Unit 4 - Common Specialist Technical Principles

Static Load

• Effect of gravity on a structure (weight)
• Doesn't move or change

Dynamic Load

• Any load on a structure that is not caused by gravity
• Does move and change

Tension

• Occurs when a pulling force is applied on both ends
• Example: rope in a tug-of-war

Compression

• Occurs when a pushing force is applied on both ends
• Example: spring in a suspension system

Bending

• Occurs when there's tension and compression applied to either side of an object's natural axis
• Example: two people on a seesaw

Torsion

• Occurs when an object is twisted
• Example: wringing out a wet towel

Shear Force

• A force acting on an object in a direction perpendicular to its length
• Example: wind pushing against a tree
-------------------- AND --------------------
• Occurs when one part of the material's surface is pushed in one direction, while another part of the surface is pushed in the opposite direction
• Example: scissors cutting paper

Tensile Strength

A measure of how much stress from tension a material can withstand before being pulled apart

Torsional Strength

A measure of how much stress from torsion a material can withstand before being twisted out of shape

Compressive Strength

A measure of how much a material can be compressed before breaking

Stiffness

A measure of how much a material can be bent before being bent out of shape

How could you determine whether a material needs strengthening for the manufacture of a particular product, and the amount of strengthening that might be required?

Consideration of dynamic and, if applicable, static forces and stresses can show if strengthening is required and how much

What is reinforcing?

A way of strengthening a material or object by adding material to improve its ability to withstand force and stress

What is webbing?

• When a strong fabric is woven into strips from yarns
• Often made from synthetic material such as nylon or polyester
• Very light, strong and flexible

What is laminating?

Bonding two or more materials to improve strength, stability, aesthetics or flexibility

What is fabric interfacing?

Used in textiles as an additional layer in specific areas where extra structure, shape or support is needed

What is the advantage of layering materials?

It absorbs the impact of dynamic forces

What are the advantages of corrugated cardboard?

• Good compressive strength
• Good insulator

What are the advantages of a concertina shape?

• Rigid
• Bendable while keeping structure
• Strong against force from air

What can springs be used for?

Resisting compressive force

What are the advantages of carbon fibre?

• Flexible and light
• Adding epoxy resin makes it rigid and stiff

What is the advantage of using a triangular shape?

Compressive resistance

What is the advantage of using a curved structure

Increased strength with decreased mass

What are composite materials?

Permanent mixture of two or more materials

What is deforestation and its effects?

• Clearing trees from a wide area
• Loss of habitat
• Reduced ability to absorb CO2

What is mining and its effects?

• Extracting raw materials from the ground
• Loss of habitat and scars the landscape

What is drilling and its effects?

• Extracting raw materials from deep under Earth's surface
• Risk of spills into waterways

What is farming and its effects?

• Growing crops or raising livestock
• Use of agrochemicals pollutes waterways

What is fracking and its effects?

• Release of gas from shale rock
• Risk of contaminating waterways
• Unknown long-term consequences

What is carbon footprint?

the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event

What is ecological footprint?

The amount of land necessary to produce and maintain enough food, water, shelter, energy, and waste

What is social footprint?

A company's impact on wellbeing of people, society and communities belonging to its ecosystem

What are the six Rs in order of sustainability?

Refuse, Rethink, Reduce, Reuse, Repair, Recycle

What does 'refuse' mean in the six Rs?

Don't use a process or product if it isn't really necessary

What does 'rethink' mean in the six Rs?

Revise the way a system or product functions

What does 'reduce' mean in the six Rs?

• Buy, use and throw away less
• Redesign products to use less materials

What does 'reuse' mean in the six Rs?

Use again, repurpose or modify something to avoid disposal

What does 'repair' mean in the six Rs?

• Replace parts instead of buying a new product
• Design products with fixability in mind

What does 'recycle' mean in the six Rs?

reprocess materials to be used again

What is primary recycling?

reusing without modification

What is secondary recycling?

modifying a product for a different purpose

What is tertiary recycling?

reprocessing materials to produce a new product

What is planned obsolescence?

The strategy of deliberately designing products to fail in order to shorten the time between purchases

What is one-off production?

one unit is produced to meet specific needs

What is batch production?

a number of similar items are produced in a set or group

What is mass production?

making large quantities of a product quickly and cheaply

What is lead time?

the time between the initiation and completion of a production process.

What is continuous production?

Manufacturing of identical high demand products, 24 hours a day

Evaluate one-off production

• Very High unit cost
• Very Low setup cost
• Very High flexibility
• Almost always handmade therefore requires highly skilled workers
• Long lead time

Evaluate batch production

• High unit cost
• Low setup cost
• High flexibility
• Can be handmade so highly-skilled workers may be required
• Very long lead time

Evaluate mass production

• Low unit cost
• High setup cost
• Low flexibility
• Mostly automated so most workers are low-skilled
• Short lead time

How do greenhouse gases affect the process of warming the Earth?

1. Solar radiation penetrates atmosphere and some is reflected away
2. Some radiation is absorbed into the surface that keeps the planet at a suitable temperature
3. Infrared radiation is reflected away and escapes the atmosphere
4. Greenhouse gases block infrared so thermal energy is reflected back to the Earth and warms it a second time

Evaluate continuous production

• Very Low unit cost
• Very High setup cost
• Very Low flexibility
• Almost completely automated so nearly all workers low-skilled
• Very Short lead time