Pre-Compression Volume on Flow Ripple Reduction of a Piston Pump

Axial piston pump with pre-compression volume（PCV） has lower flow ripple in large scale of operating condition than the traditional one. However, there is lack of precise simulation model of the axial piston pump with PCV, so the parameters of PCV are difticult to be determined. A finite element simulation model for piston pump with PCV is built by considering the piston movement, the fluid characteristic（including fluid compressibility and viscosity） and the leakage flow rate. Then a test of the pump flow ripple called the secondary source method is implemented to validate the simulation model. Thirdly, by comparing results among the simulation results, test results and results from other publications at the same operating condition, the simulation model is validated and used in optimizing the axial piston pump with PCV. According to the pump flow ripples obtained by the simulation model with different PCV parameters, the flow ripple is the smallest when the PCV angle is 13~, the PCV volume is 1.3 ~ I0-4 m3 at such operating condition that the pump suction pressure is 2 MPa, the pump delivery pressure 15 MPa, the pump speed 1 000 r/min, the swash plate angle 13~. At the same time, the flow ripple can be reduced when the pump suction pressure is 2 MPa, the pump delivery pressure is 5 MPa,15 MPa, 22 MPa, pump speed is 400 r/min, 1 000 r/rain, 1 500 r/rain, the swash plate angle is ll~, 13~, 15~ and 17~, respectively. The finite element simulation model proposed provides a method for optimizing the PCV structure and guiding for designing a quieter axial piston pump.

Grain size dependence of annealing strengthening of an extruded Mg-Gd-Zn alloy subjected to pre-compression deformation

In this work, pre-strain annealing strengthening(PSAS) effect was investigated in an extruded Mg-1.0Gd-1.5 Zn(wt.%) alloy with respect to different grain sizes. The evolution of microstructures was provided by scanning electron microscopy(SEM), electron backscattered diffraction(EBSD), transmission electron microscopy(TEM) and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM) under the initial state, pre-compression, intermediate annealing and re-compression conditions. The obtained results showed a grain size-dependent PSAS effect in the alloy. The sample with larger grain sizes corresponded to a higher strengthening effect, which mainly resulted from a more remarkable hindrance for the growth of existing twins and a larger proportion of activation for the nucleation of new twins. This was closely associated with the increase of back stress and friction stress for twin boundary motion impeded by the larger restraint of dislocations, the higher stress field surrounding solutes and the more Zn segregation. In addition to twinning behavior, Guinier Preston(G.P.) zones on basaldislocations were found after intermediate annealing and provided an extra strengthening by inhibiting the motions of gilding pre-existing dislocations and newly formed ones, but it was independent on the grain size.

Numerical Investigation of a Centrifugal Compressor with a Pre-Compression Wedge Diffuser under High Subsonic Conditions

As the total pressure ratio of centrifugal compressors increases, the diffuser inlet flow becomes highly subsonic or even supersonic, which causes additional shock loss. The shock loss leads the stage performance to drop greatly. Pre-compression is an efficient method for reducing shock loss and improving the stage performance. To study the effect of wedge diffusers with pre-compression blades on centrifugal compressor performance, wedge diffusers with various pre-compression angles, divergence angles and numbers of blades were designed and investigated via a numerical method. As a result, it is found that the compressor stage achieves high peak efficiency when the pre-compression angle ranges from 2.5° to 5.5° and when the divergence angle ranges from 7° to 9°. As the number of blades increases, the total pressure ratio and adiabatic efficiency of the compressor stage increase slightly, whereas the surge margin of the stage decreases.

Laterally pre-compressed SiC tiles against long rod impact

A combined experimental and computational study was carried out to investigate ballistic performance of laterally preload compressed SiC tile against long rod impact. A 100 x 100 by 20 mm thick SiC tile was pushed into a 5 mm thick steel frame at high temperature of 430 ℃ so that after cool down to room temperature, the lateral preload compressive stress was developed in the SiC tiles. Depth of penetration tests of the SiC tiles with and without pre-stress were performed, where tungsten alloy long rods at a nominal velocity of 1240 m/s were launched to hit the SiC tiles backed by the steel blocks. Compared with the SiC tiles without any pre-stress, the pre-compressed SiC tiles were found to reduce significantly the residual penetration in the backing block. Simulations were carried out using the LS-dyna hydrocode,taking account of preload stress. The simulations showed that the lateral preload compression strengthened the intact SiC tiles and dwell occurred in the early penetration stage, eroding the striking long rod efficiently.

Improving the room-temperature bendability of Mg-3Al-1Zn alloy sheet by introducing a bimodal microstructure and the texture re-orientation

A significant enhancement of bendability was achieved by the introduction of bimodal microstructure for AZ31B alloy sheets via pre-compression and subsequent annealing(PCA)process.This combined treatment led to the c-axis of the extracted samples that were inclined by 30°to the rolling direction(30°sample)further shifting toward the rolling direction(RD)and resulting in a higher Schmid factor(SF)value of basal slip under the RD tensile stress.Furthermore,the bimodal microstructure that was introduced by the PCA process broke the damage bands(DBs)in the initial hot rolled AZ31B alloy sheets and gave rise to a more uniform strain distribution in the outer tension region of the bending samples,in which the tensile deformation was accommodated by the equally distributed{101^(-)2}tension twinning and basal slip.Consequently,the bimodal microstructure,shifted basal texture and the modification of DBs were responsible for the significant enhancement in the bendability of the AZ31 alloys.

基于叠前地震纵横波模量直接反演的流体检测方法

流体因子是储层流体识别的重要方法,而叠前地震反演是获得流体因子的有效途径之一.本文从流体因子的构建出发,基于多孔弹性介质岩石物理模型,建立了流体因子与纵横波模量之间的直接关系,避免了流体因子计算所需的密度参数无法准确求取的问题,通过推导基于纵横波模量的Zeoppritz近似方程及弹性阻抗方程,探讨了基于弹性阻抗的纵横波模量直接反演方法,模型与实际应用表明,基于弹性阻抗的纵横波模量直接反演方法合理、可靠,减少了常规方法间接计算纵横波模量带来的累积误差,基于纵横波模量的流体因子计算方法有较好的实际应用效果.

基于Zoeppritz方程的纵横波模量反演

叠前地震反演的主要目的是根据地震数据精确地求取地下介质的弹性参数,进而进行流体识别和油藏描述。常规叠前反演方法使用Zoeppritz方程近似式计算反射系数,但是含有丰富信息的大偏移距地震数据无法被有效利用,针对这个问题,将纵横波模量引入Zoeppritz方程,建立了基于Zoeppritz方程的纵横波模量广义线性反演方法,适用于大角度地震数据。模型测试和实际地震资料应用表明,此方法能够可靠的得到地下介质的纵横波模量,相对于间接反演减小了间接反演带来的累积误差,为后续流体识别和含油气检测提供了很好的数据基础。

Intraplate Strike-Slip Reactivation of the Sinnyeong Fault in the Cretaceous Gyeongsang Basin, Korea, Due to the Concentration of Later Compressional Stress

This study focuses on the geometry and kinematics of the Sinnyeong Fault which is the most conspicuous fault among the WNW-trending Gaeum Fault System in the Gyeongsang Basin,SE Korea. The fault is traced for over ca.70 kmand has a consistent WNW-trending strike with a nearly vertical dip. It has an asymmetric fault damage zone of several meters to several tens of meters in width and a several meter-thick fault core. Its main movement is interpreted as sinistral-reverse oblique-slip or sinistral strike-slip under NE-SW compressional stress regime, although it could have experienced other faultings with different senses before/after this movement. Cylindrical folds, having the NW-trending fold axes of low angle plunge, are only observed along the southern damage zone of the fault with a continuous narrow width of several tens of meters. It is thus interpreted that the formation of the folds and sinistral movement of the fault were almost contemporaneously generated due to the concentration of the regional NE-SW compressional stress along pre-existing WNW-trending faults or densely populated fracture zone in a relatively stable intraplate region.

Restoration of modern buildings Grazia Lombardo

The present paper is part of a research that is devetoped within the sustainable building design through the revisiting of the traditional construction materials. The results obtained show that the naturat stone, enhanced by technoLogicaL innovations, are often capable of providing excellent performance. Based on the tests, it was possible to verify and validate the hypothesis that the proposed new system of external vertical opaque enclosure consisting in a panel in dry-assembled and pre- compressed blocks of natural stone through reinforcing steel has good performances when used both in the case of new design and in the case of recovery of modern buildings, when the intervention is being addressed within of an overaLL building improvement regarding the security, sustainabiLity, functionality and image. This paper reports the first results obtained by the study of the feasibility of the envelope being tested, through the definition of alL the detaits of links with the existing building structure.