Investigation of high cycle and Very-High-Cycle Fatigue behaviors for a structural steel with smooth and notched specimens

The high cycle and Very-High-Cycle Fatigue (VHCF) properties of a structural steel with smooth and notched specimens were studied by employing a rotary bending machine with frequency of 52.5 Hz. For smooth specimens, VHCF failure did occur at fatigue cycles of 7.1 x 10(8) with the related S-N curve of stepwise tendency. Scanning Electron Microscopy (SEM) was used for the observations of the fracture surfaces It shows that for smooth specimens the crack origination is surface mode in the failure regime of less than 10(7) cycles While at VHCF regime, the material failed from the nonmetallic inclusion lies in the interior of material, leading to the formation of fisheye pattern. The dimensions of crack initiation region were measured and discussed with respect to the number of cycles to failure. The mechanism analysis by means of low temperature fracture technique shows that the nonmetallic inclusion in the interior of specimen tends to debond from surrounding matrix and form a crack. The crack propagates and results to the final failure. The stress intensity factor and fatigue strength were calculated to investigate the crack initiation properties. VHCF study on the notched specimens shows that the obtained S-N curve decreases continuously. SEM analysis reveals that multiple crack origins are dominant on specimen surface and that fatigue crack tends to initiate from the surface of the specimen. Based on the fatigue tests and observations, a model of crack initiation was used to describe the transition of fatigue initiation site from subsurface to surface for smooth and notched specimens. The model reveals the influences of load, grain size, inclusion size and surface notch on the crack initiation transition. (C) 2010 Elsevier Ltd. All rights reserved

~(40)Ar~(10+)激发半导体功能材料P-Si表面的激发光谱

报道了用ECR离子源的高电荷态离子~(40)Ar~(10+)入射到p型Si表面的实验研究,通过实验测量到的Si原子和Si~(2+)离子的200nm-1000nm光谱,研究了谱线产生的机理。实验结果表明:低速高电荷态离子与固体表面相互作用中,可有效地激发原子和离子的特征谱线,分析了这一现象和相互作用过程的发光机理。

A 10,000 year record of dune activity；dust storms；and severe drought in the central Great Plains

IEECAS SKLLQG

Measurement of Be-10 in air filters using BeF- ions from BaBeF4

IEECAS SKLLQG

Disentangling geomagnetic and precipitation signals in an 80-Kyr Chinese loess record of Be-10

IEECAS SKLLQG

Pollen record from red clay sequence in the central Loess Plateau between 8.10 and 2.60 Ma

IEECAS SKLLQG

串联分子泵获得10~(-9)Pa真空的实验研究

介绍了采用两级分子泵串联系统获得 10 - 9Pa真空度的实验研究。实验证明 ,通过串联一台分子泵 ,可以有效地提高系统对氢气的压缩比 ,显著提高系统的极限压强。

~(40)Ar~(10+)轰击Al和Si固体表面形成的200～1000nm光谱

报道了利用兰州重离子加速器国家实验室ECR离子源提供的高电荷态离子~(40)Ar~(10+)入射到Al和p型Si表面所产生的Al,Si,Ar原子的200～1000nm特征光谱的实验测量结果。结果表明,低速高电荷态离子与团体表面原子相互作用可有效地激发靶原子和靶离子的特征谱线,而且由于发射二次电子的无辐射退激与辐射光子退激过程的竞争,使得在p型Si表面上Ar原子的光谱强度总体大于在Al表面上的光谱强度。