Machines Theory

Different types of material mechanical properties

Material mechanical properties are intensive attribute of some material, meaning it is a physical characteristic independent of the material’s quantity. These quantitative characteristics can be used as a measure to compare the advantages of various materials, assisting in the choice of materials.

A characteristic, like temperature, might be a function of one or more independent variables or it could be a constant. Anisotropy is the term for the tendency of a material’s qualities to fluctuate to some extent depending on the direction of the material in which they are measured. When used within a certain operating range, materials qualities that relate to various physical processes frequently behave linearly (or roughly so). The differential constitutive equations that are utilized to describe the property can be greatly streamlined by modeling them as linear functions.

Forecasting of a system’s qualities frequently uses equations defining important material properties. Utilizing established test procedures, the attributes are measured. Many of these techniques have been written up and published online by their respective user communities; see ASTM International.

Material mechanical properties

In this article, we will look at the different types of material mechanical properties

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What are the most common material mechanical properties?

Product designers can use the information from a description of some typical mechanical and physical qualities to help them choose the right materials for a particular application. The followings are the types of material’s mechanical properties:

  • Conductivity
  • Corrosion
  • Resistance
  • Density
  • Ductility/Malleability
  • Elasticity/Stiffness
  • Fracture
  • Toughness
  • Hardness
  • Plasticity
  • Strength, Fatigue
  • Strength, Shear Strength,
  • Tensile Strength, Yield
  • Toughness
  • Wear Resistance

 

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Conductivity

The amount of heat that passes through a material can be determined by its thermal conductivity. It is expressed as one degree per unit of length, cross-sectional area, and time. High thermal conductivity materials can be utilized as heat sinks, while materials with low thermal conductivity can be employed as insulators.

High thermal conductivity metals would be suitable for use in systems like heat exchangers or refrigeration. Although materials with low thermal conductivity can be employed in high-temperature applications, high-temperature components frequently need materials with high thermal conductivity, therefore it’s critical to comprehend the environment.

Similar to thermal conductivity, electrical conductivity measures the amount of electricity that passes through a material with a known cross-section and length.

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Corrosion Resistance

A material’s capacity to resist a natural chemical or electrochemical attack by the air, moisture, or other elements is referred to as corrosion resistance. There are numerous types of corrosion, including inter-granular, parting, galvanic response, and pitting (many of which will be discussed in other newsletter editions).

Based on a linear extrapolation of penetration occurring over the course of a given test or service, corrosion resistance may be defined as the greatest depth in mils to which corrosion might penetrate in a year. While certain materials benefit from the addition of plating or coatings, others are naturally corrosion-resistant. Many metals that are members of families that resist corrosion are still vulnerable to the particular environmental factors present in the environments in which they function.

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Density

The mass of the alloy per unit volume is referred to as density, which is frequently stated in terms of pounds per cubic inch, grams per cubic centimeter, etc. The weight of a component of a specific size depends on the density of the alloy.

In industries where weight matters, such as aerospace or the automotive industry, this component is crucial. Less dense alloys may be sought after by engineers who want lighter components, but they must also take the strength to weight ratio into account. If a substance with a higher density, such as steel, offers greater strength than one with a lower density, that material might be chosen. A thinner portion could be used to make up for the higher density by using less material.

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Ductility/Malleability

A material’s ductility is its capacity to stretch or bend plastically without breaking and to hold onto the new shape once the load has been removed. Imagine being able to stretch a certain metal into a wire.

In a tensile test, ductility is frequently calculated as a percentage of elongation, or the reduction in the sample’s cross-sectional area before failure. Young’s Modulus, often known as the modulus of elasticity, is a crucial stress/strain ratio that is utilized in numerous design calculations and can be obtained by a tensile test. Ductile materials are suitable for other metalworking processes, such as rolling or drawing, due to their tendency to resist cracking or breaking under stress. Metal tends to become less ductile with some additional treatments, such as cold working.

A metal’s capacity to be shaped without breaking is referred to as malleability, a physical quality. The material is rolled or pressed into thinner sheets using pressure, also known as compressive stress. High malleability materials can withstand greater pressure without cracking.

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Elasticity/Stiffness

When a distorting force is removed, a material’s ability to regain its former size and shape is referred to as its elastic property. Elastic materials will revert to their original shape when the stress is released, in contrast to materials that show plasticity (where the shape change is irreversible).

The Young’s Modulus, which contrasts the relationship between stress (the force exerted) and strain, is frequently used to assess the stiffness of a metal (the resulting deformation). The higher the modulus, the stiffer the material is since higher stress causes proportionally less deformation. Rubber is a material that exhibits low stiffness/low Modulus, whereas glass is an example of a stiff/high Modulus material. For applications where stiffness is necessary under load, this is a crucial design issue.

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Fracture/Toughness

A material’s capacity to endure shock is determined by its impact resistance. In general, the impact effect of a collision that takes place quickly is greater than the impact of a lesser force applied gradually.

Therefore, when the application involves a high danger of impact, impact resistance should be taken into account. While some metals may function satisfactorily under static stresses, dynamic loads or collisions cause them to fail. In the lab, the Charpy test, which involves striking a sample with a weighted pendulum on the other side of a machined V-notch, is frequently used to gauge impact.

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Hardness

A material’s capacity to withstand being permanently indented is referred to as its hardness (that is plastic deformation). Usually, a material’s ability to withstand wear or deformation increases with its hardness. Thus, the term “hardness” can also refer to a material’s local surface stiffness or its resistance to cutting, scratching, or abrasion.

Brinell, Rockwell, and Vicker’s methods for measuring hardness measure the area and depth of depression made by a harder material, such as a steel ball, diamond, or another indenter.

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Plasticity

The opposite of elasticity, plasticity, refers to a material’s propensity to maintain its altered shape when subjected to forming forces. It is the property that makes it possible to manipulate materials into a permanent new shape. At the yield point, a material’s behavior changes from elastic to plastic.

Strength, Fatigue

Under repetitive or fluctuating loads (such as loading or unloading) with a maximum value lower than the material’s tensile strength, fatigue can result in fracture. There is a correlation between stress and cycles to failure, with higher stresses accelerating time to failure and vice versa. Therefore, the term “fatigue limit” refers to the maximum stress that the metal (the variable) can withstand during a specified number of cycles.

The fatigue life measure, on the other hand, fixes the load and counts the number of load cycles a material can withstand before failing. When designing components that will be subject to recurrent load conditions, fatigue strength is a crucial factor to take into account.

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Strength – Shear

In applications like bolts or beams, where both the direction and the amplitude of the stress are crucial, shear strength is a factor. When directional forces cause the granular level of the metal’s internal structure to slide against itself, shearing occurs.

Strength Tensile

Tensile, or ultimate, strength is one of the most popular measures for metal properties. The amount of load that a metal segment can withstand before breaking is referred to as tensile strength. Through the region of elastic deformation, the metal will elongate during laboratory testing before returning to its original shape.

It remains the stretched shape even after the load has been removed when it reaches the point of permanent or plastic deformation (measured as Yield). The load ultimately causes the metal to fracture at the tensile point. This measurement assists in differentiating between brittle and more ductile materials. Mega Pascals (MPa) or pounds per square inch are units used to express tensile or ultimate tensile strength.

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Strength, Yield

Yield Strength describes the point at which the material under load will no longer return to its original position or shape. It is similar in concept and measurement to Tensile Strength. Plastic deformation follows elastic deformation.

To comprehend the limitations of dimensional integrity under stress, design calculations include the Yield Point. Similar to tensile strength, yield strength is expressed in pounds per square inch or Newtons per square millimeter (MPa).

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Toughness

Toughness, determined by the Charpy impact test and comparable to Impact Resistance, measures a material’s capacity to withstand impact without breaking at a specific temperature. Materials may become more brittle at low temperatures because impact resistance is frequently weaker during this time.

Where the possibility of low temperatures exists in the application (such as offshore oil platforms, oil pipelines, etc.), or where instantaneous loading is a factor, Charpy values are frequently mandated in ferrous alloys (e.g. ballistic containment in military or aircraft applications).

Wear Resistance

A material’s capacity to endure the impact of two materials rubbing against one another is referred to as wear resistance. These include adhesion, abrasion, scratching, gouging, galling, and other forms of tearing.

When the materials have varying hardnesses, the softer metal may exhibit the consequences first, and design decisions may be made to address this. Due to the presence of foreign materials, even rolling can result in abrasion. The quantity of mass lost for a specific number of abrasion cycles at a specific load can be used to quantify wear resistance.

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Other mechanical properties of materials

The followings are some other mechanical properties of materials:

  • Brittleness
  • Bulk modulus
  • Coefficient of restitution
  • Compressive strength
  • Creep
  • Durability
  • Fatigue limit
  • Flexibility
  • Flexural modulus
  • Flexural strength
  • Friction Coefficient
  • Mass diffusivity
  • Poison’s ratio
  • Resilience
  • Slip
  • Specific modulus
  • Specific strength
  • Surface roughness
  • Tensile strength
  • Viscosity
  • Young’s modules

Electrical properties

  • Capacitance
  • Dielectric constant
  • Dielectric strength
  • Electrical resistivity and conductivity
  • Electric susceptibility
  • Electrocaloric coefficient
  • Electrostriction
  • Magnetoelectric polarizability
  • Nernst coefficient (thermoelectric effect)
  • Permittivity
  • Piezoelectric constants
  • Pyroelectricity
  • Seebeck coefficient

 

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Magnetic properties

  • Curie temperature
  • Diamagnetism
  • Hall coefficient
  • Hysteresis
  • Magnetostriction
  • Magnetocaloric coefficient
  • Magnetothermoelectric power (magneto-Seebeck effect coefficient)
  • Magnetoresistance
  • Permeability
  • Piezomagnetism
  • Pyromagnetic coefficient
  • Spin Hall effect

Acoustic Properties

  • Acoustical absorption
  • Speed of sound
  • Sound reflection
  • Sound transfer
  • Third order elasticity (Acoustoelastic effect)

 

Thermal properties

  • Binary phase diagram
  • Boiling point
  • Coefficient of thermal expansion
  • Critical temperature
  • Curie point
  • Ductile-to-brittle transition temperature
  • Emissivity
  • Eutectic point
  • Flammability
  • Flash point
  • Glass transition temperature
  • Heat of vaporization
  • Inversion temperature
  • Melting point
  • Thermal conductivity
  • Thermal diffusivity
  • Thermal expansion
  • Triple point
  • Vapor pressure
  • Specific heat capacity

 

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Chemical properties

  • Corrosion resistance
  • Hygroscopy
  • pH
  • Reactivity
  • Specific internal surface area
  • Surface energy
  • Surface tension

 

Atomic properties

  • Atomic mass
  • Atomic number
  • Atomic weight

Optical properties

  • Absorbance: How strongly a chemical attenuates light
  • Birefringence
  • Color
  • Electro-optic effect
  • Luminosity
  • Optical activity
  • Photoelasticity
  • Photosensitivity
  • Reflectivity
  • Refractive index
  • Scattering
  • Transmittance

 

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Manufacturing properties

  • Castability – can the material easily undergo casting.
  • Machinability rating
  • Machining speed and feeds

Radiological properties

  • Neutron cross-section
  • Specific activity
  • Half life

In summary

In any production design, considering the mechanical properties of the material is very essential. As you can from the above listed, there are vast properties that can be obtained from materials. However, the most common properties are classified as physical, chemical and mechanical properties.

That is all for this article, where the common types of mechanical properties of materials are being discussed. I hope you get a lot from the reading, if so, kindly share with others. Thanks for reading, see you around!