An Introduction to Mechanical Vibrations [antikvár]

PREFACE In the preface to the first edition I established my reasons for writing still another vibration text, together with my thoughts on teaching mechanical vibration. Teaching the subject certainly did afiect the somewhat unusual arrangement of the topics in the book, and my thoughts on teaching mechanical vibration have not changed since the first edition of this book was published. For example, I still feel strongly that it is a pedagogical mistake to incorporate damping any earlier than Chapter 6. As a field, mechanical vibration has not changed much since the first edition. There is, perhaps, more interest in systems with multiple degrees of freedom, but this makes a thorough understanding of basic principles even more necessary. Random vibration has receded in importance, as could have been predicted. The only real source of random vibration is the rocket motor, so applications of random vibration are inevitably tied to the space program. When the space program declined, our interest in random vibration declined. There are no big changes to announce in the present edition, but there are several small changes. For example, my explanation of hys-teretic damping has been expanded and the problem collection has been expanded. If you make a comparison between the two editions, you will notice that I have added about 50 new problems and omitted some that are no longer useful. In particular, there are more problems on nonlinear vibration. I am still convinced that learning mechanical vibration is best accomplished by the working of problems. This edition uses the System Internationale (S.I.) throughout. There has been considerable debate over what units should be used in mechanical vibration, much more debate than the issue merits. Since damping ratios, frequency ratios, and amplitude ratios are dimensionless, the units used do not really matter. Most vibration measurements are measured in millimeters and recorded on strip charts running at a rate calibrated in millimeters per second. Oscillograph readings are calibrated in millimeters. S. I. units seemed logical to me, and for this edition, I have abandoned conventional units in favor of them. The subject of torsional vibration (now Chapter 9) has been separated