Question

i)Which of the defects that are unique to Ceramic materials? Use appropriate drawings in your responses..

ii)Give an example of an application of product development associated with strain hardening phenomeno

iii).Give an example of aircrafts part/component requiring use of high material toughness. Identify the class of materials used.

iv).Give an example of an engineering application requiring high material toughness.

Answer 1

Solution(1)

(i) Point defects : defined as deviations from the perfect atomic

(ii)  Ionic defects vacancies interstitial substitutional solutes

(iii)Electric defects – formed when valence electrons are excited into higher orbital energy levels

Crystalline defects in ionic materials Frenkel defects Schottky

Solution(2)  An example of strain hardening is that which occurs in metalworking processes that intentionally induce plastic deformation to exact a shape change. These processes are known as cold working or cold forming processes. They are characterized by shaping the workpiece at a temperature below its recrystallization temperature, usually at ambient temperature. Cold forming techniques are usually classified into four major groups: squeezing, bending, drawing, and shearing. Applications include the heading of bolts and cap screws and the finishing of cold rolled steel. In cold forming, metal is formed at high speed and high pressure using tool steel or carbide dies. The cold working of the metal increases the hardness, yield strength, and tensile strength.

Solution(3): The most common metals used in aircraft construction are aluminum, magnesium, titanium, steel, and their alloys.Wings develop the major portion of the lift of a heavier-than-air aircraft. Wing structures carry some of the heavier loads found in the aircraft structure. The particular design of a wing depends on many factors, such as the size, weight, speed, rate of climb, and use of the aircraft. The wing must be constructed so that it holds its aerodynamics shape under the extreme stresses of combat maneuvers or wing loading. Wing construction is similar in most modern aircraft. In its simplest form, the wing is a framework made up of spars and ribs and covered with metal.

Solution(4): A material that absorbs impact (sudden forces or shocks such as hammer blows) well is tough - this is the opposite to brittleness. [units for toughness are energy per unit area - Joules/m²]. The application of toughness of material is in railway tracks where it is requuired to absorb high shockd.