The first step to determining the materials and reasons for their use in an article is to take it apart. This is an important stage because it is a chance to see where components fit, and what their purposes might be.
An exploded diagram of components and where they fit in relation to the rest of the article is often extremely helpful. Once the article has been dismantled it may not be possible to reassemble it, and knowing the position of a component in the article is vital to understanding what its function might be. The exploded diagram helps to sort out what the purpose of components are, and therefore what might be required of their properties.
The diagram should be clear and well labelled, including scale bars.
Important properties to consider for each component could include:
- Mechanical properties: such as strength or toughness
- Electrical properties: conducting or insulating
- Aesthetic properties: is the component on display, and would the appearance be important?
- Corrosion resistance: the component will probably need to last for at least the lifetime of the product
- Density of component: it may be important that the article is lightweight
- Specific functions: some materials are chosen because they fulfil a specific function within the article (for example piezoelectric or ferromagnetic materials)
It is also important to consider economic factors, such as the costs of the raw materials and processing. The cost of a material can influence choice as much as its physical properties; for example diamond is an extremely hard material, but it is not widely used due to cost.
Each component will probably be reasonably easily identifiable as belonging to one of four classes of materials: