Operational Modal Response Characterization of a Buried Pipe Structure

2021 ◽  
Author(s):  
Haobin Chen ◽  
Ron Hugo ◽  
Ron Chik-Kwong Wong ◽  
Simon Park
Keyword(s):  
Buried Pipe ◽  
Modal Response

Development of a prototype for modelling soil–pipe interaction and its application for predicting uplift resistance to buried pipe movements in sand

2018 ◽  
Vol 55 (10) ◽  
pp. 1451-1474 ◽  
Author(s):  
Yousef Ansari ◽  
George Kouretzis ◽  
Scott W. Sloan
Keyword(s):  
Scale Effects ◽  
Reaction Force ◽  
Failure Surface ◽  
Relative Displacement ◽  
Published Data ◽  
Buried Pipe ◽  
Image Velocimetry ◽  
Close Range ◽  
Uplift Resistance

This paper presents a testing rig for measuring the reactions on rigid pipes buried in sand during episodes of relative displacement. Following a detailed presentation of the 1g prototype, the test preparation procedure, and the characterization of the test sand’s shear strength and dilation potential under the low confining stresses pertinent to the problem, the paper focuses on the workflow devised to obtain accurate measurements of friction and arching effects, and accordingly normalize them to account for scale (stress level) effects. Emphasis is put on demonstrating the effectiveness of the sand deposition method for accurately controlling the density of the sample, and on quantitatively assessing its uniformity. Measurements obtained during a series of uplift tests, including reaction force – pipe displacement curves and images of the developing failure surface, facilitated by particle image velocimetry and close-range photogrammetry techniques, are compared against published data and analytical methods. The results lead to the development of a new simplified formula for calculating the uplift resistance to buried pipe movements in sand: capable of accounting for scale effects, yet simple enough to be used for the analysis of pipes in practice.

Ice Gouge Reliability of Offshore Arctic Pipelines

2007 ◽  
Author(s):  
A. H. Younan ◽  
J. M. Hamilton ◽  
J. Weaver
Keyword(s):  
Traditional Approach ◽  
Relative Strength ◽  
First Year ◽  
Burial Depth ◽  
Buried Pipe ◽  
Element Analysis ◽  
Statistical Characterization ◽  
The Impact ◽  
Adequate Reliability

Offshore arctic pipelines must be designed with adequate reliability against damage or rupture due to the effects of ice features that gouge the seafloor. A common design approach is to bury the pipeline sufficiently deep to avoid contact by a gouging ice keel of a target rare return interval. The effects of sub-gouge soil displacements on pipe stress or strain are also assessed. It is implicitly assumed, in this traditional approach, that ice keels have infinite strength and momentum, so that gouge depths are not limited by ice keel failure and direct contact of ice on pipe results in rupture. However, many first-year ice features may not be strong enough to gouge the soil to the extreme gouge depths. Considering the high cost of incremental pipeline burial depth, it may be desirable to account for limits imposed on extreme gouge depth by soil resistance. Introducing these limits, however, gives rise to additional uncertainty and requires the development of a reliability framework to assess the consequences of direct ice contact on the buried pipe. This paper presents a methodology for evaluating the probability of ice gouging non-performance of a pipeline while explicitly accounting for the ability of the seabed soil to limit ice gouge depth based on the relative strength of soil and ice keel. Non-performance is defined either as ice contact on the pipe or exceedence of some level of acceptable pipe strain when contacted by ice. A three-step approach is followed through the use of nonlinear finite element analysis to estimate pipeline capacity, the statistical characterization of demand from ice gouging events, and the development of a reliability framework combining demand and capacity. Parameters governing the capacity of the pipeline are identified, the sensitivity of the pipeline reliability to various parameters is investigated, and the impact of allowing ice contact on pipeline reliability is presented. Relative merits and risks of allowing ice contact are discussed in the context of pipeline reliability. The presented results and discussions are believed to be of significant help in the development of burial depth criteria for future offshore arctic pipelines, and certainly in the reassessment of existing ones.

Operational Modal Response Characterization of a Buried Pipe Structure

2020 ◽  
Author(s):  
Haobin Chen ◽  
Ron Hugo ◽  
Ron Chik-Kwong Wong ◽  
Simon Park
Keyword(s):  
Reynolds Number ◽  
Transient Flow ◽  
Water Flow Rate ◽  
Research Work ◽  
Axial Direction ◽  
Dry Density ◽  
Buried Pipe ◽  
Maximum Dry Density ◽  
Vibration Transmission ◽  
Modal Response

Abstract As a novel non-invasive structural health monitoring (SHM) technique for application to buried pipelines, in-situ vibration-based detection offers an approach to achieve continuous monitoring. Modal characteristics are often quantified using vibration signals, with traditional modal analysis performed using either impact-response testing or mechanical-shaker excitation. Both methods, however, are not suitable for a buried pipeline. In this research work, the operational modal response of a buried-pipe structure is investigated, and the application of transient flow event detection is presented. Experiments are conducted on a buried 160-inch horizontal stainless-steel pipe section with an inner diameter of 2-inch. Soil compaction is performed to 95% of the maximum dry density (proctor compaction). During experiments, water flow rate through the pipe (Reynolds number) is increased and turbulent pressure fluctuations provide the varying structural excitation source. Vibration measurements are made using one tri-axial and four single-axis accelerometers. Accelerometers directly mounted to the pipe are to perform on-pipe measurement to investigate the operational modal response of the buried pipe structure. Accelerometers positioned in soil are to investigate the vibration transmission through the soil in both the horizontal and vertical directions, examining the feasibility of the modal response characterization through non-contact measurement. The operational modal response collected through on-pipe measurement showing that vibration energy is decreased due to the soil and the vibration of the axial direction (along the pipe) has highest sensitivity than the other two directions with increasing Reynolds number. The abnormal signal induced by a transient flow event is visualized using short-time spectral analysis, and its propagation and source are determined using acoustic methods. The vibration transmission of the buried pipe propagating through the soil is heavily attenuated both horizontally and vertically.

scholarly journals In-Situ Modal Response Characterization of Pipe Structures Through Reynolds Number Variation

2018 ◽  
Author(s):  
Haobin Chen ◽  
Ron Hugo ◽  
Simon Park
Keyword(s):  
Reynolds Number ◽  
Excitation Source ◽  
Pipe Material ◽  
Reliable Technique ◽  
Vibration Spectra ◽  
Modal Characteristics ◽  
Modal Response ◽  
Number Variation

The modal response characterization of structures is a proven and reliable technique used to monitor system behavior and change, providing information for condition assessment and damage identification. In traditional modal response characterization procedures, an external mass excitation source is used to excite the system, and this is modeled as an impact function. This provides system forcing across a broad range of frequencies. In this investigation, an in-situ method of system excitation is explored. The modal characteristics of externally-supported pipe structures are investigated by varying the flow Reynolds number (Red). Given the increase in flow turbulence with Reynolds number, hydrodynamic pressure fluctuations on the pipe wall provide a varying excitation source. This removes the requirement for an external excitation source. A comparative analysis of data sets collected for both Acrylic and ABS pipe material show similar pressure spectra, while vibration spectra change significantly. Pressure spectra reveal a character whereby the spectral energy increases with increasing Reynolds number. A comparison of in-situ results to those obtained using traditional impact response tests show that vibration spectra collected through Reynolds number variation successfully capture the modal characteristics of the pipe-structure.

scholarly journals THE USAGE OF GROUND-COUPLED HEAT EXCHANGERS IN SUBTROPICAL CLIMATES

2019 ◽  
Vol 111 ◽  
pp. 06022
Author(s):  
Marcelo Langner ◽  
Helenice Maria Sacht ◽  
Thais Aline Soares
Keyword(s):  
Heat Exchangers ◽  
Air Conditioning ◽  
Geothermal Systems ◽  
Climate Control ◽  
Data Logger ◽  
Buried Pipe ◽  
Humid Climate ◽  
Pipe System ◽  
Passive Air Conditioning

This study aims to identify the feasibility of using a ground-coupled heat exchanger system for air conditioning in subtropical regions. Geothermal systems are used effectively in cold climates, but little explored in hot and humid climate regions, although they show potential for passive air-conditioning environments. The tubes were installed in Southern Brazil, in Foz do Iguaçu, Paraná, which has temperatures of 0ºC in the winter and 40ºC in the summer. The methodology for the research was organized as follows: bibliographic research and geological characterization of the site, system sizing, installation of 22 meters of a 300mm PVC tube, 4 meters depth, and subsequently measurement and data collection on temperatures with use HOBO U10-001 Data Logger. The research was held from March to October 2016. The results showed that at external temperatures of 30ºC, the system was able to cool on average 6ºC, reaching peaks of 7ºC in the temperature of air exit to the environment. At temperatures below 6ºC, the system was able to heat on average 10ºC, with peaks of up to 11ºC. Based on the results, it is concluded that a buried pipe system is a viable alternative for passive climate control in subtropical climates

Morphological Characterization of Mycobacteriophage R1

1974 ◽  
Vol 32 ◽  
pp. 254-255
Author(s):  
B. L. Soloff ◽  
T. A. Rado
Keyword(s):  
Carbon Source ◽  
Stationary Phase ◽  
Growth Phase ◽  
Minimal Medium ◽  
Morphological Characterization ◽  
Logarithmic Growth Phase ◽  
Complete Lysis ◽  
Lysogenic Culture ◽  
Logarithmic Growth

Mycobacteriophage R1 was originally isolated from a lysogenic culture of M. butyricum. The virus was propagated on a leucine-requiring derivative of M. smegmatis, 607 leu−, isolated by nitrosoguanidine mutagenesis of typestrain ATCC 607. Growth was accomplished in a minimal medium containing glycerol and glucose as carbon source and enriched by the addition of 80 μg/ ml L-leucine. Bacteria in early logarithmic growth phase were infected with virus at a multiplicity of 5, and incubated with aeration for 8 hours. The partially lysed suspension was diluted 1:10 in growth medium and incubated for a further 8 hours. This permitted stationary phase cells to re-enter logarithmic growth and resulted in complete lysis of the culture.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

Characterization of Coherent, Ordered Precipitates in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 144-145
Author(s):  
B. H. Kear ◽  
J. M. Oblak
Keyword(s):  
Stable Phase ◽  
Nickel Base Superalloy ◽  
Alloy 718 ◽  
Commercial Alloy ◽  
Precipitate Morphology ◽  
Continuous Precipitation ◽  
Nickel Base ◽  
Base Superalloy ◽  
Strengthening Precipitate

A nickel-base superalloy is essentially a Ni/Cr solid solution hardened by additions of Al (Ti, Nb, etc.) to precipitate a coherent, ordered phase. In most commercial alloy systems, e.g. B-1900, IN-100 and Mar-M200, the stable precipitate is Ni3 (Al,Ti) γ′, with an LI2structure. In A lloy 901 the normal precipitate is metastable Nis Ti3 γ′ ; the stable phase is a hexagonal Do2 4 structure. In Alloy 718 the strengthening precipitate is metastable γ″, which has a body-centered tetragonal D022 structure.Precipitate MorphologyIn most systems the ordered γ′ phase forms by a continuous precipitation re-action, which gives rise to a uniform intragranular dispersion of precipitate particles. For zero γ/γ′ misfit, the γ′ precipitates assume a spheroidal.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

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