ENGINEERING MATERIALS

7.1 Introduction

Imagine you are going to make a chair to sit on when having meals at the dinning table, what factors would you consider most important the structure of the chair? Would you merely consider your weight? or other as well? Which materials would you use?

Everything you use, indicating the items packaging is a form is a form of structure made from a material selected due to the correct application of its properties. You therefore need to select the right material In this chapter, you should be able to select and appropriately use engineering materials.

Do you recognise the engineering materials used in the different articles in Figure 7 1?

7:2 Engineering Materials

We use different materials to make a number of structures and components. The primary function of an engineering material is to withstand applied

loading without breaking or exhibiting excessive deflection. Exploring engineering materials used in your environment

Activity 7.1 Exploring engineering materials used in your environment

What you need: Your school or home environment, book and pen, text books and a computer or phone with an internet connection where possible.

What to do: In pairs, carry out this activity.

1. Discuss the meaning of engineering materials. Giving examples, write short notes about engineering materials.

2. Move around your school or home environment, identify and list down items made from engineering materials.
3. Make a report and present your findings to the class.

7.3 Classification of Engineering Materials

Engineering materials are classified as follows; metal, composite plastic and ceramics.

Activity 7.4 Applying correct properties of materials for making a mould

What you need: Suitable materials, measuring and marking out tools, cutting tools (hacksaw, file), modelling materials (wire, clothes peg, paper clips, (spring type), clay, working drawing and a source of heat like a stove

What to do: In pairs or individually, carry out this activity

1. Using suitable materials, tools and drawing, make a mould for making clay pavement bricks.

Procedure of making a mould:

1. Cut a jerrycan to get the material.
2. Draw a regular hexagon of side 60 mm on a separate paper.
3. Measure and mark out the two parts of the mould with the help of the hexagon you have drawn.
4. Make deep cuts on the lines to be used for bending.
5. Drill holes where they are positioned.
6. Bend the shapes of the two parts in position using heat. Check the angles of the shape using the drawing.
7. Assemble the parts and hold them using wires or clips.
8. Prepare clay to a semi-liquid state to test the mould. Put or pour the clay in the mould and allow it to set.
9. Dismantle the two parts of the mould to allow the paving brick to dry properly.

7.4 Uses of Engineering Materials

To find more about the uses of engineering materials, collect samples o products made from engineering materials in your area and classify them

Activity 7.5 Classifying samples of products made from materials from your area

What you need: Your school and home environment, exercise book and pen

What to do: In pairs or individually, carry out this activity.

1. Collect samples of products made from engineering materials from your area.

2. Observe and classify them.
3. Include at least four examples in each group.
4. Copy and complete the following table.

7.5 Sorting Materials According to their Engineering Applications

Materials can have a number of applications in life and the suitability of the material is determined by a number of factors. These include but are not limited to the function of the product, availability, cost etc

Activity 7.6 Sorting materials according to their possible engineering applications

What you need: Some products made from different materials like library book shelf, cooking stove, benches, food/drink containers, electrical insulators, water pipes, cables etc.

7.6 Using Engineering Materials to make screw driver

Activity 7.7 Making a screw driver

What you need: Selected engineering materials, marking out and measuring tools, a working drawing, cutting tools (hacksaw, file), metal former (20 mm), a ball peen hammer and a bench vice.

What to do: Individually, carry out this activity.

Use the drawing given below to make a screw driver (Figure 7 10).