Üretim geçmişi dikkate alınarak dinamik eksenel yük altında ince cidarlı tüplerin çarpışma performansının araştırılması ve optimizasyonu
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Tarih
2019
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Yayıncı
Bursa Teknik Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
İnce cidarlı tüpler, yüksek enerji emilim kabiliyetleri, düşük ağırlıkları ve düşük maliyetleri nedeniyle, özellikle motorlu araçların ön bileşenlerinde, uçaklarda ve trenlerde yaygın olarak kullanılmaktadır. Enerji emilim amacıyla kullanılan ince cidarlı tüplerden, kontrollü bir şekilde plastik deformasyona uğrayarak kinetik enerjiyi emmesi beklenir. Bu nedenle ince cidarlı tüplerin olası bir kaza anında nasıl davrandığını anlamak, seçilecek geometri ve malzeme açısından son derece kritiktir. Tez kapsamında, ilk olarak kesit çevre ve boy uzunlukları eşit olacak şekilde kare, altıgen, sekizgen, silindir ve uzun çap/kısa çap oranları farklı üç adet elips olmak üzere toplam yedi model tasarlanmıştır. Geometrik parametreler belirlenirken tüplerin eşit kütlede olması hedeflenmiştir. Al6061-T6 alaşımı tüplerin malzemesi olarak seçilmiştir. Tüpler alt ve üst olmak üzere iki parçadan oluşturulmuş ve toplam yirmi dört adet punta kaynağı kullanılarak birleştirilmiştir. İnce cidarlı tüplerde şekillendirme sırasında kalınlık değişimleri, plastik birim şekil değişimleri ve pekleşme olabilmektedir. Bu değişimlerin tüplerin çarpışma performansı üzerinde etkili olup olmadığını gözlemleyebilmek için tüpler plastik şekil verme uygulamalarından olan derin çekme ile üretilmiştir. Bütün modellerin derin çekme analizleri sonlu elemanlar yöntemi kullanılarak yapılmıştır. Daha sonra üretim geçmişi modellere aktarılarak çarpışma analizleri tekrarlanmıştır. İnce cidarlı tüplerin yüksek ilk tepki kuvveti en büyük dezavantajlarıdır. Bu nedenle ilk tepki kuvvetini düşürmek amacıyla üretim geçmişi aktarıldıktan sonra çarpışma performansı bakımından en iyi sonucu veren modele tetikleyici mekanizması eklenmiştir. Tetikleyici mekanizmasının tüp üzerindeki konumunun ve yarıçapının tüpün çarpışma performansı üzerinde yüksek etkisi vardır. Bu nedenle en uygun konum ve yarıçapı bulmak amacıyla optimizasyon çalışması yapılmıştır. Yanıt yüzey tabanlı optimizasyon yöntemi olan Küresel Yanıt Yüzey Yöntemi (KYYY) kullanılmıştır. Sonuçlar seçilen kesit geometrisinin tüplerin çarpışma performansı üzerinde etkili olduğunu göstermiştir. Ayrıca üretim geçmişinin modellere aktarılmasıyla, modellerin deformasyon şekillerinde değişimler olmuştur. Üretim geçmişi özellikle bazı modellerde tüplerin çarpışma performansına önemli ölçüde etki etmiştir. Tetikleyici mekanizmasının eklenmesiyle, ilk katlanma tetikleyici mekanizmasının bulunduğu bölgeden başlamış ve maksimum tepki kuvvetinde %35,47 düşüş sağlanmıştır. Optimizasyon çalışması sonrası ise başlangıç tasarımına göre emilen enerji miktarında %3,991 artış, maksimum tepki kuvvetinde ise %5,79 düşüş sağlanmıştır. Daha sonra optimum tasarıma üretim geçmişi aktarılmış ve maksimum tepki kuvvetinde %3,614, emilen toplam enerji miktarında ise %5,218 düşüş olmuştur. İnce cidarlı tüplerin tasarımında SolidWorks ve CATIA yazılımlarından, sonlu elemanlar analizinin gerçekleştirilmesinde ise HyperWorks 2017.2 paket programında bulunan, HyperMesh, HyperCrash, HyperMorph, HyperStudy, HyperView, HyperGraph, ve RADIOSS yazılımlarından yararlanılmıştır. Tüm analizlerde açık zaman entegrasyon ve lineer olmayan sonlu elemanlar kodları kullanılmıştır.
Thin-walled tubes are widely used in front-components of motor vehicles, airplanes and trains, due to their high energy absorption capabilities, low weight and low costs. Thin-walled tubes used for energy absorption are expected to absorb kinetic energy by undergoing plastic deformation in a controlled manner. Therefore, understanding how thin-walled tubes behave in the event of a possible accident is extremely critical in terms of geometry and material to be selected. Within the scope of the thesis, a total of seven models with equal perimeter and longitudinal length were designed, namely square, hexagonal, octagonal, cylinder and three ellipses. In determining the geometric parameters of tubes, it is aimed to have equal mass. Al6061-T6 alloy was selected as the material of the tubes. The tubes were formed from two parts, upper and lower. A total of twenty-four spot welds were used to assemble tubes. Thin-walled tubes may have thickness changes, plastic strain and work hardening during forming. In order to observe the effect of these changes on crashworthiness of the tubes, the tubes are produced by deep drawing which is one of the plastic forming applications. Deep drawing analysis of all models was performed by using finite element method. Then, the forming history was mapped to the models and the crash analyzes were repeated for all models. The high initial crushing force of thin-walled tubes is their biggest disadvantage. Therefore, in order to reduce the initial crushing force, the trigger mechanism was added to the model which gave the best result in terms of crashworthiness after the forming history was mapped. The location and radius of the trigger mechanism on the tube have a high impact on the tube's crashworthiness. For this reason, an optimization study was performed to find the most suitable location and radius. Global Response Surface Method (GRSM) was used which is a response surface based optimization method. The results showed that the selected cross-section geometry was effective on the crashworthiness of the tubes. In addition, there have been changes in the deformation shape after forming history was mapped to the models. The production history has significantly affected the crashworthiness of the tubes, especially in some models. With the addition of the trigger mechanism, the first folding began from the region of the trigger mechanism and the peak crushing force decreased by 35.47%. After the optimization study, an increase of 3.991% in the amount of absorbed energy and a decrease 5.79% in the peak crushing force was achieved according to the initial design. Then, the forming history was mapped to optimum design and the peak crushing force decreased by 3,614% and the total amount of absorbed energy decreased by 5,218%. In the design of thin-walled tubes, SolidWorks and CATIA V5 software were used. HyperMesh, HyperCrash, HyperMorph, HyperStudy, HyperView, HyperGraph, and RADIOSS software were used for finite element analysis. Explicit and non-linear finite element codes were used in all analyzes.
Thin-walled tubes are widely used in front-components of motor vehicles, airplanes and trains, due to their high energy absorption capabilities, low weight and low costs. Thin-walled tubes used for energy absorption are expected to absorb kinetic energy by undergoing plastic deformation in a controlled manner. Therefore, understanding how thin-walled tubes behave in the event of a possible accident is extremely critical in terms of geometry and material to be selected. Within the scope of the thesis, a total of seven models with equal perimeter and longitudinal length were designed, namely square, hexagonal, octagonal, cylinder and three ellipses. In determining the geometric parameters of tubes, it is aimed to have equal mass. Al6061-T6 alloy was selected as the material of the tubes. The tubes were formed from two parts, upper and lower. A total of twenty-four spot welds were used to assemble tubes. Thin-walled tubes may have thickness changes, plastic strain and work hardening during forming. In order to observe the effect of these changes on crashworthiness of the tubes, the tubes are produced by deep drawing which is one of the plastic forming applications. Deep drawing analysis of all models was performed by using finite element method. Then, the forming history was mapped to the models and the crash analyzes were repeated for all models. The high initial crushing force of thin-walled tubes is their biggest disadvantage. Therefore, in order to reduce the initial crushing force, the trigger mechanism was added to the model which gave the best result in terms of crashworthiness after the forming history was mapped. The location and radius of the trigger mechanism on the tube have a high impact on the tube's crashworthiness. For this reason, an optimization study was performed to find the most suitable location and radius. Global Response Surface Method (GRSM) was used which is a response surface based optimization method. The results showed that the selected cross-section geometry was effective on the crashworthiness of the tubes. In addition, there have been changes in the deformation shape after forming history was mapped to the models. The production history has significantly affected the crashworthiness of the tubes, especially in some models. With the addition of the trigger mechanism, the first folding began from the region of the trigger mechanism and the peak crushing force decreased by 35.47%. After the optimization study, an increase of 3.991% in the amount of absorbed energy and a decrease 5.79% in the peak crushing force was achieved according to the initial design. Then, the forming history was mapped to optimum design and the peak crushing force decreased by 3,614% and the total amount of absorbed energy decreased by 5,218%. In the design of thin-walled tubes, SolidWorks and CATIA V5 software were used. HyperMesh, HyperCrash, HyperMorph, HyperStudy, HyperView, HyperGraph, and RADIOSS software were used for finite element analysis. Explicit and non-linear finite element codes were used in all analyzes.
Açıklama
Anahtar Kelimeler
Makine Mühendisliği, Mechanical Engineering
