A resource efficient and environmentally safe charge structure for mining in an open-pit

Purpose. The purpose is to reduce mineral losses during the explosive destruction of rocks and environmental pollution by harmful gases and fine particulate matter. Methods. To achieve the objectives of the study, methods of physicochemical analysis and mechanics of continuous media have been used. The method of physico-chemical analysis has been used to determine the quantitative and qualitative characteristics of the composition of the well stemming depending on the parameters of the well, the type of explosive, the amount and type of harmful gases formed during the explosion. Methods of solid medium mechanics have been used to establish the patterns of pressure waves during an explosion depending on the characteristics of the gap filler between the charge and the well wall. To solve the problem of the behavior of a two-layer medium during the loading of a cylindrical cavity by a nonstationary load, a numerical method based on the finite-difference McCormack predictor-corrector scheme has been used. Findings. A resource-saving and environmentally friendly charge structure for rock mining by explosion was developed. The design of the charge involves the formation of a gap between the charge and the wall of the borehole, and filling it with a suspension of calcium hydroxide or a suspension of calcium carbonate. Originality. SThe dependences of the volume of harmful gases (NO2, CO2, CO) formed during the explosive destruction of rocks and the magnitude of the pressure peak in the area close to the charge on the chemical composition of the filler of the radial gap between the charge and the well wall have been set. Practical implications. Developed charge design allows to neutralize the harmful gases formed during the explosion, to reduce the pressure peak in the area of the rock massif close to the charge, and can be widely used in non-metallic quarries that extract minerals for the production of crushed stone.

Calculation of contact pressure and contact zone in slip pairs of marine diesels

Annotation – The durability of marine diesels significantly depends on the operation of friction pairs, such as: piston rings - cylinder liner; crankshaft - bearing shell, plunger - sleeve, and others. This is primarily due to the constant contact interaction of the elements of the friction pairs at different temperatures and load. Therefore, the research of normal pressure and the definition of contact areas in the friction pairs, the studying of the influence of the quality of lubricants on these characteristics are important tasks for predicting the longevity of marine diesels. The solution of these problems is based on the application of mathematical models of processes (numerical simulations) that occur in friction pairs. This considers two main processes that occur during the operation of the friction pairs: the research of contact and tangential stresses that occur in friction pairs in the framework of elastic or elastic-plastic contact models; study of hydrodynamic processes in a thin layer of oil between the elements of the friction pairs. The combination of these processes allows to sufficiently assess the influence of the elastic-mechanical properties of the sliding vapor elements and the viscosity and hydrodynamic characteristics of the oils on the durability of the marine diesel unit. The first process is researched in this work. In particular, for the analysis of contact stresses and contact zones in friction pairs, the method of numerical modeling is used, which is based on the differential equations of the theory of elasticity. With the help of fundamental solutions (influence functions), the problem is reduced to an integra-differential equation with the Gilbert’s kernel. The solution of which is constructed using the method of orthogonal polynomials as well as easy-to-use approximation formulas. Numerical simulations were performed, as a result, the maximum pressure and contact zone parameters for some combinations of friction pairs materials of marine diesel engines were determined. In particular, the influence of the radial gap on the pressure distribution and the size of the contact zone between the elements of the friction pairs of marine diesels is established.

Mechanical Properties And Joining Mechanism of Magnetic Pulse Welded Aluminum To Titanium

Magnetic pulse welding of dissimilar aluminum and titanium was investigated to optimize process parameters in terms of discharge voltage, radial gap and overlapping length. Moreover, impacting modes at different overlapping lengths were discussed. The joining mechanism was analyzed from aspects of microstructure, composition and hardness distribution. The shear strength increased with increasing discharge voltages, whereas shear strength decreased at first and then increased with the increasing radial gap, which has a more significant influence on shear strength than discharge voltage. Three impacting modes were proposed as bidirectional impacting, overall impacting and single-orientation impacting. However, the single-orientation impacting mode has the highest effective joining ratio. The welded joints were divided into four transition layer interfaces: continuous transition zone, transition zone with cracks, intermittent transition zone, and non-transition zone. Waves and intermetallic compounds are the two characteristics of the Al-Ti joint welded by magnetic pulse welding. The metal's hardness near the joint surface is higher than that of the base metal. In addition, Al3Ti and aluminum base metal were found in the transition layer of the joint.

Low-Pressure Turbine Cooling Systems

Modern low-pressure turbine engines are equipped with casings impingement cooling systems. Those systems (called Active Clearance Control) are composed of an array of air nozzles, which are directed to strike turbine casing to absorb generated heat. As a result, the casing starts to shrink, reducing the radial gap between the sealing and rotating tip of the blade. Cooling air is delivered to the nozzles through distribution channels and collector boxes, which are connected to the main air supply duct. The application of low-pressure turbine cooling systems increases its efficiency and reduces engine fuel consumption.

Analysis of the Conditions for the Contactless Movement of Eccentric Freewheel Mechanisms

Freewheel mechanisms are used in kinematic chains of technical systems of a various functionality. When such mechanisms freewheeling, it is necessary to ensure that there is no contact of their working elements to reduce friction losses and wear. At the same time, it is necessary to ensure the minimum value of the idling angle affecting the accuracy and response time of the kinematic chain in which the mechanism is installed. The task of analyzing and determining the geometric conditions allowing ensuring a radial gap between the working elements of the eccentric freewheel mechanisms with free-running engagement has been set. To solve this problem, a design scheme is proposed and a mathematical model describing the relationship between the geometrical parameters of the mechanism is obtained. The nature of the influence of the basic geometric parameters (eccentricity, radial clearance, modulus, etc.) on the value of the idling angle is established. It is shown that when designing, the values of the module and the gap should be chosen as the minimum permissible, taking into account the load capacity and the assembly conditions. The eccentricity can be assigned based on the requirements of the manufacturing technology.

Heuristic optimization of impeller sidewall gaps-based on the bees algorithm for a centrifugal blood pump by CFD

Optimization studies on blood pumps that require complex designs are gradually increasing in number. The essential design criteria of centrifugal blood pump are minimum shear stress with maximal efficiency. The geometry design of impeller sidewall gaps (blade tip clearance, axial gap, radial gap) is highly effective with regard to these two criteria. Therefore, unlike methods such as trial and error, the optimal dimensions of these gaps should be adjusted via a heuristic method, giving more effective results. In this study, the optimal gaps that can ensure these two design criteria with The Bees Algorithm (BA), which is a population-based heuristic method, are investigated. Firstly, a Computational Fluid Dynamics (CFD) analysis of sample pump models, which are selected according to the orthogonal array and pre-designed with different gaps, are performed. The dimensions of the gaps are optimized through this mathematical model. The simulation results for the improved pump model are nearly identical to those predicted by the BA. The improved pump model, as designed with the optimal gap dimensions so obtained, is able to meet the design criteria better than all existing sample pumps. Thanks to the optimal gap dimensions, it has been observed that compared to average values, it has provided a 42% reduction in aWSS and a 20% increase in efficiency. Moreover, original an approach to the design of impeller sidewall gaps was developed. The results show that computational costs have been significantly reduced by using the BA in blood pump geometry design.

Experimental Parametric Study of the Factors Leading to Elevated Femoral Intramedullary Pressure and Fat Embolus Syndrome in Orthopaedic Procedures

During orthopaedic procedures such as total knee arthroplasty (TKA), total hip arthroplasty (THA), and intramedullary nailing, it is necessary to hammer implants into the intramedullary canal of long bones. This hammering action can generate a high intramedullary pressure, leading to the release of bone marrow fat globules into the cardiovascular system, and ultimately, the possible development of fat embolism syndrome. In the present study, the effect of parameters such as implant tip geometry, peak impact force, hammer tip material, bone to implant radial gap, and marrow viscosity, on the resulting intramedullary pressure generated when hammering implants into a simulated femur analogue was examined. The bone analogue consisted of a porous plastic cylinder, having similar porosity and pore size to human femoral bone, with bone marrow being represented by a paraffin wax/petroleum jelly mixture. It was found that intramedullary pressure is only slightly lowered by a change in implant tip geometry, and that the use of a steel tipped (as opposed to rubber) hammer resulted in an increase in average pressure in the proximal portion of the bone, but a decrease distally. A lower implant insertion speed, lower hammering force, and a larger bone to implant radial gap were found to significantly reduce the intramedullary pressure. The number of hammer strikes required to insert an implant was found to increase significantly with marrow viscosity, but the average intramedullary pressure was found to decrease with increasing viscosity. Numerical modelling was also found to offer great promise for analysing hammering procedures for orthopaedic research into fat embolism syndrome. Numerical and experimental results were matched with approximately a 20% deviation.

Experimental Parametric Study of the Factors Leading to Elevated Femoral Intramedullary Pressure and Fat Embolus Syndrome in Orthopaedic Procedures

During orthopaedic procedures such as total knee arthroplasty (TKA), total hip arthroplasty (THA), and intramedullary nailing, it is necessary to hammer implants into the intramedullary canal of long bones. This hammering action can generate a high intramedullary pressure, leading to the release of bone marrow fat globules into the cardiovascular system, and ultimately, the possible development of fat embolism syndrome. In the present study, the effect of parameters such as implant tip geometry, peak impact force, hammer tip material, bone to implant radial gap, and marrow viscosity, on the resulting intramedullary pressure generated when hammering implants into a simulated femur analogue was examined. The bone analogue consisted of a porous plastic cylinder, having similar porosity and pore size to human femoral bone, with bone marrow being represented by a paraffin wax/petroleum jelly mixture. It was found that intramedullary pressure is only slightly lowered by a change in implant tip geometry, and that the use of a steel tipped (as opposed to rubber) hammer resulted in an increase in average pressure in the proximal portion of the bone, but a decrease distally. A lower implant insertion speed, lower hammering force, and a larger bone to implant radial gap were found to significantly reduce the intramedullary pressure. The number of hammer strikes required to insert an implant was found to increase significantly with marrow viscosity, but the average intramedullary pressure was found to decrease with increasing viscosity. Numerical modelling was also found to offer great promise for analysing hammering procedures for orthopaedic research into fat embolism syndrome. Numerical and experimental results were matched with approximately a 20% deviation.

FUNDAMENTALS OF THE DESIGN OF FUNDAL MANDRELS FOR THE INSTALLATION OF THIN-WALLED WORKPIECES. PART 1

There are a number of problems in mechanical engineering technology. One of them is related to the installation on the machine and the previous processing of thin-walled rings, which are widely used in mechanical engineering. Due to the low bending stiffness of thin-walled rings after processing there are a large magnitude of rigidity of the form (deviation from roundness). As production experience has shown, in the conditions of mass production, it is advisable to use fungal mandrels and adjustments to reduce shape errors. They allow for a small radial gap between the holes of the ring and the fungal cam to have extended contact rings with cams along the angular coordinate. However, there are no methods for calculating the parameters of contact interaction with cams, considering a number of factors, primarily the radial clearance. Hence, it is impossible to calculate more accurately the error of the form after processing. In this paper (it is supposed to be continued), based on methods for calculating flat rings of construction mechanics of machines, a method for determining the stress-strain state of a thin-walled state is proposed, considering the contact pressure. In this case, the semiangle of contact of the ring with the fungal cam and the shape of the contact pressure plot are determined. This allows you to calculate the stress state of the thin-walled ring and the shape error when processing more accurately in a fungal mandrel, as well as reasonably assign the dimensions of the mandrel parts. Due to the exceptionally large number of calculations in the calculations according to the proposed method, it can only be implemented using a computer program, which creates great difficulties in analyzing different source data. Therefore, it is planned to rework the completed developments into an engineering calculation method with graphs in dimensionless form.