Applied Mechanics and Materials Vols. 121-126

Abstract: A simulation research concerning temperature field of hydrostatic thrust bearing having annular cavities multi-pad was described in order to solve the thermal deformation of the hydrostatic thrust bearing with annular cavity multi-pad in the heavy CNC equipment. The Finite Volume Method of CFX has been used to compute three-dimensional temperature field of gap fluid between the rotation worktable and base. This study theoretically analyzes the influence of rotating velocity on the bearing temperature performance according to computational fluid dynamics and lubricating theory. It has revealed its temperature distribution law. The simulation results indicate that an improved characteristic will be affected by rotating velocity easily, and oil cavity temperature increases by gradually with rotating velocity enhancing. Through this method, the safety of a hydrostatic thrust bearing having annular cavities multi-pad can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design, lubrication, experience and thermal deformation computation for hydrostatic thrust bearing in the heavy CNC equipment.

Abstract: Die casting dies are essential parts for die casting engineered metal products and usually fail due to a variety of reasons. The objective of this paper is to investigate the potential benefits and possibility of remanufacturing die casting dies. Firstly, with respect to the entire life cycle, a technical framework for die remanufacture is presented. And then based on the failure modes of die casting dies, life extending technologies covering the whole life cycle are reviewed according to the different stages: Pre-failure stage and Post-failure stage. While measurements within the Pre-failure stage are shortly and briefly surveyed, extensive effort is made to survey the recondition technologies-welding technologies which could be the only measure to put worn/failed dies into operation. The most commonly utilized welding technologies are Tungsten Inert Gas (TIG) Welding, Plasma Arc Welding (PAW) and Laser Beam Welding (LBW), and other types of welding techniques including Electro Spark Process and Cold Spray are also applied for repairing die casting dies. Lastly, research gaps and industrial challenges indicate that more research attention is required to finally commercialize the remanufacture of die casting dies.

Abstract: The machine joint surfaces are necessary to form the functions of the complex mechanical system. Because the macro or micro relative motions may appear in the machine joint surfaces, the vibration and friction phenomena will be excited, then the singularities, disturbances and faults of the mechanical system may be appeared when the machine equipments in the running process. These undesired phenomena will have adverse effect on the efficiency, precision, reliability and lifetime of the mechanical equipment. In order to ensure the functions and properties of the mechanical system, more attentions should be paid to mechanism of vibration and friction during the process of designing and manufacturing the modern machine. In this paper, machine joint surfaces are classified by different classification standards: the macro relative motions and micro contact styles between the joint surfaces. The theories and methods for researching vibration and friction mechanism are inducted and summarized and the view of non-linear should be advocated for the future research. The point of precisely quantifying for machine assembly accuracy design while considered the relevancies between the macro and micro-scale of mechanical system indicates that new directions and methods for studying vibration and friction mechanism in machine joint surfaces should be put forward.

Abstract: The stacking fault substructure was observed in the quenched martensite of 35CrMo, 2Cr13 and W6Mo5Cr4V2 steels by JEM-2100 transmission electron microscope. It is significant theoretically to discovery the stacking fault substructure and then to study its formation mechanism. The results show that the stacking faults in the martensite of steels are superfine with a few nanometers spacings, which are often concomitant with the high-density dislocations. It is considered that the stacking fault results from the crystal lattice misarrangement during the crystal lattice reconstruction from austenite to martensite in steels. The shear mechanism cannot explain the formation of the stacking fault.

Abstract: The steering system of automobiles might vibrate under external excitation loading. Severe vibration of the steering system maybe bring the drivers uncomfortable and even result to noise and damage of some parts of the steering system. In the same time, it can not be satisfied with NVH design requirement of automobiles. In this study a three- dimensional finite element model of a steering wheel of automobiles was established and finite element static and dynamic analyses were conducted in order to validate dynamic characteristics and strength of the steering system. The simulation results can provide a reference for structural design of the steering system.

Abstract: In order to overcome the poor stationarity of traction locomotive during the operation mode switching, with rotor flux oriented vector control theory based on, torque model control strategy is adopted. It can overcome the DC bus pumping as Locomotive deceleration and barking. In this system, output torque can be controlled directly, experiments verify the system has good performance of stability and reliability, which can meet the traction locomotive control requirements.

Abstract: Spur gear contacts experience a number of time-varying contact parameters including the load, surface velocities, radii of curvature, and slide-to-roll ratio. It is very hard to obtain transient elastohydrodynamic lubrication (EHL) solution of spur gears. In this study, a transient EHL model of involute spur gear tooth contacts is proposed. A full transient EHL solution of involute spur gear under impact load is obtained by utilizing the multigrid technique. The influences of impact load on the EHL of spur gear are analyzed in the paper. The numerical results show that the approach impact load has strong transient influence on the oil film thickness and pressure distribution between contact zones. The impact load may lead to instantaneous lubrication film deterioration between contact teeth of involute spur gears.

Abstract: This paper makes study on the 42CrNiMo gear contact fatigue strength, applying the rapid measure method of the gear contact fatigue stress value with a few gear samples to get the estimated value of the gear fatigue limit value precisely and rapidly. And the gear fatigue life curve and fatigue damage accumulation curve are got by MATLAB simulation. Comparing with the traditional test method, this method can reduce the cost and save the time.

Abstract: Based on the viscoelastic theory, the shape memory behavior of SMP materials is analyzed theoretically with the aid of numerical method of finite element in this paper. The stress-strain relationship depended on temperature and time of SMP materials is described by the thermal viscoelastic integral constitutive model. A numerical simulation is carried out to compare with the experiment conducted by Tobushi (2001[6], 2005[9]), and the simulation results correspond well with the experiment, thus can provide reference to experimental studies

Abstract: In the process of drilling well, the kinematics of drill string is quite complicated. The drill string not only vibrates in longitudinal, transverse and torsional direction, but also random impacts and contacts well wall. Considering the random load of drill bit and rock, contact impact of drill string and well wall, a model is proposed to simulate the contact-impact of drill string and formation. The results show that: in the condition of this article the first principal stress of the drill string can reach to 130 MPa, for the random impacts, the strength of drill collar will reduced under cyclic loading; contact-impact is the principal source of drill premature failure. In this paper, an explicit integration and nonlinear finite element was adopted to simulate the collision between the drill string and formation, the process of the collision between the drill string and formation can be revealed compressively and delicately. Through an example, we can obtain the foundation for nonlinear dynamic theory of drill string system collision in the actual work condition, and has important theory significance and academic value.