Advanced Materials Research Vols. 602-604

Abstract: Notch effect on the fracture behavior of the Ni3Al foils has been investigated as a function of notch radius and depth. Tensile tests along the rolling direction showed that notch weakening occurred with introduce of notch. The effective stress concentration factor (ke) was much lower than the theoretical stress concentration factor (Kt), which was due to the local plastic deformation at the notch root. Cracks initiated along the shear band in the RD tension.

Abstract: Tribology behaviors play an important role in logistics, the researches of bionic tribology focus on desorption and friction increasing in rencent years. In order to reveal the mechanism between biological characteristics and tribology behaviors, this paper studied the typical no-smooth surface of animals, the analysis result showed that the no-smooth body surface of dung beetle greatly impacted its desorption, but the no-smooth foot surface of tree frog and locust played an important role in friction increasing. The similar no-smooth surface could have both function of desorption and friction increasing under the different conditions. Comprehensive analysis of no-smooth surface was done by simulation technology and experiment research, and revealed the mechanism between no-smooth surface, desorption and friction increasing, which opens up a new way for the development of bionic tribology and also provides technology for the improvement of logistics equipments.

Abstract: An experimental study on friction and wear properties of carbon strip rubbing against copper contact wire was carried out on a pin-on-disc frictional tester with and without windy conditions. The result shows that wear rate of pin specimen increases observably with increasing sliding distance with and without windy conditions. While the coefficient of friction slightly decreases with increasing of electric current with and without the wind. Observing the SEM morphology of pin specimens, it can be found that delamination wear is a main wear mechanism under no windy condition. While arc erosion is a dominant wear mechanism with windy condition. Worn surfaces of the materials were analyzed by an energy dispersive X-ray spectroscopy. It can be observed that oxidation wear occurs in the frictional process due to arc erosion and high temperature rise.

Abstract: This study assumes the interface friction between dies and bounded three-layer clad cylinder as constant shear friction considering the rotation of three-layer bounded clad cylinder to establish the finite element simulation. The commercial finite element software (SUPERFORM) is used to explore effectively the effective stress, effective strain, and velocity field, forging force, and rotating torque in the three-layer clad cylinder rotating forging. Moreover, the rotating forging experiment of the three-layer clad cylinder is carried out practically to measure the forging force and the outer surface of three-layer clad cylinder. Forging force between analysis and experiment are compared to verify the acceptance of FEM simulation. This study can be offered to industries for technology establishment of rotating forging.

Abstract: For steel wire wound reinforced high-pressure hose, the static load test under internal pressure and fatigue test under combined effect of internal pressure and periodic transverse load were carried out. Test results show that water seepage or leakage on the pressing steel sleeve or on hose body itself, and bulging on hose itself near steel joint would lead to performance failure, which can be regarded as the performance failure criterion for steel wire wound reinforced high-pressure hose.

Abstract: According to the actual structure, using the finite element software ANSYS, numerical model of submarine oil flexible pipe was established. For the mechanical response of flexible pipe under the combined effect of internal pressure load and transverse load, the comparison on the result by numerical calculation and static loading test shows that the numerical model of flexible pipe is rational. Moreover, based on the numerical model of flexible pipe, this paper indicates that the maximum Mises stress occurs at the end of flexible pipe, which would lead to the bulge performance failure. Furthermore, the influence of winding angle on the mechanical properties of flexible pipe was analyzed, and the optimal winding angle 30° was suggested to adopt.

Abstract: A new method is proposed to determine the maximum energy that absorbed by axial pressured thin wall tube. Three typical collision speeds are selected, which are low speed at 30km/h, medium speed at 60km/h and high speed at 90km/h. This paper also calculates the strain rates under different automotive collision conditions. Finite element software ABAQUS was used to investigate the effect of lightweight when circular thin wall tubes with different materials absorbing maximum and equal energy. The materials for thin wall tubes are high-strength steel, aluminum alloy and plain steel. The effect of lightweight of different material tubes in low strain rate, medium strain rate, and high strain rate can be obtained using the equal energy absorption strategy. The weight that reduced by high-strength steel tube and aluminum alloy tube is higher than that of plain steel tube, at all three strain rates.

Abstract: Deformation and failure of meso-structures take great effect on the loading and energy absorption of aluminum foam under impact. We designed a split Hopkinson pressure bar (SHPB)-high speed digital camera system to monitor the meso-deformation and failure features, and measure the nonuniformity of deformation of aluminum foam under impact. The meso-deformation and failure of aluminum foam were observed successfully by the system, and it showed that there does exist remarkable nonuniform deformation along the specimen. In order to expand the experimental results, the specimen of aluminum foam with meso-structures is modeled by 3D Voronoi technique. The numerical results show that the FE model can simulate the experiment well, and shows that nonuniformity of deformation appears in aluminum foam specimen significantly. The analysis indicates that the assumption of uniform deformation of specimen in SHPB cannot be strictly satisfied for the material of aluminum foam.

Abstract: In this study, elastic-plastic stress and strain fields were analyzed on hole-edge cracks in an aluminum alloy plate under the biaxial load. And the effects of the load parallel to the crack face on failure parameters were discussed. By quantifying the effects of the crack size and the loading mode on the crack propagation driving force, J integral, and the plastic limit load, the corresponding failure assessment curves of the hole-edge cracked plate were established with the new R6 failure assessment diagram (FAD) method. The result shows that the transverse load has a larger effect on the failure assessment curve than crack length does, the safety zone of the failure assessment diagram gradually becomes smaller while transverse loading stress changes from tensile condition to compressed. Especially, when the transverse load acts as pressure, the Option 3 failure assessment diagram results to a smaller safety zone than the Option 1 failure assessment diagram does.

Abstract: A detailed elastic-plastic analysis on different semi-elliptical surface crack geometries under uniaxial and biaxial load was conducted using 3D finite element analysis for pipeline steel X100. After quantitating fracture driving force J-integral and plastic yielding load, the effects of biaxial load and crack geometry were investigated by using the Option 3 of R6 failure assessment diagram approach for the surface cracks with the different crack sizes ( aspect ratios c/a = 1, 1.5 and 3 ) and the various biaxial loading ratios λ from -1 to 2. And three option curves of the R6 assessment were compared to evaluate the applicability of R6 assessment method for the X100 steel.