Week 1 - Basic Engineering Principles

What are the 4 main points in developing a model

.Define the question and system boundary

.Sketch the system; identifying loads, flows and materials

.Choose relevant conservation laws and constitutive relationships

.State assumptions

What changes when matter flows?

.Fluid deforms continuously under applied shear stress

.Density and viscosity influence fluid behaviour

.Mass and mechanical energy constrain fluid motion

What’s the density of water

1000 kg/m³

What is the equation for hydrostatic gauge pressure at a certain depth in a stationary fluid?

pg = ρ*g*h

gauge pressure (Pa) = density (kg/m³) x gravity (9.81m/s²) x height (m)

What is the equation for hydrostatic pressure for a stationary fluid of uniform density?

p = p0 + ρ*g*h

Hydrostatic pressure (Pa or N/m²) = pressure at fluid surface ( atmospheric pressure) (Pa) + density (kg/m³) x gravity (9.81 m/s²) x height (m)

What’s the equation for steady mass flow rate?

ṁ = ρ*A*V

steady mass flow rate(kg/s) = density (kg/m³) X cross sectional area (m²) X velocity (m/s)

What’s the incompressible steady flow equation

A1 V1 = A2 V2 = A3 V3

what is the equation for steady, incompressible inviscid flow along a streamline:

p + ½ ρ V² + ρ g z = constant

Pressure (Pa or N/m²) + ½ x Density (kg/m³) x Velocity (m/s)² + Density (kg/m³) x Gravity(9.81m/s²) x Elevation (m) = constant

pressure + kinetic + elevation = constant

What is force

Push or pull with magnitude and direction

What is Force resolved into cartesian components?

Fx = F cos θ; Fy = F sin θ

What is a moment (M)?

Turning effect about a point

What is the equation for moments

M = F * d⊥

Moments (N⋅m) = Force (N) * perpendicular distance (m)

What are some rules when drawing a free body diagram?

• Choose and isolate the body

• Replace supports with appropriate reaction forces/moments

• Show all external loads, dimensions and coordinate axes

• Do not draw internal forces unless a section is cut

What is the equilibrium equation for horizontal balance?

ΣFx = 0

What’s the equilibrium equation for vertical balance

ΣFy = 0

What’s the equilibrium equation for rotational balance

ΣMo = 0

Why do substances perform differently?

• Composition and structure - influence material properties

• Processing - changes microstructure and therefore performance

• Materials - selected against loads, environment, cost and life cycle

What are the broad classes of engineering materials

Metals - strong, ductile, good conductors

Ceramics - often hard, heat resistant, brittle

Polymers - Light, corrosion resistant, temperature sensitive

Composites

What’s the equation for normal engineering stress

σ = F / A₀

Nominal stress (Pa) = Force (N) / Cross sectional area (m²)

What’s the equation for engineering strain?

ε = Δ L / L₀

Strain = change in length(m) / original length(m)

What is the equation for stress when in the linear elastic region:

σ = E * ε

Stress (Pa or N/m²) = Youngs Modulus (Pa or N/m²) * Strain