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Article
Evaluation of the stress concentration of different incisal ridge preparations of porcelain veneers (Finite element analysis)

Author: Abbas F. Al-Huwaizi عباس فيصل الحويزي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2013 Volume: 25 Issue: 4 Pages: 1-4
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Porcelain veneers are under a great deal of stress which may lead to clinical failure as fracture ordettachment. This study examined whether different finishing lines and lingual shoulder preparations in the incisalarea of the maxillary central incisor affect the bond of the porcelain veneers.Materials and methods: A two- dimensional finite element model was made. Location and magnitude of maximumVon Mises stresses were calculated in porcelain veneer. Six types of preparations were drawn as:incisal overlap of0.5mm, 1mm and 1.5mm depth and lingual shoulder, and incisal overlap of 0.5mm, 1mm and 1.5mm depth withoutshoulder preparation.Results: Stress formation is maximum in the incisal edge region. All the lingual shoulder preparations presented betterstress distribution than the non shoulder preparationsConclusion: Stress is distributed more evenly when the tested preparation possesses a good thickness of porcelainand the more the surface area with incisal overlap the less possibility of bond failure


Article
MICROMECHANICAL MODELING OF SHORT –FIBER REINFORCED POLYMERIC
النمذجة الميكانيكية الدقيقة لمركب مسلح بألواح البوليمر

Author: Kareem N. Hussien كريم نجم حسين
Journal: Muthanna Journal of Engineering and Technology(MJET) مجلة المثنى للهندسة والتكنولوجيا ISSN: 25720317 25720325 Year: 2013 Volume: 2 Issue: 2 Pages: 73-82
Publisher: Al-Muthanna University جامعة المثنى

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Abstract

This paper presents a method considering the effect of fiber geometry and volume fraction for predicting the tensile strength, shear stress and Von Mises stress. The finite element scheme for the micromechanical modeling of the behavior of fiber reinforced polymeric composites under external load is developed. The model is used to estimate the stress distribution throughout the composite domain and to identify the location where maximum stresses occur. The ratio between fiber modulus and matrix modulus must be high enough to improve the mechanical properties and to reduce the premature interfacial failure. The prediction of the stress distribution by using a simulation tool could be helpful for more understanding the real reasons behind failure of polymer composites.

يقدم هذا البحث طريقة لحساب تأثير أبعاد الألياف ونسبتها الحجمية للتنبؤ بقيم مقاومة الشد, أجهاد القص وأجهاد فون ميسيس. اعتمد هذا البحث على تطوير طريقة العناصر المحدودة لنمذجة التصرف المايكروميكانيكي للبوليمر المقوى بالألياف تحت تأثير الحمل الخارجي. أستخدم النموذح العددي لتقدير توزيع الأجهاد على مدى المادة المركبة بغرض تحديد أماكن الأجهاد الاقصى. تعتبر النسبة العالية بين معامل الليف الى البوليمر أساسا لتحسين الخواص الميكانيكية ولمنع الأنهيار المبكر . أن التنبؤ بتوزيع الأجهاد باستخدام نماذج المحاكاة الدقيقة يساهم في زيادة الفهم لأسباب الأنهيار للمواد البوليمرية المركبة.

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