Mechanical Properties of Magnesium AZ31B Alloy After Ultrasonic Nanocrystal Surface Modification

Author(s):  
Xiaoning Hou ◽  
Ruixia Zhang ◽  
Zhencheng Ren ◽  
Chang Ye ◽  
Yalin Dong ◽  
...  

An innovative surface treatment method, ultrasonic nanocrystal surface deformation (UNSM), was used to process a magnesium (Mg) AZ31B alloy in this study. In the UNSM process, ultrasonic impacts induce plastic deformation on material surface that lead to grain refinement and surface morphology changes. The hardness, tensile strength, surface morphology and weight loss from immersion testing of the materials before and after UNSM were studied systematically. Compared with the unprocessed samples, the UNSM-processed samples show significant improvements in hardness (64%) and yield stress (43%). Surface topography results reveal that UNSM generates a smooth surface with an average roughness of 93 nm. In addition, the immersion results in cell medium demonstrate that the UNSM-processed group showed lower weight loss, especially during the early immersion period. It can thus be concluded that UNSM can significantly improve the hardness and yield strength of Mg alloys and reduce the corrosion rate, indicating that UNSM is a promising new method to enhance the mechanical properties of the degradable Mg alloys.

2021 ◽  
Vol 316 ◽  
pp. 893-898
Author(s):  
Natalya Gabelchenko ◽  
Artem Belov ◽  
Artem Kravchenko ◽  
Oleg Kryuchkov

We conducted comparative tests of the wear resistance of metals operating under abrasive conditions. Samples were cut from the working parts of mixer-pneumosuperchargers. The chemical composition and mechanical properties were determined. To compare samples under abrasive wear conditions, we designed and assembled a carousel installation. The principle of its operation is based on mixing the abrasive medium by the samples being studied with a given speed. Wear resistance was evaluated by weight loss by samples after several test cycles. To determine changes in the structure of the metal during abrasive wear, metallographic studies of the samples were carried out before and after the tests. It is shown that the best complex of service and mechanical properties is possessed by 110G13L steel.


2012 ◽  
Vol 576 ◽  
pp. 3-6 ◽  
Author(s):  
R. Bhuvenesh ◽  
M.S. Abdul Manan ◽  
M.H. Norizaman

Manufacturing companies define the qualities of thermal removing process based on the dimension and physical appearance of the cutting material surface. Therefore, the roughness of the surface area of the cutting material and the rate of the material being removed during the manual plasma arc cutting process was importantly considered. Plasma arc cutter Selco Genesis 90 was used to cut the specimens made from Standard AISI 1017 Steel manually based on the selected parameters setting. Two different thicknesses of specimens with 3mm and 6mm were used. The material removal rate (MRR) was measured by determining the weight of the specimens before and after the cutting process. The surface roughness (SR) analysis was conducted to determine the average roughness (Ra) value. Taguchi method was utilized as an experimental layout to obtain MRR and Ra values. The results reveal that for the case of manual plasma arc cutting machining, the SR values are inversely proportional to the MRR values. The quality of the surface roughness depends on the dross peak that occurred during the cutting process.


Author(s):  
Haomiao Li ◽  
Leonardo Severini ◽  
Mattia Titubante ◽  
Decai Gong ◽  
Laura Micheli ◽  
...  

Abstract Aqueous cleaning of works of art on paper is one of the most important and delicate steps in a conservation process. It allows the removal of inorganic (metals) and organic substances, such as degradation products and other contaminants. These substances are responsible for yellowing, weakening, and loss of mechanical properties of paper. In this article, the cleaning effect of gellan gum was assessed on xuan paper, a traditional Chinese paper different in composition and papermaking technology compared to many Western papers. To assess the effect of gellan gum on xuan paper, its characteristics were studied before and after cleaning utilizing non-invasive and micro-invasive techniques. Results were compared to those obtained when treating Western papers and indicated that gellan gum can be applied effectively for aqueous cleaning of xuan paper.


2018 ◽  
Vol 69 (05) ◽  
pp. 381-389
Author(s):  
MENGÜÇ GAMZE SÜPÜREN ◽  
TEMEL EMRAH ◽  
BOZDOĞAN FARUK

This study was designed to explore the relationship between sunlight exposure and the mechanical properties of paragliding fabrics which have different colors, densities, yarn counts, and coating materials. This study exposed 5 different colors of paragliding fabrics (red, turquoise, dark blue, orange, and white) to intense sunlight for 150 hours during the summer from 9:00 a.m. to 3:00 p.m. for 5 days a week for 5 weeks. Before and after the UV radiation aging process, the air permeability, tensile strength, tear strength, and bursting strength tests were performed. Test results were also evaluated using statistical methods. According to the results, the fading of the turquoise fabric was found to be the highest among the studied fabrics. It was determined that there is a significant decrease in the mechanical properties of the fabrics after sunlight exposure. After aging, the fabrics become considerably weaker in the case of mechanical properties due to the degradation in both the dyestuff and macromolecular structure of the fiber


1990 ◽  
Vol 156 (6) ◽  
pp. 875-877 ◽  
Author(s):  
I. M. Anderson ◽  
S. E. Gartside ◽  
P. J. Cowen

Overnight plasma melatonin level was measured in ten healthy women before and after a 4300 kJ (1000 kcaI) diet in which they lost an average 3.1 kg. This weight loss did not significantly alter melatonin levels.


Nutrients ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 1113
Author(s):  
Takeshi Kikutani ◽  
Yoko Ichikawa ◽  
Eri Kitazume ◽  
Arato Mizukoshi ◽  
Takashi Tohara ◽  
...  

Background: In older people with psychoneurological diseases, COVID-19 infection may be associated with a risk of developing or exacerbating dysphagia. The aim of the present study was to examine the relationship between eating/swallowing function and COVID-19 infection. Methods: Subjects were 44 inpatients with confirmed COVID-19 infection being treated for schizophrenia in a psychiatric ward. Eating function was assessed using the Food Intake Level Scale (FILS) before and after infection. We also evaluated age, comorbidities, COVID-19 hospital stay, obesity index, weight loss rate, and chlorpromazine equivalent. Results: Subjects had a mean age of 68.86 years. Pre-infection, 20 subjects had a FILS score of 7–9 (presence of eating/swallowing disorder) and 24 subjects had a score of 10 (normal). Eating function after infection resolution showed decreasing FILS score compared to that before infection in 14 subjects (74.14 years). Six subjects (79.3 years) transitioned from oral feeding to parenteral feeding. A ≥ 10% weight loss during infection treatment was significantly associated with decreased eating function and a transition to parenteral feeding. Chlorpromazine equivalents, comorbidities, and number of days of hospitalization showed no associations with decreased eating function. Conclusions: Preventing malnutrition during treatment for COVID-19 infection is important for improving post-infection life prognosis and maintaining quality of life (QOL).


Biomolecules ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 726
Author(s):  
Ronald Biemann ◽  
Enrico Buß ◽  
Dirk Benndorf ◽  
Theresa Lehmann ◽  
Kay Schallert ◽  
...  

Gut microbiota-mediated inflammation promotes obesity-associated low-grade inflammation, which represents a hallmark of metabolic syndrome. To investigate if lifestyle-induced weight loss (WL) may modulate the gut microbiome composition and its interaction with the host on a functional level, we analyzed the fecal metaproteome of 33 individuals with metabolic syndrome in a longitudinal study before and after lifestyle-induced WL in a well-defined cohort. The 6-month WL intervention resulted in reduced BMI (−13.7%), improved insulin sensitivity (HOMA-IR, −46.1%), and reduced levels of circulating hsCRP (−39.9%), indicating metabolic syndrome reversal. The metaprotein spectra revealed a decrease of human proteins associated with gut inflammation. Taxonomic analysis revealed only minor changes in the bacterial composition with an increase of the families Desulfovibrionaceae, Leptospiraceae, Syntrophomonadaceae, Thermotogaceae and Verrucomicrobiaceae. Yet we detected an increased abundance of microbial metaprotein spectra that suggest an enhanced hydrolysis of complex carbohydrates. Hence, lifestyle-induced WL was associated with reduced gut inflammation and functional changes of human and microbial enzymes for carbohydrate hydrolysis while the taxonomic composition of the gut microbiome remained almost stable. The metaproteomics workflow has proven to be a suitable method for monitoring inflammatory changes in the fecal metaproteome.


2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.


2021 ◽  
pp. 232020682110065
Author(s):  
Deniz Erdil ◽  
Nilsun Bagis ◽  
Hakan Eren ◽  
Melike Camgoz ◽  
Kaan Orhan

Aim: Bruxism is defined as the involuntary recurrent masticatory muscle activity characterized by gnashing, grinding, clenching of teeth, and/or pushing the mandible. Factors creating its etiology are peripheral (morphological) or central (physiopathological and physiological), and exogenous. Recently, among physiological factors, depression and bruxism were considered to be related. A definitive treatment method does not exist for bruxism; however, botulinum toxin-A (BT-A) application is an up-to-date and effective way of treatment. The present study is aimed to evaluate the levels of depression in bruxism patients treated with BT-A application. Materials and Methods: A total of 25 individuals (23 females and 2 males) who were diagnosed as bruxism patients were included in the study. 25 U of BT-A for each masseter muscle was injected into the patients. Patients were prospectively observed for a possible change in depression levels by using Beck’s Depression Inventory. The inventory was implemented before and six months after the BT-A application. Depression levels before and six months after the injection were compared. A paired t-test was used to compare “before” and “after” treatment values. One-way analysis of variance and post-hoc Tukey tests were used to evaluate the change in Beck’s Depression Inventory scores according to age groups. Results: The mean total score was 7.80 ± 8.10 before the treatment and 7.16 ± 6.52 six months after the treatment. The decrease in the mean score was not statistically significant ( P > .05). Conclusion: In conclusion, despite the decrease in the mean Beck’s Depression Inventory scores, a statistically significant decrease in the depression levels of patients was not observed.


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