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CONTENTS
Volume 8, Number 2, June 2019
 

Abstract
Through experimental and numerical studies of metal forming processes by plastic deformation, this paper represents a numerical simulation by finite element of the mechanical behavior of the material during a permanent deformation phenomenon. The main interest of this study is to optimize the shaping processes such as folding. In this context the elastic return for the folding process has been further reduced by using the design of experiments approach. In this analysis, it is proposed to consider the following factors: bending radius, metal-sheet thickness, gap and length of the fold.

Key Words
design metal forming processes; elastic return; optimization of experiments

Address
(1) Mohamed Serier, Seif-Eddine Bendaoudi:
Department of Mechanical Engineering, Institute of Technology, University Center of Relizane, Algeria;
(2) DJazia-Leila Ben Mansour:
Department of Physics, Institute of exact sciences, University of Sidi bel Abesse, Algeria;
(3) Affaf Tabti:
Department of Process Engineering, Institute of Technology, University Center of Relizane, Algeria.

Abstract
The present research deals with the time harmonic deformation in transversely isotropic magneto thermoelastic solid with two temperature (2T), rotation and without energy dissipation due to inclined load. Lord-Shulman theory has been formulated for this mathematical model. The entire thermo-elastic medium is rotating with a uniform angular velocity. The Fourier transform techniques have been used to find the solution to the problem. The displacement components, stress components and conductive temperature distribution with the horizontal distance are computed in the transformed domain and further calculated in the physical domain using numerical inversion techniques. The effect of time harmonic source and rotation is depicted graphically on the resulting quantities.

Key Words
time harmonic sources; transversely isotropic thermoelastic; rotation; inclined load; magneto thermoelastic solid

Address
Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India.


Abstract
Polypropylene (PP) fibers for making fabric which is used for packing cement have a high strength and high tear resistance. Due to these excellent properties the present study investigates the effect of PP fibers on the mechanical strength of concrete. Mechanical strength parameters such as compressive strength, splitting tensile strength and flexural strength are evaluated. Structural integrity of concrete using Ultrasonic Pulse Velocity (UPV) was also studied. Concrete containing PP fibers in percentage of 0%, 0.15%, 0.25%, 0.5% and 0.75% was developed with a characteristic compressive strength of 25 MPa. Concrete cubes, cylinder and prismatic specimens were cast and tested. It was found that the UPV values recorded for all specimens were of the similar order. Test results indicated the used of PP fibers can significantly improve the flexural and splitting tensile strengths of concrete materials whereas it resulted a decreased in compressive strength. The relative increase in split tensile and flexural strength was optimum at a fiber dosage of 0.5% and a mild decreased were observed in 28 days compressive strength. The findings in this paper suggested that PP fibers deriving from these waste cement bags are a feasible fiber option for fiber-reinforced concrete productions.

Key Words
polypropylene fiber; waste cement bag; concrete properties; mechanical strength

Address
Department of Civil Engineering, National Institute of Technology Meghalaya, Shillong 793003, India.


Abstract
The lifetime of a gas turbine combustor is typically limited by the durability of its liner, the structure that encloses the high-temperature combustion products. The primary objective of the combustor thermal design process is to ensure that the liner temperatures do not exceed a maximum value set by material limits. Liner temperatures exceeding these limits hasten the onset of cracking which increase the frequency of unscheduled engine removals and cause the maintenance and repair costs of the engine to increase. Hot gas temperature prediction can be considered a preliminary step for combustor liner temperature prediction which can make a suitable view of combustion chamber conditions. In this study, the temperature distribution of ceramic panels for a V94.2 gas turbine combustor subjected to realistic operation conditions is presented using three-dimensional finite difference method. A simplified model of alumina ceramic is used to obtain the temperature distribution. The external thermal loads consist of convection and radiation heat transfers are considered that these loads are applied to flat segmented panel on hot side and forced convection cooling on the other side. First the temperatures of hot and cold sides of ceramic are calculated. Then, the thermal boundary conditions of all other ceramic sides are estimated by the field observations. Finally, the temperature distributions of ceramic panels for a V94.2 gas turbine combustor are computed by MATLAB software. The results show that the gas emissivity for diffusion mode is more than premix therefore the radiation heat flux and temperature will be more. The results of this work are validated by ANSYS and ABAQUS softwares. It is showed that there is a good agreement between all results.

Key Words
V94.2 gas turbine combustor; combustion chamber; temperature distribution; realistic operation conditions; 3D-FDM

Address
(1) Mohammad Javad Namayandeh, Mehdi Mohammadimehr, Mojtaba Mehrabi:
Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran;
(2) Mohammad Javad Namayandeh:
Mechanical Expert of Combined Cycle Power Plant, Kashan, Iran;
(3) Mojtaba Mehrabi:
Department of Mechanics, Faculty of Engineering, University of Isfahan, Isfahan, Iran.

Abstract
In this study, thermal effects on the mechanical properties of cement mortars with some types of fibers is investigated. The replaced fibers were made of polypropylene (PP), aramid, glass and basalt. In other words, the main goal of this paper is to study the effects of different fibers on the mechanical properties of cement mortars after subjecting to normal and sub-elevated temperatures. The experimental tests used for investigating these effects were compressive, splitting tensile, and four-point bending tests at 20, 100 and 300°C, respectively. Moreover, the microstructures of the specimens in different temperatures were investigated using scanning electron microscope (SEM). Based on the experimental results, the negative effects of sub-elevated temperatures on four-point bending tests were much more than the others. Moreover, using the fibers with higher melting points could not improve the qualities of the samples in sub-elevated temperatures.

Key Words
cement mortars; Polypropylene (PP); aramid; glass; basalt; mechanical properties; thermal properties; sub-elevated temperatures

Address
Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran.



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