scholarly journals Multi-objective optimization and linear buckling of serial chain of a medical robot tool for soft tissue surgery

2020 ◽  
Vol 9 (1) ◽  
pp. 17
Author(s):  
Grzegorz Ilewicz ◽  
Andrzej Harlecki
Keyword(s):  
Calculation Model ◽  
Load Factor ◽  
The Finite Element Method ◽  
Medical Robot ◽  
Serial Chain ◽  
Linear Buckling ◽  
Buckling Coefficient ◽  
Pareto Fronts ◽  
Euler Force ◽  
Soft Tissue Surgery

<p>The slender structures of a medical robot may have a tendency to buckling when a  force equal to the critical Euler force and an additional disturbance will work on their structures. In this work, eigenvalue problem that describes the linear buckling, is under consideration. The main goal of the article is to check when linear buckling phenomenon appears in construction of  a medical robot with serial chain due to the fact that for safety reasons of a robot’s work, it is necessary to answer the question, whether the buckling may occur in the robot’s structure. For this purpose, a numerical calculation model was defined by using the finite element method. The values of load factor coefficients that are eigenvalue are determinated and also the eigenvectors that have shapes of deformation for  the next eigenvalues are presented. The multi-criteria optimization model was determined to aim for the minimum mass of the effector and the buckling coefficient, from which the Euler force results, for the maximum. The solution was obtained on the basis of Pareto fronts and the MOGA genetic algorithm.</p>

Transverse Ribs Affect the Stability of Steel-Concrete Composite Box Beams

2014 ◽  
Vol 587-589 ◽  
pp. 1663-1667
Author(s):  
Chong Yang Zhou ◽  
Jian Rong Yang ◽  
Wan Wan Jiang
Keyword(s):  
Finite Element Method ◽  
The Finite Element Method ◽  
Box Girder ◽  
Linear Buckling ◽  
Box Beams ◽  
Buckling Coefficient ◽  
Stiffening Ribs ◽  
The Stability ◽  
Lateral Bracing ◽  
Linear Buckling Analysis

The paper uses the finite element method to the specific structure of the linear buckling analysis to study the steel - concrete buckling coefficient changes when the changes and adjustments in the case of composite box girder structure different density transverse stiffening ribs buckling coefficient bracing spacing, Thus obtained that the almost linear relationship between the change in distance between the transverse stiffening ribs and buckling coefficient. Meanwhile get when bracing spacing when a valid range, coefficient of variation of buckling structure is not particularly obvious. Which is to adjust the spacing and lateral bracing number of stiffening ribs provide a space.

scholarly journals PERFORMANCE BASED DESIGN OF UNBRACED STEEL FRAMES EXPOSED TO NATURAL FIRE SCENARIOS

2016 ◽  
Author(s):  
Carlos Couto ◽  
Thiago Silva ◽  
Martina Carić ◽  
Paulo Vila Real ◽  
Davor Skejić
Keyword(s):  
Fire Resistance ◽  
Steel Frames ◽  
Design Methods ◽  
The Other ◽  
Performance Based Design ◽  
The Finite Element Method ◽  
Natural Fire ◽  
Fire Scenarios ◽  
Buckling Coefficient ◽  
Structural Engineers

<p>According to the Eurocode 3 Part 1-2 (EN1993-1-2) (CEN 2005b), it is possible for structural engineers to consider physical based thermal actions and to do performance based design instead of using prescriptive rules based on nominal fire curves. However, some uncertainties remain in the use of such approaches. This study focus on the clarification of the use of the simplified design methods to assess the fire resistance of unbraced steel frames exposed to fire. On the other hand, a recent study (Couto et al. 2013) suggests the use of a buckling coefficient of 1.0 for all the columns except those belonging to the first storey of a pinned framed where 2.0 should be taken instead and it is unclear if the consideration of such values for the buckling lengths is adequate when using performance based designs.</p>In this study, a comparison is made between simple and advanced calculation models and it is demonstrated that the simple design methods, using the suggested buckling coefficients to calculate the fire resistance of the frames are safe sided when compared to the use of advanced calculations using the finite element method (FEM).

Modelling and Analysis of Elastic and Thermal Deformations of a Hydrodynamic Radial Journal Bearing

2016 ◽  
Vol 674 ◽  
pp. 127-132 ◽  
Author(s):  
Aki Linjamaa ◽  
Arto Lehtovaara ◽  
Marke Kallio ◽  
Sven Söchting
Keyword(s):  
Combustion Engine ◽  
Calculation Model ◽  
Journal Bearings ◽  
The Finite Element Method ◽  
Lubrication Film ◽  
Thermal Deformations ◽  
Hydrodynamic Calculations ◽  
Bearing Loads ◽  
Loaded Side ◽  
Rigid Surfaces

Journal bearings are widely used in heavy industry and in internal combustion engine applications. There is a need to increase the power density of various machine parts which leads to increased bearing loads and reduced lubrication film thicknesses. This type of development may increase deformations on the bearing surfaces which need to be considered in the bearing design process.The main purpose of this work was to develop a parameterized calculation model for hydrodynamic radial journal bearings which takes into account elastic and thermal deformations of the bearing surfaces. Hydrodynamic calculations were based on the numerical solving of the Reynolds equation by assuming rigid surfaces. Elastic and thermal deformations of the bearing and shaft surfaces were calculated by using the finite element method. It is concluded that elastic and thermal deformations are partly canceling each other out at the loaded side of the bearing and depending on the sliding speed and the external normal force either one of them could be more significant.

An Impact Analysis of Turbine Guide Bearing Stiffness on Rotating Parts’ Transverse Vibration Characteristics

2011 ◽  
Vol 117-119 ◽  
pp. 222-230
Author(s):  
Yi Zhu ◽  
Xi De Lai ◽  
Li Fa Wang
Keyword(s):  
Large Scale ◽  
Impact Analysis ◽  
Hydraulic Turbine ◽  
Calculation Model ◽  
Vibration Characteristics ◽  
Francis Turbine ◽  
Lateral Vibration ◽  
The Finite Element Method ◽  
Bearing Stiffness ◽  
The Impact

A vibration calculation model for a large-scale hydraulic turbine group is built to act on the unbalanced force between the rotor and the runner. Take the Francis turbine group for example. Using the finite element method, the units lateral vibration characteristics of rotating components were calculated and analyzed. The paper discusses the impact of location and the guide bearing stiffness on the lateral vibration characteristics of the unit. Based on the elastic supporting models, the paper also compares the results of the guide bearing stiffness modified simultaneously and respectively. Results show that the guide bearing stiffness has a significant impact on the lateral vibration characteristics of the location of the unit, which provides a reference for the reduction of vibration and the optimization of the supporting structure of the turbine unit.

scholarly journals Stress Assessment of Gear Teeth in Epicyclic Gear Train for Radial Sedimentation Tank

2020 ◽  
Vol 14 (3) ◽  
pp. 121-127
Author(s):  
Grzegorz Budzik ◽  
Tadeusz Markowski ◽  
Michał Batsch ◽  
Jadwiga Pisula ◽  
Jacek Pacana ◽  
...  
Keyword(s):  
Planetary Gear ◽  
Gear Train ◽  
Load Factor ◽  
The Finite Element Method ◽  
Gear Teeth ◽  
Gear Mesh ◽  
Sedimentation Tank ◽  
Epicyclic Gear ◽  
Comparison Of The Results ◽  
Root Stress

Abstract The paper presents the strength evaluation of planetary gear teeth designed for a radial sedimentation tank drive. A novel type of gear drive, composed of a closed epicyclic gear train and an open gear train with internal cycloidal gear mesh is proposed. Contact stress and root stress in the planetary gear train were determined by the finite element method and according to ISO 6336. The influence of the mesh load factor at planet gears on stress values was also established. A comparison of the results followed. It was observed that the mesh load factor on satellites depends mainly on the way the satellites and central wheels are mounted, the positioning accuracy in the carrier and the accuracy of teeth. Subsequently, a material was selected for the particular design of planetary gear and the assumed load. The analysis of the obtained results allowed assuming that in case of gears in class 7 and the rigid mounting of satellites and central wheels, gears should be made of steel for carburizing and hardening. In case of flexible satellites or flexible couplings in the central wheels and gears in class 4, gears can be made of nitriding steel.

scholarly journals Research on the Method and Model for Calculating Impact Load in the Rockburst Tunnel

Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 13
Author(s):  
Zhiwei Yan ◽  
Dagang Liu ◽  
Zhilong Wang ◽  
Daming Zhao ◽  
Hongtao Tian
Keyword(s):  
Impact Load ◽  
Design Method ◽  
Pressure Coefficient ◽  
Side Wall ◽  
Calculation Model ◽  
Load Factor ◽  
Circular Tunnel ◽  
Supporting Structure ◽  
The Difference ◽  
The Impact

Among several design methods of tunnel supporting structure, the load-structure method is widely used in different countries, but the determination of load is essential in this design method. The problem of rockburst is becoming more prominent as tunnel engineering enters the deep underground space. However, the research on the impact load on the supporting structure is insufficient in relevant fields. Therefore, from the perspective of energy, this paper deduces the method and model for calculating the impact load of the rockburst tunnel acting on the supporting structure by using the method of structural mechanics first, after the location effect of impact load is determined under different section types and different section sizes. The results indicated that: dynamic load factor K is related to the stiffness EI and supporting size coefficient K0 of the supporting structure, also the difference of impact load in different sections is proved. Tunnel rockburst-prone location is related to lateral pressure coefficient, thus when λ = 1, the probability of rockburst in the whole circular tunnel is the same, while side wall and vault are prone to rockburst in single-track horseshoe tunnel, and the side wall is prone to rockburst in double-track horseshoe tunnel; furthermore when λ > 1, the vault and the inverted arch are prone to rockburst; additionally, when λ < 1, the rockburst is most likely to occur in the arch waist of the circular tunnel and the side walls and the arch waist of the horseshoe tunnel. Finally, the rockburst tunnel’s local load-structure calculation model and the calculation process based on the model are provided.

scholarly journals Analysis of the stressed-deformed condition of the bearing installed

2020 ◽  
pp. 107-117
Author(s):  
Stanislav Maiorov ◽  
◽  
Iuliia Lagunova ◽  
Keyword(s):  
Calculation Model ◽  
Central Processor ◽  
The Finite Element Method ◽  
Connecting Rod ◽  
Jaw Crusher ◽  
Acceptable Range ◽  
Dependent Model ◽  
Bearing Assembly ◽  
Parameter Dependent ◽  
Model Programs

Introduction. The article considers the calculation of the strength of a bearing mounted on the connecting rod of a jaw crusher, taking into account all workloads. ISSN 0536-1028 «Известия вузов. Горный журнал», № 3, 2020 117 Object problems. When creating particularly large machines and systems, in the case of their 3D-modeling and detailed study, we are faced with an increased load on the central processor of the computer, as well as on the graphics and RAM modules, which leads to a significant slowdown in the design process and calculations particular. Research aim is to consider the task of selecting a simpler and "easier" for the calculation model programs, not difficult to parameterize, compared with the original bearing model, but providing accuracy in the calculation in an acceptable range of errors. The research also aims to analyze the stress-strain state of the bearing assembly. The main methods. In the calculations, the finite element method was used. Specialized software package APM WinMachine was also used. Computing experiment conducted. Conclusions. The results of a computational experiment satisfy the requirements and can be used to solve further problems of designing bearing assemblies. In the future, a parameter-dependent model can be created to facilitate the calculation using any type of bearing

scholarly journals Optimal Design of Electrothermal Microactuators for Many Criteria by Means of an Immune Game Theory Multiobjective Algorithm

2019 ◽  
Vol 9 (21) ◽  
pp. 4654 ◽  
Author(s):  
Adam Długosz ◽  
Paweł Jarosz ◽  
Tomasz Schlieter
Keyword(s):  
Game Theory ◽  
Optimal Design ◽  
The Novel ◽  
The Finite Element Method ◽  
Self Organizing Maps ◽  
Numerical Tests ◽  
Mechanical Field ◽  
Novel Method ◽  
Benchmark Test Functions ◽  
Pareto Fronts

The paper presents the application of the IMGAMO (immune game theory multiobective algorithm) in the optimal design of electrothermal microactuators. Several numerical tests on the mathematical benchmark test functions were performed, showing the superiority of the IMGAMO, when a large number of criteria are considered, in comparison to other multiobjective optimizers. A parametric numerical model of an electrothermal microactuaror was developed and verified. Six functionals, which depend on various thermal and mechanical quantities of the microactuator, were proposed, formulated and numerically implemented. These functionals represent real requirements asked of microactuators. The boundary-value problem of an electro-thermo-mechanical field was solved multiple times during the course of optimization by way of the finite element method (FEM). A numerical example of multiobjective optimization of chevron-type electrothermal actuators is included in the paper. Representation of the multi-dimensional Pareto fronts by means of scatter plot matrices, aided by self-organizing maps (SOMs), is presented. The novel method of selecting interesting, compromise-solutions is proposed and described.

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