scholarly journals Subfailure damage in ligament: a structural and cellular evaluation

2002 ◽  
Vol 92 (1) ◽  
pp. 362-371 ◽  
Author(s):  
Paolo P. Provenzano ◽  
Dennis Heisey ◽  
Kei Hayashi ◽  
Roderic Lakes ◽  
Ray Vanderby
Keyword(s):  
Structural Damage ◽  
Ex Vivo ◽  
Healing Process ◽  
Strain Curve ◽  
Damage Threshold ◽  
Cellular Damage ◽  
Stress Strain Curve ◽  
The Difference ◽  
Cellular Area ◽  
Natural Healing

Subfailure damage in ligaments was evaluated macroscopically from a structural perspective (referring to the entire ligament as a structure) and microscopically from a cellular perspective. Freshly harvested rat medial collateral ligaments (MCLs) were used as a model in ex vivo experiments. Ligaments were preloaded with 0.1 N to establish a consistent point of reference for length (and strain) measurements. Ligament structural damage was characterized by nonrecoverable difference in tissue length after a subfailure stretch. The tissue's mechanical properties (via stress vs. strain curves measured from a preloaded state) after a single subfailure stretch were also evaluated ( n = 6 pairs with a different stretch magnitude applied to each stretched ligament). Regions containing necrotic cells were used to characterize cellular damage after a single stretch. It should be noted that the number of damaged cells was not quantified and the difference between cellular area and area of fluorescence is not known. Structural and cellular damage were represented and compared as functions of subfailure MCL strains. Statistical analysis indicated that the onset of structural damage occurs at 5.14% strain (referenced from a preloaded length). Subfailure strains above the damage threshold changed the shape of the MCL stress-strain curve by elongating the toe region (i.e., increasing laxity) as well as decreasing the tangential modulus and ultimate stress. Cellular damage was induced at ligament strains significantly below the structural damage threshold. This cellular damage is likely to be part of the natural healing process in mildly sprained ligaments.

Study on Tensile Property and Strain Ageing Behavior of X100 Linepipe

2010 ◽  
Author(s):  
Yang Li ◽  
Weiwei Zhang ◽  
Shaotao Gong ◽  
Lingkang Ji ◽  
Chunyong Huo ◽  
...  
Keyword(s):  
Strain Curve ◽  
Tensile Specimen ◽  
Sampling Location ◽  
Stress Strain Curve ◽  
Long Distance ◽  
Noticeable Effect ◽  
Testing Method ◽  
Tension Tests ◽  
Tension Properties ◽  
The Difference

A series research programs and industrial trials of X100 linepipe have been launched by CNPC so as to build an X100 trial in China for long-distance gas pipeline in the coming years. In present paper, tests have been conducted on 20.6mm×1016mm diameter Grade X100 linepipe. The microstructures, tension properties will be presented. In order to investigate the influence of anti-corrosion coating process on the performance of pipe, strain aging tests in lab have been carried out as well. It is found that testing method, tensile specimen size and sampling location had a noticeable effect on the testing results. The difference is also observed between the flattened strap specimen and round bar. The influence of time, temperature and pre-strain amount of aging tests on the shape of S-S (stress-strain) curve, tension tests results, yield ratio of pipes are presented as well.

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.

Experimental Study on the Shearing Property of Equal Strength Recycled Coarse Aggregate Concrete

2013 ◽  
Vol 357-360 ◽  
pp. 1420-1427 ◽  
Author(s):  
Zhi Heng Deng ◽  
Yi Liao ◽  
Chao Lou Meng ◽  
Hai Feng Yang
Keyword(s):  
Strain Curve ◽  
Recycled Concrete ◽  
Stress Strain Curve ◽  
Ordinary Concrete ◽  
Equal Strength ◽  
Shearing Strength ◽  
Shear Performance ◽  
The Difference ◽  
Shearing Strain ◽  
Peak Value

For the purpose of studying the difference between recycled concrete and ordinary concrete on shearing property under the circumstance of equal strength, nine recycled concrete beams, which have equal altitude and varying width, have been produced by using different replacement rates of 0%, 50% and 100% respectively to test their shear performance. The differences between recycled concrete and ordinary concrete on shearing strength, shearing strain and constitutive relation were analyzed in this paper. The study indicates that with the same compressive strength, there is only a slight difference between recycled concrete and ordinary concrete on shearing strength. The shearing strength of the recycled concrete is similar to the tensile strength of the ordinary concrete. Recycled concretes peak value increases as shearing strength increases. The stress-strain curve of recycled concrete is similar to that of the ordinary concrete. Its shear modulus increases when shearing strength increases.

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.

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.

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