Kamyonlarda kullanılan kriko takozlarının yapısal analizi ve optimizasyonu
Structural analysis and optimization of jack mounts used in trucks
Yazar: EROL ERNEK
Danışman: PROF. DR. HİKMET KOCABAŞ
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Konstrüksiyon Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Makine Mühendisliği = Mechanical Engineering ; Otomotiv Mühendisliği = Automotive Engineering
Dizin: Hidrolik takoz = Hydraulic mount ; Kompozit polimerler = Composite polymers ; Optimizasyon = Optimization

Özet:
Bu tez, kamyonlarda kullanılan ahşap malzemeden yapılmış takozlarda ortaya çıkan problemlere odaklanmaktadır. Araçların bakımları sırasında kamyonlarda kriko kullanılması durumunda kalınabilir. Kamyonlarda genellikle lastik değişimi, bakım veya arıza durumlarında krikoyu kullanma durumu oluşur. Kamyon sürücüleri ve bakım ekipleri, genellikle güvenlik kurallarına uygun bir şekilde krikoyu kullanmalıdır. Bu durum, aracın istenmeyen bir şekilde devrilmesini veya krikonun, güvenliğini tehlikeye atacak durumları önlemek için önemlidir. Bu nedenle krikolar, konumlanırken düz zeminde konumlanması gerekmektedir. Ayrıca kamyonlarda krikonun yerleştirme yuvası ile zemin arasındaki yükseklik çeşitli seviyelerde bulunmaktadır. Bazı durumlarda krikonun kaldırma yüksekliği aracın bakım ve onarım işlemleri için yeterli olmadığı görülmüştür. Güvenlik ve yükseklik nedenlerinden dolayı düz bir zemine sahip yükseltilebilecek bir ekipmana ihtiyaç duyulmuştur. Geçmişte kamyonlardaki bu problemi, krikonun ahşap takozuyla çözülmüştür.
Ahşap takozlar, birçok katman halindeki plakaların lamine edilmesiyle veya tek bir parça halinde oluşmaktadır. Kullanılan malzemenin ham maddesi özel olarak Belarus ülkesinden ithal edilip son ürüne ulaşılmaktadır. 2014 yılında başlayan Ukrayna-Rusya çatışmalarından sonra malzeme bulunmasında bir dar boğaza doğru gidilmişti. Devamında, gelişen yıllarda Belarus'a karşı olan ambargo nedeniyle bu malzemenin tedariğinde daha büyük problemler yaşandı. Dolayısıyla parçanın malzeme değişimine gitmesi düşünüldü. Bir diğer problem ise parçanın böceklenme, mantarlanma ve bozulmasına karşı korunmaya ihtiyacı vardır, bunun için ekstra olarak koruma işlemi yapılmaktadır. Ayrıca parçanın içerisinde organik maddeler taşınabilme ihtimalinden dolayı bazı ülkelerde bu tarz ahşap malzemelerin kullanılması ve transport işlemleri için özel belgeler alınması gerekmektedir.
Bu nedenlerden dolayı, parçamızı optimize ederek daha kolay bir üretim sağlayıp bu sorunları aşmayı hedeflenmiştir. Bu bağlamda, tezde kamyon takozlarında polimer malzeme kullanımının potansiyel faydaları ve tasarım değişikliklerinin incelenmesi amaçlanmaktadır.
Tez, polimer malzemenin ahşap malzeme yerine kullanılmasının avantajlarını ele alacaktır. Polimer malzemelerin böceklenmeye karşı dirençli olmaları, dayanıklılıkları ve hafif yapıları, kamyon takozlarının performansını artırabilir ve uzun ömürlü kullanım sağlayabilir. Ayrıca, polimer malzeme kullanımının taşıma maliyetlerini azaltabileceği ve tedarik güvenliğini artırabileceği görülmüştür.
Tez aynı zamanda kamyon takozlarının tasarımında yapılacak değişikliklerin, özellikle daha hafif bir yapı oluşturarak kamyon şoförleri ve taşımacılık şirketleri için kolaylık sağlama potansiyelini değerlendirecektir. Bu değişikliklerin kamyon takozlarının kullanımı ve taşınabilirliği üzerindeki etkileri incelenecek ve sürdürülebilir olması değerlendirilecektir.
Sonuç olarak, bu tez, kamyon takozlarında polimer malzeme kullanımının ve tasarım değişikliklerinin, ahşap malzeme kaynaklı problemlere karşı çözüm sağlayarak kamyon taşımacılığı endüstrisine nasıl katkı sağlayabileceğini ortaya koymayı amaçlamaktadır.

Abstract:
Trucks are exposed to deformations due to long road conditions and the loads they carry. These deformations in trucks cause the vehicles to need maintenance and repair. Brands on the market generally offer a wide range of emergency assistance system services for their vehicles. However, in cases where this assistance service cannot be reached or the driver can do it himself, they can use the maintenance and repair kits in the vehicles.
Maintenance and repair kits are generally fixed by standards and laws. The reason for this is to ensure that vehicles are not left on the roads in emergency conditions. In some emergency situations that may occur in vehicles, the vehicle needs to be lifted to a certain height. Jacks are used to reach this height. Jacks are tools used to lift a certain load by applying little force. The important point here is that the loads lifted by the jacks can represent the fully loaded state of the vehicle. Therefore, safety precautions must be taken while lifting the jack.
When looking at the design of the jacks, the minimum height and the maximum height that it can lift to carry the load are important. Generally, jacks that provide the values of norms and standards are used in the markets.
In some cases, jacks may need an extra piece to provide the required height. This part needed by jacks is called jack wedge or jack chock. These wedges allow the jack to increase its height, provide flatness on bad ground and operate safely.
The wedge we use today is a piece with dimensions of 60x200x200 mm. It is made of wooden material. Wood material is an organic material. Therefore, it is a material suitable for decay. The part must be durable as it will lift the entire load of the jack. To ensure this strength, wooden material is subjected to various processes. In addition, due to the organic structure of the material, it is possible for different organisms to settle in it. Such situations cause problems in the transportation of the part. In countries such as China, extra documentation is required to use such organic materials. To minimize these organic effects, extra surface coating and chemical additions are made. Each process not only increases the cost of the part but also changes its emission values. Apart from these, the type of wood that is the raw material of the current material can only be specially imported from Belarusian forests. During the Ukraine-Russia war, relations with Belarus went through a difficult period. There was no raw material supply during this process.
Due to the reasons mentioned above, such as lack of raw materials, transportation problems, and durability problems, a new design and material that is simpler and lighter, and at the same time has abundant and cheap raw materials, has been studied.
In this thesis study, the structural analysis of new designs made in accordance with new materials and geometry using FEM was examined. Comments were made on the material that could be selected in accordance with the results of this analysis.
There are two main topic in the thesis study. One of these is design change. The current design has a heavy structure, and there is a high probability of deformation and deterioration due to its material. In addition, due to the material, the presence of voids or organic components in the interior during the production of the part risks the safety of the part. Therefore, the new design was made taking these problems into consideration. Nature was targeted as the main basis of the design. The structures in nature were examined and the application to the wedge was made accordingly. Various structures were created and factors such as thickness and distance changes within these structures were examined. Each design created from profiles such as square, round, triangular, segmented and hexagonal was examined in finite element analysis in the Nastran NX program. Additionally, each piece was examined in terms of production techniques. By combining all the results, the design of the most optimum part was examined. The manufacturability of the design was also examined and the results were emphasized. According to the FEM analyzes and results, as well as due to the production conditions, studies were carried out to make the part a segmented structure. First, the thickness distribution of the part between layers was examined. According to the results, the most optimum thicknesses were determined and the outlines of the geometry we will optimize were created.
In order to optimize the work done, finite element tests were carried out on sub-regions with different thicknesses and profiles. Based on the test results, it was decided to make a few more optimizations. The insides of the cylinders are reinforced to reduce the stress accumulated in the middle parts of the part. The effect of this reinforcement has been investigated. Then, corner rounding /edge blending and beam structures were created at the bottom, respectively, and the final optimum design was reached.
Another region is where the hexagonal structure is located. This structure provides strength and low weight to the part. For this reason, it was intended to be evaluated at the highest level. Each of the results was examined and material selection was studied.
The strength and recyclability of the part are important for the material. Nowadays, there are many recycled polymer materials, the most important feature of which is their high strength. The most important criterion for material selection is that it works for a long time without deformation. For this reason, the stress values found must be less than the yield values of the materials.
As a result, jack wedges/chockes are parts that ensure the safety of jacks in vehicles by creating a flat surface while using them and provide more convenient operation by creating extra height. Due to developing technology and changing vehicle types, a cheaper and easier solution is offered by using this part in vehicles with extra height. The currently used part is made of wood material. The shortage of raw materials for this material has been experienced both in the past and today. Additionally, being a wooden material causes the piece to be subjected to an extra disinfection process. Because there are problems such as insect and fungus formation in organic material. Due to this problem, shipping to other countries may also be problematic. In this thesis, what can be done to solve these problems and new design suggestions are presented. We examined whether it is possible to replace the material to be used with a polymer material instead of an organic structure. Because polymer materials can work under these load conditions without reaching the yield value. Additionally, finding a polymer material is easier than finding a wooden material. If necessary, polymer materials can easily combine with fibrous structures to form more durable materials. Various prototypes were created on the design. The profiles of these prototypes were tried to be created based on structures used in nature. Most designs have yielded positive results. As a result of the FEM analyses, tables containing the stress, deformation amount and volume values of the designs were created. According to the values seen in the tables, honeycomb structure and cylinder column structures were found to be the most suitable methods. Different optimizations have been made to make it more suitable in terms of production and ergonomics. Operations such as ribs, outer frame and edge rounding were carried out in optimization studies. The aim is to optimize in every aspect. As a result of these processes, positive results emerged in terms of volumetric, tension and displacement changes. The base surface and jack pressing surface of the created part must be specified. Otherwise, it may cause reverse loading. The parts to be made can be used instead of today's wooden materials and problems caused by wood can be solved.