Metal Volume Research Articles

Spatial distribution and consequences of contaminants in harbour sediments – A case study from Richards Bay Harbour, South Africa

Richards Bay Harbour (RBH) is situated in the industrialized area on the northeast coast of South Africa. To decipher recent human activities and accompanying environmental degradation, surface sediment was collected across RBH and analysed for granulometric and elemental composition, microfaunal assemblages, and microplastics. Microplastics occur most abundantly near recreational areas, whereas metal contamination relates to activities at bulk goods terminals from which they are imported or exported. In particular, Cr and Cu concentrations in surface sediment near bulk goods terminals exceed South African sediment quality guidelines. In metal contaminated sediment, bioindicators reflected stress and were noticeably impacted. A transect of short sediment cores reflects spatial and historical metal contamination and allows quantification of the load of metals within the sediment column. The volume of metal (Cr) contaminated sediment was estimated at almost 2 million m3.

Electrical conductivity of porous binary powder mixtures

Simultaneous data of the quasi-static compaction and electrical conductivity of porous, binary powder mixtures have been collected as a function of bulk density. The powder mixtures consist of a metal conductor, either titanium or iron, an insulator, and pores filled with ambient air. The data show a dependency of the conductivity in terms of relative bulk density and metal volume fraction on conductor type and conductor particle characteristics of size and shape. Finite element models using particle domains generated by discrete element method are used to simulate the bulk conductivity near its threshold while the general effective media equation is used to model the conductivity across the compression regime.

Bioleaching of metals from cellphones batteries by a co-fungus medium in presence of carbon materials

Today, the increased rate of electronic portable devices has led to an unprecedented amount of electronic waste. The mass production of the new generation of batteries, such as lithium-ion and lithium-ion polymer batteries used in the electronic devices releases a high volume of toxic metals to the environment, causing pollution and affecting human health. Additionally, the release of vinasse from the ethanol industry causes negative and irrecoverable effects on humans and the environment. In this paper, we investigate an innovative and eco-friendly procedure for recycling metals in lithium-ion polymer batteries in the presence of a mixed fungal culture of Aspergillus niger and Aspergillus tubingensis and pure sucrose, impure sucrose, and vinasse in three different methods: one step bioleaching, two-step bioleaching, and spent medium bioleaching. A variety of analyses, done during this investigation, indicated that the metals were recycled successfully and with high efficiency through spent medium bioleaching.

Developing thermoplastic hybrid titanium composite laminates (HTCLS) at room temperature: Low-velocity impact analyses

Hybrid titanium composite laminates (HTCLs) are high-performance light-weight fiber metal laminates (FMLs) that are being increasingly used in various industries such as aeronautical, military, and marine thanks to their optimized fracture toughness, impact resistance, and thermal performance. In the current study, the low-velocity impact (LVI) characteristics of a new generation of thermoplastic (TP) HTCLs at various energy levels are investigated. To do so, Ti-6Al-4 V sheets, carbon fabrics, and ultra-high molecular weight polyethylene (UHMWPE) fabrics are used to fabricate multiple laminates with different fiber types, metal volume fractions, and lamination layups. A low-cost resin infusion process is employed for manufacturing the laminates at room temperature by using a novel liquid thermoplastic methyl methacrylate resin, Elium® 188. Before fabrication, a multi-step surface treatment method is applied on Ti alloy sheets to enhance the interfacial properties between the composite layer and the metal alloy sheet. In addition to TP-HTCLs, equivalent thermosetting (TS) HTCLs with an epoxy resin, Epolam, are fabricated to compare the results and evaluate the possibility of fabricating recyclable TP-FMLs at room temperature with enhanced out-of-plane properties. Impact properties including contact force, deflection, energy parameters, and related damage modes are investigated and presented for each laminate. It is concluded that the newly developed TP-HTCLs can be cured at room temperature and have enhanced impact properties compared to those of TS-HTCLs. Besides, the HTCL with UHMWPE fabrics on its composite sides (before the Ti alloy sheets) performs better in LVI compared to that with carbon fibers on the top and bottom (of its composite core) since UHMWPE exhibits higher strain to failure and fracture toughness compared to carbon fibers.

CREEPING SURFACE LONGITUDINAL ACOUSTIC WAVE: MAIN PROPERTIES AND APPLICATION POSSIBILITIES

Creeping ultrasonic waves have long been successfully used for flaw detection of near-surface and near-bottom zones of metal products. However, due to the fact that the creeping wave generates a lateral transverse wave directed into the metal volume at the third critical angle, it is also possible to test internal defects in principle. At known velocities of propagation of longitudinal and transverse waves in the metal, the third critical angle is easily calculated. Therefore, the time of propagation of the ultrasonic signal along any trajectory between points on the surface and in the volume of the metal can be calculated. Usually, creeping waves are used to test products of plane-parallel shape. There are no cases of their application on curved surfaces in the literature. It is possible that the creeping wave can also propagate over a concave surface. The aim of the article is to test experimentally new ways of using creeping waves. The propagation trajectories of the creeping and lateral transverse waves were studied on a steel plate. The time of passage of the ultrasonic signal along such trajectories of different lengths was measured, and the measurement results were compared with the calculated time values. The measured and calculated values coincided with accuracy sufficient for the coherent accumulation of echo signals that passed through the metal part of the path by the creeping wave and another part of the path by the lateral transverse wave.The propagation of the creeping wave over a concave surface was studied on a steel sample with cylindrical faces of different radii. As a result, it turned out that on a concave surface, the creeping wave propagates at the same speed of longitudinal waves as on a flat surface, but it decays much more strongly with distance. Studies have shown that creeping waves can be used in ultrasonic tomography, where a preliminary calculation of the propagation trajectories of ultrasonic signals is required. The propagation of creeping waves over concave surfaces extends the capabilities of the TOFD method to the area of intube testing

Welding People and Automation

Sheet metal volume manufacture and fabrication specialists, Contracts Engineering, entered 2020 with an increasing demand for its services. In order to boost productivity and meet this rise in orders, it made its first foray into the world of welding automation

Hardness of low-carbon steels during shot blasting

Low-carbon steels are widely used in mechanical engineering. The surface of products made from such steel is often shot blasted for the purpose of cleaning it, hardening the surface layer, forming roughness, etc. Rational technological modes and efficiency of shot blasting of the surface primarily depends on the dynamic hardness of the material being processed. Some researchers [3-6] offer empirical dependences for determining dynamic hardness with a functional dependence on certain mechanical properties of the material. However, the discrepancy between the calculation results behind these dependencies differ significantly. This indicates insufficient consideration of various factors. This article proposes a method for determining the dynamic hardness of low carbon steels during shot blasting, which takes into account both the factors of the loading mode and the properties of the material. The value of dynamic hardness is calculated by dividing the consumed kinetic energy E by the volume of the extruded hole. Therefore, the process of plastic deformation of the hole under the action of the kinetic energy of the attacking shot was considered. The energy losses of the attacking shot are indicated (for elastic and plastic deformation, for internal friction, as a result of which the metal heats up, for microcutting, external friction, splitting of the shot and dissipative losses). An analytical dependence acceptable for practical use is proposed, which takes into account the loading conditions. It is shown that the dynamic hardness of low-carbon steels during shot blasting is directly proportional to the square of the mass of the attacking shot, the attack speed, depends on the coefficient of recovery of the shot speed and on the amount of energy loss, and is inversely proportional to the square of the roughness parameter and the diameter of the sphere described around the shot. The coefficients also indirectly take into account the mechanical properties of the material. The calculated values ​​of the dynamic hardness of low-carbon steels are approximately 2…3 times lower than the static one. This is due to significant energy losses due to internal friction, which causes softening of elementary volumes of metal in the affected zone due to its heating. The actual value of the dynamic hardness of low-alloy steels during shot blasting, determined behind this technique, provides a reasonable choice of rational technological modes and the effectiveness of the shot blasting process from a given result.

Early Neoproterozoic oxygenation dynamics along the northern margin of the West African Craton, Anti-Atlas Mountains, Morocco

Emerging evidence suggests widespread ferruginous marine conditions promoted global seawater phosphate depletion and the maintenance of a low oxygen world at the start of the Neoproterozoic Era. However, the large-scale deposition of marine sedimentary Fe formations, as observed in the Paleoproterozoic, is rare in the early Neoproterozoic Era. We show that at the start of the Neoproterozoic, tidal flat and shallow marine environments along the northern passive margin of the West African Craton (WAC) were fully oxygenated and low in reactive Fe content, until an abrupt and prolong episode of deep-sea hydrothermal activity overwhelmed the WAC margin with strongly reducing Fe-rich hydrothermal fluids. This unique incident is recorded in meter-thick and kilometer-wide shallow marine siliciclastic platform rocks estimated to be ~883 Ma old and containing average bulk Fe content >22 wt% in the Wanimzi Formation in the Moroccan Anti-Atlas Mountains. The abrupt and conformable contact of the Fe-rich succession with the Fe-poor lower and upper transition boundaries, together with geochemical data, suggest rapid initiation and termination of seawater fertilization by the hydrothermal fluids that formed the unmetamorphosed hematite-rich ironstones. Rare Earth Element (REE) and Fe-based redox reconstruction point to an aftermath coincident with a return to shallow siliciclastic marine habitats characterized by a low reactive Fe content and negligible hydrothermal intrusion, where aerobic microbial communities flourished in well‑oxygenated waters. We propose that the early Neoproterozoic tectonic initiation of the breakup of the supercontinent Rodinia supplied large volumes of deep sea hydrothermal Fe, trace metals, and toxic metalloids like arsenic to shallow marine habitats along the WAC, resulting in rapid seawater deoxygenation.

Isogeometric optimization of piezoelectric functionally graded material for energy harvester

Improving the energy harvesting efficiency of piezoelectric energy harvesters (PEHs) in the scientific domain is essential for the application of self-powered microelectromechanical devices. This paper proposes an isogeometric optimization method to optimize the material distribution of piezoelectric functionally graded material (PFGM) energy harvester. Firstly, we establish the isogeometric formulation of the PFGM energy harvester based on the plane strain hypothesis and Hamilton’s principle. Meanwhile, the same non-uniform rational B-splines basis functions are utilized to represent the distribution of the PFGM. Secondly, three optimization models with the specified eigenfrequency and maximum energy conversion efficiency as objective functions are established. Then we derive the analytical sensitivities by the adjoint method and use the method of moving asymptotes to update the design variables. Furthermore, several numerical examples are performed to study the convergence and accuracy of the numerical solutions and analyze the effects of the metallic volume ratio constraint and the initial design domain on the optimized material distribution. More importantly, the dynamic analysis is executed to further test the energy harvesting efficiency based on the optimized designs. The results show that the presented approach can not only realize the specified eigenfrequency but also effectively improve the energy harvesting efficiency.

Impact the parameters of metal-inducer system on its electromagnetic measurands

In this work, we propose the finite-element-based mathematical model of the metal-inducer system. This system consists of a coil with put-on C-shaped ferromagnets. We study how the measurands of the inducer, such as the coil voltage and the uncompensated force acting on metal, depend on the system parameters. We variate the geometry of the system to estimate the boundary effect impact. Also, we study how the coil voltage depends on the ferromagnets’ spacing and their number. The inhomogeneity of electric conductivity is modeled via holes in the metal volume. To estimate their impact, we defined the dependences of the measurands on the number and the size of inhomogeneities.

Bronze-casting workshops of the Vengerovo-2 settlement (Baraba forest steppe)

The formation of the early bronze-casting production in Baraba and the appearance of products of the Seima-Turbino type were completed within the 3rd — early 2nd mil. BC — during the existence of the Krotovo Cul-ture. Plenty of work has been devoted to its characterization; the presence of bronze-casting on the sites has been noted, but special studies of this type of sources are extremely few. The purpose of this paper is to present the characteristics of the production areas associated with the processing of non-ferrous metals, based on mate-rials of the Vengerovo-2 settlement of the Krotovo Culture. Production sites were studied in six dwellings of the settlement. The uniformity of the workshops has been revealed in terms of site planning and principles of organi-zation of the production, although differences in scale have been noted. The use of two types of the forges has been recorded. In all these workshops and in other sites of the culture, a multifunctional sub-rectangular hearth buried in the ground with the walls and floor lined with fragments of ceramics or clay coating was found (with di-mensions of 1.65×0.87–2.3×0.9×0.21–0.52 m). The second type of the forges is less common — a small round or oval pit (0.4–0.5 m in diameter) with the bottom and walls lined with baked clay or fragments. The smelting was carried out with forced air supply. The casting of the metal was taking place next to the forge. Crushed bones were used as fuel. The production complex demonstrates extensive external economic and commercial ties. This is manifested by penetration of significant volumes of non-ferrous metal into the ore-barren areas of the Central Baraba, as well as by the presence of imported foundry equipment (molds made of marl and talc). The simultaneous presence inside the casters’ dwellings of bones of taiga-zone animals and those living in the southern, steppe regions indicates significant length of the supply routes. The specific features and unification of the production of the manufacturing equipment, nature of the work carried out, volume of heats, and a large number of similar-type forms suggest specialization of the village in the bronze casting production.

Optimization of metallic powder filaments for additive manufacturing extrusion (MEX)

Additive manufacturing (AM) of metallic powder particles has been establishing itself as sustainable, whatever the technology selected. Material extrusion (MEX) integrates the ongoing effort to improve AM sustainability, in which low-cost equipment is associated with a decrease of powder waste during manufacturing. MEX has been gaining increasing interest for building 3D functional/structural metallic parts because it incorporates the consolidated knowledge from powder injection moulding/extrusion feedstocks into the AM scope—filament extrusion layer-by-layer. Moreover, MEX as an indirect process can overcome some of the technical limitations of direct AM processes (laser/electron-beam-based) regarding energy-matter interactions. The present study reveals an optimal methodology to produce MEX filament feedstocks (metallic powder, binder, and additives), having in mind to attain the highest metallic powder content. Nevertheless, the main challenges are also to achieve high extrudability and a suitable ratio between stiffness and flexibility. The metallic powder volume content (vol.%) in the feedstocks was evaluated by the critical powder volume concentration (CPVC). Subsequently, the rheology of the feedstocks was established by means of the mixing torque value, which is related to the filament extrudability performance.

A numerical study about the effects of the metal volume fraction on the effective properties of a porous piezoelectric composite with metalized pore boundaries

This work investigates a developed porous piezoelectric composite with metal layers introduced at the interfaces between the piezoelectric and vacuum phases. These metal layers can be added to improve the mechanical and electromechanical properties of the composite. The ordinary porous piezocomposite, which contains only vacuum pores, and the piezocomposite with metal inclusions, whose pores are filled with metal, were explored as specific cases. We constructed the finite element model for all composites understudy and determined their macro properties using the effective moduli theory, which depends on the well-known Hill-Mandel principle. We considered a simple representative unit cell cubic volume, which consists of a piezoelectric matrix with a spherical pore at its center. We compared the properties of all systems and explored the effects of the metal fraction increase on the effective moduli. There are drastic effects on the dielectric permittivity and piezoelectric properties of the considered composite due to the presence of metal inclusion. With an appropriate design of the porous piezocomposite with a metalized pore surface, better effective piezoelectric strain coefficients and transverse transduction coefficient can be achieved. As a result, it is expected that piezoelectric transducers made from this piezocomposite would perform well in piezoelectric motors, transverse piezoelectric sensors, and transverse piezoelectric energy harvesters.

Energy absorption and damage mechanism of UHMWPE-aluminum composite sandwich laminate under impact loading: An experimental investigation

This study investigates impact behavior and energy absorption of a Fiber Metal Laminate (FML) made of ultra-high molecular weight polyethylene (UHMWPE) fiber composite and aluminum 2024-T3 sheets. Specimens have been tested against two types of projectiles and failure modes are compared. The effect of different thicknesses of aluminum sheets and composite core on impact performance is investigated. To examine the influence of the lay-up sequence, two types of FML including 2/1 and 3/2 configurations have been tested. The results show that increasing the thickness of the composite core increases the absorption of energy as well as specific energy absorption (SEA). The highest amount of SEA is obtained for the sample with the lowest metal volume fraction. Damage patterns show that due to the flexibility of UHMWPE fibers and ductility of Al 2024-T3, the metal and the composite core have been deformed proportionally and more energy is absorbed. This mechanism is not seen in other conventional FMLs such as glass fiber metal laminate (GLARE). Compared with aluminum sheet and GLARE under the same conditions, the proposed FML has SEA more than 3 times that of aluminum and more than 2 times that of GLARE.

Interfacial Tension Modulation of Liquid Metal via Electrochemical Oxidation

Herein, this progress report summarizes recent studies of electrochemical oxidation to modulate the interfacial tension of gallium‐based alloys. These liquid alloys have the largest interfacial tension of any liquid at room temperature. The ability to modulate the tension offers the possibility to create forces that change the shape and position of small volumes of liquid metal. It has been known since the late 1800s that electrocapillarity—the use of potential to modulate the electric double layer on the surface of metals in electrolyte—lowers the interfacial tension of liquid metals. This phenomenon, however, can only achieve modest changes in interfacial tension since it is limited to potentials that avoid Faradaic reactions. A recent discovery suggests reactions driven by the electrochemical oxidation of gallium alloys cause the interfacial tension to decrease from ≈500 mN m−1 at 0 V to ≈0 mN m−1 at less than 1 V. This change in interfacial tension is reversible, controllable, and goes well‐beyond what is possible via conventional electrocapillarity or surfactants. This report aims to introduce beginners to this field and address misconceptions. The report discusses applications that utilize modulations in interfacial tension of liquid metal and concludes with remaining opportunities and challenges needing further investigation.

Influence of Filler on the Microstructure, Mechanical Properties and Residual Stresses in TIG Weldments of Dissimilar Titanium Alloys

The influence of titanium alloy (Ti–5Al–2.5Sn) and commercially pure titanium (cpTi) as fillers on dissimilar pulsed tungsten inert gas weldments of Ti–5Al–2.5Sn/cpTi was investigated in terms of microstructure, mechanical/nano-mechanical properties, and residual stresses. A partial martensitic transformation was observed in the weldments for all the welding conditions due to high heat input. The microstructure evolved in the FZ/cpTi interfacial region was observed to be the most sensitive to the proportion of α stabilizer in the filler alloy. Furthermore, the addition of filler alloy improved the tensile properties and nano-mechanical response of the weld joint owing to the increased volume of metal in the weld joint. As compared to the Ti–5Al–2.5Sn wire, the use of cpTi filler wire proved to be better in terms of energy absorbed during tensile and impact tests, tensile strength and ductility of the dissimilar welds. An asymmetrical residual stresses profile was observed close to the weld centerline, with high compressive stresses on the Ti–5Al–2.5Sn side for both the weldments obtained with and without filler wires. This was attributed to mainly the low thermal conductivity of Ti–5Al–2.5Sn. The presence of residual stresses also influenced the nano-hardness profile across the weldments.

Influence of bevel angle on the welding-induced residual stress and distortion based on a thermometallurgical-mechanical model in a Q345-316L dissimilar butt welded joint

Generally, residual stress and distortion are evident in dissimilar welded joint, which are easily affected by different welding parameters. The occurrence of residual stress and distortion almost is attributed to that the non-uniform expansion and contraction of the weld and surrounding base material during arc welding. Different bevel angle has a serious effect for the result of welding due to producing different thermal conduction direction and volume of filler metal. Therefore, the effect of bevel angle on residual stress and distortion in a Q345-316L dissimilar joint is studied employing finite element method and experiment. Considering thermo-metallurgical-mechanical coupling behaviors, solid phase transition effect, the isotropic hardening model and mobile heat resource were performed on the stress field and distortion in the joints of V-bevel angle 45°, 60°, 75°, and 90°. Besides, the result of the simulation was verified by the corresponding experiment result. As a result, it is found that the influence of bevel angle on the residual stress and distortion is significantly apparent in the Q345-316L dissimilar joint.

Air-Stability Improvement of Solar Selective Absorbers Based on TiW-SiO2 Cermet up to 800 °C.

A high-temperature air-stable solar selective absorber (SSA) based on TiW-SiO2 cermet is prepared by the co-sputtering method. The obtained SSA shows remarkable stability in spectrum, structure, and chemistry after air-annealing at 700 °C, demonstrating its resistance against air erosion at high temperature. Comparing with W-SiO2-based SSA, the addition of the Ti element is proved to be effective in enhancing the thermal stability of SSA. Nevertheless, as the temperature increases to 750 °C, perfectly round cavities appear and induce the deterioration of the coating. A phase transformation from α-W to β-W is found at the interface of TiW/HMVF (high metal volume fraction layer) during deposition. Consequently, the inverse phase transformation from β-W to α-W at above 750 °C results in small vacancies at the interface, being the incentive of cavity generation. Afterward, the violent morphological changes of oxidized TiW accelerate the cavities expansion. To enhance its tolerance ability of service temperature, a Cr barrier layer is introduced to prevent the diffusion of oxygen into the TiW layer. Therefore, the optimal SSA performs stably at 800 °C and the failure temperature is elevated to 850 °C, revealing that the air-stable TiW-SiO2-based SSA has outstanding potential in high-temperature photothermal conversion.

Simulation of arc crater formation and evolution on plasma facing materials

• A 2D axially symmetric arc crater model was developed by COMSOL software. • Formation and evolution of arc craters on PFMs were simulated and analyzed. • Refractory metals W and Mo are more difficult to be damaged by arcs than Cu and Al. Arc erosion on plasma facing materials in tokamak devices is a potential source of impurities and dust in plasma. A two dimensional axially symmetric COMSOL model with heat transfer, fluid dynamics including phase transition and surface tension effect has been used to describe the formation and evolution of arc craters on plasma facing materials. The formation and evolution of arc crater on W cathode is described in detail. The energy flux loading causes melting of central area within a few nanoseconds. Due to the gradients of incident pressure, the melted layer is extruded out, and thus forms the melt jets. The differences of the arc craters on several related materials in tokamaks under the same pressure and energy flux density are also discussed. The crater temperature of W and Mo is much higher than that of Cu and Al. And, the melting volume of refractory metals W and Mo is significantly lower than that of Cu and Al. Refractory metals are more difficult to be damaged by the arcs, and more suitable for plasma facing materials.

Physical Nature of Strengthening Mechanisms During Extremely Long-Term Operation of Rails

The quantitative estimation of strengthening mechanisms of rails’ surface layer is carried out on the basis of regularities and formation mechanisms of structure-phase states revealed by the methods of modern physical materials science. It is performed at different depths of the rail head along the central axis and fillet of differentially quenched 100-meter rails after the extremely long-term operation (gross passed tonnage of 1411 mln tons). A long-term operation of rails is accompanied by the formation of structural constituent gradient consisting of a regular change in the relative content of lamellar pearlite, fractured pearlite, the structure of ferrite-carbide mixture, scalar, and excess dislocation density along the cross-section of the rail head. As the distance to the rail fillet surface decreases, the relative content of metal volume with lamellar pearlite decreases. However, the relative content of metal volume with the presence of the fractured pearlite structure and ferrite-carbide mixture increases. The contributions caused by the matrix lattice friction, intraphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution strengthening, pearlite component of steel structure are estimated. It is shown that the main mechanism of strengthening in the surface layer is due to the interaction of moving dislocations with low-angle boundaries of nanometer dimensional fragments and subgrains. The main dislocation strengthening mechanism in a near-surface layer at a depth of 2-10 mm is due to the interaction of moving dislocations with immobile ones.