Development and validation of a new friction model for cutting processes

The International Journal of Advanced Manufacturing Technology - The friction model in the tool-chip interface has significant influences on predicting chip forms, cutting forces, and cutting tool...     

Visualization of Knoop Indentation Damage of Silicon Nitride by Plasma Etching

A visualizing technique for indentation damage of ceramics was developed. Plasma etching was used to enhance the view of cracks and the subsurface microcracking crush zone following Knoop indentation of hot pressed Si₃N₄. The microcracking zone was readily identified from the surface view of the indented surface as a grain-falling-off region (GFOR), defined as a region in which grains were removed by preferential etching using CF₄ gas, followed by ultrasonic cleaning. A fissure-like opening corresponding to the indentation cracks was also observed. It is inferred that the formation of the GFOR region and the fissure-like opening were caused by the etching/cleaning treatment. Meanwhile, the etching on a section which included diagonals of the impression provided a section view of the microcracking zone.     

Inclusions in commercial low and medium carbon ferromanganese

The microstructures of commercial low and medium carbon ferromanganese have been studied by optical microscopy and electron microprobe techniques. Element analysis and mapping have been performed on impurities in the matrix and nonmetallic inclusions present. The results show that the most common nonmetallic inclusion is managanese oxide, followed by complex compounds of managanese oxide, silicon oxide, and manganese sulfide. The different inclusions have been assessed according to the SS 111116 method. It follows that over 85 pct of the present nonmetallic inclusions are manganese oxides and that the amount of manganese oxide inclusions is inversely proportional to the carbon content in standard refined ferromanganese.     

Effect of bus size and operation to crash occurrences

This paper evaluates roadway and operational factors considered to influence crashes involving buses. Factors evaluated included those related to bus sizes and operation services. Negative binomial (NB) and multinomial logit (MNL) models were used in linearizing and quantifying these factors with respect to crash frequency and injury severities, respectively. The results showed that position of the bus travel lane, presence or absence of on-street shoulder parking, posted speed limit, lane width, median width, number of lanes per direction and number of vehicles per lane has a higher influence on bus crashes compared to other roadway and traffic factors. Wider lanes and medians were found to reduce probability of bus crashes while more lanes and higher volume per lane were found to increase the likelihood of occurrences of bus-related crashes. Roadways with higher posted speed limits excluding freeways were found to have high probability of crashes compared to low speed limit roadways. Buses traveling on the inner lanes and making left turns were found to have higher probability of crashes compared to those traveling on the right most lanes. The same factors were found to influence injury severity though with varying magnitudes compared to crash frequency.     

Mechanical and magnetic properties of Ni-Co dispersed Al2O3 nanocomposites

Effects of the fabrication processing on the microstructure and properties of composites were investigated. High-density Ni-Co dispersed-Al₂O₃ (Al₂O₃/Ni-Co) composites were obtained by hydrogen reduction and consolidated using hot pressing and pulse electric current sintering (PECS) of Al₂O₃, Ni(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O powder mixtures. Microstructural investigations of the hot-pressed composite fabricated using again wet/dry ball-milled powder mixture after calcination revealed that fine Ni-Co particles, about 145 nm in diameter, dispersed homogeneously at the matrix grain boundaries. In particular, fine microstructure of dispersion with the average size of 90 nm was realized for the specimen consolidated by PECS method. High strength of over 1 GPa and hardness of 19 GPa were measured for the nanocomposites prepared from the again ball-milled powder mixture. The ferromagnetism of nano-sized Ni-Co contributes to the magnetic properties of the composites. A change in the coercive force with dispersion size was observed. Also, the extent of magnetic response by an applied stress was strongly influenced by the size of Ni-Co particles. The relations between microstructure and mechanical as well as magnetic properties are discussed.     

Microstructure and mechanical properties of Y2O3/SiC nanocomposites

 Y₂O₃-based nanocomposites were fabriacted by hot-press and the microstructures and mechanical properties were investigated. Transmission-electron-microscope observations revealed that the SiC particles were distributed both within Y₂O₃ matrix grains and at the grain boundaries. Significant mechanical properties improvements were identified particularly at high temperatures above 1000 oC both in air and inert atmospheres. Received: 2 January 1997 / Accepted: 27 March 1997     

Immunohistochemistry of lymphocytes and macrophages in human celloidin-embedded temporal bone sections with acute otitis media

Immunohistochemical analyses were used to investigate the distribution of lymphocytes and macrophages in routine human temporal bone sections obtained from a subject with acute suppurative otitis media. Primary antibodies specific for human CD3 and CD43 (T-lymphocytes), CD20 (B-lymphocytes), CD45 (leukocyte common antigen), and CD68 (macrophages) were used. As a pretreatment, the sections were soaked in antigen retrieval solution (saturated sodium hydroxide-methanol solution in methanol at a ratio of 1:3). A second antigen retrieval procedure (microwave treatment in 1% zinc sulfate) was also employed for identifying CD3-positive cells. Then the avidin-biotin-peroxidase complex technique was performed. Positive reactions to all antibodies but anti-CD68 were observed in the mucosa of the eustachian tube, tympanic cavity, and mastoid air cells. Particularly, cells positive to anti-CD3 or anti-CD43 were making a diffuse invasion upon the lamina propria. CD68-positive cells were scattered only in the effusion of mastoid air cells. These results suggest that the retrospective immunohistochemical study of archival temporal bone sections is a promising approach to investigate the pathogenesis of otitis media.     

Interfacial Strain Gradients Control Nanoscale Domain Morphology in Epitaxial BiFeO3 Multiferroic Films

Domain switching pathways fundamentally control performance in ferroelectric thin film devices. In epitaxial bismuth ferrite (BiFeO₃) films, the domain morphology is known to influence the multiferroic orders. While both striped and mosaic domains have been observed, the origins of the latter have remained unclear. Here, it is shown that domain morphology is defined by the strain profile across the film–substrate interface. In samples with mosaic domains, X‐ray diffraction analysis reveals strong strain gradients, while geometric phase analysis using scanning transmission electron microscopy finds that within 5 nm of the film–substrate interface, the out‐of‐plane strain shows an anomalous dip while the in‐plane strain is constant. Conversely, if uniform strain is maintained across the interface with zero strain gradient, striped domains are formed. Critically, an ex situ thermal treatment, which eliminates the interfacial strain gradient, converts the domains from mosaic to striped. The antiferromagnetic state of the BiFeO₃ is also influenced by the domain structure, whereby the mosaic domains disrupt the long‐range spin cycloid. This work demonstrates that atomic scale tuning of interfacial strain gradients is a powerful route to manipulate the global multiferroic orders in epitaxial films.