Stress as a Reduced Variable: Stress Relaxation of SBR Rubber at Large Strains

1961 ◽  
Vol 34 (3) ◽  
pp. 884-896
Author(s):  
Robert F. Landel ◽  
Paul J. Stedry
Keyword(s):  
Stress Relaxation ◽  
Large Deformations ◽  
Strain Curve ◽  
Large Strains ◽  
Stress Strain Curve ◽  
Breaking Strain ◽  
Reduced Modulus ◽  
Relaxation Measurements ◽  
Initial Strains ◽  
Strain Function

Abstract Stress relaxation measurements on SBR were carried out at temperatures from −5 to +60° C and at initial strains of up to 550%. The effects of strain and time were found to be factorable, so that the isochronal stress-strain curve may be written as a modified Hooke's law with a time-dependent modulus: S=E(t)eƒ(α), where ƒ(α) is an appropriate function of the strain. By defining a strain-reduced stress S*=S/∫(α), i.e., a strain-reduced modulus E*(t)=E(t)ƒ(α), it can be shown that Ferry's method of reduced variables may be extended to large deformations. An appropriate strain function was obtained from the empirical Martin-Roth-Stiehler equation as ƒ(α)=α−2 exp A(α−α−1) with A=0.40. Although it cannot yet be certain that A is truly a constant and the same for all elastomers, this equation has the advantage of being valid right out to the breaking strain.

scholarly journals Mechanical Properties and Microstructural Collagen Alignment of the Ulnar Collateral Ligament During Dynamic Loading

2018 ◽  
Vol 47 (1) ◽  
pp. 151-157 ◽  
Author(s):  
Matthew V. Smith ◽  
Ryan M. Castile ◽  
Robert H. Brophy ◽  
Ashvin Dewan ◽  
David Bernholt ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Real Time ◽  
Strain Curve ◽  
Ulnar Collateral Ligament ◽  
Collagen Fibers ◽  
Stress Strain Curve ◽  
Collateral Ligament ◽  
Stress Strain ◽  
Collagen Organization ◽  
Collagen Alignment

Background: The ulnar collateral ligament (UCL) microstructural organization and collagen fiber realignment in response to load are unknown. Purpose/Hypothesis: The purpose was to describe the real-time microstructural collagen changes in the anterior bundle (AB) and posterior bundle (PB) of the UCL with tensile load. It was hypothesized that the UCL AB is stronger and stiffer with more highly aligned collagen during loading when compared with the UCL PB. Study Design: Descriptive laboratory study. Methods: The AB and PB from 34 fresh cadaveric specimens were longitudinally sectioned to allow uniform light passage for quantitative polarized light imaging. Specimens were secured to a tensile test machine and underwent cyclic preconditioning, a ramp-and-hold stress-relaxation test, and a quasi-static ramp to failure. A division-of-focal-plane polarization camera captured real-time pixelwise microstructural data of each sample during stress-relaxation and at the zero, transition, and linear points of the stress-strain curve. The SD of the angle of polarization determined the deviation of the average direction of collagen fibers in the tissue, while the average degree of linear polarization evaluated the strength of collagen alignment in those directions. Since the data were nonnormally distributed, the median ± interquartile range are presented. Results: The AB has larger elastic moduli than the PB ( P < .0001) in the toe region (median, 2.73 MPa [interquartile range, 1.1-5.6 MPa] vs 0.65 MPa [0.44-1.5 MPa]) and the linear region (13.77 MPa [4.8-40.7 MPa] vs 1.96 MPa [0.58-9.3 MPa]). The AB demonstrated larger stress values, stronger collagen alignment, and more uniform collagen organization during stress-relaxation. PB collagen fibers were more disorganized than the AB during the zero ( P = .046), transitional ( P = .011), and linear ( P = .007) regions of the stress-strain curve. Both UCL bundles exhibited very small changes in collagen alignment (SD of the angle of polarization) with load. Conclusion: The AB of the UCL is stiffer and stronger, with more strongly aligned and more uniformly oriented collagen fibers, than the PB. The small changes in collagen alignment indicate that the UCL response to load is due more to its static collagen organization than to dynamic changes in collagen alignment. Clinical Relevance: The UCL collagen organization may explain its susceptibility to injury with repetitive valgus loads.

Sequential simulation and neural network in the stress–strain curve identification over the large strains using tensile test

2017 ◽  
Vol 87 (6) ◽  
pp. 1077-1093 ◽  
Author(s):  
Ivan Jeník ◽  
Petr Kubík ◽  
František Šebek ◽  
Jiří Hůlka ◽  
Jindřich Petruška
Keyword(s):  
Neural Network ◽  
Tensile Test ◽  
Strain Curve ◽  
Large Strains ◽  
Sequential Simulation ◽  
Stress Strain Curve ◽  
Stress Strain

Effective Modulus and Stress Relaxation of Freestanding Aluminum Microtensile Beams

2004 ◽  
Vol 854 ◽  
Author(s):  
P. A. El-Deiry ◽  
N. Barbosa ◽  
W. L. Brown ◽  
R. P. Vinci
Keyword(s):  
Stress Relaxation ◽  
Strain Amplitude ◽  
Strain Curve ◽  
Effective Modulus ◽  
Strain Rates ◽  
Effective Moduli ◽  
Stress Strain Curve ◽  
Stress Relaxation Behavior ◽  
Grain Sizes ◽  
Al Thin Film

ABSTRACTFreestanding Al thin film microtensile beams 600 μm long, 100 μm wide, and with thicknesses of 0.25 μm, 0.50 μm, 0.75 μm, and 1.00 μm were tested under uniaxial tension with a custom-built microtensile system. Displacement controlled experiments employing five strain rates between 8.3 × 10−4 s−1 and 8.3 × 10−1 s−1 were performed. Three crosshead displacements of 1.00 μm (0.17% strain), 2.60 μm (0.43%), and 3.60 μm (0.60% strain) were exercised in order to investigate behavior in the elastic, anelastic, and the inelastic sections of the stress/strain curve.At a 0.17% strain amplitude, the 0.50 μm thick microtensile beams exhibit an effective modulus that increases with increasing strain rate. The 1.00 μm, 0.75 μm, and 0.25 μm microtensile beams do not show a similar trend. The 0.25 μm and the 0.75 μm thick microtensile beams have similar grain sizes and similar moduli; the 0.50 μm and the 1.00 μm microtensile beams have similar but smaller grain sizes and higher effective moduli. This suggests that grain size is more significant than film thickness in determining the effective modulus of freestanding Al thin films. Furthermore, no stress relaxation behavior was identified for any of the films during the hold at the 0.17% strain amplitude.At a strain amplitude of 0.43%, the effective moduli are very similar to the values measured at a 0.17% strain amplitude; however, the 0.50 μm and 1.00 μm thick microtensile beams show measurable stress relaxation while the 0.25 μm and 0.75 μm microtensile beams do not. This result combined with a lower observed modulus suggests that the particular anelastic mechanisms operating in these films at these time scales activate sooner and provide a faster stress relaxation process in the larger grained films.

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.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

CT Image Analysis on the Meso-Damage of Construction Waste Recycled Brick

2012 ◽  
Vol 588-589 ◽  
pp. 1930-1933
Author(s):  
Guo Song Han ◽  
Hai Yan Yang ◽  
Xin Pei Jiang
Keyword(s):  
Fractal Dimension ◽  
Strain Curve ◽  
Ct Image ◽  
Stress Strain Curve ◽  
Crack Evolution ◽  
Construction Waste ◽  
Box Counting ◽  
Industrial Ct ◽  
Ct Image Analysis ◽  
Box Counting Method

Based on industrial CT technique, Meso-mechanical experiment was conducted on construction waste recycled brick to get the real-time CT image and stress-strain curve of brick during the loading process. Box counting method was used to calculate the fractal dimension of the inner pore transfixion and crack evolution. The results showed that lots of pore in the interfacial transition zone mainly resulted in the damage of the brick. With the increase of stress, the opening through-pore appeared and crack expanded, and the fractal dimension increased.

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.

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