Investigation of Valvetrain Dynamics Using Transient Dynamic Simulation in ANSYS

Engine valvetrain is one of the complex mechanisms in internal combustion engine as it involves many components namely, cam, pushrod, rocker lever, crosshead, intake and exhaust valves etc. Due to many components, their interactions with each other and presence of valve lash makes the system complicated to simulate. Typically, engine system level valvetrain dynamic simulation is performed in 1D software. Aim of this study is to understand the physics governing interactions and motion of the components in the valvetrain. This is done by simulating an inline 6-cylinder engine valvetrain mechanism through transient dynamic analysis in Ansys. This paper describes an approach used to simulate the valvetrain mechanism in Ansys and associated learnings. Finite Element Analysis model considers actual stiffnesses of all components. Appropriate joints/contacts are used to model the interactions. The comparative assessment of the valvetrain forces between Ansys results and 1D simulation results shows a good match. Further, 3D simulation in Ansys captures the key characteristics of valvetrain like crosshead tilting, uneven valve actuations and closing. It is also able to predict uneven contact and polishing observed on valve tip face. Overall, this study helped to ascertain the validity of 3D FEA method. This method also enhances the understanding of the valvetrain dynamics which can be helpful in further design improvements. This paper also includes a discussion on further steps to improve analysis model to make it more realistic e.g. including hot valve lash, valve seat wear etc. These improvements will help to understand effects of valve lash on valve velocities, sudden impact loads on valves, valve stresses/fatigue, pushrod buckling etc.

Modification optimization-based fatigue life analysis and improvement of EMU gear

PurposeThis paper proposes an improved fatigue life analysis method for optimal design of electric multiple units (EMU) gear, which aims at defects of traditional Miner fatigue cumulative damage theory.Design/methodology/approachA fatigue life analysis method by modifying S–N curve and considering material difference is presented, which improves the fatigue life of EMU gear based on shape modification optimization. A corrected method for stress amplitude, average stress and S–N curve is proposed, which considers low stress cycle, material difference and other factors. The fatigue life prediction of EMU gear is carried out by corrected S–N curve and transient dynamic analysis. Moreover, the gear modification technology combined with intelligent optimization method is adopted to investigate the approach of fatigue life analysis and improvement.FindingsThe results show that it is more corresponded to engineering practice by using the improved fatigue life analysis method than the traditional method. The function of stress and modification amount established by response surface method meets the requirement of precision. The fatigue life of EMU gear based on the intelligent algorithm for seeking the optimal modification amount is significantly improved compared with that before the modification.Originality/valueThe traditional fatigue life analysis method does not consider the influence of working condition and material. The life prediction results by using the method proposed in this paper are more accurate and ensure the safety of the people in the EMU. At the same time, the combination of intelligent algorithm and gear modification can improve the fatigue life of gear on the basis of accurate prediction, which is of great significance to the portability of EMU maintenance.

Transient Dynamic Analysis of Unconstrained Layer Damping Beams Characterized by a Fractional Derivative Model

This paper presents a numerical analysis of the influence of mechanical properties and the thickness of viscoelastic materials on the transient dynamic behavior of free layer damping beams. Specifically, the beams consist of cantilever metal sheets with surface viscoelastic treatment, and two different configurations are analyzed: symmetric and asymmetric. The viscoelastic material is characterized by a five-parameter fractional derivative model, which requires specific numerical methods to solve for the transverse displacement of the free edge of the beam when a load is applied. Concretely, a homogenized finite element formulation is performed to reduce computation time, and the Newmark method is applied together with the Grünwald–Letnikov method to accomplish the time discretization of the fractional derivative equations. Amplitudes and response time are evaluated to study the transient dynamic behavior and results indicate that, in general, asymmetrical configurations present more vibration attenuation than the symmetrical ones. Additionally, it is deduced that a compromise between response time and amplitudes has to be reached, and in addition, the most influential parameters have been determined to achieve greater vibration reduction.

Analysis of Dynamic Response of a Railway Locomotive Using ANSYS

Transient dynamic analysis (sometimes called time-history analysis) is a technique used to determine the dynamic response of a structure under the action of any general time-dependent loads. The time scale of the loading is such that the inertia or damping effects are considered to be important. Present work is focused on performing the time history analysis of a typical locomotive coach using finite element analysis in Indian railroad conditions. Track surface irregularity in the form of an ellipsoidal bump is modelled with assumptions that the vehicle passes over the bump in 0.144 seconds, variation in displacement at different key locations of the truck and car body models is plotted against time under standard loading conditions. The response pattern of the front and rear portions of the locomotive truck and car body indicate that these locations are more susceptible to wheel excitations compared to that of the centre portions of it as they are away from the centre of gravity of the vehicle due to unbalanced mass distribution.

A Method for Characterization of Geometric Deviations in Clinch Points with Computed Tomography and Transient Dynamic Analysis

When joining lightweight parts of various materials, clinching is a cost efficient solution. In a production line, the quality of a clinch point is primarily controlled by measurement of dimensions, which are accessible from outside. However, methods such as visual testing and measuring the bottom thickness as well as the outer diameter are not able to deliver any information about the most significant geometrical characteristic of the clinch point, neck thickness and undercut. Furthermore, ex-situ destructive methods such as microsectioning cannot detect elastic deformations and cracks that close after unloading. In order to exceed the current limits, a new non-destructive in-situ testing method for the clinching process is necessary. This work proposes a concept to characterize clinch points in-situ by combining two complementary non-destructive methods, namely, computed tomography (CT) and ultrasonic testing. Firstly, clinch points with different geometrical characteristics are analysed experimentally using ex-situ CT to get a highly spatially resolved 3D-image of the object. In this context, highly X-ray attenuating materials enhancing the visibility of the sheet-sheet interface are investigated. Secondly, the test specimens are modelled using finite element method (FEM) and a transient dynamic analysis (TDA) is conducted to study the effect of the geometrical differences on the deformation energy and to qualify the TDA as a fast in-situ non-destructive method for characterizing clinch points at high temporal resolution.

A Dual Frequency Ultrasonic Cleaning Tank Developed by Transient Dynamic Analysis

At present, development of manufacturer’s ultrasonic cleaning tank (UCT) to match the requirements from consumers usually relies on computer simulation based on harmonic response analysis (HRA). However, this technique can only be used with single-frequency UCT. For dual frequency, the manufacturer used information from empirical experiment alongside trial-and-error methods to develop prototypes, resulting in the UCT that may not be fully efficient. Thus, lack of such a proper calculational method to develop the dual frequency UCT was a problem that greatly impacted the manufacturers and consumers. To resolve this problem, we proposed a new model of simulation using transient dynamics analysis (TDA) which was successfully applied to develop the prototype of dual frequency UCT, 400 W, 18 L in capacity, eight horn transducers, 28 and 40 kHz frequencies for manufacturing. The TDA can indicate the acoustic pressure at all positions inside the UCT in transient states from the start to the states ready for proper cleaning. The calculation also reveals the correlation between the positions of acoustic pressure and the placement positions of transducers and frequencies. In comparison with the HRA at 28 kHz UCT, this TDA yielded the results more accurately than the HRA simulation, comparing to the experiments. Furthermore, the TDA can also be applied to the multifrequency UCTs as well. In this article, the step-by-step development of methodology was reported. Finally, this simulation can lead to the successful design of the high-performance dual frequencies UCT for the manufacturers.