Engineering mechanics includes all areas of theoretical and applied mechanics. Engineering mechanics focuses on the mechanics of solids and fluids: continuum mechanics; dynamics; stability; properties of materials; computational, probabilistic and experimental mechanics; biomechanics; and nano- and micro-mechanics.
Edited by Matthieu Vandamme; Patrick Dangla; Jean-Michel Pereira.; and Siavash Ghabezloo
Edited by Christian Hellmich, Bernhard Pichler, and Johann Kollegger
Shuze Zhu, Nikolaos Lempesis, Pieter J. in ‘t Veld, and Gregory C. Rutledge, Macromolecules, Articles ASAP, 2018. https://pubs.acs.org/doi/10.1021/acs.macromol.7b02367
Thermoplastic polyurethanes (TPUs) are useful materials for numerous applications due in part to their outstanding resilience and ability to dissipate energy under large mechanical deformation. However, the mechanistic understanding of the origins of these mechanical properties at the molecular level remains elusive, largely due to the complex, heterogeneous structure of these materials, which arises from the segregation of chemically distinct segments into hard and soft domains. In this work, molecular simulations are used to identify the mechanism of mechanical response under large tensile deformation of a common thermoplastic polyurethane comprising 4,4′-diphenylmethane diisocyanate and n-butanediol (hard segment) and poly(tetramethylene oxide) (soft segment), with atomic resolution.The simulation employs a lamellar stack model constructed using the Interphase Monte Carlo method established previously for semicrystalline polymers, which models the interfacial zone between hard and soft domains with thermodynamically rigorous distributions of bridges, loops, and tails. Molecular-level mechanisms responsible for yield, toughening, and the Mullins effect are reported. We have found several distinct mechanisms for yield and plastic flow, which we categorize as (i) cavitation, (ii) chain pull-out, (iii) localized melting with shear band formation, and (iv) block slip. The activity of these mechanisms depends on the topology of chains in the soft domain and the direction of loading (e.g., parallel or perpendicular to the interface). Further insights regarding toughening mechanisms and the Mullins effect are obtained from cyclic loading, where mechanisms ii to iv were found to be irreversible and account for the superior resilience and dissipation at large tensile strains in thermoplastic polyurethanes.
Please see attachment for detailed information (in Chinese).
Soft materials including elastomers and gels are pervasive in biological systems and technological applications. Robust mechanical properties, such as high toughness and tough bonding, are crucial to realize the potentials of soft materials. It has been well recognized that building energy dissipation into an elastic network is one important toughening mechanism. However, it is still challenging to quantitatively predict the synergistic effect of the intrinsic fracture energy and mechanical dissipation in process zone due to the highly nonlinear deformations. We recently showed that a coupled Mullins effect and cohesive zone model can accurately predict the fracture toughness and adhesion of tough hydrogels. The coupled simulation model can be carried out with finite element software ABAQUS. With the new experimental techniques, material fabrication and numerical methods, it is very promising to rationally design novel soft tough materials and quantitatively predict the designed materials with simulations. To further promote research on fracture and adhesion of soft tough materials, we share the ABAUQS input files for simulating fracture and 90 degree peeling of tough hydrogels. Please change the files to ".inp" after you download them to run the simulations with ABAQUS.
Zhang, Teng, Shaoting Lin, Hyunwoo Yuk, and Xuanhe Zhao. "Predicting fracture energies and crack-tip fields of soft tough materials." Extreme Mechanics Letters 4 (2015): 1-8.
Yuk, Hyunwoo, Teng Zhang, Shaoting Lin, German Alberto Parada, and Xuanhe Zhao. "Tough bonding of hydrogels to diverse non-porous surfaces." Nature materials 15, no. 2 (2016): 190.
Zhang, Teng, Hyunwoo Yuk, Shaoting Lin, German A. Parada, and Xuanhe Zhao. "Tough and tunable adhesion of hydrogels: experiments and models." Acta Mechanica Sinica 33, no. 3 (2017): 543-554.
See here. Or here. In comparison, our "italian strike" where we only omit 1 session of exams was much less dramatic.
It will be interesting to follow the UK strike, because I would be surprised if so many academics let such significant part of salary be reduced.
But certainly this pension change has raised a number of problems also with students and the high fees. Corbin had already received large support in the last election with his idea of cutting fees, like today in Italy President Grasso and his new party is suggesting.
In UK the situation is dramatic, so this explains the large and unprecedented strike. If you write to any staff in strike you will receive this message.
I am off work becasue I am participating in the longest ever strike in the hisotry of higher education, to protect our pensions from unneccessary reform that will make us lose40% of our pension on retirement. Please support UK academics and related staff by emailing the VCs of prior 1992 universities in the UK. Read more at https://www.ucu.org.uk/why-we -are-taking-action-over-USS
Thank you for your message. I am away from email until Friday 2 March.
I am supporting the UCU strike action because University employers want to end guaranteed pension benefits so our future pensions accrual would depend entirely on how the stock market performs with no guaranteed return at all. That means huge uncertainty and a reduced retirement income.
The University and College Union (UCU) has repeatedly tried to negotiate with employers to no avail. At the University of Exeter, 92.6% of UCU members voting supported this strike in a legal ballot. More here:www.ucu.org.uk/strikeforuss
This is a last resort, and I apologise for any inconvenience caused. I will not be replying to emails during strike days. Please re-send any vitally important emails on the next non-strike day, marking them as urgent. I will do my very best to deal with those messages on Friday 2 March; if I do not manage to answer your query that day, I will try to get to it the following Friday or, failing that, in the week after the strike ends. Please bear with me as I work through what will no doubt be an enormous backlog (bear in mind that I work part-time, so this will take a while).
Thank you for your support.
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