- Definition of Mechanical Properties: Mechanical properties of materials are the characteristics that dictate how a material responds to mechanical forces, such as strength, toughness, and ductility.
- Strength: Material strength is the ability to withstand loads without failure or significant deformation, essential for structural applications.
- Ductility and Malleability: These properties indicate how materials deform under tensile and compressive stresses, respectively, essential for manufacturing processes.
- Creep Resistance: Creep is the gradual deformation under constant stress, critical for materials used in high-temperature environments.
- Fatigue Insights: Fatigue is the failure of a material after repeated stress applications, often starting from microscopic flaws and leading to significant damage.
To finalize the material for an engineering product or application, is it important to understand the mechanical properties of the material. The mechanical properties of a material are those which affect the mechanical strength and ability of a material to be molded in suitable shape. Some of the typical mechanical properties of a material include:
- Strength
- Toughness
- Hardness
- Hardenability
- Brittleness
- Malleability
- Ductility
- Creep and Slip
- Resilience
- Fatigue
Strength
It is the property of a material which opposes the deformation or breakdown of material in presence of external forces or load. Materials which we finalize for our engineering products, must have suitable mechanical strength to be capable to work under different mechanical forces or loads.
Toughness
It is the ability of a material to absorb the energy and gets plastically deformed without fracturing. Its numerical value is determined by the amount of energy per unit volume. Its unit is Joule/ m3. Value of toughness of a material can be determined by stress-strain characteristics of a material. For good toughness, materials should have good strength as well as ductility.
For example: brittle materials, having good strength but limited ductility are not tough enough. Conversely, materials having good ductility but low strength are also not tough enough. Therefore, to be tough, a material should be capable to withstand both high stress and strain.
Hardness
It is the ability of a material to resist to permanent shape change due to external stress. There are various measure of hardness – Scratch Hardness, Indentation Hardness and Rebound Hardness.
- Scratch Hardness
Scratch Hardness is the ability of materials to the oppose the scratches to outer surface layer due to external force. - Indentation Hardness
It is the ability of materials to oppose the dent due to punch of external hard and sharp objects. - Rebound Hardness
Rebound hardness, or dynamic hardness, measures how high a diamond-tipped hammer bounces back after being dropped from a fixed height onto the material
Hardenability
It is the ability of a material to attain the hardness by heat treatment processing. It is determined by the depth up to which the material becomes hard. The SI unit of hardenability is meter (similar to length).
Hardenability is inversely proportional to a material’s weldability, meaning materials easier to harden are typically harder to weld.
Brittleness
Brittleness describes a material’s tendency to fracture easily under stress, absorbing little energy and breaking with minimal strain. This property is the opposite of ductility and varies with temperature; for instance, some metals that are ductile at room temperature become brittle in cold conditions.
Malleability
Malleability is a property of solid materials which indicates that how easily a material gets deformed under compressive stress. Malleability is often categorized by the ability of material to be formed in the form of a thin sheet by hammering or rolling. This mechanical property is an aspect of plasticity of material. Malleability of material is temperature dependent. With rise in temperature, the malleability of material increases.
Ductility
Ductility is a property of a solid material which indicates that how easily a material gets deformed under tensile stress. Ductility is often categorized by the ability of material to get stretched into a wire by pulling or drawing. This mechanical property is also an aspect of plasticity of material and is temperature dependent. With rise in temperature, the ductility of material increases.
Creep and Slip
Creep refers to the slow, permanent deformation of a material under sustained mechanical stress, typically occurring within the yield limit from prolonged exposure. This property is exacerbated in materials exposed to high temperatures over long periods. Slip, on the other hand, is defined as the movement along a plane densely packed with atoms.
Resilience
Resilience is the ability of material to absorb the energy when it is deformed elastically by applying stress and release the energy when stress is removed. Proof resilience is defined as the maximum energy that can be absorbed without permanent deformation. The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without permanent deformation. It can be determined by integrating the stress-strain cure from zero to elastic limit. Its unit is joule/m3.
Fatigue
Fatigue is the weakening of a material due to repeated loading cycles. When cyclic loads exceed a certain threshold—yet remain below the material’s ultimate strength—microscopic cracks can form at grain boundaries. These cracks grow until they reach a critical size, causing sudden fracture. Structural design, like the presence of square holes or sharp corners, significantly influences where fatigue cracks initiate.
