Investigation on the cold deformation strengthening mechanism in MP159 alloy

Composite electron-diffraction patterns (EDPs) for any specified fcc matrix orientation containing deformation twin and/or strain-induced hexagonal close-packed ε martensite (shortened as hcp phase or hcp platelet subsequently) related to the matrix by specific orientation relationships have been computed and plotted. These results helped us to select the favorable fcc matrix orientation for distinguishing between deformation twin and hcp phase and to index experimental EDPs obtained by using transmission electron microscopy (TEM). The identification of structure features in cold-drawn MP159 alloy with 48 pct reduction in cross-sectional area was performed by using TEM, combined with the results from the computer-simulated composite EDPs. Investigation results demonstrated that the closely spaced, intersecting network of fine platelets formed during cold drawing is deformation twins, and no reliable evidence has been found for the presence of hcp phase, which was generally believed to explain the high strength attained in cold-drawn MP159 alloy in some literature. It follows that the significant increase in the strength due to cold working in MP159 alloy results predominately from the formation of the intersecting network of thin deformation twin platelets, which act as “cells” or “subgrains” and provide strong barriers to the movement of dislocations over large distances. In addition, the relatively high dislocation density makes a certain contribution to strengthening.     

An improved unified viscoplastic constitutive model for strain-rate sensitivity in high temperature fatigue

An improved unified cyclic viscoplastic material model for high temperature fatigue of P91 steel is presented. The primary enhancement over existing models is in relation to strain-rate independence of parameters, for accurate interpolation and extrapolation across a range of strain-rates and stress regimes, as relevant to flexible operation of high temperature power generation plant. The model combines a hyperbolic sine constitutive equation with anisothermal cyclic evolution of isotropic and kinematic hardening variables. The material model is developed from a thermodynamic framework and is implemented in multi-axial form within a user material subroutine. The user material subroutine is calibrated and validated for P91 steel across a range of cyclic (isothermal fatigue and thermo-mechanical fatigue) and non-cyclic high temperature loading conditions. A novel method for the identification of the cyclic viscoplastic material parameters is also presented.     

某过滤器体上白色多余物分析

某宇航设备上所用气体过滤器在使用过后,发现表面及内壁上都残留有白色物质。采用扫描电镜SEM对其成分进行能谱分析,并对白色物质形貌以及周围基体的形貌进行宏、微观观察。在与正常表面进行了对比的基础上,分析白色物质成分以及出现白色物质的原因。结果表明：此气体过滤套筒内圈存在腐蚀现象;白色物质并非套筒上滤纸所致,其氧含量较高,可能是腐蚀液体与基体作用形成的水合物。     

预热温度对三维五向Cf/Al复合材料微观组织及室温与高温力学性能的影响

以石墨纤维三维五向织物为增强体,铝合金ZL301为基体材料,采用真空辅助压力浸渗法制备了三维五向增强C_f/Al复合材料,研究了不同温度制备的复合材料微观组织特征和界面反应程度,测试了复合材料在室温和高温下的拉伸力学性能并分析了其断口形貌。结果表明：复合材料相对致密度随制备温度提高而增加,纤维局部偏聚现象也明显减少,与此同时,界面反应物Al₄C₃相随制备温度提高而显著增多,530℃到570℃复合材料室温拉伸极限强度随组织缺陷减少而增加,570℃到600℃复合材料室温极限拉伸强度随界面反应程度增大而显著降低;高温拉伸极限强度随制备温度提高而增加,适当提高界面反应程度有利于提高复合材料高温力学性能,高温拉伸中基体合金回复软化和界面结合强度弱化促进了复合材料断裂过程中的纤维拔出与界面滑移。     

Ant Colony System for a Fuzzy Adjacent Multiple-Level Warehouse Layout Problem

Accomplishing the objective of a warehouse de-pends on having a goodlayout.This paper deals witha fuzzy adjacent multiple-level warehouselayout prob-lem(FAMWLP)in which many types of items haveto be stored in the cells of a warehouse which hasmore than one level.It is desirable that a number ofitems of the same type can be stored in the same cellunless the inventory requirement exceeds the capacityof a cell.In such case,the item type will occupymore than one cell.We call thisitemtype a spli…     

某铜尾矿中磷灰石的浮选回收试验研究

为综合回收四川某铜矿尾矿中的低品位难选磷灰石，研制了新型捕收剂ZP-02，通过单矿物试验证实了ZP-02比油酸及氧化石腊皂具有更强的捕收能力和更好的选择性，并确定了水玻璃是欲分离脉石矿物石英的有效抑制剂，适宜的矿浆pH值为10。在单矿物试验的基础上，对实际尾矿样进行浮选试验，获得了P20，品位为25．32％、回收率为69．87％的磷精矿，实现了该尾矿中磷灰石的有效分选。对ZP-02中表面活性剂的增溶增效机理和水玻璃对石英的抑制机理进行了分析。     

Flexible thermoelectric materials and devices: From materials to applications

With the ever-growing development of multifunctional and miniature electronics, the exploring of high-power microwatt-milliwatt self-charging technology is highly essential. Flexible thermoelectric materials and devices, utilizing small temperature difference to generate electricity, exhibit great potentials to provide the continuous power supply for wearable and implantable electronics. In this review, we summarize the recent progress of flexible thermoelectric materials, including conducting polymers, organic/inorganic hybrid composites, and fully inorganic materials. The strategies and approaches for enhancing the thermoelectric properties of different flexible materials are detailed overviewed. Besides, we highlight the advanced strategies for the design of mechanical robust flexible thermoelectric devices. In the end, we point out the challenges and outlook for the future development of flexible thermoelectric materials and devices.     

Adoption of wide-bandgap microcrystalline silicon oxide and dual buffers for semitransparent solar cells in building-integrated photovoltaic window system

We focused on developing penetration-type semitransparent thin-film solar cells (STSCs) using hydrogenated amorphous Si (a-Si:H) for a building-integrated photovoltaic (BIPV) window system. Instead of conventional p-type a-Si:H, p-type hydrogenated microcrystalline Si oxide (p-μc-SiO_x:H) was introduced for a wide-bandgap and conductive window layer. For these purposes, we tuned the CO₂/SiH₄ flow ratio (R) during p-μc-SiO_x:H deposition. The film crystallinity decreased from 50% to 13% as R increased from 0.2 to 1.2. At the optimized R of 0.6, the quantum efficiency was improved under short wavelengths by the suppression of p-type layer parasitic absorption. The series resistance was well controlled to avoid fill factor loss at R = 0.6. Furthermore, we introduced dual buffers comprising p-a-SiO_x:H/i-a-Si:H at the p/i interface to alleviate interfacial energy-band mismatch. The a-Si:H STSCs with the suggested window and dual buffers showed improvements in transmittance and efficiency from 22.9% to 29.3% and from 4.62% to 6.41%, respectively, compared to the STSC using a pristine p-a-Si:H window.     

纳米接触问题的多尺度模拟(英文)

使用准连续介质法模拟了镍楔形光滑压头与光滑/多粗糙峰铜基体之间的多尺度纳米接触过程,研究了两模型接触过程中位移—载荷、位移—接触面积关系和基体的变形机制.结果显示粗糙峰能有效地减小粘着力,粗糙峰对接触的初始阶段影响大,该阶段的变形主要为粗糙峰的变形.随着压头位移的增加,粗糙峰对载荷和纳米接触问题的影响也随之逐渐减小.     

PID参数自整定中的新方法

PID控制是生产自动控制发展中最基本的一种控制方法,其原理简单、使用方便、适应性强,是一种目前应用最广泛的基础控制方法.但关键问题是如何方便地整定它的三个参数(比例系数Kp,积分时间常数Ti,微分时间常数Td),以使系统具有理想的性能.提出了一种以两个控制品质参数(过渡时间Ts和超调量δ)等权和最小为整定准则——控制品质加权法,通过对比分析仿真实验结果表明,该方法与ITAE相比较,其超调量减少1/2,调整时间缩短到2/3左右.