Copyright (c) 2012 All rights reserved. http://works.bepress.com/fkolkail Recent documents in Faysal A. Kolkailah en-us Sat, 24 Nov 2012 03:26:03 PST 3600 http://works.bepress.com/fkolkail/7 http://works.bepress.com/fkolkail/7 Tue, 06 Mar 2012 14:43:24 PST The design and analysis of structural components to operate at elevated temperature and severe stress levels, such as a low-cycle fatigue-limited jet engine disk, require an accurate prediction of the nonlinear stress-strain . response encountered during the cyclic loading conditions. Nonlinear analysis of such components is normally carried out by a finite element code making use of constitutive theories in which the material response is separated into the two important groups of phenomena known as rate dependent "creep" and rate independent "plasticity." A number of viscoplastic. constitutive theories in which "creep" and ''plasticity" effects are combined _into a unified plastic strain model have recently been proposed and are still undergoing active development. In this paper, an elastic-plastic finite element model incorporating the Bodner-Partom model of nonlinear time dependent material behavior is presented. The parameters in the constitutive model are numerically extracted by a least-square fit to experimental data obtained from unaxial stress-strain and creep tests at 65ifC. The finite element model of a double notched specimen is employe_d to determine the elastic-plastic strain and comparison is , made to experimental data. e The constitutive model parameters evaluated in this paper are found to be in good agreement with those obtained 'by other investigators. However, this numerical technique tends to give better agreement with the respo11Se curves than does the graphical methods used by the other investigators. The model calculated ef4$1jc-plastic strain agreed well with the experimental.

]]> Faysal A. Kolkailah et al. Articles http://works.bepress.com/fkolkail/6 http://works.bepress.com/fkolkail/6 Tue, 06 Mar 2012 14:43:21 PST This study presents an experimental investigation of the free vibration of cantilevered composite laminated plates with embedded passive damping material at different stages. A total of five composite laminated plates are considered. The lay-up sequences for the five composite laminated plates with and without two embedded layers of passive damping material are [90°/0°/90°/0°]_s, [90°/0°/90°/0°/d]_s, [90°/0°/90°/d/0°]_s, [90°/0°/d/90°/0°]_s, and [90°/d/0°/90°/0°]_s. The passive damping material employed is a 3M material, SJ-2015 ISD 112, with peak damping properties in the ambient temperature range of 32°F to 140°F. The composite material used is a carbon fiber (977-2)/epoxy resin (IM7). The effect of the passive damping system employed in this study for the composite plates are discussed. Modal testing is performed on these plates to determine resonant frequencies, amplitude and mode shape information. The study included white noise and sinusoidal dynamic testing techniques, a PC computer based data acquisition system, and a virtual instrument dynamic analysis. The different locations of the passive damping material in the cross-ply laminated plates resulted in degradation effects on the natural frequency, damping and mode of shape.

]]> E. I. Elghandour et al. Conferences http://works.bepress.com/fkolkail/5 http://works.bepress.com/fkolkail/5 Thu, 23 Feb 2012 15:26:26 PST This paper presents an investigation into the effect of reinforcing a Plexiglas tube with fiberglass/epoxy threads wound at different angles. This paper shows an experimental analysis approach to find the ultimate failure pressure of these vessels. The properties of the Plexiglas, fiberglass, orientation (wind) angle and the matrix were taken into account to determine their effects on the ultimate failure pressure of the vessels. Mandrels were wound at +/- 75, +/- 65, and +/- 55 deg, and specimen were cut out from each to 19.05 cm long, 7.62 cm inner diameter and outer diameters dependent of the wind angle. The composite material used is an E-type Fiberglass and Epoxy Laminating Systems EZ-10 epoxy with EZ-83 hardener. The Dura-Wound Inc. Cobra Filament Winding Machine was used to wind the specimens. The specimens were tested with a hydrostatic test-rig to analyze the ultimate failure pressure and failure modes. An INSTRON machine was used to test the specimens under compression to determine the Young's modulus and Poisson's ratio. The experimental results indicate that the wind angle affects the mechanical properties and has strong effects on the failure modes of the reinforced vessels. The failure mode however does not differ by varying the wind angle.

]]> Faysal A. Kolkailah et al. Conferences http://works.bepress.com/fkolkail/4 http://works.bepress.com/fkolkail/4 Thu, 23 Feb 2012 15:26:23 PST This study presents an experimental investigation of fracture mechanics for isotropic material, aluminum alloy D16AT. The problem of stable crack growth (SCG) has been addressed in this paper. Experimental results are presented for symmetrically stiffened and unstiffened three point bend specimens subjected to different modes, mode I and mixed mode. The stiffeners are doubly bonded to the fatigue pre-cracked specimens parallel to the length at a certain distance behind the crack tip using an adhesive Redux 410 NA. Results concerning load displacement variation, growth of plastic zones, instantaneous crack edge profiles, and tunneling are presented. There is evidence that the whole stable growth can be characterized by the crack opening angle criterion. The stiffening helps to increase both initiation and maximum fracture loads substantially.

]]> Abdel-Hamid I. Mourad et al. Conferences http://works.bepress.com/fkolkail/3 http://works.bepress.com/fkolkail/3 Thu, 23 Feb 2012 15:26:21 PST Modifying the stiffness of the structure is usually not a feasible solution to enhancing damping, since changing the stiffiless effects the natural frequency changing and eventually the condition of resonance will be reached. Therefore, one of the recommendatory ways to reduce the response on structural elements is to improve damping characteristics. The objectives of this study are to present empirical methodology to detect damping characteristics of structural elements, and determine the optimal location of sensor to detect structural failure by analyzed data from both experimental and numerical analysis. Using orthotropic composite plates comprised of 977-2 Carbon fiber/IM7 epoxy, the natural frequencies ofstructural bending modes and damping ratio of the composite plates were experimented by free vibration test, and then comparison was made between the experimental results and the numerical analysis done by finite element method. The effectiveness of crack on a structure in damped free vibration was confirmed by the analysis using edge-notched composite plate. The results represented the natural frequency of a composjte plate was consistent with changing sensor location, and showed good agreement for both experimental and numerical analysis.

]]> Faysal A. Kolkailah et al. Conferences http://works.bepress.com/fkolkail/2 http://works.bepress.com/fkolkail/2 Thu, 23 Feb 2012 15:26:19 PST Nonlinear analyses of structural components are normally carried out by finite element codes making Use of constitutive theories in which the material response is separated into the two important groups of phenomena known as rate‐dependent “creep” and rate‐independent “plasticity.” A number of viscoplastic constitutive theories in which creep and plasticity effects are combined into a unified plastic strain model have recently been proposed and are still undergoing active development. In this paper, the constitutive equations of the Bodner‐Partom model are used to present the time dependent, inelastic properties of Inconel 718 at 650 °C. This representation covers a wide range of loading conditions. The developed numerical technique to establish the Bodner parameters is based on simulation with fourth‐order Runge‐Kutta integration coupled to a least square measure for good curve fitting to a series of tests. To determine the eight Bodner parameters, an error function consisting of the square of the difference between experimental and model strains was minimized in the time domain by a direct search method. The specific material parameters for the Bodner model were determined to best fit sets of tensile and creep data. The parameters so obtained are in good agreement with those obtained by other investigators. The present parameters generate better response curves than those from graphical methods used in earlier investigations.

]]> Faysal A. Kolkailah et al. Articles http://works.bepress.com/fkolkail/1 http://works.bepress.com/fkolkail/1 Thu, 23 Feb 2012 15:26:17 PST In this paper presents an experimental and numerical investigation ofthe natural frequency of composite material cantilever plates. The stacking sequence of tbe composite plate is Quasi-isotropic laminated plate is [2(0j/±45°/2(90°)]" The plate was subjected to incremental cuts and tests to determine changes in new modal properties. The study included white noise and sinusoidal dynamic testing techniques and a virtual instrument dynamic analyzer. In this study also, determining the resonant frequencies of the undamaged and damaged plate, and evaluating the capabilities of piezoelectric ceramics (PZT's) for fault detection based on their sensitivity and accuracy changes in modal parameters. Numerical results are obtained using finite element software for the composite materials plates. The experimental and numerical results are very good agreement for the composite material cantilever plates with and without damage.

]]> Eltahry Elghandour et al. Conferences