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Open access

T. Domański and A. Bokota

Numerical Models of Hardening Phenomena of Tools Steel Base on the TTT and CCT Diagrams

In work the presented numerical models of tool steel hardening processes take into account thermal phenomena, phase transformations and mechanical phenomena. Numerical algorithm of thermal phenomena was based on the Finite Elements Methods in Galerkin formula of the heat transfer equations. In the model of phase transformations, in simulations heating process, isothermal or continuous heating (CHT) was applied, whereas in cooling process isothermal or continuous cooling (TTT, CCT) of the steel at issue. The phase fraction transformed (austenite) during heating and fractions of ferrite, pearlite or bainite are determined by Johnson-Mehl-Avrami formulas. The nescent fraction of martensite is determined by Koistinen and Marburger formula or modified Koistinen and Marburger formula. In the model of mechanical phenomena, apart from thermal, plastic and structural strain, also transformations plasticity was taken into account. The stress and strain fields are obtained using the solution of the Finite Elements Method of the equilibrium equation in rate form. The thermophysical constants occurring in constitutive relation depend on temperature and phase composite. For determination of plastic strain the Huber-Misses condition with isotropic strengthening was applied whereas for determination of transformation plasticity a modified Leblond model was used. In order to evaluate the quality and usefulness of the presented models a numerical analysis of temperature field, phase fraction, stress and strain associated hardening process of a fang lathe of cone shaped made of tool steel was carried out.

Open access

J.J. Domanski and T.J. Sheets

Abstract

Indirect contamination of tobacco by DDT, TDE, endrin, dieldrin, and toxaphene was investigated under field conditions. Levels of DDT + TDE in soil ranged from << 0.01 to 0.18 ppm, and those in cured leaves ranged from 0.11 to 1.69 ppm. The lower stalk position at the major test location generally had greater concentrations of DDT + TDE than the middle and upper positions, but distribution of these insecticides among leaf positions was variable for other locations. Residues of DDT in the bottom stalk position were positively correlated with those in the soil. Plant-bed soils did not appear to be a major source of DDT + TDE residues in cured tobacco. Residues of endrin and dieldrin were near or below the limit of detection (0.01 ppm) in soil and cured leaf. Residues of toxaphene ranged from << 0.1 to 4.7 ppm in soil and << 0.3 to 7.7 ppm on tobacco. Toxaphene residues in the bottom and top stalk positions were positively correlated with residues in soil. Contamination by toxaphene appeared to be attributable to uptake from soil and to movement of the insecticide as drift or vapour through the air.

Open access

T. Domański

Abstract

The resistance parameters of timber structures decrease with time. It depends on the type of load and timber classes. Strength reduction effects, referred to as creep-rupture effects, due to long term loading at high stress ratio levels are known for many materials. Timber materials are highly affected by this reduction in strength with duration of load. Characteristic values of load duration and load duration factors are calibrated by means of using probabilistic methods. Three damage accumulation models are considered, that is Gerhard [1] model, Barret, Foschi[2] and Foshi Yao [3] models. The reliability is estimated by means of using representative short- and long-term limit states. Time variant reliability aspects are taken into account using a simple representative limit state with time variant strength and simulation of whole life time load processes. The parameters in these models are fitted by the Maximum Likelihood Methods using the data relevant for Polish structural timber. Based on Polish snow data over 45 years from mountain zone in: Zakopane – Tatra, Świeradów – Karkonosze, Lesko – Bieszczady, the snow load process parameters have been estimated. The reliability is evaluated using representative short – and long –term limit states, load duration factor kmod is obtained using the probabilistic model.

Open access

J. J. Domanski, P. L. Haire and T.J. Sheets

Abstract

Average residue Ievels of DDT + TDE in flue-cured tobacco decreased from 6.1 ppm in 1970 to 0.85 ppm in 1972. DDT + TDE residues in Burley also dropped sharply from previous levels. In 1972 one sample from Kentucky contained 8.17 ppm; all other Burley samples were less than 0.25 ppm. DDT + TDE residues also declined in fire-cured and air-cured types; of these samples Tennessee dark air-cured tobacco contained the highest average residue (3.5 ppm of DDT + TDE). In 1972 over 90 % of the flue-cured samples were positive for toxaphene. Since each of our samples was a composite of tobacco from 10 farmers, we cannot conclude from this result that 90 % of the individual piles contained toxaphene. Significant amounts of toxaphene were found in other types also; for example, 50 % of the 1972 Burley samples had toxaphene concentrations greater than 0.5 ppm. Average endosulfan levels decreased between 1970 and 1972 in flue-cured and Burley tobaccos. However, in all of the dark air and dark fire-cured samples from Tennessee endosulfan residues exceeded 5 ppm. Average endrin residues were at or near the low detection limit in alI samples except fire-cured and dark air-cured tobacco from Tennessee; these averaged 0.26 and 0.17 ppm, respectively.

Open access

J. Domańska, A. Domański, T. Czachórski and J. Klamka

Abstract

This article presents the use of fluid flow approximation to model interactions between a set of TCP, UDP and XCP flows in the environment of IP routers using AQM (Active Queue Management) algorithms to control traffic congestion. In contrast to other works, independent UDP and TCP streams are considered and the model allows to start and end data transmissions in TCP, UDP and XCP streams at any time moment. It incorporates several Active Queue Management mechanisms: RED, NLRED, CHOKe.

Open access

W. Piekarska, M. Kubiak, Z. Saternus, S. Stano and T. Domański

Abstract

The work concerns the numerical modelling of coupled thermal and mechanical phenomena occurring in the laser beam welding process. Commercial Abaqus FEA engineering software is adopted to numerical computations in order to perform a comprehensive analysis of thermo-mechanical phenomena. Created in Fortran programming language additional numerical subroutines are implemented into Abaqus solver, used to describe the power intensity distribution of the movable laser beam heat source. Temperature dependent thermomechanical properties of X5CrNi18-10 steel are adopted in the numerical analysis of stress and strain states. Mathematical and numerical models are verified on the basis of a comparison between selected results of computer simulations and experimental studies on butt-welded joints.

Numerical simulations are presented for steel sheet with a thickness of 2 mm. Temperature distributions, the shape and size of melted zone as well as residual stress and deformations are presented for analyzed elements. Numerically determined deflections are compared with the measured deflection of welded joint.

Open access

Jarosław Domański, Wiesław Kotarba and Tadeusz Krupa

Abstract

This article makes a contribution to the ongoing paradigmatic debate concerning management science, aiming to define more precisely its constructs. At present, within this field there is a lack of definition, of a universally accepted way of seeing reality, which results in a clear deficit in pedagogical identity. Our proposal for a new paradigm is based on three descriptors or constructs (prisms): organization, knowledge, and safety (OKS); in this model, the leading role is played by human.

The “organization” prism, in the classic sense, concerns the organization with an emphasis on the implementation of the personalistic vision of human. The “knowledge” prism includes the technical, social, and economic aspects of the collection, processing, and use of knowledge. The “security” prism is an aspect related to the identification and prevention of crises and threats to the functioning of the OKS triad as a whole.