Conical Part Research Articles

Buckling of Stiffened Cone–Cylinder Structures Under Axial Compression

This paper studies the instability behavior of stringer-stiffened cone–cylinder shells under axial compressive load via computational finite element (FE) code, ABAQUS. First, the FE model was validated using past experiments on four cone–cylinder specimens (two unstiffened and two stringer-stiffened) fabricated in pairs using mild steel. Results show that the comparison between numerical and experimental collapse loads was less than 10%. Second, parametric study was conducted using the validated FE model to investigate the effects of the location and number of stringers on the buckling behavior of axially compressed cone–cylinder structures. It has been found that reinforcing the cone–cylinder structures tends to produce higher buckling load when compared to the unstiffened ones. The presence of stringers changes the failure mode of the structure, and the initial post-buckling curves show a less steep negative slope when compared to that of the unstiffened counterpart. Externally stiffened structures were able to sustain more load as compared to the internally stiffened counterpart. Introducing longitudinal reinforcement on the conical section and ring reinforcement on the cone–cylinder junction produces a much higher buckling load compared to having stringer-stiffeners on the conical part only.

Establishment of the unified critical wrinkling limit curve of thin-walled parts forming

Wrinkling is a common defect in sheet metal forming. Different forming conditions lead to complex stress loading paths, which is the main factor that makes wrinkling difficult to control. It is of great significance to accurately predict the wrinkling phenomenon of sheet metal under different forming loads. Three kinds of typical wrinkling tests are selected in this paper, which are Yoshida buckling test (YBT), wedge tensile test and deep-drawing test for conical parts. The numerical analysis models of three typical working conditions are established by using “Buckle + Dynamic-Explicit” algorithm in ABAQUS software. The accuracy of the simulation algorithm is verified by comparison experiments. The law of the critical wrinkling stress and strain data under three working conditions is studied. The unified critical wrinkling limit curve was established by using stress ratio and strain ratio based on MATLAB software. Finally, the accuracy of the curve is verified.

Computational assessment of effects of throat diameter on combustion and turbulence characteristics in a pre-chamber engine

Towards fundamental investigation of key physical aspects of pre-chamber combustion, the current work utilizes computational fluid dynamics to comprehend the effect of the throat diameter in an engine operated with methane. Previous studies showed that this parameter is dominant in pressure build-up and flow pattern inside the pre-chamber, suggesting that a detailed characterization is necessary. This pre-chamber type is composed of an upper conical part that lodges the spark plug and fuel injector, followed by a straight and tubular region called throat, which tip accommodates the nozzles responsible for the charge exchange between pre and main chambers. Two types of pre-chamber having distinct throat diameters are investigated, while utilizing consistent experimental data for validation of the model. The combustion process is modeled with the G-Equation model; the laminar flame speed was tabulated from a methane oxidation mechanism reduced from the GRI 3.0; the turbulent flame speed was computed using Peters' relation. The simulations were run for a full cycle, starting at exhaust valve opening. A homogeneous charge of methane is considered at the intake port, maintaining a global λ = 1.8, while 3% of total energy fuel is added through the pre-chamber. The results show that the throat changes the flow field inside the pre-chamber, impacts the air-fuel ratio, stratification, turbulence, jet dynamics, and ultimately the pre and main chambers combustion processes and heat fluxes. The combustion regime according to the Borghi-Peters diagram were found to lay in the thin reaction zone and in the flamelet regime.

Improvement on the machining accuracy of titanium alloy casing during counter-rotating electrochemical machining by using an insulation coating

Counter-rotating electrochemical machining (CRECM) is an innovative ECM method that can be used to manufacture revolving parts, especially thin-walled casings with complex convex structures. As titanium alloys are easy to passivate and difficult to machine, active NaCl solution is often used to obtain a good surface quality from ECM. However, the top surfaces of convex structures will be subjected to severe over cutting using NaCl solution, resulting in poor machining accuracy. Therefore, an insulation coating is employed to protect the non-processed area by shielding stray currents in this paper. A simulation model is established to investigate the evolution of convex structures with an insulation coating. According to the simulated convex structures, the top of the convex structure suffers from serious stray corrosion without the protection of insulation coating, and the sidewall inclination angle is 25.42°. However, the insulation coating enables convex structures without over cutting, achieving a sidewall inclination angle of only approximately 1.1°. Under the protection of insulation coating, the width and height decrease linearly with time, and the radius of the root fillet increases towards an approximately constant value. The experimental results indicate that stray currents can be shielded completely with an insulation coating, and no electrochemical dissolution occurs on the top of the convex structure. The deviation between simulation and experimental results does not exceed 10 %, demonstrating reliability of the proposed model. Cylindrical and conical parts with a grid-like convex structure are successfully produced with a surface roughness value of Ra1.8 μm. This fully verifies the effectiveness of an insulation coating and demonstrates the excellent processing capability of CRECM.

Numerical study of mean mechanical energy loss in a gas cyclone

Reducing energy loss is one of the goals of optimizing gas cyclones, which can be benefitted from a deep understanding of the energy loss mechanism in gas cyclones. In this study, the gas-solid flow in a gas cyclone was simulated using the combined computational fluid dynamics (CFD) and the discrete element method (DEM). An energy loss model for analyzing the spatial distribution and proportion of the mean mechanical energy loss of the gas cyclone was adopted and validated in terms of the total pressure drop. It is found that the near-wall region generally has high rates for both viscous dissipation and turbulent production, especially the vortex finder, the conical part, and the discharger. The effects of the inlet velocity, the wall roughness, and the particle loading ratio on the energy loss are studied. The findings reveal that increasing the inlet velocity mainly increases the viscous dissipation of the wall and the turbulent production of the core region, resulting in an increase in mechanical energy loss. In contrast to the energy loss mechanism of the pipe, the mechanical energy loss of the gas cyclone decreases slightly with increasing wall roughness, which is mainly caused by the reduction of the viscous dissipation of the wall. By injecting particles, the spatial distribution of the energy loss rate is greatly altered, and the mechanical energy loss is also reduced. Further analysis shows that increasing the particle loading ratio reduces both viscous dissipation and turbulent production.

Evaluation of Centrifugal Force, Erosion, Strain Rate, and Wall Shear in a Stairmand Cyclone

In the present study, imperative parameters including centrifugal force, erosion, streamline, strain rate, and wall shear are evaluated in a cyclone separator. The flaw of the cyclone surface due to erosion is an acute problem in the industry. According to the great importance of the centrifugal force on the separation phenomenon, a comprehensive study is conducted. A computational fluid dynamics (CFD) simulation is realized by applying a Reynolds stress turbulence model (RSM), and particle–air interactions were modeled using a discrete phase model (DPM). The result shows a good agreement between the experimental data and CFD simulation on the tangential velocity and pressure drop. The maximum deviation of the validation process is 6.8%. It is found that the centrifugal force within the cyclone is increased with an enhancement in the inlet velocity. The separation efficiency indicates an increase–decrease treatment in various inlet velocities with inlet velocity up to 16 m⋅s−1 but decreases slightly at a velocity of 20 m⋅s−1. The pressure increases proportionally with inlet velocity. The best performance with the highest separation efficiency (99%) and pressure drop (416 Pa) obtains at the inlet velocity of 16 m⋅s−1 and mass flow rate of 0.01 kg⋅s−1. In addition, the maximum erosion rate was created in the entrance and conical part of the cyclone.

Influence of roller mounting angle on the spinnability of conical spun parts with thin wall

Abstract Using self-developed automatic control spinning equipment, the shear spinning process under 20°, 30° and 40°of roller mounting angle was carried out on the thickness of 0.5 mm for 1060 aluminum alloy to study the characteristics of microstructure, wall thickness reduction, wall surface quality defects. The results show that the roller mounting angle obviously affects on the spinnability of conical spun parts with thin wall, however, it hardly affects their microstructure evolution. When the roller mounting angle is 30°, i.e. in other words the optimal mounting angle is equal to the half cone angle of the core mold. And the conical wall height of the conical spun part is the highest, and the thickness of the conical wall is uniform, the surface is smooth, and there is no obvious appearance defect. It is found that whether the roller mounting angle is larger or smaller than the half cone angle of the core mold, it will lead to negative deviation from the spinning, even if it does not reach an increase of 90°, only an increase or decrease of 10°, the conical spinning part soon appears circumferential cracking of the sidewall, and the phenomenon of material accumulation in front of the cracking all appears.

Experimental Studies on Geometrical Accuracy During Single-Point Incremental Forming of Inconel 625 Superalloy

The single-point incremental forming has been globally accepted as an advanced method of sheet metal forming due to its rapid prototyping and economic benefits. The process has sensitively released the practice of using expensive dies, making it suitable for manufacturing custom-built products in tiny batches. Further, it is getting acceptance in producing parts of shabby machinery. In recent years, superalloys have become the most commonly used materials in the transportation, automotive, aeronautics and marine industries due to their fundamental and structural applications. The input parameters considered in this study are step size, feed rate and tool spindle speed. The effects of all three process parameters on the geometrical accuracy of Inconel 625 superalloy conical parts formed by the single-point incremental forming process are considered in this work. The deviations in roundness, concentricity, half-cone angle and straightness from the target values were considered as response parameters to measure the accuracy. The results showed that the part accuracy could be enhanced by using minimum step size, feed rate and maximum tool spindle speed.

Oscillating wire arc additive manufacture of rocket motor bimetallic conical shell

This paper studies the temperature field, dynamic strain, and forming accuracy of the oscillate-WAAM conical shell in the forming process and manufactures the WAAM conical shell part. The results show that compared with the offset filling WAAM, the oscillate-WAAM conical shell shows the following characteristics: the temperature difference value between the inner and outer walls of the shell is significantly reduced, the cooling rate doubled decreased, the interlayer temperature is above 300 °C, and the average temperature gradient, the dynamic strain stability value, and deformation are reduced by about 50%. Under the same process parameters, the travel speed of oscillate-WAAM is low, which increased the heat input large and the interlayer temperature high. Meanwhile, the molten pool of oscillate-WAAM is in consistent with the width of the shell. The molten pool’s simultaneous solidifying changes the stress state of printed shell from three-dimensional to two-dimensional. All the above are conductive to stress release and reduce the strain and deformation of components. The bimetallic rocket motor shell composed of HS600 and HS950 is manufactured by oscillate-WAAM. The section roundness of the shell is 0.31 mm, and the overall forming accuracy is ± 0.625 mm. The deposited metal in HS600 part of conical shell is composed of pearlite and pro-eutectoid ferrite, while the deposited metal of HS950 is composed of pearlite, acicular ferrite, and bainite. The forming accuracy and mechanical properties of conical shell formed by oscillate-WAAM meet the requirements.

A method based on circumferential strain distribution for roller path design in conventional spinning of thin-walled conical part with curved surface

Multi-pass conventional spinning is the preferable forming technology for the forming of thin-walled conical part with curved surface (TCPCS) in aerospace field. In multi-pass conventional spinning, the design of roller path is a critical problem due to its sensitive effect on the deformation mode and forming defect during spinning process. However, at present, the roller path is still mainly designed based on experience and trial and error, which seriously restricts the high-performance spinning of TCPCS. In this work, a new quantitative method based on circumferential strain distribution was developed for the roller path design in multi-pass conventional spinning of TCPCS. In this method, the total required circumferential strain for the forming of final TCPCS by conventional spinning was firstly determined. Then, the spinning passes number was obtained through dividing the total required circumferential strain by the ultimate circumferential strain producing the spinning instability. As for the roller path profile in each pass, it is divided into two sections and determined, respectively, i.e., the attaching mandrel section and the preforming section. The attaching mandrel section presents the same profile of mandrel. The profile of preforming section is determined point by point by distributing the rest of circumferential strain to produce the final TCPCS. The point-by-point distributed circumferential strain is half of the the total required circumferential strain in the initial stage until it reaches the half of the ultimate circumferential strain, and then, it will keep the half of the ultimate circumferential strain to the end. The proposed new method of roller path design was validated by finite element simulation, where well spinning stability, wall thickness distribution and roundness were obtained. This method provides a quantitative, high-efficient and universal way for the roller path design in conventional spinning of TCPCS.

Fabrication of Conically Shaped CuCr1 Chrome Bronze Products by Wire-Feed Electron Beam Additive Manufacturing

The structure and properties of conically shaped products made of CuCr1 chrome bronze obtained by wire-feed electron beam additive technology have been investigated. The studies show that the organization of the structure in the samples fully corresponds to the peculiarities of the printing process and heat removal from the samples. The structure is represented by large grains elongated in the direction of heat removal. Chromium in the samples is mainly localized in the form of particles located between the dendrite arms. Near the substrate, intense mixing of the bronze with the substrate material (steel 321) is observed. The mechanical properties of the conical and cylindrical sample parts material are at a fairly close level. The samples are characterized by low values of yield strength, low values of tensile strength and high plasticity. Near the substrate, the mechanical properties of the specimens increase.

Non-optimality of conical parts for Newton\u2019s problem of minimal resistance in the class of convex bodies and the limiting case of infinite height

We consider Newton’s problem of minimal resistance, in particular we address the problem arising in the limit if the height goes to infinity. We establish existence of solutions and lack radial symmetry of solutions. Moreover, we show that certain conical parts contained in the boundary of a convex body inhibit the optimality in the classical Newton’s problem with finite height. This result is applied to certain bodies considered in the literature, which are conjectured to be optimal for the classical Newton’s problem, and we show that they are not.

Optimization of cyclone operating modes with intermediate dust removal using gas flow structure analysis

The analysis of works in which designs of the dust collecting devices which are often used in the industry are investigated is carried out. It is established that forecasting the work of dust collecting devices in certain conditions is most effective to perform methods of numerical modeling and simulation of the separation process, which are widely used for research of devices of this type. Using numerical simulation methods, it is defined the structure of the gas flow in the cyclone with intermediate dust removal for different modes of operation, which was obtained by suction of gas through the dust unloading holes at constant total costs. For this cyclone, the change in the radius of the tangential, radial, and axial velocity component for different operating modes is investigated. In the course of the research, it is established that in the separation space the tangential component of velocity with increasing radius changes according to the parabolic law. The maximum values are 16–17 m/s. The suction of part of the gas in the amount of up to 20 % through the dust unloading holes slightly reduces the tangential component of the speed (up to 5 %) in the separation zone. It is determined that in the conical part the maximum values of the tangential component of the velocity decrease to 6–7 m/s. The reduction occurs both due to the flow of gas flow from the descending to the ascending, and the suction of gas through the dust unloading holes. It is established that the radial component of the velocity varies from 1 m/s in the separation zone to 5.5 m/s in the conical part. It has been found that the suction of gas through dust unloading holes in the amount of more than 15 % of the total volume leads to a change in the direction of the radial velocity component in the conical part. It is determined that the axial component of the velocity of the separation zone receives maximum values of 9–11 m/s. In the conical part of the device, it decreases to 2–4 m/s. The suction of part of the air through the dust unloading holes leads to a shift of the axis of the internal vortex relative to the geometric axis of the apparatus below the lower end of the exhaust pipe.It is established that the creation of a directed flow of gas through the dust unloading holes in the additional dust collector in the amount of up to 15 % of the total gas volume contributes to a more efficient operation of the dust collector. A further increase in the amount of exhaust air leads to greater turbulence of the flow and less efficient operation of the apparatus.

Development of sheet stamping operation and stamp design for manufacturing of deep conical bottom part bushings

The possibility of high-performance stamping of conical bottom part bushings is described. It is shown that it is advisable to use continuously expanding working cavity to stamp the conical part of the part in one transition to ensure high quality of the product. At each moment when the conical part of the punch passes through certain plane of its cross-section, the die diametr in this plane equal to the punch cross-section diameter plus double the part wall thickness. To do this, the function of the die is carried out by cavity in the rollers. The rollers are rotated connected with the upper plate of the stamp, on which the punch is installed that stamps of the part. Two designs of the roller drive performs the described synchronization of the movements of the tools are described: simpler for small-scale production of parts and more complex for their large-scale production.

Мethodology for designing of obtaining process of parts by combining operations of crimping, expansion, drawing and flanging

A methodology for designing of obtaining process of conical hollow parts by combining the operations of crimping, expansion, drawing and flanging in one technological transition is presented. An example of designing and stamping of a specific conical part is given.

Numerical Study on Collection Performance of Particulates in Hemispheric-Head Cyclone Separators for Fuel Cell Vehicles

A hemispheric-head cyclone separator has higher collection performance of fine particles comparing with a conventional cyclone separator with a cylindrical head. In order to optimize the shape model with hemispheric-head, we have investigated numerically and experimentally the air flow in various shape cyclone models for industrials. The purpose of this study is to develop a cyclone model for fuel cell vehicles based on the results for industrials. Since this model is installed in a fuel cell vehicle, it must be compact due to space constraints. Therefore, as the first stage of development, based on a model of a dome-shaped cyclone separator with a cyclone diameter of 54 mm, we numerically investigated the airflow in the model by changing the dust holder size and the inlet pipe connection height. The motion of fine particles was analyzed considering only drag and gravity, and the effect of internal airflow on collection performance was investigated. As a result, it is shown that the model with the low inlet pipe connection height and the small volume of the dust holder has the highest collection efficiency. It was found that even if the entry particles in the dust holder return to the conical separator part due to small dust holder, the air flow field of the highest collection efficiency model has high centrifugal separation performance by lowering the connection height of inlet pipe. It is also the most suitable in terms of space for installation in fuel cell vehicles.

COMBINED EXTRUSION OF GLASSES WITH A CONICAL BOTTOM. METHODOLOGY FOR CALCULATING TECHNOLOGICAL PARAMETERS OF CONSTRAINED EXTRUSION AT INITIAL DEFORMATION BY SHEAR OF THE CENTRAL REGION

The methodology for calculating the energy-power and deformation parameters of the process of constrained extrusion of glasses with a conical bottom part, starting from the shear of the central region. The extrusion of both non-hardening and hardening material is considered. In the latter case, the account of the hardening of the extruded material is described in detail. The above formulas allow us to determine such important parameters of the stamping process as total and specific deforming force, maximum pressure on the die wall, and an increase in the yield stress.

Steam Generator Strength Computation for Nuclear Electric Power Plants of a Low Power

Today, the world oversees an explosive development of the nuclear power stations (NPS) of a low power. Most projects deal with pressurized water reactors and as a matter of fact with steam generators (SG). Ukraine has a well-developed engineering industry backbone that can be used for the production of the equipment required for the nuclear power plants of a low power. This scientific paper delves into the computations of the strength of elements used for the monotube steam generator with cylindrical coils that is the most presentable of all the projects in question in IAEA materials. Appropriate methods were developed to perform structural computations and steam generator strength computations. The mathematical model was developed that allows us to perform strength computations of the SG elements making use of the analytical method with reference to the Regulations and do simulations using the ANSYS software code. The specified elements include the body elements, in particular the cylindrical part, the flange, the bottom and the cover, including the heat carrier branch pipe and heat exchange tubes. The comparison of the data obtained by both methods showed their similarity and accordingly, the accuracy of the data that are indicative of the need for an increase in the wall thickness of the cylindrical part of the external branch pipe intended for the heat carrier. The body bottom strain for calculated dimensions exceeds the permissible value by 1.56 %. Since this value is 5 % lower than permissible values it is deemed that the strength condition is passed through. The simulation proved that the strength conditions are met for heat exchange tubes, for the body, the body cover, the body flange, the conical part of the external branch pipe intended for the heat carrier. Based on the analysis done, we would like to recommend performing strength computations using the normative method with the subsequent check out by the simulation using the computer code.

Modeling of formation regularities of conical surfaces

The scheme of processing conical surfaces by grinding them to a flat tool is considered and a technical solution for the implementation of such processing is proposed. Using the created device allows implementing the group method of forming conical parts with a deviation of the generatrix of the cone from straightness of not more than ± 0.00012 mm. A mathematical model of the patterns of removal of stock from a conical part with a flat tool is developed. A formula is obtained for calculating the modulus of the sliding velocity at any point on the processed conical surface, which implements engineering methods for controlling the shaping of conical parts without conducting preliminary labor-intensive experimental studies. An optimization technique for the adjustment parameters of technological equipment was proposed. The most effective axicon processing modes were revealed at the stages of preliminary, medium and fine grinding, as well as at the polishing stage, depending on the technological heredity of the workpiece from the point of view of distribution of the stock to be removed over its surface. It has been established that changes in the eccentricity between the axes of rotation of the tool and the faceplate as well as the amplitudes of the reciprocating rotational movements of the latter practically do not affect both accuracy and processing productivity, therefore, in practice, these parameters can not be optimized, but their average values can be assigned. The operating modes of the basic lever grinding and polishing machine are established, at which the required accuracy of the working surface of the tool is provided, which directly affects the straightness of the generatrix of the cone. Studies of the regularities of the shaping of the side surface of a conical lens in the conditions of free grinding are carried out and the adjustment parameters of technological equipment that affect the quality and productivity of the processing process are determined.

Investigation of influencing factors of wear in a sandblasting machine by CFD-DEM coupling

In order to study the effect of particle characteristics and operating conditions (particle diameter, density, shear modulus, initial stacking height and inlet pressure) on the wear of the sandblasting machine, the gas-solid two-phase flow inside a sandblasting machine under different operating conditions was simulated by coupling the CFD and DEM methods in this work. Combining with the Archard wear model, the erosion was calculated and the erosion distributions were obtained in different sandblasting machine parts, including the top cover, inlet pipe, cylindrical part, conical part and lower pipe. The simulation results demonstrate that severe erosion in the sandblasting machine occurs at the lower pipe near the outlet, the conical part and the joints between different parts. The erosion volume order for different parts from high to low is: the lower pipe, conical part, cylindrical part, inlet pipe and top cover. The erosion volume of the sandblasting machine increases with the increase of particle diameter, density, shear modulus, stacking height and inlet pressure. Comparatively, the initial stacking height and inlet pressure have more influence on the erosion, while the particle density and shear modulus have less influence.