Position Of Groove Research Articles

Development of automation and monitoring methods for narrow-gap hot-wire laser welding using camera images

AbstractIn this study, an image-based method was developed for hot-wire laser narrow gap welding. The welding process was monitored based on image information processed using semantic segmentation, a method of classifying images by pixel. To control the welding position, an experimental system was configured that automatically follows the welding position by recognizing the position of the welding groove from the image during welding. In monitoring weld defects, a method was developed to predict the lack of fusion occurring on the wall surface using brightness information near the wall surface. For the lack of fusion occurring at the bottom of the groove, a defect detection method was developed by monitoring the molten pool shape using semantic segmentation. Defects were generated by intentionally reducing the laser power, and the defects were monitored from images taken during processing. In the unstable state where the laser power was reduced, the shape in front of the molten pool became unstable, and the occurrence of defects was monitored by capturing the shape change. In conclusion, this research made it possible to control and monitor the welding process with a single camera.

Laser treated novel textures for adhesion performance of aluminum alloy joints exposed to corrosion

The aim of this study was to investigate novel laser-treated structures designed to improve the adhesion performance and corrosion resistance of AA7075-T6 bonded joints. The spacing, position, and surface area parameters of the laser-treated grooves were investigated to understand their role in adhesion performance even under corrosion conditions. Laser-treated surfaces were analyzed using microscopic, topographic, and chemical methods to determine their scientific contribution to adhesion and corrosion performance. Laser-treated adherends were also bonded to mechanically test their bond strength both before and after exposure to corrosion for varying periods of time. Roughness and therefore surface area have a significant effect on adhesion performance; however, it is worth noting that the best adhesion performance both before and after corrosion exposure was achieved when the required surface area was properly designed and, laser treated according to the salt water exposure directions to inhibit its diffusion into the adhesion interface. The performance of the novel laser-treated structures in terms of adhesion performance under corrosive atmosphere was also supported by failure analysis. The mixed failure mode was significantly shifted to the cohesive failure mode, especially for bonded joints with box-type laser-treated structures.

Grating-based metasurfaces for ultra-narrow near-infrared bandpass filtering with wide out-of-band suppression

Here, we present a straightforward strategy for designing silicon grating-based metasurfaces tailored for narrow near-infrared bandpass filtering. By selecting appropriate structural parameters for the grating and including periodic groove perturbations within each grating slit, transverse guided mode resonances (GMRs) propagating perpendicular and parallel to the grating slit are created to provide wide out-of-band suppression and high-Q filter responses, respectively. The destructive and constructive interference between radiations from groove perturbations are then introduced to eliminate all GMRs except one, producing a single-band bandpass filter. Simply adjusting the period of the groove perturbations allows precise tuning of the passband’s central wavelength across the operational spectral range from 1350 nm to 1750nm, throughout which the passband exhibits a Q-factor exceeding 9,000 and the attenuation level outside the passband remains below 1%. Furthermore, our proposed narrow bandpass filters are found to be robust against the potential fabrication imperfections, such as variations in groove size and position.

Surgical treatment of a bilateral superficial flexor tendon luxation

A two-year-old, male, neutered, crossbreed dog was presented to Anderson Moores Veterinary Specialists with a history of bilateral pelvic limb lameness. Right pelvic limb lameness was first noted 3 months prior to presentation. Right superficial digital flexor tendon tendinopathy and associated bursitis were diagnosed based on computed tomography scans performed by the referring veterinarian. Conservative management, consisting of analgesia and exercise restriction, did not resolve the clinical signs and referral was sought. At the time of presentation, left pelvic limb lameness of 1 week's duration was reported additionally by the owner. Clinical examination and imaging findings were consistent with bilateral superficial digital flexor tendon luxation. Surgical management consisting of relocation of the superficial digital flexor tendon into the central position of the calcaneal groove alongside a retinaculoplasty and calcaneoplasty was performed bilaterally. Half-cast dressings were placed on both pelvic limbs and were removed after 3 weeks due to mild soft tissue complications. The patient was cage rested for 5 weeks in total. The re-examination 8 weeks after surgical treatment revealed that the tendons remained stable and could not be manually luxated.

Cellular Repair of Synthetic Analogs of Oxidative DNA Damage Reveals a Key Structure-Activity Relationship of the Cancer-Associated MUTYH DNA Repair Glycosylase.

The base excision repair glycosylase MUTYH prevents mutations associated with the oxidatively damaged base, 8-oxo-7,8-dihydroguanine (OG), by removing undamaged misincorporated adenines from OG:A mispairs. Defects in OG:A repair in individuals with inherited MUTYH variants are correlated with the colorectal cancer predisposition syndrome known as MUTYH-associated polyposis (MAP). Herein, we reveal key structural features of OG required for efficient repair by human MUTYH using structure-activity relationships (SAR). We developed a GFP-based plasmid reporter assay to define SAR with synthetically generated OG analogs in human cell lines. Cellular repair results were compared with kinetic parameters measured by adenine glycosylase assays in vitro. Our results show substrates lacking the 2-amino group of OG, such as 8OI:A (8OI = 8-oxoinosine), are not repaired in cells, despite being excellent substrates in in vitro adenine glycosylase assays, new evidence that the search and detection steps are critical factors in cellular MUTYH repair functionality. Surprisingly, modification of the O8/N7H of OG, which is the distinguishing feature of OG relative to G, was tolerated in both MUTYH-mediated cellular repair and in vitro adenine glycosylase activity. The lack of sensitivity to alterations at the O8/N7H in the SAR of MUTYH substrates is distinct from previous work with bacterial MutY, indicating that the human enzyme is much less stringent in its lesion verification. Our results imply that the human protein relies almost exclusively on detection of the unique major groove position of the 2-amino group of OG within OGsyn:Aanti mispairs to select contextually incorrect adenines for excision and thereby thwart mutagenesis. These results predict that MUTYH variants that exhibit deficiencies in OG:A detection will be severely compromised in a cellular setting. Moreover, the reliance of MUTYH on the interaction with the OG 2-amino group suggests that disrupting this interaction with small molecules may provide a strategy to develop potent and selective MUTYH inhibitors.

A guidance system for robotic welding based on an improved YOLOv5 algorithm with a RealSense depth camera

Vision-based automatic welding guidance technology plays an essential role in robotic welding. A laser vision sensor (LVS) relies on manual intervention to guide the robot when near the workpiece, which reduces the autonomy of the welding robot and productivity. To solve this problem, a robot welding guidance system based on an improved YOLOv5 algorithm with a RealSense Depth Camera was proposed. A coordinate attention (CA) module was embedded in the original YOLOv5 algorithm to improve the accuracy of weld groove detection. The center of the predicted frame of the weld groove in the pixel plane was combined with the depth information acquired by a RealSense depth camera to calculate the actual position of the weld groove. Subsequently, the robot was guided to approach and move over the workpiece. Then, the LVS was used to guide the welding torch installed at the end of the robot to move along the centerline of the weld groove and complete welding tasks. The feasibility of the proposed method was verified by experiments. The maximum error was 2.9 mm in guiding experiments conducted with a distance of 300 mm between the depth camera and the workpiece. The percentage error was within 2% in guidance experiments conducted with distances from 0.3 to 2 m. The system combines the advantages of the depth camera for accurate positioning within a large field and the LVS for high accuracy. Once the position of the weld groove of the workpiece to be welded has been determined, the LVS combined with the robot can easily track the weld groove and realize the welding operation without manual intervention.

Impact Characteristics of a Bidirectional Pneumatic DTH Hammer for Unconsolidated Formations

With advantages of high efficiency and low cost, DTH hammer drilling has been highly applied in various drilling projects. When drilling in unconsolidated formations, it is prone to drilling accidents such as drilling tools sticking or burying. Thus, a bidirectional pneumatic DTH hammer is designed to drill boreholes using forward impact and release sticking drilling tools using backward impact. With a floating gas distribution mechanism, impact strokes of the DTH hammer piston can be changed when flat keys are in a different position of the key grooves on the gas distribution shaft. In drilling mode, the piston has a larger impact stroke and can impact the anvil at high speeds to drive the bit breaking rocks. When drilling tools become stuck, by changing to a smaller impact stroke, the piston can impact backward on the gas distribution valve to break rocks above the DTH hammer so sticking drilling tools can be released. According to the structure and working principle of the bidirectional pneumatic DTH hammer, a physical model based on the pneumatic transmission circuit is established; then, a simulation model is built with pneumatic transmission module components in software of SimulationX 4.1 student version. Piston velocities, displacements, and impact energy are analyzed, with main factors including piston mass, total weight of the DTH hammer, compressed air pressure, and backward impact stroke being considered. Analysis results show that working characteristics of the DTH hammer are fairly affected by piston mass and compressed air pressure. Based on the changing laws of the impact frequency, peak of impact velocity, and impact energy, a piston mass of 18 kg, total weight of 125 kg, gas source pressure of 2.2 MPa, and lifting distance of 60 mm for backward impact were recommended. To verify the performance of the bidirectional pneumatic DTH hammer, field experiments were carried out in the gravel stratums. The bidirectional DTH hammer was in good working condition and the maximum drilling rate can reach up to 1.5 m/min. By lifting the DTH hammer away from the bottom of the borehole and pumping compressed air, the DTH hammer piston could achieve a high frequency backward impact. There are no drilling tools’ sticking or burying accidents in the drilling experiments. The bidirectional pneumatic DTH hammer can effectively drill boreholes in loose formations and deal with drilling tools’ sticking or burying accidents.

Feature information extraction method for narrow gap U-type groove based on laser vision

The precise measurement of weld groove position and geometric dimensions serves as the foundation for predicting and planning welding strategies and process parameters. The steep sidewalls of narrow gap U-type grooves pose challenges for sensing and detection during the welding process. This paper presents a feature information extraction method for narrow gap U-type grooves based on laser vision technology. Firstly, the image acquisition system is calibrated using the incident plane of the laser beam. Subsequently, a digital image processing technique is employed to enhance the collected images, combining a 3D spatial domain enhancement algorithm with a laser stripe image refinement method based on Euclidean distance transformation. Finally, the transverse and vertical positions of the groove, as well as its geometric features such as width, depth, assembly gap, and misalignment, are computed and measured using feature point positioning. The proposed algorithm is experimentally verified for its accuracy, robustness, and real-time performance. The results indicate that the method effectively suppresses unevenness in laser stripe brightness and mitigates random noise in the captured images. The average measurement errors for transverse position, vertical position, width, depth, assembly gap, and misalignment of the groove are 0.0857 mm, 0.0987 mm, 0.1664 mm, 0.2216 mm, 0.0935 mm, and 0.0997 mm, respectively. Furthermore, the average image processing time per frame is 58 ms, meeting the requirements of pre-weld detection in arc welding.

A mixed-lubricated friction model of water lubricated bearing based on fractal theory

To the water lubricated bearing, its mixed-lubricated friction model is generally established based on the traditional statistical model, whose accuracy is not high due to the inaccurate characterization of surface topography. Therefore, this paper employs the fractal theory that has scale-independent characteristics and high precision to characterize the surface topography of the bearing and journal, and then establishes the fractal contact model of asperity, combining the average Reynolds equation of the film, proposes a mixed-lubricated friction model based on fractal theory. The scanning experiments of surface topography are carried out to obtain the fractal parameters and measurements of the friction coefficient are performed to verify the effectiveness of the proposed mixed-lubricated model. Subsequently, the proposed mixed-lubricated friction model is employed to analyze the effects of the number of groove, the position of groove and the fractal parameters on the lubrication and friction characteristics of the water lubricated bearing. Results indicate when the grooves are in the non-main load-carrying regions, the friction characteristics of the bearing slightly changes, and the lower surface roughness is beneficial to improve the lubrication and friction properties of the bearing.

Low-velocity impact of square conical gradient aluminium foam-filled automobile energy-absorbing boxes

In this paper, the low-velocity impact and lightweight design of the square conical gradient aluminium foam-filled automobile energy-absorbing boxes (EABes) is numerically studied. Firstly, the validity of the finite element calculation model is verified by comparing with the experimental results. Then, the influences of the conical bottom angle, tube-wall thickness, the number, position, height and depth of induction grooves, and the parameters of gradient foam on the energy absorption properties of the EABes under axial low-velocity impact are studied. After that, the mitigation and energy absorption of square conical gradient aluminium foam-filled automobile EAB are optimised. The results indicate that the aluminium tube-wall thickness has no obvious effect on improving the energy absorption properties of the EAB, and other factors have good effects on improving the energy absorption properties of the EAB. Compared with the constant cross-section EAB before optimisation, the peak impact force (F max) of the finally optimised square conical gradient aluminium foam-filled automobile EAB reduces by 22.4%, and the specific energy absorption (SEA) increases by 59.8%. The investigation is helpful for the design of the square conical gradient aluminium foam-filled automobile EAB.

Reducing phase errors in multimode interference coupler by side grooves formed on its top surface.

The performance of multimode interference (MMI) couplers is limited by the presence of phase errors that represent the deviation of the propagation constants of the modes from the quadratic dependence on their order. In this work, we propose a simple and effective method for reducing the phase errors of spatial modes to a relatively high order by forming rectangular grooves near the side edges of the MMI coupler along its entire length. The influence of the groove dimensions and position on the propagation constants of higher-order modes is analyzed using the perturbation method and strict vector simulations for high- and medium-index contrast material platforms. Through numerical simulations, we demonstrate the effectiveness of the proposed method in improving the performance of air-cladded dual-mode (T E 0 and T E 1) MMI-based 50:50 and 100:0 splitters for 1.31µm wavelength made of medium- and high-contrast materials, T i O 2:S i O 2/S i O 2 and S i/S i O 2, respectively.

Influence of Uneven Subgrade Frost Heave on Deformation and Damage of CRTSIII Slab Track

The problem of uneven frost heave deformation of high-speed railway subgrade in seasonal freezing areas seriously affects the service state and service life of slab track structures and threatens the safe operation of high-speed vehicles. Based on the damage plasticity theory of concrete, in this study, an analytical model is established for CRTSIII slab track with damage plasticity and reinforcement. The influences of various frost heaving parameters on track structure deformation, interlayer seam, as well as the stress and damage behaviors were analyzed in detail. The results show that, as compared with a linear elastic model, the damage plastic model better reflects the softening behavior and stress attenuation of track structure concrete after reaching its tensile strength. The deformation and the interlayer seam reach their maximum values when the frost heaving wave peak acts at the position that is one-sixth of the base length from the edge of the concrete base. When the frost heaving wave peak acts on grooves at the base center, initially, the track structure is seriously damaged. The interlayer seam and damage decrease with an increase in frost heaving wavelength and increase with an increase in frost heaving wave amplitude. The interlayer seam of the track structure is more sensitive to frost heave deformation having a wavelength of less than 10 m. The extent of damage to the concrete base gradually increases with a decrease in the wave/amplitude ratio. It undergoes three stages of damage evolution: (i) no damage, (ii) upper surface bending damage, (iii) reverse bending damage. In order to improve efficiency, it is recommended, during track maintenance, to focus on the position of the central groove of the base and the position that is one-sixth of the base length from the edge of the concrete base.

Spatial structures of rf ring-shaped magnetized sputtering plasmas with two facing cylindrical ZnO/Al2O3 targets

Spatial structures of the ion flux to the substrate are measured in an rf ring-shaped magnetized sputtering plasma with two facing cylindrical ZnO/Al2O3 targets at various argon gas pressures of 0.13, 0.67, and 0.93 Pa. Spatial distributions of the Hall parameter and Larmor radius of electrons and ions are also discussed by using simulated values of the magnetic flux density. The magnitude of the ion flux for 0.13 and 0.67 Pa is of the order of 1020 m−2 s−1, while for 0.93 Pa it is of the order of 1021 m−2 s−1 at a fixed rf power of 20 W. The radial profile of the ion flux has a peak at the position of the ring-shaped groove near an rf electrode and then becomes uniform further away from the electrode at all gas pressures. It is found that the axial profile of the deviation from a uniform profile estimated from the radial profile of the ion flux has two decay characteristics (1st decay length of 13.9–17.5 mm and 2nd decay length of 52.6–66.7 mm) and their decay lengths decrease with increasing the gas pressure.

Thermohydraulic performance of new minichannel heat sink with grooved barriers

Nowadays, utilization of micro/mini channel heat sinks (MCHS) has become a popular solution for cooling of electronic systems and maintaining their operating temperature in a desired range. Increasing the contact surface area between fluid and solid zones by geometrical modifications is a promising solution that significantly affects thermal performance and heat transfer in these systems. In this paper, considering thermohydraulic performance, the effect of creating grooves on the middle-placed barriers of a minichannel heat sink is investigated to access a criterion for favorable temperature performance. Evaluating different geometrical parameters of barriers and grooves including cross section, depth and position of horizontal groove as well as vertical groove distance, simultaneous employment of optimal horizontal and vertical groove in the channel at different Reynolds numbers is studied. Outputs including channel base temperature, friction factor ratio and total thermal resistance are studied to evaluate the performance of the proposed minichannel. Results indicate that vortex formation adjacent to solid walls considerably enhances the heat transfer and variation of each geometrical parameters offers a performance enhancement. Moreover, the best thermal performance is obtained by simultaneous employment of the horizontal rectangular groove (x = 0.45 mm, y = 0.2 mm and hg = 0.6 mm) and the vertical groove (dg = 0.4 mm). In the optimal case, the channel base temperature and the total thermal resistance reduces by 11.88 K and 27%, respectively.

Wind effect on scallop domes with negative amplitude and prominence using Experimental and Numerical Study

This study investigates the wind effect on hexa-sectored scallop domes using Computational Fluid Dynamics (CFD) and wind tunnel tests. Similar to the shape of a seashell, the scallop dome is one of the most common domes used to cover large spans. The scallop dome has an additional curvature equal to its sectors compared to a base dome (spherical). Hence, it has better structural efficiency compared to a spherical dome under the same condition. The curvatures on the scallop dome create alternate “ridges” and “grooves” on it. According to the computations of the article, the grooves created on this dome in the sector, as well as their position angle to the wind direction significantly affect pressure coefficient value. Due to these differences, wind pressure on scallop domes significantly differs from wind pressure on spherical domes. The results indicate that the ridges cause negative wind pressure coefficients whose magnitude reaches a maximum of −2.0 for an angle of alignment of 30°. The analyses have been conducted through Ansys-Fluent. This study presents the equation of wind pressure coefficient in the most critical of dome groove positions. The arch created between the grooves of a scallop dome is another effective parameter on maximum negative pressure. In the case study scallop dome, if the wind effect angle is considered α = 15, the maximum deformation in the structure will be created, which is 20% higher than that of α = 0.

Design of Permanent Magnet-Assisted Synchronous Reluctance Motor with Low Torque Ripple

Permanent magnet-assisted synchronous reluctance motors (PMSRMs) have been widely used in household appliances, national defense and the military, due to their advantages of low cost and high efficiency. However, their excessive torque ripple cause a series of problems, such as high vibration and noise. To solve this problem, this paper first considers the important factor that causes the torque ripple—the cogging torque. Firstly, the generating principle of the cogging torque is analyzed, and a method combining magnetic pole migration and the stator auxiliary groove is proposed. On this basis, considering the position, width, depth, quantity and shape of the auxiliary groove, the Taguchi method is used to optimize the proposed improved structure. Finally, a new motor structure that can minimize torque ripple is obtained. Compared with the original structure, the cogging torque is reduced by 57.6%, the torque ripple is reduced by 38%, and the electromagnetic torque is only reduced by 1.6%.

Numerical investigation of flow past a circular cylinder modified with a single groove at low Reynolds number

Flow past a circular cylinder modified by grooves is one of the passive control techniques to control the drag and lift forces. The presence of grooves tends to reduce the hydrodynamic drag and lift. The aim of this work was to numerically investigate the influence of a single groove modification on a circular cylinder and how it was impacting the hydrodynamic coefficients based on its position and shape at low Reynolds numbers. Three types of grooves were considered, namely, dimple, square, and triangular, with identical width and depth which is 0.1 times the diameter. The Reynolds numbers considered were 100, 150, and 200. The computational domain was set to a blockage ratio of 0.01 after carrying out a detailed domain independence test. It was observed that the drag and lift reduction was maximum at groove location 90° with the decrements being more for the square groove shape. The viscous drag showed a decrease in its values for all the groove positions located on the flow-facing side of the cylinder; however, the pressure drag showed an increment in its values for these groove locations, and these increments were relative of larger magnitudes, thus influencing a net increase in the total mean drag when compared to the smooth case; this was evident at groove locations 120° and 150°. The vorticity patterns for the grooves located on the front side showed large irregularities in magnitude between the anticlockwise and the clockwise vortices with the groove side vortices being of larger magnitudes, and for the wake side, the irregularities were negligible. The coefficient of pressure and separation angles were also investigated. The CP vs θ plots showed discontinuity at groove locations with abrupt variations at the front face of the cylinder; for the wake side grooves, these discontinuities were low and almost coincided with the CP vs θ plots of the smooth cylinder. The grooves located at 90° showed a delay in separation and at 60° the boundary layer tends to detach earlier.

Influence of the spanwise grooves on aerodynamic characteristics of the compressor cascade and rotor under different reynolds numbers

In order to study the influence of the suction surface spanwise grooves under different Reynolds numbers ( Re) on the loss characteristics of highly loaded compressor cascade and rotor. In the present study, numerical simulations were conducted to investigate the effects of the number and position of the suction surface spanwise groove on aerodynamic performance of the cascade with the final aim to extend the findings to a highly loaded transonic compressor rotor. Besides, the influence mechanism for the performance change of compressor cascade and rotor by spanwise groove at different Re was clarified. The combination 1-2-3-4-gro was selected as an optimal structure in accordance with the data weighting criterion. The investigation illustrates that, at high Re operating conditions, the spanwise grooves force the transition of boundary layer from laminar to turbulent, which causes a large turbulent boundary layer loss and increases the overall loss. But at low Re operating conditions, the laminar separation bubble is suppressed by spanwise grooves and the aerodynamic performance is improved. At Re = [Formula: see text], the total pressure loss can be reduced by 4.63% at the angle of attack of 0°. When this group scheme was applied to the highly loaded axial compressor transonic rotor, the stability margin of the rotor can be increased by 5.62% at Re = [Formula: see text] condition. Moreover, at 20 km height condition, with the increase of rotating speed, the influence of 1-2-3-4-gro groove group on rotor stability margin is not great, but its efficiency improvement effect is gradually enhanced, which shows that 1-2-3-4-gro can effectively reduce rotor flow loss and increase its aerodynamic performance within this Re range.

Investigation on Performance of Hydraulically Expanded Joint of Titanium-Steel Clad Tubesheet.

The performance of a hydraulically expanded joint between tubesheet and titanium tube was analyzed using a finite element numerical calculation. The connection strength of Q345R tubesheet and TA2-Q345R clad tubesheet was studied using a tight expansion method. The results proved that the residual contact pressure and pullout force of the tight expansion joint of TA2-Q345R clad tubesheet were greater than those of the Q345R tubesheet. However, the residual contact pressure of the expanded joint without a groove for the TA2-Q345R tubesheet and the pullout force failed to meet the requirement of connection strength. Hence, the groove was employed on the contact surface. The influences of groove position and groove width on the connection strength of the expanded joint with grooves in tubesheet hole were studied. The results show that the residual contact pressure of the clad tubesheet of grooving in the cladding layer was higher than that of grooving in the base layer. The effect of the position of groove in the cladding layer and base layer on the residual contact pressure could be neglected. A wider groove led to a higher residual contact pressure, which increased significantly when the groove width was 4 mm.

Analysis of flow torques during opening and closing of high-frequency rotary directional control valve

A 2D high-frequency rotary directional control valve with a spool having two degrees of freedom for axial linear motion and circumferential rotation is proposed in this paper. The axial linear motion decides the maximum orifice area, and the circumferential rotation lets the orifice area change continuously. One of the known elements impacting valve function is the flow force. This paper systematically analyzes the steady and transient flow torques subjected to the valve through theoretical analysis, AMESim-Fluent joint simulation and experimental tests. The results show that: under a single variable, the flow torques of the 2D high-frequency rotary directional control valve initially increase and then decrease like the sinusoid curve with the rotation of the spool and reach the maximum when the orifice opening is 1/2, and the flow torques are always in the direction of orifice closing and want to close the orifice. When the orifice area increases, the flow torques are the resistance, preventing the spool from opening; when the orifice area decreases, the flow torques are the power, pushing the spool to close. The steady flow torques are proportional to the pressure drop. The direction of the transient flow torque is independent of the relative position of the spool groove and sleeve window, which proportional to the square root of the pressure drop, orifice area and rotational speed. The flow torques are so important in the control of valve and can not be negligible.