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Polimer plakaların sürtünme karıştırma kaynağı ile birleştirilmesinde kaynak özelliklerinin geliştirilmesi

Improvement of welding properties in the joining of polymer plates through friction stir welding

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  1. Tez No: 935280
  2. Yazar: ÖMER ÇERLEK
  3. Danışmanlar: DOÇ. DR. ÖMER SEÇGİN
  4. Tez Türü: Doktora
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Sürtünme, karıştırma, kaynak, polimer, takım, birleştirme, Friction, stir, welding, polymer, tool, joining
  7. Yıl: 2025
  8. Dil: Türkçe
  9. Üniversite: Sakarya Uygulamalı Bilimler Üniversitesi
  10. Enstitü: Lisansüstü Eğitim Enstitüsü
  11. Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 247

Özet

Bu tez çalışmasında çeşitli polimer malzemelerin sürtünme karıştırma kaynağı ile birleştirilmesi üzerine çalışamalar yapılmıştır. Farklı takım geometrileri ve farklı işlem parametrelerinin malzemelerin birleşim kabiliyetine ve mekanik özelliklerine etkisi araştırılmıştır. Dört farklı polimer ile birleştirme uygulamaları yapılmıştır. Bu malzemeler; Ultra Yüksek Moleküler Ağırlıklı Polietilen (UHMWPE-PE1000), Poliamid 6(PA6), Yüksek Yoğunluklu Polietilen(HDPE) ve Polipropilen Natural(PP Natural) olarak sıralanabilir. Bu malzemelerin bir kısmı literatürde sürtünme karıştırma kaynağı ile birleştirmelerde uygulamaları olan malzemeler iken bazıları ise çok az çalışılan veya hiç çalışılmayan malzemelerdir. Geleneksel olarak sürtünme karıştırma kaynağında takım düz bir hat boyunca dönerek ilerler iken bu tez çalışmasında yeni takım yolu desenleri oluşturularak bunların kaynak özelliklerine ve kaynak kabiliyetine etkisi araştırılmıştır. Bununla birlikte silindirik uçlu ve uç yüzeyine diş çekilmiş silindirik uçlu iki farklı geometride takım tasarlanarak üretilmiş olup bunların kaynak özelliklerine etkisi incelenmiştir. Üç farklı proses parametresi ve bunların üç farklı seviyesi belirlenmiştir. İşlem parametreleri belirlenirken literatürdeki çalışmaların yanı sıra ön deneysel çalışmalar yapılarak; buralardaki tecrübe, elde edilen ölçüm değerleri ve gözlemlerden yaralanılmıştır. Burada belirlenen parametreler ile deney tasarımı planlanmıştır. Deneysel çalışmaları yürütmek üzere Taguchi L9 ortogonal dizilime göre deney tasarımları oluşturulmuştur. Birleştirme işlemleri sonucunda üç farklı mekanik özellik ölçümü ve de Taramalı Elektron Mikroskobu(SEM) görüntülemeleri yaparak takım tasarımı ve proses parametrelerinin mekanik özelliklere ve kaynak kabiliyetine etkisi araştırılmıştır. Elde edilen sonuçlar analiz yazılımı ile değerlendirilip işlem parametreleri optimize edilmiştir. Sürtünme karıştırma kaynağı ile polimer malzemelerin birleştirilmesinde takım uç geometrisinin önemli bir faktör olduğu ve diş çekilmiş uçlu takımın genel olarak kaynak kabiliyetine zarar verdiği ancak kısmi bazı uygulamalarda avantajlı sonuç sağladığı gözlemlenmiştir. Silindirik uçlu takım ile hemen tüm malzemelerde oldukça daha başarılı birleştirmeler sağlanmıştır. Malzemeye ve diğer proses parametrelerine bağlı olarak farklı çıktılarda farklı takım yolları daha iyi mekanik özellikler sağlayabilmektedir. Bu bağlamda; dört farklı malzeme ve iki takım ile 8 temel birleştirme kombinasyonu düşünüldüğünde; bunların üçünde helisel, ikisinde zikzak ve üçünde dikdörtgensel profilli takım yolu optimum sonuçları sağlamıştır.

Özet (Çeviri)

In this thesis, studies have been conducted on the joining of various polymer materials using friction stir welding. The effects of different tool geometries and process parameters on the joining capability and mechanical properties of the materials have been investigated. Joining applications were carried out with four different polymers, namely Ultra-High Molecular Weight Polyethylene (UHMWPE-PE1000), Polyamide 6 (PA6), High-Density Polyethylene (HDPE), and Natural Polypropylene (PP Natural). These materials are fundamental and widely used in the plastic industry. While some of these materials have been previously applied in friction stir welding studies in the literature, others have been rarely or never studied. The aim is to close the gap in the literature and contribute to the engineering world by working on the joining of these materials through friction stir welding technique, while presenting an innovative approach. Traditionally, in friction stir welding, the tool advances along a straight path while rotating. However, in this thesis, new tool path patterns were designed to investigate their effects on welding characteristics and joining capability. These new tool path patterns were designed with helical, zigzag, and rectangular profiles. The development of these patterns was inspired by the swinging movements performed during the welding process in electrode welding. It was thought that these new tool paths could enhance the strength of the weld seam and improve material flow. Additionally, two different tool geometries were designed and manufactured: one with a cylindrical pin and the other with a cylindrical pin threaded on its surface. The effects of these tool geometries on welding properties were examined. It has been observed in previous studies that cylindrical-pin tools generally provide the best joint quality. However, it is also known that friction stir welding applications have been conducted using threaded tools. In this context, the effect of threading only the pin of the tool, without altering its main geometry, was investigated. Thus, if the threaded tool offers an advantage in terms of material compatibility or mechanical properties, its benefits can be utilized accordingly. Three different process parameters, each with three levels, were determined. In friction stir welding, the primary process parameters are the tool rotational speed and feed rate. These two parameters are crucial for controlling the heat in the welding region. In this context, this study defines tool rotational speed and feed rate as the main continuous control parameters, while the tool path pattern is considered as a categorical parameter. While selecting these parameters, both literature studies and preliminary experimental trials were utilized, benefiting from the experience,measurement data, and observations obtained. Based on the identified parameters, an experimental design was planned. Experimental studies were conducted using the Taguchi method. The Taguchi method is a widely used experimental design and analysis method in engineering applications to ensure standardization and enable the analysis of experiments. Taguchi L9 orthogonal array design, and joining applications were carried out following this procedure. Following the joining processes, three different mechanical property measurements and Scanning Electron Microscopy (SEM) imaging were performed to investigate the effects of tool design and process parameters on mechanical properties and joining capability. Here, the response parameters are defined as weld zone hardness, tensile strength, and flexural strength of the weld joint. These mechanical properties serve as key outputs that provide insights into the joint quality and strength in material joining. The obtained results were analyzed using statistical software, and process parameters were optimized. The data obtained from the tests were placed in tables, including tool geometries, for comparison and evaluation. Additionally, variance and regression analyses were performed on all the data to examine the effect of process parameters on each tool and mechanical property separately. For each mechanical property, signal-to-noise ratio graphs were created through the analysis of the Taguchi experimental design, and optimal process parameters were determined. Furthermore, contour plots were created to investigate the effect of control parameters on mechanical properties in pairs, and the influence of parameters on the outputs was detailed. For the evaluation and optimization of the results, analyses and optimizations were carried out using the Taguchi method and the Response Surface Methodology. Verification experiments were conducted based on the data obtained from the optimization process to assess the consistency of the experimental studies. As a result of the validation experiments, mechanical measurements were obtained that align with the optimization data within a 10% margin of error. The internal structure of the weld zone formed by joining materials under heat is crucial for the quality and capability of the joint. To observe this structure, equipment such as optical microscopes or scanning electron microscopes (SEM) are used. The aim is to observe the microstructural behavior behind the differences in the mechanical properties of materials through SEM imaging. In this study, the fracture surfaces of the specimens that failed during the tensile test were subjected to SEM imaging to observe the joint line and fracture characteristics. The key factors in the formation of mechanical strength in friction stir welding include the internal fill of the weld zone, the presence or absence of voids, cracks, whether the material shows ductile or brittle fracture behavior, and the reduction in cross-section as a result of plastic deformation. In this study, the specimens exhibiting the best and worst mechanical properties of each material were compared, and the relationship between the internal structure, process parameters, tool geometry, and mechanical strength was analyzed. It is believed that, based on this experience, better joint formations can be achieved in future studies. It was observed that tool tip geometry is a significant factor in the friction stir welding of polymer materials. It has been observed that the cylindrical-pin tool enables a homogeneous heat distribution and good material flow. In contrast, the threaded-tip tool generally causes the material left behind, which is cooling down, to be damaged due to friction with the threads, leading to a brittle internal structure characterized by fragmentation. While the threaded-pin tool generally had a negative impact on joining capability, it provided advantageous results in certain specific applications. More successful joints were achieved in almost all materials using the cylindrical-pin tool without threads. Depending on the material and other process parameters, different tool paths can provide better mechanical properties for different outputs. In this context, considering eight basic joining combinations with four different materials and two tools, a helical tool path yielded optimal results in three cases, a zigzag tool path in two cases, and a rectangular-profiled tool path in three cases. Furthermore, it was understood that various mechanical properties can be improved through the use of different tool path patterns, and these properties can be further enhanced by incorporating additional process parameters such as penetration depth, dwell time, ambient temperature, and heat reinforcement during the process in future studies. In future studies on the joining of polymers using friction stir welding, it is anticipated that higher weld quality can be achieved through improvements in tool geometry, enhancements in the material clamping system, refinements in specimen cutting and preparation processes, and the optimization of other process parameters. Thus, this method has the potential to become a more cost-effective and environmentally friendly technique for material joining in the plastic industry.

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