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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]

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]

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]

• 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]