Search

Compressive stress in glass‐to‐metal seals is crucial to ensure sealing quality and service reliability. Photoluminescence spectroscopy (PS), which relies on the piezospectroscopic effect of Cr‐doped α‐Al2O3, shows promise for stress detection owing to its rapid detection, non‐destruction, and high resolution. The premise of the PS technique is to fill a glass matrix with alumina particles and detect signals from the alumina. In this study, the interaction between alumina particles and the glass matrix was analyzed to calibrate the measured stresses and investigate the stress state in the glass. Test results for glass‐to‐metal seals are believed to consist of simultaneous internal residual stress and external applied stress. The internal residual stress is formed due to the coefficient of thermal expansion mismatch between glass and alumina and is assumed to transfer by radial compression. In the experiment, it was detected by the PS technique and verified by X‐ray diffraction using an unstressed sample without metal housing. The external applied stress is formed due to metal housing compaction and possibly transferred by the shear effect. The stress distribution within the pre‐stressed sample containing metal housing was also measured by the PS technique. Then, calibrations were conducted on the measured stresses based on the deduced stress transfer relationships. Finally, finite element models were established to simulate the internal residual stress and external applied stress respectively to prove the validity of the calibration method, and mutually anastomotic results were obtained within the target margin of error. [ABSTRACT FROM AUTHOR]

To meet the requirements of alumina ceramics in delicate electronics, there is an urgent need for a low-temperature bonding technology that can realize a good combination of alumina and metal. In this work, alumina ceramics and nickel metals were successfully connected at a low temperature (25–150 °C) by Al-Ni self-propagating nanofoil as a heat source. The interface microstructure and element distributions of the solder joints from cross-section and fracture surface were investigated. In addition, the solder joint formation process was simulated by finite element analysis and molecular dynamics. These results showed that their shear strengths could be continuously improved with the growing temperature, which were 17.4 MPa (room temperature, 25 °C), 19.5 MPa (50 °C), 22.9 MPa (100 °C) and 25.69 MPa (150 °C). The Al 2 O 3 /Al-Ni nanofoil/Ni solder joints were prone to crack at the corner and boundary at Al 2 O 3 /solder interfaces due to the stress concentration. Moreover, the increase in ambient temperature not only raises the melting time and transient temperature during the self-propagating reaction, but also improves the interdiffusion of Ni and Sn atoms at the Ni/Sn interfaces. [ABSTRACT FROM AUTHOR]

Bonding technology is used as the main connection mode of coated structures of car interior trim, of which the process and structure are being continuously optimized. In this paper, ABAQUS software is applied to establish the finite element model of the bonded structure of the dash panel. Based on the cohesive zone model (CZM) method, the damage and failure process of surface joints under different displacement loading conditions are numerically simulated. The effectiveness of the finite element model based on CZM for the numerical simulation of the damage and failure processes of bonded surface joints is verified from the perspectives of the numerical calculation method, experimental verification, and numerical result analysis. The results show that the finite element model based on CZM theory can effectively simulate and evaluate the damage and failure processes of multiphase polymers or composite surface joints. By obtaining the load‒displacement curves, the stress nephogram and the damage nephogram, the dynamic processes of damage initiation, damage evolution and failure of the surface joint are observed and analysed, and the bonding strength of the interlayer model is also compared and analysed. Compared with the bonding interface between the skin and cloth, the bonding interface between the frame and cloth is less prone to damage. [ABSTRACT FROM AUTHOR]

Top seal failure of ram blowout preventer (BOP) is one of the main factors leading to well control risk. The constitutive model and parameters of nitrile butadiene rubber (NBR) were optimized by compression and tensile tests, and the failure analysis model of the contact seal of the ram BOP top seal was built. The nonlinear contact mechanical behavior of the connection part of the BOP top seal was analyzed by the finite element method. Then, the influence of corrosion and wear defects at the top seal position of the 2FZ35-70 BOP under rated working pressure on the contact seal were studied, and the results showed that the overall contact pressure distribution of the top seal corrosion defects was uniform, the local contact pressure of the corrosion pit edge increased, and the top contact pressure decreased. The overall contact pressure of the wear defect of the top seal decreased linearly, the contact pressure at the maximum depth of the wear defect was the smallest, and the contact pressure gradually decreased to both sides. Ultimately, to guarantee the safety and reliability of the ram BOP, it is suggested that the acceptable depths of the seal corrosion pit and the wear at the top of the ram BOP are 4.0 mm and 0.2 mm, respectively, thus the reliability evaluation problem of the quantitative seal of the ram BOP top seal is solved. [ABSTRACT FROM AUTHOR]

Aiming to accurately predict the leakage rate of the sealing interface, this work proposes a two-dimensional finite element model of a proton exchange membrane fuel cell, which includes the microscopic surface morphology and the asperity contact process of the components. First of all, we constructed the surface morphology of the seal by the two-dimensional W-M (Weierstrass–Mandelbrot) fractal function and explored the influence of fractal dimension (D) and scale parameter (G) on the surface profile. Furthermore, the finite element method and Poiseuille fluid theory were adopted to obtain the deformation variables of the asperity under different clamping pressures and leakage rates. Moreover, we quantitatively analyzed the impact of surface roughness on the clamping pressure and leakage rate. It was found that both the surface amplitude and surface roughness are positively correlated with G and negatively correlated with D. Surface morphology is proportional to D but has no relationship with G. Additionally, the deformation asperity decreases exponentially with growing clamping pressure, and the leakage rate is consistent with the experimental values at a clamping pressure of 0.54 MPa. With the same leakage rate, when the seal surface roughness value is less than 1 μm, a doubled roughness value leads to an increase of 31% in the clamping pressure. In contrast, when the surface roughness of the seal is greater than 1 μm, a doubled roughness value induces an increase of 50% in the corresponding clamping pressure. [ABSTRACT FROM AUTHOR]

This paper presents a new type of three-axis gyroscope. The gyroscope comprises two independent parts, which are nested to further reduce the structure volume. The capacitive drive was adopted. The motion equation, capacitance design, and spring design of a three-axis gyroscope were introduced, and the corresponding formulas were derived. Furthermore, the X/Y driving frequency of the gyroscope was 5954.8 Hz, the Y-axis detection frequency was 5774.5 Hz, and the X-axis detection frequency was 6030.5 Hz, as determined by the finite element simulation method. The Z-axis driving frequency was 10,728 Hz, and the Z-axis sensing frequency was 10,725 Hz. The MEMS gyroscope's Z-axis driving mode and the sensing mode's frequency were slightly mismatched, so the gyroscope demonstrated a larger bandwidth and higher Z-axis mechanical sensitivity. In addition, the structure also has good Z-axis impact resistance. The transient impact simulation of the gyroscope structure showed that the maximum stress of the sensitive structure under the impact of 10,000 g@5 ms was 300.18 Mpa. The gyroscope was produced by etching silicon wafers in DRIE mode to obtain a high aspect ratio structure, tightly connected to the glass substrate by silicon/glass anode bonding technology. [ABSTRACT FROM AUTHOR]

Accelerating the polymerisation of adhesives has been a long-established field of research in context of adhesive bonding technology as long curing times – sometimes up to days – represent a decisive disadvantage in contrast to most mechanical joining techniques like riveting or screwing. In addition to, e.g., curing via UV, microwave or IR radiation, electromagnetic induction represents a promising solution for speeding up the cure of polymers. With this method, adhesively bonded components are subjected to an alternating electromagnetic field (EMF) that induces heat in EMF-sensitive materials, e.g., steel or aluminium. If intrinsic EMF-sensitivity of the materials to be bonded is not given, different types of susceptors like meshes, fibres or particles are added to the adhesive in order to be heated inductively and thus cure the adhesive from the inside. Recent research has focused on a special type of susceptors, so-called Curie particles (CP), which can only be heated inductively up to their specific Curie temperature (Tc) at which CP-induced heating automatically stops. As a result, a curing process is created that eliminates the need for external temperature monitoring while simultaneously preventing overheating of the bond. As underlying curing kinetics – most importantly polymerisation enthalpy and curing time – significantly differ depending on the considered adhesive, induction times needed to achieve full cure must currently be determined through costly preliminary investigations on an experimental level. Thus, to contribute for a more efficient and controllable bonding process, the present study aimed at developing a numerical model based on the Finite Element Method (FEM) and capable of predicting the curing degree α in dependency of curing temperature profiles TCure(t) and the CP content ccp. For this purpose, the curing kinetics of two fundamentally different 2K epoxy adhesives were linked to a transient heat flow simulation based upon experimentally determined heat loads. The validation of the developed FEA technique was successfully carried out using the example application of inductively cured large-scale Glued-in rod (GiR) specimens, whereby experimentally determined temperature profiles showed excellent agreement with the numerical predictions. The present paper focused on presenting preliminary experimental work as well as all analytical methods implemented for the numerical modelling. [ABSTRACT FROM AUTHOR]

Based on a bistable mechanism, a novel low- ${g}$ MEMS inertial switch with dual functions of self-locking and reverse-unlocking is presented, along with its fabrication and verification. This MEMS switch is fabricated on a Silicon-On-Insulator (SOI) wafer by using deep reactive ion etching (DRIE), Bosch processing, and wafer bonding technologies. A two-level system is proposed to realize dual functions of this switch, which mainly consists of a spring-mass-damping system as the first level and a bistable structure as the second level. According to the finite element analysis (FEA), the theoretical formula of the bistable structure has been successfully verified to deduce the static mechanical properties. Under positive and negative acceleration excitations, the dynamic response characteristics of the switch has been systematically simulated further. Furthermore, this inertial switch has been tested by using a centrifugal acceleration turntable, and its self-locking threshold and reverse unlocking threshold are 8 ${g}$ and 105 ${g}$ , respectively. Finally, the contact resistance of this MEMS switch is measured about $0.75~\Omega $ by a probe station. [2020-0302] [ABSTRACT FROM AUTHOR]

A study on temperature dependence in gold-gold (Au–Au) thermocompression bonding was performed. Gold studs were bonded to two kinds of surfaces—cofired gold on alumina and electroless nickel covered with immersion Au on silicon. A critical bonding temperature was observed for both substrates. No bonding occurs when the temperature is below this threshold value, whereas bond strength increases with bonding temperature beyond the threshold. This critical temperature can be related to the activation of organic films on the bonding surfaces. Under similar bonding conditions, the critical temperature is lower for a harder substrate than for a softer substrate, primarily because of larger interfacial shear stresses. This is supported by the observation on the interfacial shear stress distribution at the bonding interface based on finite element simulation models of substrates with different hardness. [ABSTRACT FROM AUTHOR]

Abstract A concept for using snap-fit connectors in sandwich pipes is investigated numerically in two companion papers using a combination of 2D axisymmetric and 3D finite element models in Abaqus. In the Part 1 paper, results of key parametric studies related to the installation of sandwich pipes in deepwater are reported. The modification of the nib groove to include variable radii, the use of an elastomeric seal coupled with compressive pre-stress and an optimum resin-to-core ratio all proved to enhance the performance of the sandwich pipe snap-fit connectors. The influence of the interlayer adhesion configuration on the stress concentration experienced in the connector is also studied. Furthermore, a comparative study is performed to investigate the mechanical behaviour of the snap-fit connector concept in sandwich pipes and conventional pipe-in-pipe. In the Part 2 paper, an optimisation study is carried out for the stress relief groove (SRG) in the pin of the snap-fit connector. A combined parameter is proposed to capture the relationship between the investigated geometric properties and the stress concentration factor at the SRG. It is established that the fillet radius could indeed be used to offset the drop in performance associated with increasing the SRG depth while improving the fatigue characteristics of the connector threads. Highlights • A snap-fit connector between sandwich pipes is analysed under installation loads. • A series of FE models is used to identify stress concentration regions. • Performance-enhancing modifications of the nib groove are suggested. • Comparative analysis of sandwich pipe and pipe-in-pipe is performed. • Key areas in which sandwich pipe outperforms pipe-in-pipe are established. [ABSTRACT FROM AUTHOR]

Abstract With the increase of ultra-deep and extended reach wells, the premium threaded connections (PTCs) of tubing and casing have to withstand extremely high level of combined loads, and often occurs sealing failure under complex loads. In order to solve this problem, the sealing mechanism of PTCs should be analyzed in depth. The existing analytical method can provide the contact stress formula for PTCs, but the extremely nonlinear mechanics of thread interactions under complex load states cannot be captured due to the stringent assumptions. In this article, a nonlinear 3D elastic-plastic finite element model for 7″casing buttress PTCs with the helix angle is established to analyze the stress distribution characteristics on the sealing surface, shoulder and thread. The results show that the preload has important influence on the sealing characteristics of the PTCs, and the sealing performance of the joint depends on the contact stress on the thread, sealing surface and shoulder. The axial tensile load will increase the sealing performance on the thread and weaken the sealing performance on the shoulder and the sealing surface. When a bending moment is applied on the tool joint, the contact stress increases in the compressed side while decreases in the stretched side, and the contact stress and sealing band width of the sealing surface decline, which indicates that the complex loads greatly affect the sealing performance of the sealing surface. Especially, the sealing surface width and the stress obtained with the three-dimensional finite element model are more reasonable than the analytical method due to the consideration of the helix angle of thread and the elastic-plastic characteristics of the material. Highlights • The sealing mechanism of premium threaded connections (PTCs) under complex loads is analyzed by 3D finite element model. • In the 3D finite element model, the helical angle of thread and the elastic-plastic material are considered. • The characteristics of contact stress on the sealing surface, shoulder and thread of PTCs are revealed. • The difference between 3D elastic-plastic finite element method and the analytical method is discussed. [ABSTRACT FROM AUTHOR]

Sealing structures of high-pressure hydrogen storage vessel are always considered as one of the significant components. This paper aims to study the sealing performance of the combined sealing structure composed of a rubber D-ring and a wedge-ring used in high-pressure hydrogen storage vessel by elucidating the swelling mechanisms due to dissolved hydrogen. Comparisons of the sealing performance between the D-ring and the O-ring are made in terms of the effects of some important factors including the wedge-ring, hydrogen pressure and swelling. Three aspects of conclusions are obtained by FEA: (1) The wedge-ring with a wedge angle 45° is the most suitable, compared with the angles 30° and 60°, irrespective of the shape of rubber rings. (2) The peak contact stress for the D-ring seal is larger than that for the O-ring seal under hydrogen pressure range 0-100 MPa. (3) The O-ring seal could be replaced well by the D-ring seal, whereas the design height of the seal groove should be larger for the D-ring seal than for the O-ring seal due to swelling effect, in order to prevent the D-ring seal from extrusion through the upper side of the seal groove. [ABSTRACT FROM AUTHOR]

In order to meet the high cleanliness and high vacuum requirements of the working environment of the silicon conveyer robot, a new type of concentric biaxial stepped ferrofluid sealing structure is proposed based on the original universal ferrofluid sealing structure. The two dimensional simplified physical model of concentric biaxial stepped structure under axisymmetric condition is established by using the magnetic field finite element method. The nonlinear magnetic field distributions in the ferrofluid sealing structure are calculated and analyzed. The influences of the sealing gap, the width of the pole teeth, the ratio of the permanent magnet length to its height on the its sealing capabilities were studied. The calculation results were also analyzed and discussed. The results show that the pressure resistances of the concentric biaxial stepped ferrofluid seals significantly decrease with the increase of the sealing gap. Their pressure resistances firstly increased and then decreased with the increase of tooth width. The pressure resistance of the outer diverging stepped ferrofluid seal in the concentric biaxial stepped ferrofluid seal firstly increased and then decreased with the increase of the ratio of the permanent magnet length to its height; Their pressure resistances of inner converging stepped ferrofluid seal firstly decrease and then increase with the increase of the ratio of the permanent magnet length to its height. [ABSTRACT FROM AUTHOR]

A finite element method was presented to investigate local hot banding for sealing rings in a wet clutch. A discrete model of the sealing pair was established, and the critical speed of hot banding was obtained by numerical computation. The relationships between the critical speed and the frictional coefficient, elastic modulus, thermal conductivity, thermal expansion coefficient, and sealing ring size were determined. Experimental investigations were performed using a seal test rig, with comparisons of the calculated and experimental critical speed results made to enable an assessment of the proposed method's accuracy. The numerical and experimental results indicate the effectiveness of the finite element discrete model in simulating the hot banding of sealing rings. [ABSTRACT FROM AUTHOR]

Shield tail wire brushes (hereinafter referred to as ‘tail brush’) may need to be replaced because of excessive wear, which reduces the sealing function in long-distance tunnel projects. Surrounding soil should be strengthened to ensure construction safety when replacing the tail brush. In recent years, liquid nitrogen freezing technology has become popular due to its high efficiency. However, various schemes and different installation forms of freezing pipes have been developed, and studying them is imperative. With the tunnel project for Nanjing Metro Line 10 used as an example, three freezing schemes are numerically simulated using ADINA finite element software to establish 3D numerical models. The variation of the temperature field and the adaptability of the schemes are studied through an analysis of the calculated results in many aspects. [ABSTRACT FROM AUTHOR]

Tube hydroforming is a metal forming technology that uses internal pressure and the axial feeding force to fabricate products with complicated cross-sectional geometries. In this study, an advanced sealing system is proposed to prevent leakage during the hydroforming process. The advanced sealing system is composed of a die spring, cylindrical sleeve and punch with end fillet. The improved sealing effect originates from the increased contact because of the axial force of the punch and reaction force of the spring caused by the punch. When the proposed sealing system is used, the circumference of the tube end becomes more tightly sealed by the axial pressure between the punch and sleeve, and the axial pressure increases with increasing axial feeding. The effects of the advanced sealing system on the effectiveness of the contact between the tube end and punch were further analyzed with finite element method. The feasibility of the proposed sealing system is experimentally confirmed by hydroforming a non-axisymmetric complicated part. [ABSTRACT FROM AUTHOR]

Rubber O-ring seals have been extensively used in high-pressure hydrogen storage systems for preventing gas leakage. It is important for the design of rubber O-ring seals to clarify the sealing characteristics of the rubber O-ring under high-pressure gaseous hydrogen. In this paper, a finite element analysis model accounting for swelling due to dissolved hydrogen was developed to investigate the sealing performance of the combined seal structure constructed of a rubber O-ring and a wedge-ring under ultrahigh pressure gaseous hydrogen. The effects of wedge-ring, hydrogen pressure, and swelling on the sealing capacity of the combined seal were analyzed. Consequencely, it was found that the wedge-ring by itself can prevent the O-ring from extruding under ultrahigh pressure by filling up the clearance between the grooves, and the wedge-ring with the angle of 45°was the most suitable in comparison to those of 30°and 60°. The combined seal structure can enhance automatically the sealing capacity with increasing hydrogen pressure, and the increase of the peak contact stress was linearly proportional to that of the fluid pressure. In addition, the rising peak contact stress induced by swelling due to dissolved hydrogen could result in an improvement in sealing capacity, while the swelling may accelerate the mechanical damage of the O-ring owing to an increase in Mises stress. [ABSTRACT FROM AUTHOR]

This paper presents a finite element analysis approach to evaluate the flexural behavior of posttensioned two-way slabs depending on the tendon layout. A finite element model was established based on layered and degenerated shell elements. Nonlinearities of the materials are considered using the stress-strain relationships for concrete, reinforcing steel, and prestressing tendons. Flexural testing of the posttensioned two-way slabs was conducted to validate the developed analytical process. Comparing the analytical results with the experimental results in terms of deflections, it showed generally good agreements. Also a parametric study was performed to investigate the effects of different types of tendon layout. [ABSTRACT FROM AUTHOR]

The carbon fiber reinforced composite reentrant honeycomb structures with different gradient distributions of wall thickness were manufactured by mold hot pressing and bonding technology. The dynamic responses of composite gradient reentrant honeycomb structures under local impact load were investigated. The impact process and failure behavior of composite gradient reentrant honeycomb structures under local impact load were obtained through the foam aluminum projectile impact experiment. The influence of wall thickness gradient form on the impact resistance of composite reentrant honeycomb structure was analyzed. The results showed that the wall thickness gradient setting of the reentrant honeycomb structure could reduce the maximum transverse deformation of the rear panel, and improve the anti-impact ability of the structure compared with homogeneous reentrant honeycomb structure. In addition, compared with the positive gradient reentrant honeycomb structure, the negative reentrant honeycomb structure had better impact resistance, and the impact resistance advantage became more obvious with the increase of the impact strength. The finite element model of composite gradient reentrant honeycomb structure under local impact load was presented, and the dynamic responses and failure modes of the numerical simulation results were compared with that of the experimental results. • A novel composite reentrant honeycomb structure is designed and fabricated. • The anti-impact properties of composite reentrant honeycomb structure were explored and analyzed by experiment and finite element analysis. • The effect of wall thickness gradient form on the impact response was analyzed and revealed. • The failure mechanism of composite gradient reentrant honeycomb structure was analyzed and obtained. [ABSTRACT FROM AUTHOR]

In present study, the foam-filled composite double-arrow auxetic structures were obtained by the mold hot pressing method, bonding technology and stirring foaming process. The ballistic impact tests of the foam-filled composite double-arrow auxetic structure were carried out, and the effect of foam filling on the ballistic impact response of the composite double-arrow auxetic structure was analyzed. The ballistic impact test results indicated that the ballistic limit velocity of the foam-filled double-arrow auxetic structure with the relative density of 16.66% was 121.30 m/s. With the increase of the incident kinetic energy of the projectile, the specific energy absorption of the foam-filled auxetic structure increased first and then decreased, and remained near the horizontal line of 550 J/kg at last. Compared to unfilled auxetic structure, the ballistic limit velocity of foam-filled auxetic structure increased by 6.12% and the energy absorption property of foam-filled auxetic structure was improved. The ballistic impact performances of foam-filled composite double-arrow auxetic structures were studied by finite element method. The simulation results of foam-filled auxetic structure with RD=16.66% were in good agreement with the experimental results. The simulation results demonstrated that the ballistic limit velocities of foam-filled composite auxetic structures with relative densities of 9.08%, 16.66% and 23.06% were 86.74 m/s, 120.60 m/s and 152.80 m/s, respectively. Furthermore, the increase of relative density had a positive effect on improving the anti-penetration performance of foam-filled composite auxetic structures. • A novel foam-filled composite double-arrow auxetic structure was fabricated. • The ballistic impact experiments were conducted to evaluate the impact properties. • The effect of foam filling on the ballistic impact response was analyzed. • The finite element model was used to simulate the ballistic impact process. [ABSTRACT FROM AUTHOR]

This study investigated the power cycling performance on a transfer-molded power module with Cu clip bonding for the next-generation green automotive applications. A 700 V/900A class 2-in-1 half bridge power module was designed and fabricated by using Cu clip bonding and transfer-molding technologies. The switching was precisely controlled so that t on was 0.5 s and t off was 4.5 s by a constant current mode. The condition of the power cycling tests (PCTs) was ∆ T = 125 °C with the maximum repetition of 97,000 cycles. The performance and life of the power module was evaluated based on AQG-324, and thermal resistance of the junction (R th-ja) was monitored during PCTs. The major failure in this investigation was increase in the thermal resistance (R th). Microstructural integrity of the interconnections were characterized in detail by scanning acoustic tomography (SAT) and interfacial microstructure analysis using a scanning electron microscopy (SEM). The degradation mechanism of the interfacial material was numerically revealed through finite element method (FEM) simulations. • Power cycling performance of transfer-molded power module with Cu clip bonding was investigated. • Reliability test of A 700V/900A class 2-in-1 half bridge power module was conducted with T jmax = 175 °C and T c = 50 °C. • Increase in thermal resistance induced by IMC growth and crack propagation of the chip was main cause of module failure. [ABSTRACT FROM AUTHOR]

Solid-state dissimilar bi- or multi-metallic bonding is promising for achieving lightweight or multifunctional components in automotive, nuclear power and aerospace industries. To understand how to achieve a high-quality bonding interface between dissimilar materials, aluminium alloy (Al)–steel (Fe) bimetal gears manufactured under hot forge bonding were systematically investigated. In this work, comprehensive analyses of forge bonding mechanics, microstructure features, bonding interface behaviours and resulting mechanical properties were undertaken using ex/in-situ experiments and finite element modelling. The results revealed that the bonding behaviour and microstructure evolution were significantly affected by the mechanical property mismatch between the two dissimilar workpieces (AA6082 and E355). This mismatch could be effectively adjusted by setting different forging temperatures. The interfacial bonding strengths of AA6082 and E355, manufactured at low and high temperatures, were observed to be governed by interdiffusion and oxide particles, respectively. Balancing interdiffusion and oxide breaking appears to be key to achieving optimized interface strength for dissimilar bimetallic forge bonding technology. [Display omitted] • Bimetallic gears were proved that can be effectively manufactured through solid-state hot forge-bonding. • Correlations between processes interface properties were established. • The interface behaviours were affected by the mechanical property mismatch. • Balancing interdiffusion and oxide breaking appears key to achieving optimized interface strength. [ABSTRACT FROM AUTHOR]

Nowadays, underground equipments are widely applied to explore oil resource in deep earth. Static seal rings are important components keeping underground equipment working steadily. Since pressure and temperature under ground are much higher than those on the ground, it is not easy to predict leakage of static seal rings in underground equipment through experimental ways. So a leakage prediction calculation method is proposed in this paper. Framework of the method is firstly presented. A local contacting FE model is built based on fractal theory and a leakage prediction model for static seal ring is given. Then, the leakage prediction calculation method is realized. To validate the proposed method, a test is performed. It can be seen that the calculation method is useful to predict sealing ability of static seal rings in underground equipments. [ABSTRACT FROM AUTHOR]

Historically, large computational requirements have left contact modeling approaches unable to combine multiple-length scale effects (comprised by the macro-scale geometry of the component and sub-micron geometry of the surface roughness) into a single deterministic analysis. This work presents a three-dimensional, multi-scale, finite element contact and deformation model for a worn-in radial lip seal. The model includes elastomer bulk geometry and apex surface roughness measured from an experimentally tested elastomer seal. The work describes the modeling method used to simulate the compressed state of the seal. A statistical parameter analysis of both the compressed and uncompressed surface roughness was performed. Results are presented and discussed with respect to their potential impact on modeling efforts and the operating conditions of the seal. [ABSTRACT FROM AUTHOR]

Damage and failure process of the unidirectional fiber-reinforced ceramic matrix composites (FRCMCs) under tensile stress had been studied by many researchers in theoretical method. But because of some assumptions made in the theoretical model, it canot describe the performance of interface accurately. In this paper, evolving compliant interface (ECI) is employed to describe the properties of weak bonding interface. The ECI can respond the failure of debonding and sliding of interface efficiently. The whole damage evolution process of the material has been simulated by finite element method (FEM) and the stress-strain curve, the space of cracks at saturated state and the stress of components are discussed. The stress-strain curves of several ceramic composites were predicted by the model and compared with the experimental data. The results indicate that the tensile stress-strain curves agree well with the experimental data on consideration of Evolving compliant interfacial debonding model. [ABSTRACT FROM AUTHOR]

A three-dimensional finite element model that can simulate multiple start/stop welding process of 347H austenitic stainless steel boiler tubes was developed to estimate welding residual stress distributions. Two-dimensional axisymmetric finite element model and threedimensional finite element model that exhibit half symmetry along circumferential direction are also employed for verification purposes. Sequentially coupled thermo-mechanical finite element analyses were carried out using three different models to obtain and compare temperature fields and resulting residual stress fields. In addition, node-based temperature heat input method and element-based body flux heat input method were applied to three-dimensional half symmetry model to review the adequacy of heat input model that can best estimate welding residual stress distribution in the tubes. Finally, welding residual stresses obtained using different models were compared with measured data, and it was observed that results using three-dimensional finite element model that can take into account welding start/stop effects are in good agreement with those of measured data obtained by the X-ray diffraction (XRD) method. [ABSTRACT FROM AUTHOR]

Sealing performance of gasketed flange joints depends mainly on the behavior of gasket. In the present work, a three dimensional finite element analysis has been carried on a gasketed joint with single and twin gaskets having nonlinear material properties, to find the influence of gasket contact stress and sealing performance of the joint. Bolt preload required for safe operation of twin gasketed joints has been formulated by modifying the ASME code. A comparison is made on sealing performance of gasketed joint with single and twin gaskets. The contact pressure of twin gasketed joint is examined by varying the design parameters such as individual gasket widths and space between the gaskets. Contact pressure in single and twin gasketed flange joints at different operating conditions, viz., bolt preload and internal pressure have been investigated. It is observed that the flange joint with twin gasket can withstand higher internal pressure. [ABSTRACT FROM AUTHOR]

In order to study the performance of the dynamic seal and static seal of D-ring, the FEM models of D-ring and O-ring were built, and the process of reciprocating seal of the D-ring was simulated. In addition, the effects of pre-compression, medium pressure, friction coefficient, and rubber hardness on sealing performance were discussed. The friction coefficients between rubber sealing ring and steel part, under different lubrication conditions, were measured through the experiment. The results show that, in static seal, the maximum contact stress of the D-ring increases with the increasing of pre-compression, friction coefficient, medium pressure, and rubber hardness. Besides, O-ring can be well replaced by D-ring in static seal. Since it can avoid distortion and twisting effectively in reciprocating dynamic seal and prolong its working life, D-ring has a better sealing performance in reciprocating seal than O-ring. As the friction coefficient grows, the amplitude of the maximum contact stress fluctuation increases as well as the fluctuation of the cross-section deformation which has a bad influence on sealing performance and fatigue life of the D-ring. [ABSTRACT FROM AUTHOR]

Contact pressure distribution over the active area of proton exchange membrane fuel cell (PEMFC) has significant effects on the performance of PEMFCs. Even clamping pressure over the membrane electrode assembly (MEA) affects contact resistance, characteristics of porous media and sealing task. This paper develops a PEM fuel cell model to study the contact pressure distribution over the membrane electrode assembly using finite element model. At first, the three-dimensional model of a single cell was reduced to a two-dimensional model to decrease the calculation time. After validation of the obtained results via the pressure sensitive films, the effect of some parameters such as thickness and material of the end plates, sealant hardness, number of the stack's cells and position of the cell on the contact pressure distribution over the MEA were investigated. The results reveal that optimizing mentioned parameters leads to design PEM fuel cells with proper contact pressure distribution over the MEA. [ABSTRACT FROM AUTHOR]

This paper focuses on the dynamic characteristics of reflectors considering the effects of assembly of gores. A model is established to properly predict the assembled shape of planar gores, and nonlinear finite element method and subspace iteration method are adopted to analyze the dynamic characteristics of reflectors. A comparative study is carried out based on the dynamic analysis with ideal reflector and assembled reflector to illustrate the impacts of assembly on mode shapes and natural frequencies of the reflectors. The results show that the presence of assembly of gores and seaming tapes has significant effects on mode shapes and natural frequencies of reflectors, which will influence the shape control of reflectors. [ABSTRACT FROM AUTHOR]

Pneumatic cylinders are widely used in industrial applications owing to its several advantages like low cost, high force/volume ratios, easy installation and maintenance, and the absence of significant heat. However, its use in complex control tasks is hindered by their highly nonlinear behaviour, especially nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favourable high speed actuation. The behaviour of an elastomeric piston sealing 8-ring in high speed pneumatic cylinders is analysed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress distributions and frictional forces of the piston seal are simulated with variation of interference fits, working pressures, friction coefficients. [ABSTRACT FROM AUTHOR]

In this article threaded tool joints of gas sealing drill pipes, which are exposed to different tightening turns and tension load, are analyzed using an elaborate finite element modeling through the use of MSC.Marc13.0. The corresponding mechanics model is also established and the reliability of the model is verified by finite element simulation and full scale test. Some conclusive results have been drawn from the analysis including that the force distribution of the gas sealing joints is quite different from the API standard one, and the metal seal structure can greatly improve the seal performance of the joint under tension load. Research also shows that reasonable tightening turns can effectively reduce the thread axial load growth amplitude under the tensile load as a result improving the fatigue life of the tool joints. [ABSTRACT FROM AUTHOR]

Two premium threaded connections with buttress threads and torque shoulders are established in this paper. One premium threaded connection uses the taper difference fit model and the other uses the arc and straight line fit model for the sealing surfaces of the pipe body and the collar body. 3D models are established to consider the frictional shear stress during the make-up process. The finite element analyses of the two connection models are performed to obtain the stress distribution and deformation-induced space variation on the connection models. In addition, the characteristics of the designed structures are analyzed and the tubing and casing make-up curves are deduced based on these characteristics. Finally, an experimental test with the arc and straight line fit model is carried out. As a result, the arc and straight line fit model shows good gas seal performance in the make-up and break-out operation tests. This study is expected to provide a theoretical guide to practical operations in China, thereby reducing the damage probability of tubing and casing during make-up. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the performance of the repaired longitudinal cracks in API X65 pipelines under two different conditions: with patches (i.e., single and double patches) and without patches. The three-dimensional finite element method (FEM) was used to compute the stress intensity factors (SIF) at the crack tip. Repairing cracks under internal pressure using carbon-epoxy composites was investigated where the influence of both the single- and double-sided patches made of composite and adhesive were included. In the evaluation of the repair of the pipeline, the failure assessment diagram (FAD) was introduced to obtain the safety factor value. The obtained results indicated that the value of the factor of safety depends on both the crack length and the pressure. In addition, the results showed that the suggested technique is sufficient in predicting the behavior of the repairs. [ABSTRACT FROM AUTHOR]

• Compressive responses of canted coil spring and spring ring are well predicted. • Wear of spring-energized PTFE seals under ultra-high cycle operations is assessed. • Simulated worn seal cross section is in fair agreement with the measured one. • Sealing capability is evaluated via Reynolds equation and successfully validated. Spring-energized polytetrafluoroethylene (PTFE) seals are typically utilized to meet requirements of long service life due to their excellent temperature and chemical resistance. After high-cycle operations, the contact pressure between the seal lip and the associated counterpart possibly decrease because of the wear on the contact surface and this eventually leads to loss of the sealing capability. Evaluations of the wear and resulting sealing performance of the seal are rather essential, however, the corresponding experiments are generally time consuming and costly. Simulation procedures for the seal based on the finite element analysis were therefore developed in the current study. Experimental and numerical investigations of mechanical behaviors of the canted coil spring and PTFE materials were first performed. A wear analysis model for the spring-energized PTFE seal used in a glue dispenser with reciprocating motions for semiconductor equipment was subsequently constructed. The modified Archard model was implemented into a self-coded user subroutine of commercial finite element software to assess the amount of wear on the seal. Simulation results revealed that the geometry dimensions of the worn seal are in fair agreement with those of the corresponding samples. Contact pressure distributions of the seal lip were also examined during the operations. Peak of the contact pressure was found to gradually decrease along with the increase of cycles due to the wear, and potential fluid leakage was then assessed via the Reynolds equation. Numerical calculations showed that no leakage would occur after ultra-high cycle operations which was consistent with practical observations. [ABSTRACT FROM AUTHOR]

The accumulative roll bonding process is one of the most prominent severe plastic deformation processes for obtaining sheet materials with ultra-fine-grained microstructures and high strength. The properties of such sheets differ significantly from those of conventionally rolled sheets. It is hence desirable to have a simulation framework that can accurately predict the material properties, including the evolving texture and anisotropy during processing. Here, we propose such a framework for multiple pass rolling using explicit finite elements and embedding the visco-plastic self-consistent (VPSC) polycrystal texture model for the material response. To facilitate multiple pass rolling, we propose a novel solution mapping scheme that transfers the material state from the deformed finite element mesh to a new one. Additionally, we implement a two-level parallelization scheme – with decomposition of the FE domain using message passing interface (MPI) and thread based parallelization of the material response using openMP – to ensure reduced simulation times. The predictive capabilities of the proposed framework are demonstrated by simulating the accumulative roll bonding of aluminum alloy AA5754 sheets. The simulations validate the working of the solution mapping scheme, and clearly show the development of a through thickness gradient of texture and anisotropy in the roll-bonded sheet after two passes. [ABSTRACT FROM AUTHOR]

Planar solid oxide fuel cell (SOFC) operates at high temperature and requires a good creep strength to ensure the structure integrity. This paper presents a creep and damage analysis of a bonded compliant seal (BCS) structure of a planar SOFC considering the effect of as-bonded residual stress and thermal stress, as well as the effect of filler metal and foil thickness. A modified continuum creep-damage model is used in the finite element simulation. It demonstrates that the BCS structure meets the requirement of the long-term operation at the high temperature of 600 °C with an appropriate braze bonding process. The results show that the failure location is not in the region of maximum creep deformation due to the effect of high level multi-axial stress which drastically decreases the multi-axial ductility. Reasonably reducing the thickness of filler metal and foil can decrease the damage of the BCS structure. Based on the consideration of creep and damage, it is proposed that the thickness of filler metal and foil should not exceed 0.1 and 0.05 mm, respectively. [ABSTRACT FROM AUTHOR]

Failure analysis of cone bit bearing seals is important in reducing production cost and preventing in-service component failure. However, a generally accepted criterion for their failure has not yet been established because of complexities in both their material properties and the environment. In this study, a two-dimensional axisymmetric finite element analysis (FEA) numerical model was established. FEA software was developed based on the Mooney–Rivlin constitutive model of the rubber material, and the penalty function contact algorithm. The distributions of stress, strain and contact pressure were analyzed to establish their effect on failure. The locations and causes of the failure and preventive measures were determined by comparison with an actual failure case. It was found that stress concentration and uneven pressure distribution occur at the seal. Rubber rings are highly and unequally compressed. Metal ring structure mainly determines sealing performance. To reduce the occurrence of failure, the structure must be improved by: designing an appropriate angle-tapered metal ring end face structure instead of a plane to change the trend in pressure distribution, increasing the contact area of the metal ring end face to reduce contact pressure and make the contact pressure distribution more uniform to reduce sealing surface wear, reducing the radial thickness to reduce the compression of the rubber ring, and improving back support structures to reduce the stress concentration. Results from the study can prevent and minimize risk for future failures to increase bit life and reduce drilling costs. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a thermal–structural coupled finite element analysis method for wear prediction of seal is proposed. The methodology is built with iterative wear prediction procedure in which the geometry of the contact interface is progressively changed according to the wear model. To perform finite element simulation of wear process, a novel mesh reconstruction strategy to reflect the evolution of geometry caused by the wear is presented. Considering that friction heat in the sealing area normally has important effects on wear process, thermal behavior of wear process analysis is carried out and the friction heat flux density is calculated as one of the boundary conditions in each wear simulation circle. Two kinds of seals, namely O-shape seal (O-ring) and rectangular-section seal (R-ring), are investigated in this paper. As the sealing force is important for seals to evaluate the sealing capability, the effect of wear is reflected through the change of sealing force. The numerical results supply a suggestion for the applications of both seals. [Copyright &y& Elsevier]

A comprehensive mathematical model of the hot extrusion process for aluminum alloys has been developed and validated. The plasticity module was developed using a commercial finite element package, DEFORM-2D, a transient Lagrangian model which couples the thermal and deformation phenomena. Validation of the model against industrial data indicated that it gave excellent predictions of the pressure during extrusion. The finite element predictions of the velocity fields were post-processed to calculate the thickness of the surface cladding as one billet is fed in after another through the die (i.e., the transverse weld). The mathematical model was then used to assess the effect a change in feeder dimensions would have on the shape, thickness and extent of the transverse weld during extrusion. Experimental measurements for different combinations of billet materials show that the model is able to accurately predict the transverse weld shape as well as the clad surface layer to thicknesses of 50 μm. The transverse weld is significantly affected by the feeder geometry shape, but the effects of ram speed, billet material and temperature on the transverse weld dimensions are negligible. [ABSTRACT FROM AUTHOR]

Abstract: Solid oxide fuel cell (SOFC) requires good sealant because it works in harsh conditions (high temperature, thermal cycle, oxidative and reducing gas environments). Bonded compliant seal (BCS) is a new sealing method for planar SOFC. It uses a thin foil metal to bond the window frame and cell, achieving the seal between window frame and cell. At high temperature, a comprehensive evaluation of its creep strength is essential for the adoption of BCS design. In order to characterize the creep behavior, the creep induced by thermal stresses in SOFC with BCS design is simulated by finite element method. The results show that the foil is compressed and large thermal stresses are generated. The initial peak thermal stress is located in the thin foil because the foil acts as a spring stores the thermal stresses by elastic and plastic deformation in itself. Serving at high temperature, initial thermal displacement is partially recovered because of the creep relaxation, which becomes a new discovered advantage for BCS design. It predicts that the failures are likely to happen in the middle of the cell edge and BNi-2 filler metal, because the maximum residual displacement and creep strain are located. [Copyright &y& Elsevier]

Brush seals have been applied in more and more challenging high-temperature locations. The high speed bristle-rotor friction causes a considerable heat generation which accel-erates the bristles wear. The frictional heat generation at bristle-rotor interface becomes another major concern in brush seal applications. This study presented detailed investi-gations on the heat transfer characteristics and contact mechanics of brush seals using a combined computational fluid dynamics (CFD) and finite element method (FEM) brush seal model. The CFD model of brush seal for mass and heat transfer employed Reynolds-averaged Navier-Stokes (RANS) solutions coupled with non-Darcian porous medium approach. The nonlinear contact model of brush seal was established using FEM with considerations of internal frictions (bristle to rotor, bristle to backing plate, and bristle to bristle) and aerodynamic loads on bristles. The numerical method involved iterations between CFD and FEM models to better evaluate the heat transfer behaviors of the brush seal with consideration of bristle deflections. The frictional heat generation was calcu-lated from the product of bristle-rotor frictional force and sliding velocity. The bristle deflections and temperature distributions of the brush seal were predicted at various operational conditions using the iterative CFD and FEM brush seal model. The effects of pressure differential and rotational speed on the contact behavior, temperature distribu-tion and bristle maximum temperature of brush seals were numerically investigated using the developed approach. The detailed pressure contours and streamline distributions of the brush seal were also illustrated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The parametric study is implemented using the linear matching method and FEM. [•] Creep–fatigue strength of the steel AISI type 316N(L) weldments of types 1 and 2. [•] Function for cycles to failure is dependent on geometric parameters of weld profile. [•] Function for cycles to failure is dependent on dwell period and normalised moment. [•] Function for FSRF dependent on dwell period takes into account the effect of creep. [ABSTRACT FROM AUTHOR]

Abstract: The accumulative roll-bonding (ARB) process, which is a severe plastic deformation process, was simulated using finite element analysis, including the influence of friction, stress–strain relations, and roll diameter. The complicated distributions of equivalent strain through the thickness of ARB-processed sheets were quantified. These quantitative strain analyses would be useful for analyzing the evolution of ultrafine-grained structures in the ARB process. [Copyright &y& Elsevier]

The repairing process of structures using bonding of composite materials is an efficient and economic way of increasing service life of damaged structures. The finite element method is developed and applied to assist in the design, assessment and optimization of the proposed plans before they are implemented, therefore reducing cost and time. In this study, the finite element method is used to analyze the behavior of a repaired crack using single and double circular composite patches by determining the stress intensity factor reduction. The effects of geometrical and mechanical properties of the patch on the fracture parameters are highlighted. The results show that the thickness gain and the reduction of the asymptotic value of the SIF in the case of the double patch is 7% when compared to the single one. Thus, the gain in the thickness decreases when the thickness of the bonded patch increases up to a value eP = 0.8 mm and beyond this value, it starts increasing. However, an inverse behavior occurs for the mixed mode. In addition, whatever is the size of the strengthened crack, the gain in thickness exceeds 16% in mode I and 20% in mixed mode. [ABSTRACT FROM PUBLISHER]

Abstract: In the context of this work we present static experimental tests on nitrile-based elastomeric radial lip seals under different radial loads and with different temperatures. The outcomes of these experiments have been used to calibrate a three-dimensional finite element model for performing static analyses of a radial lip seal. Experimental results also provide an assessment of the ability of the Mooney–Rivlin constitutive model to represent the behavior of elastomeric material of the radial lip. Once calibrated, the finite element model has been used to investigate the relation between contact pressure and static design parameters, such as interference and radial offset. [Copyright &y& Elsevier]

Adhesive joints have been widely used in the automotive and aerospace fields in order to reduce the weights of products. The strength of adhesive joints, accordingly, needs to be increased and their behaviour should be predicted in order to achieve accurate designs. Studies to improve the strength of adhesive jointsviasurface treatment methods or by using two adhesives with different mechanical properties have been conducted. Various modeling methods also have been studied to predict the behaviour of adhesive joints. Unfortunately, the relationship between the bonding surface roughness and adhesive joint strength needs to be further clarified in order to be applied in practical design. As analyzing the relationship through a conventional finite element method assuming perfect bonding is challenging, the behaviour of the adhesive joints may be analyzed using a cohesive zone model or interface modeling methods from an integrating released energy point of view. The strength of adhesive joints can be improvedviamicro-patterning due to the mechanical interlocking effect. Therefore, in this study, a micro-pattern was fabricated to improve the strength of adhesive joints. Various pattern-sized single leg bending joints and end notched flexure joints were manufactured and experimented upon. In this study, characteristics of each pattern surface were independently classified and modeled with a cohesive zone model. Finite element analyses were then performed and simulation results were compared with experimental results. The numerical results satisfactorily describe the experimental results, and failure loads were predicted with a maximum relative error of 8%. From these results, it may be concluded that the present findings can be applied to practical design and that the failure load can be predicted via a finite element analysis. [ABSTRACT FROM PUBLISHER]

An optical fiber sensor surface bonded onto a host structure and subjected to a temperature change is analytically studied in this work. The analysis is developed in order to assess the thermal behavior of an optical fiber sensor designed for measuring the strain in the host structure. For a surface bonded optical fiber sensor, the measuring sensitivity is strongly dependent on the bonding characteristics which include the protective coating, adhesive layer and the bonding length. Thermal stresses can be generated due to a mismatch of thermal expansion coefficients between the optical fiber and host structure. The optical fiber thermal strain induced by the host structure is transferred via the adhesive layer and protective coating. In this investigation, an analytical expression of the thermal strain and stress in the optical fiber is presented. The theoretical predictions are validated using the finite element method. Numerical results show that the thermal strain and stress are linearly dependent on the difference in thermal expansion coefficients between the optical fiber and host structure and independent of the thermal expansion coefficients of the adhesive and coating. [ABSTRACT FROM AUTHOR]