| Dynamics of universal joints, its failures and some propositions for practically improving its performance and life expectancy
Farzad Vesali, Mohammad Ali Rezvani* and Mohammad Kashfi
The Journal of Mechanical Science and Technology, vol. 26, no. 8, pp.2439-2449, 2012
Abstract : "A universal joint also known as universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke’s joint is a joint or coupling in
a rigid rod that allows the rod to ‘bend’ in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair
of hinges located close together, oriented at 90o to each other, connected by a cross shaft. The Cardan joint suffers from one major problem:
even when the input drive shaft rotates at a constant speed, the output drive shaft rotates at a variable speed, thus causing vibration
and wear. The variation in the speed of the driven shaft depends on the configuration of the joint. Such configuration can be specified by
three variables. The universal (Cardan) joints are associated with power transmission systems. They are commonly used when there
needs to be angular deviations in the rotating shafts. It is the purpose of this research to study the dynamics of the universal joints and to
propose some practical methods for improving their performance. The task is performed by initially deriving the motion equations associated
to the universal joints. That is followed by elaborating on the oscillatory behavior in the rotational speed and the torque that transmits
through the intermediary shaft. The forces in the joint bearings are calculated by using an analytical method that is also supported by
the numerical modeling. Such models are also used in order to calculate the rhythm and the amount of the excess loads on the joint. This
is suggested as a systematic procedure in the search for the causes of the failures in these popular bearings. With the same purpose in
mind some defected bearings with deformed sections were selected for the laboratory examinations. By analyzing the loading behavior
and the surface conditions of the defected bearings and by comparison with the known fatigue theories attempts are made in order to dig
into the causes for the failures in these joints and their bearing surfaces. With the aim of improving the performance and the life expectancy
of these popular elements of the machineries, some practical recommendations are also suggested."
Keyword : Machinery failure; Bearing failure; Failure analysis; Fatigue failure; Solidworks modeling |
