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List of materials properties
List of materials properties
List of materials properties
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A material property is an intensive property of a material, i.e., a physical property or chemical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another can be compared, thereby aiding in materials selection.

A property having a fixed value for a given material or substance is called material constant or constant of matter.[1] (Material constants should not be confused with physical constants, that have a universal character.)

A material property may also be a function of one or more independent variables, such as temperature. Materials properties often vary to some degree according to the direction in the material in which they are measured, a condition referred to as anisotropy. Materials properties that relate to different physical phenomena often behave linearly (or approximately so) in a given operating range [further explanation needed]. Modeling them as linear functions can significantly simplify the differential constitutive equations that are used to describe the property.

Equations describing relevant materials properties are often used to predict the attributes of a system.

The properties are measured by standardized test methods. Many such methods have been documented by their respective user communities and published through the Internet; see ASTM International.

Acoustical properties.

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Atomic properties

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  • Atomic mass: (applies to each element) the average mass of the atoms of an element, in daltons (Da), a.k.a. atomic mass units (amu).
  • Atomic number: (applies to individual atoms or pure elements) the number of protons in each nucleus
  • Relative atomic mass, a.k.a. atomic weight: (applies to individual isotopes or specific mixtures of isotopes of a given element) (no units)
  • Standard atomic weight: the average relative atomic mass of a typical sample of the element (no units)

Chemical properties

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Main article: Chemical property

Electrical properties

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Magnetic properties

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Manufacturing properties

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Mechanical properties

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  • Brittleness: Ability of a material to break or shatter without significant deformation when under stress; opposite of plasticity, examples: glass, concrete, cast iron, ceramics etc.
  • Bulk modulus: Ratio of pressure to volumetric compression (GPa) or ratio of the infinitesimal pressure increase to the resulting relative decrease of the volume
  • Coefficient of restitution: The ratio of the final to initial relative velocity between two objects after they collide. Range: 0–1, 1 for perfectly elastic collision.
  • Compressive strength: Maximum stress a material can withstand before compressive failure (MPa)
  • Creep: The slow and gradual deformation of an object with respect to time. If the s in a material exceeds the yield point, the strain caused in the material by the application of load does not disappear totally on the removal of load. The plastic deformation caused to the material is known as creep. At high temperatures, the strain due to creep is quite appreciable.[2]
  • Density: Mass per unit volume (kg/m^3)
  • Ductility: Ability of a material to deform under tensile load (% elongation). It is the property of a material by which it can be drawn into wires under the action of tensile force. A ductile material must have a high degree of plasticity and strength so that large deformations can take place without failure or rupture of the material. In ductile extension, a material that exhibits a certain amount of elasticity along with a high degree of plasticity.[3]
  • Durability: Ability to withstand wear, pressure, or damage; hard-wearing
  • Elasticity: Ability of a body to resist a distorting influence or stress and to return to its original size and shape when the stress is removed
  • Fatigue limit: Maximum stress a material can withstand under repeated loading (MPa)
  • Flexural modulus
  • Flexural strength: Maximum bending stress a material can withstand before failure (MPa)
  • Fracture toughness: Ability of a material containing a crack to resist fracture (J/m^2)
  • Friction coefficient: The amount of force normal to surface which converts to force resisting relative movement of contacting surfaces between material pairs
  • Hardness: Ability to withstand surface indentation and scratching (e.g. Brinell hardness number)
  • Malleability: Ability of the material to be flattened into thin sheets under applications of heavy compressive forces without cracking by hot or cold working means.This property of a material allows it to expand in all directions without rupture.[4]
  • Mass diffusivity: Ability of one substance to diffuse through another
  • Plasticity: Ability of a material to undergo irreversible or permanent deformations without breaking or rupturing; opposite of brittleness
  • Poisson's ratio: Ratio of lateral strain to axial strain (no units)
  • Resilience: Ability of a material to absorb energy when it is deformed elastically (MPa); combination of strength and elasticity
  • Shear modulus: Ratio of shear stress to shear strain (MPa)
  • Shear strength: Maximum shear stress a material can withstand
  • Slip: A tendency of a material's particles to undergo plastic deformation due to a dislocation motion within the material. Common in Crystals.
  • Specific modulus: Modulus per unit volume (MPa/m^3)
  • Specific strength: Strength per unit density (Nm/kg)
  • Specific weight: Weight per unit volume (N/m^3)
  • Surface roughness: The deviations in the direction of the normal vector of a real surface from its ideal form
  • Tensile strength: Maximum tensile stress of a material can withstand before failure (MPa)
  • Toughness: Ability of a material to absorb energy (or withstand shock) and plastically deform without fracturing (or rupturing); a material's resistance to fracture when stressed; combination of strength and plasticity
  • Viscosity: A fluid's resistance to gradual deformation by tensile or shear stress; thickness
  • Yield strength: The stress at which a material starts to yield plastically (MPa)
  • Young's modulus: Ratio of linear stress to linear strain (MPa) (influences the stiffness and flexibility of an object)

Optical properties

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Main article: Optical properties

Radiological properties

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Thermal properties

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See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

List of materials properties

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from Grokipedia
A list of materials properties encompasses the measurable characteristics of substances that dictate their performance, behavior, and suitability for specific applications in , , and scientific . These properties are intrinsic or intensive attributes, independent of the sample size, and include a wide array of categories such as mechanical, , electrical, chemical, and physical traits, which engineers and scientists evaluate to select optimal materials for products ranging from structural components to . Key categories of materials properties provide a structured framework for understanding material behavior. Mechanical properties, such as strength, elasticity, , , and , describe how materials respond to forces and deformation, crucial for load-bearing applications like bridges or frames. Thermal properties, including thermal conductivity, , and , determine and stability under temperature changes, essential in heat exchangers or insulators. Electrical properties, like resistivity, dielectric constant, and , govern conductivity and insulation, vital for wiring, semiconductors, and capacitors. Chemical properties, encompassing resistance, reactivity, and , assess durability in harsh environments, such as in chemical processing equipment. Physical properties, such as , , and optical transparency, influence overall usability and appearance in everyday items like packaging or . Beyond these core categories, specialized properties like magnetic (e.g., permeability, ), optical (e.g., , ), and acoustical (e.g., sound speed, ) further expand the list, enabling tailored material selection in fields from to . Comprehensive databases and handbooks, such as those from , compile these properties with quantitative data for thousands of materials, facilitating precise comparisons and predictive modeling in design processes. Understanding and listing these properties is fundamental to advancing , as they interrelate and can be influenced by factors like composition, , and environmental conditions, ensuring innovations meet , , and standards.

Composition and Structure Properties

Atomic Properties

Atomic properties refer to the fundamental characteristics of atoms that define the elemental composition of materials. These properties, derived from the structure of the and arrangement, form the basis for understanding how materials behave at a microscopic level. Key atomic properties include the , , , and isotopic abundance, each contributing uniquely to the identity and stability of elements in various material systems. The , denoted as , is the number of protons in an atom's nucleus and uniquely identifies each . It determines the element's position in the periodic table, with having Z=1 and Z=92 in naturally occurring forms. This property governs the positive charge of the nucleus, influencing attraction and thus the atom's chemical behavior. Atomic mass, also known as atomic weight, is the weighted average of the masses of an element's naturally occurring isotopes, expressed in atomic mass units (u), where 1 u equals 1/12 the mass of a atom. It is calculated by multiplying each isotope's mass by its fractional abundance and summing the results, providing a value essential for determining material densities and molar masses in engineering applications. For instance, carbon's is approximately 12.011 u due to the predominance of . Electron configuration describes the distribution of electrons in an atom's orbitals, organized by (n) for s and subshells (s, p, d, f) based on . The dictates that electrons fill orbitals starting from the lowest , following the order 1s, 2s, 2p, 3s, 3p, 4s, 3d, and so on, as derived from quantum mechanical energy minimization. Hund's rule further specifies that within a subshell, electrons occupy degenerate orbitals singly with parallel spins before pairing, maximizing spin multiplicity and minimizing electron repulsion for the . For example, nitrogen's configuration is 1s² 2s² 2p³, with three unpaired electrons in the p subshell. Isotopic abundance refers to the relative proportions of an element's isotopes in natural samples, which directly relates to nuclear stability since more stable isotopes predominate due to less decay over geological time. isotopes have balanced neutron-to-proton ratios, enhancing and longevity. For carbon, constitutes about 98.93% of natural abundance, while makes up 1.07%, reflecting carbon-12's greater stability from its even-even nuclear structure. This distribution affects nuclear properties in materials, such as in for stability studies.

Chemical Properties

Chemical properties of materials describe the interactions between atoms and molecules that govern how substances form, react, and remain stable, serving as the foundation for their macroscopic behavior. These properties include the elemental makeup, bonding mechanisms, structural arrangements, reactivity profiles, resistance to degradation, and affinity for environmental , all of which determine a material's suitability for applications ranging from to . Chemical composition delineates the types and proportions of elements within a , which directly influences its reactivity and performance. In stoichiometric compounds like (SiO₂), the fixed ratio of one atom to two oxygen atoms yields a mass composition of approximately 46.74% and 53.26% oxygen, enabling its use as an insulating ceramic. Alloys, such as carbon steels, incorporate iron as the base (typically 98-99.8%) with controlled additions of carbon (0.02-2.1%) and elements like (up to 12% in stainless variants) to tailor strength and durability. Polymers, exemplified by , feature long chains of repeating units (-CH₂-CH₂-), resulting in a composition of about 85.6% carbon and 14.4% , which confers flexibility and chemical inertness in packaging applications. The nature of atomic bonding profoundly affects a material's cohesion, conductivity, and brittleness. Ionic bonds arise from the electrostatic attraction between cations and anions, as in (NaCl), where sodium (+1 ) transfers an to chlorine (-1), forming a rigid lattice with high points but in polar solvents. Covalent bonds involve electron sharing, creating directional links; exemplifies a covalent network solid where each carbon atom forms four equivalent sp³ bonds in a tetrahedral arrangement, yielding extreme and thermal stability. Metallic bonds feature a "sea" of delocalized valence electrons surrounding positively charged metal ions, as in , facilitating malleability and electrical conduction. Van der Waals bonds, weaker secondary interactions, encompass dispersion forces, dipole-dipole attractions, and hydrogen bonding; they dominate in molecular solids like layers or polymers, allowing easier shear and lower temperatures. The of elements subtly influences bonding tendencies, with differences dictating whether interactions lean ionic or covalent. Crystal structure refers to the periodic spatial arrangement of atoms, ions, or molecules in a solid, which underpins many physical traits through its and density. Common lattice types include face-centered cubic (FCC), where atoms reside at cube corners and face centers—as in aluminum—achieving 74% atomic packing efficiency and promoting ; body-centered cubic (BCC), with an additional atom at the cube's center, as in alpha-iron, offering 68% packing and higher strength but reduced malleability; and hexagonal close-packed (HCP), featuring stacked hexagonal layers, as in magnesium, also at 74% packing for optimal density. The , the smallest repeating volume, defines these lattices; for FCC, it spans edge length a with 4 atoms per cell. Imperfections disrupt ideal order: vacancies are empty lattice sites that increase rates, while dislocations—edge or screw types—introduce line distortions that enable plastic deformation without fracture, critical for shaping metals. Chemical reactivity quantifies a material's propensity to undergo transformations via or bond breaking, often modulated by environmental factors. Oxidation states, the formal charges assigned to atoms in compounds, dictate behavior; transition metals like iron exhibit multiple states (+2 and +3), enabling variable reactivity in or synthesis processes. pH sensitivity arises when acidity alters or structure; for example, amphoteric aluminum (Al₂O₃) dissolves in both acidic ( to Al³⁺) and basic (formation of aluminate ions) conditions, impacting its use in refractories. Catalysis potential reflects a material's capacity to lower activation energies for reactions; platinum's surface atoms provide active sites for adsorbing reactants like and oxygen, accelerating processes without net consumption. Corrosion resistance evaluates a material's endurance against oxidative degradation, particularly in aqueous environments. Mechanisms include , where dissimilar metals in contact form a spontaneous cell: the (more reactive metal) oxidizes, while the (nobler) reduces species like oxygen, driven by potential differences. This is quantified by standard electrode potentials (E°), which relate to the (K) for the half-cell reaction through the thermodynamic equation: E∘=−RTnFln⁡KE^\circ = -\frac{RT}{nF} \ln K Here, R is the gas constant (8.314 J/mol·K), T is absolute temperature, n is electrons transferred, and F is Faraday's constant (96,485 C/mol); for instance, zinc's E° of -0.76 V versus the standard hydrogen electrode makes it anodic to iron in seawater, accelerating zinc's sacrifice. Alloying with elements like chromium (≥10.5%) in stainless steels forms protective oxide layers, enhancing passivity and longevity in harsh settings. Hygroscopicity denotes the absorption or adsorption of water vapor, altering a material's mass, dimensions, or reactivity. Highly hygroscopic salts, such as calcium chloride (CaCl₂), avidly form hydrates (e.g., CaCl₂·2H₂O) via strong ion-dipole interactions, absorbing up to 100% of their weight in water under humid conditions, useful in desiccants but problematic for storage. Metals, conversely, exhibit low hygroscopicity; noble ones like gold remain unaffected due to weak surface interactions with water, while reactive metals like sodium may oxidize upon minor moisture exposure but do not absorb it intrinsically. This property contrasts sharply between ionic salts and non-polar metals, influencing handling in pharmaceuticals versus aerospace components.

Thermal Properties

Thermodynamic Properties

Thermodynamic properties of materials characterize their equilibrium energy states, phase behaviors, and responses to and changes, providing insights into macroscopic stability based on atomic and molecular composition. These properties govern how materials store and transfer energy during phase transitions and reactions, influencing applications from design to . Key thermodynamic properties include , and points, phase diagrams, of formation, and , each quantified through fundamental relations derived from classical ./13:_Heat_and_Heat_Transfer/13.2:_Specific_Heat) Specific heat capacity at constant pressure, denoted CpC_p, represents the amount of required to raise the of a unit mass of a by one while maintaining constant . It is formally defined as the of HH with respect to TT at constant : Cp=(∂H∂T)pC_p = \left( \frac{\partial H}{\partial T} \right)_p The standard unit is joules per kilogram- (J/(kg·K)). Values of CpC_p vary significantly with the phase of the ; for example, liquid has Cp≈4186C_p \approx 4186 J/(kg·K), while is approximately 2093 J/(kg·K), and around 2010 J/(kg·K), reflecting differences in molecular freedom and vibrational modes across phases. The TmT_m is the at which a achieves equilibrium between its and phases under a given , typically one atmosphere for standard conditions. For pure substances, TmT_m marks the point where the Gibbs free energies of the solid and liquid phases are equal, allowing coexistence without net phase change. Impurities and alloying elements lower TmT_m by introducing defects or forming eutectic mixtures, where a specific composition melts at a temperature below that of the pure components; for instance, the lead-tin eutectic alloy melts at 183°C compared to 327°C for pure lead. The TbT_b, or normal boiling point, is the at which the of the liquid phase equals one standard atmosphere (101.325 kPa), enabling equilibrium between liquid and vapor phases. This transition is governed by intermolecular forces, with stronger forces—such as hydrogen bonding in —resulting in higher TbT_b values; boils at 100°C, while nonpolar substances like boil at -161.5°C due to weaker van der Waals interactions. Phase diagrams map the equilibrium phases of materials as functions of , , and composition, essential for predicting stability in multi-component systems. Unary phase diagrams for single-component materials plot phases against and , showing transitions like solid-liquid-vapor. Binary phase diagrams, for two-component systems, typically display versus composition at constant , revealing regions of single-phase, two-phase, and multi-phase coexistence, such as solid solutions or eutectics. These diagrams are governed by the Gibbs , which states that the number of phases PP plus the degrees of freedom FF equals the number of components CC plus two (for and variables): P+F=C+2P + F = C + 2 For a (C=2C=2) at constant , this simplifies to F=3−PF = 3 - P, indicating invariant points (e.g., eutectics) where F=0F=0 and three phases coexist. The ΔHf∘\Delta H_f^\circ is the change for the formation of one mole of a compound from its constituent elements in their standard states (pure substances at 1 bar and 25°C). Tabulated values, such as ΔHf∘=−285.8\Delta H_f^\circ = -285.8 kJ/mol for from H2_2 and O2_2, enable calculation of reaction enthalpies via : ΔHrxn∘=∑ΔHf∘(products)−∑ΔHf∘(reactants)\Delta H_{rxn}^\circ = \sum \Delta H_f^\circ (products) - \sum \Delta H_f^\circ (reactants). This property contributes to assessing reaction spontaneity through the ΔG∘=ΔH∘−TΔS∘\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ, where negative ΔG∘\Delta G^\circ indicates a under standard conditions. Entropy SS quantifies the degree of disorder or randomness in a material's microscopic configurations, serving as a measure of unavailable for work. For a reversible , the change in is given by ΔS=Qrev/T\Delta S = Q_{rev}/T, where QrevQ_{rev} is the reversible and TT is the absolute temperature in ; the unit is J/(mol·). increases during phase transitions—e.g., from solid to —as molecular arrangements become more disordered, driving the directionality of spontaneous processes per the second law of .

Thermal Transport Properties

Thermal transport properties characterize the dynamic movement of heat through materials driven by temperature gradients, essential for applications such as heat exchangers, , and high-temperature structural components. These properties differ from thermodynamic equilibria by focusing on non-steady-state processes where and material response govern performance under varying thermal loads. Key parameters include conduction via lattice vibrations or free electrons, diffusive spreading of temperature changes, dimensional responses to heating, resistance to abrupt temperature shifts, and radiative emission at surfaces. Thermal conductivity, denoted as κ\kappa, measures a material's capacity to transfer heat through conduction and is defined by Fourier's law: the heat flux q\mathbf{q} is proportional to the negative gradient of , q=−κ∇T\mathbf{q} = -\kappa \nabla T. The SI unit is watts per meter-kelvin (W/(m·K)), reflecting energy flow per unit area, length, and difference. In metals like , conduction primarily occurs via free electrons, yielding high values around 385 W/(m·K) at , while in insulators such as , phonons—quantized lattice vibrations—dominate, achieving exceptional κ\kappa up to 2000 W/(m·K) due to strong covalent and minimal . contributions decrease with rising owing to increased , whereas electronic conduction in metals shows less sensitivity until high temperatures enhance resistivity. Thermal diffusivity, α\alpha, quantifies the rate at which disturbances propagate through a during transient conditions, given by α=κ/(ρCp)\alpha = \kappa / (\rho C_p), where ρ\rho is and CpC_p is at constant pressure. This property is pivotal in unsteady scenarios, such as cooling of castings or processing, as higher α\alpha implies faster thermal equilibration and reduced thermal gradients over time. For instance, metals exhibit α\alpha on the order of 10−510^{-5} m²/s, enabling rapid response in heat sinks, whereas polymers with lower κ\kappa and higher CpC_p have α\alpha around 10−710^{-7} m²/s, leading to slower and better insulation in transient exposures. The coefficient of , α\alpha, describes the fractional change in dimension per unit rise, with the ΔL/L=αΔT\Delta L / L = \alpha \Delta T for one-dimensional expansion and the volumetric form ΔV/V=3αΔT\Delta V / V = 3\alpha \Delta T for isotropic materials./12%3A_Temperature_and_Kinetic_Theory/12.03%3A_Thermal_Expansion) Units are typically inverse (K⁻¹), with values for metals like aluminum at approximately 23 × 10⁻⁶ K⁻¹, contrasting with steels at 12 × 10⁻⁶ K⁻¹, influencing design tolerances in thermal cycling. In crystalline materials, α\alpha exhibits due to directional bonding; for example, in hexagonal , expansion along the c-axis can be negative while positive in the basal plane, arising from anharmonic vibrations and lattice . Thermal shock resistance assesses a material's ability to withstand rapid temperature changes without cracking from induced thermal stresses, often evaluated via the figure of merit R=σ(1−ν)/(Eα)R = \sigma (1 - \nu) / (E \alpha), where σ\sigma is tensile strength, ν\nu is Poisson's ratio, and EE is Young's modulus. This parameter estimates the maximum allowable temperature difference ΔT\Delta T before failure, with higher RR indicating better performance; ceramics like zirconia achieve favorable RR through optimized σ\sigma and low α\alpha, vital for turbine blades or refractories. The formulation assumes brittle behavior and derives from equating thermal stress to fracture strength under constrained expansion. Emissivity, ε\varepsilon, represents the of a surface in emitting relative to a blackbody, ranging from 0 (perfect reflector) to 1 (ideal emitter), and appears in the Stefan-Boltzmann law for radiative : q=εσT4q = \varepsilon \sigma T^4, where σ=5.67×10−8\sigma = 5.67 \times 10^{-8} W/(m²·K⁴) is the Stefan-Boltzmann constant and TT is absolute ./14%3A_Heat_and_Heat_Transfer_Methods/14.07%3A_Radiation) Polished metals exhibit low ε\varepsilon (e.g., 0.05 for aluminum), minimizing losses in applications, whereas oxidized or rough surfaces approach 0.9, enhancing dissipation in furnaces. This property is wavelength- and temperature-dependent, critical for infrared thermography and .

Mechanical Properties

Elastic and Plastic Deformation Properties

Elastic and plastic deformation properties describe how materials respond to applied stresses, distinguishing between reversible shape changes in the elastic regime and permanent alterations in the regime, which are critical for assessing material integrity under load. In the elastic region, deformation follows , where stress is proportional to strain, allowing the material to return to its original shape upon unloading. Beyond the elastic limit, plastic deformation occurs, involving irreversible changes often mediated by microstructural mechanisms, influencing formability and in engineering applications. Young's modulus, denoted as EE, quantifies a material's in uniaxial tension or compression and is defined by as σ=Eϵ\sigma = E \epsilon, where σ\sigma is the axial stress and ϵ\epsilon is the axial strain. This modulus is typically measured in gigapascals (GPa) and determined through , where a specimen is subjected to increasing uniaxial load while strain is recorded until the proportional limit is reached. For example, exhibits a Young's modulus around 200 GPa, reflecting high resistance to elastic deformation, whereas polymers like have values near 1 GPa, indicating greater compliance. The , GG, measures resistance to shear deformation and relates τ\tau to shear strain γ\gamma via τ=Gγ\tau = G \gamma. It connects to through the isotropic relation G=E2(1+ν)G = \frac{E}{2(1 + \nu)}, where ν\nu is , allowing estimation of shear behavior from tensile data. Metals typically show shear moduli between 50 and 80 GPa, essential for analyzing torsional loading in components like shafts. The , BB, quantifies a material's resistance to uniform volumetric compression under hydrostatic , defined as B=−VdPdVB = -V \frac{dP}{dV}, where VV is and PP is . It relates to other elastic constants via B=E3(1−2ν)B = \frac{E}{3(1 - 2\nu)} for isotropic materials and is measured in GPa using techniques like ultrasonic wave propagation or hydrostatic compression tests. For example, has a bulk modulus around 160 GPa, while is about 2.2 GPa, highlighting incompressibility differences. Poisson's ratio, ν\nu, is the negative ratio of transverse strain to axial strain under uniaxial loading, capturing lateral contraction (or expansion) during deformation. For most isotropic materials, ν\nu ranges from -1 to 0.5, with common values around 0.2 to 0.3 for metals and near 0.5 for rubbers, reflecting near-incompressibility. Auxetic materials, such as certain foams or metamaterials, exhibit negative Poisson's ratios (e.g., -0.5 to -1), leading to lateral expansion under tension, which enhances energy absorption in applications like protective gear. Yield strength, σy\sigma_y, marks the transition from elastic to deformation, representing the stress at which permanent strain begins. For materials lacking a distinct yield point, such as many alloys, it is conventionally defined using the 0.2% offset method: a line parallel to the elastic portion of the stress-strain curve, offset by 0.002 strain, intersects the curve to identify σy\sigma_y. Aluminum alloys, for instance, often have yield strengths of 100-500 MPa, guiding safe design limits to prevent unintended shaping. Ductility quantifies a material's capacity for deformation before , commonly measured as percent elongation at break in tensile tests—the increase in gauge length relative to the original. Metals like exhibit high ductility, with elongations of 30-50%, enabling drawing into wires, while ceramics such as alumina show low ductility (<1% elongation) due to limited plastic flow, resulting in brittle failure. Plastic flow in crystalline materials arises from the motion of dislocations—line defects in the lattice that enable shear slip on atomic planes without fracturing bonds. Crystal defects like dislocations facilitate this irreversible deformation, allowing coordinated atomic sliding under stress. During ongoing plastic deformation, work hardening increases flow stress as dislocation density rises and interactions impede further motion, described by the Hollomon equation σ=σ0+kϵn\sigma = \sigma_0 + k \epsilon^n, where σ0\sigma_0 is the initial yield stress, kk is the hardening coefficient, ϵ\epsilon is plastic strain, and nn is the strain-hardening exponent (typically 0.1-0.5 for metals). This phenomenon enhances strength but reduces further ductility, as seen in cold-worked steels where nn decreases with prior deformation.

Strength and Hardness Properties

Strength and hardness properties characterize a material's ability to withstand applied loads without permanent deformation or failure, as well as its resistance to surface deformation under indentation. These properties are essential for assessing durability in applications ranging from structural components to tools, where materials must endure high stresses or abrasive conditions. Ultimate tensile strength and compressive strength define the maximum loads a material can bear in tension or compression, respectively, while shear strength addresses resistance to sliding forces. Hardness quantifies resistance to localized plastic deformation. Toughness measures energy absorption before fracture, and creep resistance evaluates long-term deformation under sustained loads at elevated temperatures. Specific strength normalizes strength by density for weight-sensitive applications. Ultimate tensile strength (UTS), also known as tensile strength, represents the maximum engineering stress a material can sustain in uniaxial tension before necking or fracture, typically identified as the peak on the stress-strain curve. It is expressed in megapascals (MPa) and is crucial for ductile materials like metals, where it indicates the onset of instability after yielding. For example, structural steels often exhibit UTS values around 400-600 MPa, guiding design limits in load-bearing applications. Compressive strength is the maximum compressive stress a material can endure before failure, analogous to UTS but applied under axial compression, and is particularly vital for brittle materials like concrete where tensile weaknesses are less relevant. It is also measured in MPa; for instance, high-strength concrete can achieve 100 MPa or more, enabling its use in heavy-load structures such as bridges and dams. Unlike tensile testing, compressive failure often involves crushing or buckling, especially in slender specimens. Shear strength, τy\tau_y, is the maximum shear stress a material can withstand before yielding or failure, critical for components under torsional or transverse loads like fasteners or beams. It is measured in MPa via torsion tests or punch shear tests and often estimated from tensile yield strength using the von Mises criterion as τy≈σy/3\tau_y \approx \sigma_y / \sqrt{3}
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