Establishing Safety Margins and Reliaility
A common way to establish safety margins and reliability for new products, systems, materials, substances, and equipment is to use a vibration table. A Vibratory Testing Table is used across several industries, such as building and construction, life sciences, materials and chemicals, manufacturing, aerospace and defense, energy, and automotive, to apply controlled degrees of vibration to items. Testing can be done with liquids, solids, and gasses to determine at what point a test subject will be destroyed. Taking items to their limits will help determine what improvements need to be made, where and when the use of the item is beneficial, and which materials can be used in different applications.
In building and construction, for example, it is important to know how much movement a specific steel beam can withstand and still hold up a wall or floor. A vibratory table can be used to simulate the force of strong winds, earthquakes, excessive noise, or collisions from vehicles. The beam is attached to an accelerometer and placed on the vib table. The testing conducted will create the real environment in which the beam will be placed. Measurements are taken throughout the testing as movement and noise frequencies are increased. The results will indicate the maximum capacity of the steel beam, and determine how reliable it will be, and in what applications is will be best suited. That particular beam may be perfect for sheds, ranch-style homes, and a small hotel. It may be dangerous to use in known earthquake zones, or buildings with more than three levels.
There are three basic approaches to testing. Swept-sine testing moves a frequency back and forth along the table. Random testing provides different frequencies of a noise source to represent the environment. Introduction to frequencies is at certain intervals, rather than delivered continuously. Classic shock testing releases high level shock pulses, either continuously or at intervals, until the item is destroyed. The operating system for low frequency testing is hydraulic force, and high frequency testing is completed using an electro-dynamic system. That consists of a fixed magnetic field and a moving coil. Audio power is brought to appropriate levels with specially designed amplifiers. Tables are available in many sizes and strengths to accommodate the desired force used on test subjects. Small ones, for example, are used for electronics, parts, or small samples of materials. Portable ones are available for field testing, such as pipes and joints. Large and powerful tables are mostly used in manufacturing, defense, energy, and aerospace applications.