Does Fastener Member Stiffness Need to be Multiplied by 2 in Calculations?

In summary, when calculating the spring rate for a member, it is sometimes necessary to multiply the rate by 2. This is because the objects may be able to expand or contract in two directions, rather than just one. This is the case in the problem mentioned, where the spring rate for both the cylinder head and cylinder are multiplied by 2 and added together to get the total Km.
  • #1
djdoug99
15
0
I am going through Shigley's Mechanical Design book and have a quick question on fasteners. Sometimes when calculating the spring rate for a member, you have to multiply the rate by 2, why is this? For instance in this problem
http://imgur.com/2ug9AaR

When the spring rate is calculated for both the cylinder head and cylinder, both spring rates are multiplied by 2 and then added together to get the total Km. (This is not a homework problem)

Thanks.
 
Last edited:
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  • #2
I'm not familiar with the precise context, but could it be because the objects can expand/contract radially in two directions (whereas if fixed at one end could only expand/contract axially in one)?
 

1. What is "fastener member stiffness"?

Fastener member stiffness refers to the resistance of a fastener (such as a bolt or screw) to being bent or compressed when a force is applied.

2. Why is fastener member stiffness important?

Fastener member stiffness is important because it affects the overall strength and stability of a structure. If a fastener is not stiff enough, it may fail under a load or cause the structure to be less stable.

3. How is fastener member stiffness measured?

Fastener member stiffness is typically measured in pounds per inch (lb/in) or Newtons per millimeter (N/mm) of deflection. This measurement is also known as the stiffness constant or spring rate.

4. What factors affect fastener member stiffness?

The stiffness of a fastener member can be affected by several factors, including the material and size of the fastener, the type of loading (tension, compression, shear), and the design and geometry of the connection.

5. How can fastener member stiffness be improved?

Fastener member stiffness can be improved by using thicker or stronger materials, increasing the diameter or length of the fastener, or using a different type of fastener that is better suited for the specific loading conditions.

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