Rarefaction Wave Propagation in Origami-Based Mechanical Metamaterials

2015 ◽  
Author(s):  
Hiromi Yasuda ◽  
Jinkyu Yang
Keyword(s):  
Nonlinear Waves ◽  
Strain Softening ◽  
Initial Conditions ◽  
Rarefaction Waves ◽  
Efficient Manner ◽  
Softening Behavior ◽  
Mechanical Metamaterials ◽  
Tensile Wave ◽  
Potential Applications ◽  
Linkage Model

We design origami-based mechanical metamaterials composed of Tachi-Miura Polyhedron (TMP) cells, and we numerically study the propagation of nonlinear waves in them. In order to investigate the dynamics of origami structures, we model these TMP-based metamaterials into a simple multi-bar linkage model. By using this model, we find that these TMP cells exhibit strain softening behavior under compression, which can be tuned by modifying their geometrical configurations or initial conditions. By leveraging such tunable strain softening mechanisms, we verify that the origami-based metamaterials can support the propagation of rarefaction waves. These waves feature tensile wave-fronts despite the application of compressive impact to the system. Such unusual characteristics can be exploited to disintegrate shock waves in a controllable and efficient manner, thereby leading to potential applications in impact mitigation and absorption.

scholarly journals Stationary rarefaction waves in discrete materials with strain-softening behavior

2017 ◽  
Vol 31 (10) ◽  
pp. 1742005
Author(s):  
Eric B. Herbold
Keyword(s):  
Strain Softening ◽  
Equations Of Motion ◽  
Discrete Systems ◽  
Rarefaction Waves ◽  
Weakly Nonlinear ◽  
Discrete Equations ◽  
Softening Behavior ◽  
Wave Guides ◽  
Traveling Pulse ◽  
Nonlinearity Dispersion

This article details some of the techniques used to derive exact solutions from the discrete equations of motion of strongly and weakly nonlinear discrete systems. The distinction between strongly and weakly nonlinear systems is related to the amplitude of a traveling pulse and the external confining load. Materials with an anomalous strain-softening behavior will be emphasized (i.e., [Formula: see text], [Formula: see text]), though this choice does not preclude applications for strain-hardening systems like those with Hertzian potentials. Discrete materials with tunable acoustic transmission properties and novel impact mitigation capacity have gained interest in recent years due to their practical application across many scientific fields. Wave-guides comprised of discrete materials with a nonlinear interaction potential have been used to investigate the interplay between nonlinearity, dispersion and dissipation.

scholarly journals Cryo-EM structures of an insecticidal Bt toxin reveal its mechanism of action on the membrane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Matthew J. Byrne ◽  
Matthew G. Iadanza ◽  
Marcos Arribas Perez ◽  
Daniel P. Maskell ◽  
Rachel M. George ◽  
...  
Keyword(s):  
Functional Data ◽  
Insect Pests ◽  
Economic Cost ◽  
Commercial Agriculture ◽  
Efficient Manner ◽  
Bt Toxin ◽  
Genes Encoding ◽  
Potential Applications ◽  
Chemical Pesticides ◽  
Wide Potential

AbstractInsect pests are a major cause of crop losses worldwide, with an estimated economic cost of $470 billion annually. Biotechnological tools have been introduced to control such insects without the need for chemical pesticides; for instance, the development of transgenic plants harbouring genes encoding insecticidal proteins. The Vip3 (vegetative insecticidal protein 3) family proteins from Bacillus thuringiensis convey toxicity to species within the Lepidoptera, and have wide potential applications in commercial agriculture. Vip3 proteins are proposed to exert their insecticidal activity through pore formation, though to date there is no mechanistic description of how this occurs on the membrane. Here we present cryo-EM structures of a Vip3 family toxin in both inactive and activated forms in conjunction with structural and functional data on toxin–membrane interactions. Together these data demonstrate that activated Vip3Bc1 complex is able to insert into membranes in a highly efficient manner, indicating that receptor binding is the likely driver of Vip3 specificity.

scholarly journals Variational theory for (2+1)-dimensional fractional dispersive long wave equations

2021 ◽  
pp. 23-23
Author(s):  
Xiao-Qun Cao ◽  
Cheng-Zhuo Zhang ◽  
Shi-Cheng Hou ◽  
Ya-Nan Guo ◽  
Ke-Cheng Peng
Keyword(s):  
Porous Media ◽  
Nonlinear Waves ◽  
Inverse Method ◽  
Wave Equations ◽  
Continuous Medium ◽  
Variational Principles ◽  
Variational Theory ◽  
Long Wave ◽  
Potential Applications ◽  
Fractional System

This paper extends the (2+1)-dimensional Eckhaus-type dispersive long wave equations in continuous medium to their fractional partner, which is a model of nonlinear waves in fractal porous media. The derivation is shown briefly using He?s fractional derivative. Using the semi-inverse method, the variational principles are established for the fractional system, which up to now are not discovered. The obtained fractal variational principles are proved correct by minimizing the functionals with the calculus of variations, and might find potential applications in numerical modelling.

scholarly journals Semianalytical Solution for Large Deformation of Salt Cavern with Strain-Softening Behavior

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lina Ran ◽  
Huabin Zhang ◽  
Qingqing Zhang
Keyword(s):  
Plastic Zone ◽  
Large Deformation ◽  
Strain Softening ◽  
Structural Characteristics ◽  
Strength Criterion ◽  
Geological Strength Index ◽  
Salt Rock ◽  
Salt Cavern ◽  
Softening Behavior ◽  
The Impact

A semianalytical solution of stress and displacement in the strain-softening and plastic flow zones of a salt cavern is presented. The solution is derived by adopting the large deformation theory, considering the nonlinear Hoek–Brown (H-B) strength criterion. The Romberg method is used to carry out numerical calculation, and then, the large deformation law of displacement is analyzed. The results are compared with those obtained by former numerical methods, and the solutions are validated. The results indicate that the displacement of the plastic zone decreases with the increase in distance away from the salt cavern. Similarly, it decreases with an increase in the geological strength index or running pressure, with the running pressure having a more significant effect on the displacement. It increases with the dilation angle, and the impact degree gradually increases. Compared with the softening parameter, h, of the plastic zone, the flow parameter, f, has little impact on the displacement. The displacement of the plastic zone obviously increased when considering the strain-softening of salt rock. When considering the shear dilation and softening behaviors of salt rock, the analytical solution obtained by employing the experiential regression Hoek–Brown (H-B) criterion, which considers many factors such as the structural characteristics of the salt formation and the rock mass quality, is safer and closer to the actual situation. This study can provide reference for many applications, including but not confined to analyzing the deformation of the surrounding rock of an underground salt cavern storage facility during construction.

A comparison of strain-rate enhancement approaches for concrete material subjected to high strain-rate

2017 ◽  
Vol 8 (2) ◽  
pp. 155-176 ◽  
Author(s):  
Xiangzhen Kong ◽  
Qin Fang ◽  
Hao Wu ◽  
Jian Hong
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Strain Softening ◽  
High Strain ◽  
Consistency Condition ◽  
Rate Data ◽  
Concrete Material ◽  
Rate Enhancement ◽  
Softening Behavior ◽  
Dynamic Loadings

High strain-rate induced from intense dynamic loadings will cause an obvious enhancement of concrete material frequently used in civil and defense engineering, which plays an important role in correct numerical simulations of concrete members subjected to intense dynamic loadings. In this article, the existing three strain-rate enhancement approaches for concrete material are compared by three aspects, that is, flexibility of fitting data, consistency condition, and time-dependent behavior. The so-called “overstress approach” is found to be not flexible for fitting high strain-rate data and unable to well predict the strain-softening behavior but can capture the inherent viscidity of concrete material. The “consistency approach” can describe the strain-softening behavior and the inherent viscidity but may be inconvenient and time-consuming when fitting high strain-rate data. The “simplified approach” widely used in commercial concrete material models can describe the strain-softening behavior and fit high strain-rate data by a more convenient and direct way but cannot capture the inherent viscidity of concrete material. Examples of uniaxial stress including loading and unloading under constant and varying strain-rates are presented to demonstrate the above-mentioned findings, in which the updating algorithm of dynamic stress is presented in detail.

scholarly journals Interval Nonprobabilistic Reliability Analysis for Ancient Landslide considering Strain-Softening Behavior: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zilong Zhou ◽  
Chenglong Lin ◽  
Xin Cai ◽  
Riyan Lan
Keyword(s):  
Reliability Analysis ◽  
Strain Softening ◽  
Constitutive Relations ◽  
Failure Surface ◽  
Normal Space ◽  
Probability Density Distribution ◽  
Probability Method ◽  
Uncertain Parameters ◽  
Ancient Landslide ◽  
Softening Behavior

Uncertainties in geotechnical parameters significantly affect the stability evaluation of an ancient landslide, especially when considering the strain-softening behavior. Due to the great difficulty in obtaining the probability density distribution of geoparameters, an interval nonprobability reliability analysis framework combined with numerical strain-softening constitutive relations was established in this paper. Interval variables were defined as the uncertain parameters in the strain-softening model. The interval nonprobabilistic reliability was defined as the minimum distance from the origin point to the failure surface in the standard normal space, which is the key index for describing the ability of a system to tolerate the variation of uncertain parameters. The proposed method was used to evaluate the reliability of Baishi ancient landslide. The parameter sensitivity analysis was also conducted. Through the proposed method, it is considered that Baishi ancient landslide is safe and stable, and the strain threshold kr is the dominant parameter. The results calculated by the proposed method agree well with the actual situation. This indicates the proposed method is more applicable than the traditional probability method when the data are scare.

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