The plastic zone and residual stress near a notch and a fatigue crack in HSLA steel

The plastic zone and residual stress around a notch under load and with the load removed, and around a fatigue crack (at the same stress intensity factor as for the notch) have been examined, with automated X-ray techniques and a microbeam. There is good agreement between the measured plastic zone size and Hutchinson's theory for a work hardening material. Residual stresses exist well behind the tip, and vary with depth, so that measurements of crack closure on a surface may not be directly related to closure stress (which samples the bulk). Instabilities in the dislocation arrangement can be detected by comparing X-ray line broadening of bulk specimens under load, and with the load removed. formerly Research Assistant, Department of Materials Science and Engineering, The Technological Institute, Northwestern University, Evanston, IL     

Structural distortions in the surface layer of single-crystal molybdenum after face grinding

Use of diamond grinding wheels with organic and ceramic bonds makes it possible to avoid the phenomenon of wheel glazing during fine grinding of molybdenum single crystals and to obtain a high quality ground surface with the minimum level of structural distortions. The nature of the orientation dependence of surface structural distortions is established by studying {001}, {110}, and {111} molybdenum single crystals. This is connected with features of plastic deformation during grinding. Materials Science, Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5-6, pp. 110–118, May–June, 1998.     

Criterion for judging the homogeneous and heterogeneous nucleation

A criterion for judging the nucleation form in highly undercooled liquid has, respectively, been derived from the nucleation and structure of liquid. It is found that the nucleation form of a highly undercooled liquid can be judged by determining the S _v in the liquid (where S _v is the surface area of the supposed catalyst in a unit volume of the liquid). When the determined value of S _v is equal to 10^10±1 m⁻¹, the liquid has nucleated homogeneously; it has nucleated heterogeneously if the determined value of S _v is less than 10^10±1 m⁻¹. By calculating the values of S _v in highly undercooled aluminum, copper, and silver, it is found that only silver melted under a slag has been undercooled to its undercooling of homogeneous nucleation.     

残余应力对金属材料局部腐蚀行为的影响

基于残余应力测试新方法与先进电化学测试技术的进展, 围绕残余应力类型和大小对金属材料点蚀以及应力腐蚀行为的作用机理进行了总结和归纳. 研究发现, 尽管残余压应力对腐蚀行为的抑制作用得到了大量实验的证实, 但是在不同条件下其作用方式以及机理不尽相同, 并且与材料的结构特点以及腐蚀产物等密切相关. 同时, 残余拉应力的作用尚不明确, 受到材料类型和其他因素耦合的严重影响. 另外, 在某些环境下, 影响腐蚀行为的关键是残余应力梯度或残余应力的某个临界值. 但是对有色金属的研究表明残余拉应力和压应力均会导致基体中位错和微应变等结构缺陷增加, 进而促进点蚀敏感性, 降低材料服役性能. 最后, 对目前研究存在的局限进行了讨论和展望.      

残余应力对金属材料局部腐蚀行为的影响

基于残余应力测试新方法与先进电化学测试技术的进展,围绕残余应力类型和大小对金属材料点蚀以及应力腐蚀行为的作用机理进行了总结和归纳.研究发现,尽管残余压应力对腐蚀行为的抑制作用得到了大量实验的证实,但是在不同条件下其作用方式以及机理不尽相同,并且与材料的结构特点以及腐蚀产物等密切相关.同时,残余拉应力的作用尚不明确,受到材料类型和其他因素耦合的严重影响.另外,在某些环境下,影响腐蚀行为的关键是残余应力梯度或残余应力的某个临界值.但是对有色金属的研究表明残余拉应力和压应力均会导致基体中位错和微应变等结构缺陷增加,进而促进点蚀敏感性,降低材料服役性能.最后,对目前研究存在的局限进行了讨论和展望.     

Change in homogeneous and heterogeneous sensitivity training groups.

Assigned 77 male and 73 female undergraduates to 4 homogeneous and 4 heterogeneous t groups based on expressed and wanted control behavior scores on the fundamental interpersonal relations orientation-behavior (firo-b) scale. After 14 weekly meetings, it was found that heterogeneous groups manifest significantly more positive change on the firo-b. On rating scales devised to measure positive feeling toward the group, the initial superiority of homogeneous groups was reduced by the end of the t group, and the heterogeneous groups manifested more significant increases. Results are consistent with R. Harrison and B. Lubin's (see pa, vol. 40:2814) confrontation-support model of change. The increased use of behavioral criteria of changes and the need for follow-up investigations are advocated. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

机械加工对粉末冶金铍材表面残余应力的影响

铍具有低密度、弹性模量高的特性,常用于航天结构件。粉末冶金铍材在机械加工时,表面会产生残余应力,对铍结构件的尺寸稳定性和使用寿命造成直接影响。因此,使用X-ray衍射仪测量铍材表面残余应力,测量了粗车、精车、时效工艺下残余应力沿表面的分布情况;进一步研究了不同机加工艺对铍材表面残余应力影响。结果表明,机械加工时,粉末冶金铍材残余应力均表现为压应力;残余应力与加工线速度负相关,与进刀量正相关,时效处理可有效降低铍材表面残余应力,还能有效提高残余应力的均匀性。     

Prediction of metallic materials creep deformation under multiaxial stress state

A simple function of multiaxial creep is presented hereafter. This is derived from a uniaxial creep function with only three fitting parameters. For the derivation of the multiaxial function the only assumption made was the one of material's isotropy. With the additional assumption of constant volume, the function leads to a v. Mises-type function of multiaxial creep. The equivalent stress employed has a simple form as well and leads to the v. Mises equivalent stress. The derived curves agree with the experiments, not only the ones carried out in the laboratory but also the ones taken from literature.     

金刚石复合片(PDC)表面残余应力的XRD研究

采用X射线应力测定仪测试了金刚石复合片(PDC)表面从中心到边缘5个不同位置的残余应力,结果表明:金刚石层表面残余应力的性质为压应力,最大值在PDC表面中心(达1270MPa);从中心到边缘,应力的大小逐渐降低,靠近边缘处的压应力只有143MPa。为检验测试结果的准确性,对所测规格的PDC作了有限元分析,测试结果与通过有限元分析计算出的应力分布趋势基本吻合。对测试值与有限元分析计算值出现偏差的原因进行了分析并讨论了PDC径向应力分布对PDC性能的影响及改进措施。     

Social participation in homogeneous and heterogeneous groups of chronic schizophrenics.

Responsiveness of socially withdrawn, regressed chronic schizophrenics to changes in the characteristics of their social environment was examined. It was hypothesized that withdrawn, regressed, hospitalized patients would participate more effectively in problem-solving groups that were heterogeneous in the activity level and "mental health" of its members than in homogeneous groups. 16 Ss rated as withdrawn and regressed and 16 active, improved Ss solved group problems in a homogeneous and heterogeneous group context. Ratings by independent judges, employing a scale devised for this purpose, indicated that both withdrawn and active chronic schizophrenics participate significantly more effectively in a heterogeneous group problem-solving situation than in a homogeneous setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Communication style and effectiveness in homogeneous and heterogeneous dyads of retarded children

The channels, styles, and successfulness of communication used by retarded children when teaching a simple board game to a listener of similar or dissimilar age and ability to themselves were investigated. Forty children, half of high level and half of low level (means MAs=6.6 and 3.7 years, mean CAs-15.5 and 11.2 years, respectively) instructed a naive listener either at their own or at the other level, after they had been taught the game by the experimenter. Both high- and low-level speakers altered their channels and styles of communication to low-level listeners along the dimensions found by Shatz and Gelman (1973) with nonretarded children. However, the communication shifts, particularly those produced by high-level speakers, were ineffective in producing listener understanding. We concluded than communication-skills training for retarded children must be concentrated not only on the linguistic form, but also on the functional appropriateness of the children's utterances.     

Examination of the variation of the phase composition and stress state of surface layers of VK20 hard alloy after ion bombardment

Powder Metallurgy and Metal Ceramics -     

A comparison of homogeneous and heterogeneous anxiety management training.

Compared the effectiveness of treating 31 test anxious (Achievement Anxiety Scale) and 25 speech anxious (Personal Report of Confidence as a Speaker) undergraduates in anxiety management training (AMT) groups composed of only test-anxious or speech-anxious Ss (homogeneous AMT) or a mixture of both (heterogeneous AMT). For test-anxious Ss, both forms of AMT significantly reduced state and trait test anxiety compared with controls, these gains were maintained, and Ss had higher psychology grades. Follow-up assessment evidenced nontargeted anxiety reduction for both forms of AMT, but showed that homogeneous AMT Ss reported less anxiety on the Fear Inventory than either heterogeneous AMT or control Ss. For speech-anxious Ss, heterogeneous AMT lowered speech anxiety significantly more and was the only condition to show any evidence of nontargeted anxiety reduction for Ss. Results are discussed in terms of immediate, efficient delivery of anxiety reduction services to a wide range of clients. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)