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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]

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]

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]

• 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]

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]

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: The use of self-healing glass as hermetic seals is a recent advancement in sealing technology development for the planar solid oxide fuel cells (SOFCs). Because of its capability to restore mechanical properties at elevated temperatures, the self-healing glass seal is expected to provide high reliability in maintaining the long-term structural integrity and functionality of SOFCs. To accommodate the design and evaluate the effectiveness of these engineered seals under various thermomechanical operating conditions, a computational modeling framework must be developed to accurately capture and predict the healing behavior of the glass material. In the present work, a mechanistic-based, two-stage model was developed to study the stress and temperature-dependent crack healing of the self-healing glass materials. The model initially was first calibrated by experimental measurements combined with kinetic Monte Carlo (kMC) simulation results and then implemented into finite element analysis (FEA). The effects of various factors, e.g., stress, temperature, and crack morphology, on the healing behavior of the glass were investigated and discussed. [Copyright &y& Elsevier]

Abstract: This paper considers the problem of determining the nonlinear bimodular stiffness properties, i.e., the tensile and compressive Young’s moduli and Poisson’s ratios, and the shear modulus, of particulate composite materials with particle–matrix interfacial debonding. It treats the general case in which some of the particles are debonded while the others remain intact. The Mori–Tanaka approach is extended to formulate the method of solution for the present problem. The resulting auxiliary problem of a single debonded particle in an infinite matrix subjected to a remote stress equal to the average matrix stress, for which Eshelby’s solution does not exist, is solved by the finite element method accounting for the particle–matrix separation and contact at the debonded particle–matrix interface. Because of the nonlinear nature of the problem, an iterative process is employed in calculating the stiffness properties. The predicted stiffness properties are compared to the exact solutions of the stiffness properties of particulate composites with body-centered cubic packing arrangement. [Copyright &y& Elsevier]

Abstract: This paper studies the characteristics and phenomena of a new-type ACF on the outer lead bonding for the bonding process. Firstly, this new-type ACF has a good thermal conducting effect and an excellent curing capability which offers lower bonding temperature and less curing time during the bonding process. Although the electrical resistance of new-type ACF is slight higher than the conventional-type ACF, the value is quite acceptable. Less conductive particles are trapped at edge of ACF because it has lower temperature than other regions. Using Taguchi method and finite element analysis is not completely to get the optimum parameters of the bonding process, or rather it can examine the effects of bonding process parameters on the activation capabilities of conductive particles of the new-type ACF. Moreover, the inside conductive particle of new-type ACF induced more equivalent stress than that of the outside and middle conductive particles. [Copyright &y& Elsevier]

Abstract: In the framework of test analysis pyramid, large specimens were studied. To represent the bending behaviour during postbuckling, specimens composed of a plate with a stiffener were supported on five points and loaded transversely by two points, thus being subjected to “seven point” bending. By modifying the positions of the two loading points, symmetrical and antisymmetrical buckles that led to interface failure between the flange and the skin could be simulated. First a global numerical model of the test was made in order to assess the efficiency of the approach developed in the first part of this study. Predictions were in accordance with experiments despite strong scatter. Then, a global/local test method was considered. In this method, the global model considered shell elements although the local model used volume elements. The onset of delamination was correctly predicted at local level. Finally, the method was applied to two large stiffened panels subjected to compression and shear. [Copyright &y& Elsevier]

Abstract: A multi-level analysis of skin/stiffener debonding is used for the fuselage design of future aircraft during postbuckling. The specimens composed of a laminate (the skin) to which an over-thickness (the flange) had been added were subjected to four-point bending, which led to interface failure between the flange and the skin. These tests were performed with several configurations and parameters, such as the orientation of the plies located at the interface, temperature (−50, 20 and 70°C), ageing and manufacturing mode: co-cured or co-bonded. The flange shape (tapered or not) and thickness were also considered. Test data are presented and analyzed and critical configurations are identified. Finite element models were developed and the flange debonding loads computed, firstly by use of cohesive models and then through a fracture mechanics approach (Virtual Crack Closure Technique). In both cases, the Benzeggagh–Kenane criterion was selected and proved its efficiency but the fracture mechanics approach was an order of magnitude less time consuming, which will enable future modelling to include larger sizes. [Copyright &y& Elsevier]

Abstract: A three-dimensional multi-cell model based on a prototypical, planar solid oxide fuel cell (pSOFC) stack design using compliant mica-based seal gaskets was constructed in this study to perform comprehensive thermal stress analyses by using a commercial finite element analysis (FEA) code. Effects of the applied assembly load on the thermal stress distribution in the given integrated pSOFC stack with such a compressive sealing design were characterized. A comparison was made with a previous study for a similar comprehensive multi-cell pSOFC stack model but using only a rigid type of glass–ceramic sealant instead. Simulation results indicate that stress distributions in the components such as positive electrode-electrolyte-negative electrode (PEN) plate, PEN-supporting window frame, nickel mesh, and interconnect were mainly governed by the thermal expansion mismatch rather than by the applied compressive load. An applied compressive load of 0.6MPa could eliminate the bending deformation in the PEN-frame assembly plate leading to a well joined structure. For a greater applied load, the critical stresses in the glass–ceramic and mica sealants were increased to a potential failure level. In this regard, a 0.6MPa compressive load was considered an optimal assembly load. Changing the seal between the connecting metallic PEN-supporting frame and interconnect from a rigid type of glass–ceramic sealant to a compressive type of mica gasket would significantly influence the thermal stress distribution in the PEN plate. The critical stress in the PEN was favorably decreased at room temperature but considerably increased at operating temperature due to such a change in sealing design. Such differences in the stress distribution could be ascribed to the differences in the constrained conditions at the interfaces of adjacent components under various sealing designs. [Copyright &y& Elsevier]

Abstract: In this study, a total of 13 FRP-strengthened reinforced concrete beams were tested in flexure and analyzed using the finite element method. The various variables included bonding or no bonding of the FRP, the anchorage system, the amount of prestressing, and the span length. The experiments consisted of one control beam, two non-prestressed FRP-bonded beams, four prestressed FRP-unbonded beams, four prestressed FRP-bonded beams, and two prestressed FRP-unbonded beams with different span lengths. All the beams were subjected to three-point and four-point bending tests under deflection control, with the loading, deflection and failure modes recorded to the point of failure. A nonlinear finite element analysis of the tested beams was also performed using the DIANA software; this analysis accounted for the nonlinear concrete material behaviour, the reinforcement, and an interfacial bond-slip model between the concrete and CFRP plates. The aim of this investigation was to study the flexural performance of reinforced concrete members strengthened using CFRP plates, employing different FRP bonding and prestressing methods. The failure mode of the prestressed CFRP-plated beams was not debonding, but FRP rupture. For the reinforced concrete members strengthened with externally bonded prestressed CFRP plates, debonding of the composite laminates occurred in two stages. After the debonding of the CFRP plates that occurred in the bonded cases, the behaviour of the bonded CFRP-plated beams changed to that of the unbonded CFRP-plated beams due to the effect of the anchorage system. The flexural test results and analytical predictions for the CFRP-strengthened beams were compared and showed very good agreement in terms of the debonding load, yield load, and ultimate load. The ductility of the beams strengthened with CFRP plates having the anchorage system was considered high if the ductility index was above 3. [Copyright &y& Elsevier]

The failure behaviors of flip chip solder joints under various loading conditions of the high-speed shear test (H-SST) were investigated with an experimental and non-linear 3-dimensional finite element modeling study. The solder composition used in this study was Sn-3.0Ag-0.5Cu (in wt.%). The shear forces were far greater by H-SST than by low-speed shear test (L-SST). The shear force further increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloy. Brittle interfacial fractures were more easily achieved by H-SST, especially at the higher shear speed. This was discussed in terms of the relationship between the strain-rate and work-hardening effect and the resulting stress concentration at the interfacial regions [ABSTRACT FROM AUTHOR]

The effectiveness of FRP rehabilitation of deteriorating and under-strength reinforced concrete beams depends not only on the properties of the FRP material, but also on the characteristics of other materials in the system, characteristics of the bond, and the relative nature of properties of materials at the interfaces. Response is also affected by the cracked condition of the beam prior to the external bonding of the FRP. This paper reports on a fundamental investigation into the effect of various design parameters using a finite element analysis approach, which not only provides characteristics of response but also enables identification of damage mechanisms and their progression to failure. It is shown that the highest level of strengthening is not always due to use of maxima of the parameters, but rather on the interaction between them. Interface bond strength and fracture energy are shown to have a significant effect on load capacity, ductility and transition of failure modes from debonding within concrete, to FRP rupture, and to debonding within the adhesive itself. [ABSTRACT FROM AUTHOR]

This article presents the results of numerical analyses of concrete cylinders (i.e., columns) confined in composites jackets. The specimens were subjected to uniaxial compression and the analysis was carried out using a non-linear finite element method. Various parameters such as wrap thickness, fiber orientation, concrete strength, and interfacial bonding were considered. Three different wrap thicknesses (0.9, 1.8, and 2.7 ram), fiber orientation of 0°, ±15°, ±30°, and ±45° with respect to the hoop direction, and concrete strength values ranging from 20 MPa to 40 MPa were investigated. The finite element analysis results were in good agreement with experimental data presented by other researchers. The numerical analysis results demonstrated significant enhancement in the compressive strength, stiffness, and ductility of the CFRP-wrapped concrete cylinders compared to unconfined concrete cylinders. The stress-strain response of cylinders was greatly affected by analysis parameters. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study of the block shear capacity of ten full-scale coped beams with a welded clip angle connection was presented in Part I. The test results were compared with predictions using block shear design equations in several current design standards. In general, the results showed that the existing design standards did not provide consistent predictions of the block shear capacity of coped beams with welded clip angles. In addition, the equations provided by the standards cannot accurately reflect the failure mode of the specimens observed in the tests. In order to gain a better understanding of the connection behavior, such as the stress distribution in the web near the periphery of the clip angles and the failure mechanism of the connection, an analytical study of the block shear capacity of coped beams with welded clip angles was carried out using the finite element method. Based on the limited test data and the results of the finite element analysis (FEA), a strength model was established and a design equation was proposed to evaluate the block shear strength of coped beams with welded clip angles. It was shown that the proposed design equation gave better predictions of the block shear capacity of the specimens. [Copyright &y& Elsevier]

Abstract: A new theory of fatigue crack growth in ductile solids has recently been proposed based on the total plastic energy dissipation per cycle ahead of the crack. This and previous energy based approaches in the literature suggest that the total plastic dissipation per cycle can be closely correlated with fatigue crack growth rates under mode I loading. In a recent paper, the authors have extended the dissipated energy approach to the case of fatigue crack growth in a homogeneous material under sustained mixed-mode loading conditions. The goal of the current study is to further extend the approach to mixed-mode fatigue delamination of ductile interfaces in layered materials. Attention is restricted to material combinations with identical elastic properties, but with mismatches in plastic properties (both yield strength and hardening modulus) across the interface. Such systems can occur in brazing, soldering, welding, and a variety of layered manufacturing applications, where high-temperature material deposition can result in a mismatch in mechanical properties between the deposited material and the substrate. In this study, the total plastic dissipation per cycle is obtained through plane strain elastic–plastic finite element analysis of a stationary crack in a general layered specimen geometry under constant amplitude, mixed-mode loading. Numerical results for a dimensionless plastic dissipation per cycle are presented over the full range of relevant material combinations and mixed-mode loading conditions. Results suggest that while applied mode-mix ratio is the dominant parameter, mismatches in yield strength and hardening modulus can have a significant effect on the total plastic dissipation per cycle, which is dominated by the weaker/softer material. [Copyright &y& Elsevier]

Nanoindentation is an important technique for probing the mechanical behavior of materials at small length scales. In this study, nanoindentation was used to extract the elastic and plastic properties of Cu, Sn–3.5Ag solder, Ag3Sn, and intermetallics in Cu/Sn–Ag solder joints including Cu6Sn5, and Cu3Sn. The elastic and plastic properties of Cu, Sn–3.5Ag solder, Ag3Sn, Cu6Sn5, and Cu3Sn were measured and where possible, compared to limited data available in the literature. Finite element analysis was used to simulate the indentation behavior from elastic–plastic properties of the intermetallics. The predicted values matched very well with experimental results. Finite element analysis also showed that pile-up took place in indentation of Cu and solder, while indentation sink-in was observed in Ag3Sn, Cu6Sn5, and Cu3Sn. The relative degree of pile-up/sink-in was shown to be a function of the work hardening exponent of the phase and the ratio of yield stress to Young''s modulus. [Copyright &y& Elsevier]