Advanced Materials Research Vols. 479-481

Abstract: In order to correct the endpoint effect and modal aliasing phenomenon in EMD and EEMD, improved EEMD is put forward in this paper. on the basis of the cause of the endpoint effect,the improvement measures are proposed. The pulse interference and noise pollution is suppressed by threshold noise reduction.The overshoot and undershoot phenomenon is controlled by improving 3-spline interpolation to fit envelope. The endpoint effects is lessened by signal SVM prolongation.Compared with EMD and EEMD, not only the IMF false component is reduced, the modal aliasing avoided, and effectively the endpoint effect restrained, the distortion problem in the signal decomposition produces corrected in the results of simulation signal and the measured signal by the improved EEMD in this paper.

Abstract: The time domain wavenumber analysis method can directly delay and align signals before the superposition of signals in the time domain. In this paper, estimating the direction of wavefront propagation and the slowness for seismic signals which pass through the small-size dense seismic array is described in detail. The earthquake recorder sample adopted from US Geological Survey Parkfield Dense Seismograph Array (UPSAR array) of the U.S is used for analyzing. The results indicate that, the direction of wavefront propagation cannot be determined rashly only by the connecting line of the earthquake epicenter to the seismic array. The accuracy of the apparent velocity and the direction of wavefront propagation calculated using vertical seismic recorders is higher in West-East direction and in North-South direction.

Abstract: The stability of a transverse cylindrical grinding process is investigated in this paper. The workpiece is considered as a rotating damped hinged-hinged Euler-Bernoulli beam and the grinding wheel a rotating damped spring mass system moving along the workpiece. Called regenerative force, the contact force between the workpiece and the wheel is a functional equation related to both the current and previous relative positions between the workpiece and the wheel since the regeneration exists on the surfaces of both the workpiece and the wheel. The two distinct time delays presented in the regenerative force model are inversely proportional to the rotation speeds of the workpiece and the wheel respectively. For grinding stability analysis, the regenerative effects are considered as the key factors in inducing chatter vibrations in the grinding process. The grinding stability is numerically analyzed since two distinct delays being involved in the model makes the analytical analysis extremely difficult. Finally, the grinding stability analysis is verified by numerical simulation.

Abstract: Centrifugal pump is an important installation for fluid delivery. The research on the unsteady flow in centrifugal pump is very meaningful to reducing vibration. The methods of numerical simulation were discussed. The unsteady pressure field was simulated by using Sliding Mesh (SM) model provided by Fluent. The time domain data for pressure were obtained at the monitoring points, and they were translated to frequency domain data by using FFT. The results show that the static pressure at the impeller outlet increases along the direction of impeller rotation from the position near the volute tongue. The pressure disturbance is relatively large near the volute tongue. The pressure disturbance at the impeller inlet is smaller than that at the impeller outlet. The volute tongue plays a key role in the flow induced vibration. The position, where the blade is in closest proximity to the head of volute tongue, is the turning point in the pressure fluctuation cycle. The maximum peak value of pressure fluctuation appears at 145Hz, which is the blade frequency. Other pressure peaks are evident at multiples of the blade frequency. Also the pressure amplitude decreases with increasing frequency.

Abstract: Comfort of the vibratory road roller is an important research title. A 2-DOF non-line model is set up, which is more close to the actual situation of the vibratory road roller. A simulation using MATLAB/SIMULINK is carried out to validate this model and study its dynamic characteristic and analyze the motion laws of its housing and wheel. A kind of Magneto-rheological (MR) damper is designed which has been widely used in automotive and bridge damping in recent years, and applied to a vibratory road roller to control it. The control strategy uses fuzzy control. The results indicate that the damping performance of the vibratory road roller which applied MR damper is improved remarkably.

Abstract: To determine its actual dynamic responses under the wind loads, modal identification from the field tests was carried out for the Kao Ping Hsi cable-stayed bridge in southern Taiwan. The rational finite element model has been established for the bridge. With the refined finite element model, a nonlinear analysis in time domain is employed to determine the buffeting response of the bridge. Through validation of the results against those obtained by the frequency domain approach, it is confirmed that the time domain approach adopted herein is applicable for the buffeting analysis of cable-stayed bridges.

Abstract: Topology optimization of the constrained damping cylindrical shell for the maximized modal damping coefficient is studied in this paper. According to the first 3 orders modes, a novel topological optimization model where the volume is taken as the constraint function and the function of the modal damping coefficient as the target function is proposed and analyzed. The reasonable topology configuration was obtained for the damping structure. The results show that this method can be applied to solve the problem of optimization of the constrained damping cylindrical shell with the damping materials volume constrained. Numerical simulations are performed to very the effectiveness of the presented method.

Abstract: The active vibration control is becoming an effective mean to solve the vibration control problems of the aerospace and other fields. This paper builds up the active vibration control system of simply-supported beam based on piezoelectric actuator. The mathematical model of simply supported is derived and the displacement response curve of the beam is obtained by simulation analysis through MATLAB software. The vibration tests of simply supported beam under an initial disturbance and continuous incentives were carried out, according to the experimental results it can be concluded that the proposed control method has a suitable and efficient performance for vibrations control.

Abstract: The macro-synthetic fiber is widely used to prevent the cracking at concrete members. By the way of experiment that macro-synthetic fiber-reinforced concrete ductile columns comparing with the usual fiber-reinforced columns under the action of low-frequency cyclic loading, seismic performance of the columns in different form of bars were obtained. Meanwhile, the damage pattern, hysteresis curve, ductile coefficient and equivalent viscous damping coefficient of the columns could be also obtained. The results show that the macro-synthetic fiber-reinforced concrete ductile column has the better ductility and the higher post-crack energy absorption ability.

Abstract: The vibration control platform is designed involving periodical micro- vibration in Three Dimension (3D) scanning system. The system is identified utilizing neural network based on Levenberg - Marquardt (L-M) algorithm. The L-M algorithm is the combination of the steepest decent algorithm with the Gauss - Newton algorithm so that it has the faster speed of convergence and higher approach accuracy. Compared with the rational BP, the simulation result showed the LM algorithm with learning rate speed up learning process, reduce training time with improve identification accuracy greatly. The identification effect is good.