Print ISSN: 1681-6900

Online ISSN: 2412-0758

Volume 38, Issue 3

Volume 38, Issue 3, June 2020

Influence of Recycled Fine Aggregates on Strength Properties of Reactive Powder Mortar

Doaa H. Nayyef; Shatha S. Hasan

Engineering and Technology Journal, 2020, Volume 38, Issue 3, Pages 288-294
DOI: 10.30684/etj.2021.168197

Although many researchers have done many studies on recycled aggregate concrete, information is very little about the influence of utilizing recycled aggregate in the production of reactive powder concrete. Experimental work was executed to investigate the influence of utilizing recycled concrete as fine aggregate in reactive powder concrete. Five different mixes were prepared, the first mix, or control mix, was prepared with natural sand, four additional mixes were prepared with different percentage of substitution of fine aggregates(20%,40%,60%, and 80%). The investigation was carried out using compressive strength test, direct tensile strength test and flexural strength test, and two methods of curing were used standard curing at 20 °C and steam curing at 90°C. the results indicated that the strength decreases with increased the percentage of recycled fine aggregate, and the best percentage was 40% replacement where the percentages of decrease at this percentage at 28-day steam curing were 2.46, 6.66, and 2.14 for compressive strength, flexural strength, and direct tensile strength respectively.

Investigation of the Effect of Nano Powder Mixed Dielectric on EDM Process

Rasha R. Elias

Engineering and Technology Journal, 2020, Volume 38, Issue 3, Pages 295-307
DOI: 10.30684/etj.2021.168198

In this paper, Artificial Neural Network was adopted to predict the effect of current, the concentration of aluminum oxide (Al2O3) and graphite Nanopowders in dielectric fluid for the machining of Carbon steel 304 using Electrical Discharge Machining (EDM). The process variables were utilized to find their effect on Material Removal Rate (MRR), Surface Roughness (SR), and Tool Wear Rate (TWR). It was revealed from the experimental work that the addition of aluminum oxide and graphite Nanopowders into dielectric fluid maximizing MRR, minimized the SR and TWR at various variables. Minitab software was used in the design of experiments. Analysis of the process outputs of EDM indicates that graphite powder concentration greatly influencing SR also the discharge current whereas the current and Nanopowders concentration has more percentage of influence on the TWR and MRR.

Improved Wear Rate Resistance, Compression Strength and Hardness of Polymethylmethacrylate Resin with Orange Peel Powder for Artificial Denture Base

Reem A. Mohammed

Engineering and Technology Journal, 2020, Volume 38, Issue 3, Pages 308-318
DOI: 10.30684/etj.2021.168199

The material utilized for manufacturing artificial dentures should have high-grade mechanical properties in order to resist heavy forces inside the mouth. This study includes investigation of some of the mechanical properties (wear rate resistance, compression strength, and hardness) of the specimens prepared by (hand lay-up) method. The wear behavior experiments were performed on (a pin-on-disk tester) under various factors 5%, 8%, 11%, 14%, 17% weight fraction of orange peel, (10, 15, 20 N) load applied and (5, 10, 15 minutes) sliding time, and analysis these experimentally by using the Taguchi’s experimental design (L9) (MINITAB 16). Tests explicated that the specimens (polymethylmethacrylate - 17% orange peel) composites have the best wear rate resistance, compression strength and hardness shore D (0.040×10-5 cm3/, 142 MPa, 86 shore D) respectively than other specimens (polymethylmethacrylate - 5%, 8%, 11%, 14% wt. orange peel) and these specimens better than the specimens standard polymethylmethacrylate, which could be attributed to the homogeneous dispersion of orange peel particles in the polymethylmethacrylate resin matrix. The results (signal to noise ratio) showed the factors (17% weight fraction) orange peels, (20 N) load applied, and (5 min) sliding time gives the best wear rate resistance. The results of the analysis of variance showed the sliding time (C) is the essential factor effect on the wear rate resistance followed by (A) weight fraction of orange peels and (B) load applied were less affected on wear behavior rate.

Improving the Stability and Critical Speed of Rotor Bearing System By Using External Damping Source

Tariq M. Hammza; Nassear R. Hmoad; Ehab N. Abas

Engineering and Technology Journal, 2020, Volume 38, Issue 3, Pages 319-324
DOI: 10.30684/etj.2021.168200

Improving the essential factors of rotor bearing system are the aim of this study. In addition to the presence of two ball bearings to support the rotor, two additional fluid film journal bearings have been used as an external damping sources. The ANSYS Mechanical APDL 18.0 was used to model rotor bearing system with existence of two additional fluid film journal bearings. Matlab software has been used to achieve the analytical solution. The results clearly showed that the maximum response displacement strongly decreasing and the critical speed has been enhance by using an external damping source as well as the stability of rotor bearing system has been improved due to increasing damping of rotor system where the response displacement decreasing by 99% and critical speed increasing by 0.6% when using an external damping sources. The position of damping source has an important effect on the maximum response displacement and the more decreasing value of response displacement has been achieved when the damping source become as close as possible to the disk position.

Effect of Laser Shock Peening on Fatigue Stress Concentration of Polyester Reinforced by Al-Micro Powder Composites

Ahmed N. Al- Khazraji; Ammar A. Mutasher

Engineering and Technology Journal, 2020, Volume 38, Issue 3, Pages 325-334
DOI: 10.30684/etj.2021.168201

Laser shock peening is a widely common process for materials treatment and typically used for fatigue strength enhancement especially for metals. In this paper, its effect on polymeric composite materials studied experimentally. Unsaturated polyester was used as a matrix in order to composites preparation and Aluminum powder as fillers. A Hand lay-up technique has been used for composites making. Composites with three volume fractions of Aluminum powder were prepared (2.5%, 5%, and 7.5%). Fatigue specimens as a standard and with (1mm) semi-circular notch are prepared for testing. The fatigue test was performed at room temperature and stress ratio (R=-1). Laser shock peening with two levels of energy have been applied (1Joule, and 2Joule). The results showed an increase in the endurance strength of the notch for 7.5% volume fraction especially at 1J laser energy by about 26.7056% compared with the un-treatment notched state, which in turn reduced the fatigue stress concentration by about 21.0508% compared with standard fatigue stress concentration. On the other hand, the presence of notch effect on endurance strength was increased after laser treatment of composites with 2.5% volume fraction and the reduced was by about 39.698% at 2J laser energy.

Production of Self-Cleaning SiO2/CNT Nanoparticles Substituted Cement Mortar

Layth Al-Gebory; Aseel B. Al‐Zubaidi; Ahmed A. Al‐Tabbakh

Engineering and Technology Journal, 2020, Volume 38, Issue 3, Pages 335-342
DOI: 10.30684/etj.2021.168202

Manufacturing of building materials with unique properties is one of the most important key-parameters in the development of construction engineering and building materials. The development in the nanomaterials and nanotechnology can be utilized in this field. In this paper, production of eco-friendly, low water absorption and self-cleaning cement mortar reinforced with carbon nanotubes and nano-silica with different weight percentages (0.5%, 1.5%, and 2%) is performed. Results showed prominent improvement of hardness, compression strength and a decrease of water absorption and bending resistance in the reinforced cement mortars. The results show the possibility to control the mechanical properties of the cement mortars with minimal reinforcing agents provides the possibility to design these building materials for versatile applications