 Hello everyone, myself Sachin Rathod working as an assistant professor in mechanical engineering department from Waltons Stop Technology, Sholapur. So previously we had seen the rolling contact bearing part 1, part 2. So in that we had seen how the rolling bearing are classified according to the type of the load. Then we had seen how to find out the static load carrying capacity of the bearing. Now in this session we are going to see how to find out the dynamic load acting on the bearing. So the learning outcome of this session is the students will be able or the learner will able to design the equation for the dynamic load capacity of the rolling contact bearing. So you can think about this, what is in the fatigue failure, just you can pause this video and recall the fatigue failure which already we had seen in the machine design one. So if you observe this figure, so in that you are getting the concept of the fatigue failure. So here the shaft is around the shaft we are mounting the bearing to reduce the friction and to support the shaft is the main function of this bearing. So if you observe this when it is going to in the working condition, the shaft is going to rotate by certain rpm. So due to the rotation of the shaft, continuously the cyclic load is going to act on the bearing. So this is nothing but you are the varying load or the fluctuating load is going to act on the bearing. So you are the bearing is under the fatigue failure. So for finding the fatigue failure or the dynamic load, dynamic load is nothing but the load which is going to act during the motion or during the rotation of the shaft that we are going to find out. So for finding that you should know what is the life of the bearing. The ball and the roller of the bearing are subjected to the variable loads which are repeated for large number of the cycle in its life. So already we have seen the diagram for the figure of the bearing in which the load is going to act continuously in cycle. Hence we can call the bearing are subjected to the fatigue failure. So the life of the individual ball bearings is defined as the number of revolutions or the hours of the service at given constant speed which the bearing runs before the first sign of the fatigue cracks in the balls or the races. So if you observe this figure in that the first sign of the crack of this ball is going to occur, so before to that whatever the bearing will get survive that is nothing but the life of an individual ball bearing. So the definition they had given us like this. The bearing runs before the first sign of the fatigue cracks of the balls or the races. So since it is impossible or the difficult to predict the find out the life of the single bearing, so we can define the life in terms of the statistical average life of a group of the bearing. Next one is the rated life of the bearing. The rated life of the group of the apparently identical ball bearing is defined as the number of revolutions that 90% of the bearing will complete or exceed before the first sign of the fatigue crack. Since only we can consider that only the 10% of the bearing is at the point of view of the failure then we can get what are the life of that bearing that is a rated life of the bearing. The rated life of the bearing in the catalog it is known by the letter L10 life or B10 life. The life of the individual ball bearing may be different from the rated life of the bearing because in the individual ball bearing life we have to identify for the single ball bearing and in the rated life we are considering the 90% of the bearing or the group of the bearing. So statistically the average life L50 in which the 50% of the group of the bearing will complete or exceed and it is approximately 5 times the rated life or L10 life. Now we will see the dynamic load carrying capacity of the bearing it is denoted by the letter C. So in previous session we had seen the static load carrying capacity of the bearing and it is indicating by the letter C0. So it is found that if the load acting on the bearing is increases the life of the bearing decreases. So we had seen this concept in the previous session. Hence the load carrying capacity of the bearing is always associated with the certain expected fatigue life. So you should know how to calculate the fatigue life of the bearing. The dynamic load carrying capacity of the bearing is defined as the radial load in the radial bearing or the thrust load in the thrust bearing that can carried by 90% of the bearing of the identical bearing for minimum life of 1 million revolution. So by considering these things means based on your the rated life you have to calculate the dynamic load carrying capacity of the bearing. So you can pause this video and you can think about this. You can think on which factor your the rated life is calculating which factor is affecting on the rated life of the bearing. So the next bit is equivalent bearing load for finding the life of the bearing or the rated life of the bearing you should know the load acting on the bearing. So as we are knowing there are the two forces are going to act on the bearing. One is the radial load another is the thrust load. So based on these two loads we have to find out the equivalent load on the bearing. So the radial and the thrust component acting on the bearing needs to be converted into the equivalent hypothetical load to fulfilment of the conditions applied to the dynamic load carrying capacity. So as we are knowing there are the two component is going to act on the bearing. One is the radial and another is the thrust load. So we have to consider that we have to convert the radial and the thrust load which will fulfilment of the condition of the applied dynamic load. So we will see how to convert that radial and the thrust load component into the equivalent load carrying capacity of the bearing. So the equivalent dynamic load is defined as the constant radial load in the radial bearing or the thrust load in the thrust bearing which if applied to the bearing would gives the same life as that which the bearing will attain under the actual conditions of the forces. So we will see the expression for finding the equivalent load carrying capacity or equivalent bearing load that it is indicating by the letter P suffix E. P suffix E is equal to X V FR plus Y F A where P is nothing but the equivalent dynamic load in Newton, F R and F A are the radial and the axial load which is going to act on the bearing where the X and Y are the radial and the thrust factor that factor we have to consider because for finding the equivalent load it is not like that only the radial and the axial forces are going to act that we have to consider. But simultaneously the other effect we have to consider that is why X and Y are the radial and the thrust factor we have to consider for finding the equivalent load. And V is a race rotation factor so that is depending upon your which race is going to rotate. And we are knowing there are the two races are there one is the inner race another is the outer race. So if the inner race is rotated and the outer race is stationary at that time we have to consider V is equal to 1 and if your outer race is rotated and the inner race is stationary at that time we have to consider V is equal to 1.2. So this is the expression for finding the equivalent bearing load. Load life relationship is given by the equation L10 is equal to C divided by P e raised to K where L10 is nothing but the rated life of the bearing, C is nothing but dynamic load acting on the bearing, P is nothing but the equivalent load, K is nothing but the constant which is nothing but is equal to 3 for the ball bearing and K is equal to 10 by 3 for the roller bearing. So just rearranging this equation the dynamic load is obtained above but overall the ultimate aim to find out the dynamic load acting on the bearing, the dynamic load acting on the bearing just we have to rearrange these equations you will get the dynamic load. C is equal to equivalent load P e into rated life of the bearing L10 raise to 1 by K therefore C is equal to P e into L10 raise to 1 by 3 just we are putting for the deep group ball bearing K is equal to 3 we are getting this relation for the ball bearing just we are replacing the value of the K as a 3 and for the roller bearing we have to replace the K value as a 10 by 3 we will get the another relation that is C is equal to P e into L10 raise to 3 by 10. This is the expression for finding the dynamic load for the ball bearing and the roller bearing. So I have taken a reference as a baby Vandairi book, thank you.