scholarly journals Artificial Finger Skin having Ridges and Distributed Tactile Sensors used for Grasp Force Control

2002 ◽  
Vol 14 (2) ◽  
pp. 140-146 ◽  
Author(s):  
Daisuke Yamada ◽  
◽  
Takashi Maeno ◽  
Yoji Yamada ◽  
Keyword(s):  
Reaction Force ◽  
Frictional Coefficient ◽  
Dynamic Contact ◽  
Fe Model ◽  
Tactile Sensors ◽  
Fe Method ◽  
Stick Slip ◽  
Grasping Force ◽  
Grasp Force ◽  
Finger Skin

An artificial elastic finger skin for robot fingers has been developed for controlling grasp force when weight and frictional coefficient of the grasped object are unknown. The elastic finger skin has ridges at the surface to divide the stick/slip area. It also has a pair of tactile sensors embedded per ridge similar to human fingertips. The surface of the whole finger is curved so that reaction force distributes. A Finite Element (FE) model of the elastic finger skin was made to conduct dynamic contact analysis using a FE method to design the elastic finger skin in detail. Then the elastic finger skin was made. We confirmed by calculation and experiment that incipient slippage of the ridge occurring near the edge of contact is detected. Then, grasp was controlled using the finger. Arbitrary objects were lifted by incipient slippage near the edge of contact. We found that artificial finger skin is useful for controlling grasping force when the weight and friction coefficient between the elastic finger skin and grasping object are unknown.

Linear and Nonlinear Approach of Hydropneumatic Tensioner Modeling for Spar Global Performance

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Chan K. Yang ◽  
M. H. Kim
Keyword(s):  
Coupling Effect ◽  
Ideal Gas ◽  
Fe Model ◽  
Floating Bodies ◽  
Fe Method ◽  
Stick Slip ◽  
Nonlinear Approach ◽  
The Relationship ◽  
Fully Coupled ◽  
The Ideal

This paper deals with a numerical model of top tension risers with hydropneumatic tensioner for Spar application in the Gulf of Mexico environment. The nonlinearity of the stiffness and the friction characteristics of the tensioner combined with stick-slip behavior of the riser keel joint are investigated. The relationship between tensions and strokes for the hydropneumatic tensioner is based on the ideal gas equation where the isotropic gas constant can be varied to achieve an optimum stroke design based on the tensioner stiffness. Challenges of modeling the coupling effects in the finite element (FE) method between the tensioner and hull motion are also presented. This new FE model is implemented into a fully-coupled time-domain coupled-dynamics-analysis program for floating bodies. The effect of nonlinearity of tensioner curve, tensioner friction, and riser keel friction is intensively investigated. The resultant global motion, TTR stroke, and tensions are systematically compared with those of a simple engineering approach, in which the nonlinear coupling effect is captured by linearization.

Linear and Nonlinear Approach of Hydro-Pneumatic Tensioner Modeling for Spar Global Performance

2007 ◽  
Author(s):  
Chan K. Yang ◽  
Arcandra Tahar ◽  
M. H. Kim
Keyword(s):  
Coupling Effect ◽  
Time Domain Analysis ◽  
Ideal Gas ◽  
Fe Model ◽  
Floating Bodies ◽  
Fe Method ◽  
Stick Slip ◽  
Nonlinear Approach ◽  
The Relationship ◽  
Fully Coupled

This paper presents a numerical model of top tension risers (TTRs) with hydro-pneumatic tensioner for Spar application in the Gulf of Mexico environment. Nonlinearity of the stiffness and friction characteristics of the tensioner combined with stick-slip behavior of riser keel joint is investigated. The relationship between tensions and strokes for hydro-pneumatic tensioner is based on the ideal gas equation where the isotropic gas constant can be varied to achieve an optimum stroke design based on tensioner stiffness. Challenges of modeling the coupling effects in the finite element (FE) method between the tensioner and hull motion are also presented. This new FE model is implemented into CHARM3D, a fully coupled time domain analysis program of floating bodies. The effect of nonlinearity of tensioner curve, tensioner friction and riser keel friction is intensively investigated. The resultant global motion, TTR stroke and tensions are systematically compared with those of a simple engineering approach in which the nonlinear coupling effect is captured by linearization.

A novel model of Z-pin insertion in prepreg based on fracture mechanics

2021 ◽  
pp. 095440542110144
Author(s):  
Guobiao Ji ◽  
Liang Cheng ◽  
Shaohua Fei ◽  
Jiangxiong Li ◽  
Yinglin Ke
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Analytical Model ◽  
Model Parameters ◽  
Force Model ◽  
Fe Model ◽  
Cohesive Elements ◽  
Fe Method ◽  
Insertion Force ◽  
Mechanics Model

Through-thickness reinforcement is a promising solution to the problem of delamination susceptibility in laminated composites. Modeling Z-pin–prepreg interaction is essential for accurate robotics-assisted Z-pin insertion. In this paper, a novel Z-pin insertion force model combining the classical cohesive finite element (FE) method with a dynamic analytical fracture mechanics model is proposed. The velocity-dependent cohesive elements, in which the fracture toughness is provided by the analytical model, are implemented in Z-pin insertion FE model to predict the crack initiation and propagation. Then Z-pin insertion experiments are performed on prepreg sample with metallic Z-pins at different velocities to identify the analytical model parameters and validate the simulation predictions offered by the model. Dynamics of Z-pin interaction with inhomogeneous prepreg is described and the effects of insertion velocity on prepreg contact force are studied. Results show that the force model agrees well with experiments and the fracture toughness rises with the increasing Z-pin insertion velocity.

Development and analysis of composite overwrapped pressure vessels for hydrogen storage

2021 ◽  
pp. 002199832110335
Author(s):  
Osman Kartav ◽  
Serkan Kangal ◽  
Kutay Yücetürk ◽  
Metin Tanoğlu ◽  
Engin Aktaş ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Damage Model ◽  
Pressure Vessels ◽  
Filament Winding ◽  
Burst Pressure ◽  
Fe Model ◽  
Fe Method ◽  
Liner Material ◽  
Mechanical Performances ◽  
Metallic Liner

In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance.

Non-Invasive Analysis of the Micro-Structural and Biomechanical Properties of Trabecular Bone in Human Femoral Head

2006 ◽  
Vol 321-323 ◽  
pp. 1070-1073
Author(s):  
Ye Yeon Won ◽  
Myong Hyun Baek ◽  
Wen Quan Cui ◽  
Kwang Kyun Kim
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Femoral Head ◽  
Trabecular Bone ◽  
Volume Fraction ◽  
Reaction Force ◽  
Bone Volume ◽  
Fe Model ◽  
Micro Ct ◽  
Trabecular Thickness

This study investigates micro-structural and mechanical properties of trabecular bone in human femoral head with and without osteoporosis using a micro-CT and a finite element model. 15 cored trabecular bone specimens with 20 of diameter were obtained from femoral heads with osteoporosis resected for total hip arthroplasty, and 5 specimens were removed from femoral head of cadavers, which has no history of musculoskeletal diseases. A high-resolution micro-CT system was used to scan each specimen to obtain histomorphometry indexes. Based on the micro-images, a FE-model was created to determine mechanical property indexes. While the non-osteoporosis group had increases the trabecular thickness, the bone volume, the bone volume fraction, the degree of anisotropy and the trabecular number compared with those of osteoporotic group, the non-osteoporotic group showed decreases in trabecular separation and structure model index. Regarding the mechanical property indexes, the reaction force and the Young's modulus were lower in the osteoporotic group than in non-osteoporotic group. Our data shows salient deteriorations in trabecular micro-structural and mechanical properties in human femoral head with osteoporosis.

scholarly journals Modelling human skull growth: a validated computational model

2017 ◽  
Vol 14 (130) ◽  
pp. 20170202 ◽  
Author(s):  
Joseph Libby ◽  
Arsalan Marghoub ◽  
David Johnson ◽  
Roman H. Khonsari ◽  
Michael J. Fagan ◽  
...  
Keyword(s):  
Computational Model ◽  
Three Dimensional ◽  
Basic Knowledge ◽  
Fe Model ◽  
Adult Size ◽  
Fe Method ◽  
Percentage Difference ◽  
Skull Growth

During the first year of life, the brain grows rapidly and the neurocranium increases to about 65% of its adult size. Our understanding of the relationship between the biomechanical forces, especially from the growing brain, the craniofacial soft tissue structures and the individual bone plates of the skull vault is still limited. This basic knowledge could help in the future planning of craniofacial surgical operations. The aim of this study was to develop a validated computational model of skull growth, based on the finite-element (FE) method, to help understand the biomechanics of skull growth. To do this, a two-step validation study was carried out. First, an in vitro physical three-dimensional printed model and an in silico FE model were created from the same micro-CT scan of an infant skull and loaded with forces from the growing brain from zero to two months of age. The results from the in vitro model validated the FE model before it was further developed to expand from 0 to 12 months of age. This second FE model was compared directly with in vivo clinical CT scans of infants without craniofacial conditions ( n = 56). The various models were compared in terms of predicted skull width, length and circumference, while the overall shape was quantified using three-dimensional distance plots. Statistical analysis yielded no significant differences between the male skull models. All size measurements from the FE model versus the in vitro physical model were within 5%, with one exception showing a 7.6% difference. The FE model and in vivo data also correlated well, with the largest percentage difference in size being 8.3%. Overall, the FE model results matched well with both the in vitro and in vivo data. With further development and model refinement, this modelling method could be used to assist in preoperative planning of craniofacial surgery procedures and could help to reduce reoperation rates.

scholarly journals 3D Finite Element Model Simulating the Behaviour of Filling Soils Used to Set Up a New Placement Method for Separate Sewer Systems

2019 ◽  
Vol 8 (3) ◽  
pp. 87-98
Author(s):  
Alaa Abbas ◽  
Felicite Ruddock ◽  
Rafid Alkhaddar ◽  
Glynn Rothwell ◽  
Iacopo Carnacina ◽  
...  
Keyword(s):  
Finite Element ◽  
Soil Properties ◽  
Model Simulation ◽  
New Method ◽  
Traffic Load ◽  
Scale Model ◽  
Fe Model ◽  
Fe Method ◽  
Buried Pipes ◽  
The Impact

The use of a finite element (FE) method and selection of the appropriate model to simulate soil elastoplastic behaviour has confirmed the importance and sensitivity of the soil properties on the accuracy when compared with experimental data. The properties of the filling soil play a significant role in determining levels of deformation and displacement of both the soil and subterranean structures when using the FE model simulation. This paper investigates the impact of the traffic load on the filling soil deformation when using the traditional method, one pipe in a trench, and a new method, two pipes in a single trench one over the other, for setting up a separate sewer system. The interaction between the buried pipes and the filling soils has been simulated using an elastoplastic FE model. A modified Drucker–Prager cap constitutive model was used to simulate the stress-strain behaviours of the soil. A series of laboratory tests were conducted to identify the elastoplastic properties of the composite soil used to bury the pipes. The FE models were calibrated using a physical lab model for testing the buried pipes under applied load. This allows the FE model to be confidently upgraded to a full-scale model. The pipe-soil interactions were found to be significantly influenced by the soil properties, the method of placing the pipes in the trench and the diameters of the buried pipes. The deformation of the surface soil was decreased by approximately 10% when using the new method of setting up the separate sewer.

scholarly journals Tribological functionalization of titanium alloys by Micro-Arc Oxidation for marine applications

2020 ◽  
Vol 321 ◽  
pp. 09001
Author(s):  
Aude MATHIS ◽  
Thierry MILLOT ◽  
Vincent BRANGER ◽  
Remy MULLER ◽  
Jean-Yves GUENEHEUX
Keyword(s):  
Friction Coefficient ◽  
Titanium Alloys ◽  
Pure Titanium ◽  
Dynamic Contact ◽  
Electrochemical Process ◽  
Commercially Pure Titanium ◽  
Tribological Behaviour ◽  
Stick Slip ◽  
Micro Arc Oxidation ◽  
Slip Phenomenon

Micro-arc Oxidation (MAO) process is a plasma assisted electrochemical process, which allows formation of ceramic-like dry oxides on top of light alloys surfaces. The good corrosion resistance as well as the low density of titanium alloys are recognized and so required for conception of structural parts in marine environment. However, their tribological behaviour reveals an important tendency to stick-slip phenomenon, which makes use of these alloys for dynamic contact mechanisms difficult. Through the MAO project from IRT M2P, formation of a MAO coating composed of aluminium titanate has been investigated to improve tribological behaviour of a commercially pure titanium (Grade 2) and an α+β alloy (TA6V, Grade 5). Pin-on-disc testing has been carried out to evaluate friction coefficient and the presence or not of stick-slip phenomenon in various contact configurations (involving non-treated titanium surfaces, MAO treated surfaces, with steel or titanium balls …) in dry or artificial seawater media. Those test campaigns are completed by evaluation of fatigue behaviour, and tribological testing on a demonstrator. Finally, this study highlights influence of MAO coating on diminishing (to removed) stick-slip phenomenon, accompanied by a reduction of friction coefficient, whatever the kind of contact (single treated surface or both ones) and the medium.

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