Zaera, RamónSerrano González, ÓscarFernández-Sáez, José2022-12-162022-12-162020-03-01Zaera, R., Serrano, Ó., & Fernández-Sáez, J. (2020). Non-standard and constitutive boundary conditions in nonlocal strain gradient elasticity. Meccanica, 55(3), 469–479.0025-64551572-9648 (electronic)https://hdl.handle.net/10016/36192Zaera et al. (Int J Eng Sci 138:65-81, 2019) recently showed that the nonlocal strain gradient theory (NSGT) is not consistent when it is applied to finite solids, since all boundary conditions associated to the corresponding problems cannot be simultaneously satisfied. Given the large number of works using the NSGT being currently published in the field of generalized continuum mechanics, it is pertinent to evince the shortcomings of the application of this theory. Some authors solved the problem omitting the constitutive boundary conditions. In the current paper we show that, in this case, the equilibrium fields are not compatible with the constitutive equation of the material. Other authors solved it omitting the non-standard boundary conditions. Here we show that, in this case, the solution does not fulfil conservation of energy. In conclusion, the inconsistency of the NSGT is corroborated, and its application must be prevented in the analysis of the mechanical behaviour of nanostructures.11eng© The Author(s) 2020This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Atribución 3.0 EspañaConservation of energyIll-posednessNanobeamsNon-standard boundary conditionsNonlocal strain gradientresearch articleIngeniería MecánicaMaterialeshttps://doi.org/10.1007/s11012-019-01122-zopen access4693479Meccanica55AR/0000025610