Answer:

Introduction:
A pressure vessel is a container designed to hold gases or liquids at a pressure higher than atmospheric pressure. It is important to ensure that the pressure vessel is securely sealed to prevent leakage of the contents. The hemispherical end of the pressure vessel is fastened to the cylindrical portion using gaskets, bolts, and lock nuts.

The Function of Bolts:
Bolts play a crucial role in connecting different parts of the pressure vessel. They provide the necessary clamping force to hold the hemispherical end and the cylindrical portion together. The bolts are tightened using lock nuts to ensure a secure connection.

Tensile Stress:
Tensile stress is a type of stress that occurs when a material is being pulled or stretched. In the case of the pressure vessel, the bolts experience tensile stress because they are subjected to a pulling force when tightening them. This pulling force helps to create the necessary clamping force between the hemispherical end and the cylindrical portion.

Importance of Tensile Stress:
Tensile stress is important in this scenario because it helps to ensure that the pressure vessel remains securely sealed. The bolts need to withstand the internal pressure exerted by the contents of the pressure vessel. Tensile stress helps to prevent any separation or leakage between the hemispherical end and the cylindrical portion, ensuring the structural integrity of the pressure vessel.

Other Types of Stress:
While tensile stress is the primary stress experienced by the bolts in this scenario, it is worth mentioning other types of stress that may also be present:

- Compressive Stress: Compressive stress occurs when a material is being pushed or compressed. In the case of the pressure vessel, the bolts may also experience compressive stress due to the clamping force applied by the lock nuts.

- Shear Stress: Shear stress occurs when a material is being subjected to a force that causes it to slide or deform along a parallel plane. While shear stress may not be the primary stress experienced by the bolts in this scenario, it can still be present due to the interaction between the gasket and the bolts.

- Bearing Stress: Bearing stress occurs when two surfaces are in contact and transmit forces. In the case of the pressure vessel, bearing stress may be present between the bolts and the hemispherical end or the cylindrical portion.

Conclusion:
In conclusion, the bolts used to fasten the hemispherical end of a pressure vessel to the cylindrical portion are subjected to tensile stress. This tensile stress helps to create the necessary clamping force and ensures the secure sealing of the pressure vessel. While other types of stress may also be present, tensile stress is the primary stress experienced by the bolts in this scenario.