scholarly journals A Heuristic Approach to Dynamic Stiffness Control

2021 ◽  
Author(s):  
Farhad Fakour ◽  
M. Hossein Siadati
Keyword(s):  
Weight Reduction ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Superior Performance ◽  
Dead Weight ◽  
Element Analysis ◽  
Areas Of Interest ◽  
Stiffness And Damping ◽  
Mass Participation

Abstract For appropriate and even superior performance yet cost reduction, this work was performed with the aim of weight reduction in the overall design and construction of possibly any machine tools. As far as our literature search is concerned, there does not seem to be much work published regarding successful weight reduction while maintaining performance using mass participation factor (MPF) in the areas of interest of the machine tools. In order to accomplish this task, we started with the ‘bed’ compartment of a CNC system and resorted to using the finite element analysis (FEA) software package and thoughtfully manipulated the available data/parameters until the desired results were obtained. The most important parameters were static stiffness, dynamic stiffness, and damping ratio. On the ‘bed’ of the machines’ compartment currently in production, it was so identified that there was unnecessary material (dead weight), and thus the FEA software was used in order to remove the unnecessary material by iteration. Finally, a new machine was built devoid of the unnecessary material, resulted in 9.3% weight reduction as predicted by the simulation, without sacrificing any accuracy and/or precision in performance.

scholarly journals Dynamic Properties of Pretreated Rubberized Concrete under Incremental Loading

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2183
Author(s):  
Aijiu Chen ◽  
Xiaoyan Han ◽  
Zhihao Wang ◽  
Tengteng Guo
Keyword(s):  
Stress Level ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Rubberized Concrete ◽  
Rubber Content ◽  
Rubber Particles ◽  
Energy Dissipation Capacity ◽  
Stiffness And Damping ◽  
Incremental Loading

Recycling scrap tyres as alternative aggregates of concrete is an innovative option. To clarify the dynamic properties of the pretreated rubberized concrete with some cumulative damage, the natural frequency, flexural dynamic stiffness, and damping ratio of the specimens under incremental stress level were investigated in this paper. The results indicated that the pretreatment of rubber particles improved the strength, ductility, and crack resistance of the rubberized concrete. The reduction of the flexural dynamic stiffness was clarified with the increase of concrete stress level. The addition of the pretreated rubber particles enhanced the concrete energy dissipation capacity during the destruction, and the specimen dissipated more energy with the increase of rubber content before its failure.

Dynamic Characteristics of Aerostatic Porous Journal Bearings With a Surface-Restricted Layer

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Yuta Otsu ◽  
Masaaki Miyatake ◽  
Shigeka Yoshimoto
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Porous Metal ◽  
Journal Bearings ◽  
Low Permeability ◽  
Bearing Surface ◽  
Permeability Surface ◽  
Stiffness And Damping

Aerostatic porous bearings have been successfully applied to various precision devices such as machine tools and measuring equipment to achieve a higher accuracy of motion. However, aerostatic porous bearings have a disadvantage in that they are prone to cause pneumatic hammer instability. Therefore, to avoid this instability, a surface-restricted layer that has permeability smaller than the bulk of the porous material is usually formed on the bearing surface. In this paper, the dynamic characteristics of aerostatic porous journal bearings that have a surface-restricted layer are investigated numerically and experimentally. The effects of permeability in bulk porous materials and of a surface-restricted layer on the bearing characteristics are discussed using two kinds of porous material: graphite and metal. It was confirmed that aerostatic porous metal bearings with relatively large permeability could achieve large values of dynamic stiffness and damping coefficients using a low permeability, surface-restricted layer.

Eggshell Penetration of Various Types of Hens' Eggs by Salmonella enterica Serovar Enteritidis

2007 ◽  
Vol 70 (3) ◽  
pp. 623-628 ◽  
Author(s):  
WINY MESSENS ◽  
KOEN GRIJSPEERDT ◽  
KOEN DE REU ◽  
BART DE KETELAERE ◽  
KRISTOF MERTENS ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Selective Medium ◽  
Housing System ◽  
Omega 3 ◽  
Salmonella Enterica Serovar Enteritidis ◽  
Membrane Complex ◽  
Highly Correlated ◽  
Stiffness And Damping

Egg weight, shell thickness, number of pores, cuticle deposition, eggshell strength (dynamic stiffness and damping ratio), and the ability of Salmonella enterica serovar Enteritidis (SE) to penetrate the eggshell were determined. Penetration was assessed by filling the eggs with a selective medium that allowed viewing of Salmonella growth on the inside of the shell and membrane complex. After inoculation of each shell with on average 2.71 log CFU, the eggs were stored for up to 14 days at 20°C and 60% relative humidity. Commercially available eggs were used. At 14 days of storage, only 6.0% of the eggs from free-range hens and 16.0% of the generic (i.e., eggs from hens in conventional battery cages that were given standard feed) white eggs were penetrated. The generic brown, organic, and omega-3–enriched eggs were penetrated at a frequency of 30 to 34%. In a second experiment it was shown that the layer strains of the hen (ISA-Brown Warren versus Bovans Goldline), which were kept in furnished cages, did not affect eggshell penetration by SE. For Bovans Goldline hens, the housing system (furnished cage versus aviary) did not affect penetration, while a trend was visible toward a higher fraction of penetrated eggshells when hens were fed corncob mix rather than standard feed. Eggshell penetration was observed more frequently in the absence of cuticle spots and for eggs having lower dynamic stiffness values. Shell contamination at the end of storage was highly correlated with SE penetration.

scholarly journals Improved Immune Algorithm Combined with Steepest Descent Method for Optimal Design of IPMSM for FCEV Traction Motor

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3904
Author(s):  
Ji-Chang Son ◽  
Myung-Ki Baek ◽  
Sang-Hun Park ◽  
Dong-Kuk Lim
Keyword(s):  
Optimal Design ◽  
Permanent Magnet Synchronous Motor ◽  
Torque Ripple ◽  
Descent Method ◽  
Immune Algorithm ◽  
Electric Machines ◽  
Steepest Descent Method ◽  
Superior Performance ◽  
Element Analysis ◽  
Traction Motor

In this paper, an improved immune algorithm (IIA) was proposed for the torque ripple reduction optimal design of an interior permanent magnet synchronous motor (IPMSM) for a fuel cell electric vehicle (FCEV) traction motor. When designing electric machines, both global and local solutions of optimal designs are required as design result should be compared in various aspects, including torque, torque ripple, and cogging torque. To lessen the computational burden of optimization using finite element analysis, the IIA proposes a method to efficiently adjust the generation of additional samples. The superior performance of the IIA was verified through the comparison of optimization results with conventional optimization methods in three mathematical test functions. The optimal design of an IPMSM using the IIA was conducted to verify the applicability in the design of practical electric machines.

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

The Finite Element Analysis and the Multi-Objective Optimization Design of Spindle Systems of CNC Gantry Machine Tools

2016 ◽  
Vol 693 ◽  
pp. 243-250
Author(s):  
Zhi Zhong Guo ◽  
Yun Shun Zhang ◽  
Shi Hao Liu
Keyword(s):  
Machine Tools ◽  
Optimization Design ◽  
Multi Objective Optimization ◽  
Element Analysis ◽  
Multi Objective ◽  
Vibration Resistance ◽  
Design Variables ◽  
Force Coupling ◽  
The Finite Element Analysis ◽  
Spindle Structure

It is discovered that the vibration resistance of spindle systems needs to be improved based on the statics analysis, modal analysis and heating-force coupling analysis of spindle systems of CNC gantry machine tools. The design variables of optimization are set according to sensitivity analysis, multi-objective and dynamic optimization design is realized and its designing scheme is gained for spindle structure. The research results show that vibration resistance can be improved without change of the quality and static property of spindle systems of CNC gantry machine tools.

Influencing Factors on Dynamic Response of Hydrostatic Guideways

2011 ◽  
Vol 418-420 ◽  
pp. 2095-2101 ◽  
Author(s):  
Zhi Wei Wang ◽  
Wan Hua Zhao ◽  
Bing Heng Lu
Keyword(s):  
Film Thickness ◽  
Damping Ratio ◽  
Pressure Ratio ◽  
Settling Time ◽  
Lubricating Oil ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
Maximum Value ◽  
Small Perturbation Method ◽  
Stiffness And Damping

Stiffness and damping of hydrostatic guideways are calculated by small perturbation method based on Reynolds equation in dynamic regime. The hydrostatic guideway is considered as a system which consists of the mass, the spring and the damper. The effects of some main parameters on stiffness, damping and damping ratio are analyzed which include the supply pressure, the film thickness, the pad dimension, the pressure ratio, the lubricating oil volume and the lubricating oil viscosity. The relationships between the settling time of the hydrostatic guideways and these parameters are investigated under a step load. It is shown that the slide block returns to equilibrium without overshooting under a step load, and the amplitude of the block vibration has not a maximum value under a cyclic load, due to the large damping effect( ξ>1). In addition, the settling time can be shorten with the increase of the supply pressure, the film thickness and the lubricating oil volume, and also with the decrease of the pressure ratio and the lubricating oil viscosity. The settling time get the shortest value when recess parameter( α) is 0.55.

Weight-Reduction Optimization Design for Milling Planer Bed Based on Finite Element Analysis

2012 ◽  
Vol 490-495 ◽  
pp. 2785-2789
Author(s):  
Dong Sun ◽  
Xu Dong Yang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Weight Reduction ◽  
Optimization Design ◽  
Weak Link ◽  
Three Dimensional ◽  
Production Costs ◽  
Element Analysis ◽  
Before And After ◽  
Improvement Scheme

The milling planer bed is one of the most important foundational parts for the entire machine, sufficient stiffness is required. The posterior segment of a certain milling planer bed is regarded as the optimization object in this paper. Three-dimensional modeling method is used to calculate the exact weight of the bed and then finite element analysis is used to research the static and dynamic characteristics before and after weight-reduction. The weak link of the bed is found out and a improvement scheme is put forward ensuring lower production costs under the premise of sufficient rigidity.

Finite Element Analysis for Machine Joint

2010 ◽  
Vol 26-28 ◽  
pp. 198-203
Author(s):  
Tie Neng Guo ◽  
Ling Li ◽  
Li Gang Cai ◽  
Zhi Feng Liu
Keyword(s):  
Dynamic Characteristic ◽  
Maximum Error ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Element Analysis ◽  
Mechanical Joint ◽  
Result Show ◽  
Joint Element ◽  
Stiffness And Damping ◽  
Five Axis

The stiffness and damping of mechanical joint are modeled by the zero thickness joint interfaces theory. The method is applied to analyze the dynamic characteristic of the gantry frame in a five axis turning-milling compound CNC machine tool. The model test is carried out in the gantry frame, and the maximum error of the first sixth mode is 5.63%. The experimental and analysis result show the zeros thickness joint element can provide an effective method to model the machine joint and predict the dynamic characteristic of the assembled structure.

Dynamic Analysis of Helical Milling Unit Based on Virtual Machine Tool

2011 ◽  
Vol 188 ◽  
pp. 463-468 ◽  
Author(s):  
Xu Da Qin ◽  
Qi Wang ◽  
H.Y. Wang ◽  
Song Hua
Keyword(s):  
Machine Tool ◽  
Virtual Machine ◽  
Dynamic Stiffness ◽  
Three Dimensional ◽  
Geometrical Model ◽  
Helical Milling ◽  
Response Analysis ◽  
Computer Simulation Model ◽  
Element Analysis ◽  
Virtual Machine Tool

The virtual prototype is a computer simulation model of the physical product that can be analyzed like a real machine. This paper studies the helical milling unit based on the virtual machine tool. The helical milling unit is first designed according to the kinematics of the helical milling. The main parts of the equipment include rotating mechanism, orbital agency and radial offset organization. Based on the feasibility analysis of the structure, the three-dimensional geometrical model is built in the Solidworks software. The key parts in the model are separated from the device and introduced into the finite element analysis (FEA) software, according to the cutting loads tested from experiment, static and dynamic modal analysis and harmonic response analysis are carried out for the key parts of this device. The results show that the static and dynamic stiffness can meet design requirement.

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