Fatigue Tests of Metals at Ultrasonic Frequency

Dissipation Measurements during Ultrasonic Fatigue Tests

The aim of this paper is to analyse the dissipation observed during dynamic fatigue loading at low stress range and high number of cycles. Infrared thermographic techniques were developed to estimate the mean dissipation per cycle. Results derived from tests performed at high loading frequency on pure copper specimens showed a drift of dissipative regimes incompatible with concepts of fatigue l...

the washback effect of discretepoint vs. integrative tests on the retention of content in knowledge tests

در این پایان نامه تاثیر دو نوع تست جزیی نگر و کلی نگر بر به یادسپاری محتوا ارزیابی شده که نتایج نشان دهندهکارایی تستهای کلی نگر بیشتر از سایر آزمونها است

Attenuation of ultrasonic waves in rolled metals.

Scattering of ultrasonic waves in polycrystals with texture is studied in this article. The attenuations of the three wave modes are determined as a function of dimensionless frequency and propagation direction, respectively, for given orientation distribution coefficients (ODCs). The calculation is done in the case of a statistically orthorhombic sample made up of cubic crystallites. The wave ...

Cyclic plasticity and fatigue of metals

Atomistic mechanisms of fatigue in nanocrystalline metals.

We investigate the mechanisms of fatigue behavior in nanocrystalline metals at the atomic scale using empirical force laws and molecular level simulations. A combination of molecular statics and molecular dynamics was used to deal with the time scale limitations of molecular dynamics. We show that the main atomistic mechanism of fatigue crack propagation in these materials is the formation of n...