Engineering Materials Review

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Questions and Answers

What type of stress results from forces that tend to compress or shorten a material?

Torsion stress

Tensile stress

Compressive stress (correct)

Shearing stress

Which property of a material allows it to return to its original shape after deformation?

Conductivity

Elasticity (correct)

Plasticity

Durability

What is the primary characteristic of metals that allows them to be reshaped?

Plasticity (correct)

Elasticity

Tensile strength

Yield strength

Which of the following metals has the lowest density among those listed?

Aluminium Signup and view all the answers

What is the term for the maximum stress that can be applied to a material without causing permanent deformation?

Yield strength Signup and view all the answers

Which alloying element enhances the corrosion resistance of steel?

Chromium Signup and view all the answers

In what way does quenching affect metal?

It hardens the metal Signup and view all the answers

What is the ability of a material to absorb energy before fracturing known as?

Toughness Signup and view all the answers

What is the primary purpose of the hardening process in aluminum materials?

To increase strength Signup and view all the answers

Which of the following describes the quenching process?

Rapidly cooling the metal in water Signup and view all the answers

What does the Brinell hardness tester utilize to conduct its measurements?

A hardened spherical ball Signup and view all the answers

What are phenolic resins primarily used for in civil commercial aircraft?

Cabin furnishing due to fire resistance Signup and view all the answers

What is the effect of scratches and gouges on structural strength?

They affect structural strength and require repairs Signup and view all the answers

In which temperature range is quenching generally performed?

20 to 38 °C Signup and view all the answers

What is the main cause of structural fatigue in civil commercial aircraft?

Number of flights undertaken Signup and view all the answers

Which of the following statements about adhesives is true?

They bond surfaces and distribute stress at the bonding points Signup and view all the answers

What is delamination in multi-laminate materials?

The separation of plies within the material. Signup and view all the answers

Which method is commonly used to quickly evaluate aircraft surfaces for debonding?

Tap-testing. Signup and view all the answers

What type of radiation do X-rays and gamma rays belong to?

Electromagnetic radiation. Signup and view all the answers

Why must resin or catalyst be discarded after the shelf life is exceeded?

They may not achieve sufficient strength when cured. Signup and view all the answers

Which of the following metals is least likely to corrode?

Gold. Signup and view all the answers

Magnesium and its alloys are known for what property?

High susceptibility to corrosion. Signup and view all the answers

What is the result of chemical corrosion caused by technical acids in the airframe area?

Deterioration of structural integrity. Signup and view all the answers

Which type of corrosion occurs most commonly between adjacent components of different metals?

Electrochemical corrosion. Signup and view all the answers

Study Notes

Non-Metallic and Metallic Materials

Non-metallic materials contain no metal.
Ferrous materials include iron and its alloys.

Stress and Strain

Unit stress is the force per unit area, often measured in pounds per square inch.
Tensile stress stretches or lengthens materials.
Compressive stress compresses or shortens materials.
Shearing stress causes materials to slide over each other.
Torsion stress twists materials.

Material Properties

Elasticity refers to a material’s ability to return to its original shape after deformation.
Yield strength denotes the maximum stress without permanent deformation.
Ultimate strength is the point at which a material fractures under tension, compression, or shear.
Plasticity allows metals to be reshaped.
Conductivity is the ability to transmit heat or electricity.
Durability is the ability to withstand force over time.

Lightweight Metals in Aircraft

Key lightweight metals include aluminium (density 2.7 Kg/dm³), titanium (density 4.5 Kg/dm³), and magnesium and their alloys.

Iron and Steel Properties

Pure iron (Fe) is soft, malleable, and ductile, easily formed into shapes.
Alloying elements can improve steel's resistance to corrosion.
Carbon increases strength and hardness but reduces toughness and weldability.
Silicon acts as a hardener, and chromium enhances strength, wear, and corrosion resistance.

Steel and Hardening

Selection of high-strength alloy steel relies on high tensile-to-yield ratios.
Toughness is the ability to absorb energy through deformation.
Steels require a certain carbon content for hardening.
Quenching involves rapid cooling using water or oil, typically performed within 5 to 15 seconds depending on material thickness.

Hardening Process

Solution annealing involves heating and holding the material at a specified temperature.
Natural aging occurs at room temperature while artificial aging takes place at elevated temperatures.

Hardness Testing

Brinell hardness tester uses a hardened ball to assess surface hardness.
Rockwell hardness tester measures resistance to penetration similarly.

Aircraft Structure and Materials

Structural fatigue in commercial aircraft results from the frequency of flights.
Composite materials are used to minimize weight.
Fiberglass consists of small strands of molten silica glass woven into cloth.
Core material refers to the central element of composite assemblies.

Adhesives and Resins

Adhesives bond surfaces, distributing stress, providing moisture and corrosion resistance, and reducing the need for mechanical fasteners.
Phenolic resins offer fire resistance and low toxicity, suitable for cabin components.
Epoxy resins have good mechanical properties for external components.
Proper hardener quantity in resins is crucial for performance.

Investigation and Damage Assessment

Structure Repair Manuals (SRM) and Non Destructive Test Manuals (NTM) outline appropriate investigation methods.
Damage classification includes allowable, repairable, and non-repairable categories.
Surface impacts such as scratches and gouges compromise structural integrity and must be repaired.
Delamination refers to the separation of layers in laminate materials.

Non-Destructive Testing (NDT)

Tap-testing detects debonding or trapped water.
Radiography employs X-rays or gamma rays for material evaluation.
X-rays and gamma rays are forms of electromagnetic radiation, significant for assessing material integrity.

Corrosion and Protection

Corrosion occurs as metals revert to their natural state; noble metals resist corrosion.
Pure aluminium does not readily corrode, unlike most steel and some alloys.
Protective coatings like cadmium and zinc plating are used for less resistant metals.
Anodizing is common for aluminium alloys to enhance corrosion resistance.
Magnesium alloys are particularly prone to corrosion.

Types of Corrosion

Chemical corrosion is often caused by acids present in the atmosphere.
Electrochemical corrosion occurs between adjacent metals with varying electrochemical potentials.
Steel corrosion is identified by red rust, while iron-based alloys initially produce dark corrosion products.

Hydraulic Systems

Hydraulic systems are classified into high-pressure, medium-pressure, and low-pressure categories based on their applications.

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Description

Test your knowledge on non-metallic and ferrous materials, as well as the concepts of stress, including tensile, compressive, and shearing stress. This quiz covers key definitions and principles essential for understanding material properties in engineering.