Part Of Structure Research Articles

Результаты раскопок грунтового могильника Максимовка I в лесостепном Поволжье в 2019 г.

Introduction. The work publishes some results of excavations at the Maksimovka I grave field. Goals. So, the article seeks to introduce materials of the 2019 excavations. To facilitate this, the paper shall describe and characterize the investigated archaeological complexes, establish their cultural and chronological attributions. Materials. Archaeological material from the occupation layer comprises Neolithic, Chalcolithic, Bronze Age, and eighteenth/twentieth century pottery, flint tools, and stone processing waste. Six burials were investigated at the site. Two burials had been destroyed and are nothing but heaps of heavily fragmented bones with no grave goods observed. In the third burial, the skeleton was lying on back in a northern-northwestern direction, accompanied by an iron knife and goat/sheep bones. The next burial consisted of four skulls and compact clusters of skeletal bones located nearby. The latter’s grave goods included flint arrowheads, a scraper, a bone spearhead, a pendant, beads, piercings and marmot incisors. The fifth burial contained a seated skeleton facing northeast and accompanied by a flint plate, an arrowhead and beads. In the last burial, the skeleton was lying on back in a northern-northwestern direction, accompanied by an ornamented clay vessel. A part of structure 1 was also examined. Results. The work shows that a total of three burials date back to the Late Chalcolithic, one — to the Late Bronze Age, and one — to the Middle Ages. The cultural and chronological attribution of the remaining burial has not been determined yet. Conclusions. The excavations at the Maksimovka I grave field have yielded materials from different cultures and periods, including Neolithic, Chalcolithic, Bronze Age, and Medieval complexes.

Control of the unscreened modes in AlGaN/GaN terahertz plasmonic crystals

Unscreened (ungated) plasmons in large-area grating-gate AlGaN/GaN heterostructures were studied experimentally by Fourier-transform spectroscopy. Special attention was paid to the recently discovered THz plasmonic crystal modes observed at totally depleted gated regions when plasma oscillations were localized only in ungated parts of the grating-gate structures. The frequency of these modes is still gate voltage-dependent in the limited range due to the depletion of the ungated parts located close to the gate edges. Double gate structures with an additional bottom gate were fabricated and studied to improve the gate voltage tunability of the unscreened plasmons. Since this gate is located deep below the channel, the plasmons behaved as ungated ones, but their frequency still could be tuned by this bottom gate. We show that the combined effect of the top and bottom gates allows the efficient tuning of terahertz frequencies of unscreened modes in the grating-gate AlGaN/GaN plasmonic crystals.

The Pitfalls of Reverse Engineering Topology Optimised Load-Carrying Structural Parts into Parametric Models

The Pitfalls of Reverse Engineering Topology Optimised Load-Carrying Structural Parts into Parametric Models

A discrete-module-beam hydroelasticity method with finite element theory in analyzing VLFS in different engineering scenarios

A numerical tool is developed in the framework of the Discrete-Module-Beam method to analyze hydroelasticity of very large floating structures (VLFS) such as floating offshore photovoltaic platforms (FOPV). The proposed method utilizes finite element theory to perform structural analysis. The 3D potential flow theory is used to perform a hydrodynamic analysis after macro-submodule division. For the structural analysis part, the platform is divided into macro-submodules and each macro-submodule is represented by a beam, which is then further discretized into micro beam elements with the nodes categorized into three groups, that is, the lumped mass, the boundary nodes and the inner nodes. Derivation of the lumped-mass stiffness matrix and recovery of the displacement distribution are given. Procedures to deal with interconnections, complex boundary conditions and unsteady loads are elaborated. Good agreement is obtained in different loading scenarios to the numerical and experimental results.

Analisis Perbandingan Efesiensi Biaya dan Waktu pada Pondasi Sumuran dan Pondasi Tapak Pembangunan Gedung Tipikor Polda Aceh

The foundation is a building structure located under the building. The foundation cannot be separated from the building structure because it is a structural part whose function is to transmit the load from the upper structure to the supporting soil layer beneath it to prevent collapse of the soil or settlement of the structural system. This research compares the costs and time required for pit foundation work with site foundations, with the aim of finding out whether the planned costs and implementation time have the same efficiency or not. The purpose of this research is to find out how much bearing capacity there is in the well and site foundations, how much costs are needed to plan the well and site foundations, and how long the implementation time is required. The method used in this research is a comparative study (Comparison). The comparative or comparison method is research that uses the technique of comparing an object with another object. The objects being compared, the comparative method is carried out to compare the similarities and differences of two or more facts and properties of the object being studied. From the calculation analysis, the bearing capacity of the well foundation was obtained at 1950 KN with a cost of IDR 469,046,724 and an implementation time of 78 days. Meanwhile, for the site foundation, the foundation bearing capacity was obtained at 451.11 KN at a cost of IDR 174,598,298 and a construction time of 56 days.

Deformation mechanism and microstructure evolution during superplastic deformation of friction stir processed CoCrFeNiMn high entropy alloy

Since superplastic formation offers a significant advantage in preparing the complex structure parts of HEAs, the study of their superplastic behavior is extremely important. Using friction stir processing (FSP) with an improved convex hemispherical shape tool, this study reported for the first time an equiaxed ultrafine-grained CoCrFeNiMn HEA (489 nm) with a maximum elongation of 870% at 675 °C and 3 × 10−4 s−1. This superplastic property is much larger than ever reported in the CoCrFeNiMn HEA, which is even larger than that of the nano-sized CoCrFeNiMn HEA (10 nm) prepared by the high-pressure torsion. A high proportion of high angle grain boundaries and twin boundaries, a hard Cr-rich phase, and the sluggish diffusion effect of the CoCrFeNiMn HEA were primarily responsible for the exceptional superplasticity. Additionally, this study provides the first elucidation of the mechanism underlying Cr precipitation and Cr-rich phase growth, as well as the function of low-energy annealed twins during superplastic deformation. The diffusion of Cr along dislocations and grain boundaries facilitated grain boundary sliding as the predominant deformation mechanism. This study elucidates the superplastic deformation mechanism and microstructure evolution, thereby furnishing theoretical guidance for the practical implementation of superplastic forming of complex components of HEAs. Additionally, it presents an efficient method for fabricating such components.

Theoretical and experimental study on the processing deformation of slender beam structural parts of Ti6Al4V

Theoretical and experimental study on the processing deformation of slender beam structural parts of Ti6Al4V

Simulation of two-way interaction between sealant and structural parts as applied to large-scale aircraft assembly

Simulation of two-way interaction between sealant and structural parts as applied to large-scale aircraft assembly

Poisson Effect‐Assisted Replication Lithography for Rapid Fabrication of Three‐Dimensional Microstructures

Demands for micro‐ and nano‐fabrication techniques have been increasing over recent decades due to their foundational importance in fields such as electronics, sensors, displays, biotechnologies, and energy technologies. Still, the rapid and efficient fabrication of complex 3D microstructures has long been a challenge due to the inherent limitations of conventional imprint lithography and the slow fabrication speed of maskless lithography systems using femtosecond lasers. This study introduces a novel lithographic replication method for the rapid replication of intricate 3D microstructures with closed‐loops by leveraging the Poisson effect‐driven lateral deformation of soft molds. Specifically, the suggested technique employs an elastomeric soft mold, engraved with negative cavity parts of the target structure separated by intentional gaps. Lateral deformation of the material allows the separated cavities to assemble for replication of target microstructure and defectless release from the soft mold. In addition to the experimental demonstrations of the proposed method using well‐known materials like polydimethysliloxane (PDMS) for the soft mold and UV‐curable polyurethane acrylate (PUA) for replication, essential considerations such as material selection and master mold design are discussed. The presented method not only broadens the capabilities of imprint lithographic techniques but also holds promise for the large scale, continuous fabrication of complex 3D microstructures.

The effect of span length on the flexural properties of glass and basalt fiber reinforced sandwich structures with balsa wood core for sustainable shipbuilding

The current research aims to analyze the mechanical characterization of sandwich materials through a three-point flexural test. The sandwich structures in question composed of balsa wood as a core and four different types of fiber reinforced vinyl ester composite facesheets, namely Glass, Basalt, Glass/Carbon, and Basalt/Carbon. The sandwich panels were prepared using the vacuum infused processing method. The primary objective of this investigation is to explore the feasibility of utilizing basalt fibers for the production of structural parts in shipbuilding and replacing the already existed glass fibers. The flexural test was carried out with using three-point flexural test with varying the span length from 120 mm, 180 mm, 220 mm. Additionally, an analysis of variance (ANOVA) was then carried out to compare the mean values of properties deduced from these tests. The results showed that using basalt fibers instead of glass fiber reinforced enhanced the flexural stiffness of the sandwich structure. The flexural strength and modulus are shown to depend on span length and fiber type. The flexural modulus increases with an increase in span length. Similarly, flexural strength increases in glass fiber-based structures, while a slight reduction is observed in basalt fiber-reinforced structures the larger span length. The findings of this research suggest that basalt fibers hold potential as a replacement for glass fibers in producing structural components in shipbuilding. These results offer valuable information that can aid in the design and optimization of sandwich materials in shipbuilding.

Understanding the fracture mechanisms of Ni–Co–Cr-type superalloys: Role of precipitate evolution and strength degradation

Microstructure stability directly affects the performance degradation of hot-end structural parts such as turbine discs. In this research, long-term (10–10000 h) thermal exposure experiments were conducted on a Ni–Co–Cr type superalloy at 800 °C. The mechanical properties were obtained through high-temperature (750 °C) tensile tests. Subsequently, the microstructure evolution process, including intragranular γ′ and μ phases, and the initiation and propagation of defects were systematically and thoroughly studied. The results showed that intragranular γ′ precipitates coarsened under thermal exposure. After 100 h of thermal exposure, μ phases were observed near the intergranular γ′ precipitates and grain boundaries. The size and volume fraction of the μ phase initially increased, and then remained relatively stable. Numerous cracks formed on the plane of the μ phases and intergranular γ′ precipitates. With an increase in tensile stress, these cracks interconnected and propagated along the intergranular γ′ precipitates, leading to the formation of pores. Moreover, because the size of the intragranular γ′ precipitates exceeded 80 nm, the critical resolved shear stress (CRSS) was primarily activated by the Orowan bypassing mechanism. Notably, the CRSS of dislocation motion, such as stacking fault, strong-coupled shearing, and Orowan bypassing, decreased with increasing intragranular γ′ precipitate size. Therefore, the intragranular strength also weakened and the intragranular γ′ precipitates coarsened under continuous thermal conditions. This research on precipitate evolution and failure mechanisms will contribute to a better understanding of failure mechanisms for Ni–Co–Cr-based superalloys.

Super-wideband fractal antenna of two-arm structure with broadband balun

ABSTRACT A balanced two-arm antenna has been proposed for super-wideband (SWB) operation to work efficiently over the frequency range (2.95 − 34 GHz ). The antenna proposed for SWB operation can be considered as composed of two main parts. The first part is the radiating surface of the antenna and is composed of two-arms leading to a balanced antenna structure. For wideband operation, each arm has a double-fractal (angular/radial) structure. The second part of the antenna structure is the wideband feeding balun that is responsible for realising maximum power transfer and impedance matching while feeding the balanced radiating two-arm structure from the conventional unbalanced coaxial line. A prototype has been fabricated for experimental characterisation of the proposed antenna. Both the simulation results and the experimental measurements come in good agreement with each other showing that the proposed antenna can be good candidate for many super-wideband applications of future generations of mobile communications. The proposed antenna has overall dimensions of 40.0 mm × 21.0 mm × 1.5 mm . It is shown by simulation and measurement that the proposed antenna has %BW of 168 % , RBW of 11.5 : 1 , and BDR of 2015 . The maximum gain ranges between 2.3 and 6.2 dBi. The radiation efficiency is greater than 98% over the frequency range ( 2 − 24 GHz ) and is greater than 85% over the frequency range ( 24 − 34 GHz ).

A novel mirror-assisted method for full-field vibration measurement of a hollow cylinder using a three-dimensional continuously scanning laser Doppler vibrometer system

A novel general-purpose three-dimensional (3D) continuously scanning laser Doppler vibrometer (CSLDV) system was recently developed by the authors to measure 3D vibration of a structure with a curved surface. As a non-contact system, it can avoid the mass-loading problem in 3D vibration measurement using triaxial accelerometers. In previous studies, the 3D CSLDV system was used to measure 3D full-field vibration of a turbine blade with a curved surface and identify its operating deflection shapes (ODSs) and mode shapes. The 3D CSLDV system had the same level of accuracy as that with a commercial 3D scanning laser Doppler vibrometer system, but can measure many more points in much less time than the latter. However, the 3D CSLDV system can be limited by its field of view, which is a common problem for optical-based measurement devices. Moving the 3D CSLDV system to different positions to measure different parts of a test structure is not practical during 3D CSLDV measurement, since the system has to be re-calibrated once it has been moved, which can be time-consuming and introduce measurement errors. This work proposes a novel mirror-assisted testing methodology for 3D CSLDV measurement that aims to measure vibration of difficult-to-access areas of a structure without moving the 3D CSLDV system during the test, and stitch ODSs of its different parts together to obtain its panoramic 3D ODSs. The proposed methodology includes a novel scan trajectory design method that uses virtual areas of the structure behind the mirror to conduct continuous and synchronous scanning of three laser spots, and a novel velocity transformation method that uses virtual positions of three laser heads behind the mirror to stitch ODSs of different parts of the structure together. To demonstrate the proposed methodology, 3D CSLDV measurement is conducted on an aluminum hollow cylinder specimen, which has difficult-to-access areas such as its side and back surfaces, with the assistance of the mirror to obtain its panoramic 3D ODSs corresponding to its first two modes. Comparison between identified ODSs of the hollow cylinder specimen from the experiment and mode shapes from its finite element model is made and modal assurance criterion values are larger than 0.98.

A non-uniform lattice design method for lightweight structures in 3D printing

Lightweight design is an essential topic in aerospace, automotive and other fields. In automobile manufacturing, the engine connecting rod is one of the main components; its lightweight design has a high reference value. And 3D printing provides a feasible solution for designing and manufacturing lightweight structures. Unlike the traditional geometrically homogeneous point design, this study offers a non-homogeneous point design method based on the spatial stress state of additively manufactured components. After numerical simulation of quasi-static stresses on a model of an engine connecting rod, finite element grid cells with different stress values are replaced by lattice cells with different specific stiffnesses at similar local stress levels. The overall specific stiffness of the structure is further improved by continuing the optimized design with the corresponding gradient-type reinforcement of the non-uniform lattice structure. The basic idea of this design is to perform non-uniform adaptive filling of solid parts under localized loading by employing different types of unit cells. Stereolithography 3D printing technology prepares the engine lattice structural parts for quasi-static compression comparison experiments and fracture analysis after failure. The conclusions show that the engine connecting rod members with non-homogeneous lattice have more excellent overall mechanical properties than homogeneous lattice members. This work demonstrates the feasibility of such design methods for 3D printing lightweight structures and optimization.

Microstructure evolution and mechanical properties of large-size AZ31 magnesium alloy block fabricated by wire arc additive manufacturing

With the urgent demand for lightweight and integrated structural parts in the aerospace field, the use of cold metal transfer wire arc additive manufacturing (CMT-WAAM) to form large-size magnesium alloy structural parts has become a research hotspot. In this paper, a large AZ31 magnesium alloy multilayer block with a lower porosity was successfully prepared by CMT-WAAM. The AZ31 block exhibits a fully equiaxed grain morphology, the average grain diameters of the top, middle, and bottom are 16.1 µm, 12.4 µm, and 10.4 µm, respectively. The submicron spherical particles measuring 0.09 to 0.4 µm are Mg17Al12 phases, irregular particles are Al8Mn5 + Mg17Al12 composite phases and large particles measuring 5 to 10 µm are Al8Mn5 in AZ31 block. The UTS of CMT-WAAM AZ31 block from the bottom of 239.9 ± 5.0 MPa to the top of 237.3 ± 3.1 MPa, and the EL from the bottom of 22.7 ± 0.6 % to the top of 30.0 ± 1.1 %, exceeding the casting standards. In the CMT-WAAM processed AZ31 alloy, the pre-existing coarse second phase particles in the AZ31 filaments acted as nucleating agents, and the electromagnetic stirring effect in the WAAM process broke up the dendrites and increased the number density of nucleation sites to improve the rate of nucleation, and the complex thermal conditions in the WAAM process restricted the growth of the grains and the precipitated phases. The mechanical properties of AZ31 alloy were improved by effectively refining its grain size and precipitated phase size.

Structural Behaviour and Strength Evaluation of a Venetian Church through Finite-Element Analysis

The evaluation of the structural behaviour of a masonry Venetian church with a pointed barrel vault is presented in this paper through an analysis following the necessary steps of a monument study. With a detailed geometric model and material estimation, the finite-element method is used to investigate the influence of specific structural parts of the structure, like masonry buttresses and wall connections, on the structural behaviour. The operational modal analysis is used to identify the structure dynamically. The comparison of the eigenfrequencies, which are estimated by in situ measurements and finite-element modal analysis, is used to perform a model identification. The response spectrum analysis, the static analysis after the subsistence of some parts following strengthening proposals, and the transient analysis of specific seismic excitations are used for the evaluation of the structural behaviour. The purpose of the work is to highlight the need for an interdisciplinary approach to the study of a monumental complex structure, regardless of its scale. The coexistence of structural elements of different stiffnesses, such as vaults, elongated walls, buttresses, transverse walls with pediment and belfry, as well as the concha, affects the mechanical behaviour and the pathology of the structure, which is difficult to study with simplifying models. From the analysis, it is concluded that subsidence problems, combined with seismic actions, lead to the cracking of the masonry, while the existence of buttresses limits the extension of the damage and contributes to the stabilization of the structure.

Dynamic Load Analysis of Mine-Truck Using Multibody Dynamic Analysis Method

Abstract: Vehicle load distributed on front & rear axle assembly during various working conditions is one of the most important factors influencing working performance and service life of drive axle assembly. The dynamic load on axle assembly is higher compared to the rated load because of variations in vehicle speed and road surface conditions. Early failure of structural components is caused because of higher dynamic reaction forces due to uneven road profiles. The dynamic load calculation of axle assembly is presented in this paper for a Mine-truck with various road conditions and vehicle speeds. The road load conditions consist of grade, bump & path hole. Mine-truck with payload capacities of 63 Ton is considered for the study. The behaviour of vertical force is calculated for different vehicle speeds (3 - 12 km/hr.) of the machine on the front & rear axle assembly during running conditions. Multi-body dynamic Analysis tool ADAMS is used for this study. ADAMS helps to study the dynamics of moving parts and load distribution throughout mechanical systems during motion. The Mine-truck3D model was created with the help of computer-aided design (CAD) software. Major units of Mine trucks are considered to prepare 3D models like Cabin-engine mass, Bucket, front axle assembly, rear Axle assembly & tires. Multi-body vehicle models are prepared in simulation software ADAMS by importing 3D models prepared by computer-aided design (CAD) software. This provides guidelines for selecting dynamic load factors while designing structural parts of the vehicle.

Improving awareness of foreign domestic workers during the COVID-19 pandemic using infographics: An experience during the crisis

The COVID-19 epidemic is a significant humanitarian crisis witnessed in contemporary times, necessitating the exploration of techniques and approaches that might augment the capabilities of individuals within society to mitigate the adverse consequences of this pandemic. Domestic workers have always been an important part of societal structure, and it is essential to ensure their awareness about the perils of the pandemic as well as implement preventive measures. This is crucial in order to effectively address the hazards associated with the ongoing epidemic. The primary objective of this study was to assess the efficacy of infographic technology in augmenting the level of knowledge among foreign domestic workers on the COVID-19 epidemic. The present study employed a quasi-experimental design to examine and compare the effects of infographic technology on the experimental group, while the control group received only public awareness messages disseminated to all citizens and residents. The study sample comprised (16) foreign domestic workers, who were assigned to the two research groups through a random allocation process. The development of the COVID-19 pandemic awareness scale was conducted. The measurement scale consisted of three dimensions: the cognitive awareness dimension, including a set of (12) statements; the performative awareness dimension, comprising a set of (8) statements; and the psychological awareness dimension, comprising a set of (10) statements. The findings demonstrated the superiority of the experimental group, which used the infographic approach, over the control group in fostering awareness of the COVID-19 epidemic throughout its three dimensions among the participants of the study. The study suggested the need of expanding the utilization of infographics in an attempt to enhance knowledge and awareness of the COVID-19 pandemic, alongside the establishment of varied databases for migrant domestic workers. The objective is also to develop an extensive digital awareness strategy about the impacts of the COVID-19 epidemic, so as to include an increased number of informative infographics.

Peran Pertanian dalam Pengembangan Ekonomi: Penilaian Transformasi Struktural dan Dinamika Pertumbuhan Ekonomi

By understanding the role of agriculture in economic development holistically, this research aims to provide policy makers, practitioners, and academics with deeper insights on how to enhance the role and contribution of the agricultural sector in achieving inclusive and sustainable economic growth. Through a careful evaluation of the structural transformation and dynamics of economic growth in the agricultural sector, this research is expected to provide valuable guidance in formulating more effective and future-oriented policies. In this study, the use of qualitative methods involved a variety of techniques and approaches. By using these qualitative methods, the research was able to explore various complex aspects of how agriculture plays a role in economic development, including the challenges, opportunities, social dynamics, and policies that affect it. Research results The agricultural sector is an important part of a country's economic structure, involving a wide range of activities from production to distribution of agricultural products. While agriculture is often the dominant sector in the early stages of economic development, its role continues to change as the economy develops. The role of the agricultural sector is crucial in feeding the population, creating jobs, and contributing to economic growth, especially in developing countries. However, agricultural activities can also have significant impacts on the environment, such as land degradation and ecosystem damage.

Comprehensive analysis of fused deposition modeling process conditions for enhancing mechanical properties and surface quality of 3D-Printed poly-ether-ether-ketone

Fused deposition modeling (FDM) technology is a convenient manufacturing approach for poly-ether-ether-ketone (PEEK) components. In this study, a comprehensive study of the influence of FDM process parameters on the mechanical property and surface quality of 3D-printed PEEK printed with different directions was carried out. The results show that crystallinity of PEEK materials and the pores/gaps between the printing filaments jointly affect the mechanical properties and surface quality of PEEK structural parts. Then, material-structure-property linkage mechanism was revealed. Through the research conducted, crucial processing parameters to enhance the mechanical properties and surface quality of PEEK samples was determined. High tensile strength (91.75 MPa, which was close to the performance of injection molded components) and surface quality (Ra 7.9 μm) was obtained by regulation the nozzle temperature and annealing temperature to improve the crystallinity. Meanwhile, tensile strength of z-Sample was increased from 7.36 MPa to 18.30 MPa (with an increase of 148.64%). High Young's modulus (3.09 GPa) and large plastic strain (exceed 13.91%) was achieved by regulation the nozzle temperature and printing speed to reduce the porosity between PEEK filaments.