Iraqi journal of mechanical and material engineering

A suggested solution for dynamic analysis of stiffened and un-stiffened laminated plates is presented in this work. The First order laminated plate theory is used. The equations of motion are solved by using the modal analysis of forced vibration for multi degrees of freedom. The applied load for this study aresine, rectangular, expansion, ramp and triangular pulses. The method of applied these loads is centrally and uniformly distributed across the plate.The deflection and stresses for each layer are presented for stiffened and un-stiffened, symmetrical and un-symmetrical, cross ply and angle ply, laminated composite plate with respect to the plate side-to-thickness ratio, aspect ratio, material orthotropy, and lamination scheme, number of layer of laminated plate, number of stiffeners, high to width of stiffener ratio, high of stiffener, the width of stiffener, and the stiffener properties.The results are very close compared with finite elements method using ANSYS program and withReddy 1982.

The paper describes experimental results which have been obtained for Mode I (bending) fracture of steel fiber reinforced of self- compacting concrete and normal vibrating concrete. The mode I tested specimens are 100x100x400 mm prisms with a single notch introduced at the middle of the tension side of the specimen. The fracture toughness KIc results increase with increasing fiber content. The J-integral (integral of Rice) results were nearly constant up to 0.5% of fiber content but, rapidly increase at fiber contents after this percentage which shows that this parameter is more sensitive than fracture toughness to fiber addition. However, the crack mouth opining displacement(CMOD) was independent of the maximum applied load, and sensitive to the fiber inclusion. The enhancement of cracking strength, ultimate strength and fracture toughness for the previous fiber content and orientation are reported.

This research aims to find the optimal conditions affecting the surface roughness when copper is turned. In this work the Taguchi method is used to optimize the cutting parameters. The parameters considered here are: spindle speed, feed rate, and the tool nose radius while the depth of cut has been fixed during the experiments. The tool used for conducting the experiment is High Speed Steel (HSS). Once the surface roughness is measured, the quality characteristic “smaller is the better” is applied to calculate the signal to noise ratio S/N for each experiment. Also, by using ANOVA output, the factor that has more significant in the process has been determined depending on its percentage of contribution. The results showed that the optimum combination of levels of the parameters were (3-1-1) that are corresponding to spindle speed (1120 rpm), feed rate (0.065 mm/rev), and tool nose radius (4 mm). The significant factor that has maximum contribution according to ANOVA results is the spindle speed with 58.581% followed by feed rate and tool nose radius respectively.

In this research, OXY – LPG gas flame through Robotic cutting machine was used. Many experiments had been done in order to achieve proper processing conditions for clean cut. The main parameters control the cutting process are LPG and Oxygen pressures, torch speed, the choice of nozzle and the gap between the flame and the piece. Samples of carbon steel were used with thicknesses range (25 – 35) mm under different process conditions to produce clean cut (kerf) within ( 2 ) mm width in order to apply programs capable of producing spur gear shapes and racks. The attempts succeeded only in producing spur gear with clean cut. The ability of torch to move in a circle of diameter around 2000mm which gives high maneuvering to produce large shapes under the conditions were mentioned in this research, which is out of the capability of typical production machines.

In this research have been identified diffusion coefficient of solvents with ratios(0.3salt water) , (0.5sodium hydroxide), (0.5potassium hydroxide), and it was observed melting and mechanisms of moisture in the composite material consisting of fiber glass and polyester it at (70Co)and the results were then compared to samples of composite materials with six layers of fiber to take advantage of comparison in determining the impact of the presence of diffuse temperature and without in most in dustrial applications. The samples were composite material used is composed of two types of fiber type I(fibers woven) and type II(fiber woven + random), and through the results was observed that the solvents basal have a clear impact on composite materials and increases this effect with increasing temperature, as observed that diffuse more in the first type of samples(fiber woven) of the second type of samples (fiber woven + random), in addition to the diffuse coefficient varies from one solution to another, when the temperature increase for type 1and 2 .And the results were recorded the largest percentage value of salt water ( 2.93%,3.02% ) for two types of fiber respectively, which means minimum absorption resistance , followed by sodium hydroxide and finally potassium hydroxide (1.292%,1.05%) respectively because of (maximum absorption resistance).

The purpose of this study is to investigate the effect of Al additions on corrosion resistance of high copper dental amalgam. Al addition is added in different percentages of ( 0.5, 1, 1.5, 2, 2.5 wt% ). The specimens were prepared according to ADA specification No. 1. The specimens have been stored at 37±1 Cº using glass chamber prepared for this purpose. The corrosion test has been carried out according to ASTM standard ( G5 – 87) and at37±1 Cº. Aluminum addition with mentioned percentages led to form weak passive layer, there is no improvement in corrosion resistance was found. Vickers hardness has been measured after one month from the end of trituration, and it found that the highest hardness value was of the highest aluminum content amalgam

The performance of a solar cell under sun radiation is necessary to describe the electrical parameters of the cell. The Prova 200 solar panel analyzer is used for to test a solar cell at Baghdad climate conditions (the experimental measurements had been made at weather temperature in the range between 20-28oC and average wind speed 2.5 km/hr). The results showed that as dust accumulated the solar panel loose power for the first three days, but when the dust had created several layers the power dropped in smaller intervals for the forth days to two weeks. More power and efficiency lose for more exposure days and tilt angle 0o ≥ 30o ≥ 60o ≥ 90o(The results show that modules tilted with larger angles let less dust get accumulated on surfaces) at a fixed time (exposure days) for the fourth angles respectively. Sharp reduction of energy (power) is yield up to 63.2-99.8% of PV (photovoltaic) solar cell under 5Ω resistance load was observed as a result of corresponding shaded percentage area of the cells 5.6-50% from the total cell area.

The recent emergence of nano science and nano technology has added another dimension to the staple of the modern composite technology. Instead of micron diameter fibers and particles, nanoparticles are being incorporated into polymer matrices to form a composite known as polymer nano composites (PNCs). In this study, the composites were prepared from unsaturated polyester and different weight percentages of carbon black (0, 3, 6, 9 and 12 %) nanoparticles using hand lay out. The mechanical properties – such as tensile strength, modulus of elasticity, elongation at break, hardness, bending and impact properties were studied. The results show that the tensile strength, modulus of elasticity, impact strength, fracture toughness, flexural strength and maximum shear stress was achieved at (3wt. %) of carbon black, while elongation at break decreases with an increasing of carbon black weight percentage. The hardness of composite increased with the increasing of carbon black weight percentage

This research deals with estimating the parameters and reliability function of the well known distribution, which represents the distribution of time to failure, called Weibull distribution, denoted by WEI (λ , θ) (λ is called the shape parameter and θ is the scale parameter). The method of estimation are Maximum likeli¬¬¬¬¬¬hood to obtain ( ), Minimax estimator ( ), and the proposed Bayes estimator ( ). The comparison between these estimators was done through simulation experiment for three sample size (n = 25, 50, 100), and it is also applied on real life data which represent the time to failure of (30) independent machines from State Company for Cotton Industries. From the results we fond that the best estimator for scale parameter (θ) is the Minimax estimator ( ) compared with likelihood ( ) and Bayes estimator (), which works on minimizing the maximum expected risk function.