[{"publisher":"Wiley","date_updated":"2024-09-26T11:25:10Z","author":[{"full_name":"Hamdoun, Ayoub","id":"57708","last_name":"Hamdoun","first_name":"Ayoub"},{"id":"335","full_name":"Mahnken, Rolf","last_name":"Mahnken","first_name":"Rolf"}],"date_created":"2024-05-14T09:06:26Z","title":"Experimental investigations of uniaxial and biaxial cold stretching within PC‐films and bars using optical measurements","doi":"10.1002/pamm.202300114","publication_identifier":{"issn":["1617-7061","1617-7061"]},"publication_status":"published","year":"2024","citation":{"ama":"Hamdoun A, Mahnken R. Experimental investigations of uniaxial and biaxial cold stretching within PC‐films and bars using optical measurements. <i>PAMM</i>. Published online 2024. doi:<a href=\"https://doi.org/10.1002/pamm.202300114\">10.1002/pamm.202300114</a>","chicago":"Hamdoun, Ayoub, and Rolf Mahnken. “Experimental Investigations of Uniaxial and Biaxial Cold Stretching within PC‐films and Bars Using Optical Measurements.” <i>PAMM</i>, 2024. <a href=\"https://doi.org/10.1002/pamm.202300114\">https://doi.org/10.1002/pamm.202300114</a>.","ieee":"A. Hamdoun and R. Mahnken, “Experimental investigations of uniaxial and biaxial cold stretching within PC‐films and bars using optical measurements,” <i>PAMM</i>, 2024, doi: <a href=\"https://doi.org/10.1002/pamm.202300114\">10.1002/pamm.202300114</a>.","apa":"Hamdoun, A., &#38; Mahnken, R. (2024). Experimental investigations of uniaxial and biaxial cold stretching within PC‐films and bars using optical measurements. <i>PAMM</i>. <a href=\"https://doi.org/10.1002/pamm.202300114\">https://doi.org/10.1002/pamm.202300114</a>","bibtex":"@article{Hamdoun_Mahnken_2024, title={Experimental investigations of uniaxial and biaxial cold stretching within PC‐films and bars using optical measurements}, DOI={<a href=\"https://doi.org/10.1002/pamm.202300114\">10.1002/pamm.202300114</a>}, journal={PAMM}, publisher={Wiley}, author={Hamdoun, Ayoub and Mahnken, Rolf}, year={2024} }","mla":"Hamdoun, Ayoub, and Rolf Mahnken. “Experimental Investigations of Uniaxial and Biaxial Cold Stretching within PC‐films and Bars Using Optical Measurements.” <i>PAMM</i>, Wiley, 2024, doi:<a href=\"https://doi.org/10.1002/pamm.202300114\">10.1002/pamm.202300114</a>.","short":"A. Hamdoun, R. Mahnken, PAMM (2024)."},"_id":"54281","department":[{"_id":"9"},{"_id":"154"}],"user_id":"57708","language":[{"iso":"eng"}],"publication":"PAMM","type":"journal_article","abstract":[{"text":"<jats:title>Abstract</jats:title><jats:p>Polycarbonate (PC) is an amorphous polymer that is an extremely robust material with a high tenacity, and thus suitable for a lightweight construction with glass‐like transparency. Due to these advantageous properties, PC is often used in industry for example in medical devices, automotive headlamps, sporting equipment, electronics, and a variety of other products. PC is often subjected to uniaxial and biaxial loading conditions. Therefore, reliable material models have to take into account the various resulting experimental effects. For those reasons, we investigate PC specimens under uniaxial and biaxial loading by using different stretch rates and loading scenarios. In addition to that, we propose methods for optical measurement of local stretches to obtain the approximated local true stress. In future work, the displacement fields and the resulting reaction forces will be used for parameter identification of constitutive equations.</jats:p>","lang":"eng"}],"status":"public"},{"author":[{"last_name":"Hamdoun","id":"57708","full_name":"Hamdoun, Ayoub","first_name":"Ayoub"},{"first_name":"Rolf","last_name":"Mahnken","id":"335","full_name":"Mahnken, Rolf"}],"date_created":"2024-05-14T09:05:05Z","volume":299,"date_updated":"2024-09-26T11:25:29Z","publisher":"Elsevier BV","doi":"10.1016/j.polymer.2024.126981","title":"Uniaxial and biaxial experimental investigation of glassy polymers","publication_status":"published","publication_identifier":{"issn":["0032-3861"]},"quality_controlled":"1","citation":{"chicago":"Hamdoun, Ayoub, and Rolf Mahnken. “Uniaxial and Biaxial Experimental Investigation of Glassy Polymers.” <i>Polymer</i> 299 (2024). <a href=\"https://doi.org/10.1016/j.polymer.2024.126981\">https://doi.org/10.1016/j.polymer.2024.126981</a>.","ieee":"A. Hamdoun and R. Mahnken, “Uniaxial and biaxial experimental investigation of glassy polymers,” <i>Polymer</i>, vol. 299, Art. no. 126981, 2024, doi: <a href=\"https://doi.org/10.1016/j.polymer.2024.126981\">10.1016/j.polymer.2024.126981</a>.","ama":"Hamdoun A, Mahnken R. Uniaxial and biaxial experimental investigation of glassy polymers. <i>Polymer</i>. 2024;299. doi:<a href=\"https://doi.org/10.1016/j.polymer.2024.126981\">10.1016/j.polymer.2024.126981</a>","bibtex":"@article{Hamdoun_Mahnken_2024, title={Uniaxial and biaxial experimental investigation of glassy polymers}, volume={299}, DOI={<a href=\"https://doi.org/10.1016/j.polymer.2024.126981\">10.1016/j.polymer.2024.126981</a>}, number={126981}, journal={Polymer}, publisher={Elsevier BV}, author={Hamdoun, Ayoub and Mahnken, Rolf}, year={2024} }","short":"A. Hamdoun, R. Mahnken, Polymer 299 (2024).","mla":"Hamdoun, Ayoub, and Rolf Mahnken. “Uniaxial and Biaxial Experimental Investigation of Glassy Polymers.” <i>Polymer</i>, vol. 299, 126981, Elsevier BV, 2024, doi:<a href=\"https://doi.org/10.1016/j.polymer.2024.126981\">10.1016/j.polymer.2024.126981</a>.","apa":"Hamdoun, A., &#38; Mahnken, R. (2024). Uniaxial and biaxial experimental investigation of glassy polymers. <i>Polymer</i>, <i>299</i>, Article 126981. <a href=\"https://doi.org/10.1016/j.polymer.2024.126981\">https://doi.org/10.1016/j.polymer.2024.126981</a>"},"intvolume":"       299","year":"2024","user_id":"57708","department":[{"_id":"9"},{"_id":"154"},{"_id":"321"}],"_id":"54279","language":[{"iso":"eng"}],"article_number":"126981","type":"journal_article","publication":"Polymer","status":"public"},{"date_updated":"2024-09-26T11:25:44Z","volume":94,"author":[{"first_name":"Ayoub","full_name":"Hamdoun, Ayoub","id":"57708","last_name":"Hamdoun"},{"last_name":"Mahnken","full_name":"Mahnken, Rolf","id":"335","first_name":"Rolf"}],"doi":"10.1007/s00419-024-02570-0","publication_identifier":{"issn":["0939-1533","1432-0681"]},"publication_status":"published","intvolume":"        94","page":"1221-1242","citation":{"ama":"Hamdoun A, Mahnken R. A large deformation gradient theory for glassy polymers by means of micromorphic regularization. <i>Archive of Applied Mechanics</i>. 2024;94(5):1221-1242. doi:<a href=\"https://doi.org/10.1007/s00419-024-02570-0\">10.1007/s00419-024-02570-0</a>","ieee":"A. Hamdoun and R. Mahnken, “A large deformation gradient theory for glassy polymers by means of micromorphic regularization,” <i>Archive of Applied Mechanics</i>, vol. 94, no. 5, pp. 1221–1242, 2024, doi: <a href=\"https://doi.org/10.1007/s00419-024-02570-0\">10.1007/s00419-024-02570-0</a>.","chicago":"Hamdoun, Ayoub, and Rolf Mahnken. “A Large Deformation Gradient Theory for Glassy Polymers by Means of Micromorphic Regularization.” <i>Archive of Applied Mechanics</i> 94, no. 5 (2024): 1221–42. <a href=\"https://doi.org/10.1007/s00419-024-02570-0\">https://doi.org/10.1007/s00419-024-02570-0</a>.","mla":"Hamdoun, Ayoub, and Rolf Mahnken. “A Large Deformation Gradient Theory for Glassy Polymers by Means of Micromorphic Regularization.” <i>Archive of Applied Mechanics</i>, vol. 94, no. 5, Springer Science and Business Media LLC, 2024, pp. 1221–42, doi:<a href=\"https://doi.org/10.1007/s00419-024-02570-0\">10.1007/s00419-024-02570-0</a>.","short":"A. Hamdoun, R. Mahnken, Archive of Applied Mechanics 94 (2024) 1221–1242.","bibtex":"@article{Hamdoun_Mahnken_2024, title={A large deformation gradient theory for glassy polymers by means of micromorphic regularization}, volume={94}, DOI={<a href=\"https://doi.org/10.1007/s00419-024-02570-0\">10.1007/s00419-024-02570-0</a>}, number={5}, journal={Archive of Applied Mechanics}, publisher={Springer Science and Business Media LLC}, author={Hamdoun, Ayoub and Mahnken, Rolf}, year={2024}, pages={1221–1242} }","apa":"Hamdoun, A., &#38; Mahnken, R. (2024). A large deformation gradient theory for glassy polymers by means of micromorphic regularization. <i>Archive of Applied Mechanics</i>, <i>94</i>(5), 1221–1242. <a href=\"https://doi.org/10.1007/s00419-024-02570-0\">https://doi.org/10.1007/s00419-024-02570-0</a>"},"_id":"54280","department":[{"_id":"9"},{"_id":"154"},{"_id":"321"}],"user_id":"57708","type":"journal_article","status":"public","publisher":"Springer Science and Business Media LLC","date_created":"2024-05-14T09:05:40Z","title":"A large deformation gradient theory for glassy polymers by means of micromorphic regularization","quality_controlled":"1","issue":"5","year":"2024","language":[{"iso":"eng"}],"publication":"Archive of Applied Mechanics","abstract":[{"lang":"eng","text":"<jats:title>Abstract</jats:title><jats:p>Cold forming of polycarbonate films results in the formation of shear bands in the necking zone. The numerical results obtained from standard viscoplastic material models exhibit mesh size dependency, requiring mathematical regularization. For this purpose, we present in this work a large deformation gradient theory for a viscoplastic isotropic material model published before. We extend our model to a micromorphic model by introducing a new micromorphic variable as an additional degree of freedom along with its first gradient. This variable represents a microequivalent plastic strain. The relation between the macroequivalent plastic strain and the micromorphic variable is accomplished by a micromorphic coupling modulus. This coupling forces proximity between the macro- and microvariables, leading to the targeted regularization effect. The micromorphic model is implemented as a three-dimensional initial boundary value problem in an in-house finite element tool. The analysis is performed for both uniaxial and biaxial specimens. The provided numerical examples show the ability of our model to regularize shear bands within the specimens and address the issue of localization.</jats:p>"}]},{"abstract":[{"text":"<jats:title>Abstract</jats:title><jats:p>Stretching of polycarbonate films leads to the formation of shear bands in the necking zone [1]. Standard viscoplastic material models render mesh size dependent results, which requires a mathematical regularization. To this end, we present a finite strain gradient theory for a viscoplastic, isotropic material model where we extend the model presented in [2] to a micromorphic model by introducing a new micromorphic variable as an additional degree of freedom with its first gradient [3, 4]. The variable here has the meaning of a micro plastic strain, and is coupled with the macro plastic by a micro penalty term, forcing the macro‐plastic strain to be close to the micro‐plastic strain for the targeted shear band regularization effect. We have implemented the model equations as a three dimensional initial boundary value problem in an in house FE‐tool, to simulate different geometries with different thickness and to compare it the experimental tests. The analysis is performed for a uniaxial tensile geometry as well as for a biaxial tensile geometry. The numerical examples show the ability of the model to regularize the shear bands and solve the problem of localization.</jats:p>","lang":"eng"}],"status":"public","type":"journal_article","publication":"PAMM","language":[{"iso":"eng"}],"_id":"54282","user_id":"57708","year":"2023","citation":{"apa":"Hamdoun, A., &#38; Mahnken, R. (2023). A finite strain gradient theory for viscoplasticity by means of micromorphic regularization. <i>PAMM</i>, <i>22</i>(1). <a href=\"https://doi.org/10.1002/pamm.202200074\">https://doi.org/10.1002/pamm.202200074</a>","short":"A. Hamdoun, R. Mahnken, PAMM 22 (2023).","bibtex":"@article{Hamdoun_Mahnken_2023, title={A finite strain gradient theory for viscoplasticity by means of micromorphic regularization}, volume={22}, DOI={<a href=\"https://doi.org/10.1002/pamm.202200074\">10.1002/pamm.202200074</a>}, number={1}, journal={PAMM}, publisher={Wiley}, author={Hamdoun, Ayoub and Mahnken, Rolf}, year={2023} }","mla":"Hamdoun, Ayoub, and Rolf Mahnken. “A Finite Strain Gradient Theory for Viscoplasticity by Means of Micromorphic Regularization.” <i>PAMM</i>, vol. 22, no. 1, Wiley, 2023, doi:<a href=\"https://doi.org/10.1002/pamm.202200074\">10.1002/pamm.202200074</a>.","chicago":"Hamdoun, Ayoub, and Rolf Mahnken. “A Finite Strain Gradient Theory for Viscoplasticity by Means of Micromorphic Regularization.” <i>PAMM</i> 22, no. 1 (2023). <a href=\"https://doi.org/10.1002/pamm.202200074\">https://doi.org/10.1002/pamm.202200074</a>.","ieee":"A. Hamdoun and R. Mahnken, “A finite strain gradient theory for viscoplasticity by means of micromorphic regularization,” <i>PAMM</i>, vol. 22, no. 1, 2023, doi: <a href=\"https://doi.org/10.1002/pamm.202200074\">10.1002/pamm.202200074</a>.","ama":"Hamdoun A, Mahnken R. A finite strain gradient theory for viscoplasticity by means of micromorphic regularization. <i>PAMM</i>. 2023;22(1). doi:<a href=\"https://doi.org/10.1002/pamm.202200074\">10.1002/pamm.202200074</a>"},"intvolume":"        22","publication_status":"published","publication_identifier":{"issn":["1617-7061","1617-7061"]},"issue":"1","title":"A finite strain gradient theory for viscoplasticity by means of micromorphic regularization","doi":"10.1002/pamm.202200074","date_updated":"2024-05-14T09:15:38Z","publisher":"Wiley","author":[{"last_name":"Hamdoun","id":"57708","full_name":"Hamdoun, Ayoub","first_name":"Ayoub"},{"id":"335","full_name":"Mahnken, Rolf","last_name":"Mahnken","first_name":"Rolf"}],"date_created":"2024-05-14T09:06:38Z","volume":22}]