Circular Insert Research Articles

Multistability of roller structures under parametric excitation of capillary waves in a square cell with a round protrusion in the center

In nonlinear systems with instability, multistability often occurs. When studying processes occurring in real environments, the problem arises of finding paths leading to any state of equilibrium and searching for new stable states. In two-dimensional systems, they can consist of domains and differ in orientation in space. The goal of the work is to experimentally determine the features of the generation of multidomain structures in a two-dimensional system in the presence of complex boundaries of a liquid layer that experiences periodic vertical oscillations. The paper presents the results of an experimental study of the dynamics of roller domains of parametrically excited capillary waves in a square cell with a round insert in the center of the cell. In different domains, the rollers were oriented parallel and perpendicular to the boundaries of the cuvette and the boundaries of the circular insert. It was found that the dynamics of domains is determined by the movement of their fronts, and depending on the initial and boundary conditions, stable two-dimensional roller structures can appear at the edges of a square cell with a round protrusion in the center of the cell. In different domains, the rollers had different orientations. In this case, roundings with a large radius had the strongest effect on the dynamics of defects. Multistability of equilibrium states of roller structures was discovered, characterized by the fact that, with constant system parameters, various scenarios of domain competition arose, leading to 11 different stable equilibrium states, which differed in the number of domains, their shape and the presence of spatial symmetry. It turned out that during the occurrence of defects and the growth of domain walls, slow liquid flows arise near the boundaries of the cuvette and the circular insert. The rollers begin to move, and then a new stable equilibrium state is established in the form of a single domain containing one or two domain walls. It has been experimentally shown that the most stable equilibrium states of domains arise when the circular protrusion is symmetrically positioned relative to the sides of the cuvette. The results obtained may be of interest when studying the processes of establishing stable regimes in active media under strong competition and when studying the formation of two-dimensional structures from conducting particles capable of scattering electromagnetic waves.

SEARCH OF OPTIMAL SPATIAL PARAMETERS FOR GEODETIC DELINEATION OF MOTORWAY INTERCHANGES WITH BRAKING TRANSITION CURVES

The most widespread grade-separated road junction — cloverleaf interchange — is a complex engineering structure, in which all the parameters and limitations of the plan and longitudinal profile must be coordinated with each other. The goals of the analysis: traffic safety, technical and economic indicators of the movement of transport units, the compactness of left-turn and right-turn exits and, as an additional, but extremely important aspect, the minimization of the area occupied by the entire transport structure, which is very important in tight urban conditions. 
 First, let's emphasize that the trajectories of cars at the intersection must correspond to their real variable speeds on left-turn exits, since this is traffic on curves of small radii. In our previous studies, it has been experimentally proven that cars entering a left-turning exit reduce their speed, and conversely, when leaving the exit, their speed increases. Therefore, it is necessary to use braking curves as transition curves of left-turn exits, and not clothoid curves, which are often used, and which are designed for constant speed of movement.
 Some braking transition curves designed for variable speed are also used in traffic junctions [4]. But, analyzing these curves, we came to the conclusion that they do not meet the classical purpose of the transition curve, namely, they do not provide the necessary radius at the end of the curve, which is equal to the radius of the circular insert for a smooth transition from a transition curve to a circular curve. This leads to dangerous moments of the car's movement at the junction of the transition and circular curves.
 Therefore, we previously derived the formulas of refined braking transition curves that meet the requirements of the radii of classical transition curves [1, 2]. In addition, it later turned out that these refined transition curves have, as an additional effect, the property of reducing the area occupied by the left-turn exit, as shown in Fig. 1.
 We offer a method for optimizing the spatial parameters of cloverleaf interchanges with refined braking transition curves.

Redesign in the textile industry: Proposal of a methodology for the insertion of circular thinking in product development processes

Despite the growing attention toward negative environmental impacts generated by the textile industry, companies face challenges in achieving sustainable and circular economy (CE) transition. The literature has so far lacked a systematic effort to analyze how textile companies can insert CE elements in their new product development process (NPD), especially regarding the proposition of methodologies that can better assist the companies in this regard. This study aims to identify good green innovation and CE practices in NPD adopted by textile companies and propose a methodology from Design Thinking (DT) to insert circular thinking in NPD. To that end, we conducted the research in two steps: (i) narrative bibliographic review and (ii) field research. The bibliographic review was conducted in the “Web of Science”, “Scopus”, and “Scielo” databases. The field research was executed with four textile companies. Our results show that companies tend to consider socio-environmental aspects at different stages of the development of new products. However, there is opportunities for improvement, especially through the use of ideas from DT. The proposed methodology is composed of two main cycles: the design cycle (DT stages) and the consumption cycle (subsequent stages). It encompasses the five main stages of the DT and the three macro phases of NPD of the textile industry. The ideas coming from the DT, especially creativity, focus on the user and stakeholder integration, assist in the development of innovative and circular solutions. The methodology presents how companies can work on reuse, recycling, and manufacturing issues, so that CE occurs. In the end, we evaluated, together with experts, the applicability of the proposed use of ideas of DT in practical cases. The research advances the discussions on NPD in the textile sector, especially on its potential to contribute to the transition to CE. It explores how DT assists in inserting circular thinking into the NPD and presents alternatives for companies to develop circular products and insert green innovations in their NPD.

A Novel Phantom and a Dedicated Developed Software for Image Quality Controls in X-Ray Intraoral Devices.

Background: Periodic quality control (QC) procedures are important in order to guarantee the image quality of radiological equipment and are also conducted using phantoms simulating human body. Objective: To perform (QC) measurements in intraoral imaging devices, a new and simple phantom was manufactured. Besides, to simplify QC procedures, computerized LabView-based software has been devised, enabling determination of image quantitative parameters in real time or during post processing.Material and Methods: In this experimental study, the novel developed phantom consists of a Polymethyl methacrylate (PMMA) circular insert. It is able to perform a complete QC image program of X-ray intraoral equipment and also causes the evaluation of image uniformity, high and low contrast spatial resolution, image linearity and artefacts, with only two exposures. Results: Three raters analyzed the images using the LabView dedicated software and determined the quantitative and qualitative parameters in an innovative and accurate way. Statistical analysis evaluated the reliability of this study. Good accuracy of the quantitative and qualitative measurements for the different intraoral systems was obtained and no statistical differences were found using the inter-rater analysis. Conclusion: The achieved results and the related statistical analysis showed the validity of this methodology, which could be proposed as an alternative to the commonly adopted procedures, and suggested that the novel phantom, coupled with the LabView based software, could be considered as an effective tool to carry out a QC image program in a reproducible manner.

Effect of Magnetic Field on Double Diffusive Natural Convection Inside a Square Cavity with Isothermal Hollow Insert

A numerical study is carried out to analyze both heat and mass transfer phenomena in the presence of an external magnetic field inside a square cavity with an isothermal hollow circular insert located at the centre of the cavity. In the present work, the effects of Hartmann number, Lewis number and buoyancy ratio at constant Rayleigh and Prandtl numbers are investigated simultaneously to understand the importance of these parameters on the characteristics of double diffusive natural convection. Galerkin finite element method is employed for the numerical simulations. Grid sensitivity test and code validation are performed prior to confirm the numerical accuracy of the solution. Quantitative comparison is presented by showing the influence of Hartmann and Lewis numbers for different buoyancy ratios on average Nusselt and Sherwood numbers. It is found that increment of Hartmann number results in lower heat and mass transfer rates. Higher value of Lewis number produces elevated mass transfer rate. However, Lewis number has negative impact on heat transfer rate. Moreover, buoyancy ratio has significant effect on heat and mass transfer inside the cavity.

Experiment and model of cutting force of heavy-duty milling water chamber head material

The cyclic impact load of cutting force is one of the main factors that lead to the insert failure during the milling process. According to the asymmetrical heavy-duty milling process of water chamber head, the simulation milling experiments using actual machining parameters are conducted under laboratory conditions, and the change rule of milling force with cutting parameters is analyzed. Moreover, the simulation of interrupted cutting is carried out to study the cycle changes of cutting force and stress distribution of insert during the insert cutting-in and cutting-out workpiece. The dynamic cutting force model is established by considering the irregularity of the cutting area of circular insert and the variation of asymmetric milling thickness. Based on the analysis of comparison between the calculated value of the model and the experimental value, the cutting force model can describe the dynamic change of cutting force in milling process. It is of great significance to analyze and master the changing trend of dynamic cutting force for the study of insert failure and the formulation of reasonable processing parameters in milling process.

Augmentation of thermal performance of heat exchanger using elliptical and circular insert with vertical twisted tape

ABSTRACT Present work deals with the experimental and computational investigation of thermal properties and fluid flow characteristics on circular tube with elliptical inserts. The major axis is taken equal to hydraulic diameter i.e. 6.81cm. A new parameter, height ratio (γ = b/D) has been defined with three values – 0.45, 0.66, and 0.74. The test section is 1.5 m long which is provided with a constant heat flux of 1000 W/m2 along with air as working fluid at Reynolds number ranging from 3,000 to 21,000. The results show that the augmentation in heat transfer was six times for case γ = 0.74 and the maximum thermal performance factor (TPF) obtained is 2.43 for insert with γ = 0.45 at Re = 3000 over the smooth tube. Computational fluid dynamics (CFD) investigation is also carried out for elliptical inserts, and the results are in good agreement with the experimental results where the maximum deviations in Nusselt number, friction factor, and TPF are ±9.39, ±8.68, and ±8.58%, respectively. CFD investigation for tube having circular inserts with vertical twisted tapes (CVTT) and elliptical inserts with vertical twisted tapes (EVTT) is also presented where the augmentation in heat transfer ranges 3–8 times for CVTT placed in full length and TPF is ranging 1.19–2.63 times for CVTT placed in TL length over to smooth tube.

Heat transfer augmentation by nano-fluids and circular fin insert in double tube heat exchanger – A numerical exploration

Abstract The heat transfer augmentation primary demand in industries like power plant, automobile and process industries for either heating or cooling or evaporation, in particularly in air conditioning, radiators, refrigerators, condensers etc. Such augmentation of heat transfer can either be achieved by passive and active techniques. In this paper the passive approach employed for heat transfer augmentation in double pipe heat exchanger. The four different nano-fluids are considered for the investigation like titanium dioxide nano-fluid, Beryllium oxide or beryllia nano-fluid, zinc oxide nano- fluid and copper oxide nanofluid. The role of nano-fluid is increasing the thermal conductivity of the fluid medium. The circular fin insert used for offering the flow resistance and spread the fluid to surface to enhance the heat transfer. The numerical study is investigating the thermal and flow fields utilizing various types of nano-fluids with circular fin insert in the double pipe heat exchanger. The Finite volume method employed for solve the continuity, momentum and energy equations the ANSYS 15.0 employed for conducting the numerical analysis.

Numerical investigation of non-isothermal viscoelastic filling process by a coupled finite element and discontinuous Galerkin method

In this paper, we study the challenging non-isothermal polymer filling process for the cavity with irregular inserts via a coupled finite element method (FEM) and discontinuous Galerkin (DG) method. The non-isothermal eXtended Pom-Pom (XPP) model is utilized to suitably describe the viscoelastic behavior of the branched polymer melt. As for the energy equations, we decouple the convective and diffusive terms to get two sub-equations. It is also able to receive several sub-equations from the momentum equation via splitting scheme. Then the hyperbolic and elliptic type sub-equations are solved via DG and FEM, respectively. The level set method is employed to capture the complicated transient free surface. Due to the pure convective character of the level set and XPP constitutive equations, the Runge-Kutta Discontinous Galerkin (RKDG) is used to deal with them. In this coupled algorithm, it is able to take full advantages of FEM and DG and also avoid the stabilization terms. The non-isothermal filling process of the rectangle cavity with a circular cone insert is first investigated to illustrate the feasibility and validity of the coupled method. Moreover, a more complex mould cavity, the socket with five irregular inserts, is studied as an application case to demonstrate the robustness and practicability of our coupled method. The influences of the inlet melt temperature on the stress and stretch are all analyzed.

54. Spatio-temporal generalisation of Model Observer for Low Contrast Detectability assessment of dynamic angiographic images: comparison with an innovative Statistical method and 2AFC experiments

Purpose Evaluate the feasibility of different less time consuming approaches for protocol optimisation in interventional radiology. Methods A Allura FD20 (Philips, The Netherlands) has been employed in this study. Low Dose Fluoroscopy was selected due to its spatial resolution, characterised by a lower enhancement compared to other modalities. Simulated images have been obtained adding a blurred circular insert to a series of acquired homogeneous images. A total of 3 insert dimensions (1.25, 2, 3 mm of diameter), 25 contrast levels and 4 different visualised frame rate (5, 10, 15 and 30 fps) have been selected to characterise low contrast detectability. A series of 2AFC experiments have been performed by two observers. Two different Model Observers has been considered: Non-PreWhitening Eye filter (NPWE) with spatio-temporal contrast sensitivity function and Channelized Hotelling Observer (CHO) with spatio-temporal Gabor filters. Furthermore, Low Contrast Detectability has been evaluated with a statistical method using uniform images. This analysis has been performed on an averaging of frames depending from the visualised fps. In particular, the averaging process was performed on groups of frames that correspond to the noise integration time of human eye-brain system of 200 ms, e.g. 3 frames with 15 fps. Results Analysis with both Model Observers and 2AFC experiments suffered from the general low quality of the protocol considered (Fig. 1). Nevertheless, a good agreement ( Conclusions The agreement with human observer experiments underlines the feasibility of the proposed generalisations. Thus, they could be introduced for a deeper modalities characterisation, in terms of image quality, or for clinical protocol optimization involving cine images.

Stresses in Circular Plates with Rigid Elements

Calculations of residual stress fields are carried out by numerical and static methods, using the flat cross-section hypothesis. The failure of metal when exposed to residual stresses is, in most cases, brittle. The presence in the engineering structures of rigid elements often leads to the crack initiation and structure failure. This is due to the fact that rigid elements under the influence of external stresses are stress concentrators. In addition, if these elements are fixed by welding, the residual welding stresses can lead to an increase in stress concentration and, ultimately, to failure. The development of design schemes for such structures is a very urgent task for complex technical systems. To determine the stresses in a circular plate with a welded circular rigid insert under the influence of an external load, one can use the solution of the plane stress problem for annular plates in polar coordinates. The polar coordinates of the points are the polar radius and the polar angle, and the stress state is determined by normal radial stresses, tangential and shearing stresses. The use of the above mentioned design schemes, formulas, will allow more accurate determination of residual stresses in annular welded structures. This will help to establish the most likely directions of failure and take measures at the stages of designing, manufacturing and repairing engineering structures to prevent these failures. However, it must be taken into account that the external load, the presence of insulation can lead to a change in the residual stress field.

An efficient multipoint 5-axis tool positioning method for tensor product surfaces

In this work, a robust tool-drop algorithm coupled with the bisection method is used to speed up the computations in the drop and tilt method (DTM), a multipoint tool positioning technique for 5-axis machining with a toroidal end mill. In the DTM, the tool is dropped on the surface along a predetermined tool-axis direction until it touches the surface tangentially. The position of the circular tool insert (pseudo-insert circle) through the first point of contact is then used to compute the tool-tilt angle that causes the tool to touch the surface tangentially at a second point. A previous implementation of DTM used Newton’s method to solve the system of equations for tilting the tool, but took many iterations and multiple initial seed solutions to converge to a valid solution for tool-tilt orientation. Using the bisection method coupled with the generalized tool-drop algorithm instead of a direct use of Newton’s method to determine the tool-tilt angle improves performance without compromising the accuracy. The method was implemented in C+ +, and a comparative study with an earlier method for several bi-quadratic and bi-cubic Bezier surfaces demonstrates the reliability of the developed method.

Analysis of S0/A0 elastic wave mode conversion phenomenon in glass fibre reinforced polymers

In this paper results of experimental analysis of elastic guided wave mode conversion phenomenon in glass fibre reinforced polymers GFRP are presented. Results of research presented in this paper are strictly focused on S0/A0' mode conversion caused by discontinuities in the form of circular teflon insert simulating damage and impact damage. Experimental research is based on non-contact elastic wave sensing with utilisation of scanning laser Doppler vibrometer SLDV and full wave-field measurements. In presented research influence of location of circular teflon insert on S0/A0' mode conversion is investigated. Teflon inserts were located between layers of composite material at different depth. Moreover influence of impact damage with different energy on S0/A0' mode conversion is investigated. Analysis of influence of investigated discontinuities on S0/A0' mode conversion are based on the elastic wave mode filtration in frequency-wavenumber domain. Mode filtration process allows to remove effects of unwanted type of mode propagation in forward or backward direction. Effects of S0/A0' mode conversion are characterise by mode conversion indicator based on amplitude of new mode A0'.

Heat transfer characteristics of Al2O3/water nanofluid in laminar flow conditions with circular ring insert

In this experimental investigation convective heat transfer, friction factor, and thermal enhancement characteristics of straight circular duct fitted with circular ring insert of constant heat flux boundary condition under fully developed laminar flow is presented. Tests have been conducted by using 0.1% volume concentration of Al2O3 nanofluid and water. Inserts of different pitch to diameter ratios of 6.25, 8.33, 12.5, and 16.67 with center core rod were used for this investigation. The circular ring insert shows a superior thermal performance than plain tube. The experimental results demonstrated that the Nusselt number, friction factor, and thermal enhancement factor increases with decrease in pitch to diameter ratio. The circular ring inserts of lower pitch to diameter ratio of 6.25 with nanofluid increases the Nusselt number by 165.38% compared to pure water and the friction factor, found to be 7.89 times higher than that of water. Empirical correlations are develope for Nusselt number and friction factor in terms of Reynolds number, volume concentration, and pitch ratio. The thermal performance factor was found to be greater than unity for all pitch to diameter ratios.

難削材加工に適応可能な従動式ロータリミーリング工具の開発

In order to improve milling performance of difficult-to-cut materials, a unique milling cutter with SPRT (Self-Propelled-Rotary-Tool) was developed. Use of slide bearings enables a compact SPRT mechanism, while influence of bearing friction becomes not negligible. To attain self-revolution of a circular insert regardless of the bearing friction, the cutter geometry was optimized. Through face milling experiments of Inconel 718, superior tool wear resistance was verified as compared to the conventional milling without insert rotation. Analytical result of the measured cutting forces also indicated interesting phenomena in SPRT milling.

Experimental investigations and development of cutting force model for self-propelled rotary face milling cutter in machining of titanium alloy

In self-propelled rotary tool machining, a circular cutting tool insert is used that continuously rotates about its axis during machining, as the tool is fed into the workpiece. The continuous rotation of the insert allows the insert to cool between engagements and improves tool life. In order to make use of this methodology for rough machining and bulk material removal in machining of aerospace materials, a self-propelled rotary face milling cutter is developed at Defence Research and Development Laboratory, Hyderabad. This cutter was developed to study the influence of inclination angle on the cutting forces generated during machining, and hence the cutter is provided with the provision to have the inclination angle of the insert for 20°, 30°, 40° and 50°. This article discusses the performance of the developed self-propelled rotary face milling cutter in face milling of titanium alloy at different inclination angles. The cutting forces developed in FX, FY and FZ directions are evaluated at different cutting speed, feed, depth of cut and inclination angles. The cutting forces obtained in self-propelled rotary face milling cutter is compared with that of conventional face milling cutter and the results are presented and discussed. Finally, regression models for prediction of cutting forces are developed.

Force Prediction in Cutting Operations with Self-propelled Rotary Tools Considering Bearing Friction

This paper presents a model to predict cutting force and motion of the rotating insert in cutting processes with self-propelled rotary tools (SPRT). Metal cutting utilizing rotary tools is effective to suppress tool wear and thus it is considered to be suitable to attain high performance machining of difficult-to-cut materials. It is well known that a circular insert attached to a rotational axis is self-propelled due to inclined chip flow on rake face plane by setting certain oblique angle. A resultant insert rotation speed can be easily predicted considering a frictionless rotary axis. However, friction at the rotary axis of SPRTs may not be negligible in practice especially when slide bearings are employed. In order to investigate the influence of the friction at the rotation axis on the rotary cutting process, a new cutting model is proposed. As the friction at the rotation axis causes a decrease in a speed of round insert rotation, an equivalent oblique cutting process is taken into account in the proposed model utilizing conventional theoretical model. In the equivalent process, the tangential component of the resultant cutting force corresponds to the friction force at the rotary axis. The friction force is determined by cutting force component normal to force-bearing mechanism and the bearing's friction coefficient. Considering the equilibrium condition in cutting and friction forces, the resultant cutting force and the insert rotation speed are iteratively computed in the proposed model. Edge force model is also associated with the oblique cutting model, which is not negligible especially in machining difficult-to-cut materials. The developed model is extended to simulate milling processes with SPRTs. The proposed model is experimentally verified, and influence of the bearing friction of SPRT on the process is clarified.

Thermal Efficiency of LPG and PNG-fired burners: Experimental and numerical studies

In the present work, the thermal efficiency of a conventional domestic burner is studied both experimentally and numerically for liquefied petroleum gas (LPG) and piped natural gas (PNG) fuels. Three-dimensional computational fluid dynamic (CFD) modeling of the steady-state flow, combustion and heat transfer to the vessel is reported for the first time in such burners. Based on the insights from the CFD model concerning the flow and heat transfer, design modifications in the form of a circular insert and a radiant sheet are proposed which are observed to increase thermal efficiency for LPG. For PNG, predictions showed that loading height was a much more important factor affecting efficiency than these design modifications and an optimal loading height could be identified. Experiments confirm these trends by showing an improvement in burner thermal efficiency of 2.5% for LPG with the modified design, and 10% for PNG with the optimal loading height, demonstrating that the CFD modeling approach developed in the present work is a useful tool to study domestic burners.

On the role of inserts in forced convection heat transfer augmentation

The role of inserts in internal forced convection has been widely acknowledged as a passive device in the heat transfer enhancement. The present study is aimed to empirically investigate the heat transfer enhancement in a tube fitted with a square-cut circular ring insert in the transitional and the fully turbulent flow regimes. By performing an in-depth analysis on the experimental data, the role of insert has been quantified by deriving a new non-dimensional group. This new non-dimensional group is proposed to characterize the effect of inserts on the heat transfer enhancement. While the findings show the incorporation of insert in the flow passage enhances the heat transfer rate, the characteristics of the flow in the transitional and the fully turbulent flow regimes induced by the effect of insert are distinct. The new non-dimensional group provides interesting insights into the role played by the insert. The physical significance of the non-dimensional number which provides a measure of the change of enthalpy relative to the change of flow energy in the flow direction can be used to explain the decrease of heat transfer augmentation in the turbulent flow regime relative to the transitional flow regime. Based on the analysis of the non-dimensional group, it can be deduced that the contribution of the axial pressure drop in the heat transfer augmentation is marginal albeit not negligible compared to the temperature rise in the characterization of the heat transfer augmentation with the incorporation of insert. The evaluation of heat transfer augmentation efficiency based on the rate of change of internal energy shows that the performance efficiency of an insert would be identical in different flow regimes, contradictory to the widely held axiom that the effect induced by the insert on the heat transfer augmentation diminishes in the turbulent flow regime.

Development of Custom-made Design Method of Artificial Hip Joint Stem

In the hip replacing arthroplasty, to make the stem shape of an artificial hip joint fit to the morphology of proximal femoral canal is generally effective to the fixation in an initial stage. Furthermore, it contributes to reduce a stress shielding at the proximal femur. Therefore, this paper proposed the design method of the custom-made stem corresponding to each patient in order to improve the fill ratio of the stem to the proximal femoral canal. This modeling is mainly achieved by means of a Boolean operation (logical AND operation) of the cross sectional contours of the proximal femoral canal along the circular insert axis, which is decided by the bow of the femoral canal morphology with 3D X-ray CT images and a CAD system. As a result, the fill ratio of the stem to the proximal canal by the proposed method was higher than that by a method with the simple straight type as an insert axis. Also, the fill ratio and the spatial distributions of it in the femoral canals with this proposed method were so similar between the different femoral morphology. The result is important for a design of the custom-made model corresponding to variable femoral morphologies.