scholarly journals Dynamically Tunable Friction via Subsurface Stiffness Modulation

2021 ◽  
Vol 8 ◽  
Author(s):  
Siavash Sharifi ◽  
Caleb Rux ◽  
Nathaniel Sparling ◽  
Guangchao Wan ◽  
Amir Mohammadi Nasab ◽  
...  
Keyword(s):  
Composite Structures ◽  
Stimuli Responsive ◽  
Element Analysis ◽  
Soft Robots ◽  
Composite Surface ◽  
Frictional Behavior ◽  
Novel Approach ◽  
Series Of Experiments ◽  
Spiral Channel ◽  
Opposing Surface

Currently soft robots primarily rely on pneumatics and geometrical asymmetry to achieve locomotion, which limits their working range, versatility, and other untethered functionalities. In this paper, we introduce a novel approach to achieve locomotion for soft robots through dynamically tunable friction to address these challenges, which is achieved by subsurface stiffness modulation (SSM) of a stimuli-responsive component within composite structures. To demonstrate this, we design and fabricate an elastomeric pad made of polydimethylsiloxane (PDMS), which is embedded with a spiral channel filled with a low melting point alloy (LMPA). Once the LMPA strip is melted upon Joule heating, the compliance of the composite structure increases and the friction between the composite surface and the opposing surface increases. A series of experiments and finite element analysis (FEA) have been performed to characterize the frictional behavior of these composite pads and elucidate the underlying physics dominating the tunable friction. We also demonstrate that when these composite structures are properly integrated into soft crawling robots inspired by inchworms and earthworms, the differences in friction of the two ends of these robots through SSM can potentially be used to generate translational locomotion for untethered crawling robots.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

Behaviour of Axially Loaded Composite Wall Panel by Using Finite Element Analysis

2015 ◽  
Vol 815 ◽  
pp. 49-53
Author(s):  
Nur Fitriah Isa ◽  
Mohd Zulham Affandi Mohd Zahid ◽  
Liyana Ahmad Sofri ◽  
Norrazman Zaiha Zainol ◽  
Muhammad Azizi Azizan ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Structures ◽  
Element Analysis ◽  
Steel Sheets ◽  
Linear Behavior ◽  
Non Linear ◽  
Composite Wall ◽  
Experimental Values ◽  
Civil Engineering Infrastructure

In order to promote the efficient use of composite materials in civil engineering infrastructure, effort is being directed at the development of design criteria for composite structures. Insofar as design with regard to behavior is concerned, it is well known that a key step is to investigate the influence of geometric differences on the non-linear behavior of the panels. One possible approach is to use the validated numerical model based on the non-linear finite element analysis (FEA). The validation of the composite panel’s element using Trim-deck and Span-deck steel sheets under axial load shows that the present results have very good agreement with experimental references. The developed finite element (FE) models are found to reasonably simulate load-displacement response, stress condition, giving percentage of differences below than 15% compared to the experimental values. Trim-deck design provides better axial resistance than Span-deck. More concrete in between due to larger area of contact is the factor that contributes to its resistance.

scholarly journals Use of Dynamic Analysis to Investigate the Behaviour of Short Neutral Sections in the Overhead Line Electrification

2021 ◽  
Vol 6 (5) ◽  
pp. 62
Author(s):  
John Morris ◽  
Mark Robinson ◽  
Roberto Palacin
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Simulation ◽  
Model Simulation ◽  
Analysis Tool ◽  
Overhead Line ◽  
Element Analysis ◽  
Novel Approach ◽  
Section Model ◽  
The Uk ◽  
Neutral Section

The ‘short’ neutral section is a feature of alternating current (AC) railway overhead line electrification that is often unreliable and a source of train delays. However hardly any dynamic analysis of its behaviour has been undertaken. This paper briefly describes the work undertaken investigating the possibility of modelling the behaviour using a novel approach. The potential for thus improving the performance of short neutral sections is evaluated, with particular reference to the UK situation. The analysis fundamentally used dynamic simulation of the pantograph and overhead contact line (OCL) interface, implemented using a proprietary finite element analysis tool. The neutral section model was constructed using physical characteristics and laboratory tests data, and was included in a validated pantograph/OCL simulation model. Simulation output of the neutral section behaviour has been validated satisfactorily against real line test data. Using this method the sensitivity of the neutral section performance in relation to particular parameters of its construction was examined. A limited number of parameter adjustments were studied, seeking potential improvements. One such improvement identified involved the additional inclusion of a lever arm at the trailing end of the neutral section. A novel application of pantograph/OCL dynamic simulation to modelling neutral section behaviour has been shown to be useful in assessing the modification of neutral section parameters.

scholarly journals Design and Modeling of a Bio-Inspired Flexible Joint Actuator

Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 95
Author(s):  
Ming Xu ◽  
Cheng Rong ◽  
Long He
Keyword(s):  
Hydraulic System ◽  
Driving Forces ◽  
Theoretical Models ◽  
Element Analysis ◽  
Flexible Joint ◽  
Fea Model ◽  
The Finite Element Analysis ◽  
Series Of Experiments ◽  
The Mathematical Model ◽  
Moving Speed

Spiders rely on a hydraulic system to stretch their legs but use muscles to make their legs flex. The compound drive of hydraulics and muscle makes an integrate dexterous structure with powerful locomotion abilities, which perfectly meets the primary requirements of advanced robots. Inspired by this hydraulics-muscle co-drive joint, a novel flexible joint actuator was proposed and its driving characteristics were preliminarily explored. The bio-inspired flexible joint manifested as a double-constrained balloon actuator, which was fabricated by the composite process of 3D printing and casting. To evaluate its performance, the mathematical model was deduced, as well as the finite element analysis (FEA) model. A series of experiments on the rotation angles, driving forces, and efficiencies of the flexible joint were carried out and compared with the mathematical calculations and FEA simulations. The results show that the accuracy of the two theoretical models can be used to assess the joint actuator. The locomotion test of a soft arthropod robot with two flexible joints was also implemented, where the moving speed reached 22 mm/s and the feasibility of the proposed flexible joint applied to a soft robot was demonstrated.

Finite Element Analysis of Composite Ceramic-Concrete Slab Constructions Exposed to Fire

2016 ◽  
Vol 861 ◽  
pp. 88-95
Author(s):  
Balázs Nagy ◽  
Elek Tóth
Keyword(s):  
Composite Structures ◽  
Elevated Temperatures ◽  
Cfd Simulation ◽  
Concrete Slab ◽  
Composite Ceramic ◽  
Reinforced Concrete Beam ◽  
Element Analysis ◽  
Standard Fire ◽  
Using Data ◽  
Dynamics Simulations

In this research, conjugated thermal and fluid dynamics simulations are presented on a modern hollow clay slab blocks filled pre-stressed reinforced concrete beam slab construction. The simulation parameters were set from Eurocode standards and calibrated using data from standardized fire tests of the same slab construction. We evaluated the temperature distributions of the slabs under transient conditions against standard fire load. Knowing the temperature distribution against time at certain points of the structure, the loss of load bearing capacity of the structure is definable at elevated temperatures. The results demonstrated that we could pre-establish the thermal behavior of complex composite structures exposed to fire using thermal and CFD simulation tools. Our results and method of fire resistance tests can contribute to fire safety planning of buildings.

Effect of Temperature, Reeling Speed and Pipe Tension on the Performance of Field Joint Coating During Reeling of Offshore Pipelines

2021 ◽  
Author(s):  
Rajaram Dhole ◽  
Ismael Ripoll ◽  
Sabesan Rajaratnam ◽  
Celine Jablonski
Keyword(s):  
Influential Factors ◽  
Influential Factor ◽  
Effect Of Temperature ◽  
Mechanical And Thermal Properties ◽  
Peak Strain ◽  
Element Analysis ◽  
Novel Approach ◽  
Laboratory Test Results ◽  
Coating Design ◽  
Highly Strained

Abstract Pipelines are coated with insulating material that minimizes heat losses to the environment. Reeled pipe can experience nominal bending strain in the order of 1% to 2%. Thick coating on the pipe is inherently more highly strained, because of concentrations that occur at the interface between parent coating and field joint coating. Occasionally, contractors who specialize in pipe-lay using the reeling method have experienced difficulties relating to unexpected disbondment and cracks in coating at these interfaces. Any disbonded coating is routinely identified and repaired, but it is important to understand the influential factors that could lead to this type of coating disbondment. It is known in the industry that parameters such as temperature, reeling speed and pipe tension are influential but the relative influence of the factors is not well understood. In addition, there is currently no industry code or recommended practice that proposes the strain levels that the coating could safely withstand prior to cracking. This paper addresses thermo-mechanical aspects of coating design and presents a novel approach to quantify which parameters have the largest influence. In the presented assessments, coating strain was assessed using finite element analysis. Material input was selected from a combination of typical values and specific laboratory test results for polypropylene (PP) and injection molded polypropylene (IMPP). An essential aspect was that the mechanical and thermal properties of the PP were related to temperature and strain rate. Strain rates in the coating during reeling operations were obtained from global FE models. Detailed local FE models incorporated all the material and load inputs and temperature conditions that are necessary to determine peak strain values in the coating; the peak strain values would indicate the locations of potential coating disbondment. The study is purely a strain assessment and excludes any potential for defects or delamination in the coating that could result from its manufacturing process. This strain-based study revealed that coating temperature during reeling is the most influential factor on strain level in the coating. Reeling speed and pipe tension are parameters providing secondary influences.

Advancement in the Application of Finite Element Analysis to the Optimization of Composite Yacht Structures

2011 ◽  
Author(s):  
David Fornaro
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Structures ◽  
State Of The Art ◽  
Load Case ◽  
Post Processing ◽  
Principal Stresses ◽  
Element Analysis ◽  
Current State ◽  
Case Development

Finite Element Analysis (FEA) is mature technology that has been in use for several decades as a tool to optimize structures for a wide variety of applications. Its application to composite structures is not new, however the technology for modeling and analyzing the behavior of composite structures continues to evolve on several fronts. This paper provides a review of the current state-of-the-art with regard to composites FEA, with a particular emphasis on applications to yacht structures. Topics covered are divided into three categories: Pre-processing; Postprocessing; and Non-linear Solutions. Pre-processing topics include meshing, ply properties, laminate definitions, element orientations, global ply tracking and load case development. Post-processing topics include principal stresses, failure indices and strength ratios. Nonlinear solution topics include progressive ply failure. Examples are included to highlight the application of advanced finite element analysis methodologies to the optimization of composite yacht structures.

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