The Action of Ozone in the Phenomenon of the Cracking of Rubber Subjected to Repeated Mechanical Stresses

1940 ◽  
Vol 13 (3) ◽  
pp. 566-575
Author(s):  
Silvio Eccher
Keyword(s):  
Mechanical Stresses ◽  
Sudden Increase ◽  
Static Tension ◽  
Minimum Value ◽  
Rubber Belt ◽  
Complete Revolution ◽  
Shoe Soles ◽  
Rubber Article

Abstract Various rubber articles are subjected in ordinary service to repeated stretching, compression and cutting and to combinations of such forces. Repeated flexing is frequently encountered also. All these forces cause repeated changes, either positive or negative, in the dimensions of the outside surface of the rubber article. Among the important rubber products which undergo such stresses are tires, belts and shoe soles. The stresses to which the tread of a tire is subjected are certainly complex and variable. In this particular case, there are, in addition to the initial static tension, forces of compression, flexing and torsion. A rubber belt offers a simpler problem, for in this case it is possible to distinguish the following cycle of changes on the outside surface: a constant elongation in the taut section of the belt; a sudden increase in elongation on passing over the driving pulley, during which time a constant flexing stress (which depends on the curvature of the pulley) must be added to the tension on the belt; a decreased elongation along the surface of the belt in contact with the pulley; and finally a rapid return to the minimum value existing in the belt when under no tension. An analogous cycle of changes takes place at the driven pulley. Each element of the surface of a belt undergoes, therefore, during each complete revolution, two periods of tension, between which the element is alternately in the taut and in the slack section of the belt.

Human Platelets Exposed to Mechanical Stresses Express a Potent Lipoxygenase Product

1992 ◽  
Vol 68 (05) ◽  
pp. 589-594 ◽  
Author(s):  
Alon Margalit ◽  
Avinoam A Livne
Keyword(s):  
Regulatory Volume Decrease ◽  
Human Platelets ◽  
Mechanical Stresses ◽  
Arterial Stenosis ◽  
Platelet Suspension ◽  
Suspension Flows ◽  
Lipoxygenase Product ◽  
Pathological Conditions ◽  
K Permeability ◽  
Volume Decrease

SummaryHuman platelets exposed to hypotonicity undergo regulatory volume decrease (RVD), controlled by a potent, yet labile, lipoxygenase product (LP). LP is synthesized and excreted during RVD affecting selectively K+ permeability. LP is assayed by its capacity to reconstitute RVD when lipoxygenase is blocked. Centrifugation for preparing washed platelets (1,550 × g, 10 min) is sufficient to express LP activity, with declining potency in repeated centrifugations, indicating that it is not readily replenish-able. When platelet suspension flows in a vinyl tubing (1 mm i.d.), at physiological velocity, controlled at 90–254 cm/s, LP formation increases as a function of velocity but declines as result of increasing the tubing length. Stirring the platelets in an aggregometer cuvette for 30 s, yields no LP unless the stirring is intermittent. No associated platelet lysis or aggregation are observed following the mechanical stress applications. These results demonstrate that although mechanical stresses result in LP production, the mode of its application plays a major role. These results may indicate that LP is synthesized under pathological conditions and could be of relevance to platelets behavior related to arterial stenosis.

PENERAPAN STRATEGI DRTA (DIRECTED READING THINKING ACTIVITY) UNTUK MENINGKATKAN KEMAMPUAN SISWA DALAM MENCARI GAGASAN POKOK KARANGAN NARASI PADA SISWA KELAS IV SDN 003 PAGARAN TAPAH DARUSSALAM

2017 ◽  
Vol 5 (3) ◽  
pp. 42
Author(s):  
Marnius '
Keyword(s):  
Action Research ◽  
Achievement Test ◽  
Class Action ◽  
Narrative Writing ◽  
Research Instrument ◽  
Student Activity ◽  
Average Value ◽  
Minimum Value ◽  
Directed Reading ◽  
Class Iv

This research is motivated by the low ability students in finding ideas principal authorshipnarration in class IV SDN 003 Pagaran Tapah Darussalam. Goals to be achieved in thisresearch is to improve the ability of students in the basic idea for narrative writing in class IVSDN 003 Pagaran Tapah Darussalam through DRTA Strategy (directed reading thinkingactivity) carried out for 1 month. This research was conducted in SDN 003 Pagaran TapahDarussalam. Classes are meticulous researchers are class IV by the number of students asmany as 20 people. The study of this class action commenced in early September 2014. Thisform of research is classroom action research. The research instrument consists ofinstruments teacher and student activity sheets and achievement test. Based on the results ofthe study, the research concluded that the ability to search for the key idea fourth gradestudents of SDN 003 Pagaran Tapah Darussalam can be enhanced through DRTA strategy.This is evident from the increase in the student's ability in finding the key idea of the strategyDRTA before being applied to the second cycle of the second meeting. Known frompreliminary data the average value of students is 63. If the views of classical completeness,there are 30% of students (6) who finished obtaining a minimum value of 65 (according to thestandard KKM), the first cycle the first meeting denganrata average increased to 65, 3%circuitry completeness reach 10 or 50%, while in the second meeting mkembali increased to69.5 by the thoroughness of 12 people or 60% and sikluy II first meeting back in an averageincrease of 75% with the thoroughness of 16 or 80% and increased again in meetings second,reaching 80.5% with 100% completeness. The overall ability of students increased from theinitial tests until the fourth meeting of (20%). Thus, this study was successful

Role of Mechanical Stresses at Ion Implantation of CdHgTe Solid Solutions

2013 ◽  
Vol 58 (9) ◽  
pp. 872-880 ◽  
Author(s):  
Smirnov A.B. Smirnov A.B. ◽  
◽  
Lytvyn O.S. Lytvyn O.S. ◽  
Morozhenko V.A. Morozhenko V.A. ◽  
Savkina R.K. Savkina R.K. ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Solid Solutions ◽  
Mechanical Stresses

Characterization of Microcrystalline Transition from Amorphous Silicon as a Function of Hydrogen Dilution and Substrate Temperature of Hot-wire CVD

2002 ◽  
Vol 715 ◽  
Author(s):  
Keda Wang ◽  
Haoyue Zhang ◽  
Jian Zhang ◽  
Jessica M. Owens ◽  
Jennifer Weinberg-Wolf ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Sudden Change ◽  
Chemical Vapor ◽  
Threshold Value ◽  
Ir Absorption ◽  
Sudden Increase ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Integral Absorption ◽  
Two Peaks

Abstracta-Si:H films were prepared by hot wire chemical vapor deposition. One group was deposited at a substrate temperature of Ts=250°C with varied hydrogen-dilution ratio, 0<R<10; the other group was deposited with fixed R=3 but a varied Ts from 150 to 550°C. IR, Raman and PL spectra were studied. The Raman results indicate that there is a threshold value for the microstructure transition from a- to μc-Si. The threshold is found to be R ≈ 2 at Ts = 250°C and Ts ≈ 200°C at R=3. The IR absorption of Si-H at 640 cm-1 was used to calculate the hydrogen content, CH. CH decreased monotonically when either R or Ts increased. The Si-H stretching mode contains two peaks at 2000 and 2090 cm-1. The ratio of the integral absorption peaks I2090/(I2090+I2090) showed a sudden increase at the threshold of microcrystallinity. At the same threshold, the PL features also indicate a sudden change from a- to μc-Si., i.e. the low energy PL band becomes dominant and the PL total intensity decreases. We attribute the above IR and PL changes to the contribution of microcrystallinity, especially the c-Si gain-boundaries.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

On the method of ultrasonic control of mechanical stresses

2018 ◽  
Vol 84 (7) ◽  
pp. 62-66
Author(s):  
K. V. Kurashkin
Keyword(s):  
Elastic Wave ◽  
Orientation Distribution ◽  
Elastic Wave Velocity ◽  
Mechanical Stresses ◽  
Material Structure ◽  
Stress Determination ◽  
Welded Steel ◽  
Ultrasonic Control ◽  
Cubic Crystallites ◽  
Proportional Relationship

A method of ultrasonic control of the mechanical stresses which takes into account the heterogeneity of the material structure and does not require unloading of the structure or using reference samples is considered. The procedure is based on echo-method of measuring time of the bulk elastic wave propagation and determination of the relative values ν31 and ν32 related to the material structure and mechanical stresses. It is shown that stresses violate the linearity of the relationship observed between the parameters in the absence of the mechanical stresses in the rolled material. This effect formed a basis for developing a method of the deviator stress determination. The purpose of the study is to demonstrate the main advantages of the developed method against the known ultrasonic techniques used for evaluation of the mechanical stresses, give theoretical grounds to the effect which allows taking into account the heterogeneity of the material structure, and also to exemplify the procedure. An analytical expression is derived using bulk elastic wave velocity in an orthotropic material composed of cubic crystallites and an assumption on the existence of simple proportional relationship between the coefficients of the orientation distribution function in rolled metal. Presented results of the mathematical modeling confirm the experimentally observed linear dependence between the parameters ν31 and ν32 in the absence of mechanical stresses. The results of evaluating residual stresses in a welded steel plate are presented as an example of the applicability of the developed procedure. Data of ultrasonic technique and data of strain gage measurements are compared. The features of the described method of stress determination are marked and the applicability limits are specified.

Investigation of the effect of the constructive and mode parametres of a combined rocker on the power of the drive of the working bodies

2019 ◽  
pp. 82-85
Author(s):  
Pavel Ivanovich Pavlov ◽  
Viktor Vladislavovich Korsak ◽  
Aleksandr Olegovich Vezirov ◽  
Dmitriy Vadimovich Mukhin
Keyword(s):  
Operating Parameters ◽  
Regression Equations ◽  
Drive Power ◽  
Minimum Value ◽  
Working Bodies

The regression equations and graphical dependencies are obtained, which describe the influence of design and operating parameters on the drive power of the working bodies. The value of the design and operating parameters in which the power required to drive the working bodies, will have a minimum value  are experimentally determined.

Research of the Brillouin frequency shift damage dependence from mechanical stresses in an optical sensor

2019 ◽  
Vol 9 (5) ◽  
pp. 512-521
Author(s):  
Ruslan V. Aginey ◽  
◽  
Rustem R. Islamov ◽  
Alexander A. Godunov ◽  
◽  
...  
Keyword(s):  
Frequency Shift ◽  
Optical Sensor ◽  
Mechanical Stresses

AYURVEDIC PREPARATIONS FOR THE MANAGEMENT OF THE RAS - A REVIEW

2020 ◽  
Vol 7 (9) ◽  
pp. 1-8
Keyword(s):  
General Population ◽  
Herbal Medicines ◽  
Sudden Increase ◽  
Herbal Extracts ◽  
Common Condition ◽  
Etiological Factors ◽  
Oral Ulcers ◽  
Alternative Approach

Oral ulcers are the most common condition in the general population and are caused by a variety of etiological factors. It often causes pain and discomfort. So, there are different treatments including herbal medicines that have been used for oral ulcers. Nowadays, there has been a sudden increase in the use of herbal extracts as an alternative approach to modern-day medicines. So, this review focuses on the ayurvedic preparations for the treatment of RAS.

Dynamic Behavior Analysis of the Slider Crank Linkage using ANSYS Workbench and MATLAB Program

2013 ◽  
Vol 1 (1) ◽  
pp. 42-25
Author(s):  
Nabil N. Swadi
Keyword(s):  
Graphical Method ◽  
Joint Torque ◽  
Pressure Force ◽  
Matlab Program ◽  
Element Simulation ◽  
Acceleration Method ◽  
Complete Revolution ◽  
Two Phases ◽  
Good Agreement ◽  
Ansys Workbench

This paper is concerned with the study of the kinematic and kinetic analysis of a slider crank linkage using D'Alembert's principle. The links of the considered mechanism are assumed to be rigid. The analytical solution to observe the motion (displacement, velocity, and acceleration), reactions at each joint, torque required to drive the mechanism and the shaking force have been computed by a computer program written in MATLAB language over one complete revolution of the crank shaft. The results are compared with a finite element simulation carried out by using ANSYS Workbench software and are found to be in good agreement. A graphical method (relative velocity and acceleration method) has been also applied for two phases of the crank shaft (q2 = 10° and 130°). The results obtained from this method (graphical) are compared with those obtained from analytical and numerical method and are found very acceptable. To make the analysis linear the friction force on the joints and sliding interface are neglected. All results, in this work, are obtained when the crank shaft turns at a uniform angular velocity (w2 = 188.5 rad/s) and time dependent gas pressure force on the slider crown.

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