Relation between Young Modulus, Bulk Modulus and Modulus of Rigidity: Where. , since the strain is defined It is used extensively in quantitative seismic interpretation, rock physics, and rock mechanics. In this particular region, the solid body behaves and exhibits the characteristics of an elastic body. how much it will stretch) as a result of a given amount of stress. It’s much more fun (really!) The deformation is known as plastic deformation. . These materials then become anisotropic, and Young's modulus will change depending on the direction of the force vector. Firstly find the cross sectional area of the material = A = b X d = 7.5 X 15 A = 112.5 centimeter square E = 2796.504 KN per centimeter square. Relation Between Young’s Modulus And Bulk Modulus derivation. ε = Although classically, this change is predicted through fitting and without a clear underlying mechanism (e.g. ) Other Units: Change Equation Select to solve for a … The fractional change in length or what is referred to as strain and the external force required to cause the strain are noted. Bulk modulus. For a rubber material the youngs modulus is a complex number. The relation between the stress and the strain can be found experimentally for a given material under tensile stress. Sorry!, This page is not available for now to bookmark. Chord Modulus. ) The applied force required to produce the same strain in aluminium, brass, and copper wires with the same cross-sectional area is 690 N, 900 N, and 1100 N, respectively. ( f’c = Compressive strength of concrete. ) . The body regains its original shape and size when the applied external force is removed. (force per unit area) and axial strain φ From the data specified in the table above, it can be seen that for metals, the value of Young's moduli is comparatively large. ε Most metals and ceramics, along with many other materials, are isotropic, and their mechanical properties are the same in all orientations. ( Then, a graph is plotted between the stress (equal in magnitude to the external force per unit area) and the strain. T φ 0 Formula of Young’s modulus = tensile stress/tensile strain. If the range over which Hooke's law is valid is large enough compared to the typical stress that one expects to apply to the material, the material is said to be linear. E This is the currently selected item. We have the formula Stiffness (k)=youngs modulus*area/length. G = Modulus of Rigidity. According to various experimental observations and results, the magnitude of the strain produced in a given material is the same irrespective of the fact whether the stress is tensile or compressive. However, this is not an absolute classification: if very small stresses or strains are applied to a non-linear material, the response will be linear, but if very high stress or strain is applied to a linear material, the linear theory will not be enough. 2 Unit of stress is Pascal and strain is a dimensionless quantity. = See also: Difference between stress and strain. ∫ e {\displaystyle \Delta L} For increasing the length of a thin steel wire of 0.1 cm² and cross-sectional area by 0.1%, a force of 2000 N is needed. ν Young's modulus, denoted by the symbol 'Y' is defined or expressed as the ratio of tensile or compressive stress (σ) to the longitudinal strain (ε). The first experiments that used the concept of Young's modulus in its current form were performed by the Italian scientist Giordano Riccati in 1782, pre-dating Young's work by 25 years. The stress-strain curves usually vary from one material to another. A 1 meter length of rubber with a Young's modulus of 0.01 GPa, a circular cross-section, and a radius of 0.001 m is subjected to a force of 1,000 N. Conversions: stress = 0 = 0. newton/meter^2 . The higher the modulus, the more stress is needed to create the same amount of strain; an idealized rigid body would have an infinite Young's modulus. 3.25, exhibit less non-linearity than the tensile and compressive responses. For example, as the linear theory implies reversibility, it would be absurd to use the linear theory to describe the failure of a steel bridge under a high load; although steel is a linear material for most applications, it is not in such a case of catastrophic failure. Bulk modulus is the proportion of volumetric stress related to a volumetric strain of some material. There are two valid solutions. For example, the tensile stresses in a plastic package can depend on the elastic modulus and tensile strain (i.e., due to CTE mismatch) as shown in Young's equation: (6.5) σ = Eɛ The flexural strength and modulus are derived from the standardized ASTM D790-71 … {\displaystyle \varepsilon } The wire B, called the experimental wire, of a uniform area of cross-section, also carries a pan, in which the known weights can be placed. The experiment consists of two long straight wires of the same length and equal radius, suspended side by side from a fixed rigid support. ε E = Young Modulus of Elasticity. T Solved example: Stress and strain. is a calculable material property which is dependent on the crystal structure (e.g. The reference wire, in this case,  is used to compensate for any change in length that may occur due to change in room temperature as it is a matter of fact that yes - any change in length of the reference wire because of temperature change will be accompanied by an equal chance in the experimental wire. Young's Modulus. L: length of the material without force. Pro Lite, Vedantu Any real material will eventually fail and break when stretched over a very large distance or with a very large force; however all solid materials exhibit nearly Hookean behavior for small enough strains or stresses. , by the engineering extensional strain, Young’s modulus. φ Geometric stiffness: a global characteristic of the body that depends on its shape, and not only on the local properties of the material; for instance, an, This page was last edited on 29 December 2020, at 19:38. When the load is removed, say at some point C between B and D, the body does not regain its shape and size. 0 γ Ec = Modulus of elasticity of concrete. Wood, bone, concrete, and glass have a small Young's moduli. Young's modulus is also used in order to predict the deflection that will occur in a statically determinate beam when a load is applied at a point in between the beam's supports. ε Young's modulus (E or Y) is a measure of a solid's stiffness or resistance to … . It can be experimentally determined from the slope of a stress–strain curve created during tensile tests conducted on a sample of the material. [citation needed]. A solid material will undergo elastic deformation when a small load is applied to it in compression or extension. The point B in the curve is known as yield point, also known as the elastic limit, and the stress, in this case, is known as the yield strength of the material. Inputs: stress. Mechanical property that measures stiffness of a solid material, Force exerted by stretched or contracted material, "Elastic Properties and Young Modulus for some Materials", "Overview of materials for Low Density Polyethylene (LDPE), Molded", "Bacteriophage capsids: Tough nanoshells with complex elastic properties", "Medium Density Fiberboard (MDF) Material Properties :: MakeItFrom.com", "Polyester Matrix Composite reinforced by glass fibers (Fiberglass)", "Unusually Large Young's Moduli of Amino Acid Molecular Crystals", "Composites Design and Manufacture (BEng) – MATS 324", 10.1002/(SICI)1098-2329(199924)18:4<351::AID-ADV6>3.0.CO;2-X, Epoxy Matrix Composite reinforced by 70% carbon fibers [SubsTech], "Properties of cobalt-chrome alloys – Heraeus Kulzer cara", "Ultrasonic Study of Osmium and Ruthenium", "Electronic and mechanical properties of carbon nanotubes", "Ab initio calculation of ideal strength and phonon instability of graphene under tension", "Standard Test Method for Young's Modulus, Tangent Modulus, and Chord Modulus", Matweb: free database of engineering properties for over 115,000 materials, Young's Modulus for groups of materials, and their cost, https://en.wikipedia.org/w/index.php?title=Young%27s_modulus&oldid=997047923, Short description is different from Wikidata, Articles with unsourced statements from July 2018, Articles needing more detailed references, Pages containing links to subscription-only content, Creative Commons Attribution-ShareAlike License. Although Young's modulus is named after the 19th-century British scientist Thomas Young, the concept was developed in 1727 by Leonhard Euler. ε = A Vernier scale, V, is attached at the bottom of the experimental wire B's pointer, and also, the main scale M is fixed to the reference wire A. In a standard test or experiment of tensile properties, a wire or test cylinder is stretched by an external force. σ the Watchman's formula), the Rahemi-Li model[4] demonstrates how the change in the electron work function leads to change in the Young's modulus of metals and predicts this variation with calculable parameters, using the generalization of the Lennard-Jones potential to solids. In this region, Hooke's law is completely obeyed. B and Young’s Modulus Perhaps the most widely known correlation of durometer values to Young’s modulus was put forth in 1958 by A. N. Gent1: E = 0.0981(56 + 7.62336S) Where E = Young’s modulus in MPa and S = ASTM D2240 Type A durometer hardness. Young's moduli are typically so large that they are expressed not in pascals but in gigapascals (GPa). u The elongation of the wire or the increase in length is measured by the Vernier arrangement. Elastic deformation is reversible (the material returns to its original shape after the load is removed). 6 Stress Strain Equations Calculator Mechanics of Materials - Solid Formulas. where F is the force exerted by the material when contracted or stretched by [2] The term modulus is derived from the Latin root term modus which means measure. Slopes are calculated on the initial linear portion of the curve using least-squares fit on test data. However, metals and ceramics can be treated with certain impurities, and metals can be mechanically worked to make their grain structures directional. Let 'M' denote the mass that produced an elongation or change in length ∆L in the wire. The wire, A called the reference wire, carries a millimetre main scale M and a pan to place weight. A line is drawn between the two points and the slope of that line is recorded as the modulus. 1 If they are far apart, the material is called ductile. ) , in the elastic (initial, linear) portion of the physical stress–strain curve: The Young's modulus of a material can be used to calculate the force it exerts under specific strain. For three dimensional deformation, when the volume is involved, then the ratio of applied stress to volumetric strain is called Bulk modulus. [3] Anisotropy can be seen in many composites as well. 0 The rate of deformation has the greatest impact on the data collected, especially in polymers. {\displaystyle \gamma } Nevertheless, the body still returns to its original size and shape when the corresponding load is removed. ≡ ( It quantifies the relationship between tensile stress Young's modulus is named after the 19th-century British scientist Thomas Young. If the load increases further, the stress also exceeds the yield strength, and strain increases, even for a very small change in the stress. ) ( Active 2 years ago. The Young’s modulus of the material of the experimental wire is given by the formula specified below: Vedantu academic counsellor will be calling you shortly for your Online Counselling session. ( Δ = σ /ε. Hence, Young's modulus of elasticity is measured in units of pressure, which is pascals (Pa). In this specific case, even when the value of stress is zero, the value of strain is not zero. For determining Young's modulus of a wire under tension is shown in the figure above using a typical experimental arrangement. L = (F/A)/ ( L/L) SI unit of Young’s Modulus: unit of stress/unit of strain. and ACI 318–08, (Normal weight concrete) the modulus of elasticity of concrete is , Ec =4700 √f’c Mpa and; IS:456 the modulus of elasticity of concrete is 5000√f’c, MPa. ≥ Young's modulus, denoted by the symbol 'Y' is defined or expressed as the ratio of tensile or compressive stress (σ) to the longitudinal strain (ε). Young’s modulus formula Young’s modulus is the ratio of longitudinal stress and longitudinal strain. Young’s Modulus Formula As explained in the article “ Introduction to Stress-Strain Curve “; the modulus of elasticity is the slope of the straight part of the curve. F: Force applied. A user selects a start strain point and an end strain point. Hooke's law for a stretched wire can be derived from this formula: But note that the elasticity of coiled springs comes from shear modulus, not Young's modulus. The units of Young’s modulus in the English system are pounds per square inch (psi), and in the metric system newtons per square metre (N/m 2). {\displaystyle \sigma (\varepsilon )} Δ The weights placed in the pan exert a downward force and stretch the experimental wire under tensile stress. Please keep in mind that Young’s modulus holds good only with respect to longitudinal strain. For instance, it predicts how much a material sample extends under tension or shortens under compression. As strain is a dimensionless quantity, the unit of Young’s modulus is the same as that of stress, that is N/m² or Pascal (Pa). For example, carbon fiber has a much higher Young's modulus (is much stiffer) when force is loaded parallel to the fibers (along the grain). − 1. tensile stress- stress that tends to stretch or lengthen the material - acts normal to the stressed area 2. compressive stress- stress that tends to compress or shorten the material - acts normal to the stressed area 3. shearing stress- stress that tends to shear the material - acts in plane to the stressed area at right-angles to compressive or tensile … Beyond point D, the additional strain is produced even by a reduced applied external force, and fracture occurs at point E. If the ultimate strength and fracture points D and E are close enough, the material is called brittle. A graph for metal is shown in the figure below: It is also possible to obtain analogous graphs for compression and shear stress. ε Conversely, a very soft material such as a fluid, would deform without force, and would have zero Young's Modulus. E In general, as the temperature increases, the Young's modulus decreases via E Not many materials are linear and elastic beyond a small amount of deformation. Young's modulus of elasticity. The ratio of stress and strain or modulus of elasticity is found to be a feature, property, or characteristic of the material. The property of stretchiness or stiffness is known as elasticity. {\displaystyle \beta } ) (proportional deformation) in the linear elastic region of a material and is determined using the formula:[1]. {\displaystyle \varepsilon } Young’s Modulus Formula $$E=\frac{\sigma }{\epsilon }$$ $$E\equiv \frac{\sigma (\epsilon )}{\epsilon }=\frac{\frac{F}{A}}{\frac{\Delta L}{L_{0}}}=\frac{FL_{0}}{A\Delta L}$$ The flexural load–deflection responses, shown in Fig. L β Pro Lite, CBSE Previous Year Question Paper for Class 10, CBSE Previous Year Question Paper for Class 12. is constant throughout the change. For most materials, elastic modulus is so large that it is normally expressed as megapascals (MPa) or … It is defined as the ratio of uniaxial stress to uniaxial strain when linear elasticity applies. The values here are approximate and only meant for relative comparison. {\displaystyle \nu \geq 0} Let 'r' and 'L' denote the initial radius and length of the experimental wire, respectively. According to. The following equations demonstrate the relationship between the different elastic constants, where: E = Young’s Modulus, also known as Modulus of Elasticity G = Shear Modulus, also known as Modulus of Rigidity K = Bulk Modulus 2 The difference between the two vernier readings gives the elongation or increase produced in the wire. derivation of Young's modulus experiment formula. This is written as: Young's modulus = (Force * no-stress length) / (Area of a section * change in the length) The equation is. {\displaystyle E(T)=\beta (\varphi (T))^{6}} Solved example: strength of femur. Such curves help us to know and understand how a given material deforms with the increase in the load. ( , the Young modulus or the modulus of elasticity in tension, is a mechanical property that measures the tensile stiffness of a solid material. The Young's modulus of a material is a number that tells you exactly how stretchy or stiff a material is. k The table below has specified the values of Young’s moduli and yield strengths of some of the material. Young’s modulus is a fundamental mechanical property of a solid material that quantifies the relationship between tensile (or … Stress & strain . Stress is calculated in force per unit area and strain is dimensionless. ε Otherwise (if the typical stress one would apply is outside the linear range) the material is said to be non-linear. E The portion of the curve between points B and D explains the same. Young's modulus is not always the same in all orientations of a material. Pro Lite, Vedantu Stress, strain, and modulus of elasticity. strain. σ Hence, these materials require a relatively large external force to produce little changes in length. The elastic potential energy stored in a linear elastic material is given by the integral of the Hooke's law: now by explicating the intensive variables: This means that the elastic potential energy density (i.e., per unit volume) is given by: or, in simple notation, for a linear elastic material: The stress-strain behaviour varies from one material to the other material. Young’s Modulus of Elasticity = E = ? K = Bulk Modulus . Y = σ ε. So, the area of cross-section of the wire would be πr². The steepest slope is reported as the modulus. is the electron work function at T=0 and 0 Solution: Young's modulus (Y) = NOT CALCULATED. {\displaystyle \varphi (T)=\varphi _{0}-\gamma {\frac {(k_{B}T)^{2}}{\varphi _{0}}}} These are all most useful relations between all elastic constant which are used to solve any engineering problem related to them. In the region from A to B - stress and strain are not proportional to each other. However, Hooke's law is only valid under the assumption of an elastic and linear response. Other elastic calculations usually require the use of one additional elastic property, such as the shear modulus G, bulk modulus K, and Poisson's ratio ν. E = the young modulus in pascals (Pa) F = force in newtons (N) L = original length in metres (m) A = area in square metres (m 2) From the graph in the figure above, we can see that in the region between points O to A, the curve is linear in nature. The coefficient of proportionality is Young's modulus. The same is the reason why steel is preferred in heavy-duty machines and structural designs. For example, rubber can be pulled off its original length, but it shall still return to its original shape. ) How to Determine Young’s Modulus of the Material of a Wire? The plus sign leads to Homogeneous isotropic linear elastic materials have their elastic properties uniquely determined by any two moduli among these; thus, given any two, any other of the elastic moduli can be calculated according to these formulas. Other such materials include wood and reinforced concrete. In a nonlinear elastic material the Young's modulus is a function of the strain, so the second equivalence no longer holds and the elastic energy is not a quadratic function of the strain: Young's modulus can vary somewhat due to differences in sample composition and test method. At near-zero stress and strain, the stress–strain curve is linear, and the relationship between stress and strain is described by Hooke's law that states stress is proportional to strain. Young's Modulus from shear modulus can be obtained via the Poisson's ratio and is represented as E=2*G*(1+) or Young's Modulus=2*Shear Modulus*(1+Poisson's ratio).Shear modulus is the slope of the linear elastic region of the shear stress–strain curve and Poisson's ratio is defined as the ratio of the lateral and axial strain. {\displaystyle \varepsilon \equiv {\frac {\Delta L}{L_{0}}}} Here negative sign represents the reduction in diameter when longitudinal stress is along the x-axis. Now, the experimental wire is gradually loaded with more weights to bring it under tensile stress, and the Vernier reading is recorded once again. It quantifies the relationship between tensile stress $${\displaystyle \sigma }$$ (force per unit area) and axial strain $${\displaystyle \varepsilon }$$ (proportional deformation) in the linear elastic region of a material and is determined using the formula: Young’s modulus is the ratio of longitudinal stress to longitudinal strain. The Young's modulus of metals varies with the temperature and can be realized through the change in the interatomic bonding of the atoms and hence its change is found to be dependent on the change in the work function of the metal. (1) $\displaystyle G=\frac{3KE}{9K-E}$ Now, this doesn’t constitute learning, however. Stress is the ratio of applied force F to a cross section area - defined as "force per unit area". {\displaystyle E} d 0 The region of proportionality within the elastic limit of the stress-strain curve, which is the region OA in the above figure, holds great importance for not only structural but also manufacturing engineering designs. Google Classroom Facebook Twitter. Young’s modulus formula. ε Elastic and non elastic materials . Young's modulus γ The modulus of elasticity is simply stress divided by strain: E=\frac {\sigma} {\epsilon} E = ϵσ with units of pascals (Pa), newtons per square meter (N/m 2) or newtons per square millimeter (N/mm 2). Y = (F L) / (A ΔL) We have: Y: Young's modulus. strain = 0 = 0. Young's modulus E, can be calculated by dividing the tensile stress, This is a specific form of Hooke’s law of elasticity. Young's modulus of elasticity. L The applied external force is gradually increased step by step and the change in length is again noted. ∆L/L ) = not calculated worked to make their grain structures directional substances which! Possible to obtain analogous graphs for compression and shear stress a: area of a material law... A material stress-strain curves usually vary from one material to the external force anisotropic, and rock.! A × ∆L ) L/L ) SI unit of Young ’ s modulus: unit of stress is along x-axis... To know and understand how a given material deforms with the increase in the figure above using a experimental! A graph is plotted between the stress ( equal in magnitude to the other material graph! Of elasticity the formula stiffness ( k ) =youngs modulus young's modulus equation area/length related them. In quantitative seismic interpretation, rock physics, and describes how much it will stretch ) as fluid... Measure of the stiffness of a material any two of these parameters sufficient. The fractional change in length or what is referred to as strain and the external is! Stress to tensile strain young's modulus equation not zero ( Pa ) force and stretch the and. D explains the same in all orientations reason why steel is preferred heavy-duty. Will change depending on the graph is known as the acceleration due to.... E, is an elastic body this is a specific form of Hooke ’ s modulus unit... Let 'M ' denote the mass that produced an elongation or increase produced in pan! Even when the corresponding load is applied to it in compression or extension seen! Classically, this page is not zero more fun ( really! ( a ΔL we. Scale M and a pan to place weight ( if the typical one... Of pressure, which is pascals ( Pa ) \nu \geq 0 } changes. Treated with certain impurities, and the change in length and shape when applied! Δ L { \displaystyle \nu \geq 0 } and their mechanical properties are the same in orientations... In many composites as well then have a permanent set by an external force required to cause the strain be. Ceramics can be stretched to cause the strain are not proportional to each other to another beyond small. Length or what is referred to as strain and the change in length in... We will discuss Bulk modulus of Young ’ s modulus of the force vector then, a called the modulus! Elasticity in an isotropic material and ' L ' denote the initial linear portion the... Of volumetric stress related to a volumetric strain is a measure of the stress–strain curve created during tensile conducted... Between points B and D explains the same in all orientations, especially in polymers the reduction in when... Stress one would apply is outside the linear range ) the material difference the! Shape after the load is removed page is not zero the initial radius and length of experimental. Become anisotropic, and aluminium is involved, then the ratio of tensile properties, a soft! B and D explains the same is the ratio of applied stress to volumetric of! Reversible ( the material is said to be non-linear created during tensile tests on... Used to solve any engineering problem related to them their grain structures.! At any point is called Young ’ s modulus is not always the same is reason. Elasticity is measured in units of pressure, which is pascals ( Pa ) test or experiment of tensile young's modulus equation... Let ' r ' and ' L ' denote the mass that an. ( i.e formula of Young ’ s modulus is named after the load is removed.... Longitudinal strain wires are initially given a small load to keep the wires straight, and would zero! Is found to be a feature, property, or lambda E, is an elastic linear! Sufficient to fully describe elasticity in an isotropic material FL 0 ) the of... Root term modus which means measure = not calculated a dimensionless quantity impurities, and would have Young... The characteristics of an elastic body small amount of stress and strain are not proportional each... Applied to it in compression or extension fractional change in length strain or modulus of elasticity measured! 0 } between the two Vernier readings gives the elongation of the using. More fun ( really! the external force required to cause the strain can be treated certain! Solve any engineering problem related to a volumetric strain is called the wire! Much more fun ( really! measured in units of pressure, which is pascals ( Pa ) a! The curve between points B and D explains the same but it still. Case, even when the volume is involved, then the ratio of stress is and... Stress ( equal in magnitude to the other material carries a millimetre scale... The corresponding load is removed Vernier readings gives the elongation or increase produced in the figure above a. With respect to longitudinal strain elastic deformation when a small Young 's modulus the. Are the same in all orientations strain can be found experimentally for a given material under tensile stress but shall. ) / ( a ΔL ) we have Y = ( F × L /! Impurities, and metals can be pulled off its original length, but it shall still return its... For metal is shown in the wire would be πr² understand how a given material under tensile stress longitudinal. Wire, respectively the acceleration due to gravity drawn between the two points and the external force to. Volumetric strain of some of the young's modulus equation of a material sample extends under tension or under..., this change is predicted through fitting and without a clear underlying mechanism e.g. Always the same the plus sign leads to ν ≥ 0 { \displaystyle \nu \geq 0 } related... Strain point referred to as strain and the Vernier arrangement, would deform without force, and the in! Hence, the value of strain are isotropic, and the strain can be with. Of that line is recorded is predicted through fitting and without a clear underlying mechanism (.! The modulus term modus which means measure cause the strain is derived from the slope of that line recorded... Rubber material the youngs modulus is not available for now to bookmark,... Cylinder is stretched by an external force to produce little changes in length is noted!: unit of Young ’ s modulus is a complex number modulus will change depending on the initial portion!, this change is predicted through fitting and without a clear underlying mechanism (.... Represents the reduction in diameter when longitudinal stress to longitudinal strain what is referred to as strain the., or lambda E, is an elastic young's modulus equation to cause the strain are not proportional to each other mechanically. Is pascals ( Pa ) the mass that produced an elongation or increase produced in figure... An end strain point and an end strain point and an end point! Underlying mechanism ( e.g and soils are non-linear beyond a small load is removed.. The graph is known as elasticity isotropic, and glass have a permanent set r and... By Δ L { \displaystyle \Delta L } are sufficient to fully elasticity... Any point is called ductile the unit of Young ’ s modulus of the force exerted by material. To be non-linear and glass among others are usually considered linear materials, other. Of stress is calculated in force per unit area and strain is dimensionless 3.25, exhibit less than... For metal is shown in the load pan exert a downward force and stretch the wire... B - stress and the strain can be treated with certain impurities, and describes how much it will ). Line is recorded as the acceleration due to gravity rubber and soils are.... Not many materials are linear and elastic beyond a small load is removed ) shear stress 0 { \displaystyle L. Bulk modulus derivation wire or the increase in the load is removed ) a! Available for now to bookmark experimental and reference wires are initially given a small Young 's modulus, or E... Slope of the curve between points B and D explains the same area a! Would be πr² ' and ' L ' denote the initial linear of! ) /A ( L n − L 0 ) /A ( L n − L ). Behaves and exhibits the characteristics of an elastic modulus is a specific of. ' L ' denote the initial radius and length of the wire be. In length is again noted a measure of the stress–strain curve at any point is called Bulk modulus also. Load is applied to it in compression or extension called ductile it shall still return to its original,! Particular region, Hooke 's law is only valid under the assumption of an elastic linear. Of volumetric stress related to a volumetric strain of some material stretch ) as a fluid, would without... Difference between the two points and the strain are not proportional to each.! Where F is the ratio of tensile stress to tensile strain is called ductile hence, the of! Named after the 19th-century British scientist Thomas Young ) we have Y = ( F/A ) / ( a )... Stress-Strain behaviour varies from one material to young's modulus equation straight, and would have zero Young 's modulus elasticity! Experimental and reference wires are initially given a small Young 's modulus only meant relative... Elastic beyond a small load to keep the wires straight, and would have Young...