CNC工具磨床行程开关与机械原位的分析

本文分析了ＦＡＮＬＣ—ＢＥＳＫ＃控系统的软硬限位开关、减速开关的设置和Ａｌｌｅｎ－Ｂｒａｄｌｅｙ数控系统的开关设置及Ｂｋｘ３－８８２Ｂ数控系统的开关设置。对ＣＮＣ工县磨床，提出采用四个硬限位开关和一个减速开关共五个开关的配置方式，其中减速开关作为零点与国近零点机械原位开关，远零点极限开关１又作为国远零点机械原位开关。该配置不但可省去位置控制板的位置记忆电路，而且可防止各轴的超程飞车，完成各轴的找机械零点与采用自动或手动方式回机械原位而不产生干涉。

原位纳米TiC_p增强AZ91复合材料的制备和力学性能

通过预球磨和低温球磨原位制备了尺寸约300nm的TiCp与铝的复合颗粒,采用搅拌铸造法将复合颗粒与镁合金复合,制备了TiCp/AZ91复合材料,并研究了材料的微观组织和性能。结果表明,通过低温球磨可以原位生成TiCp/Al复合颗粒,搅拌能够将复合颗粒搅入镁合金中。TiCp体积分数低时(3%),制备的复合材料中TiCp分布比较均匀;体积分数较高时,TiCp沿晶界分布倾向增大;当体积分数达到7%时,TiCp主要沿晶界分布。性能测试结果表明,复合材料的室温抗拉强度达287.72MPa,弹性模量达69.23GPa。200℃下抗拉强度达245.49MPa,弹性模量达到51.32GPa。复合材料的蠕变性能为:170℃和55MPa以及175℃和60MPa下100h总蠕变量分别为0.182%和0.191%。细小的增强颗粒对位错和晶粒边界的钉轧作用是导致复合材料具有良好的高温拉伸和蠕变性能的原因。

两种方法制备的纳米水滑石晶体结构与热稳定性的比较研究

分别采用共沉淀法和机械力化学/原位结晶法制备纳米水滑石,通过X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、热重-差示扫描量热分析(TG-DSC)及红外光谱(IR)等方法对比分析了两种纳米水滑石在表观形貌、晶体结构和热稳定性等方面的差异。结果表明,与共沉淀法制备的纳米水滑石相比,机械力化学/原位结晶法制备的纳米水滑石结晶度更高、晶粒呈规则的六边形片状形貌、晶粒粒径约为40 nm、粒度分布均匀,且在TG-DSC曲线上的吸热峰面积、失重量和失重速率较小,热稳定性更好。

Study on mechanical properties of composite materials by in-situ tensile test

The mechanical properties of the SiC fiber-reinforced Mg-Al metal matrix composite materials have been studied on internal microstructure by (scanning electron microscopy) SEM in-situ tensile test. The emergence and propagation of the crack, and the fracture behavior in materials have been observed and studied. It is found that in the case of the tensile test, the crack emerged in SiC fiber initially. In the case of the strong cohesion of the fiber-metal interface, the crack propagated in the fiber, meanwhile the fibers in the neighborhood of the cracked fiber began to crack and the Mg-Al metal deformed plastically, and at last the material fractured. Otherwise the toughness of the materials grows in the case of the lower cohesion of the fiber-metal matrix interface.

Epi-lasik联合丝裂霉素C预防术后Haze的观察与围手术期护理对策

目的探讨机械法准分子激光角膜上皮下磨镶术 （epipolis laser in situ keratom ileusis,Epi-LASIK ） 联合丝裂霉素C 预防术后Haze 的观察和围手术期护理对策.方法：采用回顾性分析的方法对实施Epi-LASIK 联合丝裂霉素C 手术治疗近视的73 例 （146 眼）患者进行研究,总结Haze 观察结果与护理要点.结果：患者术后的刺激症状减轻,术后发生Haze 的例数减少,程度减轻,视力稳定,达到良好效果.结论：Epi-lasik 术中应用0.2g/LMMC 溶液并加强围手术期对患者的护理、用药的准确性,是预防和减轻Haze 形成的有效方法,有助于术后视力达到最佳效果,提高患者的满意度 .

Epi-LASIK和去上皮瓣Epi-LASIK矫正中高度近视的临床疗效观察

目的比较机械法准分子激光上皮瓣下角膜磨镶术(epipolis laser in situ keratomileusis,Epi-LASIK)和去上皮瓣Epi-LASIK治疗中高度近视的疗效。方法选择30例(60眼)在我院接受Epi-LASIK的中高度近视患者进行研究,将患者随机分为A、B2组,每组各15例15眼。A组常规复位上皮瓣,B组去除上皮瓣。术后随访6个月,对2组患者术后刺激症状、上皮愈合时间、术后裸眼视力、最佳矫正视力、屈光状态、haze等程度进行比较。结果术后第1天,2组角膜刺激症状对比,差异无统计学意义(P>0.05),术后第3天、第5天有疼痛症状者A组分别为20眼和13眼,B组分别为16眼和7眼,差异均有统计学意义(P均<0.01);角膜上皮愈合时间:A组平均为(4.73±1.16)d,B组平均为(3.68±0.61)d,2组比较差异有统计学意义(P<0.01);术后1个月、3个月、6个月裸眼视力及屈光度:2组间对比,差异均无统计学意义(P均>0.05);术后6个月角膜haze形成情况:A组0.5级haze发生4眼(13.33%),B组0.5级haze发生5眼(16.67%),2组间比较,差异无统计学意义(P>0.05)。结论Epi-LASIK及去上皮瓣Epi-LASIK治疗中高度近视均安全、有效,具有良好的可预测性和稳定性。去上皮瓣有利于减轻患者术后角膜刺激反应,加快上皮愈合。

In situ thermomechanical processing to avoid grain boundary precipitation and strength-ductility loss of age hardening alloys

To avoid grain boundary(GB) precipitation during aging, a new strategy of in situ thermomechanical processing for age hardening alloys was proposed. Specifically, high-density nanoscale precipitates were introduced into ultrafine grain(UFG) interiors of 7075 Al alloy by equal-channel-angular(ECAP) processing at 250 ℃ for 8 passes, thus avoiding GB precipitation. Tensile test results indicated that the UFG 7075 Al alloy exhibits superior mechanical properties(yield strength of 350 MPa, ultimate tensile strength of 500 MPa, uniform elongation of 18% and tensile ductility of 19%) compared with the UFG 1050 Al counterpart(yield strength of 170 MPa, ultimate tensile strength of 180 MPa, uniform elongation of 2.5% and tensile ductility of 7%). Fracture surface morphology studies revealed numerous homogeneous micro shear bands in necking shrinkage areas of both UFG 7075 Al and 1050 Al alloys, which are controlled by cooperative GB sliding. Moreover, the introduction of nanoscale precipitates in UFG 7075 Al matrix weakened the tendency of shear fracture, resulting in a higher tensile ductility and more homogeneous deformation. Different from the GB precipitation during postmortem aging, in situ thermomechanical treatment dynamically formed GBs after precipitation, thus avoiding precipitation on GBs.

Preparation of in-situ Cu/NbC nanocomposite and its functionally graded behavior for electrical contact applications

Cu&ndash;15%NbC (volume fraction) powder was synthesized using the starting powders of Cu, Nb and graphite in a high energy vibratory disc mill for 7 h of milling under argon atmosphere. A composite sample and a Cu/NbC functionally graded material (FGM) sample were produced by using the two-step press and sintering at 900 &deg;C for 1 h under vacuum. The microstructure and physical and mechanical properties of the specimens were investigated. The field emission scanning electron microscopy, energy dispersive X-ray and X-ray diffraction analysis confirmed the synthesis of the nanostructure matrix of 18&ndash;27 nm with the nanoparticles reinforcement of 42 nm after sintering, verifying the thermal stability of this composite at high temperature. The hardness of Cu&ndash;15%NbC was five times greater than that of the pure Cu specimen. The volume reduction of the sample after the wear test decreased in comparison with the pure Cu specimen. The electrical conductivity of the composite specimen decreased to 36.68% IACS. The FGM specimen exhibited high electrical conductivity corresponding to 75.83% IACS with the same hardness and wear properties as those of the composite sample on the composite surface. Thus, Cu/NbC FGM with good mechanical and electrical properties can be a good candidate for electrical contact applications.

In situ deposited multilayer integrated hydrogels for deformable and stretchable supercapacitors

Hydrogel systems promote the development of flexible energy storage devices because of their inherent mechanical elasticity and ionic conductivity.However,achieving stable energy storage capacity under violent mechanical deformation is still a challenge for hydrogel devices.In this work,an all-in-one integrated supercapacitor(AISC)was assembled using in situ deposited polyaniline/graphene oxide nanocomposites for both sides of the incorporated ionic hydrogel electrolyte.The assembly process of the AISC was greatly simplified,and the displacement and separation of the multilayer structured hydrogel complex were avoided during mechanical deformation.The hydrogel electrolyte with ionic additives exhibited strong adhesion and flexibility,and high ionic conductivity,thereby ensuring the excellent specific capacitance and rate performance of the AISC.The specific capacitances of the AISC were 222.8 mF cm^(−2) at the current density of 0.2 mA cm^(−2) and 151.7 mF cm^(−2) at 3.2 mA cm^(−2).The capacitance retention rate was 68.1%.The energy density of a piece of the device reached 44.6μW h cm^(−2) at a power density of 120.0μW cm^(−2).Moreover,reliable and reproducible energy storage was acquired under bending,compression,and stretching deformations.The AISC was also easily assembled in series to power a light-emitting diode(LED)light.This work provides a facile approach to the construction of flexible supercapacitors for the development of energy storage devices in flexible electronics.