Repeated loading and unloading of the seabed

2010 ◽  
pp. 347-352 ◽  
Author(s):  
H Hu ◽  
K Tho ◽  
C Gan ◽  
A Palmer ◽  
C Leung
Keyword(s):  
Repeated Loading ◽  
Loading And Unloading

scholarly journals Experimental Study on the Effects of Stress Variations on the Permeability of Feldspar-Quartz Sandstone

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Fugang Wang ◽  
Zhaoxu Mi ◽  
Zhaojun Sun ◽  
Xufeng Li ◽  
Tianshan Lan ◽  
...  
Keyword(s):  
Injection Pressure ◽  
Confining Pressure ◽  
Repeated Loading ◽  
Micropore Structure ◽  
Injection Process ◽  
Reservoir Permeability ◽  
Stress Changes ◽  
Cyclic Variations ◽  
Loading And Unloading ◽  
Stress Variations

The multistage and discontinuous nature of the injection process used in the geological storage of CO2 causes reservoirs to experience repeated loading and unloading. The reservoir permeability changes caused by this phenomenon directly impact the CO2 injection process and the process of CO2 migration in the reservoirs. Through laboratory experiments, variations in the permeability of sandstone in the Liujiagou formation of the Ordos CO2 capture and storage (CCS) demonstration project were analyzed using cyclic variations in injection pressure and confining pressure and multistage loading and unloading. The variation in the micropore structure and its influence on the permeability were analyzed based on micropore structure tests. In addition, the effects of multiple stress changes on the permeability of the same type of rock with different clay minerals content were also analyzed. More attention should be devoted to the influence of pressure variations on permeability in evaluations of storage potential and studies of CO2 migration in reservoirs in CCS engineering.

Tensegrity Architecture of an Agglutinated Foraminiferan Shell

2001 ◽  
Vol 7 (S2) ◽  
pp. 54-55
Author(s):  
Roy K. Kinoshita ◽  
Karla M. Rivas-Rivera ◽  
Samuel S. Bowser
Keyword(s):  
Elastic Behavior ◽  
Repeated Loading ◽  
Objective Lens ◽  
Model Species ◽  
Sem Images ◽  
Preliminary Loading ◽  
Adhesive Matrix ◽  
Attachment Sites ◽  
In Series ◽  
Loading And Unloading

Shells of agglutinated foraminiferan protists are composed of mineral grains bound by secreted adhesives. As such, they are useful models for examining the evolution of “primitive” exoskeletons. Previous studies revealed the ultrastructure of shells in the giant Antarctic foraminiferan Astrammina rara and demonstrated that shucked specimens would reconstruct shells using glass beads. Here we further investigate shell architecture in this model species.For micromechanical testing, an intact A. rara shell was placed between a fixed plate and a facing plate in series with a calibrated load cell. Displacement was effected by a high-precision drive, and 2-3 loading cycles were used to determine shell material properties. to assay tensile properties of the adhesive matrix, a network of pseudopodia and extracellular matrix fibers (i.e., the shell adhesive component) was obtained by incubating shucked cell bodies on 200-mesh gold grids. Pseudopodia were subsequently removed by detergent washes. Fibers in the resultant isolated matrix were severed with a Nd: YAG laser using an inverted DIC light microscope equipped with a 60× objective lens. Preliminary loading experiments using glass needles showed that Sepharose 2B beads were suitable strain gauges to assess compression within reconstructed shells (Fig. 1). in this assay, shucked cell bodies were incubated with a mixture of glass and Sepharose beads, and the reconstructed shells were examined by SEM.Repeated loading and unloading demonstrated the elastic behavior of intact shells (Fig. 2). Adhesive matrix fibers snapped towards their attachment sites within 2 sec after cutting with a laser (Fig. 3), demonstrating that they are deployed under tension. SEM images of shells reconstructed with Sepharose show compressed particle profiles (Fig. 4).

Study on behaviour of geometrically scaled glass reinforced epoxy tubes subjected to non-coincident quasi static-indentation

2018 ◽  
Vol 9 (5) ◽  
pp. 675-692
Author(s):  
Fahad Almaskari ◽  
Farrukh Hafeez
Keyword(s):  
Peak Load ◽  
Repeated Loading ◽  
Damage Growth ◽  
Content Type ◽  
Starting Point ◽  
Static Indentation ◽  
Indentation Tests ◽  
Loading And Unloading ◽  
Force Displacement ◽  
Practical Implications

Purpose The purpose of this paper is to study the behaviour of glass reinforced epoxy tubes subjected to repeated indentation loads at two non-coincident indentations 180° apart. Design/methodology/approach Four geometrically scaled specimens ranging from 100 to 400 mm diameter were used in repeated indentation tests. Force, displacement and damage growth were recorded for loading and unloading until the indenter returned to its original starting point. Findings Similar scaled trends were observed between the non-coincidental loadings. Unlike reported response form coincidental loadings, the responses from non-coincidental loadings yield lower values for bending stiffness and peak load. Research limitations/implications The differences in behaviour of the specimen between non-coincident loadings were attributed to reductions in fracture toughness and circumferential modulus. Practical implications Distant non-interacting damage and delamination around the circumference does reduce the structural performance. Originality/value Behaviour of composite tubes under different loading conditions, for example low speed impact or quasi static indentation, is widely studied, however little attention has been given to the repeated loading incidents.

Fatigue Assessment of Existing Riveted Bridges

2018 ◽  
Author(s):  
Henrik Mehlsen
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Visual Inspection ◽  
Fatigue Cracks ◽  
Repeated Loading ◽  
Fe Modelling ◽  
Railway Bridges ◽  
Loading And Unloading ◽  
Fatigue Failures ◽  
Thick Layers

Fatigue failure of bridges occurs after repeated loading and unloading and hence fatigue becomes more and more severe with time. A majority of all existing riveted bridges are not explicitly designed for fatigue failures. Bridge owners should therefore have focus on fatigue life of riveted bridges. It can be difficult to discover fatigue cracks by visual inspection due to thick layers of paint and the fact that the rivets themselves may hide the cracks. Hence, it may be necessary to determine critical joints and possible fatigue cracks by using FE-modelling. Identification of critical joints may also target future inspection efforts and highlight hidden details, which may call for special inspection measures to be implemented. This paper describes a fatigue study of 11 riveted railway bridges in Denmark that includes both visual inspections and FE-modelling of bridges.

scholarly journals Experimental Studies on Axial Bolted Joint between E Glass Epoxy Flat Laminate and Steel Flat Plates Subjected to Uni-Axial Tensile Repeated Loading for 15 Cycle

2018 ◽  
Vol 68 (6) ◽  
pp. 577
Author(s):  
Sharada Prabhakar Chavali ◽  
Dilikeswar Das ◽  
Ramesh Babu
Keyword(s):  
Strain Gauge ◽  
Composite Laminate ◽  
Repeated Loading ◽  
Transverse Strain ◽  
Metal Composite ◽  
Bolted Joint ◽  
Flat Plates ◽  
Axial Tensile ◽  
Helical Angle ◽  
Loading And Unloading

<p class="p1">Axial bolted joint between EN-31 steel flat plates and E-Glass Epoxy thick, flat laminate consisting of helical winding layers with ±30° helical angle of winding and fabric prepreg layers, was realised with 3 number of M10, 12.9 property class steel fasteners on each side and assembly was tested under uni-axial tensile repeated loading and unloading up to 8.1 ton proof load and to 0 respectively, for 15 cycle. Aim of the experiment was to study the damage induced if any and further increased, in E-Glass epoxy laminate near joint regions, under tensile repeated loading and unloading for 15 cycle. Total length, width and thickness of metal composite axial bolted joint test assembly were 700 mm, 150 mm, and 22 mm, respectively. Longitudinal and transverse strain was monitored at 31 strain gauge locations in composite laminate near joint regions, in all the 15 cycle. For first cycle, longitudinal strain was plotted during loading up to proof load of 8.1 ton and unloading to 0, to check the linearity of strain variation with increase and decrease in load, respectively. It was observed that strain at all strain gauge locations was varying linearly. Maximum strain measured was 4035 micro strain in 1st cycle. Residual strain at all strain gauge locations was observed very less. No defects were induced in composite laminate after 15 cycle.</p>

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