Günümüzde otomotiv, havacılık, uzay ve inşaat gibi birçok sektörde ince cidarlı profil ve sac malzemelerin cıvatalı montajında bağlantı mukavemetini artırmak için çeşitli yöntemler uygulanmaktadır. Bu yöntemlerin başında delik bölgesine somun kaynatma ve şişme perçin somun kullanımı gibi ilave malzeme kullanımı gerektiren yöntemler gelmektedir. Son yıllarda bu yöntemlere ek olarak ilave malzeme kullanımı gerektirmeyen sürtünmeli delme yöntemi geliştirilmiştir. Malzemeden talaş kaldırmadan uygulanan bu yöntemde dönen konik ve sivri uçlu takımın delinecek malzemeye temas etmesi ve eksenel yönde baskı uygulaması sonucu ortaya çıkan sürtünme ısısı ile malzemeyi yumuşatıp malzemenin alt yüzeyine doğru ekstrüze eder ve kovan şeklinde delik açılır. Oluşturulan bu kovan içine yine benzer şekilde talaş kaldırmadan sıvama yöntemi ile kılavuz çekilerek cıvataları bağlantılarda kullanılacak yeterli derinlikte dişli delik elde edilmiş olur. Sürtünmeli delme, termal delme, sıvayarak delme, akış delme ve form delme olarak ta adlandırılır. Sürtünmeli delme uygulaması ile malzemede kayıp olmadan yeniden şekillendirilerek yapıldığı için ince cidarlı malzemelerde et kalınlığının yaklaşık üç katı uzunluğunda kovan boyu elde edilerek yeterli dayanıklılıkta cıvatalı bağlantılar yapılabilmektedir. Ayrıca bu uygulama özel makine ve ekipman kullanımı gerektirmeden gerekli güç ve devir hızına sahip standart matkap ve CNC tezgahlarında rahatlıkla gerçekleştirilebilmektedir. İşlem esnasında talaş kaldırmadan temiz bir şekilde tek bir adımda delme işlemi gerçekleştirilmektedir. Sürtünmeli delme uygulaması günümüz endüstrüsünde yoğun bir şekilde kullanılan çelik alaşımları, alüminyum alaşımları, bakır ve pirinç bir çok malzememin delinmesinde kullanılabilmektedir. Proseste kullanılan takım geometrisi, takım malzemesi, delinen malzemenin türü, kalınlığı , takım devir sayısı ve ilerleme hızı gibi parametreler elde edilen kovan yapısını ve kalitesini etkilemektedir. Bu çalışmada 6063 alüminyum, Ms58 pirinç, St37 çelik ve AISI 304 paslanmaz çelik Malzeme türlerinden kesit ölçüsü 30x30x1,5 mm olan kutu profil ve kesit ölçüsü Ø30x1,5 mm olan boru profil numunelere geleneksel talaşlı yöntemle ile delikler delinmiş ve diş açılmıştır. Aynı malzemelerden hazırlanan numunelere sürtünmeli delme yöntemi ile delikler delinmiş ve ovalama kılavuzu ile diş açılmıştır. Tüm delik delme ve diş açma işlemlerinde takım devir sayısı ve ilerleme hızları literatürde önerilen değer aralıklarında belirlenmiştir. Çalışmada 8 farklı tip malzemeden numuneler, iki farklı delme yöntemi ile delinerek 16 farklı tip numune elde edilmiştir. Daha sonra numuneler bir aparat yardımıyla çekme cihazına bağlanarak delme işlemleriyle oluşturulan dişli delikler vida sıyırma testlerine tabi tutulmuştur. Her iki yöntemle delinen numunelerde kovan geometrileri, kovan yükseklikleri, vida sıyırma kuvvetleri karşılaştırmalı olarak incelenmiştir. Elde edilen sonuçlar incelendiğinde geleneksel talaşlı delme yöntemlerinde delik bölgesinde kovan oluşmamasına karşın sürtünmeli delme yöntemi ile delinen deliklerde malzeme et kalınlığının yaklaşık 3 katı yüksekliğinde kovan oluştuğu gözlemlenmiştir. Oluşan kovanların geometrik yapıları incelendiğinde, alüminyum ve pirinç numunelerde taç yaprağı şeklinde çatlaklar ve yırtıklar oluştuğu gözlemlenmiştir. Her iki yöntem ile delinen numunelerde elde edilen vida sıyırma kuvvetleri karşılaştırıldığında sürtünme yöntemi ile delinen numunelerde geleneksel talaşlı yöntemle delinen numunelere göre %80-90 oranında artış gözlemlenmiştir. Bu çalışma, sürtünmeli delme yöntemi ile ilgili gelecekte yapılacak araştırmalar ve yöntemi üretimde kullanacak üreticiler için faydalı olacaktır. Bu çalışmanın devamında, farklı malzeme türlerinde farklı geometrilere sahip takımlar kullanılarak farklı malzeme türleri için optimum takım geometrileri belirlenebilir.
One of the prominent trends in the manufacturing industry today is the increasing use of thin-walled materials. Lightweight and high-strength materials are used to increase material and energy savings in the production of critical structures. In many industries such as automotive, aviation, aerospace and construction, various methods have been applied to increase the connection strength in bolted assembly of thin-walled profile and sheet materials. The most important of these methods are methods that require the use of additional materials such as nut welding to the hole area and the use of swelling rivet nuts. In recent years, in addition to these methods, a friction drilling method that does not require the use of additional materials has been developed. In this method, which is applied without removing chips from the material, the friction heat generated by the rotating conical and pointed tool contacting the material to be drilled and applying pressure in the axial direction softens the material and extrudes towards the lower surface of the material and a hole is drilled in the form of a bushing. A threaded hole of sufficient depth to be used in bolt connections is obtained by tapping into this sleeve with the flowtap method without removing chips in a similar way. It is also called friction drilling, thermal drilling, flow drilling and form drilling. This method was first developed in 1923 by Jan Claude de Valliere as an alternative to conventional drilling. However, its use in production only became possible 60 years later as a result of technical developments in the manufacture of tungsten carbide tools. Special tool geometries were designed to meet the needs of modern applications in the manufacturing industry, to increase the life and productivity of the tools used in drilling operations, and to perform drilling operations without causing environmental pollution, and this non-traditional drilling method has become more widely available. With friction drilling, bolted connections with sufficient durability can be made by obtaining a bushing length of approximately three times the wall thickness in thin-walled materials, since it is made by reshaping without loss in the material. In addition, this application can be easily carried out on standard drill and CNC machines with the required power and speed without the use of special machinery and equipment. Drilling is performed cleanly in a single step without removing chips during the process. Friction drilling applications can be used in the drilling of many materials such as steel alloys, aluminum alloys, copper and brass, which are used extensively in today's industry. Parameters such as tool geometry, tool material, type and thickness of the drilled material, tool speed and feed rate affect the bushing structure and quality. When the studies in the literature on friction drilling method are examined, it is seen that sufficient studies have been carried out on process parameters such as bushing height, bushing geometry, surface hardness, surface roughness in order to increase the bushing quality and joint strength in various materials. However, it is seen that there are insufficient studies on the strength of traditional machining and friction drilling processes of square and circular cross-section profiles, which are frequently used in today's industry. In this study, 5 mm diameter holes were drilled on AL 6063 aluminum, Ms58 brass, St37 steel and AISI 304 stainless steel materials with a cross-sectional dimension of 30x30x1.5 box profile and Ø30x1.5 mm pipe profile by conventional machining method and tapped by removing chips with M6 tap. On the same materials, 5.4 mm diameter holes were drilled with the friction drilling method and M6 threads were tapped with a flowtap tool. In the friction drilling and tapping operations, Flowdrill brand's standard short type tungsten carbide tool with a diameter of 5.4 mm and M6x1 TiN coated thread tap were used. For conventional machining drilling and tapping operations, a diameter 5 mm HSS drill and M6x1 standard tapping tool were used. All drilling and threading operations were performed on a Maxmill NVM-1166 model CNC vertical milling machine. In all drilling and tapping operations, the tool speed and feed rate were determined within the value ranges recommended in the literature. In the study, specimens of 8 different types of materials were drilled with two different drilling methods and 16 different types of specimens were obtained. For both drilling methods and all material types, drilling, measurement and testing processes were repeated 3 times and the results were calculated by taking the arithmetic average of the values obtained for each material type. In friction drilling and tapping operations, the rotational speeds and feed rates for each material type were carried out at the values recommended by the tool manufacturer (Flowdrill). Accordingly, the speed for friction drilling was determined as 2800 rpm for aluminum and brass materials, 2400 rpm for St37 steel material and 2000 rpm for stainless steel material. For friction tapping operations, the speed was determined as 650 rpm in all material types. The feed rate was determined as 120 mm/d in all materials. For conventional machining thread tapping operations, the speed was determined as 1500 rpm. After drilling operations, the bushing heights of the all specimens were measured with a digital caliper. When the results obtained were examined, it was observed that in the specimens drilled by conventional machining method, the bushing height is equal to the wall thickness of the material (1.5 mm). In the specimens drilled with the friction drilling method, bushes were formed at a height of approximately 3 times the material wall thickness. The measured bushing heights were grouped according to the material types and presented in comparative tables and graphs. When the specimen types drilled by friction drilling methods are compared in terms of barrel heights, the highest barrel size was 5.4 mm in AISI 304 pipe profile specimens and the lowest barrel height was 4.6 mm in 6063 aluminum box profile specimens. As a result, whether the profile type is square or tubular does not have much effect on the bushing height. When the geometric structures of the bushings formed in the hole region of the specimens drilled by friction drilling method were examined, it was observed that the bushings formed especially in aluminum and brass specimens had petal-shaped cracks and tears in their structures. This can be explained by the fact that aluminum and brass materials are more brittle than steel materials. However, these cracks and tears can be minimized by drilling at optimum parameters. The threaded holes created in the drilling processes were subjected to screw clamping tests. Screw clamping tests were performed on a Dartec MTS 250 kN capacity servo hydraulic axial tension device. The specimens were connected to the tensile device jaws with the help of an apparatus and a M6 stud bolt installed in the threaded hole on the specimen. Screw stripping tests were performed at an axial tensile speed of 5 mm/min. When conventional machining and friction drilling methods are compared in terms of clamping forces, the highest increase was achieved in Ms58 brass tube profile specimens from 2929 N to 5892 N, an increase of 124%. The lowest increase was realized in St37 steel box profile specimens from 4275 N to 7623 N, an increase of 78%. In conclusion, it is seen that the use of the friction drilling method in all material types used in this study provides an average strength increase of 100% in bolted connections. This study will be useful for future research on the friction drilling method and for manufacturers who will use the method in production. In the continuation of this study, optimum tool geometries for different types of materials can be determined by using tools with different geometries in different types of materials.
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