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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]

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]

[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]

With an increasing application of clinching in different industrial fields, the demand for knowledge of static and dynamic characteristics of clinching is increased. In the present work, the extensible die clinching process was numerically investigated using finite element method. To validate the computational simulation of the extensible die clinching process, experimental tests on extensible die clinched specimens have been carried out. Good agreement is achieved between the predictions and the experimental results. Monotonic tensile tests were carried out to measure the ultimate tensile strengths of the extensible die clinching joints and clinching-bonded hybrid joints. Deformation and failure of the extensible die clinched joints under monotonic tensile 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 extensible die clinched joints and clinching-bonded hybrid joints. [ABSTRACT FROM AUTHOR]

Self-piercing riveting (SPR) is a new high-speed mechanical fastening technique which is suitable for point-joining dissimilar sheet materials, as well as coated and pre-painted sheet materials. With an increasing application of SPR in different industrial fields, the demand for a better understanding of the knowledge of static and dynamic characteristics of the SPR joints is required. In this paper, the SPR process has been numerically simulated using the commercial finite element software LS-Dyna. For validating the numerical simulation of the SPR process, experimental tests on specimens made of aluminium alloy have been carried out. The online window monitoring technique was introduced in the tests for evaluating the quality of SPR joints. Good agreements between the simulations and the tests have been found, both with respect to the force-travel (time) curves as well as the deformed shape on the cross-section of the SPR joint. Monotonic tensile tests were carried out to measure the ultimate tensile strengths of the bonded joints, SPR joints and SPR-bonded hybrid joints. Deformation and failure of the joints under monotonic tensile 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 bonded joints, SPR joints and SPR-bonded hybrid joints. [ABSTRACT FROM AUTHOR]

• Fracture curve tilted along gear axis is modeled using analytic geometry method. • Mesh stiffness of gear with tooth tip chipping is analyzed by the proposed model. • The influences of fault severity on the vaiation of mesh stiffness are investigated. • The proposed model can evaluate mesh stiffness of gears accurately. Tooth tip chipping that the top of a tooth breaks away from lower portion is one of the common gear faults which will affect the dynamic characteristics of gears. In the assumption of plane-fracture tooth tip chipping, the tooth surface fracture line tilted configuration relatively to the gear axis is a curve, which is simplified to a straight in previous studies. However, such simplification will cause an estimate error of mesh stiffness. Therefore, to accurately estimate the mesh stiffness, failure models of tooth tip chipping for both internal gear and external gear are established by means of analytic geometry method in this paper. The fracture curve Eq. is derived by using analytic geometry method. And the mesh stiffness of the fault gear is derived via potential energy method and verified by the finite element method (FEM). The influence of different fault severity on the mesh stiffness is analyzed. The analysis results show that the proposed model can accurately evaluate the mesh stiffness of gears with tooth tip chipping and the modeling method can also be applied to other fault types. [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]