Mechanism of Rubber Cracking

1946 ◽  
Vol 19 (2) ◽  
pp. 406-416 ◽  
Author(s):  
E. F. Powell ◽  
V. E. Gough
Keyword(s):  
Laboratory Tests ◽  
Surface Film ◽  
Factors Affecting ◽  
Laboratory Conditions ◽  
Service Conditions ◽  
Exposure Conditions

Abstract Rubber and rubberlike polymers, in common with other materials which deteriorate on exposure to oxidizing or similar agents, eventually crack under normal atmospheric service conditions. The present paper confines itself to the factors affecting the type and appearance of the cracking which eventually occurs when a surface film of a rubber object (particularly when stressed) hardens and deteriorates in strength from any cause whatsoever. The importance of an understanding of the effects of exposure conditions on the character of the cracking produced cannot be too highly emphasized. This is so even if interest is confined solely to simple tests on new protective paints on an acceptance basis rather than research into surface deterioration. It is probable that many protective agencies have been accepted or rejected for extensive production tests because the initial laboratory tests have either not been representative of service or have been inadequate in scope. This still remains a major problem. The theory presented here has gradually taken shape over a period of some ten years and appears to describe adequately the general findings on the whole gamut of cracking, viz., fine check cracking and isolated deep cracks produced under service and laboratory conditions, the latter covering flexing, roof exposure, ozone and similar tests.

Factors Affecting Laboratory Accelerated Testing of Materials for Rolling Elements

1968 ◽  
Vol 183 (16) ◽  
pp. 189-193
Author(s):  
D. Scott ◽  
J. Blackwell
Keyword(s):  
Reference Materials ◽  
Laboratory Tests ◽  
Full Scale ◽  
Accelerated Testing ◽  
Factors Affecting ◽  
Rolling Elements ◽  
Service Conditions

Although laboratory tests simulating service conditions place materials and lubricants in the same order as full-scale bearing tests, considerable variation can occur between results from machines of the same type. Alignment and elimination of vibration of rolling four-ball type machines and specimen flatness of washer-type machines are important to obtain reproducible results. Results from reference materials are used to illustrate the various factors.

Laboratory Tests on Engineering Properties of Wind-Blown Sand

2012 ◽  
Vol 170-173 ◽  
pp. 706-709
Author(s):  
Zhao Lin Jia ◽  
Shu Wang Yan ◽  
Zhi Liang Huo
Keyword(s):  
Water Content ◽  
Laboratory Tests ◽  
Fine Sand ◽  
Engineering Properties ◽  
Grain Composition ◽  
Factors Affecting ◽  
Compaction Curve ◽  
Main Factors ◽  
Dry And Wet Conditions ◽  
Compaction Properties

By means of laboratory tests and theoretical calculation, the physical, mechanical properties and compaction mechanism of the wind-blown sand are studied to deal with the problem of how to use the wind-blown sand as roadbed materials. It is revealed that water content doesn’t affect the compressibility and the shear strength of the wind-blown sand obviously and the wind-blown sand can be compacted both in dry and wet conditions. The compaction curve of the ordinary fine sand is consistent with that of wind-blown sand and the main factors affecting the compaction properties are the grain composition, water content and compaction work.

scholarly journals Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations

2018 ◽  
Vol 8 (10) ◽  
pp. 1730 ◽  
Author(s):  
Md. Safiuddin ◽  
A. Kaish ◽  
Chin-Ong Woon ◽  
Sudharshan Raman
Keyword(s):  
Service Life ◽  
Concrete Structures ◽  
Real Life ◽  
Early Age ◽  
Structural Elements ◽  
Remedial Measures ◽  
Curing Conditions ◽  
Factors Affecting ◽  
Different Types ◽  
Service Conditions

Cracking is a common problem in concrete structures in real-life service conditions. In fact, crack-free concrete structures are very rare to find in real world. Concrete can undergo early-age cracking depending on the mix composition, exposure environment, hydration rate, and curing conditions. Understanding the causes and consequences of cracking thoroughly is essential for selecting proper measures to resolve the early-age cracking problem in concrete. This paper will help to identify the major causes and consequences of the early-age cracking in concrete. Also, this paper will be useful to adopt effective remedial measures for reducing or eliminating the early-age cracking problem in concrete. Different types of early-age crack, the factors affecting the initiation and growth of early-age cracks, the causes of early-age cracking, and the modeling of early-age cracking are discussed in this paper. A number of examples for various early-age cracking problems of concrete found in different structural elements are also shown. Above all, some recommendations are given for minimizing the early-age cracking in concrete. It is hoped that the information conveyed in this paper will be beneficial to improve the service life of concrete structures. Concrete researchers and practitioners may benefit from the contents of this paper.

Some local factors affecting iridic lipid infiltration in hypercholesteremic rabbits

1959 ◽  
Vol 197 (4) ◽  
pp. 842-846 ◽  
Author(s):  
Meyer Friedman ◽  
Sanford O. Byers
Keyword(s):  
Cottonseed Oil ◽  
Aortic Tissue ◽  
Factors Affecting ◽  
Experimental Animals ◽  
Local Factors ◽  
Laboratory Conditions ◽  
Intermittent Exposure ◽  
Intense Light

The influence of various factors affecting the deposition of lipid and cholesterol in the iris of rabbits fed cholesterol and cottonseed oil was studied. It was observéd that this deposition could be increased by the intraocular implantation of either normal aortic tissue or polyethylene discs. In an additional study, it was found that intermittent exposure of the eyes of cholesterol-fed rabbits to intense light also provoked an earlier and more intense iris deposition of lipid and cholesterol than was observed in the eyes of similarly fed rabbits kept either in absolute darkness or under ordinary laboratory conditions. It was postulated that the factor responsible for the greater iridic deposition observed in all these experimental animals was the iridic vasodilatation effected by these experimental measures.

Failure Analysis of a Shaft Belonging to a Ship Engine Speed Controller

1999 ◽  
Author(s):  
Miguel V. Figueiredo ◽  
Fernando M. Oliveira ◽  
Paulo T. de Castro ◽  
António A. Fernandes
Keyword(s):  
Electron Microscopy ◽  
Fracture Surface ◽  
Failure Analysis ◽  
Laboratory Tests ◽  
Engine Speed ◽  
Notch Toughness ◽  
Severe Damage ◽  
Speed Controller ◽  
Service Conditions ◽  
Scanning Electron

Abstract The fracture of a shaft belonging to the speed controller of a ship’s engine is presented. An over-speed situation occurred as a result of the fracture of this shaft, which led to severe damage to the engine. The failure examination concentrated first on the study of the available evidence, which included the analysis of the shaft’s material and fracture surface. The shaft’s material was studied as concerns chemical composition, mechanical properties and micrographic structure. The fracture surface was studied using scanning electron microscopy. Several different destructive laboratory tests were conducted on the material, in order to obtain fracture surfaces which could be used for comparison purposes, and thus help to identify the cause of the fracture. The next step of the failure analysis consisted of a stress analysis of the shaft under service conditions. A probable scenario for the failure was proposed, which helped the interested parties to reach an agreement concerning responsibilities for the failure. It was found that the shaft material presented low notch toughness. The stress levels at the time of the accident imply that it is unlikely that the fracture was due to fatigue. The probable cause of the failure was sudden blockage of the shaft.

scholarly journals On Realistically Attacking Tor with Website Fingerprinting

2016 ◽  
Vol 2016 (4) ◽  
pp. 21-36 ◽  
Author(s):  
Tao Wang ◽  
Ian Goldberg
Keyword(s):  
Background Noise ◽  
Laboratory Tests ◽  
Training Data ◽  
Web Traffic ◽  
Training Set ◽  
Data Set ◽  
Laboratory Conditions ◽  
Testing Data ◽  
In The Wild ◽  
New Algorithms

Abstract Website fingerprinting allows a local, passive observer monitoring a web-browsing client’s encrypted channel to determine her web activity. Previous attacks have shown that website fingerprinting could be a threat to anonymity networks such as Tor under laboratory conditions. However, there are significant differences between laboratory conditions and realistic conditions. First, in laboratory tests we collect the training data set together with the testing data set, so the training data set is fresh, but an attacker may not be able to maintain a fresh data set. Second, laboratory packet sequences correspond to a single page each, but for realistic packet sequences the split between pages is not obvious. Third, packet sequences may include background noise from other types of web traffic. These differences adversely affect website fingerprinting under realistic conditions. In this paper, we tackle these three problems to bridge the gap between laboratory and realistic conditions for website fingerprinting. We show that we can maintain a fresh training set with minimal resources. We demonstrate several classification-based techniques that allow us to split full packet sequences effectively into sequences corresponding to a single page each. We describe several new algorithms for tackling background noise. With our techniques, we are able to build the first website fingerprinting system that can operate directly on packet sequences collected in the wild.

scholarly journals Assessment of Skid Resistance of Asphalt Mixtures in Laboratory Conditions

2012 ◽  
Vol 58 (4) ◽  
pp. 521-534 ◽  
Author(s):  
W. Gardziejczyk ◽  
M. Wasilewska
Keyword(s):  
Asphalt Concrete ◽  
Laboratory Tests ◽  
Asphalt Mixtures ◽  
Road Surface ◽  
Skid Resistance ◽  
Mastic Asphalt ◽  
Laboratory Conditions ◽  
University Of Technology ◽  
Road Surfaces ◽  
Stone Mastic Asphalt

AbstractThe aggregate applied for the wearing course has a significant influence on skid resistance of road surfaces. However, it is difficult to evaluate the behaviour of road surface in use on the basis of the Polished Stone Value (PSV) determined for the aggregate according to the so called ‘British method’. The British method, which is currently used in many countries, does not allow to determine the influence of neither the grain size of the aggregate nor the type of the wearing course on skid resistance of road surface. The present paper suggests a method for evaluation of the British Pendulum Number (BPN) for road surfaces in laboratory conditions. The authors assumed the BPN for polished slabs, made from asphalt mixtures, as the criterion. The index was measured with the British Pendulum Tester. The simulation of the process was conducted on research stand (called slab polisher) built at Bialystok University of Technology (BUT). The results of laboratory tests indicate that surfaces from asphalt concrete (AC) have slightly higher values of BPN in comparison with the values determined for surfaces made from stone mastic asphalt (SMA).

Diesel Truck Overall Quality Analysis Based on PCA

2013 ◽  
Vol 765-767 ◽  
pp. 2233-2237
Author(s):  
Zhen Yu Yu
Keyword(s):  
Performance Indicators ◽  
Principal Component ◽  
Quality Analysis ◽  
Factors Affecting ◽  
Service Conditions ◽  
Major Factors

The quality of diesel truck overall quality is measured through a series of performance indicators. This paper analyzes the complex diesel truck systems through the use of principal component. Through the analysis, several major indicators which affect the truck service conditions are found in many of the performance indicators, and major factors affecting the serviceability of diesel truck are obtained.

scholarly journals Thermal Ageing of Power Cable Components Through Penetrations

2019 ◽  
Vol 19 (1) ◽  
pp. 36-42
Author(s):  
D. Puiu ◽  
B. Corbescu ◽  
C. Cepisca
Keyword(s):  
Temperature Increase ◽  
Laboratory Tests ◽  
Thermal Ageing ◽  
Power Cable ◽  
Power Cables ◽  
Temperature Influence ◽  
The Real ◽  
Service Conditions

AbstractThe power cables passing through penetration leads to growth of the thermal ageing mechanisms rate. The paper presents the results of the laboratory tests when the real environmental service conditions for penetration are simulated comparison with the result of the thermal computation of the power cables heating and of the temperature influence evaluation of temperature increase of the power cable components on the cable lifetime. For this particular case, a power cable with PVC insulation, we estimated a lifetime decrease about 20 years referring to lifetime (30÷40 years) for location in air.

scholarly journals COMPARATIVE STUDY OF PHYSICOMECHANICAL PROPERTIES OF ULTRABASIC ROCKS AND ANDESITES FROM CENTRAL MACEDONIA (GREECE)

2017 ◽  
Vol 50 (4) ◽  
pp. 1989 ◽  
Author(s):  
P. Petrounias ◽  
A. Rogkala ◽  
M. Kalpogiannaki ◽  
B. Tsikouras ◽  
K. Hatzipanagiotou
Keyword(s):  
Comparative Study ◽  
Water Absorption ◽  
Laboratory Tests ◽  
Volcanic Rocks ◽  
Evaluation Criteria ◽  
Industrial Applications ◽  
Physicomechanical Properties ◽  
Textural Features ◽  
Factors Affecting ◽  
Major Factors

Petrographic, geochemical and physicomechanical features were determined and inter-correlated in two representative ultrabasic samples from the Veria-Naousa ophiolite and two Pliocenic andesite samples, occurring at the east of the above complex. Results show that mineralogical and textural features are major factors affecting the physicomechanical properties in both lithotypes. The ultrabasic rocks display higher resistance to attrition and abrasion and lower water absorption values relative to the intermediate volcanic rocks, hence the first are predicted to show better in-service engineering performance. However, the degree of serpentinisation is detrimental, as a highly serpentinised ultrabasic sample yielded poor results, analogous to the andesites, in certain laboratory tests. Ophiolite complexes in Greece are abundant and they are distributed along several mainland areas. Hence setting evaluation criteria for their quality is important as they can potentially replace limestones, which are less resistant and durable, in several environmental and industrial applications

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