Effect Of Dwell Time Research Articles

Effect of dwell time on consensus in multiagent systems with time‐varying topologies

AbstractThis paper studies the effect of dwell time on consensus of high‐order multiagent systems with time‐varying topologies. In contrast to existing literature that only focuses on the convergence of consensus, the proposed work focuses on the sensitivity of consensus on the dwell time and studies its relationship with consensus behaviors. In particular, it is shown that dwell time determines the duration of agent interactions, resulting in different state dynamics, consensus values, and convergence speeds under different switching topologies. Such effects can impact the dynamical performance of the multiagent systems. To quantitatively analyze the effect, a procedure is proposed to estimate the consensus values with respect to the dwell time and switching topologies, and a condition is obtained to find the topologies that can speed up the convergence. The proposed study is applied to the regulation of microgrids, which proves to be effective in improving the performance and efficiency of controllers.

Effect of dwell time between passes on recrystallization behavior of 4043 aluminum alloy

Effect of dwell time between passes on recrystallization behavior of 4043 aluminum alloy

A rapid pressureless sintering strategy for LLZTO ceramic solid electrolyte sheets prepared by tape casting

Garnet-type electrolytes are regarded as one of the most promising solid-state electrolytes (SSEs) for lithium-ion batteries due to their potential advantages in terms of energy density, electrochemical stability and safety. To achieve the maximum energy density, it is necessary to ensure that the electrolyte layer is as thin as possible. Nevertheless, thin sheet SSE is more challenging to sinter than pellet due to the greater lithium volatilization from the high surface/volume ratio. Garnet-type SSE (Li6.5La3Zr1.5Ta0.5O12, LLZTO) green tape was prepared by the tape-casting technique. The effects of supporter, sintering temperature and dwell time on the relative density, microstructure and ionic conductivity of thin sheet were investigated. A ceramic SSE sheet with a thickness of 173 μm, a relative density of 97.2 %, an ionic conductivity of 2.02 × 10−4 S/cm at 25 °C and an activation energy of 0.25 eV, was achieved using a rapid pressureless sintering at 1250 °C for 25 min with a MgO supporter. This work offers insights into the practical production of LLZTO sheets.

CT-Guided Core and Fine Needle Aspiration Transthoracic Lung Biopsies: Multivariate Analysis of Risk Factors Associated with Pneumothorax and Effect of Dwell Time in Core Biopsies

CT-Guided Core and Fine Needle Aspiration Transthoracic Lung Biopsies: Multivariate Analysis of Risk Factors Associated with Pneumothorax and Effect of Dwell Time in Core Biopsies

Effect of peak stress and dwell time on the fatigue damage behavior of Ti-22Al-23Nb-2(Mo, Zr) alloy with lamellar microstructure

Ti2AlNb alloy is one of the candidate high strength titanium alloy materials under consideration for compressor disc, which will endure dwell loading at high peak stress level during service. In this work, low cycle fatigue (LCF) and low cycle dwell fatigue (LCDF) deformation behaviors and damage mechanism of Ti2AlNb alloy with lamellar microstructure under high loading level were investigated. The results show that fatigue life is highly dependent on the peak stress (σpeak) and dwell time (tdwell). With increasing the σpeak, the LCF life decreases gradually since higher loading stress can accelerate plastic strain accumulation and lead to faster crack propagation. When at the same σpeak, the LCDF life is lower than the LCF life due to greater plastic strain accumulation caused by dwell effect, indicating a dwell life debit of the Ti2AlNb alloy. Moreover, dwell fatigue sensitivity exhibits an increasing trend as the tdwell increases. Under different loading waveforms, the fractography shows remarkably different features. Crack source of LCF appears on sample surface, while crack source of LCDF appears on surface and sub-surface of sample. The research of LCDF behavior is relevant to aviation industry to prevent premature failure of rotating components made of Ti2AlNb alloys.

Effect of rapid cooling on residual stress and surface fracture toughness of dental zirconia

Short-time sintering of dental zirconia not only improves manufacturing efficiency of zirconia prosthetics, but also enables an attractive situation in which prosthetic treatment can be completed within a single visit. Although many studies have clarified the effects of heating rate and dwell time on the properties of dental zirconia during short-time sintering, there are only a few studies on rapid cooling. In this study, we investigated the effect of cooling rate on dental zirconia. It was found that the cooling rate had no effect on the three-point flexural strength, but a fast cooling rate improved fracture toughness at the material surface. Raman piezo-spectroscopy showed that a compressive stress layer formed in the neighborhood of the zirconia surface and that its thickness increased with increasing cooling rate. From the above results, it was concluded that the compressive stress layer formed on the surface by rapid cooling improved the apparent fracture toughness at the material surface.

An Experiment on the Dwell Time Effect of Rubber Seal O-Rings: Friction Force in Intermittent Reciprocating Motion

The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring’s rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.

Effect of mold dwell time on shrinkage defects in investment casting of superalloy turbine blade

Effect of mold dwell time on shrinkage defects in investment casting of superalloy turbine blade

Spark plasma sintering and mechanical properties of two grades of PEKK presenting different Tere/Iso ratios

AbstractTwo grades of PolyEtherKetoneKetone with different Tere/Iso ratios (PEKK 60/40 and PEKK 80/20) were consolidated using spark plasma sintering. Processing parameters were varied and their influence on mechanical properties was assessed. The study reveals that sintering at a temperature close to the melting temperature along with an applied pressure of 18 MPa leads to better mechanical properties, while the effect of dwell time remains limited. A high sintering pressure is shown to promote the cohesion of PEKK 60/40 samples when the temperature is closer to the glass transition temperature, while pressure does not play a significant role for PEKK 80/20. Post‐mortem fractographic analyses provide explanations of the underlying phenomena. PEKK samples sintered with optimal processing parameters display higher compressive yield strength and stiffness than PEKK samples elaborated from conventional processing routes. They however also exhibit a fragile behavior which can be attributed to the incomplete healing between the powder particles.

Modelling short crack growth under creep-fatigue interaction for different dwell times

The creep-fatigue interaction (CFI) short crack growth behavior of 316H steel under different dwell times at 550℃ was investigated in this work. The dwell time effect of the CFI short crack growth behavior is analyzed systematically, the results revealed that compared to the long cracks, the short cracks is more sensitive to the creep damage effect during the dwell period. Meanwhile, a CTOD-based CFI short crack growth rate predication model is proposed by introducing the creep effect during the dwell time. Compared with conventional fracture mechanics approach, the CTOD-based approach demonstrated a superior capability in providing a unified prediction result for the creep-fatigue interaction in short crack growth rates under different dwell times.

Fatigue crack growth properties of PMMA material used in underwater transparent structures

ABSTRACT Polymethyl methacrylate (PMMA) is an ideal material used in underwater transparent structures such as submersible windows and the fully-transparent pressure chamber of the sightseeing submersibles. The failure of PMMA structures usually come from small crack-like defects. In this paper, the fatigue crack growth experiments were carried out on PMMA materials with different thicknesses (B = 3, 6, 12 mm) and stress ratios (R = 0.1, 0.3) as well as plane strain fracture toughness test for unstable crack propagation conditions. Thickness effect and dwell time effect are experimentally investigated in addition to load ratio effect. The applicability of an improved crack growth rate model on PMMA material is validated by test results. The application of this model for prediction of crack growth rates can greatly save experimental time under different working conditions and can be applied in fatigue assessment of full-transparent structures under random loading.

Correlation between sintering temperature and dwell time on structural and ferroelectric properties of NiTiO3-CoFe2O4 ceramics

The 0.9NiTiO3-0.1CoFe2O4 ceramic was prepared by sol-gel method. The structural and ferroelectric properties of the ceramic were investigated. Structure of the materials was analyzed by X-ray diffraction and scanning electron microscopy. Fabricated materials consists of NiTiO3 with rhombohedral phase structure and CoFe2O4 with cubic structure. The effect of sintering temperature and dwell time on the phase, microsctructure and ferroelectric properties of the ceramics was investigated. As the sintering temperature and dwell time increased, the density of the bulk sample was improved. The material sample was sintered at 1200oC for 10 h with large particle size (~6 µm), few pores and high density ~97.5%. The composite material displayed ferroelectric properties, as evidence from the characteristic hysteresis loop observed in ferroelectric materials. At sintering temperatures of 1000°C and 1100°C for 2 and 5 h, the sample exhibited poor ferroelectric characteristics. However, when the sample was sintered at 1200°C for 10 h, a notable enhancement in ferroelectric properties was observed.

Supply Costs in Complex and Routine Inferior Vena Cava Filter Retrieval: 10 Years' Data from a Single Center

PurposeTo characterize the medical supply costs associated with inferior vena cava filter retrieval (IVCFR) using endobronchial forceps (EFs), a snare, or Recovery Cone (RC). Materials and MethodsIn total, 594 of 845 IVCFRs attempted at a tertiary referral hospital between October 1, 2012, and June 20, 2022 were categorized by intended retrieval strategy informed by, rotational cavography as follows: (a) EF (n = 312) for tilted or tip-embedded/strut-embedded filters and for long-dwelling closed-cell filters and (b) a snare (n = 255) or (c) RC (n = 27) for other well-positioned filters with or mostly without hooks, respectively. List prices of relevant supplies at time of retrieval were obtained or, rarely, estimated using a standard procedure. Contrast use, fluoroscopic time, filter type, dwell time, and patient age and sex were recorded. Mean between-group cost differences were estimated by linear regression, adjusting for date. Additional models evaluated filter type, dwell time, and patient-level effects. ResultsOf the 594 IVCFRs, 591 were successful, whereas 2 EF and 1 snare retrievals failed. Moreover, 4 EF retrievals were successful with a snare and 2 with smaller EF, 12 snare retrievals were successful with EF, 1 RC retrieval was successful with a snare and 2 with EF. Principal model indicated a significantly lower mean cost of EF ($564.70, SE ± 9.75) than that of snare ($811.29, SE ± 10.83; P < .0001) and RC ($1,465.48, SE ± 47.12; P < .0001) retrievals. Adjusted models yielded consistent results. Had all retrievals been attempted with EF, estimated undiscounted full-period supplies savings would be $87,201.51. ConclusionsEFs are affordable for complex IVCFR, and extending their use to routine IVCFR could lead to considerable cost savings.

The study investigates the effects of tool pin length, rotation speed, and dwell time on the microstructure and tensile strength of dissimilar joints between low-carbon galvanized steel and aluminium T6-6061 through friction stir spot welding

Friction stir welding is an efficient method for joining steel and aluminum plates at a point of disturbance. In many studies, the tool is only introduced into the aluminum plate, avoiding penetration into the steel plate due to its high strength and the need for a robust tool. Under such conditions, the created connection usually possesses low mechanical properties. In this research, by increasing the strength of the H13 steel tool through thermal operations, the possibility of penetration and bonding of aluminum 6061 with galvanized low-carbon steel has been provided. Moreover, by penetrating the steel plate, the integration of galvanized layers in the disturbance region has been facilitated. The examined variable parameters include pin length, rotational speed, and tool dwell time. Mechanical properties such as tensile strength, fracture force, and Vickers hardness were investigated. Furthermore, the weld microstructure and intermetallic layers were examined using scanning electron microscopy (SEM) and EDS analysis. Tensile and shear strength increase with an increase in pin length, rotational speed, and tool dwell time. Shear fracture loading showed a decrease with increasing pin length, then reached its maximum value when using long pins, while continuously increased with higher rotational speed and longer tool dwell time. As we approach the center of the weld in both the steel and aluminum parts, smaller grain sizes are observed due to increased plastic deformation, more material mixing, and increased mechanical tool pressure, while in the heat-affected zone, a coarse grain structure forms. Hardness in the aluminum plate decreased in the heat-affected zone and reached its minimum value in the thermo-mechanical-affected zone, then increased to the maximum value in the nugget zone, while hardness changes in the steel plate were uncertain. The most influential parameter on mechanical and microstructural properties was pin length, followed by rotational speed and tool dwell time.

Effect of pin geometry, rotational speed, and dwell time of tool in dissimilar joints of low-carbon galvanized steel and aluminum 6061-T6 by friction stir spot welding

In this study, aluminum 6061-T6 plates were joined with low-carbon galvanized steel using friction stir spot welding. Three conical pins with varying lengths (short, medium, and long) were utilized, along with different dwell times and rotation speeds of the tool. The objective of this research was to compare the simultaneous effects of several important process parameters on mechanical and welding properties. The results indicate that the use of short conical pins significantly increased the microhardness in the upper aluminum plate. Conversely, increasing the pin length led to higher microhardness in the lower steel plate. Tensile shear loading was greater for short pins compared to medium pins, attributed to the influence of the tool shoulder. However, with increasing pin length, failure loading reached its highest value due to the dispersion of particles in the weld. The failure mode for short pins exhibited a mixed pattern, which transitioned to a ductile shape in all conditions as pin length increased. Overall, the most influential parameter was the tool penetration depth, which positively affected the obtained properties. The rotational speed of the tool was the second most significant parameter, followed by the dwell time.

Highly textured 3D-printed translucent alumina through pressure-assisted sintering

Templated grain growth is a promising method for the fabrication of translucent alumina ceramics and a possible way to circumvent light scattering due to birefringence. In the present paper the effect of temperature, heating rate and dwell time on grain size, orientation, hardness and in-line transmittance is investigated on 3D-printed textured alumina. The samples were prepared by lithography-based ceramic manufacturing (LCM) of suspensions with fine-grained alumina, seeded by high aspect ratio templates and sintered by spark plasma sintering (SPS). A fully developed textured microstructure was achieved at 1600 °C for 1 h, whereas sufficient in-line transmittance of 54.6 % at 550 nm was achieved at 1700 °C for 3 h, albeit at the cost of considerable grain growth and loss of microstructural texturing.

Effects of Cold Rolling Reduction, Austenitizing Temperature and Dwell Time on Microstructure of the AS150 Coating

Effects of Cold Rolling Reduction, Austenitizing Temperature and Dwell Time on Microstructure of the AS150 Coating

The effect of temperature and dwell time on diamond-WC brazed joint quality using low-melting point active Ag-Cu-In alloy

The recent demand for developing micro-pin Diamond grinding tools has gained tremendous importance in tool manufacturing industries. A successful development of these tools requires joining Diamond grits to carbide surface firmly. In this context, the present paper demonstrates the joining of Diamond grits to WC-cermet surface via brazing route using Ag-Cu-24.3In-3Ti active alloy (Incusil-ABA). All brazing experiments were conducted using a resistance type heating furnace under a highly controlled vacuum environment to eliminate contamination. Experimental findings of this investigation indicate that both brazing temperature and dwell time have significant influence on microstructure and other related properties of the alloy. Titanium present in the alloy was found to segregate towards Diamond-alloy interface. It was expected that such segregation would ensure a proper wetting by the alloy. However, the overall morphology of the brazed joint revealed that improper melting and poor wetting by alloy on cermet surface were two major challenges. The current study showcases that a careful control on brazing temperature and dwell time demonstrates a remarkable improvement in wetting characteristics and alloy morphology. It has been observed that a brazing temperature of 780 °C and dwell time of 15 min resulted in a good brazed joint morphology. The study also investigated the effect of said brazing temperature on grits physical characteristics using Raman spectroscopy. At the end, scratch test and wear characteristics of the filler are investigated in detail. The outcome of this investigation will be of immense interest to tool manufacturing industries associated with development of brazed micro-pin Diamond grinding tools using alloys having low melting point.

Templated grain growth in rapid sintered 3D-printed alumina ceramics

Textured microstructures in ceramics have gained interest due to their beneficial effect on structural and functional properties. For instance, morphologically textured grains in alumina-based ceramics can increase their damage tolerance. Texturing of alumina ceramics may be achieved through templated grain growth (TGG) occurring during sintering at high temperatures with prolonged dwell times (hours) and may be further enhanced by the presence of a liquid phase. In this study, we demonstrate the feasibility of texturing 3D-printed alumina ceramics within minutes by combining rapid heating (∼450 °C/min) and short dwell times (<20 min). The effect of sintering temperature and dwell time is investigated on samples with and without liquid phase. Experimental findings show highest texture degree for samples rapid sintered at 1600 °C for 16 min, opening the path for tailoring the microstructure of 3D-printed ceramics using pressure-less rapid sintering protocols.

Effect of tool temperature and dwell time in the tool for press hardening on the mechanical properties of modern high-strength steel with 3% Mn

The production of sheet safety parts for car bodies is currently carried out using press hardening technology. This technology enables the creation of complex-shaped profiles even from high-strength steels without a significant spring-back effect. In combination with modern high-strength steels, which have retained austenite in their structure, it is possible to achieve high ultimate strength and ductility values. As a result, these parts are used in bodywork areas with high energy absorption requirements during impact. To achieve the required mechanical properties, suitable processing parameters must be selected. High-strength steel with 0.2%C, 3%Mn and 2%Al was used for the experiment. Press-hardening was carried out in a tool fixed in a hydraulic press and can be heated up to temperatures around 450 °C. Different tool temperatures of room temperature and 425 °C were tested and different holding times in the tool from 1 s to 600 s. After hardening in a tool at RT, the ultimate strength of about 1400 MPa with a ductility of 18 % was obtained. But quenching and holding in the preheated tool caused the ductility to increase to 28% with a drop in ultimate strength to 1050 MPa.