Advanced Materials Research Vols. 314-316

Abstract: Engine lathe has many advantages, such as low cost, multi-use of one machine, etc. In this paper, the design method of reforming C630 engine lathe to a deep-hole machine tool has been researched. In addition, the cutting fluid system and other mechanism of deep-hole machine tool have been researched too.

Abstract: In order to develop magnesium alloy sheets with high formability at room temperature, the anisotropy of deformation behavior of AZ31 magnesium alloy sheets produced by equal channel angular rolling were examined, which were compared with that of the sheets produced by the unidirectional hot rolling. The differences in the deformation behavior of the sheets at the rolling direction (0°), 45° and the transverse direction (90°) were discussed in term of the texture and microstructure. Compared with the as-received specimens, the anisotropy of deformation behavior of AZ31 magnesium alloy sheet produced by equal channel angular rolling was enhanced, which was following with an improved ductility and a large work hardening phenomenon. These could be due to the non-basal texture, which was induced by the continuous shearing deformation during equal channel angular rolling procedure. The fracture mechanism transferred from the cleavage fracture for the unidirectional rolling to the quasi-cleavage fracture for the sheets produced by equal channel angular rolling, which proved that the non-basal texture was in favor of the ductility of magnesium alloy.

Abstract: Ensemble Empirical Mode Decomposition (EEMD) can overcome the mode mixing problem in Empirical Mode Decomposition (EMD) effectively. The Hilbert-Huang transform still exists end effect in applications, in order to improve the end effect, this paper put forward a method of fault feature extraction based on improved EEMD and Hilbert transform which combines support vector regression (SVR) machine with mirror extension to continue the signal. The analysis on simulation experiments results show that the method can restrain the end effect effectively, get a more accurate instantaneous frequency and instantaneous amplitude.

Abstract: The material removal is investigated in electrorheological (ER) fluid-assisted polishing of conductive materials. The combination structure of ER particles with abrasive particles in ER polishing fluid is discussed when the electric field is applied. The forces exerted on the abrasive particles for material removal are analyzed. According to Preston’s equation, a model for material removal of the polished conductive workpiece is derived. Polishing experiments with diamond particles for WC is conducted and the experimental results are compared with the theoretical predictions, which confirm the validity of the presented model.

Abstract: There exist hotspots, fatigue cracks, and stress fracture on friction surfaces of steel or iron brake disc during service, and these thermal damages greatly contribute to the fatigue crack failure of the friction surfaces. So, it is very significant for researching on the forming mechanism of thermal damages above to prevent the fatigue failure of the friction surfaces from occurring. The method used in the paper is to combine FEM analysis with theoretical analysis. Forming mechanism, influencing factors and preventive measures of the thermal damages above was studied by use of the method. The temperature condition and microstructure evolution of hotspots, the behavior of thermal crack initiation and propagation and the distribution of thermal stress contributed to five constraints all were focused on.

Abstract: This paper deals with an experimental research on wear properties and mechanisms of coated carbide tools in dry turning of 300M steel which are widely used to manufacture the central spindle, wheel gear, aerofoil fastener and so on. Based on Makarow’s theory, the minimum surface wear rate hs = 2.88 μm and the optimal cutting speed v = 200 m/mim were attained under the condition of the feed rate f = 0.1 mm/r and the depth of cut ap = 0.15 mm. Analysis carried out with the SEM suggests that adhesion of workpiece material and chipping are dominant wear mechanisms. There was no observation of oxygen existing based on the analysis of EDS which indicated no oxidation wear generated during the turning machining.

Abstract: According to high strain gradients characteristic at the junction between pressure vessel and nozzle, based on simulating shape plate of pressure vessel nozzle, weak-conforming element models are established for two types of special shape plates, which satisfied weak continuous conditions between elements. The weak-conforming element methods do not need satisfy stress equilibrium conditions. It can solve the conventional finite element difficult to adapt to the singularity of the field. The stresses are obtained by means of weak-conforming element method. The calculation results are in accordance with those of experiment results. This paper provides the foundation for the design of special shape plates and analysis of extending crack.

Abstract: According to the problems of low efficiency and high cost in blisk manufacturing, based on large margin slotting and rough machining, a kind of compound and efficient powerful milling process was proposed, that is, disc milling-plunge milling-flank milling. In order to compare the effect of this new process and the traditional plunge milling or flank milling, experiment on disc milling and plunge milling processing performance was carried out. Compared with plunge milling, the cutting force and tool vibration of disc milling are larger, but its processing efficiency was improved significantly. The experiment proved that the compound and efficient powerful milling process is feasible and effective for the large margin slotting and rough machining of blisk.

Abstract: A high temperature split Hopkinson pressure bar (SHPB) test system is used to investigate the effects of temperature as well as those of strain and strain-rate. Effects of temperature for the vanadium alloy (V-5Cr-5Ti) are investigated by developing a high temperature SHPB test system. In this work, high temperatures greater than 1100°C are attained in the SHPB test specimens by using a synchronically assembled heating system .When testing with the high-temperature SHPB apparatus, care is required to prevent oxidation of the surface of the specimen, and to prevent an inhomogeneous temperature distribution from developing in the specimen. To determine the true flow stress–true strain relationship, specimens are tested from 15°C to 1100°C and at a strain-rate of about 3000 s-1: The parameters for a Johnson–Cook constitutive equation is determined from the test results. The Johnson–Cook constitutive equation is suitable for expressing the dynamic behavior of the V-5Cr-5Ti vanadium alloy.

Abstract: The effect of δ phase content on the hot deformation behavior of alloy IN718 has been investigated using isothermal compression tests. The results indicated that the δ phase has a significant effect on the deformation behavior of alloy IN718 during hot working. After the peak stress, the decreasing speed of the stress raises as the increase in the δ phase content. The deformation activation energy for alloy IN718 increases with the raise of the δ phase content. And the peak strain for the alloy decreases with the increase of the δ phase content, which indicates that the δ phase can stimulate the occurrence of dynamic recrystallization during hot working.