Groove Geometry Research Articles

Improving the performance of profile grinding wheels with helical grooves

Helically grooved grinding wheels have been shown to improve the performance of flat grinding processes by reducing the forces and spindle power during grinding. However, to date, helical grooves have never been applied to a profile grinding process. In this paper, we demonstrate experimentally that helical grooves are highly beneficial to profile, creep feed grinding processes—in some cases, allowing depths of cut up to 300% larger than a conventional profile grinding wheel. In addition, we extend the existing grooved grinding wheel theory to profile grinding wheels and, for the first time, describe a generalized method for calculating the groove factor for any grooved/textured profile grinding wheel. The experimental results of this paper suggest that it may be possible to optimize groove geometry for a given profile, as nearly identical groove geometries showed different results for two different grinding wheel profiles.

ANALYSIS OF FRICTION JOINING OF PRESSED GRATING FLATS

The aim of the paper is to analyse the friction forces in joints of pressed platform flat and transverse bars. Actual friction forces could have been determined based on the diagrams of force changes in the process of removal of a transverse bar from a groove in a flat bar. The paper presents diagrams of pressing and removing forces of transverse bars. The measurement of forces has been done for three distances between grooves in flat bars, i.e. 11.1 mm, 22.2 mm, and 33.3 mm. A significant variation of force values has been observed during both pressing and the extrusion of the bars. It has been assumed that one of the main causes of variation is the groove geometry. On the groove, walls there are stamp material shearing areas and breaking areas. The shearing area determines the friction force values.

ANALYSIS OF THE LOAD-CARRYING CAPACITY OF A HYDRODYNAMIC WATER-LUBRICATED BEARING IN A HYDROELECTRIC POWER PLANT

The paper presents an analysis of the load-carrying capacity of a historic hydrodynamic water-lubricated radial bearing of an unconventional segment design installed in the Braniewo Hydroelectric Power Plant. The aim of the calculations was to determine whether the bearing operates in the conditions of hydrodynamic or mixed lubrication, as well as to establish the optimal geometry of the axial grooves allowing for the highest load-carrying capacity. Computer simulations were performed using proprietary ARTbear software developed at Machine Design and Vehicles Department of Gdańsk University of Technology. The calculation results led to the creation of the technical documentation of the bearing’s modernization serving to increase its lifespan and reliability.

Operculum of a Water Snail is a Hydrodynamic Lubrication Sheet

Water snails developed a distinct appendage, the operculum, to better protect the body against predators. When the animal is active and crawling, part of the underside of the shell rests on the outer surface of the operculum. We observed the water snails (Pomacea canaliculata) spend ~3 hours per day foraging, and the relative angular velocity between the shell and operculum can reach up to 10 °·s−1, which might inevitably lead to abrasion on the shell and operculum interface. However, by electron microscopy images, we found that the underside of the shell and outer surface of the operculum is not severely worn, which indicates that this animal might have a strategy to reduce wear. We discovered the superimposed rings distributed concentrically on the surface, which can generate micro-grooves for a hydrodynamic lubrication. We theoretically and experimentally revealed the mechanism of drag reduction combing the groove geometry and hydrodynamics. This textured operculum surface might provide a friction coefficient up to 0.012 as a stability-resilience, which protects the structure of the snail’s shell and operculum. This mechanism might open up new paths for studies of micro-anti-wear structures used in liquid media.

Design of neural network arc sensor for gap width detection in automated narrow gap GMAW

An approach to develop an arc sensor for gap width estimation during automated NG-GMAW with a weaving electrode motion is introduced by combining arc sensor readings with optical measurements of the groove shape to allow precise analyses of the process. The two test specimen welded for this study were designed to feature a variable groove geometry in order to maximize efficiency of the conducted experimental efforts, resulting in 1696 individual weaving cycle records with associated arc sensor measurements, process parameters and groove shape information. Gap width was varied from 18 mm to 25 mm and wire feed rates in the range of 9 m/min to 13 m/min were used in the course of this study. Artificial neural networks were applied as a modelling tool to derive an arc sensor for estimation of gap width suitable for online process control that can adapt to changes in process parameters as well as changes in the weaving motion of the electrode. Wire feed rate, weaving current, sidewall dwell currents and angles were defined as inputs to calculate the gap width. The evaluation of the proposed arc sensor model shows very good estimation capabilities for parameters sufficiently covered during the experiments.

Material wear map for ground-engaging steels based on scratch tests

The present work examines the scratch resistances of a series of candidate ground-engaging steels. A range of microstructures is considered: tempered martensite, nano-bainite, pearlite, and austenite. Scratch testing was performed using tungsten carbide and diamond spherical tip sliders with tip radii ranging between 25 µm and 1.3 mm. Wear grooves were analysed and material loss determined. A material property wear map based on hardness and ‘scratch ductility’ is introduced. The map is analogous to those frequently employed in the literature to compare the strength and ductilities of structural alloys. A simple analytical wear model is developed and this is employed to enable comparison between candidate materials for differing scratching conditions. It is seen that the role of hardness dominates over that of ductility for high loads and smaller abrasive tip radii. This leads to a number of striking changes in relative wear rates of the candidate materials examined and these are effectively captured in the proposed map. The groove geometry due to the plastic flow of the material was also found to be the key parameter of the wear model and prediction of the wear mechanism.

Viscous dewetting of metastable liquid films on substrates with microgrooves

We present a combined experimental and theoretical investigation of dewetting on substrates with parallel microgrooves. A thin, static liquid film has an equilibrium thickness so as to minimize the sum of the surface free energy and the gravitational potential energy. When the thickness of a liquid film is less than the equilibrium thickness, the film seeks the equilibrium through contraction of the wetted area, which is referred to as dewetting. We experimentally observed the dewetting of thin, metastable liquid films on substrates with parallel microgrooves. The experiments revealed that the films retract in the direction along the grooves and leaves liquid residues with various morphologies. We classify the residue morphologies into three modes and elucidate the dependence of the mode selection on the groove geometry and the equilibrium contact angle of the liquid. We also experimentally examined the dynamic motion of the receding contact lines of the dewetting films, and developed a mechanical model for the receding speed. Our results provide a basis for controlling liquid films using microstructures, which is useful for lubricant-impregnated surface production, painting, spray cooling, and surface cleaning.

Strategic Design and Fabrication of Nerve Guidance Conduits for Peripheral Nerve Regeneration.

Nerve guidance conduits (NGCs) have been drawing considerable attention as an aid to promote regeneration of injured axons across damaged peripheral nerves. Ideally, NGCs should include physical and topographic axon guidance cues embedded as part of their composition. Over the past decades, much progress has been made in the development of NGCs that promote directional axonal regrowth so as to repair severed nerves. This paper briefly reviews the recent designs and fabrication techniques of NGCs for peripheral nerve regeneration. Studies associated with versatile design and preparation of NGCs fabricated with either conventional or rapid prototyping (RP) techniques have been examined and reviewed. The effect of topographic features of the filler material as well as porous structure of NGCs on axonal regeneration has also been examined from the previous studies. While such strategies as macroscale channels, lumen size, groove geometry, use of hydrogel/matrix, and unidirectional freeze-dried surface are seen to promote nerve regeneration, shortcomings such as axonal dispersion and wrong target reinnervation still remain unsolved. On this basis, future research directions are identified and discussed.

Experimental investigation into metal micro-patterning by laser on polymer-metal hybrid joining

Surface modification pretreatment on laser direct joining of glass fibre reinforced polyamide to steel was studied to assess its effect on the joint's mechanical performance. The steel part was structured by laser radiation to accomplish a proper mechanical interlock when joining with the polymer. In a second step, the opposite side of the micro-structured metal was irradiated by a continuous wave (cw) fibre laser system until reaching the melting temperature of the polymer in both materials interface. The metal micro-structuring was produced by two different laser sources (nanosecond pulses (ns) and cw) in order to study the effect of different groove geometries on the joint's failure force under tensile-shear tests. The impact of structure density and clamping pressure was also assessed. A tight dependence of aspect ratio and recast material height of patterns on joint’s failure force was found for the micro-patterns that were produced by nanosecond pulses. The greatest strength was achieved in the case of patterns produced by ns-pulses. The trend concerning the effect of structure density was validated for the patterns that were produced by ns-pulses and cw-radiation. The changes in clamping pressure did not evidence a significant influence on the joint quality. The morphological features of the detached surfaces showed that the micro-geometric structure aspect ratio has a meaningful effect on the failure mode in the case of structures that were generated by nanosecond pulses.

AMOEBA Polarizable Atomic Multipole Force Field for Nucleic Acids.

The AMOEBA polarizable atomic multipole force field for nucleic acids is presented. Valence and electrostatic parameters were determined from high-level quantum mechanical data, including structures, conformational energy, and electrostatic potentials, of nucleotide model compounds. Previously derived parameters for the phosphate group and nucleobases were incorporated. A total of over 35 μs of condensed-phase molecular dynamics simulations of DNA and RNA molecules in aqueous solution and crystal lattice were performed to validate and refine the force field. The solution and/or crystal structures of DNA B-form duplexes, RNA duplexes, and hairpins were captured with an average root-mean-squared deviation from NMR structures below or around 2.0 Å. Structural details, such as base pairing and stacking, sugar puckering, backbone and χ-torsion angles, groove geometries, and crystal packing interfaces, agreed well with NMR and/or X-ray. The interconversion between A- and B-form DNAs was observed in ethanol-water mixtures at 328 K. Crystal lattices of B- and Z-form DNA and A-form RNA were examined with simulations. For the RNA tetraloop, single strand tetramers, and HIV TAR with 29 residues, the simulated conformational states, 3 J-coupling, nuclear Overhauser effect, and residual dipolar coupling data were compared with NMR results. Starting from a totally unstacked/unfolding state, the rCAAU tetranucleotide was folded into A-form-like structures during ∼1 μs molecular dynamics simulations.

An Experimental Analysis of Laser Machining for Dental Implants

In the recent years, the scientific progress in both technological and medical sectors has led to an evolution of materials and fabrication techniques used for dental prosthetics. This paper proposes laser subtractive process to manufacture dental implants and explores the behavior of a CO2 laser beam effects on biocompatible materials, namely zirconia and PMMA. The aims of the experiments are the study of CO2 laser beam effects on biocompatible materials and the creation of a mathematical model to relate the process parameters with groove geometry and surface finish.

Mould design for manufacturing of isogrid structures in composite material

In the transport industry, fuel consumption and emissions can be reduced introducing very light parts. An optimal solution to these problems consists in the construction of isogrid structures made of composite materials, whose manufacturing process is a critical step, since it can induce some damages that cause the rejection of the produced part. The forming technology, the necessary equipment and the process parameters must be carefully chosen, since they strongly affect the part quality. The mould shape has to be carefully designed since the part presents a complex geometry, due to the presence of ribs, that could present a bad compaction.The aim of this work is to introduce and verify through structural tests a design methodology for the manufacturing of isogrid structures made of composite materials. In particular, the mould groove geometry was defined in order to obtain the right compaction degree. Then, different experimental tests were carried out to determine the quality of the produced structures.

Optical measurement of groove geometry

Feature recognition and measurement in manufactured parts can be used for correcting tool paths, deciding suitable process parameters and verifying the quality of a completed production step. In this study, V-groove with root face in a butt joint between two steel parts with machined bevels are measured using a commercial optical triangulating sensor consisting of a laser source and a digital camera. This feature is difficult to measure due to reflections off the machined sides of the groove. This study demonstrates top gap, root gap and groove depth measurement, as well as tack weld detection.

Rolling simulation system for non-symmetric groove types

An extension of a previously developed rolling simulation system is presented. Complicated groove dimensions, which have no longer symmetry on any of the coordinate axis, are successfully implemented. The thermo-mechanical numerical solution, considering ideal plastic deformation and obeying von-Mises flow rule, is based on meshless local radial basis function collocation method. During the solution procedure, 2D discrete cross sectional slice of a groove and rolled material become a computational domain at a given time, parallel to each other and aligned perpendicular to the rolling direction. Groove slice, or groove surface lines, are created with the help of imaginary groove surface points for each slice position. The implementation of roll contact at the boundaries is done by considering possible contacts of a slice and groove surface line at multiple sections with different deformation rates and boundary conditions. Coulomb model of friction is considered at the contact boundaries. The design of non-symmetric (in vertical or/and horizontal direction) type of rolling schedule is quite complicated since keeping the rolled product at the center may become problematic and unexpected deformation in one direction could ruin the desired final shape. The computational model, capable of coping with non-symmetric groove geometries provides an essential simulation tool for these type of roll pass designs. To increase the stability and the accuracy, the number of collocation nodes over the slices as well as groove surface points may be suitably increased or redistributed. The simulation results are shown in terms of temperature, displacement, strain and stress fields as well as roll forces and torques. A user friendly computer application is created for industrial use based on C# and .NET.

Milling of Fir-Tree Slots in Allvac 718 plus

For the machining of profiled grooves in turbine discs made out of nickel based alloys, broaching is still state of the art. However, the broaching process entails some disadvantages like high costs and long delivery times for the machine tools and the broaches in combination with inflexibility with regard to the groove geometry and machining task. An alternative to the broaching process is the integration of the profile slotting on a 5-axis milling center. This paper deals with an approach for machining a fir-tree slot via different milling process chains. The two roughing strategies, ceramic side milling and carbide end milling, are depicted with regard to tool wear and the economy. The finished fir-tree slot will be evaluated in terms of dimensional stability. In addition, the possibility of finish broaching on a five-axis machine tool is shown.

A Rolling Simulation System for Reversing Rolling Mills

In this work a rolling simulation system has been developed for rolling schedules which consists of multiple reversing rolling mills. A slice model approach is applied where the position of a slice can only be determined by considering total deformation. Each slice is parallel to each other and perpendicular to the rolling direction. The solution of coupled thermal and mechanical models over each slice, at a given time and position, are achieved by a novel meshless Local Radial Basis Function Collocation Method (LRBFCM). Mechanical material model obeys ideal plastic flow rule defined by Von Mises. Unknown fields over the slices are interpolated by a certain number of collocation points distributed over the physical domain and its boundary. A system of equations is solved for each collocation point considering its local neighbouring points in the range between 5 and 7. A non-linear system of equations is solved by direct iteration. Groove geometries of each roll are implemented in a compatible way with the slice model and every roll has a horizontal orientation. In between each rolling pass the billet is rotated either 90 or 45 degrees clockwise or counter clockwise. Reduction at each of the passes can be very high, and in such cases, the material completely fills up the groove. This requires a special attention regarding the contact boundary conditions and the collocation node distribution due to numerical instability issues. Coulomb model of friction or sticking boundary conditions are used at the contact boundaries and Gauss-Seidel iterative elliptic node generation algorithm is used for redistributing collocation nodes over the physical domain, when necessary. The simulation results for arbitrary initial position of the slice in the billet are shown in terms of temperature, displacement, strain and stress fields as well as roll forces and torques. A user friendly computer application is created for industrial use based on C# and .NET.

Fabrication of Inner Grooved Hollow Fiber Membranes Using Microstructured Spinneret for Nerve Regeneration

Nerve conduits with topographical guidance have been recognized as the efficient repair of damaged peripheral nerves. In this study, polymeric hollow fiber membranes (HFMs) with grooved inner surface have been fabricated from a microstructured spinneret using a dry-jet wet spinning process for nerve regeneration studies. The effectiveness of HFM inner grooves has been demonstrated during an in vitro study of chick forebrain neuron outgrowth. It is of great importance that the groove geometry can be controllable to meet various needs in promoting nerve regeneration performance. While the overall groove geometry is determined by the spinneret design, fabrication conditions are also indispensable in fine-tuning the final groove geometry such as the groove height and width on the order of 10 μm or less. It is found that the bore fluid flow rate can be utilized to effectively adjust the resulting groove height by at most 52% and groove width by at most 61%, respectively, without modifying the spinneret geometry. This enables a new approach to fabricate different grooved HFMs using the same spinneret. By comparing to the influences of bore fluid flow rate, the dope fluid flow rate is less effective in regulating the groove height and width when using the same microstructured spinneret. Both bore and dope fluid flow rates should be carefully selected for fine groove width tuning.

Development of Technology for Detachment of Calandria Tube Rolled Joint of Pressurised Heavy Water Reactors

Coolant channel assembly of PHWRs consisting mainly of pressure tube and calandria tube undergoes sag due to irradiation enhanced creep during its life time. Typical service life of the pressure tube is limited to about 15 full power years due to such ageing related degradation. On account of the degradation the pressure tube needs replacement more than twice during the licensed period of reactor operation. As the sag in the calandria tube is also excessive, it has to be replaced to facilitate installation of new and straight pressure tube during retubing and to avoid interference of sagged calandria tube with horizontal reactivity devices. The calandria tube and the tube sheet are joined by sandwich type rolled joints. For detaching the joint an improved technique has been developed that helps to detach the joint without affecting the groove geometry and integrity of the tube sheet. The system works on the principle of fast thermal cycle of heating and cooling of the insert and calandria tube in the rolled joint region while applying axial load to the calandria tube. Though rolled joint detachment by induction heating technique has been in use in CANDU reactors for removal of pressure tubes and calandria tubes, the present design incorporates a liquid nitrogen for faster cooling and simultaneous application of load with a gripping module for detachment and removal of calandria tube and the insert from the tube sheet of end shield in shorter time. This paper describes the methodology of rolled joint detachment, challenges involved in the design, features of the detachment system, findings of experimental trials and observations.

Flow characterization in periodic microchannels containing asymmetric grooves

Characterization of two-dimensional flows in microchannels with anisotropic periodic grooves is numerically carried out by using the lattice Boltzmann method. Periodically placed microstructures, consisting of novel nozzle-diffuser-like grooves are deliberately designed to introduce a flow-direction dependent resistance. Simulations were conducted for a low-to-moderate Reynolds number in the laminar-transition flow regime. Different channel geometries, defined by the half-angle ϕ of the periodic grooves are considered. The influence of the half-angle on both the flow field and the onset of oscillatory flow regime at different driving body forces is analyzed. At a low Reynolds number, the flow is observed stationary and fully reversible, regardless of the groove geometry. In this regime, higher Reynolds numbers were observed when the geometry acts as a diffuser (negative flow) than as a nozzle (positive flow) for a given driving body force. At sufficiently high Reynolds number the flow turns from a steady state to a time-dependent oscillatory regime through a Hopf bifurcation. Successive flow bifurcations lead the flow structure from a periodic regime to a quasi-chaotic regime with three-dimensional structures. The onset of unsteady flow occurs earlier for positive flows and geometries with small half-angles. For higher driving forces, there is a reduction in the volume flow rate due to the advected material in the transversal direction, causing consequently a decrease in the Reynolds number.

An intelligent wheel position searching algorithm for cutting tool grooves with diverse machining precision requirements

Abstract Searching for and adjusting to the appropriate wheel positions for designed grooves are among the key issues in the manufacturing of the end mill, drill and other integral cutting tools. Along with the increasing requirements of product categories and quality, a large number of non-traditional and customized grooves continuously appear. However, as multivariable, nonlinear and multiple target problems, it is difficult to obtain the desired wheel position. Therefore, we introduce an intelligent method to search for the optimum wheel position for the designed groove with the known wheel geometry. According to practice, the basic parameters of the groove and wheel geometries are introduced, and the problems studied in this paper are explained. As a foundation, a robust algorithm is built to predict machined grooves with a series of equal distribution points and three parameters: the rake angle, core radius and groove width. The influence that the wheel positions have on groove geometries is then analyzed. Then, an objective function considering different machining requirements is built, and the optimum wheel positions are searched for while the function is solved. Furthermore, an enhanced niche particle swarm optimization (NPSO) algorithm is developed to solve the problem. Finally, 6 experiments are carried out to verify and analyze the algorithm. The results show that the algorithm can effectively find the desired wheel positions according to different machining precision requirements.