Joint Sealants Research Articles

Microstructural Aspects on Brazing Stainless Steels for High Temperature Applications

A wide range of applications request components that work in an environment where they are subject to high temperatures, combined with a corrosive action of the same environment. The components with a complex geometry can be obtained only using some assembling processes, among which are welding and brazing. One of the most important advantages of these processes is the possibility to obtain a sealed joint, that guarantees it to be waterproof. In comparison with welding process, brazing process has also an important technological advantage: it is a process that is able to produce a quality joint in a very small, narrow and tight places., where is very difficult or almost impossible to reach with other welding processes (e.g. GMAW/MIG – Gas Metal Arc Welding, GTAW/TIG – Gas Tungsten Arc Welding, SMAW – Shield Metal Arc Welding, FCAW - Flux Cored Arc Welding, SAW – Submerged Arc Welding). The research in this direction carried out in University Politehnica Timisoara, was focused on using brazing as a joining process to obtain a complex geometry part working in these environments. The brazed joint will create a dissimilar joint, putting in contact stainless steel with a Ag-Cu brazing alloy, which creates diffusion processes at microstructural level as well as phase transformations (due to thermal cycle and diffusion) which have a large impact on operating behavior of these joints. This paper presents some results on investigation phase and microstructural constituents transformations that took place in these brazed joints.

Fire resistance of linear joint seals depending on the joint width and the type of mineral wool used

Fire resistance of linear joint seals depending on the joint width and the type of mineral wool used

The influence of the conditions of applying sealing polymer materials on the deformation resistance of the sealanter to sclofibro concrete

The article deals with the features of the treatment of solid surfaces with a primer before using sealing materials. The adhesive strength of the sealant to the area of adhesion is the basis for sealing the joints. Lack of adhesion leads to the ingress of water, dirt, precipitation and other climatic effects, which eventually lead to the destruction of the seams. Therefore, it is extremely important to observe the seam treatment technology before applying the sealant. Proper treatment of seams with a primer, observing the time of application to the base, before using sealing materials will increase the durability and service lifespan of the sealed joint. To improve the adhesive strength between the adhesive and the substrate, as a rule, the hard surface (substrate) is pre-treated with a primer based on polyurethane foam or epoxy resins. These primers are used because when exposed to a hard surface, a polymer matrix is formed, which, upon further contact with the sealant, increases the adhesion strength in the contact zone. In surface defect zones with moisture content, a new surface layer is also formed due to the participation of polymer groups in forming intramolecular hydrogen bonds. The formation of a polymer layer on a solid surface containing defective zones requires a certain time. Tests were carried out to determine the resistance to deformations of a combination of sealant/primer sealing materials in combination with glass fiber reinforced concrete samples and to establish the influence of the conditions for applying a primer/sealant to the surface of a glass fiber reinforced concrete composition on resistance to a series of character cycles of equal loads and temperature changes, with a deformation of the sealing material of 25% . It has been established that the time of treatment of a solid surface with a primer should be at least 5 minutes. If this condition is not observed when sealing materials are applied to glass fiber reinforced concrete, it may cause the sealant to separate from the base.

Fuzzy Rule Based System of Optimal Pavement Maintenance and Rehabilitation Strategies for Yangon-Mandalay Expressway

Purpose: Systematic pavement management plays a vital role in the better Road Asset Management system. The lifespan of pavement can be preserved and prolonged by adequate maintenance measures in proper time. By early detection and repair of defects at initial stages with predictive maintenance reduces the rapid deterioration of the pavement. Moreover, inaccuracy in pavement deterioration prediction leads to an improper maintenance with wastage of time, cost and labor strength. To overcome all of these obstacles, this paper attempts an approach on optimal pavement maintenance strategy by means of fuzzy rule-based system. Materials and Methods: In this research, four pavement indicators of PCI, IRI, PSR and PSI have been taken into account as antecedents and five different types of pavement maintenance as consequents. In this research, ASTM D-6433, Road Lab Pro software, AASHTO guidelines and Fuzzy Logic (Mamdani) model have been used to evaluate the current pavement condition and optimal pavement maintenance strategies. Findings: According to research area, 130 total pavement sample units were undertaken to study for the mean pavement condition of PCI value 54.93 (poor), IRI 7.01 (fair), PSR 3.33 (fair) and PSI 3.35 (fair). Due to 13 years-old life span of traffic volume, temperature and other external factors, this expressway is suffering from potholes, bleeding, longitudinal and transverse cracking, weathering, joint reflection cracking for Asphalt Concrete (AC) overlay and linear cracking, joint seal failure, scaling, faulting, depression, lane/shoulder drop off for existing concrete pavement. According to the fuzzy logic model results, 42 numbers of fuzzy If-Then maintenance rules were verified as the most relevant pavement maintenance and rehabilitation strategies for Yangon-Mandalay Expressway. Implications to Theory, Practice and Policy: This research provide implications to the study and contributions to theory, practice and policy. This research paper insights into effective infrastructure maintenance and investment, emphasizing the role of advanced computational techniques in transportation economics. The key advantage of this research paper is to be effective, supportive, easy and accessible decision-making tool for transportation and pavement engineers, expressway planners and highways department authorities especially from developing countries.

Stress Distribution along the Structural Sealant Joint Length of a Cylindrically Curved Glazing Panel

It has been identified that current standardised method for structural sealant joint dimensioning is applicable to flat rectangular panels only and no provisions are made for panels with curved surfaces. The purpose of this study is to investigate the stress distribution along the sealant joint of a cylindrically curved glass panel subjected to wind pressure and to establish if the panel curvature influences the stress distribution along the joint length. Using numerical method, several curved units were analysed and the results have shown that the out of plane wind action generate compression and shear forces within the joint, both occurring at the same time. This means that in the case of a structurally bonded curved panel, additionally to the shear caused by differential thermal expansion of elements or glass self-wight which is covered by ETAG 002 and EN 13022 the designer must also consider the shear stress induced due to the panel curvature. The magnitude and location of this additional shear stress and also of the tension/compression stress can be identified using Finite Element Analysis.

Enabling efficient regional seismic fragility assessment of multi‐component bridge portfolios through Gaussian process regression and active learning

AbstractRegional seismic fragility assessment of bridge portfolios must address the embedded uncertainties and variations stemming from both the earthquake hazard and bridge attributes (e.g., geometry, material, design detail). To achieve bridge‐specific fragility assessment, multivariate probabilistic seismic demand models (PSDM) have recently been developed that use both the ground motion intensity measure and bridge parameters as inputs. However, explicitly utilizing bridge parameters as inputs requires numerous nonlinear response history analyses (NRHAs). In this situation, the associated computational cost increases exponentially for high‐fidelity bridge models with complex component connectivity and sophisticated material constitutive laws. Moreover, it remains unclear how many analyses are sufficient for the response data and the resulting demand model to cover the entire solution space without overfitting. To deal with these issues, this study integrates Gaussian process regression (GPR) and active learning (AL) into a multistep workflow to achieve efficient regional seismic fragility assessment of bridge portfolios. The GPR relaxes the probability distribution assumptions made in typical cloud analysis‐based PSDMs to enable heteroskedastic nonparametric seismic demand modeling. The AL leverages the varying standard deviation to select the least but most representative bridge‐model‐ground‐motion sample pairs to conduct NRHA with much‐improved efficiency. Both independent and correlated multi‐output GPRs are proposed to deal with bridge portfolios with seismic demand correlations among multiple components (column, bearing, shear key, abutment, unseating, and joint seal). Considering a single benchmark highway bridge class in California as the case study, the AL‐GPR framework and the associated component‐level fragility results are investigated in terms of their efficiency, accuracy, and robustness. The fragility results show that 70 AL‐selected samples would enable the GPR to derive bridge‐specific fragility models comparable to the ones using the multiple stripes analysis approach with 1950 ground motions considered for each individual bridge. The AL‐GPR model also successfully captures the physics of how bridge span length, deck area, column slenderness, and steel reinforcement ratio would change the damage state exceedance probabilities of different bridge components. The efficiency of AL stems from the fact that, with the multi‐output independent GPR, a stable and reliable fragility model can be achieved using 50 AL‐selected samples compared to at least 270 randomly chosen samples. The proposed methodology advances the state of the art in enabling more efficient and reliable regional seismic fragility assessment of multi‐component bridge portfolios.

Influence of Materials of Moulds and Geometry of Specimens on Mechanical Properties of Grouts Based on Ultrafine Hydraulic Binder.

Ultrafine hydraulic binder grout injection is a technique utilised for repairing masonry, either to connect sections, seal joints, or fill voids due to its great capacity for penetration and higher mechanical strength than lime grout. In this research, the mechanical properties of ultrafine hydraulic cement grout are analysed considering the influence of the mould material for preparing the specimens and their geometry characteristics in the context of the specifications set out in several international standards. The test campaign to ascertain compressive and flexural strength in different circumstances is supplemented with a physical and chemical characterisation of both binder and fresh and hardened grout. Significant differences in mechanical properties between specimens prepared with absorbent or non-absorbent-water material are found due to the influence of drying shrinkage and decanting binder during the curing process. Furthermore, the slenderness of specimens is presented as an important factor in determining the compressive strength of mixtures.

Impact of coating and curing temperature on the formation of CFRP/sealant gradient interphase

Flexible sealant joints are extensively utilized for sealing aircraft wing fuel tanks due to the excellent stress transfer release of gradient interphase. This study investigates the impact of coating and curing temperature on the formation of CFRP/sealant gradient interphase. The interphase quality was identified using SEM equipped with EDS, and a detailed analysis of element concentration transition was performed to understand the interplay between different mechanisms. Contact angle calculation and FTIR-XPS combined spectral analysis were conducted to determine the interfacial physicochemical state. The results showed that coating enhances compatibility and broadens interphase, whereas opposite results were observed at higher temperatures. The improvement of surface energy and wettability, chemical groups, and molecular bonding sites provided by coating promotes interfacial reactivity and molecular mobility. Elevated cure temperature accelerates the formation of cross-linked networks that restricts sealant chain mobility, indicating that vulcanization dominates over diffusion under high cure temperature.

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

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

Reactivation of variably sealed joints and permeability enhancement in geothermal reservoir rocks.

The online version contains supplementary material available at 10.1186/s40517-023-00271-5.

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.

Characterization of Hot-Applied Joint Sealants and Their Components in Terms of Their Chemical Composition and Basic Performance Properties.

Hot- and cold-applied joint sealants are materials commonly used for the surface repairs of the upper layers of asphalt or concrete road surfaces. Our investigations covered six hot-applied joint sealants, classified as the high-extension type N1 (elastic) or low-extension type N2 (normal), in accordance with the standard EN 14188-1; the sealants were obtained commercially from four European manufacturers. The present paper focuses on the characterization of the consistency of the joint sealants, the bituminous binders that contain them, and the characterization of their insoluble components. Additional testing methods included an FTIR analysis of the sealants and the extracted binders, as well as SEM, EDS, and sieving analyses of the insoluble material. Joint sealants are complex formulations and include a broad range of base asphalt binders and other components. Their compositions may vary widely, while still fulfilling the performance specifications. Through the extraction of the solvents and the separation of the crack sealants, it was found that radically different compositions of crack sealants resulted in the comparatively similar performance of the tested material. The EDS and FTIR analysis methods provided insights into the composition of the crack sealants and the types of mineral materials used.

Leak tightness tests of mechanical seal joints for HL-2M tokamak under thermal cycle loads

The mechanical seal joints used in HL-2M tokamak mainly include vacuum coupling radius seals (VCRs) and conflat flanges (CF), which are usually employed as a part of the cooling flow channels of the advanced divertor. Some of the joints which are located in the vacuum vessel would be used together with the cooling pipes (CPs) as the vacuum boundary structure. Their sealing performance must be extremely reliable, otherwise leak may occur, thus affecting the safe operation of the tokamak machine. One of the worst conditions is that the joints are baked from room temperature (RT) to 350 °C, which is kept for a long time, then cooled to RT again. In addition, they will go through many cycles of baking during the lifetime of the tokamak. Therefore, it is essential to carry out the baking tests of the mechanical seal joints for the leak tightness performance under thermal cycle loads. The experimental results show that the sealing performance of VCRs is still good after 28 thermal cycles, while for CF25, its airtightness will gradually fail after more than 20 thermal cycles, so it should be used within limited times during its lifetime.

Investigation of the suitability of adhesive tapes for sealing building structures of various surfaces

Adhesive sealing tapes play an important role in ensuring the air tightness of the building, affecting the indoor microclimate and efficient energy use. However, there is still a lack of objective indicators that would demonstrate the ability of the sealing tape to ensure the long-term air tightness of the sealing joints of various building structures. Therefore, the purpose of this work is to investigate the indicators demonstrating the suitability of adhesive sealing tapes for sealing building structures of different surfaces and deformation, to provide detailed analyses of the results, and to propose practical recommendations. The investigated self-adhesive tapes differed in backing (nonwoven material, plastic reinforced film, paper, metal foil) and adhesives (acrylic and butyl). The materials of the sealed structural joints were plywood, OSB, plasterboard, cement sawdust board, plastered board, and plastic. The thickness, deformability, peel and shear adhesion of the self-adhesive tapes were used to determine its suitability for sealing of different structural joints. It was determined that tapes with higher deformability are more versatile, as they are suitable for sealing joints subjected to small and large deformations. The higher peel adhesion is typical for tapes of an air-permeable non-woven material backing and a thin adhesive layer. Tapes with a thicker adhesive layer are most suitable for sealing complex-shaped joints. Tapes with acrylic adhesive have a higher peeling force from smooth and moderately smooth surfaces, whereas butyl adhesive creates better contact with uneven surfaces in highly deformable joints.

Microstructure analysis of pressure resistance seal welding joint of zirconium alloy tube-plug structure

Pressure resistance welding is usually used to seal the connection between the cladding tube and the end plug made of zirconium alloy. The seal welded joint has a direct effect on the service performance of the fuel rod cladding structure. In this paper, the pressure resistance welded joints of zirconium alloy tube-plug structure were obtained by thermal-mechanical simulation experiments. The microstructure and microhardness of the joints were both analyzed. The effect of processing parameters on the microstructure was studied in detail. The results showed that there was no β-Zr phase observed in the joint, and no obvious element segregation. There were different types of Widmanstätten structure in the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ) of the cladding tube and the end plug joint because of the low cooling rate. Some part of the grains in the joint grew up due to overheating. Its size was about 2.8 times that of the base metal grains. Due to the high dislocation density and texture evolution, the microhardnesses of TMAZ and HAZ were both significantly higher than that of the base metal, and the microhardness of the TMAZ was the highest. With the increasing of welding temperature, the proportion of recrystallization in TMAZ decreased, which was caused by the increasing of strain rate and dislocation annihilation.

Semi-Analytical Methods for the Joint Strength and Sealing Performance in the Failure Process of the Subsea Pipeline Compression Connector

Radial seals are sensitive to axial overload failure and may cause leaks. This paper presents two semi-analytical methods for the joint strength and sealing performance of the subsea pipeline compression connector under axial overload failure. The method for the joint strength consists of two parts: One is the analytical model for the joint strength of the connection and seal under axial tension and compression conditions. The models are based on membrane theory, considering the hardening and bending effects. The other is a two-dimensional, axisymmetric finite element model for the joint strength of the radial metal seal. The semi-analytical method for the overload sealing performance is derived using a finite element model and the Reynolds equation of the laminar flow. The effects of critical parameters on the joint strength and the overload sealing performance are analyzed. The experiments are carried out with specimens and prototypes to evaluate the evolution of the sealing interface and the joint strength. The results show that both the internally turned sealing surface and the deflection of the pipe can improve the joint strength. In addition, the compression-type connector can remain sealed under the maximum axial overload. The proposed methods allow the prediction and identification of the overload joint strength and the sealing condition of the compression-type connector and provide a better understanding of the radial metal seal under the axial overload condition.

Analysis and determination of bolt tightening process factors for composite structures under multiple working conditions

When developing the tightening process for composite bolts, ensuring that the target preload( F) required by design is achieved is a key scientific issue in meeting the mechanical properties of the connected structure. Variations in complex process factors during tightening have a large effect on the tightening torque( T)-preload curve( F), and the mechanism by which the tightening process factor affects the target preload must be considered. Using experimental means, the significance and coupling effects of tightening speed, lubrication conditions, tightening areas, joint sealants and washers have been systematically investigated. The tightening torque( T), torque coefficient( K), preload( F) and the peak stress coefficients X( σ) and interlaminar stress coefficients Y( σ) within the composite laminate are used as the main response variables, and a mathematical model between each response variable and the process factor is established to analyse the effect of significant factors on the response variables from a quantitative perspective. Finally, with a certain size of preload( F) as the optimisation target, the optimisation analysis of the tightening speed is carried out for four working conditions with different sealing conditions and different tightening area, and the optimum tightening speed for each working condition is determined. Based on the above study, an analytical method was proposed to determine the reasonable interval of tightening process parameters in this paper.

High purity Al2O3 ceramic:Metallizing strategy, microstructure and sealing properties

ABSTRACT A high purity Al2O3 ceramic (HPAOC) metallizing strategy was developed via gradient coating process of metallizing pastes with different ratios of Mo to manganese glass (MnG) contents, to improve the wettability and reactivity of metallized layer (ML) to the ceramic substrate and the secondary metallizing layer or sealed metals. Self-made HPAOC samples firstly coated by a layer of metallizing paste with a lower proportion of Mo:MnG and superposed a layer of metallizing paste with a higher proportion of Mo:MnG were fired at 1450°C in hydrogen atmosphere. The crystal phase structure, microstructure and element distribution of the metallized samples wer characterized by XRD, SEM and EDS. The results of sealing properties show that the tensile sealing strength of as high as 121MPa and the He leakage rate of as low as 4.2 × 10−11 Pa.m3/s can be obtained of the sealed joints of the as-metallized HPAOC and Kovar.

Pre-Compressed Foam Sealing Tapes to Seal Joints between Building Envelope Components Watertight: An Experimental Assessment

Currently there is gaining interest in pre-compressed foam sealing tapes to seal joints watertight between different building envelope components. Little to no information is available on the parameters affecting the resistance of these foam tapes to driving rain. On the other hand, several research studies have shown that water leakages can be expected at relatively low-pressure differences and that drainage should be provided. Therefore, a study was designed to on the one hand assess the material and installation parameters that affect the watertightness of pre-compressed polyurethane foam sealing tapes impregnated with an acrylic polymer dispersion and on the other hand evaluate the potential of providing drainage possibilities, either as a two-barrier system or by means of integrated drainage cavities. It was found that the joint width, the presence of an airtight coating, and the position of the tape relative to the exterior surface affected the watertightness of the sealed joints. Notably, 87% of the evaluated foam tapes applied as a single barrier showed water leakages at pressure differences of 600 Pa or lower. Foam tapes with integrated drainage cavities, on the other hand, resulted in watertight joints up to an average pressure difference of 825 Pa.

Seismic performance analysis of shallow-buried large-scale three-box-section segment-connected pipeline structure under multiple actions

To ensure the safety operation of inter-basin water transfer project, it is important to understand the seismic performance of shallow-buried large-scale segment-connected pipeline structure under earthquake and other multiple actions. In this paper, a 3D FE model is built in details for the seismic assessment of large-scale prestressed concrete inverted-siphon shallow-buried under riverbed, and a method is proposed to realize multiple interactions of the viscoelastic boundary elements to finite elements, the compressible fluid to structure and the sealed joints made of rubber belt between adjacent segments. The inverted-siphon is longitudinally composited by 58 segments in total length of 858.64 m, and transversally consisits of three rectanguler-section boxes with net dimension of each box of 6.5 m width and 6.6 m height. The main influencing factors are set as the thickness of overburden soil, the flow condition and the engineering geological condition. The time-history analysis is carried out on the 3D FE model under Elcentro seismic wave excitation. The numerical analyses figures out the main vibration modes and vibrational frequency of this inverted-siphon, reveals the regions of peak tensile stress appeared on the concrete surface and the risk sealed joints with extremum relative displacement. This provides a scientific reference to take specific prevention measures of anti-earthquake, based on a deep understanding to the seismic cracking of concrete and the tearing broken of sealed joints for this kind of segment-connected pipeline structure.