Tightness Of Joints Research Articles

Inspection of press joints based on the analysis of their deformation patterns under local thermal loading

The results of experimental studies of the possibility of using strain gauges under local pulsed thermal loading to evaluate the tension of the press connections of bearing rings with shafts are presented. Samples of press joints with tightness in the range from 38 to 118 microns were made. As a result of the study of the patterns of heat flow propagation in bearing rings and tension samples by contact method and means of thermal imaging, the possibility of separating deformations associated with the influence of temperature on the deformation measurement area and the temperature gradient in the heating area is shown. The methods of inspecting the press joint when exposed to a heater ring with a heat power capacity of 80 kJ and a temperature of 200°C and measuring the deformations of the ring and shaft by an opto-polarizing sensor with a base of 60 mm and a resolution of 2×10 — 7 relative deformations have been experimentally implemented. A correlation has been established between the time of reaching the maximum of local deformations of the shaft with the tightness of the press joints and the sign of deformations of the bearing ring with the tightness of the press fit, the gap between the ring and the shaft.

Mechanically Joined Extrusion Profiles for Battery Trays

In the context of electromobility, ensuring the leak tightness of assemblies is of paramount importance, particularly in battery housings. Current battery housings, often featuring base assemblies crafted from extruded aluminum profiles, address the challenge of leak tightness at joints through methods like friction stir welding, a process known for its time and cost intensiveness. The aim of this study is to develop and implement a new type of extruded profile concept to produce tight base assemblies for battery housings by a longitudinal mechanical single stroke joining process. The geometry, the process and the properties of the aluminum profiles are investigated to get a joint that meets the tightness requirements and achieve high load-bearing capacities in agreement with the high homologation requirements set to vehicles with high-voltage systems. The joint is formed by means of a single stage press stroke, which eliminates the need for complex tool designs that are necessary for continuous joining (roll joining). Flat steel contact surfaces are used as joining tools. To evaluate the joint quality, force curves from the joining process are analyzed and the resulting joint geometries are assessed using micrographs. The resulting leak tightness of the linear joints is measured by a helium sniffer leak detector and the load-bearing capacities are investigated by shear lap and bending tests and fatigue strength test. The study also explores whether a difference in strength between the two joining partners has a positive effect on the joint properties.

Study of the Influence of Macrogeometry Parameters on the Tightness of Shaft–Seal Joints

The factors influencing the reliability and durability of the joint between a shaft and a rubber reinforced seal are analyzed. It has been established that the theory of tightness of such joints has not yet been developed. The quality of a joint is usually assessed by the amount of leakage. It has been revealed that the amount of leakage depends on the materials from which the shaft and seal are manufactured, the roughness of the shaft surface, the presence of dust in the friction zone, the quality of the sealed liquid, and the operating temperature. In addition, the durability of the work is influenced by macrogeometry parameters like deviation from the perpendicularity of the seal to the shaft, deviation from coaxiality, and radial runout of the shaft. A multifactorial experiment has been carried out, as a result of which an empirical relationship has been established between the radial runout of the shaft, rotational speed, and interference in the joint according to the criterion of the onset of leaks. Analysis of the obtained dependence showed that the radial runout should be compensated by interference in the joint, and with an increase in the rotation speed, the compensation value should be greater due to the fact that the working edge of the seal does not have time to follow the shaft. An empirical relationship between the amount of interference and leakage has been obtained, which indicates that with lower interference, leakage will be greater. The research results can be used at the stage of designing assembly units with seals to reduce the influence of radial runout and deviations from the coaxiality of the shaft relative to the seal.

Influence of Manufactured-Part Design and Gasket Material on the Tightness of Flanged Joints Under Sharp Thermal Cycles in the Environment

Influence of Manufactured-Part Design and Gasket Material on the Tightness of Flanged Joints Under Sharp Thermal Cycles in the Environment

Elimination of defects in a welded joint in a niobium superconducting resonator

The possible reasons for the appearance of defects during welding of a niobium superconducting coaxial halfwave resonator (HWR) are investigated, which consist in the deviation of the shape of the welded surface from the given one, in the deviation of the angle of incidence of the beam from the perpendicular to the welded surface, in fluctuations in the thickness of the welded edges, and also the presence of some instability (pulsation) accelerating voltage, beam currents and focusing of the electron beam gun. The possibilities of preventing the appearance of defects during welding are determined, which consist in regulating the operating parameters of the electron beam gun depending on possible errors in the manufacture and preparation of the welded edges. Methods for elimination of defects in welding of niobium superconducting coaxial HWR are studied. A method has been developed for repairing defects in welded joints such as burn-throughs on the type of resonator under study using electron-beam deposition. The results of measuring the resonant frequency of the HWR before the onset and after the recovery of burn-through are presented, which showed that the melting of the hole did not lead to a change in the electrical characteristics. Vacuum and cryogenic tests at liquid nitrogen temperature confirmed the tightness of the welded joints. The results obtained can be used in the development of basic technologies for the restoration and repair of expensive and difficult-to-manufacture elements of accelerator technology – superconducting high-frequency resonators made of high-purity niobium sheet.

Investigation of the leak tightness of structural adhesive joints for use in battery housings considering mechanical and corrosive loads

ABSTRACT Due to increasing legal requirements to reduce emissions from vehicle fleets, vehicle manufacturers are focusing on the electrification of the powertrain. In entirely electrically driven vehicles, the energy is stored in traction batteries integrated below the passenger cell between the axles and thus located in the vehicle’s wet area. Therefore, high requirements apply to the protection of the sensitive cells against mechanical stress as well as against moisture penetration. In addition, one of the main requirements for the connections of the battery housing is to ensure gas tightness over the entire service life. Adhesive bonding technology as a planar joining process offers the potential to produce functionally tight connections. However, there is a lack of reliable test methods for validating the long-term tightness of structural adhesive joints under mechanical and corrosive loads. For this reason, the paper deals with developing a test concept with laboratory-scale test specimens for leak testing under mechanical loading. Various leakage test methods investigate the leakage rate of structurally bonded joints. An analysis of the leakage rate under superimposed cyclic mechanical shear tensile loading follows this. The test method is validated on a specially developed sample battery housing on a laboratory scale.

Structural and technological support of tightness of interference fits

The conditions for contact interaction of mating parts in interference fit joints are considered. It is shown that the main factor determining the strength and tightness of joints is the state of the surface layer. Ways are established to control the performance of joints with an interference fit by using surfactants, both in the technological preparation of parts before assembly, and in the assembly of joints. Keywords: contact interaction of surfaces, real contact area, joint tightness, influence of surfactants. kurnosov-ne@mail.ru

Determining the Vapour Resistance of Breather Membrane Adhesive Joints.

Due to increasingly stringent requirements, tapes and adhesive joints are a commonly used method to ensure tightness and energy efficiency in modern building envelopes. Previous studies have researched and tested properties such as the strength and tightness of adhesive joints. So far, water vapour resistance has been neglected. This article aims to determine the vapour resistance and shed light on possible consequences of vapour-tight adhesive joints in breather membranes used in roof assemblies. Laboratory measurements of vapour resistance were conducted according to NS-EN ISO 12572:2016, known as the cup method. Eleven products of breather membranes were tested. Results from the laboratory measurements were used to evaluate the impact of vapour-resistant adhesive joints related to the drying of built-in moisture. The simulation programs WUFI 2D and WUFI Mould Index VTT were used to model scenarios for moisture transport and risk for mould growth. Laboratory results show that the vapour resistance of breather membrane adhesive joints varies from 1.1 to 32 m in sd-value. Three of the tested products have a vapour resistance larger than 10 m, while four products have an sd-value less than 2.0 m. The sd-values of the membranes themselves range between 0.027 and 0.20 m. All tested adhesive joints are considerably more vapour tight than the Norwegian recommended value for breather membranes (<0.5 m). However, the mould growth analysis shows that the risk of mould growth is low in most practical cases, except when using adhesive joints with the highest vapour resistance in roofs assembled during autumn.

Parametric Assessment of Surface Topography and Its Influence on Joint Tightness of Non-Separable Joints for Thin Wall Applications

This article describes the research carried out on six thin-walled groups of samples produced from the aluminum alloy 6060 T4 by a turning and milling operation. Additionally, the analysis of the surface topography was carried out, focusing on three-dimensional parameters, such as Sq, Ssk, Sku, Sp, Sv, Sz, Sa, Spd, and Spc. Moreover, the article contains the tests of the tightness of various types of surfaces with different clamping forces of the tested elements. Furthermore, an attempt was made to find significant representatives of the surface topography to obtain the smallest leakage between the mating surfaces. The maximum clamping force obtained in the tests between the pairs was 9060 N. Finally, it is worth mentioning that the presented surface tests can serve as the required parameters for joined elements in the production of non-detachable joints by, for example, clinching.

МЕТОД ПІДСИЛЕННЯ ЗАЛІЗОБЕТОННИХ МОСТОВИХ ОПОР УЛАШТУВАННЯМ БІТРАПЕЦЕІДАЛЬНОЇ ОБОЙМИ

The paper contains developed the method of reinforcement of reinforced concrete bridge supports by arrangement of reinforced concrete casing on the example of an emergency bridge structure located on the state road M-12 in the Gajsin town, Vinnitsa region. Have been proven that for the further long-term operation of bridge supports, in addition to the reinforcement device, it is also necessary to seal the expansion joints of the span structure located directly above the supports. Have been described the main components of intermediate bridge supports erected in Ukraine during the second half of the 20th century. Have been considered typical defects, which were occurred on the two-cantilever supports of bridge structures during long-term operation. Have been estimated the degree of danger of each of the defects. Have been proved the systemic nature of defects and damages of prefabricated reinforced concrete crossbars.&#x0D; Have been considered the probable causes of defects at the bridge supports are considered, namely, destruction of bridges expansion joints. As a result, regular, long-term non-project soaking of supports; violation of the solidity of the concrete protective layer of the working reinforcement of the cantilever parts of the crossbars due its overload; destruction of the mixture from the seams of monolithic semi-crossbars due to its low strength; reinforcement corrosion; loss of frost resistance of concrete; increase in dynamic influences. Have been considered the design and typical defects of standard prefabricated concrete trusses, which are installed on bridge supports for direct perception of loads from the span structure. Have been considered the standard methods of strengthening bridge supports and trusses, their advantages and disadvantages. The paper focuses on the importance and necessity of restoring the tightness of expansion joints by using modern Maurer type constructions in conjunction with the installation of waterproof monolithic or overhead plates of reinforced span structures. Have been proposed an original form of clips for double-console bridge supports in the form of double-trapezoids which significantly improve their architectural expressiveness and optimize the structural scheme of supports. Have been proposed to use self-compressing concrete to save material costs and time during the construction of temporary special and auxiliary devices (formwork) for monolithic casing. Have been proposed an effective methodology and a rational technological sequence for performing work on strengthening.&#x0D; Have been summarized the practical experience of performing construction and installation works on monolithic supports with self-compacting concrete mixes according to the method proposed by the authors of the article which were made according to the technology of Sika. Have been summarized the experience of bridge operation after sealing expansion joints and overhaul of bridge supports.

Mechanical Properties and Leak-Tightness of Polymeric Pipe Adhesive Joints

This paper presents issues related to the determination of the selected mechanical properties of adhesive joints made of polymeric pipes and the evaluation of the leak-tightness of the adhesive joints. The article attempts to demonstrate that the type of adhesive may affect the quality of adhesive joints in terms of both tightness and strength of joints. Five types of the polymer pipes differing in a polypropylene and a polyvinyl chloride, diameter and a wall thickness were used in the experiments. Two types of the adhesives were used to make the adhesive joints: Loctite 3430 A&amp;B Hysol, a two-component epoxy adhesive, and Loctite 406, a one-component cyanoacrylate adhesive. Based on the leak-tightness tests results, it was possible to determine the quality of their adhesive joints without damaging the samples, while their tensile strength was determined through the strength tests. The tests performed allowed for the conclusion that the use of the polyvinyl chloride pipes and Loctite 406 one-component adhesive is recommended for this type of adhesive joints.

ВПЛИВ ГЕРМЕТИЧНОСТІ ДЕГАЗАЦІЙНОГО ГАЗОПРОВОДУ НА ПРИПЛИВИ ПОВІТРЯ І КОНЦЕНТРАЦІЮ МЕТАНУ

concentrations in the vacuum degassing gas pipeline. Methods. Analytical dependencies for determining the absolute pressure, volume flow rate and temperature of the gas mixture in link of degassing gas pipeline and an empirical dependence for determining the volume flow rate of air in the inflows coming through the flange connections of the gas pipeline links were used in the studies. Results. With these assumptions in mind, the formula for determining the gap in the flange joint of the degassing gas pipeline links has been obtained. The results of calculating air inflows and methane concentrations along the length of the horizontal section of the degassing gas pipeline have been presented. Analysis of the results showed that air inflows through the flange joints of the degassing gas pipeline links increase in the direction of the gas mixture flow, while the methane concentration, on the contrary, decreases. In this case, the increase in air inflows is due to an increase in vacuum in the degassing gas pipeline, while the decrease in methane concentration is due to an increase in the volume flow of the gas mixture. Based on the analysis of the methane concentration character of change along the length of the horizontal section of the degassing gas pipeline, the distance from the beginning of the pipeline where the methane concentration value becomes below the permissible value and the probability of ignition of the gas mixture arises. It has been established that methane concentration varies insignificantly along the length of the gas pipeline at normative airflows. Scientific novelty. A formula is derived for determining the size of the gap between the flat rubber gasket and a shoulder of a flange connection of the degassing gas line links, at which the total air inflows in the gas line coincide with the standard value. Practical significance. The determination of the size flange joint clearance of the degassing gas pipeline links makes it possible to calculate the air inflows and assess the tightness of the gas pipeline flange joints on the basis of measurements of the gas mixture volume flow rate, methane concentration and the depression value.

Soldered joints of piezoelectric products

The paper considers issues related to the use of capillary luminescent flaw detection for monitoring glass-metal soldered joints of piezoelectric products. Standard methods of leakproofness testing of piezoelectric products are analysed; the framework for the applicability of each of them at the stages of the life cycle of piezoelectric products is established. Based on the results of the studies, a capillary luminescent control method was chosen to check the tightness of glass-metal soldered joints in piezoelectric products. The stages of conducting a capillary luminescent method for monitoring glass-metal soldered joints of piezoelectric products are presented. A method for monitoring the tightness of piezoelectric products using the capillary luminescent method has been developed.

METHODOLOGY OF CHOOSING PARAMETERS FOR DIAGNOSING ELEMENTS OF URBAN ELECTRIC VEHICLES

The operation of various vehicles in the field of urban electric transport is accompanied by high costs to maintain their working condition throughout the service life. Preservation of serviceability of vehicles is provided by performance of planned and preventive works on maintenance (MOT) and repair, and also the unscheduled repairs which are carried out for elimination of failures which arise in the interprophylactic periods, and malfunctions. As already noted, in the planned preventive maintenance and repair system, the vehicle after a certain mileage (time) is forcibly subjected to preventive actions in the prescribed amount. At the same time, despite the adjustment of maintenance and repair modes depending on a number of factors, there is no individual approach to each rolling stock. However, there is a need for such an approach, because even when rolling stock under the same conditions, the technical condition of each of them at the same time due to a number of reasons (individual characteristics of rolling stock, driving quality, maintenance, etc.) can differ significantly. Not every rolling stock requires all the operations provided by the "hard" volume of a particular type of maintenance. Execution of these "unnecessary" operations leads, on the one hand, to incomplete realization of individual properties of a rolling stock, increase in expenses for MOT, on the other, at all does not promote improvement of its technical condition. On the contrary, more frequent interventions in the work of joints of units and mechanisms contribute to increased wear of bonded surfaces, the appearance of damage to joints, violation of the tightness of joints. Significant losses of labor and material resources are also associated with a large amount of repair work due to late detection of failures. The fullest use of individual capabilities of rolling stock and ensuring on this basis the high efficiency of rolling stock during operation can be done through the widespread introduction into the technological process of maintenance and repair of diagnosing the technical condition of rolling stock. To increase the efficiency of the vehicle, use, methods and diagnostic tools have been developed, which are used both during maintenance and repairs, and as an independent technological process. Diagnosis allows to increase the coefficient of readiness and probability of trouble-free operation of vehicles, to reduce the complexity and cost of operation, to increase the maintainability and controllability of vehicles.

Apparatus for testing He leakage through flange gaskets at elevated pressure and temperature

The study focuses on the measurement of He leakage from the cooling circuits of the helium-cooled GFR (gas-cooled fast reactor). It is necessary to measure two phenomena, namely losses of He from the pipeline circuit through flange joints and the contamination of helium inside the pipeline by the diffusion of permanent gases from the external environment (i.e. against the pressure gradient). Methods for determining the tightness of flange joints according to current standards are not fully suitable for these purposes. For this reason, a self-designed apparatus was constructed in order to measure both effects at pressures up to 20 MPa and temperatures within the range from ambient values up to 400 °C. Gas chromatography with a PDHID detector was used to determine the rate of diffusion of nitrogen and other permanent gases through the flange into pure He. On the other hand, the He leakage through the piping flange joint into the external environment was measured using a gas chromatograph with a high sensitivity TCD. The issues of heat distribution within the high-pressure measuring vessel are discussed as well.

Soldered Joints of Piezoelectric Products

The paper considers issues related to the use of capillary luminescent flaw detection for monitoring glass-metal soldered joints of piezoelectric products. Standard methods of leakproofness testing of piezoelectric products are analysed; the framework for the applicability of each of them at the stages of the life cycle of piezoelectric productsis established. Based on the results of the studies, a capillary luminescent control method was chosen to check the tightness of glass-metal soldered joints in piezoelectric products. The stages of conducting a capillary luminescent method for monitoring glass-metal soldered joints of piezoelectric products are presented. A method for monitoring the tightness of piezoelectric products using the capillary luminescent method has been developed.

The sealing of fixed joints

The article is devoted to the study of the seals of fixed joints. The mechanisms of leakage occurrence at different values of roughness and pressure on the joint surfaces are considered taking into account the real contact area. The estimation of deformations and forces in the contact zone was carried out taking into account the profile of surfaces, limit deviations of shape and location of surfaces, as well as physical and mechanical properties of materials of the sealed joint. The obtained theoretical dependence allows to evaluate the tightness of the fixed connection depending on the main parameters of the seal roughness, manufacturing errors and the location of the interfaces, their physical and mechanical properties and characteristics of sealed liquid, including differential pressure and the nominal pressure in the joint. A new law of probability density distribution is proposed, which more adequately describes the considered boundary conditions of the experiment. Relations for the probabilistic evaluation of the contact area and surface deformations taking into account the characteristics of the material are obtained. Simple engineering relations for the estimation of probability of contact of the projections and offset surfaces for the two profiles are obtained. The simulation of the process of leakage depending on these conditions is carried out. It is shown that the complete tightness of rigid joints is insufficient even with low roughness provided by the finishing methods of processing and in the absence of deviations in the shape of the joint surfaces. The comparison of experimental data with the obtained theoretical results showed that the proposed engineering dependences provide a good match with the experimental data.

The measurement of helium leakages through flange gaskets for gas-cooled fast reactors

The study deals with the development of a method that would reliably determine the tightness of flange joints of the helium circuit of a gas-cooled fast reactor (GFR). The proposed procedure and equipment enable the parallel measurement of the helium leakage from a high-pressure cell and He contamination in the cell by the diffusion of gases from the ambient atmosphere against the pressure gradient. The self-designed apparatus is constructed for the performance of long-term tests of both parameters (i.e. both He leakage and its contamination) at a temperature of 400 °C and a pressure of 20 MPa. Nevertheless, the construction limits of the device at which the measurement can be safely carried out are 450 °C/35 MPa. The permanent gases diffusing into helium through the gasket were analyzed by a gas chromatograph with a PDHID detector, whereas the He leakage was determined using a high-sensitivity TCD. The article presents continuous results of tests carried out at ambient temperature. The procedures for data measurement and evaluation are demonstrated on one selected type of gasket with the inner diameter of 44 mm, the outer diameter of 79 mm and the thickness of 14.2 mm.

High precision multi-spindle wrench for automated sealing of joints during assembly of products operating at high pressures

Based on the theoretical and experimental analysis of achievable accuracy and stability of main forces of automated tightening of threaded joints, a multi-spindle nut has been developed, which ensures tightness of joints of articles operating at high pressures.

Tightness of flange joints: A case study

One of the negative technological factors that often have a significant impact on the environment is the leakage of operating media (so-called fugitive emissions), which most often occurs at different separable joints. Therefore, high demands are placed on the joints – they must have sufficient strength to maintain pressure and other loads and also be tight enough to avoid undesired leaks. For a large part of such joints, standard flanges or flanges designed according to standards are used, in the European Union in particular according to EN 1092-1, EN 1591-1 and EN 13445-3. Although the strength of such flanges is sufficient for most applications, the basic design methods do not cover the tightness of flange joints and their emissions completely. A case inspired by industrial practice with a history of insufficient tightness resulting in leaks is investigated using FEA and EN 1591. The flange joint is modelled in software ANSYS 2019 R2 with parts of adjacent shells to take their effect into account. The goal of the analyses is estimation of gasket contact pressures resulting from load history. The pressures are directly related to the seal tightness. Lastly, effect of shell shape modification on the gasket pressures is also investigated and the results are compared with those from the original configuration. Effects of resulting pressures on seal tightness are discussed.