Mechanical properties and microstructural analysis of an AgPd alloy cast under different temperatures

The metal restorations are used in Dentistry a long time ago. Nowadays we have resources that can get casting more accurate, with new material and equipments and techniques more precise. The purpose of this study was to evaluate the metallurgical and mechanical aspects of the AgPd dental alloy when it was submitted to different casting temperatures. It was used 30 specimens, divided in three groups (n=10): a) control group (no cast); b) casting temperature in accordance with the manufactures’ instructions (T1); b) casting temperature above manufactures´ instructions (like a torch) (T2). It was evaluated chemical and metallographic aspects, mechanical properties and Vickers hardness. The results showed a microstructure similar to T1 and T2 conditions, but with greater amount of light phase and particles in this last one. It was observed that the rupture tensile strength for the T1 condition was greater than the T2. The alloy in the no cast condition presented greater hardness but there was no statistically significant difference between T1 and T2. Supporting by the metallographic and mechanical results, it may predict that when elevated temperatures was used, above manufacture´s recommendations, it can occur failures in the prosthesis, like porosities, fissures or cracks.

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Suppression of transforming growth factor-β by mesenchymal stem-cells accelerates liver regeneration in liver fibrosis animal model

Zinc supplementation improves heme biosynthesis in rats exposed to lead ◽

10.18051/univmed.2021.v40.29-35 ◽

2021 ◽

Vol 40 (1) ◽

pp. 29

Author(s):

Nur Anna C Sa’dyah ◽

Agung Putra ◽

Bayu Tirta Dirja ◽

Nurul Hidayah ◽

Salma Yasmine Azzahara ◽

...

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Growth Factor ◽

Liver Fibrosis ◽

Transforming Growth Factor ◽

Healing Process ◽

Enzyme Linked Immunosorbent Assay ◽

Control Group ◽

Significant Difference ◽

T1 And T2

Introduction Liver fibrosis (LF) results from the unregulated chronic wound healing process in liver tissue. Transforming growth factor-beta (TGF-β) is the major contributing cytokine of LF promotion through activation of quiescent hepatic stellate cells (HSCs) into myofibroblasts (MFs) and increased extracellular matrix (ECM) deposition such as collagen leading to scar tissue development. Mesenchymal stem cells (MSCs) have an immunomodulatory capability that could be used as a new treatment for repairing and regenerating LF through suppression of TGF-β. This study aimed to examine the role of MSCs in liver fibrosis animal models through suppression of TGF-β levels without scar formation particularly in the proliferation phase. Methods In this study, a completely randomized design was used with sample size of 24. Male Sprague Dawley rats were injected intraperitoneally (IP) with carbon tetrachloride (CCl4), twice weekly, for eight weeks to induce LF. Rats were randomly assigned to four groups: negative control, CCl4 group, and CCL4 + MSC-treated groups T1 and T2, at doses of 1 x 106 and 2x106 cells, respectively. TGF-β levels were analyzed by enzyme-linked immunosorbent assay (ELISA). One-way ANOVA and a least significant difference (LSD) was used to analyse the data. Results The TGF levels of LF rat models decreased on day 7 after MSC administration. The levels of TGF-β in both MSC groups T1 and T2 decreased significantly compared with the control group (p<0.05). The TGF-β suppression capability of T2 was optimal and more significant than that of T1. Conclusion MSCs can suppress TGF levels in liver fibrosis induced rats.

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Stir zone material flow patterns during friction stir welding of heavy gauge AA5056 workpieces and stability of its mechanical properties

Metal Working and Material Science ◽

10.17212/1994-6309-2021-23.4-140-154 ◽

2021 ◽

Vol 23 (4) ◽

pp. 140-154

Author(s):

Tatiana Kalashnikova ◽

◽

Vladimir Beloborodov ◽

Kseniya Osipovich ◽

Andrey Vorontsov ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Friction Stir Welding ◽

Elevated Temperatures ◽

Thin Sheet ◽

Stir Zone ◽

Clear Correlation ◽

Material Structure ◽

Friction Stir ◽

Significant Difference

Introduction. Friction stir welding and processing are almost identical processes of severe plastic deformation at elevated temperatures. These technologies differ mainly in the purpose of its use: the formation of a hardened surface layer or producing a welded joint. However, it is known that both during welding and during processing of heavy gauge workpieces temperature gradients occur. As a result, the conditions of adhesive interaction, material plastic flow, and the formation of the stir zone change as compared to thin-sheet workpieces with fundamentally different heat dissipation rates. In this connection, the purpose of the work is to determine the regularities of the structure formation and stability of the mechanical properties in different directions in the material of 35-mm-thick aluminum-magnesium alloy samples produced by friction stir welding/processing. Research Methodology. The technique and modes of friction stir welding and processing of AA5056 alloy workpieces with a thickness of 35 mm are described. Data on the equipment used for mechanical tests and structural research are given. Results and discussion. The data obtained show the excess mechanical properties of the processing zone material over the base metal ones in all studied directions. Material structure heterogeneities after friction stir welding/processing of heavy gauge workpieces have no determining effect on the stir zone properties. At the same time, there is no clear correlation between the tensile strength values and the load application direction, nor is there any significant difference in mechanical properties depending on the location of the samples inside the stir zone. The average ultimate tensile strength values in the vertical, transverse, and longitudinal directions are 302, 295 and 303 MPa, respectively, with the yield strength values of 155, 153 and 152 MPa, and the relative elongation of 27.2, 27.5, 28.7 %.

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Effects of High Temperatures on the Physical and Mechanical Properties of Carbonated Ordinary Concrete

Advances in Materials Science and Engineering ◽

10.1155/2019/5753232 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 4

Author(s):

Qifang Xie ◽

Lipeng Zhang ◽

Shenghua Yin ◽

Baozhuang Zhang ◽

Yaopeng Wu

Keyword(s):

Mechanical Properties ◽

Weight Loss ◽

Elastic Modulus ◽

High Temperatures ◽

Elevated Temperatures ◽

Physical And Mechanical Properties ◽

Surface Characteristics ◽

Time Service ◽

Different Temperatures ◽

Cooling Methods

Fires are always known for seriously deteriorating concrete in structures, especially for those with certain carbonation due to long-time service. In this paper, 75 prism specimens were prepared and divided into four groups (three carbonated groups and one uncarbonated group). Specimens were tested under different temperatures (20, 300, 400, 500, 600, and 700°C), exposure times (3, 4, and 6 hours), and cooling methods (water and natural cooling). Surface characteristics, weight loss rate, and residual mechanical properties (strength, initial elastic modulus, peak, and ultimate compressive strains) of carbonated concrete specimens after elevated temperatures were investigated and compared with that of the uncarbonated ones. Results show that the weight loss rates of the carbonated concrete specimens are slightly lower than that of the uncarbonated ones and that the cracks are increased with raising of temperatures. Surface colors of carbonated concrete are significantly changed, but they are not sensitive to cooling methods. Surface cracks can be evidently observed on carbonated specimens when temperature reaches 400°C. Residual compressive strength and initial elastic modulus of carbonated concrete after natural cooling are generally larger than those cooled by water. The peak and ultimate compressive strains of both carbonated and uncarbonated concrete specimens increase after heating, but the values of the latter are greater than that of the former. Finally, the constitutive equation to predict the compressive behaviors of carbonated concrete after high temperatures was established and validated by tests.

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Diet-related changes in mechanical properties of rat vertebrae

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1992.262.2.r318 ◽

1992 ◽

Vol 262 (2) ◽

pp. R318-R321 ◽

Cited By ~ 2

Author(s):

G. J. Salem ◽

R. F. Zernicke ◽

R. J. Barnard

Keyword(s):

Mechanical Properties ◽

Vertebral Body ◽

Calcium Metabolism ◽

Bone Mineralization ◽

Maximum Load ◽

Control Group ◽

Buffer Solution ◽

Cross Sectional ◽

Lumbar Vertebral Body ◽

Significant Difference

High fat and sucrose (HFS) diets may induce glucose intolerance, alter calcium metabolism, and lead to deficits in bone mineralization, development, and mechanical properties. To determine the mechanical and structural consequences of a HFS diet on rapidly growing vertebrae, female Sprague-Dawley rats (8 wk) were assigned randomly (2:1) either to a control group (n = 20) fed a low-fat complex-carbohydrate diet or an experimental group (n = 10) fed a HFS diet for 10-12 wk. The sixth lumbar vertebral body (L6) was isolated from the pedicles, morphological measures were taken, and compression was tested at a fast strain rate, while immersed in a warmed (37 degrees C) isotonic physiological buffer solution. No significant difference in body mass existed between HFS and control groups; nevertheless, HFS L6 cross-sectional areas, lengths, and volumes were significantly smaller than controls. The HFS L6 also had significantly lower mechanical properties, including initial maximum load, energy at initial maximum load, and strain energy density at initial maximum load. Diets high in sucrose and fat content have been associated with changes in calcium metabolism, and the results of the current study suggest that in immature vertebrae, a HFS diet may adversely affect vertebral body mechanical integrity and strength.

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Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties

Metals ◽

10.3390/met10070884 ◽

2020 ◽

Vol 10 (7) ◽

pp. 884 ◽

Cited By ~ 1

Author(s):

Seyed Vahid Sajadifar ◽

Emad Scharifi ◽

Ursula Weidig ◽

Kurt Steinhoff ◽

Thomas Niendorf

Keyword(s):

Mechanical Properties ◽

Elevated Temperatures ◽

Tensile Tests ◽

Uniaxial Tensile ◽

Forming Process ◽

Softening Mechanism ◽

Rate Dependent ◽

Heat Treated ◽

Different Temperatures ◽

Die Forming

This study focuses on the high temperature characteristics of thermo-mechanically processed AA7075 alloy. An integrated die forming process that combines solution heat treatment and hot forming at different temperatures was employed to process the AA7075 alloy. Low die temperature resulted in the fabrication of parts with higher strength, similar to that of T6 condition, while forming this alloy in the hot die led to the fabrication of more ductile parts. Isothermal uniaxial tensile tests in the temperature range of 200–400 °C and at strain rates ranging from 0.001–0.1 s−1 were performed on the as-received material, and on both the solution heat-treated and the thermo-mechanically processed parts to explore the impacts of deformation parameters on the mechanical behavior at elevated temperatures. Flow stress levels of AA7075 alloy in all processing states were shown to be strongly temperature- and strain-rate dependent. Results imply that thermo-mechanical parameters are very influential on the mechanical properties of the AA7075 alloy formed at elevated temperatures. Microstructural studies were conducted by utilizing optical microscopy and a scanning electron microscope to reveal the dominant softening mechanism and the level of grain growth at elevated temperatures.

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Influence of Annealing Temperature and Time on the Mechanical Properties of Selected Steels for Heavy Forgings

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.647.38 ◽

2015 ◽

Vol 647 ◽

pp. 38-46

Author(s):

Jakub Horník ◽

Petr Zuna ◽

Jaroslav Malek ◽

Tomáš Jetmar ◽

Josef Kasl ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Grain Boundary ◽

Impact Energy ◽

Experimental Evaluation ◽

Annealing Temperature ◽

Elevated Temperatures ◽

Long Time ◽

Grain Boundary Embrittlement ◽

Boundary Embrittlement

Two types of steels used for production of heavy forgings were selected for the experimental evaluation of the effect of long time dwell at elevated temperatures and cooling during heat treatment on their mechanical properties in order avoid the possibility of grain boundary embrittlement. Samples from evaluated steels 26NiCrMoV14-5 and 22CrNiMoWV8-8 were austenitized for 2 hours at temperature of 1200°C and oil quenched. Subsequently the annealing at temperatures (200 - 700)°C for 1 hour and 100 hours was applied. Selected mechanical properties, especially hardness and impact energy, were monitored. It was found that for steels 26NiCrMoV14‑5 and 22CrMoNiWV8-8 exist the temperature intervals (300 - 400)°C and (500 ‑ 600)°C respectively with the possible potential for toughness decreasing.

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Effect of 5% Calcium Hypochlorite on Mechanical Properties of Root Dentin: An in vitro Study

Journal of Operative Dentistry & Endodontics ◽

10.5005/jp-journals-10047-0012 ◽

2016 ◽

Vol 1 (2) ◽

pp. 56-59

Author(s):

Natanasabapathy Velmurugan ◽

Poornima Reddy ◽

Suma Balla ◽

Sandhya S Raghu ◽

Garlapati T Gupta ◽

...

Keyword(s):

Mechanical Properties ◽

Flexural Strength ◽

Modulus Of Elasticity ◽

In Vitro Study ◽

Chlorine Concentration ◽

Control Group ◽

Calcium Hypochlorite ◽

Significant Difference ◽

Root Dentin

ABSTRACT Introduction The aim of this study was to compare in vitro the effect of 5% calcium hypochlorite [Ca(OCl)2] and 5% sodium hypochlorite (NaOCl) on flexural strength and modulus of elasticity of root dentin. Materials and methods The available chlorine concentration of each solution was determined using iodometric titration. Standardized planoparallel dentin bars (n= 20) were divided into two test groups and one control group. The control, group 1, consisted of dentin bars stored in normal saline. The dentin bars in the two test groups were treated by exposure to following solutions: Group 2 to 5% Ca(OCl)2; and group 3 to 5% NaOCl. All the three test solutions were changed once in 15 minutes for 30 minutes. The dentin bars were then loaded to failure using three-point bend test. Results Available chlorine concentration was 64% in both the test solutions. There was a significant reduction in the flexural strength of 5% NaOCl group compared to 5% Ca(OCl)2-treated ones. A significant difference in modulus of elasticity was observed between the test groups and the control groups and also between the 5% Ca(OCl)2 and 5% NaOCl groups. Conclusion Within the limitations of this study, 5% NaOCl reduced the flexural strength and modulus of elasticity of root dentin bars more when compared to 5% Ca(OCl)2. How to cite this article Reddy P, Balla S, Raghu SS, Velmurugan N, Gupta GT, Sahoo HS. Effect of 5% Calcium Hypochlorite on Mechanical Properties of Root Dentin: An in vitro Study. J Oper Dent Endod 2016;1(2):56-59.

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Influence of Concentrations of Methacrylate and Acrylate Monomers on the Properties of Fiber Reinforced Polymethyl Methacrylate Denture Base Materials

Acta Chemica Iasi ◽

10.2478/achi-2018-0020 ◽

2018 ◽

Vol 26 (2) ◽

pp. 329-350 ◽

Cited By ~ 2

Author(s):

Faik Tugut ◽

Mehmet Turgut ◽

Dursun Saraydin

Keyword(s):

Mechanical Properties ◽

Impact Strength ◽

Testing Machine ◽

Weight Ratio ◽

Acrylic Resin ◽

Bending Test ◽

Control Group ◽

Test Machine ◽

Fiber Reinforced ◽

Significant Difference

Abstract The study aimed to evaluate the effects of adding different concentrations of 2 hydroxyethyl methacrylate (HEMA), 2-hydroxyethyl acrylate (HEA), ethyl methacrylate (EA) and isobutyl methacrylate (IBMA) monomers on the structural, thermal and mechanical properties of a fiber reinforced heat-polymerized acrylic resin. For each test, 126 acrylic resin specimens were fabricated and divided into 6 groups with 7 specimens each. One group was the control group, the other one is a fiber reinforced group and others were the test groups, which were formed according to the different concentrations of monomers. 6 mm length, and the weight ratio of 3% short glass fibers are added to acrylic powder polymerized by heating. The 2%, 5%, 10%, at 20 % ratios of different comonomers added to a monomer of MMA are composed of copolymer structures. Flexural strength was assessed with a three-point bending test using a universal testing machine. Impact strength testing was conducted using an impact test machine by the Charpy method. The analysis of the connection between acrylic resin and fiber by SEM and structural changes in the acrylic resin was investigated by FTIR spectroscopy. Data analyses using analysis of Kruskal-Wallis and Mann-Whitney U tests (α=0.05) significant difference tests showed that adding 2%, 5% HEMA and IBMA monomers significantly increased the flexural and impact strength compared to the control, only fiber and others group (P< 0.05). It is observed that the process of adding low concentration of HEMA and IBMA monomers improved certain mechanical properties of fiber reinforced with polymethylmethacrylate.

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Experimental and Theoretical Investigation on the Thermo-Mechanical Properties of Recycled Aggregate Concrete Containing Recycled Rubber

Frontiers in Materials ◽

10.3389/fmats.2021.655097 ◽

2021 ◽

Vol 8 ◽

Author(s):

Yunchao Tang ◽

Wanhui Feng ◽

Zheng Chen ◽

Yumei Nong ◽

Minhui Yao ◽

...

Keyword(s):

Mechanical Properties ◽

Elevated Temperatures ◽

Microstructural Analysis ◽

Strain Curve ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Stress Strain ◽

Aggregate Concrete ◽

Recycled Rubber

The utilization of recycled aggregates made from construction wastes and recycled rubber made from waste tires is an effective method to realize the sustainable development. Thus, this study aims to determine the feasibility of using recycled aggregate concrete containing rubber, named rubberized recycled aggregate concrete (RRAC) as a new type of green-building material. The experimental carbon emissions test verified RRAC as a low-carbon material. In addition, the residual mechanical properties of RRAC were investigated under elevated temperatures. After exposure at 200, 400, and 600 C for 60 min, the stress−strain curve, compressive strength, energy absorption capacity, and spalling resistance of RRAC with recycled aggregate replacement ratios of 50 and 100%, rubber contents of 0, 5, 10, and 15% were explored with microstructural analysis. Moreover, empirical models were proposed to describe the effects of heated temperatures and rubber contents on the stress–strain relationship of RRAC. The results indicated that the rubber particles could reduce the spalling of specimens based on the vapor pressure theory. Therefore, this study provided scientific guidance for the design of structures made with RRAC for resisting high temperatures.

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Teratogenic effects of Metoprolol in the chick embryos

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v39i1.196 ◽

2015 ◽

Vol 39 (1) ◽

pp. 49-55

Author(s):

Abbas Razzaq Abed

Keyword(s):

Histopathological Examination ◽

Inflammatory Cells ◽

Heart Tissue ◽

Control Group ◽

Control Groups ◽

Teratogenic Effects ◽

Fourth Group ◽

The Third ◽

Significant Difference ◽

T1 And T2

This study was conducted to demonstrate the effect of Metoprolol on chicken embryos during the period of cuddling automated .This study was completed in Babylon hatchery dedicated to the production of chick chickens, which is located in the province of Babylon. One hundred eggs (Belgian origin, CZ 1924) were divided into equal four groups. The first group injected eggs by Metaprolol at dose 10 mg /70kg BW, and the second group eggs was injected by Metoprolol at dose 15 mg /70kg BW, while eggs in the third group was injected by physiological normal saline only and the fourth group did not inject their eggs any material and considered the control group and all the eggs used in this experiment to take on the fourth day of cuddling. The results of this study showed a decrease in the percentage hatching in groups injected with Metoprolol (T1 and T2 groups, 4% and 13%, respectively) compared to the T3 and the control groups. Also showed the results of the current study, no significant difference at the level of (P <0.05) in the weights of embryos after hatching. While histopathological examination showed the presence of pathological lesions in the heart tissue in injected eggs groups by Metoprolol (T1 and T2 groups) and included these changes infiltration of inflammatory cells, thickening in epicardium and the presence of vacuolation in heart tissue with the appearance of edema, heart tissue damage, congestion in the blood vessels and the occurrence of hemorrhage.

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