Edge Of Groove Research Articles

Improvements of hybrid laser arc welding for shipbuilding T-joints with 2F position of 8 mm thick steel

One of the main concerns in the early stages of manufacturing flat units of shipbuilding is to ensure the quality of the joints throughout the structure. The flat units are constituted by butt welded flat plates, on which longitudinal T-welded reinforcements are placed to rigidize the structure. Among the different welding technologies, Hybrid Laser Arc Welding (HLAW) is becoming a mature process, profitable and highly productive. In addition, more innovative welding equipment are being developed nowadays, offering greater work flexibility, and raising expectations of achieving better quality, and economic viability. Another key point of HLAW to keep in mind is that structural distortions are reduced, resulting in decreasing the cost and time of straightening work.In the present contribution, the influence of HLAW parameters on the quality of fillet joints of naval steel has been analysed. Experimental HLAW tests were performed with a high power disk laser to join EH36 naval steel plates, with a T configuration. The influence of different processing parameters has been analysed, as the laser power, welding speed, wire feed rate and the configuration of the HLAW processes (including head angle and laser/arc leading process). In addition, FEM simulations were carried out in order to estimate residual stresses and distortion of welded part. The distortion values provided by FEM presented excellent agreement with the measured experimental results. To evaluate the welds, non destructive tests including X-ray tests, metallographic analysis of cross sections, and microhardness mapping tests were performed.Full penetration 8 mm T welds were obtained for the first time at an industrially applicable 2F position with a reasonable HLAW head angle, in one single step without sealing root, and using zero gap square groove edge preparation. The present contribution presents welding rates up to 2.2 m/min for 2F T-joints of this steel thickness, a much higher processing velocity than previously reported for industrial applications.

Investigation of the application of a magnetic abrasive finishing process using an alternating magnetic field for finishing micro-grooves

A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces. In an alternating field, the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate, which will not only continuously replace the abrasive particles in contact with the workpiece, but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece. In this paper, the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed. The feasibility of this process for finishing micro-grooves is investigated. Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area. The experimental results show that the process is feasible for finishing micro-grooves, with an excellent deburring effect on the groove edges.

The effect of a time-varying contact surface on interfacial tribological behaviour via a surface groove and filler

In this work, the effect of a time-varying contact surface on friction-induced vibration and noise (FIVN) and surface wear performance was studied experimentally. A certain size groove was fabricated on a surface of compacted graphite iron, then filled with pure phenolic resin and phenolic resin with MoS2 additives to obtain a surface with time-varying contact characteristics. The experiment was carried out in a ball-on-flat configuration. The results show that introducing the filler of phenolic resin with MoS2 additives into the groove is effective not only at suppressing the generation of FIVN and improving surface wear performance, but also at alleviating the impact vibration between the groove edge and the ball. More importantly, the time-varying contact surfaces designed in this work are valuable for exploring the role played by debris in the modification of wear state and the formation of interfacial characteristics, and how this finally affects the generation of FIVN. The investigation shows that a time-varying contact surface filled with suitable materials can realize the aim of FIVN reduction.

Effects of Textured Surface Combined with Sn-Ag-Cu Coating on Tribological Properties and Friction-Induced Noise of Ti-6Al-4V Alloy

To improve the tribological properties and suppress the friction-induced noise of Ti-6Al-4V alloys (TC4), TC4 with smooth surfaces (TSs), groove antifriction surfaces (GAs), Sn-Ag-Cu coating surfaces (SCs), and composite self-lubricating surfaces (CSs) with grooves and Sn-Ag-Cu coating were prepared. Experimental studies on the tribological properties and friction-induced noise were carried out. The results showed that TSs produced high-frequency scream for adhesive wear. GSs suppress the scream noise but induce low-frequency chattering. CSs with uniform profiles and smaller wrinkles showed tribochemical wear characteristics, which produced the various intermetallic compounds and oxides, improving the surface profiles and suppressing the microdefects. The synergistic effects of grooves and Sn-Ag-Cu coating on CSs reduce the high contact stresses of groove edges and suppressed the adhesive wear and friction-induced noise. The friction and noise reduction mechanisms of CSs are beneficial to obtain surfaces with the best antifriction performance and bearing capacity by improving the profiles.

Thermomechanical Coupling Simulation and Analysis of Wet Multi-Disc Brakes During Emergency Braking

The main reason for the thermal failure of wet multi-disc brakes during emergency braking is thermoelastic instability due to thermomechanical coupling. To analyse the phenomena, a three-dimensional finite element model of a wet multi-disc brake friction pair is built and numerical simulation is carried out with thermal-structural coupling method, based on ANSYS software. The contact pressure distribution, temperature and stress field during emergency braking are obtained. The results show that high temperature is located at the outer diameter of friction linings during emergency braking, large temperature gradient and stress gradient are generated at edges of radial grooves, which lead to the friction disc warp. Through simulation and analysis, this paper can provide a basis for engineering application and design research of wet multi-disc brakes.

Experimental Study on High Speed Cutting of 7075 Aluminum Alloy

A 4-edge cemented carbide end mill with a diameter of 6 mm was used to mill a single factor groove of 7075 aluminum alloy. The results show that the surface roughness of the bottom surface of the narrow groove decreases with the increase of the cutting speed in the range of variable cutting speed. Moreover, when the cutting speed is the highest, the burr on the edge of the narrow groove is not completely eliminated, and there are more burr and curling. When the feed rate is selected as a variable, the surface roughness of the bottom surface of the milling narrow groove increases with the increase of the feed rate. When the cutting depth is selected as a variable, the surface roughness of the bottom surface of the milling narrow groove increases with the increase of the cutting depth. There are obvious extrusion bulge marks between the two intersecting steps on the bottom surface of the milling narrow groove. The reason of extrusion bulge on the bottom surface of milling may be due to the large width and elastic deformation of 7075 aluminum alloy material, which results in large plastic flow under the cutting extrusion of milling tool.

Mechanical properties and joining mechanism of electrohydraulic expansion joints for 6063 aluminum alloy/304 stainless steel thin-walled pipes

A joining process for aluminum alloy/stainless steel pipes, named electrohydraulic expansion joining was presented. The process experiment, simulation analysis and mechanical tests were conducted. The results revealed that the deformation degree increased with the increase of the discharge voltage and the groove width, which further improved the joint performance. The ultimate pull-out load was 18.57 kN. The joints had two failure modes: pull-out of the aluminum alloy pipe from the groove and tearing of the aluminum alloy pipe at the leading groove edge. The velocity distribution and deformation process of the inner pipe were analyzed to reveal the joining mechanism.

New methods for determination of the keyhole position in the lateral suboccipital approach to avoid transverse-sigmoid sinus injury: Proposition of the groove line as a new surgical landmark

PurposeThe asterion is frequently used as an anatomical landmark to determine the location of a keyhole in the lateral suboccipital approach used in craniotomies. However, the asterion may not be ideal because of large individual differences among patients. We examined a simple and safe method for determining an optimal keyhole position (KP) using the digastric groove as a new landmark in the lateral suboccipital approach. MethodsThirty-three patients with trigeminal neuralgia who underwent surgery in our institute between April 2014 and December 2018 were included. The groove line (GL) was designed accurately, extending the digastric groove on the surface of the occipital bone, as the x-axis. The y-axis was depicted from the posterior edge of the digastric groove (the groove point: GP) vertical to the GL. The x–y coordinates represented the distances from GP on each axis. The x–y coordinates of median edge of the transverse-sigmoid sinus (TSJ point), asterion, and the intersection of the GL and transverse sinus (the transverse point: TP) were investigated, based on intraoperative findings and recorded videos. ResultsThe x–y coordinated of the TSJ point were (23.9±3.9, 7.2±3.6). In all patients, the TSJ point was located superior to the GL. The x–y coordinates of the asterion were (27.3±6.0, 8.9±4.1), and in 28 of the 33 patients, their coordinates exceeded the TSJ points. The x-coordinate of the TP was 29.5±4.5, and was located behind the TSJ point on the GL in all patients. The shortest distance between the TSJ points and TP was approximately 3mm. According to these measurements, we decided that the optimal KP would be at 20mm from the GP, subjacent to the GL. ConclusionsOur methods of using the GL as a new surgical landmark for setting the optimal KP is simple, safe, and useful.

Chip-free surface patterning of toxic brittle polycrystalline materials through micro/nanoscale burnishing

Brittle crystalline materials have important applications in optics and optoelectronics. However, their powders are highly toxic; thus, the chips generated in material removal processes such as cutting, grinding, and polishing are harmful to human health and the environment. In this study, micro/nanoscale burnishing tests were conducted on polycrystalline zinc selenide (p-ZnSe) to explore the feasibility of high-precision surface patterning of a toxic material by local plastic deformation without chip generation. The local deformation behaviours and subsurface damage formation mechanisms were investigated under dry and oil-lubricated conditions. Two types of cracks occurred when the force exceeded a critical value: cracks along the slip planes at the groove bottom and cracks along the cleavage planes at the groove edge. Below the critical force value, however, a crack-free surface was obtained with lower surface roughness than those for diamond-turned surfaces. No phase transformation was detected after burnishing, but lattice distortion appeared in the subsurface layer. A model was developed to predict the activated slip planes by calculating the maximum Schmid factors of the slip systems, and the distribution of subsurface defects was clarified by cross-sectional direct observations. It was also found that the use of a lubricating oil could greatly reduce material pile-ups around the tool. As test pieces, microgrid patterns were fabricated by crossing and overlapping the grooves, and smooth surfaces with surface roughness of 1.85 nm Sa and 4.5 nm Sa, respectively, were achieved. The findings from this study demonstrate the feasibility of chip-free surface patterning on toxic brittle polycrystalline materials by micro/nanoscale burnishing, which is an effective alternative to cutting and grinding for the fabrication of micro structured optical elements and microfluidics.

Determination of Rational Design and Geometric Parameters of a High-Performance Drill Based on a Mathematical Model of the Cutting Part

Processing of high-precision holes in one technological operation is an urgent problem of advanced manufacturing. Processing of precise holes in parts for aerospace and machine-building industries with a diameter of up to 30 mm is performed during countersinking, deployment or grinding operations. These operations are applied only if there already exists a pre-treated hole. Monolithic three-fluted drills have been becoming common for processing high-precision holes of 7-8 quality over the last few years. The processing of various types of materials such as stainless steels, cast iron and heat-resistant steels requires rational geometric and structural parameters of the cutting tool. The nature of the load distribution between all the teeth during drilling plays a huge role in the processing efficiency. Even load distribution between the three teeth and a positive geometry improves self-centering and reduces the deviation from the specified axis of the hole. The drill sharpening provides positive geometry along the entire main cutting edge. The influence of the geometric parameters of the cutting edge of the screw groove on the shape of the drill bit is equally important. Existing approaches to the design of the thinning do not account for the influence of the geometric parameters of the cutting edge on the section of the screw groove. Analytical approaches to modelling of the main cutting edges are typically married with difficulties associated with achieving a smooth change in the angle of inclination to the tangent of the cutting edge. The complexity of the aforementioned task is largely due to the presence of critical points at the interface of the spiral groove and thinning. Determining the rational shape of two sections of the main cutting edge performed in this study is a complicated task that includes several steps needed to find the number of nodal points. Achieving a positive rake angle in the normal section to the cutting edge at the gash area that was formed via a special sharpening is one of the most important results of this paper. The rational shape of the cutting edge and the front surface provides an increase in the strength of the cutting part by 1.3 times.

A computational study of heat transfer and material removal in picosecond laser micro-grooving of copper

A 2D two-temperature model (TTM) is developed for picosecond laser micro-grooving of copper (Cu) and discretized using the finite difference scheme, to explore the temperature evolution and groove formation process. For lattice and electron subsystems, as well as the coupling strength between them, comprehensive temperature-dependent properties are employed and updated in real time to make the calculation more accurate. The model verification is then conducted and a reasonable good agreement has been found between predicted and measured groove depths. Using the verified model, computational studies of temperature field evolution are carried out in different fluence levels. For low fluence of around 0.283 J/cm2, phase change can be neglected, and the temperature difference between two subsystems decreases with an increase in pulse width and can be neglected when the pulse width is over 200 ps. In contrast, for high fluence of about 10.61 J/cm2, the maximum lattice temperature increases rapidly to boiling point within 3 ps, and the peak electron temperature is around 10 times higher, leading to material removal via evaporation. Under this high fluence level, groove depth around 0.25 μm is obtained within a 12 ps single pulse irradiation. In addition, thermal diffusion occurs from the residual hot zone adjacent to groove edge towards surrounding area during the off-pulse period, as the heat affected zone depth is up to 1 μm after 500 ps and over 4 μm after 6 ns, and the peak residual lattice temperature drops to about 396 K from boiling point within 53 ns. Moreover, the groove depth and groove profile show a periodically evolving manner with respect to scanning times, and for each scanning, a slow-fast-slow pattern has been observed in groove depth increase and profile development.

Mechanisms and predictive force models for machining with rake face textured cutting tools under orthogonal cutting conditions

The cutting performance and mechanisms of rake face textured carbide cutting tools in orthogonal machining of a carbon steel are investigated. Micro-grooves at 15.5 μm top width and different depth-to-width ratios are fabricated on the tool rake face using a femtosecond laser. It is found that the textures can significantly enhance the surface wettability of the cutting tools to an emulsified cutting fluid, and a fast liquid infiltration along the micro-grooves takes place. The machining tests show that cutting tools with the rake face grooves can reduce the thrust force by up to 14.68% in comparison with the untextured cutting tools, as a result of the decreased frictional force between the tool and chip. It is shown that the reduced tool-chip actual contact area due to the rake face textures and reduced tool-chip contact length due to the thinning of chip are the main reasons for this frictional force reduction. It is further found that the ploughing action between the groove edges and chip material tends to increase the frictional force while the chip material deposition to the textural structures reduces the functionality of the textures. Plausible trends of the reduction of the cutting forces with respect to the textural parameters are discussed, from which grooves in parallel to the cutting edge at 0.6 depth-to-width ratio and about 90 μm spacing are found to perform the best. A cutting force model for orthogonal machining using rake face textured cutting tools are then developed using the classical thin shear zone theory and the unified mechanics of cutting approach. The model is finally verified experimentally which shows that the model predictions agree well with the corresponding experimental data for cutting with and without a cutting fluid.

Computation of residual stresses, distortion, and thermogravimetric analysis of Inconel 625 weld joints

In the current investigation, Inconel 625 weld joints were fabricated by Activated tungsten inert gas (A-TIG) and Tungsten inert gas (TIG) welding techniques. The joint configurations employed square butt and V groove edge preparations. Residual stresses measurement was carried out by X-ray diffraction using the Proto iXRD measurement system. Distortion in weld joints was estimated by measuring the vertical displacement on the grids marked on the weld joints before and after welding by using an electronic height gauge. Weldment revealed distinctive microstructure, peak tensile residual stress, and angular distortion. A-TIG weld joint exhibited lower residual stresses and distortion compared to the TIG weld joint. Thermogravimetric analysis (TGA) has inferred that the fusion zone of A-TIG and TIG weldments revealed better hot corrosion resistance at high temperatures.

Understanding the intrinsic compression in polycrystalline films through a mean-field atomistic model

Mullins’ theory predicts the buildup of adatoms during surface diffusion at the edges of grooves where grain boundaries emerge to the surface of a polycrystalline film. However, the mesoscopic nature of this theory prevents the identification of the atomic-scale physical mechanisms involved in this phenomenon. Here, we interpret the buildup of adatoms in atomistic terms through a mean-field rate-equation model and demonstrate both its kinetic nature and its impact on the intrinsic stress in these systems. Furthermore, the model provides estimates of the surface profile of intrinsic stress, of its typical mean values, and of the dependence of stress on temperature and deposition flux for different growth stages. These estimates agree well with reported experimental results obtained from recent advances in nanoscale mapping of mechanical stresses on the surface of polycrystalline films.

Promote anti- /de- frosting by suppressing directional ice bridging

Condensation frost is one of the most common types of icing encountered in nature and industrial applications, while its accretion induces multiple non-negligible negative impacts. Many passive anti-/de- frosting approaches by tailoring surface topology and chemistry have been reported recently. To date, however, reliable engineered surfaced that can be compatible with heat exchangers from both mechanical and economic perspectives are limited. In this paper, we present a hierarchically structured surface that can profoundly reduce the frost coverage, and meanwhile promote the rapid removal of frost melts. This surface consists of microgroove pattern and nanoblade structure, where the former provides preferential sites for the growth of condensed droplets, and the latter promises a robust water repellent nature. During frosting, the ice phase spreads only among droplets on groove edges while condensed droplets in valleys are completely evaporated off, yielding a typical pattern that ice stripes distribute discretely in the dry background. During defrosting, frost melts coalesce into large droplets that spontaneously depart the substrate surface. Our results open up a new avenue for surface engineering, particularly on the design of economic and scalable anti-/de- frosting surfaces.

Analytical Modeling of Flux-Reversal Permanent-Magnet Machines

An analytical model is proposed for the prediction of electromagnetic quantities of slotted flux-reversal permanent magnet (FRPM) machines. Equivalent current theory is used to model the effects of permanent magnets (PMs), stator slots and rotor grooves. First, the stator slots and rotor grooves are nullified and the Poisson equation is solved in a slotless stator and cylindrical rotor machine. The effects of the stator slots and rotor grooves are then considered by injecting equivalent magnetization currents (EMCs) respectively on the stator slots wall and on the rotor groove edges. The PMs are also replaced by EMCs. Finally, the results of the proposed analytical model are verified by means of the finite element analysis.

Flow-driven collapse of lubricant-infused surfaces

Abstract

Lateral force calibration for atomic force microscope cantilevers using a suspended nanowire

Friction measurement via atomic force microscope (AFM) relies on accurate calibration for the torsional spring constant of the AFM cantilever and its lateral deflection sensitivity. Here we describe a method that employs a suspended nanowire (SNW) as a reference beam to quantify the torsional spring constant of AFM cantilevers. Based on the fact that a uniform SNW with cylindrical symmetry has an identical spring constant when bent in any direction perpendicular to its axis, the spring constant of the SNW in a normal direction is determined by an AFM cantilever with a known normal spring constant, and is subsequently used as a force transfer standard to calibrate the torsional spring constant of the AFM cantilever. The lateral deflection sensitivity can be accurately measured by pushing the AFM tip laterally on the groove edge. The calibration result is compared to the well-known diamagnetic lateral force calibrator method and shows an uncertainty of 15% or better. The presented method is applicable for the lateral force calibration of AFM cantilevers in a wide range of instruments including inverted configurations and in an ultrahigh vacuum.

Laser-induced regular nanostructure chains within microgrooves of Fe-based metallic glass

Femtosecond laser-induced surface structures have been extensively investigated over decades, however, their formation is not well controlled especially for the practical use in the photonic field. We here report the highly regular nanostructure formation within the grooves of the Fe-based metallic glass, upon irradiation of two temporally delayed femtosecond laser beams. For the case of micrometer-sized groove, multiple chains of spindle-like nanostructures are developed, with the spatial periods of 667 nm and 180 nm for the chain and spindle distributions, respectively. Their arrangement properties can be modulated by varying laser parameters. On the other hand, for the case of submicrometer-sized groove, there is only one chain of spindle-like nanostructures formed inside with the improved regular appearance. Two physical effects, including the plasmonic field generation from the groove edges and the surface magnon polariton excitation within the groove, are considered responsible for the phenomena, which consequently result in the spatial interlocking of two types of ripples. The theoretical analyses match well the experimental observations.

Deciphering the Origins of P1-Induced Power Losses in Cu(In Ga1–)Se2 (CIGS) Modules Through Hyperspectral Luminescence

Abstract In this report, we show that hyperspectral high-resolution photoluminescence mapping is a powerful tool for the selection and optimization of the laser ablation processes used for the patterning interconnections of subcells on Cu(Inx,Ga1−x)Se2 (CIGS) modules. In this way, we show that in-depth monitoring of material degradation in the vicinity of the ablation region and the identification of the underlying mechanisms can be accomplished. Specifically, by analyzing the standard P1 patterning line ablated before the CIGS deposition, we reveal an anomalous emission-quenching effect that follows the edge of the molybdenum groove underneath. We further rationalize the origins of this effect by comparing the topography of the P1 edge through a scanning electron microscope (SEM) cross-section, where a reduction of the photoemission cannot be explained by a thickness variation. We also investigate the laser-induced damage on P1 patterning lines performed after the deposition of CIGS. We then document, for the first time, the existence of a short-range damaged area, which is independent of the application of an optical aperture on the laser path. Our findings pave the way for a better understanding of P1-induced power losses and introduce new insights into the improvement of current strategies for industry-relevant module interconnection schemes.