How to calculate the bearing force according to the bolt grade

1. Tool torque = friction force of bolt connection pair + clamping force. The pressure can be calculated only when the actual clamping force is known or measured. Generally, the friction force accounts for 80-90% of the tool output, and case by case should be analyzed and determined according to the situation.

2.

Stress sectional area of M6 nut: 20.1 square mm

so the shear stress = 50 * 9.8 / 20.1 = 24.38mpa. If the bolt is of grade 4.8, its tensile strength is 400MPa, and the shear strength is about half of the tensile strength, 200MPa

200 / 24.38 = 8.2, so the safety factor is large, no problem

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the stress cross-sectional area of M1 bolt: 0.46

the stress cross-sectional area of M2 bolt: 2.07

the stress cross-sectional area of M3 bolt: 5.03

the stress cross-sectional area of M4 bolt: 8.78

the stress cross-sectional area of M5 bolt: 14.2

the stress cross-sectional area of M6 bolt: 20.1

the stress cross-sectional area of M8 bolt: 36.6

the stress cross-sectional area of M10 bolt: 58

the stress cross-sectional area of M12 bolt Stress section area of bolt: 84.3

stress section area of M14 bolt: 115

stress section area of M16 bolt: 157

stress section area of M18 bolt: 192

stress section area of M20 bolt: 245

stress section area of M22 bolt: 303

stress section area of M24 bolt: 353

stress section area of M27 bolt: 459

stress section area of M30 bolt: 5 61

M33 bolt stress section area: 694

M36 bolt stress section area: 817

M39 bolt stress section area: 976

II. Bolt code meaning

8.8 grade bolt meaning is bolt strength grade mark code by "•" It consists of two separated numbers. In the marking code "&" 8226; " Carbon steel: metric bolt mechanical property grade can be divided into: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 13.5

1, bolt material nominal tensile strength of 800MPa The first 8)

2, the yield ratio of bolt material is 0.8 The second 8 is 0.8)

3. The nominal yield strength of bolt material is 800 × 3. The relationship between shear stress and tensile force has been proved by experiments. For general steel, the relationship between allowable shear stress and allowable tensile stress is as follows: plastic material [t] = 0.6-0.8 [b]; Brittle material [t] = 0.8-1.0 [b]

part stress value

the maximum stress value of parts or components in mechanical design or engineering structure design. In order to determine whether the working stress of a part or component is too high or too low after loading, it is necessary to determine a measurement standard in advance, which is the allowable stress. When the working stress of a part or component does not exceed the allowable stress, the part or component is safe in operation, otherwise it is unsafe. Allowable stress is the basic data in mechanical design and engineering structure design. In practical application, the allowable stress value is generally stipulated by the national engineering department according to the principles of safety and economy, material strength, load, environmental conditions, processing quality, calculation accuracy and the importance of parts or components. The allowable stress is equal to the failure stress (yield limit or strength limit in static strength design and fatigue limit in fatigue strength design) of the material after considering various influencing factors, divided by the safety factor. Plastic materials (most structural steels and aluminum alloys) are based on the yield limit, divided by the safety factor to obtain the allowable stress, i.e[ σ]=σ s/nn=1.5~2.5; For brittle materials (cast iron and high strength steel), the allowable stress is obtained by dividing the strength limit by the safety factor, i.e[ σ]=σ b/n(n=2~5)( N is the safety factor)

3.

Different models bear different tensile capacity

There are nine grades, and each grade corresponds to the corresponding tensile strength

calculation:

according to material and effective diameter (area)

if the material of the bolt is Q235 and the effective diameter is 10.3mm, the maximum bearing force of the bolt is 210 × three point one four × 10.3/2^2

4. According to the tensile strength of the material used for the screw and the diameter of the screw (according to the inner diameter of the thread), calculate the force it can bear (force = tensile strength x cross-sectional area). If necessary, consider the factor of safety.

5.

The shear stress is σ= Ws/Akg/mm^2

normal stress: σ= W / a (kg / mm ^ 2) W: tensile or compressive load (kg) a: sectional area (mm ^ 2) (2 is the square)

shear stress: σ= WS / a (kg / mm ^ 2) ws: shear load (kg) a: sectional area (mm ^ 2) (2 is the square)

there are also: strain, elastic molus, Poisson's ratio, stress concentration, thermal stress, allowable stress and safety factor, etc

the shear force of ordinary bolt connection is transferred by the shear resistance of bolt bar and bearing pressure of hole wall, and the pretension is very small when the nut is tightened, and its influence can be ignored

In addition to the high material strength, the high strength bolt also exerts a large pre tension force on the bolt, which proces extrusion force between the connecting members, thus causing a great friction force perpendicular to the screw direction, and the pre tension force, anti slip coefficient and steel type all directly affect the bearing capacity of the high strength bolt

extended data:

the working principle of high-strength bolt connection is to intentionally exert a large pre tension on the bolt, so as to proce extrusion force between the contact surfaces of the connected parts, so there is a large friction force perpendicular to the screw direction, and the shear force of connection is transferred by this friction force

The torque method and angle method are generally used in common high-strength bolts. In order to control the pretension force, the tail of the bolt is twisted

the construction of high-strength bolts must be done after initial tightening, and the initial tightening of high-strength bolts needs impact electric wrench or torque adjustable electric wrench; The final tightening of high-strength bolts has strict requirements. The final tightening of high-strength bolts must use the torque electric wrench, and the final tightening of high-strength bolts must use the torque electric wrench

6.

According to material and effective diameter (area)

if the material of the bolt is Q235 and the effective diameter is 10.3mm, the maximum bearing force of the bolt is 210 × three point one four × 3 / 2) ^ 2

check the national standard GB / T 3098.1 bolt guarantee load

In other words, the ordinary bolt (grade 4.8) can work normally under the tension of less than 26100n (or the weight of less than 2660kg)

7. Different levels have different forces, please give the bolt level, I will help you calculate OK

8. First of all, we need to know what grade of bolt is. The ordinary bolt is grade 4.8, and the tensile stress is basically about 400MPa. The stress area can be calculated from the thread diameter. According to the formula stress = stress / stress area, we can calculate the tensile force we can bear. This is only a general algorithm. In actual situation, we should also consider factors such as safety factor
the grades of bolts are as follows: (3.6), 4.8, (6.8), 8.8, 10.9, 12.9, etc

9. There are more than 10 performance grades of bolts, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. The bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and heat treated (quenched and tempered). They are generally called high strength bolts, and the rest are called ordinary bolts. There are two parts in the performance grade of bolt, which are the nominal tensile strength value and yield strength ratio of bolt material. For example:
the bolt with performance grade 4.6 means:
1. The nominal tensile strength of bolt material reaches 400MPa
2. The yield ratio of bolt material is 0.6
3. The nominal yield strength of bolt material is 400 × 6 = 240mpa
performance grade 10.9 high strength bolt, the material after heat treatment can reach:
1, the nominal tensile strength of bolt material can reach 1000MPa
2. The yield ratio of bolt material is 0.9
3. The nominal yield strength of bolt material is 1000 × 0.9 = 900MPa
the meaning of bolt performance grade is an international standard. Bolts with the same performance grade have the same performance regardless of their material and origin. Only performance grade can be selected in design< The so-called 8.8 and 10.9 strength grades refer to the shear stress grades of 8.8gpa and 10.9gpa
8.8 nominal tensile strength 800N / mm2 nominal yield strength 640n / mm2
General bolts are made of & quot; X.Y" X * 100 = the tensile strength of the bolt, X * 100 * (Y / 10) = the yield strength of the bolt (because according to the marking: yield strength / tensile strength = Y / 10)
If grade 4.8
then the tensile strength of the bolt is 400MPa; The yield strength is 400 * 8 / 10 = 320MPa
the selection of bolts can refer to hg20592-20635 upper fasteners