A wide range of welding and surface treatment processes involve the use of a heat source which is moving at a constant speed over the component. The numerical simulation of such processes implies a transient analysis ...A wide range of welding and surface treatment processes involve the use of a heat source which is moving at a constant speed over the component. The numerical simulation of such processes implies a transient analysis using a very refined mesh in order to follow properly the path of the heat source. The 3D-mesh size can be very large if one consider the welds length or the heat-treated surface size in industrial components. To reduce the computational time to acceptable values, several techniques have been investigated. The first type is to use analytical methods such as Rosenthal equations. The second type of solutions consists in performing a transient analysis using adaptive meshing. But, for a large proportion of the involved processes, practical experience demonstrates the existence of quasi steady state conditions over the major part of the heat source path. Numerical algorithms have therefore been developed to directly compute the steady temperature, metallurgical phase proportion and stress distributions. This paper gives a general overview of the different numerical methods used to simulate welding and surface treatment processes with a special emphasis on the steady state calculation. The benefits and limitations of each of them are discussed and applications are presented.展开更多
The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide...The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide （CTAB） were studied by using various techniques such as surface tension, conductivity, steady-state fluorescence and dynamic light scattering. Surface tension measurements were used to determine the critical micelle concentration （CMC） and thereby the free energy of micellization （AGmic）, free energy of adsorption （AG^ds）, surface excess concentration （F） and minimum area per molecule （A）. Conductivity measurements were used to determine the critical micelle concentration （CMC）, critical aggregation concentration （CAC）, polymer saturation point （PSP）, degree of ionization （tr） and counter ion binding （l]）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants. The ratio of the first and third vibronic peaks （11/Is） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions. Aggregation number （N）, number of binding sites （n） and free energy of binding （AGb） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.展开更多
文摘A wide range of welding and surface treatment processes involve the use of a heat source which is moving at a constant speed over the component. The numerical simulation of such processes implies a transient analysis using a very refined mesh in order to follow properly the path of the heat source. The 3D-mesh size can be very large if one consider the welds length or the heat-treated surface size in industrial components. To reduce the computational time to acceptable values, several techniques have been investigated. The first type is to use analytical methods such as Rosenthal equations. The second type of solutions consists in performing a transient analysis using adaptive meshing. But, for a large proportion of the involved processes, practical experience demonstrates the existence of quasi steady state conditions over the major part of the heat source path. Numerical algorithms have therefore been developed to directly compute the steady temperature, metallurgical phase proportion and stress distributions. This paper gives a general overview of the different numerical methods used to simulate welding and surface treatment processes with a special emphasis on the steady state calculation. The benefits and limitations of each of them are discussed and applications are presented.
基金financially supported by Pakistan Science foundation(PSF)and Higher Education Commission(HEC) Pakistan
文摘The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide （CTAB） were studied by using various techniques such as surface tension, conductivity, steady-state fluorescence and dynamic light scattering. Surface tension measurements were used to determine the critical micelle concentration （CMC） and thereby the free energy of micellization （AGmic）, free energy of adsorption （AG^ds）, surface excess concentration （F） and minimum area per molecule （A）. Conductivity measurements were used to determine the critical micelle concentration （CMC）, critical aggregation concentration （CAC）, polymer saturation point （PSP）, degree of ionization （tr） and counter ion binding （l]）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants. The ratio of the first and third vibronic peaks （11/Is） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions. Aggregation number （N）, number of binding sites （n） and free energy of binding （AGb） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.
