Experimental and numerical investigation on destructive effect of gas pipeline buried in silty clay under surface explosion

Identifying the damage effects of buried multiple-operating-pressure gas pipelines subjected to various magnitude blasting load is a prerequisite for pipeline safety assessment. In this study, the dynamic response and damage effect are assessed by a combination of both field experiments and numerical simulation. It is indicated that the error between the numerical calculation and the field measured data is small and the reliability of the model is high. The dangerous section of the whole pipeline lies directly below the explosion source. The peak particle velocity (PPV) and the peak particle effective stress (PES) on the explosion-prone side of the section are the largest. Moreover, the PPV and PES increase with the increase of the working pressure of the pipeline. Results show that the empty pipe with no working pressure is the safest state among various pipe working state. There is a certain functional relationship among the explosive charge on the ground surface, working pressure, and PES of the pipeline.

Dynamic Response Analyses of Plastic Greenhouse Structure considering Fluctuating Wind Load

Wind load is one of the main factors of plastic greenhouse collapse. To solve the dynamic response problem of greenhouses under wind load and determine the dangerous section of a skeleton structure, the investigated lump method is presented for the dynamic response analysis of a plastic greenhouse, considering pulsating wind on the basis of Timoshenko beam theory. First, the investigated lump is designed according to the Timoshenko beam microbody concept. On the basis of Timoshenko beam theory, the governing equations of the skeleton structure of the greenhouse are derived, and the realization process of the algorithm is also provided. Second, the accuracy and effectiveness of the proposed numerical method are verified by an example in which the bending wave of a variable cross section beam with free ends propagates. Finally, the dynamic response of the steel skeletons of plastic greenhouses is analyzed under the effect of the simulation wind speed, and the spatial distribution of the maximum node displacement and the section maximum stress of the steel skeleton are obtained. Computational results show that the displacement peak is near the top of the plastic greenhouse. The most dangerous section of the top chord in the steel skeleton is near the leeward bottom, which has a maximum stress of 219.4 MPa, and the most dangerous section of the bottom chord is near the 1 m height on the leeward side of the plastic greenhouse, which has a maximum stress of 248.5 MPa. Bending stress is the main factor of the rapid increase of stress at the bottom of the skeleton. The maximum node displacement and cross-sectional stress caused by fluctuating wind loads are higher than those caused by average wind loads. The fluctuating wind load should be considered in the wind-induced response analyses of plastic greenhouses.

Influence of cover splices on the stress-strain state of plate-ribbed wood-composite panels

Wooden-composite plate-ribbed bent panels with structural plywood and oriented strand board sheathing with breaks are considered. An overview of studies researching and improving the effectiveness of different types of panels is presented. On the basis of the theory of calculation of composite rods by A.R. Rzha- nitsyn, a mathematical model has been compiled, which makes it possible to calculate the stress-strain state of these structures, taking into account the pre- sence of breaks in the sheathing and the flexibility of the mechanical fasteners of the sheathing and ribs. An equation for finding the coordinates of the most dangerous section of wooden ribs in the presence of breaks in the sheathing, which may not match with the middle of the span, is obtained. Panels with sheathing in a compressed zone with different locations of joints, symmetrically relative to the middle of the panel span are considered. Panels without joints in the skin are considered to compare the results. The graphs of the dependence of the maximum tensile stresses in the ribs in the most dangerous section and the maximum vertical displacements from the stiffness coefficient of the shear ties and the location of the breaks in the sheathing are presented. The values of the coefficients for the engineering design of panels, taking into account the decrease in the strength and deformation characteristics of the composite section of panels with breaks in the sheathing, as compared to panels with a solid sheathing, are obtained. The conclusions and recommendations, based on the results of the investigations, which can be used in the design of wooden-composite plate-ribbed structures, are formulated.

THE INFLUENCE OF HYDRO BLASTING ON THE EN-DURANCE LIMIT OF SPECIMENS WITH A CUT UNDER BENDING AND STRETCHING-COMPRESSION

The hydro blasting influence on an endurance limit of cylindrical specimens with circular cuts of a semicircular profile of 0,3 mm radius under bending and stretching-compression in a case of symmetric cycle has been examined. Specimens of 10 mm diameter for fatigue tests were made of steels 30ХГСА, 12Х18Н10Т, ЭИ961,45 and aluminum alloys В93, Д16Т.The influence of surface hardening on an endurance limit of specimens with cuts was valuated by two criteria: residual stresses on the concentrator surface and the average integral residual stresses calculated through the part’s dangerous section surface layer thickness equal the critical depth of a non-propagating fatigue crack. On results of residual stresses and specimens with cuts endurance limits determination it’s been stated that coefficients of surface hardening influence on an endurance limit increase under bending and stretching-compression by two criteria are approximately equal. Besides, the coefficient of the influence by the average integral residual stresses criterion changes within essentially lesser limits than the coefficient of the influence by the residual stresses on the concentrator surface criterion. So the average integral residual stresses criterion should be used for the evaluation of a surface hardening influence on an endurance limit of parts with concentrators.On an example of specimens within and without peening in a dangerous section it’s been shown that peening doesn’t influence the endurance limit of a surface hardened part. The compressive residual stresses only influence the endurance limit of these parts.

THE ESTIMATION OF ROLLER STRENGTHENING INFLUENCE ON THE ENDURANCE LIMIT OF SHAFTS WITH PRESSURIZED HUB

The influence of roller strengthening on endurance limit under bending of the 25 mm and 50 mm diameter shafts made of steel 20 and 25 mm diameter shafts made of steel 40X with a pressurized hub has been examined. It’s been stated that the endurance limit of roller strengthened shafts with a pressurized hub depends not only on a value of compressive residual stresses in their dangerous section but on the character of its distribution. The valuation of a surface hardening influence on the endurance limit of shafts by the surface residual stresses criterion and the average integral residual stresses criterion has been shown that the average integral residual stresses criterion calculated through the part’s dangerous section surface layer thickness equal the critical depth of the non-propagating fatigue crack can be recommended for the hardened shafts with a pressurized hub endurance limit increase prediction. It’s been shown that on a diameter of a shaft with a pressurized hub raising it is necessary to increase a thickness of a hardened surface layer with compressive residual stresses.

Development of methodology for calculation of discontinuous circular welds in torsion

The main criterion for the performance of welds is the strength. The least durable are the corner joints used to perform various types of welded joints. In the literature, the methods of calculating the strength of welded joints with solid seams are considered in sufficient detail. Methods of calculation of connection interrupted sutures absent. In this case, the greatest difficulty is the calculation of connections using circular intermittent seams, which are often performed in welded drums and pulleys. They work on torsion. Therefore, the development of methods for calculating circular intermittent seams for torsion is quite important. Shear stresses in welds from torque are determined depending on the value of the polar moment of resistance of its dangerous section. When determining the polar moment of resistance of the dangerous section of a circular discontinuous seam, it was represented by a set of sections in the form of a sector of a circular ring. The method of calculation of the polar moment of resistance of the rotated dangerous section of a circular discontinuous weld, which takes into account the relative length of the weld areas and their number, is proposed, as well as the method of accurate and approximate calculation of shear stresses in the weld.

Dependence of the limit endurance of specimens with notches from the depth of hardened surface layer

It is shown that, growth of the layer with compressive residual stresses at advanced surface plastic deformation of smooth samples leads to an increase in the endurance limit of the notched specimens due to an increase in the compressive residual stresses in their dangerous section. The study was conducted on the specimens with outer diameterDequal to 10 and 25 mm and on a 25 mm specimen with inner diameterd= 15 mm which were subjected to air shot blasting and roll-in. Residual stresses in smooth specimens were determined by the mechanical method. Circular incisions (R= 0.3 and 0.5 mm) were applied on hardened smooth samples with a shaped cutter. Residual stresses in notched specimens were determined by a numerical method calculating the redistribution of the residual stresses upon the incision. As the diameter of the samples increases with the same strengthening surface treatment,the depth of the layer with the compressive residual stresses increases due to an increase in the rigidity of the samples. The effect of surface hardening on the endurance limit of notched specimens was evaluated according to the criterion of the average integral residual stresses, which takes into account both the magnitude and completeness of the residual stresses. This criterion was calculated from the depth of the non-propagating fatigue crack that occurs in the surface layer in the dangerous section of the specimen during the fatigue test at the limit endurance. Fatigue tests are carried out in symmetrical cycle, the test base being 3 × 106cycles of loading. Estimation of the increment of the limit endurance of surface-hardened cylindrical specimens with semicircular notches gave the results acceptable for practice. The use of the proposed method can significantly reduce long-term and expensive fatigue tests.

Panorama laser lane system based IoT

Background/Objectives: Lane marking to recognize road condition helps driver safely drive. Device in this study is developed as a complement because existing lane marking is able to difficult to identify lane according to its environment.Methods/Statistical analysis: Lane marking has been built by spraying tiny particles of glass on a paint for the purpose of retro-reflection against headlamps in automobile at night. But paint with tiny particles of glass is eliminated by automobiles and function of retro-reflection tends to lost over time. That makes lanes invisible well on rainy days at night. Panorama laser lane system based on mobile network with remote control is designed to irradiate laser beam sequentially toward the road on rainy or snowy day at night for safety guidance.Findings: The system provides visible lane markings on rainy days or at night because laser beam lights the lane on the road to help avoid traffic accident.Improvements/Applications: Smart road to provide safety drive will be built by the installation of system at 20 meters in the road particularly dangerous section of road or accident black spot.

Synthesis of methods and principles of ensuring the reliability of one-off and serial production machines

The paper considers the development of methods for managing the reliability of single-production machines (lunar rover, rover, rolling mill, president’s car of the country, etc.). Many years of experience in the field of machine reliability allowed the leading specialists of the department of AS and DS to develop a method for managing reliability for serial and mass machines. in the case of evaluating the reliability of single-production machines, development of algorithms based on sample data and data obtained during the transition from the sample to the set of values was carried out. The resource of the parts is defined as the main parameter, which, irrespective of their purpose, form the sampled samples of units of finite volume. Given that the main parameter of the details the resource depends on the strength and loading parameters, the correlation between the strength parameters and the acting stresses (endurance limit, active stress in the dangerous section, strength increase coefficients and the coefficient of increasing the acting voltage) is used in the studies. In such conditions, the estimated resource should relate to each entity of the population or a sample from it. During the research, a parameter is defined as the minimum resource that will determine the homogeneity of the sample (the aggregate), while the main condition for ensuring the same main parameters of parts with sudden failures is the Veler-Sørensen-Kogayev formula based on the experimental initial fatigue and loading statistics . Thus, a method has been developed to ensure the reliability of single-source machines, based on the synthesis of two methods and principles for serial and single-purpose machines.