On the Inclusion of Sliding Kinematical Effects on the Biodynamical Modeling of Symmetrical Lifting Activities

2009 ◽  
Author(s):  
Mohammed M. Hassan ◽  
E. M. Bakr ◽  
A. A. Hegazy
Keyword(s):  
Present Model ◽  
Compressive Force ◽  
Dynamic Responses ◽  
Normal Range ◽  
Body Postures ◽  
Symmetric Lifting ◽  
Angular Velocities ◽  
Severe Back Pain ◽  
Vast Range ◽  
Good Agreement

In this paper, A new biodynamical model was developed with the objective of analyzing the dynamic responses of the human back during the exertion of symmetric lifting activities. More emphasis was placed on the study of the lumbosacral disc located between the fifth lumbar and first sacral vertebrae (L5/S1). The present model accounts for the sliding components of velocity and acceleration as well as the Coriolis acceleration in the kinematical equations of the human back. The inclusion of those terms has enabled a more accurate computation of the generated sliding effect of the flexible disc as well as the change in its height and width which normally occurs during the gross body rotation of the back. This has turned to have a significant effect on the resulting compressive force applied at the L5/S1 region. A computer model was developed in this study to automate the biodynamical simulation processes for workers of different genders and for a vast range of body postures. Results indicated that the inclusion of the sliding components of velocity and acceleration do actually have a significant effect on the whole range of lifting activities in which an angular velocity exceeding 24 degree/sec is employed. Results obtained in this paper were compared with the experimental and computational (simulated) results of recent relevant publications. The comparison shows that there are good agreements between the results for angular velocities exceeding 24 degree/second, which is known as the normal range of operation in lifting activities. Results obtained in this paper were in good agreement with NIOSH action and maximum limits which make it reliable for use as a guideline to help workers in industry to avoid hostile lifting activities and bring to attention an early warning to avoid engaging industrial labors with postures leading to severe back pain problems.

A Compact Model for Spherical Rough Contacts

2004 ◽  
Author(s):  
M. Bahrami ◽  
M. M. Yovanovich ◽  
J. R. Culham
Keyword(s):  
Pressure Distribution ◽  
Entire Range ◽  
Present Model ◽  
Numerical Solutions ◽  
Contact Radius ◽  
Bulk Deformation ◽  
Dimensional Parameters ◽  
Maximum Contact ◽  
Good Agreement ◽  
Key Parameter

The contact of rough spheres is of high interest in many tribological, thermal, and electrical fundamental analyses. Implementing the existing models is complex and requires iterative numerical solutions. In this paper a new model is presented and a general pressure distribution is proposed that encompasses the entire range of spherical rough contacts including the Hertzian limit. It is shown that the non-dimensional maximum contact pressure is the key parameter that controls the solution. Compact expressions are proposed for calculating the pressure distribution, radius of the contact area, elastic bulk deformation, and the compliance as functions of the governing non-dimensional parameters. The present model shows the same trends as those of the Greenwood and Tripp model. Correlations proposed for the contact radius and the compliance are compared with experimental data collected by others and good agreement is observed.

Inspection and Model Experiment of a Damaged Arch Bridge

2007 ◽  
Vol 340-341 ◽  
pp. 223-228
Author(s):  
Ying Fang Fan ◽  
Zhi Qiang Hu ◽  
Jing Zhou
Keyword(s):  
Model Experiment ◽  
Dynamic Test ◽  
Dynamic Responses ◽  
Dynamic Tests ◽  
Arch Bridge ◽  
Mechanical Responses ◽  
Organic Glasses ◽  
Bridge Model ◽  
Static And Dynamic Tests ◽  
Good Agreement

The structural behavior of an old six-span reinforced concrete arch bridge, which has been in service for about 40 years, is investigated. Field monitoring (inclusive of test of material property, static and dynamic test of the bridge) was conducted, static and dynamic responses of the bridge are obtained. Based on the primitive bridge, a scaled one-span bridge model was fabricated by organic-glasses. Both the static and dynamic tests were executed on the bridge model in the laboratory. Since the arch rib is the crucial member for the arch bridge, 7 notches were cut on both arch ribs of the bridge model to simulate different damages of the arch rib. Mechanical responses of the bridge with different damages on the arch ribs were achieved. FEM analyses were preformed on the bridge as well. Numerical results show good agreement with the experimental results.

Estimating Critical Speeds of Stepped Shafts with Flexible Bearings

1971 ◽  
Vol 8 (03) ◽  
pp. 327-333
Author(s):  
R. H. Salzman
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Design Stage ◽  
Normal Range ◽  
Critical Speeds ◽  
Stepped Shaft ◽  
Bearing Stiffness ◽  
Variable Support ◽  
Method Show ◽  
Good Agreement

This paper presents a semi-graphical approach for finding the first critical speed of a stepped shaft with finite bearing stiffness. The method is particularly applicable to high-speed turbine rotors with journal bearings. Using Rayleigh's Method and the exact solution for whirling of a uniform shaft with variable support stiffness, estimates of the lowest critical speed are easily obtained which are useful in the design stage. First critical speeds determined by this method show good agreement with values computed by the Prohl Method for the normal range of bearing stiffness. A criterion is also established for determining if the criticals are "bearing critical speeds" or "bending critical speeds," which is of importance in design. Discusser E. G. Baker

Isothermal Bubble Motion Through a Rotating Liquid

1972 ◽  
Vol 94 (1) ◽  
pp. 187-192 ◽  
Author(s):  
D. L. Schrage ◽  
H. C. Perkins
Keyword(s):  
Radial Direction ◽  
Terminal Velocity ◽  
Distilled Water ◽  
Analytical Prediction ◽  
Bubble Motion ◽  
Large Pressure ◽  
Rotating Liquid ◽  
Angular Velocities ◽  
Large Pressure Gradient ◽  
Good Agreement

An analytical and experimental study of isothermal bubble motion through a liguid which is itself in motion is presented. Both analytical and experimental results are reported for the velocities and trajectories of oxygen bubbles moving through a liquid annulus which is rotating at angular velocities ranging from 500 to 1500 rpm. Results are presented for both distilled water and glycerin. The analytical prediction of the trajectories and velocities showed good agreement with the experimental data. It was found that the bubbles, which were injected at the exterior of the liquid annulus, spiralled inward rapidly and, due to the large pressure gradient in the radial direction, did not reach a constant or terminal velocity.

A model for the vibrator–ground coupling vibration and the dynamic responses under excitation of sweep signal

2019 ◽  
Vol 22 (8) ◽  
pp. 1855-1866 ◽  
Author(s):  
Gang Li ◽  
Zhi-Qiang Huang ◽  
Zhang-Hua Lian ◽  
Lei Hao
Keyword(s):  
Dynamic Stiffness ◽  
Low Frequency ◽  
Dynamic Responses ◽  
Coupling Vibration ◽  
Lower Velocity ◽  
Dynamic Damping ◽  
Velocity Response ◽  
Cell Test ◽  
Three Stages ◽  
Good Agreement

To analyze the behavior of the vibrator–ground coupling vibration, a model containing equivalent dynamic stiffness and equivalent dynamic damping to describe the interaction between the vibrator and the ground is established based on half-space theory. According to load cell test, this model shows a good agreement with the experimental data. Dynamic responses of the structure are analyzed on displacement, velocity, acceleration, and ground force. Results show that the stroke and pump displacement are main constraints that limit the bandwidth of vibrator toward low frequency, and the stroke of conventional vibrator is not long enough to achieve lower frequency. Analysis of velocity response indicates that with the increase of frequency, a larger mass results in a lower velocity under external force. The influence of the ground acting on the baseplate is limited, and the acceleration of the baseplate is determined by its own mass beyond 80 Hz. Analysis of ground force shows that the response of the structure can be divided into three stages. The reaction mass, the baseplate, and the ground play different roles in dominating the ground force at different frequency bands.

Simulating Dynamic Activities Using a Five-Axis Knee Simulator

2005 ◽  
Vol 127 (1) ◽  
pp. 123-133 ◽  
Author(s):  
Lorin P. Maletsky ◽  
Ben M. Hillberry
Keyword(s):  
Sagittal Plane ◽  
Compressive Force ◽  
Knee Prostheses ◽  
Plane Model ◽  
Knee Simulator ◽  
Specific Loading ◽  
Total Knee ◽  
Five Axis ◽  
Cadaveric Knee ◽  
Good Agreement

This work describes the design and capabilities of the Purdue Knee Simulator: Mark II and a sagittal-plane model of the machine. This five-axis simulator was designed and constructed to simulate dynamic loading activities on either cadaveric knee specimens or total knee prostheses mounted on fixtures. The purpose of the machine was to provide a consistent, realistic loading of the knee joint, allowing the kinematics and specific loading of the structures of the knee to be determined based on condition, articular geometry, and simulated activity. The sagittal-plane model of the knee simulator was developed both to predict the loading at the knee from arbitrary inputs and to generate the necessary inputs required to duplicate specified joint loading. Measured tibio-femoral compressive force and quadriceps tension were shown to be in good agreement with the predicted loads from the model. A controlled moment about the ankle-flexion axis was also shown to change the loading on the quadriceps.

Damper force Characteristics of a Separated Dual-chamber Single-rod Type Damper utilizing an Elastomer Particle Assemblage in the Case of both Chambers Containing Particles

2020 ◽  
pp. 1-27
Author(s):  
Atsushi Toyouchi ◽  
Yasushi Ido ◽  
Yuhiro Iwamoto ◽  
Makoto Hanai
Keyword(s):  
Friction Force ◽  
Vibration Frequency ◽  
Compressive Force ◽  
Packing Fraction ◽  
Dual Chamber ◽  
Hard Particles ◽  
Large Hysteresis ◽  
Particle Dampers ◽  
Force Characteristics ◽  
Good Agreement

Abstract Particle dampers that use soft/hard particles are attracting attention as a solution to problems such as oil leakage of oil dampers and the temperature dependence of their characteristics. Particle dampers effectively attenuate vibration using the friction and inelastic normal collisions generated between particles or between particles and walls. Here, the effects of the packing fraction of particles, the vibration frequency, and hardness of the material on the damper force characteristics of a separated dual-chamber single-rod type damper with elastomer particle assemblages were investigated experimentally. The maximal damper force and its hysteresis increased with the packing fraction, the vibration frequency, and the Young's modulus of the particle material. Numerical simulations using the discrete element method were performed to confirm the behavior of the elastomer particles when they were packed in both chambers. The compressive force distribution and velocity vector diagram of particles in the simulations showed that friction and compression between particles due to particle movement, friction between particles and the chamber walls, and the viscosity of the elastomer particles caused a large hysteresis in the damper force. The maximum damper force is affected by the viscoelastic component force and the friction force in the same proportion, and the hysteresis is dominated by the friction force. The simulation results were confirmed to be in good agreement, both qualitatively and quantitatively, with the experimentally measured damper force characteristics.

Serum Iron Determination

1956 ◽  
Vol 2 (3) ◽  
pp. 175-183 ◽  
Author(s):  
George R Kingsley ◽  
Gloria Getchell
Keyword(s):  
Serum Iron ◽  
Isoamyl Alcohol ◽  
Photometric Measurement ◽  
Normal Range ◽  
Iron Determination ◽  
Acid Hydrolysate ◽  
Dry Ashing ◽  
Reproducible Method ◽  
Good Agreement ◽  
Ferrous Complex

Abstract 1. A sensitive, reproducible method for serum iron determination has been developed employing extraction of serum acid hydrolysate with isoamyl alcohol and development of a highly colored ferrous complex of 4,7-diphenyl-1, 1O-phenanthroline for quantitative photometric measurement of iron. 2. The method gives good recoveries and also good agreement with the dry-ashing procedure. 3. A normal range of 120-200 µg./100 ml. (average 160) for the female and 125-238 µg./100 ml. (average 182) for the male for serum iron was obtained by the method.

Breathing patterns in anesthetized cats and the concept of minimum respiratory effort

1988 ◽  
Vol 64 (1) ◽  
pp. 31-41 ◽  
Author(s):  
S. C. Luijendijk ◽  
J. Milic-Emili
Keyword(s):  
Present Model ◽  
Minute Ventilation ◽  
Driving Pressure ◽  
Theoretical Studies ◽  
Pressure Waveform ◽  
Respiratory Effort ◽  
Breathing Patterns ◽  
Optimal Duration ◽  
Predicted Values ◽  
Good Agreement

Theoretical studies dealing with the principle of minimal respiratory effort usually make use of sinusoidal or saw-tooth-like breathing patterns. Recent observations in anesthetized cats have shown that the driving pressure waveform for inspiration can be described by a power function of time and that most of expiration is passive. This driving pressure waveform, however, results in breathing patterns that differ from those described above. For this reason, we have reevaluated in anesthetized cats the principle of minimal respiratory effort by computing optimal duration of inspiration (TI) and optimal tidal volume (VT) for different ventilatory conditions using actual driving pressure waveforms. The results are in qualitative agreement with the experimental observations; i.e., optimal TI decreases and optimal VT increases with increasing minute ventilation. On the average, a good agreement is found between measured and computed values of TI. In some cats, however, there are substantial differences between observed and predicted values of TI, which can probably be ascribed to inaccuracies in the data used in our computations. Despite its limitations, the present model analysis is more realistic than previous ones because actual driving pressure waveforms are used together with actual values of effective inspiratory impedance.

The Capillary Force Between an AFM Tip and a Surface at Different Humidity

2008 ◽  
Author(s):  
Sheng Chau Chen ◽  
Jen Fin Lin
Keyword(s):  
Relative Humidity ◽  
Capillary Force ◽  
Present Model ◽  
Hydrophobic Surface ◽  
Contact Angles ◽  
Solid Surfaces ◽  
Hydrophilic Surface ◽  
Solid Bodies ◽  
Force Equilibrium ◽  
Good Agreement

In the present study, the meniscus profiles of water bridges formed at different relative humidity are determined using the geometric relationships including the Kelvin equation and the force equilibrium formula established for the meniscus. The pull-off forces predicted by the present model show good agreement with the experimental results reported in the literatures. When the contact angles at two solid bodies are equal, the pull-off force is slightly elevated by an increase of the relative humidity of air, and is significantly elevated by an increase of the asperity radius. Furthermore, two hydrophobic surfaces with equally large contact angles lower the pull-off force. If a difference exists between the contact angles of two solid surfaces, the asperity with a hydrophilic surface incorporating with a smooth flat plate with a hydrophobic surface reduces the pull-off force.

Sign in / Sign up

Export Citation Format

Share Document