Strain-Cycling Fatigue Behavior of Ten Structural Metals Tested in Liquid Helium, Liquid Nitrogen, and Ambient Air

2009 ◽  
pp. 378-378-19 ◽  
Author(s):  
AJ Nachtigall
Keyword(s):  
Liquid Helium ◽  
Liquid Nitrogen ◽  
Fatigue Behavior ◽  
Ambient Air ◽  
Structural Metals ◽  
Strain Cycling

Water accumulation as a function of temperature on specimens in an electron microscope cold stage

1986 ◽  
Vol 44 ◽  
pp. 114-115 ◽  
Author(s):  
M.K. Lamvik ◽  
D.A. Kopf ◽  
S.D. Davilla ◽  
J.D. Robertson
Keyword(s):  
Electron Microscope ◽  
Mass Loss ◽  
Liquid Helium ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Cold Stage ◽  
Water Accumulation ◽  
Better Than

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

Surface Engineering of Polycrystalline Silicon Microelectromechanical Systems for Fatigue Resistance

2002 ◽  
Vol 729 ◽  
Author(s):  
C.L. Muhlstein ◽  
W.R. Ashurst ◽  
E.A. Stach ◽  
R. aboudian ◽  
R.O. Ritchie
Keyword(s):  
Stress Corrosion ◽  
Fatigue Resistance ◽  
Reaction Layer ◽  
Polycrystalline Silicon ◽  
Microelectromechanical Systems ◽  
Fatigue Behavior ◽  
Ambient Air ◽  
Degradation Process ◽  
Native Oxide ◽  
Premature Failure

AbstractRecent research has established that for silicon structural films used in microelectromechanical systems (MEMS), the susceptibility to premature failure under cyclic fatigue loading originates from a degradation process that is confined to the surface oxide. In ambient air environments, a sequential, stress-assisted oxidation and stress-corrosion cracking process can occur within the native oxide on polycrystalline silicon (referred to as reaction-layer fatigue); for the structural films of micron-scale dimensions, such incipient cracking in the oxide can lead to catastrophic failure of the entire silicon component. Since the degradation process is intimately linked to the thin reaction layer on the silicon, modification of this surface and the access of the environment to it can dramatically alter the fatigue resistance of the material. The purpose of this paper is to evaluate the efficacy of modifying the fatigue behavior of polycrystalline silicon with alkene-based monolayers. Specifically, 2-μm thick polysilicon fatigue structures were coated with a monolayer film based on 1-octadecene and cyclically tested to failure in laboratory air. By applying the coating, the formation of the native oxide was prevented. Compared to the fatigue behavior of untreated polysilicon, the lives of the coated samples ranged from 105 to >1010 cycles at stress amplitudes greater than ∼90% of the ultimate strength of the film. The dramatic improvement in fatigue resistance was attributed to the monolayer inhibiting the formation of the native oxide and stress corrosion of the surface. It is concluded that the surprising susceptibility of thin structural silicon films to premature fatigue failure can be inhibited by such monolayer coatings.

Epr of Mn2+ in Ni(CH3COO)2 4H2O and K2 Ni(SO4)2 6H2O

1980 ◽  
Vol 3 ◽  
Author(s):  
Sushil K. Misra ◽  
M. Jalochowski
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Single Crystals ◽  
Liquid Helium ◽  
Liquid Nitrogen ◽  
Spin Hamiltonian ◽  
Paramagnetic Resonance ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

ABSTRACTThe technique of electron paramagnetic resonance has been applied to study the magnetic properties of nickel acetate and nickel potassium tutton salt single crystals, using Mn2+ ion as probe. From the values of spin Hamiltonian parameters and linewidths at room, liquid nitrogen and liquid helium temperatures it is concluded that these crystals do not become magnetically ordered as the temperature is lowered to 3.2K, and thus the transition temperature, below which the crystal would order either ferromagnetically, or antiferromagnetically, for these crystals, should be below 3.2K.

Fatigue Behavior of Hybrid Ceramic Ball Bearings in Liquid Nitrogen

2003 ◽  
Vol 46 (4) ◽  
pp. 494-498 ◽  
Author(s):  
L. Gu ◽  
L. Wang ◽  
Y. Jin ◽  
X. Li
Keyword(s):  
Liquid Nitrogen ◽  
Fatigue Behavior ◽  
Ball Bearings ◽  
Ceramic Ball ◽  
Hybrid Ceramic

Fatigue in Ti-6Al-4V at Very High Cycles

2007 ◽  
Vol 561-565 ◽  
pp. 259-262 ◽  
Author(s):  
X.J. Cao ◽  
M.R. Sriraman ◽  
Qing Yuan Wang
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Weight Ratio ◽  
High Strength ◽  
Ambient Air ◽  
Ti Alloys ◽  
Structural Applications ◽  
Ultrasonic Fatigue ◽  
Reversed Loading ◽  
Very High

The importance of determining and understanding the very high cycle fatigue behaviors of materials has gained strength in recent years. Ti-alloys, in view of their high strength-to-weight ratio, have a range of structural applications. Of these, Ti-6Al-4V, belonging to the alpha-beta type is the most widely used. The present paper deals with investigations on the fatigue behavior of TC4, the Chinese equivalent to Ti-6Al-4V, up to very high cycles. Fatigue testing was carried out on a piezoelectric ultrasonic fatigue machine operating at 20 kHz frequency. Hourglass shaped resonant specimens were tested in ambient air at room temperature under completely reversed loading conditions (R = -1). Failure in the alloy was seen to occur right up to the gigacycle regime, with the fractures being found to initiate from the surface unlike in steels. The fracture surfaces exhibit brittle characteristics containing river patterns and cleavage facets, as well as striations.

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