Simple constitutive models to represent the effect of mechanical damage and abrasion on the short-term load-strain response of geosynthetics

2018 ◽  
pp. 279-287
Author(s):  
A.M. Paula ◽  
M. Pinho-Lopes
Keyword(s):  
Constitutive Models ◽  
Mechanical Damage ◽  
Strain Response ◽  
Short Term

Characterization of Hyperelastic (Rubber) Material Using Uniaxial and Biaxial Tension Tests

2012 ◽  
Vol 570 ◽  
pp. 1-7
Author(s):  
Yawar Jamil Adeel ◽  
Ahsan Irshad Muhammad ◽  
Azmat Zeeshan
Keyword(s):  
Shear Test ◽  
Biaxial Tension ◽  
Constitutive Models ◽  
Hyperelastic Material ◽  
Strain Response ◽  
Stress Strain ◽  
Rubber Material ◽  
Tension Tests ◽  
Planar Shear

Hyperelastic material simulation is necessary for proper testing of products functionality in cases where prototype testing is expensive or not possible. Hyperelastic material is nonlinear and more than one stress-strain response of the material is required for its characterization. The study was focused on prediction of hyperelastic behavior of rubber neglecting the viscoelastic and creep effects in rubber. To obtain the stress strain response of rubber, uniaxial and biaxial tension tests were performed. The data obtained from these tests was utilized to find the coefficients of Mooney-Rivlin, Odgen and Arruda Boyce models. Verification of the behavior as predicted by the fitted models was carried out by comparing the experimental data of a planar shear test with its simulation using the same constitutive models.

Effect of microcracking on the deformation of ice

1992 ◽  
Vol 29 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Ian J. Jordaan ◽  
Barry M. Stone ◽  
Richard F. McKenna ◽  
Mark K. Fuglem
Keyword(s):  
Strain Rate ◽  
Field Experiments ◽  
Constant Strain Rate ◽  
Creep Damage ◽  
Future Research ◽  
Strain Response ◽  
Short Term ◽  
Large Fluctuations ◽  
Response To Stress ◽  
Stress States

Tests in the field and full-scale experience with arctic structures show that the crushing of ice is accompanied by large fluctuations in load. Field experiments show that, in addition to variations of load in time, significant spatial variations across the contact surface also occur. The deformation is observed to take place in a thin layer of damaged ice, which appears near the structure or indenter surface. It is important to model the deformation and strength of ice in this zone. Various aspects of modelling are discussed in the paper, in particular, measures of damage and the relation to the deformation of ice. The relevance of various components of deformation (elastic, viscous, delayed elastic) is outlined, and two mathematical formulations for the deformation are discussed. The behaviour was investigated by a series of tests at constant strain rate as well as tests in which the strain response to stress of damaged and undamaged ice was measured. The creep rate in damaged ice is shown to be significantly enhanced, even for short-term loading. Comparisons of theory and experiment are given for constant strain-rate tests. The models have been calibrated to the experimental data described in the paper. It is a matter for future research to generalize the models to all damage levels and stress states. Key words : creep, damage, deformation, ice, microcracking, visco-elasticity.

scholarly journals Modelling of undrained shearing of soft natural clays

2019 ◽  
Vol 92 ◽  
pp. 15001
Author(s):  
Alexandros L. Petalas ◽  
Mats Karlsson ◽  
Minna Karstunen
Keyword(s):  
Triaxial Compression ◽  
Constitutive Models ◽  
Strain Response ◽  
Rate Dependency ◽  
Induced Anisotropy ◽  
Stress Strain ◽  
Soft Soils ◽  
Model Simulations ◽  
Rate Effects ◽  
Natural Clays

stress-strain response of soft natural clays is characterised by anisotropy, destructuration and rate-dependency. An accurate constitutive description of these materials should take into consideration all of the characteristics above. In this paper, two constitutive models for soft soils, namely the SCLAY1S and Creep-SCLAY1S models are used to simulate the undrained response of two soft natural clays, Gothenburg clay from Sweden and Otaniemi clay from Finland. The SCLAY1S model accounts for the effect of inherent and induced anisotropy and destructuration, while the Creep-SCLAY1S accounts also for the creep and rate effects. The model simulations are compared against triaxial compression and extension tests on anisotropically consolidated samples. The results demonstrate the need to incorporate all features represented in the Creep-SCLAY1S model when modelling structured natural clays.

scholarly journals GENTLE CABBAGE HARVESTING

2020 ◽  
Vol 15 (2) ◽  
pp. 72-76
Author(s):  
Sergey Alatyrev ◽  
Irina Kruchinkina ◽  
Aleksey Alatyrev
Keyword(s):  
Product Quality ◽  
Technological Process ◽  
Mechanical Damage ◽  
Severely Injured ◽  
Combine Operation ◽  
Medium Term ◽  
Short Term ◽  
Long Term Storage ◽  
Term Storage

When harvesting cabbage by machine, the heads of cabbage are severely injured. Mechanically damaged heads of cabbage are poorly stored. Therefore, the machine technology of cabbage harvesting should provide protection of heads of cabbage from mechanical damage. The purpose of the research is to study the qualitative indicators of the operation of a multivariate cabbage harvester with various harvesting technological schemes. The considered technological schemes for harvesting cabbage include: careful shipment of heads in bulk of a universal vehicle (Scheme 1); careful point shipment of heads of cabbage into containers installed in the back of a vehicle (diagram 2); shipment of heads of cabbage on a flexible flooring installed in the vehicle, with their subsequent careful transfer to containers manually (Scheme 3); stowing heads of cabbage into containers on an accompanying trailer manually (Scheme 4). During the production check, under conditions typical for the main regions of mass marketable production of cabbage, the multivariate cabbage harvester steadily performed the technological process. At the same time, its quality indicators met the established agrotechnical requirements. Combine operation according to schemes 3 and 4 ensured the preservation of product quality to the maximum extent: damage to heads of cabbage did not exceed 5 ... 6%, the completeness of cabbage leaves removal was 95 ... 100%. Therefore, its use according to schemes 1 and 2 is recommended mainly when harvesting cabbage for short-term and medium-term storage, according to schemes 3 and 4 - when harvesting heads of cabbage intended for long-term storage

scholarly journals Resistance of Geosynthetics against the Isolated and Combined Effect of Mechanical Damage under Repeated Loading and Abrasion

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3558
Author(s):  
Filipe Almeida ◽  
David Miranda Carlos ◽  
José Ricardo Carneiro ◽  
Maria de Lurdes Lopes
Keyword(s):  
Hydraulic Properties ◽  
Construction Materials ◽  
Mechanical Damage ◽  
Tensile Tests ◽  
Repeated Loading ◽  
Short Term ◽  
Engineering Structures ◽  
Wide Range ◽  
Materials Used ◽  
Reduction Factors

The behaviour of materials used for developing engineering structures should be properly foreseen during the design phase. Regarding geosynthetics, which are construction materials used in a wide range of engineering structures, the installation on site and the action of many degradation agents during service life may promote changes in their properties, endangering the structures in which they are applied. The evaluation of the damage suffered by geosynthetics, like installation damage or abrasion, is often carried out through laboratory tests. This work studied the behaviour of five geosynthetics (three geotextiles and two geogrids) after being individually and successively exposed to two degradation tests: mechanical damage under repeated loading and abrasion. The short-term mechanical and hydraulic behaviours of the geosynthetics were analysed by performing tensile tests and water permeability normal to the plane tests. Reduction factors were determined based on the changes occurred in the tensile strength of the geosynthetics. Findings showed that mechanical damage under repeated loading and abrasion tended to affect the mechanical and hydraulic properties of the geosynthetics and that the reduction factors calculated according to the traditional method may not be able to represent accurately the damage suffered by the materials when exposed successively to the degradation mechanisms.

Performance of SiO2-impregnated flax fibre reinforced polymers under wet dry and freeze thaw cycles

2020 ◽  
Vol 55 (2) ◽  
pp. 251-263
Author(s):  
Kenneth Mak ◽  
Amir Fam
Keyword(s):  
Tensile Strength ◽  
Mechanical Damage ◽  
Tensile Modulus ◽  
Flax Fibre ◽  
Short Term ◽  
Freeze Thaw ◽  
Post Exposure ◽  
Flax Fibres ◽  
Pull Out ◽  
Term Performance

Flax fibres are of growing interest as a reinforcing fibre; however, they are susceptible to moisture and have demonstrated poor bond to conventional hydrophobic resins. Although there are multiple approaches to address these issues, research has heavily focused on their short-term performance. In this research program, the performance of flax fibre reinforced polymer (FFRP), manufactured using SiO2-impregnated flax fibre, is assessed for its short-term performance as well as its long-term performance when exposed to wet-dry (WD) and freeze-thaw (FT) cycles. Treated FFRP showed improved bond between the fibre and resin as well as resistance to fibre pull-out. It exhibited a tensile strength of 144 ± 15 MPa and a tensile modulus of 8.6 ± 0.35 GPa. When exposed to WD cycles, delamination between the fibre and resin were observed. The onset of statistically significant mechanical damage occurred after four WD cycles, with a final 3% reduction in strength and a 6% reduction in modulus post-exposure. When exposed to FT cycles, FFRP experienced cracking within the fibre, as well as delamination at the interface. The onset of statistically significant mechanical damage occurred after 50 FT cycles, which manifested as a final 5% reduction in tensile strength and 10% reduction in tensile modulus post-exposure. Regardless of treatment, FFRP demonstrated the same damage mechanisms as untreated variants.

Towards a Mechanism for Bioprosthetic Valve Failure

2000 ◽  
Author(s):  
Ivan Vesely ◽  
J. Edward Barber ◽  
W. John Mako ◽  
Norman B. Ratliff
Keyword(s):  
Mechanical Damage ◽  
Collagen Fibers ◽  
Tissue Mechanics ◽  
Bioprosthetic Valve ◽  
Short Term ◽  
Aortic Valves ◽  
Primary Mechanism ◽  
Bioprosthetic Valves ◽  
Made In

Abstract Porcine bioprosthetic valves are commonly used to replace the native cardiac valves when they become diseased and dysfunctional. One class of bioprosthesis consists of whole pig aortic valves, tanned in glutaraldehyde and mounted on plastic or wire frames. These devices work very well in the short term (< 5 years) but eventually begin to fail gradually and typically do not last more than 15 years [1]. Many have tried to elucidate a mechanism of bioprosthetic valve failure, but little progress has been made, until recently. Historically, calcification has been thought to be the primary mechanism of bioprosthetic valve failure [2]. Recently, however, it has become recognized that mechanical damage to bioprosthetic valves can occur independently from calcification [3]. This shift in opinion has been supported by a number of observations. For example, Purinya et. al. [4] have shown that after four years of implantation, bioprosthetic valve explants have lower failure stresses and fail at greater strains than fresh porcine bioprostheses. Similar observations have been made in valves fatigued in vitro [5]. Others have shown that these mechanical changes are accompanied by biochemical changes in the collagen fibers [6]. We have shown previously in preliminary studies that glycosaminoglycans (GAGs) are lost from implanted bioprosthetic valves [7]. Since GAGs are responsible for maintaining tissue viscoelasticity, loss of GAGs would have detrimental effects on tissue mechanics. In separate studies, we have demonstrated that damage to elastin can also have detrimental effects on tissue mechanics, and on valve durability as a whole [8].

scholarly journals Effect of Different Aggregates on the Mechanical Damage Suffered by Geotextiles

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4229 ◽  
Author(s):  
David Miranda Carlos ◽  
José Ricardo Carneiro ◽  
Maria de Lurdes Lopes
Keyword(s):  
Water Permeability ◽  
Hydraulic Properties ◽  
Unit Area ◽  
Construction Materials ◽  
Mechanical Damage ◽  
Repeated Loading ◽  
Short Term ◽  
Loading Tests ◽  
Natural Aggregates ◽  
Useful Lifetime

The installation process of geosynthetics can be, in some applications, one of the most relevant degradation mechanisms of these construction materials, affecting their performance and useful lifetime. In this work, three nonwoven geotextiles with different masses per unit area were submitted to mechanical damage under repeated loading tests with corundum and with different natural aggregates. The damage occurred in the geotextiles was evaluated by visual inspection and by monitoring changes in their short-term tensile and puncture behaviors (mechanical properties) and in their water permeability behavior normal to the plane (hydraulic property). The mechanical damage under repeated loading tests provoked relevant changes in the mechanical and hydraulic properties of the geotextiles. These changes depended on the mass per unit area of the geotextiles and on the characteristics of the aggregates. The results enabled the establishment of a correlation between the loss of mechanical strength and the variation of the water permeability normal to the plane of the geotextiles.

Short-Term Test of ±55 ̊ Filament Wound GRE Composite Pipes under Multiaxial Stress Ratios

2014 ◽  
Vol 554 ◽  
pp. 371-375
Author(s):  
Krishnan Pranesh ◽  
M.S. Abdul Majid ◽  
Mohd Afendi ◽  
Haslan Marzuki ◽  
Mohd Nor Fakhzan Mohd Kazim
Keyword(s):  
Pressure Sensors ◽  
Axial Loading ◽  
Wall Stress ◽  
Strain Response ◽  
Short Term ◽  
Stress Strain ◽  
Filament Wound ◽  
Short Term Test ◽  
Stress Ratios ◽  
Composite Pipes

This paper discusses the the development of an automated pressure testing rig to perform a short term test; Ultimate Elastic Wall Stress (UEWS) for ±55 ̊ glass fibre reinforced epoxy (GRE) composite pipe under various stress ratios. The prototype is capable of determining the stress-strain response caused by the static and cyclic pressure. This developed rig is to provide an alternative solution for the current qualification procedure explained in ISO14692 through ASTM 2992. As part of the work, an automated testing rig powered by labview program is developed with the aid of pressure sensors, solenoid valves and strain gauges which are interfaced through hardware modules from National Instruments. The UEWS test for the five stress ratios namely pure hydrostatic (2H:1A), pure hoop (1H:0A), pure axial (0H:1A), hoop to axial (1H:1A) and quad hoop to axial loading (4H:1A) were performed upon the ±55° filament wound glass-reinforced epoxy pipes. The changes in the stress strain response are captured from the strain gauge measurements and the UEWS failure points are calculated for all the loading conditions. The failure envelope developed from the failure points can be used to predict the long term performance of the GRE pipes and provide the benchmark for the design of composite pipes under various stress ratios.

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