Kesme pimi tasarımında çentik geometrisi parametrelerinin pim dayanımına etkisinin incelenmesi
Kesme pimi tasarımında çentik geometrisi parametrelerinin pim dayanımına etkisinin incelenmesi
Dosyalar
Tarih
2025-06-20
Yazarlar
Yitim, Mehmet Ozan
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
İTÜ Lisansüstü Eğitim Enstitüsü
Özet
Yapısal bileşenler, mühendislik sistemlerinin temelini oluşturur ve makinelerin ve sistemlerin güvenli ve verimli çalışması için hayati öneme sahiptir. Tasarımları; statik ve dinamik yükler, çevresel faktörler (korozyon, sıcaklık değişimleri), malzeme seçimi, üretim yöntemleri, maliyet ve estetik gibi çeşitli kriterleri dikkate alarak mühendislik prensiplerinin titizlikle uygulanmasını gerektirir. En uygun çözümü bulmak için bu kriterleri dengelemek çok önemlidir. Temel tasarım unsurları arasında yük taşıyıcı bileşenler (kirişler, kolonlar, plakalar) ve bağlama elemanları (cıvatalar, pimler, kaynaklar, perçinler) bulunur. Bağlama elemanları, yapısal bütünlük için kritik öneme sahiptir; yanlış seçim veya hatalı tasarım, sistem güvenilirliğini ciddi şekilde tehlikeye atabilir. Bağlama elemanlarının tasarımı, kuvvetlerin analizini, uygun malzeme ve boyut seçimini, gerilme konsantrasyonlarının minimize edilmesini ve kolay montajı gerektirir. Kesme pimleri, mekanik sistemleri aşırı yüklenmeye karşı korumak için güvenlik mekanizmaları olarak tasarlanmış özel bağlama elemanlarıdır. Belirli bir yükte kasıtlı olarak kesilerek (makaslama yaparak) daha kritik ve pahalı bileşenlerin zarar görmesini engellerler. Kesme pimleri için en önemli tasarım faktörü, malzemelerinin ve kesit alanlarının, sistemin izin verilen maksimum yükü için uygun olmasını sağlamaktır. Pimin kesme mukavemeti, normal çalışma yükünün üzerinde ancak koruduğu bileşenlerin hasar eşiğinin altında olmalıdır. Kesme piminin geometrisi de tekdüze gerilme dağılımı ve kontrollü kesme için hayati öneme sahiptir. Bu çalışma, kesme pimi tasarımlarını etkileyen mukavemet ve geometrik parametreleri araştırmayı, özellikle farklı çentik geometrilerinin pimin kesme mukavemetini, öngörülebilirliğini ve mekanik olaylarla ilişkisini nasıl etkilediğine odaklanmayı amaçlamaktadır. Metodoloji, mekanik ve malzeme kimyasal testlerinin analitik hesaplamalar ve sonlu elemanlar analizi (SEA) ile korelasyonunu içeriyordu. Bu, farklı geometrilere sahip pim modellerinin karşılaştırılmasına olanak sağladı. Başlangıçta, kimyasal bileşimini belirlemek için V şeklinde çift kesme düzlemi çentiği olan bir kesme pimi numunesi üzerinde spektral analiz yapıldı. Malzeme, akma dayanımı 440 MPa olan 1.0727 kodlu 46S20 otomat çeliği (DIN 100087 sınıfı) olarak tanımlandı. ISO 8749-1986'ya göre, kesme düzlemini çentik bölgesine konumlandıran bir kesme test aparatı tasarlandı ve üretildi. Mekanik kesme testleri, hidrolik bir sıkıştırma test makinesi kullanılarak, pimin merkezi bölümüne yer değiştirme kontrollü bir yük uygulanarak yapıldı. Pim eş zamanlı olarak iki düzlemde kesildi ve elde edilen kuvvet-yer değiştirme verileri analiz edildi. Yer değiştirme, ISO 8749-1986'nın 13mm/dakika sınırı içinde, 5mm/dakika hızında uygulandı. Bu sonuçlar, sonraki korelasyon çalışmaları için kullanıldı. Pimin elastik sınırı test sonuçlarından belirlendi ve akma dayanımı sayısal değerlendirme için kabul edildi. Sayısal yöntem (analitik hesaplama ve SEA) arasındaki korelasyon kabul edilebilir sapma ile elde edildi. SEA için ANSYS Mechanical yazılımı kullanıldı ve kafes modeli için 3B katı hekzahedral elemanlar (SOLID186) kullanıldı. Pimin baş ve uç bölgelerini altı serbestlik derecesinde sabitleyen sınır koşullarıyla ve orta bölümün yüzeyine radyal yük uygulayan statik bir yapısal analiz kurulumu oluşturuldu. Çalışma, üç farklı çentik geometrisi (V şekilli, U şekilli ve dairesel) ve üç farklı kesme çentik genişliği kullanarak bir test matrisi oluşturdu. Pimin minimum çentik çapı 9 mm, nominal çapı ise 14 mm idi. Pim numunesi testlerinde kullanılan malzeme özellikleri, akma gerilme sınırı 440 MPa olan 1.0727 otomat çeliği idi. Sonuçlar, analizden elde edilen üç ana parametreye göre karşılaştırılmıştır; bunlar pim radyal kesme rijitliği, çentik bölgesindeki maksimum Von Mises gerilmesi ve çentik bölgesindeki ortalama Von Mises gerilmesidir. Çentik geometrisindeki değişiklikler bu değerleri doğrudan etkilemiştir. Çentik genişliğinin belirli bir noktanın ötesine artırılması, gerilme tensörünün kesme ağırlıklıdan eğilme ağırlıklıya kaymasına neden oldu ve bu da çentik bölgesindeki yükün pimin orta ve uç kısımları tarafından taşınmasına yol açtı. Belirli bir eşik çentik genişliği olmalı; bunu aşmak çentik bölgesinin kesme ağırlıklıdan eğilme ağırlıklıya geçişine neden olacaktır. Aynı nominal ve kesme çaplarına sahip pimler için, V profilli çentik en iyi sonuçları verdi. Bu durum, V çentiğin çentik yük taşıma bölgesinde en fazla malzeme stoğuna izin vermesinden kaynaklanmaktadır. Çalışmanın gelecek aşamaları, kesme gerilmesi altındaki malzemenin akma sınırının detaylı araştırma, test ve analitik yöntemlerle belirlenmesini iyileştirmeye odaklanacaktır. Kesme pimlerine özgü metodolojik yaklaşımlar derinleştirilecektir. Ek olarak, test kampanyası farklı çentik parametreleri, kesme ve nominal çapları içerecek şekilde genişletilecek, böylece parametrik test verileri artırılacak ve bulgular doğrulanacaktır. Bu, çentik genişliği için eşik değerini belirlemeye ve farklı parametrelerin pimin yapısal özellikleri üzerindeki etkisini ortaya çıkarmaya yardımcı olacaktır.
Constructive structures form the bedrock of engineering systems, playing a vital role in ensuring a machine or system operates both safely and efficiently. Designing these structures demands the meticulous application of engineering principles, taking into account a range of critical design criteria. These primarily include the static and dynamic loads the structure will encounter, environmental factors like corrosion and temperature changes, material selection, manufacturing methods, cost, and aesthetic considerations. Balancing these criteria to achieve an optimal solution is absolutely essential throughout the design process. The core design elements of constructive structures encompass load-bearing components (such as beams, columns, plates, etc.), fastening elements, and supports. Load-bearing components are responsible for safely transferring a system's main loads, while fastening elements connect different parts. Fasteners like bolts, pins, welds, and rivets are incredibly important. They're critical components that ensure structural integrity, and if they're chosen incorrectly or poorly designed, the system's reliability can be severely jeopardized. When designing fasteners, you must follow some fundamental rules. These include accurately analyzing the forces the connection will face, selecting the appropriate materials and dimensions, minimizing stress concentrations, and ensuring ease of assembly. For example, with a bolted connection, you need to consider various load types such as tension, shear, and bending. You also have to apply the correct tightening torque and take precautions against loosening. For pin connections, the strength of the pin material, the pin diameter, and the geometry of the connecting elements should all be designed to prevent failures like shearing and crushing. Shear pins are specialized fasteners specifically designed to protect mechanical systems in overload situations. Functioning as a safety mechanism, shear pins are engineered to shear (or break) in a controlled manner when a certain load level is reached. This prevents damage to more critical and expensive components within the system. The most crucial factor in designing shear pins is to ensure that the pin material and cross-sectional area are appropriately determined for the maximum allowable load of the system they are meant to protect. The pin's shear strength must be above the load the system can withstand under normal operating conditions, but below the strength of the components that should not be damaged in case of a failure. The geometry of the shear pin also plays a significant role in its design. Suitable shapes should be chosen to ensure that shear stresses are distributed homogeneously and to facilitate controlled shearing at the desired point. This study aims to examine the strength and geometric parameters considered in shear pin designs as mechanical safety elements. Specifically, it focuses on investigating how different shear notch geometries impact the pin's shear strength, evaluating its predictability, and ensuring its correlation with mechanical phenomena. The methodology involved first establishing a correlation between mechanical and chemical test on material of the pin, followed by analytical calculations and finite element analysis (FEA). This approach allowed for comparisons between pin models with varying geometries. To achieve this, a spectral analysis was initially performed on a shear pin sample featuring a V-shaped double shear plane notch to determine its chemical composition. This chemical composition was identified as belonging to 1.0727 code 46S20 free-cutting steel (DIN 100087 class). Mechanical properties for the pin were determined, with a yield strength accepted as 440 MPa. Subsequently, a shear test fixture was designed and manufactured according to the ISO 8749-1986 standard, positioning the shear plane within the notch region for mechanical testing. The mechanical shear test itself was conducted using a hydraulic compression testing machine, applying a displacement-controlled load to the central section, which was designated as the load application area. The pin was sheared and fractured simultaneously across two shear planes, and the resulting force-displacement data was meticulously analyzed. The displacement was applied at 5 mm/min, remaining within the ISO 8749-1986 standard's maximum speed limit of 13 mm/min. These results were then used for subsequent correlation studies. From the test results, the pin's elastic limit was determined, and its yield strength was accepted for numerical evaluation. An acceptable deviation was achieved in the correlation between the numerical method (analytical calculation and finite element analysis). For the finite element analysis (FEA) studies, the ANSYS Mechanical software package, including its preprocessor, solver, and post-processor, was utilized. The finite element mesh model employed 3D solid hexahedral elements (SOLID186). A static structural analysis setup was created, with boundary conditions fixing the pin's head and end regions in six degrees of freedom, and radial loading applied to the surface of the middle section. The study created a test matrix using three different notch geometries (V-shape, U-shape, and circular) and three different shear notch widths. The minimum diameter in the pin notch geometry, on the shear plane, was 9 mm, with a nominal diameter of 14 mm. For the pin sample material tests, the material was assumed to be 1.0727 free-cutting steel with a yield stress limit of 440 MPa, and the studies proceeded with this assumption. The results were compared based on three main comparative parameters: the pin's radial shear stiffness, the maximum Von Mises stress in the notch region, and the average Von Mises stress in the notch region, all obtained from the analysis results. Accordingly, it was observed that changes in the notch geometry directly impacted these values. Beyond a certain point, increasing the notch width shifted the stress tensor from shear-dominant to bending-dominant, causing the load in the notch region to be carried by the pin's middle and end sections as well. It's clear that the notch width must have a threshold value; exceeding this threshold will cause the pin's notch region to transition from a shear-dominant to a bending-dominant state. For pins with the same nominal and shear diameters, the V-profile notch yielded the best results. This can be attributed to the V-notch allowing for the greatest material stock in the notch's load-bearing region. In the subsequent phases of the study, efforts will focus on refining the determination of the material's yield limit under shear stress through detailed research, testing, and analytical methods. Methodological approaches specific to shear pins will be deepened. Additionally, the conducted test campaign will be expanded to include different notch parameters, shear, and nominal diameters, thereby increasing the parametric test data and enabling a more robust validation of the findings. This will facilitate the determination of the threshold value for notch width and reveal the impact of various parameters on the pin's structural properties.
Constructive structures form the bedrock of engineering systems, playing a vital role in ensuring a machine or system operates both safely and efficiently. Designing these structures demands the meticulous application of engineering principles, taking into account a range of critical design criteria. These primarily include the static and dynamic loads the structure will encounter, environmental factors like corrosion and temperature changes, material selection, manufacturing methods, cost, and aesthetic considerations. Balancing these criteria to achieve an optimal solution is absolutely essential throughout the design process. The core design elements of constructive structures encompass load-bearing components (such as beams, columns, plates, etc.), fastening elements, and supports. Load-bearing components are responsible for safely transferring a system's main loads, while fastening elements connect different parts. Fasteners like bolts, pins, welds, and rivets are incredibly important. They're critical components that ensure structural integrity, and if they're chosen incorrectly or poorly designed, the system's reliability can be severely jeopardized. When designing fasteners, you must follow some fundamental rules. These include accurately analyzing the forces the connection will face, selecting the appropriate materials and dimensions, minimizing stress concentrations, and ensuring ease of assembly. For example, with a bolted connection, you need to consider various load types such as tension, shear, and bending. You also have to apply the correct tightening torque and take precautions against loosening. For pin connections, the strength of the pin material, the pin diameter, and the geometry of the connecting elements should all be designed to prevent failures like shearing and crushing. Shear pins are specialized fasteners specifically designed to protect mechanical systems in overload situations. Functioning as a safety mechanism, shear pins are engineered to shear (or break) in a controlled manner when a certain load level is reached. This prevents damage to more critical and expensive components within the system. The most crucial factor in designing shear pins is to ensure that the pin material and cross-sectional area are appropriately determined for the maximum allowable load of the system they are meant to protect. The pin's shear strength must be above the load the system can withstand under normal operating conditions, but below the strength of the components that should not be damaged in case of a failure. The geometry of the shear pin also plays a significant role in its design. Suitable shapes should be chosen to ensure that shear stresses are distributed homogeneously and to facilitate controlled shearing at the desired point. This study aims to examine the strength and geometric parameters considered in shear pin designs as mechanical safety elements. Specifically, it focuses on investigating how different shear notch geometries impact the pin's shear strength, evaluating its predictability, and ensuring its correlation with mechanical phenomena. The methodology involved first establishing a correlation between mechanical and chemical test on material of the pin, followed by analytical calculations and finite element analysis (FEA). This approach allowed for comparisons between pin models with varying geometries. To achieve this, a spectral analysis was initially performed on a shear pin sample featuring a V-shaped double shear plane notch to determine its chemical composition. This chemical composition was identified as belonging to 1.0727 code 46S20 free-cutting steel (DIN 100087 class). Mechanical properties for the pin were determined, with a yield strength accepted as 440 MPa. Subsequently, a shear test fixture was designed and manufactured according to the ISO 8749-1986 standard, positioning the shear plane within the notch region for mechanical testing. The mechanical shear test itself was conducted using a hydraulic compression testing machine, applying a displacement-controlled load to the central section, which was designated as the load application area. The pin was sheared and fractured simultaneously across two shear planes, and the resulting force-displacement data was meticulously analyzed. The displacement was applied at 5 mm/min, remaining within the ISO 8749-1986 standard's maximum speed limit of 13 mm/min. These results were then used for subsequent correlation studies. From the test results, the pin's elastic limit was determined, and its yield strength was accepted for numerical evaluation. An acceptable deviation was achieved in the correlation between the numerical method (analytical calculation and finite element analysis). For the finite element analysis (FEA) studies, the ANSYS Mechanical software package, including its preprocessor, solver, and post-processor, was utilized. The finite element mesh model employed 3D solid hexahedral elements (SOLID186). A static structural analysis setup was created, with boundary conditions fixing the pin's head and end regions in six degrees of freedom, and radial loading applied to the surface of the middle section. The study created a test matrix using three different notch geometries (V-shape, U-shape, and circular) and three different shear notch widths. The minimum diameter in the pin notch geometry, on the shear plane, was 9 mm, with a nominal diameter of 14 mm. For the pin sample material tests, the material was assumed to be 1.0727 free-cutting steel with a yield stress limit of 440 MPa, and the studies proceeded with this assumption. The results were compared based on three main comparative parameters: the pin's radial shear stiffness, the maximum Von Mises stress in the notch region, and the average Von Mises stress in the notch region, all obtained from the analysis results. Accordingly, it was observed that changes in the notch geometry directly impacted these values. Beyond a certain point, increasing the notch width shifted the stress tensor from shear-dominant to bending-dominant, causing the load in the notch region to be carried by the pin's middle and end sections as well. It's clear that the notch width must have a threshold value; exceeding this threshold will cause the pin's notch region to transition from a shear-dominant to a bending-dominant state. For pins with the same nominal and shear diameters, the V-profile notch yielded the best results. This can be attributed to the V-notch allowing for the greatest material stock in the notch's load-bearing region. In the subsequent phases of the study, efforts will focus on refining the determination of the material's yield limit under shear stress through detailed research, testing, and analytical methods. Methodological approaches specific to shear pins will be deepened. Additionally, the conducted test campaign will be expanded to include different notch parameters, shear, and nominal diameters, thereby increasing the parametric test data and enabling a more robust validation of the findings. This will facilitate the determination of the threshold value for notch width and reveal the impact of various parameters on the pin's structural properties.
Açıklama
Tez (Yüksek Lisans)-- İstanbul Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2025
Anahtar kelimeler
pim tasarımı,
pin design,
pin çentik geometrisi,
pin notch geometry