A Theoretical and Experimental Analysis of the General Wool Fiber Stress-Strain Behavior with Particular Reference to Structural and Dimensional Nonuniformities

1969 ◽  
Vol 39 (2) ◽  
pp. 121-140 ◽  
Author(s):  
J. D. Collins ◽  
M. Chaikin
Keyword(s):  
Structural Variation ◽  
Strain Curve ◽  
Fiber Material ◽  
Effective Area ◽  
Stress Strain Curve ◽  
Fiber Stress ◽  
Stress Strain ◽  
Strain Behavior ◽  
Area Variation ◽  
The Relationship

The general wool-type three-region behavior (i.e., Hookean, yield, and post-yield regions) is examined both theoretically and experimentally. In order to account for the influence of structural variation, the concept of effective area is introduced and it is shown that this effective area may differ according to the region in which the fiber is being extended. The general effects of effective-area variation on the regions of the stress-strain curve are derived and these are applied to a number of theoretical situations to demonstrate the stress-strain possibilities. It is shown that the relationship between the stress-strain curves for different sets of conditions can be quite complex since the nonuniformity relationships for the various regions of the curves and between curves may vary according to the conditions of testing. Two examples are given of the application of the theory in practice. The behavior of fibers in water and hydrochloric acid are compared and it is shown that there are variations in the effect of the acid within the fiber. The behavior of abraded fibers is examined and it is found that differences previously attributed by other workers to differences between the ortho and para components of the fibers are actually due to variable bond breakdown within the fiber material.

Understanding Dynamic Recrystallization Behavior through a Delay Differential Equation Approach

2007 ◽  
Vol 558-559 ◽  
pp. 441-448 ◽  
Author(s):  
Jong K. Lee
Keyword(s):  
Differential Equation ◽  
Strain Rate ◽  
Critical Strain ◽  
Strain Curve ◽  
Single Peak ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Behavior ◽  
Delay Differential

During hot working, deformation of metals such as copper or austenitic steels involves features of both diffusional flow and dislocation motion. As such, the true stress-true strain relationship depends on the strain rate. At low strain rates (or high temperatures), the stress-strain curve displays an oscillatory behavior with multiple peaks. As the strain rate increases (or as the temperature is reduced), the number of peaks on the stress-strain curve decreases, and at high strain rates, the stress rises to a single peak before settling at a steady-state value. It is understood that dynamic recovery is responsible for the stress-strain behavior with zero or a single peak, whereas dynamic recrystallization causes the oscillatory nature. In the past, most predictive models are based on either modified Johnson-Mehl-Avrami kinetic equations or probabilistic approaches. In this work, a delay differential equation is utilized for modeling such a stress-strain behavior. The approach takes into account for a delay time due to diffusion, which is expressed as the critical strain for nucleation for recrystallization. The solution shows that the oscillatory nature depends on the ratio of the critical strain for nucleation to the critical strain for completion for recrystallization. As the strain ratio increases, the stress-strain curve changes from a monotonic rise to a single peak, then to a multiple peak behavior. The model also predicts transient flow curves resulting from strain rate changes.

Predictive Stress-Strain Models for High Strength Concrete Subjected to Uniaxial Compression

2014 ◽  
Vol 567 ◽  
pp. 476-481
Author(s):  
Nasir Shafiq ◽  
Tehmina Ayub ◽  
Muhd Fadhil Nuruddin
Keyword(s):  
Predictive Models ◽  
High Strength Concrete ◽  
Cement Content ◽  
Strain Curve ◽  
High Strength ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strength Concrete ◽  
Strain Behavior ◽  
Four Cylinders

To date, various predictive models for high strength concrete (HSC) have been proposed that are capable of generating complete stress-strain curves. These models were validated for HSC prepared with and without silica fume. In this paper, an investigation on these predictive models has been presented by applying them on two different series of HSC. The first series of HSC was prepared by utilizing 100% cement content, while second series was prepared by utilizing 90% cement and 10% Metakaolin. The compressive strength of the concrete was ranged from 71-87 MPa. For each series of HSC, total four cylinders of the size 100×200mm were cast to obtain the stress-strain curves at 28 days.It has been found that the pattern of the stress-strain curve of each cylinder among four cylinders of each series was different from other, in spite of preparing from the similar batch. When predictive models were applied to these cylinders using their test data then it was found that all models more or less deficient to accurately predict the stress-strain behavior.

scholarly journals Predicting Specific Stress of Cotton Staple Ring Spun Yarns: Experimental and Theoretical Results

2017 ◽  
Vol 25 (0) ◽  
pp. 43-47 ◽  
Author(s):  
Muhammad Zubair ◽  
Bohuslav Neckář ◽  
Zilfiqar Malik
Keyword(s):  
Reasonable Agreement ◽  
Twist Angle ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Fiber Stress ◽  
Stress Strain ◽  
New Approach ◽  
Contraction Ratio ◽  
Spun Yarns ◽  
Theoretical Results

The aim of this research is to predict the yarn specific stress from fiber specific stress and fiber stress utilisation. In this paper a new approach is introduced to predict the specific stress-strain curves of cotton carded and combed yarns. The force on single fiberis worked out and these fiber forces are combined together to obtain forces acting on yarn. The theoretical model introduces the utilisation of fiber stress on the basis of the fiber specific stress-strain curve, twist angle, fiber directional distribution parameter C and contraction ratio. A comparison of experimental results suggests that the specific stress-strain curves predicted have reasonable agreement with the experimental yarn specific stress-strain curves for all types of yarns. Thus this model is valid to predict the specific stress-strain curves for carded and combed cotton ring spun yarns.

A Probabilistic Methodology for Random Stress-Strain Curves

1991 ◽  
Author(s):  
H. R. Millwater ◽  
S. V. Harren ◽  
B. H. Thacker
Keyword(s):  
Finite Element Analysis ◽  
Numerical Evaluation ◽  
General Procedure ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behavior ◽  
Engineering Parameters ◽  
Analysis System

Abstract This paper presents a methodology for analyzing structures with random stress-strain behavior. Uncertainties in the stress-strain curve of a structure are simulated by letting a small number of engineering parameters which describe the stress-strain curve be random. Certain constraints are imposed on the engineering parameters in order to have a physically realizable material. A general procedure to handle correlation among the stress-strain parameters has also been developed. This methodology has been integrated into the NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) probabilistic structural analysis system. With this system, probabilistic finite element analysis of structures with random stress-strain behavior can be analyzed in an accurate, automated fashion. An example problem is presented to demonstrate the capabilities of the code. The problem analyzed is that of a pressure vessel fabricated with a material exhibiting random stress-strain behavior.

Technical Basis for the Extension of ASME Code Case N-494 for Assessment of Austenitic Piping

1996 ◽  
Vol 118 (4) ◽  
pp. 513-516 ◽  
Author(s):  
J. M. Bloom
Keyword(s):  
Lower Bound ◽  
Pressure Vessel ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Failure Assessment Diagram ◽  
Strain Behavior ◽  
Failure Assessment ◽  
Asme Code ◽  
Constraint Effects

In 1990, the ASME Boiler and Pressure Vessel Code for Nuclear Components approved Code Case N-494 as an alternative procedure for evaluating flaws in light water reactor (LWR) ferritic piping. The approach is an alternate to Appendix H of the ASME Code and allows the user to remove some unnecessary conservatism in the existing procedure by allowing the use of pipe specific material properties. The Code case is an implementation of the methodology of the deformation plasticity failure assessment diagram (DPFAD). The key ingredient in the application of DPFAD is that the material stress-strain curve must be in the format of a simple power law hardening stress-strain curve such as the Ramberg-Osgood (R-O) model. Ferritic materials can be accurately fit by the R-O model and, therefore, it was natural to use the DPFAD methodology for the assessment of LWR ferritic piping. An extension of Code Case N-494 to austenitic piping required a modification of the existing DPFAD methodology. Such an extension was made and presented at the ASME Pressure Vessel and Piping (PVP) Conference in Minneapolis (1994). The modified DPFAD approach, coined piecewise failure assessment diagram (PWFAD), extended an approximate engineering approach proposed by Ainsworth in order to consider materials whose stress-strain behavior cannot be fit to the R-O model. The Code Case N-494 approach was revised using the PWFAD procedure in the same manner as in the development of the original N-494 approach for ferritic materials. A lower-bound stress-strain curve (with yield stress comparable to ASME Code specified minimum) was used to generate a PWFAD curve for the geometry of a part-through wall circumferential flaw in a cylinder under tension and bending. Earlier work demonstrated that a cylinder under axial tension with a 50-percent flaw depth, 90 deg in circumference, and radius to thickness of 10, produced a lower-bound FAD curve. Validation of the new proposed Code case procedure for austenitic piping was performed using actual pipe test data. Using the lower-bound PWFAD curve, pipe test results were conservatively predicted (failure stresses were predicted to be 31.5 percent lower than actual on the average). The conservative predictions were attributed to constraint effects where the toughness values used in the predictions were obtained from highly constrained compact test specimens. The resultant development of the PWFAD curve for austenitic piping led to a revision of Code Case N-494 to include a procedure for assessment of flaws in austenitic piping.

Mathematical Modelling of the Stress-Strain Curve for 31VMn12 Ecological Steel

2017 ◽  
Vol 54 (3) ◽  
pp. 409-413
Author(s):  
Carmen Otilia Rusanescu ◽  
Cosmin Jinescu ◽  
Marin Rusanescu ◽  
Maria Cristiana Enescu ◽  
Florina Violeta Anghelina ◽  
...  
Keyword(s):  
Mathematical Modelling ◽  
Strain Curve ◽  
Torsion Test ◽  
Processing Parameters ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Hollomon Parameter ◽  
Relationship Of ◽  
The Mathematical Model ◽  
The Relationship

In this paper, optimum hot formation processing parameters for 31VMn12 steel were established, the torsion deformation of 31VMn12 steel was investigated at temperatures from 900, 1000, 11000C and strain rates from 0.05 s-1 to 3 s. -1. There were studied the structural aspects of materials, in microstructures by electronic microscopy. The stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zenner-Hollomon parameter. The mathematical model presented in the paper describes the relationship of tension strain, voltage and temperature coefficient 31VMn12 steel at high temperatures. The stress-strain curves determined by the torsion test allowed the calculation of the Zenner-Hollomon parameter corresponding to the maximum stress. By using this parameter has established a set of equations that reproduce completely stress-strain curve, including the hardening, the restoration and dynamic recrystallization area. Comparisons were made between the experimental results and the predicted and confirmed that constitutive equations developed can be used for mathematical modelling and other attempts (forging, compression) and other types of steel.

Quantitative Characterization of Cure. I. Relationship between Modulus and Strain of Pure-Gum Natural-Rubber Vulcanizates

1952 ◽  
Vol 25 (3) ◽  
pp. 430-439 ◽  
Author(s):  
R. F. Blackwell
Keyword(s):  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Quantitative Characterization ◽  
Strain Data ◽  
Tentative Explanation ◽  
Natural Rubber Vulcanizates ◽  
The Relationship ◽  
Mooney Equation

Abstract The object of this investigation was to determine whether the relationship between strain (elongation) and modulus is sufficiently close for one to be calculated from the other. Stress-strain data have been recorded for loads of 2–10 kg. per sq. cm. for a series of ACS1 and other pure-gum compounds. It is shown that the strain at a fixed stress (5 kg. per sq. cm.) is uniquely related to the load required to produce an elongation of 100 per cent. A tentative explanation of this observation is given in terms of the Mooney equation for the stress-strain curve. It is shown that the second constant of this equation does not vary greatly from rubber to rubber.

Effect of Gamma-Irradiation towards Stress-Strain Curve of Single Die QFN Package

2011 ◽  
Vol 694 ◽  
pp. 620-624 ◽  
Author(s):  
Wan Yusmawati Wan Yusoff ◽  
Azman Jalar ◽  
Norinsan Kamil Othman ◽  
Irman Abdul Rahman
Keyword(s):  
Gamma Irradiation ◽  
Strain Curve ◽  
Stress And Strain ◽  
Flexural Stress ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Three Point Bending ◽  
Strain Behaviour ◽  
The Relationship ◽  
Different Doses

The aim of the research was to establish the relationship between stress-strain behaviour of single die Quad Flat No lead (SDQFN) and degradation by gamma irradiation. The SDQFN was exposed to Cobalt-60 with different doses from 0.5 Gy, 1.5 Gy, 5.0 Gy, 10.0 Gy and 50.0 kGy. The three-point bending technique was used to measure the flexural stress and strain of the package behaviour relations. After exposing with gamma radiation, the result showed the decreasing in the strength of the package behaviour of irradiated SDQFN when increasing the dose of gamma irradiation. The highest gamma irradiation dose used in this work produced the highest change in stress-strain behaviour of irradiated SDQFN.

The Stress-Strain Behavior of Densified Mix Design of Concrete

2002 ◽  
Vol 18 (4) ◽  
pp. 185-192
Author(s):  
Ping-Kun Chang
Keyword(s):  
High Performance ◽  
Strain Softening ◽  
High Performance Concrete ◽  
Strain Curve ◽  
Type I ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Behavior ◽  
Slump Flow

ABSTRACTThis paper investigates the compressive strength and workability of High-Performance Concrete (HPC) which yields a slump at 250 ± 20mm and a slump flow at 650 ± 50mm. From the complete stress-strain curve, it shows the peak strain will be higher while the strength increases. Two kinds of the post failure models can be distinguished. The first type (Type I) is called strain softening and the second type (Type II) is called strain snapping back. Also, it is found that the modulus of elasticityEcdecreases as the volume of cementitious pasteVpincreases. On the other hand, Poisson's ratio ν increases asVpincreases.

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