Antarctic subglacial drill rig. Part II: Ice and Bedrock Electromechanical Drill (IBED)

A new, modified version of the cable-suspended Ice and Bedrock Electromechanical Drill (IBED) was designed for drilling in firn, ice, debris-rich ice and rock. The upper part of the drill is almost the same for all drill variants and comprises four sections: cable termination, a slip-ring section, an antitorque system and an electronic pressure chamber. The lower part of the IBED comprises an auger core barrel, reamers, a core barrel for ice/debris-ice drilling and a conventional geological single-tube core barrel or custom-made double-tube core barrel. First, the short and full-scale field versions of the IBED were tested at an outdoor testing stand and a testing facility with a 12.5 m-deep ice well. Then, in the 2018–2019 summer season, the IBED was tested in the field at a site ~12 km south of Zhongshan Station, East Antarctica, and a ~6 cm bedrock core was recovered from a 198 m-deep borehole. A total of 18 d was required to penetrate the ice sheet. The retrieved core samples of blue ice, basal ice and bedrock provided valuable information regarding the Earth's paleo-environment.

Light curve variation caused by accretion column switching stellar hemispheres

We investigate switching of the accretion column between the stellar hemispheres in the magnetosphere of a star with the dipole magnetic field aligned with the stellar rotation axis. We show that such switching can produce “hiccups” in the observed lightcurves. The intensity of emitted radiation from the stellar surface as seen by distant observers is computed from our two dimensional axisymmetric viscous and resistive magnetohydrodynamic numerical simulations. This result is used to construct a three-dimensional model of a star with the ring-shaped hot spots from the accretion columns at the stellar surface. We compute the intensity from such hot spots. To obtain a non-axisymmetric model with arc-shaped hot spots, we remove a ring section in the azimuthal direction from the hot-spots and compute the intensity of the radiated emission. Such models can be used to relate physical parameters in the simulations to the observations. We show an example with the intensity computed from our model compared to observational light curve.

Textile Industry Hazard Identification and Risk Assessment by Using HAZAN Method

Background: Today with industry growth, hazards are increasing. The most important parts of these industries are human resources and employees, that face with many various hazards. Therefore, in order to protect and increase the productivity these hazards must be identified and analyzed to be controlled. Methods: The present study focused on hazard identification and risk assessment in spinning sector of a textile industry as one of the important and strategic industries by using HAZAN method. For data gathering, different methods including HAZAN worksheet, risk detecting checklist, walking, talking, process plots and documents were used, and then risk assessment was carried out. Results: The finding represented 102 risks in the production line. Most of the risks were found in ring section (n=33), Flyer (n=26), Autoconer (n=18), Tightening (n=15) and Packing (n=10) respectively. 20.59% of these risks were 2nd rank (undesirable), 16.67% were 3rd rank (acceptable if controlled) and 62.74% were 4th rank (acceptable). In addition, high-risk jobs were feeding the empty bobbin during the shift and bobbin handling from the Autoconer unit. Also, analyses were performed based on the risk assessment method and statistical tests were not required. Conclusion: The 4th rank risk was the largest group that’s acceptable. It is notable that 2nd risk rank should be turned into 3rd risk rank in reliable time. For 3rd risk rank making sure that existing control is in place is sufficient. For making a safe work environment and increasing productivity, minimizing risk by safety training and other measures are useful.

Investigation of the Influence of the Initial Composition of Heavy Concrete Designed for the Manufacture of Ring-Section Products on its Properties

The authors conducted the analysis of scientific and technical references relating to the issue of increasing maintenance reliability of pre-stressed reinforced concrete by means of taking into account concrete non-homogeneity in the calculations of strength, deformability and crack resistance of the reinforced concrete products with annular section. The authors stated the opportunity to increase the quality of concrete intended for centrifugation by means of regulating the properties of used materials. It was identified that applying disperse-reinforced fibers resulted in increase in bending tensile strength, decrease in shrinkage, increase in crack resistance and material resistance towards alternate freezing and thawing, drying and humidification cycles. Upon the results of conducted research and comparison of the properties of various fibers, the authors obtained regularities and application rules on fiber use and gave recommendations in terms of applying one of another fiber type. On the basis of the analysis of obtained results the authors made the conclusion that the highest effect in all tests was observed at the application of basalt fibers as they provide for a higher dispersion of cement rock reinforcement while the basalt fiber itself has a higher strength comparing with any other polymer fiber. Further, the authors conducted the research of mechanical properties characteristic for test beams made of heavy concrete to manufacture the annular section products by means of centrifugation. The obtained dependences allow making a conclusion that the percentage ratio of applied crushed stone fractions Fr 5-10 / Fr 5-20 = 50 / 50 under otherwise equal conditions has the highest influence on the heavy concrete ground strength.

NUMERICAL AND EXPERIMENTAL RESEARCH OF YIELDING SUPPORTS IN DYNAMIC LOADING

Dynamic impacts of emergency nature occur in industrial enterprises and protective structures of civil defense. An effective way to reduce the dynamic impact is the use of yielding supports in the form of annular tubes. To assess the effect of deformation of yielding supports on reinforced concrete structures, it is necessary to determine the features of dynamic deformation of the crumpled inserts of the ring section. In theoretical calculations, characteristics obtained as a result of static testing yielding supports are currently used. Data on the dynamic characteristics of yielding supports are not available. This paper presents results of experimental and numerical studies on yielding supports under dynamic loading. Using the ANSYS finite element program, a numerical model is developed for the yielding support consistent with the obtained experimental data.

COMPUTER MODELING AND ANALYSIS OF VIBRATIONS IN ANNULAR CONCENTRATOR OF ULTRASONIC SYSTEM

The paper provides substantiation on application of elastic annular concentrators of ultrasonic systems which allows to increase an intensity of tool vibrations. It has been shown that elastic elements are used as resonators and tools in a number of ultrasonic technological systems. However an application of the elastic elements as concentrators of ultrasonic vibrations has been insufficiently studied and requires research and development of recommendations for usage. For this purpose theoretical studies have been carried out and they have helped to perform modal and harmonic analysis of several variants for a computer model of a ring with outer diameter D = 50 mm. Models of rings with various hole sizes from 20 to 40 mm have been analyzed while changing hole axis position relative to ring axis. The paper shows modes of ring flexural vibrations which can be either flat or three-dimensional depending on frequency of forced oscillations. It has been pointed out that an increase in a ring internal diameter is accompanied by higher amplitude of bending oscillations in the thinnest ring section. The same effect is achieved by increasing eccentricity of a hole axis. The paper contains recommendations for determination of rational geometric parameters which allows to increase an oscillation amplitude gain ratio and it is determined as ratio of ring section thickness. It has been established that decrease in section thickness is accompanied by higher number of frequencies for ring resonance oscillations. So, if a concentric ring and a ring with small hole diameter have only one resonance frequency, then thin-walled rings with a variable cross-section have not less than three natural resonance frequencies of oscillations that makes it possible to increase a range of vibration frequencies and technological capabilities of the ultrasonic system. It has been also found that an intensity in fluctuations of the ultrasonic system is increased even more if at the same time a cross-section of a ring with variable stiffness is decreased as along thickness so across the width.

Calculating Failure Pressure Under Different Failure Modes in the Roof-to-Shell of a Vaulted Tank

In this study, two failure modes, yield buckling of the compression ring section and strength failure in the roof-to-shell of the tank, have been proposed for a vertical vaulted tank. The failure criteria of the two failure modes in the roof-to-shell of vault tanks are established via finite element analysis of three tanks of 640 m3, 3200 m3, and 6800 m3 in volume. The finite element models are built with axisymmetric elements and spatial multi-elements. Based on the strength failure criterion, the failure pressure formula in the vaulted tank roof-to-shell is derived. The maximum relative error between the theoretical calculation and numerical simulation is 9.7%. Finally, we verify the strength failure criterion through a tank failure test; the maximum relative error between the test and theoretical calculation is 9.6%. The failure pressure of both failure modes has been compared and analyzed. The failure pressure of the yield buckling in the compression ring section is about 1.65 times that of the strength failure in the roof-to-shell of the tank.

Study on the Dynamic Radial Tensile Test Method of Thin-Walled Tube Structure with Special Ring Section

Combined with numerical simulation, a radial-directional dynamic tensile experimental method was proposed based on conventional split Hopkinson tensile bar(SHTB) for a thin-walled tube structure with special ring section. A special clamp was designed and a hollow transmission bar was used to magnify the transmission signals. For the stainless steel thin-walled tube structure, some dynamic tensile experiments are implemented under different strain rates. The results show that this test method is applicable to thin-walled tube structure with special ring section. This structure has a long plastic stage and its fracture strain is reduced with strain rate increasing. Moreover, its tensile strength is obviously enhanced with strain rate increasing