Groove Geometry Research Articles

Evaluation of through-thickness residual stresses in conventional and narrow grooved stainless steel welds

Thick AISI 304L stainless steel plates were welded using the gas metal arc welding process, and through-thickness residual stresses were evaluated by finite element simulation and the deep hole drilling technique. 3D moving heat source-based thermo-mechanical models were implemented to evaluate through-thickness residual stresses. The effects of the weld groove geometries and external restraints on the pattern of through-thickness residual stresses were studied. The maximum magnitude of locked-in residual stresses was recorded beneath the top surface, at a depth of around 6 mm. In comparison to conventional weld groove, the narrow weld groove configuration exhibited a 20–40% reduction in peak residual stresses. A significant rise in residual stresses was observed in constrained welds. The effect of the yield strength of the filler material on the evaluation of the through-thickness residual stress distribution in the course of finite element modeling was illustrated. The evolution of through-thickness residual stresses was also assessed concerning each weld pass.

Enhanced Performance of Fabry–Perot Tunable Filter by Groove Geometry Design of Double Folded Cantilever

Different grooves (v-shaped groove, trapezoidal groove and rectangular groove) are introduced into the traditional double-folded cantilever of Fabry–Perot Tunable Filter (FPTF) for the optical sensor. Using finite element simulation, the influence of groove geometry on the voltage–displacement relationship, stress distribution and reflector flatness of the FPTF are studied. The results show that the reflector supported by double folded cantilever with rectangular groove has a maximal displacement of 0.88 μm under 8 V driving voltage, which is 95% higher than double folded cantilever without groove. At 0.5 μm, the best flatness (warping angle of reflector) is only 0.0032° for reflector supported by double folded cantilever with rectangular groove, where the generated maximal stress in the double folded cantilever is 8.49 MPa. Compared with other double folded cantilevers with v-shaped groove, trapezoidal groove and without groove, the unique properties of double folded cantilever with rectangular groove are attributed to lower elastic modulus. The double folded cantilever with rectangular groove enlarges displacement results in wide range of bandpass wavelength of FPTF, and a best flatness to enhance the monochrome of bandpass wavelength.

Mesh-based tool path calculations for tubular joints

Manufacturing of large steel tube structures is faced with excessive welding, fit-up and rework times in tube joints, due to various types of deviation from nominal shape of the tubes. This article presents a procedure and geometry calculus for generating cutting and welding paths based on measured geometries. The procedure poses the two measured meshes as per construction specification and invokes a mesh intersection procedure to get the mesh intersection path; performs an optional smoothing; interpolates the smoothed path to a specified angular resolution; estimates the two surface normal vectors and the two surface tangents in the plane spanned by the normals at each interpolation point; calculates the cutting tool and welding tool approach directions for obtaining the specified welding groove geometry at each interpolation point; and finally stores all the data parameterized by the interpolation angle. Illustrations of results with both synthetic, representative meshes and meshes obtained from scanning of actual tubes at the shop-floor at a manufacturer are presented. The reference implementation for the developed software tool is based on Python and uses the mesh modeller from the 3D creation suite Blender as platform.

Investigation on the modeling and dynamic characteristics of a fast-response and large-flow water hydraulic proportional cartridge valve

In large-power and high-pressure hydraulic systems, the maximum instantaneous flow rate is often several thousand liters per minute. Normal proportional valves are often difficult to meet their requirements for large flow rate and fast response at the same time. And the leakage of hydraulic oil will seriously pollute the environment. Therefore, a novel water hydraulic proportional valve with fast response and high flow capacity is presented for the large transient power hydraulic system in this paper. The valve utilizes a two-stage structure with two 2/2-way water hydraulic proportional valves as the pilot stage and a cartridge poppet valve as the main stage to achieve fast-response and large-flow capacity simultaneously. A detailed and precise nonlinear mathematical model of the valve considering both structural parameters and flow force is developed. A comprehensive performance optimization has been carried out, which can be mainly divided into computational fluid dynamics simulation optimization based on reducing flow force and multi-objective optimization based on genetic algorithm. The effects of double U-grooves' parameters on the flow force (flow-induced loads) have been studied in detail by numerical simulation. Through the grooves geometry optimization, the maximum flow force can be reduced by 10%. Then, the influences of structure parameters on the performance of step response have been studied, and the optimal parameters of the valve have been obtained by multi-objective optimization based on genetic algorithm. The maximum overshoot has been reduced from 15% to 6% (about 60%) and the adjusting time has been reduced from 58 ms to 48 ms. The dynamic characteristics of the valve have been improved effectively. Finally, a test apparatus which has the ability to provide transient large flow is built. The accuracy of simulation model and optimization design method is verified by test results.

Effect of scratch direction on densification and crack initiation of optical glass BK7

It is known from nano-indentation studies that optical glass material undergoes a certain densification deformation during ductile scratching. In this study, nano-scratch experiments were conducted under different scratch directions (face-forward and edge-forward of the same indenter) and normal loads to explore the differences in densification of material in ductile removal mode. Furthermore, inherent differences in densification deformation were utilized to explore the effect of scratch direction on the crack resistance (CR) or ductile-to-brittle transition (DBT) of material under brittle removal mode. Based on quantitative evaluation of densification deformation induced by indentation and scratching, a high-temperature annealing procedure was employed to determine the changes of the scratch groove geometry and volume before and after the release of the scratch-induced densification deformation under different scratch directions (edge-forward and face-forward). The geometric parameters of scratch grooves under edge-forward and face-forward directions showed similar changes after annealing. It is found that in ductile removal mode, the densification ratio to the total scratching volume in edge-forward scratching is greater than that in face-forward scratching. It is likely that the greater densification deformation of edge-forward scratching led to stronger crack resistance and smaller tensile residual stress. Therefore, lateral cracks are more likely to initiate and propagate under face-forward scratching under brittle removal mode, which is consistent with the experimental results.

Application of machine learning to predict the product quality and geometry in circular laser grooving process

Micro-grooves have various applications in different industries. Circular laser grooving is a new method for manufacturing micro-grooves on the circumference of cylindrical parts. In this process, the selection of appropriate parameters to reach experimentally the desired groove aspect ratio along with minimum dross formation requires tremendous efforts. Here, the role of a decision-making technique, similarly machine learning is highlighted to evaluate the significance of process inputs and provide the appropriate model for prediction concerning the input parameters. The experiments were conducted with the various inputs such as workpiece rotational speed, laser beam position, duty cycle, power and frequency. The outputs are the groove geometry in terms of width and depth of the circular groove as well as the groove quality considering the dross formation. Then, Random Forest (RF) technique was utilized to derive the most influential inputs on the outputs. The RF analysis revealed that the rotational speed, laser position and duty cycle are the most decisive process parameters in the groove geometry and groove quality. Also, the enhancement of the assist gas pressure does not improve the process outputs according to the results of RF analysis.

Experimental Study on Energy Consumption of Rock Cutting under Different Groove Geometry

Abstract The Polycrystalline Diamond Compact (PDC) cutter is a kind of rock breaking tool that is widely used in oil and gas exploitation. PDC cutter directly contacts with the rock during the process of the rock cutting. Therefore, it is of great significance to investigate the rock breaking mechanism of the PDC cutter to improve the rock breaking efficiency. This article sets up a test bench of rock cutting, which consists of a single cutter, high-speed cameras, and several data collectors, to monitor the cutting force, mechanical specific energy, energy dissipation, and the chip formation process. The results show that a frequent fluctuation of the value of the tangential force is related to the fly leaping phenomenon and particle size of debris. The ratio coefficient of the cross section describes the relations of energy dissipation between different sections. While changing the distribution density of the PDC cutter on the drilling bit, a minimum value of rock-breaking specific work will appear, and the rock breaking efficiency can be improved. The arc length back virtual work and the virtual crushing work express the storage and release of rock internal energy, which can explain the fracture phenomenon from the aspect of energy dissipation.

Effect of weld groove volume on the mechanical and metallurgical performance of GTA welded martensitic stainless steel (AISI 410 SS) joints

Effect of three groove volumes on mechanical and metallurgical performance of 6 mm thick butt welded martensitic stainless steel (AISI 410 SS) joints was studied. Three weld groove geometries (using a single-V design) that resulted in the ratio of theoretical volumes (prior to welding) as 1:1.2:1.3 were made in 6 mm thick cold rolled AISI 410SS base plates. Metallurgically compatible filler was used to weld these plates using a suitable combination of gas tungsten arc welding parameters such that sound quality in these joints was achieved. The findings indicate that variation in the weld groove volume exerts a significant influence on the tensile and impact energy absorption behaviour of these joints, besides resulting into significant microstructural changes across different zones of the weldments. Amongst all welds, the smallest groove volume of 7358.7 mm3 possessed the maximum ultimate tensile strength of 758.34 MPa. Post weld heat treatment of 750˚C/70 min. followed by slow/furnace cooling enhanced the tensile strength of these joints but the ductility reduced to a marginal extent. Microhardness values decreased due to post weld heat treatment as microstructural grain coarsening occurred in these welds. Thermocouple measurements made across different welds indicate that small groove volume resulted into higher cooling rates. Maximum impact toughness of 110.6 J and 123.8 J was possessed by the joints made using the smallest groove volume in the as welded as well as the post weld heat treated condition respectively. This study establishes that smaller weld groove volume should be preferred for improved metallurgical as well as impact toughness performance of these welds.

Effects of laser microtextured surfaces in condensation heat transfer

Some major application areas of microtextured surfaces are found in the energy, biomedical, transportation and aerospace sectors. In relation to the energy sector, microtextured surfaces provide an energy efficient and cost-effective passive mechanism for increased heat transfer during matter’s phase change in energy recovery systems. This study explores the viability of laser microprocessing as an attractive manufacturing route for generating textured surfaces and compares with the results from a previous study involving microgeometries created by micro-wire electro discharge machining (µWEDM). Two types of stainless steel SS316L insert, produced via casting followed by machining, as well as by selective laser melting (SLM), were used as the workpieces. A number of microtextured geometries were produced on the workpieces’ planar top faces using a nanosecond fibre laser (1064 nm wavelength) operating with 0.066 and 0.25 mJ laser energy, 10 and 80 kHz frequencies, 400, 600 and 700 mm/s beam scanning speeds, and 25 and 60 µm set distances between the unidirectional textured grooves/laser tracks. The textured surfaces were subsequently scanned using a 3D optical scanner for evaluating the depth and width of the geometries. The scanning electron micrographs showed comparable groove geometries produced via both laser and µWEDM. During condensation experiments, the laser textured surfaces typically exhibited higher differential temperature, ΔT (~11.9-28.9%) with respect to the unstructured specimens. Additionally, the textured SLM samples generally showed greater heat transfer quality (~3.7-5.7% higher ΔT) than their cast and machined counterparts.

Welded Combined Rotor for the Steam Turbine K-325-23.5

The development data of the welded combined average-pressure rotor for the steam turbine of a new generation К-325-23.5 produced by JSC “Turboatom” have been given. To develop it, we used the data given in experimental-&-engineering and research papers devoted to the selection of the rational forms of individual discs and the loci of circular cofferdams with welded seams to provide an acceptable level of stresses, which is one of the main requirements to be met when designing welded rotors. The mode of deformation of some options of a new rotor structure was defined using the method of finite elements and the software of IPMach of the National Academy of Sciences of Ukraine. In addition to the stresses that arise under the action of centrifugal forces and thermal stresses we took into account during our computations low bending alternating stresses caused by weight loads and these stresses are very dangerous due to their cyclic character. When combined with tensile stresses caused by centrifugal forces at the bottom run of welded seams, these can result in an increased amount of possible defects. The experimental-&-engineering research done by us allowed for the transformation of aggravating stresses caused by centrifugal forces at the bottom run of welded seams into compressive stresses. A special research was done to select the weld groove geometry, electrodes, the weld technology and thermal treatment modes after the welding to remove residual stresses. Welded specimens with the welded seams of a different configuration (type of weld groove geometry) and the specimens cut out of the welded seams of the end parts of full-scale model were subjected to fatigue tests. A high workability and unavailability of drawbacks that are peculiar for the rotors with capped discs individualize this type of rotor advantageously in comparison with the latter. Expensive balancing work requires the reduction of start operations by a factor of two. A combined “composite” rotor behaves in a more consistent manner with the spin up during the transition across critical rotation frequencies and at rated revolutions; a smoother operation is observed.

Optimization of Flat Ends in Pressure Vessels.

The application of flat ends in pressure boilers is inevitably associated with the presence of stress concentration, which is observed in the vicinity of the junction of the cylinder and the closing flat plate. The analyzed flat end plates with stress relief grooves fall into the group of solutions recognized by the respective Standards of Calculations of Pressure Vessels. Unfortunately, no clear evidence is given in the Standards on how to choose the best groove parameters. This opens up the problem of the optimal choice of the groove parameters providing a minimum stress level. Even for the optimal values defining the stress relief groove geometry, certain plastic deformations are observed in the groove area for materials which exhibit elastic-plastic properties. Such a situation is completely unacceptable during exploitation, and a suitable reduction of the operating pressure is necessary. This paper discusses the effectiveness of other designs for flat ends used in pressure vessels. The proposed modifications took the form of external ribs applied around the top of the endplate circumference. The dimensions of these ribs were set using parametric optimization. The results of the study encouraged the authors to perform a more general analysis with the use of topology optimization. The results of all performed studies proved that the reduction of stress concentration and the full elimination of plastic deformation are possible. All numerical calculations were made using the finite element code (FEM), Ansys.

Evaluation of a bone groove geometry for fixation of a cochlear implant electrode.

Electrode migration is a rare, but relevant complication in cochlear implant (CI) surgery. An effective countermeasure is to create a bone groove in the facial recess to secure the electrode lead. We use this method routinely since 2013, but still experienced sporadic electrode migration events most likely due to an improper surgical execution. The aim of this study was to determine the optimum groove geometry. Grooves of defined geometry were created in specimens of fresh porcine femur compacta by use of a CNC milling machine. Electrode dummies were fixed in the groove and then exposed to tensile stress. Force measurements were carried out to examine the effect of groove diameter and opening width on the holding force. The mechanical impact on the electrode cable during insertion into the groove was recorded and the electrode lead was examined under microscopic magnification to assess potential structural damage. Optimum groove geometry (diameter 1.10mm, opening width 0.90mm) ensured an average holding force of 830mN which is equivalent to the established fixation by use of a titanium clip. None of the microscopic inspections revealed any morphological deterioration of the electrode lead. The fixation of a CI electrode in a bone groove in the facial recess appears to be effective and safe. Furthermore, this method does not require additional costs or foreign material. The optimum geometry defined in this study helped us to refine our surgical standard produce and to generate more consistent results.

Influence of micro grooves of diamond tool on silicon cutting: a molecular dynamic study

ABSTRACTDuring single-point diamond turning of hard and brittle materials, tool wear is a dominant factor that influences machinability. In the wear process, micro grooves on the flank face is an important character of tool wear, which leads to the formation of subcutting edges and the ductile to brittle transition. In this paper, classical molecular dynamic simulations of nanometric cutting of silicon by a diamond tool with V-shape grooves were carried out to explore the effect of groove geometry on the workpiece and tool integrity. The evolution of tool wear and machined surface integrity was discussed. Simulation result shows that grooves have a significant influence on the stress and temperature distributions of the tool, which has a great influence on tool deterioration. Grooves with sharp edges will lead to severe tool wear and bring deep subsurface damage of the machined surface. However, the subsurface damage of the machined surface can be restrained with blunt grooves since the pressure is reduced. With a comprehensive understanding and controlling of groove, tool wear can be suppressed and high-quality surface can be achieved.

Air-water meniscus shape in superhydrophobic triangular microgroove is dictated by a critical pressure under dynamic conditions

We bring out a critical force for shape transition of air-water meniscus in superhydrophobic triangular microgrooves under dynamic conditions, considering an intricate interplay of the viscous and capillary forces. A closed form theoretical expression for the critical force depicts its explicit dependence on the groove geometry and relevant physical properties. A negative value of this critical force denotes a convex meniscus shape, whereas a positive value signifies a concave meniscus shape. Considering the shape transition, the critical pressure is further interpreted to denote a physical condition under which the meniscus is nontrivially flat, despite the existence of surface tension forces. Our analysis opens up a paradigm by which the meniscus shape in a groove can be virtually controlled at will, consistent with the specific requirements such as drag reduction, as demanded by the application on hand.

Unconformities, neptunian dykes and mass-transport deposits as an evidence for Early Cretaceous syn-sedimentary tectonics: new insights from the Central Apennines

This work presents the results of a geological mapping project performed on the Narni-Amelia Ridge (Central Apennines, Italy). Fieldwork was aimed at defining the rift and post-rift architecture of the Jurassic to Cretaceous part of the Umbria-Marche-Sabina basin succession, which is characterised by Jurassic rift-related pelagic carbonate platform (PCP)/basin systems. While the effects of the Early Jurassic rifting are well documented in the regional literature, a phase of post-rift extensional tectonics in the late Early Cretaceous is a relatively under-investigated subject. This normal faulting was apparently widespread at a super-regional scale, and the Narni- Amelia Ridge carries direct and indirect evidence for this episode of revived deformation:(i) the occurrence of limestone megabreccias (Mt. Cosce Breccia) resting unconformably, through an erosional surface, on a Jurassic (and Cretaceous) horst-block. Stepped unconformities are associated with spur and groove geometries of the escarpment, suggesting topographic backstepping due to rock- fall processes;(ii) millimetre to decametre-scale neptunian dykes and sills made of Mt. Cosce Breccia and of Maiolica pelagites. These fractures cut the footwall-block of Cretaceous faults, made of Calcare Massiccio Fm (Hettangian), sub-orthogonal to its master- bedding. Dykes are associated with tension gashes filled with chert (silicification of fracture zones). The steep walls of those neptunian dykes filled with Maiolica-type deposits also exhibit a thin chert band;(iii) the onlap of Aptian-Albian Marne a Fucoidi Fm on the Hettangian Calcare Massiccio Fm. This is an unicum in the whole Umbria- Marche-Sabina Domain;(iv) the presence of mass-transport deposits (slumps and debris flows) in the uppermost part of the Maiolica Fm and lower part of the Marne a Fucoidi Fm.These stratigraphic anomalies are collectively interpreted as the products of normal faulting, which caused the retreat of the original Jurassic margins of the PCPs, rejuvenating the submarine palaeotopography. A middle Barremian age for this phase of syn- sedimentary extension is indicated by the nannofossil assemblage of Maiolica-type facies sampled from the Mt. Cosce Breccia and from the neptunian dykes.

Discontinuous grooves in thrust air bearings designed with CAPSO algorithm

Spiral groove thrust air bearings suffer from low load capacity. Although there have been studies on optimizing the groove geometry of spiral groove thrust air bearings to enhance the load capacity, all of them found so far have focused on continuous grooves only. Here, a novel groove optimization method, which allows the flexibility of generating either continuous or discontinuous grooves, is introduced for maximizing the load capacity of spiral groove thrust air bearings. In the proposed method, computational fluid dynamics is combined with the chaos-enhanced accelerated particle swarm optimization algorithm to search for the optimal groove geometry. A case study is given where the optimization of an initial spiral groove thrust air bearing is implemented. The optimized grooves are found to be discontinuous and of new geometry. Numerical analysis shows that the optimized discontinuous grooves can achieve higher load capacity than the optimized continuous grooves, the conventional herringbone, and the initial spiral grooves. The effect of the proposed method is further verified in experiments.

Control of short-pulsed laser induced periodic surface structures with machining -picosecond laser nanotexturing with magnetic abrasive finishing-

An active area of research is the altering of surface functions (e.g., wettability and cell adhesion) by controlling fine surface structures such as laser-induced periodic surface structures (LIPSS). It has been found that micrometer-scale grooving (produced, for example, using ultraprecision cutting) followed by short-pulsed laser irradiation can result in efficient LIPSS coverage of a large area. However, micrometer-scale grooves can remain on the surface after short-pulsed laser irradiation. In this paper, to clarify the phenomenon and processing principle of groove-assisted short-pulsed laser irradiation, a finite-difference time-domain simulation is developed and experiments are conducted using 304 stainless steel and nickel-phosphorus (Ni–P) plating layer substrates. The use of magnetic abrasive finishing (MAF) is proposed for fabricating sub-micrometer-deep straight grooves with various peak-to-peak distances (pitch length) prior to the short-pulsed-laser irradiation. The subsequent short-pulsed-laser irradiation produces sub-micrometer-deep straight structures superimposed on the MAF-produced surface. While the pattern and depth of LIPSS are influenced by the groove depth made by MAF prior to the short-pulsed laser irradiation, the pitch length of LIPSS is dependent on the laser wavelength. This demonstrates the ability of MAF to produce grooves that guide the LIPSS and the efficacy of the developed method for fabricating fine LIPSS. The geometry of the sub-micrometer deep grooves—made prior to the short-pulsed laser irradiation—is the dominant factor in determining the pattern and geometry of the LIPSS.

Effect of groove structure on penetration performance of annular grooved projectiles impacting metal targets

With the continual development of advanced ammunition, a study on the effect of groove geometry on penetration performance is conducted. Based on ogive nose, an annular grooved projectile (AGP) was proposed and can generally be divided into two types (groove A and B) when considered the transition ways between groove and projectile nose. Difference in groove structures result in various penetration performance. According to dynamic cavity expansion theory and FEM simulation, the nose shape coefficient N*, depth of penetration (DOP) and acceleration curves were analysed comparatively. The results also indicated that the firm embedded behaviour of groove B nose projectile is mainly due to the filling-material in the groove rather than the friction on contact surface, unlike traditional nose shape. Furthermore, a good agreement in calculation and simulation proved the analysis method was reasonable and feasible, and would have application potential in new concept warheads.

Normal shock wave attenuation during propagation in ducts with grooves

Experimental investigations and numerical simulations of normal shock waves of different strengths propagating inside ducts with roughness are presented. The roughness is added in the form of grooves. Straight and branching ducts are considered in order to better explore the mechanisms causing attenuation of the shock and the physics behind the evolution of the complex wave patterns resulting from diffraction and reflection of the primary moving shock. A well-established finite-volume numerical method is used and further validated for several test cases relevant to this study. The computed results are compared with experimental measurements in ducts with grooves. Good agreement between high-resolution simulations and the experiment is obtained for the shock speeds and complex wave patterns created by the grooves. High-frequency response time histories of pressure at various locations were recorded in the experiments. The recorded pressure histories and shock strengths were found in fair agreement with the two-dimensional simulation results as long as the shock stays in the duct. Overall, the physics of the interactions of the moving shock and the diffracted and reflected waves with the grooves are adequately captured in the high-resolution simulations. Therefore, shocks propagating in ducts with different groove geometries have been simulated in order to identify the groove shape that diminishes shock strength.

Numerical and experimental research on engagement process of wet multi-plate friction clutches with groove consideration

A numerical model is established to investigate the effects of the influencing factors such as design parameters and operating conditions on the performance and behavior of the engagement process of the wet clutch based on the Navier–Stokes equations, contact mechanics, and heat transfer theory. A finite element contact model called KE contact model is used to analyze the rough contact during engagement process and thermal effect on the viscosity is considered based on heat transfer theory. The integration of the grooving into the simulation and the method of coupled finite element by domain decomposition of groove and ungrooved areas are put forward to facilitate the analysis. The experimental results agree well with the numerical model which takes the normal pressure, the temperature of ATF, relative revolution speed, the permeability and the groove geometry into account. The results of numerical simulation and the experiment indicate that the applied pressure not only affects the engagement time, but also has influence on the value of the engagement torque. Besides, the engagement time is roughly proportional to the relative revolution speed. The influencing factors such as the temperature of ATF, the permeability, grooves, the torque judders and effects of PID control parameters are also discussed in the paper. The performance and behavior of the engagement of the wet clutch were studied by two methods of numerical calculation and experimental research, which make the working process of the wet clutch more detailed.