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Questions and Answers
What is the definition of strain in materials?
What is the definition of strain in materials?
Which term describes the load per square inch at which a material shows a specified elongation under load?
Which term describes the load per square inch at which a material shows a specified elongation under load?
According to Hooke’s Law, what is the relationship between stress and strain?
According to Hooke’s Law, what is the relationship between stress and strain?
What is the maximum tensile load per square inch known as?
What is the maximum tensile load per square inch known as?
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Which of the following tests is used to determine hardness in materials?
Which of the following tests is used to determine hardness in materials?
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What is the primary purpose of normalizing steel?
What is the primary purpose of normalizing steel?
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What operation is involved in hardening steel?
What operation is involved in hardening steel?
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Which statement accurately describes tempering?
Which statement accurately describes tempering?
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Which method is used to add carbon to steel?
Which method is used to add carbon to steel?
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What is the purpose of case hardening?
What is the purpose of case hardening?
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What type of tubing is used specifically for fuel and oil lines?
What type of tubing is used specifically for fuel and oil lines?
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Which alloy is particularly noted for its high strength and is used in bearings and bushings subject to heavy loads?
Which alloy is particularly noted for its high strength and is used in bearings and bushings subject to heavy loads?
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Which type of bronze is used for manufacturing bolts, valve discs, and electric contacts?
Which type of bronze is used for manufacturing bolts, valve discs, and electric contacts?
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What is the primary alloying element in bronze, apart from copper?
What is the primary alloying element in bronze, apart from copper?
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What casting method uses sand to create complex shapes and is ideal for producing few required parts?
What casting method uses sand to create complex shapes and is ideal for producing few required parts?
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Which aluminum alloy casting technique utilizes a metal mold for better accuracy?
Which aluminum alloy casting technique utilizes a metal mold for better accuracy?
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Which copper alloy is specifically designed for use in contact with salt water?
Which copper alloy is specifically designed for use in contact with salt water?
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In which scenario will pure aluminum exhibit decreased resistance to atmospheric corrosion?
In which scenario will pure aluminum exhibit decreased resistance to atmospheric corrosion?
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What is the main characteristic of brazing compared to welding?
What is the main characteristic of brazing compared to welding?
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Which type of electric resistance welding method is specifically used for structural corrosion-resistant steel?
Which type of electric resistance welding method is specifically used for structural corrosion-resistant steel?
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What is a key property of thermosetting synthetic adhesives used in aircraft construction?
What is a key property of thermosetting synthetic adhesives used in aircraft construction?
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What type of corrosion is characterized by its invisibility and internal damage to metals?
What type of corrosion is characterized by its invisibility and internal damage to metals?
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What is the primary benefit of using cycle annealing compared to other processes?
What is the primary benefit of using cycle annealing compared to other processes?
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Which component gives steel its hardening qualities?
Which component gives steel its hardening qualities?
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In what welding process is a tungsten or carbon electrode used, surrounded by inert gas?
In what welding process is a tungsten or carbon electrode used, surrounded by inert gas?
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Which process is suitable for increasing ductility and toughness in small sizes of deep-hardening steels?
Which process is suitable for increasing ductility and toughness in small sizes of deep-hardening steels?
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Which welding method employs power-driven rollers as electrodes to create a continuous weld?
Which welding method employs power-driven rollers as electrodes to create a continuous weld?
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What distinguishes gas carburizing from other carburizing methods?
What distinguishes gas carburizing from other carburizing methods?
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What occurs during the process of spheroidizing?
What occurs during the process of spheroidizing?
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What is the main characteristic of annealed steel?
What is the main characteristic of annealed steel?
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Which surface hardening method is known for its speed and low cost but is rarely used in aircraft work?
Which surface hardening method is known for its speed and low cost but is rarely used in aircraft work?
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Which filler metal is commonly used in soft soldering applications to make electrical connections?
Which filler metal is commonly used in soft soldering applications to make electrical connections?
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What is a notable drawback of using nitriding in welding applications?
What is a notable drawback of using nitriding in welding applications?
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Which plating method is primarily used in aircraft construction for its corrosion resistance?
Which plating method is primarily used in aircraft construction for its corrosion resistance?
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Which structure is typically the hardest and most brittle form of steel?
Which structure is typically the hardest and most brittle form of steel?
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Which process is specifically tailored for hardening small sizes of steel parts while minimizing distortion?
Which process is specifically tailored for hardening small sizes of steel parts while minimizing distortion?
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During normalization, how does the ductility of steel change compared to annealed steel?
During normalization, how does the ductility of steel change compared to annealed steel?
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Which method is primarily used to resolve ductility in the sheet and wire industries?
Which method is primarily used to resolve ductility in the sheet and wire industries?
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Which method is utilized to improve the fatigue and abrasion resistance of metal parts?
Which method is utilized to improve the fatigue and abrasion resistance of metal parts?
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What is the purpose of refining the core in the carburizing process?
What is the purpose of refining the core in the carburizing process?
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What is the purpose of normalizing welded parts after fabrication?
What is the purpose of normalizing welded parts after fabrication?
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What is a key characteristic of ferrite in carbon steels?
What is a key characteristic of ferrite in carbon steels?
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Study Notes
Aircraft Materials and Processes
- Hardness: Resistance to penetration or permanent distortion. Increased by hammering, rolling, working. Heat treatment can also increase hardness in aluminum alloys. Annealing is a modified heat treatment that softens metals.
- Brittleness: Resistance to change in molecular position. Tendency to fracture without change of shape. Harder materials tend to be more brittle.
- Malleability: Property of metals to be bent or permanently distorted without rupture. Opposite of brittleness. Processes include bending and hammering. Products include sheet metal, bar stocks, forgings, and fabricated parts.
- Ductility: Property of metals to be drawn out without breaking. Products include wire and tubing. Process includes drawing. Ease of forming and resistance to shock loads.
- Elasticity: Property of returning to original shape when force is removed. All aircraft structural design is based on this property. Elastic limit is the point beyond which loading causes permanent distortion.
- Density: Weight of a unit volume of a material.
- Fusibility: Property of being liquefied by heat. Processes such as welding. Fuse temperature of steel is 200°F and aluminum alloys is 1100°F.
Physical-Test Terms
- Strain: Deformation of a material caused by an applied load.
- Stress: Load acting on a material.
- Tensile Strength: Ultimate tensile strength, maximum tensile load per square inch. Formula: Max load/Cross-sectional Area (PSI)
- Elastic Limit: Greatest load per square inch a material can withstand without permanent deformation.
- Proportional Limit: Load per square inch beyond which strain increase is not directly proportional to stress increase.
- Hooke's Law: Proportionality between stress and strain.
- Proof Stress: Load per square inch a material can withstand without permanent elongation more than 0.0001 inch of gage length.
- Yield Strength: Load per square inch at which a material exhibits special limiting permanent set or specified elongation under load.
- Elongation (Percentage): Difference in gage length before and after stress and rupture.
Heat Treatment Terms
- Critical Range: Temperature range between 1300°F and 1600°F where internal structure of steel is altered. Heat treatment of steel is based on this phenomenon.
- Annealing: Process of heating steel above critical range, holding until uniform, and then cooling. Relieves internal strains.
- Normalizing: Similar to annealing but cooling in still air, is faster. Relieves internal strains, and slightly softens the metal. Strength increases about 20% compared to annealing process.
- Heat Treatment: Series of operations to improve physical properties of a material.
- Hardening: Heating the metal above the critical range, then quenching in brine, water, or oil.
- Quenching: Immersing heated metal in liquid (oil or water) to accelerate cooling.
- Tempering: Reheating hardened steel to temperature below critical range, then cooled/quenched in oil or water (AKA drawing).
Testing Aircraft Materials
- Brinell Hardness Test: Pressing a hardened steel ball under known pressure into a flat surface of the specimen being tested.
- Rockwell Hardness Test: Measuring penetration of a diamond cone or hardened steel ball under definite loads. Larger difference between major and minor loads indicates lower hardness (softer material).
Steel and its Alloys
- Plain Carbon Steels: Classified by carbon percentage. Contain small amounts of silicon, sulfur, phosphorus, and manganese. Silicon and manganese are beneficial, while sulfur and phosphorus are harmful impurities.
- Carbon: Combines readily with iron to form iron carbide (cementite). Higher carbon content corresponds to higher hardness but lower ductility, malleability, toughness, and weldability. Includes low carbon steal (for deep drawing, excessive mechanical work, formed fittings, and welded parts) and high carbon steel (for great hardness).
Effect of Individual Elements (Additional elements in various steels):
- Manganese: Deoxidizes and desulfurizes steel to produce a cleaner metal improving forging qualities.
- Silicon: Acts as an excellent deoxidizer and improving steel's ductility.
- Sulfur: Undesirable impurity that causes brittleness at higher temperatures.
- Phosphorus: Undesirable impurity associated with cold shortness (brittleness at low temps).
- Nickel: White metal, malleable, ductile, weldable, increases strength, yield point, and hardness, but slows the rate of hardening. Also improves corrosion resistance in alloys.
- Chromium: Hard gray metal with high melting point, improves hardness, strength, wear resistance, and corrosion resistance (18-8 or 18% Cr., 8% Ni, non magnetic)
- Tungsten: High-speed steel; used in tools that retain cutting edge even when heated.
- Titanium: Often added to 18-8 corrosion-resisting steels for reducing embrittlement at operating temperatures of exhaust stacks or collectors.
Steel Numbering System
- Ca-Ni-Chro-Mo-Chro-CV-Tu-Na-SM: System used for categorization and identification of various steels.
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Description
Test your knowledge on the fundamental properties of aircraft materials, including hardness, brittleness, malleability, ductility, and elasticity. Understand how these properties affect the manufacturing and structural integrity of aircraft components. This quiz covers essential concepts that are vital in the aerospace industry.
