Thermal Stress and Material Properties

This video tutorial covers the concepts of thermal stress and strain, focusing on three problems. The first problem involves calculating the compressive force on a steel rod as temperature increases. The second problem examines the thermal stress on an aluminum bar when the temperature decreases. The final problem determines the maximum temperature a concrete block can withstand without fracturing. Key equations and concepts such as elastic modulus, coefficient of linear expansion, and thermal stress calculations are discussed.

What happens to a steel rod placed between two fixed supports when the temperature increases?

• It melts.

• It remains the same length.

• It expands but is prevented from doing so by the supports.

• It contracts.

Which formula represents the relationship between stress, strain, and Young's modulus?

• Strain = Stress / Young's modulus

• Stress = Strain / Young's modulus

• Young's modulus = Stress / Strain

• Young's modulus = Strain / Stress

How is the area of a circular rod calculated?

• πd

• 2πr^2

• πr^2

• 2πr

What is the compressive force exerted by the supports on the steel rod when the temperature increases from 15°C to 40°C?

• 1.88 x 10^6 N

• 2.00 x 10^6 N

• 1.50 x 10^6 N

• 2.50 x 10^6 N

What type of force is exerted on an aluminum bar when the temperature decreases?

• No force

• Shear force

• Tensile force

• Compressive force

How is thermal stress calculated for a material?

• Thermal stress = Coefficient of linear expansion x Temperature change

• Thermal stress = Area x Temperature change

• Thermal stress = Elastic modulus x Coefficient of linear expansion x Temperature change

• Thermal stress = Elastic modulus x Area

What is the thermal strain in the aluminum bar when the temperature changes?

• 5 x 10^-4

• 7 x 10^-4

• 3 x 10^-4

• 1 x 10^-4

What is the ultimate compressive strength of concrete?

• 40 x 10^6 N/m^2

• 30 x 10^6 N/m^2

• 20 x 10^6 N/m^2

• 10 x 10^6 N/m^2

What is the maximum temperature a concrete block can withstand without fracturing if the initial temperature is 20°C?

• 83.3°C

• 113.3°C

• 93.3°C

• 103.3°C

What happens to the thermal stress in concrete if the temperature exceeds its ultimate compressive strength?

• It remains constant.

• It decreases.

• It causes the concrete to fracture.

• It causes the concrete to expand.