Seal Strips Research Articles

Study on sealing performance and optimization design of a new type non-standard seal strip of submarine pipeline maintenance dry cabin

The submarine pipeline maintenance dry cabin can improve inspection accuracy and repair quality. However, there is no reference standard for the selection and design of the seal strip of a large underwater cabin. Therefore, in this paper, the seal strip's sealing characteristics were studied using the finite element software ABAQUS, and the structure of the non-standard seal strip is designed and optimized. The simulation results show that the D-section seal strip can provide high contact stress while maintaining low Mises stress. To further improve the sealing performance, a new type D seal strip composed of rubber and EPDM foam was designed. The ratio of the two materials affects the overall performance of the seal. Therefore, considering the contact stress integral, maximum contact stress, and maximum Mises stress, the comprehensive optimal structure was obtained based on the Response Surface Methodology. Finally, experimental results verified the accuracy of the simulation calculation.

单张封口条离型纸剥离机理分析和机构设计

单张封口条离型纸剥离机理分析和机构设计

Numerical modelling of braided ceramic fiber seals by using element differential method

• A multi-physical coupled model is proposed for the braided ceramic fiber seals. • The coupled fields contain the process of heat conduction, seepage and deformation. • Element differential method (EDM) is used to solve the multi-physical problems. • The material-dependent parameters in model are obtained by an inverse procedure. • Compared to FEM, EDM is more easy and efficient dealing with the coupled model. A new kind of dynamic seal with braided ceramic fibers has been designed to seal the movable panels in the scramjet engines, which are used for the propulsion of hypersonic vehicle. The braided ceramic fiber structure can provide buffer forces when the seals are subjected to the external dynamical preloads. However, it also makes the seals difficult to analyze. Up to now, the analysis of the seals still uses 1D models so that one cannot implement the coupled analysis of seals and their surrounding structures and flows. In this paper, a novel 2D and 3D mechanics-thermal-seepage coupled model is proposed to describe these seals, which provides a possibility for the aforementioned coupled analysis. Meanwhile, a strong-form numerical method, element differential method (EDM) is employed to discretize the governing equations of the coupled model due to its efficiency and robustness. Three examples are given. The first one is to invert the material-dependent parameters of three kinds of seal strips from the experimental data by Levenberg-Marquardt (LM) algorithm. Other two implement the analyses of 3D square and circular cross-section seals, respectively, which verify that EDM is more efficient than FEM in seal analysis when using the same mesh sizes.

An Immersed Boundary–Lattice Boltzmann Approach to Study Deformation and Fluid–Structure Interaction of Hollow Sealing Strip

A combined immersed boundary–lattice Boltzmann approach is used to simulate the dynamics of the fluid–structure interaction of a hollow sealing strip under the action of pressure difference. Firstly, the multiple relaxation times LBM model, hyper-elastic material model and immersed boundary method were deduced. According to the strain characteristics of hyper-elastic materials and the specific situation of friction between the elastic boundary and solid boundary, the internal force and the external force on the immersed boundary were discussed and deduced, respectively. Then, a 2D calculation model of the actual hollow sealing strip system was established, during which technical problems such as the equivalent wall thickness of the sealing strip and the correction of the stiffness of the contact corner were solved. The reliability of the model was verified by comparing results of FEM simulation of quasi-static deformation. Following this, the simulation results of three typical cases of sealing strips were presented. The results show that when the sealing strip fails, there will be a strong coupling phenomenon between the flow field and the sealing strip, resulting in the oscillation of the flow field and the sealing strip at the same frequency.

Variable Gap Sealing Technology of a Hydraulic Cylinder Based on Magnetic Shape Memory Alloy

The synergistic control of resistance reduction and sealing poses challenges to enhancing the rapid dynamic response ability of servo hydraulic cylinders; the key to solving this problem is effectively controlling the sealing gap value. In this study, a micro-variation between the hydraulic cylinder and the piston based on the disadvantage of conventional seals, constant gap seals, and lip gap seals was constructed; MSMA assist support blocks were designed on the piston to form a gap seal strip; then, the sealing gap value could be changed by controlling the magnetic field intensity. Simultaneously, the effects of magnetic field strength, parts-manufacturing precision, temperature, and hysteresis on the micro-variation in the MSMA were analyzed, and effective solutions were proposed. Finally, experiments on the magnetic field, temperature, and hysteresis were conducted by the measurement system. The results showed that the variable value of the sealing gap with the MSMA is feasible under ideal conditions, and can effectively change the amount of MSMA expansion by controlling the magnetic field strength, temperature, preload, etc., and then change the amount of the sealing gap of the hydraulic cylinder. This is the key to achieving friction and sealing control, which plays a crucial and active role in improving the efficiency of hydraulic systems. However, the impact of hysteresis effects cannot be ignored, which will be the main problem to be solved in the future.

Influence of automobile sealing rib structure on sound insulation performance and optimization of section parameters

The door sealing strip plays an important role in the sound insulation of the car, and its sound insulation performance has a great influence on the sound quality and comfort of the vehicle. The sound insulation performance of the seal can be analyzed by Finite Element-Statistic Energy Analysismodel. There are great differences in the cross-section of the door sealing strip system at different positions, which leads to the difference of sound insulation. Therefore, it is very important to study the sound insulation performance of the sealing strip by studying the parameters of different sections. This paper explores the influence of the structure of automobile sealing rib on the sound insulation performance. Taking the sound power of the receiving end of the sealing strip as the index, the orthogonal optimization test is carried out for the simplified section shape of the door seal strip: the wall thickness of the sealing strip, the height of the sealing strip and the rib length. The optimal combination of a set of sealing strip sections is established, and the sound insulation performance of the sealing strip is improved.

An equivalent NVH model of vehicle door seal strip and its application in door vibration problem

The vehicle door seal strip has complex dynamic characteristics and is a critical component in the vibration and sound transmission of the vehicle system. However, in noise, vibration, and harshness (NVH) analysis, the seal strip is commonly simulated as a linear spring model, which results in inaccurate vibration and sound prediction. Thus, it is necessary to propose an alternative model, which allows characterising the complex dynamic behaviour of the seal strip accurately. In the present study, an overlay material model of rubber was encoded and embedded in ABAQUS with the UMAT subroutine. The overlay model was used in a seal strip finite element model validated by the quasi-static and dynamic measurements. By analysing the effects of frequency, amplitude, and pre-compression on the dynamic stiffness of a seal strip, an equivalent NVH model consisting of spring and damping elements was proposed. The proposed model was validated by comparing the simulated mode and vibration transfer function results with experimental ones. Using the spring model, the deviations of vibration transfer function with the experimental results are 37% and 8.3% at the first and second peaks, respectively. The corresponding deviations are only 4.6% and 2.6% employing the proposed model, demonstrating that the proposed model provides higher accuracy than the spring model. With the assist of the proposed model for vibration transmission analysis, a typical door vibration problem was successfully addressed, which proved the effectiveness of the equivalent model in engineering practice.

Validation of a New Method for the Sputum Cytology Test During the COVID-19 Epidemic

Objective: To explore a new way to test sputum and alveolar lavage fluid samples that may contain pathogenic bacteria or viruses in the departments of pathology of middle and small scale hospitals, which are short of professional protection capability during COVID-19 epidemic. Methods: All pathological specimens were divided into two groups, samples of control group were conducted in the biological safety cabinet, and others were tested after put into pathological specimen storage bags and sealed with the seal strip. The sputum and alveolar lavage fluid were directly immersed and pretreated with 75% medical alcohol. After that, samples were performed by cell smears, liquid based cell slides and immunohistochemical staining. Then the cell morphology and tumor cell discrimination were analyzed and the expression of tumor markers was observed in samples of two groups. Result: We found that samples pre-treated with 75% medical alcohol showed clear cell structure and morphology. There was no significant difference on the morphological observation of tumor cells between these two groups. In addition, immunohistochemical results showed that the antigens are specifically expressed in tumor cells and the distribution and localization of tumor cells was diffuse and accurate after pretreatment with 75% medical alcohol, which were consistent with that of the control group. Conclusion: There was no significant effect on cell morphology, antigens and antibodies expression by using disinfectant. Our study provided a new method for technicians to test samples that may contain pathogenic bacteria or viruses without direct contact so that to protect themselves against virus during COVID-19 outbreak. Funding Information: This study was supported by the Sponsored by Shanghai Sailing Program (No.19YF1427600) and National Nature Science Foundation of China (No. 81900438). Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: MISSING

Analysis of Low Temperature Compression Characteristics of Rubber Seal Strip of Shelter based on ABAQUS

The extreme low temperature of the alpine region is easy to have a bad effect on the sealing performance of the rubber seal strip of the shelter. In this paper, ABAQUS software is used to simulate and analyse the compression characteristics of the seal strip of the shelter at 23°C and -55°C, the Von Mises stress and the surface contact stress at two different temperatures are obtained. The result shows that the compression performance of rubber seal strip is sensitive to the extreme low temperature, and it is prone to low-temperature failure. The simulation results in this paper can provide an important reference for the subsequent low-temperature environmental test, so as to more comprehensively analyse the low-temperature failure mechanism of the rubber seal strip of the shelter in the alpine region.

Sealing System Analysis of Rotary Piston Pump

Rotary piston pump is designed by the Wankel engine. The structure, working feature and sealing system of rotary piston pump are introduced. The mathematical model of the internal cylinder profile and the theoretical flow are obtained by analysing the structural characteristics of the new pump. The axial seal and face seal of the rotary piston pump and their structures are analysed. The force analysis of the sealing strip is carried out in various cases. It can be concluded from the analysis that, for axial sealing, the key parameters that affect seal strip wear are working pressure, rotate speed of the crankshaft and the friction coefficient between sealing strip and inner wall of the cylinder. For axial sealing, the force of the spring under the curved sealing strips, the size of the sealing rings and curved sealing strips and material of them are the key design parameters.

Experimental Study on Waterproofing Properties of Putty-Based Composite Rubber Strip for Underground Post-Tensioned Precast Concrete Structures

The proper assembly of underground precast concrete structures is often critical in the construction of underground structures. In particular, interfacial waterproofing between precast concrete segments is a key factor influencing use, safety, and life span. Current practice is to incorporate waterproofing rubber strips in the design. During the installation process, compressive stress is applied to the strip by post-tensioning to achieve performance. For this paper, lateral constraint compression tests were carried out on composite rubber seal strips that utilize putty. Special waterproofing and sealing test devices were designed to investigate corresponding relationships between water pressure and compressive stress (or strain). A relationship between water resistance pressure and compression stress and strain of the putty-based composite rubber strip was proposed based on the series tests and the control target of the minimum compression strain of the putty composite rubber strip was then suggested. Finally, full-scale waterproofing tests on tunnel joints were conducted. The experimental results provide a scientific reference for the engineering application and design of composite sealing rubber strips putty for underground post-tensioned precast concrete structures.

Experimental Verification of the Dynamic Model of Turbine Blades Coupled by a Sealing Strip

This paper presents the experimental-numerical comparison of a bladed system with flexible strip dampers. The experimental results constitute, to the authors’ knowledge, the first published experimental evidence on strip dampers. They explore the in-phase and out-of-phase mode of vibration of two blades coupled by a strip damper. The great influence the mode of vibration has on the strip behaviour and consequent effect on the blades’ response is highlighted, analyzed and successfully simulated numerically. Experiments are made possible by a purposely developed loading system based on compressed air. This non-contact system enables the experimenter to apply a realistic value of contact pressure on the strip without adding spurious stiffness to the system or modifying the contact conditions. The availability of experimental data obtained by imposing realistic contact conditions constitutes a true added value. It is here shown how the full stick linear FRFs (Frequency Response Functions), typically used to predict the response in case of limited excitation on blades coupled by rigid dampers, do not offer significant results in the case of flexible strip dampers.

Shape Descriptor-Based Local Contour Profile Registration and Measurement for Flexible Automotive Sealing Strips

For vision-based measurement, there are few research or professional tools for local contour positional errors of flexible automotive rubber strips. To support the automatic measurement of contour positional errors, a novel local contour registration and measurement method based on shape descriptors is proposed. In this method, a shape descriptor is proposed to find correspondence between a reference local contour and a desired local contour. First, a shape descriptor that includes the shape representation and restrictions of the local contour is extracted from the reference contour. Second, several tolerable shape descriptors for a desired actual local contour are constructed by adding some loosening factors to the ideal descriptor, and an angular similarity-based searching strategy is used to find the best actual local contour. Finally, from the matched local point sets, a quantitative calculation step provides the desired deviation values. This method is implemented in a sealing strip cross section measurement system, and numerous cross-sectional profiles are tested. The experimental results verify the stability and effectiveness of the proposed method. Important progress toward the automatic measurement of flexible products is demonstrated.

Material Selection for Turbine Seal Strips using PROMETHEE-GAIA Method

Material selection plays a very vital role in the designing of a product. Designers often face with the problem of choosing the best material for a product under conflicting criteria. A variety of Multi-Criteria Decision Making (MCDM) tools have been developed by the researchers to aid the designers in making the best choice for material for product. One of the most popularly used MCDM tool is PROMETHEE (Preference ranking organization method for enrichment evaluation). The visual aid developed using PROMETHEE is the PROMETHEE-GAIA software. In the present work material selection for seal strips used in turbines has been done. Five potential materials used for the purpose were: AISI 304, 310, 316, 321 and 430 stainless steels. The criteria on which the selection was made were: Creep strength, Resistance to oxidation, Coefficient of thermal expansion, Yield strength, Toughness and Limit strain. AISI 321 was found to be the optimum material for the seal strips. The Results shows that AISI 316 stainless steel is found to be the most suitable material for the turbine seal strips.

A Study on Dynamic Performance of Deviation-Based Sliding-Door in Closed State

This paper presents a flexible deviation model of sliding-doors developed using influence coefficient method. By introducing the deviation factors such as seal strip reaction force and door’s dynamic deformation, the closed-loop relationship of size of the sliding-door system when it is in closed state is further established. Then based on the influencing relationship of the sliding-door deviation on the system flexibility and stiffness, the influence of the deviation on the door dynamic performance is obtained. Finally, through analyzing the frequency response of a real sliding-door, the optimal door deviation design is proposed and the effectiveness of the method is also verified.

A Clinical Study to Evaluate Denture Adhesive Use in Well‐Fitting Dentures

The objective of this study was the assessment of retention and stability and functional benefits of denture adhesive applied to well-fitting and well-made dentures. This was a randomized, crossover study to compare two marketed denture adhesives (test cream, Super Poligrip® Free, and test strip, Super Poligrip® Comfort Seal Strips) and an unmarketed cream adhesive (GlaxoSmith Kline Consumer Healthcare) with no adhesive as the negative control. Thirty-six subjects completed the study. One hour after the application of denture adhesive, retention and stability were measured using the Kapur Index and maxillary incisal bite force. Two hours after application, functional tests were used to assess denture movement and peanut particle migration under the denture. Subjects also rated confidence, comfort, satisfaction with dentures, and denture wobble in conjunction with the functional tests. Denture adhesives significantly (p < 0.05) improved retention and stability of well-fitting dentures. Subjects experienced significantly (p < 0.05) fewer dislodgements while eating an apple after adhesive was applied to dentures. Significant (p < 0.05) increases in subjective ratings of confidence and comfort as well as decreases in denture wobble were associated with the use of adhesive. There was significant (p < 0.05) improvement in satisfaction ratings for cream adhesives. A single application of each denture adhesive was well tolerated. The results of this study provide evidence that use of Super Poligrip® denture adhesives can enhance aspects of performance of complete well-fitting dentures as well as provide increased comfort, confidence, and satisfaction with dentures.

An approximated method of calculating the cellular insert influence in the carrying capacity of the direct-flow labyrinth seal

A method for calculating the flowrate of the gas flowing through the cellular insert cells over the labyrinth seal strip is proposed. The gas density is taken to be average with respect to the decisive section. It is assumed that jets flowing out of cells disrupt the direct flow of the labyrinth seal. A practical implementation of the method is confirmed by the known experimental data.

The development of an optimum manufacturing and material selection process for the fabrication of labyrinth seal strips

A systematic material selection process using the digital logic model was developed. Material performance requirements were analyzed and alternative solutions were evaluated among various austenitic, ferritic and martensitic stainless steels. The analysis of metallurgical and mechanical properties of failed seal strips was carried out and the main failure parameters were determined and used for the selection of the optimum material. Also mechanical and chemical properties, including creep strength, formability, scaling and corrosion resistance, as well as availability and cost, were used as the key parameters in the material selection and manufacturing stages. The analysis led to the AISI 321 austenitic stainless steel as the most appropriate material. Various manufacturing processes were analyzed and finally a combination of roll forming and three-roll bending was selected as the optimum fabrication method. Rollers and guides were designed, fabricated and used in this investigation. The results indicated that the selected manufacturing procedure is adequate and leads to the expected tolerances required for these materials. Labyrinth seal strips were fabricated from the selected material using the above fabrication method and were approved in industrial scale.

Modelling of the flow at the rotor disc in a geothermal turbine of 110 MW

To elucidate an excessive erosion damage produced by solid particles in the fourth stage rotor disc of a 110 MW double flow geothermal turbine, a bi-dimensional modelling investigation has been conducted. The study was based on a set of results from a computational model using a Reynolds stress, RSM, turbulence model. The predicted results confirmed characteristic flow conditions that may play a main role in the serious erosion of the fourth stage rotor disc governor side, which has been detected in periodic overhauls. The results show a jet of vapour that hits the disc transition radius surface at velocities around 112 m/s. These conditions are produced by the flow outgoing from the labyrinth seal, which passes through a drastic cross-section reduction in the last seal strip. The flow was then simulated introducing specific changes to the geometry and the grid in order to modify the flow patterns favourably. Actually, the suggested changes have been envisaged indeed to be practically feasible of being implemented. The new results showed that it is possible to reduce the erosion process up to 86% by increasing the distance from the labyrinth seal to the rotor disc, which produces a 38% velocity reduction of the vapour flow in that zone. The design proposed in this work produces a flow pattern of a lower velocity on disc surface together with a modified angle of flow incidence. Furthermore, the proposed design also reduces a recirculating flow at the exit of the last seal strip. Based on these results, an analysis of erosion against velocity demonstrates that the redesigned rotor disc proposed here leads to the duplication of the time period used at present between maintenance repairs.

Flow Induced Vibration in a Heat Exchanger With Seal Strips

Flow induced vibration tests using water as the shell side medium were conducted on a shell and tube exchanger with single segmental baffles and various tube layouts. The heat exchanger was of the externally packed floating head type with seal strips that directed the water flow into the bundle to prevent by-passing of the fluid between the bundle and the shell. High localized velocities exist in the vicinity of the seal strips and contributed directly to the vibration problem. The tube natural frequency for various baffle spacings was measured at the vibration point and a gap velocity at the critical section of the bundle was estimated. A correlation was then made with these parameters and the fluidelastic excitation theory. A discussion of the velocity profile through the heat exchanger is included.