Calculation of a bolted connection with prestress. Loading by axial or tangential force. The calculation is carried out in metric or English units. With the ANSI standard set, the calculation is performed in English units, with corresponding bolt dimensions also included.
Input Parameters
| Ψ |
Tightness factor - With a prestressed bolted connection, the distance between materials is undesirable (due to the bad quality of surface, for example) and this safety factor is introduced to prevent it. Tightness factor k = 1 + Ψ (additional tightness factorΨ = 0.5 - 1.5). Recommended minimum value is 1.2. |
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F a |
maximum operation axial force |
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n |
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F t |
maximum operation tangential force |
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f |
joint friction factor (between the connected materials) |
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z |
number of bolts |
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d |
thread diameter |
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p |
thread pitch |
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d s |
mean bolt diameter |
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d min |
minimum bolt diameter |
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S y |
Yield strength |
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k s |
safety factor (The value is selected according to the required safety level of the joint.) |
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p A |
allowable thread pressure (nut) |
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E 1 |
elasticity module of bolt |
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f 1 |
thread friction factor between the nut and the bolt |
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f 2 |
friction factor in the contact surface of the nut or bolt |
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L |
width of connected material |
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E 2 |
elasticity module of connected material |
Calculated Parameters
According to the following calculation formulas, the program calculates geometric dimensions of the bolt from the specified nominal bolt diameter:
Minimum diameter of the nut thread
D 1 = d - 1.082531 p
Pitch diameter of the thread
d 2 = d - 0.649519 p
Calculation of Bolted Connection:
Working force in the joint - determined by the axial force, has to secure the transfer of tangential force by friction of connected materials. Also affected by the requirement on tightness expressed by the factor of joint tightness.
Prestress force - based on the working force of the joint, takes into account the elastic yielding of bolts and flanges by using the c n yielding constants.
where:
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c 1 = c 10 + (1 - n) c 20 |
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c 2 = n c 20 |
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for steel a = 10 |
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for cast iron a = 8 |
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for aluminum and its alloys a = 6 |
Required tightening moment - determined by the prestress force and affected by the friction factor in threads between the nut and bolt, and by the friction factor in the contact surface of the nut or bolt.
Calculated tensile stress in the bolt
Calculated torsion stress in the bolt
Reduced stress in the bolt
Stress caused by maximum force loading the bolt
Calculated pressure in the thread
Calculation check - stress in the bolt during tightening the joint and during the operation (respecting the specified joint safety), and the check of allowable pressure in threads.
σ red ≤ S y / k s and σ max ≤ S y / k s and p c ≤ p A