Fillet Radius Research Articles

Revamping Shaft Design for Combating Fatigue Failure

This paper gives insights on the failure analysis of the non-drive shaft of a conveyor in a coke plant of an integrated steel plant. The failure of the shaft was investigated in order to determine the root cause and contributing factors. Investigation methods included visual examination, optical and scanning electron microscope analyses, chemical analysis of the material, mechanical tests and life calculations based on design. The overall appearance of the fracture surface of the 45C8 grade shaft indicated rotating bending fatigue failure from a step location. Microstructural analysis revealed a crack from the sharp step and no metallurgical abnormalities. Apart from the metallurgical analysis, the design of shaft was also verified by calculating step profile, fillet radius and calculated stress in actual condition. It revealed that a shaft with a minimum diameter of 70 mm, made of 45C8 steel, can withstand the actual stress acting on it. In this design, the shaft diameter was found to be 65 mm which is insufficient to bear the actual stress. Shaft failures can be reduced by preventive mechanical maintenance and using safe design. To enhance the shaft life without an increase in shaft diameter, we recommend that the material be changed to 42CrMo4 grade steel, which, when appropriately heat treated, has higher stress limit, along with a modification in the step profile with a proper fillet radius.

Effect of rib shape and fillet radius on thermal-hydrodynamic performance of microchannel heat sinks: A CFD study

New designs for ribbed microchannels (semi-circular and semi-elliptic) and filleted ribs are numerically studied in the present paper. Four presented configurations include: microchannel with semi-circular ribs (MC-SCR), microchannel with semi-elliptic ribs (MC-SER), microchannel with semi-circular ribs and filleted corner (MC-SCR-FR) and microchannel with semi-elliptic ribs and filleted corner (MC-SER-FR). Thermal and hydraulic performance of these configurations are evaluated by comparing Nusselt number, fanning friction factor, and performance evaluation criteria (PEC). Based on the results, the ribs corner curvature leads to a significant increase in heat transfer coefficient, accompanied by a minor increase in pressure drop. Compared to MC-SCR and MC-SER heat sinks, the two designs of MC-SCR-FR and MC-SER-FR enhance Nusselt number about 18–21% and 0.5–10%, increase the fanning friction factor about 0.1–7% and 1–9%, and improve the performance evaluation criteria (PEC) about 19–22% and 19–21%, respectively. In addition, because of the re-development of thermal boundary layer and higher mixing level, MC-SCR-FR configuration revealed the best performance among all other configurations. Moreover, the effect of relative fillet radius on thermal-hydrodynamic performance of MC-SER-FR configuration is investigated, and R* > 1.2 is selected as the appropriate value for design of microchannel heat sinks.

CFD Assisted Evaluation of In Vitro Experiments on Bearingless Blood Pumps.

This paper presents a comparative study of computational fluid dynamics (CFD) simulations and in vitro hemolysis examinations of a bearingless centrifugal blood pump. The outcomes of the in vitro study are analyzed with the help of CFD hemolysis models. Several pump prototypes were manufactured and tested. Each model was implemented in a CFD framework and simulated with different Eulerian hemolysis models. The outcomes are compared to experimental data. The model achieving the highest correlation is used to explain the in vitro outcomes in detail. It is shown that a double-stage model achieves the best correlation. The sensitivity of the simulation is considerably lower than that of in vitro tests. The CFD model reveals that most of the cell destruction is caused in the radial gap of the pump. Further critical regions are the bottom volume and the shroud clearance gap. Only 0.5% of the priming volume is subject to overcritical shear stress. Cell compatibility can be improved by increasing the radial gap, lowering the shroud and hub clearance gaps, and increasing the fillet radius of the inlet nozzle. CFD models can be used to examine the cell damage effects and help to further improve the pump design. This paper compares different Eulerian CFD hemolysis models, parameter sets, and equivalent shear stresses to several in vitro hemolysis tests. The sensitivity of the models is compared to that of in vitro studies. It is shown that CFD simulations have their limitations but can help with interpreting the outcomes of in vitro studies.

Experimental investigation and numerical modeling of strength properties of iron ore sinter based on pilot-scale pot tests and X-ray computed tomography

One of the most concerned quality in iron ore thermal agglomeration process is the mechanical strength of sinter and thus the size degradation of sinter product which occurs during transportation could be minimized. Due to the complexities of porous structure and brittle nature of sinter, it is difficult to determine their influences on the mechanical properties. Under this prospect, pilot-scale sinter pot tests have been carried out under the conditions of a wide range of coke rates. X-ray computed tomography was applied to reconstruct the sinter porous structures with the resolution of 40 µm and following simulations for obtaining the distribution of stress and displacement in the compressed sinter samples at the micro level were performed. The strength of sinter product was also experimentally evaluated by the shatter and tumbler tests at the macro level. The obtained experimental and numerical results showed that, sinters produced in the low coke rate cases have relatively large porosity and irregular structures, exhibiting more locations with high stress values including bridges with the small cross-sections and pore-shaped notches with the small fillet radius. Those sinters are more easily to be breaked at the macro scale, resulting in their smaller mean diameter and tumbler strength index compared to the sinters under the condition of high coke rates. The increase of coke rate greatly increases the maximum bed temperature in flame front, promoting the melt formation, material coalescence and densification therefore sinters with better mechanical property could be achieved.

Wheel shape optimization approaches to reduce railway rolling noise

A wheel shape optimization of a railway wheel cross section by means of Genetic Algorithms (GAs) is presented with the aim of minimizing rolling noise radiation. Two different approaches have been implemented with this purpose, one centred on direct Sound poWer Level (SWL) minimization, calculated using TWINS methodology, and another one emphasizing computational efficiency, focused on natural frequencies maximization. Numerical simulations are carried out with a Finite Element Method (FEM) model using general axisymmetric elements. The design space is defined by a geometric parametrization of the wheel cross section with four parameters: wheel radius, a web thickness factor, fillet radius and web offset. For all wheel candidates, a high-cycle fatigue analysis has been performed according to actual standards, in order to assure structural feasibility. Rolling noise reductions have been achieved, with a decrease of up to 5 dB(A) when considering the wheel component. Response surfaces have been also computed to study the dependency of the objective functions on the geometric parameters and to test the adequacy of the optimization algorithm applied.

Waveguide transmission line parameter analysis based on the FDTD method

AbstractIn order to quickly analyze discontinuity or periodic structure transmission characteristics, the combination of finite‐difference time‐domain method and singular value decomposition is applied. A double‐ridge waveguide (WRD) and its improvement are studied. According to the simulation results about propagation constant and eigen‐functions, the transmission performance of WRD can be improved by adding fillets and enlarging the radius of fillets or filling dielectric material. Guided wave and mode characteristics of substrate integrated waveguide (SIW) are also researched in detail. Simulation carried out for different periodic SIW structures shows that due to the periodic gap, electromagnetic energy leakage is present in the metallized via waveguide wall of the SIW. It is significant for the future improvement and application of SIW structure.

Moment capacity of cold-formed channel beams with edge-stiffened web holes, un-stiffened web holes and plain webs

Cold-formed steel (CFS) channel beams are an increasingly popular choice as load-carrying members in building structures. Such channel beams often include web holes for installation of services. Traditional web holes are normally punched and are un-stiffened. This can restrict the size and spacing of web holes. Recently, a new generation of CFS channel beams with edge-stiffened web holes has been developed and used widely in New Zealand. However, no experimental investigation has been reported in the literature for such channel beams under bending. In this paper, a total of 215 results comprising 16 four-point bending tests and 199 finite element analysis (FEA) are reported on the moment capacity of CFS channel beams with both edge-stiffened and un-stiffened web holes. For comparison, channel beams without web holes were also tested. For all specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element (FE) model was also developed, and the results showed good agreement with the test results. A parametric study was conducted using the validated FE model to investigate the effects of beam length, hole diameter, stiffener length and fillet radius on the moment capacity of CFS channel beams. It is shown that for the case of a channel beam with five edge-stiffened web holes, the moment capacity increased by as much as 14.5%, compared to that of a plain channel beam. For comparison, the same section with un-stiffened web holes had a 13.6% reduction in moment capacity, compared to that of a plain channel beam. Furthermore, the accuracy of current design guidelines in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZ) standards were verified by comparing the tests and FEA results against the design strengths for moment capacity of CFS channel beams without web holes. On the other hand, for CFS channel beams with web holes, the moment capacity obtained from tests and FEA were compared against the moment capacity calculated from the design equations of Moen and Schafer. Upon comparison, it was found that the AISI and AS/NZS can closely predict the moment capacity of CFS channel beams without web holes. The Moen and Schafer design equations were found to be over-conservative by around 11% and 28% for moment capacity of CFS channel beams with un-stiffened and edge-stiffened web holes, respectively.

The Effect of Bolt Locking Sequences and Anchor Bolt Design on Machine Tool

Machine tool is an important role in the industry because the mechanical components or products are manufactured by machine tools. The machine tools are assembled by components. The surface between two components is the combined or contact surface. Different bolt locking sequences will affect the combined surface in the machine tool. In this study, the SolidWorks software is used to create the CAD model. The finite element simulation is used the ANSYS software to simulate the influence of bolt locking methods on the combined surface of column structure and guideway and the fillet radius design on the deformation of anchor bolts. From the simulation results, the minimum deformation of the column is observed in the locking sequence from middle to both sides. The stress distribution of the combined surface is slightly difference of three locking methods. The simulation results of the guideway show that the minimum displacement of combined surface is obtained by using locking sequence from outside to the middle. The maximum displacement is obtained locking sequence from right to the left order. From the simulation results of anchor bolt, increasing the fillet radius of anchor bolt decreases the deformation of anchor bolts. The deformation of anchor bolts drastically decreases with increasing the fillet radius from R8 to R60. The simulation models and results provide the reference for the bolt locking sequence and anchor bolt fillet radius design.

Analysis and Optimization of Passive Wall Solar Chimney through Taguchi’s Technique

In this paper, the influence of the geometrical parameters of a solar chimney on mass flow rate has been studied through numerical simulation. Also, Taguchi based design of experiment method has been applied to maximize the mass flow rate on the solar chimney. Chimney entry shape, bottom opening height, chimney exit width, cornered fillet radius, absorber wall material, absorber wall inclination, the height of the absorber wall are the geometrical parameters considered in this optimization. These parameters are varied through three levels of values. L18 orthogonal array is employed with a quality objective function of bigger is the better. The eighteen cases are analyzed for the solar radiation of 1000 and 300 W/m2 through the numerical simulation technique. The results have been analyzed for the optimum conditions using the signal-to-noise ratio (S/N ratio). Finally, ANOVA calculation is performed and reported that the exit chimney width, absorber wall height influences more on mass flow rate and the remaining parameters influence is less than 10%. The optimum value of the identified parameters enhance the mass flow rate as 0.54634 kg/s and reduce the indoor temperature by 2.1°C.

RelationBetween Mechanical Properties and 3DPrinter Configurations Parameters Using PLA at Open-Source PrusaI3

This paper presents an experimental study on specimens made with the additive manufacturing (AM) Fused Deposition Material (FDM) technique with PLA material. Several configurations of geometry and printing temperature were made in order to evaluate these parameters over a tensile test. The geometry of the specimen was fabricated according to the ASTM D638 and the curvature of fillet radius were varied (76-std, 144, 244mm and straight) to obtain optimal fillet radius for tensile test. The nozzle temperature was varied (200, 210, 220 and 230°C) to show its influence on PLA stress-strain behavior. Results have shown that the fillet radius of the specimen and the printer parameters affect material quantity deposited during 3D printing process, leaving to progressive damage areas. Better performance was obtained at 210 °C printing temperature with a fillet radius of 144 mm. A modification geometry specimen were proposed in order to change the increase Z nozzle level point that generates a stress concentrator at the specimen avoiding failure zone at calibrating length of the specimen.

Axial strength of back-to-back cold-formed steel channels with edge-stiffened holes, un-stiffened holes and plain webs

Cold-formed steel (CFS) back-to-back channels are becoming a popular choice for use in load-carrying members in building structures. These built-up channels often include web holes for installation of services. Traditional web holes are un-stiffened, which can restrict the size and spacing of holes. Recently, a new generation of CFS channels with edge-stiffened holes has been developed and used widely in New Zealand. No research has been reported in the literature to investigate the axial strength of back-to-back channels with edge-stiffened holes. Experiments are required on back-to-back channels with edge-stiffened holes so to understand the effects of composite actions between the back-to-back channels on the axial strength of such channels. This paper presents a total of 162 new results comprising 27 axial compression tests and 135 finite element analysis (FEA) results on the axial strength of back-to-back channels with edge-stiffened holes, un-stiffened holes and plain webs. Prior to compression tests, initial geometric imperfections were measured using a laser scanner. Tensile coupon tests were also conducted to determine the material properties of both the flat and corner portions of the channels. The test results show that for the case of back-to-back channels with edge-stiffened holes, the axial strength increased by 6.6% on average, compared to a back-to-back plain channel. For comparison, the same section with un-stiffened holes had a 12.4% reduction on average in axial strength, compared to a back-to-back plain channel. A nonlinear elasto-plastic finite element (FE) model was then developed, and the results showed good agreement with the test results. The validated FE model was used to conduct a parametric study involving 135 FE models to investigate the effects of column slenderness, diameter of hole, screw spacing, stiffener lengths and stiffener fillet radius on the axial strength of such channels. Finally, the tests and parametric study results were compared against the design strengths calculated in accordance with the American Iron and Steel Institute (AISI) (2016) and Australian and New Zealand Standards (AS/NZS) (2018) for back-to-back plain channels and against the design equations of Moen and Schafer (2011) for back-to-back channels with un-stiffened holes. It was found that the AISI (2016) and AS/NZS (2018) are only 3% conservative to the test results. The Moen and Schafer equations (2008, 2009, 2011) are conservative by 21% on average for back-to-back channels with un-stiffened holes.

Fabrication of micro channels for titanium PEMFC bipolar plates by multistage forming process

Bipolar plates made of ultra-thin titanium sheet metals feature high corrosion resistance, electrical conductivity and strength-weight ratio. They are considered as a satisfying candidate for the proton exchange membrane fuel cell (PEMFC) used in vehicles. Bipolar plates have fine and complex sub-millimeter channel features which are employed to guide the flow of hydrogen, oxygen and cooling medium, to support the reaction space, to provide sealing structure, etc. Stamping process is an efficient method to fabricate those micro features with high precision and efficiency. However, the aspect ratio of those micro features is limited by the low forming limit of titanium sheet metals. Improving the aspect ratio of metallic bipolar plates could facilitate the uniform heat and mass transfer and further improve the efficiency and performance of PEMFC. Hence a challenging issue for the stamping process of bipolar plates is how to further improve the limit aspect ratio after forming. The multistage forming process is an efficient method to increase the ultimate forming depth and the accuracy by reducing the deformation localization tendency. This work aims to investigate the applicability of that process in fabricating high-aspect-ratio micro-channels on titanium sheet metals. Single stage forming experiments of the micro channels featured with fillet radius of 0.15 mm are first conducted. It is found that the ultimate forming depth of the channels parallel to the rolling direction is 12.67% higher than in the transverse direction. Furthermore, a series of punches and dies with three different fillet radii are employed in the multistage forming process. The ultimate depth of formed channels is revealed to increase from 438.1 to 621.0 μm, i.e. the aspect ratio from 0.46 to 0.67, comparing to the single stage forming process. Hence titanium bipolar plates with a higher aspect ratio could be achieved by utilizing the presented method. The contact resistances of the samples fabricated via single and three-stage forming were further tested to find out that the samples with a higher aspect ratio formed in a three-stage manner have an evident lower contact resistance.

Influence analysis of the geometrical parameters on the electro-mechanical stability of HTS Roebel cables

Under high-power applications, high-temperature superconducting (HTS) Roebel cables may subjected to heavy tensile load due to electromagnetic forces or due to external factors during the production process of these cables. The meander structure of Roebel strands is prone to these loads which mechanically weakens the stability of Roebel cables due to localized stress concentration. The applied transport current and exposure to an external or self-magnetic field induce AC loss in Roebel cables. In the present work, the influence of geometrical parameters on the electro-mechanical stability of Roebel cables is carefully investigated using 3D finite element tools. The parameters such as inner fillet radius, outer fillet radius, Roebel angle, strand width at crossing section and the gap between stacks of strand in the straight section are varied and its influence on mechanical stability and electromagnetic characteristics are observed. First a default geometry is modelled and its electro-mechanical simulation is performed against various load conditions. Each parameters of the Roebel cable are then altered on this default geometry. After each set of variation, electro-mechanical simulations are performed and its influence is compared with the default geometry.

About the Influence of the Corrosion Defect Geometry on Repaired Pipes Stress Distribution

Abstract This paper proposes a new approach in dealing with volumetric surface defects (VSD) in pipelines. Using three-dimensional (3D) scanning and reverse engineering techniques, along with finite element analysis, we studied and evaluated comparatively the stress distributions in the defect area for different shapes and positions of the machined VSD, in order to find the best solution for the repairing process using composite materials. Our main conclusion is that instead of machining the VSD such as to generate a rectangular shaped machined defect, with edges parallel/perpendicular to the pipe axis, it is better to mold the VSD. Another possible solution would be to machine the real VSD such as to generate an inclined rectangle that circumscribes the defect. This paper also studies the influence of the machined defect filet radius to the bottom of the VSD.

Highly reliable electromagnetic MOEMS scanning grating mirror based on folded torsion beam with fillet corners

To overcome the problems of poor structural reliability, high driving voltage and small scanning angle, a novel electromagnetic MOEMS scanning grating mirror (SGM) with folded torsion beam is reported in this work. Compared with the conventional straight torsion beam, the folded torsion beam has better elastic torsion property and can effectively improve the structural reliability of the MOEMS SGM. Furthermore, the fillet structure is added to the folded torsion beam to prevent stress concentration. The stress analysis and impact resistance of the proposed MOEMS SGM are simulated by FEM (ANSYS 18.2), and the simulation results are compared with that of the MOEMS SGM without fillet structure. The stress simulation is carried out under different fillet radius of 40–70 [Formula: see text]m, the maximum stress can be reduced to 85[Formula: see text] and the stress is redistributed uniformly. Meanwhile, in the impact resistance simulation, the impact displacement can be reduced by 10.1[Formula: see text]. A prototype is fabricated and tested, it has a large mirror area of 6 mm ×7 mm. The MOEMS SGM can reach the maximum scanning half angle of [Formula: see text] at 7.63 V under resonance (@602.1 Hz), which means that the full mechanical scanning angle of the MOEMS SGM can reach [Formula: see text].

Numerical modelling of extruded aluminium alloy T-stubs connected by swage-locking pins: FE validation and parametric study

The structural behaviour and design of extruded aluminium alloy T-stubs connected by swage-locking pins are studied in the present paper. Finite element (FE) models were developed and validated against test results on extruded aluminium alloy T-stubs connected by swage-locking pins carried out in the companion paper [1]. Prior to the numerical modelling of the T-stubs, refined and simplified FE models of swage-locking pins were developed, and evaluated by comparing with experimental results; the refined model explicitly takes into account the geometries and load-slip behaviour of the swage-locking pins and provides accurate predictions of the test results, while the simplified model is developed through application of a four-step calibration methodology, and has been shown to provide similar accuracy with the refined model, but with significantly reduced computational time. Upon validation, an extensive parametric study was performed to investigate the effect of key parameters, including the preload in the swage-locking pins, the pin diameter, the fillet radius at the web-to-flange junction and the pitch distance between pins, on the structural performance of the T-stubs. The numerically derived results were also compared with the resistance predictions according to the design method in EN 1999-1-1 (EC9). The comparisons indicated that the EC9 provides safe-sided, yet somewhat conservative and scattered, resistance predictions for extruded aluminium alloy T-stubs connected by swage-locking pins, owing principally to inaccurate predictions of the distance between two plastic hinges formed in the T-stub flange. A new design method was proposed for more accurate predictions of the plastic hinge distance, resulting in improved accuracy and consistency over EC9 for calculating the resistance of extruded aluminium alloy T-stubs connected by swage-locking pins.

A high-cycle fatigue failure analysis for the turbocharger shaft of BELAZ 75131 mining dump truck

Fatigue fracture is one of the most common causes of failure in many rotating machinery components. In this paper, the fatigue behavior of a typical shaft, which is widely used in the turbocharger of BELAZ 75131 mining dump trucks, is studied both theoretically and experimentally. There is one diameter change along the shaft and investigations show that the dominant cause of failure is fatigue caused by cyclic loadings. The fatigue life of the shaft subjected to cyclic bending loads is analytically estimated according to the modified Goodman, Gerber, ASME-elliptic and Soderberg criteria. Finite element based numerical simulations are also performed by MSC Fatigue software to demonstrate the accuracy of the experimental results. In addition, a fatigue testing machine is developed to obtain the fatigue life of the shaft experimentally and validate the theoretical results. The effect of constant torsional loading and the fillet radius at the diameter change on the fatigue life of the shaft under a cyclic bending load is also studied.

Computational Fatigue Analysis of Auxetic Cellular Structures Made of SLM AlSi10Mg Alloy

In this study, a computational fatigue analysis of topology optimised auxetic cellular structures made of Selective Laser Melting (SLM) AlSi10Mg alloy is presented. Structures were selected from the Pareto front obtained by the multi-objective optimisation. Five structures with different negative Poisson’s ratios were considered for the parametric numerical analysis, where the fillet radius of cellular struts has been chosen as a parameter. The fatigue life of the analysed structures was determined by the strain–life approach using the Universal Slope method, where the needed material parameters were determined according to the experimental results obtained by quasi-static unidirectional tensile tests. The obtained computational results have shown that generally less auxetic structures tend to have a better fatigue life expectancy. Furthermore, the fillet radius has a significant impact on fatigue life. In general, the fatigue life decreases for smaller fillet radiuses (less than 0.3 mm) as a consequence of the high-stress concentrations, and also for larger fillet radiuses (more than 0.6 mm) due to the moving of the plastic zone away from the edge of the cell connections. The obtained computational results serve as a basis for further investigation, which should be focused on the experimental testing of the fabricated auxetic cellular structures made of SLM AlSi10Mg alloy under cyclic loading conditions.

An Analytical Solution for the Maximum Tensile Stress and Stress Concentration Factor Investigations for Standard, Asymmetric fillets, Asymmetric Pressure Angle and Profile Shifted Helical and Spur Gears

This research introduces a developed analytical method to determine the nominal and maximum tensile stress and investigate the stress concentration factor. The required tooth fillets parametric equations and gears dimensions have been reformulated to take into account the asymmetric fillets radiuses, asymmetric pressure angle, and profile shifting non-standard modifications. An analytical technique has been developed for the determination of tooth weakest section location for standard, asymmetric fillet radiuses, asymmetric pressure angle and profile shifted involute helical and spur gears. Moreover, an analytical equation to evaluate gear tooth-loading angle at any radial distance on the involute profile of spur and helical gears, (taking into account the effect of profile shift factor) has been derived. In addition, numerical solution for the evaluation of the maximum fillet tensile stress and the combined tensile stress concentration factor for the verification of the analytical method using computer-aided engineering software (ANSYS Version 18.1). The analytical and FE result have been compared and found to be very close. The most effective method for reducing the stress concentration factor have been found by applying negative profile shifting on asymmetric tooth with lower unloaded pressure angle and high loaded pressure angle and fillet radius, which can lead to an enhancement percentage of (20%) when using a (35o/20o) asymmetric spur gear of a (24) teeth number with a shift factor of (-0.3mo) compared with standard (20o) one.

Study on Gas Bulging Forming and Contradictive Cooling Bonding of AZ31/Al7475 Bimetal Composite Tube

Mg/Al bimetallic tubes can give full play to the excellent properties of magnesium alloys and aluminum alloys, such as light weight, high strength and good corrosion resistance. In this study, gas bulging forming and contradictive cooling bonding process was used to form AZ31/Al7475 hexagonal section composite tubes and showed a good result. In addition, the finite element analysis method was utilized to simulate the process and optimize the forming parameters. The results show that the process could be divided into four stages: free bulging stage, sidewall sticking stage, fillet filling stage and contradictive cooling stage. The maximum thinning rate and fillet radius of AZ31/Al7475 composite tube were 10.60% and 7.00 mm, respectively, at 450 °C, 6 MPa, and 600-720 s. And the interface between the inner and outer layers was closely combined. The bonding force of the rounded corner part of the forming part was 2.04, and 2.30 MPa for the straight wall part. The experimental value of the binding force was about 28% higher than the maximum theoretical value.