Advanced Materials Research Vols. 97-101

Abstract: Mental rubber material is a new kind of high elastic and large damping material. In this paper the static deformation of mental rubber components had been studied from stretch, compression and shearing experiment. By the method of high-order polynomial fitting, the empirical formula of static deformation characters of mental rubber component had been established, and some deformation rules of mental rubber had been obtained.

Abstract: Coating is one of important parts in fiber-reinforced composite. Under cyclic loading, the effect of coating on interfacial fatigue is investigated based on double shear-lag model. Stresses of components are obtained. Relationship for analyzing interfacial debonding is established by the Paris Formula. Interfacial fatigue on fiber/coating and coating/matrix is simulated. It can be seen that interfacial debonding on different interfaces meet energy conservation law in general.

Abstract: The various damage mechanisms in 3D-C/SiC composites are identified using acoustic emission (AE) signal parameters, and the Felicity effect is studied on different unloading stress. As a result, the damage mechanisms in 3D-C/SiC composites can be identified successfully by the amplitude, average frequency and relative energy, and there are several damage modes together during uniaxial tensile process. The Kaiser effect is almost absent and the Felicity ratio fluctuates at 0.95 on lower stress stage and drops when the relative stress is above 65%.

Abstract: The tempering resistance in double tempering of a new type of tool steels used in magnesium die casting machine quenched at 1080°C, 1120°C and 1150°C respectively was investigated. 4 hours of first tempering and double tempering at 600°C, 630°C, 660°C, 690°C and 720°C are applied. The minimum hardness value is 53.4HRC quenched at 1150°C and then tempered. The decomposition of tempered martensite lath was retarded after adding a number of alloying elements such as Cr, Co, W, Mo, V, according to observations by transmission electron microscopy. It also shows that the fine dispersion secondary carbide precipitates along the martensite grain surface and grain boundary. The use of X-ray diffraction has revealed that secondary carbides precipitates takes the form of M6C carbide and the retained austenite has transformed to martensite completely quenching at 1150°C. These microstructures would lead to the better tempering resistance.

Abstract: The hydrophilic-lipophilic balance (HLB) parameters of surfactants have a significant effect on properties of surfactants and determine the effects of surfactants. The magneto-rheological fluid (MRF) is prepared by using the two typical HLB parameters of surfactants including Polyethylene Glycol and oleic acid in order to improve the property of MRF. Polyethylene Glycol (PEG) whose HLB parameter is 20 has strong hydrophilic. Oleic acid whose HLB parameter is 1 has strong lipophilic. The results indicate that magnetic properties of magnetic particles and rheological properties of MRF can hardly be changed by adding surfactants. The sedimentary stability of MRF adding lipophilic surfactants is superior to that of MRF adding hydrophilic surfactants, and the stability of MRF adding two surfactants increases significantly.

Abstract: The purpose of this paper is to evaluate the vibration of the small bore pipe in nuclear piping under the fatigue loading due to flow fluctuation. The vibration speeds of the pipe-lines were measured to get the effective velocity which is found larger than the allowable value calculated from EDF evaluation method. To perform the piping vibration assessment and construction, the natural shape and the vibration stress at the socket weld position was evaluated by finite element analysis with ABAQUS. From the linear cumulative damage theory, the fatigue life is predicted with the results that lower than the designation level. According to the position of the maximum vibration speed calculated from FEA simulations, the valve is fixed by the rigid support. The natural frequency and the corresponding mode shape are discussed with much lower vibration velocity and vibration stress.

Abstract: The equation of fatigue crack propagation rate is indispensable to precisely predict the fatigue life of structure containing three-dimensional crack under constant amplitude loading. Considering the crack closure effects and thickness effects in real structures, the equation of fatigue crack propagation rate under tri-axial stress state is presented. And the fatigue propagation lives of LY12-BCZYU aluminium alloy plate specimens with central through crack are predicted by this equation and validated by experimental results. Validation against calculations by the model and experimental data shows a good agreement.

Abstract: The strain-based fatigue tests of 42CrMo alloy steel were conducted by controlling six sets of total strain range, and stress range data was obtained under each strain range. The results of fatigue test revealed that fatigue performance of 42CrMo alloy steel was of tremendous dispersivity all though materials were strictly chosen, heat-treated and machined. Cyclic stress-strain (CSS) curves were compared with monotonic tensile curve, which showed that 42CrMo alloy steel quenched and tempered was a kind of cyclic softening material. Evaluation results revealed that LND was the best probability function to describe cyclic stress of strain fatigue for 42CrMo steel. Cyclic stress range under the median and high probability was evaluated by means of stochastic performance probability models.

Abstract: The Cr2O3/Cu composites with different Cr2O3-content performed in this paper were prepared by surface internal oxidation of Cu-Cr solid alloy. The Cr2O3/Cu composite wires were slid against a copper-based powder metallurgy strip under unlubricated conditions. The wear behavior of Cr2O3/Cu composite was researched under different currents from 0-50A and sliding distance from 0-72Km. Worn surfaces of the Cr2O3/Cu composite were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The results indicate that the wear rate of Cr2O3/Cu composite increases with the increase in electrical current and sliding distance. The wear rate increases abruptly at the beginning and smoothly subsequently. And the variety of electrical currents has slight influence on the wear rate. The wear rate of the Cr2O3/Cu composites decreases with the increase in Cr2O3-content. The wear rate of 0.478 Cr2O3/Cu composite is 2-3 times that of 1.25Cr2O3/Cu composite at the same experimental conditions. Abrasive wear and electrical erosion wear are the dominant wear mechanisms during the electrical sliding wear processes.

Abstract: Combining the constitutive equation of piezoelectric ceramic with elastic-dynamical equations and coupling theory of FEM, the finite element control equation for piezoelectric actuator is established. Detailed calculation of the electro-mechanical coupling field parameters is made by the SP1 type longitudinal-bending vibrator and results show it can be used for the transparent calculation for piezoelectric intellectual structure and avoid the black box operation in FEM software. The model lays the foundation to develop the special program for piezoelectric actuator and to study the non-linear constitutive equation of piezoelectric ceramic driven by high-power.