Tag Archives: накопление повреждений
The article is devoted to the issues of safety provision during gas consumption and gas distribution in cities and residential areas. The performed analysis of the literature showed that significant part of the pipelines transporting gas to the residential areas is applied for operation for more than 40 years. The dependency of the number of accidents of gas supplying and gas distributing networks on the increase of the total length of the network determined on the basis of Rostekhnadzor of RF data shows the tendency of emergency situations increase. On the one hand this is connected with the increase of the service life of the pipelines and accumulation of damages in the pipelines material. Moreover, it was found out that control of the residential buildings networks is not under the supervision of the regulatory authorities due to the amendment of norms and regulations in the field of industrial safety.
Due to the fact that operation of gas distribution systems is performed in the quasi-static mode of loading, these facilities do not considered from the point of view of accumulation of damages in the gas pipelines material and there is no applicable regulations regarding its safety operation period. However, from the literary sources it is well known that complex processes occur in the material on micro and macro levels during the operation period of the equipment. This causes accumulation of damages, locally obtaining limiting state, and creates the possibility of brittle failure in case of an emergency situation.
Carried out research showed that thermal expansion distribution coefficient in the area of welded joint of the material of the gas pipelined made of steel 20 is unstable. This means that stress appeared in the result of the strength load is also distributed irregularly. In the result, accumulation of damages in the areas with the increased stress, which locally could achieve the yield limit, occurs faster.
The article describes the possibility of application of nondestructive method of evaluation of the stress state in the welded joints of the gas pipelines which could provide the possibility to register the rate of accumulated damages in the potentially hazardous elements of the gas distribution systems.
The paper deals with the assessment of the residual life of shell structures, operated under long-term static loading. Existing techniques of an estimation of the residual life in the capacity of parameters of a technical condition of vessels and apparatuses use the measured magnitudes of the originated faults, the data about change of physical and chemical characteristics of materials, and also number of cycles of a loading. Thus the irreversible structural changes of the material which has originated while in service are not considered. For an estimation of a technical condition of the equipment of a shell-type construction it is offered to develop integrated criterion for evaluating the accumulated damage in the material, applicable for conditions of static loading. Experimental researches showed that in a material under the influence of long static loading there are the changes of an internal structure related with adaptation to external impact when the material exhausting one adaptation mechanism passes to another and thus there is the accumulation of damages. Found that the velocity of ultrasonic waves, magnetic field strength, voltage of the electric signal response and the surface energy are the parameters that are sensitive to the accumulation of damage in the material. The establishment of threshold values for these parameters that characterize the level of accumulated damage will measure the time of the limit state and to determine the residual life the structure.
The paper deals with the influence of fluctuations in loading piping systems under the simultaneous effect of cyclic and vibration loads. The paper shows the dependencies between the forced oscillations at the resonant frequency and reducing durability of the material of the object.
Assessment of equipment material damage by using the degree of attenuation the response of the electrical signal
The article describes the method for assessing the degree of damage to equipment material, maintained in the conditions of fatigue loading, by using the degree of attenuation of transition process the response of electrical signal. As a result of research, optimal settings of eddy current probe were identified and experimental dependencies allowing to monitor the condition of equipment material were obtained.
Two-parameter control of various stages of elastic-plastic loading of specimens produced from steel 09G2S
This article focuses on the general mechanisms of material properties changing using electromagnetic and ultrasonic methods of nondestructive testing. As a research results experimental dependences of the response duration variation of the ultrasonic and electromagnetic signals occurring in the specimen’s material under the influence of static tensile loading were obtained.