The term bearing is derived from the verb ‘to bear’, a bearing being a machine element that allows one part to bear (i.e., to support) another. Bearings are highly engineered, precision made components that enable machinery to move at extremely high speeds and carry remarkable loads with ease and efficiency. Generally speaking, bearings are devices that are used to enable rotational or linear movement, while reducing friction and handling stress. Bearings are considered to be the most critical components of machinery. Bearings are machine elements that constrain relative motion and reduce friction between moving parts to only the desired motion. The design of the bearings may provide for free linear movement of the moving part or for free rotational around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Many bearings also facilitate the desired motion as much as possible, such as by minimizing friction. Bearings can have many forms, but supports only two types of motions namely linear motion or rotary motion. There are two types of bearings, contact and noncontact. Contact bearings – They have mechanical contact between elements, and they include sliding, rolling, and flexural bearings. Mechanical contact means that stiffness normal to the direction of motion can be very high, but wear or fatigue can limit their life. Fig 1 shows different types of sliding and rolling bearings. Non contact bearings – They include fluid bearings and magnetic bearings. The lack of mechanical contact means that static friction can be eliminated, although viscous drag occurs when fluids are present; however, life can be virtually infinite if the external power units required to operate them do not fail.

1. Ques) The main bearing of a steam engine is 100mm in diameter and 175mm long. The
bearing supports a load of 28KN at 250 r.p.m. If the ratio of the diametral clearance to the
diameter is 0.001 and the absolute viscosity of the lubricant is 0.015kg/m-s. Find:
1) The coefficient of friction
2) The heat generated at the bearing due to friction.
#include<conio.h>
#include<iostream.h>
void main()
{
clrscr();
float d,l,W,N,Z,u,Qg,v,x,p;
cout<<"Enter The Diameter Of Bearing ";
cin>>d;
cout<<"Enter The Length Of Bearing ";
cin>>l;
cout<<"Enter The Bearing Load In KN ";
cin>>W;
cout<<"Enter The Absolute Viscosity Of Lubricant ";
cin>>Z;
cout<<"Enter The Speed Of Engine ";
cin>>N;
cout<<"Enter The Diametral Clearance To The Diameter Ratio ";
cin>>x;
p=(W*1000)/(l*d);
u=((0.0033*Z*N)/(p*x*10000))+0.002;
v=(3.14*d*N)/60000;
Qg=(u*W*1000*v);
cout<<"nCoefficient Of Friction u="<<u
<<"nHeat Generated at The Bearing Due To Friction Qg="<<Qg;
getch();
}