Search Results (12)

To investigate the mechanism of texture formation during the cold rolling of Ti-3Al-2.5V tubes for aerospace hydraulic systems, this study examines the microstructure at various locations of two deformation cones with ‘Q’ ratios of 1.055 and 1.300, respectively, in a single cold-rolling pass, revealing their continuous texture evolution. The results indicate that the cold-rolling texture primarily forms during the sinking section. A higher ‘Q’ ratio leads to a stronger tendency for the c-axis of grains to align parallel to the radial direction of the tube, resulting in enhanced radial texture intensity. Beyond influencing texture through dislocation slip, a higher ‘Q’ ratio also elevates the Schmid factor for {10$\stackrel{\mathrm{-}}{1}$2} twinning. This twinning mechanism primarily forms the radial texture by altering the stress state. Consequently, this change not only facilitates twin activation but also modifies the rotation direction of grains during the twinning process. Compared to the cone with a ‘Q’ ratio of 1.055, the deformation cone with a ‘Q’ ratio of 1.300 contains a greater number of twins oriented along <0001>//RD, leading to a stronger radial texture in the tube. Full article

The loss of the MV Estonia has been investigated by various organizations since the accident in September 1994. The root cause of the accident has been assumed to be known and the consequent sinking process well established. However, in September 2020, a new video recording by an underwater ROV was published, showing a new, previously unknown, penetrating damage on the starboard side of the MV Estonia wreck lying on the seabed. Based on this new evidence, the Estonian Safety Investigation Bureau (ESIB) initiated a preliminary assessment of the new information on the MV Estonia accident. Whether the New Side Damage (NSD) on the starboard side was already present while the MV Estonia was afloat on the surface, or whether it resulted from the collision of the sinking vessel with the seabed somewhat later, is an important issue needing clarification: In the first case, the validity of the conclusions on the root cause of the accident presented in the previous studies could prove premature. One of the goals of the present investigation by the Hamburg Ship Model Basin (HSVA) is to shed light on this question: The results of the numerical simulations of the sinking process carried out for various damage configurations in seaway using not only single simulations, but also a statistical approach are presented. Full article

This study presents a finite element-based numerical simulation of a shipwreck scenario at the 4th-century BC underwater archaeological site near the island of Žirje, integrating engineering analysis with archaeological interpretation. The site is notable for the wide scattering of amphorae across the seafloor. A scaled model, based on the well-documented Kyrenia shipwreck, found off the coast of Cyprus, was developed to approximate the estimated parameters of the Žirje vessel, incorporating reduced dimensions, an adjusted freeboard, and a total deadweight of approximately six tons. The finite element model of the ship, its cargo, and the seabed was developed using LS-DYNA R11.1. software. Instead of fluid modelling, the study employed explicit dynamic analysis with a rigid seabed, gravitational loading, and automatic contact to reduce computational cost. A series of parametric simulations explored the effects of roll, yaw, and varying gravitational forces on the sinking behaviour and cargo dispersion. Results indicate that only certain non-uniform sinking conditions, combined with seabed currents, accurately replicate the archaeological distribution of the amphorae. This approach underscores the value of integrating finite element analysis (FEA) with archaeological data to generate digitally supported hypotheses, demonstrating how numerical reconstruction can enhance the interpretation of complex underwater archaeological sites. Full article

In order to solve the problems of wrinkling, cracking, and springback that occur during the single deep drawing forming process of household stainless steel sinks without annealing, the deep drawing process of thin SUS304 stainless steel was studied using a DYNAFORM numerical simulation and experimental analysis. The uniaxial tensile test results indicate that 304 stainless steel exhibits different levels of plasticity in different directions. The TD direction, which is perpendicular to the rolling direction, has the lowest elongation, which is 11.8% lower than that in the rolling direction. The maximum bulging depth of the thin specimens in the finite element simulation reached 17.142 mm, and the maximum bulging depth of the specimens with cracks in the experiment was 16.572 mm, indicating that the results of the finite element simulation were in good agreement with those of the experiment. Finally, through simulation and experimentation, the optimal process for forming stainless thin steel sinks was obtained when the fillet radius R was 5 mm, the stamping speed was 20 mm/s, the blank holder force was 3 MPa, and the friction coefficient was 0.120. Full article

This paper investigated pre-concentration of a low-grade Upper Group 2 (UG2) ore to assess the possibility of rejecting waste at a typical discard Platinum Group Metals (PGMs) grade of <0.4 g/t at mass rejection to floats greater than 16% by comparing feed prepared by High pressure grinding rolls (HPGR) to Conventional crushers (Cone crushers). Heavy Liquid Separation (HLS) was conducted as a benchmark test to Dense Medium Separation (DMS) to determine the expected grade, recovery, and mass yield for various size classes and crusher. The comparison between fine size classes −9.5 + 1.18 mm and −6.7 + 1.18 mm crushed by HPGR and conventional crushing showed that, under the conditions tested, the conventional crusher outperformed HPGR in terms of high sinks grade and a higher percentage of material exposed to pre-concentration. Looking at coarser size fractions (+12 mm), HLS results showed that under the conditions tested, size fraction −20 + 1.18 mm crushed by a conventional crusher at an optimum density of 3.4 g/cm³ is an optimized size fraction to run the DMS plant. The pilot DMS cyclone testwork showed that 61.1% by mass could be rejected to the floats stream based on Run of Mine (ROM) feed at 1.12% Cr₂O₃ and 0.42 g/t Total PGMs + Au grade, a typical discardable PGMs grade. Full article

To provide the necessary theoretical models of sphere–soil interaction for the structural design, motion control, and simulation of spherical robots, this paper derives analytical expressions for traction force and driving torque when spherical robots slide and sink into sandy terrain, based on terramechanics and multibody dynamics. Furthermore, orthogonal experimental analysis identifies the load, joint angular acceleration, and maximum joint angular velocity of spherical robots as influencing factors, highlighting that the load significantly affects their longitudinal motion performance. Experimental results indicate that rolling friction and additional resistance on sandy terrain cannot be ignored. The corrected theoretical model effectively replicates the temporal variation of driving torque exerted by spherical robots on sandy terrain. Numerical computations and experimental analyses demonstrate that increasing the radius of the sphere shell, the load, and the slip ratio all lead to increased traction force and driving torque. However, traction force and driving torque begin to decrease once the slip ratio reaches approximately 0.5. Therefore, in the design of spherical robot structures and control laws, appropriate parameters such as load and slip ratio should be chosen based on the established sphere–soil interaction theoretical model to achieve high-quality longitudinal motion performance on sandy terrain. Full article

Theoretical influence of the buoyancy and thermal radiation effects on the MHD (magnetohydrodynamics) flow across a stretchable porous sheet were analyzed in the present study. The Darcy–Forchheimer model and laminar flow were considered for the flow problem that was investigated. The flow was taken to incorporate a temperature-dependent heat source or sink. The study also incorporated the influences of Brownian motion and thermophoresis. The general form of the buoyancy term in the momentum equation for a free convection boundary layer is derived in this study. A favorable comparison with earlier published studies was achieved. Graphs were used to investigate and explain how different physical parameters affect the velocity, the temperature, and the concentration field. Additionally, tables are included in order to discuss the outcomes of the Sherwood number, the Nusselt number, and skin friction. The fundamental governing partial differential equations (PDEs), which are used in the modeling and analysis of the MHD flow problem, were transformed into a collection of ordinary differential equations (ODEs) by utilizing the similarity transformation. A semi-analytical approach homotopy analysis method (HAM) was applied for approximating the solutions of the modeled equations. The model finds several important applications, such as steel rolling, nuclear explosions, cooling of transmission lines, heating of the room by the use of a radiator, cooling the reactor core in nuclear power plants, design of fins, solar power technology, combustion chambers, astrophysical flow, electric transformers, and rectifiers. Among the various outcomes of the study, it was discovered that skin friction surges for 0.3 $\le F_1\le$ 0.6, 0.1 $\le k_1\le$ 0.4 and 0.3 $\le M\le$ 1.0, snf declines for 1.0 $\le G_r\le$ 4.0. Moreover, the Nusselt number augments for 0.5 $\le R\le$ 1.5, 0.2 $\le N_t\le$ 0.8 and 0.3 $\le N_b\le$ 0.9, and declines for 2.5 $\le Pr\le$ 5.5. The Sherwood number increases for 0.2 $\le N_t\le$ 0.8 and 0.3 $\le Sc\le$ 0.9, and decreases for 0.1 $\le N_b\le$ 0.7. Full article

Based on the Environmental Kuznets Curve (EKC) hypothesis, this paper examines whether rural broadband adoption affects agricultural carbon reduction efficiency (ACRE), using panel data from 30 Chinese provinces from 2011 to 2019. This paper achieves a measurement of ACRE by taking the carbon sink of agricultural as one of the desired outputs and using a Slacks-Based Measure (SBM) model and the global Malmquist–Luenberger (GML) index. The results show that: (1) Rural broadband adoption has a positive effect on ACRE. The relationship between the income of rural residents and ACRE was an inverted U-shaped, which confirms the EKC hypothesis. (2) Land transfer has a significant promoting effect on the relationship between rural broadband adoption and ACRE. When the land transfer rate is high, the positive effect of broadband adoption is obvious. (3) The positive effect of broadband adoption on ACRE was more obvious when farmers invested more in production equipment, that is to say, it has a significant positive moderating effect. As farmers in many developing countries suffer from increasingly frequent and severe extreme weather events, we believe that the results of this study also have implications for the implementation of agricultural carbon reduction and smart agricultural equipment roll-out in many countries. Full article

Sakiadis rheology of a generalised polymeric material, as well as a heat source or sink and a magnetic field, are all part of this study. Thermal radiations have been introduced into the convective heating process. The translation of a physical situation into a set of nonlinear equations was achieved through mathematical modelling. To convert the resulting partial differential equation into a set of nonlinear ordinary differential equations, appropriate transformations have been used. The velocity and temperature profiles are generated both analytically by HAM and numerically by the Runge–Kutta method (RK-4). In order to analyse the behaviour of the physical quantities involved, numerical and graphical depictions have been offered. To show that the acquired findings are correct, a nonlinear system error analysis has been offered. The heat flux study has been shown using bar charts. For the essential factors involved, the local Nusselt number and local Skin friction are calculated in tabular form. The fluid particles’ molecular mobility was slowed due to the magnetic field and porosity, and the heat transfer rates were demonstrated to be lowered when magnetic and porosity effects are present. This magnetic field and porosity effects regulating property has applications in MHD ion propulsion and power production, the electromagnetic casting of metals, etc. Furthermore, internal heat absorption and generation have diametrically opposed impacts on fluid temperature. The novelty of the present study is that no one has investigated the Sakiadis flow of thermal convection magnetised Oldroyd-B fluid in terms of a heat reservoir across a porous sheet. In limited circumstances, a satisfactory match is revealed when the collected values are compared to the existing work published corroborating the current attempt. The findings of this study are expected to be applicable to a wide range of technical and industrial processes, including steel extrusion, wire protective layers, fiber rolling, fabrication, polythene stuff such as broadsheet, fiber, and stainless steel sheets, and even the process of depositing a thin layer where the sheet is squeezed. Full article

Steel products are coated with Aluminum (Al) and Zinc (Zn) alloys to improve their corrosion properties. Bulk steel products are coated in batches; however, steel sheets are coated by a continuous hot-dip galvanizing process. Steel sheets are guided into and out of the molten Al-Zn-Si (AZ) bath with the help of stainless-steel rolls, known as guiding, and sink rolls. These rolls are subjected to excessive surface corrosion with molten AZ bath and, hence, are replaced frequently. The surface deterioration of the immersed rolls has been a long-standing issue in the galvanizing industry. In this study, 316L stainless-steel (SS) rods are immersed in the AZ alloy at 600 °C. The immersion time varied from 1 day to 7 days under the static melt conditions in the iron (Fe)-saturated AZ bath. Microstructural analysis of the immersed SS samples revealed two distinct intermetallic compound (IMC) layers forming between the SS substrate and AZ alloy. The IMC layer 1 (AL-1) formed between the SS substrate and IMC layer 2 (AL-2), growing in thickness from 68 µm to 120 µm within 5 days of immersion. The AL-2, which formed between AL-1 and AZ alloy after 24 h of immersion, then grew in thickness up to 150 µm with an uneven trend. The AL-1 is composed of Fe₂Al₅ and that of AL-2 is composed of FeAl₃ that were predicted by the FactSage thermodynamic analysis. Crack development between AL-1 and AL-2 layers, and disintegration of AL-2 into the AZ bath, are key findings of this study. A drastic hardness increase was observed because the IMC layers produce a hard and brittle sink roll surface. Full article

This paper discusses the Darcy–Forchheimer three dimensional (3D) flow of a permeable nanofluid through a convectively heated porous extending surface under the influences of the magnetic field and nonlinear radiation. The higher-order chemical reactions with activation energy and heat source (sink) impacts are considered. We integrate the nanofluid model by using Brownian diffusion and thermophoresis. To convert PDEs (partial differential equations) into non-linear ODEs (ordinary differential equations), an effective, self-similar transformation is used. With the fourth–fifth order Runge–Kutta–Fehlberg (RKF45) approach using the shooting technique, the consequent differential system set is numerically solved. The influence of dimensionless parameters on velocity, temperature, and nanoparticle volume fraction profiles is revealed via graphs. Results of nanofluid flow and heat as well as the convective heat transport coefficient, drag force coefficient, and Nusselt and Sherwood numbers under the impact of the studied parameters are discussed and presented through graphs and tables. Numerical simulations show that the increment in activation energy and the order of the chemical reaction boosts the concentration, and the reverse happens with thermal radiation. Applications of such attractive nanofluids include plastic and rubber sheet production, oil production, metalworking processes such as hot rolling, water in reservoirs, melt spinning as a metal forming technique, elastic polymer substances, heat exchangers, emollient production, paints, catalytic reactors, and glass fiber production. Full article

This work presents the simple and rapid fabrication of a polymer-based microfluidic prototype manufactured by rolling up thin films of polymer. The thin films were fabricated via a casting method and rolled up around a center core with the aid of plasma activation to create a three-dimensional (3D) spiral microchannel, hence reducing the time and cost of manufacture. In this work, rolled-up devices with single or dual fluidic networks fabricated from a single or two films were demonstrated for heat sink or heat exchanger applications, respectively. The experimental results show good heat transfer in the rolled-up system at various flow rates for both heat sink and heat exchanger devices, without any leakages. The rolled-up microfluidic system creates multiple curved channels, allowing for the generation of Dean vortices, which in turn lead to an enhancement of heat and mass transfer and prevention of fouling formation. These benefits enable the devices to be employed for many diverse applications, such as heat-transfer devices, micromixers, and sorters. To our knowledge, this work would be the first report on a microfluidic prototype of 3D spiral microchannel made from rolled-up polymeric thin film. This novel fabrication approach may represent the first step towards the development of a pioneering prototype for roll-to-roll processing, permitting the mass production of polymer-based microchannels from single or multiple thin films. Full article