The influence of explosive-driven shock prestraining at 35 GPa and of high deformation on the structure/property behavior of 316 L austenitic stainless steel

The mechanical responses of high-explosive (HE)-driven “Taylor-Wave” shock prestrained, 20 pct quasistatically uniaxially compressed, and 32 pct cross-rolled 316 L austenitic stainless steel (SS) samples were investigated in compression and tension at room temperature. The results of the compression and tension tests were compared to the deformation results of the annealed microstructure at a strain rate of 10⁻³ s⁻¹. The mechanical behavior of the 316 L SS following explosive shock prestraining exhibits a factor of 2 increase in yield stress over that observed for the annealed material. A significant reduction in ductility due to the Taylor-wave shock prestraining of the 316 L SS was also observed in tension. The microstructure and substructure evolution of the shock-prestrained 316 L SS samples were investigated using optical metallography and transmission electron microscopy (TEM). Microstructural analyses revealed a high density of deformation twins following Taylor-wave shock prestraining and cross-rolling to 32 pct strain. These microstructures were compared to those of the 20 pct quasi-statically uniaxially prestrained 316 L SS. The current experimental results were found to agree with previous literature results on SS samples shock-prestrained utilizing “square-topped” and explosive Taylor-wave shock-pulse loading.     

Analytical prediction of contact stiffness and friction damping in bolted connection

This paper presents an analytical method to predict contact stiffness and friction damping in bolted connections. Despite its importance in machine design, analytical prediction of the contact parameters has not been realized because of difficulty in time-history nonlinear analysis of sticking/sliding contact. In this study, a torsional contact model around a connecting bolt is developed. Linear phenomena are extracted and solved by FEM analysis, and then linear combination of the FEM results is calculated iteratively to search sticking/sliding zones in torque equilibrium. Proposed model is experimentally validated, and it will lead to fully analytical modelling of practical machines.     

A suitable model of microbial survival curves for beer pasteurization

Published isothermal inactivation data indicated that beer can undergo under- or over-processing depending on the target log reduction and the shape of the survival curve of a microorganism if traditional first-order model is used. This was demonstrated for a mold, yeasts and lactic acid bacteria by use of a more flexible and convenient model than the first-order model, namely Weibull model. The parameters of the Weibull model can be reduced from two to one with a very a slight loss of goodness-of-fit. The validity of the proposed model should also be checked for mixed populations of microorganisms in beer and non-isothermal treatments for beer. Beer can be the first product to validate the proposed model in industrial base since it has been free from problems with pathogenic microorganisms. If the model provides the requirements then it can also be used in other food products. This will minimize the energy expenditure for pasteurization and provide minimal processing to achieve a better food quality.     

An Electronic Tone Ringer for the Telephone

To meet with the increasing demand for a replacement of the electromechanical ringer in telephone sets, a tone ringer has been developed to fulfill the requirements of pleasantness and detectability in a noisy environment. Paired comparison tests and word profile tests have been carried out on a number of tones. To generate the most preferable tone appearing economically feasible, circuits have been developed that are operated by the normal ringing current. A small size dynamic loudspeaker with ample efficiency and width of frequency range has been chosen as the transducer and properly mounted in a Contempra telephone set. Tests of total subjective loudness gave better results than those of electromechanical ringers. Investigations are continuing to determine user acceptance.     

A Theoretical Study on Nitrourea and its Tautomers

In the present study, nitrourea and its possible tautomers have been subjected to theoretical analysis by performing Hartree-Fock and also density functional theory (DFT) calculations. The optimized geometries, vibrational frequencies, and some thermodynamical values for the presently considered species have been obtained in their ground states.     

Efficiency of pulse pressure treatment for inactivation of <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Listeria innocua</Emphasis> in whole milk

Escherichia coli ATCC 11775 and Listeria innocua ATCC 33090 in whole milk were inactivated by single- and multi-pulsed (up to 10 pulses) high hydrostatic pressure (HHP) treatments. Both bacteria showed similar resistance to single- and multi-pulsed HHP. The efficiency of pulsed pressure treatment depends on the combination of holding time of each pulse and number of pulses. It was observed that multi-pulsed pressure treatment instead of traditional single-pulsed HHP could be used to pasteurize milk at a lower pressure level. Nevertheless, an optimization is necessary between the pulse holding time, number of pulses, and pressure levels to reach the desirable log-reduction of microorganisms compatible with industrial application. This study was partly presented in Joint 21st AIRAPT and 45th EHPRG International Conference on High Pressure Science and Technology held September 17–21, 2007 in Catania (Italy).