Sprawozdanie z badań podczas próbnego obciążenia wiaduktu 0-1 przeprawy drogowej przez rzekę Wisłę w ciągu Północnej Obwodnicy Puław
Przedmiotem niniejszego opracowania jest obciążenie próbne wiaduktu 0-1 przeprawy drogowej przez rzekę Wisłę w ciągu Północnej Obwodnicy Puław. Opracowanie zawiera wyniki badań obiektu podczas próbnego obciążenia oraz analizę porównawczą i weryfikację wyników teoretycznych i wyników badań.
Towards Understanding of Mechanics of Hernia Managed by Synthetic Mesh in Laparoscopic Operation: A Single Case Study
In this paper a research towards understanding of mechanics of ventral hernia operated with the use of Physiomesh Open image in new window implant and SecureStrap Open image in new window staples is described. Experimental and numerical studies are conducted for that purpose. Experimental works cover uni-axial tension tests of the implant samples and of the implant-staples-tissue system. Also experiments on implant-staples-tissue models, representing operated hernia, subjected to impulse pressure loading are performed. Based on that, constitutive model of the mesh has been identified and failure load of the staples has been determined. In the experiments on the operated hernia systems subjected to pressure loading safe loading level has been determined and failure modes connected to higher pressure values have been observed. Finally, in the numerical simulations of the operated hernia model, built according to FEM rules, it has been proved that failures observed experimentally result from exceeding of the load bearing capacity of the staples considered in this study.
Sensitivity analysis based on non-intrusive regression-based polynomial chaos expansion for surgical mesh modelling
The modelling of a system containing implants used in ventral hernia repair and human tissue suffers from many uncertainties. Thus, a probabilistic approach is needed. The goal of this study is to define an efficient numerical method to solve non-linear biomechanical models supporting the surgeon in decisions about ventral hernia repair. The model parameters are subject to substantial variability owing to, e.g., abdominal wall parameter uncertainties. Moreover, the maximum junction force, the quantity of interest which is worthy of scrutiny due to hernia recurrences, is non-smooth. A non-intrusive regression-based polynomial chaos expansion method is employed. The choice of regression points is crucial in such methods, thus we study the influence of this choice on the quantity of interest, and look for an efficient strategy. For this purpose, several aspects are studied : (i) we study the quality of the quantity of interest, i.e. accuracy of the mean and standard deviation, (ii) we perform a global sensitivity analysis using Sobol sensitivity indices. The influence of uncertainties of the chosen variables is presented. This study leads to the definition of an efficient numerical simulation dedicated to our model of implant.
Surface sliding in human abdominal wall numerical models: Comparison of single-surface and multi-surface composites
Determining mechanical properties of abdominal soft tissues requires a coupled experimental-numerical study, but first an appropriate numerical model needs to be built. Precise modeling of human abdominal wall mechanics is difficult because of its complicated multi-layer composition and large variation between specimens. There are several approaches concerning simplification of numerical models, but it is unclear how far one could go to still maintain fairly good results. The study compares behaviour of two different shell models: a simpler one, consisting of a single composite shell incorporating all abdominal wall layers and a more complicated one, consisting of three respective muscle-fascia composites allowed to slide on one another, representing a more realistic abdominal wall behaviour. Both models were subjected to the same loading and boundary conditions in a series of different non-linear analyses, including implicit, explicit, static and dynamic variants. The study shows that the two tested models differ greatly in terms of the obtained displacements, thus the sliding mechanism of muscle-fascia layers should not be ignored. As a side task, several finite element types were tested for proficiency in this particular computation.
In machine industry, stresses are often calculated using simple linear FEM analysis. Occasional failures of elements designed in such a way require recomputation by means of more sophisticated methods, eg. including plasticity and non-linear effects. It usually leads to investigation of failure causes and improvement of an element in order to prevent its unwanted behavior in the future. The study presents the case where both linear and non-linear analyses show some load capacity reserve and do not justify failure occurring in reality. Some non-standard causes are pointed out, including residual stress of a leading role.