Dimensionless Groups of Parameters Governing the Ice-Seabed Interaction Process

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Hamed Azimi ◽  
Hodjat Shiri
Keyword(s):  
Deep Understanding ◽  
Efficiency Coefficient ◽  
Element Analysis ◽  
Design Factor ◽  
Dimensionless Groups ◽  
Group A ◽  
Seabed Interaction ◽  
Subsea Pipelines ◽  
Expensive Model ◽  
High Range

Abstract Prediction of subgouge soil deformation during an ice gouging event is a challenging design factor in Arctic subsea pipelines. An accurate assessment of ice keel–seabed interaction requires expensive model testing and large deformation finite element analysis. Proposing reliable analytical/empirical solutions needs a deep understanding of the key parameters governing the problem. In this study, dimensional analysis of subgouge soil deformations was conducted and eight dimensionless groups of parameters were identified to facilitate proposing potential new solutions. A comprehensive dataset was established for horizontal and vertical subgouge deformations in both sand and clay seabed. Using the identified dimensionless groups, linear regression (LR) models were developed to estimate the horizontal and vertical deformation. Moreover, a sensitivity analysis (SA), as well as an uncertainty analysis (UA), was carried out to identify the superior LR models and the most influential parameter group. A high range of correlation coefficient (R), Nash-Sutcliffe efficiency coefficient (NSC), and variance accounted for (VAF) along with a low range of errors was achieved for the best LR model. The results of the superior LR models were also compared with the existing empirical equations. The study showed that the shear strength parameters of the seabed soil and the ratio of gouge depth to gouge width are the governing dimensionless parameters to model the horizontal and vertical subgouge soil deformations.

scholarly journals Failure Mechanisms of Cu–Cu Bumps under Thermal Cycling

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5522
Author(s):  
Kai-Cheng Shie ◽  
Po-Ning Hsu ◽  
Yu-Jin Li ◽  
Dinh-Phuc Tran ◽  
Chih Chen
Keyword(s):  
Thermal Cycling ◽  
Grain Boundaries ◽  
Maximum Stress ◽  
Failure Mechanisms ◽  
Deep Understanding ◽  
Bonding Interface ◽  
Triple Junctions ◽  
Element Analysis ◽  
Resistance Change ◽  
Hybrid Joints

The failure mechanisms of Cu–Cu bumps under thermal cycling test (TCT) were investigated. The resistance change of Cu–Cu bumps in chip corners was less than 20% after 1000 thermal cycles. Many cracks were found at the center of the bonding interface, assumed to be a result of weak grain boundaries. Finite element analysis (FEA) was performed to simulate the stress distribution under thermal cycling. The results show that the maximum stress was located close to the Cu redistribution lines (RDLs). With the TiW adhesion layer between the Cu–Cu bumps and RDLs, the bonding strength was strong enough to sustain the thermal stress. Additionally, the middle of the Cu–Cu bumps was subjected to tension. Some triple junctions with zig-zag grain boundaries after TCT were observed. From the pre-existing tiny voids at the bonding interface, cracks might initiate and propagate along the weak bonding interface. In order to avoid such failures, a postannealing bonding process was adopted to completely eliminate the bonding interface of Cu–Cu bumps. This study delivers a deep understanding of the thermal cycling reliability of Cu–Cu hybrid joints.

Machine Learning for Subsea Pipeline Reeling Mechanics

2020 ◽  
Author(s):  
Eric Giry ◽  
Vincent Cocault-Duverger ◽  
Martin Pauthenet ◽  
Laurent Chec
Keyword(s):  
Design Of Experiments ◽  
Wall Thickness ◽  
Large Diameter ◽  
Local Buckling ◽  
Statistical Regression ◽  
Element Analysis ◽  
Excessive Strain ◽  
Weld Area ◽  
Subsea Pipelines ◽  
Pipeline Design

Abstract Installation of subsea pipelines using reeling process is an attractive method. The pipeline is welded in long segments, typically several kilometers in length, and reeled onto a large diameter drum. The pipeline is then transported onto such reel to the offshore site where it is unreeled and lowered on the seabed. The deformation imposed on the pipeline while spooled onto the drum needs to be controlled so that local buckling is avoided. Mitigation of such failure is generally provided by proper pipeline design & reeling operation parameters. Buckling stems from excessive strain concentration near the circumferential weld area resulting from strength discontinuity at pipeline joints, mainly depending on steel wall thickness and yield strength. This requires the characterization of critical mismatches obtained by trial and error. Such method is a long process since each “trial” requires a complete Finite Element Analysis run. Such simulations are complex and lengthy. Occasionally, this can drive the selection of the pipeline minimum wall thickness, which is a key parameter for progressing the project. The timeframe of such method is therefore not compatible with such a key decision. The paper discusses the use of approximation models to capitalize on the data and alleviate the design cost. To do so, design of experiments and automation of the computational tool chain are implemented. It is demonstrated that initial complex chain of FEA computational process can be replaced using design space description and exploration techniques such as design of experiments combined with advanced statistical regression techniques in order to provide an approximation model. This paper presents the implementation of such methodology and the results are discussed.

Dynamic Performance of Composite Pavements Under Impact

1997 ◽  
Vol 1570 (1) ◽  
pp. 163-171 ◽  
Author(s):  
Samir N. Shoukry ◽  
D. R. Martinelli ◽  
Olga I. Selezneva
Keyword(s):  
Impact Load ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Deep Understanding ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Asphalt Overlay ◽  
Explicit Finite Element Analysis ◽  
Vertical Displacements ◽  
Pavement Layers

The importance of developing a deep understanding of the behavior of pavement layers under the action of dynamic loads, and the availability of cutting-edge computational and visualization technologies, led to the study presented in this paper. Explicit finite-element analysis was used to investigate the propagation of dynamic displacements induced in pavement layers under the action of an impact load similar to the one applied in a falling weight deflectometer test. The time-dependent dynamic response of a rigid pavement with straight asphalt concrete overlay was studied for two cases of unbonded and fully bonded interfaces between different layers. Significant differences in behavior were observed. Three-dimensional computer graphics and animation of the deformed model were used to display the propagation of vertical dynamic displacements through pavement layers. It was found that in the absence of a perfect bond between all pavement layers, the displacements measured on the top surface correlated little with the deformation measured in subsequent layers. In this case, a complicated pattern of behavior took place between the asphalt overlay and the concrete. The time histories of vertical displacements at selected surface locations and on the top and bottom of every layer were plotted. The plots revealed the existence of time shifts between the maximum displacements experienced by each layer, irrespective of the type of bond assumed between the interfaces.

Reduced Stiffness Criteria for the Safe Buckling Design of Thin Shells and its Numerical Validation

2014 ◽  
Vol 905 ◽  
pp. 283-286
Author(s):  
Hong Tao Wang
Keyword(s):  
Lower Bounds ◽  
Design Method ◽  
Thin Shells ◽  
Test Results ◽  
Element Analysis ◽  
Design Factor ◽  
Critical Design ◽  
Large Sets ◽  
Experimental Design Method ◽  
Marine Engineering

Thin metallic shells have long been adopted as major structural components in weight-sensitive applications, especially in marine engineering. Imperfection sensitive buckling is a critical design factor when these structures are loaded in compression. Traditional experimental design method depends on deriving lower bounds to the scatter of large sets of test results. This paper aims to present an analytical approach, the so-called reduced stiffness method (RSM) to the lower-bound buckling of thin-metallic shells. The validity of the RSM for the prediction of the safe lower bounds to the buckling of thin shells is verified through carefully controlled finite element analysis and the comparative studies confirm the reliability of the RSM.

Fatigue Prediction Verification of Fiberglass Hulls

2001 ◽  
Vol 38 (04) ◽  
pp. 278-292
Author(s):  
Paul H. Miller
Keyword(s):  
Finite Element ◽  
Fatigue Tests ◽  
Boiling Water ◽  
Tensile Failure ◽  
Analytical Models ◽  
Ship Motions ◽  
Long Term Effects ◽  
Element Analysis ◽  
Design Factor

The growing use of marine composite materials has led to many technical challenges and one is predicting lifetime durability. This analysis step has a large uncertainty due to the lack of data from in-service composite vessels. Analytical models based on classical lamination theory, finite-element analysis, ship motions, probability and wind and wave mechanicswere used in this project to predict hull laminate strains, and fatigue tests were used to determine S-N residual stiffness properties of coupons. These predictions and test data were compared against two cored fiberglass sisterships having significantly different fatigue histories and undamaged laminates representing a new vessel. Strains were measured while underway and good correlation was achieved between predictions and measurements. Fatigue damage indicators were identified which could be used in vessel inspection procedures. Endurance limits were found to be near 25% of static failure load, indicating that a fatigue design factor of four is required for infinite service with this material. Standard moisture experiments using boiling water were compared with long-term exposure. Results indicated the boiling water test yielded significantly conservative values and was not a reliable means of predicting long-term effects. Panel tests were compared with a combined coupon and finite-element procedure. Results indicated the proposed procedure was a viable substitute, at least for the materials studied. A rational explanation for using thicker outer skin laminates in marine composites was identified through single-sided moisture flex tests. These showed that the reduced strength and stiffness due to moisture of the outer hull skin laminate could be compensated by increased thickness. Although the resulting unbalanced laminate is not ideal from a warping standpoint, the approach leads to consistent tensile failure of the inner skin when subjected to normal loads. Permeability considerations make this desirable for hull laminates.

Modelling spatial variability in as-laid embedment for high pressure and high temperature (HPHT) pipeline design

2016 ◽  
Vol 53 (11) ◽  
pp. 1853-1865 ◽  
Author(s):  
Z.J. Westgate ◽  
W. Haneberg ◽  
D.J. White
Keyword(s):  
Spatial Variability ◽  
Mitigation Measures ◽  
Physical Mechanisms ◽  
Lateral Resistance ◽  
Project Costs ◽  
Seabed Interaction ◽  
Subsea Pipelines ◽  
Design Analyses ◽  
Pipeline Design ◽  
The Impact

Subsea pipelines are being designed to accommodate higher temperatures and pressures. Current modelling approaches that adopt constant lateral seabed resistance along the pipeline do not capture the high spatial variability in as-laid pipeline embedment from field observations, which strongly affects the lateral resistance. Ignoring spatial variability when designing pipelines with engineered buckles leads to higher predictions of axial force along the pipeline, with reduced likelihood of buckle formation. This can result in excessive mitigation measures being adopted, such as sleepers or counteract structures, which significantly increase project costs. Spatial variability of pipeline embedment is not currently handled rationally in design because an understanding of the physical mechanisms that cause as-laid embedment and methods for accurately predicting it have only recently emerged. This paper illustrates how the influence of these physical mechanisms that drive embedment can be extracted from field survey data and then modelled synthetically in design analyses. The impact of embedment variability and the resulting variation in lateral seabed resistance on the lateral buckling response is illustrated. The framework represents an improvement in the way geotechnical uncertainty and variability is handled in pipeline–seabed interaction analyses for use in pipeline design, and has already begun to be implemented in practice.

Research on Pipe Clamps Made of Resin Matrix Composites

2015 ◽  
Vol 1120-1121 ◽  
pp. 545-549
Author(s):  
Song Mei Li ◽  
Zhuo Wang ◽  
Bo Zhang ◽  
Jian Yong Zhang
Keyword(s):  
Steel Structure ◽  
Oil Field ◽  
Resin Matrix ◽  
Strength Analysis ◽  
Matrix Composites ◽  
Analysis Model ◽  
Element Analysis ◽  
Resin Matrix Composite ◽  
Subsea Pipelines ◽  
Offshore Oil

When offshore oil field has been completed and put into production, the new subsea pipelines and cable will need to be established. Cable protection pipe clamp is used to fix cable protection pipe on the jacket. In order to avoid the problem of traditional steel structure clamps which was difficult to joint, align and fasten when it installed cable protection pipe underwater, reduce the risk and workload underwater, This paper will study a new type of portable connecting riser clamp made of resin matrix composites which can solve the installation problem which is difficult to install cable protection pipes underwater. The main structure of pipe clamps made of resin matrix composites used three divided-plates type of structure. The load characteristic of clamps was determined by Morison equation which is a classical theory and clamps underwater mechanics analysis model was established. The results show that the strength of the base of clamps meet the requirements after strength analysis with finite element analysis method, stability and strength experiments, which means the clamps made of resin matrix composite is feasible.

A Simplified Fatigue Assessment Method for ASME VIII-2

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Jun Shen ◽  
Mingwan Lu ◽  
Heng Peng ◽  
Yinghua Liu ◽  
Zhiwei Chen
Keyword(s):  
Evaluation Method ◽  
Failure Modes ◽  
Economic Cost ◽  
Material Design ◽  
Assessment Method ◽  
Element Analysis ◽  
Design Factor ◽  
Screening Criteria ◽  
Detailed Assessment ◽  
Fatigue Evaluation

Abstract Fatigue is one of the most common and important failure modes in pressure vessel. ASME VIII-2 provides three screening criterion and three detailed assessment method for fatigue failure. With the decrease of material design factor and the extension of fatigue curve to high cycle, the applicable scope of the three screening criteria become relatively smaller and the economic efficiency is also reduced. Meanwhile, the three fatigue evaluation methods given in ASME VIII-2 Code are all based on detailed numerical calculations (such as finite element analysis (FEA)). Both economic cost and requirements of technical personnel of engineers are higher. In this paper, a simplified fatigue evaluation method is proposed, which gives simple implementation procedures and relatively conservative fatigue evaluation results. Compared with the screening criteria method A, the main advantage is that the scope of its application is wider, that is: (1) the number of significant load cycle can be considered is extended from 1000 to 105; (2) there is no upper limit to the range of pressure fluctuation, which is 20% in method A. Compared with the screening criteria method B, the main advantage is that this method is much simpler and for most materials, design fatigue curves are not required during calculation and evaluation. Compared with the three detailed assessment methods given in ASME VIII-2, this method is very convenient and does not require detailed FEA. The method proposed in this paper can simplify the evaluation process of fatigue analysis in a certain range and provide a more cost-effective engineering assessment method.

Further Improvements to ASME Section XI Code Case N-806 in a Proposed Second Revision

2019 ◽  
Author(s):  
Robert O. McGill ◽  
George A. Antaki ◽  
Mark A. Moenssens ◽  
Douglas A. Scarth
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Nuclear Industry ◽  
Metal Loss ◽  
Soil Reaction ◽  
Buried Pipe ◽  
Element Analysis ◽  
Design Factor ◽  
Evaluation Procedures ◽  
Need To Evaluate

Abstract ASME Section XI Code Case N-806, for evaluation of metal loss in Class 2 and 3 metallic piping buried in a backfilled trench, was first published in 2012. This Code Case has been prepared by the ASME Section XI Task Group on Evaluation Procedures for Degraded Buried Pipe. The Code Case addresses the nuclear industry need for evaluation procedures and acceptance criteria for the disposition of metal loss that is discovered during the inspection of metallic piping buried in a back-filled trench. In a second revision of the Code Case, several changes are proposed. First, guidance is provided for analytical evaluation of greater detail including finite element analysis methods. A new nonmandatory appendix is included to provide procedures for the evaluation of soil and surcharge loads using finite element analysis. Next, a second new nonmandatory appendix is provided giving detailed guidance on the evaluation of seismic loads. Finally, the need to evaluate the fatigue life of buried piping subjected to cyclic surface loading is now included and a design factor applied to the modulus of soil reaction is introduced. This paper presents details of the proposed changes to Code Case N-806-1 and their technical basis where applicable.

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