scholarly journals ASSESSMENT OF APPLE DAMAGE CAUSED BY A FLEXIBLE END-EFFECTOR

2020 ◽  
pp. 309-317
Author(s):  
LingXin Bu ◽  
ChengKun Chen ◽  
GuangRui Hu ◽  
JianGuo Zhou ◽  
Adilet Sugirbay ◽  
...  
Keyword(s):  
Contact Force ◽  
Mechanical Damage ◽  
Von Mises Stress ◽  
End Effector ◽  
Damage Degree ◽  
Interaction Control ◽  
Fin Ray ◽  
Von Mises ◽  
Non Destructive ◽  
Maximum Contact

In recent years, apple harvesters have become a research hotspot. Interaction control between the robot end-effector and the fruit is crucial to reduce mechanical damage to the fruit and achieve high picking performance. In this article, the damage degree was also quantified using a damage factor based on the damage plasticity model. A flexible three-finger end-effector was designed based on the Fin-Ray effect, and finite element models were established in ABAQUS to simulate the cortex damage during grasping. The results showed that the maximum von Mises stress was 0.159 MPa for the apple skin, 0.082 MPa for the cortex, and 4.178 N for the contact force, respectively. The result of the verification test showed that the maximum contact force was 4.572 N, and the relative error between the simulation and experimental results was 8.62%. Simulation and verification tests showed that the flexible three-finger end-effector achieved non-destructive grasping of apples.

scholarly journals Influence of Full-Life Cycle Wheel Profile on the Contact Performance of Wheel and Standard Fixed Frog in Heavy Haul Railway

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
He Ma ◽  
Jinming Zhang ◽  
Jun Zhang ◽  
Tao Tao Jin ◽  
Chun Yu Song
Keyword(s):  
Contact Force ◽  
Lateral Displacement ◽  
Dynamic Interaction ◽  
Von Mises Stress ◽  
Static Contact ◽  
Heavy Haul ◽  
Wheel Profile ◽  
Wheel Profile Wear ◽  
Von Mises ◽  
Heavy Haul Railway

Wheel wear is unavoidable, which affects the contact performance of the wheel and rail. This article explores the effects of wheel profile wear on the static contact and dynamic interaction between wheel and standard fixed frog in heavy haul railway. The coupling dynamic models of the vehicle-fixed frog system are established to calculate the change regulation of displacement, contact force, and acceleration when a vehicle passes through the standard fixed frog at a speed of 50 km/h in the facing move in the diverging line. Besides, the finite element models of wheel and standard fixed frog at key positions are developed to simulate the contact patch and distribution of von Mises stress in the regions of the wheel-fixed frog. Compared with the standard profile, the maximum lateral displacement of the worn profile can be reduced by up to 9 mm. The vertical contact force can be reduced from 750 kN to 320 kN, and the decrease is 57.3%. The von Mises stress could decrease up to 34% compared with the standard. And the results show that the wheel profile wear changes the positions of the wheel-rail contact points along the longitudinal direction and affects the dynamic interaction of vehicle and standard fixed frog. For the measured worn wheel profiles in this article, profile wear relieves the dynamic responses and it is good for the nose rail.

Three-Dimensional Local Yield Maps of Hard Coating Under Sliding Contact

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
P. Y. Zhang ◽  
D. F. Diao ◽  
Z. J. Wang
Keyword(s):  
Three Dimensional ◽  
Elastic Half Space ◽  
Sliding Contact ◽  
Hertzian Contact ◽  
Hard Coating ◽  
Von Mises Stress ◽  
Contact Radius ◽  
Stress Distributions ◽  
Von Mises ◽  
Maximum Contact

The local yield maps for the identification of the yield initiation positions of hard coating on three-dimensional (3D) elastic half space under sliding contact were developed. In this study, the semi-analytical method (SAM), which is based on the conjugate gradient method (CGM) and the discrete convolution and fast Fourier transform (DC-FFT) technique, was employed to analyze the contact problem. By using this method, the von Mises stress distributions for various combinations of coating thicknesses, friction coefficients, and elastic moduli of the coating and substrate were calculated. Then, the positions of yield initiation were found with the calculated results by comparing the critical maximum contact pressure Pmax,c for von Mises yielding at or in the different positions (surface, coating, interface, and substrate), and the 3D-local yield maps were introduced in relation to the yield strength ratio of the coating to the substrate (Yf/Yb) and the ratio of the coating thickness to the Hertzian contact radius (t/a0). Finally, the effect of critical friction coefficient on the transition of yielding positions was discussed.

Computational Analysis of Stress Field and Contact Pressure for Rubber Seal Based on Non-Linear Finite Element

2012 ◽  
Vol 268-270 ◽  
pp. 1080-1083 ◽  
Author(s):  
Jian Bing Sang ◽  
Li Fang Sun ◽  
Su Fang Xing ◽  
Dong Ling Zhang
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Stress Field ◽  
Contact Stress ◽  
Von Mises Stress ◽  
Rubber Seal ◽  
Linear Finite Element ◽  
Maximum Contact Stress ◽  
Von Mises ◽  
Maximum Contact

This paper aims to research on the sealing capability of rubber seal by utlizing non-linear finite element analysis. After discussion on various types of strain energy functions of rubber like materials, material parameters of Mooney-Rivilin model are determined by curve fitting based on the stress strain curve from the uniaxial tensile experiment. Axis symmetric and isotropic finite element model is developed to analyze the stress field and contact pressue of O-ring seal and lip seal at different medium pressure. Von-mises stress distribution rule and contact stress distribution curve on contact surface are achieved. The results show that maximum Von Mises stress increase with the increases of oil pressure. The maximum contact stress appears on the middle contact zone and the maximum contact stress and contact width increases obviously with the increases of oil pressure. In the meanwhile, the maximum contact stress is greater than midum pressure which can prevent the leakage of midum and achieve the function of sealing. The research results will be a useful technique for predicting the properties of rubber seal and providing reference for engineering design.

scholarly journals Effects on the Various Aluminum Foam Fenders of a Tripod Offshore Wind Turbine Collision Due to a Ship

2020 ◽  
Vol 54 (1) ◽  
pp. 79-96
Author(s):  
Zhiwei Han ◽  
Xinlei Zhao ◽  
Chun Li ◽  
Qinwei Ding
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Dynamic Response ◽  
Contact Force ◽  
Aluminum Foam ◽  
Offshore Wind ◽  
Von Mises Stress ◽  
Offshore Wind Turbine ◽  
Structural Dynamic ◽  
Von Mises

AbstractThe interest in offshore wind energy is growing all over the world. Increasingly, offshore wind turbines (OWTs) are being installed close to shipping lanes, which puts them at risk of potential collisions with ships during their service period. This article aims to investigate the structural dynamic response of OWTs to a ship collision. Considering the structure size of the fender as well as the nonlinear characteristics of the structural materials, a finite element model of a 5,000-ton ship colliding with a 4-MW tripod OWT has been developed using the explicit finite element code LS-DYNA. By observing the collision energy conversion, contact force, fender performance, Von Mises stress on the tripod, shear stress, and dynamic response of a nacelle in differently sized fender collision scenarios, it was observed that when the thickness of the fender surpasses 1.1 m, it can protect the OWT from a collision more effectively than with no fender case. Otherwise, the local contact force is cushioned by aluminum foam materials, whose contact force leads to a whole movement of the bearing tripod. The tripod with the aforementioned 1.1-m fender generates a contact force, Von Mises stress, and a shear stress, as well as the anticollision characteristics of a fender and the dynamic responses of a nacelle in 15 scenarios. Therefore, the structural design of the fender is essential in the safety of a tripod foundation in a collision. This article will provide a better understanding of the collision characteristics of the fender in the future.

Effects of occlusal scheme on All-on-Four abutments, screws and prostheses: A three-dimensional finite element study

2020 ◽  
Author(s):  
Nurullah Türker ◽  
Hümeyra Tercanlı Alkış ◽  
Steven J Sadowsky ◽  
Ulviye Şebnem Büyükkaplan
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Good Prognosis ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Group Function ◽  
Occlusal Contact ◽  
Maximum Deformation ◽  
Contact Points ◽  
Von Mises

An ideal occlusal scheme plays an important role in a good prognosis of All-on-Four applications, as it does for other implant therapies, due to the potential impact of occlusal loads on implant prosthetic components. The aim of the present three-dimensional (3D) finite element analysis (FEA) study was to investigate the stresses on abutments, screws and prostheses that are generated by occlusal loads via different occlusal schemes in the All-on-Four concept. Three-dimensional models of the maxilla, mandible, implants, implant substructures and prostheses were designed according to the All-on-Four concept. Forces were applied from the occlusal contact points formed in maximum intercuspation and eccentric movements in canine guidance occlusion (CGO), group function occlusion (GFO) and lingualized occlusion (LO). The von Mises stress values for abutment and screws and deformation values for prostheses were obtained and results were evaluated comparatively. It was observed that the stresses on screws and abutments were more evenly distributed in GFO. Maximum deformation values for prosthesis were observed in the CFO model for lateral movement both in the maxilla and mandible. Within the limits of the present study, GFO may be suggested to reduce stresses on screws, abutments and prostheses in the All-on-Four concept.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

2020 ◽  
Vol 1 (1) ◽  
pp. 93-102
Author(s):  
Carsten Strzalka ◽  
◽  
Manfred Zehn ◽  
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
A Priori ◽  
High Stress ◽  
Von Mises Stress ◽  
Detailed Knowledge ◽  
Variable Loading ◽  
Numerical Effort ◽  
Von Mises

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

scholarly journals Imitation learning-based framework for learning 6-D linear compliant motions

2021 ◽  
Author(s):  
Markku Suomalainen ◽  
Fares J. Abu-dakka ◽  
Ville Kyrki
Keyword(s):  
Contact Force ◽  
Free Space ◽  
Prior Information ◽  
Goal Area ◽  
Imitation Learning ◽  
Learning From Demonstration ◽  
End Effector ◽  
Localization Accuracy ◽  
Novel Method ◽  
Contact Tasks

AbstractWe present a novel method for learning from demonstration 6-D tasks that can be modeled as a sequence of linear motions and compliances. The focus of this paper is the learning of a single linear primitive, many of which can be sequenced to perform more complex tasks. The presented method learns from demonstrations how to take advantage of mechanical gradients in in-contact tasks, such as assembly, both for translations and rotations, without any prior information. The method assumes there exists a desired linear direction in 6-D which, if followed by the manipulator, leads the robot’s end-effector to the goal area shown in the demonstration, either in free space or by leveraging contact through compliance. First, demonstrations are gathered where the teacher explicitly shows the robot how the mechanical gradients can be used as guidance towards the goal. From the demonstrations, a set of directions is computed which would result in the observed motion at each timestep during a demonstration of a single primitive. By observing which direction is included in all these sets, we find a single desired direction which can reproduce the demonstrated motion. Finding the number of compliant axes and their directions in both rotation and translation is based on the assumption that in the presence of a desired direction of motion, all other observed motion is caused by the contact force of the environment, signalling the need for compliance. We evaluate the method on a KUKA LWR4+ robot with test setups imitating typical tasks where a human would use compliance to cope with positional uncertainty. Results show that the method can successfully learn and reproduce compliant motions by taking advantage of the geometry of the task, therefore reducing the need for localization accuracy.

scholarly journals Numerical Investigation of the Deformable Porous Media Treated by the Intermittent Microwave

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 757
Author(s):  
Tianyi Su ◽  
Wenqing Zhang ◽  
Zhijun Zhang ◽  
Xiaowei Wang ◽  
Shiwei Zhang
Keyword(s):  
Porous Media ◽  
Heat Transport ◽  
Liquid Water ◽  
Von Mises Stress ◽  
Temperature Deformation ◽  
Local Maxima ◽  
Whole Process ◽  
Surface Areas ◽  
Pulse Ratio ◽  
Von Mises

A 2D axi-symmetric theoretical model of dielectric porous media in intermittent microwave (IMW) thermal process was developed, and the electromagnetic energy, multiphase transport, phase change, large deformation, and glass transition were taken into consideration. From the simulation results, the mass was mainly carried by the liquid water, and the heat was mainly carried by liquid water and solid. The diffusion was the dominant mechanism of the mass transport during the whole process, whereas for the heat transport, the convection dominated the heat transport near the surface areas during the heating stage. The von Mises stress reached local maxima at different locations at different stages, and all were lower than the fracture stress. A material treated by a longer intermittent cycle length with the same pulse ratio (PR) tended to trigger the phenomena of overheat and fracture due to the more intense fluctuation of moisture content, temperature, deformation, and von Mises stress. The model can be extended to simulate the intermittent radio frequency (IRF) process on the basis of which one can select a suitable energy source for a specific process.

scholarly journals Finite Element Analysis of Composite Repair for Damaged Steel Pipeline

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 301
Author(s):  
Jiaqi Chen ◽  
Hao Wang ◽  
Milad Salemi ◽  
Perumalsamy N. Balaguru
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Hoop Stress ◽  
Pipe Wall ◽  
Von Mises Stress ◽  
Repair System ◽  
Composite Repair ◽  
Steel Pipeline ◽  
Von Mises ◽  
Infill Material

Carbon fiber reinforced polymer (CFRP) matrix composite overwrap repair systems have been introduced and accepted as an alternative repair system for steel pipeline. This paper aimed to evaluate the mechanical behavior of damaged steel pipeline with CFRP repair using finite element (FE) analysis. Two different repair strategies, namely wrap repair and patch repair, were considered. The mechanical responses of pipeline with the composite repair system under the maximum allowable operating pressure (MAOP) was analyzed using the validated FE models. The design parameters of the CFRP repair system were analyzed, including patch/wrap size and thickness, defect size, interface bonding, and the material properties of the infill material. The results show that both the stress in the pipe wall and CFRP could be reduced by using a thicker CFRP. With the increase in patch size in the hoop direction, the maximum von Mises stress in the pipe wall generally decreased as the maximum hoop stress in the CFRP increased. The reinforcement of the CFRP repair system could be enhanced by using infill material with a higher elastic modulus. The CFRP patch tended to cause higher interface shear stress than CFRP wrap, but the shear stress could be reduced by using a thicker CFRP. Compared with the fully bonded condition, the frictional interface causes a decrease in hoop stress in the CFRP but an increase in von Mises stress in the steel. The study results indicate the feasibility of composite repair for damaged steel pipeline.

scholarly journals 3D Finite Element Analysis of Rotary Instruments in Root Canal Dentine with Different Elastic Moduli

2021 ◽  
Vol 11 (6) ◽  
pp. 2547 ◽  
Author(s):  
Carlo Prati ◽  
João Paulo Mendes Tribst ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Alexandre Luiz Souto Borges ◽  
Maurizio Ventre ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Root Canal ◽  
Elastic Moduli ◽  
Reaction Force ◽  
Von Mises Stress ◽  
Elastic Behavior ◽  
Element Analysis ◽  
Heat Treated ◽  
Von Mises

The aim of the present investigation was to calculate the stress distribution generated in the root dentine canal during mechanical rotation of five different NiTi endodontic instruments by means of a finite element analysis (FEA). Two conventional alloy NiTi instruments F360 25/04 and F6 Skytaper 25/06, in comparison to three heat treated alloys NiTI Hyflex CM 25/04, Protaper Next 25/06 and One Curve 25/06 were considered and analyzed. The instruments’ flexibility (reaction force) and geometrical features (cross section, conicity) were previously investigated. For each instrument, dentine root canals with two different elastic moduli(18 and 42 GPa) were simulated with defined apical ratios. Ten different CAD instrument models were created and their mechanical behaviors were analyzed by a 3D-FEA. Static structural analyses were performed with a non-failure condition, since a linear elastic behavior was assumed for all components. All the instruments generated a stress area concentration in correspondence to the root canal curvature at approx. 7 mm from the apex. The maximum values were found when instruments were analyzed in the highest elastic modulus dentine canal. Strain and von Mises stress patterns showed a higher concentration in the first part of curved radius of all the instruments. Conventional Ni-Ti endodontic instruments demonstrated higher stress magnitudes, regardless of the conicity of 4% and 6%, and they showed the highest von Mises stress values in sound, as well as in mineralized dentine canals. Heat-treated endodontic instruments with higher flexibility values showed a reduced stress concentration map. Hyflex CM 25/04 displayed the lowest von Mises stress values of, respectively, 35.73 and 44.30 GPa for sound and mineralized dentine. The mechanical behavior of all rotary endodontic instruments was influenced by the different elastic moduli and by the dentine canal rigidity.

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