New Mathematical Stress Analysis in the Compressive Stage of the High-Pressure Torsion Process

S. Hadi,F. Rahimzadeh lotfabad,M. H. Paydar,R. Ebrahimi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

In this study, a mathematical analysis based on the slab method is used to drive a formula to calculate the average hydrostaticpressure in the compressive stage of the HPT process. The analytical method used here leads to a relationship for describingthe average hydrostatic pressure as a function of the material shear strength, sample volume, cavity volume and force. Basedon the results obtained and by employing the Sturm’s theorem for polynomials, a general expression for the minimum forcerequired to start the deformation of the material under compressive force and creation of flash is developed. The analyticalresults were confirmed by carrying out some experiments by using commercial pure aluminum and copper as test materials. The experimental results showed good congruence with the analytical calculations. The most important outcome of thisanalysis is that with an appropriate selection of the sample volume, considering the capacity of the HPT press facility andthe proper choice of the die cavity volume, favorable average hydrostatic pressure, necessary for the purpose of applicationcan be achieved.

Thermoelastoplastic response of FGM linearly hardening rotating thick cylindrical pressure vessels

Tayebeh Ebrahimi,Mohammad Zamani Nejad,Hamid Jahankohan,Amin Hadi 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.2

An analytical solution is presented to analyze the thermoelastoplastic response of a rotating thick-walled cylindrical pressure vessel made of functionally graded material (FGM). The analysis is based on Tresca's yield condition, its associated flow rule and linear strain hardening material behaviour. The uncoupled theory of thermoelasticity is used, and the plane strain condition is assumed. The material properties except for Poisson's ratio, are assumed to vary nonlinearly in the radial direction. Elastic, partially plastic, fully plastic, and residual stress states are investigated. The heat conduction equation for the one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the vessel. It is assumed that‏ the inner surface is exposed to an airstream and that the outer surface is exposed to a uniform heat flux. Tresca's yield criterion and its associated flow rule are used to formulate six different plastic regions for a linearly hardening‏ condition. All these stages are studied in detail. It is shown that the thermoelastoplastic stress response of a rotating FGM pressure vessel is affected significantly by the nonhomogeneity of the material and temperature gradient. The results are validated with those of other researchers for appropriate values of the system parameters and excellent agreement is observed.

The experimental and numerical study of the effects of welding angle on forming multilayered sheets in U-bending operations

Ali Adelkhani,Hadi Ebrahimi,Mohammad Mahdi Attar 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

Performed was a set of experimental tests to scrutinize the effect of the welding angle and material properties on the spring-back and the displacement as well as the amount of required load in the standard bending test according to ASTM B820-18 with some numerical simulation conducting to compare those results and calculate stress through the bending process. The applied sheets were made of Copper, Aluminum and St12, DIN1623 with a thickness of 1 mm. In this study, prepared is a welding line at three angles, 30 0 , 45 0 and 90 0 whilst two punch’s radiuses have been considered. Additionally, three orientations 0 0 , 45 0 and 90 0 have been considered to check the homogeneity of the plate. Added to this, a numerical analysis utilizing finite element methods was conducted to validate the results obtained from the experimental tests. based on results, there wasn’t seen any considerable difference (less than 10 %) in terms of un-homogeneity in results while the minimum springback pressure for the St12-Cu sheet was equal to 3.6, and measured 3.70 for St12-Al. In the numerical solution, the maximum stress for the welding angle, 30, in St12-Al sheet was 305 MPa with the springback decreasing from 0.1 to 0.5 whenever the pitch radius changing from 5 to 10 mm.

Effect of Selenium Supplementation on Expression of SIRT1 and PGC-1α Genes in Ulcerative Colitis Patients: a Double Blind Randomized Clinical Trial

( Maryam Khazdouz ),( Naser Ebrahimi Daryani ),( Foroogh Alborzi ),( Mir Hadi Jazayeri ),( Farnaz Farsi ),( Motahareh Hasani ),( Javad Heshmati ),( Farzad Shidfar ) 한국임상영양학회 2020 Clinical Nutrition Research Vol.9 No.4

Selenium (Se) supplementation may decrease the severity of ulcerative colitis (UC) through the activation of genes responsible for immune modulation. The present research was aimed to assess the effect of Se supplementation on the expression of silent information regulator 1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) in UC patients. In a double-blind randomized parallel clinical trial, 100 patients with mild-to-moderate active UC met inclusion criteria and divided into 2 groups of treatment (50 patients received selenomethionine [200 μg daily]) and placebo (50 patients received placebo [1 capsule daily]) for 10 weeks. The expression rates of SIRT1 and PGC-1α were examined in the peripheral blood mononuclear cell (PBMC) using the real-time polymerase chain reaction. There was no considerable difference in the mean of baseline demographic and clinical characteristics between groups. Also, there were no significant differences in total energy intake, macronutrients, and micronutrients between groups. The SIRT1 gene expression in the Se group was significantly increased compared to the placebo (p < 0.001). An increase in the expression of the PGC-1α gene in the Se group was not statistically significant. It seems that Se supplementation caused a significant decrease in the inflammatory response of the colon by a significant increase in the expression of the SIRT1 gene.

The effect of adding ethanolic saffron petal extract and vitamin E on growth performance, blood metabolites and antioxidant status in Baluchi male lambs

Fereshteh Alipour,Ali Reza Vakili,Mohsen Danesh Mesgaran,Hadi Ebrahimi 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.11

Objective: This study investigated the effects of the administration of ethanolic saffron petal extract (SPE) and vitamin E (Vit E) on growth performance, blood metabolites and antioxidant status in Baluchi lambs. Methods: Thirty-two Baluchi male lambs (35.22±5.75 kg) were randomly divided into 4 groups. The 1st (control), 2nd (injectable saffron petal extract [ISPE]), and 3rd (Vit E) groups were respectively injected subcutaneously with either physiological saline (5 mL), SPE (25 mg/kg body weight [BW]) or DL-α-tocopheryl acetate (225 IU) once a week. An oral dose of SPE (500 mg/kg BW) was also administered to the 4th group (oral saffron petal extract [OSPE]). Feed intake and BW were measured for 42 days and blood samples were taken on days 1, 14, 28, and 42. The lambs were slaughtered, and tissue samples were taken. Results: Growth performance and many blood metabolites were not affected (p>0.05) by the treatments. Cholesterol of plasma in the ISPE and Vit E groups was similar and less (p< 0.01) than both the OSPE and control groups. Although there was no significant difference between the control and other groups for plasma triglyceride, the ISPE group showed lower (p<0.05) triglyceride than the OSPE and Vit E groups. The highest (p<0.01) plasma glutathione peroxidase (GPx) was detected in the OSPE group, while the ISPE and Vit E groups showed higher (p<0.01) superoxide dismutase (SOD) of plasma than the control. Malondialdehyde of plasma in the ISPE group was lower (p<0.05) than the OSPE. No differences (p>0.05) were observed among the groups for antioxidant status of both longissimus dorsi muscle and liver. However, the activity of GPx in the kidney and heart, as well as SOD activity in the kidney, were influenced (p≤0.01) by the treatments. Conclusion: Adding ethanolic SPE improved antioxidant status and lowered lipids oxidation in lambs. The SPE and Vit E demonstrated similar effects on antioxidant status in lambs.

Influence of barley grain treated with alkaline compounds or organic extracts on ex vivo site and extent of digestion of starch

Reza Naseroleslami,Mohsen Danesh Mesgaran,Abdolmansour Tahmasbi,Seyed Alireza Vakili,Seyed Hadi Ebrahimi 아세아·태평양축산학회 2018 Animal Bioscience Vol.31 No.2

Objective Two ex vivo experiments were conducted to verify the effect of barley grain (Nusrat cultivar) treated with alkaline compounds (AC) including alum, ammonium, and sodium hydroxide or cation-exchanged organic extracts (OE) prepared from alfalfa hay, sugar beet pulp and Ulva Fasciata, on extent and digestion of starch. Methods In the first study, the in vitro first order disappearance kinetic parameters of dry matter (DM), crude protein (CP) and starch were estimated using a non-linear model (D(t) = D(i) · e(−kd · time) + I, where: D(t) = potentially digestible residues at any time, D(i) = potentially digestible fraction at any time, kd = fractional rate constant of digestion (/h), I = indigestible fraction at any time). In the second experiment, the ruminal and post-ruminal disappearance of DM, CP, and starch were determined using in situ mobile nylon bag. Results Barley grains treated with alum and alfalfa extract had a higher constant rate of starch digestion (0.11 and 0.09/h) than others. Barley grain treated with OE had a higher constant rate of CP digestion and that of treated with AC had a higher constant rate of starch digestion (0.08 and 0.11/h) compared with those of the other treatments. The indigestible fraction of starch treated with alum and sugar beet pulp extract was higher than that of the control group (0.24 and 0.25 vs 0.21). Barley grain treated with AC and OE had significant CP disappearance in the rumen, post-rumen and total tract, and also starch disappearance for post-rumen and total tract compared with the untreated (p<0.001). Conclusion This study demonstrated that AC and OE might have positive effects on the starch degradation of the barley grain. In addition, treating barley grain with alum and sugar beet pulp extract could change the site and extend digestion of protein and starch.