scholarly journals Approximation of the Mechanical Response of Large Lattice Domains Using Homogenization and Design of Experiments

2020 ◽  
Vol 10 (11) ◽  
pp. 3858
Author(s):  
Diego Montoya-Zapata ◽  
Diego A. Acosta ◽  
Camilo Cortés ◽  
Juan Pareja-Corcho ◽  
Aitor Moreno ◽  
...  
Keyword(s):  
Design Of Experiments ◽  
Material Properties ◽  
Mechanical Response ◽  
Von Mises Stress ◽  
Local Geometry ◽  
Stress Strain ◽  
Strain Behavior ◽  
Compressive Loads ◽  
Von Mises ◽  
Large Domains

Lattice-based workpieces contain patterned repetition of individuals of a basic topology (Schwarz, ortho-walls, gyroid, etc.) with each individual having distinct geometric grading. In the context of the design, analysis and manufacturing of lattice workpieces, the problem of rapidly assessing the mechanical behavior of large domains is relevant for pre-evaluation of designs. In this realm, two approaches can be identified: (1) numerical simulations which usually bring accuracy but limit the size of the domains that can be studied due to intractable data sizes, and (2) material homogenization strategies that sacrifice precision to favor efficiency and allow for simulations of large domains. Material homogenization synthesizes diluted material properties in a lattice, according to the volume occupancy factor of such a lattice. Preliminary publications show that material homogenization is reasonable in predicting displacements, but is not in predicting stresses (highly sensitive to local geometry). As a response to such shortcomings, this paper presents a methodology that systematically uses design of experiments (DOE) to produce simple mathematical expressions (meta-models) that relate the stress–strain behavior of the lattice domain and the displacements of the homogeneous domain. The implementation in this paper estimates the von Mises stress in large Schwarz primitive lattice domains under compressive loads. The results of our experiments show that (1) material homogenization can efficiently and accurately approximate the displacements field, even in complex lattice domains, and (2) material homogenization and DOE can produce rough estimations of the von Mises stress in large domains (more than 100 cells). The errors in the von Mises stress estimations reach 42 % for domains of up to 24 cells. This result means that coarse stress–strain estimations may be possible in lattice domains by combining DOE and homogenized material properties. This option is not suitable for precise stress prediction in sensitive contexts wherein high accuracy is needed. Future work is required to refine the meta-models to improve the accuracies of the estimations.

scholarly journals Biomechanical Behavior Evaluation of a Novel Hybrid Occlusal Splint-mouthguard for Contact Sports: 3D-FEA

2021 ◽  
Author(s):  
Les Kalman ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Talita Suelen de Queiroz ◽  
João Paulo Mendes Tribst
Keyword(s):  
Stress Concentration ◽  
Mechanical Response ◽  
Compressive Loading ◽  
Von Mises Stress ◽  
Occlusal Splint ◽  
Total Deformation ◽  
Contact Sports ◽  
Biomechanical Behavior ◽  
Custom Made ◽  
Von Mises

Orofacial injuries are common occurrences during contact sports activities; however, there is an absence of data regarding the performance of hybrid occlusal splint mouthguards, especially during compressive loading. To evaluate the total deformation and stress concentration, a skull model was selected and duplicated to receive two different designs of mouthguard devices: one model received a conventional custom-made mouthguard (MG) with 4-mm thickness and the other received a novel hybrid occlusal splint-mouthguard (HMG) with the same thickness. Both models were subdivided into finite elements. The frictionless contacts were used, and a nonlinear analysis was performed simulating the compressive loading in occlusion. The results were presented in von-Mises stress maps (MPa) and Total Deformation (mm). A higher stress concentration in teeth was observed for the model with the conventional MG, while the HMG design displayed a promising mechanical response with lower stress magnitude. The HMG de-sign displayed a higher magnitude of stress on its occlusal portion than the MG design. The hybrid mouthguard (HMG) reduced (1) jaw displacement during chewing and (2) the generated stresses in maxil-lary and mandibular teeth.

Analysis of Displacement-Controlled Fretting Between a Hemisphere and a Flat Block in Elasto-Plastic Contacts

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Huaidong Yang ◽  
Itzhak Green
Keyword(s):  
Material Properties ◽  
Large Range ◽  
Three Dimensional ◽  
Fretting Wear ◽  
Von Mises Stress ◽  
Partial Slip ◽  
Ductile Material ◽  
Element Analysis ◽  
Metallic Contact ◽  
Von Mises

This work employs a three-dimensional (3D) finite element analysis (FEA) to investigate the fretting metallic contact between a deformable hemisphere and a deformable flat block. Fretting is governed by displacement-controlled action where the materials of the two contacting bodies are set to have identical properties; studied first is steel-on-steel and then copper-on-copper. At contact onset, a normal interference (indentation) is applied, which is then followed by transverse cyclic oscillations. A large range of coefficients of friction (COFs) is imposed at the interface. The results show that the maximum von Mises stress is confined under the contacting surface for small COFs; however, that maximum reaches the contacting surface when the COFs are sufficiently large. It is also shown that fretting under sufficiently large COFs forms large plastic strains in “ring” like patterns at the contacting surfaces. Junction growth is found where the contacting region is being stretched in the direction of the fretting motion. At large COFs, pileups show up at the edges of the contact. The fretting loops of the initial cycles are found along with the total work invested into the system. At certain interference, there exists a certain COF, which results in the largest work consumption. The magnitude of the COF is found to produce either partial slip (prone for fretting fatigue) or gross slip (prone for fretting wear). A scheme of normalization is proposed, and it is shown to be effective for the two said materials that have vastly different material properties. Hence, the normalized results may well characterize a range of contact scales (from micro to macro) of various ductile material pairs that behave in an elastic–plastic manner with strain hardening.

Contact Analysis of a Soft-Coated Asperity During Loading–Unloading Process in Consideration of Strain Hardening Effects

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yi Wang ◽  
Yi Cui ◽  
Shuo Liu ◽  
Xinhui Wang ◽  
Xinwei Tian ◽  
...  
Keyword(s):  
Power Law ◽  
Material Properties ◽  
Element Model ◽  
Von Mises Stress ◽  
Main Bearing ◽  
Plastic Properties ◽  
Medium Speed ◽  
Wide Range ◽  
Dimensional Finite Element ◽  
Von Mises

Abstract In this paper, the flattening process of a coated single asperity by a rigid flat is studied based on a two-dimensional finite element model under different contact interferences. The soft coating and hard substrate materials of the main bearing shell in a medium-speed vehicle diesel engine are both considered to follow the power-law hardening elastic-plastic properties. For both loading and unloading processes, the effects of geometrical and material properties, including the coating thickness, Young’s modulus, Poisson’s ratio, yielding stress, and hardening exponent, on the contact behaviors are studied in a wide range to cover the real material properties. The von Mises stress on the interface is also analyzed in order to improve the bonding strength between coating and substrate. The main contribution of this paper is to provide a method to determine the contact properties caused by different material and geometric properties of soft coating and substrate materials, which follow the power-law hardening properties.

Falling Simulation of Free-Standing Museum Cultural Relics Supported by Soft Pad

2014 ◽  
Vol 670-671 ◽  
pp. 715-719
Author(s):  
Qian Zhou
Keyword(s):  
Material Properties ◽  
Element Model ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Acceleration Response ◽  
Response Curves ◽  
Free Standing ◽  
Cultural Relic ◽  
Von Mises ◽  
Cultural Relics

Free-standing museum cultural relics are easy to fall off exhibition booth and get damaged under earthquakes. To find an effective method to mitigate damage of cultural relics due to fall off, influences of soft pad under relic was studied by ANSYS/LS-DYNA program. A bronze relic supported by a soft pad was selected for analysis. Based on material properties of both the relic and the pad, finite element model of the relic was built. By simulation, Von mises stress distributions, acceleration response curves as well as kinetic energy curves of the relic were obtained; effects of the soft pad to mitigate damage of the relic were discussed. Results show that collision between the falling museum cultural relic and ground can be mitigated by soft pad due to its buffer as well as energy absorption effects. It is suggested to use soft pad under relic to provide protection. Besides, by ANSYS/LS-DYNA program, falling off process of free-standing museum cultural relics can be effectively simulated.

Simulation of Brain Response to Noncontact Impacts Using Coupled Eulerian–Lagrangian Method

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Miao Na ◽  
Timothy J. Beavers ◽  
Abhijit Chandra ◽  
Sarah A. Bentil
Keyword(s):  
Brain Tissue ◽  
Mechanical Response ◽  
Brain Regions ◽  
Von Mises Stress ◽  
Fe Model ◽  
Brain Response ◽  
Fe Method ◽  
Angular Velocities ◽  
Von Mises ◽  
The Brain

Abstract Finite element (FE) method has been widely used for gaining insights into the mechanical response of brain tissue during impacts. In this study, a coupled Eulerian−Lagrangian (CEL) formulation is implemented in impact simulations of a head system to overcome the mesh distortion difficulties due to large deformation in the cerebrospinal fluid (CSF) region and provide a biofidelic model of the interaction between the brain and skull. The head system used in our FE model is constructed from the transverse section of the human brain, with CSF modeled by Eulerian elements. Spring connectors are applied to represent the pia-arachnoid connection between the brain and skull. Validations of the CEL formulation and the FE model are performed using the experimental results. The dynamic response of brain tissue under noncontact impacts and the brain regions susceptible to injury are evaluated based on the intracranial pressure (ICP), maximum principal strain (MPS), and von Mises stress. While tracking the critical MPS location on the brain, higher likelihood of contrecoup injury than coup injury is found when sudden brain−skull motion takes place. The accumulation effect of CSF in the ventricle system, under large relative brain−skull motion, is also identified. The FE results show that adding relative angular velocities, to the translational impact model, not only causes a diffuse high strain area, but also cause the temporal lobes to be susceptible to cerebral contusions since the protecting CSF is prone to be squeezed away at the temporal sites due to the head rotations.

scholarly journals Multi-layered bird beaks: a finite-element approach towards the role of keratin in stress dissipation

2012 ◽  
Vol 9 (73) ◽  
pp. 1787-1796 ◽  
Author(s):  
Joris Soons ◽  
Anthony Herrel ◽  
Annelies Genbrugge ◽  
Dominique Adriaens ◽  
Peter Aerts ◽  
...  
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Speckle Pattern ◽  
Young Modulus ◽  
Von Mises Stress ◽  
Fe Model ◽  
Element Approach ◽  
Von Mises ◽  
The Impact

Bird beaks are layered structures, which contain a bony core and an outer keratin layer. The elastic moduli of this bone and keratin were obtained in a previous study. However, the mechanical role and interaction of both materials in stress dissipation during seed crushing remain unknown. In this paper, a multi-layered finite-element (FE) model of the Java finch's upper beak ( Padda oryzivora ) is established. Validation measurements are conducted using in vivo bite forces and by comparing the displacements with those obtained by digital speckle pattern interferometry. Next, the Young modulus of bone and keratin in this FE model was optimized in order to obtain the smallest peak von Mises stress in the upper beak. To do so, we created a surrogate model, which also allows us to study the impact of changing material properties of both tissues on the peak stresses. The theoretically best values for both moduli in the Java finch are retrieved and correspond well with previous experimentally obtained values, suggesting that material properties are tuned to the mechanical demands imposed during seed crushing.

FATIGUE AND DURABILITY OF A NOVEL PERCUTANEOUS AORTIC VALVE STENT

2011 ◽  
Vol 23 (01) ◽  
pp. 45-49
Author(s):  
Gideon Praveen Kumar ◽  
Lazar Mathew
Keyword(s):  
Aortic Valve ◽  
Fracture Behavior ◽  
Stress Component ◽  
Von Mises Stress ◽  
Stress Strain ◽  
Deformation And Fracture ◽  
Biomedical Scientist ◽  
Von Mises ◽  
Percutaneous Valve

To design against mechanical failure, most implants such as valve stents are assessed on the basis of survival on a long term. However, accurate investigation of the stress/strain distributions in such valve stents, which govern their deformation and fracture behavior, is essential for their prolonged, and safe use. With this background, an S–N type fatigue analysis was done on three stents with Von Mises stress component having the infinite life at 1.e + 006. The results of this study may aid a biomedical scientist to zero in on the material that could be used to analyze and fabricate percutaneous valve stents.

Finite Element Method and Parametric Study on Material Properties and Friction Coefficients for Design of Mechanical Components

2018 ◽  
Author(s):  
Yu Hua Li ◽  
Seung Ki Moon ◽  
Zhong Yang Chua ◽  
Teck Hui Ngo ◽  
Jun Jie Tou ◽  
...  
Keyword(s):  
Numerical Method ◽  
Material Properties ◽  
Parametric Study ◽  
Mechanical Efficiency ◽  
Von Mises Stress ◽  
Friction Coefficients ◽  
Air Compressor ◽  
Twin Screw ◽  
Von Mises ◽  
Screw Rotors

In this study, a parametric study on material properties and friction coefficient of mechanical components are investigated through simulating the real working conditions by a numerical method. As the screw rotors are the key components in an air compressor system, the rotors are exposed to complicated loading conditions during operation. The objective of this study is to investigate the effects on the input moment, peak Von Mises stress and the mechanical efficiency of the air compressor system subjected to varying parameters of the material properties of the female rotor and friction coefficients. From the simulation results, the peak Von Mises stress is greatly affected by the parameters of the material property of the female rotor, and the input moment and the mechanical efficiency are slightly influenced in the first condition. And, the peak Von Mises stress is significantly affected by the parameters of the friction coefficients, in the decreasing trend. The input moment is also increased with the increasing parameters of the friction coefficients. The mechanical efficiency is inversely correlated with the input moment, whereby efficiency is greatly reduced with an increase in input moment. The study shows that the proposed numerical method is efficient and suitable to establish the parameters study on the twin screw rotors, and provides an effective approach to investigate the twin screw rotors and improve the design of the system.

The Biomechanical Determinants of Concussion: Finite Element Simulations to Investigate Tissue-Level Predictors of Injury During Sporting Impacts to the Unprotected Head

2015 ◽  
Vol 31 (4) ◽  
pp. 264-268 ◽  
Author(s):  
Declan A. Patton ◽  
Andrew S. McIntosh ◽  
Svein Kleiven
Keyword(s):  
Finite Element ◽  
Corpus Callosum ◽  
Strain Rate ◽  
Tissue Level ◽  
Von Mises Stress ◽  
Tolerance Limits ◽  
Stress Strain ◽  
Head Impacts ◽  
Strain And Strain Rate ◽  
Von Mises

Biomechanical studies of concussions have progressed from qualitative observations of head impacts to physical and numerical reconstructions, direct impact measurements, and finite element analyses. Supplementary to a previous study, which investigated maximum principal strain, the current study used a detailed finite element head model to simulate unhelmeted concussion and no-injury head impacts and evaluate the effectiveness of various tissue-level brain injury predictors: strain rate, product of strain and strain rate, cumulative strain damage measure, von Mises stress, and intracranial pressure. Von Mises stress was found to be the most effective predictor of concussion. It was also found that the thalamus and corpus callosum were brain regions with strong associations with concussion. Tentative tolerance limits for tissue-level predictors were proposed in an attempt to broaden the understanding of unhelmeted concussions. For the thalamus, tolerance limits were proposed for a 50% likelihood of concussion: 2.24 kPa, 24.0 s−1, and 2.49 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively. For the corpus callosum, tolerance limits were proposed for a 50% likelihood of concussion: 3.51 kPa, 25.1 s−1, and 2.76 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively.

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