Investigations on fretting fatigue in aircraft engine compressor blade

An investigation of several cracked blade tangs in the military aircraft engine compressor was conducted to identify the root cause of the failure. These cracks were found during the scheduled maintenance with fluorescent penetration inspection. The engine compressor blade made of Ti–6Al–4V is attached to compressor rotor by means of inserting retaining pin through rotor and blade tang. By analyzing the fracture surface of the failed blade tang, it is found that the crack in the blade tang was initiated by fretting fatigue and propagated under low cycle fatigue. Stress analysis of the blade using a non-linear finite element method is coincident with the results of fractography. The clearance between retaining pin and tang hole caused small amplitude of sliding motion leading to fretting wear during engine operation. Consequently, the damaged area due to fretting wear acts as a stress raiser inside tang hole and contributes to accelerate fretting fatigue.     

Interfacial properties of XLPE/EPDM laminates

Interfacial properties such as space charge accumulation and breakdown characteristics in crosslinked polyethylene (XLPE)/ethylene propylene diene terpolymer (EPDM) laminates were investigated. Homocharge is observed in EPDM containing 1,4-hexadiene while heterocharge is observed in EPDM containing 5-ethylene-2-norbornene. Interfacial charge develops when the EPDM is laminated with XLPE. The polarity of this interfacial charge reverses at less than a few tens of hours heat treatment at 80°C dc breakdown voltage shows a sequential change of an increase, a decrease and a slight increase as a function of heat treatment time, which holds true for both interfacial and volume breakdown voltages. A maximum breakdown voltage is observed at 20 to 24 h heat treatment. After long heat treatment, silicone grease used in the interface shows lower interfacial breakdown voltage than silicone oil for the dc case, which was attributed to the additives in the grease and the molecular weight of silicone molecules in oil and grease. Details of the results are given and their origins discussed     

Data-driven glass/ceramic science research: Insights from the glass and ceramic and data science/informatics communities

Data-driven science and technology have helped achieve meaningful technological advancements in areas such as materials/drug discovery and health care, but efforts to apply high-end data science algorithms to the areas of glass and ceramics are still limited. Many glass and ceramic researchers are interested in enhancing their work by using more data and data analytics to develop better functional materials more efficiently. Simultaneously, the data science community is looking for a way to access materials data resources to test and validate their advanced computational learning algorithms. To address this issue, The American Ceramic Society (ACerS) convened a Glass and Ceramic Data Science Workshop in February 2018, sponsored by the National Institute for Standards and Technology (NIST) Advanced Manufacturing Technologies (AMTech) program. The workshop brought together a select group of leaders in the data science, informatics, and glass and ceramics communities, ACerS, and Nexight Group to identify the greatest opportunities and mechanisms for facilitating increased collaboration and coordination between these communities. This article summarizes workshop discussions about the current challenges that limit interactions and collaboration between the glass and ceramic and data science communities, opportunities for a coordinated approach that leverages existing knowledge in both communities, and a clear path toward the enhanced use of data science technologies for functional glass and ceramic research and development.     

Prediction of homogeneous combustion by modification of the fuel combustion mechanism in a DME fueled CI engine

Journal of Mechanical Science and Technology - This study was performed to predict numerically the homogeneous combustion characteristics where the fuel combustion mechanism was modified in a DME...     

Recent Progress and Development in Extrusion of Rare Earth Free Mg Alloys: A Review

Mg and its alloys are the lightest structural metals available and are extremely attractive for applications as lightweight components, particularly in the automobile, electronic, and aerospace industries. The global market for wrought Mg alloys has steadily expanded over the past decade. And numerous studies have been carried out to meet this increasing demand of high-performance Mg alloys. However, Mg extrusion alloys have had a very limited usage so far. To overcome existing industrial challenges, one desirable approach is the development of low-cost rare earth(RE) free Mg extrusion alloys with superior mechanical properties. This review will introduce the recent research highlights in the extrusion of Mg alloys, specifi cally focusing on low-cost RE-free Mg alloy. The results from both the literature and our previous study are summarized and critically reviewed. Several aspects of RE-free Mg extrusion alloys are described in detail:(1) novel alloying designs including Mg–Al-, Mg–Zn-, Mg–Ca-, Mg–Sn-, and Mg–Bi-based alloys,(2) advanced extrusion techniques, and(3) extrusion-related severe plastic deformation(SPD) processing. Accordingly, considering the large gap in mechanical properties between the current RE-free Mg alloys and high-performance aluminum alloys, new alloy design, processing route control, and recommendations for future research on RE-free Mg extrusion alloys are also proposed. We hope this review will not only off er insightful information regarding the extrusion of RE-free Mg alloys but also inspire the development of new Mg extrusion technologies.     

A study on operational ability comparing drone-centric and user-centric control in external piloting

Multimedia Tools and Applications - Drone manipulation can be divided into external piloting and internal piloting. Internal piloting is a technique where a user monitors the status of a drone and...     

Is smartphone addiction different from Internet addiction? comparison of addiction-risk factors among adolescents

ABSTRACT

We investigated the similarities and differences among four addiction groups in Korean adolescents: Non-Addiction (NONE), Smartphone Addiction (SA), Internet Addiction (IA), and Internet-Smartphone Addiction (BOTH). For the dependent variables, we examined 12 addiction-risk factors related to psychology, family, and school environment that can influence the adolescents’ normative developmental path. To collect data, we conducted an addiction-risk factor comparison survey with 768 Korean adolescents in their first year of junior high school. Depending on the addiction groups, a multivariate analysis of variance or Tukey HSD post-hoc test was used to analyze statistical differences among the 12 addiction-risk factors. Our analysis yielded two key findings on how Internet addiction and smartphone addiction differ in terms of addiction-risk factors: (a) there were more similarities between the SA and NONE groups than between the IA and NONE groups, and (b) there were more similarities between the IA and BOTH groups than between the SA and BOTH groups.     

Structural Characterization of Receptor–Receptor Interactions in the Allosteric Modulation of G Protein-Coupled Receptor (GPCR) Dimers

G protein-coupled receptor (GPCR) oligomerization, while contentious, continues to attract the attention of researchers. Numerous experimental investigations have validated the presence of GPCR dimers, and the relevance of dimerization in the effectuation of physiological functions intensifies the attractiveness of this concept as a potential therapeutic target. GPCRs, as a single entity, have been the main source of scrutiny for drug design objectives for multiple diseases such as cancer, inflammation, cardiac, and respiratory diseases. The existence of dimers broadens the research scope of GPCR functions, revealing new signaling pathways that can be targeted for disease pathogenesis that have not previously been reported when GPCRs were only viewed in their monomeric form. This review will highlight several aspects of GPCR dimerization, which include a summary of the structural elucidation of the allosteric modulation of class C GPCR activation offered through recent solutions to the three-dimensional, full-length structures of metabotropic glutamate receptor and γ-aminobutyric acid B receptor as well as the role of dimerization in the modification of GPCR function and allostery. With the growing influence of computational methods in the study of GPCRs, we will also be reviewing recent computational tools that have been utilized to map protein–protein interactions (PPI).     

Glass structure and crystallization via two distinct thermal histories: Melt crystallization and glass crystallization

This study focuses on the effect of structural inhomogeneity of 44.4CaO-33.2SiO₂-8.8Na₂O-6.2Al₂O₃-7.4B₂O₃ glass on its crystallization behavior. The crystallization behavior of the investigated lime-sodium aluminoborosilicate glass system is explored for the two thermal histories of melt crystallization and the heat treatment of quenched glass. The results show that sodium melilite (CaNaAlSi₂O₇) and larnite (β-Ca₂SiO₄) are the dominant crystalline phases during heating (glass crystallization) and cooling (melt crystallization), respectively. In the glass structure from the heat treatment at 610 °C, both Si₂O₇ and AlO₄ units (i.e., four-coordinated Al) are dominant. This may induce sodium melilite (CaNaAlSi₂O₇) crystallization, connecting Si₂O₇ and AlO₄ units with O and linking Ca and Na between interlayers. The melt structure, meanwhile, has more SiO₄ and AlO₆ units in its silicate and aluminate. Therefore, larnite (β-Ca₂SiO₄) crystallizes on cooling by combining SiO₄ units and Ca. The crystallization behavior is further discussed considering the inhomogeneity structure of supercooled liquids before nucleation.