Technical Software Consulting

The stress increment directing inwards of the current subloading surface does not always lead to an elastic unloading process without a plastic strain increment. This fact must be taken account for the loading criterion in the elastic predictor step of the return-mapping projection. The exact formulation for the loading criterion in the elastic predictor step will be given for the initial and the extended subloading surface models.

The multiplicative elastoplastic constitutive equation is formulated based on the extended subloading surface model with the translation of the elastic-core. It is to be the only unconventional elastoplasticty model extended to the multiplicative hyperelastic-based plasticity model which is capable of describing finite deformation/rotation exactly.

Abstract After outlining the different requirements for tire models to be used in full vehicle simulations, a general tire interface to ADAMS will be presented. This interface consists of a library of different tire models and allows user-defined models, too. Special attention will be drawn to the determination of the Pacejka constants from standard tire measurements.

Some theoretical and experimental studies are presented on magnetostrictive anisotropy (stress induced anisotropy) in a long circular steel bar. An explicit analytical solution to the problem of uniform axial alternating current (ac) distribution in a cylindrical bar which retains magnetic and electrical anisotropy was established. By relating the stress level to the amount of magnetic anisotropy in the material, an electromagnetic stress model was then developed for cylindrical bars under uniaxial stress using the analytical solution. For the application of this model, experimental stress measurements on mild steel bars with different radii were conducted based on the alternating current potential difference (ACPD) technique. During the test, a form of alternating current field measurement (ACFM) instrumentation, known as the ACFM crack microgauge, was used to inject a uniform ac current into the steel bars and to measure the electrical field on the bar surface. The ACPD stress measurement results showed that the theoretical stress model could predict the stress values with the calibration of a magnetic anisotropic parameter.

The efficiencies with which chrysotile fibers in water are retained by polycarbonate (PC) and mixed cellulose ester (MCE) filters have been measured. The studies demonstrate that, for filtration of water samples, PC filters of 0.2 μm pore size or less and MCE filters of 0.22 μm porosity or less are satisfactory filters for determination of the concentrations of asbestos fibers of all lengths in water samples, but that the presence of surfactant may introduce a negative bias in the shorter fiber sizes. The results show that the observed fiber densities on 0.22 μm porosity MCE filters increase with plasma etching, and also exhibit a positive bias due to a variable degree of shrinkage which occurs during the filter collapsing procedure. In a second series of measurements, using a procedure similar to that used by the pharmaceutical industry for testing the retention of bacteria by membrane filters, it was found that all of the filters tested were capable of yielding reduction factors of better than approximately 107. However, for 0.22 μm porosity MCE filters, sporadic reduction factors as low as 102 occurred, and when surfactant was added to the water, these low reduction factors were observed consistently, and measurable proportions of the fibers up to approximately 2 μm long passed through the filters.

Two International Standards for measurement of asbestos in air by transmission electron microscopy (TEM) have been approved. A key feature of the ISO TEM methods is the ability, from a single examination, to derive fiber concentrations for comparison with all known legislated control limits, and to provide a coded description of the size and nature of each asbestos structure to assist in the interpretation of health effects. The direct-transfer TEM method for determination of asbestos in air (ISO 10312) was published as an International Standard in May 1995. Voting on an indirect-transfer TEM method (ISO 13794) has been completed, and the final draft has been submitted for publication. A method for determination of the concentration of inorganic fibers in air, based on scanning electron microscopy (SEM), has recently been submitted for voting as a Draft International Standard, currently designated as ISO/DIS 14966. A new working group, ISO/TC 146/SC 6/WG4, was formed in late 1996, to develop International Standards for sampling strategy for determination of asbestos and other mineral fibers in building atmospheres.