Philosophical Magazine A最新文献

Mechanisms of short-fatigue-crack initiation and propagation in a β-Ti alloy β-钛合金短疲劳裂纹萌生与扩展机制

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240444

U. Krupp, Wilhelm Floer, J. Lei, Yunming Hu, H. Christ, Alexander Schick, C. Fritzen

{"title":"Mechanisms of short-fatigue-crack initiation and propagation in a β-Ti alloy","authors":"U. Krupp, Wilhelm Floer, J. Lei, Yunming Hu, H. Christ, Alexander Schick, C. Fritzen","doi":"10.1080/01418610208240444","DOIUrl":"https://doi.org/10.1080/01418610208240444","url":null,"abstract":"Abstract The microstructurally short-crack initiation and early propagation were studied on the metastable β-Ti alloy TimetalĽB in the solution heat-treated bcc β microstructure under symmetrical pull-push fatigue testing. By means of a finite-element treatment in combination with local displacement measurements applying a laser interferometric strain-displacement gauge (ISDG), it was shown that elastic anisotropy gives rise to high mechanical stresses at certain grain boundaries (GBs). Large-angle GBs were observed to be preferred sites for short-crack initiation. Two modes of fatigue crack initiation were found: one is crack formation along slip bands, often resulting in transgranular crack propagation; the second is intergranular cracking of GBs. Using electron back-scattered diffraction (EBSD), local crystallographic orientations were determined and hence the role of GB types in the process of short crack initiation and growth could be taken into account. On the basis of the experimental observations and measurements, the preferred crystallographic conditions for short crack initiation and growth were revealed. The ISDG system was applied to measure the local crack opening displacements of short cracks in order to characterize the dependence of the short-crack closure phenomena on the applied load.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129115480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 22

Crack deflection in compositionally graded Cu-W composites 成分梯度Cu-W复合材料的裂纹挠度

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240450

J. Chapa-cabrera, I. Reimanis

引用次数: 11

Ageing of free bubble clusters 自由气泡团的老化

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208239627

M. Rosa, L. Afonso, M. Fortes

引用次数: 6

Raman spectra, structural units and durability of nuclear waste glasses with variations in composition and crystallization: Implications for intermediate order in the glass network 拉曼光谱，结构单元和核废料玻璃的组成和结晶变化的耐久性:对玻璃网络中间秩序的影响

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208239634

S. Raman

{"title":"Raman spectra, structural units and durability of nuclear waste glasses with variations in composition and crystallization: Implications for intermediate order in the glass network","authors":"S. Raman","doi":"10.1080/01418610208239634","DOIUrl":"https://doi.org/10.1080/01418610208239634","url":null,"abstract":"Abstract The Raman spectra of nuclear waste glasses are composed of large variations in half-width and intensity for the commonly observed bridging (Q0) and non-bridging (Q1 to Q4) bands in silicate structures. With increase in waste concentration in a boroaluminosilicate melt, the bands of quenched glasses are distinctly localized with half-width and intensity indicative of increase in atomic order. Since the nuclear waste glasses contain disparate components, and since the bands depart from the typical random network, a systematic study for the origin of these bands as a function of composition and crystallization was undertaken. From a comparative study of Raman spectra of boroaluminosilicate glasses containing Na2O-ZrO2, Na2O-MgO, MgO-Na2O-ZrO2, Na2O-CaO-ZrO2, Na2O-CaO, and Na2O-MgO-CaF2 component sets and orthosilicate crystals of zircon and forsterite, intermediate order is inferred. An edge-sharing polyhedral structural unit is proposed to account for narrow bandwidth and high intensity for Q2 antisymmetric modes, and decreased leaching of sodium with ZrO2 concentration in glass. The intense Q4 band in nuclear waste glass is similar to the intertetrahedral antisymmetric modes in forsterite. The Raman spectra of zircon contains intratetrahedral quartz-like peaks and intertetrahedral non-bridging silicate peaks. The quartz-like peaks nearly vanish in the background of forsterite spectrum. This difference between the Raman spectra of the two orthosilicate crystals presumably results from their biaxial and uniaxial effects on polarizability ellipsoids. The results also reveal formation of 604, 956 and 961 cm−1 defect bands with composition and crystallization.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123347554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Mechanisms of brittle intergranular fracture in Al-Li alloys and comparison with other alloys Al-Li合金脆性晶间断裂机理及与其它合金的比较

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240447

S. Lynch, B. C. Muddle, T. Pasang

{"title":"Mechanisms of brittle intergranular fracture in Al-Li alloys and comparison with other alloys","authors":"S. Lynch, B. C. Muddle, T. Pasang","doi":"10.1080/01418610208240447","DOIUrl":"https://doi.org/10.1080/01418610208240447","url":null,"abstract":"Abstract Evidence that brittle intergranular fracture in Al-Li alloys is associated with segregation of lithium, and maybe the formation of two-dimensional grain-boundary phases, is briefly reviewed. Particular attention is drawn to similarities between embrittlement of Al-Li alloys and segregation-induced embrittlement in other materials such as steels. High-resolution fractographic studies of Al-Li alloys to elucidate the atomic mechanisms of brittle intergranular fracture are then described. Brittle intergranular fracture surfaces were often featureless when examined by scanning electron microscopy, but transmission electron microscopy of replicas often revealed very shallow dimples, indicating that crack growth occurred by a very localized microvoid-coalescence process. The observations are explained in terms of decreased cohesion across grain boundaries due to lithium enrichment and grain-boundary structural changes. Low cohesion may facilitate void nucleation by decohesion (in the absence of grain-boundary precipitates in very underaged alloys) and may promote void growth by facilitating the emission of dislocations from crack tips. The applicability of the proposed mechanism to brittle intergranular fracture in other materials is also briefly discussed.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133120646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 31

An approach to dry friction and wear for small volumes 小体积干摩擦和磨损的一种方法

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240446

W. Gerberich, N. Tymiak, D. Kramer, A. Daugela, J. Jungk, M. Li

{"title":"An approach to dry friction and wear for small volumes","authors":"W. Gerberich, N. Tymiak, D. Kramer, A. Daugela, J. Jungk, M. Li","doi":"10.1080/01418610208240446","DOIUrl":"https://doi.org/10.1080/01418610208240446","url":null,"abstract":"Abstract Fracture and contact mechanics can synergistically contribute to the fundamental understanding essential to scaling of small volumes. Consider two levels of scale in terms of contact area: (i) light wear of tribological contacts at the nanometre level; (ii) delamination of hard protective coatings or ductile metal films at the micrometre level. We first briefly address two phenomena—one showing that oxide film fracture is responsible for yield excursions during nanoindentation and the other showing that analysis of acoustic events can sort out some of the discontinuous events of yield and fracture on the nanometre scale. These concern mostly the fracture process concomitant with a localized plasticity event. However, they do not address the fundamental aspects of what controls the size of the yield event or what controls the size of a localized fracture event, for example delamination. We propose that one way of understanding these two levels of scale and their interconnectivity is through a volume-surface area concept. At present, we show two levels of understanding for contacts to single-crystal surfaces and how these provide insight and potentially quantification of light wear contact.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"92 3-4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132364784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Dangerous defect distributions in snow 雪中的危险缺陷分布

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240434

G. Michot, H. Kirchner

引用次数: 2

Fatigue crack nucleation of pure copper single crystals in 1M NaNO2 aqueous solution 纯铜单晶在1M NaNO2水溶液中的疲劳裂纹形核

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240443

H. Miyamoto, T. Mimaki, S. Hashimoto

{"title":"Fatigue crack nucleation of pure copper single crystals in 1M NaNO2 aqueous solution","authors":"H. Miyamoto, T. Mimaki, S. Hashimoto","doi":"10.1080/01418610208240443","DOIUrl":"https://doi.org/10.1080/01418610208240443","url":null,"abstract":"Abstract The cyclic deformation of pure copper single crystals has been investigated to examine the corrosion fatigue crack nucleation in an oxide-film-forming NaNO2 solution. The corrosion fatigue tests were performed in a wide range of plastic strain amplitudes under a rest potential and a passive potential. It was found that the number of cycles to failure was reduced under the passive potentials, and crystallographic features of crack nucleation are clearly different between the tests conducted under a rest potential and a passive potential. Under the rest potential where oxide films were not formed, crack nucleation was observed at persistent slip bands (PSBs) and appeared identical with that in air. Under the passive potential, however, a number of cracks were nucleated by cleavage failure at PSBs, and the planes of the cracks were parallel to {110} planes. Crystallographic features of the cracks were essentially identical in nature to stress corrosion cracking (SCC) under monotonic deformation of copper single crystals. Variations in anodic current demonstrated that emerging PSBs caused film rupture and local anodic dissolution. The results confirmed that PSBs assisted the nucleation of SCC and thus reduction in corrosion fatigue resistance in a film-forming environment.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128194277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Models to describe brittle and ductile fracture in ferritic steels 描述铁素体钢脆性和韧性断裂的模型

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240454

G. Smith, A. Crocker, R. Mosković, P. Flewitt

{"title":"Models to describe brittle and ductile fracture in ferritic steels","authors":"G. Smith, A. Crocker, R. Mosković, P. Flewitt","doi":"10.1080/01418610208240454","DOIUrl":"https://doi.org/10.1080/01418610208240454","url":null,"abstract":"Abstract Theoretical models have been developed to describe the various fracture mechanisms that occur in polycrystalline α-iron and ferritic steels over a range of temperature which spans the ductile-to-brittle transition. At low temperatures, the models enable the proportions of transgranular cleavage and intergranular brittle failure to be explored for different ratios of the fracture energies for the two mechanisms. This allows, for example, the effect of embrittlement arising from grain-boundary segregation of minor alloying and impurity elements to be investigated. In addition the effect of texture on the predictions obtained has been considered and the results are presented. At higher temperatures, the models have been developed to accommodate ductile fracture. They have also been extended to consider the influence of prior creep cavitational damage at grain boundaries on both low- and high-temperature fracture processes and the corresponding fracture energies. The effect of this prior damage on subsequent ductile failure is explored. The predictions show that, if fewer than about 20% of the grain boundaries are fully cavitated, then there is little change in either the mechanism of the fracture process or the fracture strength of the material. These predictions are compared with measured upper-shelf fracture toughness values obtained for a Cr-Mo-V ferritic steel containing proportions of up to about 40% of prior creep damage.","PeriodicalId":114492,"journal":{"name":"Philosophical Magazine A","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128415593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 19

Transmission electron microscopy observations of deformation and fracture in nanolaminated Cu-Ni thin films 纳米层化Cu-Ni薄膜变形与断裂的透射电镜观察

Philosophical Magazine A Pub Date : 2002-11-01 DOI: 10.1080/01418610208240448

D. Kramer, T. Foecke

引用次数: 30