Strength Of Materials MCQ Questions & Answers | Mechanical Engineering

Poisson's ratio: It is the ratio of lateral strain to longitudinal strain when a material is subjected to axial loading.

Value for cast iron: For cast iron, Poisson's ratio typically ranges between 0.23 and 0.27, depending on its composition and grade.

Reason: Cast iron exhibits brittle behavior and has a lower Poisson's ratio compared to ductile materials, which tend to have higher values. The lower range of Poisson's ratio reflects the limited lateral expansion in cast iron under axial compression or tension.

Significance: Understanding the Poisson's ratio of cast iron is crucial for analyzing its deformation characteristics and ensuring its appropriate use in engineering applications, such as engine blocks and machine parts.

Hooke's law is a fundamental principle in mechanics that states that the strain in a material is directly proportional to the applied stress, provided the material's elastic limit is not exceeded.

Limit of Proportionality: This is the point up to which Hooke's law is valid. Beyond this limit, the material will not follow the linear relationship between stress and strain, as it starts to experience non-linear deformation.

Yield Point: This is the point where the material begins to deform plastically. While Hooke's law is valid up to this point, it is specifically associated with the limit of proportionality, which is slightly before the yield point.

Breaking Point: This is the point at which the material fails and breaks. Hooke's law does not apply here as the material has surpassed its elastic limit.

Elastic Limit: This is the maximum extent to which a material can be stretched or compressed and still return to its original shape. Hooke's law is valid up to the elastic limit, but the term "limit of proportionality" is more precise for this specific context.