Strength of Materials interview questions

• Stress: Stress is the internal force per unit area within a material that arises from externally applied forces. It is measured in Pascals (Pa) or N/m². Mathematically, stress (σ) = Force (F) / Area (A).
• Strain: Strain is the deformation or displacement of a material per unit length due to applied stress. It is a dimensionless quantity. Mathematically, strain (ε) = Change in Length (ΔL) / Original Length (L).

The modulus of elasticity, also known as Young's modulus (E), is a measure of the stiffness of a material. It is the ratio of stress to strain in the linear elastic region of the material's stress-strain curve. It is expressed in Pascals (Pa) or N/m². A higher modulus indicates a stiffer material

Poisson's ratio (ν) is the ratio of the lateral strain to the axial strain in a material subjected to uniaxial stress. It is a measure of the deformation in the perpendicular direction to the applied load. For most materials, Poisson's ratio ranges between 0.2 and 0.3. Mathematically, ν = - (Lateral Strain) / (Axial Strain).

• Ductile Materials: Ductile materials can undergo significant plastic deformation before failure. Examples include steel and aluminum. They typically exhibit a large amount of strain and can be drawn into wires.
• Brittle Materials: Brittle materials fracture without significant plastic deformation. Examples include glass and concrete. They fail suddenly and absorb less energy before breaking.

Yield strength is the stress at which a material begins to deform plastically. Before the yield point, the material will deform elastically and return to its original shape when the load is removed. Beyond the yield point, permanent deformation occurs. It is a critical property for designing structures to ensure they remain within the elastic region under load.

The stress-strain curve is a graphical representation of a material's mechanical properties. Key points on the curve include the proportional limit, yield point, ultimate strength, and fracture point. It provides insights into the material's behavior under different loading conditions, including its elasticity, plasticity, toughness, and ductility.

• Elastic Deformation: Temporary deformation that disappears upon the removal of the applied load. The material returns to its original shape, and the relationship between stress and strain is linear.
• Plastic Deformation: Permanent deformation that remains even after the load is removed. It occurs when the material is stressed beyond its yield strength, and the relationship between stress and strain is nonlinear.

The moment of inertia (I) is a measure of an object's resistance to bending or torsion. It depends on the geometry of the cross-section and its distribution relative to an axis. In structural engineering, it is crucial for analyzing and designing beams and other structural elements to ensure they can withstand applied loads without excessive deflection or failure.

Torsion refers to the twisting of an object due to an applied torque or rotational force. The analysis of torsion involves calculating the shear stress (τ) and angle of twist (θ) in the material. For a circular shaft, the shear stress is given by τ = T*r / J, where T is the applied torque, r is the radius, and J is the polar moment of inertia. The angle of twist is θ = TL / GJ, where L is the length of the shaft and G is the modulus of rigidity

• Bending Moment (M): The bending moment at a section of a beam is the internal moment that causes the beam to bend. It is calculated as the sum of moments about the section and is expressed in units of force times length (e.g., Nm).
• Shear Force (V): The shear force at a section of a beam is the internal force parallel to the section. It is calculated as the sum of vertical forces acting on one side of the section and is expressed in units of force (e.g., N).