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In vivo deformability of human lumbar spine segments in pure centric tension measured during traction bath therapy

Kurutz M., Lovas A., Bene E.

Acta of Bioengineering and Biomechanics

2003

Vol. 5, nr 1

67-92

In vivo tensile deformability of human lumbar spine segments has been measured during the usual ,traction bath hydrotherapy of patients when the effect of muscles can be excluded, and the lumbar spine is subjected to pure centric tensile load. Elongations of segments LIII-IV, LIV-V and LV-SI have been measured by using a special computerised subaqueous ultrasound measuring method developed by the authors. Influence of biomechanical parameters, aging, sex, body weight and height, body mass index (BMI) has been established; moreover, time-dependence of deformability has also been measured. The aim of the experiments was double: partly to clear the tensile effect of the traction bath therapy, and partly obtain the in vivo numerical traction model of human lumbar motion segments. This report deals with in vivo tensile deformability of lumbar segments only. The biomechanical parameter analysis and the time-dependent numerical creep model of human lumbar spine segments will be reported in forthcoming papers.

Imperfection-sensitivity analysis by using classical and catastrophe theory methods

Kurutz M., Gáspár Z.

Computer Assisted Mechanics and Engineering Sciences

2001

Vol. 8, No. 4

567-577

Comparison of the classical methods and the tools of the catastrophe theory is presented through the imperfection-sensitivity analysis of the classical stable-symmetric bifurcation problem. Generally, classical global methods are related to a large interval, while catastrophe theory concerns the neighborhood of the critical point only, being a local method. Unfortunately, in most cases of practical problems, by using classical global methods, there can hardly be obtained analytical solutions for the multivalued imperfection-sensitivity functions and the associated highly folded imperfection-sensitivity surfaces. In this paper, an approximate solution based on the catastrophe theory is presented, in comparison with the exact solution obtained in graphical way. It will be shown that by considering the problem as an imperfect version (at a fixed imperfection) of a higher order catastrophe, a topologically good solution can be obtained in a considerably large, quasi in a nonlocal domain.