Yay tahrikli bir darbe deney cihazının tasarımı, geliştirilmesi ve verimliliğinin araştırılması
Spring-actuated impact test device: Design, development, and efficiency assessment
- Tez No: 942795
- Danışmanlar: PROF. DR. ALİ SARI
- Tez Türü: Doktora
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2025
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Yapı Mühendisliği Bilim Dalı
- Sayfa Sayısı: 115
Özet
Mühendislik malzemelerinin kısa süreli dinamik yükler altındaki davranışlarını ve dayanımlarını belirlemek mühendislik tasarımları için oldukça önemlidir. Bu özelliklerin belirlenmesiyle Savunma Sanayi, Petrol ve Gaz endüstrisi, Kimyasal ve Nükleer Tesisler, Darbe ve Patlama Mühendisliği, İnşaat ve Yapı Sektörü, Makine-İmalat Sektörü, Havacılık Sektörü, Otomotiv Sektörü ve Üniversitelerin AR-GE laborauvarları için de ayrıca hayati bilgiler elde edilmekte ve bu sektörlerin/alanların gelişiminde çok büyük katkılar sağlamaktadır. Gerçek hayatta malzemelerin ve bu malzemelerden üretilmiş çeşitli elemanların kısa süreli dinamik yükler altındaki davranışlarını belirlemek için çeşitli deney yöntemleri mevcuttur. Bu yöntemler; patlatma, sarkaç yöntemi, ağırlık/kütle düşürme, hava basınçlı yöntemler, hidrolik aktuatör ve yay tahrikli olabilmektedir. Bu tez kapsamında, yeni bir yay tahrikli darbe deney cihazı geliştirildi ve mevcut kısa süreli dinamik yük için uygulanan deney yöntemlerine göre çeşitli üstünlükleri ortaya koyuldu. Tasarlanan cihaz, malzemelerin (seramik, metal, plastik, kompozit vs.) veya bu malzemelerden yapılmış çeşitli elemanların yatay darbe etkileri altındaki davranışlarını deneysel olarak elde etmek için kullanılabilecektir. Bu deney cihazı, kullanıcının talebine göre uygulanacak darbe yükünde hız, kütle, temas yüzeyi geometrisi ve temas rijitliği deney parametrelerinin kolay bir şekilde çeşitlendirilmesine imkan tanımaktadır. Ayrıca cihaz deney uygulanacak numuneleri cihaza bağlarken kullanıcıya bu konuda da çeşitlilik sağlamaktadır. Cihaz belirli karakteristiklere sahip yaylara depolanan enerji ile bir kütlenin yer çekiminden bağımsız olarak yatayda tek doğrultuda fırlatılması ilkesi ile çalışmaktadır. Fırlatılan kütlenin etkidiği deney numunelerine hangi hızla çarptığı ve çarpışma sırasında numune üzerinde oluşturduğu yük-zaman verileri uygun ve kolayca alınmaktadır. Tez çalışması kapsamında geliştilen cihazın çalışma verimliliğini araştırmak için fırlatılan farklı kütlelerin hızları farklı yay germe miktarlarına göre ölçüldü. Yapılan ölçümler değerlendirildiğinde cihazın kütle, hız ve yay germe miktarı gibi parametrelere göre öngörülebilir bir şekilde çalıştığı ortaya koyuldu. Ek olarak cihaz ile çelik plaka, lamine cam ve prekast donatılı gazbeton (PDG) panel ve duvar kağıdı gibi birçok sektörde kullanılabilen elemanlar üzerinde deney yapılarak sınandı. Deneylerde yayın istenilen düzeyde gerilip serbest bırakılabilmesi, fırlatılan kütlelerin hızlarının kolay bir şekilde ve yeterli doğrulukta ölçülebilmesi, darbe yükü verilerinin ölçülebilmesi ve farklı deney başlıklarının kolay bir şekilde deney cihazına adapte edilebilmesi deney cihazının malzemelerin ve bu malzemelerden yapılan çeşitli elemanların kısa süreli dinamik yükler altında davranışlarının belirlenmesi konusunda önemli bir geliştirme olduğu ortaya koyuldu.
Özet (Çeviri)
Engineering structures and materials are frequently subjected to high-speed, short-duration dynamic loads, such as those generated by explosions, impacts, and ballistic events. These dynamic loadings induce significantly different mechanical behaviors and damage mechanisms compared to static or quasi-static conditions. Specifically, variations in strain rate can cause substantial changes in a material's strength, ductility, and strain hardening capacity, often resulting in unpredictable failure modes. Despite the critical importance of understanding material behavior under these conditions, conventional testing methods are often inadequate for replicating the rapid loading scenarios encountered in real-life applications. Therefore, there is a clear need for advanced experimental setups that can accurately simulate high strain-rate loading in a controlled laboratory environment, providing reliable data for material characterization and engineering design. Accurate characterization of material behavior under dynamic loading conditions is critical for ensuring the structural integrity and safety of components used in various high-risk applications. Industries such as defense, oil and gas, chemical and nuclear facilities, impact and explosion engineering, construction, machinery manufacturing, aerospace, automotive, and academic research and development laboratories rely heavily on precise testing data to develop materials and systems capable of withstanding extreme conditions. The insights gained from dynamic load testing play a fundamental role in advancing these sectors, enabling innovation in materials design, improving safety standards, and enhancing overall performance. Various experimental methods are utilized to evaluate the behavior of materials and structural components under short-duration dynamic loads. Common approaches include explosion tests, pendulum impact devices, mass drop systems, air pressure-driven mechanisms, hydraulic actuators, and spring-actuated testing devices. While explosion tests can replicate extreme load scenarios, they are often costly, difficult to control, and pose significant safety risks. Pendulum and mass drop methods offer simpler setups but suffer from limited control over impact velocity and energy precision. Air pressure and hydraulic systems provide greater control and repeatability; however, they typically involve complex and expensive equipment. In contrast, spring-actuated devices present a cost-effective and versatile alternative, offering reliable control over impact parameters with simpler operational requirements. Despite these available techniques, challenges remain in achieving consistent, accurate, and repeatable test conditions that faithfully replicate real-life dynamic loading scenarios. To ensure the reliability and accuracy of experimental studies, it is critical to replicate realistic loading conditions that structural and non-structural elements are likely to experience in practice. Laboratory testing systems must offer a wide range of controllable parameters to simulate different loading scenarios effectively. In structural dynamics, the response of an element is closely related to the ratio between its natural period and the duration of the applied load, which categorizes the response into three regions: equivalent static, impulsive, and dynamic. Accurately representing these loading conditions is essential for valid experimental outcomes. In this context, the novel spring-actuated impact test device developed in this study provides a highly controlled, flexible, and cost-effective solution for simulating short-duration dynamic loads. Unlike conventional methods, this system allows sufficiently precise adjustment of impact velocity, impactor mass, and contact characteristics, enabling tailored testing scenarios that replicate real-world dynamic events with improved accuracy and repeatability. The spring-actuated impact test device developed is designed to evaluate the horizontal impact behavior of various materials, including ceramics, metals, plastics, and composites. Additionally, the device is equipped with an adaptable mounting system that enables quick and secure attachment of various test specimens, enhancing its versatility for different experimental configurations. The device operates by releasing a mass that is accelerated horizontally through the stored potential energy of pre-tensioned springs, functioning independently of gravitational forces. The mechanical properties of the springs —such as stiffness, preload level, and damping characteristics— directly influence the velocity, impact energy, and consistency of the test results. By selecting springs with appropriate characteristics, the system can precisely control the kinetic energy delivered to the test specimen, ensuring repeatability and accuracy across a wide range of test scenarios. Furthermore, the load-time response generated during the collision is accurately captured, providing essential data for evaluating material performance under dynamic loading conditions. The two critical components of the device are the tension springs and the release mechanism. The design of the tension springs considers key geometric parameters, including wire diameter, number of coils, and material properties, all of which directly influence the spring constant and overall mechanical performance. These characteristics are meticulously determined through both theoretical calculations and experimental validation, ensuring precise control over the energy stored and released during testing. The force-extension behavior of each spring is evaluated and compared with theoretical models to guarantee consistency and accuracy. This level of control allows researchers to fine-tune the impact energy and velocity according to the specific requirements of different testing scenarios. As a result, the system offers enhanced flexibility, enabling it to accommodate a wide variety of specimens and experimental conditions, from brittle ceramics to ductile metal components. In this study, the release mechanism was designed with a dual-hook system to ensure the symmetrical and balanced release of the stored energy, minimizing any lateral forces on the impact carriage. The hooks are held in place by a locking mechanism that maintains tension until release is initiated. Upon activation, rotational bearings apply a moment to the hooks, overcoming the frictional resistance at the locking interface. This triggers the simultaneous and stable release of both hooks, allowing the impact carriage to accelerate smoothly along its track. The effectiveness and precision of this release system were validated through experimental testing, demonstrating consistent alignment with the theoretical predictions of energy transfer and impact velocity. These results confirm the reliability and repeatability of the device's operation under various loading conditions. To evaluate the operational efficiency and consistency of the device, a series of experiments were conducted in which the velocities of projectiles with varying masses were measured under different spring extension conditions. Impact velocities were recorded using a high-precision optical sensor system positioned along the carriage's trajectory, ensuring accurate and real-time data acquisition. The experimental results demonstrated a strong correlation between the spring extension length, projectile mass, and the resulting impact velocity, validating the predictability of the device's performance. Multiple trials under identical conditions confirmed the repeatability of the system, with minimal variations being observed between tests. This consistency ensures the reliability of the test data for further analysis and material characterization. To demonstrate the versatility and efficiency of the impact test device developed, a series of experiments were conducted on various structural elements commonly used across different industries, including steel plates, laminated glass, reinforced autoclaved aerated concrete (AAC) panels, and wall coverings. Both equivalent static and dynamic impact tests were performed using standardized cylindrical impact heads and support conditions. The experimental setup allowed for precise control of parameters such as spring extension length, impact velocity, and projectile mass, ensuring consistent test conditions. Comparative analyses of the load-displacement responses revealed that impact loads generated by the device were significantly higher than those observed under equivalent static loading for the same displacement levels, highlighting the increased energy transfer during dynamic events. Furthermore, energy assessments demonstrated a strong correlation between the kinetic energy of the impact carriage and the energy absorbed by the test specimens, validating the accuracy and reliability of the device. The recorded force-time and displacement-time curves provided detailed insights into the dynamic response behaviors, showing that higher impact velocities resulted in greater central displacements and impact forces on the steel plate specimens. Compared to conventional testing methods, the device developed offers enhanced adaptability, allowing efficient testing of a wide range of materials and configurations with superior control over test parameters and repeatability. An equivalent static two-point bending test was initially conducted on steel plate specimens to establish baseline load-displacement behavior. Subsequently, dynamic impact tests were performed under identical boundary conditions using the spring-actuated device developed. During these impact tests, key parameters such as impactor velocity, applied load, specimen displacement, and energy absorption were meticulously measured. It was observed that the impactor velocity, determined through high-speed sensors, decreased upon contact due to energy transfer to the specimen, confirming the system's accurate energy delivery and data reliability. The close correlation between pre-impact and post-impact velocity measurements validated the consistency of the experimental data. Additionally, the dynamic increase factors (DIF) were calculated by comparing the peak impact loads to those obtained in equivalent static tests across varying impact velocities. These findings demonstrated a significant enhancement in load-bearing capacity under dynamic conditions, emphasizing the importance of strain rate effects in structural material performance assessments. In the laminated glass impact experiments, a spherical steel impactor head with a specified mass was launched toward the specimens using the developed spring-actuated device. The impact tests were conducted with varying spring extension lengths to control the impact energy applied to the glass panels. Key performance indicators such as impact resistance, impact force duration, and central displacement were measured with precision. The laminated glass demonstrated varying levels of damage depending on the impact energy, with permanent displacements observed at the center of the specimen. These displacements were attributed to both the compression of the interlayer band within the glass assembly and localized fracture of the glass layers. The experiments provided valuable insights into the failure mechanisms and energy absorption capacity of laminated glass panels under high-speed impact conditions, which are critical for safety evaluations in architectural and automotive applications. Impact tests were conducted on reinforced autoclaved aerated concrete (AAC) panels, which were mounted onto a reinforced concrete frame using steel plates to replicate realistic boundary conditions. To further examine energy dissipation and its effects on impact resistance, Energy Damping Connections (EDC) were integrated into the experimental setup. Wooden components were placed at the support points, and rubber materials were utilized at the loading points to minimize localized damage during testing. The impact tests revealed that while a portion of the energy stored in the springs was dissipated due to system friction, the impactor consistently delivered sufficient energy to induce measurable responses in the AAC panels. Analysis of the impact load-time graphs showed that increasing the impactor's velocity led to higher peak loads; however, the duration of load application remained relatively constant across all tests. In scenarios without EDC implementation, the reinforced AAC panels exhibited shear failure under short-duration dynamic loads. In contrast, the use of EDC effectively reduced the peak impact loads and extended the duration of the load application. This energy dissipation mechanism prevented structural damage in the reinforced AAC panels, although permanent deformation was observed in the EDC components themselves. These findings underscore the critical role of energy damping systems in enhancing the impact resistance of reinforced AAC panels by absorbing and redistributing impact energy, thereby mitigating potential damage to structural elements. In accordance with the TS 5228-3-2 EN 259-2 standard, heavy-duty wallpaper samples adhered to gypsum panels of specified thickness were subjected to controlled impact testing using the spring-actuated device. The tests were conducted at a defined angle relative to the horizontal plane to simulate real-life application scenarios. A cylindrical steel impact head was utilized to deliver consistent impact energy to the specimens. Following each impact event, the test samples were examined in a standardized inspection chamber under controlled lighting conditions to assess the extent of surface damage. Irreversible damage was defined as any visible tearing, cracking, or permanent deformation of the coating material that compromised its protective or aesthetic function. The damage threshold was determined based on the energy level at which such permanent defects consistently appeared in repeated trials. This methodology ensured a reliable assessment of the coating's durability and its ability to withstand mechanical impact without compromising its integrity or appearance. In this study,“irreversible damage”was defined as any crack, rupture, or structural failure of the coating layer that extended through to the underlying gypsum plaster panel, in accordance with the criteria outlined in TS 5228-3-2 EN 259-2. Impact tests conducted at the specified energy levels demonstrated that the wall coverings maintained their structural integrity, with no occurrences of irreversible damage observed throughout repeated trials. The experimental findings demonstrate that the developed spring-actuated impact test device provides a versatile, precise, and cost-effective solution for evaluating the behavior of materials and structural components under short-duration dynamic loads. The system's ability to adjust spring tension, control impactor velocity, accurately measure impact forces, and easily adapt different test heads enables comprehensive and repeatable testing across a wide range of materials. This research significantly advances material characterization methodologies by offering a practical and scalable alternative to more complex and costly dynamic testing systems. The reliable performance and adaptability of the device make it a valuable tool for both research and industrial applications, particularly in fields where understanding material response to high strain-rate loading is critical, such as defense, aerospace, and construction industries.
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