Finite Element Analysis of Precursors to Macroscopic Stick–Slip Motion in Elastic Materials: Analysis of Friction Test as a Boundary Value Problem

In this study, we apply the finite element method to investigate precursor to frictional sliding phenomena arising immediately prior to macroscopic stick–slip transitions in elastic bodies within the framework of a continuum theory. Using a numerical model that mimics an actual experimental system, we study the behavior of contact surface nodes to assess the influence of stiffness, driving velocity, initial conditions, and discretization conditions on the propagation characteristics of microscopic slips. In particular, we show that the initial distribution of frictional stress arising due to the Poisson effect has a significant effect on the propagation characteristics in slip regions. Next, based on the results of a finite element analysis of precursor phenomena that accounts for the influence of bulk compliance, we consider the determination of parameters in rate-dependent friction models. With regard to the behavior of sliding friction, we show that the relationship between friction tests and friction models is fundamentally different from the relationship between material tests and constitutive models for material deformation. We conclude that a proper understanding and classification of friction tests, friction models, and the relationship between these tests and boundary value problems are crucial ingredients in the application of computer-aided engineering techniques to sliding-friction phenomena; indeed, friction tests must ultimately be treated as boundary value problems.     

Validating the usefulness of examiners’ forward citations from the viewpoint of applicants’ self-selection during the patent application procedure

In this study, we validated the usefulness of examiners’ forward citations, especially from the viewpoint of the applicants’ self-selection (ASS) decisions during the patent application procedure. We believe that the ASS in an early stage would be decided by a potential-value comparison among patent applications. We focused on six self-selection decision points of the applicants: whether to file patent applications in foreign countries, request for examination, request for accelerated examination, reply to a notification of reasons for refusal, appeal after receiving a decision of refusal, and register after receiving a decision to grant a patent as patent value parameters. We found that application groups that selected “Yes” have a significantly larger number of examiners’ forward citations than groups that selected “No” at all decision points. In addition, we confirmed that applications that were finally granted and those that were renewed for a full term after grant have a significantly large number of examiners’ forward citations. We concluded that the number of examiners’ forward citations would be a useful indicator of the potential value of patent applications in macroscopic analysis.     

Enhanced Light Storage of SrAl2O4 Glass‐Ceramics Controlled by Selective Europium Reduction

A luminescent Eu, Dy: SrAl₂O₄ glass‐ceramics with high transparency in the visible region was successfully synthesized using the frozen sorbet technique with the control of O₂ partial pressure () for the oxidation of Eu²⁺ ions. The glass‐ceramics include Eu²⁺, Eu³⁺, and Dy³⁺ ions, and thus exhibits three characteristic types of emission bands, 4f–5d at around 520 nm (Eu²⁺ ions), 4f–4f at 610 nm (Eu³⁺ ions), and 480 nm (Dy³⁺ ions). The Eu, Dy: SrAl₂O₄ glass‐ceramics provide remarkable long‐persistent luminescence under dark condition. The glass‐ceramics also exhibits color‐changing luminescence in the visible region based on their remarkable light storage properties. The luminescent Eu, Dy: SrAl₂O₄ glass‐ceramics using the frozen sorbet technique with control of are promising materials for application in novel photonic and light storage materials.     

Measurement of heat/mass transfer at second stage vane endwall according to step heights

Journal of Mechanical Science and Technology - Recently, domestic gas turbines are primarily operated under partial loads. Hence, thermal expansion of components decreases, leading to a...     

Characterization of alternative plasticizers in poly(vinyl chloride) sheets for blood containers

This study aimed to optimize the ratio of dioctyl 4‐cyclohexene‐1,2‐dicarboxylate (DOTH) and di‐isononyl‐cyclohexane‐1,2‐dicarboxylate (DINCH^®) for use as plasticizers in poly(vinyl chloride) (PVC) sheets. We also evaluated the biological safety of DOTH for its potential to be part of a safe PVC‐based blood container. The suppression of hemolysis in mannitol‐adenine‐phosphate / red cell concentrates (MAP/RCC) with DOTH/(DINCH^®‐PVC) sheets and the elution of plasticizers from the sheets increased with higher DOTH compositions. The properties of the PVC sheet containing DOTH and DINCH^® in the ratio of 25:33 parts against PVC 100 parts as a weight were almost identical to the PVC sheet made of di(2‐ethylhexyl) phthalate. From a subchronic toxicity test, DOTH did not show any adverse effects on all organs, including the testes, epididymis, liver, and kidneys. The no‐observed‐adverse‐effect level was 300 mg/kg body weight/day in a rat. These results suggest that DOTH/DINCH^® (25:33) is a promising candidate for the replacement of di(2‐ethylhexyl) phthalate in blood containers. J. VINYL ADDIT. TECHNOL., 22:520–528, 2016. © 2015 Society of Plastics Engineers     

Applicability of the generalized scaling law to a pile-inclined ground system subject to liquefaction-induced lateral spreading

The generalized scaling law is based on the concept of two-stage scaling and allows currently available centrifuge facilities to model a large-scale prototype expanding over the spatial dimension ranging from 30 m or larger subject to earthquake motions. This paper presents the results of investigation on the applicability of the generalized scaling law to the fully nonlinear regime of soil-structure system with the induced strain level of 10% in the order of magnitude. The centrifuge model tests performed in this study under the modeling of models scheme consist of a pile model embedded in a inclined ground subject to liquefaction-induced lateral spreading. Four different centrifugal accelerations ranging from 13g to 50g are used whereas the actual size of the physical model is kept constant with an overall scaling factor of 1/100. The models are exposed to tapered sinusoidal input accelerations of frequency 0.59 Hz and amplitude 3.0 m/s² in prototype scale, and the results are compared in terms of prototype by applying the generalized scaling law. As for the response of the ground during shaking, essentially identical accelerations and excess pore water pressures are recorded for all cases, while the lateral displacement shows a variation ranging from 5% to 9% in terms of shear strain due to a slight variation in experimental conditions (e.g., input peak acceleration, achieved density distribution). Practically the same responses are measured among the cases in the dissipation phase of excess pore water pressure. With regard to pile behavior, nearly identical responses for the lateral displacements and bending moments are obtained for all cases both during and after shaking. These results demonstrated that the generalized scaling law is applicable to the fully nonlinear regime of soil-structure system subject to the cumulative shear strain in the order of 10% due to cyclic mobility of sands during earthquakes.     

Influence of Acid Modification on Selective Phenol Hydrogenation Over Pd/Activated Carbon Catalysts

The influence of the acid treatment on cyclohexanone selectivity of phenol hydrogenation over Pd on active carbon was studied in liquid phase reaction and by temperature-programmed desorption. Acid treatment of activated carbon led to an increased cyclohexanone/cyclohexanol ratio. Acid modification of the carbon support enriched the electron density of Pd, and enhanced the desorption of the phenoxy species, which resulted in improved cyclohexanone selectivity in phenol hydrogenation.     

Controlled radical polymerization with polyolefin macroinitiator: a convenient and versatile approach to polyolefin-based block and graft copolymers

This paper introduces the new synthetic methodology of polyolefin-based block and graft copolymers with polar segments [e.g., polystyrene and poly(meth)acrylates]. Various brominated polyolefins were prepared by bromination of polyolefins with N-bromosuccinimide. The resulting brominated polyolefins were able to initiate the controlled radical polymerization of polar monomers, such as methyl methacrylate, ethyl acrylate, t-butyl acrylate, styrene and 2-(dimethylamino)ethyl acrylate, using a CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine catalyst system, leading to a variety of polyolefin-based copolymers with a different content of the corresponding polar segment. Because of the accessible synthesis of polyolefin macroinitiators, this synthetic methodology is expected to result in the preparation of a wide range of polyolefin-based block and graft copolymers.     

Thermal decomposition of cellulose/synthetic polymer blends containing grafted products. V. Cellulose/polystyrene blends

Homogeneous grafting of styrene onto cellulose was carried out in a dimethylacetamide/lithium chloride solvent system. The grafted products were added to cellulose/polystyrene (PS) blends as compatibilizers. The thermal decomposition behavior of the blends was investigated by thermogravimetry. The thermal stability of the blends decreased with an increase in grafted product content. The crystallinity of the blends decreased with grafted product content. The microphase‐separated structures of the blends became finer with grafted product content. The glass transition temperatures for cellulose and PS in the blends were lowered with grafted product content. Differences in thermal decomposition behavior of the blends were correlated with compatibility. Thermogravimetry was effective for compatibility estimation in cellulose/PS blends containing grafted products. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Numerical simulation of critical current performance in Nb3Sn strand subjected to periodic bending deformation

In the ITER Engineering Design Activity (EDA), four NB₃Sn model coils were developed and successfully tested. However, it was revealed that the critical current of the conductor degraded with the increase of electromagnetic force. One of the explanations of this phenomenon is a strand bending caused by enormous electromagnetic force. The authors therefore developed a simulation code using the distributed circuit model to investigate dependency of the critical current performance on the periodic bending deformation. The simulation results were in good agreement with the experiments. The dependence of the critical current on the periodic transverse load, temperature, periodic load pitch, thickness of Ta barrier which prevents Cu stabilizer from being contaminated by Sn, twist pitch of the strand, and RRR of the bronze matrix was investigated using the developed code. The results showed that the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that the shorter cabling pitch and the larger bending stiffness prevent the critical current degradation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 7–15, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20923