What are the factors that affect nondestructive testing?

　　The role of non-destructive testing technology in the quality assurance system is increasingly showing its importance and necessity, and it has become an important means to control product quality and ensure the safe operation of in-service equipment. However, its important role depends on the correct selection of non-destructive testing methods and whether the test results are reliable. This is important from the perspective of product quality. From a purely economic point of view, reliability is also necessary to reduce total cost expenditure. In recent years, due to the mutual competition in the product market, high quality is an important factor in improving competitiveness. Therefore, many departments and enterprises have gradually attached importance to strengthening the quality inspection system. For those responsible for quality inspection, it is very important and necessary to study and understand the various factors that affect the reliability of non-destructive testing results.

　　The factors that affect the reliability of the test results can be analyzed from two aspects. The first is the influence of human factors, which can be divided into three aspects:

　　⒈ The technical level, operating skills, knowledge level, etc. of the testing personnel; ⒉ The testing personnel's sense of responsibility for work; ⒊ The psychological and physiological conditions of the testing personnel during the operation.

　　The above three aspects are interrelated, but among the three aspects, the technical level and operating skills of the inspectors are the main ones. It is impossible for personnel without technology to obtain highly reliable test results. Therefore, it is an important measure to improve the reliability of non-destructive testing results to conduct grade training for non-destructive testing personnel so that they can reach the technical level and operating skills specified by the grade through training. Grade training is the work of standardizing the knowledge level and operating skills of non-destructive testing personnel, so that operators of different levels can reach the same level after training, so that it is possible to obtain roughly the same test results when testing the same workpiece, and achieve better comparability, reliability and credibility.

　　It goes without saying that the work responsibility of the inspectors is very important. Nondestructive inspectors with the same technical level may get different test results due to different work responsibilities. Mistakes caused by lack of work responsibility may have unimaginable serious consequences. Educating nondestructive inspectors to establish a responsible work attitude is an important part of improving the reliability of nondestructive testing results.

　　The physical and physiological condition of the test personnel during the operation will also affect the reliability of the test results. Excessive fatigue due to physical exhaustion or long working hours will affect the operator's concentration, which will have an adverse effect on the test results and cause errors.

　　In order to minimize the adverse effects of human factors in the non-destructive testing process, in addition to paying attention to personnel training, professional ethics education and the correct use of personnel, the development of non-destructive testing automation technology is an important way to improve the reliability of test results and reduce the degree of human participation in the entire testing process.

　　In addition to the main human factor, the reliability of the test results is also affected by objective factors, which can also be divided into three points:

　　⒈ The influence of the performance of testing instruments and equipment; ⒉ The influence of testing working environment conditions; ⒊ The influence of the limitations of different non-destructive testing methods.

　　The performance of the testing instrument will also affect whether the test results are correct. The performance of modern ultrasonic waves has been greatly improved in terms of function and applicability. The results of modern ultrasonic flaw detectors with microcomputers are far more reliable and important than those of early ultrasonic flaw detectors. Regardless of the non-destructive testing method, the performance of instruments and equipment will affect the reliability of the test to varying degrees. For example, if there are differences in performance when using the same type of probe, the test results will also be different. Therefore, improving and improving the performance of non-destructive testing instruments and equipment is an important aspect of improving the reliability of testing.

　　The influence of the working environment on the test results is often easily overlooked. Under laboratory conditions, the surrounding environment can be strictly controlled, the room temperature is more suitable, the environment is quieter, and the operation time is not strictly limited. Therefore, the test results will obtain higher test reliability than on-site conditions. For example, under laboratory conditions, the object to be tested can be fully cleaned to remove the oil stains on the object to be tested, and satisfactory test conditions can be obtained, so as to obtain higher test sensitivity, which is difficult to achieve under on-site conditions. For example, on-site noise, unsuitable temperature, etc. will affect the psychological and physiological conditions of the test personnel and affect the test results. Therefore, improving environmental conditions is also an important part of improving test reliability.

　　In addition to the above, another important factor affecting the reliability of detection is the limitation of nondestructive testing methods. Different nondestructive testing methods are based on different physical principles, which determines that each nondestructive testing method has its own characteristics and limitations. Therefore, when testing, attention should be paid to the characteristics of a certain method and avoiding its limitations. For example: for the weld inspection of pressure vessels, the use of both X-ray and ultrasonic methods can obtain higher detection reliability than using only one of the methods. Some defects can only be found by ultrasound, while others, such as small pores or small slag inclusions, are easy to detect by radiography, so the results obtained by using only one method for detection are not comprehensive. Because different methods have their own limitations, only by using multiple methods for detection can higher reliability be achieved.

　　When talking about the reliability of nondestructive testing, the reliability of nondestructive testing results should not be confused with the reliability of equipment or products. These are two different issues, but they are related. The reliability of equipment and products is not only related to the reliability of nondestructive testing results, but also closely related to design, material selection, processing, technology, and operating conditions.

　　In addition, the reliability of nondestructive testing does not mean that all defects on the inspected object must be detected, because absolutely defect-free material does not exist, and any nondestructive testing method has its limit detection sensitivity. Therefore, nondestructive testing personnel can only be required to detect defects of a certain equivalent size that are not allowed to exist inside or on the surface of the workpiece according to the standard.

　　In summary, in order to improve the reliability of non-destructive testing results, various non-destructive testing methods should be regarded as a complete system, giving full play to the characteristics of different methods, and obtaining as much useful information as possible to make correct judgments. Even if it is a testing method, it should be regarded as a complete system.

　　As a detection system, the following three items are the most basic requirements to improve the reliability of detection:

　　⒈ General criteria for judging the performance of the detection system;

　　⒉ It should have the inspection standard of the inspected object;

　　⒊ Operators should be trained and qualified.