scholarly journals SCC and Corrosion Fatigue characterization of a Ti-6Al-4V alloy in a corrosive environment – experiments and numerical models

2014 ◽  
Vol 8 (30) ◽  
pp. 84-94 ◽  
Author(s):  
S. Baragetti ◽  
F. Villa
Keyword(s):  
Corrosion Fatigue ◽  
Numerical Models ◽  
Corrosive Environment

Fatigue Strength Assessment of a Structure Considering Corrosion Wastage and Corrosion Fatigue

2018 ◽  
Author(s):  
Norio Yamamoto ◽  
Tomohiro Sugimoto ◽  
Kinya Ishibashi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Life Assessment ◽  
Actual State ◽  
Corrosive Environment ◽  
Corrosion Fatigue Crack ◽  
Long Life

It is known that the fatigue strength decreases in corrosive environment and many experiments were carried out to comprehend the decrease in fatigue strength in corrosive environment. In order to comprehend the actual state, a cycle speed of fatigue test loads should correspond to a wave frequency. Therefore, an experiment in the long life region is practically difficult, then the corrosion fatigue data available for the life assessment of the structure is quite limited. In this study, the fatigue strength of the welded joints in long life service was evaluated according to the calculations of corrosion fatigue crack propagation subjected to the random loadings which followed an exponential distribution. In the crack propagation calculations, the progress of corrosion wastage from the plate surface and the resultant stress increase were considered simultaneously. In the high stress and the short life region, the decrease in fatigue strength due to the accelerated crack propagation in corrosive environment was dominant because the progress of corrosion wastage was little. On the other hand, in the low stress and the long life region, the decrease in fatigue strength became dull as longer the fatigue life because the corrosion fatigue crack propagation was suppressed by the corrosion wastage, but after that the fatigue strength showed the precipitous decrease due to the increase in stress resulted by the progress of corrosion wastage.

scholarly journals Characterization of the unsteady aerodynamic response of a floating offshore wind turbine

2020 ◽  
Author(s):  
Simone Mancini ◽  
Koen Boorsma ◽  
Marco Caboni ◽  
Marion Cormier ◽  
Thorsten Lutz ◽  
...  
Keyword(s):  
Numerical Models ◽  
Aerodynamic Performance ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
High Fidelity ◽  
Aerodynamic Damping ◽  
Unsteady Aerodynamic ◽  
Future Work ◽  
Good Agreement

Abstract. The disruptive potential of floating wind turbines has attracted the interest of both industry and scientific community. Lacking a rigid foundation, such machines are subject to large displacements whose impact on the aerodynamic performance is not yet fully acknowledged. In this work, the unsteady aerodynamic response to an harmonic surge motion of a scaled version of the DTU10MW turbine is investigated in detail. The imposed displacements have been chosen representative of typical platform motions. The results of different numerical models are validated against high fidelity wind tunnel tests specifically focused on the aerodynamics. Also a linear analytical model, relying on the quasi-steady assumption, is presented as a theoretical reference. The unsteady responses are shown to be dominated by the first surge harmonic and a frequency domain characterization, mostly focused on the thrust oscillation, is conducted involving aerodynamic damping and mass parameters. A very good agreement among codes, experiments and quasi-steady theory has been found clarifying some literature doubts. A convenient way to describe the unsteady results in non-dimensional form is proposed, hopefully serving as reference for future work.

Three-Dimensional Strain-Based Model for the Severity Characterization of Dented Pipelines

2018 ◽  
Vol 1 (3) ◽  
Author(s):  
Chike Okoloekwe ◽  
Muntaseer Kainat ◽  
Doug Langer ◽  
Sherif Hassanien ◽  
J.J. Roger Cheng ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Numerical Models ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Computation Time ◽  
Order Continuity ◽  
Element Analysis ◽  
The Mathematical Model ◽  
Derivatives Of

Oil and gas pipelines traverse long distances and are often subjected to mechanical forces that result in permanent distortion of its geometric cross section in the form of dents. In order to prioritize the repair of dents in pipelines, dents need to be ranked in order of severity. Numerical modeling via finite element analysis (FEA) to rank the dents based on the accumulated localized strain is one approach that is considered to be computationally demanding. In order to reduce the computation time with minimal effect to the completeness of the strain analysis, an approach to the analytical evaluation of strains in dented pipes based on the geometry of the deformed pipe is presented in this study. This procedure employs the use of B-spline functions, which are equipped with second-order continuity to generate displacement functions, which define the surface of the dent. The strains associated with the deformation can be determined by evaluating the derivatives of the displacement functions. The proposed technique will allow pipeline operators to rapidly determine the severity of a dent with flexibility in the choice of strain measure. The strain distribution predicted using the mathematical model proposed is benchmarked against the strains predicted by nonlinear FEA. A good correlation is observed in the strain contours predicted by the analytical and numerical models in terms of magnitude and location. A direct implication of the observed agreement is the possibility of performing concise strain analysis on dented pipes with algorithms relatively easy to implement and not as computationally demanding as FEA.

Material Model Development of Sandwich Composite: Numerical-Experimental Investigation of Head Dummy Impacting at Vehicle Interior Components

2019 ◽  
Vol 827 ◽  
pp. 55-60
Author(s):  
A. Vettorello ◽  
G.A. Campo
Keyword(s):  
Numerical Models ◽  
Fibre Composite ◽  
Model Development ◽  
Material Model ◽  
Sandwich Composite ◽  
Crash Analysis ◽  
Vehicle Interior ◽  
Polymeric Foam ◽  
Glass Fibre Composite

This paper shows the applicability of a non-linear Finite Element (FE) methodology to analyse the elasto-plastic behaviour and the energy absorption of a padding noise-protection material applied to the vehicle interior components. This material is a sandwich built from alternating layers of polymeric foam and of glass fibre composite. The approach considers two design steps. The first one involves the experimental characterization of the material while the latter deals with the assessment of the numerical models validated for a full-vehicle crash analysis.

Crack Growth Rates and Corrosion Fatigue of Austenitic Stainless Steels in High Chloride Solutions

2011 ◽  
Vol 488-489 ◽  
pp. 97-100 ◽  
Author(s):  
Clemens Vichytil ◽  
G. Mori ◽  
Reinhard Pippan ◽  
M. Panzenböck ◽  
Rainer Fluch
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Limit ◽  
Corrosion Fatigue ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Propagation Rate ◽  
Corrosive Environment

Purpose: Applications for highly corrosive environments and cyclic loading are often made out of austenitic stainless steels. Corrosion fatigue and crack propagation behaviour has been studied to determine failure processes and damage mechanisms. Approach: CrNiMo stabilized austenitic stainless steel and CrMnN austenitic stainless steel in solution annealed and cold worked condition are compared. S/N curves and crack propagation rate curves are recorded in 43 wt% CaCl2solution at 120 °C, which resembles most severe potential service conditions. For comparison these experiments are also performed in inert glycerine. Additionally, the electrochemical behaviour of these materials has been studied. Findings: The CrMnN steels have excellent mechanical properties but are very susceptible to stress corrosion cracking in the test solution. The fatigue limit as well as the threshold for long crack growth are significantly reduced in corrosive environment. Moreover these steels exhibit a remarkable increase in the propagation rate, which is extremely pronounced in the near threshold region. This effect is enhanced by cold working. CrNiMo steels also show a reduction in the fatigue limit, but it is less pronounced compared to CrMnN steels. The threshold is significantly reduced in corrosive environment, but propagation rate is lower in corrosive environment compared to inert glycerine. Possible explanations of this surprising behaviour are discussed.

scholarly journals Characterization of Particle Flow in a Free-Falling Solar Particle Receiver

2015 ◽  
Author(s):  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
David Romano ◽  
Julius Yellowhair ◽  
Nathan Siegel
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Models ◽  
Particle Flow ◽  
Concentrating Solar Power ◽  
Power Cycles ◽  
Solar Particle ◽  
Free Falling

Falling particle receivers are being evaluated as an alternative to conventional fluid-based solar receivers to enable higher temperatures and higher efficiency power cycles with direct storage for concentrating solar power applications. This paper presents studies of the particle mass flow rate, velocity, particle-curtain opacity and density, and other characteristics of free-falling ceramic particles as a function of different discharge slot apertures. The methods to characterize the particle flow are described, and results are compared to theoretical and numerical models for unheated conditions.

scholarly journals Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

2020 ◽  
Vol 10 (18) ◽  
pp. 6534
Author(s):  
Chiara Bedon ◽  
Martina Sciomenta ◽  
Massimo Fragiacomo
Keyword(s):  
Mechanical Characterization ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Small Scale ◽  
Load Bearing ◽  
Timber Constructions ◽  
Technical Interest ◽  
Push Out

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

scholarly journals Wave-based optical coherence elastography: the 10-year perspective

2021 ◽  
Author(s):  
Fernando Zvietcovich ◽  
Kirill V Larin
Keyword(s):  
Numerical Models ◽  
Disease Diagnosis ◽  
Major Advance ◽  
Optical Coherence ◽  
Future Directions ◽  
Translation Research ◽  
Mechanical Waves ◽  
Complex Boundary ◽  
Remarkable Progress

Abstract After ten years of progress and innovation, optical coherence elastography (OCE) based on the propagation of mechanical waves has become one of the major and, perhaps, one of the most studied OCE branches, producing a fundamental impact in the quantitative and nondestructive biomechanical characterization of tissues. Preceding previous progress made in ultrasound and magnetic resonance elastography; wave-based OCE has pushed to the limit the advance of three major pillars: (1) implementation of novel wave excitation methods in tissues, (2) understanding new types of mechanical waves in complex boundary conditions by proposing advance analytical and numerical models, and (3) the development of novel estimators capable of retrieving quantitative 2D/3D biomechanical information of tissues. This remarkable progress promoted a major advance in answering basic science questions and improving medical disease diagnosis and treatment monitoring in several types of tissues leading, ultimately, to the first attempts of clinical trials and translational research. This paper summarizes the fundamental up-to-date principles and categories of wave-based OCE, revises the timeline and the state-of-the-art techniques and applications lying in those categories, and concludes with a discussion of current challenges and future directions, including clinical translation research.

Testing of Composite Material for Transport Tanks for LNG

2019 ◽  
Vol 809 ◽  
pp. 625-629
Author(s):  
Philipp Werner Kutz ◽  
Jan Werner ◽  
Frank Otremba
Keyword(s):  
Numerical Models ◽  
Ambient Air ◽  
Insulation Material ◽  
Combustion Engines ◽  
Glass Fiber Reinforced Plastic ◽  
Glass Fiber Reinforced ◽  
Reinforced Plastic ◽  
Steel Tanks ◽  
Cryogenic Conditions

To reduce the emission of carbondyoxide (CO2) of combustion engines, liquefied naturalgas (LNG) is used as an alternative fuel. LNG is transported via truck, ship or railway for longdistances. Double walled stainless steel tanks are used for transportation, which are heavy and expensive.The vacuum insulation between the two walled structure ensures that the LNG stays liquid overthe transportation time (boiling point of LNG: −162 °C). This causes a high temperature differencebetween the transported good and the ambient air. A simplified tank construction is used to reduce the weight and price of the tank. Instead of stainlesssteel, glass fiber reinforced plastic (GFRP) is used. The designed is changed to a single walledconstruction with a solid insulation material outside on the GFRP structure. Goal of this work is the characterization of a suitable insulation material and configuration as wellas the analysis of the mechanical properties of GFRP under cryogenic conditions. Several experimentsare carried out. Numerical models of these experiments can then be used for parameter studies.

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