Pressure caused by clamping base and cover

In summary: Overall, the formula and calculations seem to be correct and it would be best to consult with the electrical engineer for any further advice. In summary, the conversation discusses a problem at work involving clamping an assembled unit with compressive material and determining the pressure caused by the clamping. The formula for calculating this pressure is given, but the torque coefficient for stainless steel is unknown. The units for surface area and the resulting pressure are also discussed. It is suggested to consult with the electrical engineer for further advice.
  • #1
anlouk
2
0
Hello, I've posted this on the pyshics forum but no-one has replied so I thought I might try this one.

I have been asked to solve the following problem at work. Unfortunately I haven’t done anything like this since college (over 12 years) and am a bit confused now.

We have an assemblied unit, consisting of an aluminium base and cover with a PCA clamped between. The unit is clamped using 27 screws (M2 SS Pan TORX SEMS) with a torque value of 0.35Nm. The electrical engineer wants to place some compressive material into a milled pocket in the base, which will allow for tolerance build up in an area of the PCA and therefore needs to know the pressure caused by clamping the unit together.

I was given the following formula by another of the electrical engineers:
T = (C x D x P x A) / n

T = torque per screw (Nm)
C = torque coefficient
D = nominal screw size (m)
P = desired pressure (force per unit area) (N/sq m)
A = surface area (sq mm) – is this unit correct should this not be sq m?
n = no of screws

Could anyone confirm if this is the correct formula?
Also I can only find the torque coefficient for aluminium/steel (0.45 dry) and not stainless steel, does anyone know what this value is?
Will this affect the answer greatly as I worked out the formula using the aluminium/steel value (0.45 dry).

Depending on the surface area unit (surface area of unit is 8604.8788mm²) I am getting the pressure to be either:

Using surface area in mm² = 1.220238Nm² = 1.220238 Pa
Using surface area in m² = 1220238Nm² = 1220.238 kPa

Both values seem to be a bit extreme and when comparing to the data sheet of the compressive material, the graphical range for the pressure in kPA is in units of 100 upto 700kPa.

I would appreciate any advice given. Thank You.
 
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  • #2
The formula you were given is correct. The torque coefficient for stainless steel is usually around 0.2. This will affect the answer, but not greatly. As for the units, surface area should be in m², so your result of 1220.238 kPa looks correct. The range of 100-700 kPa on the data sheet is probably just a suggestion. Depending on the material and the size of the pocket, you may need a higher or lower pressure than that.
 

Related to Pressure caused by clamping base and cover

1. What is pressure caused by clamping base and cover?

The pressure caused by clamping base and cover refers to the force applied to the base and cover of an object when they are securely fastened together. This pressure is created by the tightening of screws, bolts, or other clamping mechanisms, and is typically measured in pounds per square inch (psi).

2. Why is pressure caused by clamping base and cover important?

The pressure caused by clamping base and cover is important because it ensures that the base and cover are tightly sealed and held together. This is crucial for maintaining the structural integrity and functionality of the object, especially in cases where pressure or force is applied to the object.

3. How does pressure caused by clamping base and cover affect the object?

The pressure caused by clamping base and cover can have various effects on the object, depending on the material and design of the object. In some cases, it may create a strong and secure bond between the base and cover, while in others it may cause distortion or damage to the object if the pressure is too high.

4. What factors can influence the pressure caused by clamping base and cover?

The pressure caused by clamping base and cover can be influenced by a variety of factors, including the type and size of the clamping mechanism, the material and thickness of the base and cover, and the amount of force applied while tightening the clamps. Other factors such as temperature and surface finishes may also play a role.

5. How can the pressure caused by clamping base and cover be measured?

The pressure caused by clamping base and cover can be measured using a pressure gauge or sensor that is placed between the base and cover. This device will provide a reading in psi or other units of pressure, allowing for accurate measurement of the clamping pressure. Alternatively, calculations based on the amount of force applied and the surface area of the base and cover can also provide an estimate of the clamping pressure.

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