,840 | 2.7 |
Marble | — | 15 | 2.6 |
Concrete | — | 2–5 | 2.7 |
Carbon fiber | — | 1,600 for laminates, 4,137 for fibers alone | 1.75 |
Carbon fiber (Toray T1100G) [19] (the strongest human-made fibres) | 7,000 fibre alone | 1.79 | |
Human hair | 140–160 | 200–250 [20] | |
Bamboo fiber | 350–500 | 0.4–0.8 | |
Spider silk (see note below) | 1,000 | 1.3 | |
Spider silk, Darwin's bark spider [21] | 1,652 | ||
Silkworm silk | 500 | 1.3 | |
Aramid (Kevlar or Twaron) | 3,620 | 3,757 | 1.44 |
UHMWPE [22] | 24 | 52 | 0.97 |
UHMWPE fibers [23] [24] (Dyneema or Spectra) | 2,300–3,500 | 0.97 | |
Vectran | 2,850–3,340 | 1.4 | |
Polybenzoxazole (Zylon) [25] | 2,700 | 5,800 | 1.56 |
Wood, pine (parallel to grain) | 40 | ||
Bone (limb) | 104–121 | 130 | 1.6 |
Nylon, molded, 6PLA/6M [26] | 75-85 | 1.15 | |
Nylon fiber, drawn [27] | 900 [28] | 1.13 | |
Epoxy adhesive | — | 12–30 [29] | — |
Rubber | — | 16 | |
Boron | — | 3,100 | 2.46 |
Silicon, monocrystalline (m-Si) | — | 7,000 | 2.33 |
Ultra-pure silica glass fiber-optic strands [30] | 4,100 | ||
Sapphire (Al2O3) | 400 at 25 °C, 275 at 500 °C, 345 at 1,000 °C | 1,900 | 3.9–4.1 |
Boron nitride nanotube | — | 33,000 | 2.62 [31] |
Diamond | 1,600 | 2,800 ~80–90 GPa at microscale [32] | 3.5 |
Graphene | — | intrinsic 130,000; [33] engineering 50,000–60,000 [34] | 1.0 |
First carbon nanotube ropes | ? | 3,600 | 1.3 |
Carbon nanotube (see note below) | — | 11,000–63,000 | 0.037–1.34 |
Carbon nanotube composites | — | 1,200 [35] | — |
High-strength carbon nanotube film | — | 9,600 [36] | — |
Iron (pure mono-crystal) | 3 | 7.874 | |
Limpet Patella vulgata teeth (goethite whisker nanocomposite) | 4,900 3,000–6,500 [37] | ||
Element | Young's modulus (GPa) | Yield strength (MPa) | Ultimate strength (MPa) |
---|---|---|---|
Silicon | 107 | 5,000–9,000 | |
Tungsten | 411 | 550 | 550–620 |
Iron | 211 | 80–100 | 350 |
Titanium | 120 | 100–225 | 246–370 |
Copper | 130 | 117 | 210 |
Tantalum | 186 | 180 | 200 |
Tin | 47 | 9–14 | 15–200 |
Zinc | 85–105 | 200–400 | 200–400 |
Nickel | 170 | 140–350 | 140–195 |
Silver | 83 | 170 | |
Gold | 79 | 100 | |
Aluminium | 70 | 15–20 | 40–50 |
Lead | 16 | 12 |
Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversible upon removing the stress. Ductility is a critical mechanical performance indicator, particularly in applications that require materials to bend, stretch, or deform in other ways without breaking. The extent of ductility can be quantitatively assessed using the percent elongation at break, given by the equation:
Young's modulus is a mechanical property of solid materials that measures the tensile or compressive stiffness when the force is applied lengthwise. It is the modulus of elasticity for tension or axial compression. Young's modulus is defined as the ratio of the stress applied to the object and the resulting axial strain in the linear elastic region of the material.
In engineering, deformation may be elastic or plastic. If the deformation is negligible, the object is said to be rigid.
In physics and materials science, plasticity is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces. For example, a solid piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from elastic behavior to plastic behavior is known as yielding.
In engineering and materials science, a stress–strain curve for a material gives the relationship between stress and strain. It is obtained by gradually applying load to a test coupon and measuring the deformation, from which the stress and strain can be determined. These curves reveal many of the properties of a material, such as the Young's modulus, the yield strength and the ultimate tensile strength.
Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displacement develops perpendicular to the surface, it is called a normal tensile crack or simply a crack; if a displacement develops tangentially, it is called a shear crack, slip band, or dislocation.
The field of strength of materials typically refers to various methods of calculating the stresses and strains in structural members, such as beams, columns, and shafts. The methods employed to predict the response of a structure under loading and its susceptibility to various failure modes takes into account the properties of the materials such as its yield strength, ultimate strength, Young's modulus, and Poisson's ratio. In addition, the mechanical element's macroscopic properties such as its length, width, thickness, boundary constraints and abrupt changes in geometry such as holes are considered.
In mechanics, compressive strength is the capacity of a material or structure to withstand loads tending to reduce size (compression). It is opposed to tensile strength which withstands loads tending to elongate, resisting tension. In the study of strength of materials, compressive strength, tensile strength, and shear strength can be analyzed independently.
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. Toughness is the strength with which the material opposes rupture. One definition of material toughness is the amount of energy per unit volume that a material can absorb before rupturing. This measure of toughness is different from that used for fracture toughness, which describes the capacity of materials to resist fracture. Toughness requires a balance of strength and ductility.
Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture.
Work hardening, also known as strain hardening, is the process by which a material's load-bearing capacity (strength) increases during plastic (permanent) deformation. This characteristic is what sets ductile materials apart from brittle materials. Work hardening may be desirable, undesirable, or inconsequential, depending on the application.
In materials science, fracture toughness is the critical stress intensity factor of a sharp crack where propagation of the crack suddenly becomes rapid and unlimited. A component's thickness affects the constraint conditions at the tip of a crack with thin components having plane stress conditions and thick components having plane strain conditions. Plane strain conditions give the lowest fracture toughness value which is a material property. The critical value of stress intensity factor in mode I loading measured under plane strain conditions is known as the plane strain fracture toughness, denoted . When a test fails to meet the thickness and other test requirements that are in place to ensure plane strain conditions, the fracture toughness value produced is given the designation . Fracture toughness is a quantitative way of expressing a material's resistance to crack propagation and standard values for a given material are generally available.
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible and is known as plastic deformation.
In materials science, hardness is a measure of the resistance to localized plastic deformation, such as an indentation or a scratch (linear), induced mechanically either by pressing or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter.
The strain hardening exponent, usually denoted , is a measured parameter that quantifies the ability of a material to become stronger due to strain hardening. Strain hardening is the process by which a material's load-bearing capacity increases during plastic (permanent) strain, or deformation. This characteristic is what sets ductile materials apart from brittle materials. The uniaxial tension test is the primary experimental method used to directly measure a material's stress–strain behavior, providing valuable insights into its strain-hardening behavior.
Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. It applies physics, chemistry and mathematics to the understanding of how mantle convection leads to plate tectonics and geologic phenomena such as seafloor spreading, mountain building, volcanoes, earthquakes, faulting. It also attempts to probe the internal activity by measuring magnetic fields, gravity, and seismic waves, as well as the mineralogy of rocks and their isotopic composition. Methods of geodynamics are also applied to exploration of other planets.
The mechanical properties of carbon nanotubes reveal them as one of the strongest materials in nature. Carbon nanotubes (CNTs) are long hollow cylinders of graphene. Although graphene sheets have 2D symmetry, carbon nanotubes by geometry have different properties in axial and radial directions. It has been shown that CNTs are very strong in the axial direction. Young's modulus on the order of 270 - 950 GPa and tensile strength of 11 - 63 GPa were obtained.
Material failure theory is an interdisciplinary field of materials science and solid mechanics which attempts to predict the conditions under which solid materials fail under the action of external loads. The failure of a material is usually classified into brittle failure (fracture) or ductile failure (yield). Depending on the conditions most materials can fail in a brittle or ductile manner or both. However, for most practical situations, a material may be classified as either brittle or ductile.
In Earth science, ductility refers to the capacity of a rock to deform to large strains without macroscopic fracturing. Such behavior may occur in unlithified or poorly lithified sediments, in weak materials such as halite or at greater depths in all rock types where higher temperatures promote crystal plasticity and higher confining pressures suppress brittle fracture. In addition, when a material is behaving ductilely, it exhibits a linear stress vs strain relationship past the elastic limit.