This article elaborates and discusses the role and application methods of non-destructive testing technology in the quality supervision and control of military construction projects, and puts forward corresponding opinions on its current situation and development direction.

1. Preface

National defense construction projects have special functions and roles, which determine that their engineering quality must not only ensure structural safety and meet the requirements of military readiness and training in peacetime, but also withstand multiple strikes from destructive weapons and strong impacts from other factors during wartime. So, how to supervise and control the quality of engineering projects and build high standards is an important responsibility of engineering quality supervision workers.

In the process of engineering quality supervision and control, with the continuous development of supervision methods and testing instruments, the technological content of quality supervision work is also constantly increasing. The non-destructive testing technology introduced and used in recent years is a good example. The so-called non-destructive testing technology is to calculate the engineering quality indicators of materials and structures through in-situ detection of certain physical quantities (such as rebound value, ultrasonic wave velocity, vibration frequency, infrared radiation, etc.) without affecting the performance of engineering structures, such as strength value, thickness value, internal defect points, steel bar position, composition content, etc. It has more attractive characteristics than conventional detection methods: non-destructive, random, long-distance detection, on-site detection, and so on; And the detection data can be continuously collected, and through mathematical analysis and logical judgment, the condition of engineering quality can be accurately estimated, thus making up for the previous practice of simply inferring the quality of engineering through visual inspection and appearance quality control deviation in quality supervision, and making the results of supervision and detection more authentic, scientific and reliable. Especially for military preparedness and protection engineering, accurately identifying and evaluating their quality status is related to the safety of soldiers' lives and the safety of armed facilities. Therefore, it is of great significance to fully utilize non-destructive testing technology and strictly control the quality.

2. Current status of non-destructive testing technology

2.1 Non destructive testing technology for construction projects in China has developed rapidly in the past 20 years, and several individual technologies have entered a good level of research and application. Since the 1980s, through multiple technical collaborations and breakthroughs, regulations for non-destructive testing of concrete strength have been developed, including rebound method, ultrasonic rebound comprehensive method, core extraction method, and pull-out method. These industry standards and association standards have effectively promoted the application of non-destructive testing technology in engineering. So far, most of the secondary testing centers in China have the conditions to carry out non-destructive testing services.

2.2 The non-destructive testing technology system is becoming increasingly advanced. In addition to commonly used ultrasound, infrared imaging technology, radar technology, wave analysis technology, electromagnetic, laser and other technologies are also gradually being applied. For example, there are precedents in various provinces and cities across the country for using far-infrared imaging to detect the quality of exterior wall tile pasting, radar ground penetrating to detect the quality of roads and highways, and wave analysis to detect the quality of pile foundations.

2.3 The supporting development and research of testing equipment and instruments have evolved into the era of digital intelligence, with comprehensive and analytical functions for test results and calculations. Test data has also entered information processing from simple mathematical statistics. Most of them have been equipped with laptops and random keyboards, and are even as simple as the "one click, everything can be managed" fool type.

3. The role of non-destructive testing technology in engineering quality supervision and control

The application of non-destructive testing technology in engineering has become increasingly widespread. The on-site, practical, and rapid characteristics of non-destructive testing technology provide a good scientific means for engineering quality supervision work, and its role in the overall construction quality monitoring is becoming increasingly important.

3.1 Non destructive testing technology is one of the legal methods for detecting and handling engineering quality accidents. In the "Code for Construction and Acceptance of Concrete Structure Engineering"

In GB50204-92, it is explicitly stipulated that "when the strength representativeness of concrete specimens is affected, non-destructive testing methods or the method of drilling core samples from structures or components can be used to estimate the strength of concrete in structural components according to relevant standards, as a basis for whether treatment should be carried out

3.2 Non destructive testing technology is an effective means of engineering quality pre control and supervision. With the improvement of the reliability of non-destructive testing, its testing results are not only a commonly used basis for quality treatment, but also increasingly used as a quality control method in the construction process, allowing non-destructive testing technology to intervene in construction management. For example, the rapid testing instrument for fresh concrete can test the cement content and water cement ratio in the fresh concrete discharged from the tank within a few minutes, and estimate the strength value at 28 days, playing a role in pre monitoring. The steel bar position and protective layer measuring instrument can simulate the diameter of the steel bars inside the concrete and the thickness of the protective layer, thus more effectively monitoring the quality behavior of the construction process.

3.3 Non destructive testing technology is an important basis for engineering evaluation and quality assessment. Based on the evaluation of engineering quality represented by the measured values of standard test blocks, the comparison of non-destructive testing results can not only verify the authenticity of the test blocks, but also reflect the true quality and differences of the building. In some major and secondary vocational cities such as Beijing, it has been explicitly stipulated that a certain proportion of newly constructed buildings must undergo mandatory non-destructive testing, which serves as an important basis for project acceptance.

4. Discussion and Reflection on the Application of Non destructive Testing Technology in Quality Inspection

As an important means of quality control, structural acceptance, and supervision in national defense construction projects, non-destructive testing technology bears a heavy responsibility, but there is still a certain gap in its development and application level. There are both technical shortcomings and application issues here.

4.1 In terms of technology, the accuracy of its testing and estimation needs to be improved. For example, when using the ultrasonic rebound comprehensive method to determine the strength of concrete, the ultrasonic velocity is greatly affected by external humidity and temperature. In comparative tests at several construction sites, the measured values of the test block (due to its high relative moisture content in the curing pool) often deviate greatly; The standard parameter curve provided randomly varies in different regions, resulting in relative errors. The use of shock wave method to determine the thickness of airport runway panels involves two factors: firstly, there are differences between the measurement and evaluation standards, and secondly, the vibration wave is affected by the operator's professional proficiency, resulting in human error. The application of electromagnetic waves to determine the position and protective layer of steel bars has too many limitations, and cannot effectively distinguish between double-layer steel bars and multi-layer reinforcement.

4.2 The detection performance is relatively single, and the comprehensive quality assessment is pending. With the continuous emergence of new structural forms and hybrid structures, in quality assessment, it is not only necessary to infer the quality condition of concrete, but also to involve factors such as the quality of steel bars, steel structure quality, masonry construction quality, and the interaction between concrete and steel bars. Only in this way can the entire project be comprehensively and comprehensively evaluated.

4.3 The regulations of the national and * existing inspection and evaluation standards limit the application of non-destructive testing technology in engineering evaluation. Taking the concrete inspection and evaluation standards as an example: the current construction acceptance specifications stipulate that the statistical results of the concrete strength of standard specimens are used as the basis for judgment. The lack of legal procedures for non-destructive testing results will inevitably lead to a contradiction between construction inspection and supervisory testing. Therefore, further legislation is needed to establish the legal status of non-destructive testing and enable it to play a greater role in the process of engineering quality supervision and control.

5. Application and development of non-destructive testing technology in quality supervision

Based on the characteristics of the current construction situation and in accordance with the principle of "based on the existing, developing high-tech, comprehensive application, and constantly exploring", I personally believe that in quality supervision and control, the characteristics of non-destructive testing should be fully utilized, and the frequency of its application should be increased to further strengthen the strength of quality supervision and control, ensure the quality of *, and make it exert greater military benefits.

5.1 Establish corresponding supervision and testing management systems, clarify the application status of non-destructive testing in engineering quality supervision. One is that the country has introduced corresponding non-destructive testing trial standards to standardize the implementation of testing. The second is to establish its position in engineering quality supervision. Non destructive testing is an important component of quality supervision, and supervision work is based on testing data, relying on the authenticity of testing data to achieve fairness in supervision. The third is to strengthen the application program of non-destructive testing. For structural engineering, 10% of the components must be selected for overall non-destructive on-site testing. For general engineering, random single item testing can be conducted at least twice during quality supervision, and this can be used as the basis for engineering verification and evaluation.

5.2 Establish corresponding non-destructive testing institutions and organizations, equip technical personnel, and lay the foundation for conducting non-destructive testing work. Testing serves the supervision of engineering quality, and in order to improve the scientific and impartial nature of supervision, it is necessary to rely on testing as a scientific means. Therefore, I personally believe that all quality supervision institutions should take non-destructive testing as an indicator to build and establish non-destructive testing rooms that are relatively independent of the quality supervision department, in order to cooperate with quality supervision work; On the other hand, internal supervision of the quality of quality supervision work can also be carried out. Its personnel composition must be relatively stable and must undergo professional training in non-destructive testing.

5.3 Strengthen the research on non-destructive testing theory and methods, improve the accuracy and practicality of testing, and lay the foundation for the development of non-destructive testing. Given the current status of non-destructive testing technology and the continuous development of scientific testing techniques, it is necessary to summarize and demonstrate non-destructive testing work through a large number of factual testing cases. Therefore, this process requires us to continuously accumulate work experience and strengthen close cooperation and assistance with various scientific research and testing institutions, achieving "resource sharing and information exchange". Only in this way can we improve the accuracy and practicality of testing based on continuous summarization.

5.4 The application value of non-destructive testing technology in other aspects of quality. Such as airport pavement quality testing, anti impact strength testing of positions and caves, thickness testing of protection and camouflage, evaluation of the quality and safe use of old military engineering, etc. In short, with the development of technology and the demand for quality, non-destructive testing technology will have increasingly larger applications.