Steel Properties and Applications Quiz

Which property of steel makes it suitable for bridge construction?

• High thermal conductivity

• High tensile strength

• Low density

• High electrical resistance

Answer explanation

Steel's high tensile strength allows it to withstand heavy loads and resist deformation, making it ideal for bridge construction. Other properties like thermal conductivity and density are less relevant for this application.

Explain why mild steel is commonly used in structural applications.

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Answer explanation

Mild steel is favored in structural applications due to its excellent strength-to-weight ratio, ductility, and weldability, making it ideal for construction and manufacturing where durability and flexibility are essential.

A steel rod with a cross-sectional area of 50 mm² is subjected to a tensile force of 50 kN. Determine the tensile stress in the rod.

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Answer explanation

Tensile stress is calculated using the formula: stress = force / area. Here, stress = 50,000 N / 50 mm² = 1,000,000 N/m² or 1 MPa. Thus, the tensile stress in the rod is 1 MPa.

Compare the mechanical properties of mild steel and stainless steel and discuss how their properties influence their applications.

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Answer explanation

Mild steel is ductile and malleable, making it ideal for construction. Stainless steel is corrosion-resistant and strong, suitable for medical and food applications. Their properties dictate their use in various industries.

The graph below shows a stress-strain curve for mild steel. Identify the key points and explain what happens at each stage.

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Answer explanation

The stress-strain curve for mild steel has key points: 1) Proportional limit - linear relationship; 2) Yield point - permanent deformation begins; 3) Ultimate tensile strength - maximum stress; 4) Fracture - material breaks.

Explain why mild steel is used in reinforced concrete structures, while high-strength alloy steel is used in aircraft landing gear.

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Answer explanation

Mild steel is ductile and cost-effective, making it ideal for reinforced concrete structures that require flexibility and strength. High-strength alloy steel, being lightweight and strong, is essential for the demanding conditions of aircraft landing gear.

A steel cable in a bridge has a diameter of 50 mm and carries a load of 200 kN. Calculate the stress in the cable.

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Answer explanation

Stress is calculated using the formula: Stress = Load / Area. The area of the cable is π*(d/2)² = π*(25 mm)². Convert to meters and calculate: Stress = 200 kN / (π*(0.025 m)²) = 101.32 MPa.

Compare the use of steel in civil and aeronautical engineering, discussing the key properties required for each application.

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Answer explanation

In civil engineering, steel's strength and durability are crucial for structures. In aeronautical engineering, lightweight and high strength-to-weight ratio are essential for performance and fuel efficiency.

Why is aluminium used instead of steel for aircraft fuselages?

• Aluminium is stronger than steel.

• Aluminium is cheaper than steel.

• Aluminium has a lower density, reducing weight.

• Aluminium has better fatigue resistance than steel.

Answer explanation

Aluminium is preferred for aircraft fuselages because it has a lower density than steel, which significantly reduces the overall weight of the aircraft, enhancing fuel efficiency and performance.