How to calculate the torque when driving bolts

1.

Torque coefficient: k = t / (P · d), where: K - torque coefficient, T - torque applied, n · M D - thread size of bolt, mm, P - axial force of bolt. The initial tightening is about 50% of the construction torque. For example, M20 is about 220

According to article b.0.3 of Appendix B on page 65 of code for acceptance of construction quality of steel structure engineering (GB 50205-2001):

1. Final tightening torque T = k * p * D, K torque coefficient, refer to the manufacturer's test report and site retest report, P standard value of construction pretension, bolt diameter

The value of initial and final screwing is 0.5, and the value of torsional shear initial screwing is t = 0.065p * D

extended data:

calculation

high strength bolts exert pretension and transfer external force by friction. Ordinary bolt connection relies on bolt bar shear resistance and hole wall pressure to transfer shear force. When the nut is tightened, the pre tension is very small, and its influence can be ignored. In addition to the high material strength, the high strength bolt also imposes a large pre tension on the bolt, which makes the connecting members proce extrusion force, so that there is a great friction force perpendicular to the screw direction The bearing capacity of high-strength bolts is directly affected by the anti slip coefficient and the type of steel

According to the stress characteristics, it can be divided into pressure bearing type and friction type. The minimum size of high-strength bolt is M12, and M16 ~ M30 are commonly used. The performance of super large size bolt is unstable, so it should be used carefully in design

high strength bolt refers to the bolt grade, hard bottom and other properties are relatively strong, also known as high strength bolt. Generally, it refers to grade 8.8 or above. For example, grade 10.9 bolts and grade 12.9 bolts have strong hardness performance and strong torque performance.

calculation of high strength bolt length

the length of high strength bolt connection must be strictly controlled. The length of the torsional shear high strength bolt is the length from the lower bearing surface of the screw head to the notch of the screw tail; For high strength hexagon head bolts, the thickness of a washer should be added, as shown in Fig. & quot In the picture* Is the thickness of the plate;! Is the bolt length)

The general formula for calculating the length of

high strength bolt is as follows:

L = L & # 39&# 39;+ Where △ L = m + ns + 3P

where l is the length of high strength bolt

L'&# 39;— Total thickness of connecting plate layer

△ L - additional length, that is, the lengthening value of fastening length

m - nominal thickness of high strength nut

n-number of washers, 1 for torsional shear high strength bolt, 2 for high strength large hexagon head bolt

s-nominal thickness of high strength washer

p-pitch of thread

the lengthening value of tightening length of high-strength bolt = bolt length plate thickness. Generally, according to the thickness of the connecting plate plus the length value in Table L, and taking the integral multiple of 5mm

Before the construction of high-strength bolt, the torque coefficient of high-strength bolt connection pair should be inspected according to the factory approval, 8 sets of each approval, the average value of 8 sets of torque coefficient should be in the range of 0.110 ~ 0.150, and the standard deviation should be less than or equal to 0.010. The re inspection method of torque coefficient is in accordance with the code for acceptance of construction quality of steel structures (GB 50205). High strength bolts should be installed in a short time after the test

The construction torque of

high strength bolt is determined by the following formula:

TC = 1.05k · PC · d

Tc - construction torque (n · m)

k - average value of torque coefficient of high strength bolt connection pair

PC - construction pretension of high strength bolt (KN), see Table 1

D - screw diameter of high strength bolt (mm)

Table 1 pretension PC (KN)

the torque wrench used before high strength bolt construction must be corrected before use, and its torque error shall not be greater than ± 5%, qualified before use. The torque error of the torque wrench used for correction shall not be greater than ± 3%

2. Use the average torque coefficient of high-strength bolt (which can be known only through re inspection) x pretension of high-strength bolt x diameter of high-strength bolt. OK

3.

Torque is equal to the proct of force and arm of force. The international unit is nm. In addition, we can see torque units such as kg · m and LB ft

unit torque multiplied by system pressure is equal to motor output torque. Of course, this is theoretical data. It needs to be multiplied by mechanical efficiency

engine torque refers to the torque output from the crankshaft end. When the power is fixed, it is inversely proportional to the engine speed

Under the condition of fixed power, it is inversely proportional to the engine speed. The faster the speed is, the smaller the torque is, and vice versa. It reflects the load capacity of the vehicle in a certain range. The external torque is called torque or external force couple moment, and the internal torque or internal force couple moment

engine torque refers to the torque output from the crankshaft end. When the power is fixed, it is inversely proportional to the engine speed. The faster the speed is, the smaller the torque is, and vice versa. It reflects the load capacity of the vehicle in a certain range

Like power, torque is one of the main indexes of automobile engine, which is reflected in automobile performance, including acceleration, climbing ability and so on. Its exact definition is the cross proct (m) of position vector (L) and force (f). In physics, it refers to the force that makes the object rotate multiplied by the distance to the rotating shaft. It can express the force output by the engine (because the radius of the crankshaft in the engine is fixed)

4. Thread regular tightening torque (N.m)
performance grade 5.6 performance grade 8.8 performance grade 10.9
M6 5-7 6-10 11-14
M8 12-15 19-24 22-29
M8 × 1 14-18 21-28 24-31
M10 24-30 35-47 43-53
M10 × 1.25 28-32 41-53 48-59
M10 × 1 30-36 42-54 51-58
M12 42-53 60-72 80-101
M12 × 1.5 44-56 66-82 88-107
M12 × 1.25 47-60 72-85 94-114
M14 72-87 96-126 144-175
M14 × 1.5 80-96 106-132 160-204
M16 108-127 156-200 199-234
M16 × 1.5 116-144 168-204 214-252
M18 156-180 192-226 240-260
M18 × 1.5 162-192 204-240 250-300
M20 216-243 312-372 384-439
M20 × 1.5 240-264 324-384 433-480
in addition, the tightening torque can also be calculated according to t = KDF, where k is the torque coefficient, D is the nominal diameter, and F is the bolt preload

&;

5. Explanation: bolt tightening torque refers to bolt tightening torque
generally speaking, the tensile strength and shear strength of screws are certain. In actual use, the tightening force should be calculated according to the specific connection stress, and then the screws and bolts with appropriate specifications should be selected
bolt tightening torque calculation
t = KFD
t: tightening nut torque
k: torque coefficient (approximately 0.2)
F: preload
D: bolt diameter
remarks:
generally, steel bolt connection is recommended to be determined according to the following relationship:
carbon steel: F & lt= 6 ~ 0.7) OS A1
alloy steel: F & lt= 5 ~ 0.6) OS A1
OS: yield limit of bolt material
A1: dangerous section area of bolt

6. There is a simple formula, t = KFD
where k is the torque coefficient, usually 0.2, which is similar to the friction coefficient..
F is the axial force of the bolt
D is the nominal diameter of the bolt
, This calculation is discussed in detail in the fastening and connection section of the mechanical design manual

7. Allowable error of international screw torque standard ± 10% a, in fact, the torque is the force distance of the material in the torsion deformation, so it is easy to realize the test drive form from freedom justice to obsessive-compulsive disorder, so it will be widely used. In fact, this kind of rotation force distance is the leverage principle learned in school.

8. There is a torque table, which can find out the required reference torque according to the nominal diameter and strength level of the bolt
refer to this link:
http://..com/question/381619301.html?an=0&si=2

9.

There are calculation formulas for the torque applied to the bolt and the axial force on the bolt. The detailed calculation is complicated (see the mechanical design manual for details). There is a simple formula, t = KFD. Where k is the torque coefficient, usually 0.2, which is similar to the friction coefficient, and F is the axial force of the bolt. D is the bolt. This calculation is discussed in detail in the fastening and connection section of the nominal diameter mechanical design manual

extended data:

the axial force is inertial force. When an object rotates, e to the existence of angular velocity, it will proce a centripetal acceleration. Generally, when an object rotates, it has an instantaneous axis. This object can be regarded as rotating around the instantaneous axis, so the centripetal acceleration points to the instantaneous axis. The direction of inertial force is just opposite to that of centripetal acceleration, which is called axial force

generally, the magnitude of inertial force is related to the angular velocity, mass, shape, and centroid of an object, which can not be solved by a simple formula. When a particle rotates around a fixed axis, the centripetal force F = m * W ^ 2 * r. m is the mass of the particle, W is the angular velocity of rotation, and R is the radius of rotation. If a rigid body rotates on its fixed axis, it will proce inertial force, which belongs to static balance and dynamic balance

10. Why should the bolt be driven twice when torque is applied
it is mainly for the uniform stress of each bolt
when one bolt is tightened separately, the other bolts are not in place, so the deformation is completely borne by one bolt, and the whole is deformed. Take turns to tighten graally, there is no such problem.