Stress intensity factors for multiple edge cracks in rotating hollow discs

The calculation of stress intensity factors for one to four equal length, equally spaced radial edge cracks at the inner and outer surfaces of a rotating hollow circular disc is presented. The technique used for the solutions is the modified mapping-collocation method. Data are presented for two wall ratios.

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Résumé On présente un calcul des facteurs d'intensité de contrainte dans le cas de une à quatre fissures radiales d'égales longueurs et également équidistantes situées en bordure des surfaces internes et externes d'un disque cylindrique creux en rotation. La technique utilisée pour les solutions consiste à recourir à une méthode modifiée de collocation (MMC). Les données sont fournies dans le cas de deux rapports de parois.

     

Finite element analysis of rotating laminated composite annular discs

A computationally efficient finite element model that can provide accurate numerical solutions to the problem of rotating laminated composite annular discs is presented. Numerical results showing the effects of composite material properties and laminate designs on the stress field and deformed shape of the disc are also presented and discussed.     

超高分子量聚乙烯的性能、改性及应用

本文介绍了超高分子量聚乙烯的性能、改性及应用情况 ,并对其生产消费情况进行了分析     

Boundary layers on rotating cones,discs and axisymmetric surfaces with a concentrated heat source

Summary A concentrated heat source is situated at the tip of an otherwise adiabatic rotating cone. Due to centrifugal forces, velocity and thermal boundary layers spread on the surface. After a similarity transform, the governing equations reduce to set of nonlinear, ordinary differential equations which are then integrated numerically. The related cases of rotating discs and other axisymmetric surfaces are considered.     

高阻尼设计反应谱阻尼修正系数的评估

针对目前提出的多种阻尼修正系数计算公式,选取了120条II类场地强震记录建立了10%、20%、30%三种不同阻尼比的高阻尼反应谱,通过比较精确谱和近似谱对5种典型计算公式的适用性进行分析。鉴于位移谱和加速度谱之间的转换是建立在拟谱关系上,且这种关系仅在结构阻尼较小以及忽略正余弦差异时才成立,因此对适用于建立高阻尼加速度谱和位移谱的阻尼修正系数计算公式分别进行了评价。通过分析可知,对II类场地而言,LinChang和中国建筑抗震设计规范建议的阻尼修正系数计算公式分别在估计高阻尼位移谱和加速度谱时有较好的适用性。     

Property modification of polyethylene tapes by acetylene-sensitized gamma irradiation

Gamma-irradiation techniques for improving the creep performance of polyethylene tapes (draw ratio 6.5) have been investigated. With acetylene present during irradiation, the optimum dose required for maximum suppression of yielding under tensile stress coupled with minimum embrittlement was found to be 5–10 kGy. This is one-tenth that required for irradiation in vacuum. Creep performance was also improved at 100 °C. Creep experiments at higher loads have shown that the optimum acetylene-sensitized treatment is more effective in reducing creep rate than the optimum vacuum-irradiation treatment.     

Development of MMC Gamma Detectors for Nuclear Analysis

Non-destructive assay (NDA) of nuclear materials would benefit from gamma detectors with improved energy resolution in cases where line overlap in current Ge detectors limits NDA accuracy. We are developing metallic magnetic calorimeter gamma-detectors for this purpose by electroplating \(\sim \) 150  \(\upmu \) m thick Au absorbers into microfabricated molds on top of Au:Er sensors. Initial tests under non-optimized conditions show an energy resolution of \(\sim \) 200 eV FWHM at 60 keV. Monte Carlo simulations illustrate that this resolution is starting to be sufficient for direct detection of \(^{242}\) Pu in plutonium separated from spent nuclear fuel.     

A conceptual framework for interpretation of MMC fatigue

A previously developed conceptual framework for interpretation of fatigue of polymer matrix composites (PMCs) is revisited for the purpose of the interpretation of fatigue in metal matrix composites (MMCs). With appropriate modifications, the basic features in the mechanisms based fatigue life diagrams of PMCs are found to hold for MMCs as well. Fatigue data for different MMC systems are examined with the interpretative framework and some observed trends are clarified. Approaches to fatigue life modeling are discussed for the different regions of behavior interpreted by the fatigue life diagram concept.     

Crack identification in rotating shafts by coupled response measurements

In this paper a new method is applied in rotating cracked shafts to identify the depth and the location of a transverse surface crack. A local compliance matrix of different degrees of freedom is used to model the transverse crack in a shaft of circular cross section, based on available expressions of the stress intensity factors and the associated expressions for the strain energy release rates. It is known that when a crack exists in a structure, such as a beam, then the excitation in one-direction causes coupled vibrations in other directions. This property is used here to identify the crack. The shaft is modeled as a rotating Timoshenko beam including the gyroscopic effect and the axial vibration due to coupling. The method used here is based on the measurements of the axial vibration response due to different excitation frequencies and shaft revolutions. The figures presented are used to identify the crack.