Advanced Materials Research Vol. 1016

Abstract: The drilling operation is considered by manufacturers as complex and difficult process (rapid wear of the cutting edge as well as problems of chip evacuation). Faced with these failures, manufacturers have shifted in recent years towards the drilling process assisted by forced vibrations. This method consist to add an axial oscillation with a low frequency to the classical feed movement of the drill so as to ensure good fragmentation and better chip evacuation. This paper presents a model for prediction of cutting forces during a drilling operation assisted by forced low-frequency vibration. The model allows understanding the interaction between the tool and the workpiece and identifying numerically the three-dimensional evolution of the cutting force components generated by the vibratory drilling operation. The effects of cutting parameters, tool parameters and those of forced vibrations on the cutting forces distributions will be discussed.

Abstract: Numerical studies were carried out on the dynamics of the Basic Finner missile under supersonic velocity based on the three-dimensional unsteady N-S equation. Second-order upwind NND scheme finite volume was used to discretize the spatial derivative term of the flow-controlled equation group. The LU-SGS containing dual time steps was used to obtain higher efficiency and precision of time solution. A numerical model representing the relationship between the unsteady aerodynamic force/moment coefficients and state variables under single DOF (degree of freedom) pitching and rolling movements was built from the Etkin unsteady aerodynamic model. The numerical algorithm for solving damping-in-pitch derivatives and damping-in-roll derivatives by forced-harmonic analysis was proposed. The M910 target practice, discarding sabot with tracer (TPDS-T) was used as a validation example and proved that the numerical calculation gives the same result as the experiment. By simulating the forced pitching and rolling vibration of Basic Finner, the numerical identification succeeded in obtaining the damping-in-pitch derivative and damping-in-roll derivative to a higher precision than the calculated result obtained by the quasi-steady Euler equation. Besides, to address the longitudinal and horizontal cross coupling induced by the pitching movement, numerical identification was also carried out on the cross coupling derivative of Basic Finner when under forced pitching vibration.

Abstract: Twin-rotor piston engine (TRPE) is a new differential rotary engine, which is still under developing. In this paper, a rigid-flexible coupling dynamics model was established for the prototype TRPE-350. By combining the multi-body dynamics simulating software RecurDyn and the finite analysis software ANSYS, the TRPE′s performances were studied. Vibration analysis for rigid-flexible coupling model was analyzed. The simulation results can be found that the simulated overall changing trends match with the actual movement of the TRPE very well. So it provides a theoretical tool for further optimization and improvement of this engine.

Abstract: Design considerations related to noise pollution have become extremely important recently in many industries. Despite the wide range of applications and various noise spectrum the methodology remains quite common. The power products operating in the power systems are very often affected by a noise emission side effect and must be carefully designed with respect to the resulting noise emission and its influence on the surrounding environment consequently. Noise management, design concept examples as well as the modern techniques for noise sources characterization in transformers are presented in this paper.

Abstract: The article deals with the specification of unknown force within dynamic analysis of slider crank mechanism by three various access. The method of virtual work was used at the analytical solution; the principle of superposition was used at the graphical solution and the software PTC Creo was used at the solution with computer aid. All three types of the solution have their self-advantages and disadvantages. The final decision, which of methods should be selected for the solution, depends on required result precision and on the abilities of investigator. In all cases, however, it is necessary to know the basic principles of mechanics.

Abstract: The stress distribution and modal characteristics of a space inflatable torus is investigated using the nonlinear finite element method. This paper focused on the effect of enclosed air on the modal analysis of the torus, including the effect of follower pressure load and the effect of the interaction between the enclosed air and the torus structure. Research shows that follower pressure stiffness significantly reduces the natural frequencies and changes mode shapes order. The fluid-structure interaction obviously reduces the natural frequencies, and the in-plane translation mode is observed. Follower pressure stiffness has no effect on the in-plane translation mode. Fluid-structure interaction decreases the natural frequencies of the modal considering the follower load effect, but it does not change mode shapes order. The effect of enclosed gas seriously reduces the natural frequencies, changes mode shapes order, and produces the in-plane translation mode.

Abstract: The monitoring and vibratory analysis of gear transmission allow the prediction of a possible malfunction and breakdowns. As the gear transmission product non-stationary signals its treatment is too difficult with the usual tools of signal processing witch can product errors in its interpretation. As the characteristics of gear frequencies are predetermined, it is proposed to monitor (fault identification) using wavelet analysis. To simulate the signal to be analyzed, we intentionally introduced a spalling defect. We chose the Daubechies wavelet type which are the most used in diagnostic. The aim of this work is to try to control the various parameters related to the wavelet analysis for reliable and inexpensive detection, i.e., the order of the wavelet and level decomposition. The approach witch was previously used for bearings, consists on observing the kurtosis for several orders wavelet based on the default severity..

Abstract: The Response Surface Method (RSM) and Simulated Annealing Algorithm (SAA) are utilized to analysis and optimize the vibro-acoustic properties of gear system. A simple case is illustrated to demonstrate the capabilities of the acoustic optimization design method. The results show that the method of acoustic optimization design based on RSM and SAA can effectively reduce radiation noise, and provide theoretical fundament and guidance for further study on acoustic optimization design of complicated gear system.

Abstract: In this study, we discussed the sound sources localization and characterization for a spur gear transmission, which deals with a vibro-acoustic surveillance for predictive maintenance. The technique uses is based on the near-field Beam forming using Bartlett and Capon estimators. The measurements done on the gear transmission with a rectangular phased array of microphones were performed in acoustics and vibration laboratory (LVA) of the INSA of Lyon, in a semi-anechoic room. The gear transmission was considered sometimes open and sometimes closed. The results are presented as an image showing the acoustic field distribution radiated by the gear transmission at the most energetic frequencies. Both estimators have satisfactory results, but even better for the method with high resolution capon.

Abstract: Classroom speech intelligibility has become one of the main concerns in schools and other learning institutions development nowadays. This is because the qualities of student’s perceptions towards teacher are essentials in learning development. Measures have been introduced by the acoustical association to tackle the speech intelligibility problems in the classroom such as room renovations. Room’s acoustics standards have been introduced in several countries but still the questions on whether the standards fits on every classroom in different countries are still arise. Studies have also shown that most of the researches that have been conducted were only focusing on the conventional type classroom which depends only on the teacher’s vocal power. This paper will formulate the measurement protocol on measuring the speech intelligibility in the sound reinforced (multiple speaker) classroom. Finally it was found that the speech intelligibility in the sound reinforced classroom is better than the conventional classroom by using Linear Discriminant Analysis.