Fillet Radius Research Articles

Acoustic mechanism and noise reduction optimization of globe valve in air conditioning system

The globe ball valve will invariably emit inevitably generates noise during operation. The flow field characteristics and sound field characteristics inside the shut-off throttle were obtained by numerical calculations. In order to suppress the noise, this paper proposes an optimized model for this type of valve. Optimization valves were set up for different simulation groups to identify the appropriate fillet radius. The effect of the two strategies on noise reduction is examined in terms of noise distribution, path lines form, and turbulence distribution. The results show that the main throttling area of the valve generates more noise compared to the secondary throttling area. The sound power level values are highest in the center and decrease from there to the wall. The best noise reduction effect was achieved by rounding the radius of 8 mm in the primary throttling area. The maximum noise reduction in the primary throttling area is 0.45 dB, and the maximum noise reduction in the secondary throttling area is 7.5 dB. For sensitive locations in the secondary throttling area, rounded corners improve local noise reduction, with radius of 5 mm providing the best noise reduction. Maximum sound power level values are reduced by 5.8 dB and 6.86 dB in the primary and secondary throttling areas, respectively.

Influence of geometric imperfections on the mechanical behavior for Invar 36 alloy lattice structures fabricated by selective laser melting

The studies on the mechanical behavior of Invar 36 alloy lattice structures prepared by additive manufacturing process are limited. In this paper, the influence of geometric imperfections generated during the additive manufacturing process on the mechanical behavior of Invar 36 alloy lattice structures was investigated. To realize lightweight and high load-bearing capacity, lattice structures with different fillet radii were designed and subsequently fabricated by selective laser melting (SLM) process. Compression tests based on in-situ X-ray computed tomography (X-CT) were conducted to evaluate the manufacturing quality and corresponding mechanical behavior. Differences between design models and fabricated lattices were quantitatively compared. Various geometric imperfections, including strut waviness, varying cross-sections, visible surface defects, visible defects at strut intersections, and roughness on struts, were observed. Additionally, deformation patterns at different loading stages were also obtained, primarily manifesting as the yielding of the nodes and the buckling of the struts. Importantly, struts with varying cross-sections possess the most significant influence on the deformation behavior.

Performance evaluation of 3D-printed ABS and carbon fiber-reinforced ABS polymeric spur gears

Acrylonitrile butadiene styrene (ABS) polymer and carbon fiber reinforced acrylonitrile butadiene styrene (CF/ABS) spur gears were 3D-printed using fusion deposition modeling (FDM) with different fillet radii of 0.25, 0.50, and 0.75 mm. The performance of the fabricated gears was studied with the effect of fillet radius on varying load and speed conditions. The thermal properties of the gears were also investigated. The results indicated that 3D-printed CF/ABS spur gear exhibited better performance than the pure ABS. The 3D-printed CF/ABS gear with fillet radius of 0.25 mm recorded the highest wear and thermal stresses. However, the optimum performance was exhibited by the gear sample with highest fillet radius of 0.75 mm. Repeated gear tooth loading during service caused an increase in gear temperature due to the hysteresis and friction. Using optical microscopy, the tooth structures of both 3D-printed ABS and CF/ABS spur gears were analyzed before and after loading conditions to establish their failure mechanism. Evidently, various applications of the FDM 3D-printed spur gears depend on their different performances under loads and operating speeds. The methods and findings of this work can be regarded as helpful for future related work related to cellulosic reinforcing particles in a polymer matrix.

Experimental studies on the characteristics of chisel picks in coal cutting for bucket wheel excavators

Chisel pick is a basic and important rock cutting tool, and the performance of chisel pick directly affects rock mining. In this paper, a rock cutting device was developed for chisel picks cutting experiments. The influence of the depth of cutting, width of chisel pick, rake angle, back clearance angle and tip fillet radius on the cutting performance such as cutting force, normal force, and specific energy has been comprehensively studied. In addition to the general conclusions, the experimental results show that the back clearance angle has an influence range on the cutting, and the ratio of the normal force to the cutting force decreases with the increase of the rake angle; the tip fillet radius greatly improve the mean cutting force and specific energy. The experimental results will provide data support for the design of chisel picks on rock excavation machinery and a more reasonable chisel pick cutting rock mechanics model.

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Precise tooling is vital for defect-free production of micro injection moulded (μ-IM) or hot-embossed products. The demoulding stage of such moulding and forming processes poses a serious challenge to the integrity of thin miniature features because of friction, adhesion, and thermal stresses. Typically, micro moulds involve geometrically textured patterns or features such as linear ridges, pillars, channels, and holes, the characteristic dimensions of which range from 10 to 300 μm. Realistically complex mould designs, containing precision micro features (enhanced fillet radius and positive draft angle) and high surface quality, are presented in this work. Electropolishing based on forward pulse currents (PC) has been used to shape and polish Ni micro moulds that contain sets of micron-scaled linear ridges and star patterns in order to ease the separation of moulded polymeric parts from the metallic mould during ejection and demoulding. The use of forward pulsed currents improved the mould design by increasing the fillet radii and draft angle while keeping the surface roughness low and maintaining a good surface shine. An optimization study of forward PC using a green solution of nickel sulfamate varied EP times (0–70 min) and duty cycles (40, 50, 60, and 70%) at a process conditions of 2.8 V, 50 °C, and 250 rpm. The best topographical and morphological changes were observed for a typical microfluidic channel (w × h, 100 × 110 μm) with an EP time of 70 min and 50% duty cycle: fillet radius increased by 3.8 μm, draft angle by 3.3°, and the channel width reduced by 11.4% while surface roughness changed by 8.6% and surface shine improved by 48.9%. Experimental validation was performed using hot embossing wherein the electropolished Ni mould replicated the micro channels and star patterns in PMMA chips with notably fewer burrs, material pile up, and no feature distortion. Moreover, there was a reduction in the side wall roughness of micro channels in PDMS casting with electropolished Ni mould by 16%. Hence, this work presents a significant scientific contribution to improving the efficiency of micro mould tools and reduces the defects caused by friction and adhesion in replicated polymeric parts.

Die Design and Forging Analysis of Piston Connecting Rod of Aluminum Alloy

The piston connecting rod is an indispensable in the internal structure of the automobile. As one of the important components in the internal combustion engine system, the piston connecting rod needs to meet the requirements of high fatigue and impact load resistance. Forged piston connecting rod can obtain high strength and fatigue resistance. In this study, the parting line, draft angle, forging tolerance, die fillet radius, shrinkage and scrap are considered in the design of forging die. The process parameters and die dimensions of the forging process of aluminum alloy piston rod are simulated by finite element analysis. The aluminum alloy piston rod with high dimensional accuracy is then forged according to the finite element simulation results.

Increasing the durability of drive ball joints control bridges by structural solution

The results of experimental studies of the influence of the radius of the fillet in the zone of transition of the rod of the ball bearings of the leading steerable axles of all-wheel drive vehicles into the flange on the durability are presented. The dependence of durability on the radius of the fillet in the zone of transition of the rod of a specific design of the ball bearing into the flange is given. Keywords ball joint, driving steerable axle, durability, fillet radius, bench tests

Optimization analysis of cold extrusion process parameters for valve screws

This study focuses on valve screws and establishes a cold extrusion simulation model using DEFORM-3D software to analyze the deformation characteristics and influencing factors during the extrusion process. Supported by the theory of rigid-plastic finite element, an orthogonal experimental design is conducted to establish a four-factor three-level simulation scheme with general fillet radius, die clearance, extrusion speed, and friction coefficient as the simulation variables, and maximum equivalent stress on the convex die, forming damage of the blank, and maximum wear depth on the concave die as the objective values. The prediction model based on BP neural network algorithm and orthogonal experimental data shows high accuracy. The optimization problem is simplified into a dimensionless numerical analysis problem using GC grey correlation analysis, and the optimal solutions within each variable range are determined using range analysis. The simulation results after optimization show a 20 5% reduction in maximum equivalent stress on the convex die compared to the original scheme, a 4.9% reduction in forming damage of the extruded part, and a 24.24% reduction in maximum wear depth on the concave die compared to before optimization. The actual verification confirms the good forming effect of valve screw extrusion, with well-formed contours and a uniform surface without wrinkles or defects. Finite element simulation provides valuable guidance for practical production.

Weight optimization of 200 mm diameter rocket motor tube using finite element method

The lightweight design of the rocket motor tube is a critical requirement for enhancing the rocket's flight performance. This study assesses the impact of wall thickness, cap thickness, and fillet radius on structural strength and the optimization of rocket motor tube weight using the finite element method with the assistance of Ansys software. A total of 12 finite element model variations, utilizing Aluminium 6061-T6, were developed and subjected to a uniform internal operating pressure load of 10 MPa. The design includes wall thickness variations of 8 and 10 mm, cap thickness options of 25 and 30 mm, and fillet radius dimensions of 20, 25, and 30 mm, allowing for a comprehensive comparison to achieve the required minimum safety factor while minimizing structural weight. The research concludes that increasing the fillet radius is a more recommended approach compared to increasing wall thickness and cap thickness. The results indicate that Model 9, with wall thickness, cap thickness, and fillet radius dimensions of 10 mm, 25 mm, and 30 mm, respectively, is the optimal choice due to its lightweight construction.

Stability prediction and optimization of multi-regenerative weak stiffness grinding system based on microstructured tool

Chatter is a serious problem in grinding, which will directly affect machining accuracy, efficiency, tool wear and even damage machine tools. In order to understand and avoid grinding chatter, a stability prediction and optimization method of multi-regenerative weak stiffness grinding system based on microstructured tool is innovatively proposed. It is the first time to use microstructured tools to ensure the system stability without sacrificing the material removal rate, which offers promise for weak stiffness grinding. Firstly, a multi-random geometric model of microstructured grinding wheel is established, considering the shape, distribution, microstructure patterns and truing conditions of abrasive grains. On this basis, considering the regulating effect of microstructure patterns on workpiece regeneration delay and tool wear delay of grinding system with large aspect ratio, a multi-regeneration stability model based on microstructure tool is established. Then, the experiments of grinding wheel microstructuring, internal thread grinding and profile measurement are carried out. The results show that the theoretical model established can accurately predict the grinding stability boundaries. The microstructure types can be arranged in descending order according to the optimization degree of grinding chatter: composite type, cross type, oblique type and linear type. Compared with the grinding wheel without microstructures, the microstructured grinding wheel can increase the speed limit deviation by 12.2 % − 54.0 %, which basically solves the chatter problem at high rotation speed. The wear resistance of microstructured grinding wheel is improved by 44.2 %, the tooth profile angle error and bottom fillet radius of workpiece are reduced by 92.3 % and 90.4 % respectively, and the maximum tooth height difference and average tooth height error are reduced by 90.6 % and 87.5 % respectively.

Microstructure Optimization for Design of Porous Tantalum Scaffolds Based on Mechanical Properties and Permeability.

Porous tantalum (Ta) implants have important clinical application prospects due to their appropriate elastic modulus, and their excellent bone growth and bone conduction ability. However, porous Ta microstructure designs generally mimic titanium (Ti) implants commonly used in the clinic, and there is a lack of research on the influence of the microstructure on the mechanical properties and penetration characteristics, which will greatly affect bone integration performance. This study explored the effects of different microstructure parameters, including the fillet radius of the middle plane and top planes, on the mechanics and permeability properties of porous Ta diamond cells through simulation, and put forward an optimization design with a 0.5 mm midplane fillet radius and 0.3 mm top-plane fillet radius in order to significantly decrease the stress concentration effect and improve permeability. On this basis, the porous Ta structures were prepared by Laser Powder Bed Fusion (LPBF) technology and evaluated before and after microstructural optimization. The elastic modulus and the yield strength were increased by 2.31% and 10.39%, respectively. At the same time, the permeability of the optimized structure was also increased by 8.25%. The optimized microstructure design of porous Ta has important medical application value.

Process Parameters Optimization of One-Step Spin Forming of Top Cover with Center Flanged Hole

To assist the low-cost manufacturing of tanks, a one-step method of marginal-restraint mandrel-free spin forming is therefore proposed in this study for the forming of top covers with flanged holes. With the finite element simulation analysis, three different forming strategies are discussed, and the best spinning process is identified. The proposed forming strategies involve preforming the flanged surface first and then preforming the spherical and flanged surfaces in a subsequent trajectory and is proved to have better forming accuracy. Furthermore, the forming quality of the spun parts is improved and optimized by employing more passes, smaller feed ratios, and larger roller fillet radii. It was experimentally verified that the marginal-restraint mandrel-free spinning one-step method with five passes, a feed ratio of 1 mm/r, and a roller fillet radius of 60 mm for the cylindrical roller can achieve accurate forming of a top cover with a center flange hole.

A comparative study of purge slot exit shape on the film cooling effectiveness of a gas turbine shroud

To achieve higher efficiency and performance, a modern gas turbine withstands the extremely high thermal environment. In the turbine endwall passage, a high and non-uniform heat transfer appears due to various secondary flow. The purge flow injected through the upstream slot between the stationary and rotating pars can thermally protect the endwall surface by forming air film layer on it. However, since an excessive amount of purge flow reduce the system efficiency, it is needed to effectively inject the purge flow with a limited amount. Accordingly, in the present study, the effect of purge slot exit shape on the film cooling effectiveness (hereby FCE) of a shroud surface was discussed. As nondimensional design parameters of the purge slot, L/Ws, RW/Ws, and RL/Ws were defined, representing the geometric features: the slot width (Ws), the fillet radius at the windward side (RW) and fillet radius at the leeward side (RL) of slot exit, respectively. The measurement of the FCE was performed in a five-blade linear cascade rig using the PSP (Pressure sensitive paint) technique. The results showed that the FCE increased for wider slot width at a given blowing ratio condition. In addition, the fillet radius at the windward side (RW) has a negative effect on the FCE regardless of blowing ratio condition since the purge flow was easily disturbed by the accelerated mainstream injection. On the other hand, the Case 7 with the RW/Ws = 0.9 showed 5.1 % of the improvement of FCE at a higher blowing ratio M = 0.25 compared with the Case 2 with RW/Ws = 0, which represents the sharp edge at the windward side of the slot exit.

Mechanical characteristics of a corset type structure with negative Poisson’s ratio

For mechanical metamaterials and their vibration isolation ability, a new corset type structure (CTS) is designed from the inward hexagonal steel structure by applying fillet at the inward corners. Ten CTS cells are born by using the different fillet radius. The fillet radius is 10 mm to 100 mm, but the cell mass remains constant when the plate has the same thickness. The static deformation, vibration modality and harmonic response of these NPR structures are analyzed in this paper. These CTS cells are modeled by using the finite element method (FEM) with a uniform grids. In static analysis, a surface load and a point load on the top plate are respectively considered to study the elastic deformation, the NPR and the stiffness of CTS cells with different fillet radii and thicknesses. These CTS cells have a greater NPR and a higher stiffness than the original inward hexagonal steel structure. In modal analysis, the natural frequency, the eigenmode and the fixed modality are numerically computed. These frequency values and displacement distributions of CTS cells show that these CTS cells have a higher vibration frequency than the origin inward hexagonal structure cell. In harmonic response analysis, the frequency domain is from 1 Hz to 1000 Hz, and the excitation force is on the top surface of the upper plate. All displacement responses of these CTS cells are analyzed. The harmonic response analysis result shows that the resonance magnitude can be significantly suppressed by these new CTS cells. The analysis result presents the characteristics of this new CTS, and it is beneficial for the vibration isolation in engineering application.

Analysis of fatigue fracture incident of centrifugal compressor blades in a small turbojet engine

In this study, performance verification tests were conducted on a small turbojet engine, during which a failure occurred at the root of the centrifugal compressor blades, which are made of aluminum alloy. A detailed disassembly and inspection was carried out to reveal the reason of the failure. It was found that the failure of one blade at the root led to jamming of other blades. Then the jammed blades experience sever rubbing and contact with the intake duct. Experimental measurements of material properties and a retrospective examination of the manufacturing process revealed that the yield strength of the material was lower than the design value, and the fillet radius at the blade root was smaller than specifications. The root cause of the fatigue failure of the compressor blades in this incident was attributed to substandard machining quality and material properties, which leads to crack initiation and fatigue propagation until failure occurred. The experience of identifying the root cause would provide engineering guidance for other small turbojet engines.

Creep damage and crack propagation behavior of printed circuit heat exchanger manufactured by diffusion welding: from material to structure

The printed circuit heat exchanger (PCHE) is extensively used in several applications due to exceptional compactness and heat transfer efficiency. However, the dominant failure mode of PCHE is creep fracture in its diffusion welding joints. Therefore, an accurate prediction of the creep crack propagation behavior for diffusion welding joints is essential for assessing the life of PCHE. In this paper, based on the research route from material to structure, the creep properties of 316L stainless steel base metal and its diffusion welding joint are firstly measured. On this basis, a constitutive model incorporating a time-hardening term for describing the creep damage is established. Furthermore, the creep damage and service life of the PCHE structure under working conditions (600 °C, 20 MPa) are analyzed, along with the effects of structure factors on the creep crack propagation behavior. The results show that the initial decelerating stage and the steady state stage play a dominate role in the creep curve of the diffusion welding joint, differing from the base metal's creep curve. Besides, the creep rate of the joint is approximately 30 times that of the base metal. The established creep damage constitutive model effectively characterizes the creep crack propagation behavior of diffusion welding joints. The maximum creep strain occurs at the weld metal and continuous operation for 100,000 h can be achieved at the designed working condition (600 °C, 20 MPa). For the purpose of lifetime extension by restraining the creep crack, it is recommended to increase the spacing and fillet radius while reducing the diameter during design process.

Influence of PMMA 3D Printing Geometries on the Mechanical Response

This work presents a study regarding the mechanical characterization of polymethyl methacrylate (PMMA) patterned samples manufactured via material-extruded additive manufacturing. In recent years, literature about mechanical analysis in additive manufacturing has been growing increasingly, especially for material extrusion-based techniques. However, this trend surpasses the speed of information released by standard councils, existing no clear specifications for polymer characterization apart from conventional techniques. This issue has led to premature breakage as well as fracture not located in the constant cross-section region of samples. The main purpose of this present research is focused on the analysis of diverse modifications of the standard injection geometries to tackle the mentioned problems. Several printing methodologies were compared, changing slicing and geometrical parameters such as number of walls, and fillet radius. Then, the manufacturing of PMMA samples with a material extrusion printer took place to characterize both the material and the effective properties of the structures. With the information post-processed from tensile and compression tests, disparities were found between different geometrical designs for both elastic modulus and ultimate stress. Moreover, diverse location of fractures were observed for the studied geometries. The data obtained from the analysis was valuable to establish a proper protocol for further studies. The experiments suggest that for tensile tests the golden standard is selecting rectangular specimens since they do not induce premature breakage nor fracture outside of gauge length.

Influence of impact-centrifugal hardener on microhardness of workpiece surface made of aluminium alloys

This article develops a tool for impact-centrifugal processing and establishes processing modes that increase the microhardness of the surface. An experimental study was carried out, where the tightening force, the number of working strokes, the rotation frequency of the hardener and the motion were proposed as technological parameters of impact-centrifugal processing. The experiments were carried out using flat machine-cut samples based on aluminium alloy D16T. A prototype of the rotary hardener with the standard fastening was designed and manufactured. During the experiment, it was revealed that, for the variation in average microhardness, the contribution of the rotation frequency is higher than that of the longitudinal motion. A significant influence of the tension on the surface microhardness is noted: following processing with a rotary hardener, it increases. It is shown that, to a greater extent, this increase depends on the technological tightening force and to a lesser extent on the rotation speed of the tool; it is recommended to increase these parameters. It was found that a 2-fold increase in tightening force resulted in an increase in microhardness by 70 HV 0.1, while increasing the tool rotation speed by 200 rpm led to an increase in microhardness by 42 HV 0.1. However, technological parameters must be selected taking into account the operability of the hardener. It was shown that the longitudinal motion has little influence on the increase in microhardness. The prototype of the designed tool can be used for processing at milling, boring, and grinding machines with computerised numerical control through a standardised fastening unit. This ensures sufficient technological flexibility and allows it to be used for reinforcing flat surfaces and fillet radii. The forecasted increase in the surface microhardness of the D16T sample using a rotary hardener amounts to 38.5% of the initial value in the experimental area with satisfactory productivity.

A Fatigue Method in the Tension-Compression Axial Stress Control Test of Automotive Sheet Steel

Abstract Focused on the common problem of easy buckling of specimens in the tension-compression axial stress control fatigue test of automobile sheet steel, a stress fatigue test method for thickness less than 2.5 mm was proposed. For two kinds of automobile sheet materials with different strength levels and thicknesses, fatigue specimens with different widths of test section, parallel lengths, and fillet radii are designed. Without the anti-buckling device, high-cycle fatigue tests with a stress ratio Rs = −1 at different stress levels were carried out, and the shape and size of the fatigue specimens of automobile sheet materials were determined by the number of fatigue life cycles of specimens with different sizes under the same stress cycle form. The results show that for automobile sheet steel with a thickness of 1.0–2.5 mm, the recommended sizes of the uniform-gauge fatigue specimens are width of test section w = (1–3) t, parallel length Lp = (1–3) w, and fillet radius r = (3–10) t. For automobile sheet steel with a thickness less than 1 mm, because the time-displacement curve jitters during the test, it is recommended to install an anti-buckling device, specifically the anti-buckling device with mortise and tenon structure by self-design and with a flattop structure recommended by ISO 1099-2017, Metallic Materials—Fatigue Testing—Axial Force-Controlled Method.

Effect of Cold and Hot Compounds Forming on Microstructures and Mechanical Properties in the Deformation Zone of Sharp-Edged High-Strength Steel Sections.

We researched the cold and hot composite-forming process, setting the forming speed at 2 m/min, the induction heating frequency at 40 KHz, and the induction current at 3000 A, and manufactured curtain wall steel with sharp corners. We analyzed the microstructure and mechanical properties of the deformation zone of the sharp-edged section using a tensile test, impact test analysis, metallographic observation (OM), fracture morphology observation, and electron backscatter diffraction (EBSD) analysis. The results show that the formed profile had a 96% reduction in the radius of the outer fillet and a 76% increase in the thickness of the corner compared to the pre-formed shape. The tensile strength increased by 3.6%, and the elongation after break increased by 13%. A forming temperature of 850 °C and forming deformation of 70% were determined as the optimum process parameters.