Wyniki wyszukiwania - Biblioteka Nauki

1

Free vibration analysis of thick disks with variable thickness containing orthotropic-nonhomogeneous material using finite element method

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Zafarmand H. , Kadkhodayan M.

Journal of Theoretical and Applied Mechanics

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2015

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tom Vol. 53 nr 4

1005--1018

EN

Free vibration analysis of thick functionally graded nanocomposite annular and solid disks with variable thickness reinforced by single-walled carbon nanotubes (SWCNTs) is presented. Four types of distribution of uniaxial aligned SWCNTs are considered: uniform and three kinds of functionally graded (FG) distribution through radial direction of the disk. The effective material properties of the nanocomposite disk are estimated by a micro mechanical model. The axisymmetric conditions are assumed and employing the graded finite element method (GFEM), the equations are solved. The solution is considered for four different thickness profiles, namely constant, linear, concave and convex. The achieved results show that the type of distribution and volume fraction of CNTs and thickness profile have a great effect on normalized natural frequencies.

2

An Invesigation Into the Influence of Blankholder Force on Springback in U-Bending

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Kadkhodayan M. , Zafarparandeh I.

Archives of Metallurgy and Materials

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2009

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tom Vol. 54, iss. 4

1183-1190

EN

Springback is the main defect in U-channel forming process. Applying the blankholder force is one of the ways of solving the problem. On the other hand the value of the blankholder force should be chosen carefully. In this paper the relation of the blank-holder force and final springback, taking a benchmark of NUMISHEET'93 2-D draw bending and using a commercial FEM code has been studied. The simulations are pre-formed for AA5754-O and DP-Steel. In order to probe the relation, five different values are utilized in simulations. It is found that springback increases for the middle values of the blankholder force where the stretching and bending have equal effects on the blank. The maximum required punch loads are compared for the different values of blankholder force.

PL

Sprężynowanie jest głównym mankamentem w procesie formowania zagięć typu „U”. Zastosowaie siły dociskacza jest jednym ze sposobów rozwiązania tego problemu. Z drugiej strony, wartość siły dociskacza powinna być precyzyjnie wyznaczana. W niniejszej pracy omawiany jest związek siły dociskacza i końcowego sprężynowania, przy zastosowaniu wzorca NUMISHEET' 93 2-D oraz wykorzystaniu dostępnego na rynku kodu FEM. Symulacje zostały wykonane dla stali DP i AA5754-O. W celu przetestowania wspomnianego związku, w symulacjach wyznaczono pięć różnych wartości. Zaobserwowano, iż zginacze mają taki sam wpływ na materiał. Porównywane są maksymalne wymagane obciążenia tłocznika dla różnych wartości siły dociskacza.

3

A comparison of axial fatigue strength of coarse and ultrafine grain commercially pure titanium produced by ECAP

80%

Naseri R. , Hiradfar H. , Shariati M. , Kadkhodayan M.

Archives of Civil and Mechanical Engineering

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2018

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tom Vol. 18, no. 3

755--767

EN

Commercially pure titanium (CP-Ti) has been recently used as metallic biomaterials due to excellent biocompatibility and specific strength. CP-Ti has less static and dynamic strength as compared to other metallic biomaterials. Processing by the equal channel angular pressing (ECAP) as one of the most effective severe plastic deformation (SPD) method could lead to an increase in the mechanical strength of materials, significantly. In this study, Grade 2 CP-Ti billet is inserted into Al-7075 casing, and is then deformed by ECAP, with the channel angle of 135°, through 3 passes at route BC and room temperature. The purpose of using casing is to attain higher deformation homogeneity and more material ductility in the billet. The microstructural analysis shows that the coarse grain (CG) CP-Ti is developed to ultra-fine grain (UFG) structures after ECAP. In order to investigate the static and dynamic strength of CG and UFG CP-Ti, the tensile and axial fatigue tests are conducted. The results represent that UFG CP-Ti has much more tensile and fatigue strength than CG CP-Ti, and it could be utilized as biomaterials for production of implants. Surface features of fatigue fracture are also investigated. It should be noted that the investigation of fatigue strength of UFG CP-Ti produced by ECAP at RT utilizing casing, has not been conducted so far.