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Article
Effectiveness of Naphthalene in Grain Refinement of Commercially Pure Aluminum and Zinc Ingot Castings

Author: Assifa M. Mohamad
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2011 Volume: 29 Issue: 8 Pages: 1545-1553
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

It is well established that the properties of cast metals are greatly improved by refinement of their grain size. The method employed in this study for the refinement of grain size of commercially pure aluminum and zinc castings is inoculation of naphthalene in powder form to the mould prior to pouring the molten metal. The results show that theaddition of naphthalene remarkably suppresses the formation of columnar grains and refines the structure. Increasing the amount of naphthalene addition also minimizes and may eliminate the formation of the shrinkage cavity. Furthermore, the ability of castingsfor mechanical working increases as the naphthalene addition increases


Article
Wear Performance of a Laser Surface Hardened ASTM 4118 Steel
سلوك البلیان للفولاذ 4118 ASTM المصلد سطحیا باللیزر

Author: Assifa M. Mohamad
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2013 Volume: 31 Issue: 17 Part (A) Engineering Pages: 3235-3244
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

In this investigation ASTM 4118 steel was treated by using pulse Nd: YAGlaser with wave length 1064nm and pulse duration 100ns. In order to assess thenew tribological properties of laser surface hardened ASTM 4118 steel, the wearresistance between specimens treated with laser and those of conventionallyhardened under dry sliding conditions was compared. The change of wearmechanisms in laser hardened 4118 steel resulted in distinct difference in wearrates.The results showed that quenched zones not only had sufficient depth ofhardening and higher hardness, but had more retained austenite and finer carbidesbecause of a higher degree of carbide dissolution. Laser surface hardened ASTM4118 steel specimens exhibited superior wear resistance to their conventionallyhardened specimens due to the change in the microstructure hardening, highhardness. The wear mechanism for both the laser quenched layer andconventionally hardened layer was highly similar, generally involving adhesivewear mechanism , material transfer, wear induced oxidation and plowing. Also theresults of hardness show that increases with increasing of laser energy by 70%.


Article
Influence of Cut Out Way on the Elastic-Plastic Behavior of AL-Cu Alloy
تأثير طريقة القطع على التصرف المرن- اللدن لسبيكة الالمنيوم- نحاس

Authors: Farag M. Mohammed --- Assifa M. Mohamad --- Dunia H. Escander
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2010 Volume: 28 Issue: 15 Pages: 5000-5013
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The influence of cut out way on the elastic-plastic behavior of AL-Cu alloy was studied in the present work experimentally and numerically using finite element method with aid of ANSYS-11 software. Central circular hole were introduced in (ASTM B 557-02a) tension specimens of alloy using drill and punch at cold and warm working conditions with (3.5, 4.25 and 6) mm diameters. Based on the results from experimental tension tests, as the hole diameter increases the mechanical properties of the alloy decreases. Tensile strength and yield stress with using bunch are less than that of using drill by 4% and 6% at cold condition, while at warm working condition by 34% and 42% respectively. But the elongation at maximum tensile strength of using punch is greater than that of using drill at cold working condition and vice versa at warm working condition. The fractures with using punch happen faster than that of using drill at lower strain rate. The apparent stress concentration factor ranged from 1.19 to 2.9 with using drill, and from 1.25 to 3.39 with using punch. The numerical results present the von Mises Stress distribution to identify the location that possiblyinitializes the fracture, and to estimate the stress concentration factor in which ranged from 2.13 to 2.39 and have reasonable agreement results with literatures.

في هذا البحث تمت دراسة تأثير طريقة القطع على التصرف المرن -اللدن لسبيكة(ANSYS- الالمنيوم-نحاس عمليا وعدديا باستخدام طريقة العناصر المحددة بمساعدة برنامج ( 11 (ASTM B 557-02a) على الحاسبة. تم عمل ثقب دائري مركزي في عين ات اختبار الشد ,4.25 , باستخدام المثقاب والسلبك وعند ظروف تشغيل على البارد و على الساخن وعند أقطار ( 3.5 6) ملم. حيث بينت نتائج الاختبار العملي ان الخواص الميكانيكية تقل كلما ازداد قطر الثقب وان% مقاومة الشد واجهاد الخضوع باستخدام السلبك تقل عن مثيلاتها باستخدام المثقاب بنسبة 4% و 6 عند التشغيل على البارد و بنسبة 34 % و 42 % عند التشغيل على الساخن على التوالي . ان الاستطالة عند مقاومة الشد الأعظم باستخدام السلبك تكون اكبر منها باستخدام المثقاب للتشغيل علىالبارد والعكس بالعكس للتشغيل على الساخن. الكسر يحدث عند استخدام السلبك اسرع منه عند استخدام المثقاب. ان معامل تركيز الاجهاد الظاهري يتراوح من 1.19 الى 2.9 باستخدام المثقاب (von Mises) ومن 1.25 الى 3.39 باستخدام السلبك. نتائج التحليل العددي تظهر توزيع اجهاد والذي يساعد على استدلال موقع بداية حدوث الكسر وكذلك حساب معامل تركيز الاجهاد والذي وجدبين 2.13 و 2.39 وهذا يعطي توافقا مقبولا مع النتائج الموجودة في الدراسات السابقة.

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