Hy-24 Anti-Slip Coefficient Testing Instrument

• After-sales Service: Whole Life
• Warranty: Whole Life
• Max Diameter of Workpiece: <500mm
• Mass Scope of Workpiece: 2000kg
• Type: Strength Testing Machine
• Maxcapacity: <1000KN
• Accuracy Grade: 1
• Load Way: Electronic Load
• Loading Method: Static Load
• Display: Digital
• Control: Manual Control
• Weight: 500-1000Kg
• Power Source: AC220V
• Oil Cylinder Position: Top
• Function: Anti-Slip Tightening Machine
• Axial Force Detection Range: 20-500kn
• Torque Detection Range: 10-2000nm
• Relative Resolution: ±0.5%
• Test Machine Axial Force Repeatability: ≤1%
• Bolts Nuts: M16/20/22/24/27/30
• Bolt Length Range: 50-260mm
• Platform Spindle Center Height: ≧100mm
• Twist Direction: Forward Reverse
• Display Method: Computer Control Display
• Torsion Shear Wrench (Optional for M16-3: 1 Set
• Torsion Wrench Socket (Optional for M16-: 1 Set
• Transport Package: Plywood Case
• Specification: 1600X600X1200
• Trademark: Chenji or OEM ODM
• Origin: Jinan or Others

Product Description

 30kN- 400kN HY-24 Anti-slip coefficient testing Instrument

Steel structure high-strength bolt connectors have been widely used in building steel structures and bridge steel structures. The connection quality of each connection point on it is directly related to the quality of the entire project. The quality of the main parameter anti-slip coefficient also directly affects the quality of steel structure engineering. In order to ensure the connection quality of high-strength bolts of steel structures, this paper uses experimental methods to study the factors that affect the anti-slip coefficient of high-strength bolted connections of steel structures based on theoretical analysis, so as to improve and improve the high-strength bolt connections of steel structures. Quality is the key point.
The high-strength bolt connection of steel structure has been developed into one of the main connection forms of steel structure simultaneously with welding. It has the advantages of good stress performance, fatigue resistance, good seismic performance, high connection stiffness, and convenient construction. It is widely used in construction steel. In the engineering connection between structure and bridge steel structure, it has become one of the main means of steel structure installation.
   Steel structure high-strength bolt connections can be divided into friction-type connections, friction-pressure-bearing connections, pressure-bearing connections, and tension-type connections according to their stress conditions. Among them, the friction type connection is the basic connection form widely used at present. The main component steel structure high-strength bolts can be divided into two types: large hexagon bolts and torsion shear type bolts. According to the performance level, they can be divided into 8.8 and 10.9. Level, Level 12.9, etc. At present, there are two types of large hexagon head bolts in use in my country, 8.8 and 10.9, and there is only one type of high-strength bolt for torsion shear steel structure 10.9.
    Steel structure high-strength bolt connections are generally used for important structures that directly bear dynamic loads. The main feature is to transmit shear force through contact with the friction surface. The connection strength and anti-loose performance are directly related to the quality of the project. In order to ensure the quality of steel structure high-strength bolt connections, the author has conducted experiments on the determination of the anti-slip coefficient of steel structure high-strength bolts for many years. for reference.
1. Function description
The anti-slip coefficient detector can carry out large hexagon head high-strength bolt connection pairs (M16, M20, M22, M24, M27, M30) and torsion shear type high-strength bolt connection pairs (M16, M20, M22, M24, M27, M30) and Anti-slip coefficient detection of sliding plate. There are four physical channels, and there are 24 logical channels in 6 groups. It has parameter backup and recovery functions, automatic calibration function, and peak holding function according to the detection requirements of high-strength bolts.
In order to facilitate the user to move the machine, a high-strength tie-rod instrument box is specially customized to ensure the safety and stability of the instrument. It can be connected to the computer with an RS232 interface, which can transmit data to the computer (this function requires a special order), and after further processing, print the test report.

1.Technical Parameter    
Measuring range: 30~400kN
Resolution: ±0.1kN
Indication error: ±1.0%
Display mode: LCD display                     
2.Standard Configuration List

Name	Qty	Note
HY-24LCD Control Panel	1 set
Load Sensor
120kN	4 PCS	Used for M16
180kN	4 PCS	Used for M20
220kN	4 PCS	Used for M22
260kN	4 PCS	Used for M24
330KN	4 PCS	Used for M27
400KN	4 PCS	Used for M30

      
 
3. Specimen and test
(1) Specimen
The test piece is processed by the manufacturer. The test piece and the represented steel structural member should be made of the same material, made in the same batch, using the same friction surface treatment process and having the same surface condition, and should be connected with the same batch of high-strength bolts of the same performance level Vice, stored under the same environmental conditions.
The thickness t1 and t2 of the steel plate of the test piece should be determined according to the thickness of the representative plate in the steel structure engineering. At the same time, it should be considered that the net section of the steel plate of the test piece is always in an elastic state before the friction surface slips. The width b can refer to the value specified in Table 1. L1 should be determined according to the requirements of the universal machine fixture.
The surface of the test piece should be flat, free of oil, and no flash or burr on the edge of the hole and the plate.

Chart 1   Specimen Board Width(mm)

Bolt Diameter d	16	20	22	24	27	30
Board Width b	100	100	105	110	120	120

 

1. method
2. Before the test, first select a high-strength bolt connection pair of sufficient length according to the thickness of the sliding plate and the thickness of the pressure sensor, and then drive the punching nail into the positioning hole of the test piece, and then replace it with a high-strength bolt connection pair equipped with the corresponding sensor or torsion shear high-strength Bolt connection pair. Connect the sensor to the control instrument according to the corresponding serial number. After the instrument is cleared, tighten the nut as required. After the high-strength bolt is tightened, the pre-tension value of each bolt with the sensor should be 0.95P~1.05P. When the force value of the sensor reaches the specified requirement, the control instrument starts to alarm for about 4 seconds. In order to facilitate observation, a straight line for observing slippage should be drawn on the side of the test piece.
3. Place the assembled test piece on the tensile testing machine. The axis of the test piece should be strictly aligned with the center of the fixture of the testing machine. When loading, 10% of the anti-slip design load value should be added first, and after stopping for 1 minute, then load steadily. The loading speed is 3-5kN/s, until it is pulled to slip, and the slip load is measured.
4. In the test, when one of the following situations occurs, the corresponding load can be determined as the slip load of the test piece.
5. a) Needle back phenomenon occurs in the testing machine;
6. b) The line drawing on the side of the specimen is misaligned;
7. c) The force value suddenly decays;
8. d) Sudden "bang" noise occurs on the test piece.
9. The anti-slip coefficient should be calculated according to the actual measured value of the slip load and bolt pretension P measured in the test, and it should be calculated by the following formula, and should take two significant digits after the decimal point.

 
   In Above:-- Slip load measured by test(kN):
           --Number of friction surfaces, take=2;
     --The sum of the actual measured values of the pre-tension of the high-strength bolts on the sliding side of the specimen (or the average value of the pre-tension of the bolt connections of the same batch) (take three significant figures)(kN):
     -- Number of bolts on one side of test piece,take =2.
 
 4. Factors affecting the anti-slip coefficient of the friction surface of the steel structure high-strength bolt
4.1 The influence of high-strength bolt connection of steel structure.
4.1.1 Factors of torque coefficient (or tightening axial force): Torque coefficient (or tightening axial force) is one of the main parameters for testing of high-strength bolt connections in steel structures, and its value has always affected the height of steel structures. The measured value of the anti-slip coefficient of the strength bolt is the main factor affecting it. The anti-slip coefficient can be determined only on the basis of the qualified torque coefficient. Before we test the anti-slip coefficient, when assembling the high-strength bolt connection of the large hexagon steel structure, it is necessary to determine the tightening torque value T applied to the nut. The formula is derived from K=T/(P·d) T=K ·P·d[K-torque coefficient; T-applied torque, in Newton-meters (N·m); P-bolt pretension, in kilonewtons (kN); d-nominal diameter of bolt thread, in unit of Millimeters (mm)]. The value of the tightening torque T is related to the degree of contact tightness of the friction surface of the high-strength bolt connection of the steel structure. The value of torque coefficient K also directly affects the value of torque T. During construction, we must strictly control the tightening torque. Too small a tightening torque can easily cause under-tightening of high-strength steel structure bolt connections and a small slip coefficient; too much tightening torque can easily cause over-tightening of steel structure high-strength bolt connections. The high-strength bolts of the steel structure are damaged, and the slip coefficient is invalid. The average value of the torque coefficient must always be kept between 0.110~0.150, and the single value of the torque coefficient is allowed to exceed the range of 0.110~0.150, and the standard deviation of the torque coefficient should be less than or equal to 0.0100. Torsion is mainly observed when assembling high-strength bolts of torsion shear steel structure. Unscrewing condition of the tail end of the shear bolt: if the tail end of the torx head is unscrewed, it shall be deemed that the bolt tightening torque meets the qualified quality standard, and the tail end of the torx head shall not be unscrewed according to GB50205-2001 "Code for acceptance of construction quality of steel structure engineering" Only the torque method or the rotation angle method required by the above can meet the qualified quality standards. The tightening axial force and standard deviation should meet the requirements of the following table:
 4.1.2 Factors of bolt pretension: From the calculation formula of torque coefficient K=T/P·d [K-torque coefficient; T-tightening torque/(N·m); P-bolt pretension/(kN) ; D-Nominal diameter of bolt thread/(mm)] It can be seen that the bolt pretension P directly affects the torque coefficient in the formula, and the value of the bolt tightening torque T when tightening the friction surface of the high-strength bolt of the steel structure. The bolt pretension value P (kN) should be controlled within the range specified in the table below. If it exceeds this range, the measured torque coefficient is invalid.

 4.1.3 Factors of bolt storage, transportation, loading and unloading.
    4.1.3.1 The storage period of high-strength bolts for steel structures is generally six months. In addition to the mechanical properties of general high-strength bolts, it emphasizes the stability of the torque coefficient during the connection process. Only when the torque coefficient is stable can the anti-slip coefficient be guaranteed. Therefore, the steel structure high-strength bolts must undergo surface phosphating treatment in the production process to increase the stability of the torque coefficient. If the phosphated steel structure high-strength bolts are placed long before use, the phosphated surface will react in the air and fail, and ultimately cannot ensure the accuracy of the torque coefficient, which will affect the anti-slip coefficient.
   4.1.3.2 During transportation, loading and unloading of steel structure high-strength bolts, care must be taken not to destroy the phosphate layer on the surface, and at the same time to prevent thread damage; pay attention to moisture, so as to prevent water vapor from corroding the screws and causing the screws to grow. Rust affects the torque coefficient, and ultimately cannot ensure the correctness of the anti-slip coefficient
    4.2 The influence of the plates of high-strength bolted connections of steel structures.
4.2.1 The factors of the material of the connecting piece: the high-strength bolted connecting piece of the steel structure usually adopts two common steel materials of Q235 and Q345, which have the advantages of high strength, good toughness, and large ductility. When testing the anti-slip coefficient of steel structure high-strength bolt connections, the thickness of the steel plate of the test piece should be determined according to the thickness of the representative plate in the steel structure engineering. The net section of the steel plate is always in an elastic state, that is to say, the slip load value measured when the connector is stretched is the force value obtained before the steel plate is not deformed (before yielding), so that the slip load value is finally calculated The anti-slip coefficient of is effective; the width can refer to the value specified in the following table, and the length should be determined according to the requirements of the testing machine fixture.

 4.2.2 Treatment factors for the friction surface of the connecting piece plate: the surface of the steel structure high-strength bolt connecting piece usually has sandblasting, shot blasting, grinding wheel polishing, pickling, manual rust removal and other treatment methods, which should generally be carried out according to the design requirements, no requirements Appropriate methods can be used for construction at the time of construction. However, different surface treatments have different effects on the anti-slip coefficient: in general, the design of the friction surface with a large anti-slip coefficient (such as 0.45, 0.55) should be sandblasted, shot blasted, and sandblasted (shot). The surface treatment method for post-grown red rust is completed; the design friction surface anti-slip coefficient value is small (such as 0.30, 0.35), it is better to use manual rust removal, sandblasting (shot) and then coating with inorganic zinc-rich paint and galvanized surface. . 2.2.3 Reusable factors of the friction surface of the connecting piece plate: the plate specimen used for the anti-slip coefficient test should be a material that has not been stretched. The stretched specimen is qualitatively damaged due to the internal structure of the plate. Change, the yield has also increased a lot, and the friction surface has also changed, and some even deformed. If it is reused in this way, it will inevitably affect the size of the anti-slip coefficient.

  4.2.4 Assembly factors of connecting piece plates.
  4.2.4.1 The hole diameter of the high-strength bolts on the connecting piece plate should be slightly larger than the bolt diameter. Gas cutting and reaming should not be used, and drilling and forming methods should be used; the bolt holes should be able to ensure that the high-strength bolts can penetrate freely. Damage to the screw affects the torque coefficient and the tightening torque, resulting in an inaccurate anti-slip coefficient. If it cannot be penetrated freely, it can be trimmed with a reamer. After trimming, the maximum diameter of the hole diameter should not be greater than 1.2 times the bolt diameter. Refer to the table for the hole diameter: the hole diameter is too large. Larger, the effective surface of the nut contacting the plate will be smaller, which will easily cause the connector to be screwed in place, which will affect the slippage under force.
    4.2.4.2 After the high-strength bolts are finally screwed on the connecting plate, the bolt threads should be exposed to 2 to 3 buckles, of which 10% of the bolt threads are allowed to expose 1 or 4 buckles. Too much affects the tightening, and the lack of tightening is easy to slip, and the connector is easy to crack when it is stretched, which affects the tightening of the plate and the slippage of the connector.
    4.2.4.3 When the connecting plate is assembled with high-strength bolts, the side of the nut with the round table should face the chamfered side of the washer, and the chamfered side of the washer under the bolt head should face the bolt head, so that when tightening It is unlikely to slip; and when tightening high-strength bolts, you should try to tighten them from the middle to the four sides, so that the tightened joints can be tightly sealed, with high friction and large anti-slip coefficients, to meet the requirements.
    4.3 The influence of the accuracy of the test instrument.
    4.3.1 The torque wrench used for tightening must be calibrated before use, and its torque error shall not exceed 2%.
    4.3.2 Axial force gauge shall be used for bolt pretension, and its error shall not be greater than 2% of the measured bolt pretension, and the minimum indicated value of the axial force gauge shall be less than 1kN.
    4.3.3 The error of the tensile testing machine used to measure the anti-slip coefficient should be within 1%.
    4.4 Influence of the test process
    4.4.1 The anti-slip coefficient test shall adopt the tensile test piece of two bolts splicing with double friction surfaces.
    4.4.2 When fastening high-strength bolts, the connecting plate shall be divided into initial and final tightening. The initial tightening should reach about 50% of the standard value of the bolt pretension; the final tightening torque is calculated by the formula Tc=K×Pc×d[K-average value of torque coefficient, Pc-construction pretension, d-nominal diameter of high-strength bolt]. After the test piece is assembled, a straight line for observing the slip should be drawn on its side. Placed on the tensile testing machine, the axis of the test piece should be strictly aligned with the center of the fixture of the testing machine. When loading, you should add 10% of the anti-slip design load value, stop for 1 min, and then load steadily. The loading speed is 3~5kN/s, and the sliding load NV is measured. When one of the following situations occurs, the corresponding load can be defined as the slip load of the test piece: The needle back phenomenon occurs on the testing machine; The line drawing on the side of the test piece is misaligned; The deformation curve on the X-Y recorder changes suddenly; The test piece suddenly made a "boom" noise.
    Calculate the anti-slip coefficient according to the formula. The anti-slip coefficient is tested for a set of three pieces, and the MIN must be equal to or greater than the specified value of the design.
    Nowadays, steel structure high-strength bolt connection projects are rushing, the market competition is fierce, and more and more problems are exposed in it. The factors are also complicated, such as poor quality of high-strength bolts, poor anti-slip coefficients of connectors, etc. From here. In order to ensure the quality of steel structure high-strength bolt connection projects, people need to constantly sum up experience in daily work, find out more influencing factors, analyze the reasons, and improve steel structure high-strength bolt connection projects to a worry-free situation.