Determination of confinement and plastic strain dependent post-peak strength of intact rocks

2017 ◽  
Vol 218 ◽  
pp. 187-196 ◽  
Author(s):  
Jun Peng ◽  
Ming Cai ◽  
Guan Rong ◽  
Meng-Di Yao ◽  
Qing-Hui Jiang ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Peak Strength ◽  
Strain Dependent

scholarly journals Stored Energy of Plastic Deformation in Tube Bending Processes

2013 ◽  
Vol 18 (1) ◽  
pp. 235-248 ◽  
Author(s):  
Z. Śloderbach ◽  
J. Pająk
Keyword(s):  
Plastic Deformation ◽  
Service Life ◽  
Plastic Strain ◽  
Analytic Method ◽  
Stored Energy ◽  
Tube Bending ◽  
Cold Bending ◽  
Tension And Compression

The paper presents an aproximate analytic method for determination of the stored energy of plastic deformation during cold bending of metal tubes at bending machines. Calculations were performed for outer points of the tube layers subjected to tension and compression (the points of maximum strains). The percentage of stored energy related to the plastic strain work was determined and the results were presented in graphs. The influence and importance of the stored energy of plastic deformation on the service life of pipeline bends are discussed.

Determination of the Anand Viscoplasticity Model Constants for SnAgCu

2005 ◽  
Author(s):  
Bryan Rodgers ◽  
Ben Flood ◽  
Jeff Punch ◽  
Finbarr Waldron
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Test Specimen ◽  
Strain Curve ◽  
Temperature Cycling ◽  
Displacement Rate ◽  
Experimental Measurements ◽  
Strain Rates ◽  
Constant Displacement

The major focus of this work was the determination of the nine constants required for Anand’s viscoplastic constitutive model for a lead-free solder alloy, 95.5Sn3.8Ag0.7Cu and to compare them with those for SnPb. The test specimen was a cast dog bone shape based on ASTM E 8M-01, with a diameter of 4mm and a gauge length of 20mm. A series of tensile experiments were carried out: constant displacement tests ranging from 6.5 × 10−5/s to 1.0 × 10−3/s at temperatures of 20°C, 75°C, and 125°C; constant load tests at a range of loads from 10MPa to 65MPa, also at temperatures of 20°C, 75°C, and 125°C. A series of non-linear fitting processes was used to determine the model constants. Comparisons were then made with experimental measurements of the stress-plastic strain curves from constant displacement rate tests: it was found that the model matched the experimental data at low strain rates but did not capture the strain hardening effect, especially at high strain rates. A finite element model of the test was also constructed using ANSYS software. This software includes the Anand model as an option for its range of viscoplastic elements, requiring that the nine constants be input. In this case, an 8-noded axisymmetric element (VISCO108) was used to model the test specimen under constant displacement rate loading. The model was then used to predict the stress-plastic strain curve and this was compared to both the experimental measurements and the fitted Anand model. Reasonable agreement was found between the Anand model and the FE predictions at small strain rates. Finally, a BGA device was simulated under accelerated temperature cycling conditions using ANSYS with the fitted Anand for the SnAgCu solder joints. A Morrow-type fatigue life model was applied using empirical constants from two published sources and good agreement was found between experiment and predicted fatigue life.

scholarly journals Dynamic Properties of Clean Sand Modified with Granulated Rubber

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Dervis Volkan Okur ◽  
Seyfettin Umut Umu
Keyword(s):  
Shear Modulus ◽  
Dynamic Characteristics ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Relative Size ◽  
Cyclic Behavior ◽  
Damping Capacity ◽  
Resonant Column ◽  
Strain Dependent

Waste automobile tires are used as additives or replacements instead of traditional materials in civil engineering works. In geotechnical engineering, tires are shredded to certain sizes and mixed with soil, especially used as backfill material behind retaining walls or fill material for roadway embankments. Compared to soil, rubber has high damping capacity and low shear modulus. Therefore, it requires the determination of the dynamic characteristics of rubber/soil mixtures. In this paper, the cyclic behavior of recycled tire rubber and clean sand was studied, considering the effects of the amount and particle size of the rubber and confining stresses. A total of 40 stress-controlled tests were performed on an integrated resonant column and dynamic torsional shear system. The effects of the relative size and proportion of the rubber on the dynamic characteristics of the mixtures are discussed. The dynamic properties, such as the maximum shear modulus, strain-dependent shear modulus, and damping ratio, are examined. For practical purposes, simple empirical relationships were formulated to estimate the maximum shear modulus and the damping ratio. The change in the shear modulus and damping ratio with respect to shear strain with 5% of rubber within the mixture was found to be close to the behavior of clean sand.

scholarly journals Determination of the Plastic Strain by Spherical Indentation of Uniaxially Deformed Sheet Metals

2015 ◽  
Vol 651-653 ◽  
pp. 950-956 ◽  
Author(s):  
Mohamad Idriss ◽  
Olivier Bartier ◽  
Gérard Mauvoisin ◽  
Charbel Moussa ◽  
Eddie Gazo Hanna ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Accurate Determination ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Instrumented Indentation ◽  
Forming Process ◽  
Hardening Law ◽  
Indentation Tests

This work consists of determining the plastic strain value undergone by a material during a forming process using the instrumented indentation technique (IIT). A deep drawing steel DC01 is characterized using tensile, shear and indentation tests. The plastic strain value undergone by this steel during uniaxial tensile tests is determined by indentation. The results show that, the identification from IIT doesn’t lead to an accurate value of the plastic strain if the assumption that the hardening law follows Hollomon law is used. By using a F.E. method, it is shown that using a Voce hardening law improves significantly the identification of the hardening law of a pre-deformed material. Using this type of hardening law coupled to a methodology based on the IIT leads to an accurate determination of the hardening law of a pre-deformed material. Consequently, this will allow determining the plastic strain value and the springback elastic strain value of a material after a mechanical forming operation.

Encapsulation of Nisin and Lysozyme in Liposomes Enhances Efficacy against Listeria monocytogenes

2004 ◽  
Vol 67 (5) ◽  
pp. 922-927 ◽  
Author(s):  
LILIAN M. WERE ◽  
BARRY BRUCE ◽  
P. MICHAEL DAVIDSON ◽  
JOCHEN WEISS
Keyword(s):  
Antimicrobial Activity ◽  
Listeria Monocytogenes ◽  
Bacterial Growth ◽  
Fluorescence Probe ◽  
Size Exclusion ◽  
Phospholipid Liposomes ◽  
Exclusion Chromatography ◽  
Delivery Vehicles ◽  
Strain Dependent

The efficacy and stability against Listeria monocytogenes of nisin and lysozyme encapsulated in phospholipid liposomes was evaluated. Antimicrobial-containing liposomes were prepared by hydrating dried lipids with buffer containing nisin, nisin plus the fluorescence probe calcein, or calcein and lysozyme. Mixtures were then centrifuged and sonicated, and encapsulated liposomes were collected using size-exclusion chromatography. Antimicrobial concentration in liposomes was determined by bicinchoninic acid assay prior to determination of antimicrobial activity against strains of L. monocytogenes. When nisin was encapsulated in liposomes, protein concentrations of 0.39, 0.27, and 0.23 mg/ml for phosphatidylcholine (PC), PC-cholesterol (7:3), and PC–phosphatidylglycerol (PG)–cholesterol (5:2:3), respectively, were obtained. Encapsulation of nisin with calcein yielded protein concentrations of 0.35, 0.39, and 0.28 mg/ml for PC, PC-cholesterol, and PC-PG-cholesterol, respectively. Encapsulation of calcein with lysozyme resulted in protein concentrationsof 0.43, 0.26, and 0.19 mg/ml for PC, PC-cholesterol, and PC-PG-cholesterol, respectively. Encapsulated nisin in 100% PC and PC-cholesterol liposomes inhibited bacterial growth by >2 log CFU/ml compared with free nisin. Growth inhibition with liposomal lysozyme was strain dependent, with greater inhibition observed for strains 310 and Scott A with PC-cholesterol and PC-PG-cholesterol liposomes. Inhibition of L. monocytogenes indicated the potential of liposomes to serve as delivery vehicles for antimicrobials in foods while improving stability of antimicrobials.

Analysis of Hysteresis Loop on the Basis of Variable-Amplitude Loading

2016 ◽  
Vol 250 ◽  
pp. 94-99
Author(s):  
Bogdan Ligaj
Keyword(s):  
Plastic Strain ◽  
Hysteresis Loop ◽  
Strain Energy ◽  
Energy Parameter ◽  
Stress Strain ◽  
Variable Amplitude Loading ◽  
Loading Cycle ◽  
Variable Amplitude ◽  
Plastic Strain Energy

The aim of this paper is to present a method to be used for analysis of stress-strain loops under variable amplitude loading. The method for determination of plastic strain energy parameter ΔWpl consists in determination of envelopes around stress-strain branches (increasing and decreasing) formed in effect of application of a loading program. The method involves development of envelopes to determine energy parameter from the highest (for the highest loading cycle) to the lowest (for the lowest cycle). The paper includes results of stress-strain loop for steel C45.

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