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Article
Effects of Rice Husk Ash–Magnesium Oxide Addition on Wear Behavior of Aluminum Alloy Matrix Hybrid Composites
تأثير إضافة رماد قشور الرز – اوكسيد المغنسيوم على سلوك البلى لمواد متراكبة هجينة ذات أساس من األلمنيوم

Authors: Abbas Y. Awad --- Mohammed N. Ibrahim --- Mohamed K. Hussein
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2018 Volume: 25 Issue: 4 Pages: 16-23
Publisher: Tikrit University جامعة تكريت

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Abstract

A336.0 aluminum alloy used to fabricate hybrid composites using rice husk ash (RHA) and MgO particles as reinforcement. The influence of the particles on the wear behavior of A336.0 aluminum alloy as a matrix that reinforced with MgO and RHA was investigated. Firstly, the rice husk burned at 700°C and then heat treated at 1100°C for 2 hrs. The ash characterized by X-ray florescence and X-ray diffraction. Less than 53 and 125 micron are the particle sizes of MgO and RHA respectively. The hybrid composites manufactured using stir casting method in two steps. A336.0 aluminum alloy reinforced with 4:0, 3:1, 2:2, 1:3 and 0:4 of RHA: MgO with 10 wt% total reinforcement phase. Optical microscope and X-ray diffraction were used to characterize the prepared hybrid composites. Dry slidingwear, hardness, apparent density, percentage of porosity and coefficient of friction were examined. Results indicated that porosity, apparent density and hardness enhanced with increasing MgO, while increasing wt% of RHA decreased the apparent density. Results indicated that with inceasing the applied load the wearrate of the composites was enhanced. Coefficient of friction varies inversely with applied load and wt% of RHA. Hardness increased with increasing RHA while the friction coefficient and the wear rate decreased. The minimum wear rates were at 10% RHA and Al-alloy-(RHA-MgO) [3:1] composites, while the minimum friction coefficients were at 10% RHA composites.

تم استخدام سبيكة ألمنيوم نوع 0.A336 لتحضير مادة متراكبة باستخدام رماد قشور الرز )RHA )مع اوكسيد المغنسيوم )MgO )كمواد تقوية. اجريت دراسة تأثير الدقائق المضافة على سلوك البلى للمادة المتراكبة الناتجة. تم تحضير الرماد بحرق قشور الرز عند 700 مئوي ثم اجراء معاملة حرارية للرماد المتكون عند 1100مئوي ولمدة ساعتين بعدها اجريت فحوصات للرماد لتحديد كمية االكاسيد باستخدام االصدار الفلوري لالشعة السينية )XRF )وكذلك استخدام حيود االشعة السينية )XRD )لتحديد االطوار المتكونة. حجم دقائق المسحوق لكل من اوكسيد المغنسيوم والرماد كانت اقل من 53 و125 مايكرون على التوالي. عملية االنتاج كانت باستخدام طريقة الدوامة على مرحلتين لخلط :RHA (MgO )مع منصهر سبيكة االلمنيوم وبنسب وزنية )0:4 ,1:3 ,2:2 ,3:1 ,4:0 )لنسبة خلط كلية 10 .%تم اختبار كل من الصالدة، معدل البلى، معامل االحتكاك، النسبة المئوية للمسامية والكثافة الظاهرية باإلضافة الى اجراء اختبار حيود االشعة السينية والفحص المجهري لعينات المتراكبات الناتجة. اظهرت النتائج ان زيادة نسبة اوكسيدالمغنسيوم يزيد من نسبة المسامات والكثافة الظاهرية باإلضافة الى رفع صالدة المركبات الناتجة، حيث عند 10 %من اوكسيد المغنسيوم ستزداد المسامات ألعلى مستوى وتقل الكثافة. كما تبين ان الصالدة تزداد مع زيادة نسبة الرماد بينما يقل معدل البلى ومعامل االحتكاك. لوحظ ايضا ان معامل االحتكاك يتناسب عكسيا مع ازدياد نسبة الرماد والحمل المسلط. اقل معدل بلى كان عند العينة 10%RHA والعينة ]1:3( ]MgO: RHA ،)بينما اقل معامل احتكاك كان عند العينة 10%RHA.


Article
Repairing of Reactive Powder Concrete T-Beams Containing Web Opening by CFRP Strips
اصلاح عتبات خرسانة المساحيق الفعالة ذات المقطع T الحاوية على فتحات في منطقة الجذع بشرائخ االلياف

Authors: Mazin B. Abdulrahman --- Husham Mohammed Rashid
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2019 Volume: 26 Issue: 1 Pages: 9-19
Publisher: Tikrit University جامعة تكريت

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Abstract

In modern buildings, transverse openings are often used beams for the purpose of supplying and service pipes. Due to the presence of the openings in the concrete beams lead to the formation of cracks around the openings due to the stresses concentration in a small area above and below of the opening. The repairing, maintenance, and upgrading of structural members, are maybe one of the most pivotal problems in civil engineering applications. In this research, an experimental work is conducted to study the behavior of the reinforced RPC T-beams that containing openings and repair this beams using CFRP strips. The Experimental program of the present study includes two parts, the first part includes testing of seven reinforced reactive powder concrete RPC T-beams, which casted and tested, one beam is without opening as a reference beam and the rest, were provided with an opening. and these beams are divided into two groups. The first group was used to study the effect of the openings shape (circular and square) and the second group was used to study the effect of the openings locations, which consists three locations (Lc/2, Lc/3 and Lc/4). These are measured from the support center to the openings center. While the second part including a repaired all beams in the first part the using carbon fiber polymer. The test results indicated that the presence of openings in the beams web caused a reduction in the reinforced RPC T-beams ultimate load carrying capacity with about (10-55)%, Also lead to increasing in deflection compared to control beam before repairing at same loading. Studying the shape effect showed that the beams with square openings have average ultimate load carrying capacity lower by 36% compared with the control beams. While beams with containing circular openings have average ultimate load carrying capacity lower 29%. From the test results, it could be concluded that the presence of the openings in the shear region led to a decrease in ultimate load carrying capacity a about 38% to 49% for opening of opening at (Lc/3 and Lc/4) respectively. While the presence of openings in the flexural region led to a decrease in the ultimate load carrying capacity rate of 11%. Related to the repairing study part it was found that the average ultimate load carrying capacity for repairing beams was 103% compared with the not repairedbeams.

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