Applied Mechanics and Materials Vols. 764-765

Abstract: Nowadays, absorbing energy from vibration is one of the most promising technologies. In general, the vibrations may be very large, such as the vibrations of tall buildings, large flexible bridges, and ocean platform and so on in some environmental loading. With the global concern on energy and environmental issues, energy absorbing from large-scale vibrations for structural health monitoring purposes is more attractive and becomes a research frontier. A type of damped dynamics vibration energy absorber, where two masses are connected in series with the energy transducer and spring, is built and analyzed in this paper. The relationships among electrical damping ratio, excitation frequency ratio and dimensionless power are analyzed in frequency domain. The optimal parameters for maximizing the power output are discussed in analytical form while taking the parasitic mechanical damping of the system into account. In addition, the numerical simulations in time domain are calculated. The results indicate that when the system is excited by the larger peak of local optimal excitation frequency, more power can be obtained. It is helpful for design of energy absorber device.

Abstract: In the Roll-to-Roll (R2R) system, the design and development for a roller path and control system are mainly performed by the expert’s experience. There are some important issues in the numerical analysis method of R2R system. This study proposes an efficient R2R system analysis method. The first one is the Approximated Winding Length Estimation (AWLE) algorithm which can calculate the analytic winded length of the workpiece. The core winder is approximated with line and arc segments in this algorithm. As a result, in the numerical model of R2R system, we can replace the winder characteristics with the approximated winding length estimation (AWLE) algorithm. The second one is the contact algorithm between workpiece and rollers. This contact algorithm must be stable and fast for precise analysis. The third one is the flexible workpiece model. The workpiece can be modeled by the finite elements. By implementing these some important issues, this paper proposes an efficient R2R system analysis method.

Abstract: Bearings are one of the most important components in rotating machineries. Their failures will lead to great production loss and increase the maintenance cost. So, condition monitoring work of bearings can save and avoid the potential loss caused by bearing fault. Lucy-Richardson deconvolution (LRD) algorithm, as an image processing technique, started to be used in bearing fault diagnosis. However, only data of bearings working in electric motor are used to validate the method. In engineering cases, most bearings are working in gearbox. Therefore, the bearing fault signals are very weak compared to the gear vibration signal. It is usually difficult to detect the bearing fault in this case. LRD algorithm is used to enhance the bearing fault diagnosis and some characteristics in this case are discussed. Experiment data analysis demonstrates that LRD can enhance the periodic impulse signal effectively. Otherwise, if the desired fault signal is weak compared to non-desired signal, then, the desired fault signal will be continued weaken by LRD which is not benefit to bearing’s incipient fault detection.

Abstract: PET prefom surface temperature distribution is a key factor for getting the better quality of construction a bottle by stretch blow molding (SBM) machine. To get a better temperature distribution, different types of prefom under different number of infrared lamps heating conditions are worth to investigate the position of each lamp as well as its power intensity. In this study, we first try to use adaptive finite volume method to estimate the proper intensity of each lamp so that the combination strength will make good result about the temperature distribution. Then we make experiments to confirm each case. We have five, six, and seven heating lamps cases to present. With these estimations, we find that five lamps case can do equal quality about the temperature distribution comparing with six and seven lamps cases. This means that we offer a method for finding one saving energy way to produce PET bottle by SBM machine. A more detail analysis about inside PET bottle temperature distribution will be deliberated in future.

Abstract: Health assessment and fault diagnosis for rolling bearings mostly adopt traditional methods, such as time-frequency, spectral, and wavelet packet analyses, to extract the feature vector. These methods are suitable for processing data with a linear structure. However, for the non-linear and non-stationary signal, the result of these methods is not ideal. Thus, this study proposes a suitable method to extract the feature vector in nonlinear signals. Local tangent space alignment of a manifold algorithm is employed to extract the feature vector from the rolling bearings. Results verify the advantage of the manifold algorithm for non-linear and non-stationary signals.

Abstract: This study uses FEM simulation based on Deform 3D commercial software to explore the plastic behaviors in the rotating compression of double-layer bounded clad ring under constant shear friction. The effective stress, the effective strain, the velocity field, the compression force under various forming conditions can be determined from FEM simulation. The realistic experiment has been performed to verify the acceptance of FEM simulation. From the comparisons, the compression force and free surfaces of outer and inner diameters shows a good agreement with the experiments, it proves the FEM simulation can be accepted as industry references.

Abstract: Finite element analysis on natural properties of a micro drill with ultrasonic vibration is considered to study. Because getting smaller aperture in the printed circuit board (PCB), it tends to be more severe due to vibration. The vibration has adverse effects to machining accuracy and surface roughness which will increase tool abrasion and further accelerate the destruction from material fatigue. There are many ways to produce perforations, such as laser micro-machining and micro-drilling. The industry still adopts micro drill piercing process due to the cost and technical considerations. In order to enhance the cutlery life and the quality of the drilling process, the cutting characteristic of bur is important. Hence, the vibration during drilling must be suppressed. This study is to investigate the natural properties of a micro drill under ultrasonic vibration (50 kHz) excited with a piezoelectric-driven actuator and numerically by using finite element analysis.

Abstract: This paper presents the magnetostatic field analysis of a coaxial magnetic gear device proposed by Atallah and Howe. The structural configuration and speed reduction ratio of this magnetic gear device are introduced. The 2-dimensional finite-element analysis (2-D FEA), conducted by applying commercial FEA software Ansoft/Maxwell, is performed to evaluate the magnetostatic field distribution, especially for the magnetic flux densities within the outer air-gap. Once the number of steel pole-pieces equals the sum of the pole-pair numbers of the high-speed rotor and the low-speed rotor, the coaxial magnetic gear device possesses higher magnetic flux densities, thereby generating greater transmitted torque.

Abstract: The aircraft environmental control system (ECS) is a critical aircraft system that provides the appropriate environmental conditions to ensure the safe transport of air passengers and equipment. The functionality and reliability of ECS have elicited an increasing amount of attention in recent years. The heat exchanger is a particularly significant component of ECS because its failure reduces the system’s efficiency and can lead to catastrophic consequences. Health assessment and fault diagnosis for the heat exchanger are necessary to perform maintenance and prevent risks in a timely manner. This paper presents fault-related parameter estimation methods based on strong tracking filter (STF) and logistic regression (LR) algorithm for heat exchanger health assessment and root cause classification, respectively. Heat exchanger fault simulation is conducted to generate performance degradation data, through which the proposed methods are validated. Results demonstrate that the proposed methods are capable of providing stable, effective, and accurate heat exchanger health assessment and root cause classification.

Abstract: Using heat sink to increase the cooling area is the most familiar and fundamental method in LED heat management technology. We develop a new configuration of finned heat sink for LED lamp. It is a circular cylinder with many plate fins radially arranged on the external surface. There are many straight ducts inside the peripheral wall of the cylinder. These ducts form the chimney effect to enhance the heat transfer. This work experimentally investigated the chimney effect on the heat transfer characteristics of the finned heat sink under the free convection state. The aluminum-alloy plate spreader with two vertical plate fins was selected as the control group. The experimental group was the heat sink having the same configuration of the control group but had a vertical passage within the spreader. The results show that the vertical passage did strengthen 8.3~12.1% free convection performance for the present test heat sink.