A Time Effect in the Rapid Elongation of Rubber

1939 ◽  
Vol 12 (3) ◽  
pp. 518-519 ◽  
Author(s):  
V. Hauk ◽  
W. Neumann
Keyword(s):  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Steep Ascent ◽  
Decisive Effect ◽  
Elapsed Time ◽  
Adiabatic Curve ◽  
Thermodynamic Effects ◽  
The Difference ◽  
Thermodynamic Basis

Abstract It has already been pointed out elsewhere (Monatshefte für Chemie 72, 32 (1938); Rubber Chem. Tech. 12, 64(1939)) that the difference between the adiabatic and isothermal stress-strain curves of rubber is too great to be explained on a thermodynamic basis alone. It was suggested that the position of the adiabatic curves might be governed by the fact that the rate of stretching itself has a decisive effect on the behavior of the chains of molecules during stretching. To throw light on this phenomenon, stress-strain curves were obtained, by means of the stretching apparatus already described in the paper mentioned, at various rates of elongation which still fell within the range of adiabatic stretching. The operation was carried out in such a way that a chronometer started electrically when the rubber began to elongate, and stopped again when the rubber reached an elongation of 450 per cent. With the aid of this contrivance, stress-strain curves were obtained at rates corresponding to 0.68, 2.5, 5.7 and 9.1 seconds' elapsed time for the stretching. For comparison, an isotherm was obtained by loading rubber strips of the same dimensions with various weights. A vulcanizate containing 2 per cent of combined sulfur was used as experimental material. The temperature was 13° C. The results of these measurements are shown graphically in Fig. 1. It may be seen that the adiabatic curve corresponding to the highest rate of elongation has the least steep ascent, i.e., at the highest rate of elongation the stress is greatest at a given elongation. With increase in the time of stretching, the curves approach nearer and nearer to the isothermal stress-strain curve. This would seem to prove that the rate of elongation plays an important part, wholly independent of any thermodynamic effects. Perhaps during rapid stretching there is actual rupture of chains which are still coiled and which mutually obstruct the smooth course of the stress-strain curve. It can also be seen from the position of the curves that the decisive effect shown by the time factor is of the order of seconds, since the difference between the curves corresponding to 0.68 and 2.5 seconds is very small, whereas the difference between the curves corresponding to 2.5 and 5.7 seconds appears to be considerable.

The Behavior of Raw Rubber When Stretched Isothermally

1938 ◽  
Vol 11 (4) ◽  
pp. 647-652 ◽  
Author(s):  
H. Hintenberger ◽  
W. Neumann
Keyword(s):  
Room Temperature ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Steep Ascent ◽  
Flow Effect ◽  
Vulcanized Rubber ◽  
Flow Phenomena ◽  
Entropy Effect ◽  
The Subject

Abstract The S-shaped form of the stress-strain curve of rubber is today explained in a quite satisfactory way. In the first part of the curve, i. e., the gradual ascent, work must be expended because of the van der Waals forces of attraction of the molecules; in the second part, i. e., the steep ascent, the elasticity is chiefly an entropy effect, which is finally exceeded by crystallization phenomena. The phenomenon of crystallization itself has been the subject of extensive investigations, but in most cases vulcanized rubber has been employed, and because of the various accelerators and fillers which the rubber has contained, the products have been rather ill-defined. It is evident that the phenomena involved in crystallization would be much more clearly defined if the substance under investigation were to be in a higher state of purity. If experiments are carried out with raw rubber, a flow effect is added to the various other phenomena. As a result of this flow effect, Rosbaud and Schmidt, and Hauser and Rosbaud as well, found that the stress-strain curve depends on the rate of elongation at very low extensions, with a greater stiffness at high rates of elongation. As found recently by Kirsch, there is no evidence of any flow phenomena in vulcanized rubber at room temperature. Most investigations have been so carried out that the stress has been measured at a definite elongation. It was therefore of interest to determine the elongation at constant stress, and the changes in this relation with time and with temperature, of various types of raw rubber.

Anisotropy of the Stress-Strain Curves for Line Pipe Steels

2010 ◽  
Author(s):  
Kensuke Nagai ◽  
Yasuhiro Shinohara ◽  
Shinya Sakamoto ◽  
Eiji Tsuru ◽  
Hitoshi Asahi ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Strain Curve ◽  
Longitudinal Direction ◽  
Stress Strain Curve ◽  
Forming Process ◽  
Stress Strain ◽  
Line Pipe ◽  
Lower Aging Temperature ◽  
House Type ◽  
The Difference

To suppress the appearance of Lu¨ders strain and to decrease yield to tensile strength ratio in the L-direction (longitudinal direction), as well as the C-direction (circumferential direction), have been more important for strain-based design. In this study, conventional UOE and ERW pipes were examined in terms of tensile properties in both directions. In the case of UOE pipes, yield point was clearly observed on the stress-strain curve in the C-direction. However, stress-strain curves in the L-direction showed the round-house type. This difference became prominent after heat treatment for the anti-corrosion. Namely, clear Lu¨ders strain appeared in the C-direction at a lower aging temperature compared with that in the L-direction. On the other hand, contrasting results were obtained in the case for ERW pipes. Thus far, it’s been thought that the difference between UOE and ERW pipe was caused by the direction of final strain during the pipe forming process. There are also differences in the occurrence of Lu¨ders strain between each grade. A stress-strain curve maintained the round-house type in X100 grade pipe after the heat treatment at 240°C for five minutes; however, X70 grade pipe showed the stress-strain curve in the L-direction with Lu¨ders strain after the heat treatment at the same temperature.

Determination of the Constants of Zerilli-Armstrong Constitutive Relation Using Genetic Algorithm

2011 ◽  
Vol 264-265 ◽  
pp. 862-870
Author(s):  
G.H. Majzoobi ◽  
S. Faraj Zadeh Khosroshahi ◽  
H. Beik Mohammadloo
Keyword(s):  
Genetic Algorithm ◽  
High Strain ◽  
Optimization Technique ◽  
Strain Curve ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Material Models ◽  
The Difference

Identification of the constants of material models is always a concern. In the present work, a combined experimental, numerical and optimization technique is employed to determine the constants of Zerilli-Armstrong model. The experiments are conducted on a compressive Hopkinson bar, the simulations are performed using finite element method and optimization is carried out using genetic algorithm. In the method adopted here, there is no need for experimental stress-strain curve which is always accompanied by restricting phenomenon such as necking in tension and bulging in compression. Instead of stress-strain curve, the difference between the post-deformation profiles of specimens obtained from experiment and the numerical simulations is adopted as the objective function for optimization purposes. The results suggest that the approach introduced in this work can substitute costly instrumentations normally needed for obtaining stress-strain curves at high strain rates and elevated temperature.

Experimental Study on Stress-Strain Curve of Recycled Coarse Aggregate Concrete under Uniaxial Compression

2013 ◽  
Vol 357-360 ◽  
pp. 1415-1419 ◽  
Author(s):  
Zhi Heng Deng ◽  
Li Chen ◽  
Jian Qian ◽  
Chao Lou Meng
Keyword(s):  
Coarse Aggregate ◽  
Strain Curve ◽  
Recycled Concrete ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Recycled Coarse Aggregate ◽  
Rational Expression ◽  
The Difference ◽  
Two Stages

In order to study the mechanical properties of recycled concrete with the same strength, three kinds of recycled concrete have been made which their intensities reached C25, C30, C35 at the recycled coarse aggregate replacement ratios (0%, 50%, 100%), and severally completed the stress-strain curve test on the same strength of recycled concrete, separately analyzed the variance about failure pattern and peak strain, elastic modulus that all belonged to recycled concrete under the condition of the same strength. Studies have shown that the overall shape of recycled concretes stress-strain curves is similar to normal concretes under the same strength, and the difference is small, modulus of elasticity decreases with the increase of recycled coarse aggregate replacement ratio, while the peak strain basicly remains unchanged. Their curves can be used two stages respectively and also be represented by three fitting polynomial and rational expression, their descent stages steepened gradually with the increase of recycled coarse aggregate replacement rate.

A Study on the Direct Applicability of a Set of Grooves of Multi-Roll Wire Mills for Different Materials

2000 ◽  
Vol 123 (2) ◽  
pp. 272-278
Author(s):  
Kouichi Kuroda ◽  
Takashi Kuboki ◽  
Masayoshi Akiyama ◽  
Chihiro Hayashi
Keyword(s):  
Strain Curve ◽  
Roll Force ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Roll Type ◽  
The Difference ◽  
The Stability ◽  
Direct Applicability

Investigations were carried out on the direct applicability of a set of grooves of multi-roll wire mills for different materials having different stress-strain curves. Special evaluation was made on the stability of the geometry among different materials when rolled under the same mill setting conditions. Influence of inter-stand tension generated by the change in roll force due to the difference in stress-strain curve was studied both numerically and experimentally. A group of three-roll and four-roll-type mills is superior to two-roll-type mill in getting rid of the time for mill setting.

Use of Chip Tension to Obtain a Stress-Strain Curve From Metal Cutting Tests

1963 ◽  
Vol 85 (4) ◽  
pp. 351-355 ◽  
Author(s):  
I. Finnie ◽  
J. Wolak
Keyword(s):  
Metal Cutting ◽  
Strain Curve ◽  
Commercial Purity ◽  
Compression Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Wide Range ◽  
Shear Strains ◽  
The Difference ◽  
Commercial Purity Aluminum

By pulling the chip at various angles during metal cutting, it has been possible to greatly decrease the shear strains and thus to obtain a wide range of shear strains with a single tool. Using this technique, stress-strain curves for commercial purity aluminum have been obtained at −320 deg F (78 deg K) and 68 deg F (293 deg K). These results lie above those obtained from compression tests on the same material and the difference is ascribed largely to strain rate. Limits are imposed on the chip-pulling technique by an instability which appears when the direction of pulling makes too great an angle with the tool face and by fracture.

scholarly journals THERMO-MECHANICAL PROPERTIES OF NITI CLOSED COIL SPRINGS – FORCE DEGRADATION AND FORCE REGENERATION OVER TIME, VISCOUS PROPERTIES

2013 ◽  
Vol 56 (2) ◽  
pp. 41-46 ◽  
Author(s):  
Aleš Bezrouk ◽  
Libor Balský ◽  
Martin Smutný ◽  
Tomáš Nosek ◽  
Jiří Záhora ◽  
...  
Keyword(s):  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Large Hysteresis ◽  
Plateau Area ◽  
Stress Cycling ◽  
The Difference ◽  
Mechanically Stabilized ◽  
The Impact ◽  
Over Time

Introduction: The aim of this study was to find out the impact of degradation and regeneration of force over time at NiTi springs on the value and course of the final acting force and to verify the possibility of using these phenomena for a directed transition to the reverse plateau and its maintaining. Methods: Static and cyclic mechanical loadings were performed. At first unused springs were tested. Afterwards the springs were mechanically stabilized by stress cycling and finally tested again. The difference in shape of the working curves was assessed. For simulation and description of the force degradation the modified Voight model was used. Results: New springs, mainly those with large hysteresis, showed a significant stress-strain curve movement and shape changes during the cycling. The effect of the stress-strain curve course change disappeared fully in the stabilized springs. Multiple loading led to an overall decrease of force value during the measurement. The effect of force degradation and regeneration over time by simple static loading varies in the range of percentage of the nominal force in the plateau area. The transition between stress-strain curve phases caused by the degradation or regeneration of the force wasn’t observed in case of mechanically stabilized springs. Conclusions: Springs should be mechanically stabilized before their application. The degree of force degradation over time is insignificant for mechanically stabilized springs. Degradation or regeneration of force over time, mechanical stabilization or micromovements in the mouth don’t cause any transition between individual stress-strain curve phases.

A Comparison of the Rate of Combination of Sulfur with Rubber and the Rate of Vulcanization

1929 ◽  
Vol 2 (2) ◽  
pp. 209-215
Author(s):  
E. R. Bridgwater
Keyword(s):  
Strain Curve ◽  
General Characteristic ◽  
Sulfur Compounds ◽  
The State ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Heat Degradation ◽  
Maximum Stiffness ◽  
The Difference

Abstract The following general conclusions can be drawn from these experiments: 1—The low combined sulfur at correct cure which is, in general, characteristic of fast curing compounds is due both to the stiffening or polymerizing action of the accelerator and to the fact that fast curing compounds suffer less heat degradation during the cure. Some accelerators have a greater physical stiffening or polymerizing effect than others, that being the only way one can account for the difference in the rate of sulfur combination between Vulcanol and mercaptobenzothiazole, since Vulcanol which causes the combination of sulfur at a lower rate causes physical vulcanization or stiffening of the rubber at a higher rate. 2—The differences in the combined sulfur required to produce correct cure between one accelerator and another are not large as compared to the differences which result from changing the percentage of any given accelerator. 3—Accelerators differ among themselves in the benzol absorption which they impart to compounds. Neither the stress-strain curve nor the combined sulfur gives any information as to what the benzol absorption may be. The benzol absorption at any given state of physical cure depends even more upon the rate of cure of the compound than upon the accelerator used. In general, the higher the percentage of accelerator the lower is the benzol absorption. The effect of high sulfur is apparently due to the rate of cure and not to the sulfur itself because the high sulfur compounds which swell relatively little in benzol have low combined sulfur. It is indicated that oil resisting stocks should be highly accelerated but not overcured. In no case has curing beyond the point of maximum stiffness of the stress-strain curve caused a decrease in the benzol absorption. Referring to Table I, there is but little difference between the benzol absorption between 90 and 45 minute cures of either of the first three stocks. To state it another way, benzol absorption depends nearly as much upon the rate of cure as upon the state of cure. These facts should be borne in mind in compounding oil resisting stocks.

A modified version of MATLAB application window for predicting the weld bead profile and stress–strain plot of AA5052 CMT weldment using ER4043

SIMULATION ◽  
2021 ◽  
pp. 003754972110315
Author(s):  
B Girinath ◽  
N Siva Shanmugam
Keyword(s):  
Strain Curve ◽  
Weld Bead ◽  
Welding Parameters ◽  
Bead Geometry ◽  
Hybrid Technique ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Weld Bead Geometry ◽  
Inference System ◽  
Engineering Stress

The present study deals with the extended version of our previous research work. In this article, for predicting the entire weld bead geometry and engineering stress–strain curve of the cold metal transfer (CMT) weldment, a MATLAB based application window (second version) is developed with certain modifications. In the first version, for predicting the entire weld bead geometry, apart from weld bead characteristics, x and y coordinates (24 from each) of the extracted points are considered. Finally, in the first version, 53 output values (five for weld bead characteristics and 48 for x and y coordinates) are predicted using both multiple regression analysis (MRA) and adaptive neuro fuzzy inference system (ANFIS) technique to get an idea related to the complete weld bead geometry without performing the actual welding process. The obtained weld bead shapes using both the techniques are compared with the experimentally obtained bead shapes. Based on the results obtained from the first version and the knowledge acquired from literature, the complete shape of weld bead obtained using ANFIS is in good agreement with the experimentally obtained weld bead shape. This motivated us to adopt a hybrid technique known as ANFIS (combined artificial neural network and fuzzy features) alone in this paper for predicting the weld bead shape and engineering stress–strain curve of the welded joint. In the present study, an attempt is made to evaluate the accuracy of the prediction when the number of trials is reduced to half and increasing the number of data points from the macrograph to twice. Complete weld bead geometry and the engineering stress–strain curves were predicted against the input welding parameters (welding current and welding speed), fed by the user in the MATLAB application window. Finally, the entire weld bead geometries were predicted by both the first and the second version are compared and validated with the experimentally obtained weld bead shapes. The similar procedure was followed for predicting the engineering stress–strain curve to compare with experimental outcomes.

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