Restraint Analysis of Fixtures Which Rely on Surface Contact

Total restraint analysis is used to evaluate the ability of a machining fixture to restrain workpiece motion. Thus far models have been limited to point contact and frictionless planar contact. This paper shows how to apply restraint analysis to a fixture which relies on frictionless or frictional surface contact. It presents models of the wrench systems defined by frictionless and frictional planar, spherical, and cylindrical contact as well as hard point contact. These models are applicable to the restraint analysis of other work holding devices such as gripper and assembly fixtures. In addition, they are the basis for other types of fixture analysis. This paper also presents a linear program which uses static equilibrium constraints to directly prove the existence of total restraint. Both the models and the linear program are applied to the analysis of a modular fixture.

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Rough Surface Contact of Curved Conformal Surfaces: An Application to Rotor–Stator Rub

Journal of Tribology ◽

10.1115/1.4032786 ◽

2016 ◽

Vol 138 (4) ◽

Cited By ~ 7

Author(s):

Philip Varney ◽

Itzhak Green

Keyword(s):

Rough Surface ◽

Contact Force ◽

Contact Stiffness ◽

Point Contact ◽

Contact Model ◽

Industrial Society ◽

Real Surface ◽

Linear Elastic ◽

Surface Contact ◽

Rough Surface Contact

Rotating machines and associated triboelements are ubiquitous in industrial society, playing a central role in power generation, transportation, and manufacturing. Unfortunately, these systems are susceptible to undesirable contact (i.e., rub) between the rotor and stator, which is both costly and dangerous. These adverse effects can be alleviated by properly applying accurate real-time diagnostics. The first step toward accurate diagnostics is developing rotor–stator rub models which appropriately emulate reality. Previous rotor–stator rub models disavow the contact physics by reducing the problem to a single esoteric linear contact stiffness occurring only at the point of maximum rotor radial deflection. Further, the contact stiffness is typically chosen arbitrarily, and as such provides no additional insight into the contacting surfaces. Here, a novel rotor–stator rub model is developed by treating the strongly conformal curved surfaces according to their actual nature: a collection of stochastically distributed asperities. Such an approach is advantageous in that it relies on real surface measurements to quantify the contact force rather than a heuristic choice of linear contact stiffness. Specifically, the elastoplastic Jackson–Green (JG) rough surface contact model is used to obtain the quasistatic contact force versus rotor radial deflection; differences and similarities in contact force between the linear elastic contact model (LECM) and JG model are discussed. Furthermore, the linear elastic model's point contact assumption is assessed and found to be inaccurate for systems with small clearances. Finally, to aid in computational efficiency in future rotordynamic simulation, a simple exponential curve fit is proposed to approximate the JG force–displacement relationship.

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Study on Micro-Characteristics of Microbe-Induced Calcium Carbonate Solidified Loess

Crystals ◽

10.3390/cryst11121492 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1492

Author(s):

Xiaojun Liu ◽

Chaofan Pan ◽

Jing Yu ◽

Jinyue Fan

Keyword(s):

Calcium Carbonate ◽

Contact Area ◽

Structural Characteristics ◽

Point Contact ◽

Silty Clay ◽

Indirect Contact ◽

Soil Particles ◽

Pore Area ◽

Surface Contact ◽

Before And After

Microbial-induced carbonate precipitation (MICP) has outstanding characteristics in solidifying soil, such as good fluidity, ecological environmental protection, adjustable reaction, etc., making it have a good application prospect. As a typical silty clay, the composition of loess is fine, and the microstructure is quite different from that of sand. Previous research has found that the unconfined compressive strength of loess cured by MICP can be increased by nearly four times. In this paper, by comparing the changes of structural characteristics of undisturbed loess before and after MICP solidification, the mechanism of strength improvement of loess after MICP solidification is revealed from the microscopic level. Firstly, the microstructure of loess before and after solidification is tested by scanning electron microscope, and it is found that the skeleton particles of undisturbed loess are granular, and the soil particles coexist in direct contact and indirect contact, and the pores in soil are mainly overhead pores compared with the microstructure of solidified loess, it is found that the surface contact between aggregates increases obviously, and calcium carbonate generated by MICP is adsorbed around the point contact between aggregates, which makes the contact between soil particles change from point contact to surface contact. Then, Pores (Particles) and Cracks Analysis System (PCAS) is used to quantitatively analyze the pores of loess before and after solidification. The results show that the total pore area, the maximum total pore area and porosity of soil samples decrease, and the total number of pores decreases by 13.2% compared with that before MICP solidification, indicating that a part of calcium carbonate produced by MICP reaction accumulates in tiny pores, thus reducing the number of pores. One part is cemented between soil particles, which increases the contact area of particles. Therefore, some pores of loess solidified by MICP are filled and densified, the contact area between soil particles is increased, and the strength of loess under load is obviously improved.

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KINEMATIC PAIRS: NOVEL KINDS AND SCIENTIFIC CLASSIFICATION

Bulletin of Science and Technical Development ◽

10.18411/vntr2021-161-5 ◽

2021 ◽

Vol 161 ◽

pp. 38-74

Author(s):

Stephen P. Radzevich

Keyword(s):

Point Contact ◽

Contact Geometry ◽

Line Contact ◽

General Sense ◽

Gear Design ◽

Functional Surfaces ◽

Surface Contact ◽

Scientific Classification

This paper deals with kinematic pairs in the most general sense, and, in particular, with those used in gear design. The paper begins with a brief overview of the earlier performed research in the field. Different kinds of kinematic pairs are distinguished, namely, point-contact kinematic pairs, line-contact kinematic pairs, and surface-to-surface-contact kinematic pairs. Contact geometry of functional surfaces in kinematic pairs is involved into the analysis aiming more in detail analysis of design, and the development of a scientific classification of kinematic pairs. A scientific classification of all possible kinds of kinematic pairs is developed. All known designs of kinematic pairs are covered by the classification. Moreover, kinematic pairs of all notknown yet designs are also covered by the classification. This means that the proposed classification of kinematic pairs possesses predictive properties.

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Surface-Contact Systems

Scientific American ◽

10.1038/scientificamerican12271902-22561supp ◽

1902 ◽

Vol 54 (1408supp) ◽

pp. 22561-22562

Keyword(s):

Surface Contact

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Point-contact spectroscopy of quasi-1D conductors with CDW

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:19991045 ◽

1999 ◽

Vol 09 (PR10) ◽

pp. Pr10-179-Pr10-181

Author(s):

A. A. Sinchenko ◽

Yu. I. Latyshev ◽

S. G. Zybtsev ◽

I. G. Gorllova

Keyword(s):

Point Contact ◽

Point Contact Spectroscopy

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A Modified Thromboplastin Screening Test

Thrombosis and Haemostasis ◽

10.1055/s-0038-1654580 ◽

1961 ◽

Vol 06 (03) ◽

pp. 492-497 ◽

Cited By ~ 2

Author(s):

Janet C. Macpherson ◽

R. M Hardisty

Keyword(s):

Standard Method ◽

Comparative Studies ◽

Screening Test ◽

Incubation Mixture ◽

Surface Contact ◽

Modified Test ◽

Effect Of Surface

SummaryA modification of the thromboplastin screening test of Hicks and Pitney is described, in which the effect of surface contact on the test plasma is controlled by the addition of a suspension of kaolin to the incubation mixture before recalcification.Comparative studies show the modified test to give more reproducible results than the standard method.

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