Al-Qadisiyah Journal for Engineering Sciences

Recently, Shape Memory Alloys (SMAs) has been on the forefront of research. SMAs are unique alloys in that they can remember an original shape after being deformed. They have been used for a wide variety of applications in various fields. The natural frequencies have been identified as one of the most critical parameter in vibration study which may lead to structure failure during resonance. In present work, an analytical solution for the calculation of natural frequencies of composite cantilever beams with embedded SMA wires was studied. The beams were clamped at one end and free in other end. A mathematical model is developed to describe the behavior of the natural frequencies of a cantilever composite beam embedded by SMA wires and solved by using Matlab program. The natural frequencies found from the analytical were compared with previous research and got a good agreement error. It was found that the natural frequencies of beams decreased with increasing the number of embedded SMA wires at a temperature below martensite temperature transformation and increased with increasing the number of embedded SMA wires at a temperature above austenite finish transformation. Some geometrical factors and mechanical properties were studied in this work, such as width of beam, thickness of beam, length of beam, diameters of SMA wires, modulus of elasticity of Glass fiber epoxy, and austenite ratio in SMA wires. Increasing these factors caused increasing in the natural frequencies of composite beam while the increase of length of beam resulted in decreasing in natural frequencies.

In this paper, fatigue crack growth rate (FCGR) analyses were conducted on compact specimens of an AISI 4340 alloy to study the behavior over a range in load ratios (0.1 ≤ R ≤ 0.95) and constant maximum stress intensity factor (Kmax) condition. Previous study had indicated that high R > 0.7 and constant Kmax test conditions near threshold conditions were suspected to be free crack-closure and that any differences were caused by Kmax effects, from threshold to near fracture conditions. Cracks in high-cycle fatigue (HCF) components spend a large portion of their fatigue life near threshold conditions. In order to characterize the evolution of damage and crack propagation during these conditions, fatigue crack growth rate (FCGR) data at threshold and near-threshold conditions are essential in predicting service life and in determining the proper inspection intervals. Fatigue crack growth model, namely Forman were examined, this model implicit the effect of R ratio and ease of curve fitting to measured data. The Forman model may be suggested for use in critical applications in studying fatigue crack growth for different load ratios.

A bone waste was utilized as a cost effective catalyst for the transesterification of Indian mustard oil. This high efficient and low-cost waste catalyst could make the biodiesel production from Indian mustard oil competitive with petroleum diesel.The catalysts samples were calcined at different temperatures (800oC, 900oC and 1000oC) for 2 hrs. The samples were characterized by using X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and BET surface area analyzer. A simple model was used to study the kinetics of hydroxyapatite-catalyzed transesterification of mustard oil. The optimum conditions for biodiesel production were (reaction temperature (60oC), a methanol-to-oil molar ratio (20:1) and catalyst amounts (18% based on oil weight). Two steps were concluded for the transesterification process, the initial one is the triglyceride (TG) mass transfer controlled region, The second one is the chemical reaction controlled region. The high adsorbed methanol concentration and the lower availability of active specific catalyst surface caused the TG mass transfer controlled region.Increasing the catalyst amount in the transesterification process caused increasing both the TG mass transfer and chemical reaction rates.The effect of mixing conditions in the transesterification process was predicted in the modeling strategy.

The region of a slab in the vicinity of a support could fail in shear by developing a failure surface in the form a truncated cone or pyramid. This type of failure, called "Punching Shear Failure", is usually the source of collapse of flat-plate and flat-slab structures. An experiment to be conducting to investigate the punching shear strength and failure behavior of self concrete (SCC) slabs using carbon fiber reinforced polymer (CFRP) bars as internal strengthening in connection region for slab-column. Seven interior slab-column connections tested including same concrete compressive strength and ratio of the reinforcement. All slabs will be tested as a simply supported and subjected to punching loading by interior column. Test results show that the internal strengthening technique by using high tensile strength CFRP bars improves the bearing capacity of RC two-way slabs.
Based on the experimental results, it is possible to increase punching shear capacity by using internally reinforced with CFRP bars concentrated in slab-column zone, this increase is about (33-100%) compared with the unstrengthened (control) slab.
The effectiveness of the CFRP bars is depended substantially on distributed or arrangement manner in slab-column region. Also, it is found that, the use of NSM CFRP bars is an effective technique to enhance shear capacity of SCC slab-column models and nearly provided the same efficiency of internal reinforcement.
Even efficient to increase the punching shear load, the top reinforcement of CFRP bars will not change the brittle-type punching shear failure mode compared with bottom CFRP bars reinforcement.

The quality of an electrical power plays an important factor in any industrial process, these factors relate to the economic and technical benefits. The cement industry used many of the miscellaneous equipment's, which are classifying as non-linear loads such as induction motors, transformers and etc. The electrical equipment's are absorbing additional currents called "inductive reactive currents"; the effects of additional currents making electrical network inefficient, result of reducing the power factor. However, the low power factor will affect the increase the loads on the power station on the one hand and on the efficiency of the equipment's, capacity of transformer's, sizes of cables and capacity of switchgears on the other hand this in relation to the cement plant.
In this paper, the effects of low power factor on main motors which use in AL-Najaf cement plant analyzed, such as raw material mill, cement mill and the clinker cooler. The necessary reactive power for the capacitor bank calculated according to practical readings for equipment's information that printed on the name-plates, by using two methods for calculation (the mathematical equations and table of factor K). The influence of power factor correction on the motors, transformers and sizes and losses of electrical cables calculated. The advantages of power factor correction are analyzed for economic and technical sides.

In this study commercially pure aluminum sheets were welded using friction stir welding (FSW) process. Three rotational speeds of 800, 1100 and 1500 rpm were used. The axial force, passing speed, and tool geometry were constant. Parameters were optimized depending on the results of the macrograph, micrographic, microhardness, and tensile strength. The results showed that the sound joint with the best possible microstructure and mechanical properties was obtained at a rotational speed of 1100 rpm. The microscopic and local mechanical properties proposed that mechanical mixing is the main material flow mechanism in the formation of the nugget zone (NZ).

This study aims to perform an experimental study of heat transfer by forced convection for three cylinders (with 12 triangular, rectangular shape fins and without fins) made of aluminum. The inner and outer diameters of these cylinders considered in this study ware (16 mm) and (48 mm) respectively .The study has been performed for different,geometry, slope angles ( ) and range of air velocities (0.5-4m/s). The three cylinders ware heated by a constant heat flux generated by passing an alternative current (AC) through a resistance placed inside the internal space for each cylinder . The effects of air velocity , inclined angle and geometry of fins have been studied in this study for a range of heat fluxs (13-247) W. The results show that the rate of heat transfer increases as the air velocity increases but it decreases with increasing inclined angle. The heat transfer coefficient increases generally with increasing Reynolds number (Re) and the heat transferred from triangular test sample (12) fins is greater than that from rectangular test sample and without fin type. An empirical relationships between Reynolds number (Re) and Nusselt number (Nu) is concluded: