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Piezoelectric material has widely used in various applications with its high liable performance and quite smart electro-mechanical characteristics. However, solutions for number of troubles in strength and behavior of fracture have not sufficiently clarified yet. Among these associated solutions, the double torsion (DT) technique is the particular and effective method to measure toughness of fracture and growth behavior of slow crack in ceramic material. From the results of this work, it obtained the practical feasibility of the DT technique for finding growth behavior of crack initiated by kinds of cyclic electric fatigue on piezoelectric ceramics, and found that the initiated crack is able to propagate by using a relatively lower cyclical voltage than before cases under a constant mechanical load if the DT technique is used. In this study, it is also established the experimental method of the crack propagation by cyclic electric fatigue for the piezoelectric ceramics using DT technique, and found the possibility of the power law based on the classical Paris’ equation for analyzing the result of electric fatigue crack test.

Injuries to the lower extremities were common in female field hockey players. This study aimed to determine the potential association between in-game performance parameters recorded via global positioning system (GPS) and non-contact knee and ankle injuries in elite female field hockey players. Thirty two elite female field hockey players free from sports injuries of the knee and ankle joint were participated in this study. GPS tracking was used to record the distance covered while running at various speeds, time spent sprinting, and maximum speed during the international competitions (December 2015–June 2016). And all injury events were also recorded. Data were analyzed using descriptive statistics, the independent t-test, and binary logistic regression. Low-intensity running distance was significantly higher in players who did not experience injury throughout the duration of the study ( $$t = 2.182,\, p = 0.037$$ ). The risk for in-game knee injury decreased with increasing distance covered while running at low speed (odds ratio = 0.8; 95% confidence interval = 0.6–1.0; $$\chi ^{2} = 3.964;\, p = 0.046$$ ). Our findings can be applied to develop strategies for preventing sports-related injuries during field hockey competitions, and confirm the utility of GPS technology for real-time monitoring of fast and complex movement.

Background The role of adjuvant radiotherapy (RT) and setting proper RT target volumes have not been clearly demonstrated for extrahepatic bile duct (EHBD) cancer, due to the rarity of the disease and the lack of randomized trials. This study was conducted to evaluate the indication and treatment volume for adjuvant RT in EHBD cancer patients by identifying the prognostic factors for loco-regional (LR) failure, and analyze the patterns of LR failure. Methods Ninety-three patients with EHBD cancer, who underwent resection without adjuvant RT, at 2 medical centers, between 2001 and 2016, were analyzed retrospectively. Univariable and multivariable analyses were performed to find the prognostic factors for LR recurrence. The initial patterns of failure were recorded, especially those of LR recurrence, and categorized according to the Japanese classification. Results The median follow-up duration was 30 months, and 38 (40.9%) patients experienced LR recurrence during this period. With regards to LR recurrence, close or positive resection margin (RM) status (p

The linear contribution of total energy release rate for fracture of ferroelectric materials was studied based on the linear theoretic framework of piezoelectricity using the double-torsion technique. It was found that three linear contributions of the total energy release rate for piezoelectric material are definitely associated with pure mechanical compliance, electromechanical compliance, and pure electrical capacitance. To confirm the entity of contributions, mechanical and electromechanical compliances were analyzed obtained from result of load vs. displacement measured on each electric field, and electrical capacitance was obtained from property and geometry of samples.

To accomplish long-term use of specific parts of steel, welding technology is widely applied. In this study, to compare the efficiency in improving mechanical properties, rolled steel (SS400) was welded with stainless steel (STS304) by both CO2 welding method and MIG (metal inert gas) welding method, respectively. Multi-tests were conducted on the welded specimen, such as X-ray irradiation, Vickers’ Hardness, tensile test, fatigue test and fatigue crack growth test. Based on the fatigue crack growth test performed by two different methods, the relationship of da/dN was analyzed. Although the hardness by the two methods was similar, tensile test and fatigue properties of MIG welded specimen are superior to CO2 welded one.

Numerical simulation and experimental study of the Vickers indentation testing of the Al2O3 ceramic coated by diamond-like carbon (DLC) layer were conducted. The numerical analysis was implemented by a two-dimensional finite element (FE) axis symmetry model. FE analysis results gave insight into the fracture mechanism of DLC films coated on brittle ceramic (Al2O3) substrates. The maximum principal stress field was used to locate the most expected area for crack formation and propagation during the Vickers indentation testing. The results show that the median crack initiates in the interface under indenter, before ring crack occurs as the indenter presses down. Finally, the plastic deformation appears when the indenter penetrates into the substrate. The thicker DLC coating increases the Vickers hardness and fracture toughness.

A method allowing for the stable growth of carbon nanotubes (CNTs) on the surface of a fibrous metal mesh substrate (SUS304) was developed with the assistance of the microwave plasma-enhanced chemical vapor deposition process. The controlled addition of up to ∼13% of O2 to the CH4 plasma reacting gas flow was found to promote the growth of the CNTs by oxidizing the amorphous carbon and removing the active H2 radicals. However, excessive amounts of O2 (i.e., fraction of O2 > ∼13%) and H2 were found to play a negative role in the growth of the CNTs. The control of the density and length of the CNTs was also achieved by varying the H2 plasma reduction time and CH4 plasma reacting time, respectively. Longer H2 reduction pretreatment of the catalytic metal islands resulted in the formation of a less dense CNT forest with craters. When the growth time of the CNTs was increased to ∼20 min, their length was increased to ∼10 μm. However, when the growth time of the CNTs exceeded 20 min, their length was significantly decreased, indicating that the continuous presence of O2 in the CH4 plasma destroys the preformed CNTs due to the oxidation reaction.

The interfacial reaction between 42Sn-58Bi solder (in wt.% unless specified otherwise) and electroless Ni-P/immersion Au was investigated before and after thermal aging, with a focus on the formation and growth of an intermetallic compound layer, consumption of under bump metallurgy (UBM), and bump shear strength. The immersion Au layer with thicknesses of 0 µm (bare Ni), 0.1 µm, and 1 µm was plated on a 5-µm-thick layer of electroless Ni-P (with 14–15 at.% P). The 42Sn-58Bi solder balls were then fabricated on three different UBM structures by using screen printing and pre-reflow. A Ni3Sn4 layer formed at the joint interface after the pre-reflow for all three UBM structures. On aging at 125°C, a quaternary phase, identified as Sn77Ni15Bi6Au2, was observed above the Ni3Sn4 layer in the UBM structures that contain Au. The thick Sn77Ni15Bi6Au2 layer degraded the integrity of the solder joint, and the shear strength of the solder bump was about 40% less than the nonaged joints.

An analytic approach has been employed to study condensate film thickness distribution inside cave-shaped cavity of a flat plate heat pipe. The results indicate that the condensate film thickness largely depends on mass flow rate and local velocity of condensate. The increasing rate of condensate film for circular region reveals about 50% higher value than that of vertical region. The physical properties of working fluid affect significantly the condensate film thickness, such as the condensate film thickness for the case of FC-40 are 5 times larger than that of water. In comparison with condensation on a vertical wall, the average heat transfer coefficient in the cave-shaped cavity presented 10-15% lower values due to the fact that the average film thickness formed inside the cave-shaped cavity was larger than that of the vertical wall with an equivalent flow length. A correlation formula which is based on the condensate film analysis for the cave-shaped cavity to predict average heat transfer coefficient is presented. Also, the critical minimum fill charge ratio of working fluid based on condensate film analysis has been predicted, and the minimum fill charge ratios for FC-40 and water are about ??? = 3~7%, ???/=0.5-1.3%, respectively, in the range of heat flux ?"=5~90kW/㎡

The air gap formation process at the casting/mold interface of a hollow cylinder casting was investigated for alloys solidifying in a mushy type by measuring the displacements of the casting and the mold surfaces during solidification. The formation process of the air gap between the convex casting surface and the outer mold and the heat-transfer coefficient through the gap have been well documented by previous publications. However, the air gap between the concave casting surface and the inner mold, or the core, was found to form differently during mushy solidification, in which the air gap formed during solidification, reached a maximum gap distance, and then decreased due to the contraction of the solidified casting on the expanding inner mold. The gap formation was caused by an inward collapse of the coherent dendrite networks at the concave interface because of low pressure inside of the casting due to solidification shrinkage. The coherent dendrite networks at the convex interface did not collapse inward. The heat-transfer coefficients estimated by measuring the air gap thickness showed a similar tendency to the calculated values obtained by the inverse heat-conduction analysis.