Vehicle Lifts: The Hyperstatic Problem

1999 ◽  
Author(s):  
Ralph L. Barnett ◽  
Peter J. Poczynok
Keyword(s):  
Horizontal Plane ◽  
Friction Resistance ◽  
Point Support ◽  
Random Forces ◽  
Loss Of Resistance ◽  
Set Up ◽  
Vehicle Chassis

Abstract Occasionally, vehicles topple off of structurally sound automobile lifts, even when they are properly supported at their lift points. This happens with a family of lifts that use four arms to position lifting pads under the vehicle chassis. The arms operate in a horizontal plane and are positioned by swinging and telescoping. Gravity loading of the pads and the attendant horizontal friction resistance cannot be relied upon to maintain the set-up position of the pads. There is a non-obvious structural phenomena called hyperstatic behavior that may easily lead to minimal, or even zero, pad loading with the attendant loss of resistance to horizontal pad movement. Unless otherwise restrained, the bumping and jostling associated with vehicle maintenance can produce random forces that will push a pad from beneath the vehicle. The resulting three-point support almost always leads to toppling of the vehicle from the lift.

scholarly journals Numerical analysis of asphalt concrete milling process based on multicomponent modeling

2020 ◽  
Author(s):  
Liqun Zhou ◽  
Yi Liu ◽  
Zhennan Wang ◽  
Yuping Li ◽  
Kui Zhang ◽  
...  
Keyword(s):  
Asphalt Concrete ◽  
Research Work ◽  
Milling Process ◽  
Friction Resistance ◽  
Main Research ◽  
Element Simulation ◽  
Set Up ◽  
Working Parameters ◽  
Cutting Processes ◽  
Aggregate Particles

Abstract In this paper, according to the different physical properties of each component of asphalt concrete, a finite element simulation is used to build a mechanical constitutive model for the concrete cutting processes. When the machine cutter contacts different aggregate particles, the variation rules of mechanical information are obtained and studied. The main research work includes: (1) The track and force of the tool in the cutting process are defined, and then the track equation of the tool tip and the calculation formula of friction resistance are obtained. The relationship between the friction resistance and working parameters is clarified. (2)From the multicompont modeling, the internal components of asphalt concrete are refined, and the mechanical properties of asphalt mortar and aggregate particles are set up. Random feeding of different aggregate particles in asphalt concrete specimens is completed by using Python software and Monte carlo method. After the simulation, the results are imported into numerical software to generate the variation curve of tool friction resistance, so as to obtain the rule of its change with various factors, and according to the above studies, the optimal working parameters combination of the milling planer are summarized.

Investigation of the Horizontal Drifting Effects on Ships With Forward Speed

2009 ◽  
Author(s):  
Sheguang Zhang ◽  
Kenneth M. Weems ◽  
Woei-Min Lin
Keyword(s):  
Horizontal Plane ◽  
Mathematical Formulation ◽  
Low Frequency ◽  
Second Order ◽  
Wave Loads ◽  
Forward Speed ◽  
Large Amplitude Motions ◽  
Domain 3 ◽  
Set Up ◽  
Control Surfaces

This paper is concerned with the horizontal drifting effects on ships moving with forward speed in waves. The ship configurations can be a single or multiple ships operating alongside one another. In close-in position (CIP) ship operations, the position of the ships often needs to be maintained relatively steady by means of Dynamic Positioning (DP) systems that incorporate thrusters or control surfaces. In developing such systems, especially those using wave feed-forward (WFF) control algorithms, the mean or low frequency drift force and moment in the horizontal plane are required to set up the control loop. The present study uses the Large Amplitude Motions Program (LAMP), a time domain, 3-D panel code for the prediction of motions and wave loads for a ship or ships in waves, to calculate the drifting forces in the horizontal plane for ships moving with or without forward speed. Since the drifting effects are second order in association with the incident wave amplitude, the formulation in LAMP has been expanded to account for the additional second order terms. This paper presents the mathematical formulation — including the second order drifting effects, its numerical implementation in LAMP, and the results from several validation cases — for a single body with or without forward speed. The analysis of the horizontal drifting effects on two-ship configurations with or without a DP system will be conducted in a future study.

Some contemporary problems in road vehicle dynamics

2000 ◽  
Vol 214 (1) ◽  
pp. 137-148 ◽  
Author(s):  
R. S. Sharp
Keyword(s):  
System Thinking ◽  
Handling Qualities ◽  
Complex Process ◽  
Control Intervention ◽  
Research Programmes ◽  
Full Picture ◽  
Firm Basis ◽  
Set Up ◽  
Vehicle Chassis ◽  
And Control

It is argued that there is great commercial value in transferring as much of vehicle-handling qualities assessment as possible from the prototype testing domain to the predictive engineering domain. Man—machine system thinking is necessary to provide a firm basis for progress. Also, the newer opportunities in vehicle chassis engineering to introduce information enhancement and control intervention systems pose human factors problems. It is possible for such systems to do more harm than good. Some descriptions of conventional mixtures of prediction and testing are given and the driving activity is analysed. A conceptual framework involving the specification of vehicle characteristics, which contribute to the subjective judgements made by drivers, is set up. Examples in the categories are explained. The major chassis enhancement systems in production or in late development and their contributions in the various categories are discussed. Quality judgements are shown to be made by a very complex process, containing conflict and requiring very wide-ranging test conditions for the full picture to be revealed. It is considered that a conceptual classification, such as that put forward, is necessary to allow the design of research programmes which will yield fundamental, generic and practically useful results.

scholarly journals The Effect of w/c Ratio of Compacted Bored Pile to Friction Resistance of Unjani Clay

2021 ◽  
Vol 20 (1) ◽  
pp. 83-93
Author(s):  
Agus Sulaeman ◽  
Muhamad Agung ◽  
Regi Fasya Septrian
Keyword(s):  
Clay Soil ◽  
Small Scale ◽  
Pile Capacity ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Friction Resistance ◽  
Direct Shear Tests ◽  
Bored Pile ◽  
Loading Tests ◽  
Set Up

The small scale physical model of drum type was set-up to obtain the effect of water cement ratio (w/c) to pile capacity and original soil. The simulation of the process of providing bored piles model, soils model, installation and tests (pile loading tests and direct shear tests) under different water cement ratio of mortar and various moisture content of clay were done. The results reveal that the higher water content of original clay the bigger friction resistance, α value as clay soil is softer and the optimum w/c-ratio (w/c = 0,4) provides more pile capacity. It is understandable that water plays an important role, contributes to the change of surrounding clay properties. The improvement of Su ( % increase) due to compaction of concrete in bored pile, migration of moisture and reaction with surrounding clay leads to take benefit of design and construction of bored pile in clay soil for the sake of efficiency and stability.

The Effects of Drying Techniques on Clay-Rich Soil Texture

1974 ◽  
Vol 32 ◽  
pp. 466-467
Author(s):  
T. G. Naymik
Keyword(s):  
Critical Point ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Drying Methods ◽  
Air Drying ◽  
Freeze Dried ◽  
Critical Point Drying ◽  
Set Up ◽  
The Relationship ◽  
Quartz Grains

Three techniques were incorporated for drying clay-rich specimens: air-drying, freeze-drying and critical point drying. In air-drying, the specimens were set out for several days to dry or were placed in an oven (80°F) for several hours. The freeze-dried specimens were frozen by immersion in liquid nitrogen or in isopentane at near liquid nitrogen temperature and then were immediately placed in the freeze-dry vacuum chamber. The critical point specimens were molded in agar immediately after sampling. When the agar had set up the dehydration series, water-alcohol-amyl acetate-CO2 was carried out. The objectives were to compare the fabric plasmas (clays and precipitates), fabricskeletons (quartz grains) and the relationship between them for each drying technique. The three drying methods are not only applicable to the study of treated soils, but can be incorporated into all SEM clay soil studies.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Eels Under Standing Wave Conditions

1982 ◽  
Vol 40 ◽  
pp. 492-495
Author(s):  
O.L. Krivanek ◽  
J. TaftØ
Keyword(s):  
Standing Wave ◽  
Wave Conditions ◽  
Set Up ◽  
A Site ◽  
Complex Crystal

It is well known that a standing electron wavefield can be set up in a crystal such that its intensity peaks at the atomic sites or between the sites or in the case of more complex crystal, at one or another type of a site. The effect is usually referred to as channelling but this term is not entirely appropriate; by analogy with the more established particle channelling, electrons would have to be described as channelling either through the channels or through the channel walls, depending on the diffraction conditions.

Low-Loss Images in a Stem/Tem Microscope

1976 ◽  
Vol 34 ◽  
pp. 496-497 ◽  
Author(s):  
David C. Joy ◽  
Dennis M. Maher
Keyword(s):  
High Resolution ◽  
Surface Topography ◽  
Beam Direction ◽  
Low Loss ◽  
Specimen Holder ◽  
Glancing Angle ◽  
High Resolution Images ◽  
Set Up ◽  
Conventional Manner ◽  
Objective Type

High-resolution images of the surface topography of solid specimens can be obtained using the low-loss technique of Wells. If the specimen is placed inside a lens of the condenser/objective type, then it has been shown that the lens itself can be used to collect and filter the low-loss electrons. Since the probeforming lenses in TEM instruments fitted with scanning attachments are of this type, low-loss imaging should be possible.High-resolution, low-loss images have been obtained in a JEOL JEM 100B fitted with a scanning attachment and a thermal, fieldemission gun. No modifications were made to the instrument, but a wedge-shaped, specimen holder was made to fit the side-entry, goniometer stage. Thus the specimen is oriented initially at a glancing angle of about 30° to the beam direction. The instrument is set up in the conventional manner for STEM operation with all the lenses, including the projector, excited.

UHV-TEM studies of laser-induced damage

1991 ◽  
Vol 49 ◽  
pp. 632-633
Author(s):  
T.S. Savage ◽  
R. Ai ◽  
D. Dunn ◽  
L.D. Marks
Keyword(s):  
Surface Science ◽  
Rapid Heating ◽  
Local Heating ◽  
Routine Practice ◽  
Transmission Electron ◽  
Northwestern University ◽  
Laser Induced Damage ◽  
Set Up ◽  
Focusing Lens ◽  
Diffusion Of Impurities

The use of lasers for surface annealing, heating and/or damage has become a routine practice in the study of materials. Lasers have been closely looked at as an annealing technique for silicon and other semiconductors. They allow for local heating from a beam which can be focused and tuned to different wavelengths for specific tasks. Pulsed dye lasers allow for short, quick bursts which can allow the sample to be rapidly heated and quenched. This short, rapid heating period may be important for cases where diffusion of impurities or dopants may not be desirable.At Northwestern University, a Candela SLL - 250 pulsed dye laser, with a maximum power of 1 Joule/pulse over 350 - 400 nanoseconds, has been set up in conjunction with a Hitachi UHV-H9000 transmission electron microscope. The laser beam is introduced into the surface science chamber through a series of mirrors, a focusing lens and a six inch quartz window.

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