INTRODUCTION

This chapter describes some of the more common types of vibration testing machines which are used for developmental, simulation, production, or exploratory vibration tests for the purpose of studying the effects of vibration or of evaluating physical properties of materials or structures. A summary of the prominent features of each machine is given. These features should be kept in mind when selecting a vibration testing machine for a specific application. Digital control systems for vibration testing are described in Chap. 27. Applications of vibration testing machines are described in other chapters.

A vibration testing machine (sometimes called a shake table or shaker and referred to here as a vibration machine) is distinguished from a vibration exciter in that it is complete with a mounting table which includes provisions for bolting the test article directly to it. A vibration exciter, also called a vibration generator, may be part of a vibration machine or it may be a device suitable for transmitting a vibratory force to a structure. A constant-displacement vibration machine attempts to maintain constant-displacement amplitude while the frequency is varied. Similarly, a constant-acceleration vibration machine attempts to maintain a constant-acceleration amplitude as the frequency is changed.

The load of a vibration machine includes the item under test and the supporting structures that are not normally a part of the vibration machine. In the case of equipment mounted on a vibration table, the load is the material supported by...