CN104680517A - Looseness detection method of bolt - Google Patents

Abstract

The invention relates to a detection method for bolt looseness, which belongs to the technical field of mechanical state detection and maintenance. First, mark the bolts to be tested after tightening. After the bolts to be tested are loosened, take photos of the bolts. The photos include the first mark, the second mark and the complete image of the bolts to be tested; after taking the image, use the calculation algorithm of the image angle, Through image grayscale, image binarization, edge detection, and judgment of feature symbols, the coordinate positions of the first mark and the second mark in the photo are respectively identified; according to the coordinate position, the relative rotation angle between the two marks is calculated; The relative rotation angle is compared with the set angle threshold, and the loose bolts are tightened. The method of the invention improves the pertinence of bolt loosening detection and ensures safe and reliable operation of equipment.

Description

A method for detecting bolt looseness

technical field

The invention relates to a detection method for bolt looseness, which belongs to the technical field of mechanical state detection and maintenance.

Background technique

At present, as a connecting piece, bolts are widely used in various fields of national production, such as railway transportation, aerospace, wind power generation, machining, etc. The tightening state of the bolt will directly affect the working performance of the equipment, and if there is a problem, it may cause disastrous consequences.

Usually, the failure of bolts mainly includes fracture and loosening, among which loosening is the most common problem. At present, there are many detection methods for bolt looseness, such as detection of changes in pre-tightening force, detection of nonlinear characteristics of connection systems, and detection of acoustic emission signals. These methods can indeed detect the loosening of bolts, but their operations are often complicated and the efficiency is relatively low, which is not conducive to the application in actual production. Moreover, as an important connection method, the bolt connection is used in a huge amount, and it is difficult to detect the state of each bolt by the above-mentioned method.

Taking railway trains as an example, rail locomotives are very important means of transportation in daily life, and their safety cannot be ignored. In order to ensure the safe operation of the locomotive, the staff needs to check its condition every day. One of the inspection items is to check whether the bolts are loose. Usually, there are hundreds or even more bolts on a car, and there are many trains in a day, so the detection of bolt looseness is an extremely heavy work. There are two main methods of traditional inspection of bolts: one is that regardless of whether the bolts have been loosened, the workers will tighten the bolts with a wrench to ensure that the bolts are in a tightened state; the other is that the bolts are on the bolts and nuts after the first tightening Use a line to mark the tightening state. When checking, you only need to check whether the dashed lines on the bolt and nut are aligned. If they are not aligned, tighten them until they are aligned. The first method has a large workload, low efficiency, and is not targeted, while the second method is likely to cause visual fatigue to the workers after inspecting a large number of bolts, resulting in false inspections and missed inspections, especially for the high-speed trains currently in operation, which require workers It can quickly and accurately complete the detection of bolts. Moreover, the above-mentioned methods for detecting bolt looseness are all qualitative detections, and cannot quantitatively indicate the degree of bolt looseness, which is not conducive to focusing on monitoring individual easy-to-loose bolts. Ensuring a good connection state of bolts is one of the prerequisites for safe train operation, and the existing detection methods for bolt connection state are difficult to meet the needs of railway operations in terms of operability, cost, speed, and accuracy. It is necessary to explore new methods to detect the loose state of bolts.

Contents of the invention

The purpose of the present invention is to propose a detection method for bolt looseness, aiming at overcoming the problems of low efficiency, time-consuming and labor-intensive, fatigue misjudgment and the like existing in the traditional detection of bolt looseness. Through the image analysis technology, the relative rotation angle of the marking symbol on the bolt before and after loosening is calculated, and the angle of bolt loosening is quantified, which provides a fast and accurate method for the detection and maintenance of the bolt connection state.

The detection method of bolt looseness proposed by the present invention may further comprise the steps:

(1) Mark the bolt to be tested after tightening, make the first mark on the fixed part of the bolt, and make the second mark on the rotating part of the bolt. The first mark and the second mark are on a straight line, and the symbol of the mark is straight lines or dots,

(2) After the bolt to be tested is loosened, take a photo of the bolt, the photo includes the first mark, the second mark and the complete image of the bolt to be tested;

(3) After the image is captured, the coordinate positions of the first mark and the second mark in the photo are recognized respectively through image grayscale, image binarization, edge detection, and feature symbol judgment using the calculation algorithm of the image angle;

(4) According to the coordinate positions of the first mark and the second mark, the relative rotation angle α between the first mark and the second mark is calculated by a plane geometry method;

(5) Set the threshold α ₀ of the relative rotation angle, compare the relative rotation angle α in step (4) with the threshold α ₀ of the relative rotation angle, if α≥α ₀ , then tighten the bolt to be tested, if α <α ₀ , then detect the next bolt.

The identification method of bolt looseness that the present invention proposes, its advantage is:

(1) The bolt loosening detection method proposed in the present invention can simply mark the fixed part and the rotating part of the bolt to be measured; then conveniently take the bolt image through the camera, and identify and quantify the bolt loosening angle by image angle; when the relative rotation angle exceeds the set When the angle threshold is reached, it can automatically alarm, improve the pertinence of bolt loosening detection, and ensure the safe and reliable operation of the equipment;

(2) The bolt loosening identification method proposed by the present invention can store the detection results of each bolt in the database, and through long-term data accumulation, it is beneficial to evaluate the long-term loosening law of the bolts, and enter the basic data of equipment operation and maintenance as quantitative data information Archives, thereby improving the evaluation and monitoring of the safety and reliability of equipment bolt fastening.

Description of drawings

Fig. 1 is a flow chart of the detection method for bolt looseness proposed by the present invention.

Fig. 2 is a schematic diagram of bolt loosening marks in the detection method for bolt loosening proposed by the present invention, wherein (a) is a schematic diagram when the bolt is tightened; (b) is a schematic diagram of the bolt after the bolt is loose.

In Fig. 2, 1 is the fixed part in the bolted connection, 2 is the first mark on the fixed part, 3 is the rotating part in the bolted connection, and 4 is the second mark on the rotating part.

detailed description

The detection method of bolt looseness that the present invention proposes, its flow chart as shown in Figure 1, comprises the following steps:

(1) Mark the bolt to be tested after tightening, as shown in Figure 2, make the first mark 2 on the fixed part 1 of the bolt, make the second mark 4 on the rotating part 3 of the bolt, the first mark 2 and the second mark The mark 4 is on a straight line, and the symbol of the mark is a straight line or a dot. In one embodiment of the present invention, the first mark and the second mark are straight lines;

(2) After the bolt to be tested is loosened, take a photo of the bolt, the photo includes the first mark, the second mark and the complete image of the bolt to be tested;

(3) After the image is captured, the coordinate positions of the first mark and the second mark in the photo are recognized respectively through image grayscale, image binarization, edge detection, and feature symbol judgment using the calculation algorithm of the image angle;

(4) According to the coordinate positions of the first mark and the second mark, the relative rotation angle α between the first mark and the second mark is calculated by a plane geometry method;

(5) Set the threshold α ₀ of the relative rotation angle, compare the relative rotation angle α in step (4) with the threshold α ₀ of the relative rotation angle, if α≥α ₀ , then tighten the bolt to be tested, if α <α ₀ , then detect the next bolt.

The relative rotation angles of the first mark and the second mark detected by the method of the present invention can be stored in the database, and a series of follow-up processing can be carried out according to the rotation angle obtained by multiple detections, for example, the rotation angle can be marked in the photo , and compare the detected rotation angle value with the preset threshold value, if the detected value exceeds the set threshold value, corresponding prompts and operation suggestions will be given, such as a prompt to judge that the bolt is seriously loose and needs to be re-tightened The detection data of the bolt loosening angle in the use stage can be used for the evaluation of the safety and reliability of the bolt fastening of the equipment.

Claims (1)

1. A detection method for bolt looseness, characterized in that the detection method may further comprise the steps: (1) Mark the bolt to be tested after tightening, make the first mark on the fixed part of the bolt, and make the second mark on the rotating part of the bolt. The first mark and the second mark are on a straight line, and the symbol of the mark is straight lines or dots, (2) After the bolt to be tested is loosened, take a photo of the bolt, the photo includes the first mark, the second mark and the complete image of the bolt to be tested; (3) After the image is captured, the coordinate positions of the first mark and the second mark in the photo are recognized respectively through image grayscale, image binarization, edge detection, and feature symbol judgment using the calculation algorithm of the image angle; (4) According to the coordinate positions of the first mark and the second mark, the relative rotation angle α between the first mark and the second mark is calculated by a plane geometry method; (5) Set the threshold α ₀ of the relative rotation angle, compare the relative rotation angle α in step (4) with the threshold α ₀ of the relative rotation angle, if α≥α ₀ , then tighten the bolt to be tested, if α <α ₀ , then detect the next bolt.