Lesson 6

1. Find in the text English equivalents for the following Ukrainian words and word combinations:

пом’якшення, випадкова вібрація, підсилення, перебороти, ударне навантаження, постачальник, випромінювальна здібність, зіткнення, зсунення, обладнання, пристосування, пружина, пошкодження, збільшення, ходова частина, твердість, механічний удар, система ізоляції, траплятися, переміщення, частота, діяти, перехідний процес.

2. Read and translate the text:

Random Vibration. Design Rules of Thumb

Random vibration is often perceived as steady vibration. However, sinusoidal vibration is a steady-state phenomenon. Mechanical shock is transient vibration an impact. Random vibration is a series of transient vibrations one right after the other.

Random vibration is typically sourced from within the equipment, but it can also come from outside. Outside the equipment, it is usually sourced in the truck, rail, or air transportation environment.

Random vibration is evaluated through the use of statistics rather than the math that is used in sine vibration and mechanical shock. Random vibration is controlled with the use of a damped spring, as with mechanical shock or sine vibration.

Random vibration can be dealt with by pure accommodation of the anticipated transient displacements, ensuring that no secondary collisions occur. Or an isolation system can be developed within the structure to act as a filter in the frequency band in which the random vibration occurs. The solutions to overcoming the challenges of mechanical environments are synergistic. Each type of disturbance has its own discreet solution.

Mechanical design must be considered in every phase of the product design from conceptualization to the final prototype and preproduction, production, and later enhancement phases of a product. One way to approach this is to use suppliers as a source of information.

A vibration mount becomes an isolator at frequencies that exceed the square root of 2 multiplied by the isolation system's natural frequency. The equipment design merely determines the mass loading on the vibration mount. The information available from the vendor tells what natural frequency and transmissibility characteristics to expect. Based on that, engineers know that it frequencies exceed the square root of 2 times the natural frequency, the vibration mount will act as a vibration isolator. The greater the difference between the system's natural frequency and the disturbing frequency specified for the product, the greater the level of isolation.

Another rule of thumb is that the structure of the chassis system must be protected from amplifications that occur. Essentially, the structure must be as stiff as possible. Since frequencies vary with the square root of stiffness, the structure will always be at least a factor of 3 higher in frequency than the isolator resonance. This places any structural response well within the area of isolation, and structural amplifications are negated.

The design engineer must clearly define the stiffness characteristic of the shock and vibration product for high-strain environments, such as mechanical shock, compared to the stiffness it would displace for low-strain environments, such as vibration. By reconciling both, the engineer may use one component as an effective vibration isolator and shock mount, providing protection from both vibratory and impact disturbances. When specifying the vibration and shock mount, the supplier must be consulted to ensure the resilient support will operate within the temperature range. Problems with stiffening may occur due to low temperatures and with softening due to high temperatures. This can cause the required frequencies to vary so that efficient vibration isolation and effective shock attenuation are compromised.

Suppliers may provide software to help engineers to calculate, specify, or predict the performance of products and systems. The role of the shock and vibration isolator and attenuator is the same as with any engineered product. Careful specification and specialized support from a knowledgeable vendor are critical. A great deal of care goes into an intelligent shock and vibration protection system. Such a system can be compromised by allowing the hardware to be fulfilled by vendors that do not have the necessary materials or dynamic analysis capabilities.