Metal Bridge Research Articles

Novelty in Intelligent Controlled Oscillations in Smart Structures

Structural control techniques can be used to protect engineering structures. By computing instantaneous control forces based on the input from the observed reactions and adhering to a strong control strategy, intelligent control in structural engineering can be achieved. In this study, we employed intelligent piezoelectric patches to reduce vibrations in structures. The actuators and sensors were implemented using piezoelectric patches. We reduced structural oscillations by employing sophisticated intelligent control methods. Examples of such control methods include H-infinity and H2. An advantage of this study is that the results are presented for both static and dynamic loading, as well as for the frequency domain. Oscillation suppression must be achieved over the entire frequency range. In this study, advanced programming was used to solve this problem and complete oscillation suppression was achieved. This study explored in detail the methods and control strategies that can be used to address the problem of oscillations. These techniques have been thoroughly described and analyzed, offering valuable insights into their effective applications. The ability to reduce oscillations has significant implications for applications that extend to various structures and systems such as airplanes, metal bridges, and large metallic structures.

Spatial distribution of corrosion products from a bridge pier

AbstractThis paper studies the spatial distribution of corrosion by-products by a bridge pier within a conductive medium. An electrochemical impedance spectroscopy (EIS) technique was used to investigate an uncoated metallic bridge pier submerged in static distilled water. An equivalent circuit model, derived from EIS results, served as the foundation for the study. Further, the role of diffusion was analysed, considering its significance in characterising the transfer of particles from the pier into the surrounding water. This exploration revealed the complex interaction between the diffusion processes of various corrosion by-products as a function of distance. In addition, by evaluating the spatial distribution of iron (II) corrosion by-products and modelling nanoparticle diffusion, the research examined the impact of diffusion and concentration on corrosion particle transmission. The findings, analysed via Nyquist and Bode plots, demonstrate significant differences between theoretical and empirical diffusion coefficients. Results indicated that under natural corrosion conditions, the primary product of the corrosion reaction, iron (II), disperses into the medium when oxidation occurs. The elevated resistivity due to the presence of iron (II) underscores the diffusion effect, leading to corrosion product precipitation and reaching saturation level. Additionally, the results demonstrated ideal values for the diffusion coefficient, which are crucial for advanced corrosion modelling. The results emphasised the need for empirical data to improve corrosion prediction models and informed maintenance strategies for submerged structures.

Centrifugal directional freezing and pressure infiltration: Tailoring gradient structures and mechanical properties in Al/B4C composites

Inspired by the gradient structures found in natural materials like bone, this study presents a novel fabrication method combining centrifugal freeze casting and pressure infiltration to produce Al/B4C composites with a tunable gradient layered structure, effectively addressing the challenge of achieving both high strength and toughness in metal-matrix composites. By precisely controlling key parameters such as centrifugal speed, ceramic content, particle size distribution, and freezing temperature, we achieved a gradient transition from high hardness and strength in the outer layers to lower hardness and higher toughness in the inner layers, mimicking the performance characteristics of natural materials. Specifically, higher centrifugal speeds and multi-sized ceramic particles promoted a more pronounced gradient structure, with larger particles concentrating in the outer regions for enhanced strength. While increasing ceramic content improved overall strength, it also affected toughness, highlighting the need for optimization. Freezing temperature influenced the ice-crystal structure and interlayer ceramic bridging, impacting both the gradient and overall composite properties. The optimized composites exhibited a unique combination of low density, high strength, and exceptional fracture toughness, primarily attributed to strong interfacial bonding, effective crack deflection and metal bridging, and formation of an interpenetrating structure. This study provides a versatile, cost-effective and scalable pathway for fabricating bioinspired high-performance metal–ceramic composites.

Toward Limited Durability of Load-Bearing Beams of Metal Bridge Spans

The paper considers the limited durability as a structural property which continuously maintains operability during certain time under random loading of beam elements and proposes the definition for durability as the main criterion of failure and destruction of beam elements or beam as a whole.Methodology: Structural analysis; cumulative model of quasi-monotonic damage accumulation and failure of beam elements.Purpose: To develop methods to determine the durability based on damages representing a random, non-stationary loading process.Research findings: The damage accumulation is calculated for beams. The process is considered as quasi-monotonic. Stress-strain curves are obtained, including changes in probabilistic characteristics of not only structural materials, but also loading modes from the damage growth. The durability limitations of span girders are estimated both by nominal stresses and total damage in the more dangerous section.

Floating Island Structure With Metal Bridge to Resolve the Turn-On Recovery Problem

Floating Island Structure With Metal Bridge to Resolve the Turn-On Recovery Problem

Towards Resource Durability of Bridge Spans

The paper studies durability of metal bridge spans as resource reliability and operability characterized by their performance specifications and maintainability before the limiting state. The ultimate condition of superstructures, in which further operation is impractical without restoration work to ensure operation conditions. The qualitative assessment of the resource durability of superstructures is based on the supposition that they maintain the normative operability at least for the specified operational period from incubation and service life to residual resource, indicating the possibility of removing the superstructure beyond the "serviceable" limit.

Numerical Modeling and Simulation of Vehicular Crashes into Three-Bar Metal Bridge Rail

Advanced finite element (FE) modeling and simulations were performed on vehicular crashes into a three-bar metal bridge rail (TMBR). The FE models of a sedan, a pickup truck, and a TMBR section were adopted in the crash simulations subject to Manual for Assessing Safety Hardware (MASH) Test Level 2 (TL-2) and Test Level 3 (TL-3) requirements. The test vehicle models were first validated using full-scale physical crash tests conducted on a two-bar metal bridge using a sedan and a pickup truck with similar overall physical properties and sizes to their respective vehicles used in the simulations. The validated vehicular models were then used to evaluate the crash performance of the TMBR using MASH evaluation criteria for structural adequacy, occupant risk, and post-impact trajectory. The TMBR met all MASH TL-2 requirements but failed to meet the MASH TL-3 Criteria H and N requirements when impacted by the sedan. The TMBR was also evaluated under in-service conditions (behind a 1.52 m wide sidewalk) and impacted by the sedan under MASH TL-3 conditions. The simulation results showed that the TMBR behind a sidewalk met all safety requirements except for the occupant impact velocity in the longitudinal direction, which exceeded the MASH limit by 3.93%.

Ni3C nanosheets and PVA nanocomposite based memristor for low-cost and flexible non-volatile memory devices

Two-dimensional (2D) MXenes have gained extensive attention in the field of memristors due to their high ion mobility, chemical stability and tunable electrical and surface properties. Moreover, MXenes have tunable interlayer bonding which enables enhancement in memristor performance. In this work, we synthesize a novel nanocomposite of Ni3C nanosheets and polyvinyl alcohol (PVA) and fabricate a flexible memristor with Ag/Ni3C-PVA/ITO/PET configuration for non-volatile memory applications. Ni3C nanosheets were synthesized from Ni-MAX (Ni3AlC2) through a solvothermal etching and exfoliation process. The nanosheet like structure of Ni3C is confirmed through Scanning Electron Microscopy (SEM) and Transmission Electron microscopy (TEM). Characterization techniques like X-ray diffraction (XRD), Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) reveal the crystalline phases, surface functional groups and chemical bonds present in Ni3C nanosheets and Ni3C-PVA nanocomposite. The memristor was fabricated through a facile low cost solution processed based fabrication technique. The Ag/Ni3C-PVA/ITO/PET memristor exhibits bipolar non-volatile switching characteristics. The device with optimised mass ratio of 4:3 (Ni3C: PVA) shows a decent off/on ratio of 2.09 × 102, long retention time of 104 s, and an endurance of 102 DC cycles. The SET voltage of the as-fabricated device is 2.8 V and the RESET voltage is −5.33 V. The flexible memristor exhibits outstanding mechanical robustness over 500 bending cycles. The high charge carrier mobility of Ni3C results in lower switching voltage and the dielectric property of PVA improves data retention and off/on ratio of the memristor. The resistive switching behaviour is explained through conductive metallic bridge mechanism. The conduction mechanism follows Ohmic conduction in ON state and trap controlled space charge limited current (TCSCLC) mechanism in OFF state. The results demonstrate that the nanocomposite with its superior resistive switching effects is suitable for cost-effective, high-performance, flexible non-volatile memory devices.

Heat and mass transfer behavior in CMT plus pulse arc manufacturing

The metal transfer mode, temperature distribution, flow behavior, and microstructure characteristic in the process of cold metal transfer plus pulse (CMT+P) arc manufacturing were investigated by the in-situ observation and numerical simulation. A novel coupling model for droplet-pool interaction under the CMT+P arc was established, along with a new heat source model that considered Marangoni forces on droplets. These innovations provided significant insights into the heat and mass transfer mechanisms in the CMT+P hybrid arc manufacturing process. The results show that the droplets generated by the CMT+P hybrid arc exhibited a mixed transfer mode: short-circuit transfer in the CMT period and projected transfer of one droplet per pulse during the pulse period. The short-circuit transfer was more stable than the projected transfer, attributed to the smooth transfer of droplets to the molten pool through the liquid metal bridge, dominated by surface tension and Marangoni forces. The main energy of the molten pool was provided by droplets, which had a dominant ability to melt the substrate. However, the liquid metal bridge in the CMT period slowed down the heat transfer to the molten pool and had significant oscillating and stirring effects. During the pulse period, the droplet was accelerated and projected transfer by gravity and electromagnetic force. After solidification, the microstructure exhibited an alternating distribution of columnar and equiaxed grains from the bottom-up in the monolayer deposited layer, with a deflected fusion interface towards the scanning direction. At the top of the deposited layer, coarse columnar grains were distributed obliquely or laterally, inhibiting the growth of equiaxed grains and forming a distinct boundary with the equiaxed grains below.

Simulation-Guided Analysis towards Trench Depth Optimization for Enhanced Flexibility in Stretch-Free, Shape-Induced Interconnects for Flexible Electronics.

In this paper, we present an optimization of the planar manufacturing scheme for stretch-free, shape-induced metal interconnects to simplify fabrication with the aim of maximizing the flexibility in a structure regarding stress and strain. The formation of trenches between silicon islands is actively used in the lithographic process to create arc shape structures by spin coating resists into the trenches. The resulting resist form is used as a template for the metal lines, which are structured on top. Because this arc shape is beneficial for the flexibility of these bridges. The trench depth as a key parameter for the stress distribution is investigated by applying numerical simulations. The simulated results show that the increase in penetration depth of the metal bridge into the trench increases the tensile load which is converted into a shear force Q(x), that usually leads to increased strains the structure can generate. For the fabrication, the filling of the trenches with resists is optimized by varying the spin speed. Compared to theoretical resistance, the current-voltage measurements of the metal bridges show a similar behavior and almost every structural variation is capable of functioning as a flexible electrical interconnect in a complete island-bridge array.

Integration of HGIS/HBIM to Reveal and Reconstruct the Vanished Metal Bridge Heritage of the Chinese Eastern Railway Main Line

Integration of HGIS/HBIM to Reveal and Reconstruct the Vanished Metal Bridge Heritage of the Chinese Eastern Railway Main Line

Major Failures and Key Risks Linked to Dental Fixed Prostheses: An in vivo Clinical Study

This clinical investigation aimed to identify factors leading to fixed partial denture failures and their implications, crucial for enhancing clinical outcomes. Conducted in Tripoli, Libya, with 75 patients contributing 235 units, the study utilized John F. Johnston's and John J. Manappallil’s classifications to categorize failure causes. Mechanical issues, predominantly in female patients, were identified as the primary cause of dental bridge failure, particularly in porcelain fused to metal (PFM) bridges with a "Fixed-Fixed" design, mostly in the upper jaw. The study underscores the importance of a multifactorial approach in preventing and managing fixed partial denture failures, emphasizing meticulous prosthesis design, manufacturing, and placement, alongside patient selection, diagnosis, treatment planning, and oral hygiene education.

TECHNOLOGICAL ASPECTS OF PRODUCTION OF EPOXY ASPHALT CONCRETE BY ADDING CARBON ADDITIVES

Epoxy asphalt concrete is a durable, high-quality material consisting of epoxy resins, hardeners, and the mineral part itself. Accordingly, slow-hardening epoxy asphalt concrete has high physical properties and low sensitivity to temperature changes, which makes it usable as a rigid pavement and applicable even on metal and concrete bridge decks. However, a downside of epoxy asphalt concrete is its ability to gain strength over a long period of operation (up to 1 year). It is a disadvantage when using such coatings in the upper layer of the road surface. In addition, a long period of strength gain during intensive use of the road pavement leads to critical destruction of the pavement itself, plastic deformation, and a reduction in the service life (which may differ much from the standard). Using metal fibre substantially increases the strength and keeps the area from collapsing. The use of metal elements can significantly reduce the performance of the tires of vehicles that will drive on the road and even create a hazard in the event of destruction of the epoxy asphalt concrete area. Using epoxy binders notably increases the strength characteristics of road materials, especially at high temperatures, and boosts their ability to resist rutting. At the same time, the characteristics of epoxy concrete do not decrease during operation and at low temperatures, which indicates the versatility of such a material. The only drawback that cancels out all the positive features of epoxy asphalt concrete is its long strength gain. This disadvantage not only led to the problems mentioned above but also delayed the opening of traffic, which, especially on roads of higher categories, caused traffic disruption and inconvenience to the movement of vehicles. The authors proposed a solution to this problem by developing an improved epoxy asphalt concrete composition by introducing fibre ash into the developed composition as a reinforcing and structuring additive that accelerates the pavement formation time and strengthens the asphalt matrix in epoxy asphalt concrete. Keywords: epoxy asphalt concrete, additive, fibre, fly ash, combustion products.

Development and Fabrication of Microdosimeter Arrays Based on Single‐Crystal Diamond Schottky Diodes

The interest in microdosimetry is growing thanks to the advancement in microdosimetric technologies, improving detector performance and reliability. Herein, the fabrication and characterization of a novel diamond‐based microdosimeter are proposed. The microdosimeter consists of an array of single‐crystal diamond Schottky diodes about 1.5 μm thick connected in parallel. The detector prototypes are characterized using the ion beam‐induced charge technique, employing a 6 MeV carbon ions microbeam. Despite a good overall response, the first prototypes are affected by the “bridge effect”: a charge collection beneath the metallic bridges connecting the sensitive volumes (SVs), which alters the energy deposition spectrum. To mitigate the bridge effect, different technological solutions are explored: the selective growth of intrinsic diamond layers and the use of an insulating material such as photoresist. These second prototypes reveal a good SV spatial definition without any charge collection from the bridges and a good response homogeneity within the SVs ranging between 3% and 5% full‐width‐half‐maximum among the different prototypes. While the cell‐like thickness and lateral dimensions of SVs make the diamond microdosimeter array ideal for radiobiological applications, its array configuration can make it highly versatile to perform under different fluence rate conditions in particle therapy.

Experimental investigation on initial arc formation in high-current drawn vacuum arc

Initial arc formation in high-current drawn vacuum arc was investigated experimentally and analyzed quantitatively in this paper. Experiments were conducted in a demountable vacuum chamber. Characteristics of molten metal bridges evolution and arc voltage indicated that initial arc formation could be divided into three stages. The correlation between the rupture of molten metal bridges and the fluctuation of arc voltage in stage 2 was analyzed. In addition, characteristics in stage 2 under different arc currents and opening speeds were analyzed quantitatively.

Thermally stressed state of asphalt concrete layer on a metal base

The results of a finite element study of the thermally stressed and deformed states of a fragment of a two-layer bridge structure, consisting of a bearing metal orthotropic slab with a layer of asphalt concrete applied on it, are presented. It is believed that the materials of the layers are characterized by different thermomechanical parameters, which determine the inhomogeneity of the stress and strain fields. An analogue of these phenomena can be the effect of transformation in electric thermal relays of thermal action on a bimetallic plate with different coefficients of thermal linear expansion into its mechanical displacements, which are used to actuate the switch and switches. Using the method of computer modeling, it was found that these factors lead to the concentration of stresses and strains and changes in the stress-strain state in all elements of the bridge structure end are not taken into account in the modern practice of designing and operating bridges, as well as are one of the reasons for the premature destruction of asphalt concrete pavements. To eliminate these shortcomings, on the basis of finite element algorithms, a theoretical analysis of the thermally stressed state of a metal bridge slab with an asphalt concrete pavement at various ratios of their thicknesses is carried out. It is shown that an increase in the thickness of the upper layer can lead to an increase in shear and normal tensile stresses initiated in it. Therefore, when designing bridge structures, these features should be additionally taken into account.

Tailor-joining of Ti6Al4V skin with V-shaped assembly error using enhanced PLBW scheme: Keyhole dynamics and metal bridging behavior

Building thin-walled titanium alloy skin using conventional laser beam welding (LBW) frequently suffers from undesirable seam quality due to the V-shaped notch; a typical assembly error occurs after skin rolling with a specific sheet thickness range. This work proposed an improved scheme with metal bridging capacity and liquid film stability to overcome this by executing a pulsed laser beam and spot irradiation in a flat-top mode. Welding was performed on 1.5 mm-thick Ti6Al4V sheets configured in the butt joint with a reserved notch geometry, which is 20 degrees between the groove surface. We also conducted numerical modeling and solutions concerning the heat-flow-phase dynamics using an enhanced ray tracing algorithm. Results show that the as-build weld beads, characterized by middle rippers, slight depression, and edge ridges, present superb continuity and uniformity when applying an average heat input of 40–90 J/mm and a pulse energy of 187.5–750 J. Effective metal bridging across the notch error is achieved at both pulse duration and interval phases due to not only the complete melting of welding side but also the enhanced melt film stability against the surface tension. The cooling of the weld pool starts with a sharp temperature drop at ∼3×105 K/s (on average) during the keyhole collapsing regime, then slows down due to the damped up-down oscillation of the free surface combined with the natural convection-conduction effect. The flow pattern of molten metal changes from squeezing-like to vortexes and finally to a backfilling mode, depending on the evolution of keyhole geometry. Although the keyhole dynamics differs, various process conditions regarding heat input and pulse energy yield effective metal bridging of a single weld spot and sufficient refusion between the adjacent weld spots, ensuring the well-overlapped weld bead formation.

SYMULACJA I MODELOWANIE KOMPUTEROWE DYNAMIKI KONSTRUKCJI MOSTÓW Z WYKORZYSTANIEM ANSYS

This study focuses on utilizing computer modeling and simulation techniques, specifically the ANSYS software, to analyze the dynamics of bridge structures. The primary objective was to study the vibrations of a riverbed metal bridge structure and determine their characteristics. The research involved theoretical dynamic calculations considering the design features of the bridge components and the materials used in their construction. The obtained results enabled the determination of resonance frequencies for the vibration modes. By utilizing the ANSYS software, a three-dimensional virtual model of the bridge structure was created, allowing for a detailed analysis of its dynamic behavior. The first three vibration modes of the riverbed metal bridge structure were calculated, and numerical results were obtained for six modes. The findings of this research have practical significance as they provide informed decision-making support during the construction, maintenance, and modernization of bridge structures. The study of bridge dynamics using advanced technologies contributes to enhancing the safety, reliability, and longevity of these vital infrastructure assets.

Research on the Liquid Metal Bridge Formation Process at Contact Separation Moment of DC Air Circuit Breaker

Research on the Liquid Metal Bridge Formation Process at Contact Separation Moment of DC Air Circuit Breaker

Three-Dimensional Au Octahedral Nanoheptamers: Single-Particle and Bulk Near-Field Focusing for Surface-Enhanced Raman Scattering.

Herein, we present a synthetic approach to fabricate Au nanoheptamers composed of six individual Au nanospheres interconnected through thin metal bridges arranged in an octahedral configuration. The resulting structures envelop central Au nanospheres, producing Au nanosphere heptamers with an open architectural arrangement. Importantly, the initial Pt coating of the Au nanospheres is a crucial step for protecting the inner Au nanospheres during multiple reactions. As-synthesized Au nanoheptamers exhibit multiple hot spots formed by nanogaps between nanospheres, resulting in strong electromagnetic near-fields. Additionally, we conducted surface-enhanced Raman-scattering-based detection of a chemical warfare agent simulant in the gas phase and achieved a limit of detection of 100 ppb, which is 3 orders lower than that achieved using Au nanospheres and Au nanohexamers. This pseudocore-shell nanostructure represents a significant advancement in the realm of complex nanoparticle synthesis, moving the field one step closer to sophisticated nanoparticle engineering.