Advanced Materials Research Vols. 415-417

Abstract: Shape memory alloy (SMA) wire actuators have broad application prospects in many fields. But due to the nonlinearity of inherent hysteresis of SMA, the precise position control system is difficult to be obtained to these kinds of actuators. Therefore, it is significant to research the control technology of SMA wire actuators to extend the application of SMA wire actuators. In the current paper, a shape memory alloy wire actuator is designed to control the displacement of an adaptive beam. The dynamic model of SMA wire actuator is derived based on Brinson’s model and two types of inputs are used to produce different displacements. Then, PID control strategy for the SMA actuators is established and implemented to active control the position. Also, real-time control (RTC) is applied to the SMA wire actuators, which can concurrently generate real-time codes and accelerate the process of simulation. Through the comparison of different amplitudes and frequencies of current inputs, the different control abilities and characteristics to acquire the maximal displacement can be approximately achieved. Significantly, the position can basically remain stable. The results demonstrate the SMA wire actuators can be used to stably control the displacement of the adaptive beam.

Abstract: Combined with numerical simulation, a radial-directional dynamic tensile experimental method was proposed based on conventional split Hopkinson tensile bar(SHTB) for a thin-walled tube structure with special ring section. A special clamp was designed and a hollow transmission bar was used to magnify the transmission signals. For the stainless steel thin-walled tube structure, some dynamic tensile experiments are implemented under different strain rates. The results show that this test method is applicable to thin-walled tube structure with special ring section. This structure has a long plastic stage and its fracture strain is reduced with strain rate increasing. Moreover, its tensile strength is obviously enhanced with strain rate increasing

Abstract: Precise crystal structure determination of the Halloysite is extremely challenging because Halloysite naturally occurs as small cylinders and the ideal single crystal sample is unavailable. The up-to-date ICSD does not have the cystal structure data of Halloysite. With the development of computer science and technologies, the X-ray powder diffraction technologies have been commonly used in the crystal structure determination. This paper attempts to obtain the refined crystal structure of Halloysite by using the X-ray powder diffraction, on the assumption that the Halloysite and Kaolinite have a similar cystal structure, that is, the 1:1 phyllosilicates structure. The structure refinement program Rietica 2010 is used in this paper.

Abstract: Bedding materials are very important for cows in freestalls, because they can provide a high degree of comfort to these cows. But techniques of assessing their surface comfort on in the field still remain rather subjective. The objective of this study was to assess softness of bedding materials for use in cow free-stall bases in China. The Clegg Impact values of rubber-coated slatted floor, Solid wood floor and concrete floor are measured in order to compare with the value of pasture. The softest bedding material was the wood (40.43CIV/L) followed by rubber-coated slatted floor (64.23 CIV/L). The hardest material was the concrete floor (132.21 CIV/L).Clegg Impact Tester with a 1-kg hammer was used in this study. The impact of the hammer on bedding materials results in a digital display based on peak deceleration of the hammer’s impact with the free-stall base in tens of gravities (CIV/L). The CIV/L value, as measured by the Clegg Impact hammer, is based on peak deceleration of the 1-kg hammer’s impact with the surface, from a height of 30 cm. The reasonable suggestions of bedding materials used as the free-stall bases are recommended for the farmer in China.

Abstract: Mechanical structures with power sources experience repeated force produced by motors. As a result, the life of the pipes reduces and ultimately, the pipes collapse. In most cases, the U-shape pipe is made from a straight pipe by complicated bending work. During this work process, plastic deformation of the pipe produces residual stress in the pipe. The residual stress significantly affects the fracture behavior of the pipe. In this paper, fatigues tests of U-shape bending pipe are performed by uniaxial testing machine and residual stresses were evaluated by FEM analysis. So we established the relation between residual stress and fatigue life. And we suggested new equation for fatigue life prediction using the residual stress of U-shape bending pipe.

Abstract: In this paper, theoretical and experimental researches were done to find the repeated cracking reason of stuffing box in a super hyper pressure compressor. The mathematical expression of the assembly pressure was deduced in interference fit. From macro and micro perspectives, residual stresses were measured by X-ray diffraction in typical position of stuffing box when the packing box in combination and separation states. Besides, metallography and fracture examinations were carried out. The results showed that the real magnitude of shrink range of the failed stuffing box was only account for 12% of the designed size requirements, however, under this working condition this stress was not sufficient to cause cracking; Unqualified smelting process and tensile stress concentration in tank caused micro crack, which finally results in fracture of the stuffing box under fatigue mode.

Abstract: Composite stiffened panels are widely used in the modern aircraft structure with the advantages of light weight, structural efficiency and good crack performance. But the stiffened panels have poor performance at thickness direction, especially for low-velocity impact. First of all, compressive tests were investigated and analyzed for two types of composite stiffened panels, which are integrated specimens and post-impact specimens. And the effect of low-velocity impact to the supporting capacity of composite stiffened panels was researched. Secondly，the finite element model was established to simulate the CAI (Compression After Impact)strength with the equivalent hole method. It is found that the analyze results match the experimental results well. According to the experimental results, structural damage and the maximum load caused by impact energy are scattering. Then the imperfect factors were introduced to reflect the initial imperfection, namely the initial deflection at thickness direction. The effect of different imperfect factors to the maximum load was discussed.

Abstract: Mechanical and physical properties of a unidirectional carbon fiber reinforced epoxy matrix (T700/3234) composite have been evaluated after being vacuum thermal cycled (133-413 K, 10^-3 Pa) up to 300 cycles. The fracture surface morphology of the tested specimens was examined by SEM. It was shown the mass loss ratio of either the composite or the epoxy matrix increased with increasing thermal cycles and then leveled off after 50 cycles. The tensile strength at 90º of the composite was found to decrease at the initial stage of thermal cycling, increase after 50 cycles, and tend to level off after about 100 cycles. The results also showed that the interlayer shear strength of the composite was nearly not affected by thermal cycling. It is suggested that debonding of fiber/epoxy interface and post curing in matrix during vacuum thermal cycling should be responsible for evolvement of mechanical properties of the T700/3234 composite.

Abstract: This paper describes the mixed-mode bending test fracture toughness of composite adhesive J116-b. The test theory and experimental requirements are introduced. The fracture toughness of mode I, mode II, and different mode mixture of 0.4, 0.6, and 0.8 are obtained. It is found that the total fracture toughness is increasing with the increasing of mode mixture. It is also obtained that the technique of calculating fracture toughness by considering the influence of the weight of lever and attach apparatus is more accurate.

Abstract: The copper matrix composites reinforced by different WC_P volume fraction were fabricated via Vacuum Hot-pressed Sintering technique. The tensile performance and fracture behavior of WC_P/Cu composites were studied by uniaxial tension tests and the fracture surfaces were examined by SEM. The test results of mechanical properties show that the WC_P/Cu composites exhibit obvious improvement of tensile property comparing with that of the matrix. The fracture surface morphology indicate a trend that the fracture of WC_P/Cu composites changes from debonding to cleavage with the increase of the WC_P volume fraction.