片状石墨断裂机理初步研究

本文作者采用电子显微断口分析及断口金相分析方法对HT250和P-Cr-Cu灰口铸铁中的片状石墨的断裂机理进行了研究。高倍观察表明,断口上片墨的形貌具有如下特征:(1)片墨解理断裂,呈现长条纹和六角畴与形变结构;(2)裂纹沿石墨与基体界面扩展,导致石墨与基体脱开;(3)片墨有自身的疲劳断裂特征。这些形貌特征与加载方式、应力水平、裂纹扩展方向及片墨的取向密切相关。本文作者认为,根据传统的观点,把石墨看作相当于铸铁中的裂纹或孔洞是不够的,应该把石墨看作铸铁中的一个基本相,对其自身的断裂机理进行系统的研粉。     

TiAl基合金层状组织中裂纹扩展区的塑性变形

本文通过观察ＴｉＡｌ合金层片组织四点弯曲试样侧面裂纹扩展与滑移迹线之间的关系，分析讨论了层状组织中塑性变形对裂纹扩展的影响。发现不论层片相对裂纹处于何种取向，沿层片方向都有一定程度的塑性变形，这种变形对于平行，倾斜，垂直于片层扩展的主裂纹都可引起裂尖钝化，从而引发构成各种韧化机制。     

TiAl基合金层状组织中裂纹扩展区的塑性变形

本文通过观察ＴｉＡｌ合金层片组织四点弯曲试样侧面裂纹扩展与滑移迹线之间的关系，分析讨论了层状组织中塑性变形对裂纹扩展的影响。发现不论层片相对于裂纹处于何种取向，沿层片方向都有一定程度的塑性变形，这种变形对于平行、倾斜、垂直于片层扩展的主裂纹都可引起裂尖钝化，从而引发构成各种韧化机制     

碳氮共渗处理对Ti-6Al-4V合金空蚀行为的影响

利用碳氮共渗处理方法对Ti-6Al-4V合金表面进行改性,制备出了硬质涂层。利用SEM、EDS、XRD和Vickers显微硬度仪分别对处理后试样表面形貌和显微结构、化学组成、显微硬度进行了表征,并利用空蚀设备研究了处理后试样的空蚀行为。结果表明通过碳氮共渗处理在Ti-6Al-4V合金表面形成了均匀、致密、无裂纹的硬质涂层。该涂层具有的细晶结构,在空蚀过程中增加了裂纹萌生难度和扩展路径,减小了裂纹尖端应力和裂纹扩展速率,使其能够吸收、耗散更多的空蚀破坏能量,从而显著地改善了Ti-6Al-4V合金的耐空蚀性能。     

40CrNiM0齿轮材料点蚀破坏的金相研究

用金相试验方法,对40CrNiMo中等硬度齿轮材料在接触疲劳过程中的表面破坏形态、裂纹的萌生与扩展等问题进行了研究,并从金属学角度对材料失效破坏过程进行了分析.结果表明,经过一定周次的循环后,试验滚轮表面产生的接触疲劳破坏是属点蚀破坏,从滚轮表面产生的塑性变形和金属流变层是表面产生点蚀破坏的重要原因.     

40CrNiMo齿轮材料点蚀破坏的金相研究

用金相试验方法,对40CrNiMo中等硬度齿轮材料在接触疲劳过程中的表面破坏形态,裂纹的萌生与扩展等问题进行了研究,并从金属学角度对材料失效破坏过程进行了分析,结果表明,经过一定周次的循环后,试验滚轮表面产生的接触疲劳破坏是属点蚀破坏,从滚轮表面产生的塑性变形和金属流变层是表面产生点蚀破坏的重要原因。     

V型钢导轨表面裂纹分析

对V型钢导轨在热处理后的磨削加工中出现的表面裂纹进行了宏、微观分析，硬度测试及热酸蚀试验。结果表明，磨削不当是导致V型钢导轨出现表面裂纹的主要原因。提出了改进措施。     

30CrMnSiNi2A钢构件焊缝边缘裂纹研究

研究了飞机主起落架半轮叉在使用过程中出现于３０ＣｒＳｉＮｉ２Ａ焊缝边缘的裂纹的形态，断口特征，形成及扩展原因。发现焊缝加强高凸部分和内侧板弧形表面的交角过小，引起应力集中；焊趾表层疏松及打磨的痕迹，蚀坑等促使裂纹萌生，主起落架在滑行，刹车，转弯的力矩使裂纹扩展。     

取向硅钢横剪切口边缘绝缘涂层的破损形貌分析

采用斜刃横剪的加工方式对厚度为0.23mm的取向硅钢进行加工,研究加工过程中取向硅钢表面绝缘涂层的破损情况。在剪切加工过程中,取向硅钢表面由T2涂层(磷酸铝)与C2涂层(硅酸镁)组成的绝缘涂层在刀具作用下发生破损,其破损形貌分为裂纹区、压碎区以及剥落区。裂纹区和剥落区出现在塌角侧表面,而压碎区出现在毛刺侧表面。随着剪切侧隙的增加裂纹区宽度增大,压碎区基本保持稳定,剥落区略微增加。随着剪切速度的增加,毛刺侧表面涂层破损宽度先减小后增大。同时可观察到剥落区绝缘涂层发生了两种剥离形式,一种是T2涂层与C2涂层之间的层间剥离,另一种是C2涂层与基体之间发生的界面剥离。     

某型弹用尾翼片裂纹分析

目的分析弹用尾翼片淬火、回火后表面裂纹产生的原因。方法通过对存在裂纹的尾翼片进行金相检测、化学成分分析、硬度检测、断口检测、力学性能检测,对尾翼片产生的原因进行了分析和讨论。结果确定了尾翼片裂纹的性质和产生原因。结论尾翼片裂纹为淬火裂纹;尾翼片裂纹产生的主要原因是由于原材料钢板剪尾翼片条料过程中,在条料的表面产生了冷变形开裂缺陷,出现了较深的线状缺口,导致淬火热处理时产生了严重的应力集中,诱发了裂纹的萌生,同时,原材料钢板中存在的魏氏组织和硫化物夹杂等材质缺陷,也对促进了淬火裂纹的萌生。     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

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.