Flexible Seal Research Articles

Effect of Mixing Methods and Black Conductive Fillers on Properties of Natural Rubber Composites

Carbon black, graphite, carbon nanofibers, carbon nanotubes, and metal fillers increase composite conductivity in natural rubber, which is electrically insulating. Depending on dispersion, conductive filler lowers insulating material resistivity. These materials are frequently used for electromagnetic/radio frequency interference (EMI/RFI) shielding, conductive flexible seals gaskets, and conductive mats used to prevent electrostatic damage to electronic devices. These elastomers could be used to make flexible solar cells or mechanical-to-electricity devices. Temperature, mixing time, shear rate, and cross-linking during vulcanization affect rubber electrical conductivity of composite. To study shear rate effects, vulcanizate of Natural Rubber-based composites filled with carbon black, millable carbon fiber powder, and synthetic graphite powder was prepared by open mixing (two roll mill) and close mixing (internal mixer). We compared how shear rate affects cure, stress-strain, and volume resistivity of conductive filler-based Natural Rubber composites. Increment in clearance of two roll mill during addition of rubber additives along with rubber of reduced the shearing force resulted in less dispersive and distributive mixing and stagnant points due to band formation on roll surface compared to intermix where compound movement had no stagnation point and long wings pushed material axially and two nogs pushed material in other chamber. Compared to two roll mill samples, the compound reached every point of the mixing chamber for best homogeneity, reducing cure time and improving stress-strain and volume resistivity.

S930 Colonic Insufflation Management Using a Custom Flexible Rectal Seal

S930 Colonic Insufflation Management Using a Custom Flexible Rectal Seal

Flexible yet impermeable composites with wrinkle structured BNNSs assembling for high-performance thermal management

Efficient thermal management has become one of the most critical issues of electronics because of the high heat flux generated from highly integrated, miniaturized, and increased power. Here we report highly flexible composites with aligned and overlapping interconnected boron nitride nanosheets (BNNSs) assembled in wrinkle structures. Besides high in-plane thermal conductivity of more than 26.58 W m−1 K−1, such structure rendered enhanced through-plane conduction along with increasing pre-stain. As thermal interface materials (TIMs) of both rigid and flexible devices, the composites revealed an outstanding thermal cooling capability outperforming some commercial TIMs. During a record-long bending process of more than 3000 cycles, the maximum temperature fluctuation of the flexible device with 100%-prestrained composite was only within 0.9 °C, less than one-third of that with commercial thermal pad. Moreover, the composite revealed a superior impermeability for flexible seals. Our results illustrate that the composites could be an ideal candidate for the thermal management of emerging flexible electronics.

Research on Micro Gap Flow Field Characteristics of Cylindrical Gas Film Seals Based on Experimental and Numerical Simulation

Flexible support cylindrical gas film seals (CGFSs) adapt well to rotor whirling and have a good gas lubrication effect during thermal deformation. However, when a CGFS operates under the “three high” (high interface slip speed, high-pressure differential, and high ambient temperature) operating conditions, the complex deformation of the support structure is a crucial factor affecting the stability of the CGFS. A thorough and systematic analysis of the micro gap flow field characteristics of flexible support CGFSs is a fundamental problem when we study the deformation of the support structure under multiple physical field conditions. This study uses a cylindrical gas film high-speed rotor test rig to study and compare the sealing characteristics of experiments and numerical simulations and then optimizes and verifies the accuracy and effectiveness of the simulation model. A cross-scale gas film grid model is used to analyze the flow field characteristics and seal ability of different groove models and compare the mechanical characteristics and sealing performance. We also analyze the gas film pressure distribution in micro gaps and explore the impact of dynamic pressure groove microstructure on flow field characteristics. Results show that micro gaps are the primary conditions for generating hydrodynamic effects, and high rotational speed, high-pressure differential, and large eccentricity have a significant effect on improving hydrodynamic effects and enhancing gas film stability. However, an increase in these parameters can cause an increase in leakage rate. A single flow channel makes it easier to improve the hydrodynamic effect, gas film load-bearing ability, and gas film stability while reducing leakage rate. The analyses in this study supplement and improve the theory of the flow field characteristics of cylindrical annular micro gaps and provide a theoretical basis for exploring the relation between the support structural parameters of the CGFS and the mechanical characteristics of the micro gap flow field. This study provides important guidance to the establishment of a quantitative design theory of supporting structures.

Facile method for 3D printing conformally onto uneven surfaces and its application to face masks

Conventional additive manufacturing processes, where parts are built through layer-wise deposition of material on a horizontal plane, can be limiting when a part must be printed or fit onto uneven surfaces. Such situations will arise with increasing frequency as additive manufacturing application areas such as construction and medical devices continue to grow. In this work, we develop a simple and practical approach to generate toolpaths to print 3D structures onto uneven surfaces conformally. The algorithm uses only conventional planar toolpaths of both the structure to be printed and the substrate to be printed on and converts these to non-planar toolpaths, allowing easy integration with existing additive manufacturing workflows. The technique is demonstrated by printing flexible seals onto bespoke rigid face mask frames conformally via a conventional single-material 3D printer using the generated conformal toolpath. A notable improvement in air seal performance was observed for customized face masks with conformal soft seals compared to conventionally 3D-printed fully rigid face masks. This also shows the potential of the developed toolpath generation method to aid in the prototyping and fabrication of conformal medical and other devices.

Use of volumetric additive manufacturing as an in-space manufacturing technology

Computed Axial Lithography (CAL) is a recent advancement in volumetric additive manufacturing (VAM) that delivers a light dose to a photopolymer volume through tomographic reconstruction. The precursor liquid or gel itself generally supports the emerging object, eliminating the need for wasteful dedicated solid supporting structures. A challenge, however, is that desired geometry can shrink or expand during solidification and on Earth, if the precursor material's viscosity is low enough. These effects may result in sinking or floating of the component, which can blur the geometry.In principle, CAL is promising for in-space manufacturing because, unlike layer-based processes, CAL does not require a flat liquid–gas interface to be maintained during printing. With suitable development, CAL is potentially capable of manufacturing parts such as organic tissue, flexible seals, rigid trusses, and microstructures for space exploration, as well as repairing existing tools and parts. ‘SpaceCAL’ flew on a microgravity parabolic flight in May 2022 to demonstrate the capabilities of CAL and analyse a CAL system in a microgravity. Initial findings show that 0.12 Pa-s low viscosity precursor can be printed in microgravity with less geometric distortion than an Earth-based gravity counterpart.

Experimental study on wave motion of partial air cushion supported catamaran

To study the performance of partial air cushion-supported catamaran (PACSCAT), which is sailing with a flexible air seal in waves, this paper uses the model tests, and research the motion characteristics of PACSCAT at different wavelengths, by monitoring the boundaries of heave, pitch, acceleration, air cushion pressure. Firstly this paper introduces the test situation of PACSCAT in the towing tank and introduces the test method, equipment, and test conditions. Second, this paper extracts the test data, analyzes the features of heave, pitch, acceleration, and air cushion pressure, and studies their linear and nonlinear changes in regular waves. Thirdly this paper analyzes the nonlinear air leakage flow of the bow of PACSCAT in detail under the test conditions and studies the internal and external free liquid surface under different conditions.

Effects of edge-seal design on the mechanical and thermal performance of vacuum-insulated glazing

Although vacuum-insulated glazing (VIG) has been proposed as a promising solution towards developing energy-efficient buildings, VIGs have not become popular in the market due to several technical challenges including the complexity of the fabrication process. In particular, the edge-seal is a key component that significantly affects the thermal insulation and mechanical performance, and the development of edge-seal with adequate thermal insulation, mechanical strength, and reasonable processing cost is essential to overcome such technical issues in VIG. For this purpose, effects of edge-seal design parameters on the VIG performance should be identified. In this research, we analyzed the edge-seal for thermal transport as well as structural stresses to study the effects, and then identified and evaluated the material mixes for the edge-seal requirements. The finite element simulations showed the significance of VIG corner calculation on overall thermal transmittance and the importance of seal conductivity below 1 W/m.K. The experiments with the flexible seals with different ratios of fine glass powder demonstrated that the measured shear strength values for the seal with less than 30% glass powder were more than 10 times larger than the calculated shear stress values. Based on these simulation and experimental results, a flexible sealant was developed using a proprietary mix of ceramic materials that meets the requirements of the designed VIG edge-seal, including structural as well as thermal stress resistance and a low conductivity. Moreover, the sealant is self-curing under atmospheric conditions, and thus it does not require costly inline process of laser curing or oven baking.

Study of wear and friction heat generation models of finger seals based on energy theory of tribology system

Finger seals have a good application prospect in gas and steam turbine for power generation as an advanced contact flexible seal. The wear and friction heat generation properties of the finger seal have significant effects on leakage and life. In this study, a bilateral wear model and friction heat generation model were established to calculate the wear volume and temperature of the finger seal and rotor. In particular, the friction heat generation model considered the effect of wear and deformation (centrifugal and thermal) of both the finger seal and rotor. Both models were expressed as functions of the finger seal configuration, material properties, operating conditions, and several relevant parameters. To determine these parameters, a ball-disk friction and wear experiment and a finger seal wear and friction heat generation experiment were conducted. Both models were validated with experimental data, and both errors were less than 12%.

Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

A Photogrammetric Technique for Developing Boundary Equations for Flexible Sheath Waterless Trap Seals as Used in Building Drainage Systems

The water trap seal is still the main method of protecting building inhabitants from the ingress of foul contaminated air and noxious gases from the sewer. This seal can become compromised when water is lost in the trap by processes including evaporation and siphonage from excessive system suction pressures. A recent innovation is the waterless trap seal, which uses flexible sheaths, typically made from silicone rubber to form the seal. The sheath opens in response to a sub-atmospheric air pressure and will shut tightly under a supra-atmospheric pressure in order to form a seal. Full system numerical modelling of building drainage systems has offered insight into system responses to pressure transients and has opened up the evaluation of building wastewater systems to predictive modelling which has assisted in producing improvements to public health. A requirement of any predictive model is a mathematical representation of the physical characteristics of the system. This research develops a technique for developing boundary equations so that predictive modelling is possible. We combine photographic and pressure data analysed by Fourier analysis to develop the model. The technique is applicable to any device were the fluid structure interaction plays a significant role in its operation.

Numerical Investigations of Leakage Performance Degradations in Labyrinth and Flexible Seals Due to Wear

Abstract The finite element analysis (FEA) and computational fluid dynamics (CFD) methods are utilized to investigate the leakage performance degradations in two kinds of flexible seals (i.e., forward bending and backward bending) and two kinds of shroud labyrinth seals (i.e., with straight fins and chamfered fins) in rubbing events. With the existing experimental data, FEA methods for contacting simulations and CFD methods for leakage rate and flow pattern predictions are carefully examined. The wear characteristic and leakage performance between labyrinth seals and flexible seals are compared before and after rub. The results show that, in rubbing process, the labyrinth seal with straight (symmetrical) fins is likely to undergo the mushrooming damage, whereas the labyrinth seal with chamfered (asymmetrical) fins is likely to undergo the tooth-bending damage. In rubbing process, compared with the labyrinth seal, the flexible seal has a superior characteristic in resisting the wear damage due to increased flexibility of fin. For a labyrinth seal with 0.3 mm design clearance and a flexible seal with 0.15 mm design clearance, the 0.5 mm radial displacement of rotor will result in 110% increase of leakage rate for labyrinth seal, and 7% increase of leakage rate for flexible seal after wear. Under the same conditions, the forward bending flexible seal has a lower leakage rate than the backward bending flexible seal before and after rub.

Research on the wear model of carbon/carbon composite finger seal

Finger seal is a new type of contacting flexible gas seal which can be used in gas turbine. The seal is often works in high velocity, high temperature and high pressure operating conditions. So wear is a prominent issue with the finger seal. A Carbon/Carbon (C/C) composite material finger seal is proposed to reduce the wear between seal and shaft with the self-lubricating properties of C/C composites. In order to determine the wear properties between C/C composite finger seal and rotor, a pin-on-disc high temperature friction and wear tester was used to study the friction and wear behavior between the pair of C/C composite and 40CrNiMoA material under dry friction. According to the friction and wear performance of the tribo-pair, the friction coefficient and wear volume were obtained under different working conditions. The test results show that when the load increases, the friction coefficient increases but the amount of wear does not increase monotonically. As the sliding speed increases, the coefficient of friction decreases and the amount of wear increases significantly. In a higher temperature environment, the coefficient of friction decreases while the amount of wear increases with increasing temperature, and adhesive wear becomes more obvious. Based on the multifactor orthogonal test results, a regression analysis model of the relationship between the material wear rate and the load, speed, and ambient temperature was established. Considering the difference between the speed of the test machine and the actual working conditions of the finger seal, the regression wear model was corrected with reference to the high-speed operating conditions of Brake disc. The calculated results of the modified wear rate regression model are compared with the wear rate obtained from the finger seal test. The relative error is within 20%, which verifies the wear rate calculation method of the C/C composite finger seal proposed in this paper. The work provides the basis for numerical analysis and life prediction of C/C composite finger seal wear behavior.

Study on the Influence of High Temperature and High Speed Working Conditions on the Leakage Characteristics of Flexible Bristle Brush Seal

Compared with the metal bristles, the flexible bristles can reduce the heat and wear caused by the friction between the bristles bundle and the rotor, and improve the working stability and working life of the brush seal. In this paper, the L-shaped numerical mode is established to analyze leakage characteristics of flexible bristle brush seal. The flow field of brush seal is analyzed, and the effects of differential pressure, rotating speed and temperature on the leakage rate were studied as well. The leakage rate of the flexible bristles brush seal under different pressure and rotating speed was measured and compared with the numerical results. The results show that: Pressure drop mainly occurred in bristles pack; Small pressure difference, high temperature and high speed can improve the sealing performance, which, shows that the flexible bristles brush seal can well adapt to high temperature and high speed conditions; The leakage rate after running-in is slightly lower than that before running-in, and has better sealing performance, and the brush bristles arrangement is complete and tight after test, indicating that the flexible bristle brush seal has the ability of lasting and stable seal; The error between experimental results and numerical simulation results is less than 10%, and the variation trend is consistent, confirming the accuracy of the leakage rate obtained by numerical simulation.

Ground Reaction Forces generated by a Lower Body Negative Pressure Exercise Device for Space Flight

Loss of bone and muscle are leading concerns among astronauts during prolonged space flight. Lower body negative pressure (LBNP) chambers generate gravitational and cardiovascular stresses to maintain musculoskeletal strength and fitness by means of suction pressure. Ground reaction forces (GRFs) generated underneath the user’s feet are directly proportional to the level of negative pressure applied. However, the exact mechanism of GRF generation remains unresolved. We hypothesize that increasing the cross‐sectional area (CSA) of the user’s waist in contact with a flexible waist seal will increase the GRFs generated at a given vacuum pressure. To test our hypothesis, we collected GRFs generated by 6 healthy subjects under two conditions: original (unchanged) CSA of their waist and a greater waist CSA using expanded cushioning around waist of the same subjects. GRFs were measured with LBNP levels ranging from 0 (ambient pressure) to 50 mmHg with subjects lying in supine position to simulate microgravity. The original CSA of 467.7 cm2 ± 69.0 cm2 generated 118 % ± 31 % body weight at −50 mmHg. However, the larger CSA of 1,451.0 cm2 ± 331.0 cm2 generated a mean GRF of 146 % ± 31% body weight at −50 mmHg. A one‐way ANOVA test resulted in p‐values < 0.05 for all pressures, denoting statistically significant increases in larger compared with original CSA GRF. The GRF generated with larger CSA followed this equation GRF = −1.8211 (LBNP) + 0.7899 while the GRF generated with original CSA followed the equation: GRF = −1.5079 (LBNP) + 0.3995. These data support our hypothesis that GRFs generated by LBNP are directly proportional to the waist CSA. Using this new concept, astronauts may generate GRFs at lower LBNP levels to prevent pre‐syncopal symptoms during exercise in space.Support or Funding InformationSupported by NASA grants NNX13AJ12G and NSSC19K0409.Average weight measurements with varying pressures for six volunteers; red is original CSA of subject's waist and blue is larger CSA.Figure 1

Theoretical and Experimental Investigation of Variable Stiffness Finger Seal

A finger seal is a flexible and dynamic contact seal, and many researches and experiments have proved its application potential in aviation engines, gas turbines, and other equipment. However, the contradiction between hysteresis leakage and wear life in the design and initial installation condition of finger seals seriously affects the integrated performance design effect. A variable stiffness finger seal is investigated in the present study to resolve the aforementioned problems, and the influence of initial installation condition is considered. First, a theoretical model of the finger seal is established to calculate the hysteresis characteristic and contact pressure between finger feet and rotor. The performances of the variable stiffness finger seal and traditional involute curved finger seal are compared to confirm the advantages of the variable stiffness finger seal. The results show that the initial conditions such as rotor structure and support bearing clearance have an important influence on the accuracy of finger sealing performance calculation. In addition, the variable stiffness structure improves the hysteresis characteristic of the finger seal with virtually no loss of wear life under low pressure differential and reduces the hysteresis rate by more than 50%. Under high pressure differential, the variable stiffness structure reduces the average contact pressure by more than 25%. Therefore, the leakage and wear performance of the finger seal are simultaneously improved by the variable stiffness structure. This characteristic does not change with an increase in rotor excitation. This indicates that the variable stiffness finger seal provides good synthetic performance and high dynamic adaptability to random operating conditions.

Multi-material 3D printed hydraulic actuator for medical robots

Purpose This study aims to investigate the potential of using polymer multi-material additive manufacturing (MMAM) to produce miniature hydraulic piston actuators combining rigid structures and flexible seals. Such actuators offer great potential for medical robots in X-ray and magnetic resonance environments, where conventional piston actuators cannot be used because of safety issues caused by metal components. Design/methodology/approach Hydraulic pistons with two different integrated flexible seal shapes are designed and manufactured using MMAM. Design 1 features a ring-shaped seal made from a flexible material that is printed on the surface of the rigid piston shaft. Design 2 appears identical from the outside, yet an axial opening in the piston shaft is added to enable self-reinforced sealing as fluid pressure increases. For both designs, samples with three different outer diameters are fabricated leading to a total of six different piston versions. The pistons are then evaluated regarding leakage, friction and durability. Findings Measurement results show that the friction force for Design 2 is lower than that of Design 1, making Design 2 more suitable for the intended application. None of the versions of Design 2 shows leakage for pressures up to 1.5 MPa. For Design 1, leak-tightness varies with the outer diameter, yet none of the versions is consistently leak-tight at 1.5 MPa. Furthermore, the results show that prolonged exposure to water decreases the durability of the flexible material significantly. The durability the authors observe may, however, be sufficient for short-term or single-use devices. Originality/value The authors investigate a novel design approach for hydraulic piston actuators based on MMAM. These actuators are of particular interest for patient-specific medical devices used in radiological interventions, where metal-free components are required to safely operate in X-ray and magnetic resonance environments. This study may serve as a basis for the development of new actuators, as it shows a feasible solution, yet pointing out critical aspects such as the influence of small geometry changes or material performance changes caused by water absorption.

PROSES MANUFAKTUR ALAT PELEPAS SEAL SUSPENSI DEPAN JENIS TELESCOPIC FORK SEPEDA MOTOR

One of the most common damages to motorcycles is damage to the seals on the motorcycle suspension, which results in a large amount of oil leakage. To repair the damage a seal removal tool is needed which functions as a Special Service Tool (SST) which is often used in motorcycle workshops. The variety of types and brands of motorcycles, causing motorcycle workshops must have complete equipment, according to the motorcycles brand that is repaired, this results in the expenditure of excess money, especially in the supply of seal removal devices according to the motorcycle brand. The purpose of this research is to create a flexible Telescopic Fork front suspension seal release device, which can be used for all types of motorcycle brands. The method used in this research is tool design, tool manufacturing process, and testing the application of seal removal tools. It is evidenced from the results of the usage test that the resulting seal removal tool can be used for all types of motorcycle brands, this tool can shorten the processing time, and also does not cause new damage to the repaired components. However, it is necessary to examine the application of occupational safety and health to prevent work accidents in the process of making this seal removal device.

The COSMIC Bubble Helmet: A Non-Invasive Positive Pressure Ventilation System for COVID-19.

Goal: COSMIC Medical, a Vancouver-based open-source volunteer initiative, has designed an accessible, affordable, and aerosol-confining non-invasive positive-pressure ventilator (NIPPV) device, known as the COSMIC Bubble Helmet (CBH). This device is intended for COVID-19 patients with mild-to-moderate acute respiratory distress syndrome. System Design: CBH is composed of thermoplastic polyurethane, which creates a flexible neck seal and transparent hood. This device can be connected to wall oxygen, NIPPVs including Continuous Positive Airway Pressure and Bi-level Positive Airway Pressure, and mechanical ventilators. Discussion: Justification of CBH design components relied on several factors, predominantly the safety and comfort of patients and healthcare providers. Conclusion: CBH has implications within and outside of the pandemic, as an alternative to invasive mechanical ventilation methods. We have experimentally verified that CBH is effective in minimizing aerosolization risks and performs at specified clinical requirements.

Automated installation of flexible annular rubber seals into outer grooves of cylindrical parts

Description of operation of automated device for installation of elastic rubber ring seals in external grooves of cylindrical parts is performed and power parameters of assembly are justified.