Hole Diameter Research Articles

An equivalent circuit approach for remnant thickness evaluation and flaw sizing using pulsed thermography

Active thermography using pulsed heating is a fast and reliable method for detecting flaws in composite and metallic materials. This paper analyzes the temperature decay that occurs immediately after flash heating the front surface of stainless steel specimens as a function of time, based on a novel application of the equivalent circuit approach (ECA). The temperature decay from the front surface is equated to the discharge of a capacitor. The ECA is based on the charging (temperature rise due to flash heating) of a capacitor, followed by its discharge (temperature decay) through a series of resistors (which depends on the conductivity of the material) and capacitance (which depends on the thermal capacitance of the layers) through which the heat is dissipated. The proposed approach analyzes the sequences of temperature data obtained at each pixel location during cooling from a step wedge and a specimen with multiple flat-bottom holes. Time constant maps derived from the analysis are used to ascertain the thickness of the step wedge, detect the flaws, and evaluate the remnant thickness of the flaws. A correlation has been established between the thickness and the time constants. The above approach has been used to estimate the diameter of the flat-bottom holes.

Adaptive Machining Method for Helical Milling of Carbon Fiber-Reinforced Plastic/Titanium Alloy Stacks Based on Interface Identification.

CFRP/Ti stacks composed of carbon fiber-reinforced plastic composites (CFRP) and titanium alloys (Ti) are widely used in aerospace fields. However, in the integrated hole-making process of CFRP/Ti stacks, the machining characteristics of various materials are significantly different, and constant machining parameters cannot simultaneously meet the high-quality machining requirements of two materials. In addition, errors exist between the actual thickness of each material layer and the theoretical value, which causes an impediment to the monitoring of the machining interface and the corresponding adjustment of parameters. An adaptive machining method for the helical milling of CFRP/Ti stacks based on interface identification is proposed in this paper. The machining characteristics of the pneumatic spindle and the interface state in the helical milling of CFRP/Ti stacks are analyzed using self-developed portable helical milling equipment, and a new algorithm for the real-time monitoring of the machining interface position and adaptive adjustment of the machining parameters according to the interface identification result is proposed. Helical milling experiments were carried out, the results show that the proposed method can effectively identify the position of the machining interface with good identification accuracy. Moreover, the proposed parameter-adaptive optimized machining method for CFRP/Ti stacks can significantly improve hole diameter accuracy and machining quality.

Investigation of magnetic hysteresis in biased Ta/Pt/Co/FeMn/Ta antidots: Influence of structural dimensions

There exists a controversy in the literature concerning the values of coercive and bias fields in antidots magnetic structures formed by a hexagonal network of nanoholes. The coercive fields (HC) and the exchange bias fields (∣HEXC∣) for antidots (deposited on ultrathin anodic aluminum oxide, namely, AAO) are either increased or diminished by comparison with the same magnetic nanostructures grown on continuous substrates (namely, CML). We propose to elucidate these debates by showing the importance of the easy axis of the magnetization, the direction of the applied magnetic field, the thicknesses of the layers, and the 3D-topology of nanoholes, as well as the magnetic and thermal history of the magnetic measurements. Here, biased Ta(5 nm)/Pt(5 nm)/Co(0.6 nm)/Fe50Mn50(X)/Ta(5 nm) antidots are investigated by extraordinary Hall effect measurements at 5 K, where X varies in the (0–5.5) nm range. The substrate consists in a hexagonal array of holes, described by the pair of (p,d) values, respectively, the period as the distance from center to center of two consecutive holes and the hole diameter. The dimensions of antidots are (p≈100 and d≈40 nm) for X=(2–5.5) nm, (p≈150 and d≈60 nm) for X=3.5 nm, and (p≈100 and d≈60 nm) for X=0. A continuous stack using Si/SiO2(100 nm) is used for comparison. HC and ∣HEXC∣ gradually increase when X is enhanced for both substrates, with nevertheless a weak decrease at high X for the continuous system. Perpendicular magnetic anisotropy is only observed for both unbiased samples, the X=2 nm continuous sample, and both X=5 nm samples that have undergone field cooling treatment from 500 to 5 K under −2 T. Usually, HC(AAO)>HC(CML), ∣HEXC(AAO)∣>∣HEXC(CML)∣, and ∣HA(AAO)∣<∣HA(CML)∣ (HA designating the anisotropy field). However, for certain conditions, as, for instance, for FC-procedures starting from high temperatures and/or strong magnetic field, other situations might be observed. A discussion pertaining to the amplitudes of HC, ∣HEXC∣ and the anisotropy field (∣HA∣) of continuous and discontinuous samples is given for our experimental results as well as for published data in the literature, in the light of structural characteristics (wedge-to-wedge distance, porosity, or coverage ratio). Such biased perpendicular antidots might be particularly used in specific nanomaterials devoted to spintronics.

Dynamic gas liberation from water-immersed anthracite coal with varying wetting states under heating conditions: Unveiling the gas breakthrough phenomena

During coalbed methane recovery, the effective extraction of gas trapped in narrow pore throats encounters challenges due to the water blocking effect. To shed light on this phenomenon during thermal recovery of coalbed methane, this study investigated the breakthrough behaviors of CO2 traversing through a 0.2 mm diameter hole in water-immersed anthracite coal at varying temperatures (23 °C, 40 °C, and 60 °C). The measurements of breakthrough pressure (defined as the pressure at which the bubble achieves a semi-spherical shape with a minimum curvature radius), growth characteristics of CO2 bubbles, and coal wettability were conducted under varying thermal conditions and water immersion durations. The results showed that the breakthrough pressure initially increased continuously as water immersed into the coal and then gradually stabilized. During this process, the coal's water wettability increased, leading to a decrease in the diameter of the bubble's three-phase contact line, which in turn affected the breakthrough pressure. Moreover, higher temperatures accelerated the rate of water immersion, augmenting the coal's hydrophilicity. The elevated temperature also resulted in a decrease in water surface tension, consequently contributing to a lower breakthrough pressure. Interestingly, compared to CO2, He exhibited a faster increase in breakthrough pressure during water immersion. This disparity can be attributed to He's superior diffusion capacity and lower viscosity, enabling a swifter transformation of the coal's wetting state during water imbibition. This study revealed the dual mechanism of heating to reduce gas breakthrough pressure, as well as the effects of surface water content and gas properties. These findings highlight potential benefits of thermal treatment on coalbed methane recovery and provide valuable insights for its exploitation under different geological conditions.

The Effect of Internal Combustion Engine Nozzle Needle Profile on Fuel Atomization Quality

This article presents the results of research on the impact of changing the cross-section of an atomizer’s flow channel, which is caused by changing the flow geometry of the passive part of the needle on the drop diameter distribution of the fuel spray. A three-hole type H1LMK, 148/1 atomizer with hole diameters, dN, equal to 0.34 mm, is analyzed. A nozzle with a standard (i.e., unmodified) needle and three nozzles using needles with a modified profile in the flow part of the needle, marked by the code signatures 1L, 2L, and 3L, are tested. An increasing level of fuel turbulence characterizes the needles during the flow along their flow part due to the use of one (1L), two (2L), and three (3L) de Laval toroidal nozzles, respectively, obtained by mechanically shaping the outer surface of the flow part of the spray needle. The spray produced is tested using the Malvern Spraytec STP 500 device cooperating with the dedicated Malvern version 4.0. During the tests, measurements and an analysis of the spray droplet size distribution over the entire injection duration, equal to 7 ± 2 ms, are made for each nozzle. The experiment makes it possible to determine the effect of the nozzle needles’ profiles on the time distribution of the actual droplet diameters; the time distribution of the Sauter mean droplet diameters, D[3,2]; the percentile shares of the droplet diameters Dv (10), Dv (50), and Dv (90); the distribution span during the development of the spray stream; and the time distribution of the shares of the droplets with diameters belonging to selected diameter classes D[x1−x2] in the spray. The results of the measurements of the drop diameter distribution indicate that using atomizers with a modification to the flow channel allows for an increase in the share of droplets with smaller diameters compared to the standard atomizer.

Analysis of Macular Pigment Optical Density in Macular Holes with Different Border Phenotypes.

We conducted a cross-sectional study to compare macular pigment optical density (MPOD) in eyes with idiopathic macular holes with bumpy (bbMH) and smooth borders (sbMH) and toassess the relation between MPOD and optical coherence tomography findings. Thirty eyes from thirtypatients affected by idiopathic macular hole were studied. All patients underwent SD-OCT and macular pigment optical density (MPOD) analysis. Comparison between the two border phenotypes were estimated at baseline, as wellasthe differences inMPOD, minimum and basal hole diameter, tractional hole index (THI), macular hole index (MHI), diameter hole index (DHI), and ELM integrity metricsbetween the two groups. The mean MPOD was 0.09 ± 0.08 in bbMHs and 0.16 ± 0.11 in sbMHs (p = 0.010). Correlation analysis between MPOD and minimum hole diameter revealed a negative association (rho = -0.707, p = 0.008) in bbMH and a positive association (rho = 0.702, p = 0.019) in sbMH. MPOD and basal diameter were negatively correlated in bbMH (rho = -0.77, p = 0.001) and positivelycorrelated in sbMH (rho = 0.675, p = 0.019). Indeed, MPOD is negatively correlated with THI and MHI in sbMH (rho = -0.684 p = 0.019; rho = -0.665 p = 0.019, respectively) and positively correlated in bbMH (rho = 0.593 p = 0.037; rho = 0.658 p = 0.018, respectively). MPOD is significantly reduced in bbMHs compared to sbMHs. The two border phenotypes also differ for tractional and tangential indexes, possibly reflecting a different pathogenesis.Further studies are needed to understand the prognostic role of MPOD.

A comprehensive study for improving the working parameters for the design of a PSA-based oxygen concentrator

Oxygen concentrators (OC) are medical devices that supply oxygen by separating nitrogen from the atmospheric air. The functionality of PSA-based OC majorly depends on internal pressure dynamics, cycle timing accuracy, orifice dimensioning for flow and pressure regulation, selection of zeolite, air moisture content, and others. This study aimed to develop an improved OC with sustainable performance by optimizing these key parameters. Initially, lithium and sodium-based zeolite adsorbents were experimentally compared, and it was determined that lithium-based 13X zeolite with particle size 0.4–0.8 mm is more effective for OC. An optimization study was performed for the orifice diameter for the required flow rate, purity, and pressure. The 1 mm hole diameter orifice was concluded to deliver the most optimal functionality. The results were validated via analytical and numerical study, which can further be interpolated for higher flow rate OC. After investigation, it was concluded that filters having zeolite with 10%–15% alumina would effectively remove moisture from the air for sustainable OC. An intensive experimental study was conducted to evaluate the cycle timing under optimum operating circumstances, and it was determined that the overall cycle timing is 12–14 s, with flushing accounting for 5%–8% and recharging accounting for 8%–10% of production time. The research developed 10 LPM OC with 95% purity, a recovery rate of 38.46%, and a BSF of 57.2 kgs/TPDO2. Later, the OC was certified by an ISO-13485 prototyping facility and tested in various hospitals, followed by commercialization. The system’s performance was found to be superior to that of other commercialized products.

First and second law analysis of a heat exchanger equipped with perforated wavy strip turbulator in the presence of water-CuO nanofluid

For the first time, three alternative techniques were used in this research to enhance the thermal performance of a double pipe heat exchanger: the air bubble injection method, the use of a perforated wavy strip turbulator, and the use of Nano fluids as the working fluid. Distinct bubble injection flow rates ranging 2–6 LPM and turbulators with variable hole diameter ratio (D/L) were used in the experiments. Working fluids have included water, air/water, CuO-water, and air/CuO-water with different volume fractions ranging 0.25 % to and 1 %. Based on the findings, the use of Nano fluid, the PWST and bubble injection method increased the heat transfer by 56, 53 and 14.1 %, respectively. Also, the simultaneous employment of these three techniques increases heat transfer and exergy losses up to 2.15 and 1.82 times greater than those of plain pipe, respectively. The double pipe heat exchanger equipped with a perforated wavy strip turbulator with a hole diameter ratio of 6 and bubble injection with m˙a = 6 LPM was chosen as the best-case utilizing net profit per unit transferred heat load (ηp) and thermal performance factor (TEF). In this case, the maximum amount of ηp and TEF are equal to 2.124 × 10−9 and 1.24, respectively.

Simulation and Analysis of a Split Drill Bit for Pneumatic DTH Hammer Percussive Rotary Drilling

Reverse circulation impact drilling has the advantages of high drilling efficiency and less dust, which can effectively form holes in hard rock and gravel layer. As integral reverse circulation drill bits used in the conventional down-the-hole (DTH) hammers are only suitable for specific formations, the whole set of DTH hammer needs to be replaced when drilling different formations. In this paper, several types of split drill bits for different drilling technologies are designed. The flow field characteristics of one of the split drill bits is analyzed based on the computational fluid dynamics (CFD) method, with four technic parameters considered, which are input flow rate, number of inlet holes, angle of injection exhaust holes, and diameter of injection exhaust holes, respectively. Three parameters are selected as indicators to evaluate the rationality and performance of the split drill bit, which are injection exhaust hole outlet mass flow rate, ratio of the mass flow rate out of injection exhaust holes to the whole inlet mass flow rate, and maximum pressure at the upper end of the split drill bit. According to the CFD analysis results, the above four technic parameters influence the flow rate and pressure in different rules. Considering the injection capacity, pressure loss, and bit strength, inlet holes of 10, injection exhaust holes with an angle of 50°, and injection exhaust holes with a diameter of 12 mm are recommended to obtain ideal reverse circulation. Different types of split drill bits were manufactured, and drilling experiments were carried out in unconsolidated formations. The maximum drilling rate can reach 1.5 m/min in the drilling experiments. The split drill bit proposed in this paper exhibits excellent adaptability for reverse circulation drilling in loose formations.

Enhanced rotordynamic performance under various structural arrangements of hole diaphragm labyrinth seal

In this study, we study the influence of five drilling hole arrangements on the rotordynamic and leakage performance of hole diaphragm labyrinth seal (HDLS) type seals with precise CFD analysis. Key findings reveal that hole distance significantly affects direct and cross-coupled stiffness, thereby impacting stability and leakage. Notably, the smallest hole in rectangle four holes(RF)-HDLS does not yield the minimum leakage. Vortex structure analysis, employing the Q-criterion, elucidate horizontal two holes(HT)-HDLS's superior leakage reduction owing to enhanced turbulence eddy dissipation. Seals with larger hole diameters, down single hole(DS)-HDLS and up single hole(US)-HDLS, demonstrate stable rotordynamic performance, with DS-HDLS exhibiting a notable 106.3% improvement in cross-coupled stiffness. In contrast, seals with holes positioned farther away, DS-HDLS, US-HDLS and vertical two holes(VT)-HDLS, experienced increased leakage with whirl frequency. HT-HDLS and RF-HDLS displayed a decrease, attributed to the stronger centrifugal effect. Comparing to center single hole(CS)-HDLS, VT-HDLS and US-HDLS achieved a significant 159.3% direct stiffness improvement and 432.7% reduction in cross-coupled stiffness. Despite a maximum 4.2% leakage increase, this substantial enhancement in rotor stability should not be overlooked. Moreover, all seals exhibited lower leakage rates than the traditional labyrinth seal.

Effects of the position and perforation parameters of the delta winglet vortex generators on flow and heat transfer in minichannels

Minichannel with delta winglet vortices generator (VG) is widely used in heat exchangers. However, there is limited research in the literature on using VG with holes in opposite wall surfaces within a channel, and there are few reports on whether the use of VG with holes in minichannel will necessarily enhance heat transfer. In this work, we consider two different VG arrangements placed on opposite walls of a channel and three parameters for opening hole diameter (0.05, 0.15, and 0.25mm). Additionally, three different pitch values (15mm∼30mm∼45mm) are examined. Under a Reynolds (Re) number ranging from 3000 to 5500, the influence of VGs placement and hole parameters on the flow and heat transfer performance through calculations of parameters such as Nusselt number (Nu), friction coefficient (f), and thermal performance factor (TPF) are evaluated. Furthermore, the vortex structures are checked using the Q method and secondary vortex strength (Se). The results are shown to demonstrate that different VG placements mainly affect the main longitudinal vortices (MLVs), secondary longitudinal vortices (SLVs), and induced corner vortices (ICVs) structures downstream of the VGs. As the opening area increases, the shape of both vortices downstream of the VGs is significantly suppressed due to the generation of a jet flow, and the ICVs may even disappear (r=0.25mm). Case 1 (the right angle of the triangular wing is close to the center of the channel) has a larger TPF value. The opening of the hole reduces the heat transfer performance compared to the non-punched case, and their Nu number and f value are reduced by 0.2%−6.9% and 0.1%−8.3%, respectively. Case 1 obtained the maximum TPF value at Re=3000, which is 1.15, and P=15mm.

Experimental study of solar air heater with c shaped ribs coated with zeolite

A study was conducted to determine the heat transmission rate and friction properties of a solar air heater's (SAH) absorber by including c-shaped rib, with and without perforations, and the efficiency of this absorber with and without zeolite coating was investigated. This research is carried out by varying Reynolds numbers (Re) ranges between 3000 to 18000, height of the C-shaped rib (e) ranges between 2 mm to 4 mm, and the embedded hole diameter in the c-shaped rib ranges between 1 mm to 3 mm. The impact of rib height, hole diameter, and zeolite coating on thermal efficiency and Nusselt number is compared to a flat channel under the same flow environments. A strong secondary flow is created by the free shear layer reattaching more often at higher rib heights, and a smaller hole can exaggerate heat transfer and enhance the cross-flow effect. The thermal efficiency and Nusselt number of the solar air heater with c-ribs (Rib height = 4mm and hole diameter = 1mm) and zeolite coating on the absorber increased by 29.67% and 62.16% over the flat absorber. Ribs 4mm high can increase duct friction by up to 3.1 times compared to a smooth duct.

Enhancing Dimensional Geometry Casting using Computer Modeling

Sand casting method is used to produce many useful products for many applications. The aim of the study is to manufacture a product with excellent dimensional geometry is achieved in sand casting process at low cost. We would expect manuscripts to show how design and/or manufacturing problems have been solved using computer modeling, simulation and analysis. In this work, the important mechanical properties of hardness and surface roughness are investigated on Aluminum 6063 cast material with and without incorporating the copper tubes as a vent hole in sand casting process. Since copper has high thermal conductivity when compared to other metals, the heat transfer rate will be varying from existing system. The copper tubes have made different diameters of holes on outer surfaces with selective distance of intervals. The specific number of copper tubes with various diameters are designed by CATIA modeling software and analyzed with Taguchi Design of Experiment. Taguchi L9 orthogonal array is used proficiently in the optimal value of hardness and surface roughness. The results are revealed that the maximum hardness value of 104 BHN is attained for 10mm distance of holes made on copper tube with an angle of 90o degree. The minimum surface roughness of 2.11 micron is achieved for 20mm distance of holes made on copper tube with 45o of angle as a vent hole in sand casting process.

Grinding as a slaughter method for farmed black soldier fly (Hermetia illucens) larvae: Empirical recommendations to achieve instantaneous killing.

At least 200 billion black soldier fly (Hermetia illucens) larvae (BSFL) are reared each year as food and feed, and the insect farming industry is projected to grow rapidly. Despite interest by consumers, producers, and legislators, no empirical evidence exists to guide producers in practicing humane - or instantaneous - slaughter for these novel mini-livestock. BSFL may be slaughtered via freezing, boiling, grinding, or other methods; however standard operating procedures (SOPs) and equipment design may affect the likelihood of instantaneous death using these methods. We tested how larval body size and particle size plate hole diameter affect the likelihood of instantaneous death for black soldier fly larvae that are slaughtered using a standard meat grinder. Larval body size did not affect the likelihood of instantaneous death for larvae that are 106-175 mg in mass. However, particle size plate hole diameter had a significant effect on the likelihood of instantaneous death, with only 54% of larvae experiencing an instant death when using the largest particle size plate (12-mm hole diameter) compared to 84% using the smallest particle size plate (2.55 mm). However, a higher percentage of instantaneous death (up to 99%) could be achieved by reducing the proportion of larvae that become stuck in the machine. We conclude by outlining specific recommendations to support producers in achieving a 99% instantaneous death rate through specific SOPs to be used with similarly designed machines. We also develop a protocol for producers that wish to test their own grinding SOPs.

Effect of outer spherical shell opening structure on the sensitivity of double spherical shell electric field sensor.

A double spherical shell (DSS) electric field sensor based on charge sensing has characteristics of small size and simple fabrication, which are appropriate for measuring complex electric field environments, but the sensitivity is low. To improve the sensitivity of the DSS electric field sensor, we theoretically analyze the effect of the diameter of the outer spherical shell opening on the sensitivity of the sensor. The sensors with outer spherical shell apertures of 2, 4, and 6mm are designed and manufactured, and the sensor's sensitivity, linearity, hysteresis, and repeatability are tested. The relative error of the sensor is evaluated by measuring the rotational characteristics of the sensor. The experimental results show that the sensor sensitivity increases with the increase in hole diameter, while the sensor has good linearity, hysteresis, and repeatability after opening the hole. The rotational characteristics experiments' results show that the sensors' relative errors with different apertures are 18, 23, and 31%, respectively. The DSS open-hole structure is more suitable for electric field measurements than the conventional flat plate structure.

РЕЗУЛЬТАТЫ ПОИСКА ОПТИМАЛЬНЫХ ПАРАМЕТРОВ ПАССИВНОГО ИЗМЕЛЬЧИТЕЛЯ ПРИ ПРИГОТОВЛЕНИИ ПШЕНИЧНОЙ ПАТОКИ

In order to grain molasses preparing process studying, a laboratory installation has been developed. This installation’s working process’s research results at wheat molasses preparation are presented. Information on the passive shreddering device, one of the feature of which is under either specific grain crop reconfiguration possibility is given. The spring wheat (sort of Moskovskaya 35, it had grown in the Nizhny Novgorod region in 2022) characteristic in specific energy consumption process experiments using is given. According to the search experiments’ results it was revealed that a nozzle with a hole with diameter of 25 mm using leads to specific energy consumption in 18% more increasing then with one of 40 mm. The small distance from the nozzle to the grill also a negative effect has had. In the «Statistica» statistical analysis’s frame, a desirability function with a value of 0,809 for the criterion Y (average values of specific energy consumption E, W/h/kg) at selected factors X1 (grid’s inclination angle is α, deg.) and X2 (grid’s hole diameter is d, mm) optimization was constructed. In order to the optimal values of the studied factors and their mutual influence on this installation’s workflow determining, a matrix of a complete experiment factor 32 was implemented. After that, an adequate response’s function at a given significant level α = 0,05 was obtained. At the same time, it is noted that the X1 factor is more important than X2 one. According to these response function’s extremum studies results, the extreme point X1 = 0,2, so as X2 = 0,19 are revealed, at which the the function’s extremum is Y min = E = 43,27 W/h/kg. Based on technological considerations, the passive shreddering’s optimal tuning parameters at wheat molasses preparation are α = 30° and d = 6 mm, at that the specific energy consumption will be 41,5 W/h/ kg.

Polyvinyl alcohol/Polyvinylpyrrolidone/Chitosan Nanofiber Scaffold with Hydroxyapatite from Sand Lobster Shells (Panulirus homarus) for Bone Tissue Engineering

In this work, nanofiber scaffold membrane polyvinyl alcohol (PVA)/polyvinylpyrrolidone (PVP)/Chitosan (CS)/hydroxyapatite (HAp) from sand lobster (SL; Panulirus homarus) shells have successfully synthesized to mimic the extracellular matrix (ECM) nanoscale in the native bone. HAp was synthesized by co-precipitation method with Ca/P was 1.67, then nanofiber membrane PVA/PVP/CS/HAp was synthesized by electrospinning method. Nanofiber solution was prepared from PVA 10% (w/v) polymer solution that dissolved in the distilled water, then the PVP/CS 15% (w/v) polymer solution was dissolved in acetic acid 1% (v/v) separately. The PVA polymer solution and PVP/CS solution were mixed with a ratio of 8.5: 1.5 (v/v). HAp dispersed into mixture solution with variation concentration 0, 1, 3, and 5 wt%. The composite solution was put into a 10 ml syringe with a hole diameter = 0.5 mm. Electrospinning was carried out at a 10 kV voltage, the flow rate at 0.1 ml/h, and the distance between the collector to the tip was 12 cm. Nanofiber scaffold membrane was characterized using SEM, FTIR, and XRD. The addition of HAp into the fiber showed incorporation into nanofiber with small agglomeration in the concentration of HAp at 1, 3, and 5 wt%. Based on the physicochemical analysis, the nanofiber scaffold PVA/PVP/CS/HAp 5 wt% with a fiber diameter of 0.328 ± 0.049 μm has the most potential to be used for bone tissue engineering.

Effect of Laser Process Loops on the Hole Diameter and Hole Formation of Laser Micro Drilling on TC4

Laser micro drilling stands as a precise manufacturing method that employs a focused laser beam to craft accurate, small holes within a diverse array of materials. Its applications span across vital industries like aerospace, medical, and electronics, playing a pivotal role in creating components like fuel injectors, medical implants, and microelectronics. Within this context, a notable challenge emerges in obtaining a refined surface finish during laser micro drilling. This study delves into the impact of a laser loop, a crucial parameter, on the surface quality of TC4, also known as Ti6Al4V—an aerospace staple. Employing a Conventional Fiber Laser with a peak output of 30 W, the experiment meticulously directs the laser beam onto the TC4 surface via a microscope objective lens. The drilling process unfolds in controlled conditions, mitigating external variables such as temperature and humidity. Assessment of drilled hole surfaces transpires through both light and 3D microscopes. Interestingly, holes subjected to higher laser power and increased laser loop rates demonstrate enhanced surface smoothness. In essence, this inquiry demonstrates the substantial influence of laser loop on TC4’s surface finish during laser micro drilling. Elevating the laser loop factor leads to heightened surface refinement and diminished roughness in drilled holes. It was found that the diameter entry of the micro-holes was increased by 61% - 89.35% and the diameter exit of the micro-holes also increased by 55.55% - 62.79%. The outcomes of this investigation offer valuable insights for refining the laser micro drilling process to achieve premium surface quality on TC4 and comparable materials. As such, these findings extend guidance for optimal laser loop settings in the realm of laser micro drilling across various materials, benefiting future manufacturing endeavors.

The influence of the particle size on rheological properties of magneto fluidized bed of strontium hexaferrite

Powder metallurgy processes are in general less polluting and more sustainable than the traditional mechanical manufacturing. In order to organize technological processes with the ferromagnetic powders, one usually applies special methods to change the coefficient of inner friction of particulate systems. We studied the regimes of the magnetic fields that form magneto fluidized bed from the strontium hexaferrite (SrFe12O19) powder and provide the decrease of the inner friction coefficient. The magneto fluidized bed was formed by the effect of the crossed constant and alternating gradient magnetic fields. The results of electromagnetic parameters influence on rheological properties of the magneto fluidized bed formed from strontium hexaferrite powders with various average particle sizes are presented in the paper. The dependencies of the strontium hexaferrite stimulated fluidity speed through a 2 mm diameter hole from the electromagnetic field parameters were studied. The obtained results show the possibility of using dry ferromagnetic powders in the permanent magnets production in powder metallurgy.

Numerical modelling of hydrogen leakages in confined spaces for domestic applications

The UK government tentatively plans to use hydrogen for domestic applications by 2035. While the use of hydrogen aims to reduce the dependence on hydrocarbons, certain factors need consideration. Since hydrogen is much lighter, and more reactive than methane, it is crucial to understand the change in risk for accident scenarios involving hydrogen in a domestic setting. Numerical modelling was used to simulate the leakage of hydrogen and methane in small, enclosed spaces such as kitchen cupboards. The k- ε turbulence model was used along with the species transport model to simulate the leakage of gas for different inlet locations and leak diameters (1.8 mm–7.2 mm). From the modelling study, it was observed that hydrogen and methane both tend to stratify from top of the control volume to the bottom. The key finding was that, under adverse conditions (leak from a 7.2 mm diameter hole) and due to greater volumetric flow, hydrogen tends to reach equilibrium concentration 45s faster than methane for a total leak duration of 600s. Additionally, it was noted that cases with leak inlet locations near corners had 28% lower hydrogen concentrations, and 25% lower methane concentrations as compared to leak inlet locations near the centre of the cupboard.