Çatlağın Re-entrant ve Balpeteği Yapıların Mekanik Davranışlarına Etkisinin Sonlu Eleman Analizi

Teknolojideki gelişmeler yeni malzemeler, daha hafif ve daha verimli yapıları ve ayrıca yeni üretim yöntemlerini gerektirmektedir. Bu çalışmada, topoloji optimizasyonu, düzenli balpeteği yapıları ve re-entrant yapılar hakkında araştırmalar yapıldıktan sonra düzenli balpeteği ve re-entrant yapılar tasarlanmış ve sonrasında Ti6Al4V malzeme, sonlu elemanlar analizinde kullanılmak üzere seçilmiştir. Sonlu elemanlar analizlerinde balpeteği ve re-entrant yapılara 1 mm, 1,5 mm ve 2 mm olmak üzere üç farklı kiriş kalınlığı atanmıştır. Ayrıca, modellerde çatlak oluşturulmuş ve sonrasında 2 boyutlu sonlu elemanlar analizleri y ekseni boyunca uygulanan çekme kuvvetleri altında hem çatlaklı hem çatlaksız balpeteği ve re-entrant yapılar için yapılmıştır. Daha sonra, çatlağın gerilme yığılma faktörü, gerilmeler, gerinimler ve yer değiştirmelere etkileri elde edilmiş ve düzenli balpeteği yapıların ve reentrant yapıların ökzetik davranışı karakterize edilmiştir. Ayrıca, her bir yapı için kiriş kalınlığındaki artış gerilme ve gerinimleri azaltmaktadır. Dahası, re-entrant yapılar geometrik özelliklerinden dolayı negatif poisson oranına sahiptirler ve çatlağın re-entrant yapıdaki eşdeğer gerilmeye etkisi balpeteği yapısına kıyasla dikkate değer bir şekilde ortaya çıkmaktadır. Sonuç olarak, sadece 1mm kiriş kalınlığına sahip balpeteği yapısında analizlerden elde edilen gerilme yığılma faktörünün balpeteği yapının kırılma tokluğundan büyük olmasından dolayı kırılma gözlemlenmesi beklenmektedir.

Finite element analyzing of the effect of crack on mechanical behavior of honeycomb and reentrant structures

Developments in technology require the new materials, lighter and more efficient structures and also new manufacturing methods.In this study, after doing researches about topology optimization, regular honeycomb and re-entrant structures; the regularhoneycomb and re-entrant structures were designed, and then Ti-6Al-4V material was chosen for these structures in finite element(FE) analyzing. The three different rib thickness values (t) of 1 mm, 1.5 mm and 2 mm were assigned for honeycomb and re-entrantstructures in FE analyses. Also, the crack was created on the models, and then 2-D FE analyses were done for both cracked andun-cracked honeycomb and re-entrant structures under tensile forces through y axis. Afterwards, the effect of crack on stressintensity factor, stresses, strains and displacement were obtained and characterized the auxetic behavior of the regular honeycomband re-entrant structures. Furthermore, increase in rib thickness decreases stress and strains for each structure. Moreover, re-entrantstructures have negative Poisson’s ratio due to their geometric properties and the notable effect of crack on the equivalent stress inre-entrant was emerged in comparison with honeycomb structure. As a result, the only possible fracture in honeycomb for thicknessof 1 mm might be observed owing to stress intensity factor obtained from analyses bigger than fracture toughness of honeycombstructure.

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