In this work, the stability of a flexible thin cylindrical workpiece in turning is analyzed. A process model is derived based on a finite element representation of the workpiece flexibility and a nonlinear cutting for...In this work, the stability of a flexible thin cylindrical workpiece in turning is analyzed. A process model is derived based on a finite element representation of the workpiece flexibility and a nonlinear cutting force law. Repeated cutting of the same surface due to overlapping cuts is modeled with the help of a time delay. The stability of the so obtained system of periodic delay differential equations is then determined using an approximation as a time-discrete system and Floquet theory. The time-discrete system is obtained using the semi-discretization method. The method is implemented to analyze the stability of two different workpiece models of different thicknesses for different tool positions with respect to the jaw end. It is shown that the stability chart depends on the tool position as well as on the thickness.展开更多
Barefoot slips contribute to over 37% of recurrent fall-related injuries across all age groups.To study slip risk across a wide range of flooring conditions,slip meters with barefoot surrogates(i.e.,sensors,as per AST...Barefoot slips contribute to over 37% of recurrent fall-related injuries across all age groups.To study slip risk across a wide range of flooring conditions,slip meters with barefoot surrogates(i.e.,sensors,as per ASTM standard nomenclature)such as animal skins and rubbers have been used to date,which exhibit biomechanical and frictional properties widely different from the barefoot human skin.Development of a surrogate which can accurately simulate the human heel skin properties would be immensely beneficial for realistic assessment of barefoot slipping risk.A novel surrogate was developed using 3D scanning and printing,and biomimetics,which precisely simulates the biomechanical and frictional properties of the barefoot human heel skin.Mechanical slip testing was conducted with this surrogate on three common bathroom floorings and with six different contaminants.Coefficient of Friction(COF)results similar to human slipping experiments,high repeatability and reproducibility across wet and oily flooring conditions,were confirmed through experiments with the developed heel skin surrogate.The heel skin surrogate would be an indispensable model for accurate estimation of barefoot risk against slips and falls in bathrooms,bathtubs,and swimming pools.展开更多
基金partially done while Arnab Chanda visited the University of Stuttgart from September 2010 to May 2011 under DAAD-IIT Sandwich Master Program funded by a DAAD M.Sc.ScholarshipThe doctoral research of Achim Fischer was funded since 2010 by the Baden-Wrttemberg Stiftung and the Stuttgart Cluster of Excellence Simtech
文摘In this work, the stability of a flexible thin cylindrical workpiece in turning is analyzed. A process model is derived based on a finite element representation of the workpiece flexibility and a nonlinear cutting force law. Repeated cutting of the same surface due to overlapping cuts is modeled with the help of a time delay. The stability of the so obtained system of periodic delay differential equations is then determined using an approximation as a time-discrete system and Floquet theory. The time-discrete system is obtained using the semi-discretization method. The method is implemented to analyze the stability of two different workpiece models of different thicknesses for different tool positions with respect to the jaw end. It is shown that the stability chart depends on the tool position as well as on the thickness.
文摘Barefoot slips contribute to over 37% of recurrent fall-related injuries across all age groups.To study slip risk across a wide range of flooring conditions,slip meters with barefoot surrogates(i.e.,sensors,as per ASTM standard nomenclature)such as animal skins and rubbers have been used to date,which exhibit biomechanical and frictional properties widely different from the barefoot human skin.Development of a surrogate which can accurately simulate the human heel skin properties would be immensely beneficial for realistic assessment of barefoot slipping risk.A novel surrogate was developed using 3D scanning and printing,and biomimetics,which precisely simulates the biomechanical and frictional properties of the barefoot human heel skin.Mechanical slip testing was conducted with this surrogate on three common bathroom floorings and with six different contaminants.Coefficient of Friction(COF)results similar to human slipping experiments,high repeatability and reproducibility across wet and oily flooring conditions,were confirmed through experiments with the developed heel skin surrogate.The heel skin surrogate would be an indispensable model for accurate estimation of barefoot risk against slips and falls in bathrooms,bathtubs,and swimming pools.
