Core Content

Engineering design process (IDPE)

Investigating

develop a comprehensive design brief
- Client gives you description of what they want. This goes in the design briief.
identify and assess existing solutions or similar products that are identified using a variety of research skills
research and critique materials and components relevant to the design brief
consider different and appropriate sources of energy

Devising

produce annotated pictorial drawings of design ideas
produce annotated orthographic drawings of design ideas
analyse and justify the choice of option to be used as the solution

Producing

present specifications for the selected solution
- dimensioned pictorial and orthographic drawings
- orthographic drawings and sketches as 3rd angle projections and include the following;
  - lines – outlines, hidden detail and centerlines
  - dimensioning – linear, radii, circles, holes through or partial depth with flat base
- list and/or descriptions of selected materials with justification of choices
- parts lists
- costing of prototype or working model
- develop and use a timeline for construction and testing of solution
- construct solutions by selecting and using appropriate tools and machines and by following safe work
- test the solution for correct function and document using checklists and test data

Evaluating

evaluate the final solution in terms of:
- meeting the requirements of the design brief
- safety, function and finish of product
- modifications and changes to the design and processes during production
- refinements and changes for future development

Materials

Define Types of Materials
- Metals (pure)
- Alloys
  - Ferrous
  - Non-Ferrous
- Polymer
define physical properties of materials
- density
- Elasticity
- Plasticity
- Strength
  - Tensile Strength
  - Compressive Strength
- Stiffness
- Toughness - ✓Absorb Energy 𐄂 Fracture
- Ductility - ⇮Plastic Deformation 𐄂 Fracture
  - Brittleness - ⯯Plastic Deformation ✓Fracture
- Malleability
- Conductivity
  - Electrical Conductivity
  - Thermal Conductivity
- corrosion resistance
fitness for purpose
- identify and justify the required properties of a material for a specified application

Fundamental engineering calculations

Volume

cubes, rectangular right prisms and triangular right prisms
cylinders
- $V=\pi r$
spheres
- $V=\frac{4}{3} \pi r^3$
  Density
$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$
$\text{measured in }kg/m^-3$
Quantity estimates
determine volume, mass and density of geometric forms
- individual or simple combinations
- hollow or solid

Energy

$E = Pt$
1 joule = 1 watt × 1 second
1 kW h = 1000 watts × 1 hour

Efficiency

calculate efficiency as a percentage = $\frac{output}{input} \times 100$

Unfamiliar formula

determine an unknown factor in unfamiliar formula given sufficient data to complete the calculation

Engineering in society

Life cycle analysis of engineered products

the stages of the Life Cycle
- materials acquisition
- processing materials
- manufacture
- packaging
- transport
- maintenance/operation
- reuse/recycle/disposal
impacts for society, business and the environment that occur during the life cycle of engineered products

Specialist Field - Mechanical

Materials

define Factor of Safety (FS) as the ratio of Ultimate Failure Stress to safe working stress
use the formula to determine one unknown variable
- $\text{Factor of Safety (FS)}= \frac{\sigma_{LTS}}{\sigma_\text{safeworking}}$

Statics

calculate second moment of area for material cross-sections
- vertical rectangular solid section $I_{XX}=\frac{bh^3}{12}$
- round solid section $I_{xx}=\frac{\pi D^4}{64}$
- circular tube section $I_{xx}=\frac{\pi(D^4_{o})-D_{i}^4}{64}$

Deflection of beams

calculate one unknown variable using one of the four beam deflection formulae
deflection scenarios, when solving for ‘ $y$ ’, are to be calculated in isolation and a maximum of two load scenarios in total may be combined to give the final deflection sum

Addendum 1

Second moment of area (Ixx) values for differing beam cross-sections beyond the three specified under the ‘Second moment of area’ heading can be directly provided for use in deflection calculations.

Addendum 2

Maximum bending moment calculations are only to be dealt with in the context of bending moment diagram problems – not in deflection questions.

cantilevered beam with a single load at its unsupported end $y=\frac{FL^3}{3EI_{xx}}$
cantilevered beam with a universally distributed load along the whole length of the beam (can be self-weight of beam) $y=\frac{F_{UDL}L^3}{8EI_{xx}}$
centrally loaded beam simply supported at both ends $\frac{FL^3}{48EI_{xx}}$
universally loaded beam, simply supported at both ends. The UDL is spread along the whole length of the beam (can be self-weight of beam) $y=\frac{5F_{UDL}L^3}{384EI_{xx}}$

Method of Sections

use the $\Sigma CWM = \Sigma ACWM$ formula to determine the reaction forces at the supports of horizontal, simply supported pin-jointed trusses, where all external forces are vertical

This wants more than just Warren Trusses.

calculate the forces in no more than three members in a simple pin-jointed truss by using the method of sections. Sectioning lines shall remain straight whilst crossing the maximum three members. The moment arm, not the force, shall be the variable requiring trigonometry in determining any particular moment required. All external forces are to be vertical only.

So we are suppsoed to think in terms of the moment arm, not the force.

Dynamics

Syllabus PDF

Apply the formulae to find one unknown variable in constant acceleration, straight line motion.
- $F = ma$
- $a=\frac{v-u}{t}$
- $v^2=u^2+2as$
- $s=ut+\frac{1}{2}at^2 \quad \text{ (not Quadratic)}$
Define Potential Energy as energy of position or state
Define Kinetic Energy as energy of motion
Solve problems involving energy and energy conversion using;
- $E_p=mgh$
- $E_k=\frac{1}{2}mv^2$
- $\Delta E_p= \Delta E_k$
Apply the formula for Work to find one unknown variable
- $W=Fs$
Define Efficiency ( $\eta$ ) and apply the formula to find one unknown variable
- $\eta \% = \frac{\text{Work done in moving load}}{\text{Work done by the effort}} \times 100$
Apply the Power formula to find one unknown variable
- $P=\frac{Fs}{t}$

Mechanics

Syllabus PDF

Types of Motion

Linear, Rotary, Oscillating and reciprocating
Transformation
- Identify and describe examples
  - Rotary $->$ Linear
  - Rotary $->$ Reciprocating
  - Rotary $->$ Oscillating

Mechanical Drive Systems

Recognise and describe general characteristics and applications for:
- Pulley belt
- Chain and sprocket
- Spur gear drive
- Compound gear drive
- Worm and worm wheel
- Rack and pinion

Calculations

Velocity Ratio = $\frac{\text{Distance moved by effort}}{\text{Distance moved by load}}$
Mechanical Advantage = $\frac{Load}{Effort}$
Pulley belt ratio = $\frac{\text{ØFollower Pulley}}{\text{ØDriver Pulley}}$ = Input Revolutions : 1 Output Revolution
Chain and sprocket ratio = $\frac{n\degree \text{ teeth follower gear}}{n\degree \text{ teeth driver gear}}$ = Input Revolutions : 1 Output Revolution
Gear Ratio = $\frac{n\degree \text{ teeth follower gear}}{n\degree \text{ teeth driver gear}}$ = Input revolutions : 1 output revolution
- Pinion Gear
- Idler Gear
- Pitch
Compound Gear Drive Ratio = $\prod_{i=1}^T VR_i$ = Input revolutions : 1 output revolution
- same thing as $VR_T=VR_1 \times VR_2 \times VR_3 ...$
Worm and worm wheel ratio = $\frac{n\degree \text{Teeth Follower gear}}{1}$ = Input revolutions : 1 output revolution
Rack and Pinion
- Distance Moved = $\frac{n\degree \text{ teeth pinion} \times n\degree \text{revolutions}}{n\degree \text{ teeth per metre of rack}}$
Speed / Velocity
- velocity ( $v$ ) = $\frac{\text{Distance}}{\text{time}}$ = $\frac{(\text{rpm})(2\pi r)}{60}$
- Output Speed (rpm) = $\frac{\text{Input speed} (\text{rpm})}{\text{gear or pulley ratio}}$

Quantities

Quantity	Unit name	Symbol
Speed/velocity (v)	Metre per second	$m/s^{-1}$
Distance	Metre	m
Time (t)	Second	s