What physical and mechanical properties of materials does product design depend on, and how are they defined and measured?
The physical and mechanical properties of materials (strength, hardness, toughness, ductility, malleability, elasticity, plasticity, density, conductivity, durability) and how they govern the suitability of a material for a product.
A focused answer to OCR A-Level Product Design on the physical and mechanical properties of materials: tensile and compressive strength, hardness, toughness, ductility, malleability, elasticity, plasticity, density and conductivity, with definitions, the calculation of density, and how each property governs material choice.
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What this dot point is asking
OCR wants you to define the physical and mechanical properties of materials precisely, calculate density, and explain how each property decides whether a material suits a product. Properties are the link between a material's structure and its job in a product.
Strength: tensile and compressive
Strength is measured as a stress (force per unit area), so it is independent of the size of the test piece, which lets designers compare materials directly.
Hardness, toughness and the trade-off between them
This trade-off is a favourite exam point: a product that must stay sharp needs hardness, a product that must survive being dropped needs toughness, and a designer often has to balance the two.
Ductility, malleability, elasticity and plasticity
Elastic behaviour is reversible; plastic behaviour is permanent. Most forming processes (pressing, bending, deep drawing) work by pushing a material past its elastic limit into plastic deformation so the new shape stays.
Physical properties: density, conductivity and durability
Density is the property most often calculated, because Component 01 uses it to work out a component's mass and therefore its material cost and the weight a user must carry.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20204 marksDefine toughness and define hardness, and for each name one product where that property is critical, justifying your choice.Show worked answer →
A Component 01 short-answer question. One mark for each definition and one for each justified product.
Award marks for: toughness is the ability of a material to absorb energy and resist impact or sudden shock without fracturing (it resists crack propagation); a critical product is a hard hat or a power-tool casing made from ABS, because it must survive being dropped or struck without shattering. Hardness is the ability of a material to resist scratching, indentation and surface wear; a critical product is a chisel blade or a drill bit made from high carbon (tool) steel, because the cutting edge must resist abrasion and stay sharp.
A common dropped mark is swapping the two: toughness is about impact and energy absorption, hardness is about surface wear and indentation. They often trade off, because a very hard material is frequently brittle (low toughness).
OCR 20224 marksA block of aluminium has a mass of 540 g and measures 100 mm by 50 mm by 40 mm. Calculate its density in kg per cubic metre, showing your working, and state one product application where aluminium's density makes it a good choice.Show worked answer →
A Component 01 calculation question. Marks for the volume, the substitution, the answer with units, and the application.
Convert to SI units. Volume cubic metres. Mass g kg. Density kg per cubic metre. A good application is an aircraft or bicycle component (or a drinks can), because aluminium's low density gives a high strength-to-weight ratio, saving weight while keeping useful strength.
A common dropped mark is leaving the volume in cubic centimetres or millimetres; convert lengths to metres first, or convert the final answer carefully. The accepted value for aluminium is about kg per cubic metre.
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