Study on Contact Fatigue Life and Failure Mechanism of Subquenched 42CrMo Steel

The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.

Cross-sensitivity of Fiber Grating Solved by FFP Triangle Notch Filter

Employing a fiber Fabry-Perot (FFP) interferometer has been considered as a triangle notch filter to demodulate the wavelength of fiber Bragg grating (FBG) sensor.The single parameter of strain has been demodulated,and the cross-sensitivity influence of temperature has been eliminated.The principle of this method is simple and easy to be implemented,and has been used to design a 30 t fiber grating weightbridge successfully.The maximal temperature drift error of the weightbridge is 4 με,which means that the full scale error is 8‰. The result reveals that the accuracy is high enough to be used in measurement.

Improving Reliability of Communication in RS-485 Design

Three aspects of RS 485 application, which affect the reliability of communication of data system are analyzed and discussed. In network configuration, it presents the optimal configuration for the bus of RS 485, the better rule for derivative line and the choice for termination. In hardware design, it presents three parts of driver’s peripheral circuit. In control software design, it presents a method of using 75176’s DE line to control the driver.

Atmospheric Drag Perturbation in an Autonomous Orbit Determination for Satellite

In this paper, an autonomous orbit determination method for satellite using a large field of view star sensor is presented. The simulation of orbit under atmospheric drag perturbation are given with expanded Kalman filtering. The large field of view star sensor has the same precision as star sensor and a sufficient filed of view. Therefore ,the refraction stars can be observed more accurately in real time. The geometric relation between the refracted starlight and the earth can be determined by tangent altitude of the refraction starlight. And then the earth center can be determined in satellite body frame. The simulation shows that the precision of the mean square deviation of satellite’s position and velocity is 5m and 0.01m/s respectively. The calculated decrement of the semi-major axis in one day is close to the theoretical result, and the absolute error is in the range of decimeter when the altitude of orbit is 750 km. The simu- lateion of orbit of different initial semi-major axis shows that the higher the altitude of orbit is, the smaller the dec- rement of the semi-major axis is, and when the altitude of orbit is 1700 km the decimeter of the semi-major axis is 10-7 km.

Investigations of high-frequency induction hardening process for piston rod of shock absorber

The microhardness of piston rods treated with different induction hardening processes was tested. The experimental results reveal that the depth of the hardened zone is proportional to the ratio of the moving speed of the piston rod to the output power of the induction generator. This result is proved correct through the Finite Element Method (FEM) simulation of the thermal field of induction heating. From tensile and impact tests, an optimized high frequency induction hardening process for piston rods has been obtained, where the output power was 82%×80 kW and the moving speed of workpiece was 5364 mm/min. The piston rods, treated by the optimized high frequency induction hardening process, show the best comprehensive mechanical performance.

Hardness variations during aging process of deformed W-Ni-Fe ternary alloys with high nickel-to-iron ratios

The aging precipitation behavior of beta phase in two kinds of alloys with7/3 and 9/1 ssickel4o-iron ratios during aging at 800 deg C after deformation was studied. Theresults show that there are two different kinds of aging hardness variation mechanisms (thesoftening mechanism and the hardening mechanism) deciding the hardness variations of the alloys.when Ni/Fe is smaller than8/2, there is only the softening mechanism which results from the decreasing of dislocation densityand recovery or re-crystallization. And when NI/Fe is greater than 8/2 besides the softeningmechanism there is still the hardening mechanism that is induced by the precipitation of beta phase.

Study on J-integral with SENB specimens in a condenser material

A series of tests was performed with three-point single-edge-notched-bend (SENB) specimens in a condenser material (Titanium alloy). Results show that the J-integral values of welded joint and HAZ are obviously smaller than those of the base metal. It signifies that the welding process can result in a reduced toughness of Titanium alloy and the effect of crack orientation on toughness value is not negligible for engineering applications. Besides, the J-integral values of L-T direction specimens are much higher than those of L-S ones. The J-integral values of rolled ring are:JC-R>JC-L>JL-R.

EFFECT OF SUBMERGED ENTRY NOZZLE (SEN) PARAMETERS AND SHAPE ON 3-D FLUID FLOW IN MOULD FOR BEAM BLANK CONTINUOUS CASTING

According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200mm. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.

Scheduling and control of failure prone systems with demand uncertainty and job overlaps

Given that the overlapping of jobs is permitted, the paper studies the scheduling and control of failure prone production systems, i.e. so-called settings with demand uncertainty and job overlaps. Because a variable demand resource is involved in the production and corrective maintenance control problems of the system, which switched randomly between zero and a maximum level, it is difficult to obtain the analytical solutions of the optimal single hedging point policy. An asymptotic optimal scheduling policy is presented and a double hedging point policy is offered to control simultaneously the production rate and the corrective maintenance rate of the system. The corresponding analytical solutions and approximate solutions are obtained. Considering the relationship of production, corrective maintenance and demand variable, an approximate optimal single hedging point control policy is proposed. Numerical results are presented.

Study of Surface Modification Mechanism of Calcined Kaolin by MAS NMR

The 29 Si and 27 Al in modified and unmodified calcined kaolin were researched and compared by using MAS NMR. The result shows that the chemical shift of -106×10 -6 of 29 Si almost keeps unchanged after being modified, but 27 Al changes obviously. The chemical shift of 5.44×10 -6 and 65.69×10 -6 of 27 Al are separately shifted to 3.8×10 -6 -4.4×10 -6 and 54.6×10 -6 -59.9×10 -6 after being modified. And the chemical modification of kaolin is completed by linking with Al on the surface of it.

Research on an Intelligent Maintenance Decision-making Support System

A new synthetic model of maintenance decision-making, which is made by anartificial neural network (ANN) , expert system (ES) and emulation technology, is put forward. Bymeans of this model all kinds of maintenance resources with low cost can be effectively harmonized;accordingly, the reliability, maintenance efficiency and quality of equipment can be improved, soservice life of equipments is enhanced.

Security analysis and modification of a chaotic encryption system

A type of digital chaotic eneryption system was proposed in Ref. [1] which uses a class of 1-D piecewise linear (PWL) map to realize chaotic encryption and decryption system through the inverse system approach. In the general structure of encryption system, a dynamical system ∑ (·) is used to connect the linear combination of n-order delay with the input terminal. In this paper we show that this cryptosystem can not frustrate chosen-cipher text attack. A type of chaotic encryption system based on self-synchronizing stream cipher is proposed. This system can avoid chosen-cipher text attack and has higher security.

Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy （HRTEM）, x-ray diffraction （XRD） and Ftaman spectra, respectively. The nanocrystalline grains are averagely with 80hm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses （100） dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

Electrical Capacitance Tomography Measurement of Flow Patterns and Film Thickness in a Thermosyphon

An experimental study was performed to evaluate the suitability of using an electrical capacitance tomography (ECT) system to visualize the flow patterns, and to measure the film thickness of the annular flow in a two-phase closed thermosyphon (TPCT). The performance of the ECT system was examined over a range of flow conditions.The experimental data were compared with the visual observations and existing correlations. Results indicated that the ECT system, with the linear back projection (LBP) algorithm, could be used to give an on-line qualitative image of the flow patterns. The Landweber iteration algorithm with optimal step length was implemented off-line to reconstruct high-resolution images. Then, the images were analyzed to obtain the film thickness of the annular flow. The experimental data compared well with the Nusselt's equation in low vapor velocity range, but showed an increasing deficiency with the increase of vapor velocity.

A Feasibility Study on ECT Monitoring of Froth Molding of Polyurethane

This paper presents our recent experimental investigation on the feasibility of monitoring the froth molding, a special case of solidification process, of polyurethane by using electrical capacitance tomography. The major challenge is the extremely low solid density of the solidified material during the process due to the very large expansion ratio. Suitable calibration method is sought and adequate image reconstruction algorithm is applied for such a task. Different expansion modes have been observed during experiment and corresponding images reconstructed. This visualization technique clearly revealed the expansion process by a time series of images of the solid density. The test results proved the capability of electrical capacitance tomography in monitoring the expansion of polyurethane. Future ways for improvement are also suggested.