Mechanics and Advanced Technologies

Numerical Study on Simulating the Deposition Process of Cold Spray Multi-Particle Al-6061 based on CEL Method

Kun Tan — 2024-03-19

Cold spray is a solid-state deposition technique that improves the performance of part surfaces. Most scholars use the CEL framework to simulate the deposition of single particles on the substrate; Single particle depositions cannot fully characterize coating conditions. This article proposes to use the CEL method to simulate the deposition process of cold spray multi-particles on the Al6061 substrate. A multi-particle wrapped model is nested in a deposition model created by CEL to simulate the cold spray multi-particle deposition process. The Euler-Lagrangian method has the characteristics of high accuracy and robustness, and was selected as the method for multi-particle deposition model simulation; The CEL framework is a feasible method to simulate the actual cold spray multi-particle deposition process. The results show that the CEL framework can simulate the deposition of cold sprayed Al6061 multi-particles on the Al6061 substrate, observe the EVF Void value of the coating, and monitor the porosity of the coating after deposition. It is observed that the maximum substrate surface temperature after deposition is 528.2K and is located at the junction of particle and particle impact; By analyzing the temperature change curve of five points collected on the substrate over time, the curve appears multiple inflection points, indicating that heat transfer occurs between the particles and the substrate during the deposition process; the substrate first heats up and then cools down. During the multi-deposition process, the particles undergo plastic deformation and continuously squeeze the coating, thereby achieving interconnection between the particles and the substrate; Mechanical interlocking between particles forms a coating.

Development of powder delivery nozzles for laser gas-powder cladding

Mykola Anyakin — 2024-03-19

Along with processing parameters, material properties of the workpiece and the powder, the quality of focusing of gas-powder stream is the key parameter that can influence the productivity, quality and costs of laser gas-powder cladding, rapid prototyping by selective laser sintering and surface modifications. Unfortunately, there is almost no information on the methodology for the design of gas-powder streams delivery and simple methods for the control and measurement of gas-powder stream characteristics.
Development of the methodology for the design gas-powder streams delivery nozzles that are used in laser gas-powder cladding and simple methods for the control of gas-powder stream characteristics.
Numerical methods of vector optics, gas dynamics and image analysis were used.
Original systems for the implementation of laser gas-powder cladding with increased productivity and low rate of powder waste were designed, manufactured and verified experimentally.
It was established that the use of multi-channel nozzles for the delivery of gas-powder stream into laser beam processing zone increase the productivity of technological processes of laser cladding (especially for the cases when workpiece is not positioned perpendicularly to the laser beam) if compared with traditional coaxial and one-channel nozzle. Another benefit of multi-channel nozzles is that it is possible to introduce simultaneously two or more different powder mixtures into the processing zone.

The effect of deformation rate on the process of hot extrusion with dispensing of round hollow semi-finished products

Volodymyr Dragobetskyi — 2024-03-19

Background. Stamping of round hollow semi-finished products by hot reverse extrusion is one of the initial operations in the manufacture of hollow products for special purposes. The force and shape change of the metal during hot plastic forming is significantly affected by the deformation rate or the speed of movement of the deforming tool. For special-purpose products, certain mechanical properties are required in the wall height and bottom part. The wall height properties are ensured at subsequent stretching transitions with thinning of the semi-finished product obtained by hot extrusion, which involves working out the metal structure by plastic deformation to achieve the required properties. Therefore, it is an urgent task to study the effect of the deformation rate on the force and shape change of the metal during hot reverse extrusion of hollow semi-finished products.
Goal. To determine the influence of the deformation rate on the parameters of hot reverse extrusion with the dispensing of hollow semi-finished products from round and square billets by means of finite element method (FEM) modeling and to compare the results of theoretical researches.
Methodology of implementation. Theoretical researches of extrusion power modes, specific forces, and the stress-strain state of metal were carried out by modeling using the FEM in the DEFORM software environment.
Results. The FEM was used to model the process of hot reverse extrusion with dispensing of round hollow semi-finished products from mild steel with protrusions at the end of the bottom part on the side of the cavity and on the outer surface. The deformation rate was in the range of 20 to 80 mm/sec. Round and square cross-sectional blanks were used. The dependence of the extrusion force on the punch displacement was determined. The distribution of specific forces on the deforming tool was determined. The stress-strain state and temperature distribution in the deformed metal at the end of extrusion were determined. The development of the metal structure by hot plastic deformation was evaluated and the results obtained were compared
Conclusions. The effect of the deformation rate on the parameters of hot reverse extrusion with dispensing of round hollow semi-finished products was determined

Functional reliability of means of fixation for complex pelvic fractures. Part 1: Materials and methods

Marianna Dyman — 2024-03-19

Due to the military aggression of the Russian Federation against Ukraine, a large number of soldiers and civilians were wounded and injured. Along with fractures of the long bones of the limbs, skull injuries, limb amputations, the number of injuries in the pelvic area with fractures of the pelvic bones as a result of being hit by high-velocity projectiles (shrapnel, bullets) has increased.
This work is devoted to the preparation and research of the characteristics of stiffness and reliability of fixation of complex fractures of the pelvic bones in the area of the sacroiliac joint and the upper and lower branches of the pubic bone, which may occur as a result of injury by high-velocity projectiles that injure.
The sacroiliac area was fixed with two cancellous screws with a parallel arrangement at the intersection of the horizontal and vertical planes (a typical technique for stabilizing the posterior parts of the pelvis). The anterior parts of the pelvic bones were stabilized with rod devices of external fixation with a typical location of the rods in the upper anterior iliac spine. The upper branch of the pubic bone was synthesized with a bony reconstructive plate with a typical location.

The influence of imbalances on the dynamic characteristics of the laboratory centrifuge HERMLE Z306

Andriy Babenko — 2024-03-19

Laboratory centrifuges are used in various industries. During operation, vibrations occur that lead to resonant frequencies, which in turn impair functionality. This paper presents an overview of the computational model of the HERMLE Z306 laboratory centrifuge used in medical laboratories to separate mixtures of different fractions to determine the dynamic characteristics. The zones of stable operation of the centrifuge and the influence of the rotation speed on the natural frequencies are analytically determined. Experimental results are presented with the influence of imbalances on the dynamic characteristics of the HERMLE Z306 centrifuge. As a result of the modeling, the amplitude-frequency characteristics are determined and a Campbell diagram is constructed.

Objective: Modeling of dynamic processes in laboratory centrifuges by studying the influence of imbalances on the quality of mixture separation. Determination of zones of stable operation of the centrifuge.
Purpose: Construction of amplitude-frequency characteristics of the centrifuge, determination of zones of stable operation of the laboratory centrifuge during separation and Campbell diagram showing the dependence of natural frequencies on the rotation speed of the HERMLE Z306 centrifuge. This diagram makes it possible to determine the resonance zones.

Methods of implementation: Based on the use of the Lagrange equation of the second kind, a model is obtained that makes it possible to determine the zones of stable operation of the centrifuge. Using experimental equipment, determine the frequency response of the centrifuge and analyze the Campbell diagram to determine the resonance zones.
Results: The zones of stable operation of a laboratory centrifuge were analytically determined. The amplitude-frequency characteristics of the HERMLE Z306 centrifuge were constructed, the trajectories of the free end of the shaft were built taking into account the corresponding imbalances, and the resonance zones were experimentally determined.

Conclusions: Experimental studies have shown that the free end of a laboratory centrifuge shaft moves along a surface whose shape and, accordingly, the path of movement depend on both the angles of rotation and translational movement that arise as a result of deformations of elastic supports. The analytical and experimental studies made it possible to identify unstable modes and thereby determine the areas of the centrifuge's operating modes. The separation process will be stable if the roots of the equation have a negative real part, and moreover, the motion will be asymptotically stable in the presence of resistance forces. An experimental technique for determining the dynamic parameters of the centrifuge has been developed. On its basis, the effect of the rotation speed on the natural frequencies was determined.

Finding and analyzing of the energy and force parameters of the flange formation process by orbital stamping by rolling

Qiang Li — 2024-03-19

The study was carried out based on the developed mathematical model of the discrete hydraulic actuator. The model is characterized by considering the nonlinear friction based on the LuGre model, the bidirectional motion of the asymmetric hydraulic cylinder, and the elastic properties of the fluid. A series of simulation experiments on the braking process of the hydraulic actuator in the discrete control mode were carried out. The quantitative relationship between the rod braking time, the maximum peak pressure in the hydraulic cylinder chambers, the value of the initial rod velocity and the inertial mass of the moving parts are determined. Based on the research results it is possible to predict the braking time of the rod and the maximum peak pressure in the hydraulic cylinder chambers under various operating conditions and inertial loads. These predictions can be used in the settings and design process of hydraulic actuators.

Study of motion stability of a viscoelastic rod

Iryna Kostyushko — 2024-03-19

Stability of non-conservatively loaded elastic and inelastic bodies - a classic section of deformable solid mechanics that has been of interest for many years. In this paper, we study the motion stability of a free rod subjected to a constant tracking force on one of its ends. The defining ratio of the rod material is the Kelvin-Voigt model. The solution is presented in the form of an expansion in terms of beam functions. The number of terms of this expansion is substantiated. The values of the critical load in the presence and absence of viscosity are determined. The given analytical results are confirmed by numerical calculations.

Implicit direct time integration of the heat conduction problem in the Method of Matched Sections

Igor Orynyak — 2024-03-19

The paper is devoted to further elaboration of the Method of Matched Sections as a new branch of finite element method in application to the transient 2D temperature problem. The main distinction of MMS from conventional FEM consist in that the conjugation is provided between the adjacent sections rather than in the nodes of the elements. Important feature is that method is based on approximate strong form solution of the governing differential equations called here as the Connection equations. It is assumed that for each small rectangular element the 2D problem can be considered as the combination of two 1D problems – one is x-dependent, and another is y-dependent. Each problem is characterized by two functions – the temperature, , and heat flux . In practical realization for rectangular finite elements the method is reduced to determination of eight unknowns for each element – two unknowns on each side, which are related by the Connection equations, and requirement of the temperature continuity at the center of element. Another salient feature of the paper is an implementation of the original implicit time integration scheme, where the time step became the parameter of shape function within the element, i.e. it determines the behavior of the Connection equations. This method was early proposed by first author for number of 1D problem, and here in first time it is applied for 2D problems. The number of tests for rectangular plate exhibits the remarkable properties of this “embedded” time integration scheme with respect to stability, accuracy, and absence of any restrictions as to increasing of the time step.

Harmonic oscillations of a piezoceramic functional-graded sectional cylinders with account of energy dissipation

Liudmyla Hryhorieva — 2024-03-29

Harmonic oscillations of piezoceramic functional-gradient sectioned hollow cylinders are studied, taking into account energy dissipation. A cylinder of finite length is considered, consisting of an even number of sections polarized in the circular direction, which are connected to each other by similar sides. The material is considered to be functionally heterogeneous in the direction of the previous polarization. The cylinder is loaded by the potential difference applied to the flat faces of the sections. The calculation is performed by the finite element method. The forming of damping matrix and determining the coefficients corresponding to the four ways of introducing Rayleigh damping into the FEM is described. Amplitude-frequency responses taking into account damping are built for displacements, charge on the electrodes, electrical admittance and its logarithm. The consideration of energy dissipation according to the Rayleigh damping model is related to the experimental data due to the Q factor of the piezo element. The frequencies of electrical resonances, anti-resonances and the corresponding electromechanical coupling coefficients for functionally inhomogeneous and homogeneous cylinders are determined. For the functional-gradient piezoelectric element of the considered configuration, the maximum CEMC occurs at the frequency of the second electrical resonance. At this frequency, the dynamic stress-strain state of the cylinder is investigated. Forms of oscillations and distribution of stress amplitude values are constructed. The largest normal stresses according to the Coulomb-Mohr strength theory are determined and compared with the von Mises strength theory. FEA allows three-dimensional calculation of harmonic oscillations of functional-gradient piezo elements of complicated geometry. The determined frequencies of electrical resonance and anti-resonance and the corresponding CEMC make it possible to choose the most effective operating mode of the piezo element. The FEM mathematical apparatus makes it possible to quickly and qualitatively evaluate the strength, determine the charge on the electrodes, the current in the circuit, build the amplitude-frequency characteristics of admittance and impedance, and evaluate the efficiency of energy conversion.

Plasma-chemical synthesis of carbide-based vacuum-plasma functional coatings and study of tribological characteristics of friction pairs

Alex Sagalovych — 2024-03-19

The work is devoted to the search for new materials with high functional characteristics using the Avinit vacuum-plasma technologies developed by us, based on the complex use of coating methods (plasma-chemical CVD, vacuum-plasma PVD (vacuum-arc, magnetron), processes of ion saturation and ion surface treatment), stimulated by non-equilibrium low-temperature plasma.
Processes of controlled plasma-chemical synthesis of the formation of multicomponent coatings in "metal-carbon" systems – Avinit coating (TiC, MoC) using vacuum-arc sources of ionized atomic fluxes of titanium and molybdenum in an argon-benzene plasma environment were developed and their characteristics were studied depending on their conditions formation.
Metallographic studies confirm the possibility of low-temperature application of high-quality wear-resistant high-hard "metal-carbon" coatings with a hardness of 18,000-30,000 MPa, while ensuring good adhesion to the substrate materials (steel DIN 1.2379) without reducing strength and without deteriorating the cleanliness class of the original surface.
The conducted tribological tests using the "cube-roller" scheme reveal high tribological characteristics of steel DIN 1.2379 tribopairs with developed coatings and testify to the promisingness of the developed multi-component multilayer coatings Avinit (Ti-C, MoS) for increasing wear resistance and reducing the coefficient of sliding friction in friction nodes.
The developed plasma-chemical vacuum-plasma coatings are applied to mock-up samples of the working compressor blades of the GTE of aircraft engines. Proven modes allow to get high-quality, uniform coatings with high adhesion.
This gives reason to consider the developed process as an alternative for expanding the range of new Avinit vacuum-plasma erosion-resistant coatings and developing structures of anti-friction wear-resistant coatings to increase the performance of friction pairs in "coating-steel" and "coating-coating" systems.

Structure and properties of samples made from XH50BMTJuB-VI (EP648-VI) alloy produced by using selective laser melting process

Konstantyn Balushok — 2024-03-28

The paper presented examines the composition, the structure and properties of samples made from the XH50VMTJuB-VI (hereinafter EP648-VI) alloy obtained by using the selective laser melting process (the SLM-process) in relation to manufacturing parts for aviation purposes. The authors carried out a comparative study of the samples’ structure and properties upon conducting such operations as depositing in two directions (horizontal and vertical), separate heat treatment and after hot isostatic pressing (HIP) followed by a standard heat treatment process applied for deformable semi-finished products made from the XH50VMTJuB-VI
(EP648-VI) alloy. The authors inform that the manufacturing of samples by means of the SLM-process involved powders obtained through the technology of the vacuum-induction spraying of the molten metal jet with an inert gas (argon). The paper has established that samples obtained by using the HIP process with the application of the heat treatment (a vacuum high-temperature homogenization followed by a long-term aging) demonstrated the best set of mechanical properties, since the implemented complex process ensured the “healing” of pores and discontinuities in the structure, and strengthening by means of the intermetallic g¢-phase, while separations of the excess, needle-shaped a -Cr phase are fine and evenly distributed in the material structure. The authors noted that mechanical properties of samples under analysis were generally in compliance with the requirements set forth in the regulatory documentation for deformable semi-finished products made from the XH50VMTJuB-VI (EP648-VI) alloy, while underlining the increase in the level of impact strength of samples that underwent the HIP process, and the long-term strength of samples manufactured in the vertical direction compared to other options studied. Following the results of the analysis, the authors established that the SLM-process made it possible to manufacture products whose level of mechanical properties was close to the level of the deformable material, and even exceeded it in some cases.