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Featured Application: This study represents a breakthrough in the engineering of turning processes for manufacturing. By examining dynamic properties and vibration response during turning, it provides key insights for real-time machining system monitoring. The findings can improve surface quality and stability, particularly for slender, flexible shafts. Industries such as automotive, aerospace, and heavy equipment manufacturing can leverage these insights to optimize machine performance, reduce downtime, and boost productivity. This marks a significant stride towards more efficient manufacturing. The chatter that occurs during the turning operation, especially when cutting a slender and flexible shaft, determines the surface quality of the workpiece and the stability of the machining system. However, when building a dynamic model of a slender workpiece with a chuck and tailstock, it is generally regarded as a cantilever or simply supported beam, without consideration of the axial force and supported stiffness effect. In this work, a dynamic model for thin and flexible workpieces with different clamping boundary conditions was first built. Then, a finite element analysis (FEA) was used to study the influence of the axial force and supporting stiffness on the mode frequencies of the workpiece. A further analysis found that the relationship between support stiffness, axial force, and the dynamic response of the workpiece is nonlinear and far more complex than that of the simply supported beam model. The clamping force directly influenced the magnitude of the vibration response with the decrease of shaft stiffness during the turning process. These results were verified experimentally by measuring the vibrational response of slender shafts with different clamping modes using an on-rotor sensing (ORS) system. It proved that the proposed model shows advantages for the identification of dynamic vibration and quality control when machining slender workpieces. [ABSTRACT FROM AUTHOR]

Wear is one of the most common failures of hydrodynamic bearings. The main purpose of the present work was to investigate the effects of wear on lubrication performance and acquire efficient vibration signatures for fault diagnosis. In this paper, a finite element model (FEM) for a two-disk rotor supported on worn hydrodynamic bearings is presented in which the oil film force is evaluated by linear and nonlinear models. Numerical and experimental results indicate that the static and dynamic characteristics of the bearing are significantly changed by wear, leading to a drop in system critical speeds due to the deterioration of the constraint status provided by the bearings to the rotor. As the wear depth increases, the onset speed of oil whirl increases, while that of oil whip becomes lower, and large amplitudes of resonance and oil whip are more likely to be excited. More notably, all of the above vibration signatures in the y-direction are more sensitive to wear compared to those in the x-direction, which means that wear faults can be diagnosed by differences in vibration characteristics between the x- and y-directions. This research can provide a theoretical foundation and engineering guidance for the hydrodynamic bearing wear fault diagnosis. [ABSTRACT FROM AUTHOR]

Grinding residual stress (GRS) has been understood to have a great impact on the strength of gear fatigue life. However, there are lack of detailed studies on the influences in terms of mechanism and magnitude. To fill this gap, this study proposed a new method based on finite element analysis (FEA) to calculate the overall meshing stress on a gear tooth surface by including both the GRS and elastohydrodynamic lubrication (EHL) film pressure. Applying this method to a spiral bevel gear has resulted in a number of interesting results that GRS produced to reveal its mechanism of action through a full meshing cycle. The acquired understanding would be useful for development of manufacturing processes. [ABSTRACT FROM AUTHOR]

To understand the effects of vibration of cylinder liners on engine combustion performance, tribological behaviour and vibro-acoustic radiations, this study investigates the dynamic responses of cylinder liners by finite-element modelling and experimental validation. The finite-element model is established in this study to predict the dynamic responses of cylinder liners to two significant sources: combustion shock and piston side thrust. It takes into account both the characteristics of structural modes and nonlinearities of assembly constraints when selecting adequate elements for efficient computation of the responses under both the highly nonlinear combustion pressure excitations and subsequent piston slap impacts. The predictions are then evaluated against experimental results under different engine operating conditions. To suppressing noise in measured signals, continuous wavelet analysis is employed to process the complicated responses for characterizing key response events and their frequency ranges. The results show agreeable correspondences between the numerical predictions and measured vibration signals, paving the way for investigating its effect on the combustion and lubrication processes. [ABSTRACT FROM AUTHOR]

Self-piercing riveting (SPR) is a high-speed mechanical fastening technique which is suitable for point-joining advanced lightweight sheet materials that are dissimilar, coated, and hard to weld. Major advances have been made in recent years in SPR technique. Latest literature relating to finite element analysis (FEA) of SPR joints is reviewed in this paper. The recent development in FEA of SPR joints are described with particular reference to three major factors that influence the success of SPR technique: SPR process, failure mechanism, and mechanical behavior of SPR joints. The main FE methods used in FEA of SPR joints are discussed and illustrated with brief case studies from the literature. Areas where further useful progress can be made are also identified. [ABSTRACT FROM AUTHOR]

To ensure reliable and efficient operation of gas turbines, multiple model (MM) approaches have been extensively studied for online fault detection and isolation (FDI). However, current MM-FDI approaches are difficult to directly apply to gas path FDI, which is one of the common faults in gas turbines and is understood to mainly be due to the high complexity and computation in updating hypothetical gas path faults for online applications. In this paper, a fault contribution matrix (FCM) based MM-FDI approach is proposed to implement gas path FDI over a wide operating range. As the FCM is realized via an additive term of the healthy model set, the hypothetical models for various gas path faults can be easily established and updated online. In addition, a gap metric analysis method for operating points selection is also proposed, which yields the healthy model set from the equal intervals linearized models to approximate the nonlinearity of the gas turbine over a wide range of operating conditions with specified accuracy and computational efficiency. Simulation case studies conducted on a two-shaft marine gas turbine demonstrated the proposed approach is capable of adaptively updating hypothetical model sets to accurately differentiate both single and multiple faults of various gas path faults. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesh stiffness model of opening-crack tooth with elastoplastic deflection is built. • The model can accurately estimate the mesh stiffness of gears with crack failure. • Impacts of failure severity on the mesh stiffness and load sharing are analyzed. • Tooth deflection affects mesh stiffness, load sharing and meshing zone ratio. In the gear transmission system, tooth root crack often occurs due to the impact of machining technology and cyclic load. The appearance of tooth root cracks will affect its mesh stiffness and change the vibration characteristics of the system, thereby reducing system reliability and service life. In previous studies on the modeling of the mesh stiffness of cracked gears, the cracks were often supposed to be in a closed state, and the elastoplastic deflection of the fault gear teeth was also neglected, resulting in significant errors in the estimation of the mesh stiffness. When a tooth root crack occurs, the engaged gear teeth will deviate from the theoretical meshing position due to the elastoplastic deflection of the fault tooth. Therefore, an accurate mesh stiffness estimation model in view of the opening crack and elastoplastic deflection of the cracked tooth is put forward in this study. Firstly, the actual meshing position of the tooth pairs is derived considering the elastoplastic deformation in the crack opening state; Then, the improved potential energy method is adopted to calculate the mesh stiffness, and the finite element method (FEM) is applied to verify it. At last, the influence of failure severity and elastoplastic deflection degree on mesh stiffness and load sharing is analyzed. The results show that the severity of the crack failure and elastoplastic deflection has a significant impact on the mesh stiffness and load-bearing. This research can provide stiffness input for the study of fault dynamics of the gear transmission system. [ABSTRACT FROM AUTHOR]

With an increasing application of clinching in different industrial fields, the demand for a better understanding of the knowledge of static and dynamic characteristics of the clinched joints is required. In this paper, the clinching process and tensile–shear failure of the clinched joints have been numerically simulated using finite element (FE) method. For validating the numerical simulations, experimental tests on specimens made of aluminium alloy have been carried out. The results obtained from tests agreed fairly well with the computational simulation. Tensile–shear tests were carried out to measure the ultimate tensile–shear strengths of the clinching joints and clinching-bonded hybrid joints. Deformation and failure of joints under tensile–shear loading were studied. The normal hypothesis tests were performed to examine the rationality of the test data. This work was also aimed at evaluating experimentally and comparing the strength and energy absorption of the clinched joints and clinching-bonded hybrid joints. [ABSTRACT FROM AUTHOR]