Question

Q

4 Based on your previous researched in the mechanical engineering solve this. Steel is securely tightened onto a bolt in an industrial environment. After several months, the nut is found to contain numerous cracks, even though no externally applied load acts on the nut. (1) Explain why cracking might have occurred? (2) How to prevent it? 5 An oil company has air compressor systems in their facilities. The pipeline is aluminum alloys. The technician removed the inlet air filter to increase the air pressure efficiency. After a long period of working time, the company has stopped using this system for almost two years. The company has noticed sever corrosion damage outside the pipe under rubber gaskets of pip coupling (two closely fitted parts). What type of corrosion would you think occurs in this system? What would be the reasons for this type of corrosion to take place?

Answer 1

4.

The nut is under a constant stress of holding the steel tight over a long period of time. This results in slow and progressive deformation of the material which leads to the rupture or cracks in the nut. This phenomenon is known as creep.

To avoid creep, following design considerations to be made in the nut

• Grain boundaries in material has a great impact on the creep resistance. Larger grain size leads to better resistance to creem than the finr grains. Hence, use of single crystal material with large grains will help avoid creep.
• Always refer Creep test data during material selection. Check the type of service application of the material.
• Use of optimum size of the nut and bolt should be taken to increase the strength of nut.

5.

As the filter is removed, unwanted particles have enterd the pipeline and made their way to the small gaps in the gaskets where they got stuck. The presence of these particles has led to a corrosion in that part of the pipeline.

Poultice Corrosion occurs in such conditions where there is an expoure to foreign particles which get accumulated under the rubber gaskets. When these come in contact with aluminium they become soggy and air entrapment occurs. This is the reason why oxygen occulsion may occure leading to corrosion of aluminium alloy. Hence, to prevent such kind of corrosion, a proper filter should be used which will prevent the entry of foreign particles.