Extensibility changes of calcified soft tissue strips from human aorta

1987 ◽  
Vol 65 (9) ◽  
pp. 1878-1883 ◽  
Author(s):  
M. H. Sherebrin ◽  
H. A. Bernans ◽  
Margot R. Roach
Keyword(s):  
Breaking Strength ◽  
True Strain ◽  
Testing Machine ◽  
High Stress ◽  
Strain Curve ◽  
Human Aorta ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Tensile Testing Machine ◽  
Calcified Tissue

Some degree of calcification was noted in more than half of the 59 aortas of individuals aged from 15 to 88 we have examined at autopsy. The calcification, which is determined by x-raying the opened and flat aorta, is in patches. We have studied the influence of calcification on stress versus strain, breaking strength, and modulus of elasticity of strips of aorta to determine its importance in vascular disease. Strips of aortic wall 5 × 30 mm were cut with orientation parallel or perpendicular to the vessel axis. Elongation versus load was measured with an Instron tensile testing machine. The true stress and true strain were calculated for both calcified and uncalcified strips from the thoracic and abdominal regions in both orientations. From the stress–strain curve the following values were selected: strain, stress, and slope at 80 mmHg equivalent pressure (1 mmHg = 133.3 Pa); maximum stress, strain, and slope; and breaking stress, strain, and slope if the sample broke. There were statistically significant differences in 13 of the 36 categories between calcified and uncalcified strips. The breaking strength and strain is lower in the calcified strips. The stress–strain curve for the uncalcified strip was mathematically transformed by reducing the amount of elongation so that the curve coincided with that of the calcified strip for eight matched pairs from the same individuals. The calcification appears to immobilize part of the strip, probably causing the boundary of the calcified tissue to be a region of high stress where tissue breakdown can occur.

The Stress-Strain Relationship in Ebonite

1934 ◽  
Vol 7 (1) ◽  
pp. 197-211
Author(s):  
B. L. Davies
Keyword(s):  
Tensile Strength ◽  
Plastic Flow ◽  
Testing Machine ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Tensile Testing Machine ◽  
Hooke’S Law ◽  
Hooke's Law ◽  
Soft Rubber

Abstract 1. A simple “extensometer” has been devised for the more accurate measurement of small elongations in hard rubber samples, thus enabling stress-strain curves to be obtained on a standard tensile testing machine. 2. The form of the curve has been described more fully than heretofore. It shows that hard rubber does not deform exactly in accordance with Hooke's Law, but exhibits plastic flow. 3. Deviations from Hooke's Law shown by the experimental curves depend upon the speed of stretching. Increased speed of elongation has been found to give higher readings of tensile strength. 4. Prolonged mastication of the rubber gives a weaker product, similar effects being obtainable by the use of a neutral softener. 5. The effects of increasing time of vulcanization have been described. The range of curves showing transition from over-cured soft rubber to ebonite indicates that the hard rubber curve is possibly related to the initial portion of the soft rubber curve. The plasticity of the overvulcanized rubber, as indicated by the deviation from Hooke's Law, increased with time of vulcanization until the “semi-ebonite” stage was reached. 6. The leather-like “semi-ebonites” differed from soft and hard rubber inasmuch as they were extremely sensitive to small changes in time of vulcanization, and inasmuch as their plasticity was such that the velocity of plastic flow was comparable with the rate of pulling (1 in. per minute), at a particular point in the test they experienced a large elongation at constant load, i. e., the velocity of flow was equal to the speed of pulling. Their plasticity decreased with further vulcanization. 7. The longest cures in the above-mentioned group gave products which were rigid at room temperature. Since these must be more resistant to shock than vulcanizates in a higher state of cure, it seems that the best technical cure of ebonite for mechanical purposes is that which gives maximum tensile strength combined with the property of undergoing considerable plastic flow (of the order of 5 per cent) at the constant maximum load, and at an arbitrarily fixed rate of stretching, the temperature being commensurate with the thermal conditions of service. Such a cure is clearly indicated by the stress-strain curve. 8. Accelerated ebonite mixings are more sensitive to time of cure than rubber-sulfur stocks without accelerators. An accelerator may produce very little effect on the tensile strength and breaking elongation, but may yield a stock which “scorches” readily. This prevulcanization was detrimental to the mechanical properties of the vulcanizate, even though it was so slight that its presence was not detected during normal processing. 9. Mineral rubber in ebonite stocks has been shown to accelerate the cure as indicated by the stress-strain curve. 10. Stocks containing high loadings of gas black gave vulcanizates which were weak and brittle. The effect of the black on the stiffness was similar to that produced by further cure. 11. The stress-strain curve provides a reliable means whereby stocks containing different accelerators and other compounding ingredients may be compared at equivalent states of vulcanization.

Stress-Strain Curves for Oxygen-Free High Conductivity Copper at Shear Strain Rates of up to 103s-1

1970 ◽  
Vol 185 (1) ◽  
pp. 1149-1158 ◽  
Author(s):  
K. Bitans ◽  
P. W. Whitton
Keyword(s):  
Shear Strain ◽  
Testing Machine ◽  
Shear Bands ◽  
Strain Curve ◽  
Strain Rates ◽  
Adiabatic Shear Bands ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
The Given ◽  
Tubular Specimens

Shear stress-shear strain curves for o.f.h.c. copper at room temperature have been obtained at constant shear strain rates in the range 1 to 103s-1, using thin walled tubular specimens in a flywheel type torsion testing machine. Results show that, for a given value of strain, the stress decreases when the rate of strain is increased. Moreover, the elastic portion of the stress-strain curve tends to disappear as the rate of strain is increased. It is postulated that these effects are due to the formation of adiabatic shear bands in the material when the given rate of strain is impressed rapidly enough. A special feature of the design of the testing machine used is the rapid application of the chosen strain rate.

The Development of a Machine for High-Speed Testing of Materials

1937 ◽  
Vol 135 (1) ◽  
pp. 467-483
Author(s):  
R. J. Lean ◽  
H. Quinney
Keyword(s):  
Mild Steel ◽  
Yield Point ◽  
High Speed ◽  
Testing Machine ◽  
Strain Curve ◽  
Maximum Point ◽  
Variable Speed ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
High Speed Machine

The paper contains an account of a research into the effect on metals of different speeds of fracture, using a specially designed high-speed testing machine which is described in detail. The experiments were conducted both in this machine and in a 5-ton variable-speed autographic tensile machine, on five steels, the rate of loading being varied for each. With the high-speed machine toughness, ductility, time to produce fracture, and the stress-strain curve were obtained. The results of these combined tests, given in tables and graphs, show that there is a marked increase in stress due to higher speed of testing; and also that the work required to cause fracture increases with the speed. For mild steel the stress at the initial yield point was found to be in excess of that at the maximum point, when the speed of testing was increased the ductility did not appear to suffer.

Mechanical Behavior of Materials under Tensile Loads

2004 ◽  
pp. 13-31
Keyword(s):  
Tensile Test ◽  
Mechanical Behavior ◽  
Tensile Deformation ◽  
True Strain ◽  
Strain Curve ◽  
Tensile Specimen ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Mathematical Expressions ◽  
Reduction In Area

Abstract This chapter focuses on mechanical behavior under conditions of uniaxial tension during tensile testing. It begins with a discussion on the parameters that are used to describe the engineering stress-strain curve of a metal, namely, tensile strength, yield strength or yield point, percent elongation, and reduction in area. This is followed by a section describing the parameters determined from the true stress-true strain curve. The chapter then presents the mathematical expressions for the flow curve. Next, it reviews the effect of strain rate and temperature on the stress-strain curve. The chapter then describes the instability in tensile deformation and stress distribution at the neck in the tensile specimen. It discusses the processes involved in ductility measurement and notch tensile test in tensile specimens. The parameter that is commonly used to characterize the anisotropy of sheet metal is covered. Finally, the chapter covers the characterization of fractures in tensile test specimens.

A Tensile Characterization Study of Metal Sheet in Large-Strain

2006 ◽  
Author(s):  
W. J. Dan ◽  
W. G. Zhang ◽  
S. H. Li ◽  
Z. Q. Lin
Keyword(s):  
Large Strain ◽  
True Strain ◽  
Digital Camera ◽  
Strain Curve ◽  
Plastic Instability ◽  
Tensile Specimen ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Tension Tests ◽  
Tensile Experiment

A method for determining the strain-stress curve of larger-strain is proposed when plastic instability occurs in standard tension tests. Thin tested steel sheet is subjected to tension loading until fracture occurs. The deformation process is captured with a digital camera. Displacement and strain field of material deformation can be calculated by a mesh-free PIM method. A tensile experiment is simulated to verify that local measuring stress-strain curve by PIM method near the center of the specimen can describe a full stress-strain curve clearly. Numerical simulation results, at different location along the specimen axial, present that different parts of specimen have different deformation distribution in tensile and the center fracture part of tensile specimen is the only region which can experience full strain. The true stress- true strain curves, based on the estimated parameters, are validated in all strain regions by comparison with curves from standard tension tests. The measured curves by PIM method are very stabilization. Compared with several material constitutive equations, The Swift’s equation is very close to experiment curve at plastic deformation.

Experimental analysis of stresses in weld metal subjected to tensile load

2016 ◽  
Vol 13 (4) ◽  
pp. 281-287 ◽  
Author(s):  
Sampath S.S. ◽  
Nethri Rammohan ◽  
Reema Shetty ◽  
Sawan Shetty ◽  
Chithirai Pon Selvan M.
Keyword(s):  
Power Plants ◽  
Thermal Stresses ◽  
Thermal Power ◽  
Testing Machine ◽  
Tensile Load ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Content Type ◽  
Hardness Number

Purpose Stainless steel is one of the most important elements in structural design and application, and due to its excellent properties, it is widely used in industries for conventional structural engineering applications, such as thermal power plants, nuclear power plants, civil constructions, etc. (Mishra et al., 2014). A traditional tensile testing machine cannot determine the transversal stress–strain curves (Olden, 2002, 2013). Design/methodology/approach In the present study, identical mild steel specimen parts are welded at different intervals and then subjected to tensile loading. Welding is carried along the length of the specimen. Induced stresses are determined at the welded intervals and the stress–strain curve is obtained. Findings By considering the temperature of the weld at the interface, thermal stresses are determined. Brinell hardness number is determined at the interface and the base metal. Also, the change in the hardness at the heat-affected zone (HAZ) is found. Validation is carried out by comparing the results with the original stress–strain curve. Originality/value In the HAZ, there is a drop in the hardness number, which means that there is a change in the material property due to welding. The thermal stresses which develop at the interface can also play a very important role for property change. Results show that the stress developed due to the rise in temperature is lesser than that of normal stresses.

The New Design Idea about Rock Direct Tensile Testing Machines Based on the Magnetic Levitation Principle

2014 ◽  
Vol 909 ◽  
pp. 148-153
Author(s):  
Zhong Hu Zhao ◽  
Lan Ning Sun
Keyword(s):  
Tensile Testing ◽  
Magnetic Levitation ◽  
Testing Machine ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Tensile Testing Machine ◽  
Technical Effect ◽  
Design Idea ◽  
Tensile Experiment ◽  
Direct Tensile

Direct tensile testing machines are the necessary to study tensile property of rocks. However, a traditional testing machine has the weakness of absenting effective subjacent brace. So, the whole tensile experiment can not be done completely. By using elastic brace, the whole tensile experiment really can be finished, then we can get the stress-strain curve. But, the samples are destroyed around incorrect planes. Aiming at the disadvantage of the machines, the author brings forward a new method of improving the direct tensile testing machine by using two magnets as the subjacent brace with magnetic levitation function. In this article, the author analyses the reasons why magnetic levitation can offer support and explains the components of the brace, its installation and principles. At last, the authors analyze the design idea and the technical effect of the brace.

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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