Effect Of Fasteners Research Articles

Design procedures for cold-formed stainless steel built-up columns assembled from equal-leg angles

In this paper, the structural behaviour of cold-formed stainless steel (CFSS) built-up T- and cruciform-section columns is studied experimentally and numerically, and the effect of discrete fasteners on their flexural and torsional rigidity is considered. To build the singly symmetrical built-up T-section columns, two equal-leg angle sections made of lean-duplex grade EN 1.4162 were assembled back-to-back. The doubly symmetrical built-up cruciform-section columns were composed of four star-oriented equal-leg angle sections made of austenitic grade EN 1.4301. They were connected using M8 bolts of class 8.8. Two pin-ended built-up T-section columns with length of 1000 mm, and four built-up cruciform-section columns with lengths of 600 mm and 2400 mm with semi-rigid support conditions, were tested under pure axial compression. As observed in the tests, built-up T-section columns experienced flexural-torsional buckling failure, whereas built-up cruciform-section columns failed in torsional buckling mode. Finite element models were validated against the conducted experiments and used to perform a parametric study of the structural behaviour of CFSS built-up T- and cruciform-section columns. The study included the column length, cross-sectional dimensions and bolt spacing as variables. The experimental and numerical data, i.e., the column strengths and failure modes, were compared against the results obtained based on the European and North American Specifications alongside a recent method established for cold-formed carbon steel equivalents and based on the Direct Strength Method (DSM). It is shown that the DSM-based approach predicts the ultimate buckling resistances of the considered built-up columns more accurately than the available codified design methods.

Exploration of Alkyl Group Effects on the Molecular Packing of 5,15-Disubstituted Tetrabenzoporphyrins toward Efficient Charge-Carrier Transport.

The high design flexibility of organic semiconductors should lead to diverse and complex electronic functions. However, currently available high-performance organic semiconductors are limited in variety; most of p-type materials are based on thienoacenes or related one-dimensionally (1D) extended π-conjugated systems. In an effort to expand the diversity of organic semiconductors, we are working on the development of tetrabenzoporphyrin (BP) derivatives as active-layer components of organic electronic devices. BP is characterized by its large, rigid two-dimensionally (2D) extended π-framework with high light absorptivity and therefore is promising as a core building unit of organic semiconductors for optoelectronic applications. Herein, we demonstrate that BP derivatives can afford field-effect hole mobilities of >4 cm2 V-1 s-1 upon careful tuning of substituents. Comparative analysis of a series of 5,15-bis(n-alkyldimethylsilylethynyl)tetrabenzoporphyrins reveals that linear alkyl substituents disrupt the π-π stacking of BP cores, unlike the widely observed "fastener effect" for 1D extended π-systems. The n-octyl and n-dodecyl groups have the best balance between high solution processability and minimal π-π stacking disruption, leading to superior hole mobilities in solution-processed thin films. The resulting thin films show high thermal stability wherein the field-effect hole mobility stays above 1 cm2 V-1 s-1 even after heating at 160 °C in air, reflecting the tight packing of large BP units. These findings will serve as a good basis for extracting the full potential of 2D extended π-frameworks and thus for increasing the structural or functional diversities of high-performance organic semiconductors.

Study on Vibration Reduction Effect of Rail Fastener with High Lateral Stiffness: Theoretical Considerations and In-Situ Verification

Study on Vibration Reduction Effect of Rail Fastener with High Lateral Stiffness: Theoretical Considerations and In-Situ Verification

Fabrication and characterization of thin-film field-effect transistors with alkyl-phenyl[n]phenacenes (n = 4–6)

3-Decyl-10-phenyl[5]phenacene (PhC10-PIC) molecule shows good FET characteristics in case of using ZrO2 gate dielectric, owing to strong fastener effect and large π-overlap.

An experimental study on mechanical behavior and failure mechanism of sleeved fasteners and conventional bolt for composite interference-fit joints

This paper aims to reveal the effect of different fasteners on the mechanical behavior and failure mechanism of composite interference-fit joints under assembly and quasi-static loading conditions. Composite single-lap and double-lap joints joined by conventional bolt and sleeved fasteners were focused on and their joint deformation and failure were characterized by the means of digital image correlation (DIC) and scanning electron microscope (SEM). Differences in failure load, bearing strength, joint stiffness, joint deformation and failure mode under different fastener fit types including neat-fit, interference-fit and interference-fit with sleeved fasteners were evaluated. Results show that the interference-fit with sleeved fasteners significantly improves the bearing performance of the joints. Under the same interference-fit, the initial failure load and ultimate bearing strength of sleeved fasteners for the composite double-lap joints are 33% and 12% greater than conventional bolt respectively. Moreover, the interference-fit with sleeved fasteners strengthens the joint bending stiffness and further alleviates the surface strain concentration compared with the interference-fit with conventional bolt. The conclusions in this article have a guiding significance for the design of composite interference-fit joints.

Predicting the Effectiveness of Mg-Rich Primers in Mitigating Galvanic Corrosion of Al Alloys Coupled with SS316 Fasteners Using Finite Element Modeling

Aerospace aluminum alloys, such as AA2024-T3 and AA7075-T6, are widely used in aerospace applications due to their high strength-to-weight ratio. However, because of their heterogeneous microstructure, they are susceptible to localized corrosion in chloride-containing environments. Corrosion attack is aggravated at fastener/sub-structure joining locations, where the Al alloy is in contact with more noble alloys, such as stainless steels. To protect these structures against corrosion attack, organic coatings are commonly used. Typical coating systems are usually composed of three layers: a conversion coating, a primer, and a topcoat. Historically, Al alloys have been protected by chromate-based coating systems. However, Cr(VI) has carcinogenic effects; thus, environmental regulations are restricting its use, stimulating the research in alternative corrosion protection technologies. Metal-rich primers, such as Mg-rich primers, have emerged as an effective and environmentally-friendly alternative to chromate-based primers. Depending on the type of the metallic pigment, these primers can provide chemical and electrochemical protection mechanisms to Al alloys.Localized corrosion of coated Al alloys can be affected by a vast number of variables, such as water layer thickness, electrolyte chemistry, salt loading density, pigment volume concentration of primer, chemistry of the primer, galvanic effects of pigment and noble fasteners, and component geometry. Thus, it is difficult to predict and quantify damage by localized corrosion, in addition to the efficacy and lifetime of a coating system. In this context, modeling can be used as a valuable assessment of parameter space, increasing the efficiency of experimental work. The objective of this work was to model the protection mechanisms offered by MgRP and investigate the influence of different environmental and geometric parameters on the effectiveness of the MgRP protection mechanisms in mitigating galvanic corrosion around fastener/substructure joints. The mechanisms of importance include protection via (a) the Mg pigment particles acting as sacrificial anodes, (b) the barrier to ion transport affected by the organic coating, and (c) changes in the electrolyte chemistry from the dissolution of the Mg pigment particles. The models consider each of these protection mechanisms in isolation as well as in combination. Ultimately, this model will provide a better understanding and prediction of the protection mechanisms of the MgRP, and it will elucidate critical conditions that should be further investigated with experimental work.Acknowledgements:Financial support from the SERDP program through the Office of Naval Research (C. Sanders) via Contract N00173-19-1-G011 as well as the DOD Corrosion Program Office through the US Air Force Academy via Contract FA7000-18-2-0006 is gratefully acknowledged. Technical discussions with Prof. John Scully (University of Virginia) and Dr. R.J. Santucci (Naval Research Laboratory) are also gratefully acknowledged.

Effects of Metal Fasteners of Ventilated Building Facade on the Thermal Performances of Building Envelopes

Thermal bridging in the building envelope is one of the main causes of energy losses, even in high-efficiency ventilated building façades. In this study, the effects of point-thermal bridges attributed to metal fasteners on the heat transferred through different types of bricks were predicted. All the structural details of the substrate wall were included as well. This was accomplished with a multi-scale, finite element modelling approach used to enhance the thermal insulation efficiency of the building envelope. The effects of the metal fastener length, diameter, density and location were examined to elucidate any opportunity to minimize the heat losses caused by thermal bridging. The results demonstrated that increases in the lengths of fasteners yielded higher energy losses compared with those generated when the diameter increased. Additionally, metal fasteners caused higher energy losses by up to 30% when fixed on mortar, compared with the energy losses incurred when they were fixed on bricks.

A Computational Study on Buckling Behavior of Cold-Formed Steel Built-Up Columns Using Compound Spline Finite Strip Method

This paper presents a computational methodology to compute the critical buckling stress of built-up cold-formed steel columns joined with discrete fasteners. The fasteners are modeled as three-dimensional beam elements, and their effect is integrated into the spline finite strip framework, evolving the compound strip methodology. Although this technique has been presented in the literature, this paper presents yet another robust framework for the buckling load evaluation of compound cold-formed steel columns with arbitrarily located fasteners. The proposed framework is applied to study the effect of fasteners on the formation of local, distortional, and global buckling modes of built-up section and a comparison is drawn with the buckling behavior of a single section. In this study, the proposed formulations are also used to get insights into the stability behavior of single-span and multi-span compound cold-formed steel columns in the presence of (i) fasteners with varied spacings with respect to span and (ii) the presence of the additional restraining system such as wall panels. For different buckling modes, a significant increment in buckling stress for a built-up section from a single section is observed when the fastener spacing is kept less than the critical buckling half-wavelength of the respective buckling modes. The study on the effect of wall panels shows that in comparison to unsheathed wall studs, the sheathed wall studs that produce additional constraints lead to the elimination of the global buckling deformations. The proposed formulations are simple, yet rigorous and have been validated using finite element-based numerical results.

The vibration reduction optimization of the body tube fastening of EM rail launcher

In order to further optimize the vibration reduction effect of the body tube fastening of the electromagnetic rail launcher, the vibration reduction optimization scheme of the body tube fastening is determined by the modal superposition method. The electromagnetic rail launcher is simplified to Bernoulli-Euler beam, the vibration equation of the rail is established, and the inherent characteristics of the rail are analyzed. The multi-field coupled finite element model of the electromagnetic rail launcher is established and the complete transient launching process of the launcher is simulated. Based on the modal analysis of the system stiffness at the critical velocity, the optimal position of the tube fastening is determined, and the influence of different fastening positions on the damping effect is analyzed. The results show that the fastening of the body tube can effectively improve the structural stiffness of the electromagnetic rail launcher, and the damping effect of the fastening is affected by the vibration characteristics of the fastening position. The addition of fastening leads to the stress concentration in the adjacent part of the rail, which increases the requirement of rail strength. When the fastening is set in the front part of the rail, the vibration reduction effect is obvious. When it is set in the back part, the resonance range of the critical velocity should be avoided and the priority should be given to the position before the critical velocity.

Comparative study of mechanical properties of orange peel filled epoxy composites joined by a mechanical fastener

Abstract The present investigation explores the effect of mechanical fastening of natural filler (orange peel) based epoxy composite on the tensile, flexural, and impact strength. Open mold casting technique used to fabricate composites with the orange peel of average size 500 µm as filler material and epoxy and as a matrix material. Four compositions of samples were fabricated, having 0, 5 and 10 wt% of orange peel in the composite. For the examination of joining strength, the composite samples were fastened with single and double nut and bolt. Results suggested that fastened composites samples exhibit slightly low tensile and flexural strength than parental composites but exhibit higher impact energy capability. Bearing and shearing strength was found to be higher, having higher filler content and fastened by double nut and bolts. Highest tensile (42.89 MPa) and flexural strength (48.86 MPa) were observed for O0 samples while O8 sample showed highest impact energy (2.5 J), shear (4.26 MPa) and bearing strength (21.18 MPa).

Odd-Even Effect on the Spin-Crossover Temperature in Iron(II) Complex Series Involving an Alkylated or Acyloxylated Tripodal Ligand.

In the context of magneto-structural study, a relatively short alkyl group was introduced to anionic spin-crossover (SCO) building blocks based on [Fe(py3CR)(NCS)3]-, where py3CR stands for tris(2-pyridyl)methyl derivatives. The linear alkyl and acyloxyl derivatives of Me4N[Fe(py3CR)(NCS)3] with R = CnH2n+1 (n = 1-7) and CnH2n+1CO2 (n = 1-6) were synthesized, and the magnetic study revealed that all the compounds investigated here exhibited SCO. The SCO temperature (T1/2) varied in 289-338 K for the alkylated compounds, and those of the acyloxylated ones were lower with a narrower variation width (T1/2 = 216-226 K). The crystal structures of the former with n = 3, 4, and 5 and the latter with n = 1, 4, 5, and 6 were determined, and various molecular arrangements were characterized. There is no structural evidence for a molecular fastener effect. The plots on T1/2 against n displayed a pronounced odd-even effect; the SCO temperatures of the homologues with even n are relatively higher than those of the homologues with odd n. The odd-even effect on T1/2 may be related with the entropy difference across the SCO, rather than crystal field modification or intermolecular interaction. The present work will help molecular design to fine-tune T1/2 by means of simple chemical modification like alkylation and acyloxylation.

The Effect of Fastener Type (Clamex P14 and Tenso P14) and Adhesive Type on Compression and Tension Performance

In this study, the effects of different fasteners (Clamex P14 and Tenso P14) for medium density fiberboard (MDFLamM) surfaced with synthetic resin sheet wood-based materials as well as several adhesives (PVAc-D4) and PU-D4) on diagonal tension and compression forces, were analysed. In the study, melamine coated medium density fiberboard (MDF-Lam) was used as wood-based material, Clamex P14 and Tenso P14 were used as fasteners and polyvinylacetate (PVAc-D4) and polyurethane (PU-D4) glues were used as adhesive agents. The diagonal tension and compression force tests were applied on 120 pieces of test samples prepared in this respect based on the principles of ASTM D 1037. As a result, The diagonal compression and tensile forces values were found in the highest Clamex P14 fastener and polyvinylacetate adhesive bond (PVAc-D4), the lowest was in the joint with Tenso P14 fastener without any adhesive agent. For L type corner-joints, it is suggested to use Clamex P14 as a fastener and polyvinylacetate adhesive (PVAc-D4) as the type of the adhesive agent.

Effect of mechanical fastener induced pre-stress on power efficiency of soft PZT energy harvesters

Experiments to determine the effects of mechanical fastener induced pre-stress on a piezoelectric energy harvester (PEH) were conducted. Using a mechanical pre-stress fixture and an electro-dynamic MTS material tester, experiments conducted on soft-PZT showed that are optimized PEH by modulating the magnitude of pre-stress induced on the soft-PZT. Experiments also showed that by adjusting the number of mechanical fasteners used to induce the pre-stress, the energy harvesting capabilities of a PEH may be further optimized.

The Effect of the Wood Defects on Fire Resistance

In the case of charcoal speeds, the defects of the wood and the effect of the metal fixing elements are not taken into account. The aim of our research was to analyze and investigate the effect of wood defects and fasteners on fire resistance. During the experiments we investigated the effect of the defects in the wood and the effect of the metal fasteners on the fire resistance. In the first part of the experiments we examined the effect of wooden defects (knots, thread direction, cracks, insect repellent) on fire resistance. We assumed that the higher hardness or density of the knots and the different fiber direction would facilitate the burning of the wood in the vicinity of the knot. In our experiments, we also examined the effects of cracks and insect pests. The second part of our experiment was to test the switching elements under the effect of heat load.res.

유한요소해석을 통한 침목고정장치가 무도상 판형교 강성에 미치는 영향

무도상 판형교는 거더에 도상이 없이 궤광을 직접 연결하는 구조로 되어있으며, 침목고정장치를 이용하여 궤광을 고정하고 있다. 궤도의 종·횡방향 저항력은 침목고정장치에 따라 변화하며, 교량의 수직, 횡 및 종방향 강성에도 영향을 미칠 수 있다. 이 논문에서는 침목고정장치에 따른 무도상 판형교의 강성 변화를 확인하기 위하여 3차원 solid요소를 이용한 유한요소해석을 수행하였다. 해석조건은 침목고정장치가 없는 경우, T-볼트형 침목고정장치를 적용한 경우 및 궤광구속형 침목고정장치를 적용한 경우의 3가지로 구분하였다. 해석결과 수직 및 종방향에 비하여 횡방향의 경우 침목고정장치의 체결조건에 따라 교량의 강성이 상대적으로 크게 변화하는 것으로 나타났으며, 일반적으로 1차 모드가 횡방향으로 나타나는 무도상 판형교의 경우 유한요소해석 시 침목고정장치의 영향을 고려할 필요가 있는 것으로 분석되었다.

The effect of adhesive tape versus endotracheal tube fastener in critically ill adults: the endotracheal tube securement (ETTS) randomized controlled trial

BackgroundThe optimal securement method of endotracheal tubes is unknown but should prevent dislodgement while minimizing complications. The use of an endotracheal tube fastener might reduce complications among critically ill adults undergoing endotracheal intubation.MethodsIn this pragmatic, single-center, randomized trial, critically ill adults admitted to the medical intensive care unit (MICU) and expected to require invasive mechanical ventilation for greater than 24 h were randomized to adhesive tape or endotracheal tube fastener at the time of intubation. The primary endpoint was a composite of any of the following: presence of lip ulcer, endotracheal tube dislodgement (defined as moving at least 2 cm), ventilator-associated pneumonia, or facial skin tears anytime between randomization and the earlier of death or 48 h after extubation. Secondary endpoints included duration of mechanical ventilation and ICU and in-hospital mortality.ResultsOf 500 patients randomized over a 12-month period, 162 had a duration of mechanical ventilation less than 24 h and 40 had missing outcome data, leaving 153 evaluable patients randomized to tube fastener and 145 evaluable patients randomized to adhesive tape. Baseline characteristics were similar between the groups. The primary endpoint occurred 13 times in 12 (7.8%) patients in the tube fastener group and 30 times in 25 (17.2%) patients in the adhesive tape group (p = 0.014) for an overall incidence of 22.0 versus 52.6 per 1000 ventilator days, respectively (p = 0.020). Lip ulcers occurred in 4 (2.6%) versus 11 (7.3%) patients, or an incidence rate of 6.5 versus 19.5 per 1000 patient ventilator days (p = 0.053) in the fastener and tape groups, respectively. The endotracheal tube was dislodged 7 times in 6 (3.9%) patients in the tube fastener group and 16 times in 15 (10.3%) patients in the tape group (p = 0.03), reflecting incidences of 11.9 and 28.1 per 1000 ventilator days, respectively. Facial skin tears were similar between the groups. Mechanical ventilation duration and ICU and hospital mortality did not differ.ConclusionThe use of the endotracheal tube fastener to secure the endotracheal tubes reduces the rate of a composite outcome that included lip ulcers, facial skin tears, or endotracheal tube dislodgement compared to adhesive tape.Trial registrationClinicalTrials.gov NCT03760510. Retrospectively registered on November 30, 2018

Effects of Fasteners Damping on Dynamical Characteristics of Track Structure

Track structure is modelled as an Euler beam that is supported by a series of discrete points. Further, the governing equations of the track structure subjected to moving harmonic excitation are established. On the basis of the dynamical characteristics and principle of superposition in frequency domain of periodic structure subjected to moving harmonic excitation, for any point, theoretical expression of the amplitude-frequency response is derived. Consequently, the nature characteristic and the effects of fasteners damping on dynamical characteristics of track structure subjected to moving harmonic excitation are investigated. The researches reveal that influences of damping on resonant peak bandwidth and peak value of the track structure are no obvious. While the effects of damping on dynamic response are very obvious on non-resonant high frequency band, and with the increasing of damping the dynamical responses of the track structure obviously decrease. The dynamic characteristics of the fastener bearing points and the midpoint on track structure are almost similarity, while there is a certain difference only in the frequency range far away from the excitation frequency.

Thermal bridges of metal fasteners for aerogel-enhanced blankets

The use of silica aerogel-enhanced blankets as a thermal insulation material is one of the most promising solutions to reduce the heat loss through the building envelope. Aerogel-enhanced blankets provide exceptionally high thermal resistance, thanks to a thermal conductivity value as low as 0.014 W/mK. However, a challenge in the use of aerogel-enhanced blankets is represented by the way to connect these highly flexible panels to the backing support. This paper describes the effect of mechanical fasteners over the thermal performance of a brick wall covered with an aerogel-enhanced blanket investigated. The effective thermal transmittance of the selected aerogel-enhanced blanket due to the presence of the metal fasteners is evaluated experimentally using a calibrated chamber. The laboratory measurements are also compared with theoretical calculations conducted both for metal and plastic fasteners. Finally, some conclusions about the ways to reduce the thermal bridging effects during the installation of aerogel-enhanced blankets are provided, and the effective thermal conductivity of aerogel blankets considering different materials (plastic or metal anchors) for their fastening are reported.

Structure and magnetic property of µ-oxo bridged dinuclear iron(III) complex with trialkylated tridentated ligands

µ-Oxo bridged dinuclear iron(III) complex with trialkylated tridentate ligand [Fe2(µ-O)(3C8-bzimpy)2Cl4]·CHCl3 (1, and 3C8-bzimpy = 2,6-bis(N-octylbenzimidazol-2′-yl)-4-octyloxypyridine) was synthesized and the magnetic property was investigated. Single crystal X-ray structural analysis of complex 1 revealed µ-oxo bridged dinuclear structure with N3OCl2 donor set. Complex 1 has constructed one-dimensional chain structure by CH–π interactions and CH–Cl hydrogen bonds, and further formed a two-dimensional layer parallel to the ab plane by fastener effect of trialkylated ligands. Magnetic susceptibility measurement of 1 showed the antiferromagnetic interactions through µ-oxo bridge, and the best fits for their behavior gave the following parameters: J = −12.7 cm− 1, g = 2.

07.13: On extending the direct strength method to the design of cold‐formed steel built‐up columns

ABSTRACTThis paper presents a numerical investigation of the effects of discrete fasteners on the buckling behaviour of cold‐formed steel (CFS) built‐up columns and concludes with the assessment of the applicability of the current direct strength method (DSM) to the design of these members. To this end, the compound strip method is first utilised to accurately model the buckling behaviour of CFS built‐up columns under axial compression via introducing connecting elements to represent the contribution of discrete fasteners. A series of elastic buckling analyses with different levels of composite action are carried out to obtain the “signature curves” corresponding to the considered CFS built‐up sections. The performed studies comprise of variations in cross‐sections, end boundary conditions and fastener spacing. Utilising the developed numerical techniques, the ultimate strength of the sections are estimated and an adjustment procedure is suggested to extend the current DSM equations to the design of CFS built‐up columns. The proposed adjustment is verified against the existing experimental data and shown to be capable and accurate in capturing the expected behaviour of CFS built‐up members with or without stiffeners.