Advances in Farm Tractor Modelling and Simulation

2003 ◽  
Author(s):  
G. Mastinu ◽  
M. Gobbi ◽  
G. Previati ◽  
M. Ribaldone
Keyword(s):  
Working Conditions ◽  
High Speed ◽  
Experimental Tests ◽  
Steering System ◽  
Transmission System ◽  
The Body ◽  
Suspension Systems ◽  
Farm Tractor ◽  
Inertia Parameters ◽  
Speed Up

The paper deals with the modelling of the dynamics of farm tractors in order to simulate their motion on smooth or rough surface, on road or off road and in different loading situations. The aim is to develop reliable models to speed-up the design and development activities. The derived farm tractor models can simulate the working conditions of the farm tractor while hauling a plough or running at relatively high speed on a rough soil, or steering soil, or steering on a sloped, soft surface. Two models of farm tractors have been developed and experimentally validated. The first model is based on a proprietary software. able to quickly simulate the motion of a vehicle on smooth or rough soil. The second model has been developed with the software ADAMS/Car® which allows to model complicated transmission and suspension systems. In both of the models, the tires, the transmission system, the suspension system, the steering system, the engine and the body inertia are carefully described mathematically. Particular attention has been devoted to the measurements of the tire characteristic and of the inertia parameters of the farm tractor body. Both of the models are defined in a parametric way. Parameters sensitivity analysis a strong influence of the transmission system on the tractor dynamic response in all of the considered working conditions. Experimental tests have realized to validate the two models.

Effects of Mechanical Preloads on the Rotordynamic Performance of a Rotor Supported on Three-Pad Gas Foil Journal Bearings

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Kyuho Sim ◽  
Bonjin Koo ◽  
Jong Sung Lee ◽  
Tae Ho Kim
Keyword(s):  
Test Data ◽  
High Speed ◽  
Experimental Tests ◽  
Journal Bearings ◽  
Test Results ◽  
Performance Measurements ◽  
Displacement Sensors ◽  
Single Top ◽  
Speed Up ◽  
The One

This paper presents the rotordynamic performance measurements and model predictions of a rotor supported on three-pad gas foil journal bearings (GFJBs) with various mechanical preloads. The rotor with its length of 240 mm, diameter of 40 mm, and weight of 19.6 N is supported on two GFJBs and one pair of gas foil thrust bearings (GFTBs), being a permanent magnet rotor of a high speed electric motor. Each bearing pad consisting of a top foil and a bump-strip layer is installed on a lobed bearing housing surface over the arc length of 120 deg along the circumference. Test three-pad GFJBs have four different mechanical preloads, i.e., 0 μm, 50 μm, 70 μm, 100 μm with a common radial nominal clearance of 150 μm. A series of speed-up tests are conducted up to 93 krpm to evaluate the effects of increasing mechanical preloads on the rotordynamic performance. Two sets of orthogonally positioned displacement sensors record the rotor horizontal and vertical motions at the thrust collar and the other end. Test results show that the filtered synchronous amplitudes change little, but the onset speed of subsynchronous motions (OSS) increases dramatically for the increasing mechanical preloads. In addition, test bearings with the 100 μm preload show a higher OSS in load-on-pad (LOP) condition than that in load-between-pads (LBP) condition. A comparison with test results for a one-pad GFJB with a single top foil and bump-strip layer reveals that three-pad GFJB has superior rotordynamic performance to the one-pad one. Finally, the test data benchmark against linear rotordynamic predictions to validate a rotor-GFJB model. In general, predicted natural frequencies of the rotor-bearing system and synchronous rotor motions agree well with test data. However, stability analyses underestimate OSSs recorded during the experimental tests.

Quality Assurance of Laser Welded Axisymmetric Sandwich Structure

2013 ◽  
Vol 549 ◽  
pp. 529-534 ◽  
Author(s):  
Kimmo Illikainen ◽  
Kalle Holappa ◽  
Kari Mäntyjärvi
Keyword(s):  
Quality Assurance ◽  
Working Conditions ◽  
Sandwich Structure ◽  
Visual Inspection ◽  
Experimental Tests ◽  
The Body ◽  
Destructive Testing ◽  
Great Strength ◽  
Static Tests

This study focuses on quality assurance in a laser welded axisymmetric sandwich structure that functions as the body of an electric machine. The manufacturing quality of the structure was measured using destructive testing and visual inspection. The destructive tests included both fatigue and static tests in addition to a macrographic examination. The visual inspection comprised ocular estimates of the laser welded seams as well as their requirements. Compared with the real working conditions of the machine, the experimental tests were exhaustive. Nevertheless, in the tests, the bodies held up very well which shows the great strength of the structure.

scholarly journals Selection of the characteristics of the suspension system of the high-speed tracked robot

2021 ◽  
Vol 1 (2) ◽  
pp. 63-70
Author(s):  
YE.B. Sarach ◽  
◽  
YA.A. Tkachev ◽  
M.E. Krokhin ◽  
◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Resonant Mode ◽  
Suspension System ◽  
The Body ◽  
Suspension Systems ◽  
A Value ◽  
Dirt Road ◽  
Suspension Stiffness ◽  
Selection Of

Currently, the field of mechanical engineering is rapidly developing, including the creation of robotic high-speed vehicles. The design of suspension systems for such vehicles must be accompa-nied by the fulfillment of certain requirements, which are currently not formulated. Considering the thing that there is no person in the body of a high-speed robot, the application of the requirements for the suspensions of crew vehicles is not justified. In order to develop recommendations on the choice of characteristics of suspension systems for high-speed tracked robots, the research objects, which mass is in the range from 1000 to 10000 kg are determined. No suspension system is required for objects weighing less than 1000 kg. Objects weighing more than 10,000 kg will be created on the basis of existing serial vehicles. The study is based on the provision that the considered class of vehicles is not subject to re-strictions on the range of natural frequencies of body vibrations. Considering that one of the main requirements remains for high-speed tracked robots - ensuring a high average speed, it is proposed to increase the suspension stiffness in order to exclude resonance from the range of possible travel speeds. Using the accepted provisions, a study of the suspension system of increased stiffness is carried out. The movement along the tracks of a harmonic profile in resonance mode and a broken dirt road is simulated. The results of the study show that the characteristics of the suspension system, selected accord-ing to the proposed method, make it possible to move along the line of the harmonic profile in the resonant mode without suspension breakdowns. The speed of movement on a broken dirt road is limited to a value, which exceeding leads to sig-nificant vibrations of the body and an increase in the load on the elements of the suspension system. The absence of breakdowns leads to a decrease in the loading of the suspension, which makes it possible to reduce the mass of its elements.

Ride Quality of High-Speed Trains Traveling Over the Corrugated Rails

2006 ◽  
Author(s):  
H. Farahpour ◽  
D. Younesian ◽  
E. Esmailzadeh
Keyword(s):  
High Speed ◽  
Ride Comfort ◽  
The Body ◽  
Ride Quality ◽  
Comfort Index ◽  
Suspension Systems ◽  
Power Spectral ◽  
High Speed Trains ◽  
Train Speed ◽  
Secondary Suspension

Ride comfort of high-speed trains is studied using Sperling's comfort index. Dynamic model is developed in the frequency domain and the power spectral density (PSD) of the body acceleration is obtained for four classes of tracks. The obtained acceleration PSD is then filtered using Sperling's filter. The effects of the rail roughness and train speed on the comfort indicators are investigated. A parametric study is also carried out to evaluate the effects of the primary and secondary suspension systems on the comfort indicators.

Effects of Mechanical Preloads on the Rotordynamic Performance of a Rotor Supported on 3 Pad Gas Foil Journal Bearings

2014 ◽  
Author(s):  
Kyuho Sim ◽  
Bonjin Koo ◽  
Jong Sung Lee ◽  
Tae Ho Kim
Keyword(s):  
Test Data ◽  
High Speed ◽  
Experimental Tests ◽  
Journal Bearings ◽  
Test Results ◽  
Performance Measurements ◽  
Displacement Sensors ◽  
Single Top ◽  
Speed Up ◽  
The One

The paper presents the rotordynamic performance measurements and model predictions of a rotor supported on three-pad gas foil journal bearings (GFJBs) with various mechanical preloads. The rotor with its length of 240 mm, diameter of 40 mm, and weight of 19.6 N is supported on two GFJBs and one pair of gas foil thrust bearings (GFTBs), being a permanent magnet rotor of a high speed electric motor. Each bearing pad consisting of a top foil and a bump strip layer is installed on a lobed bearing housing surface over the arc length of 120 deg along the circumference. Test three-pad GFJBs have four different mechanical preloads, i.e., 0 μm, 50 μm, 70 μm, 100 μm with a common radial nominal clearance of 150 μm. A series of speed-up tests are conducted up to 93 krpm to evaluate the effects of increasing mechanical preloads on the rotordynamic performance. Two sets of orthogonally positioned displacement sensors record the rotor horizontal and vertical motions at the thrust collar and the other end. Test results show that the filtered synchronous amplitudes change little, but the onset speed of sub-synchronous motions (OSS) increases dramatically for the increasing mechanical preloads. In addition, test bearings with the 100 μm preload show a higher OSS in load-on-pad (LOP) condition than that in load-between-pads (LBP) condition. A comparison to test results for a one-pad GFJB with a single top foil and bump strip layer reveals that three-pad GFJB has superior rotordynamic performance to the one-pad one. Finally, the test data benchmark against linear rotordynamic predictions to validate a rotor-GFJB model. In general, predicted natural frequencies of the rotor-bearing system and synchronous rotor motions agree well with test data. However, stability analyses underestimate OSSs recorded during the experimental tests.

Hyperthermia in running sled dogs

1981 ◽  
Vol 51 (1) ◽  
pp. 135-142 ◽  
Author(s):  
C. J. Phillips ◽  
R. P. Coppinger ◽  
D. S. Schimel
Keyword(s):  
Body Weight ◽  
Working Conditions ◽  
Rectal Temperature ◽  
High Speed ◽  
Heat Storage ◽  
Coat Color ◽  
Genetic History ◽  
Sled Dogs ◽  
Speed Up ◽  
Laboratory Investigations

Hyperthermia, as measured by increase in rectal temperature, was studied in a group of 22 adult mongrel sled dogs that had been selectively bred for high-speed (up to 33 km/h) races 16–50 km in distance. Under normal working conditions, rectal temperature in the sled dogs increased significantly during initial 15–20 min of run (gathered gallop) after which temperature usually stabilized or decreased slightly. Amount of increase in rectal temperature was correlated directly with ambient temperature but not with speed or distance. Significant differences in degree of hyperthermia were found among dogs but these differences were not correlated with such factors as sex, size, coat color, weight, or genetic history. Training was found to significantly diminish amount of increase in rectal temperature during work. Data from the present study were compared to those of other laboratory investigations and relationships of heat storage and radiative surface area to body weight are discussed.

Scanning x-ray fluorescence microscopy and principal component analysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1752-1753
Author(s):  
Brian Cross
Keyword(s):  
Principal Component Analysis ◽  
Fluorescence Microscopy ◽  
Spatial Resolution ◽  
High Speed ◽  
Image Acquisition ◽  
Principal Component ◽  
Fluorescence Microscope ◽  
Acquisition Rate ◽  
X Ray ◽  
Speed Up

A relatively new entry, in the field of microscopy, is the Scanning X-Ray Fluorescence Microscope (SXRFM). Using this type of instrument (e.g. Kevex Omicron X-ray Microprobe), one can obtain multiple elemental x-ray images, from the analysis of materials which show heterogeneity. The SXRFM obtains images by collimating an x-ray beam (e.g. 100 μm diameter), and then scanning the sample with a high-speed x-y stage. To speed up the image acquisition, data is acquired "on-the-fly" by slew-scanning the stage along the x-axis, like a TV or SEM scan. To reduce the overhead from "fly-back," the images can be acquired by bi-directional scanning of the x-axis. This results in very little overhead with the re-positioning of the sample stage. The image acquisition rate is dominated by the x-ray acquisition rate. Therefore, the total x-ray image acquisition rate, using the SXRFM, is very comparable to an SEM. Although the x-ray spatial resolution of the SXRFM is worse than an SEM (say 100 vs. 2 μm), there are several other advantages.

Assessment of indicators of nervous and emotional stress in medical center personnel depending on the characteristics of their professional activity

2020 ◽  
Vol 60 (10) ◽  
pp. 650-657
Author(s):  
Irina V. Fedotova ◽  
Tatyana N. Vasilyeva ◽  
Tatyana V. Blinova ◽  
Irina A. Umnyagina ◽  
Yuliya V. Lyapina ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Emotional Stress ◽  
Functional State ◽  
Working Conditions ◽  
Medical Staff ◽  
Medical Center ◽  
The Body ◽  
Office Workers ◽  
Glutathione System ◽  
Medical Centers

Introduction. Digital technologies are actively used in the work of specialists of medical centers of various profiles, which causes the impact on employees of a number of professional factors that determine the characteristics of their work. The aim of the study is to evaluate the influence of professional factors on the functional state of the employees' body and the glutathione system as an objective indicator of stress based on the analysis of the subjective perception of the medical center employees of the specifics of working with personal computers and psychophysiological testing. Materials and methods. The study involved 109 specialists of medical centers (25 ophthalmologists, 31 representatives of the secondary medical staff - nurses and paramedics, 53 office employees). The anonymous survey concerned the assessment of working conditions and their impact on the functional state of the body of the respondents. Performance and stress tolerance indicators were evaluated using three standard questionnaires. The study of 66 subjects' levels of glutathione in the blood: total, reduced, oxidized and the ratio of reduced and oxidized - was used to analyze the relationship of the neuro-emotional nature of labor with the reaction of oxidative stress. Statistical processing of the obtained data was carried out using traditional methods of variation statistics and calculating the value of the odds ratio (OR) with a 95% confidence interval (CI). Results. The survey revealed a significant proportion of people in all groups of respondents who constantly use computer technology in their work. Describing the quality of the processed information, doctors more than representatives of other groups note its complexity, importance, negative emotional color, a high degree of responsibility and tension. Doctors more often than average medical staff and office workers associate the manifestation of fatigue with an uncomfortable state of the visual organ, nervous system, and musculoskeletal system. The subjects showed reduced performance and stress tolerance with the most pronounced negative trends in the group of doctors. Changes in the glutathione system were detected, indicating the presence of oxidative stress in 40% of ophthalmologists and office workers, and in half of nurses. Conclusions. The work of specialists of medical centers of various profiles in accordance with their assessment is characterized by high nervous and emotional stress, due to the need to process a significant amount of complex and important professionally significant information. Subjectively noted by respondents the influence of working conditions on the functional state of the body is confirmed by indicators of the glutathione system, which can be used as indicators of nervous and emotional stress.

Yaw Galloping of a TLWP Platform Under High Speed Currents by Analytical Methods and its Comparison With Experimental Results

2017 ◽  
Author(s):  
Francisco Lamas ◽  
Miguel A. M. Ramirez ◽  
Antonio Carlos Fernandes
Keyword(s):  
High Speed ◽  
Production Systems ◽  
Experimental Tests ◽  
Experimental Results ◽  
Analytical Methodology ◽  
New Approach ◽  
Laboratory Facilities ◽  
Polynomial Curve ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses

Flow Induced Motions are always an important subject during both design and operational phases of an offshore platform life. These motions could significantly affect the performance of the platform, including its mooring and oil production systems. These kind of analyses are performed using basically two different approaches: experimental tests with reduced models and, more recently, with Computational Fluid Dynamics (CFD) dynamic analysis. The main objective of this work is to present a new approach, based on an analytical methodology using static CFD analyses to estimate the response on yaw motions of a Tension Leg Wellhead Platform on one of the several types of motions that can be classified as flow-induced motions, known as galloping. The first step is to review the equations that govern the yaw motions of an ocean platform when subjected to currents from different angles of attack. The yaw moment coefficients will be obtained using CFD steady-state analysis, on which the yaw moments will be calculated for several angles of attack, placed around the central angle where the analysis is being carried out. Having the force coefficients plotted against the angle values, we can adjust a polynomial curve around each analysis point in order to evaluate the amplitude of the yaw motion using a limit cycle approach. Other properties of the system which are flow-dependent, such as damping and added mass, will also be estimated using CFD. The last part of this work consists in comparing the analytical results with experimental results obtained at the LOC/COPPE-UFRJ laboratory facilities.

Some Special Aspects of Hypersonic Flow Fields

1959 ◽  
Vol 63 (585) ◽  
pp. 508-512 ◽  
Author(s):  
K. W. Mangler
Keyword(s):  
Hypersonic Flow ◽  
High Speed ◽  
Flow Fields ◽  
The Body ◽  
Lower Velocity ◽  
Bow Wave ◽  
Total Head ◽  
Bow Shocks ◽  
Lower Entropy ◽  
Subsonic Region

When a body moves through air at very high speed at such a height that the air can be considered as a continuum, the distinction between sharp and blunt noses with their attached or detached bow shocks loses its significance, since, in practical cases, the bow wave is always detached and fairly strong. In practice, all bodies behave as blunt shapes with a smaller or larger subsonic region near the nose where the entropy and the corresponding loss of total head change from streamline to streamline due to the curvature of the bow shock. These entropy gradients determine the behaviour of the hypersonic flow fields to a large extent. Even in regions where viscosity effects are small they give rise to gradients of the velocity and shear layers with a lower velocity and a higher entropy near the surface than would occur in their absence. Thus one can expect to gain some relief in the heating problems arising on the surface of the body. On the other hand, one would lose farther downstream on long slender shapes as more and more air of lower entropy is entrained into the boundary layer so that the heat transfer to the surface goes up again. Both these flow regions will be discussed here for the simple case of a body of axial symmetry at zero incidence. Finally, some remarks on the flow field past a lifting body will be made. Recently, a great deal of information on these subjects has appeared in a number of reviewing papers so that little can be added. The numerical results on the subsonic flow regions in Section 2 have not been published before.

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