Analysis Of Stress-strain Curves Research Articles

Analogy between the stress-strain curves of crystalline polymers and the van der Waals isotherms for low-molecular-weight substances

On the basis of an x-ray diffraction study of the changes in the supermolecular organization of oriented polyethylene during reorientation, an analogy is drawn between the reorientation stress-strain curves and the van der Waals isotherms for low-molecular-weight substances. This analogy makes it possible to explain a number of published results and propose new modes of analysis of the stress-strain curves.

On the analysis of stress-strain curves by means of empirical equations

On the analysis of stress-strain curves by means of empirical equations

A System for Computer Analysis of Stress-Strain Curves

Abstract A system for recording and processing of data obtained in tensile tests is described. The electronics (hardware) consists of signal amplifiers (load and elongation), digital voltmeters with binary code decimal output, serializer, and incremental magnetic tape recorder. The operation sequence is controlled by a system of relays, time delays, and an electronic clock. The computer program calculates not only the typical mechanical properties such as yield stress, ultimate stress, and uniform and total elongation, but also more sophisticated properties such as strain-hardening coefficient and Reed-Hill coefficient, which are difficult to obtain by other means. The computer output is in the form of tabulated data and plotted curves. The system has been used in over 300 tests of Zircaloy and aluminum samples. Most of the tests were done on irradiated ring samples cut from the cladding of boiling water reactor fuel rods, but also tube- and plate-type samples have been tested. There was good agreement between the computer-generated values and the values calculated by conventional methods.

On the analysis of stress-strain curves

On the analysis of stress-strain curves

Pseudoelasticity in Au-Cd thermoelastic martensite

Abstract Thermoelastic martensitic transformation has been studied by the analysis of stress-strain curves in binary Au-Cd alloys, containing 46·5, 47·5, 48·5, 49, 49·5, and 50 at. % Cd, respectively. The pseudoelastic characteristics, i.e. superelastic and ferroelastic behaviour upon tension compression test and that the origin of the shape memory effect bears a close relation to the ferroelastic loop, have been explained on the basis of the lattice softening, that is. the shear elastic constant, C′ = (C11-C12)/2, decreases toward zero in the vicinity of the transition temperature. In particular the critical condition for obtaining the ferroelastic loop can be experimentally determined by assuming a critical stress, which is termed ‘ferroelastic limit’. The ferroelastic limit may depend upon the elastic anisotropy of alloys and lies in the region 6 Kg/mm- in the Au-Cd alloy.

Influence of the precipitate-free zone width on the tensile properties of an Al-6 Wt pct Zn-1.2 Wt pct Mg alloy

The mechanical properties of an Al-6 wt pct Zn-1.2 wt pct Mg alloy with various width of precipitate-free zones have been investigated. The width of the precipitate-free zone (PFZ) has been changed by the quench interruption technique without any appreciable change in the size and distribution of precipitates. An important relationship has been observed between the width of the PFZ and the quench-interruption period;i.e., the width of the PFZ increases in proportion to the square root of the holding time at 200°C. From the analysis of stress-strain curves as well as the observation of dislocation arrangements in slightly deformed specimens, the plastic deformation has been found to occur preferentially in the PFZ. The initial stage of deformation is much affected by the change in the width of the PFZ, but in the later stage, the work-hardening rate seems to be almost independent of the PFZ width. Tensile tests show that the ultimate tensile strength and the 0.2 pct proof stress decrease very little with increasing width of the PFZ, while the uniform elongation is practically constant regardless of the reduction in the nonuniform elongation. The work-hardening rate at the initial stage of deformation is found to decrease in proportion to the reciprocal of the PFZ width. This relationship can be explained from the dislocation model for work hardening.

An empirical analysis of titanium stress-strain curves

Stress-strain curves of titanium of two purity levels were analyzed by a Criissard and Jaoul method that assumes the Ludwik equation υ= υ 0 + kep n in the form where υ is the true stress ande p the true plastic strain. The analysis shows that High purity titanium conforms to a simpler behavior pattern than commercial purity titanium. In the absence of twinning the deformation behavior of high purity titanium can be described by a single power law, while that of commercial purity titanium is better portrayed in terms of two power laws; one holding for Small strains and the other for large. However, dynamic strain aging produces a single power law description in commercial purity titanium between 400 and 700 K. The Hollomon method was also applied to the data. This analysis was less sensitive to changes in deformation behavior.

A Congenital Hair Defect: Trichoschisis With Alternating Birefringence and Low Sulfur Content

Hair from a four year old white girl with a history of brittle hair since birth did not show any previously reported defect with light microscopy. Examination with polarized light revealed regular alternating areas of birefringence and non-birefringence, suggesting a patterned abnormality of hair keratiniziation. Fractures occurred only in the non-birefringent zones. Examination of hairs from each member of the patient's family, and from normal children of the same age, did not show this pattern. Scanning electron micrographs of the defective hair shaft and fracture sites were compared with normal hair and artificially fractured hair and revealed a marked anatomic defect of the cuticle and of the fracture sites. Stress strain curve analysis of the defective hair showed a very low elongation prior to breakage, usually less than 10%. Friction coefficients between crossed hair pairs were lower than normal and correlated with the defective cuticle formation. Electron-probe x-ray microanalysis of the defective hair shaft revealed a marked deficiency of sulfur, the periodicity of which differs from that found in the normal hair. Total sulfur content of the defective hair shafts was markedly decreased. Copper content of the hair shaft was greater than the normal control. However, the copper content of the root and the root/hair shaft ratio were less than normal. Complete amino acid analysis of the patient's hair demonstrates a major decrease in the amount of cystine-cysteine. Urine amino acid analysis detected two peaks not present in normal urine. Preliminary evidence indicates that the unidentified peaks represent peptides of complex composition. Argininosuccinic acid, reported in association with trichorrhexis nodosa, was not found.

An Analysis of Stress-Strain Curves of Soda Treated Wool Fiber

An Analysis of Stress-Strain Curves of Soda Treated Wool Fiber

Analysis of Stress Strain Curves

It is gratifying to learn from Mr. Nicholls (May 1955, p. 364) that he is favourably impressed with the exponential function, and it is to be hoped that he, and others interested in stress-strain relationships, may find it to be of practical value.While the modifications which he suggests are quite legitimate, they tend to mask the essential simplicity of the function. It would be difficult to obtain the asymptotic stress from his first equation. The second can be easily solved for strain, but the converse process is complicated by the fact that the current stress appears both inside and outside the exponential. It is surely much more straightforward, and infinitely quicker, to plot the stress-strain curve from the proof stress data and analyse it in the normal way.

A New Concept of the Mechanical Behavior of Fibers

The first portion, Part I, of this paper presents a review of the various theories of mechanical behavior of fibers. It is shown that the linear three-element model gives a fairly good qualitative description of relaxation, creep, and stress-strain phenomena. With this linear model extended to give a dis tribution of relaxation times, the time scales of the relaxation and creep functions are expanded to ranges which approach those observed experimentally. However, the more compli cated linear model is cumbersome, particularly when used to explain stress-strain data, and it does not yield the proper values of the elastic and viscous constants when the rate of strain is changed by a large factor. The three-element model with Hookean springs and Eyring dashpot is discussed, and it is shown that it accomplishes the extension of the time scale for relaxation and creep, and also yields relationships involving changes in the rate of elongation of stress-strain experiments which agree quite well with data on acetate rayon. The use fulness of graphical methods of analysis of stress-strain curves is pointed out. For other fibers, the agreement with experi ment is not so good. Efforts to generalize the Eyring model by considering the "energy barriers" to be asymmetric, em ployment of non-Hookean springs, and increasing the number of elements in the model have given better agreement of theory with experiment but leave much to be desired in the explana tion of the behavior of wool fibers.