Sheet Thickness Research Articles

Design and Application of Real‐Time and High‐Precision Seismic Acquisition Station in Antarctic Region

ABSTRACTIn this study, a polar seismic acquisition station based on the FPGA + ARM architecture was successfully developed. This system can achieve real‐time multifunctional acquisition and transmission of seismic signals and environmental information in the extreme low‐temperature environment of Antarctica at −40°C. The system adopts a modular design, with high‐precision data acquisition encoded by the main controller and uploaded to the host computer in real‐time. Integrated display controls enable real‐time data display and acquisition station location mapping for user interaction. We propose improving data transmission in traditional seismic acquisition stations by adopting a distributed computing model with data segment return. Integrating the first arrival picking algorithm as an IP core will reduce computational demands on the data processing center. This acquisition system features high precision (24‐bit), a wide dynamic range (> 130dB), low noise (0.5 V rms@40dB), and high‐precision timing control (200 ns). It supports real‐time wireless data transmission over 120 channels up to 1 km. The system also implements a self‐storage plus wired and wireless networking solution, allowing flexible networking based on actual needs. Test results indicate that the ice sheet thickness at the acquisition site is approximately 526.49 m, validating the experimental design's effectiveness and providing technical support for subsequent drilling and seismic exploration.

Sensitivity of Wavelet-Based Optical Flow Velocimetry (wOFV) to Common Experimental Error Sources

Abstract The influence of several potential error sources and non-ideal experimental effects on the accuracy of a wavelet-based optical flow velocimetry (wOFV) method when applied to tracer particle images is evaluated using data from a series of synthetic flows. Out-of-plane particle displacements, severe image noise, laser sheet thickness reduction, and image intensity non-uniformity are shown to decrease the accuracy of wOFV in a similar manner to correlation-based PIV. For the error sources tested, wOFV displays a similar or slightly increased sensitivity compared to PIV, but the wOFV results are still more accurate than PIV when the magnitude of the non-ideal effects remain within expected experimental bounds. For the majority of test cases, the results are significantly improved by using image pre-processing filters and the magnitude of improvement is consistent between wOFV and PIV. Flow divergence does not appear to have an appreciable effect on the accuracy of wOFV velocity estimation, even though the underlying fluid transport equation on which wOFV is based implicitly assumes that the motion is divergence-free. This is a significant finding for the broader applicability of planar velocimetry measurements using wOFV. Finally, it is noted that the accuracy of wOFV is not reduced notably in regions of the image between tracer particles, as long as the overall seeding density is not too sparse i.e., below 0.02 particles per pixel. This explicitly demonstrates that wOFV (when applied to particle images) yields an accurate whole field measurement, and not only at or adjacent to the discrete particle locations.

Design and damping characterization of sandwich composite made of particle-filled hollow spheres and steel sheets

Sandwich composites made of particle-filled hollow sphere structures (PHSS) and steel sheets offer excellent lightweight and damping properties, ideal for high-speed machine tool components under dynamic loads. Previous research has focused on single particle-filled hollow sphere (PHS) and small PHSS, leaving a gap understanding of PHSS/steel sandwich composites. In this study a test rig was developed, and Design of Experiments and Response Surface Analysis were used to investigate the effects of sheet and core thickness (design parameters), filling ratio, and particle size (particle parameters) on the damping performance of PHSS/steel sandwiches. The results indicate that the design parameters have a significant influence on damping performance. The interaction between design and particle parameters also substantially affects damping. Minimizing particle size, increasing filling ratio, thinning the face layer, and thickening the core layer significantly improve structural damping. To address manufacturing tolerances, a finite element (FE) model-based optimization was developed to accurately determine PHSS material parameters. These parameters were used in an FE model of the PHSS-steel composite, with identified contact parameters minimizing measurement and simulation differences. The homogenized material model and the linear model using global damping parameters accurately reproduce the dynamic properties of the PHSS-steel sandwich composite in low vibration modes.

Investigation of Low Velocity Impact Behavior of Aluminum Honeycomb Sandwich Structures with GFRP Face Sheets by Finite Element Method

The aim of this study is to examine the low velocity impact behavior of aluminum honeycomb sandwich structures with glass fiber reinforced plastic (GFRP) face sheets with the help of finite element method. In the study, low velocity impact tests were carried out in the LS DYNA finite element program to examine the effects of face sheets thickness, core number, wall thickness, impact location and impact velocity on maximum contact force, absorbed energy efficiency and damage mode. Progressive damage analysis based on the Hashin damage criterion and the combination of Cohesive Zone Model (CZM) and the bilinear traction-separation law was performed using the MAT-54 material model. At the end of the study, it was determined that the face sheets thickness in sandwich structures had a significant effect on the impact resistance up to a certain impact energy. It has been observed that as the impact velocity gradually increases, there is a decrease in the contact force after a certain threshold value. As the impactor velocity increases, the energy absorption efficiency also increases. It has been determined that the location of the impact is very effective on peak force and energy absorption efficiency. The effect of the number of core layers depends on the face sheets thickness. When the face sheets thickness was not damaged at first contact, the peak force value increased in parallel with the number of layers. It was determined that the dominant damage mode after impact was matrix damage. It has been observed that as the energy level of the impactor increases, damage also occurs on the back surfaces.

Single-point incremental formability of Monel 400: Coupled grey relational and principal component analyses

This study reports the effects of single-point incremental forming (SPIF) process variables like vertical step down (0.2, 0.4, 0.6 mm), tool diameter (6, 8, 10 mm), feed rate (300, 600, 900 mm/min), spindle speed (300, 450, 600 rpm), lubricant (dry, oil, grease) and sheet thickness (0.6, 0.8, 1.0 mm) on the formability of Monel 400. Based on the varying wall angle tests conducted, it was found that the vertical step down was the parameter most influential in achieving maximum wall angle. The forming limit diagram constructed with the data obtained from straight groove tests revealed the parameter combination for low, moderate, and high formability while forming along different directions (0°, 45°, 90°). Also, it was observed that the formability has been positively influenced by increased tool diameter in the case of 0° orientation, spindle speed in the case of 45° orientation, and vertical step down in the case of 90° orientation. Based on the fractography study, it is concluded that more number of voids enhanced the forming limit. This may be due to the coalescence of voids and their slow aggregation. Based on the combined grey relational analysis and principal component analysis, it is obtained that the order of influencing parameters is vertical step down, tool diameter, sheet thickness, spindle speed, lubricant, and feed rate for obtaining the maximum sum of strains (0°, 45° 90°) and maximum wall angle.

Spiral wind-up of vortex sheets

A model of the spiral wind-up of a vortex sheet by the flow induced by a perpendicular vortex is developed, first in the Euler limit of zero viscosity, then taking account of viscous diffusion. The wind-up of a vortex sheet by a propagating vortex pair is also considered; in this case, the vorticity grows exponentially near the two saddle points of the flow in the moving frame of the vortex pair. Estimates are obtained for the maximum vorticity ω m and maximum enstrophy Ω m attained through this process in terms of the wind-up Reynolds number Re and the initial dimensionless sheet thickness δ 0 . This paper is dedicated to Andrew Soward, whose sustained research in Dynamo Theory and Fluid Mechanics has been brilliantly inspiring for more than 50 years. Happy 80th, Andrew!

Biomechanical and Physical Characteristics of Dental Dam Sheets Used for Absolute Isolation.

This study aimed to evaluate the mechanical and physical properties of dental dam sheets used for absolute isolation and to correlate the mechanical parameters with cost. Twenty-one dental dam sheets were tested: ALLPRIME; Madeitex; Sanctuary non-latex, Sanctuary latex black, green, and blue; Nic Tone blue and black; Mk Life; Elastidam; Bassi; Pribanic; Care; OK; MDCDental; Keystone; Dura Dam; Flexidam; Sanctuary blue; Nic Tone blue; Ehros; and USE. The thicknesses of the dental dam sheets were measured using a digital micrometer (Mitutoyo). The dental dam sheets (n=15) were prepared by cutting the samples with dimensions of 80 × 10 mm with a 1.7 mm hole made at the center of each specimen, following the ISO 9001 standard. The specimens were tested using a universal testing machine (Emic) at a speed of 500 mm/min until rupture to calculate rupture force (RF, N), elongation (%), and ultimate tensile strength (UTS, MPa), their thickness (mm) was measured using a digital micrometer, and scanning electron microscopy and X-ray energy dispersive spectroscopy were performed to analyze the structure and composition. The radiopacity was measured using digital radiography. Thickness, UTS, RF, and elongation data were analyzed by one-way ANOVA and Tukey's test (α=0.05). The Flexidam dental dam had the largest thickness (0.5 mm), while Nic Tone had a median thickness of 0.3 mm; the RF value (41.3 N) was higher for the thicker dental dams. The other dental dams had RF values ranging from 19 to 30 N. The highest elongation was obtained for the non-latex Sanctuary dental dam (600 mm). The Bassi dental dam had the highest UTS value (15 MPa), and medium and small particles were observed in most of the gums. A loss of continuity was detected in the structure of Sanctuary green and blue media. The predominant elements in the sheets were carbon, magnesium, sulfur, silicon, and calcium. The UTS, RF, and elongation varied substantially, indicating insufficient standardization of dental dam sheets. Nonetheless, most of the tested dental dams exhibited mechanical and physical properties suitable for clinical use. The correlation between the cost and mechanical properties of the dental dams was very low.

Flexural response of metallurgically bonded steel-aluminium foam-steel panels and composite beams

This paper presents the results of an experimental and numerical campaign aimed at investigating the flexural behaviour of both metallurgically bonded steel-aluminium foam-steel sandwich (MBSAFS) panels and steel-MBSAFS composite beams. Three-point bending tests were carried out and the obtained results were used to validate the accuracy of analytical models to predict the stiffness and resistance of both MBSAFS panels and the composite beams. The predictive capacity of the analytical equations was further verified against the results of parametric finite element simulations, which were also carried out to investigate the influence of the thickness of the steel sheet, the foam thickness, the strength of the materials, the span length, and the type of beam profile. The comparative analysis demonstrated that the predictive formulae accurately provide both stiffness and resistance. The stiffness was predicted with a mean ratio (analytical/FEM) equal to 1, accompanied by a coefficient of variation (CoV) equal to 0.02. The plastic resistance of the composite beam was predicted with a mean accuracy of 0.96 and a coefficient of variation of 0.01.

Bending response and energy absorption of sandwich beams with combined reinforced auxetic honeycomb core

This study introduces a reinforced star-shaped auxetic honeycomb (RSSAH) sandwich beam, enhanced with hollow thin-walled tubes to improve bending resistance and energy absorption performance. The bending performance of the RSSAH is systematically investigated through quasi-static three-point bending tests and finite element numerical simulations. The findings suggest that when subjected to mid-span stress, the RSSAH displays both localized indentation and overall bending deformation, accompanied by notable negative Poisson’s ratio (NPR) impact under bending loads. Parametric studies are undertaken by numerical simulations to investigate the impact of compression position, auxetic angle, and face sheet thickness on the bending mode of the auxetic honeycomb sandwich beam. The analysis shows that the RSSAH can exhibit excellent bending performance and, at one of the compression positions, displays double-plateau stress characteristics. It is also found that altering key geometric parameters, such as the auxetic angle and panel thickness ratio, can greatly improve the bending capabilities of the RSSAH, achieving stable plastic deformation and high energy absorption. Finally, compared to star-triangle honeycomb (STH) sandwich beam, traditional reentrant honeycomb (RH) sandwich beam and star-shaped auxetic honeycomb (SSAH) sandwich beam, the RSSAH demonstrates superior bending performance and energy absorption capacity. This study offers insights and references for the development of innovative reinforced auxetic honeycomb sandwich beams.

Investigating formability of AZ31B magnesium alloy sheet with different texture and thickness in combination of the Erichsen experiment and CPFEM model

In this study, the formability of the AZ31B magnesium alloy sheets was investigated in combination of experiment and CPFEM modelling. The deformation mechanisms during the Erichsen forming were revealed and the effect of the related parameters were discussed. It was shown that the simulation results based on the normalized Cockcroft-Latham criterion are consistent with the experimental results. The maximum stress and strain concentrate at the center of dome, and exhibit an elliptical distribution shape. The difference of asymmetry situation between the sheets results from the different textures. The basal <a> slip is the dominant mode, and the prismatic <a> slip is also active to accommodate plastic strain in sheet plane. The relative activity of the pyramidal <c+a> slip is low, but very effective to accommodate the plastic strain in thickness direction. The sheet with higher relative activity of the prismatic <a> and pyramidal <c+a> slips exhibit higher formability. The sheet thickness influences the formability through changing the stress-strain response, as well as the orientation-relationship between stress state and grains which can affect the deformation mechanisms. The formability depends on the plastic strain accommodation ability that is comprehensively related to the averaged plasticity, orientation-relationship between stress state and grains, r-value and n-value. CPFEM modeling is convenient pathway to predict the formability.

Lightweighting an automotive fuel tank through formability analysis

For lightweighting automotive sheet metal parts, it is important to use the right grade/material with the minimum possible initial blank thickness in the forming processes. Fuel tank is one of the most critical sheet metal parts in automobiles due to its complex shape and large depth. In this work, a simulation-based approach has been employed to study the feasibility of lightweighting an automotive fuel tank (for two wheelers) by reducing blank thickness and changing steel grade. Formability analysis has been carried out using numerical simulations of a 0.8 mm thick sheet of Extra Deep Drawing (EDD) steel which is being used to manufacture the fuel tanks. Simulations have been performed to find out the minimum initial sheet thickness which can be formed successfully without failure or excessive thinning. From the predictions of formability, thinning, and strain distributions in the formed parts, it has been found that the weight of the part can be reduced by 12.5% by reducing the initial thickness from 0.80 to 0.70 mm. To reduce the thickness further, simulations have also been carried out by changing the grade from EDD steel to Interstitial Free (IF) steel which has superior drawability than EDD steel. It has been found that the blank thickness can be further reduced to 0.65 mm in the case of IF steel which is expected to result in 19.0% reduction in the weight of the component. The predictions have been validated by the actual press trials in the industry with reduced sheet thickness. The predicted strain distribution and thinning in the formed parts have also been validated with the experimental press trails. In addition to the weight reduction, the proposed change in thickness and grade would lead to a reduction of 16.5% and 4.0%, respectively, in the raw material cost of the fuel tank.

Thermal, mechanical, and electrical properties of Si-stacked nanosheet transistors using machine learning interatomic potentials

Thermal and mechanical properties play a key role in optimizing the performance of nanoelectronic devices. In this study, the lattice thermal conductivity (κL) and elastic constants of Si nanosheets at different sheet thicknesses were determined using recently developed machine learning interatomic potentials (MLIPs). A Si nanosheet with a minimum thickness of 10 atomic layers was used for model training to predict the properties of sheets with greater thicknesses. The training dataset was efficiently constructed using stochastic sampling of the potential energy surface (PES). Density functional theory (DFT) calculations were used to extract&#xD;the MLIP, which served as the basis for further analysis. The Moment Tensor Potential (MTP) method was used to obtain the MLIP in this study. The results showed that, at sub-6 nm sheet thickness, the thermal conductivity dropped to ∼ 7 % of its bulk value, whereas some stiffness tensor components dropped to ∼ 3 % of the bulk values. These findings contribute to the understanding of heat transport and mechanical behavior of ultrathin Si nanosheets, which is crucial for designing and optimizing nanoelectronic devices. The technological implications of the extracted parameters on nanosheet field-effect transistor (NS-FET) performance at advanced technology nodes were evaluated using TCAD device simulations.

Seismic in-plane behavior of composite masonry walls strengthened with cold rolled steel sheets

The seismic behavior of masonry walls strengthened by cold rolled steel sheets is numerically evaluated in this study using finite element modeling in ABAQUS. Cold-rolled steel sheets cover two sides of an unreinforced masonry wall and are bolted together to form a composite masonry wall. The behavior of the composite masonry walls is compared to that of the corresponding unreinforced masonry walls with various failure mechanisms. The finite element models of the unreinforced masonry walls are validated through experimental data in the literature. Then, cold-rolled steel sheet-strengthened walls are simulated, and variations in strength, ductility, and failure mode are investigated. A thorough sensitivity analysis is conducted on the effects of the aspect ratio, boundary condition, axial load ratio, steel sheet thickness, and connection bolt configuration on the in-plane strength and failure mode of the walls. It is observed that the steel sheets affect the local and global behavior of the masonry walls and change their failure modes. The use of through-thickness bolts to connect steel sheets to the masonry wall provides a composite action between steel sheets and the masonry wall against in-plane lateral loads. The cold-formed steel sheets not only resist a portion of the lateral load but also significantly increase the lateral strength of the masonry walls and the ductility of the whole wall system. Based on the analysis results it can be concluded that strengthening masonry walls with cold-rolled steel sheets is a promising technique for the seismic improvement of existing conventional masonry buildings and for the design of new masonry buildings.

Halvorsen chaotic system based microwave absorber modelling for fighter jet stealth technologies

This study focuses on the development and detailed analysis of a broadband microwave absorber utilizing Halvorsen chaotic dynamics, that focuses at enhancing stealth capabilities for fighter jets. The investigation begins by exploring the mathematical formulation of the Halvorsen chaotic system and conducting a parametric sweep of its control parameters to generate distinct two-dimensional and three-dimensional chaotic attractor plots. These plots are then post-processed using Julia set theory to develop intricate fractal patterns, which serve as the foundation for the absorber design. Image processing techniques, including filtering and thresholding, are employed to refine the patterns by removing artifacts and noise, ensuring they are suitable for practical implementation. The refined fractal patterns are then imported into a computational electromagnetic simulation environment where they are patterned onto a 0.035 mm thick copper sheet. Moreover, the Magtrex 555 substrate with a thickness of 1.52 mm, is selected for its high permittivity and low-loss characteristics. A comprehensive series of parametric studies are conducted to evaluate the influence of various design parameters such as side length, unit cell geometry, and substrate thickness on the absorber’s electromagnetic performance. Important parameters include the effects of chaotic control parameter optimization and the electromagnetic boundary conditions applied during the simulations. Extensive simulations are performed across the 2–20 GHz frequency range to evaluate absorption efficiency, focusing on key metrics like absorptivity, surface current distribution, and electric field distribution. The final design achieves over 90 % absorption efficiency within the target frequency band when the chaotic control parameters are optimized. Finally, comparative analysis using different commercially available substrates, including FR-4 and Rogers RO3003, reveals that Magtrex 555 offers superior absorption performance. The study concludes with a detailed presentation of the final absorber design, alongside an indepth discussion of the frequency range, parametric variations, and the impact of chaotic system dynamics on the absorption properties. This research provides crucial insights into the design and optimization of chaotic-system-based microwave absorbers, that advances the development of stealth technology in military applications.

Microstructural evolution and mechanical performance of friction stir spot welded ultrafine carbide-free bainitic steel: Role of dwell time

This study focuses on unraveling the role of dwell time on microstructural evolution, mechanical performance, and failure characteristics of friction stir spot welded ultrafine carbide-free bainitic steel. Results clarify that the microstructures of the different weld zones exhibit a receptive behavior to extended dwell time, by which not only coarser martensite is acquired within the stir zone (SZ), thermo-mechanically affected zone (TMAZ), and fine-grain heat affected zone (FGHAZ) but also sub-critical heat affected zone (SCHAZ) experiences a more pronounced tempering. Applying a dwell time of 3 s is sufficient to make an ample bonding width containing refined martensite, being effective in retarding the crack propagation, and in turn, delivering a joint with the highest load-bearing capacity. However, enlarging the bonding width at dwell times beyond 3 s fails to provide higher peak loads owing to the formation of coarse martensite within the SZ. The failure modes of the welds are classified into two distinct modes: interfacial and partial pullout. The reduced upper sheet thickness (∼685 μm) paves the way for crack propagation along the thickness direction, allowing for partial pullout failure to occur.

Three-dimensional analysis of force distribution on maxillary dentition while distalization of first and second molars simultaneously with clear aligners

Objective: To explore the force distribution on the maxillary dentition when the first and second molars distalized simultaneously with different step sizes using clear aligners in vitro in order to provide a theoretical basis for the rational design of molar distalization. Methods: Clear aligners were designed to simultaneously distalize the maxillary first and second molars bilaterally, with rectangular attachments placed on the buccal surfaces of the first and second premolars, as well as the second molars. Based on different step sizes, the aligners were divided into three groups: Group A (0.15 mm per step), Group B (0.20 mm per step), and Group C (0.25 mm per step). Ten aligners were fabricated for each group using 0.76 mm thick polyethylene terephthalate glycol (PET-G) sheets. A three-dimensional force measurement system was used to measure the forces exerted on each tooth by the aligners, the first and second molars served as the target teeth and the remaining teeth as anchorage teeth. The three-dimensional force data were compared among the three groups. Results: In the mesiodistal direction, the forces on the central and lateral incisors were relatively small among all three groups, with no statistically significant differences (P>0.05). However, significant differences were observed in the forces on the canines, first premolars, second premolars, first molars, and second molars (P<0.05). The distal forces on the second molars in Groups B and C were (6.13±1.45) N and (6.83±1.58) N, respectively, significantly higher than that in Group A [(3.51±1.01) N] (P<0.05). The distal force on the first molars in Group C [(6.62±0.89) N] was significantly higher than that in Groups A and B (P<0.05). The mesial reactive forces on the first and second premolars in Groups B and C were significantly higher than those in Group A (P<0.05). The mesial reactive force on the canines in Group C [(-2.98±1.33) N] was significantly higher than that in Group A [(-1.69±0.68) N] (P<0.05), while there were no significant differences between Groups B and C in the forces on the canines, first premolars, and second premolars (P>0.05). In the buccolingual direction, there were no statistically significant differences in the forces on the central and lateral incisors among three groups (P>0.05), but significant differences were observed in the forces on the canines, second premolars, and second molars (P<0.05). The buccolingual forces on the canines, second premolars, and second molars in Group B were (-0.56±0.54), (-2.07±0.95), (1.13±0.55) N, respectively, significantly higher than those in Group A (P<0.05), but there were no significant differences compared to Group C (P>0.05). Compared to the mesiodistal and buccolingual forces, the vertical forces on the target and anchorage teeth were relatively small in all three groups. Conclusions: When using 0.76 mm thick PET-G sheets to fabricate clear aligners for simultaneous molar distalization, a step size of 0.20 mm per step is recommended. To prevent buccal tipping of the molars during distalization, it is advisable to design lingual displacement for the molars and buccal displacement for the adjacent anchorage teeth to counteract the unfavorable forces, with attachments placed on the primary anchorage teeth.

Modified cure cycles for increased fatigue performance of fiber metal laminates

Modified (MOD) cure cycles that deviate from the manufacturer’s recommended cure profile can reduce the inherent thermally induced residual stresses (TRS) in fiber metal laminates (FML). Literature shows that MOD cycles do not adversely affect the material properties but enhance the quasi-static material strength. However, the literature does not comprehensively discuss the impact of MOD cycles on material performance during cyclic fatigue loading. This paper, therefore, investigates how MOD cycles influence the fatigue characteristics of different FML layups made of carbon fiber-reinforced polymer (CFRP) and steel. The experimental results confirm that the quasi-static material strength and the modulus of the FML are increased when using MOD cure cycles. The evaluation of fatigue tests with digital image correlation, thermography, and electrical resistance measurements of notched specimens shows that a reduction of TRS delays damage initiation in the metal facesheets and decreases the crack growth rate until facesheet failure. The results further show that layup-dependent parameters, the maximum stress in the metal sheets, and metal sheet thickness significantly govern the evolution of fatigue damage. In summary, modified cure cycles are an efficient tool to enhance the quasi-static and fatigue performance of CFRP-steel hybrid laminates.

Mechanical Properties of Full-Scale Wooden Beams Strengthened with Carbon-Fibre-Reinforced Polymer Sheets

The strengthening, rehabilitation and repair of wooden beams and beams made of wood-based materials are still important scientific and technical issues. This is reflected, among other things, in the number of scientific articles appearing and the involvement of research centres around the world. This is also related to society’s growing belief in the importance of ecological and sustainable development. This article presents an overview of the latest work in this field and the results of our own research on strengthening solid wooden beams with carbon-fibre-reinforced polymer (CFRP) sheets. The tests were carried out on full-size solid beams with nominal dimensions of 70 × 170 × 3300 mm. A 0.333 mm thick CFRP sheet was used for reinforcement. The research analysed various reinforcement configurations and different reinforcement ratios. For the most effective solution, a 46% increase in load capacity, 35% stiffness and 249% ductility were achieved with a reinforcement ratio of 1.7%. Generally, the higher the reinforcement ratio and coverage of the surface of the wood, the higher the strengthening effectiveness. The brittle fracture of wood in the tensile zone for unreinforced beams and the ductile crushing of wood in the compressive zone for reinforced beams were obtained. The most important achievement of this work is the description of the static work of beams in previously unanalysed configurations of strengthening and the confirmation of their effectiveness. The described solutions should extend the life of existing wooden buildings and structures and increase the competitiveness of wooden-based structures. The results indicate that, from the point of view of optimizing the cost of reinforcement, it is crucial to develop cheaper ways of combining wood and composite than to verify different types of fibres.

Multi-Response Optimization of Single Point Incremental Forming of Al 6061 Sheet Through Grey-Based Response Surface Methodology

The single point incremental forming process (SPIF) is materialized to form the desired shapes in low-cost sheet metal processing and well suited for low batch components and customized designs. Many modifications have been attempted in recent years to maximize the formability, geometric accuracy and quality of the SPIF formed parts. In this work, an attempt has been made to analyse the influence of process parameters namely ball tool diameter, step size, spindle speed and sheet thickness on final wall thickness, forming force and surface roughness. The optimized results exhibit the desirable formability when the roller ball tool diameter of the tool is 12 mm. The results also project that formability of the sheet metal is minimized when the spindle speed is increased and the ball diameter maximizes the accuracy and surface roughness. Also minimizing the step size increases the product quality features. Upon conducting this multi-response optimization by grey based response surface methodology (RSM) technique It is identified that 12 mm ball diameter of the tool, 0.25 mm step size, 2445 rpm spindle speed, and 2 mm sheet thickness are the obtained optimized SPIF process parameters as confirmed through confirmation experiments.

Grain Microstructure in Friction-Stir-Welded Dissimilar Al/Mg Joints of Thin Sheets with/without Ultrasonic Vibration.

Electron backscattered diffraction (EBSD) characterization was conducted on the typical regions in friction-stir-welded dissimilar Al/Mg joints of 2 mm thick sheets with/without ultrasonic assistance. The effects of ultrasonic vibration (UV) on the grain size, recrystallization mechanisms, and degree of recrystallization on both sides of the Al-Mg bonding interface and the intermetallic compounds (IMCs) were investigated. It was found that on the Mg side of the weld nugget zone (WNZ), the primary dynamic recrystallization (DRX) mechanisms were discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), with geometric dynamic recrystallization (GDRX) playing a secondary role. On the Al side of the WNZ, CDRX was identified as the primary mechanism, with GDRX as a secondary contributor. While UV did not significantly alter the DRX mechanisms in either alloy within the WNZ, it promoted the aggregation and rearrangement of dislocations. This led to an increase in high-angle grain boundaries (HAGBs) and an enhanced degree of recrystallization in the welds. The average grain size in both the Al and Mg alloys of the WNZ followed a pattern of initially increasing and then decreasing along the thickness direction, reaching a maximum in the upper-middle part and a minimum at the bottom. The influence of UV on the average grain size in the WNZ was minimal, with only slight grain refinement observed, and the minimum refinement degree was only 0.9%. The Schmid factor (SF) on the WNZ and thermo-mechanically affected zone (TMAZ) boundary regions of the advancing side (AS) indicates that the application of UV increased the likelihood of basal slip and extension twinning in the crystal structure. In addition, UV reduced the thickness of IMCs and improved the strength of the Al-Mg bonding interface. These results suggest a higher probability of fracture along the TMAZ and WNZ boundary on the AS when UV was applied.