65Mn卡箍氢脆断裂失效分析

厚度0.5 mm飞机座舱照明用65Mn卡箍装配过程中出现裂纹,扳动后断裂。采用能谱分析、扫描电镜等对断口处进行分析,结果表明:卡箍断裂件化学成分符合标准;断口大多为沿晶断裂,晶界面上有发纹线,未发现二次裂纹,部分断裂为穿晶断裂,未发现断口边缘有加工损伤痕迹;能谱分析未在晶界上发现杂质元素;金相组织为回火索氏体;显微硬度符合标准要求。卡箍产生断裂的主要原因:由于壁厚太薄,拐角较锐利,镀锌时致使大量氢聚集并呈弥散分布,进而形成沿晶裂纹,在外力作用下,导致沿晶脆性断裂。     

螺钉氢脆断裂失效分析

螺钉在装配时发生断裂。采用扫描电镜和金相检查对螺钉断口进行宏观和微观分析,并进行硬度及化学成分检测。螺钉断口均呈沿晶形貌,局部有韧窝,晶界面上有细小条状的撕裂棱线;金相组织为回火索氏体;化学成分符合标准要求;显微硬度值明显高于正常螺钉硬度值。结果表明,螺钉热处理不当,造成抗拉强度明显过高;同时酸洗过程中,螺钉在酸溶液中浸泡时间过长,致使大量氢渗入螺钉,增大了螺钉氢脆的敏感性,最终导致螺钉氢致脆性断裂。     

扭转弹簧氢脆断裂失效分析

直径0.6 mm的70#冷拔碳素弹簧钢丝镀镉后,制成中径4.0 mm扭转弹簧,在装配时发生断裂。采用能谱分析(EDS)、金相分析和扫描电镜(SEM)对断口进行了宏观和微观检测及分析。结果表明:弹簧在绕制过程中的残余拉应力以及在镀前接触了含氢介质,致使大量的氢残留并呈弥散分布形态,进而形成沿晶裂纹,在外力作用下,导致弹簧沿晶脆性断裂。     

内六角螺钉断裂失效分析

ML40Cr钢12.9级内六角螺钉在装配过程中发生断裂。对断口进行宏观和微观检验分析,结果表明:螺钉表面组织为回火屈氏体及回火索氏体+少量未溶铁素体,表面硬度平均值443.7 HV0.3,断口附近氢质量分数为4.47×10-6,断裂源区及其余外缘均为沿晶断裂形貌,部分晶粒表面出现类似鸡爪纹或发纹特征,表现出氢致延迟断裂的特征,扩展区和终断区主要为沿晶和韧窝的混合断裂形貌。建议采用ML35CrMo或42CrMoA钢制造,改进原材料酸洗工艺;热处理前增加去鳞工序;改善热处理工艺以降低螺钉的抗拉强度和硬度值,增加驱氢工艺,并对该批次螺钉进行48 h氢脆验证试验。     

20 Mn螺钉氢脆断裂分析

利用化学成分分析、断口宏观和微观观察、显微组织检验、渗碳层深度测定、氢含量检测等方法,对断裂螺钉与无质量问题螺钉进行分析比较.结果表明,螺钉断裂符合氢脆的延迟断裂、沿晶断裂的特征,为氢致断裂,不良品含氢量较高及硬度值偏大增加了氢脆敏感性.     

大型铝合金支架断裂原因分析

文章通过化学成分分析、微观组织观察等实验方法,结合有限元仿真计算,对一种Al-Zn-Mg系铝合金铸造成型支架结构件断裂的原因进行分析。结果表明：浇注过程中支架转角处缩松,气孔等铸造缺陷以及设备运动过程导致的高应力集中是支架产生裂纹以及断裂失效的主要原因。     

后车轮螺栓断裂失效分析

载重车后车轮螺栓在安装轮胎螺母时断裂。为了分析断裂的原因,应用扫描电子显微镜、能谱仪、光学显微镜、直读光谱分析仪对该螺栓进行了宏观、微观、化学成分等分析,同时还进行了硬度和拉伸试验。检测结果表明:由于螺栓存在较严重的偏析、疏松缺陷,在安装预紧力作用下缺陷处产生裂纹并不断扩展,导致螺栓脆性断裂。     

扭转弹簧断裂原因分析

1.3 mm SWP-B弹簧钢丝生产的扭转弹簧在客户装配前发生断裂,弹簧断口以沿晶断裂为主。分析材料化学成分和组织,对弹簧断口附近和正常组织进行纵截面显微硬度测定,采用扫描电镜对断口进行宏观和微观检查,并用X射线能谱仪对断口进行分析。结果表明:扭转弹簧在电镀锌初期局部产生非正常组织马氏体,由于马氏体存在组织应力,与在酸洗和电镀锌时弹簧基体中的氢造成的内应力相互作用,导致扭转弹簧出现裂纹并滞后断裂。     

压铆螺钉断裂失效分析

针对汽车压铆螺钉安装时未现异常,安装后第二天螺钉断裂问题,应用扫描电子显微镜、光学显微镜、直读光谱分析仪、测氢仪、硬度计等对断裂螺钉的宏观和微观组织形貌、硬度、化学成分、氢含量等进行分析。结果表明:该批螺钉热处理不当造成硬度过高,经电镀处理后渗氢没有及时去除,使螺钉氢含量过高遗留氢脆隐患,在安装应力的作用下诱发氢致延迟断裂。建议高强度螺栓最好不采用电镀。如果采用电镀工艺,在电镀后4 h内必须及时进行除氢处理,必要时可延长除氢时间。     

钢丝绳钢芯早期断裂失效分析

用户在使用搁置3 a的钢芯钢丝绳时,由于钢芯首先断裂,导致用后不久发生断股事故。经检验,钢芯的断裂为疲劳断裂,疲劳断裂的原因是由于钢丝绳生产工艺控制不严以及服役过程中受到弯曲振动载荷,使芯丝表面磨损和硬化,并在磨损面上出现纵横向裂纹和蚀坑,成为疲劳源,裂纹扩展导致芯丝过载断裂,直至钢芯断裂,从而导致绳股破断。钢丝绳因其钢芯过早断裂而报废,与钢丝绳芯丝抗拉强度波动、表面缺陷以及钢芯疲劳寿命与其钢丝绳疲劳寿命匹配较差有关。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press