Relationship Between the Parameters of Acoustic Structural Noise and the Mechanical Properties of Structural Steels
- PDF / 1,032,148 Bytes
- 7 Pages / 594 x 792 pts Page_size
- 14 Downloads / 280 Views
RELATIONSHIP BETWEEN THE PARAMETERS OF ACOUSTIC STRUCTURAL NOISE AND THE MECHANICAL PROPERTIES OF STRUCTURAL STEELS V. D. Myndyuk,1, 2 N. I. Chaban,1 I. V. Rybitskyi,1 and O. M. Karpash1
UDC 620.179.18
We perform the comparative analysis of the parameters of acoustic structural noise in specimens of 40G structural steel with the use of ultrasonic flaw detectors with phased arrays. It is shown that the parameter of integral density of B-scan images most completely reproduces the variations of energy of acoustic vibrations reflected from the microstructural inhomogeneities (grain-size inhomogeneity, changes in the ratios of the phase components). The relationship between the parameter of integral density of the image of acoustic structural noise Ro and the mechanical properties of 40G steel is established. We propose an improvement of the well-known method of determination of the yield limit σ y of steels according to the results of measurements of the HB hardness. To do this, we added the parameter Ro to the equation used for computations. As a result, we deduced a new equation of the form σ y = f (Ro , HB) for the yield strength of 40G steel within the specified range of its values.
Keywords: degradation of properties, nondestructive testing, acoustic images of structural noise, yield limit, hardness, technical state of the metal.
Introduction In order to guarantee the possibility of long-term operation under the conditions of high levels of wear of machines, equipment, and structures in various branches of industry, it is necessary to improve the methods used for the evaluation of their actual technical state, as well as the systems for maintenance and repair. In view of the existing large time intervals between the tests and repairs, the appearance of defects in the equipment cannot be detected in the early stage. The presence of mechanical defects, action of corrosive media and high loads of various origins, violation of the operating conditions, and insufficient amount of monitoring and diagnostic inspections serve as the main causes of the appearance of the corrosion abrasive wear and fatigue fracture [1]. The procedure of technical diagnostics of various kinds of the industrial equipment in the process of operation makes, generally speaking, possible to detect and monitor the development of crack-like defects caused by the in-service factors. However, in the process of operation, well before the appearance and development of these defects, certain local structural transformations take place in the bulk of the metal, which leads to changes in the space distribution of its physicomechanical characteristics. The degradation of the properties of materials is connected with the accumulation of microdefects. Their coalescence leads to the formation of macrodefects and the loss of the initial characteristics of the metal [2, 3]. As one of the ways to improve the informativity of evaluation of the actual technical and limiting states of structural elements with regard for the microstructure, especially in the cours
Data Loading...
