The Effect of Anisotropy on Thin-Walled Tube Bending

K. Hasanpour,B. Amini,M. Poursina,M. Barati 한국소성가공학회 2011 기타자료 Vol.2011 No.8

Thin-walled tube bending has found many of its applications in the automobile and aerospace industries. The rotary-draw-bending method which is a complex physical process with multi-factor interactive effects is one of the advanced tube forming processes with high efficiency, high forming precision, low consumption and good flexibility for bending angle changes. However it may produce a wrinkling phenomenon, over thinning and cross-section distortion if the process parameters are inappropriate. Wrinkles propagate permanently in thin-walled tube, but finally, localize in a finite zone and lead to failure. The prediction of wrinkling in thin-walled tube bending processes has been a challenging topic. In this paper, firstly, the plastic deforming behavior and wrinkling mechanism for a thin-walled tube is simulated and the results will compare with the available experimental ones. Then, the effect of anisotropy on ovalization, thickness and wrinkling of tube will be investigated using FEM. Extensive numerical results are presented showing the effects of the various kinds of materials and geometric parameters on wrinkling using anisotropic yield function.

Biochemical, Hematological, and Electrocardiographic Changes in Buffaloes Naturally Infected with Theileria annulata

A. Hasanpour,G. A. Moghaddam,Ahmad Nematollahi 대한기생충학열대의학회 2008 The Korean Journal of Parasitology Vol.46 No.4

The effect of anisotropy on wrinkling of tube under rotary draw bending

Kourosh Hasanpour,Mahmoud Barati,Behnaz Amini,Mehrdad Poursina 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.3

Rotary draw tube bending is one of the most complex tube forming processes subject to different process parameters such as mate-rial properties and geometry. This process is being practiced in more and more applications in industry due to its high efficiency, high forming precision and quality. However, improper process parameters can lead to wrinkling which restrict the thin walled tube bending. Therefore, the prediction and prevention of wrinkling is very important. Despite its importance, the effect of anisotropy on the occurrence of wrinkling was not considered in the literature up to now. In this investigation, a quantitative study on the wrinkling of thin walled tube bending is carried out through a finite element model of the process using velocity integral parameter, which is used for the detection of wrinkles. The other methods usually warn the wrinkling initiation with no precise location prediction. In addition, the effects of some process parameters, specially normal and planar anisotropy on the tube wrinkling are investigated. It is shown that increasing normal and planar anisotropy (increasing r0 and r90 values) result in a decrease in tube wrinkling.

In situ horizontal stress effect on plastic zone around circular underground openings excavated in elastic zones

Komurlu, Eren,Kesimal, Ayhan,Hasanpour, Rohala Techno-Press 2015 Geomechanics & engineering Vol.8 No.6

In this study, effect of horizontal in situ stress on failure mechanism around underground openings excavated in isotropic, elastic rock zones is investigated. For estimating the plastic zone occurrence, an induced stress influence area approach (Bray Equations) was modified to define critical stress ratio according to the Mohr-Coulomb failure criterion. Results obtained from modified calculations were compared with results of some other analytical solutions for plastic zone thickness estimation and the numerical modelling (finite difference method software, FLAC2D) study. Plastic zone and its geometry around tunnels were analyzed for different in situ stress conditions. The modified equations gave similar results with those obtained from the other approaches. However, safer results were calculated using the modified equations for high in situ stress conditions and excessive ratio of horizontal to vertical in situ stresses. As the outcome of this study, the modified equations are suggested to use for estimating the plastic zone occurrence and its thickness around the tunnels with circular cross-section.

A new hardening rule for metallic foam plasticity

Azam Surmiri,Kourosh Hasanpour 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.5

Metallic foams are a class of porous materials widely used in the industry because of their advantages. In recent years, extensive studies on the behavior of these materials have been conducted. Several constitutive equations have also been presented and applied. This study proposes a new constitutive equation that predicts metallic foam behavior using the stress–strain curve in uniaxial compression. The proposed model offers a new functionality for work hardening and is evaluated for both isotropic and combined hardening. The constitutive equations are implemented in MATLAB and integrated using return mapping algorithm. The material parameters are identified using genetic algorithm and through a comparison of the experimental and numerical results. The aluminum foams discussed in this paper are the commercially available types, Foaminal and Alporas. The comparison of numerical and experimental results indicate that this new constitutive equation predicts foam behavior in a reasonable manner. Moreover, a good agreement is observed between the experimental and computational curves.

High Incidence of Virulence Factors among Clinical Enterococcus faecalis Isolates in Southwestern Iran

Hamid Heidari,Somayeh Hasanpour,Hadi Sedigh Ebrahim-Saraie,Mohammad Motamedifar 대한감염학회 2017 Infection and Chemotherapy Vol.49 No.1

Background: Over the past two decades, enterococci have emerged as an important agent responsible for hospital acquiredinfection. Several virulence factors contribute to the adherence, colonization, evasion of the host immune response, and pathogenicityand severity of the infection. Enterococcus faecalis is the most common and virulent species causing infections in hospitalizedpatients. The aim of the present study was to examine the prevalence of genes encoding virulence factors and antimicrobialresistance patterns of E. faecalis strains isolated from hospitalized patients in Shiraz, south west of Iran. Materials and Methods: A total of 51 E. faecalis isolates from the urine, blood, pleural fluid, peritoneal fluid, eye discharge,endotracheal tube (ETT) and transjugular intrahepatic portosystemic shunt (TIPS) specimens of patients were identified by phenotypicand genotypic methods. Antimicrobial sensitivity tests and detection of virulence factors were performed using standardmethods. Results: The efa and asa1 were the most frequently detected gene (100%) among the isolates, followed by esp (94.1%), ace(90.2%), gelE (80.4%), cylA (64.7%), and hyl (51%). More than half of the isolates (52.9%) were high level gentamicin resistant(HLGR). Vancomycin resistance was observed among 23 (45.1%) isolates. The lowest antimicrobial activity was related to erythromycin(3.9%), tetracycline (5.9%) and ciprofloxacin (9.8%). No isolate was found resistant to fosfomycin and linezolid. Conclusion: Our data indicated a high incidence of virulence factors among E. faecalis strains isolated from clinical samples. Colonization of drug resistant virulent isolates in hospital environment may lead to life threatening infection in hospitalized patients. Therefore, infection control procedures should be performed.

Effect of Copper Substitution on Structural and Magnetic Properties of NiZn Ferrite Nanopowders

Mohammad Niyaifar,Hoda Shalilian,Ahmad Hasanpour,Hory Mohammadpour 한국자기학회 2013 Journal of Magnetics Vol.18 No.4

In this study, nickel-zinc ferrite nanoparticles, with the chemical formula of Ni0.3Zn0.7-xCuxFe₂O₄ (where x = 0.1-0.6 by step 0.1), were fabricated by the sol-gel method. The effect of copper substitution on the phase formation and crystal structure of the sample was investigated by X-ray diffraction (XRD), thermo-gravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD result shows that due to the reduction of Zn content,the crystallite size of the sample increased. The results of the vibration sample magnetometer (VSM) exhibit an increase in saturation magnetization value (Ms) for samples with x ≤ 0.3 and a linear decrease for samples with x > 0.3. The variation of saturation magnetization and coercivity of the samples were then studied.

Effect of clofibrate on reducing neonatal jaundice: a systematic review and meta-analysis

Fatemeh Eghbalian,Lotfollah Karimi,Roya Raeisi,Ayda Hasanpour Dehkordi,Hamid Bouraghi 질병관리본부 2022 Osong Public Health and Research Persptectives Vol.13 No.3

In neonates, bilirubin tends to be deposited in body tissues, especially the skin and mucous membranes. Jaundice is an early symptom of bilirubin excretion disorders. Therefore, the aim of this study was to investigate the effect of clofibrate on reducing neonatal jaundice. In this systematic review, international databases, including PubMed, Scopus, Web of Science, Embase, Cochrane, and Google Scholar, were searched without time and language restrictions. The reference lists of all studies ultimately included were manually searched. In the 17 articles reviewed, with a sample size of 665 people published between 2005 and 2019, the average weight of the neonates varied from 2,186 g to 4,000 g. Furthermore, the average age of neonates varied from 2.09 days to 9.8 days. Four doses of clofibrate (25, 30, 50, 100 mg/kg of neonatal body weight) were used. The bilirubin level of neonates significantly decreased in the intervention group 24, 36, 48, and 72 hours after the start of treatment. Clofibrate administration decreased total serum bilirubin, especially from the second day onwards, and also reduced hospitalization time, hospital costs, and side effects from hospitalization.

Slope variation effect on large deflection of compliant beam using analytical approach

Khavaji, A.,Ganji, D.D.,Roshan, N.,Moheimani, R.,Hatami, M.,Hasanpour, A. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.3

In this study the investigation of large deflections subject in compliant mechanisms is presented using homotopy perturbation method (HPM). The main purpose is to propose a convenient method of solution for the large deflection problem in compliant mechanisms in order to overcome the difficulty and complexity of conventional methods, as well as for the purpose of mathematical modeling and optimization. For simplicity, a cantilever beam of linear elastic material under horizontal, vertical and bending moment end point load is considered. The results show that the applied method is very accurate and capable for cantilever beams and can be used for a large category of practical problems for the aim of optimization. Also the consequence of effective parameters on the large deflection is analyzed and presented.

Slope variation effect on large deflection of compliant beam using analytical approach

A. Khavaji,D.D. Ganji,N. Roshan,R. Moheimani,M. Hatami,A. Hasanpour 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.3

In this study the investigation of large deflections subject in compliant mechanisms is presented using homotopy perturbation method (HPM). The main purpose is to propose a convenient method of solution for the large deflection problem in compliant mechanisms in order to overcome the difficulty and complexity of conventional methods, as well as for the purpose of mathematical modeling and optimization. For simplicity, a cantilever beam of linear elastic material under horizontal, vertical and bending moment end point load is considered. The results show that the applied method is very accurate and capable for cantilever beams and can be used for a large category of practical problems for the aim of optimization. Also the consequence of effective parameters on the large deflection is analyzed and presented.