@article{SponagelAkbayBecker1985, author = {Sponagel, Stefan and Akbay, U. and Becker, E.}, title = {Instability of plane Couette flow of viscoelastic liquids}, series = {Journal of non-Newtonian fluid mechanics. 18 (1985), H. 2}, journal = {Journal of non-Newtonian fluid mechanics. 18 (1985), H. 2}, isbn = {0377-0257}, pages = {123 -- 141}, year = {1985}, language = {en} } @article{SponagelUngerSpies2003, author = {Sponagel, Stefan and Unger, J. and Spies, K. H.}, title = {H{\"a}rtebegriff im Zusammenhang mit Vernetzung, Bruchdehnung und Dauerfestigkeit eines Elastomers}, series = {Kautschuk Gummi Kunststoffe. 56 (2003), H. 11}, journal = {Kautschuk Gummi Kunststoffe. 56 (2003), H. 11}, isbn = {0948-3276}, pages = {608 -- 613}, year = {2003}, language = {de} } @article{BaroudWuBohneretal.2003, author = {Baroud, G. and Wu, J.Z. and Bohner, M and Sponagel, Stefan and Steffen, T.}, title = {How to determine the permeability for cement infiltration into osteoporotic cancellous bone}, series = {Medical Engineering \& Physics. 25 (2003), H. 4}, journal = {Medical Engineering \& Physics. 25 (2003), H. 4}, issn = {1350-4533}, pages = {283 -- 288}, year = {2003}, abstract = {Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm4/N.s) reduced to approximately 63\% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice.}, subject = {Osteoporose}, language = {en} } @article{SponagelSpaltofski1987, author = {Sponagel, Stefan and Spaltofski, R.}, title = {Hochmolekulare Zus{\"a}tze verbessern die Leichtlaufeigenschaft und die Tragf{\"a}higkeit von Schmierfilmen / Sponagel, S. ; Spaltofski, R.}, series = {Mineral{\"o}ltechnik. 32 (1987), H. 3}, journal = {Mineral{\"o}ltechnik. 32 (1987), H. 3}, isbn = {0341-1893}, pages = {28 S.}, year = {1987}, language = {de} } @article{SponagelSpaltofskiSteinhilper1988, author = {Sponagel, Stefan and Spaltofski, R. and Steinhilper, W.}, title = {Hochmolekulare Additive f{\"u}r die Gleitlagerschmierung. Spaltofski, R.; Sponagel, S.; Steinhilper, W.}, series = {Tribologie und Schmierungstechnik. 35 (1988), H. 5}, journal = {Tribologie und Schmierungstechnik. 35 (1988), H. 5}, isbn = {0036-6218}, pages = {236 -- 241}, year = {1988}, language = {de} } @article{SponagelBaroudFalketal.2004, author = {Sponagel, Stefan and Baroud, G. and Falk, R. and Crookshank, M.}, title = {Experimental and theoretical investigation of directional permeability of human vertebral cancellous bone for cement infiltration. G. Baroud, R. Falk, M. Crookshank, S. Sponagel, T. Steffen}, series = {Journal of Biomechanics. 37 (2004), H. 2}, journal = {Journal of Biomechanics. 37 (2004), H. 2}, isbn = {0021-9290}, pages = {189 -- 196}, year = {2004}, language = {en} } @article{StaatSponagelNguyen2010, author = {Staat, Manfred and Sponagel, Stefan and Nguyen, Nhu Huynh}, title = {Experiment and material model for soft tissue materials}, series = {Constitutive models for rubber VI : proceedings of the sixth European Conference on Constitutive Models for Rubber, Dresden, Germany, 7 - 10 September 2009 / eds. Gert Heinrich ...}, journal = {Constitutive models for rubber VI : proceedings of the sixth European Conference on Constitutive Models for Rubber, Dresden, Germany, 7 - 10 September 2009 / eds. Gert Heinrich ...}, publisher = {CRC Press}, address = {Boca Raton [u.a.]}, isbn = {978-0-415-56327-7}, pages = {465 -- 470}, year = {2010}, language = {en} } @article{SponagelMueller1983, author = {Sponagel, Stefan and M{\"u}ller, H.}, title = {Exakte instation{\"a}re L{\"o}sungen der Navier-Stokes-Gleichung. H. M{\"u}ller, S. Sponagel}, series = {Zeitschrift f{\"u}r angewandte Mathematik und Mechanik: ZAMM. 63 (1983)}, journal = {Zeitschrift f{\"u}r angewandte Mathematik und Mechanik: ZAMM. 63 (1983)}, isbn = {0044-2267}, pages = {T273 -- T275}, year = {1983}, language = {de} } @article{SponagelGroling1983, author = {Sponagel, Stefan and Groling, G.}, title = {Eine Bemerkung zum Beweis des \&\#960; Theorems. G. Groling, S. Sponagel}, series = {Zeitschrift f{\"u}r angewandte Mathematik und Mechanik: ZAMM. 63 (1983)}, journal = {Zeitschrift f{\"u}r angewandte Mathematik und Mechanik: ZAMM. 63 (1983)}, isbn = {0044-2267}, pages = {T258 -- T259}, year = {1983}, language = {de} } @article{SponagelLutz1990, author = {Sponagel, Stefan and Lutz, Th.}, title = {Ein Beitrag zur Bestimmung der Haertewerte von Elastomeren}, series = {Kautschuk Gummi Kunststoffe. 43 (1990), H. 10}, journal = {Kautschuk Gummi Kunststoffe. 43 (1990), H. 10}, isbn = {0022-9520}, pages = {861 -- 865}, year = {1990}, language = {de} }