اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدForce-induced breakdown of flexible polymerized membrane
59
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We consider the fracture of a free-standing two-dimensional (2D) elastic-brittle network to be used as protective coating subject to constant tensile stress applied on its rim. Using a Molecular Dynamics simulation with Langevin thermostat, we investigate the scission and recombination of bonds, and the formation of cracks in the 2D graphene-like hexagonal sheet for different pulling force $f$ and temperature $T$. We find that bond rupture occurs almost always at the sheet periphery and the First Mean Breakage Time $<tau>$ of bonds decays with membrane size as $<tau> propto N^{-beta}$ where $beta approx 0.50pm 0.03$ and $N$ denotes the number of atoms in the membrane. The probability distribution of bond scission times $t$ is given by a Poisson function $W(t) propto t^{1/3} exp (-t / <tau>)$. The mean failure time $<tau_r>$ that takes to rip-off the sheet declines with growing size $N$ as a power law $<tau_r> propto N^{-phi(f)}$. We also find $<tau_r> propto exp(Delta U_0/k_BT)$ where the nucleation barrier for crack formation $Delta U_0 propto f^{-2}$, in agreement with Griffiths theory. $<tau_r>$ displays an Arrhenian dependence of $<tau_r>$ on temperature $T$. Our results indicate a rapid increase in crack spreading velocity with growing external tension $f$.
قيم البحث
اقرأ أيضاً
Coarse-grained molecular-dynamics simulations were used to study the morphological changes induced in a Nafion$^{tiny textregistered}$-like ionomer by the imposition of a strong electric field. We observe the formation of novel structures aligned a
long the direction of the applied field. The polar head groups of the ionomer side chains aggregate into clusters, which then form rod-like formations which assemble into a hexatic array aligned with the direction of the field. Occasionally these lines of sulfonates and protons form a helical structure. Upon removal of the electric field, the hexatic array of rod-like structures persists, and has a lower calculated free energy than the original isotropic morphology.
Dry solid friction is often accompanied by force modulations originating from stick-slip instabilities. Here a distinct, quasi-static mechanism is evidenced leading to quasi-periodic force oscillations during sliding contact between an elastomer bloc
k, whose surface is patterned with parallel grooves, and finely abraded glass slides. The dominant oscillation frequency is set by the ratio between the sliding velocity and the period of the grooves. A mechanical model is proposed that provides a quantitative prediction for the amplitude of the force modulations as a function of the normal load, the period of the grooves and the roughness characteristics of the substrate. The models main ingredient is the non-linearity of the friction law. Since such non-linearity is ubiquitous for soft solids, this fingerprint effect should be relevant to a large class of frictional configurations and might in particular have important consequences in human (or humanoid) active digital touch.
We report the development of a scanning force microscope based on an ultra-sensitive silicon nitride membrane transducer. Our development is made possible by inverting the standard microscope geometry - in our instrument, the substrate is vibrating a
nd the scanning tip is at rest. We present first topography images of samples placed on the membrane surface. Our measurements demonstrate that the membrane retains an excellent force sensitivity when loaded with samples and in the presence of a scanning tip. We discuss the prospects and limitations of our instrument as a quantum-limited force sensor and imaging tool.
The breakage of a polymer chain of segments, coupled by anharmonic bonds with applied constant external tensile force is studied by means of Molecular Dynamics simulation. We show that the mean life time of the chain becomes progressively independent
of the number of bonds as the pulling force grows. The latter affects also the rupture rates of individual bonds along the polymer backbone manifesting the essential role of inertial effects in the fragmentation process. The role of local defects, temperature and friction in the scission kinetics is also examined.
We predict the new type of phase transition in quasi one-dimensional system of interacting electrons at high magnetic fields, the stabilization of a density wave which transforms a two dimensional open Fermi surface into a periodic chain of large poc
kets with small distances between them. We show that quantum tunneling of electrons between the neighboring closed orbits enveloping these pockets transforms the electron spectrum into a set of extremely narrow energy bands and gaps that decreases the total electron energy, thus leading to a emph{magnetic breakdown induced density wave} ground state analogous to the well-known instability of Peierls type.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
