Transactions of the Canadian Society for Mechanical Engineering
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Volume 39 (2015), Issue 4
Application of Fluid-structure interaction to numerical simulations in the left ventricle
Matthew G. Doyle, Stavros Tavoularis, Yves Bougault
Numerical simulations of blood flow and myocardium motion for an average canine left ventricle (LV) with fluid-structure interaction were performed. The temporal variations of the LV cavity pressure and wall stress during the cardiac cycle were consistent with previous literature. LV cavity volume was conserved from one period to the next, despite sub-physiological ejection volumes and brief periods of backflow during early filling. This study improves on previous ones by presenting details of the models and results for both the fluid and solid components of the LV.
Effect of static eccentricity and stator inter-turn short circuit composite fault on rotor vibration characteristics of generator
Yu-Ling He, Meng-Qiang Ke, Fa-Lin Wang, Gui-Ji Tang, Shu-Ting Wan
This paper investigates the radial rotor vibration characteristics under static air-gap eccentricity and stator inter-turn short circuit composite faults. The air-gap magnetic flux density is firstly deduced to obtain the unbalanced magnetic pull (UMP) on rotor. Then the rotor vibration characters, as well as the developing trend between the faulty parameters and the vibration amplitudes, are analyzed. Finally, the experiments are taken on a SDF-9 type simulating generator. It is shown that the radial deformation possibility, the 2nd, 4th, and 6th harmonic vibrations will be caused by the composite faults. Besides, the development of the inter-turn short circuit, the increment of the static eccentricity, and the rise of the exciting current will all get the deformation trend and the vibration amplitudes increased.
Research and experiment of thermal water de-icing device
Zicheng Zhu, Xuejun Zhang, Qiang Wang, Weijun Chu
By analyzing the deficiencies of existing de-icing methods, a new de-icing method which combines thermal de-icing with water-jet cutting de-icing technology is coming into being. This paper introduces the construction of thermal water-jet de-icing equipment. Through repeated experiments, the factors which would affect de-icing have been researched and experimentally verified, including jet pressure, nozzle aperture, standoff, and jet injection angles, etc. Analysis of experimental results shows that this device can perform well and satisfy design requirements.
POD analysis of three-dimensional harmonically forced wake flow of a circular cylinder
Negar Nabatian, Xiaofei Xu, Njuki Mureithi
A 3D numerical simulation of a circular cylinder wake is presented in this paper. The cylinder is harmonically forced in the stream-wise direction. The objective of the present work is to investigate the effect of the oscillation amplitude on the secondary transition of the wake. The frequency of the lift force is then linked to the form of the vortex shedding mode. The relation between these vortex shedding modes using POD analysis of the transverse velocity and the unsteady lift coefficient of 3D simulation is in good agreement with the 2D model. Results show that the 3D spanwise effect, which can change the wake structure, is suppressed at Re = 200 by streamwise oscillation of the cylinder. Thus the 2D analysis can effectively model the temporal instability of the wake flow.
A numerical approach to calculate creep in roller follower valve train basing on friction and lubrication modeling
Muhammad Khurram, Riaz Ahmad Mufti, Muhammad Usman Bhutta, Yousaf Habib, Arslan Ahmed, Naqash Afzal
A numerical approach basing on friction and lubrication analysis has been developed to determine the creep at cam/roller interface in end pivoted roller finger follower valve train. The kinematic and dynamic analysis at the geometrical mating surfaces of cam and roller follower has been carried out to predict the required instantaneous motion parameters and normal loading whereas the oil film thickness is determined using lubrication analysis. The tangential forces have been computed precisely using elastohydrodynamic and mixed lubrication concept for a complete cam cycle. At low camshaft operating speeds, the creep proves to be low whereas the creep increases significantly under the influence of high tangential loading at higher operating speeds.
Load sequence analysis in fatigue life prediction
Moises Jimenez, Jose Martinez, Ulises Figueroa
In this work, the load sequence effect is analyzed in fatigue test. One of the assumptions of the Minerís rule is that the total damage is equal to the sum of the damages absorbed; however, different models have been proposed to take the effect of the load sequences under two load levels into account. To analyze this effect, a case study of a rear axle mounting bracket has been performed, analyzing six different sequences of three load levels, defined as Low, Medium and High. A Finite Element Analysis was also performed using MSC Tools. With these results and a series of test at constant amplitude, the component S-N curve was made. 24 tests at room temperature were performed in order to evaluate the damage process. It was found that, under a block of three load levels, the sequence of each block has an effect in the total amount of damage under the same number of cycles. With this information it is possible to improve the life prediction through the modification of the damage rule. The proposed model uses a factor which depends on the ultimate strength and yield point. This is an advantage over other approaches, as the other models need additional dynamic tests to obtain coefficients to perform the life prediction.
A crashworthiness simulation for a light aircraft constructed of composite materials
Pu-Woei Chen, Kuan-Jung Chen
This study analyzes the crashworthiness of a light aircraft that is constructed from composite materials. The finite element method is employed to conduct dynamic impact simulations on carbon fiber composite fuselages. The results show that the safe impact speed for an aluminum alloy cockpit crashed at a 30° impact angle is 9.59 m/s, but a cockpit made of composite material can withstand a speed greater than 18.05 m/s. The safe impact angle for an aluminum alloy cockpit is 16.56°, but that for a composite cockpit is 84.9°. The safety crash zone for a composite material cockpit is 160% greater than that for an aluminum alloy cockpit.
Characteristics of AA7075-T6 and AA6061-T6 friction welded joints
Sathish Rengarajan, Vaddi Seshagiri Rao
In this experimental study dissimilar materials of AA6061-T6 and AA7075-T6 having distinctive difference in physical and thermal properties were welded using continuous direct drive friction welding. High strength was achieved by high friction, upset pressure, low burn off length and medium rotational speed. Mechanical characterization and Micro structural behavior of the joint were given the paramount importance in this experimental analysis. The macro structure indicates that change in the direction of flow of grains perpendicular to the initial grain direction of the parent metal. Also the micro structural analysis at the interface zone showed the presence of eutectic particles that are formed as fragmented agglomerates.
Vibration induced failure analysis of a high speed rotor supported by active magnetic bearings
Sarvat M. Ahmad, Osman A. Ahmed, Zaharuddin Mohamed
Active Magnetic Bearings (AMBs) are increasingly used in various industries and a quick re-levitation of AMBs supported high speed flexible rotor is necessary in case of vibration induced failure. A robust fault diagnosis algorithm is presented to detect suspected saturation type of nonlinearity associated with a power amplifier. A five degree-of-freedom AMB system consisting of four opposing pair of radial magnets and a pair of axial magnets is considered. In this paper failure of an industrial grade AMB system is investigated using Sinusoidal Input Describing Function (SIDF) method. SIDF predicts the gain and frequency at which failure occurs. It is demonstrated that the predicted frequency is in agreement with the frequency at which failure occurs.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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