scholarly journals Edge Crack Behavior and Strengthening Mechanism of Width-limited Rolled AZ31 Magnesium Sheet with Large Reduction

2021 ◽  
Vol 57 (8) ◽  
pp. 146
2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
M. Saravani ◽  
M. Azizi

V-notches are the most possible case for initiation of cracks in engineering structure. Cracks on the notch tip can be characterized by opening angle, tip radius, and depth of the V-notch. In this study, the effects of V-notch's opening angle on stress intensity factor and on -stress of the crack have been investigated in detail. Our calculation has been performed in a number of opening angles and various crack lengths in mode I loading using photoelasticity method. We show that as opening angle grows at constant crack's length, SIF and -stress decrease. Furthermore, as the crack's length increases, the V-notch effect diminishes and the crack behavior can be considered as a single-edge crack specimen. Finally, the obtained results were found to be in good agreement with outcome of numerical finite element analysis.


Author(s):  
T. Y. Tan ◽  
W. K. Tice

In studying ion implanted semiconductors and fast neutron irradiated metals, the need for characterizing small dislocation loops having diameters of a few hundred angstrom units usually arises. The weak beam imaging method is a powerful technique for analyzing these loops. Because of the large reduction in stacking fault (SF) fringe spacing at large sg, this method allows for a rapid determination of whether the loop is faulted, and, hence, whether it is a perfect or a Frank partial loop. This method was first used by Bicknell to image small faulted loops in boron implanted silicon. He explained the fringe spacing by kinematical theory, i.e., ≃l/(Sg) in the fault fringe in depth oscillation. The fault image contrast formation mechanism is, however, really more complicated.


2021 ◽  
pp. 002203452110038
Author(s):  
C.E. Fernández ◽  
C.A. Maturana ◽  
S.I. Coloma ◽  
A. Carrasco-Labra ◽  
R.A. Giacaman

The dental profession has experienced a dramatic acceleration in the use of communication systems and information-based technologies over recent years, originating new paradigms for the prevention and promotion of oral health. The purpose of this systematic review was to determine the effect of teledentistry-based (telematic) strategies, reported in randomized controlled trials and quasi-randomized trials, with a focus on oral health prevention and promotion–related outcomes in patients of all ages. We searched Medline via PubMed, SCOPUS, and Web of Science from inception until August 2020, regardless of the language of publication. We selected studies for inclusion and conducted data extraction, assessed risk of bias (Cochrane tool), and evaluated the certainty of the evidence (GRADE approach) in duplicate and independently. Out of 898 potentially eligible references, we selected 43 for full-text screening, of which 19 studies proved eligible: 18 randomized controlled trials and 1 quasi-randomized study. Virtual interventions were mostly asynchronous via apps ( n = 9), text messages ( n = 9), or computer-aided learning ( n = 1). The use of teledentistry as compared with conventional strategies may result in a large reduction in the plaque index (standardized mean difference, −1.18; 95% CI, −1.54 to −0.82; I2 = 92%; low certainty) and will likely result in a large reduction in the gingival index (standardized mean difference, −2.17; 95% CI, −3.15 to −1.19; I2 = 97%; moderate certainty) and in the incidence of white spot lesions (risk ratio, 0.48; 95% CI, 0.35 to 0.66; I2 = 0%; moderate certainty), with an increased effect over time. Evidence suggests that teledentistry, particularly mHealth (messages and apps), is a promising clinical tool for preventing and promoting oral health, especially under the accelerated virtualization of dentistry. Future studies should include a broader spectrum of the population, including adults and elders, to better inform policy and implementation of teledentistry (PROSPERO: CRD42020192685).


Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 842
Author(s):  
Wenming Jin ◽  
Jianhao Yu ◽  
Zhiqiang Zhang ◽  
Hongjie Jia ◽  
Mingwen Ren

Contact solution treatment (CST) of Al–Zn–Mg–Cu alloys can shorten solution time to within 40 s in comparison with 1800 s with traditional solution treatment using a heating furnace. Heating temperature is the key factor in solution treatment. Considering the short heating time of CST, the ultra-high solution temperature over 500 °C of Al–Zn–Mg–Cu alloys was studied in this work. The effects of solution temperatures on the microstructures and the mechanical properties were investigated. The evolution of the second phases was explored and the strengthening mechanisms were also quantitatively evaluated. The results showed that solution time could be reduced to 10 s with the solution temperature of 535 °C due to the increasing dissolution rate of the second phase and the tensile strength of the aged specimen could reach 545 MPa. Precipitation strengthening was the main strengthening mechanism, accounting for 75.4% of the total strength. Over-burning of grain boundaries occurred when the solution temperature increased to 555 °C, leading to the deterioration of the strength.


2021 ◽  
Vol 692 (3) ◽  
pp. 032068
Author(s):  
Xue Zhang ◽  
Jin Du ◽  
Guosheng Su ◽  
Tingting Zhou ◽  
Chongyan Zhang ◽  
...  

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