bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research and Development of Viscous Fluid Dampers for Improvement of Seismic Resistance of Thermal Power Plants: Part 8 — Evaluation of Vibration Control Performance Using Experimental Design Method
Authors: Minagawa Keisuke , Aida Kiyoshi , Tanaka Go , Fujita Satoshi 
Published: November 2019

Abstract
After Great East Japan Earthquake, coal-fired thermal power generation is a very important power source in Japan. In addition, Hokkaido Eastern Iburi Earthquake occurred in Japan in 2018, and damage of coal-fired thermal power plants by this earthquake caused blackout in very wide area. Therefore improvement of the seismic performance of the thermal power plants is a very important issue. In general boilers of coal-fired power plants are suspended from the upper end of support structures in order to allow thermal expansion of the boilers. Therefore boilers are structures that easily sway by earthquakes. In order to suppress the vibration, stoppers made of steel are generally installed between boilers and their support structures. Although stoppers made of steel can suppress the vibration effectively and economically, further improvement of seismic performance is required from the viewpoint of abovementioned issue. Therefore authors have proposed and developed a vibration control damper for coal-fired power plants instead of the stopper made of steel. Construction of the damper is similar to oil dampers, but inner fluid is viscous fluid. In PVP 2017, the basic performance of the proposed damper was presented. In PVP 2018, influence of dispersion of damper properties was also investigated. In addition, seismic response analyses using various earthquakes that include long period and long duration earthquake waves were carried out. As a result of previous investigations, it was confirmed that the proposed damper has good performance in its lifetime. However, parameters of dampers were selected manually. Therefore, influence of parameters of dampers on the vibration control performance were evaluated theoretically by using the experimental design method in this paper. The experimental design method is one of the effective techniques for research such as investigation of the influence of the habitat environment on the growth of crops. The selection of damper parameters is complex optimization, because so many variables need to be optimized. Therefore the experimental design method is suitable technique for the evaluation of damper parameters. This paper will evaluate vibration control performance from the viewpoint of the experimental design method.
Prediction of Fracture Location in Tensile Test of Short-Fiber-Self-Reinforced Polyethylene Composite Plates
Authors: Tada Naoya , Jin Ming , Uemori Takeshi , Sakamoto Junji 
Published: November 2019

Abstract
Composite materials such as carbon-fiber-reinforced plastics (CFRP) and glass-fiber-reinforced plastics (GFRP) have been attracting much attention from the viewpoint of lightweight solution of automobiles and airplanes. However, the recyclability of these composite materials is not sufficient and the environmental load is large. Recently, self-reinforced polymer (SRP), in which similar polymer is used for reinforcing fibers and matrix, has been proposed. High-density polyethylene (HDPE) reinforced with ultra-high-molecular-weight polyethylene (UHMWPE) fibers, so-called self-reinforced PE (SRPE), is one of the promising thermoplastic composites. In this study, SRPE plates were made and the tensile tests were carried out. After the effect of reinforcement of UHMWPE fibers was evaluated on the basis of the tensile strength, the relationship between the distribution of UHMWPE fibers and the location of the final fracture line was examined. It was found from these experimental results that the fracture tends to occur along the regions with low area fraction of fibers or along those with low area fraction of fiber/matrix boundaries. This fact suggests that the fracture location of SRPs is predictable from the distribution of reinforcing fibers.
Evaluation of Fatigue Crack Propagation by ΔJ Approach
Authors: Li Jia , Ancelet Olivier , Double Alexandre , Chapuliot Stephane 
Published: November 2019

Abstract
An analysis of fatigue crack growth is required for large cast components to evaluate the possible defect evolution during the service life. These components are subjected to both mechanical loading and thermal loading. Due to their high thickness, temperature variations through the thickness can be significant. Thus, a conventional elastic analysis of fatigue crack propagation could be over conservative.
In order to take into account the effect of plasticity, the ΔJ approach of fatigue crack propagation evaluation is implemented in FE software SYSTUS [9]. The quarter of cycle method [11] (or twice-yield method in ASME code) will be used in this work to calculate ΔJ values under both thermal transient and mechanical loadings. Two strategies will be proposed to create the virtual monotonically increasing loading in 3D elastic–plastic FE calculations. The result in terms of numerical scheme will be validated by comparing with FE software CAST3M [10] and the RSE-M [3] simplified ΔKcp method.
Numerical Investigation on Strength of Tee Pipes Under In-Plane/Out-of-Plane Cyclic Loading
Authors: Nakamura Izumi 
Published: November 2019

Abstract
It is known that the expected failure mode of piping systems under excessive seismic motion would be the fatigue failure at elbows or tees. Although there are a lot of experimental and analytical investigations on the strength and the failure behavior of elbows under seismic loading, there are a few studies on tee pipe joints particularly in the inelastic range. To clarify the characteristics of the strength of tee pipes under elastic-plastic region, investigations by FEM analysis were conducted. In this analytical investigation, steel butt-welding type tee pipe joints were considered. Two kinds of parameters were considered; 1) the loading direction (in-plane bending / out-of-plane bending), 2) the branch size (equal tee / unequal tee).
From the analytical examination, the load-displacement relationship and the distribution of the accumulated plastic strain concentration position were obtained. The difference of the strength in the loading direction and the expected failure locations depending on the branch pipe size and the loading direction are discussed.
A Fluidelastic Model for the Nonlinear Dynamics of Two-Dimensional Inverted Flags
Authors: Tavallaeinejad Mohammad , Païdoussis Michael P. , Legrand Mathias , Kheiri Mojtaba 
Published: November 2019

Abstract
A nonlinear fluid-elastic model is proposed for the study of the dynamics of inverted flags. The quasi-steady version of Theodorsen’s unsteady aerodynamic theory is used for inviscid fluid-dynamic modelling of the deforming flag in axial flow. Polhamus’s leading edge suction analogy is employed to model flow separation effects from the free end at moderate angles of attack via a nonlinear vortex-lift force. The flag is modelled structurally via a geometrically-exact Euler-Bernoulli beam theory. Using the extended Hamilton’s principle, the nonlinear partial-integro-differential equation governing the dynamics of the inverted flag in terms of the angle of rotation of the flag is obtained. The equation of motion is discretised spatially via the Galerkin method and is integrated in time via Gear’s backward differentiation formula. The bifurcation diagrams are obtained using a time-integration method and pseudo-arclength continuation. It is shown that inverted flags undergo multiple bifurcations with respect to flow velocity, and they generally exhibit four dynamical states: (i) stretched-straight, (ii) buckled, (iii) deflected-flapping, and (iv) large-amplitude flapping. Also, flapping of inverted flags probably develops through fluid-elastic instabilities. Our findings suggest that the system dynamics is sensitive to the mass ratio. It is shown that the mass ratio parameter does not affect the stability of the stretched-straight state and the onset of divergence; however, it controls the possibility of a direct transition from static undeflected equilibrium to large-amplitude flapping motion and it affects the amplitude of large-amplitude flapping.
Influence of an Elevated Temperature Environment on the Tensile Mechanical Properties of a 3D Printed Thermoplastic Polymer
Authors: Torres Jose E. , Onwuzurike Otito N. , McClung Amber J. W. , Ocampo Juan D. 
Published: November 2019

Abstract
The purpose of this study is to examine the effects of the environment on 3D printed Polylactic Acid (PLA), a biodegradable thermoplastic polymer. The experimental program was specifically designed to explore the influence of print temperature and aging temperature on the mechanical performance of the printed material. Printing at the elevated temperatures (30–40°C) resulted in slight mechanical property changes. In order to understand which of the changes could also be caused by simply storing the materials at the elevated temperature, samples were printed at 25°C and subsequently aged (at 30–45°C) before mechanical testing. All mechanical testing was performed in standard laboratory temperature on an MTS Criterion. All of the mechanical properties were not greatly altered by printing or aging at elevated temperatures, suggesting that printing and using in extreme weather environments could be reasonable. The yield stress is not affected by storage at elevated temperatures, but is increased (or enhanced) by printing at elevated temperatures. The maximum stress is increased (or enhanced) by both aging and printing at elevated temperatures, but is accompanied by a large reduction in strain capacity. Changes that are observed in mechanical properties will be incorporated in future material models to accurately capture material behavior.
European Project ATLAS+: Evaluation of a Shear Modified Gurson Model by Comparison to Experimental Fracture Tests on SENT Fracture Specimens
Authors: Bolinder Tobias , Moinereau Dominique , Le Delliou Patrick , Dahl Anna , Besson Jacques 
Published: November 2019

Abstract
This paper will assess the capability of the shear modified Gurson model developed by Nahshon and Hutchinson which is used by Kiwa Inspecta within the ATLAS+ project. This is done by comparison to experimental results from SENT fracture tests performed by EDF and ARMINES. The procedure for parameter identification for the standard and shear modified Gurson model is also summarized.
The work presented in this paper is part of Work Package 3 within the ATLAS+ project. WP3 focus mainly on ductile tearing predictions for large defects in components. Models exists to accurately predict ductile tearing and to consider phenomena such as stress triaxiality effects. These advanced models include local approach coupled models or advanced energetic approaches. However, there is a need to validate these models for use in industrial applications. This will be done within the ATLAS+ project by predicting the results of the large scale component tests where input to the models are given from small size laboratory specimens.
Within the paper a description of the shear modified Gurson model is given, as developed by Nashson and Hutchinson [1]. Furthermore, the procedure in determining the material model parameters is discussed. To determine the material parameters for the shear modified Gurson model a uniaxial tensile test, a fracture test and shear tests are used. The material that is used is the ferritic steel WB 36 (15 NiCuMoNb 5) which will be used for the large scale component tests within the ATLAS+ project. The procedure is also evaluated by comparing predictions done with the shear modified Gurson model to experimental results from SENT specimens performed by EDF and ARMINES.
A comparison of the capability in predicting the ductile tearing in the SENT experiments between the standard Gurson model and the shear modified Gurson model is also presented within the paper.
High Temperature Performance of Bonded Composite Repairs for Pressure Vessels
Authors: Alnaser Ibrahim A. , Kiani Mahdi , Walker Roger , Keller Michael W. 
Published: November 2019

Abstract
Bonded composite repairs are commonly used as both a temporary and permanent repair method to restore damaged pressure vessels and pipelines. This repair approach is used in a wide variety of industries, including the oil and gas industry. Design and qualification of repair method have been standardized by the ASME post-construction codes. Significant literature has been generated to understand the behavior of these repairs under a variety of loading conditions, both static and dynamic. However, this repair type has typically only been investigated at or near room temperature. As the application possibilities for these repairs expand, higher service temperatures have become a focus for both repair manufacturers and operators. High temperatures (&gt; 250°F) have a number of impacts on polymer composites, including reducing the elastic modulus of the repair material, which tends to reduce the repair strength. Therefore, it is critical to understand the effect of temperature on both the individual composite components, as well as the overall composite repair system. The research presented here studies the influence of temperature on bonded composite repair systems at service pressure (3000 psi) and high temperature conditions. This high temperature is generated using a heating element inside the repaired vessel while contained inside an insulated oven. Strain measurements of the repair are also investigated during a quasi-static testing.
Wavelet Analysis of FIV Response for Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side
Authors: Neumeister Roberta Fátima , Petry Adriane Prisco , Möller Sergio Viçosa 
Published: November 2019

Abstract
Flow induced vibration of a single cylinder and two cylinders assembled in the configurations tandem and side-by-side are experimentally investigated in the present study. The rigid cylinder free to vibrate is fixed in two blades, forming two different configurations, to allow transversal and longitudinal vibration, respectively. The mass ratio, m* ranged between 158 and 643 while the damping ratio, ζ, ranged between 0.0006 and 0.005. The pairs of cylinders present a space ratio of 1.26 (P/D and L/D) and one of the cylinders is fixed while the second one is free to vibrate. The aerodynamic channel used in the analysis presents test section with 0.146m height and 0.193m width, the study is executed using accelerometer and hot wire anemometry. The velocity on the test section is varied and generates reduced velocity, Vr = U/fnD, between 4 and 30. The displacement amplitudes, Y/D, are obtained using integration of the acceleration signals, and the root mean square results are adopted. Fourier spectral analysis and continuous wavelets are employed in the analysis of acceleration and velocity signals. The higher amplitudes happen in two distinct reduced velocities and were associated with the vibration modes of the cylinder free to vibrate. In the case with two cylinders side-by-side the amplitude is higher and present small variation on the reduced velocity of occurrence in comparison with single cylinder. For the case with cylinders in tandem the presence of the cylinder in the wake of the cylinder free to vibrate generated amplification of the response in high reduced velocities.
Use of Engineered Materials to Reduce Both Strainer Head Loss and Fiber Bypass for Emergency Core Cooling Systems
Authors: Bilanin Alan J. , Kaufman Andrew E. , Bilanin Warren J. 
Published: November 2019

Abstract
Testing has shown that the use of engineered materials that can be combined with Loss of Cooling Accident generated debris has the ability to reduce debris head loss for boiling water and pressurized water reactors on Emergency Core Cooling System strainers. This engineered material has also been shown to reduce the amount of fiber that penetrates a strainer and continues downstream toward the fuel. Large scale testing is described that demonstrates that engineered materials can reach the strainers and reduce head loss. Small scale testing is described that demonstrates that engineered material can reduce the amount of fiber that can penetrate a strainer.
Adjusted J-R Toughness Curve for Pipes Using J-A2 Crack Constraint of CT Specimens and 3D Crack Meshes
Authors: Thorwald Greg , Bagnoli Ken 
Published: November 2019

Abstract
The objective of this paper is to use two-parameter fracture mechanics to adjust a material J-R resistance curve (i.e. toughness) from the test specimen geometry to the cracked component geometry. As most plant equipment is designed and operated on the “upper shelf”, a ductile tearing analysis may give a more realistic assessment of flaw tolerance. In most cases, tearing curves are derived from specimen geometries that ensure a high degree of constraint, e.g., SENB and CT Therefore, there can be significant benefit in accounting for constraint differences between the specimen geometry and the component geometry.
In one-parameter fracture mechanics a single parameter, K or J-integral, is sufficient to characterize the crack front stresses. When geometry dependent effects are observed, two-parameter fracture mechanics can be used to improve the characterization of the crack front stress, using T-stress, Q, or A2 constraint parameter. The A2 parameter was be used in this study.
The usual J-R power-law equation has two coefficients to curve-fit the material data (ASTM E1820). The adjusted J-R curve coefficients are modified to be a function of the A2 constraint parameter. The measured J-R values and computed A2 constraint values are related by plotting the J-R test data versus the A2 values. The A2 constraint values are computed by comparing the HRR stress solution to the crack front stress results of the test specimen geometry using elastic-plastic FEA. Solving for the two J-R curve coefficients uses J values at two Δa crack extension values from the test data. A closed-form solution for the adjusted J-R coefficients uses the properties of natural logarithms. The solution shows the adjusted J-R exponent coefficient will be a constant value for a particular material and test specimen geometry, which simplifies the application of the adjusted J-R curve.
A different test specimen geometry can be used to validate the adjusted J-R curve. Choosing another test specimen geometry, having a different A2 constraint value, can be used to obtain the adjusted J-R curve and compare it to the measured J-R curves.
The geometry of the component is also expected to have a different A2 constraint compared to the material test specimen. The example examined here is an axial surface flaw in a pipe. The A2 constraint for an axial surface cracked pipe is computed and used to obtain an adjusted J-R curve. The adjusted J-R curve shows an increase in toughness for the pipe as compared to the CT measured value. The adjusted J-R curve can be used to assess flaw stability using the driving force method or a ductile tearing instability analysis.
Towards Understanding Two-Phase Flow Induced Vibration of Piping Structure With a U-Bend
Authors: Bamidele Olufemi E. , Ahmed Wael H. , Hassan Marwan 
Published: November 2019

Abstract
The current work investigates two-phase flow induced vibrations in 90° U-bend. The two-phase induced vibration of the structure was investigated in the vertical, horizontal and axial directions for various flow patterns from bubbly flow to wavy and annular-dispersed flow. The void fractions at various locations along the piping including the fully developed void fraction and the void fraction at the entrance of the U-bend were fully investigated and correlated with the vibration amplitude. The results show that the excitation forces of the two-phase flow in a piping structure are highly dependent on the flow pattern and the flow conditions upstream of the bend. The fully developed void fraction and slip between phases are important in modelling of forces in U-bends and elbows.
Towards a Viable Field Deployable Ultrasonic Technique for Detection of Type IV Creep Damage in CSEF Steels at an Early Stage
Authors: Kumar Harendra , Lambert Jack W. , Nageswaran Channa , Nadendla Hari Babu , Gan Tat-Hean 
Published: November 2019

Abstract
It is now apparent that welds in many of the creep strength enhanced ferritic (CSEF) steel grades are susceptible to Type IV creep damage. Furthermore, due to the complex nature of incubation and growth of localized creep damage in such alloys, state-of-the-practice non-invasive techniques such as hardness, replication and strain measurement alone are insufficient for reliable assessment. Consequently, there is concern in the industry regarding the integrity of existing and proposed installations that utilize CSEF steels such as ASME Grade 91 and Grade 92. To address this concern, in addition to pressing demands for increased efficiency and from environmental regulation, extensive research is underway on various fronts including fracture assessment, online health monitoring and life extension technologies. These rely heavily on the effectiveness of non-destructive testing (NDT) techniques. Therefore, volumetric non-invasive techniques that enable detection and characterization of damage are sought to facilitate effective assessment of welded components operating at high temperature and pressure.
Several NDT methods were reviewed in order to understand the current state-of-the-art in terms of their sensitivity to early stage Type IV damage and their readiness for field implementation. Most of the advanced methods proposed for assessment of creep damage are based on the inversion of certain parameters to correlate to the extent of damage. This limits their selectivity, ability to characterize and determine the severity of localized damage. Using recent developments in electronics and signal processing instrumentation, ultrasonic testing was identified as having the potential to be developed as a reliable approach for detection of Type IV creep damage at an early stage.
This paper presents the outcome of an industry-focused research effort with the goal of developing and validating an ultrasonic technique for reliable detection of Type IV creep damage at an early stage. In this framework, supported by the Core Research Programme at TWI, an ultrasonic technique was developed and tested on a number of creep-exposed specimens. Ultrasonic data was processed and correlated with controlled metallographic investigations to determine the detection, positioning and characterization performance of Type IV creep damage within the heat affected zone of welds.