Simulating Compliant Crease Origami With a Bar and Hinge Model

2019 ◽  
Author(s):  
Yi Zhu ◽  
Evgueni T. Filipov
Keyword(s):  
Three Dimensional ◽  
Small Scale ◽  
Spring Stiffness ◽  
Mechanical Behaviors ◽  
Proposed Model ◽  
Plate Models ◽  
Modeling Techniques ◽  
Rigid Model ◽  
Stiffness Characteristics ◽  
Hinge Model

Abstract Small-scale origami inspired assemblages are usually made with soft compliant plates to serve as creases because it is difficult to fabricate real hinges at those scales. In most conventional origami modeling techniques, these soft and compliant creases are usually neglected and simplified as concentrated rotational springs. Such simplification does not capture the three dimensional geometry correctly and also neglects torsional and extensional deformations of the compliant creases. These deformations could be significant for determining advanced mechanical behaviors of the origami such as bistablity and multistablity. In this paper an improved formulation of a simple bar and hinge model is proposed to capture the geometry and flexibility of compliant creases. Equations for assigning bar areas and spring stiffness are derived based on the theoretical plane stress plate models and the pseudo-rigid model. These equations are next verified against finite element simulations for both infinitesimal stiffness and large deformation stiffness. It is found that the proposed model can predict stiffness characteristics of compliant crease origami relatively well. Furthermore, two examples are used to demonstrate the efficiency and capability of the proposed model.

A Greenwood-Williamson Model of Small-Scale Friction

2005 ◽  
Vol 74 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Reese E. Jones
Keyword(s):  
Numerical Method ◽  
Recursion Formula ◽  
Three Dimensional ◽  
Interfacial Friction ◽  
Small Scale ◽  
Analytical Estimate ◽  
Normal Loading ◽  
Proposed Model ◽  
Loading Case ◽  
Transition Length

A Greenwood and Williamson based model for interfacial friction is presented that incorporates the presliding transition phenomenon that can significantly affect small devices. This work builds on previous similar models by developing: an analytical estimate of the transition length in terms of material and surface parameters, a general recursion formula for the case of slip in one direction with multiple reversals and constant normal loading, and a numerical method for the general three-dimensional loading case. In addition, the proposed model is developed within a plasticity-like framework and is shown to have qualitative similarities with published experimental observations. A number of model problems illustrate the response of the proposed model to various loading conditions.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2018 ◽  
Author(s):  
Feng Jie Zheng ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Pressure Fluctuation ◽  
Large Scale ◽  
Three Dimensional ◽  
Industrial Process ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial process. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operation such as rapid valve opening/closing. To investigate the pressure especially the pressure fluctuation in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled by a zero-dimensional virtual point, the pipe is modeled by a one-dimensional MOC, and the valve is modeled by a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted, in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve are obtained. The results show that the proposed model is in good agreement with the full CFD model in both large-scale and small-scale spaces. Moreover, the proposed model is more computationally efficient than the CFD model, which provides a feasibility in the analysis of complex RPV system within an affordable computational time.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Feng Jie Zheng ◽  
Chao Yong Zong ◽  
William Dempster ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Large Scale ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Dimensional System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial processes. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operations such as rapid valve opening or closing. To investigate the pressure response, with particular interest in the pressure fluctuations in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled as a zero-dimensional virtual point, the pipe is modeled as a one-dimensional system using the MOC, and the valve is modeled using a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve is obtained. The results show that the proposed model is in good agreement when compared with a high fidelity CFD model used to represent both large-scale and small-scale spaces. As expected, the proposed model is significantly more computationally efficient than the CFD model. This demonstrates the feasibility of analyzing complex RPV systems within an affordable computational time.

scholarly journals THREE-DIMENSIONAL SIMULATION OF A SMALL-SCALE ELECTRODIALYSIS PROCESS FOR DOMESTIC USE

2020 ◽  
Vol 14 (2) ◽  
pp. 83-96
Author(s):  
Noureddine Bensedira ◽  
Mohammed-Salah Aggoune ◽  
Mabrouk Chabane ◽  
Said Drid
Keyword(s):  
Fluid Velocity ◽  
Three Dimensional ◽  
Ionic Transport ◽  
Ionic Concentration ◽  
Ion Concentration ◽  
Small Scale ◽  
Three Dimensional Modeling ◽  
Proposed Model ◽  
Domestic Use ◽  
Dimensional Simulation

The hydrodynamic by MHD driving force and ionic transport characteristics of an electrolytic solution in a small-scale electrodialysis process are taken into account in this new approach. A three-Dimensional modeling and simulation of coupling Magnetohydrodynamic-Ionic transport are carried out. The numerical values and the effects of applied voltage and magnetic induction on the fluid velocity and ionic concentration of species present in the solution are displayed graphically. The results show that a high decrease of ion concentration is achieved and suggest that the proposed model which has no moving parts can be practically implemented.

A Bar and Hinge Model for Simulating Bistability in Origami Structures With Compliant Creases

2020 ◽  
Vol 12 (2) ◽  
Author(s):  
Yi Zhu ◽  
Evgueni T. Filipov
Keyword(s):  
Finite Element ◽  
Finite Element Simulations ◽  
Simulation Framework ◽  
Bistable Behavior ◽  
Proposed Model ◽  
Modeling Techniques ◽  
Hinge Model

Abstract Active origami structures usually have creases made with soft and compliant plates because it is difficult to fabricate real hinges and actuate them. However, most conventional origami modeling techniques fail to capture these compliant creases and simplify them as concentrated rotational springs, which neglects torsional and extensional deformations of the creases. In this paper, an improved formulation of a bar and hinge model is proposed to explicitly capture the geometry and the flexibility of compliant creases with nonnegligible width in an origami, and the model is verified against finite element simulations. The verification shows that the model performs relatively well despite being simple and computationally inexpensive. Moreover, simulation examples demonstrate that the proposed model can capture the bistable behavior of the compliant crease origami with nonnegligible crease width because it explicitly includes the extensional stretching energy into the simulation framework and allows torsional crease deformations.

Research on modeling and mechanical behaviors of matched angular contact ball bearings

2020 ◽  
pp. 095440622093703
Author(s):  
Jianguo Gu ◽  
Yimin Zhang
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Transformation Method ◽  
Axial Position ◽  
Ball Bearings ◽  
Mechanical Behaviors ◽  
Heavy Load ◽  
Rotating Speed ◽  
Proposed Model ◽  
Stiffness Characteristics

In engineering applications, angular contact ball bearings are usually mounted in pairs to accommodate the high-speed and heavy-load conditions. The usability, security, and stability of rotating machinery systems are heavily dependent on the mechanical behaviors of matched angular contact ball bearings. However, few related works about matched bearings have been reported. Consequently, it is of great significance to investigate the mechanical properties of matched bearings. This paper presents an analysis of the stiffness and fatigue life characteristics of matched angular contact ball bearings under axial position preload. First, an improved quasi-static model is proposed by using universal coordinate transformation method to investigate the stiffness characteristics of matched bearings. On basis of this, the fatigue life of matched bearings under running condition can be calculated. Then, the validity of the proposed model is verified via comparison between calculated results with previously published experimental results. Finally, a pair of 7206B bearings is taken as a numerical example to illustrate the application of the proposed model. The effects of bearing configuration form, preload, external loads, rotating speed on the stiffness, and fatigue life of matched bearings are discussed in detail.

Extrusion-Based 3D Printing for Pharmaceuticals: Contemporary Research and Applications

2019 ◽  
Vol 24 (42) ◽  
pp. 4991-5008 ◽  
Author(s):  
Mohammed S. Algahtani ◽  
Abdul Aleem Mohammed ◽  
Javed Ahmad
Keyword(s):  
Cosmetic Surgery ◽  
Fused Deposition Modeling ◽  
Personalised Medicine ◽  
Organ Transplant ◽  
Three Dimensional ◽  
Dosage Forms ◽  
Release Profile ◽  
Small Scale ◽  
Drug Release Profile ◽  
Fused Deposition

Three-dimensional printing (3DP) has a significant impact on organ transplant, cosmetic surgery, surgical planning, prosthetics and other medical fields. Recently, 3 DP attracted the attention as a promising method for the production of small-scale drug production. The knowledge expansion about the population differences in metabolism and genetics grows the need for personalised medicine substantially. In personalised medicine, the patient receives a tailored dose and the release profile is based on his pharmacokinetics data. 3 DP is expected to be one of the leading solutions for the personalisation of the drug dispensing. This technology can fabricate a drug-device with complicated geometries and fillings to obtain the needed drug release profile. The extrusionbased 3 DP is the most explored method for investigating the feasibility of the technology to produce a novel dosage form with properties that are difficult to achieve using the conventional industrial methods. Extrusionbased 3 DP is divided into two techniques, the semi-solid extrusion (SSE) and the fused deposition modeling (FDM). This review aims to explain the extrusion principles behind the two techniques and discuss their capabilities to fabricate novel dosage forms. The advantages and limitations observed through the application of SSE and FDM for fabrication of drug dosage forms were discussed in this review. Further exploration and development are required to implement this technology in the healthcare frontline for more effective and personalised treatment.

An isotropic elasto-damage-plastic micromechanical framework of innovative pothole patching materials featuring high-toughness, low-viscosity nanomolecular resin

2021 ◽  
pp. 105678952110286
Author(s):  
H Zhang ◽  
J Woody Ju ◽  
WL Zhu ◽  
KY Yuan
Keyword(s):  
Strain Energy ◽  
Three Dimensional ◽  
Elastic Strain Energy ◽  
Companion Paper ◽  
Computational Algorithms ◽  
Mechanical Behaviors ◽  
High Toughness ◽  
Low Viscosity ◽  
Innovative Materials ◽  
Continuum Thermodynamic

In a recent companion paper, a three-dimensional isotropic elastic micromechanical framework was developed to predict the mechanical behaviors of the innovative asphalt patching materials reinforced with a high-toughness, low-viscosity nanomolecular resin, dicyclopentadiene (DCPD), under the splitting tension test (ASTM D6931). By taking advantage of the previously proposed isotropic elastic-damage framework and considering the plastic behaviors of asphalt mastic, a class of elasto-damage-plastic model, based on a continuum thermodynamic framework, is proposed within an initial elastic strain energy-based formulation to predict the behaviors of the innovative materials more accurately. Specifically, the governing damage evolution is characterized through the effective stress concept in conjunction with the hypothesis of strain equivalence; the plastic flow is introduced by means of an additive split of the stress tensor. Corresponding computational algorithms are implemented into three-dimensional finite elements numerical simulations, and the outcomes are systemically compared with suitably designed experimental results.

scholarly journals Quantification of Measurement and Model Effects in Monopile Foundation Scour Protection Experiments

2021 ◽  
Vol 9 (6) ◽  
pp. 585
Author(s):  
Minghao Wu ◽  
Leen De Vos ◽  
Carlos Emilio Arboleda Chavez ◽  
Vasiliki Stratigaki ◽  
Maximilian Streicher ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Flow Field ◽  
Three Dimensional ◽  
Small Scale ◽  
Maximum Wave Height ◽  
Chaotic Flow ◽  
The Mean ◽  
Scour Protection ◽  
Damage Number ◽  
Measurement Effects

The present work introduces an analysis of the measurement and model effects that exist in monopile scour protection experiments with repeated small scale tests. The damage erosion is calculated using the three dimensional global damage number S3D and subarea damage number S3D,i. Results show that the standard deviation of the global damage number σ(S3D)=0.257 and is approximately 20% of the mean S3D, and the standard deviation of the subarea damage number σ(S3D,i)=0.42 which can be up to 33% of the mean S3D. The irreproducible maximum wave height, chaotic flow field and non-repeatable armour layer construction are regarded as the main reasons for the occurrence of strong model effects. The measurement effects are limited to σ(S3D)=0.039 and σ(S3D,i)=0.083, which are minor compared to the model effects.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

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