纤维预热温度对连续Al2O3f/Al复合材料力学性能的影响

选用Nextel610型Al₂O₃纤维为增强体、ZL210A连续氧化铝合金为基体,采用真空压力浸渗法制备纤维增强铝基复合材料(Al₂O_3f/Al),纤维的体积分数为40%,预热温度分别为500、530、560和600℃,研究了纤维预热温度对Al₂O_3f/Al复合材料的微观组织、纤维损伤和力学性能的影响。结果表明：随着纤维预热温度的提高复合材料的致密度随之提高,最大达到99.2%,材料的组织缺陷最少,纤维的分布均匀;随着纤维预热温度的提高从复合材料中萃取出来的Al₂O₃纤维的拉伸强度不断降低,纤维预热温度为600℃的复合材料中Al₂O₃纤维的拉伸强度仅为1150 MPa,纤维表面粗糙,有大尺寸附着物。纤维的预热温度对Al₂O_3f/Al复合材料的拉伸强度有显著的影响。预热温度为500、530、560和600℃的复合材料其拉伸强度分别对应于298、465、498和452 MPa。组织缺陷、纤维损伤和界面结合强度,是影响连续Al₂O_3f/Al复合材料强度的主要因素。     

激光多层熔覆纳米陶瓷层工艺参数优化

为了深入了解激光多层熔覆工艺与涂层性能之间的关系,采用压片预置式激光多层熔覆工艺制备了纳米Al2O3-13%TiO2(质量分数)陶瓷层;通过3因素3水平正交试验分析了激光熔覆熔池闭环控制温度、超声振动频率及保温箱预热温度对涂层结合强度的影响,并对激光熔覆工艺参数进行了优化;通过扫描电镜(SEM)和结合强度测试研究了最优工艺下所得涂层的形貌和性能。结果表明:影响涂层结合强度的因素主次顺序依次为熔池闭环控制温度、保温箱预热温度、超声振动频率;激光多层熔覆纳米Al2O3-13%TiO2涂层最佳工艺参数为熔池闭环控制温度2 500℃,超声振动频率50 kHz,保温箱预热温度400℃;优化工艺熔覆的涂层各层之间无明显界面,涂层内部致密、连续,基本无孔隙及贯穿性大裂纹,涂层结合强度明显提高,达66.3 MPa。     

棉秆皮预处理对棉秆皮纤维/PP复合材料力学性能的影响研究

用碱处理、蒸汽闪爆、蒸汽闪爆结合碱处理这3种预处理方法制备的棉秆皮纤维作为增强体,通过热压成型制备了棉秆皮纤维/聚丙烯复合材料。首先优化了制备该复合材料的棉秆皮纤维长度、热压温度、压力以及时间等工艺参数,并以此优化工艺为基础,研究了3种预处理方法制备的棉秆皮纤维对复合材料拉伸、弯曲、冲击性能以及微观形貌的影响。结果表明:在棉秆皮纤维长度为8cm、热压温度170℃、热压压力3MPa、热压时间4min条件下制备的复合材料性能较优;在3种预处理方法中,采用蒸汽闪爆与碱预处理棉秆皮纤维制备的复合材料性能最优,复合材料拉伸强度为36.290MPa、拉伸模量为4557.40MPa、弯曲强度为63.31MPa、弯曲模量为4780.00MPa、冲击强度为485.0J/m。     

烧结温度对Cf/SiC复合材料结构及性能的影响

以碳纤维为增强体, 热压烧结制备了C_f/SiC复合材料, 研究了烧结温度对C_f/SiC复合材料密度、结构及性能的影响. 研究发现: 提高烧结温度能够促进C_f/SiC复合材料的致密度; 当烧结温度低于1850℃时, 升高烧结温度, 复合材料的强度和断裂韧性也随之提高. 当烧结温度为1850℃时, 复合材料的性能最优, 弯曲强度达500.1MPa, 断裂韧性为16.9MPa·m ^1/2. 当烧结温度达到1880℃时, 复合材料性能反而下降.     

Al_2O_3修饰3D-SiC/Al复合材料的制备与性能

用Al_2O_3作为界面修饰剂,通过反应烧结,在SiC颗粒之间形成莫来石界面,制备SiC预制件,采用无压熔渗法制备3D-SiC/Al互穿式连续结构复合材料。基于正交实验研究了Al_2O_3添加量、预制件烧结时间、熔渗温度和熔渗时间对3D-SiC/Al复合材料抗弯强度和热导率的影响。实验结果表明,Al_2O_3添加量对复合材料抗弯强度和热导率影响显著,复合材料获得最大抗弯强度344 MPa和热导率165 W/(m·K)的制备工艺为:氧化铝添加量2.0%(原子分数),预制件烧结时间2h,熔渗温度950℃,熔渗时间1h。     

偏磷酸铝粘结剂在真空液相浸渗制备Cf/Al复合材料中的应用研究

采用真空压力浸渗工艺,以高强高模碳纤维M40J增强AlMg5为研究对象,研究了预制件抗压强度提高技术和高温粘结剂偏磷酸铝对复合材料中纤维平直度、复合材料性能的影响.结果表明,预制件中偏磷酸铝的加入使复合材料中纤维的平直度及分布的均匀性提高,用P/A1 15:1、浓度为10wt%偏磷酸铝溶液处理后的预制件经真空液相浸渗后制得的复合材料,纤维不仅保持了较好的平直度,而且弯曲强度比未经粘结剂处理的提高近102%左右,达到535MPa.     

碳纤维-尼龙6混编织物复合材料的制备及性能

为了探究合适的碳纤维表面处理方法,改善碳纤维-尼龙6织物复合材料界面结合效果,提高复合材料的力学性能,通过混编的方式制备碳纤维-尼龙6预制件,将预制件浸泡在不同浓度的醇溶尼龙无水乙醇溶液中,最后将预制件通过热压成型,制备碳纤维织物-尼龙6复合材料。采用万能拉伸试验机、SEM、TGA、DSC、XRD分析碳纤维-尼龙6复合材料的力学性能、微观形貌、耐热性能、结晶度及晶型变化。结果表明:将预制件在浓度为1wt%的尼龙溶液处理后,并采用1℃/min的降温速率制备的碳纤维-尼龙6织物复合材料力学性能最佳,抗拉强度、弹性模量、弯曲强度、弯曲模量、冲击强度分别为449.32 MPa、5.32 GPa、657.67 MPa、44.08 GPa、138.42 kJ/m2。纤维拔出后,单根碳纤维表面附着部分尼龙基体,碳纤维与尼龙基体形成了良好的界面层。碳纤维-尼龙6织物复合材料的起始分解温度较尼龙6纤维提高了13℃,耐热性有所增强,尼龙6树脂主要以α晶型存在,结晶较为完善。      

先驱体浸渍-裂解SiC界面改性涂层对气相渗硅3D-C_f/SiC复合材料力学性能的影响

界面改性涂层对调节复合材料的力学性能起到重要作用。特别是在气相渗硅(GSI)制备C_f/SiC复合材料时,合适的界面改性涂层一方面保护C纤维不受Si反应侵蚀,另一方面调节C纤维和SiC基体的界面结合状况。通过在3D-C纤维预制件中制备先驱体浸渍-裂解(PIP)SiC涂层来进行界面改性,研究了PIP-SiC涂层对GSI C_f/SiC复合材料力学性能的影响。结果表明:无涂层改性的GSI C_f/SiC复合材料力学性能较差,呈现脆性断裂特征,其弯曲强度、弯曲模量和断裂韧性分别为87.6 MPa、56.9GPa和2.1 MPa·m~(1/2)。具有PIP-SiC界面改性涂层的C_f/SiC复合材料力学性能得到改善,PIP-SiC涂层改性后,GSI C_f/SiC复合材料的弯曲强度、弯曲模量和断裂韧性随着PIP-SiC周期数的增加而降低,PIP-SiC为1个周期制备的GSI C_f/SiC复合材料的力学性能最高,其弯曲强度、弯曲模量、断裂韧性分别为185.2 MPa、91.1GPa和5.5 MPa·m~(1/2)。PIP-SiC界面改性涂层的作用机制主要体现在载荷传递和"阻挡"Si的侵蚀2个方面。     

中间热处理对薄壁C/CSiC构件制备及力学性能的影响

采用“化学气相渗透法+先驱体浸渍裂解法”（CVI+PIP）混合工艺制备了薄壁C/C-SiC复合材料构件,研究了C/C多孔体的热处理对C/C-SiC构件密度、变形量及力学性能的影响。研究结果表明：中间热处理可提高C/C的开孔率,有利于SiC的渗入,制备出密度较高的C/C-SiC复合材料构件;中间热处理对构件的层间剪切性能影响不大,但影响构件面内拉伸强度和整体承压性能;中间热处理会导致薄壁C/C-SiC构件在内外径和高度方向发生变形;合适的热处理温度（1600~1800℃）使C/C-SiC构件界面结合强度适中,面内拉伸强度及整体承压性能有了极大的提高;而较高的热处理温度（2100~2300℃）使碳纤维强度下降,使构件拉伸强度及整体承压性能大幅下降。     

化学气相反应法制备SiC涂层对C/C复合材料力学性能影响

采用化学气相反应法在C/C复合材料表面制备了SiC涂层,利用X射线衍射仪、扫描电镜及能谱等分析手段研究了涂层的形貌和结构,并采用三点弯曲试验研究了材料的力学性能,讨论了SiC涂层及制备工艺对复合材料断裂行为的影响.结果表明:涂层后材料的弯曲强度和最大断裂位移明显增大.未涂层C/C复合材料的平均弯曲强度为172.4MPa,而涂层后C/C复合材料的平均弯曲强度为239.8MPa,弯曲强度提高了39.1%.涂层试样强度的提高主要与制备过程中部分蒸气扩散渗透反应引起的界面强化及SiC颗粒的增强作用有关.此外,涂层后材料的断裂模式未发生明显转变,断裂过程中试样表现出一定的假塑性和韧性断裂特征.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to