Advanced Materials Research Vols. 291-294

Abstract: The electrochemical degradation of chitosan was studied with using graphite as anode and cathode, NaCl solution as supporting electrolyte. The effects of current density, temperature, NaCl concentration, pH, chitosan concentration on the degradation dynamics were investigated. It was shown that the electrochemical degradation of chitosan obeys the rule of random degradation, and the kinetic equation was established.

Abstract: In milling process, tool wear has important influence on product machining quality. A measuring method for tool wear of ball-end cutter is proposed in order to predict effectively tool wear. The measuring method maps tool wear shape on a block of metal material by milling hole mode after finishing each milling experiment. These formed holes are measured on CMM (coordinate measure machine) by using the planned measuring method. The measuring process is established to attain tool wear of ball-end cutter. The experiments results show that the proposed measuring method can effectively attain tool wear to provide a foundation for tool wear modeling and monitoring.

Abstract: The severe vibration and noise caused by inertia forces within a manufacturing machine are often the bottleneck in increasing the manufacturing speed. Based on kinematics analysis of the applied driving mechanism, this paper proposes an optimal design method for partially canceling the inertia force in pressing machine by using limited number of weight-balancing blocks. The proposed method has been validated by simulations.

Abstract: This paper describes the hull design, structural analysis and dynamic performance analysis of an Underwater Robotic Vehicle (URV). The dynamic performance analysis was made with the help of computer simulations. The main purpose of this URV is to carry out fundamental tests on its station keeping ability, attitude control, and position tracking accuracy. Its configuration is similar in appearance to a general open frame ROV for underwater works. The octagonal frame was designed to sustain obstacle collision and the material, stainless steel 316L, was chosen to maximize the resistance to corrosion in seawater. The navigation of the vehicle is controlled by an on-board computer and underwater sensors. This gives us an ideal platform to develop various algorithms needed for the further development of URV technology.

Abstract: Vibration frequencies during high-speed milling processes are investigated. Based on the resonant theory and three critical stats of phase position of successive two cutter teeth, six kinds of spindle speeds are shown, which divide the stable region in stability limit diagram into four parts. Furthermore, using optimal control theory, a novel stable region is proposed, which divides the region into three parts (unconditional stable, optimal stable, and conditional stable region).

Abstract: The steady bubble shape as one of the basic research, plays a decisive role in the cavitation’s study, To study it clearly will be not only basis for the study of non-steady cavitation, but also provide the necessary basis for the design of the control for cavitation bubble. In this paper, cavity shape produced by submerged body is studied, and related to the use of foreign experimental results, super-cavitation resistance, drag reduction is discussed.

Abstract: A test methodology for rheological behaviors of MR greases based on double rotational coaxial cylinder shear mode is presented in this paper. Both flow velocity profiles and shear stress profiles of MR greases in shear channels are analytically explored. The theory relationship between shear stress acted on MR greases and transmission torques is established, an approximate algorithm is put forwarded to acquire nominal shear stresses by transmission torques. On the basis of differential equation and its rational boundary conditions from stress equilibrium of MR greases micro-unit, an approximate corresponding algorithm is worked out for nominal shear strain rates by rotor angular velocities. The relationship between average value of magnetic flux density in annular channels and excitation electrical currents are experimentally obtained. Based on test methodology above-mentioned, a rheometer is fabricated and modulated, in which torque sensor, angular velocity sensor and ampere meter are respectively used to test transmission torque, angular velocity and electrical current. Rheological parameters of MR grease from the rheometer, whose shear rate is more than 2000 1/s and magnetic flux density acting on MR greases exceed 0.6T, are in good agreement with those from test conduced by commercial theological rheometer.

Abstract: In this paper, based on the study of steering wheel vibration problem of a middle-sized passenger car under idle condition, the reason is found out with the help of testing and analyzing, and the result shows that it is its first-order natural frequency, which is too close to the engine’s second-order frequency under idle condition that causes resonance. Through the optimization of the steering column system the problem is solved, and a satisfying result is obtained.

Abstract: Based on the unsteady Reynolds equation with Reynolds boundary, two-dimensional (2D) Reynolds equation is transformed into one-dimensional (1D) by taking the assumption of parabolic pressure distribution in axial direction in oil film field. Finite difference method was employed to solve 1D Reynolds equation, and the approximate pressure distribution was obtained in oil film field. Dynamic behaviors of a flexible rotor system with fixed-tilting pad journal bearings support were analyzed while the inertia of the pads was taken into consideration in the model. Imbalance responses of a symmetrical rotor-combination journal bearings (fixed-tilting pad journal bearings) system were investigated using Poincaré map and self-adaptive Runge-Kutta method. Numerical results reveal rich and complex nonlinear phenomena, such as periodic, quasi-periodic motion, etc.

Abstract: In the drilling process, axial vibration, transverse vibration and torsional vibration happen to drilling string. And the coupled vibration is more complex. In the resonance state, drilling string collides with the wall, which causes serious damage on drilling string in a short time and results in economic loss to the drilling operation. In this paper, the regularity of coupled vibration is analyzed by using finite element method. The model of full-hole drilling strings is established. The distribution regularities of coupled resonant frequency are obtained through computer analysis. The coupled model is more accurate than single vibration model. And the gaps of high rotary speed resonance regions are larger. Resonance state can be avoided by changing rotary speed, and drilling accidents can be reduced.