Influence of Plasticity and Friction on the Contact Mechanics of Auxetic Materials

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Shreya Saxena ◽  
Ahmed Fardan ◽  
Rehan Ahmed
Keyword(s):  
Contact Mechanics ◽  
Strain Energy ◽  
Indentation Depth ◽  
Tribological Behavior ◽  
Element Model ◽  
Elastic Contact ◽  
Auxetic Materials ◽  
Pile Up ◽  
Stress Profiles ◽  
Depth Curves

Abstract Contact interactions play an important role in the tribological behavior of engineering materials. This paper develops a finite element model to investigate the contact mechanics and stress distribution of auxetic materials, i.e., materials with negative Poisson’s ratio. The model results are compared with numerical and mathematical models for isotropic auxetic polymers. The indentation of auxetic materials is analyzed for the effects of friction, plasticity and allowing separation after contact with a spherical indenter using a commercial software, abaqus. The results are discussed in terms of stress profiles, force-indentation depth curves, plasticity, friction, internal energy, compressibility, sink-in, and the pile-up of material. It is concluded that for purely elastic contact, the indentation resistance increases for auxetic materials and the inclusion of friction shifts subsurface stresses closer to the surface. However, the introduction of plasticity negates the improvement of increased indentation resistance. The pile-up of material around the indent reduces for auxetic materials which makes them more suitable for rolling/sliding contacts. The internal strain energy decreases for purely elastic contact and increases for an elastic/plastic contact.

scholarly journals A numerical analysis of skin–PPE interaction to prevent facial tissue injury

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rikeen D. Jobanputra ◽  
Jack Hayes ◽  
Sravani Royyuru ◽  
Marc A. Masen
Keyword(s):  
Strain Energy Density ◽  
Strain Energy ◽  
Tissue Injury ◽  
Soft Materials ◽  
Element Model ◽  
Healthcare Systems ◽  
Skin Injury ◽  
Energy Density Distribution ◽  
The World ◽  
The Face

AbstractThe use of close-fitting PPE is essential to prevent exposure to dispersed airborne matter, including the COVID-19 virus. The current pandemic has increased pressure on healthcare systems around the world, leading to medical professionals using high-grade PPE for prolonged durations, resulting in device-induced skin injuries. This study focuses on computationally improving the interaction between skin and PPE to reduce the likelihood of discomfort and tissue damage. A finite element model is developed to simulate the movement of PPE against the face during day-to-day tasks. Due to limited available data on skin characteristics and how these vary interpersonally between sexes, races and ages, the main objective of this study was to establish the effects and trends that mask modifications have on the resulting subsurface strain energy density distribution in the skin. These modifications include the material, geometric and interfacial properties. Overall, the results show that skin injury can be reduced by using softer mask materials, whilst friction against the skin should be minimised, e.g. through use of micro-textures, humidity control and topical creams. Furthermore, the contact area between the mask and skin should be maximised, whilst the use of soft materials with incompressible behaviour (e.g. many elastomers) should be avoided.

Validation of a finite element model of the human elbow for determining cartilage contact mechanics

2013 ◽  
Vol 46 (10) ◽  
pp. 1767-1771 ◽  
Author(s):  
Ryan T. Willing ◽  
Emily A. Lalone ◽  
Hannah Shannon ◽  
James A. Johnson ◽  
Graham J.W. King
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Contact Mechanics ◽  
Element Model

Simulation of Deep Spherical Indentation Using Eulerian Finite Element Methods

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
D. Anderson ◽  
A. Warkentin ◽  
R. Bauer
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Large Deformations ◽  
Radial Strain ◽  
Element Model ◽  
Spherical Indentation ◽  
Eulerian Formulation ◽  
Pile Up ◽  
Deep Indentation ◽  
General Material

Simulation of deep indentation, and the associated pile-up effects, requires a robust and accurate finite element model capable of naturally handling the large deformations present. This work successfully demonstrates that the Eulerian formulation is capable of accurately reproducing the forces and general material response of deep indentation. It was found that, in the absence of friction, sink-in dominates at indentation depths less than 1.1% of the indenter radius, there is a transition from sink-in to pile-up from 1.1% to 2.3% of the indenter radius, and pile-up is fully developed at indentation depths larger than 13.2% of the indenter radius for the 4340 steel workpiece and the 0.508 mm radius indenter presented in this work. Friction tended to marginally increase the sink-in and transition depths as well as reduce the material height at the onset of fully developed pile-up due to a reduction in the tensile radial strain directly under the indenter.

A CUBIC ARRANGED SPHERICAL DISCRETE ELEMENT MODEL

2014 ◽  
Vol 11 (05) ◽  
pp. 1350102 ◽  
Author(s):  
WEI GAO ◽  
YUANQIANG TAN ◽  
MENGYAN ZANG
Keyword(s):  
Strain Energy ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Laminated Plate ◽  
Discrete Elements ◽  
Elastic Continuum ◽  
Vibration Process ◽  
Spring Constants ◽  
Dem Model

A 3D discrete element model (DEM model) named cubic arranged discrete element model is proposed. The model treats the interaction between two connective discrete elements as an equivalent "beam" element. The spring constants between two connective elements are obtained based on the equivalence of strain energy stored in a unit volume of elastic continuum. Following that, the discrete element model proposed and its algorithm are implemented into the in-house developed code. To test the accuracy of the DEM model and its algorithm, the vibration process of the block, a homogeneous plate and laminated plate under impact loading are simulated in elastic range. By comparing the results with that calculated by using LS-DYNA, it is found that they agree with each other very well. The accuracy of the DEM model and its algorithm proposed in this paper is proved.

scholarly journals The influence of edge effects on crack propagation in snow stability tests

2014 ◽  
Vol 8 (1) ◽  
pp. 229-257
Author(s):  
E. H. Bair ◽  
R. Simenhois ◽  
A. van Herwijnen ◽  
K. Birkeland
Keyword(s):  
Crack Propagation ◽  
Strain Energy ◽  
Wave Speed ◽  
Strain Energy Release Rate ◽  
Field Tests ◽  
Strain Energy Release ◽  
Element Model ◽  
Fe Model ◽  
Test Length ◽  
Column Tests

Abstract. Propagation tests are used to assess the likelihood of crack propagation in a snowpack, yet little is known about how test length affects propagation. Guidelines suggest beams with lengths around 1 m for Extended Column Tests (ECTs) and Propagation Saw Tests (PSTs). To examine how test length affects propagation, we performed 163 ECTs and PSTs 1 to 10 m long. On days with full crack propagation in 1.0 to 1.5 m tests, we then made videos of tests 2 to 10 m long. We inserted markers for particle tracking to measure collapse amplitude, collapse wave speed, and wavelength. We also used a finite element model to simulate the strain energy release rate at fixed crack lengths. We find that: (1) the proportion of tests with full propagation decreased with test length; (2) collapse was greater at the ends of the beams than in the centers; (3) collapse amplitudes in the longer tests were consistent with the shorter tests and did not reach a constant value; (4) collapse wavelengths in the longer tests were around 3 m, 2 × greater than what is predicted by the anticrack model. Based on our field tests and FE models, we conclude that the shorter tests fully propagated more frequently because of increased stress concentration from the far edge. The FE model suggests this edge effect occurs for PSTs up to 2 m long or a crack to beam length ratio ≥ 0.20. Our results suggest that ECT and PST length guidelines may need to be revisited.

Polymer mechanics and tribology

2018 ◽  
Vol 70 (4) ◽  
pp. 764-772 ◽  
Author(s):  
Nikolai K. Myshkin ◽  
Alexander Kovalev
Keyword(s):  
Polymer Composites ◽  
Contact Mechanics ◽  
Tribological Behavior ◽  
Tribological Performance ◽  
Memory Storage ◽  
Polymer Mechanics ◽  
Micro Electro Mechanical Systems ◽  
Content Type ◽  
Storage Devices ◽  
Functional Additives

Purpose The purpose of this paper is to review the advances in mechanics and tribology of polymers and polymer-based materials. It is focused on the understanding of the correlation of contact mechanics and the tribological behavior of polymers and polymer composites by taking account of surface forces and adhesion in the contact. Design/methodology/approach Mechanical behavior of polymers is considered a viscoelasticity. Tribological performance is estimated while considering the parts of deformation and adhesion in friction arising in the contact. Surface energy, roughness, load and temperature effects on the tribological behavior of polymers are evaluated. Polymer composites produced by reinforcing and by the addition of functional additives are considered as materials for various applications in tribology. Particular attention is given to polymer-based nanocomposites. Findings A review of studies in tribology has shown that polymer-based materials can be most successfully used as self-lubricating components of sliding bearings. The use of the fillers provides changes in the tribological performance of neat polymers and widens their areas of application in the industry. Thin polymer films were found to be prospective lubricants for memory storage devices, micro-electro-mechanical systems and precision mechanisms. Further progress in polymer tribology should be achieved on solving the problems of contact mechanics, surface physics and tribochemistry by taking account of the scale factor. Originality/value The review is based on the experience of the authors in polymer mechanics and tribology, their research data and on data of many other literature sources published in this area. It can be useful for specialists in polymer research and industrial engineers working in tribology and industrial lubrication.

Effects of interference assembly of a tibial insert on the tibiofemoral contact mechanics in total knee replacement

2019 ◽  
Vol 233 (9) ◽  
pp. 948-953 ◽  
Author(s):  
Zhenxian Chen ◽  
Jing Zhang ◽  
Yongchang Gao ◽  
Shibin Chen ◽  
Xuan Zhang ◽  
...  
Keyword(s):  
Total Knee Replacement ◽  
Contact Mechanics ◽  
Knee Replacement ◽  
Articular Surface ◽  
Peak Load ◽  
Element Model ◽  
Fixed Bearing ◽  
Locking Mechanism ◽  
Tibial Insert ◽  
Total Knee

Tibial locking mechanism design is adopted to limit the backside micromotion in fixed-bearing total knee replacement. However, the effect of the interference assembly of a tibial insert on the tibiofemoral contact mechanics was usually ignored. Finite element model of a fixed-bearing total knee replacement with full peripheral locking mechanism was established to simulate the interference assembly of the tibial insert, and the corresponding effects on the tibiofemoral contact mechanics were predicted. Due to the interference assembly of the tibial insert, a maximum Mises stress of 3.24 MPa was found for the tibial insert before loading. Furthermore, the contact stress was increased by 8.77%, and the contact area was decreased by 5.43% under peak load. The interference assembly of the tibial insert in a fixed-bearing total knee replacement changed the tibiofemoral contact mechanics. This study indicated that the level of interference fit should be cautiously designed for the tibial locking mechanism in fixed-bearing total knee replacement for balancing the articular surface wear and the backside wear of the modular tibial insert.

scholarly journals Influence of Dynamic Loading on Fracture Behaviour of DCB Sandwich Specimen

2019 ◽  
Vol 29 ◽  
pp. 02003 ◽  
Author(s):  
Vyacheslav N. Burlayenko ◽  
Tomasz Sadowski ◽  
Daniel Pietras
Keyword(s):  
Finite Element ◽  
Dynamic Fracture ◽  
Strain Energy ◽  
Fracture Behaviour ◽  
Sandwich Beam ◽  
Strain Energy Release ◽  
Element Model ◽  
Dynamic Finite Element ◽  
Sandwich Specimen ◽  
The Finite Element Model

Numerical simulations of dynamic fracture behaviour of a double cantilever sandwich beam subjected to uneven bending moments in plane conditions are carried out using the dynamic finite element analyses with the ABAQUSTM code. The strain energy release rate was evaluated by means of the finite element model developed within the two-dimensional (2-D) linear elastodynamic theory. This demonstrates the capability and the reliability of the finite element modelling as an extremely useful numerical tool for solving dynamic fracture mechanics problems. Also, the dynamic behaviour of fracture parameters and interface crack progression is discussed.

Sign in / Sign up

Export Citation Format

Share Document