Bent Form Research Articles

Using HSM Technology in Machining of Thin-Walled Aircraft Structures

Abstract Subtracting manufacturing technologies have entered that realm of production possibilities which, even a few years ago, could not be directly adapted to direct production conditions. The current machines, i.e. heavy, rigid cutting machines using high spindle speed and high feed speed, allow for manufacturing very thin and relatively long parts for use in the automotive or aerospace industry. In addition, the introduction and implementation of new 70XX aluminium alloys with high strength parameters, as well as monolithic diamond cutting tools for special machining, have had a significant impact on the introduction of high-speed machining (HSM) technologies. The main advantage of the applied manufacturing method is obtaining a very good smoothness and surface roughness, reaching even Sz = 6–10 μm and Sa <3 μm, and about four times faster and more efficient machining compared to conventional machining (for the beam part). Moreover, fixed and repeatable milling process of the HSM method, reduction of operational control, easy assembly of components and increase in the finishing efficiency compared to other methods of plastic processing (forming) are other benefits. The authors present a method using HSM for the manufacturing of aircraft parts, such as the chassis beam at the front of a commuter aircraft. The chassis beam assembly is made of two parts, front and rear, which – through a bolted connection – form a complete element replacing the previous part made using traditional technology, i.e., cavity machining, bending and plastic forming. The implementation of HSM technology eliminates many operations related to the construction of components, assembling the components (riveting) and additional controls during construction and assembly.

Регулирование скоростей электроприводов клети толстолистового прокатного стана в режиме формирования «лыжи»

Задача формирования изгиба переднего конца раската в форме «лыжи» является актуальной для электроприводов клетей толстолистовых прокатных станов. Неконтролируемый изгиб раската вверх может привести к повреждению оборудования клети, изгиб вниз - к ударам и застреванию при транспортировке по рольгангу. На основании анализа литературных источников установлено, что причинами неконтролируемого изгиба переднего конца могут быть множество технологических факторов. Основными являются несоответствие скоростей верхнего и нижнего валков, температурный градиент по толщине раската, различие коэффициентов трения и др. Рассогласование скоростей, помимо влияния на форму раската, определяет соотношение моментов электроприводов валков. На примере горизонтальной клети стана 5000 ПАО «Магнитогорский металлургический комбинат» (ПАО «ММК») показано, что при прокатке тяжелых профилей моменты двигателей могут отличаться в три раза. При этом по мере уменьшения толщины раскатов по проходам соотношение нагрузок главных электроприводов верхнего и нижнего валков (ВГП и НГП) меняется на противоположное. Для согласования скоростных и нагрузочных режимов в систему включен регулятор деления нагрузок (РДН). Недостатком является то, что он осуществляет регулирование нагрузок в функции разницы скоростей ВГП и НГП. Представлены осциллограммы, подтвердившие невозможность обеспечения заданного соотношения скоростей в динамическом режиме, возникающем при входе металла в клеть. Для устранения недостатка разработан способ управления электроприводами, согласно которому регулирование скоростей в режиме лыжеобразования осуществляется пропорционально разности сигналов заданий на входах регуляторов скоростей ВГП и НГП. Представлена структурная схема, поясняющая реализацию способа путем включения на вход РДН дополнительного регулятора согласования скоростей. Приведена схема имитационной модели электромеханических систем верхнего и нижнего валков, взаимосвязанных через металл. В результате моделирования установлено, что реализация способа обеспечивает рассогласование скоростей на уровне, близком к заданному, в течение всего времени формирования «лыжи». Алгоритм управления, реализующий разработанный способ, внедрен в АСУ клети стана 5000. Представлены осциллограммы, подтвердившие основные теоретические выводы. Разработанный алгоритм позволяет снизить задание «лыжи» более чем в два раза. За счет этого происходит повышение точности геометрии и сокращение длины изогнутого участка, что обеспечивает меньшее рассогласование моментов двигателей ВГП и НГП и более быстрое их выравнивание. Помимо разгрузки электродвигателей по моменту это обеспечивает повышение их КПД.

Composite mechanical deformation based semi-analytical prediction model for dynamic loaded contact pressure of thin-walled aerospace spiral bevel gears

An innovative semi-analytical prediction model for dynamic loaded contact pressure is proposed for thin-walled aerospace spiral bevel gear transmission under both high speed and heavy load conditions. To distinguish with the traditional rotor dynamic analysis focusing on vibration effect for global system, a new dynamic loaded tooth contact analysis (DLTCA) focusing on loaded contact effect for local contact area is developed. In particular, for thin-walled gear structure including tooth flank, web, hub and supporting shaft, its composite mechanical deformation in forms of bending, shearing, torsion and other combinations are introduced into DLTCA solution for prediction. Firstly, considering tooth flank flexural behaviors, tooth flank simulation and finite element modeling is developed by using universal motion concept (UMC) machine settings. Then, for different deformation types at different parts of gear structure, the accurate composite mechanical deformations are determined for tooth flank, web, hub and supporting shaft, respectively. Moreover, DLTCA considering composite mechanical deformations is performed to get a semi-analytical prediction model for dynamic loaded contact pressure having systematically time-varying characteristics. Finally, the given numerical instance is provided to verify the proposed method.

Microstructure and Fatigue Damage of 316L Stainless Steel Manufactured by Selective Laser Melting (SLM).

In this paper, 316L stainless steel powder was processed and formed by selective laser melting (SLM). The microstructure of the sample was studied using an optical microscope, and the fatigue failure of the sample and the characteristics of crack initiation and propagation were analyzed, providing a research basis for the application of SLM-316L. Due to the influence of microstructure and SLM process defects, the fatigue cracks of SLM-316L mainly emerged due to defects such as lack of fusion and pores, while the cracks of rolled 316L initiated at the inclusions near the surface of the specimen. After fatigue microcrack initiation of the SLM-316L specimen, due to the existence of shear stress and tear stress, the crack tip was passivated and Z-shaped propagation was formed. The existence of internal defects in SLM-316L made the microcrack initiation random and diverse. At the same time, the existence of defects affected the crack propagation in the form of bending, bifurcation and bridge, which made the main crack propagation deviate from the maximum load direction.

The Study of Bending and Twisting Input Modalities in Deformable Interfaces

The deformable input provides users with the ability of physical operation equipment to interact with the system. In order to facilitate further development in flexible display interactive technology, we devised FlexSheet, an input device that can simulate the deformation environment. This paper presents two forms of deformation input, bending and twisting, with regard to three selection techniques. We conduct a controlled experiment to select discrete targets by combining two input forms and three selection strategies, taking into account the influence of visual feedback. Further, we use the deformation angle to reflect the degree of deformation and map it to the experimental variables. In accordance with the experimental results, we analyze the experimental performance under three evaluation indexes and prove the viability of our selection technology in bending and twisting input modes. Finally, we provide suggestions on the control level in bending and twisting input modes, respectively.

Twisted Tower – A Feasibility Study for Cold‐Bent Insulating Glass Units with an Elastic Edge Seal

This paper describes a case study of cold bent insulating glass units (IGUs) for use in facades or roofs using the example of a demonstrator called the “Twisted Tower”. Modern designs often try to combine a curved shape with transparency. Cold bending IGUs is a cost efficient method to achieve both. In such applications the bending angles are often limited by the allowable deformations of the primary seal which ensures the gas tightness of the IGU. This investigation shows IGUs with much more acute bending angles than in standard applications were achieved using a flexible yet durable thermoplastic spacer ensuring superior gas tightness. This work investigates the geometry, the deformations and fixing options for the bent IGU form. The results demonstrate the advantages of using such spacer systems for these applications.

Early Crack Propagation in Single Tooth Bending Fatigue: Combination of Finite Element Analysis and Critical-Planes Fatigue Criteria

Mechanical components, such as gears, are usually subjected to variable loads that induce multiaxial non-proportional stress states, which in turn can lead to failure due to fatigue. However, the material properties are usually available in the forms of bending or shear fatigue limits. Multiaxial fatigue criteria can be used to bridge the gap between the available data and the actual loading conditions. However, different criteria could lead to different results. The main goal of this paper is to evaluate the accuracy of different criteria applied to real mechanical components. With respect to this, five different criteria based on the critical plane concept (i.e., Findley, Matake, McDiarmid, Papadopoulos, and Susmel) have been investigated. These criteria were selected because they not only assess the level of damage, but also predict the direction of crack propagation just after nucleation. Therefore, measurements (crack position and direction) on different fractured gear samples tested via Single Tooth Bending Fatigue (STBF) tests on two gear geometries were used as reference. The STBF configuration was numerically simulated via Finite Elements (FE) analyses. The results of FE were elaborated based on the above-mentioned criteria. The numerical results were compared with the experimental ones. The result of the comparison showed that all the fatigue criteria agree in identifying the most critical point. The Findley and Papadopulus criteria proved to be the most accurate in estimating the level of damage. The Susmel criterion turns out to be the most conservative one. With respect to the identification of the direction of early propagation of the crack, the Findley criterion revealed the most appropriate.

Finite Element and Applied Models of the Stem with Spike Deformation

This article examines the static and dynamic deformation of the stem of an ear of wheat and of the individual grain. The purpose of the article is to determine the factors of influence on the ear of wheat to isolate the grain. Two stages of grain ripening are considered: in the early stage, the grain is attached to the spike by the stem; in the second, there is no stem, and the grain is attached to the ear by the scales. The ear fluctuations are considered within the Euler–Bernoulli bar theory. The developed model divides the study of the dynamics of the stem of an ear and the dynamics of the grain into two stages. The first stage studies the dynamics of the plant as a whole, while the second stage studies the dynamics of an individual grain in a moving system associated with the ear in bending and vertical fluctuation forms. The model of the ear and the grain fluctuation uses the mechanical characteristics of elastic bonds and elastic bodies, which are determined by spring stiffness, elastic moduli, etc. The results show that in the vertical forms of grain fluctuation, the frequency of fluctuation is much higher than in the bending ones. This article presents the natural fluctuation frequencies of grain at full ripeness and in the early phases of maturation, at which point it is released from the ear.

Extracting RLC Parasitics From a Flexible Electronic Hybrid Assembly Using On-Chip ESD Protection Circuits

The presence of RLC line parasitics in a flexible hybrid electronic assembly can lead to signal integrity issues, and their progression over time can lead to catastrophic failures. A technique for extracting the RLC line parasitics from a flexible hybrid electronics assembly is presented. The proposed extraction method exploits the on-chip ESD protection circuits of an IC chip to extract the parasitics of the printed conductors bonded to the chip. This is performed through a single test access port, i.e., two test points. While the parasitics LC are extractable through one-port reflection-based techniques such as time domain reflectometry; the parasitic R requires a two-port measurement such as Kelvin test, which is extremely difficult to perform for printed conductors bonded to small surface-mount IC package devices. The accuracy of the extracted RLC parameters with the proposed method are verified with a prototype developed on a rigid FR4 substrate. Subsequently, the proposed technique is utilized to track the variation of the RLC parasitics for prototypes developed on Kapton Polyimide substrate subjected to different forms of bending.

Three-layer structure hot bending/diffusion bonding process of reactive sintering Ti-22Al-25Nb alloy and its load response at high temperature

Three-layer structure part as a ideal structure part, that had light weight and enough strength to be widely used, was prepared combining hot bending and diffusion bonding processes in this paper. The Ti-22Al-25Nb sintered alloy that owned better using temperature was applied to manufacture three-layer structure part. The forming processes of manufacturing three-layer structure was divided into hot bending forming of the core sheet and diffusion bonding of three layers sheets. Firstly, the hot bending of core sheet was performed at 1423K for 10MPa in a vacuum furnace. Secondly, the diffusion bonding of three layers sheets was carried out at 1473K for 120min and 10MPa. Furthermore, in order to evaluate the quality and performances of three-layer structure, the microstructure of bonding joint of three layers sheets was analyzed by SEM, and the properties of three-layer structure part were tested at 1073K by compressing test and three-point bending test. Compressing load and compressing strength were 9014N and 10MPa, respectively. Bending strength was up to 54MPa. In addition, the experimental results also indicated that three-layer structure that prepared using the Ti-22Al-25Nb sintered alloy owned good properties.

Acute and Chronic Toxicity of a glyphosate on Danio rerio

Glyphosate herbicides are the most widely produced and used herbicides in the world. The intensive applications of glyphosate and its half-life in water result into many aquatic ecosystems. The present study focuses on the evaluation of glyphosate toxicity on the early life stages of the fish Danio rerio. Analysis of the test results revealed that glyphosate is toxic to zebrafish. This effect is marked by the increase in percent mortality at peak concentrations. Long-term exposure to glyphosate affects the hatching rate, heart rate and swimming ability of zebrafish. Significant malformations were observed at the highest concentration in the form of tail bending or fin absence.

The effect of bending deformation on flexible electrodes during charging and discharging

As the typical deformation mode, the bending deformation accompanies the entire useful life of flexible batteries. Due to the coupling of electrochemical processes, this bending behavior can severely damage flexible batteries. Herein, a complete physical model is developed to investigate the effect of bending deformation on flexible thin-film electrodes during the charge/discharge cycle. And the rate-dependent plastic flow in the electrode is modeled based on the evolution of the excess energy stored in the material. Two different bending forms of the flexible thin-film electrode are studied, and the stress and strain spectrums of the electrode during cyclic deformation are thoroughly discussed. The results show that the bending deformation has a significant effect on the evolution of the stress and strain of the electrode. Both constant bending deformation and cyclic bending deformation produce accumulated strain, but for entirely different reasons. The present work sheds light on the physical origin of strain accumulation for the flexible thin-film electrode and provides guidance for material design and the application of flexible batteries.

Optical Control of Phosphatidic Acid Signaling.

Phosphatidic acids (PAs) are glycerophospholipids that regulate key cell signaling pathways governing cell growth and proliferation, including the mTOR and Hippo pathways. Their acyl chains vary in tail length and degree of saturation, leading to marked differences in the signaling functions of different PA species. For example, in mTOR signaling, saturated forms of PA are inhibitory, whereas unsaturated forms are activating. To enable rapid control over PA signaling, we describe here the development of photoswitchable analogues of PA, termed AzoPA and dAzoPA, that contain azobenzene groups in one or both lipid tails, respectively. These photolipids enable optical control of their tail structure and can be reversibly switched between a straight trans form and a relatively bent cis form. We found that cis-dAzoPA selectively activates mTOR signaling, mimicking the bioactivity of unsaturated forms of PA. Further, in the context of Hippo signaling, whose growth-suppressing activity is blocked by PA, we found that the cis forms of both AzoPA and dAzoPA selectively inhibit this pathway. Collectively, these photoswitchable PA analogues enable optical control of mTOR and Hippo signaling, and we envision future applications of these probes to dissect the pleiotropic effects of physiological and pathological PA signaling.

Forging, Bending, and Breaking: Enacting the “Illiberal Playbook” in Hungary and Poland

In recent years, Central and Eastern Europe have furnished several examples of illiberalism in power. The most prominent and consequential cases are Fidesz, which has ruled in Hungary since 2010, and Law and Justice (PiS), which has ruled in Poland since 2015. In both cases, illiberal governments have embarked upon an extensive project of political reform aimed at dismantling the liberal-democratic order. We examine the nature, scope, and consequences of these processes of autocratisation. We first argue that illiberal changes are ideologically founded and identify how both populism and nativism figure in the policymaking of illiberals in power. We then show how these practices emerge from a common “illiberal playbook”—a paradigm of policy change comprising forms of forging, bending, and breaking—and elaborate on the notion that illiberal governments are using legalism to kill liberalism. The fine-grained approach that we employ allows us to distinguish between different rationales and gradations of illiberal policymaking, and assess their implications for the rule of law, executive power, and civil rights and freedoms

Self-stressed steel-reinforced concrete floor slab stress-strain state numerical analysis taking into account the concreting stages

In steel-reinforced concrete floor slabs, structurally ensuring the joint operation of monolithic reinforced concrete slab and steel crossbars, a successful combination of its components positive qualities is realized at a high level: compression forces are perceived by monolithic slab, and tensile forces by steel beams. Reinforced concrete slabs in such structures have a relatively equal weight with a payload on interfloor slabs for public buildings. Having effectively developed the sequence of concreting the slab through the span in two stages, it is possible to create pre-stressing in the floor steel crossbars, located in the spans of the second concreting stage, and in monolithic reinforced concrete slab of the first concreting stage. In this sense, the term “self-stressed” is used in this work. By creating pre-stresses in the steel crossbars of the floor, it is possible to reduce their cross-section or to increase their span and to achieve savings in metal costs on the building frame. Pre-stressing of the monolithic reinforced concrete slab of the first concreting stage in the opposite to operational bending form, will increase crack resistance of the specified sites of a monolithic overlapping and will give the chance to reduce its reinforcement.

NUMERICAL DIFFERENTIATION OF BEND FORMS OF THE LONG ELASTIC RODS

The technique of numerical differentiation of the bend forms of long elastic rods is presented. This technique is based on search for new bend forms of the rod by solving the equations of oscillations with using the time integration method and the polynomial spline-functions that are being described the current bend form. In it, the spline-functions are found by current bend form approximation where each of the found functions is responsible to certain point of rod elastic line and describes the position of nearby points. Using the described approximation technique with subsequent numerical differentiation, the dependences of the derivatives on an arbitrary bend form of the rod with a length that is equal to 100 m are shown. To confirm the reliability, the results of numerical differentiation of the bend forms of the elastic rods described by given functions are presented and the numerical results obtained using the proposed method are compared with the results of analytical differentiation of the original functions. The graphs of values derivatives dependence to rod length are drawn and tables with numerical values of differentiation results are shown. It is concluded that the considered technique of numerical differentiation of rods bend forms allows to do the research of dynamics of rod systems. It gives the exact result of differentiation, provides the continuity and smoothness of all four derivatives functions of spline that are being described the bend form with considerable length. Described technique was realized in a computer program with graphic user interface. Program allows to monitor for dynamics of the oscillatory motion of the modeled system in real-time by calculating and drawing the current band forms of the rotating rod during the oscillation.

Transferable, flexible white light-emitting diodes of GaN p–n junction microcrystals fabricated by remote epitaxy

The remote epitaxy of GaN p – n homojunction microcrystals (μCs) is demonstrated for fabricating transferable, flexible white light-emitting diodes (WLEDs). The GaN p – n junction μCs are randomly grown on graphene-coated Al 2 O 3 (0001), which are then delaminated for mass-transfer onto conducting copper tape. The μCs-LED shows electrical rectification and white electroluminescence (EL) emission. The μCs-WLED exhibits reliable LED performances after repetitive bending deformations and cycling temperature environments. Based on the transferability, the μCs-WLEDs are patterned and assembled to matrix arrays, which exhibit homogeneous, reliable performances even at a bent form. We discuss that the origin of white EL emission is mixing of blue and yellow–red EL emissions from p -GaN and n -GaN sides, respectively, based on photoluminescence spectroscopic measurements. This study opens a way of fabricating the transferable, flexible, and modular light panels through remote epitaxy. • Transferable, flexible white light-emitting diode (WLED) is demonstrated via remote epitaxy of GaN p – n junction microcrystals (μCs). • The WLED is reliably operated in repetitive bending deformation and thermal shock cycling tests. • Matrix arrays of WLED were easily assembled by transfer–printing method owing to excellent transferability endowed from remote epitaxy.

Wall thinning behaviors of high strength 0Cr21Ni6Mn9N tube in numerical control bending considering variation of elastic modulus

Wall thinning, as one of the key defects in tube bending determined the forming quality and limit, is more easily to occur due to the specific properties of high strength 0Cr21Ni6Mn9N stainless steel tube (0Cr21Ni6Mn9N-HS tube). To achieve tube accuracy numerical control (NC) bending forming, the wall thinning characteristics of the 0Cr21Ni6Mn9N-HS tube should be clarified. An analytical model was proposed to reveal the essential relation between tube parameters and wall thickness distribution. Considering the varied elastic modulus, a finite element (FE) model was applied to explore the wall thinning under different geometrical and process parameters. Using the modified multi-parameter sensitivity analysis method combined with FE simulation, the sensitivity of the wall thinning to geometrical and process parameters was carried out. The experiments of NC tube bending were conducted to validate the analytical and simulate results. The results show that the varied elastic modulus can enhance the wall thinning degree, but has no obvious effect on wall thinning characteristics. The wall thinning characteristics under different geometrical and process parameters are revealed and the reasonable parameters ranges for the 0Cr21Ni6Mn9N-HS tube in NC bending are obtained. The most sensitive parameter on wall thinning is the relative bending radius, while the bending angle is the least one.

Enhanced UV photodetectivity in solution driven ZnO nanosheets via piezo-phototronic effect

Here in, we report the fabrication of thin two dimensional (2D) ZnO nanosheets (NSs) flexible piezo-phototronic ultraviolet (UV) photodetector (PD). The morphological and optical properties of the as-synthesized ZnO NSs is characterized in detail. The flexible Ag–ZnO NSs-Ag lateral PDs are fabricated on the polyethylene terephthalate (PET) substrate. A striking photoresponse is observed for 2D-ZnO under UV illumination. Furthermore, by introducing a strain (in the form of bending) the photocurrent and responsivity of this PD can be modulated via piezo-phototronic effect, emerging from the ZnO nanosheets. The photocurrent enhancement under bending could be attributed to the piezo polarization charges produced at ZnO/Ag interface due to strain. This piezo polarization charges result in the modulation of Schottky barrier (SB) height at the semiconductor/metal interface and induce improved photogenerated charge carriers and reduced recombination probability to result enhanced performances from the ZnO NSs photodetector. The physical mechanism involved in the enhancement of photocurrent via piezo-phototronic is proposed to explain change in SB height at semiconductor/metal interface using the band diagrams. This results demonstrates an efficient prototype of the piezo-phototronic PD based on thin ZnO NSs, which provides an effective pathway to enhance the performance of optoelectronic devices.

Microbial signatures from speleothems: A petrographic and scanning electron microscopy study of coralloids from the Koněprusy Caves (the Bohemian Karst, Czech Republic)

AbstractExotic carbonate – siliceous coralloid speleothems of the Koněprusy Caves, which consist of dominant aggregates of feather‐like, radial fibrous, dogtooth and gothic‐arch calcite crystals, contain a diversity of petrified fossil microbes entombed in siliceous parts of the speleothems. Although a complete diagenetic continuum of SiO2 polymorphs, ranging from opal‐A, through opal‐CT, to moganite and crystalline quartz, was identified to form thin irregular laminae and the infills of secondary pores throughout the speleothems, the microbes have been preserved only in opal aggregates concentrated in younger growth zones of the speleothems. The identified biomorphic bodies included ovoid and spheroidal forms, interpreted as coccoid microbes, and tubular, bent and elongated forms believed to represent putative silicified filamentous microbes of unknown taxonomic affinity. Other biomorphic microstructures resembling biofilms, and plastic deformations and binary fissions of individual coccoid microbes have also been recognized. The silicified microbes, most of which have been heavily encrusted in situ, still reveal the presence of organic carbon and other biogenic elements detectable beneath their opal coats. Micro‐cavities beneath and around coccoid microbes, interpreted as micro‐borings, suggest that the microbes were able to remove the opal substrate by chemical etching. The morphology and mineralization styles of the microbes, the age of which was estimated to be in the range of 100 to 102 ka, exhibit similarities to silicified microbes from present‐day siliceous hot‐spring geysers and travertines. In contrast to the siliceous parts of the coralloids, the calcite crystals forming the matrix of the speleothems do not contain any calcified microfossils. However, deeply etched calcite crystals, spiky calcite sub‐crystals, needle‐fibre calcite and sparmicrite grains indicate that the processes of calcite dissolution–precipitation mediated by the microbes may have also affected the speleothem exteriors.