Folding-mediated soft elasticity and bandgap variation in mechanical metamaterials

2021 ◽  
pp. 2150239
Author(s):  
Guoli Wang ◽  
Ning An ◽  
Shanwen Sun ◽  
Jinxiong Zhou
Keyword(s):  
Strain Curve ◽  
Nonlinear Effects ◽  
Underlying Mechanism ◽  
Stress Strain Curve ◽  
Nonlinear Responses ◽  
Mechanical Metamaterials ◽  
Highly Nonlinear ◽  
Soft Elasticity ◽  
And Control ◽  
Nonlinear Behaviors

Soft mechanical metamaterials with hinge-like elements can undergo multi-step reconfiguration through folding and contacts, and thus exhibit highly nonlinear responses. Numerical simulation of the nonlinear behaviors is essential for the design and control of the mechanical metamaterials, but it remains a challenge due to complicated nonlinear effects. Here, we report the finite element modeling of multi-step reconfiguration of a shape-changing metamaterial, and elucidate the underlying mechanism of soft elasticity. The predicted stress–strain curve together with the folding angles of hinge elements shows excellent agreement with experimental data reported in the literature. Moreover, we explore the influence of reconfiguration and folding-induced internal stress on the bandgap distribution of the mechanical metamaterials. Our efforts provide useful guidelines for the design and application of mechanical metamaterials for both static and dynamic situations.

Design and Control of the 3 Axes Pneumatic Servo Micromanipulator for the Biological Technology

2009 ◽  
Author(s):  
Ming-Chang Shih ◽  
Hung-Yi Chen
Keyword(s):  
Fuzzy Controller ◽  
Dead Zone ◽  
Nonlinear Effects ◽  
Control Technique ◽  
Positioning Precision ◽  
Pneumatic Control ◽  
Biological Technology ◽  
Highly Nonlinear ◽  
A Cell ◽  
And Control

This paper describes the servo pneumatic control technique, which is applied to the biomedical and biological technology. A cell micromanipulator is built by a 3-axes servo pneumatic micromanipulator system, which is set horizontally or vertically and driven by pneumatic cylinders. Due to the nonlinear characteristic of the air flow and the compressibility of air, the system is highly nonlinear system. Therefore, the compensators must be designed to reject those nonlinear effects and to improve the positioning precision. The dead-zone of the 3 axes pneumatic servo micromanipulator is measured, and the relation of velocity and voltage is plotted. Finally, a hybrid fuzzy controller, with dead zone, and velocity compensation, is designed to control the positioning precision of the 3 axes pneumatic servo micromanipulator. From the experimental results, the pneumatic servo micromanipulator has the positioning accuracy of 40 nm with different displacements. The system can be potentially used for the cell extraction, puncture, cutting and microinjection of the biological technology.

scholarly journals Can-Crush Model and Simulations for Verifying Uncertainty Quantification Method for Sparse Stress-Strain Curve Data

2016 ◽  
Author(s):  
J. F. Dempsey ◽  
V. Romero ◽  
N. Breivik ◽  
G. Orient ◽  
B. Antoun ◽  
...  
Keyword(s):  
Strain Curve ◽  
Element Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Response Variance ◽  
Highly Nonlinear ◽  
Time Histories ◽  
Standard Response ◽  
Ductile Steel ◽  
Weld Time

This work examines the variability of predicted responses when multiple stress-strain curves (reflecting variability from replicate material tests) are propagated through a transient dynamics finite element model of a ductile steel can being slowly crushed. An elastic-plastic constitutive model is employed in the large-deformation simulations. The present work assigns the same material to all the can parts: lids, walls, and weld. Time histories of 18 response quantities of interest (including displacements, stresses, strains, and calculated measures of material damage) at several locations on the can and various points in time are monitored in the simulations. Each response quantity’s behavior varies according to the particular stress-strain curves used for the materials in the model. We estimate response variability due to variability of the input material curves. When only a few stress-strain curves are available from material testing, response variance will usually be significantly underestimated. This is undesirable for many engineering purposes. This paper describes the can-crush model and simulations used to evaluate a simple classical statistical method, Tolerance Intervals (TIs), for effectively compensating for sparse stress-strain curve data in the can-crush problem. Using the simulation results presented here, the accuracy and reliability of the TI method are being evaluated on the highly nonlinear input-to-output response mappings and non-standard response distributions in the can-crush UQ problem.

scholarly journals Simple Effective Conservative Treatment of Uncertainty From Sparse Samples of Random Variables and Functions

2018 ◽  
Vol 4 (4) ◽  
Author(s):  
Vicente J. Romero ◽  
Benjamin B. Schroeder ◽  
James F. Dempsey ◽  
Nicole L. Breivik ◽  
George E. Orient ◽  
...  
Keyword(s):  
Strain Curve ◽  
Random Variable ◽  
Element Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Nonlinear Input ◽  
Highly Nonlinear ◽  
Ductile Steel ◽  
Sparse Samples ◽  
Response Variation

This paper examines the variability of predicted responses when multiple stress–strain curves (reflecting variability from replicate material tests) are propagated through a finite element model of a ductile steel can being slowly crushed. Over 140 response quantities of interest (QOIs) (including displacements, stresses, strains, and calculated measures of material damage) are tracked in the simulations. Each response quantity's behavior varies according to the particular stress–strain curves used for the materials in the model. We desire to estimate or bound response variation when only a few stress–strain curve samples are available from material testing. Propagation of just a few samples will usually result in significantly underestimated response uncertainty relative to propagation of a much larger population that adequately samples the presiding random-function source. A simple classical statistical method, tolerance intervals (TIs), is tested for effectively treating sparse stress–strain curve data. The method is found to perform well on the highly nonlinear input-to-output response mappings and non-normal response distributions in the can crush problem. The results and discussion in this paper support a proposition that the method will apply similarly well for other sparsely sampled random variable or function data, whether from experiments or models. The simple TI method is also demonstrated to be very economical.

A modified version of MATLAB application window for predicting the weld bead profile and stress–strain plot of AA5052 CMT weldment using ER4043

SIMULATION ◽  
2021 ◽  
pp. 003754972110315
Author(s):  
B Girinath ◽  
N Siva Shanmugam
Keyword(s):  
Strain Curve ◽  
Weld Bead ◽  
Welding Parameters ◽  
Bead Geometry ◽  
Hybrid Technique ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Weld Bead Geometry ◽  
Inference System ◽  
Engineering Stress

The present study deals with the extended version of our previous research work. In this article, for predicting the entire weld bead geometry and engineering stress–strain curve of the cold metal transfer (CMT) weldment, a MATLAB based application window (second version) is developed with certain modifications. In the first version, for predicting the entire weld bead geometry, apart from weld bead characteristics, x and y coordinates (24 from each) of the extracted points are considered. Finally, in the first version, 53 output values (five for weld bead characteristics and 48 for x and y coordinates) are predicted using both multiple regression analysis (MRA) and adaptive neuro fuzzy inference system (ANFIS) technique to get an idea related to the complete weld bead geometry without performing the actual welding process. The obtained weld bead shapes using both the techniques are compared with the experimentally obtained bead shapes. Based on the results obtained from the first version and the knowledge acquired from literature, the complete shape of weld bead obtained using ANFIS is in good agreement with the experimentally obtained weld bead shape. This motivated us to adopt a hybrid technique known as ANFIS (combined artificial neural network and fuzzy features) alone in this paper for predicting the weld bead shape and engineering stress–strain curve of the welded joint. In the present study, an attempt is made to evaluate the accuracy of the prediction when the number of trials is reduced to half and increasing the number of data points from the macrograph to twice. Complete weld bead geometry and the engineering stress–strain curves were predicted against the input welding parameters (welding current and welding speed), fed by the user in the MATLAB application window. Finally, the entire weld bead geometries were predicted by both the first and the second version are compared and validated with the experimentally obtained weld bead shapes. The similar procedure was followed for predicting the engineering stress–strain curve to compare with experimental outcomes.

scholarly journals Collagen metabolism as a regulator of proline dehydrogenase/proline oxidase-dependent apoptosis/autophagy

Amino Acids ◽  
2021 ◽  
Author(s):  
Jerzy Palka ◽  
Ilona Oscilowska ◽  
Lukasz Szoka
Keyword(s):  
Cell Metabolism ◽  
Underlying Mechanism ◽  
Collagen Biosynthesis ◽  
Proline Metabolism ◽  
Proline Dehydrogenase ◽  
Histone Demethylases ◽  
Proline Oxidase ◽  
Prolyl Hydroxylases ◽  
Transport Chain ◽  
And Control

AbstractRecent studies on the regulatory role of amino acids in cell metabolism have focused on the functional significance of proline degradation. The process is catalysed by proline dehydrogenase/proline oxidase (PRODH/POX), a mitochondrial flavin-dependent enzyme converting proline into ∆1-pyrroline-5-carboxylate (P5C). During this process, electrons are transferred to electron transport chain producing ATP for survival or they directly reduce oxygen, producing reactive oxygen species (ROS) inducing apoptosis/autophagy. However, the mechanism for switching survival/apoptosis mode is unknown. Although PRODH/POX activity and energetic metabolism were suggested as an underlying mechanism for the survival/apoptosis switch, proline availability for this enzyme is also important. Proline availability is regulated by prolidase (proline supporting enzyme), collagen biosynthesis (proline utilizing process) and proline synthesis from glutamine, glutamate, α-ketoglutarate (α-KG) and ornithine. Proline availability is dependent on the rate of glycolysis, TCA and urea cycles, proline metabolism, collagen biosynthesis and its degradation. It is well established that proline synthesis enzymes, P5C synthetase and P5C reductase as well as collagen prolyl hydroxylases are up-regulated in most of cancer types and control rates of collagen biosynthesis. Up-regulation of collagen prolyl hydroxylase and its exhaustion of ascorbate and α-KG may compete with DNA and histone demethylases (that require the same cofactors) to influence metabolic epigenetics. This knowledge led us to hypothesize that up-regulation of prolidase and PRODH/POX with inhibition of collagen biosynthesis may represent potential pharmacotherapeutic approach to induce apoptosis or autophagic death in cancer cells. These aspects of proline metabolism are discussed in the review as an approach to understand complex regulatory mechanisms driving PRODH/POX-dependent apoptosis/survival.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

CT Image Analysis on the Meso-Damage of Construction Waste Recycled Brick

2012 ◽  
Vol 588-589 ◽  
pp. 1930-1933
Author(s):  
Guo Song Han ◽  
Hai Yan Yang ◽  
Xin Pei Jiang
Keyword(s):  
Fractal Dimension ◽  
Strain Curve ◽  
Ct Image ◽  
Stress Strain Curve ◽  
Crack Evolution ◽  
Construction Waste ◽  
Box Counting ◽  
Industrial Ct ◽  
Ct Image Analysis ◽  
Box Counting Method

Based on industrial CT technique, Meso-mechanical experiment was conducted on construction waste recycled brick to get the real-time CT image and stress-strain curve of brick during the loading process. Box counting method was used to calculate the fractal dimension of the inner pore transfixion and crack evolution. The results showed that lots of pore in the interfacial transition zone mainly resulted in the damage of the brick. With the increase of stress, the opening through-pore appeared and crack expanded, and the fractal dimension increased.

Stress-strain curve of paper revisited

2012 ◽  
Vol 27 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Svetlana Borodulina ◽  
Artem Kulachenko ◽  
Mikael Nygårds ◽  
Sylvain Galland
Keyword(s):  
Three Dimensional ◽  
Strain Curve ◽  
Failure Behavior ◽  
Three Dimensional Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Bonding Parameters ◽  
Particle Level ◽  
The Impact

Abstract We have investigated a relation between micromechanical processes and the stress-strain curve of a dry fiber network during tensile loading. By using a detailed particle-level simulation tool we investigate, among other things, the impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds. This is probably the first three-dimensional model which is capable of simulating the fracture process of paper accounting for nonlinearities at the fiber level and bond failures. The failure behavior of the network considered in the study could be changed significantly by relatively small changes in bond strength, as compared to the scatter in bonding data found in the literature. We have identified that compliance of the bonding regions has a significant impact on network strength. By comparing networks with weak and strong bonds, we concluded that large local strains are the precursors of bond failures and not the other way around.

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