Material Science: Key Physical and Chemical Attributes

Sensory Properties

Sensory properties can be perceived through the senses:

• Surface finish and texture (tells us if the surface is rough or polished).
• Specific gravity (the weight of material per unit volume).
• Optical characteristics (such as transparency or opacity, and luminescence to an external excitation).
• Acoustic characteristics (corresponding to the sound the material makes).
• Olfactory characteristics (which are identified by their smell).

Electrical Properties

These include:

• Resistivity (the measure of a material's opposition to the passage of electric current).
• Electrical conductivity (measured by the material's permittivity to the flow of electrons).

Ecological Properties

These properties consider the environmental damage caused by both the use and procurement of the material. They also ensure that, once the product's life cycle ends, it can be recovered and recycled.

Material Composition Tests

Characteristics Tests

These analyze the material composition and internal structure. They include determining the melting and solidification temperatures of each material, and the presence or absence of a desired component using metallographic techniques.

Mechanical Properties Tests

These tests check for hardness, tensile strength, impact resistance, wear, and material fatigue. They are destructive tests because they affect the materials discussed:

• Test of Resilience: Done by measuring the energy absorbed when a pendulum strikes a calibrated portion of material that has a notch.
• Wear Test: Wear resistance is measured by rotating and rubbing two rolls of the material to be tested, calculating the weight loss caused by the work done.
• Hardness Test: Performed by observing the trace element that causes a calibration of a spherical or pointed element under pressure on the material with a given force.
• Tensile Test: Measures the ultimate strength, yield strength, elasticity, and toughness of the material. Different values are obtained by measuring increases in length when applying a specified force on a calibrated portion of the material.
• Fatigue Test: Based on different theories that assign varying importance to factors including resistance to fatigue.