Analysis on Damage and Detection of Steel Wire Rope

introduction
Wire rope is a commonly used equipment component in various industrial and mining enterprises. Its safe and reliable use is a prerequisite for safe production, and an important guarantee for the life safety of operators and the safety of national property. Like many countries and regions in the world, my country attaches great importance to the management and use of wire ropes. We always adhere to the basic policy of safety production management of "safety first, prevention first". In recent years, more and more attention has been paid to the safe use of wire ropes. Correctly understanding the damage forms and causes of wire ropes and using scientific methods and means to detect them are important links to prevent problems before they occur.

1. Damage forms and causes of wire ropes
Due to the special working environment and structural characteristics, in addition to the normal working load, the steel wire rope will be affected by various uncertain loads, harsh external working environment and improper human operation during the working process, resulting in friction Wear, corrosion, broken wires and other phenomena cause damage and decrease in bearing capacity, affecting service life.
1.1 Friction and wear
The main reasons for friction and wear are:
(1) During normal operation, there is a slight misalignment between the inner strands of the wire rope. Long-term fretting friction will cause the wear of the steel wire, which is an unavoidable loss of the steel wire rope during normal operation. Regular lubrication and maintenance can slow down the progress of the wear and tear.
(2) When the wire rope works for a period of time and is used dry, the wire rope itself will be subjected to various loads and impact forces, and a certain degree of plastic deformation will occur. If two adjacent and contacting steel wire ropes have different degrees of deformation due to different loads during operation, they will slide against each other during operation, resulting in certain wear on their surfaces.
(3) During the normal operation of the wire rope, the outer surface will produce contact wear, which is mainly the wear of the outer layer of steel wire;
(4) When the wire rope is working, it is wound on the reel. If two adjacent turns are not wound on the reel in order, but are wound together, causing the rope to bite and friction damage during work; Some dust and solid particles adhere to the surface of the wire rope, which will also aggravate the wear of the wire rope during operation.
In the initial stage of friction and wear, the most intuitive change in the characteristics of the wire rope is the change in the diameter of the wire rope. The friction and wear will also cause stress concentration, which greatly destroys the tensile strength of the wire rope. The development of friction and wear can cause wire breakage.
1.2 Corrosion
Because the working environment of steel wire rope is generally harsh, it is easily corroded when exposed to various chemical substances or in a dark and humid environment.
As one of the phenomena of corrosion, rust is more serious in a dark and humid environment. Corrosion not only affects the mechanical properties of wire ropes, but is also difficult to quantitatively evaluate. In addition, the steel wire rope will inevitably come into contact with corrosive chemicals during work, and it will also be corroded. After the corrosion occurs, the steel wire on the outer layer will loosen to a certain extent, which affects the performance of the steel wire rope itself to a large extent.

1.3 Broken wire
There are many reasons for wire breakage. In addition to the friction and wear and corrosion mentioned above, the development of the wire rope will cause wire breakage. Fatigue, overload and kink will also cause wire breakage.
(1) Fatigue: When the wire rope bears a certain tension, it is repeatedly bent around the drum or pulley. Under the action of this alternating stress, the steel wire is broken due to metal fatigue. This kind of broken wire generally occurs on the surface first. If it is not found in time, it will be carried out to the inside of the wire rope, causing a safety hazard. Fatigue new cracks will cause the wire rope to suddenly concentrate in a short range in a short period of time, new wires, new strands or even broken ropes, which is more harmful. around
The more times the reel or pulley is passed and the smaller the radius, the greater the bending deformation of the steel wire, the greater the bending stress, and the faster the fatigue damage of the steel wire.
(2) Overload: Each wire rope has its own bearing range, except that it needs to bear the static load of goods, self-weight, etc. during normal operation. The wire rope is also subjected to dynamic loads caused by acceleration and impact at any time. When the tensile force or impact load of the wire rope exceeds the bearing range, it will cause the wire to break.
(3) Kink: When using the wire rope incorrectly, it will cause deformation problems such as kink in the wire rope. If it is not handled in time, the wire rope will suddenly crack during operation, causing serious accidents.

2. Application of non-destructive testing technology in wire rope damage detection
2.1 Visual inspection method
Visual inspection is a traditional and intuitive method for inspecting the condition of wire ropes. The method mainly detects the wire rope through visual observation and with the help of some simple detection tools. Direct visual inspection of the wire rope can visually see the wear and corrosion phenomenon, but it is impossible to quantitatively determine the degree of wear and corrosion, and whether it meets the standard of scrapping. We can use magnifying glass, vernier caliper and other tools to measure the diameter of the wire rope, get the value of the rope diameter, calculate the wear amount of the wire rope, and draw corresponding conclusions. The advantage of the visual method is that it is more intuitive and easy to operate. However, because the visual inspection method can only detect the wear, corrosion and broken wires on the surface of the wire rope, it is difficult to detect the broken strand defects in the wire rope. Therefore, it is necessary to combine the more advanced detection technology to comprehensively determine the status of the wire rope.
2.2 Magnetic flux leakage detection method
The magnetic flux leakage detection method is produced on the basis of the traditional defect detection method. The principle is: the magnetizer introduces the magnetic energy into the wire rope. A leakage magnetic field is generated, and sensors such as a Hall element or an induction coil installed in the middle of the magnetizer will sense the change of the magnetic field, and convert the change of the magnetic field into an electrical signal that can be measured and transmitted. After processing, the final judgment basis for damage is formed. The magnetic flux leakage detection method is a local defect detection method, which is effective for the detection of local wire damage, especially the broken wire problem. The advantage of the magnetic flux leakage detection method is that it reduces the labor intensity and improves the detection efficiency. It can detect not only the surface but also the internal wire damage. However, due to its susceptibility to electromagnetic interference and other environmental influences, it is impossible to quantitatively detect the damage of the new wire rope. The Muyugan steel wire rope needs to pass through the detection instrument. When the broken wire is lifted, the sensor probe will be scratched.
2.3 Ultrasonic testing method
Ultrasonic testing is a method of flaw detection using the principle that ultrasonic energy penetrates into the interior of the material and propagates along the material medium. When one section enters another section, reflection occurs at the edge of the interface. Therefore, when the ultrasonic beam is emitted from the surface of the wire rope to the interior, it will reflect when it encounters the broken wire and the bottom surface. The specific state of the interior of the wire rope is obtained by analyzing the reflected waveform. Using ultrasonic detection method to detect the damage of wire rope can improve the accuracy and efficiency of wire rope detection. The ultrasonic testing system is composed of ultrasonic control processing system, emission system, signal processing system, etc. The required information can be obtained by adjusting technical parameters such as frequency. The ultrasonic testing method can detect the defects inside and on the surface of the wire rope, but when the defect is detected at a long distance, the detection accuracy and accuracy are not enough due to the excessive ultrasonic energy loss.
2 4 Image detection methods for basic machine vision
Machine vision inspection technology is a non-contact non-destructive inspection technology that has developed rapidly in recent years. The principle of this technology is to convert the inspected target into image signals through machine vision products (such as CCD industrial cameras), and transmit them to the image processing system to obtain the captured image. The information of the target, such as pixel distribution, brightness, color, etc., is then digitally processed, and the information is subjected to the operation of extracting the target features according to the needs, and then the corresponding judgment is made according to the result.
Limited by software and hardware technology, the application of machine vision inspection technology in wire rope inspection is limited to the measurement of dimensions, such as the measurement of wire rope diameter. In recent years, with the rapid development of machine vision technology and the rapid improvement of software and hardware conditions, wire rope detection technology based on machine vision technology has been more and more applied. The characteristics of this method are non-contact, and the sensor probe will not be scratched by broken wires, but it has strict requirements on lighting conditions, and has high requirements on the form and brightness of the light source. It can only detect surface damage, but cannot detect internal damage. . However, the requirements for the surface cleanliness of the steel wire rope are relatively high. If there is oil pollution, dust, etc., it is easy to cause misjudgment.

3. Summary
To sum up, wire rope is one of the most important parts of cranes, elevators and many other equipment, and is closely related to the production of enterprises and people's lives. The safe and normal use of wire rope is an important guarantee for safe production. Correctly understanding the cause of the damage of the wire rope and doing targeted daily maintenance can improve the service life of the wire rope. According to the actual situation, selecting the appropriate detection method for safety detection is also essential for safe production and avoiding production accidents. Since different detection methods have their own advantages and certain limitations, one or more combinations of detection methods can be selected in actual use to improve the damage detection rate and reduce misjudgments and missed judgments.