Cover

Aims and Scope
Editorial Board

1. Aprediction study for the behaviour of fuel cell membrane subjected to hygro and thermal stresses in running PEM fuel cell

Maher A.R. Sadiq Al-Baghdadi

Faculty of Engineering, University of Kufa, Najaf, Iraq.

Abstract: A three-dimensional, multi–phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel cell has been used and developed to investigate the hygro and thermal stresses in polymer membrane, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the membrane during operation of a unit cell has been studied and investigated under real cell operating conditions. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. These stresses in the membrane may explain the occurrence of cracks and pinholes in the membrane under steady–state loading during regular cell operation. The results show that the maximum displacements in membrane for the low, intermediate and high load conditions were 2.58, 2.66, and 2.78  respectively.

Volume 7, Issue 3, 2016, pp.189-200.

2. A suggested analytical solution of buckling investigation for beam with different crack depth and location effect

Muhannad Al-Waily, AlaaAbdulzahra Deli

Mechanical Engineering Department, Faculty of Engineering, Al-Kufa University, Ministry of Higher Education & Scientific Research, Iraq.

Abstract: In this research the buckling load of a cracked beam is investigated analytically by solution the general equation of beam with crack effect and numerically by finite element method using of ANSYS program ver. 14 with different crack depth and location effect and the results is compared. The analytical results of the effect of a crack in a continuous beam by calculating the equivalent stiffness, EI, for a rectangular beam to involve an exponential function with depth and location of crack effect, with solution of assuming equivalent stiffness beam (EI) using of Fourier series method. And, the beam materials studied are different beam materials with different beam length, width and depth beam. A comparison made between analytical results from theoretical solution of general equation of motion of beam with crack effect with numerical by ANSYS results, where the biggest percentage error is about (3.8 %). Also it is found that the buckling load of beam when the crack is in the middle position is less than the buckling with crack near the end position and the buckling load of beam decreasing with increasing of crack depth due to decreasing of beam stiffness at any location of crack in beam.

3. Effect of fluid damping on vibration response of immersed rotors

Mahmud Rasheed Ismail¹, Mustafa Asaad Hussein²

1Prosthetics and Orthotics Engineering Department, AL-Nahrain University, Ministry of Higher Education & Scientific Research, Iraq.

2Mechanical Engineering Department, AL-Nahrain University, Ministry of Higher Education & Scientific Research, Iraq.

Abstract: As immersed rotors vibrate in a viscous media such as fluid, a considerable amount of damping may be generated due to the interaction phenomena between the rotor components and the fluid media. Such damping is depending on many factors such as; fluid drag, fluid friction, turbulence, vortex and so on. Immersed rotors find their application in many engineering fields such as Marines machines, gear box, turbine and pumps. In the present work, a mathematical model is attempted to investigate the dynamical behavior immersed rotor. The model takes into account the effects of the most rotor dynamic parameters, namely; fluid drag, damping and stiffness of bearing, unbalance and gyroscopic effects of the attached disc, and elastic bending and internal damping of rotor shaft. Four types of fluid are employed as a fluid immersing media which are; Air, Water, SAE 20 and SAE 40oils.The experimental apparatus includes a sample rotor with single disc and plastic fluid container. Two proximate sensors are employed for measuring the unbalance response and orbits shapes under different rotor speeds, and discs size and locations. Modal analysis is employed for solving the governing equation of vibration motion. To check the validity of the mathematical model the theoretical results are compared with the experimental results. It is found that; the theoretical results are in a good agreement with the experimental ones, where the maximum error is not exceeded (6.8 %), and that; the fluid damping can highly reduce the peak amplitude of the unbalance response (up to 60 %) however, it has slight effect on the critical speeds which are highly affected by the size and location of the attached disc.

4. Theoretical analysis of fundamental natural frequency with different boundary conditions of isotropic hyper composite plate

AbdulkareemAbdulrazzaq Alhumdany¹, Muhannad Al-Waily², Mohammed Hussein Kadhim¹

1Mechanical Engineering Department, College of Engineering, Kerbala University, Ministry of Higher Education & Scientific Research, Kerbala, Iraq.

2Mechanical Engineering Department, Faculty of Engineering, Al-Kufa University, Ministry of Higher Education & Scientific Research, Najaf, Iraq.

Abstract: This research presented isotropic hyper composite plates structures, which are made of (resin and fiber with powder as a reinforcement material). The basic item of this research is to improve the dynamical properties of the composite structure. This item has been verified by adding the powder as a reinforcement material. Square and rectangular hyper composite plates (AR=1 and 1.5) are made with different volume fractions for glass powder, resin and short fiber. Different boundary conditions are used (SSSS, CCSS, CCCC, CFFF, SSFF and CCFF) to support these plates. The dynamical properties of hyper composite models are calculated numerically with considering these different parameters. The results showed that the natural frequency increases by increasing the volume fraction of powder or short fiber with decreasing the resin. It can be concluded that the fundamental natural frequency in aspect ratio (AR=1) increased successively with the boundary conditions (CFFF, SSFF, SSSS, CCFF, CCSS, and CCCC) in ascending order, because the increasing in stiffness of the composite plate depends on the supporting conditions. And, for aspect ratio (AR=1.5), the fundamental natural frequency is increased successively with the boundary conditions (CCFF, CFFF, SSFF, SSSS, CCSS, and CCCC) in ascending order. Also the results showed that the fundamental natural frequency of aspect ratio 1 is larger than 1.5, because the ratio between stiffness to weight for AR=1 is larger than AR=1.5. A comparison made between present numerical results and results presented by former published paper Abdulkareem et.al. [8]and theoretical results by Muhannad Al-Waily [9] for simply supported plate with aspect ratio (AR=1, a=b=25 cm and h=5 mm) and different volume fractions of resin, powder and short fiber and good agreement were the maximum error between numerical and experimental is results is about 5.73% (with 20% short reinforcement fiber, 30% powder reinforcement and 50% resin materials while the maximum error between numerical present results and theoretical results; Muhannad Al-Waily, [9] is about 12.86% (with 30% short reinforcement fiber, 20% powder reinforcement and 50% resin materials).

5. Primary instability regions of square plates subjected to uniaxial in-plane periodic compression load

Ahmed A. Al-Rajihy¹, AbdulkareemAbdulrazzaq Alhumdany², AdilHabeeb Al-Hussaini²

1Automobile Engineering Department, Almssaieb College of Engineering, University of Babylon, Ministry of Higher Education & Scientific Research, Iraq.

2Mechanical Engineering Department, College of Engineering, Kerbala University, Ministry of Higher Education & Scientific Research, Iraq.

Abstract: The purpose of this paper is to investigate the dynamical behavior and the parametric primary instability of thin square elastic plate subjected to uniform in-plane uniaxial periodic compression load. The plate is assumed to be simply supported along its four edges (SSSS). Based on small deflection theory of plates, the value of natural frequency of free vibration and buckling load are determined by assuming the mode shape of vibration of plates simply supported along all edges. If the plate subjected to parametric excitation the plate lose its stability dynamically by flutter. The instability regions are found according to Bolotin's concept. In the present research the effects of excitation parameter and load value are studied. It is found that increasing both of the excitation parameter and loading value cause an increase in the regions of instability. An experimental work is conducted to verify the accuracy of the mathematical model. Good agreement between the theoretical and experimental results is obtained within 8% error.

6. Mechanical and thermal stresses analysis in diesel engine exhaust valve with and without thermal coating layer on valve face

Maher A.R. Sadiq Al-Baghdadi,Sahib Shihab Ahmed, NabeelAbdulhadiGhayadh

Faculty of Engineering, University of Kufa, Najaf, Iraq.

Abstract: This paper investigates mechanical and thermal stresses that arise in the exhaust valve due to its operating with and without thermal coating layer (ceramic) on face exhaust valve. Three dimensional models of an exhaust valve four cylinders, four stroke, and direct injection diesel engine have been presented. The governing equations were discretized using a finite-volume method (FVM) and solved using multi-physics COMSOL® package Version 5. The engine’s exhaust valve crown is coated with various materials in different thermal conductivity such as (Gd₂Zr₂O₇), over a 150μm thickness of bond coat. The maximum thickness of coating is about 300 μm.  Results indicate that after creating a coating layer exhaust valve the temperature distribution, temperature gradients distribution, von-Mises stress distribution and displacement distribution are decreased.

7. Optimization of Ni-Ti-Cu shape memory effect using minitab program

Dania F.Abbas¹, Kadhim K.Resan¹, Ayad M. Takhakh²

1College of Engineering, AL-MustansiriyaUniversity, Baghdad, Iraq.

2College of Engineering, AL-NahrainUniversity, Baghdad, Iraq.

Abstract: This study focuses on the manufacturing of Nickel-Titanium-Cupper shape memory alloys using powder metallurgy (PM) method, 50% Ti, 47% Ni and 3% Cu powder mixture was prepared by mixing in a ball mill for two hours and compacted in a press machine using various compacting pressure (600, 700 and 800) MPa, samples was then sintered in an electrical tube furnace using three sintering temperature of (850, 900 and 950) ˚C. Optimization of the shape memory effect (SME) using Minitab program was conducted; the result showed increasing in the shape recovery with increasing of compacting pressure and reduction in sintering temperature.