Advanced Materials Research Vol. 842

Abstract: The influences of different vibration amplitude and pouring temperature on solidified structure of superalloy K4169 under the action of mechanical vibration were investigated. The vibration amplitudes and pouring temperatures used were 1.5, 1.75 and 2 mm and 1380, 1430, 1480 and 1530°C, respectively. The experimental results show that application of mechanical vibration leads to increase in grain refinement and proportion of equiaxed grains of superalloy K4169. The dendrite growth is restrained and the microstructure is changed from well-developed dendrite grains to fine equiaxed grains. Grain size of the alloy decreases as vibration amplitude increases. With the increase of the pouring temperature, grain size of the alloy increases firstly, then decreases and the turning point is 1430°C. When the pouring temperature is 1380°C, grain size of the alloy with mechanical vibration treatment is the finest.

Abstract: During the hot stamping of ultra-high strength steel (UHSS), the quenching effect of the mold on the sheet plays an important role to achieve the transition from austenite to martensite. Thus a finite element model for the quenching process of UHSS is established in this paper. The key points of the model include contact thermal conduction and the latent heat processing of phase transforming. Finite element program has been developed to calculate the temperature field of the UHSS quenching process, and temperature measurement device was used to get the temperature-time curve of the mold and the sheet to validate the calculation results. It can be concluded that the latent heat and thermal contact resistance have a critical influence on the temperature filed of the sheet during the hot stamping process. Finally, the parallel computation technology based on GPU(Graphics processing unit) was adopted to accelerate the calculation.

Abstract: Varnish now becomes the severe problem of gas turbine, nuclear power plant and other industry which use lubricant oil and hydraulic fluid. The cause of varnish formation is heat, oxidation and contamination. Varnish can cause many turbine problems. The Membrane Patch Colorimetry (MPC) test can be used to measure varnish. Partial or all oil change, Filtration with Cellulose Media and System Chemical Cleaning can be applied to mitigate varnish.

Abstract: Establishing bias and central entity model of slider-crank mechanism in this paper, then the bias model is imported into the ADAMS for kinematics simulation, and we can get the sliders law of motion. Then using ANSYS and ADAMS jointly to establish the multiple rigid body and the coupled model of slider-crank mechanism, and carrying on kinematics and dynamics simulation analysis to compare the two simulation results. Through build simulation of the coupled model with UG, ANSYS and ADAMS, the result of this calculation is better to reflect the true movement of the mechanism.

Abstract: In order to accurately study a tracked vehicle movement on the ground in hard and soft features, this paper uses multi-body dynamics simulation software RecurDyn tracked vehicle subsystems Track (LM), establishing a three-dimensional multi-body vehicle dynamics model. For tracked vehicles at an inclination of 10 degrees slope, through the soft and hard ground steering process dynamics simulation and comparative analysis. This paper provides an accurate basis for the future in-depth research on Tracked vehicle.

Abstract: In order to identify the geometrical parameters of parallel kinematics machines tools (PKM), a new parameters identification method is presented. The identification method is proposed based on a pose discrepancy model, which is deduced from the error between the nominal and measurement relative distance of two different spatial locations of the moving platform. In the identification method, an error sensitivity matrix, which expresses the sensitivity between the pose error and geometrical structural parameters error of PKM, can be created with numerical methods. The results of different numerical methods are analyzed. A measurement method to get the precise lengths of legs is presented, which decrease the number of identified parameters. In an experiment, the error of PKM is reduced from 6.71mm to 1.144mm. Therefore, the identification method is verified effective and feasible.

Abstract: This paper discusses accelerated stress conditions of ore particles in the vertical impact test machine rotor passage through numerical analysis method, and to determine the relationship between the movement of particles and the power and the machine parameters.The results show that:In the test machine rotor, motion law of ore particles is determined, and by expression for the particle displacement, speed and power of the numerical analysis method.If the test machine, gravity effects are negligible;Speed is the main factor affecting the characteristics of particle movement, but should not exclude the influence of particle volume and surface quality;Chasing is never occur in the process of particles;With calculated by the theoretical formula of reasonable size of rotor.

Abstract: A key issue of the machining for the small line block is to improve the machining feedrate while keeping the machining precision and satisfying the acceleration constraints. In this paper, a new approach for continuous small line blocks high speed machining is proposed to avoid the impact of Computer Numerical Control (CNC) equipments caused by acceleration gust. This approach uses the small line flag to distinguish whether the path is small line block. While the paths are continuous small line blocks, this approach can automatically adjust the number of look-ahead segments, and predigest the velocity calculation method of the connection point. We first define what a path is small line block. Then we analyze the restrictions for velocity linking of adjacent processing paths, and propose the approach for continuous small line blocks machining. Finally we design a simulation experiment on 30 points processing of the spline track. The result of the simulation shows that this algorithm can obviously shorten the processing time and make control system more harmonious in high speed machining.

Abstract: Considering the degradation effect of corrosion damage on fatigue behavior of aero aluminum alloy, the present thesis made a research on corrosion fatigue crack growth rate. Taking into account the effect of load frequency on fatigue crack growth, a concept of corrosion fatigue frequency factor is proposed. Based on the fact that low frequency will lead to high corrosion fatigue crack growth rate, and frequency higher enough will make little difference between corrosion fatigue and pure mechanical fatigue behavior, an exponential expression of corrosion fatigue frequency factor is proposed. The crack growth rate prediction from proposed formula is proved to be in good agreement with experimental results for steadily extended corrosion fatigue crack.

Abstract: Targeting at realizing analysis of resonance reliability sensitivity for cam mechanism system, considering the uncertainty of the design parameters, the performance function of the resonance reliability of the cam mechanism is established based on stability criterion of vibration. The perturbation method is employed to calculate the resonance reliability of cam mechanism. Combined with the sensitivity technology, the effects of random variables on occurring resonance failure of cam mechanism system were discussed. The study results can provide theoretical reference for anti-resonance design of cam mechanism system.