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Questions and Answers
What type of stress results from forces that tend to compress or shorten a material?
Which property of a material allows it to return to its original shape after deformation?
What is the primary characteristic of metals that allows them to be reshaped?
Which of the following metals has the lowest density among those listed?
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What is the term for the maximum stress that can be applied to a material without causing permanent deformation?
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Which alloying element enhances the corrosion resistance of steel?
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In what way does quenching affect metal?
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What is the ability of a material to absorb energy before fracturing known as?
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What is the primary purpose of the hardening process in aluminum materials?
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Which of the following describes the quenching process?
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What does the Brinell hardness tester utilize to conduct its measurements?
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What are phenolic resins primarily used for in civil commercial aircraft?
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What is the effect of scratches and gouges on structural strength?
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In which temperature range is quenching generally performed?
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What is the main cause of structural fatigue in civil commercial aircraft?
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Which of the following statements about adhesives is true?
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What is delamination in multi-laminate materials?
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Which method is commonly used to quickly evaluate aircraft surfaces for debonding?
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What type of radiation do X-rays and gamma rays belong to?
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Why must resin or catalyst be discarded after the shelf life is exceeded?
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Which of the following metals is least likely to corrode?
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Magnesium and its alloys are known for what property?
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What is the result of chemical corrosion caused by technical acids in the airframe area?
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Which type of corrosion occurs most commonly between adjacent components of different metals?
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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.
