Stability of bucket movement and directionof movement of the continuous unit to form the underlying layer of the road

Introduction. The unit of continuous action for the formation of the underlying layer is designed to increase labor productivity in the construction of roads and other objects, for the construction of which it is necessary to remove the upper layer of soil. The working bodies of the unit are buckets that cut and transport soil. To balance these forces and moments in the transverse-vertical plane, relative to the direction of movement of the buckets, support bars with support hydraulic cylinders are used. To create and regulate the pressure in the support hydraulic cylinders, two hydraulic pneumatic accumulators for controlling the supporting strips are installed on the power device. Part of the forces and moments through the supporting strips, support hydraulic cylinders, the frame of the working part of the unit is transmitted to the energy device that serves to drive the unit. During the operation of the unit, the resistance of the soil to cutting changes continuously. Therefore, the forces and moments transmitted to the energy device change. During operation, the stability of the rectilinear course of the unit is necessary. To ensure the stability of the movement of buckets and the direction of movement of the unit, you should first consider the process of filling the buckets with soil.The method of research. On the basis of the constructive layout, the number of buckets filled with soil was revealed. Suppose the filling of buckets with soil occurs gradually and evenly. Hence, an increase in the load on the right and left support bar was revealed by each subsequent bucket as it is filled. By adding the vertical forces, the value and position of the total load on the supporting bars are determined. The resistance to the movement of the left and right wheels of the working part of the unit, due to the load from the buckets to the supporting strips, the gravity of the raised soil, the gravity of the working part of the unit, is determined. The total horizontal force, the impact of soil on the buckets, directed along the course of the unit, was revealed. The method of calculating the position of the thrust vector of the energy device is given.Results. On the basis of the developed technique, the diameters of the support hydraulic cylinders and the nominal pressure in the hydraulic pneumatic accumulators of the control of the right and left support strips were determined. A constructive layout of the hinged energy device and a system for automatic adjustment of the position of the thrust vector of the energy device depending on the properties of the developed soil is proposed.Conclusion. On the basis of theoretical studies, the diameters of the support hydraulic cylinders and the nominal pressure in the hydraulic pneumatic accumulators of the control of the right and left support strips were calculated. An example of calculating the position of the thrust vector of an energy device is given. The constructive arrangement of the system of automatic adjustment of the position of the thrust vector of the energy device depending on the properties of the developed soil and the general layout of the energy device is proposed. The conducted theoretical studies allow to ensure the stability of the movement of buckets and the direction of movement of the continuous unit for the formation of the underlying layer of roads.

Assessment of the effectiveness of lubrication of Ti-6Al-4V titanium alloy sheets using radial basis function neural networks

The aim of the research presented in this article was to determine the value of the friction coefficient using a simple tribological test and to build an empirical model of friction with the use of radial basis function artifi-cial neural networks. The friction tests were carried out on a specially designed friction simulator that allows a sheet metal strip to be drawn between two fixed dies. The test materials were sheets of Ti-6Al-4V titanium alloy with a thickness of 0.5 mm. The friction tests were carried out with variable contact forces of counter-samples with rounded surfaces and in various lubrication conditions. Mineral oils and bio-degradable oils with the addition of boric acid (5 wt %) were tested. Based on the results of friction investigations, neural models of friction were built using RBF artificial neural networks. The good properties of the RBF network 2:2-35-1:1 were confirmed by a high value of the determination coefficient R2 = 0.9984 and a low value of the S.D. ratio equal to 0.0557. It was found that the COF value was the highest for the average values of both the nominal pressure and kinematic viscosity. Over the entire range of nominal pressures applied, SAE10W-40 engine oil ensured the most effective reduction of the COF. The COF value was the highest for the average values of both the nominal pressure and kinematic viscosity.

Evaluation of Shock Tube Retrofitted with Fast-Opening Valve for Dynamic Pressure Calibration

Accurate dynamic pressure measurements are increasingly important. While traceability is lacking, several National Metrology Institutes (NMIs) and calibration laboratories are currently establishing calibration capacities. Shock tubes generating pressure steps with rise times below 1 µs are highly suitable as standards for dynamic pressures in gas. In this work, we present the results from applying a fast-opening valve (FOV) to a shock tube designed for dynamic pressure measurements. We compare the performance of the shock tube when operated with conventional single and double diaphragms and when operated using an FOV. Different aspects are addressed: shock-wave formation, repeatability in amplitude of the realized pressure steps, the assessment of the required driver pressure for realizing nominal pressure steps, and economy. The results show that using the FOV has many advantages compared to the diaphragm: better repeatability, eight times faster to operate, and enables automation of the test sequences.

Gas Supply of Multi-Storey Building

When the pressure of natural gas changes, a significant level difference appears between the gas control point and the location of the consumer. In this case, the pressure value may exceed safety standards. In buildings, supplying gas to the burner with a value other than the nominal pressure causes incomplete combustion of the fuel and the formation of carbon monoxide. Leakage of natural gas at pressures above the nominal leads to a rapid increase in the percentage of gas in the room air above the lower concentration limit of explosiveness, which makes the mixture explosive. In this regard, in some countries, building codes do not allow gasification of buildings above 10 floors. In Georgia, such a ban does not exist and this problem becomes relevant, since a large number of high-rise buildings have been built in the country and almost 100% of them are gasified.

Influence of Narrow Rectangular Channel ( AR = 1 : 4 ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications

Effective cooling of blades with a nominal pressure drop is essential for performance augmentation and thermal management of gas turbines. Hence, present work is aimed at determining the heat transfer enhancement and friction for W- and V-shaped ribs inside a rectangular cooling channel having hydraulic diameter ( D h ) of 0.048 m and aspect ratio ( AR ) 1 : 4. Ribs are fixed facing downstream with angle of attack ( α ) 45° on opposite walls. Pitch ( P ) between two successive ribs is 25 mm for both cases. Continuous V- and W-shaped ribs with height to channel hydraulic diameter ratio ( e / D h ) 0.052 and 0.0416 and pitch to height ratio ( P / e ) 10 and 12.5, respectively, have been examined for Reynolds number ( Re ) range 20000-80000. Heat transfer augmentation achieved at Re 80000 is 1.94 and 1.8 times higher than Re 20000 for V- and W-shaped ribs, respectively. Streamwise and spanwise variations in local Nusselt number ratio are highest for V-shaped ribs, which are estimated to be 31% and 12%. For W-shaped ribs, variations are 17.5% and 3.5%. Nusselt number ( Nu ) is highest along span length 0.5 w for V-shaped ribs due to dominance of apex induced secondary flow. For W-shaped ribs, Nusselt number along the span lengths is found to be nearly same view uniformity in secondary flow. Maximum enhancement ( Nu / N u o ) estimated for both the rib shapes is 3.9 at Re 20000. Due to increased rib height, friction losses for V-shaped ribs are higher than W-shaped ribs. Maximum friction loss increment is estimated to be 85% for V-shaped ribs and 42% for W-shaped ribs between Re 20000 and 40000. For both rib shapes, impact of ribs is found to be greatest at Re 40000. Thermohydraulic performance ( THP ) for W-shaped ribs is superior to V-shaped ribs. Best THP achieved for W- and V-shaped ribs are 3.7 and 3.4 at Re 20000.

Finite element analysis of cutting balloon expansion in a calcified artery model of circular angle 180°: Effects of balloon-to-diameter ratio and number of blades facing calcification on potential calcification fracturing and perforation reduction

Calcified artery lesions cause stent under-expansion and increase the risk of in-stent restenosis and stent thrombosis. Cutting balloons facilitate the fracturing of calcification prior to stent implantation, although vessel dissection and perforation are potential issues. In clinical practice, calcifications having maximum calcium angles ≤ 180° are rarely fractured during conventional balloon angioplasty. We hypothesize that the lesion/device diameter ratio and the number of blades facing a non-circular calcified lesion may be crucial for fracturing the calcification while avoiding vessel injury. The geometries of the cutting balloons were constructed and their finite-element models were generated by folding and wrapping the balloon model. Numerical simulations were performed for balloons with five different diameters and two types of blade directions in a 180° calcification model. The calcification expansion ability was distinctly higher when two blades faced the calcification than when one blade did. Moreover, when two blades faced the calcification model, larger maximum principal stresses were generated in the calcification even when using undersized balloons with diameters reduced by 0.25 or 0.5 mm from the reference diameter, when compared with the case where one blade faced the calcified model and a balloon of diameter equal to the reference diameter was used. When two blades faced the calcification, smaller stresses were generated in the artery adjacent to the calcification; further, the maximum stress generated in the artery model adjacent to the calcification under the rated pressure of 12 atm when employing undersized balloons was smaller than that when only one blade faced the calcification and when lesion-identical balloon diameters were used under a nominal pressure of 6 atm. Our study suggested that undersized balloons of diameters 0.25 or 0.5 mm less than the reference diameter might be effective in not only expanding the calcified lesion but also reducing the risk of dissection.

Optimal In Situ Fenestration Technique With Laser Perforation and Balloon Dilation for Aortic Stent-Grafts

Purpose: To evaluate the response of various stent-grafts after laser fenestration and dilation with noncompliant balloons to determine the optimal therapeutic combination for this treatment technique. Materials and Methods: Five aortic stent-grafts were evaluated ex vivo: the Bolton RelayPlus, Jotec E-vita Thoracic 3G, Medtronic Valiant, Cook Zenith Alpha, and Vascutek Anaconda. Small holes were created using an excimer laser with the grafts submerged in saline. Five rows of 5 fenestrations were created, 4 holes in each row were dilated once with a 6-, 8-, 10-, or 12-mm-diameter noncompliant balloon to the specified nominal pressure (one hole served as the control). The saline solution from each stent-graft was collected and qualitatively analyzed for debris. The fenestrations were evaluated under light and scanning electron microscopes. The maximum diameter and area for each fenestration were measured. The direction and length of tears were assessed. Results: The fenestration was feasible and reproducible in all the stent-grafts. The mean area of fenestration ranged from 7.63±1.63 to 14.75±0.73 mm2 when using balloons of 6- and 8-mm diameter, respectively. The 10- and 12-mm-diameter balloons caused a significant increase in area, variability, and tearing. The Anaconda graft tended to tear in the weft direction, while the other devices tore in the warp direction when using the 10- and 12-mm-diameter balloons. Dilation of the RelayPlus and Anaconda grafts with 6- and 8-mm-diameter balloons provided minimal tearing and precise fenestrations. Melted fiber remnants were observed after filtration of the saline solution for all devices. Conclusion: Laser fenestration and dilation with noncompliant balloons is a relatively simple and reproducible option for revascularization in urgent, complex aortic endovascular repairs. In our model, large balloons (ie, >10 mm) increased the destruction and tearing of the fabric. The maximum dilation recommended is 6 to 8 mm to avoid significant tears. Development of stent-grafts or novel fabrics designed explicitly for fenestration is needed to reduce potential complications.

Influence of gas equipment of gas-distributing plant on the operating mode of low-pressure gas networks

The peculiarity of the gas distribution system is the need to ensure the continuous opera-tion of its elements. Possible situations associated with damage of the main equipment at gas-distributing plant and their impact on the operating mode of gas networks are analyzed. The hy-draulic calculation is made in such a way that the failure of any piece of equipment at the gas con-trol point ensures the maintenance of the nominal pressure at the most distant subscriber.