Investigation into the effect of material properties and arrangement of each layer on the formability of bimetallic sheets
JOURNAL OF MANUFACTURING PROCESSES
Authors: Darabi, Roya; Azodi, Hamed Deilami; Bagherzadeh, Saeed
Abstract
The application of bimetallic sheets composed of two dissimilar sheet metals with distinct properties has increasingly developed in recent years. Enhancement of bimetallic sheet's formability by designing of appropriate layers is an important challenge for industrialization of these sheets. The main objective of this paper is investigation on the influence of material properties of layers on the formability of bimetallic sheets analytically and experimentally. The analytical model was developed to predict forming limit diagram (FLD) based on M-K(model using both the Hill's and Barlat-Lian yield functions. The experimental works was performed on Aluminum (AL3105)/Carbon steel (St14) sheets for verification of analytical model. Results showed that the formability of bimetallic sheet is enhanced by increasing of the strain hardening and strain rate sensitivity exponents of layers, although variation of the exponent coefficient of the layer with higher formability was more effective than layer with lower formability. In addition, the results demonstrated a significant nonlinear effect of variation in thickness of layers on the FLD0 index. It is found that the influence of anisotropy coefficient of layers is negligible in comparison with other material parameters, but the arrangement of anisotropic steel layer with isotropic aluminum layer as well as the arrangement of layers in the aligned rolling direction (0-0) can slightly improve the formability of two-layer sheets. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
Clonal Expansion of Macrolide-Resistant Sequence Type 3 Mycoplasma pneumoniae, South Korea
EMERGING INFECTIOUS DISEASES
Authors: Lee, Joon Kee; Lee, Joon Ho; Lee, Hyunju; Ahn, Young Min; Eun, Byung Wook; Cho, Eun Young; Cho, Hwa Jin; Yun, Ki Wook; Lee, Hoan Jong; Choi, Eun Hwa
Abstract
To investigate the genetic background for the emergence of macrolide resistance, we characterized the genetic features of Mycoplasma pneumoniae using multilocus sequence typing. Of the 146 M. pneumoniae strains collected during the 5 consecutive outbreaks of M. pneumoniae pneumonia during 2000-2016 in South Korea, macrolide resistance increased from 0% in the first outbreak to 84.4% in the fifth. Among the 8 sequence types (STs) identified, ST3 (74.7%) was the most prevalent, followed by ST14 (15.1%). Macrolide-susceptible strains comprised 8 different STs, and all macrolide-resistant strains were ST3 (98.3%) except 1 with ST14. The proportion of macrolide-resistant strains in ST3 remained 2.2% (1/46) until the 2006-2007 outbreak and then markedly increased to 82.6% (19/23) during the 20102012 outbreak and 95.0% (38/40) during the 2014-2016 outbreak. The findings demonstrated that clonal expansion of ST3 M. pneumoniae was associated with the increase in macrolide resistance in South Korea.