rubber compression calculation

Calculation: Load / Area = 720lb / 72 in² = 10 lb/in² Compression: From the Compression Force Deflection Curve, HT-800 will compress approximately 30%. (Note: compressing more than 50% may rupture cells and damage material)

Full Answer

How much compression should a rubber gasket have?

Rubber gaskets are compressed or squeezed by a percentage of their original size. A gasket that compresses too much or too little will not form a proper seal. The ideal compression percentage is 40, the maximum is 50, and the minimum is between 10 to 15.

What is the deformation of the rubber pad during compression?

The deformation of the circular rubber pad is irregular during compression, and hence the assumption of cylindrical deformation of the rubber pad is unrealistic; it should be close to elliptical deformation.

What happens to the bearing area of the rubber when compressed?

Diagram of circular rubber pad when compressed. During the deformation, the rubber cover is regarded as a rigid body, and hence the bearing area of the rubber pad does not change, but the free area of the rubber pad changes.

Why do we need to calculate the stiffness of rubber springs?

Therefore, it is necessary to accurately calculate the stiffness of rubber springs to effectively calculate and predict the performance of the trains. With the increasing geographical range covered by the trains, the operating temperature range of the rubber springs is large, normally ranging from −60°C to +60°C.

How much does rubber compression?

Rubber gaskets are compressed or squeezed by a percentage of their original size. A gasket that compresses too much or too little will not form a proper seal. The ideal compression percentage is 40, the maximum is 50, and the minimum is between 10 to 15.

How is rubber deflection calculated?

To calculate rubber deflection take the shape factor raised to the power of 2, then add 1. Next, multiply the result from above by the young's modulus of the rubber. Finally, divide the load acting on the rubber in PSI by the result from above.

How is compression set calculated?

Compression set A is defined as the percentage of original specimen thickness after the specimen has been left in normal conditions for 30 minutes. CA, the compression set A is given by CA = [(to - ti) / to] * 100 where to is the original specimen thickness and ti is the specimen thickness after testing.

How do you calculate compressed size?

To determine the compression ratio, divide the size of outputFile value by the length (-l 200000 ). For example, if the size of outputFile value is 66 000 bytes, then the compression ratio is 66000/200000 or 0.33 (3:1 compression).

What is compression set in rubber?

Compression set testing measures the ability of rubber to return to its original thickness after prolonged compressive stresses at a given temperature and deflection. As a rubber material is compressed over time, it loses its ability to return to its original thickness.

What is compression deflection?

Compression deflection is the measure of the compressive strength of a cellular product. It is measured by the force required to compress a material. For example, to 25% of its original thickness. It can be expressed in lb/in² (pounds per square inch) or kPa (Kilopascal).

What is good compression set?

Good compression set properties are mostly to do with good rubber choice and fully chemically cross linked and post cured products. The compression set test is a common test in our laboratory. A standard test specimen is measured then compressed in a jig to a certain percentage of its original thickness.

How much does EPDM compression?

Typical EPDM values are in the 1000 PSI range. Elasticity, a measure of a material's ability to resume its normal shape after being stretched or compressed, is expressed as a percentage. With EPDM, this percentage is typically in the 300% range.

What is the compressibility of a gasket?

Compressibility and recovery values vary greatly between different materials. For example, expanded PTFE has a compressibility of around 68% but recovery of just 12%, while the same numbers for a neoprene gasket could be 7 to 17% compressibility and 50% recovery.

What is compressor ratio?

To put it simply, a compressor's ratio knob controls how aggressively the compressor clamps down on a sound. Higher ratios cause the compressor to react aggressively. This will tightly control dynamics and dramatically reduce the difference in volume between the loudest and softest parts of the performance.

What does a compression ratio of 20 1 mean?

Please use a compression ratio that is less than 20:1. It means the Photo Tool won't handle your photo because it thinks that is of low quality.

How do you calculate compression ratio from PSI?

Calculate the PSI to compression ratio. For example, if you have a manometer reading of about 15 and your compression ratio is supposed to be 10:1, then your PSI should be 150, or 15×10/1.

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When a part is compressed, does it want to expand out laterally?

When a part is compressed it wants to expand out laterally and that movement changes the shape factor. This is particularly noticeable if the surfaces are lubricated. However, if the surfaces are bonded to a substrate such as metal, the shape factor remains the same.

How thick is a 92A pad?

You have a 92A durometer (hardness) isolation pad that is 6" long by 3" wide and 2" thick, that is under a 3,600 lb load. You want to know how much deflection it will have.

Is polyurethane compressible?

Polyurethane, unlike rubber, is a non-compressible elastomer, meaning its volumne will not change. In other words if you squeeze it in one place, it will bulge the same amount in another place. For that reason, it makes an excellent material for load-bearing applications.

How long does it take for a compression sponge to recover?

ASTMD 1056 points out that open cell sponges require 30 minutes recovery before re-measuring whereas closed cell varieties require 24 hours recovery before re-measuring.

What happens when a sponge is compressed?

When the sponge is compressed, the air inside each cell is compressed and depending on the amount of compression the rubber content is compressed some. With the open cell sponge the air has gone straight away but with the closed cell sponge the air cannot escape but is compressed.

What is the ideal compression percentage for rubber gaskets?

A gasket that compresses too much or too little will not form a proper seal. The ideal compression percentage is 40, the maximum is 50, and the minimum is between 10 to 15.

What happens when a gasket is compressed?

Here, it helps to think about a closed door. When a door is closed the gasket is compressed and fills the gap between the door and the door jamb. This seals out the environment.

What happens if you over compress a door gasket?

If you over compress a door gasket, however, the rubber will not bounce back and can’t seal the gap. If the problem is that your gasket compression percentage is less than 10, you might not get contact between the two surfaces you’re trying to seal – and that will not keep out air, dust, or water.

What are some examples of rubber gaskets?

Examples include hatch seals on military vehicles and the dishwasher seals on appliances. With the latter example, the use of hot water and detergents can affect a rubber gasket’s material properties and degrade its performance.

Can compression cause a rubber gasket to fail?

Gasket compression can support enclosure sealing or contribute to gasket failure. That’s because rubber gaskets are resilient, but only to a point. Compressing a rubber gasket within allowable limits forms a reliable seal. If the gasket is over-compressed, however, the rubber won’t rebound when the compressive stresses are removed.

What temperature does rubber change?

During the operation of railway vehicle bogies, the temperature of rubber components changes continuously, normally in the range of −60°C to +60°C. If the temperature changes, the volume of rubber will change because of thermal expansion and contraction.

Why does rubber stiffen with stress?

This is because the increase in stress leads to a change in both geometric and material nonlinearity. When the rubber element is compressed, the specimen becomes anisotropic, as the molecular chain is oriented more in the transverse direction.

What temperature does crosslinked rubber crystallize?

When a normal cross-linked rubber is at a temperature above 0°C, the effect of crystallization is significantly weak. Young’s modulus and stiffness of the rubber increase significantly with decrease in temperature when the temperature is below 0°C.

What happens to rubber at high temperatures?

At high temperatures, the degree of cross-linking of rubber increases gradually with increase in temperature, which leads to an increase in hardness and Young’s modulus of the rubber. If the temperature increases further, the molecular chain of the polymer will break. It is not necessary to consider the role of degradation, as the engineering application range is normally not higher than 60°C. When the temperature of rubber is lower, the molecular activity is weakened, and the rubber will crystallize. This condition leads to an increase in Young’s modulus of the rubber at low temperatures.

What happens when rubber pads are deformed?

When the rubber pad is deformed, the middle part protrudes outward; it is assumed that the bulging part of the rubber pad is a semiellipse in the vertical section, and that the semiaxes of the inner and outer semiellipses are equal, as shown in Figure 1 (c).

Is rubber a hyperelastic material?

Rubber is a type of hyperelastic material; for an ideal rubber material, the conformational entropy of molecular net chain can be used for elastic analysis. The microscopic theory starts with the actual structure, the complex structure is simplified using some assumptions, and the ideal structure is constructed to facilitate calculation and analysis. Based on certain experimental results, the following assumptions are made: (1) The intersection points are fixed at their average positions (2) Microdeformations and macrodeformations are in the same proportion; thus, affine deformation is considered (3) The chain of intersection points is a Gaussian chain, which conforms to the Gaussian statistical law (4) The internal energy of the system is independent of the conformation of each chain

Does Young's modulus increase with temperature?

In theory, Young’s modulus increases with temperature, but in most cases, the measured stiffness decreases with temperature. This seemingly contradictory phenomenon is explained by ( 33 ). (5) There is a nonlinear relationship between prepressure and precompression amplitude. Their influence on stiffness is different.

What is the expected range of force needed to compress an oring 20% with a 0.070” diameter cross section

The expected range of force needed to compress an oring 20% with a 0.070” diameter cross section (purple) that is 50 durometer is between 4.5 and 14 pounds per linear inch.

Which material has the highest compressive modulii?

Nitrile, Fluorosilicone, and Fluorocarbon are midrange. Silicone and EPDM generally have higher compressive modulii. The “per linear inch” scale is used to account for orings and seals of different sizes.