Understanding extensibility of paper: Role of fiber elongation and fiber bonding

TAPPI Journal ◽  
2020 ◽  
Vol 19 (3) ◽  
pp. 125-135
Author(s):  
JARMO KOUKO ◽  
TUOMAS TURPEINEN ◽  
ARTEM KULACHENKO ◽  
ULRICH HIRN ◽  
ELIAS RETULAINEN
Keyword(s):  
Strain Curve ◽  
Tensile Tests ◽  
Pulp Fibers ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Fiber Networks ◽  
Strain Behavior ◽  
Softwood Kraft Pulp ◽  
Random Fiber Networks

The tensile tests of individual bleached softwood kraft pulp fibers and sheets, as well as the micro-mechanical simulation of the fiber network, suggest that only a part of the elongation potential of individual fibers is utilized in the elongation of the sheet. The stress-strain curves of two actual individual pulp fibers and one mimicked classic stress-strain behavior of fiber were applied to a micromechanical simulation of random fiber networks. Both the experimental results and the micromechanical simulations indicated that fiber bonding has an important role not only in determining the strength but also the elongation of fiber networks. Additionally, the results indicate that the shape of the stress-strain curve of individual pulp fibers may have a significant influence on the shape of the stress-strain curve of a paper sheet. A large increase in elongation and strength of paper can be reached only by strength-ening fiber-fiber bonding, as demonstrated by the experimental handsheets containing starch and cellulose microfi-brils and by the micromechanical simulations. The key conclusion related to this investigation was that simulated uniform inter-fiber bond strength does not influence the shape of the stress-strain curve of the fiber network until the bonds fail, whereas the number of bonds has an influence on the activation of the fiber network and on the shape of the whole stress-strain curve.

Stress-strain curve of paper revisited

2012 ◽  
Vol 27 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Svetlana Borodulina ◽  
Artem Kulachenko ◽  
Mikael Nygårds ◽  
Sylvain Galland
Keyword(s):  
Three Dimensional ◽  
Strain Curve ◽  
Failure Behavior ◽  
Three Dimensional Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Bonding Parameters ◽  
Particle Level ◽  
The Impact

Abstract We have investigated a relation between micromechanical processes and the stress-strain curve of a dry fiber network during tensile loading. By using a detailed particle-level simulation tool we investigate, among other things, the impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds. This is probably the first three-dimensional model which is capable of simulating the fracture process of paper accounting for nonlinearities at the fiber level and bond failures. The failure behavior of the network considered in the study could be changed significantly by relatively small changes in bond strength, as compared to the scatter in bonding data found in the literature. We have identified that compliance of the bonding regions has a significant impact on network strength. By comparing networks with weak and strong bonds, we concluded that large local strains are the precursors of bond failures and not the other way around.

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.

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.

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.

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.

Strain-Rate Effects on Constitutive Behavior of Sn3.8-Ag0.7-Cu Lead-Free Solder

2009 ◽  
Author(s):  
Kok Ee Tan ◽  
John H. L. Pang
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Strain Curve ◽  
Tensile Tests ◽  
Lead Free ◽  
Indentation Hardness ◽  
Strain Rates ◽  
Test Results ◽  
Stress Strain Curve ◽  
Stress Strain

In this paper, the strain-rate dependent mechanical properties and stress-strain curve behavior of Sn3.8Ag0.7Cu (SAC387) solder is presented for a range of strain-rates at room temperature. The apparent elastic modulus, yield stress properties and stress-strain curve equation of the solder material is needed to facilitate finite element modeling work. Tensile tests on dog-bone shaped bulk solder specimens were conducted using a non-contact video extensometer system. Constant strain-rate uni-axial tensile tests were conducted over the strain-rates of 0.001, 0.01, 0.1 and 1 (s−1) at 25°C. The effects of strain-rate on the stress-strain behavior for lead-free Sn3.8Ag0.7Cu solder are presented. The tensile yield stress results were compared to equivalent yield stress values derived from nano-indentation hardness test results. Constitutive models based on the Ramberg-Osgood model and the Cowper-Symond model were fitted for the tensile test results to describe the elastic-plastic behavior of solder deformation behavior.

scholarly journals A study of the Cu0.95Al0.05 alloy: stress-strain curve and microstructure

2018 ◽  
Vol 20 (2) ◽  
Author(s):  
Emilio Medrano ◽  
Mauro Quiroga ◽  
Felipe A. Reyes
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Strain Curve ◽  
Tensile Tests ◽  
Optical Microscope ◽  
Metal Alloys ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Electrolytic Copper ◽  
Mechanical Traction

After fabricating five metallographic specimens of the Cu0.95Al0.05 alloy from electrolytic copper and aluminum, these ones were both microstructurally characterized by using a metallographic optical microscope at room temperature and subjected to mechanical traction in order to chart the stress-strain curve. From the characterization, it has been found out that the Cu0.95Al0.05 microstructure is composed of a single phase, and from the tensile tests, it has been obtained its rupture point, 249.361 MPa. The obtained results were explained in the framework of the theory of metals and metal alloys.

scholarly journals Study on The Mechanical Properties of Steel - Basalt Fiber Composite Reinforcement (SBFCBs)

2020 ◽  
Vol 165 ◽  
pp. 05028
Author(s):  
Lei Zhao ◽  
Shengjiang Sun ◽  
Wei Qi
Keyword(s):  
Elastic Modulus ◽  
Fiber Composite ◽  
Low Cost ◽  
Basalt Fiber ◽  
Strain Curve ◽  
Tensile Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Failure Patterns ◽  
Steel Bars

Steel bar and Basalt Fiber are combined to obtain a new structural material with high strength, high elastic modulus, high toughness, corrosion resistance, low cost and other excellent comprehensive performance: Steel Basalt Fiber Composite Bars (SBFCBs). In this paper, three different types of composite bars were tested by monotonic tensile tests, and the failure patterns of steel bars were introduced in the process of stretching, and the yield strength, ultimate strength, elastic modulus and stress-strain curves of steel bars were obtained. Test results showed that the stress-strain curve of SBFCBs was obviously double-folded, and SBFCBs exhibited stable post-yielding stiffness after the reinforcement yielded. The stress-strain curve model of SBFCBs under uniaxial tension was derived according to the material’s compounding rule. By sorting the experimental data and comparing it with theoretical values, we could prove the accuracy of the model.

Subultimate Prestrain and Aging in Mild Steel

1965 ◽  
Vol 87 (2) ◽  
pp. 319-324 ◽  
Author(s):  
D. K. Felbeck ◽  
W. G. Gibbons ◽  
W. G. Ovens
Keyword(s):  
Mild Steel ◽  
High Speed ◽  
Strain Curve ◽  
Local Stress ◽  
Tensile Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Limited Region ◽  
Small Increments ◽  
Necessary And Sufficient

Room-temperature tensile straining of mild steel followed by aging at 350 F causes return of the upper yield and a raising of the stress-strain curve. Tensile tests on a special rimmed steel of low Mn/C ratio show not only the expected raising of the stress-strain curve, but raising by an additional amount when several small increments of strain are each followed by aging at moderate temperatures. Longitudinal tensile prestrain by rolling gives substantially the same results. Tests of specimens prestrained in a limited region by impact or in slow tension and aged indicate that embrittlement of the whole specimen may result. The combined theories of Griffith and Orowan, plus an extension of the Ludwik triaxiality concept, can provide a consistent description of the local stress and average stress (energy) criteria that are necessary and sufficient for high-speed low-energy fracture to occur.

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