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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]

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]