scholarly journals The dynamic response of the bicycle rider’s body to vertical, fore-and-aft, and lateral perturbations

2019 ◽  
Vol 234 (7) ◽  
pp. 1944-1957
Author(s):  
Georgios Dialynas ◽  
Jelle W de Haan ◽  
Alfred C Schouten ◽  
Riender Happee ◽  
Arend L Schwab
Keyword(s):  
Dynamic Response ◽  
Random Noise ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Longitudinal Direction ◽  
Apparent Mass ◽  
Motion Platform ◽  
Trunk Motion ◽  
Damped System ◽  
Two Wheeler

The objective of this study was to identify the dynamic response of the bicycle rider’s body during translational perturbations, in an effort to improve two-wheeler safety and comfort. A bicycle mock-up was equipped with sensors measuring three-dimensional seat and trunk accelerations and rider’s force responses at the seat, handlebars, and footpegs. The bicycle mock-up was driven by a hexapod motion platform that generated random noise perturbations in the range of 0–10 Hz. Twenty-four healthy male adults participated in this study. Responses are represented as frequency response functions capturing three-dimensional force interactions of the rider’s body at the seat, handlebars and footpegs in terms of apparent mass, and rider’s trunk motion (one-dimensional) as function of seat motion as seat-to-sternum transmissibility. Results showed that the vertical and longitudinal apparent mass for most of the bicycle interfaces followed the resonance of the seat-to-sternum transmissibility. A twice as high magnitude was observed at the resonance, although a more heavily damped system was apparent in the seat-to-sternum transmissibility. Resonant frequencies were considerably higher in the vertical direction compared to the longitudinal direction. Different dynamics were observed for the lateral measurements, where all magnitudes decreased after the base frequency, and no resonance was observed.

About the Development of Brick-Design in Russia

2020 ◽  
Vol 787 (12) ◽  
pp. 21-24
Author(s):  
Y.A. Bozhko ◽  
◽  
K.A. Lapunova ◽  
Keyword(s):  
Functional Role ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Basic Unit ◽  
Design Development ◽  
European Cities ◽  
Unique Material ◽  
Decisive Action ◽  
Color Combinations ◽  
Insufficient Number

The article reflects the authors view on the technical and aesthetic side of the use of face bricks in the architecture of our country. The term brick design combines such indicators of brickwork as the color, size and surface of the brick itself, as well as the type of masonry and seam parameters. Unfortunately, the analysis of the current situation shows that the culture of consumption of face bricks in Russia remains at a low level, which is due to the lack of proper knowledge and insufficient number of qualified master masons. The main goal of brick design development is to popularize various types of three-dimensional masonry and reveal the potential of using bricks as a basic unit. The comparison shows the architecture of European cities, which does not differ in the complexity of architectural forms, but has advantages in the form of unusual masonry, color combinations, vertical direction of masonry and other elements of technical aesthetics. The use of bricks in various levels of brick design will allow you to avoid using architectural decoration on the facades of buildings, while preserving its authenticity and individuality. The brick, as a basic unit, is self-sufficient and is able to fulfill not only its functional role, but also its aesthetic one. In this situation, a necessary and decisive action will be competent communication with industry specialists, architects and designers, leading manufacturers and technologists who realize that we have a unique material that does not need additional wrapping when used efficiently.

scholarly journals Dynamic response analysis for multi-degrees-of-freedom parallel mechanisms with various types of three-dimensional clearance joints

2021 ◽  
Vol 18 (3) ◽  
pp. 172988142110177
Author(s):  
Jia Yonghao ◽  
Chen Xiulong
Keyword(s):  
Dynamic Response ◽  
Multibody Systems ◽  
Parallel Mechanism ◽  
Three Dimensional ◽  
Response Analysis ◽  
Parallel Mechanisms ◽  
Dynamics Model ◽  
Clearance Joints ◽  
Clearance Joint ◽  
Spatial Parallel Mechanism

For spatial multibody systems, the dynamic equations of multibody systems with compound clearance joints have a high level of nonlinearity. The coupling between different types of clearance joints may lead to abundant dynamic behavior. At present, the dynamic response analysis of the spatial parallel mechanism considering the three-dimensional (3D) compound clearance joint has not been reported. This work proposes a modeling method to investigate the influence of the 3D compound clearance joint on the dynamics characteristics of the spatial parallel mechanism. For this purpose, 3D kinematic models of spherical clearance joint and revolute joint with radial and axial clearances are derived. Contact force is described as normal contact and tangential friction and later introduced into the nonlinear dynamics model, which is established by the Lagrange multiplier technique and Jacobian of constraint matrix. The influences of compound clearance joint and initial misalignment of bearing axes on the system are analyzed. Furthermore, validation of dynamics model is evaluated by ADAMS and Newton–Euler method. This work provides an essential theoretical basis for studying the influences of 3D clearance joints on dynamic responses and nonlinear behavior of parallel mechanisms.

3-D elastic coupling vibration and acoustical radiation characteristics of cracked gear under elastic support condition

2015 ◽  
Vol 23 (9) ◽  
pp. 1548-1568 ◽  
Author(s):  
Shao Renping ◽  
Purong Jia ◽  
Xiankun Qi
Keyword(s):  
Dynamic Response ◽  
Support System ◽  
Three Dimensional ◽  
Elastic Support ◽  
Dynamic Responses ◽  
Tooth Root ◽  
Support Condition ◽  
Elastic Boundary ◽  
Root Crack ◽  
Elastic Disc

According to the actual working condition of the gear, the supporting gear shaft is treated as an elastic support. Its impact on the gear body vibration is considered and investigated and the dynamic response of elastic teeth and gear body is analyzed. On this basis, the gear body is considered as a three-dimensional elastic disc and the gear teeth are treated as an elastic cantilever beam. Under the conditions of the elastic boundary (support shaft), combining to the elastic disk and elastic teeth, the influence of three-dimensional elastic discs on the meshing tooth response under an elastic boundary condition is also included. A dynamic model of the gear support system and calculated model of the gear tooth response are then established. The inherent characteristics of the gear support system and dynamics response of the meshing tooth are presented and simulated. It was shown by the results that it is correct to use the elastic support condition to analyze the gear support system. Based on the above three-dimensional elastic dynamics analysis, this paper set up a dynamics coupling model of a cracked gear structure support system that considered the influence of a three-dimensional elastic disc on a cracked meshing tooth under elastic conditions. It discusses the dynamic characteristic of the cracked gear structure system and coupling dynamic response of the meshing tooth, offering a three-dimensional elastic body model of the tooth root crack and pitch circle crack with different sizes, conducting the three-dimensional elastic dynamic analysis to the faulty crack. ANSYS was employed to carry out dynamic responses, as well as to simulate the acoustic field radiation orientation of a three-dimensional elastic crack body at the tooth root crack and pitch circle with different sizes.

Consistent Hydrodynamic Mass for Parallel Prismatic Beams in a Fluid-Filled Container

1984 ◽  
Vol 106 (3) ◽  
pp. 270-275
Author(s):  
J. F. Loeber
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Incompressible Fluid ◽  
Finite Element Methods ◽  
Mass Matrix ◽  
Three Dimensional ◽  
Beam Length ◽  
Step Process ◽  
Beam Bending

In this paper, representation of the effects of incompressible fluid on the dynamic response of parallel beams in fluid-filled containers is developed using the concept of hydrodynamic mass. Using a two-step process, first the hydrodynamic mass matrix per unit (beam) length is derived using finite element methods with a thermal analogy. Second, this mass matrix is distributed in a consistent mass fashion along the beam lengths in a manner that accommodates three-dimensional beam bending plus torsion. The technique is illustrated by application to analysis of an experiment involving vibration of an array of four tubes in a fluid-filled cylinder.

Experimental and Numerical Investigation of Air-Particle Two-Phase Flow in Centrifugal Separator

2000 ◽  
Author(s):  
H. J. Kang ◽  
B. Zheng ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Velocity Distribution ◽  
Separation Efficiency ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Tangential Direction ◽  
Cylinder Surface ◽  
Centrifugal Separator ◽  
Two Phase ◽  
Dust Collection ◽  
Numerical Solver

Abstract The velocity distributions inside a centrifugal separator with outside and inside diameters of 152.4 mm (6″) and 76.2 mm (3″), respectively, have been investigated experimentally and numerically to obtain optimum separation efficiency. Two 12.7 mm (1/2-inch) holes were drilled on the external surface of the separator to measure the velocity distribution in the separator. Two direction velocities (tangential direction along the cylinder surface and axial along the vertical direction) were measured to compare with the numerical simulation results. A 6060P Pitot probe was employed to obtain the velocity distribution. The dust samples (a mixture of steel particle and dust) from the dust collection box were analyzed using a Phillips XL30 Scanning Electron Microscope. FLUENT code is used as the numerical solver for this fully three-dimensional problem. The fluid flow in the separator is assumed to be steady and incompressible turbulent flow. The standard k–ε model was employed in this study. Non-uniform, unstructured grids are chosen to discretize the entire computation domain. Almost 100,000 cells are used to discretize the whole separator. The constant velocity profile is imposed on the inlet plane. The pressure boundary condition is adopted at outlet plane. Comparing the velocity distribution and separation efficiency from the experiment and the numerical modeling shows that the experimental results and the estimated data agree fairly well and with a deviation within ±10%.

scholarly journals Study of a temperature gradient metamorphism of snow from 3-D images: time evolution of microstructures, physical properties and their associated anisotropy

2014 ◽  
Vol 8 (6) ◽  
pp. 2255-2274 ◽  
Author(s):  
N. Calonne ◽  
F. Flin ◽  
C. Geindreau ◽  
B. Lesaffre ◽  
S. Rolland du Roscoat
Keyword(s):  
Temperature Gradient ◽  
Physical Properties ◽  
Time Evolution ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Large Set ◽  
Correlation Lengths ◽  
Snow Properties ◽  
Cold Room ◽  
Anisotropy Coefficients

Abstract. We carried out a study to monitor the time evolution of microstructural and physical properties of snow during temperature gradient metamorphism: a snow slab was subjected to a constant temperature gradient in the vertical direction for 3 weeks in a cold room, and regularly sampled in order to obtain a series of three-dimensional (3-D) images using X-ray microtomography. A large set of properties was then computed from this series of 3-D images: density, specific surface area, correlation lengths, mean and Gaussian curvature distributions, air and ice tortuosities, effective thermal conductivity, and intrinsic permeability. Whenever possible, specific attention was paid to assess these properties along the vertical and horizontal directions, and an anisotropy coefficient defined as the ratio of the vertical over the horizontal values was deduced. The time evolution of these properties, as well as their anisotropy coefficients, was investigated, showing the development of a strong anisotropic behavior during the experiment. Most of the computed physical properties of snow were then compared with two analytical estimates (self-consistent estimates and dilute beds of spheroids) based on the snow density, and the size and anisotropy of the microstructure through the correlation lengths. These models, which require only basic microstructural information, offer rather good estimates of the properties and anisotropy coefficients for our experiment without any fitting parameters. Our results highlight the interplay between the microstructure and physical properties, showing that the physical properties of snow subjected to a temperature gradient cannot be described accurately using only isotropic parameters such as the density and require more refined information. Furthermore, this study constitutes a detailed database on the evolution of snow properties under a temperature gradient, which can be used as a guideline and a validation tool for snow metamorphism models at the micro- or macroscale.

Three Dimensional Seismic Isolation System Using Hydraulic Cylinder

2002 ◽  
Author(s):  
Shinichiro Kajii ◽  
Naoki Sawa ◽  
Nobuhiro Kunitake ◽  
K. Umeki
Keyword(s):  
Seismic Isolation ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Hydraulic Cylinder ◽  
Seismic Load ◽  
3D Seismic ◽  
Isolation System ◽  
Response Characteristics ◽  
Seismic Motion ◽  
Hydraulic Cylinders

A three-dimensional (3D) seismic isolation system for FBR building is under development. The proposed vertical isolation system consists form hydraulic cylinders with water-based liquid and accumulators to support large vertical static load and to realize low natural frequency in the vertical direction. For horizontal isolation, laminated rubber isolator or sliding type isolator will be combined. Because the major part of the feasibility of this isolation system depends on the sealing function and durability of the hydraulic cylinder, a series of feasibility tests of the hydraulic cylinder have been conducted to verify the reliability against seismic load and seismic motion. This paper describes the specification of the seismic isolations system, seismic response characteristics and the results of the feasibility tests of the seal. This study was performed as part of a government sponsored R&D project on 3D seismic isolation.

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