Radius Research Articles

Effect of Weld-Pass Morphology and Molten-Pool Flow on Lack of Fusion Formed in the Fully Automatic Welded Joint at 6 o’Clock Direction

Compared with traditional shielded metal arc welding and semi-automatic welding, fully automatic welding has the advantages of fast welding speed, high welding quality as well as a high qualification rate on the premise of ensuring the comprehensive performance of the girth weld joint. Meanwhile, the proportion of welding defects also changed from porosity and slag inclusion to lack of fusion. Therefore, from the view of the macroscopic and dynamic evolution behavior, the paper aims to reveal the influence of the coupling of weld-pass morphology and molten-pool flow on the formation of lack of fusion using macroscopic metallographic observation and high-speed photography. The results indicate that the weld morphology is prone to convex reinforcement and larger penetration depth in the 6 o’clock direction of the pipeline girth weld under the reference parameters. The excessive reinforcement of the pass to be welded is one of the sufficient conditions for the formation of a lack of side fusion in the 6 o’clock direction. Excessive reinforcement could lead to welding arc heat mainly used to melt the raised weld metal to be welded, which results in insufficient heat flow to both sides of the molten pool metal. Furthermore, due to the larger curvature radius at the groove and the increase of the surface tension of the molten pool with lower relative temperature, the flow resistance of the molten pool increases and the fluidity decreases.

Effect of Curvature Shape on the Impact Strength of Additively Manufactured Acrylonitrile Butadiene Styrene Parts Produced via Fused Deposition Modeling

Additive manufacturing (AM) has greatly revolutionized manufacturing due to its ability to manufacture complex shapes without the need for additional tooling. Most AM applications are based on geometries comprising curved shapes subjected to impact loads. The main focus of this study was on investigating the influence of infill density and the radius of curvature on the impact strength of parts manufactured via an FDM process. Standard geometrical specimens with varying part infill densities and radii of curvature were produced and subjected to Charpy impact tests to evaluate their impact strength. The results suggest that the impact strength increases with the increased density caused by higher amounts of material as well as by the changing cross-sectional areas of the beads. Also, the radius of curvature of the parts shows a clear inverse relationship with the impact energy absorbed by the specimens (i.e., increasing the radius decreased the impact energy of the parts) produced via an FDM process, which can be explained using the beam theory of structural mechanics. The maximum value of impact strength obtained was 287 KJ/m2, and this was achieved at the highest infill density (i.e., solid) and for the smallest radius of curvature.

Subaperture moving strategy and related systematic errors in stitching interferometry of X-ray mirrors

For high-precision metrology of X-ray mirrors, the subaperture moving strategy significantly impacts the accuracy of stitching interferometry. In this work, we investigated the systematic errors associated with various subaperture moving strategies of rotational stitching (RS), rotational displacement stitching (RDS), and displacement stitching (DS) in measuring X-ray mirrors. The effects of stitching strategies on a flat mirror and a spherical mirror with a radius of curvature (RoC) of 180 m and 60 m were compared. For the mirror with RoC of 60 m, the DS strategy showed the smallest height error of 3.3 nm (RMS) between algorithm-based stitching and the Nanometer Optical component Measuring machine (NOM), while RS showed a large error of 37.4 nm (RMS). The different regions of the interferometer aperture have different amplitudes of retrace errors, defocusing errors, and lateral distortion, which can lead to accumulations of systematic errors using the RS strategy. By reducing the pixel size from 0.268 mm/pixel to 0.089 mm/pixel, the measurement accuracy using the same RDS strategy improved from 7.4 nm (RMS) to 4.4 nm (RMS). Based on the optimal stitching strategy, the measurement accuracy of residual figure error of the X-ray mirror with a radius of curvature of 30 m reaches 0.2 nm (RMS).

Analytical determination of internal stresses in galvanic coatings during restoration of parts

The flexible cathode method is considered, recommended for the analytical determination of internal stresses in galvanic coatings when restoring worn machine parts. To determine the absolute values of internal stresses in coatings, formulas are proposed that take into account the thickness of the cathode, coating, and radius of curvature of the cathode-coating system. The proposed method is simple and free from many of the disadvantages inherent in many common mechanical methods for measuring and calculating internal stresses in electroplated coatings.

Cyclic and torsional fatigue resistance of two replicalike and original brand reciprocating system

The aim of this study was to evaluate the cyclic and torsional fatigue resistance of two replicalike in comparison of the original brand reciprocating system. Material and methods: A total of 60 reciprocating instruments were used to perform the cyclic and torsional fatigue test of following systems: Reciproc Blue 25.08 (RB 25.08), Only One File Blue (OFB 25.08) and RC Blue 25.08 (RCB 25.08) (n=20). The cyclic fatigue test was performed using an artificial stainless steel canal with 60º angle of curvature and a 5-mm radius of curvature. The instruments were activated until failure occurred. The time to failure (TF) and number of Cycles to failure (NCF) were evaluated. The torsional test was performed following the ISO 3630-1. Three millimeters of the instrument tip was fastened to a small load cell and the maximum torsional strength and angular deflection were recorded using the torsion testing machine software. The fractured surface of each instrument was assessed by scanning electron microscopy (SEM). The data were analyzed using one-way analysis of variance ANOVA and Tukey’s test for Multiple comparisons at a significance level of 5%. Results: The cyclic fatigue tests demonstrated that OFB 25.08 had the highest TF and NCF than among the groups (P<0.05). RCB 25.08 exhibited lowest TF and NCF (P>0.05). Regarding the torsional test, the RCB 25.08 and OFB 25.08 had the highest torque than the other groups (P<0.05). Additionally, RB 25.08 and OFB 25.08 exhibited highest angular deflection values than the other groups (P><0.05). Conclusion: The OFB 25.08 demonstrated highest TF and NCF than the instruments tested. The RCB 25.08 exhibited lowest cyclic fatigue resistance and angular deflection.> P<0.05). RCB 25.08 exhibited lowest TF and NCF (P>0.05). Regarding the torsional test, the RCB 25.08 and OFB 25.08 had the highest torque than the other groups (P<0.05). Additionally, RB 25.08 and OFB 25.08 exhibited highest angular deflection values than the other groups (P><0.05). Conclusion: The OFB 25.08 demonstrated highest TF and NCF than the instruments tested. The RCB 25.08 exhibited lowest cyclic fatigue resistance and angular deflection.> P<0.05). Conclusion: The OFB 25.08 demonstrated highest TF and NCF than the instruments tested. The RCB 25.08 exhibited lowest cyclic fatigue resistance and angular deflection.

Closed-form solution of the deflection of a prestressed multilayer cantilever

Abstract In this work, a closed-form solution for the deflection of a multilayer cantilever with initial residual stress in each layer is presented. In particular, this model aims to take into account the relaxation of stresses due to the curvature of the cantilever and to calculate the curvature radius and the bending moment due to stresses. Stress-induced deflections and force & stress-induced deflections of cantilever with different shapes (rectangular, triangular, truncated triangular, V-shaped and truncated V-shaped cantilevers) are obtained from the Euler-Bernoulli beam theory. Taking a SiN/SiO2/Si multilayer as an example, the calculated stress-induced profiles do not depend on the shape of the beam and are in good agreement with finite element results. A comparison with results obtained from a model under generalized plane strain condition is discussed. Stress \& Force-induced deflections are also successfully compared to finite element results. Finally, a new formula is proposed to accurately determine the stress in a thin film material from the study of the curvature of a multilayer cantilever. As illustrated by the example of a virtual SiO2/Si bi-layer rectangular cantilever, the initial stress value which is an input parameter of the finite element analysis is calculated back from the simulated curvature with an accuracy of 0.2%.

Research on track vibration characteristics and rail corrugation based on fastener failure

Based on the measured rail corrugation data on the curve, a rigid-flexible coupling vehicle-track system dynamic model is established. The stiffness and damping of the fasteners were changed to simulate the failure behavior of the track structure, and the influence of fastener failure on the vibration characteristics of the system was studied to determine the causes of rail corrugation. The research results show that: (1) The number of peaks on wheel-rail vibration significantly increases after fastener failure, which increases the probability of wheel-rail resonance. The fastener failure causes more frequent wheel-rail resonance, leading to severe system vibration and increased wheel-rail wear. (2) The simulated wavelength of 57 mm on the slight radius curve with the highest proportion of corrugation is similar to the measured wavelength of 55 mm. The fastener failure is related to the generation of rail corrugation, which verifies the existence of rail corrugation on site. (3) The smaller the curve radius, the greater the lateral and longitudinal creep forces and wear number, indicating that the degree of rail corrugation on slight radius curve is more severe. When the slight radius curve and fastener failure are satisfied together, the lateral and longitudinal creep forces and wear number reach their maximum values, which further accelerates the generation of rail corrugation.

Effects of surface curvature on rain erosion of wind turbine blades under high-velocity impact

Rain erosion induced by raindrops impacting wind turbine blades at high velocity can change the aerodynamic characteristics of the blades and increase maintenance costs. Previous numerical studies on rain erosion have not considered the curvature of the blade leading-edge surfaces and assumed them to be flat surfaces. This study established a fluid-solid coupled numerical model combining the finite element method and smooth particle hydrodynamics. It models a water droplet with a diameter of 2.74 mm impacting the curved leading-edge surface of wind turbine blades with radii of curvature of 1.35 mm, 6.75 mm, 67.5 mm, and infinite at 110 m/s, and the effects of the radius of curvature on the impact response were analyzed. The results show that as the radius of curvature of the leading-edge surface increases, the surface obstructs the water droplet more significantly, and the lateral jetting of the water droplet is enhanced. A larger radius of curvature causes more droplet impact energy to be transferred to the curved surface, increasing the contact force between the water droplet and the surface. The increased transferred impact energy results in higher stress and plastic strain values. The decrease in the radius of curvature of a curved surface increases the error in the stress and strain results obtained by assuming it to be a flat surface.

Effect of depth ratio on frozen wave instability in immiscible liquids

In the present experimental work, a two-liquid system with comparable densities (density ratio = 0.543) undergoing lateral sinusoidal oscillation [along the length (L) of the container] has been considered. Under high forcing frequency condition (ω≫ν/L2), frozen waves appear at the interface of two-liquid system. Different depth ratios (hr) (or filling levels of liquid-1 and liquid-2) have been used to investigate the variations in the instability thresholds, wave amplitudes, wavelengths, and wave profiles of the frozen waves. Instability threshold of frozen waves shows unidirectional nature with varying depth ratios. A coefficient of relative velocity (c1) has been used to non-dimesionalize the variation of threshold amplitude (Aoc) and wave amplitude (Ar) with respect to depth ratios. Variation of normalized wave amplitude with modified Froude number shows existence of two regimes viz. gravity and surface tension dominated beyond which waves become three dimensional. A significant variation in wave profiles has been observed at high amplitude of forcing and reported in terms of radius of curvature. The three-dimensional frozen waves with temporally and spatially periodic doubling have been discussed.

From Kinematics to the Formulas for the Radius of Curvature

From Kinematics to the Formulas for the Radius of Curvature

Phase transitions, shadows, and microstructure of Reissner-Nordström-Anti-de-Sitter black holes from a geometrothermodynamic perspective

We study the thermodynamic properties of the Reissner-Nordström black hole with cosmological constant, expressed in terms of the curvature radius, using the approach of shadow thermodynamics and the formalism of geometrothermodynamics. We derive explicit expressions for the shadow radius in terms of the horizon, photon sphere, and observer radii. The phase transition structure turns out to strongly depend on the value of the curvature radius, including configurations with zero, one, or two phase transitions. We also analyze the black hole's microscopic structure and find differences between the approaches of thermodynamic geometry and geometrothermodynamics, which are due to the presence of the curvature radius. We impose the important condition that the black hole is a quasi-homogeneous thermodynamic system to guarantee the consistency of the geometrothermodynamic approach.

Micro-scale modeling and analysis on material removal mechanisms for flexible ball-end tool polishing incorporating the curvature effect

Optical freeform surfaces (OFS) have been extensively employed as core components in advanced optical systems for their excellent performances. However, the surface complexity and the high surface accuracy do impose challenges to the processing of OFS, especially the surface form maintaining or control during polishing. As one of the promising ultra-precision machining technologies to fabricate OFS, the flexible ball-end tool (FBET) polishing becomes available due to its attractive technical advantages. Nevertheless, there are still lack of more comprehensive insights on material removal mechanisms for FBET polishing incorporating the curvature effect, particularly from a microscopic scale, which is of great significance to determine the surface quality and form control in ultra-precision polishing process. In this paper, different from those published macro-scale Preston law-based models, a micro-scale material removal model is developed based on the mutual interaction of the slurry, polishing pad and curved workpiece among the FBET polishing interfaces with micro-contact theory and tribology theory, wherein various parameters embodied in FBET polishing are formulated quantitatively, such as slurry characteristics, pad properties, tool features, processing conditions, as well as workpiece curvature effect. The FBET is designed and adopted to conduct the spot polishing experiments within the concave curvature radius range from 75 mm to 225 mm, wherein the curvature radius range from 225 mm to 800 mm is theoretically chosen as an extension of this research. The predicted results agree well with the experimentally measured section profiles of polishing spots, thereby demonstrating the correctness and effectiveness of the proposed model. Furthermore, the effective relative velocity U together with the separation gap d between reference plane and workpiece surface are known as the two key parameters to account for the material removal mechanisms, and the latter is figured out to be the sensitive one to the curvature effect rather than the former. Through the analysis of key parameters, the established model is capable of helping to strengthen the understanding of material removal mechanisms for FBET polishing with the consideration of curvature effect, addressing those cannot be interpreted by the classical Preston equation previously, which is meaningful for precision control of material removal during polishing of OFS.

Impact of flexible walls of curved channel on biological flow of Reiner-Rivlin fluid

In this study, the Reiner-Rivlin fluid model is opted for examination as the complex dynamical fluid and is flowing on account of the waves travelling on the walls of flexible curved channel. The governing equations are solved analytically up to the first order to analyse the velocity profiles. As the governing equation is highly nonlinear, so the problem is solved by regular perturbation technique about small wave number. After the implication of regular perturbation, the second order Cauchy Euler ordinary differential equations are obtained for both the systems. A detailed analysis is conducted on the effects of diverse factors, such as the rheological properties of fluid, the curvature radius of the channel, the wave amplitude and the wall properties. The velocity of the fluid enhanced by increasing wall properties parameters, wave number, Reynolds number and the amplitude ratio parameter. It is also observed that the Reiner-Rivlin fluid flows slowly as compare to the Newtonian fluid, this type of findings can be helpful for the understanding of many physiological processes, like blood flow and food swallowing. This study enlightens the interaction between the curved nature of the channel and Reiner-Rivlin fluid flow in peristalsis that can be a great contribution for the designing of biomedical devices. Such types of problems have great significance in many physiological processes and engineering applications like microfluidic devices and drug delivery systems.

[formula omitted]RTube: A new geometry concept for MPGD technologies

This article presents a novel detector concept that optimizes the Micro Pattern Gas Detector (MPGD) geometry for low-cost, large-area applications while maintaining comparable performance. The project’s aim is to demonstrate a complete proof-of-concept for a tubular μRWELL detector (μRtube). This prototype integrates the best features of several technologies into an innovative geometry, significantly reducing the number of electronic channels per unit area. The μRtube advances MPGD technology to an unprecedented curvature radius (less than 1 cm) for imaging and particle identification applications. A short report on the detector concept, full simulation results, and test beam validation will be presented.

Hydrogen behavior and microstructural evolution in flexible IGZO thin films under stress

In this study, we investigated the effect of mechanical stress on hydrogen diffusion in flexible amorphous InGaZnO (a-IGZO) thin films and the resulting microstructural changes. The cyclic bending test under different curvature radii (R) revealed significant morphological evolution and bond state changes in IGZO thin films. As the curvature radius decreases from 20 mm to 5 mm, the surface of the sample gradually becomes rough and cracks appear. Simultaneously, changes in nanoscale topological structure and chemical composition exhibit stronger hydrogen diffusion and structural relaxation: The oxygen-hydrogen (O-H) bond content increased from 19 % to 55 %, while the metal-oxygen (M − O) bond content decreased from 50 % to 28 %. The M − H content increased, and In-H related structures underwent transformation. The radius of gyration (Rg) increasing from 1.652 nm to 1.812 nm. These results provide quantitative insights into the stability and performance of IGZO-based flexible electronic devices under mechanical deformation.

Design of magnetic field with high homogeneity for single-turn coil

Abstract Single-turn coil (STC) is a kind of destructive pulsed magnet aiming at ultra high magnetic field. In this study, the simple geometry optimization approach to improve the magnetic field homogeneity of STC is proposed. By making the conductor inner surface concave, the amplitude of the magnetic field is decreased by only 15%, while the space volume of the homogeneous magnetic field is increased by 200-600%. Through three STC examples with different conductor inner diameters and different discharge currents, the effectiveness of this method is validated. In particular, it is theoretically proven that the volume of the homogeneous magnetic field increases as the inner surface concave curvature radius decreases. This geometry optimization method provides the theoretical support for homogeneous field design of STC.

Mechanism of novel phenomenon of rail corrugation on small radius curves with rail joint in mountainous city metros

Purpose The purpose of this study is to systematically investigate the novel phenomenon of rail corrugation on small radius curves with rail joints in mountainous city metros, characterized by the coexistence of short and long wavelengths (30–40 mm and 150–200 mm) on the low rail. Design/methodology/approach The finite element model of the wheel-rail system in the section with rail joint is constructed based on field surveys. The friction-coupled vibration characteristics of the wheel-rail system are studied from the perspective of friction self-excited vibration of the wheel-rail system and feedback vibration of the rail irregularity. Findings The rail corrugation with short wavelength is primarily induced by the friction self-excited vibration of wheel-rail system. In contrast, the rail corrugation with long wavelength is predominantly caused by the feedback vibration of rail joint irregularity. Additionally, the feedback vibration of corrugated irregularity accelerates the progression of corrugation depth without triggering the emergence of rail corrugation with new wavelength. Originality/value The research advances the understanding of the vibration inducement behind rail corrugation in mountainous city metros.

Compensation of temperature effects on imaging quality of thermal imaging objectives using deep learning techniques

Thermal imaging objectives are made from infrared materials with large thermal expansion coefficients, such as Ge, Si, and ZnSe. When the temperature changes, it leads to variations in the refractive index, curvature radius, and thickness of the lens, causing defocus shifts that degrade the image quality of the thermal imaging system. In this paper, we propose a novel method to compensate for the effects of temperature variations on the quality of thermal imaging objectives by using deep learning techniques. The temperature variations are measured using a thermal sensor. Subsequently, a U-Net network is employed to mitigate the impact of temperature on the imaging quality of the thermal imaging objectives without requiring any optical displacement or replacement of the lens. Simulation results show that the proposed method performs the effectively compensation for the influence of temperature changes on thermal imaging objective over a wide temperature range from -5 °C to 50 °C.

Comparing IOP-Induced Scleral Deformations in the Myopic and Myopic Glaucoma Spectrums.

To compare changes in macular curvature following acute IOP elevation across a range of myopic conditions. We studied 328 eyes from 184 subjects, comprising 32 emmetropic controls (between +2.75 and -2.75 diopters), 50 eyes with high myopia (<-5 diopters; HM), 108 highly myopic with glaucoma (HMG) and 105 pathologic myopia (PM) eyes, and 33 PM with staphyloma (PM+S) eyes. For each eye, we imaged the macula using optical coherence tomography (OCT) under the baseline condition and under acute IOP elevation (to ∼40 mm Hg) achieved through ophthalmodynamometry. We manually aligned the scans (baseline and IOP elevation) using three vascular landmarks in the macula tissue. We then automatically segmented the sclera and the choroid tissues using a deep learning algorithm and extracted the sclera-choroid interface. We calculated the macula curvatures, determined by the radius of curvature of the sclera-choroid interface in the nasal-temporal and superior-inferior direction. Differences in macula curvatures between baseline and elevated IOP scans were calculated at corresponding locations, and the mean curvature difference was reported for each eye. IOP elevation resulted in a significantly higher macula curvature change along the nasal-temporal direction in the PM+S (13.5 ± 8.2 × 10-5µm-1), PM (9.0 ± 7.9 × 10-5µm-1), and HMG (5.2 ± 5.1 × 10-5µm-1) eyes as compared to HM (3.1 ± 2.7 × 10-5µm-1) eyes (all P < 0.05). Interestingly, HM and HMG eyes had the same curvature change in the nasal-temporal direction as emmetropic control eyes (4.2 ± 4.3 × 10-5µm-1). Our findings indicate that the macula in HMG, PM, and PM+S eyes showed greater curvature changes under IOP elevation compared to HM and emmetropic eyes. These preliminary results suggest that HM eyes with conditions such as glaucoma or staphyloma are more sensitive to acute IOP elevation.

One-way fluid–structure interaction modeling and multi-objective optimization of horizontal-axis wind turbine blades equipped with winglets

ABSTRACT This study aims to investigate the effects of backward-directed winglets applied on the NREL Phase-II reference wind turbine geometry on structural and aerodynamic characteristics and to reveal optimized configurations. The aerodynamic pressure distributions on the blades were imposed as boundary conditions for the FEM analyses since the structural characteristics of the turbine were analyzed by adopting a one-way Fluid Structure Interaction (FSI) approach. The Taguchi analysis with an L27 orthogonal array revealed the descending order of importance of design variables on the coefficient of power ( C P ): height, cant angle, toe angle, curvature radius, and finally twist angle. For von-Mises stress, the descending order of importance is height, cant angle, toe angle, twist angle, and curvature radius. A multi-objective genetic algorithm using artificial neural network (ANN) models was used to optimize the objectives C P and von-Mises stress. Pareto-optimal solutions with off-design points were obtained, and their performances were compared to the reference NREL Phase-II geometry. As a result, it was observed that there was an increase in C P from 8.07% to 15.56% and the von-Mises stress showed a considerable increase up to 231.13%. The study demonstrates the aerodynamic benefits and structural drawbacks of various winglet designs in horizontal axis wind turbines.