Each product starts with an idea, but in order to implement it, there are countless stages that we have to go through.

One of the first steps is the choice of material from which we want to make a given item. Often, when thinking about a product, we already know at the idea stage what it will be made of, whether it will be some kind of metal or maybe a plastic. The material we use depends on the following factors:

• product strength
• amount of workpiece
• cost
• dimension
• form complexity
• production possibilities

If our product is composed of several different elements that have different functions (housing, mechanism, connecting element), then often in one product we include several different parts made of different engineering materials that have the features necessary to perform a given function.

In this article, we want to show you the basic materials from which we make various types of products, what are the characteristics of a given material and how they can be useful in one of your products. In addition, we will describe a few rules on how to choose the right material.

Let's start with something obvious, which is what an engineering material actually is. This is what we call condensed (solid) substances whose properties make them useful to humans because complex products of work are made of them. The most common materials used in the industry are described below.

BASIC ENGINEERING MATERIALS? LET'S START WITH METALS

Source: http://hart-metale.pl/

Metals are substances that in a condensed state are characterized by the presence of free electrons not associated with any atoms, which are able to move in the entire capacitance of the metal. We include the majority of chemical elements and their alloys as metals. Metals are solid at room temperature (except for mercury, which is a liquid under these conditions)

The most important metal from a technological point of view is iron- Fe, which is the most important component of steel. The other technically important metals are called non-ferrous metals. Metals with a density lower than 4.5 g*cm3 are classified as light metals (magnesium, aluminum, sodium, potassium and beryllium), and those with a density greater than 4.5 g*cm3 are classified as so-called heavy metals. Among them, an important group consists of non-ferrous metals (copper, tin, lead, zinc), used for the production of various alloys and the most chemically resistant precious metals (gold, silver and platinum). The classification of metals into: ferrous metals (steel, iron, cast iron, cast steel) and non-ferrous metals (other metals) or metals that refine steel is also often used.

The most important features of metals include high values ​​of modulus of elasticity - their properties can be shaped (increased) not only by heat and mechanical treatment, but even in the smelting process - by introducing appropriate alloying additives. The characteristic feature of metals is ductility. The ductility of metals should be seen as the reason for their resistance to fatigue. Of all engineering materials, metals are the least resistant to corrosion.

CERAMICS AND GLASSES AS ENGINEERING MATERIALS

Ceramic materials are inorganic compounds of metals with nitrogen, oxygen, boron, carbon and other elements. After forming, the ceramic materials are annealed at elevated temperatures. Ceramics are made of ceramic mass, which includes:

• cooling materials (e.g. sand) that reduce shrinkage during firing and drying;
• plastic materials (e.g. kaolins, clays) that facilitate molding; fluxes, facilitating the process of binding particles.

The raw materials used in the production of ceramics can be divided into:

• basic (substances with a high content of pure carbon, such as: charcoal, soot, natural graphite);
• binding (their task is to bind a mixture of finely ground particles); additional ( are used to give the materials special properties).

The properties of ceramics are:

• high values ​​of modulus of elasticity (like metals), but they are brittle (unlike metals),
• they are generally not easy to use as engineering plastics (as opposed to metals),
• high stiffness, hardness, abrasion resistance (that's why they are used for cutting tools),
• excellent corrosion resistance.

PLASTICS AND THEIR POPULARITY AMONG ENGINEERING MATERIALS

Plastics are utility engineering materials obtained on the basis of polymers, resulting from their combination with various additives. The task of polymer additives is to modify the properties of the polymer and create a new usable material.

Plastics are currently widely used in various industries, from the automotive industry, through the mining industry, to the production of pharmaceuticals. They are increasingly used as substitutes for materials of natural origin. Nowadays, there are rarely situations where natural material cannot be replaced by the right type of plastic. This is due to the large number of plastics, which currently reaches up to seven hundred.

Source: https://www.cheminst.ca/magazine/article/green-chemistry-brings-its-virtues-to-the-classroom/

The basic properties of plastics include:

• ease of forming products with complex shapes in the final form,
• quite high, and often even very high chemical resistance,
• good mechanical properties and also often very good electrical properties
• low density and most often associated with a very favorable ratio of mechanical strength to density
• the ability to easily obtain products with an aesthetic appearance
• possibility of dyeing and obtaining transparent products.

Another advantage of plastics is the possibility of using them in various forms. They can be used as coating materials, engineering plastics, adhesives and putties, synthetic fibers, binders. However, the most important direction in the use of plastics is their use as construction materials, for the production of elements of devices and machines as well as everyday objects. Of course, plastics also have disadvantages that limit their use. Compared to metals, they are characterized by lower mechanical strength and lower hardness, and also flow under a much lower load (creep process) and have mostly low heat resistance.

COMBINATION OF ENGINEERING MATERIALS - COMPOSITES

A composite is a material that is made by combining two or more materials. One of them is binding, while the others play a reinforcing role and are introduced in a fibrous, granular or layered form. As a result of this process, a combination of properties (usually mechanical properties) is obtained that is impossible to achieve in the starting materials. A valuable property of composites is the ability to plan their structure in order to obtain the assumed properties. As a result, composites are widely used in modern technology and their further dynamic development is expected.

Composites consist of a matrix and a second component with much higher strength properties or increased hardness, called reinforcement, located in it.

Purpose of composites:

• construction (easy to assemble, low weight, corrosion resistance, maintenance-free and easy to maintain),
• household goods (insulation, dimensional stability, temperature resistance),
• aviation (stiffness, mechanical strength, low weight).

Source: http://www.archidemat.com/materialy-kompozytowe-kompozyty/

DESIGN PROCES AND SELECTION OF ENGINEERING MATERIALS

The material selection process is based on the analysis of the product's functional properties. It consists in selecting from the group of all engineering materials successively a subgroup, a reduced set of materials and finally a specific material that meets the assumed criteria.

The main factors determining the selection of materials:

• General: relative cost, density;
• Mechanical properties: modulus of elasticity, strength, fracture toughness, fatigue index;
• Thermal properties: thermal conductivity, diffusivity, heat capacity, melting point, glass transition temperature, coefficient of thermal expansion, heat shock resistance, creep resistance;
• Wear: wear indicator;
• Corrosion resistance: corrosion indicator;
• Comparison of the possibility of using engineering materials in wear conditions.

The selection of engineering materials for operation in wear conditions is based on several principles:

• the material should be chemically, mechanically or thermally stable in operating conditions,
• nominal contact stresses should not exceed the limit,
• elasticity of the material,
• in conditions of abrasive wear, the hardness of the material should be higher than that of the abrasive,
• the conditions of use must be adapted to the capabilities of the material used.

Computer aided selection of engineering materials

To this day, a very important factor determining the selection of engineering materials for specific applications is the designer's experience and intuition, and even his habits. Nowadays, within the CAD (computer aided design) and CAM (computer aided manufacturing) systems, computer aided materials selection (CAMS) systems also find their due place.

CONCLUSION

Summarizing the above article, we can see that the current market of engineering materials is very large. In fact, many products can be made of a similar type of material and the deciding factor in choosing a particular type may be the price or the ease of creating a given product.

We hope that after reading this short guide on engineering materials, you will be able to start implementing your dream product with greater awareness.

Mateusz Szczerbetka
Junior Designer