UNIVERSITI KUALA LUMPUR

MALAYSIAN INSTITUTE OF AVIATION TECHNOLOGY

PHYSICS AND AERODYNAMICS 1 ( AAB20103 )

ASSIGNMENT MECHANICAL PROPERTIES

1BME 2

NATASHA NABILA BINTI RANI

53259313224

MDM SHARIFAH FATHIN ADLINA

Choose 5 out of 8 of the mechanical properties. Define the term, give formula related, give example related to an aircraft and give reason why it is important to the aircraft.

HARDNESS

DEFINITION

Hardness refers to the ability of a material to resist abrasion, penetration, cutting action, or permanent distortion. It can withstand shape change, scratches and wear.

FORMULA

Measure the size of an indentation made by some indenter under a known load and the depth to which an indenter penetrates under specified conditions.

Example formula using Microhardness Test

KHN = F/A = P/CL2

F = applied load in kgf

A = the unrecovered projected area of the indentation in mm2

L = measured length of long diagonal of indentation in mm

C = 0.07028 = Constant of indenter relating projected area of the indentation to the

square of the length of the long diagonal.

EXAMPLE

piston engine case for small aircraft

REASON

It can resist stress without breaking. Engine is high pressure part, thus it have to withstand stress on it by using material that have hardness properties.

MALLEABILITY

DEFINITION

Malleability refers to the ability of a material which can be hammered, rolled, or pressed into various shapes without cracking, breaking, or leaving some other detrimental effect.

FORMULA

Tensile Stress Formula

EXAMPLE

Turbine engine cowling

REASON

This property is necessary in sheet metal use on aircraft because it can be worked into curved shapes without give any damage to it.

TOUGHNESS

DEFINITION

Toughness refers to the ability of a material which can withstand tearing or shearing and may be stretched or otherwise deformed without breaking or cracking.

FORMULA

Young Modulus Formula

F = applied axial force

lo = original length

A = area of cross-section

Δ l = change in length

E = modulus of elasticity

EXAMPLE

Carbon brake

REASON

aircraft requires far tougher material and offer much higher performance. Toughness is a desirable property in aircraft metals.

DUCTILITY

DEFINITION

Ductility refers to the ability of a material which permits it to be permanently drawn, bent, or twisted into various shapes without breaking.

FORMULA

Strain Formula

x = Change in dimension,

L = Original dimension.

Percent Elongation =  Final length (in) - Initial Length (in)   x 100Initial Length (in)

EXAMPLE

Skin, ribs and spar on aircraft wing

REASON

This property is essential for metals used in making wire and tubing. Ductile metals are greatly preferred for aircraft use because of their ease of forming and resistance to failure under shock loads.

CONDUCTIVITY

DEFINITION

Conductivity refers to the ability of a material which enables a metal to carry heat or electricity.

FORMULA

Thermal Conductivity Formula

λ = Q × L / (A × ΔT)

λ is thermal conductivity

Q is quantity of heat

L is distance

A is surface of a unit area

ΔT is a unit temperature gradient

EXAMPLE

Strut for kit landing gear

REASON

The heat conductivity of a metal is especially important in welding because it governs the amount of heat that will be required for proper fusion. Conductivity of the metal, to a certain extent, determines the type of jig to be used to control expansion and contraction. In aircraft, electrical conductivity must also be considered in conjunction with bonding, to eliminate radio interference.