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As electrofusion (EF) technology is widely used in connecting polyethylene (PE) pipes and other plastic pipes or composite pipes, research in safety assessment of EF joints has been of major concern. EF joints with defects are very common in practical applications. These defects may greatly reduce the mechanical performance of the EF joints and threat safety running of the pipeline system. To evaluate hazard of these defects and provide a basic understanding for the failure mechanism of EF joints, a comprehensive study on defects and failure modes is conducted in this work. The defects in EF joints are classified into four categories: poor fusion interface, over welding, voids, and structural deformity. The forming reasons of these defects are analyzed in detail. The mechanical properties of EF joint containing these defects are investigated by conducting peeling tests and sustained hydraulic pressure tests. Test results show that there are three main failure mode of EF joint under inner pressure, that is, cracking through the fusion interface, cracking through the fitting, and cracking through copper wire interface.

A novel substrate-triggered grounded-gate NMOS (GGNMOS) is verified in 65 nm CMOS silicide process. The trigger element is a PMOS controlled by the VDD bus line and no other detection circuit is needed. Compared to traditional GGNMOS, with a 50 mm trigger PMOS, the trigger voltage of the single finger structure can be reduced from 7.15 to 4.97 V and it also has lower overshoot voltage. Also the ultrathin gate oxide can be effectively protected, which is very important in nanometre circuits. For the multi-finger structure, with a 30 mm trigger PMOS the proposed structure showed a 15.9% reduction in trigger voltage and a 13.5% increment as to failure current compared to traditional GGNMOS.

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With the increasing application of electrofusion (EF) welding in connecting polyethylene (PE) pipes for gas distribution, more effort has been invested to ensure the safety of the pipeline systems. The objective of this paper is to investigate and understand the temperature distribution during EF welding. A one-dimensional transient heat-transfer model was proposed, taking the variation in the rate of power input, the phase transition of PE, and the thermal contact conductance between heating wire and PE into consideration. Then, experiments were designed to verify the power input and the temperature. The measured values of the power input were shown to be in good agreement with the analytical results. Based on ultrasonic test (UT), a new “Eigen-line” method was presented, which overcomes the difficulties found in the thermocouples’ temperature measurements. The results demonstrate good agreements between prediction and experiment. Finally, based on the presented model, a detailed parametric study was carried out to investigate the influences of the variation in the power input, the physical properties of PE, and the thermal contact conductance between heating wire and surrounding PE.

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Currently, on-board storage cylinders of compressed hydrogen for land vehicles primarily use fully-wrapped carbon fiber reinforced cylinders with an aluminum liner. Due to the multi-layer structure of the hydrogen storage cylinder, nondestructive testing of the cylinder is facing great challenges and the nondestructive testing methods given in the standard are mainly internal and external surface testing by using visual inspection or an endoscope, causing that many internal defects cannot be identified. Industrial computed tomography is able to intuitively display three-dimensional information of the examined object, and thus this technology is expected to detect internal defects of the cylinders. In this study, the loading system of the cylinder, including limit plates, support blocks and support columns, was designed and manufactured. The industrial computed tomography test method with the use of a filter was established, and the delamination defects at the cylinder neck, shoulder, and cylindrical shell were systematically researched. It was found that the delamination defect width at the neck was the largest, followed by the defect width at the shoulder, and the defect width at the cylindrical shell was the smallest. In addition, the whole cylinder was detected by using spiral scan, demonstrating that this test method had the potential to be a common tool to monitor the cylinder defects.