Iraqi journal of mechanical and material engineering

The aim of this study is to find the influence of different fibersparameters such as volume, aspect ratio, type, and shape of fibers on the workabilityof the fresh concrete and some of the mechanical properties of selfcompactingconcrete made from locally available materials. One reference concrete mix, whichall other mixes develop from, has been designed in this work. The results indicatethat the addition of fibers decreases the slump flow, increases T50., decreases L-boxflow and increases Tv. The effect of fibers on the fresh properties of SCC dependson the content, length, type and shape of fibers. Steel fibers had a marginal effect oncompressive strength of FRSCC, the higher percent of increase in compressivestrength was (2.38 %). All fiber mixes demonstrated higher splitting tensilestrength, flexural strength and impact strength relative to plain mix at all curingages. The strengths increased as the fiber content and/or the aspect ratio increasedand it increased by using crimped fibers. The fibers slightly decrease the U.P.V at28 days.

The aim of this study is to investigate the influence of the concrete age on the measurement of the nondestructive tests. This study involves two types of the Investigational work; first type deals with field investigation on existing concrete, which the effect of concrete age on measurements of two types of nondestructive, rebound hammer and ultrasonic pulse velocity tests, was investigated in concrete structure of a multistory buildings under construction. Repetitive nondestructive measurements were taken from the same location in different ages, the age of concrete under test at ranging 90 to 365 days. Measurements results of the nondestructive testes exhibit slight growing with age, the average increase rate in the rebound number is 14.75% and the average increase rate in the ultrasonic pulse velocity is 2.4%. Second type was the laboratory investigation for effect of concrete age on the nondestructive tests , where numbers of specimens from concrete mixes with 28 days strength ranging from 25-55 MPa were prepared and tested with nondestructive , rebound hammer and ultrasonic pulse velocity tests, were investigated for all mixes at 7, 28, 60, 90, 120 , and 180 days . Results demonstrate that in general, nondestructive exhibit continuous increase with increasing in curing age and the mainly of was there increasing in the early ages, the increase percentage for rebound number and ultrasonic pulse velocity at age of 180 days are ranged between (15-19) % and (6.4-10.9) %, respectively as compared with that of 28 days age.

The goal of the present work is to investigate the effect of adding Cement kiln Dust ( CKD ), produced from Kufa cement plant on some properties of concrete. Four different concrete mixes were prepared, with 0%, 5%, 10% and 15% CKD by weight of cement was replaced. Two methods were used to study the absorption, the full immersion and the capillary rise. The effect of absorption on some properties of concrete (compressive, tensile, flexural) strength were studied. The compressive strength of concrete specimens decreased with the increasing of the quantity of CKD. However, there was no significant difference in the compressive strength of 0 and 5% CKD cement concretes. A similar trend was noted in the splitting, flexural tensile strength and concrete absorption. The performance of concrete with 5% CKD was almost similar to that of concrete without CKD.

To assess the pollution of heavy metal in roadside dust at Hilla city ,this research characterise road dust properties in roadside soils of two sites: along road with dense traffic (60 street, high traffic volume) and secondary road with lower traffic, a local road (40 street , low traffic volume).Road dust samples (40 in total) were collected under stable weather conditions during the hot, dry season (August and September) of 2011. Road dust were collected from a total of 40 locations and analyzed for lead (Pb), Zinc (Zn), Nicle (Ni) , Chromium (Cr(III)) , Cobalt (Co) and Cadmium (cd) concentrations.The results showed that all heavy metal contents except Cd and Cr, are higher than acceptable values in natural soils. High contents of these elements could be attributed to anthropogenic effects related to traffic sources. The results of this study were compared with several cities around the world.

Mechanical properties of vinyl ester resin reinforced with different weight percentage (20%,40%,60%) glass fibers was studied theoretically using Ansys program version (11) and these properties included tensile and flexural strength. The standard specification (ISO-R-527)+(ASTM D790) were used to fabricant the tensile and flexural test samples respectively by Ansys program. The theoretical results shows that high tensile and flexural strength value for vinyl ester resin after reinforcing with glass fibers due to high elastic modulus for these fibers and this strength will increase with increasing percentage of fibers, which agree with the experimental results obtained from tensile test .

This paper presents the application of Genetic Algorithms for the optimum cost design of reinforced concrete beams based on ACI Standard specifications. The produced optimum design satisfies the strength, serviceability, ductility, durability and other constraints related to good design and detailing practice. While most of the approaches reported in the literature consider the steel reinforcement and the cross-sectional dimensions of the beam as the variables taking into account the flexural only, in this research the dimensions and reinforcing steel were introduced as a design variable, taking into account flexural, shear and torsion effects on the beam. The constant parameters include the number of bays, span’s lengths, support conditions, loads, material properties and unit costs. The forces, moments and deformations needed in the GA constraints will be found from analysis. The beam dimensions are corrected to the nearest 25 mm and the areas of longitudinal and transverse steel obtained from the design are converted into a least weight detailing of steel reinforcements. This is achieved by generating a database of reinforcement templates containing different available reinforcement bar diameters in a pre-specified pattern, satisfying the user specified bar rules and other bar spacing requirements. The optimum design results are compared with those in the available literature, and the results are presented. It is concluded that the proposed optimum design model yields rational, reliable, economic and practical designs.

In this paper, the artificial neural networks (ANNs) model in predicting the torsional strength of reinforced concrete (RC) beams is done. Experimental data of 85 rectangular RC beams under pure torsion from an existing database in the literature were used to develop ANN model. The input parameters affecting the torsional strength were selected as dimensions of beams, spacing of stirrups, dimensions of closed stirrups, yield strength of stirrup and longitudinal reinforcement, steel ratio of stirrups, steel ratio of longitudinal reinforcement and concrete compressive strength. A back propagation neural network (BPNN) with the log-sigmoid activation function is adopted due to its accuracy of prediction. In addition to the ANN model is compared with well-known the building codes provisions for the design of RC beams under pure torsion. The study shows that the ANN models give reasonable predictions of the ultimate torsional strength of RC beams better than existing equations for torsion

In order to achieve both the good stiffness and strength, PMMA-ABS blend have been developed. The physical and mechanical properties of PMMA-ABS blend were examined. It has been found that the experimental and theoretical densities of the blend matched perfectly. Rockwell hardness is found to decrease linearly with increasing the ratio of ABS in the blend as ABS is softer than PMMA. However, at ratio of 70% of ABS the hardness was less than that for pure ABS. This is may be due to the effect of partial immiscibility of the two polymers that can be noticed through the visual test. The mechanical properties, i.e. compressive and flexural strength of the blend, found to be enhanced, up to limit, with increasing the ratio of ABS. Moreover, for all these properties, the blend exhibits higher mechanical properties than that for its two constitutes. It has been found that the blend with the ratio of 55% ABS produces the best combination of the stiffness and the strength.

Friction Stir Welding ( FSW ) is a solid –state process leads to several advantage over fusion welding methods. This process used a non-consumable tool to generate frictional heat required to performance sound joint. Tool pin profile, rotational speed, welding speed, play a major role to determine the weld quality .In this study, the effect of welding parameters (tool pin profile, rotational speed, welding speed) on mechanical properties and microstructure of 6061-T651 aluminum alloy joints are investigated. Results showed that tensile strength increases with welding speed and reaches a maximum value (235.7MPa)with welding parameters 900rpm,189mm/min threaded cylindrical pin and impact energy increased from 11J to 20j at weldingparameters:900rpm,116mm/min for threaded cylindrical pin. Also microstructure showed a fine grains with defect- free in weld zone.

Numerical results of a finite difference scheme are presented for the developing mixed forced – free laminar boundary layer flow in a vertical concentric annulus with a uniformly heated inner cylinder. The effect of a superimposed aiding or opposing free convection on the developing velocity profiles is investigated for a fluid with Pr=0.7 over the ranges of heat flux 50 ≤q≤250 (W/m2), Reynolds number 200≤Re≤1200 , and radius ratio 0.2≤N≤0.9. The effects of heat flux , Reynolds number , and radius ratio on the developing of the axial velocity profiles , temperature profiles , and local Nusselt number along annulus are discussed. Results show that the growth of the thermal boundary layer along the annulus increases as heat flux increases and Reynolds number decreases. Computer program in Fortran language was developed to carry out the necessary calculation.

Externally bonded, CFRP sheets are currently being studied and applied around the world for the repair and strengthening of structural concrete members.The experimental work includes investigation of four groups of beams. The first group includes two beams tested under combined torsion and bending (when torsion prevails T / M > 1). The second group includes two beams tested under pure torsion. The third group includes two beams tested under combined torsion and bending (when bending prevails T / M < 1). The fourth group includes two beams tested under pure bending.Test results were discussed based on torque – twist behavior, bending moment-deflection, beam elongation, failure modes and influence of CFRP on ultimate torque, ultimate bending moment.

In this research, an experimental work has been conducted to show the effect of adding of copper (Cu) and nickel (Ni) on the thermal properties of pure aluminum (AL) which were density of alloy, specific heat at constant volume (Cv), thermal conductivity (k) and thermal diffusivity .Ten alloys have been prepared by changing percentages addition of copper and nickel to pure aluminum and the percentages are (5,10,15,20&25%). The effect of an average deviation and variability on the thermal properties after an addition of copper and nickel through use of normal probability plot. The results shows as that copper addition percentage is increased lead to, increasing the alloy density by (57.7%), the thermal conductivity by (15.78%), decreasing the specific heat by (14.3%) and thermal diffusivity by (14.4%). Also as the nickel addition percentage is increased cause, increasing the alloy density by (67.3%), and decreasing the thermal conductivity by (18.6%),the specific heat by (11.8%) and the thermal diffusivity by (44.8%). Through this study it was found that the best addition is 25% (Cu) addition percentage for pure aluminum, gives highest thermal properties (Cv,k, ) compared with the same addition percentage of nickel . The greater average of deviation was the property of the specific heat when adding nickel and the greater variability was the property of the thermal conductivity when adding nickel.

An investigation to the turbulent lubrication performance of journal bearing considering journal misalignment and bearing elastic deformation has been established and validated through this work. Oil film pressure, side leakage flow rate, friction coefficient and misalignment moments at variant journal misalignment and bearing elastic deformation are calculated based on the modified Reynolds equation to include the effect of turbulent flow of oil due to high speeds of journal .Suitable models for journal misalignment and bearing elastic deformation have been used and included to the oil film thickness. Some of the results obtaind through this work have been compared with that obtained by the other workers and found to be in agood agreemnt. It has been shown that the combined effect of the bearing shell elastic deformation and the journal misalignment has a considerable effect on the bearing parametres and can not be neglected.

In this research, molds from fifteen concrete mixes were prepared to find the compressive strength and shrinkage using five levels of silica fume and three ratios of steel fibers. Based on the results of the study, the addition of steel fibers lead to reduce the 90 days shrinkage up to 59% , while the silica fume lead to an increase in the shrinkage of the concrete up to 84%.Results were compared with shrinkage of four supported models, the first model of equation (CEB), second model of equation (GL2000), third model of equation (B3) and the fourth of (ACI 209-93). Results of the comparison showed that the shrinkage by the ACI equation is the least.Shrinkage, High strength concrete, Steel fibers, Silica fume

In this study, the building of civil engineering department which includes the civil, environmental and architecture engineering departments were selected to study noise level during the year of 2010-2011. Noise level measurement was done at classrooms, teaching staff rooms and the main courtyard of the building by using two sound level meters type (2237 fulfici).This study covered about 70 day in order to give real measurement of noise level. After recording of daily measurement of noise level the hourly average for each part of the building and the whole building was calculated as well as the total average of noise level was calculated in order to compare it with the allowable limits of Environment Protection Agency (EPA) for educational institutions.The results of this study showed that the average of noise level for this building was 76.7 dB which is greater than the allowable limits that required range of 30-40 dB for such institution.