...
If we observe the given grade of a bolt (8.8), the first digit represents the ultimate tensile strength in hundreds of MPa . The and the second digit represents the yield to tensile strength ratio. The preload force should be less than the yield strength to prevent plastic deformation - 70% is the factor that is often used in practice.
To determine how much preloading force is applied, there are three methods:
Torque method (±25% accurate): use a torque wrench to measure the amount of applied torque and isolate the preload force in the equation T = F⋅D⋅K.
Turn of nut method (± 15% accurate): tighten the suit enough to bring the two mating surfaces together and then turn it through a defined angle. The amount of preload force will depend on the thread pitch, bolt length, and the material’s Young modulus.
Bolt elongation method (± 1-5% accurate): measure the elongation of the bolt from before the point in which torque is applied and after. It is assumed that preload force will linearly increase as the bolt elongates. F = k⋅ΔL. 'ΔL’ is the change in length of the bolt due to tightening. ‘k' is the bolt's stiffness, which can be calculated using the bolt's material properties and geometry k = (E⋅A)/L. 'E' is the Young's modulus, 'A' is the cross-sectional area, and 'L' is the effective length of the bolt.
We will continue with the 3rd method as it's the most accurate1st method. This force over the area of the bolt will be compared to 70% of the yield strength value, and the lower value will be taken to prevent bolt damage.
...
According to my current calculations, each clamp can support a maximum load of around 100 N before occurring plastic deformation (which could be an incorrect result). This value is greater than the expected load a given clamp will receive. See Figure X for fixture and force setup and results.
With these two questions answered, I it can determine be determined how many two-clamp fasteners are needed to support the load of the aerobody. To be clear, since each clamp has two bolts, the amount of load the system can hold considers both bolts totaled.
...
Misc notes:
Could also FEA the entire body to determine the positioning of the fasteners, but it's not that accurate.If there are two bolts for every clamp, does this mean each bolt will provide a given frictional force, or is it total?