Friction stir welding (FSW) is the most widely used solid-state joining method for sheet and plate-like materials, valued for being a highly adaptable, environmentally sound, and energy-efficient process. The literature has repeatedly shown that FSW is a reliable joining technique for high-demand technological applications, particularly for high-strength aluminum and titanium alloys used in aerospace, which are difficult to join with traditional fusion welding methods. To describe the microstructural changes caused by solid-state FSW, many studies analyze mechanical parameters of FSW joints, including tensile strength, bending, torsion, elasticity, and fatigue responses. In recent years, the push to expand FSW's use, broaden the range of compatible alloy systems, and improve the resulting mechanical properties has led to significant advancements in this joining method. Accordingly, this review study provides a comprehensive investigation into the methodology and the materials relevant to this specific field.

The robot arms often follow a certain trajectory depending on the type of end effector with functions of spray-painting, arc welding, bonding or machining etc. Therefore, trajectory-tracking control is a very important issue in robot arm applications. Also, the robot must be able to follow the determined trajectory stably under the influence of external forces or machining forces it encounters in its operations. In this study, a Model Predictive Control (MPC) for trajectory tracking control of a 2 Degrees of Freedom (DoFs) Selective Compliant Assembly Robot Arm (SCARA) under an external force acting to the tip of the robot along the trajectory was performed. The effectiveness of the MPC method used has been demonstrated by simulation applications. According to simulation studies, successful results were obtained.

This study investigates the vibrational characteristics of multi-layered graphene sheets with variable thickness (VTGSs) by using molecular dynamics (MD) simulations. It is aimed to determine how the natural frequencies and vibration damping ratios of variable-thickness graphene change with respect to temperature. Atomistic models for six distinct geometries (1L, 3LT, 3LTB, 5LT, 5LTB, and 9LTB) were generated to analyze the influence of structural design and temperature on their natural frequencies. The simulations were performed using the Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with an AIREBO potential to represent interatomic carbon interactions. Natural frequencies of all atomistic models were extracted by applying the Fast Fourier Transform (FFT) method to the Velocity Autocorrelation Function (VACF) data obtained from the simulations. In addition, the analysis was conducted at three different temperatures: 250 K, 300 K, and 350 K. Key findings reveal that an increase in the number of graphene layers results in a decrease in the fundamental natural frequency due to the increased mass of the structure. Moreover, it was noted that natural frequencies decrease with increasing temperature. It is attributed to the reduction in structural rigidity at higher thermal energies. These results provide critical insights into how geometric and thermal variations affect the dynamic behavior of complex multi-layered graphene structures.

This study investigated the dynamic properties of a spherical sandwich composite structure made of carbon fiber face sheets and a Nomex honeycomb core. The structure was produced using the hand lay-up method. The results from Experimental Modal Analysis (EMA) and the numerical model created in ANSYS showed high consistency. The natural frequency difference was only 0.73% for the second mode, with the largest discrepancy of 6.5% was observed in the first mode. These differences are thought to be related to structural variations from the manufacturing process, such as resin distribution, carbon fiber fabric stacking, and air voids and the experimental challenges such as double hit errors, measurement resolutions related to force sensor and accelerometer and environmental noise. The vibration damping capability of the sandwich structure was investigated. Some modes exhibited high damping, while others had relatively lower values. The highest and the lowest damping ratios were obtained as 0.83% for the third mode and 0.23% for the fourth mode. A numerical equivalent model of the structure was created in ANSYS to determine its natural frequencies and vibration modes, confirming its effectiveness in modeling complex structures.

This study comprehensively investigates the dynamic vibration behavior of multilayer carbon nanotubes with stepped cross-sectional geometries under various boundary conditions, which is crucial for their advanced engineering applications. The methodology integrates classical molecular dynamics simulations to determine the bending stiffness of single-walled and multi-walled atomistic structures, which are subsequently utilized in the Euler–Bernoulli beam theory based on nonlocal elasticity for vibration analysis. The research focuses on elucidating the influence of the μ/L ratio (a key length parameter) and different support conditions on the natural frequencies and mode shapes of these nanostructures. Key findings reveal that the cross-sectional geometry significantly impacts the vibrational characteristics. A consistent trend observed across all examined boundary conditions is a decrease in natural frequencies as the μ/L ratio increases, indicating that increased free length or reduced fixed length leads to lower stiffness and, consequently, reduced natural frequencies. The study presents Frequency Response Functions (FRFs) and the first four mode shapes, which visually confirm these dynamic characteristics. Graphical representations further reinforce the sensitivity of natural frequencies to both the μ/L ratio and support conditions. The systematic analysis presented in this work provides vital data for predicting resonance phenomena, optimizing structural stability, and enabling precise control over the vibrational response of these advanced nanomaterials in diverse engineering applications.

Parçacık darbesi ile sönümleme, ana yapı üzerindeki boşluk veya boşluklara çok sayıda küçük boyutlu parçacıklar yerleştirilerek sistemdeki titreşim enerjisinin azaltıldığı pasif bir sönümleme yöntemidir. Titreşimi azaltılacak sistem üzerinde oluşturulan hücreler içine yerleştirilen çok sayıdaki küçük taneli parçacıklar titreşim esnasında hareket ederler ve hücre içerisinde birbirlerine ve hücre duvarlarına çarparlar. Bu sayede ana sistemin titreşimini bir miktar sönümlerler. Bu çalışmada, yatay doğrultuda zeminden tahrikli tek serbestlik dereceli bir yapının titreşim seviyesinin düşürülmesinde parçacık darbesi ile sönümleyicinin performansı incelenmiştir. Ana yapı üzerine açılan hücreler içerisine çok sayıda küresel parçacıklar yerleştirilmiştir. Parçacıkların birbiri ve hücre duvarları ile olan dinamik etkileşimini modellemek için Ayrık Elemanlar Yöntemi kullanılmış ve parçacık sayısına bağlı olarak çok sayıda doğrusal olmayan denklem takımı elde edilmiştir. Bu denklemlerin sayısal olarak çözülmesiyle sistemin zamana bağlı olarak titreşim genlikleri ve her parçacığın hücre içerisindeki hareketi elde edilmiştir. Yapılan sayısal uygulamalarda parçacıkların ana sistemin titreşimlerini önemli ölçüde sönümlediği görülmüştür.