Thorough purging of all four bearing seals on each universal joint can help alleviate the possibility of mixing incompatible greases. U-joint cross, broken at a bearing surface. U-joints seldom break off at the bearing surface. It takes a very large shock load to cause this type of failure. It is also very difficult to inspect for this type of failure because they, many times, start as a small crack and progress into a complete failure some time further âdown the roadâ.
A quantity called the slew rate, which is the rate of change of gradient amplitude is usually quoted in evaluating gradient performance and potential physiological effects (e.g. a maximum slew rate of 200 Tm-1s-1).
In other cases, a maximum slew rate is specified in order to limit the high frequency content present in the signal, thereby preventing such undesirable effects as ringing or radiated EMI. In amplifiers, limitations in slew rate capability can give rise to non-linear effects. S R â¥ 2 Ï f V p k , {\displaystyle \mathrm {SR} \geq 2\pi fV_{\mathrm {pk} },}. where f is the operating frequency, and V p k {\displaystyle V_{\mathrm {pk} }} is the peak amplitude of the waveform.