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Multi-jackbolt tensioners (MJTs), registered under the trademark Superbolt or Supernut, are designed to decrease the torque required to tighten large bolted joints. One of the major problems associated with traditional bolt tightening methods is as the diameter of the bolt increases, the amount of torque required to tighten it increases in the third power of the diameter. [1]
The curve representing a clamped parts-to-bolt stiffness ratio of 0.01 shows that when the relative stiffness of the clamped parts is very low, almost all of the load is transferred to the bolt, down to the point where a compressive load equals the preload, and separation at the bolt head occurs, reducing the force in the bolt to zero.
The force and torque vectors that arise in applying Newton's laws to a rigid body can be assembled into a screw called a wrench. A force has a point of application and a line of action, therefore it defines the Plücker coordinates of a line in space and has zero pitch. A torque, on the other hand, is a pure moment that is not bound to a line ...
Rd 30° [5]DIN 405 / DIN 20400 Acme thread [6]: 29° ASME/ANSI B1.5-1988 [7]: Metric trapezoidal threads [1]: Tr 30° DIN 103 Buttress threads [6]: S 45° DIN 2781 German buttress threads [6]
Using the free body diagram in the right side of figure 3, and making a summation of moments about point x: = + = where w is the lateral deflection. According to Euler–Bernoulli beam theory , the deflection of a beam is related with its bending moment by: M = − E I d 2 w d x 2 . {\displaystyle M=-EI{\frac {d^{2}w}{dx^{2}}}.}
The actual thread heights on both the internal (nut) and external (bolt) threads differ from P / 2 by allowances (or clearances): A minimum root-crest clearance of 0.01 in (0.25 mm) (diametral) between opposing threads with 10 tpi (threads-per-inch) or fewer, and 0.005 in (0.13 mm) for finer pitches.
The threads 11 on rod 4 have one pitch (e.g. 25 tpi, blue), while the threads 10 in the barrel 1 have another (e.g. 20 tpi, orange). A full turn of the thimble 12 rotates the nut sleeve 13 and its two threads ( 20 tpi outside and 25 tpi inside ) to move the rod 1 / 20 - 1 / 25 = 0.01 in (0.25 mm) relative to the barrel.
When the applied service load doesn't exceed the clamping force of the fastener, the strain of the fastener will be lower than when the preloading is smaller than the applied load. It is therefore beneficial in high-frequency high-load situations with a higher risk of fatigue related failure, like a bolted down cylinder head , to use torque to ...