Vibration Damping: What Is It and What Rubber Is Best for It?

Posted By:  Sperry & Rice

Sometimes in products, or in industrial applications, vibration is an issue that requires a solution. In our business, we create solutions called vibration damping, and we do it with extruded rubber components.

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In fact, when vibration is an issue, the right rubber formulation can make all the difference. But first, let’s get back to basics. What is vibration?

Vibration is a mechanical occurrence where shaking or oscillations occur due to imbalances in a rotating part (like a motor) or uneven friction. If vibration isn’t controlled, it can cause damage to the entire assembly or unit, specific parts, or even worse, fail and cause damage far beyond a part failure. To prevent any of these bad things from happening, you need vibration damping materials and components.

Vibration damping uses materials, often rubber, to absorb vibrations caused by machinery or moving parts. It 

can take the form of rubber vibration mounts, pads, washers, isolators, or gaskets, and can be made with a variety of rubber compounds, but are commonly made of natural rubber, EPDM, neoprene, and butyl rubber.

We’ll cover these materials one by one, but first, a few qualities that vibration dampeners require: adhesion to substrates, durometer, and resistance to other substances (ie, chemicals, oils, heat). Which material you choose for your vibration damping needs will depend on your application, and it’s important to know how different rubber compounds perform under different conditions.

Substrate Adhesion

No material can deaden vibrations if it doesn’t adhere to your parts or components. If a rubber doesn’t adhere well to your substrates, it will fall off and render the damping useless. 

Durometer

Making sure the rubber used in your damping components isn’t too hard or too soft is crucial. Too hard and you may lose damping ability; too soft and your part may tear and fall off. It’s important to test different formulations to determine the exact right durometer for your project.

Resistance

Considering the environment in which your rubber components will be used is extremely important. Vibration dampeners need to survive and lead a productive life, so understanding what elements the rubber will be exposed to is crucial. Temperature, oils, chemicals, weather, etc., can wear down parts and cause failure so it’s vital to understand rubbers’ interactions with its environment.

There are a few different vibration damping rubber materials used in most applications:

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Natural Rubber

Natural rubber is a good vibration damping material that features high tensile strength, but its main drawback is that it doesn’t hold up well outdoors or in conditions that feature oils, due to its poor oil resistance.

EPDM

EPDM is a synthetic rubber that features high resistance to heat and weather and features excelled substrate adhesion and durometer. It can also be formulated in numerous different compounds for many different applications.

Neoprene

Neoprene excels in two specific areas for vibration damping: its superior adhesion to substrates, and its resistance to oil. Neoprene is a bit more expensive than other rubbers but its ability to stick to substrates (especially metal) and its ability to perform in oily conditions makes it a great damping option.

Butyl Rubber

Butyl rubber is a synthetic rubber that features low gas and moisture permeability and is extremely resistant to heat, abrasion, and tearing, which makes it an excellent option for damping vibrations.

As you can see, vibration damping parts and components can be made with a variety of rubbers, but it is crucial to find the best performing and most cost-effective option for your project. But that can be difficult unless you are a rubber expert. Fortunately, Sperry & Rice has a trained team of engineers experienced in all rubber formulations to help you determine which is right for your next project.

Sperry & Rice offers innovative engineering, advanced manufacturing processes, and comprehensive quality controls to produce precision extruded synthetic rubber components for the HVAC, automotive, transportation, and appliance industries. Our reputation lies in making sure that the rubber we provide makes the finished products of our clients reliable, and of the highest quality. 

Transmissibility is the ratio of the vibrational force being measured in a system to the vibrational force entering a system. For example, if a material used for vibration isolation has a transmissibility of 75%, that means 75% of the vibrating force energy is being transmitted (or 25% transmission loss) through the materials and measured on the other side.

Natural frequency is the frequency (number of cyclic motions per unit time) at which an object or structure vibrates naturally or resonates. A structure vibrating at natural frequency will vibrate forever unless an outside force interferes with it. Thankfully, in nature, there’s always some force affecting a vibrating object, removing energy and eventually dissipating the vibration; these forces collectively are commonly referred to as vibration damping.

So how do all these concepts and definitions help determine if vibration damping or isolation is the way to go in controlling vibrations in various products? The first step is to identify the offending source and frequencies of concern, which in many cases arise from features outside of a product designer’s control. If the object or structure is simple enough, it may be possible to use isolation to shift a single critical natural frequency away from the excitation source frequency. However, for most practical product applications there are typically so many natural frequencies and dynamic loads that they all can’t be shifted; energy dissipation via damping is the only way control the dynamic response and reduce transmissibility.

Vibration Control Process for Practical Applications

With the above as background, it becomes clear that vibration control comes down to managing the response near (multiple) resonances fr, and, as shown schematically in Figure 1, near what is called the coincidence frequency or fc for some applications with complicated excitation sources. This energy management can be accomplished using geometric design variables such as isolation or shaping to change transmission paths or by introducing materials to dissipate energy. However, if we assume that for most practical applications the structure, object or equipment’s shape are defined by basic functionality then materials like Countervail® that deliver high levels of damping must be used to control vibrations.