Static and Dynamic Collapse Characteristics of Scale Model Corrugated Tubular Sections

1975 ◽  
Vol 97 (4) ◽  
pp. 357-362 ◽  
Author(s):  
P. H. Thornton
Keyword(s):  
Scaling Laws ◽  
Dynamic Testing ◽  
Plastic Hinge ◽  
Rate Sensitivity ◽  
Scale Model ◽  
Complex Deformation ◽  
Collapse Characteristics ◽  
Rate Effects ◽  
Deformation Processes ◽  
Tubular Sections

The collapse load of a series of scale model, corrugated tubular sections was determined, both by quasi-static and by dynamic testing. Provided that the material from which the models are made is identical to that of the full size component, then the scaling laws for structures undergoing complex deformation processes will be obeyed. The dynamic collapse response, which occurred by the operation of a plastic hinge mechanism, is governed by the strain rate sensitivity of the material; structural rate effects do not affect the collapse process.

Acoustic Emission Testing of Concrete Frame during Pseudo Dynamic Loading

2006 ◽  
Vol 13-14 ◽  
pp. 195-200
Author(s):  
Athanasios Anastasopoulus ◽  
S. Bousias ◽  
A. Tsimogiannis ◽  
T. Toutountzakis
Keyword(s):  
Acoustic Emission ◽  
Dynamic Testing ◽  
Frame Structure ◽  
Scale Model ◽  
Reinforced Concrete Frame ◽  
Energy Rate ◽  
Concrete Frame ◽  
Emission Testing ◽  
Real Size ◽  
Acoustic Emission Testing

Acoustic Emission (AE) monitoring was performed during Pseudo-Dynamic Testing of a torsionally unbalanced, two-storey, one-by-one bay reinforced concrete frame structure. The structure represented a 0.7-scale model of a real-size frame structure designed and detailed according to the standards prevailing in Greece in 60's, without engineered earthquake resistance. Real time monitoring of AE activity versus the complex applied load resulted in semi quantitative damage characterization as well as comparative evaluation of the damage evolution of the different size columns. Evolution of the AE energy rate per channel, as revealed from zonal location, and the energy rate of linearly located sources enabled the identification of damage areas and the forecast of crack locations before cracks were visible with naked eye. In addition to that, the results of post processing evaluation allowed for the verification of the witnessed damaged areas and formed the basis for quantitative assessment of damage criticality.

scholarly journals Dislocation/Twin/Interface Interactions during Deformation of PST TiAl Single Crystals, an AFM Study

2002 ◽  
Vol 753 ◽  
Author(s):  
Yali Chen ◽  
David P. Pope ◽  
Vaclav Vitek
Keyword(s):  
Displacement Vector ◽  
Fixed Ratio ◽  
The Other ◽  
Deformation Bands ◽  
Twin Interface ◽  
Complex Deformation ◽  
Deformation Processes ◽  
The Individual ◽  
Macroscopic Displacement ◽  
Total Shear

ABSTRACTPST TiAl crystals oriented such that the deformation axis lies in the (111) interfacial planes have been deformed in compression. This deformation produces so-called “channeled flow” in which the strain perpendicular to the (111) interfaces is zero, while the other two strains are equal and opposite in sign. Thus the sample simply shortens axially and spreads laterally in the channels defined by the (111) interfacial planes. We have examined the fine structure of deformation bands on the free surface of these deformed samples using AFM to see how the deformation processes interact with the boundaries. By measuring the offset angle at the surface we have been able to show that not only is the macroscopic displacement vector parallel to the lamellar boundaries, but the total shear vector in each layer is also parallel to the lamellar boundaries. However these deformation bands have very different characters, requiring complex deformation processes at the boundaries in order to satisfy this requirement. Some consist of either just super dislocations or just ordinary dislocations with Burgers vectors lying in the interface. But others consist of a special combination of twinning and ordinary dislocations in fixed ratio, such that the net shear vector also lies in the boundary, even though the individual twinning and dislocation shear directions are inclined to it. This results in deformation that is homogeneous and completely ‘channeled’ inside each lamella with no shear vector perpendicular to the lamellar boundaries. We have also shown that the cooperative twinning and slip is homogeneous on the nano-scale, i.e., the twinning and slip occurs in the same volume of material.

The Effect of Materials Testing Mode on Mechanical Behavior Under Temperature Influence in Complex Deformation Processes

2007 ◽  
Author(s):  
S. Anurag ◽  
Y. B. Guo
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Material Testing ◽  
Materials Testing ◽  
Plasticity Model ◽  
Complex Deformation ◽  
Material Constants ◽  
Dynamic Mechanical ◽  
Dynamic Mechanical Behavior ◽  
Deformation Processes

Complex deformation processes such as forming and machining involve large strain, high strain rate, high temperatures, strain rate/temperature coupling, and potential loading history effects. The conventional empirical and semi-empirical plasticity models are not adequate for characterizing dynamic mechanical behavior of work materials at the complex loading scenarios. The accuracy of characterizing the dynamic mechanical behavior in deformation processes using any constitutive models is strongly affected by materials testing data in which a constitutive model is fitted. Tension or compression tests have been widely used to approximate material properties in various manufacturing processes. However, it has been a critical question whether tension or compression test should be utilized for capturing the true nature of complex material deformations. In this study, the influences of two material testing modes on mechanical behavior of AISI52100 steel (62 HRc) were investigated using the internal state variable (ISV) plasticity model. Twenty material constants have been found by nonlinear fitting the ISV plasticity model to the base line test data obtained from each deformation mode. It has shown that the material testing modes have profound effects on some materials constants of the ISV model. The stress sensitivity study to ISV model parameters has identified the critical material constants for reflecting the nature of material deformation. The different testing modes have significant influence on the material constants associated with isotropic hardening rather than kinematic hardening.

scholarly journals Scratching Cu|Au Nanolaminates

Lubricants ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 44 ◽  
Author(s):  
Adrien Gola ◽  
Lars Pastewka
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Layer Thickness ◽  
Wear Track ◽  
Complex Deformation ◽  
Normal Forces ◽  
Deformation Processes ◽  
Dynamics Simulations

We used molecular dynamics simulations to study the scratching of Cu|Au nanolaminates of 5 nm layer thickness with a nanoscale indenter of 15 nm radius at normal forces between 0.5 μ N and 2 μ N. Our simulations show that Au layers wear quickly while Cu layers are more resistant to wear. Plowing was accompanied by the roughening of the Cu|Au heterointerface that lead to the folding of the nanolaminate structure at the edge of the wear track. Our explorative simulations hint at the complex deformation processes occurring in nanolaminates under tribological load.

Scaling Effect on Dynamic Impact Response of Structures in Fluid Fields

2013 ◽  
Author(s):  
Zhongheng Guo ◽  
Lingyu Sun ◽  
Taikun Wang ◽  
Junmin Du ◽  
Han Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Dimensional Analysis ◽  
Large Scale ◽  
Scaling Laws ◽  
Scaling Law ◽  
Fluid Pressure ◽  
Structural Safety ◽  
Scale Model ◽  
Small Scale ◽  
Water Tank

At the conceptual design phase of a large-scale underwater structure, a small-scale model in a water tank is often used for the experimental verification of kinematic principles and structural safety. However, a general scaling law for structure-fluid interaction (FSI) problems has not been established. In the present paper, the scaling laws for three typical FSI problems under the water, rigid body moves at a given kinematic equation or is driven by time-dependent fluids with given initial condition, as well as elastic-plastic body moves and then deforms subject to underwater impact loads, are investigated, respectively. First, the power laws for these three types of FSI problems were derived by dimensional analysis method. Then, the laws for the first two types were verified by numerical simulation. In addition, a multipurpose small-scale water sink test device was developed for numerical model updating. For the third type of problem, the dimensional analysis is no longer suitable due to its limitation on identifying the fluid pressure and structural stress, a simulation-based procedure for dynamics evaluation of large-scale structure was provided. The results show that, for some complex FSI problems, if small-scale prototype is tested safely, it doesn’t mean the full-scale product is also safe if both their pressure and stress are the main concerns, it needs further demonstration, at least by numerical simulation.

The Performance of a Loop Seal in a CFB Boiler

2006 ◽  
Vol 128 (2) ◽  
pp. 135-142 ◽  
Author(s):  
Andreas Johansson ◽  
Filip Johnsson ◽  
Bengt-Åke Andersson
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Fluidized Bed ◽  
Scaling Laws ◽  
Circulating Fluidized Bed ◽  
Vertical Direction ◽  
Scale Model ◽  
Corrosive Environment ◽  
Cfb Boiler ◽  
Load Conditions

High in-bed heat transfer and low corrosive environment imply that the loop seal of a circulating fluidized bed (CFB) boiler is an advantageous location for superheaters. In order to increase the knowledge on the flow pattern and the heat transfer distribution to the tubes within a loop seal, measurements were performed in the loop seal of a 30MW CFB boiler as well as in a 1∕3 scaled-down seal operated according to simplified scaling laws. The scale model measurements show that the solids recirculation flux can be maintained with a substantial decrease of the fluidization flow in the seal compared to that currently used at full load conditions. It was also possible to significantly decrease the fraction of the bottom of the seal that was fluidized without affecting the solids flux through the seal. A gradient in the solids flow were detected in the vertical direction.

Numerical Investigation on the Plastic Response of a Small-Scale Laterally Impacted Tanker Double Hull Structure

2012 ◽  
Author(s):  
Richard Villavicencio ◽  
Young-Hun Kim ◽  
Sang-Rai Cho ◽  
C. Guedes Soares
Keyword(s):  
Dynamic Response ◽  
Strain Rate ◽  
Scaling Laws ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Plastic Response ◽  
Hull Structure ◽  
Double Hull ◽  
The Impact

Numerical simulations are presented, on the dynamic response of a one-tenth scaled tanker double hull structure struck laterally by a knife edge indenter. The small stiffeners of the full-scale prototype are smeared in the small-scale model by increasing the thicknesses of the corresponding plates. The dynamic response is evaluated at an impact velocity of 7.22 m/s and the impact point is chosen between two frames to assure damage to the outer shell plating and stringers. The simulations are performed by LS-DYNA finite element solver. They aim at evaluating the influence of strain hardening and strain rate hardening on the global impact response of the structure, following different models proposed in the literature. Moreover, the numerical model is scaled to its full-scale prototype, summarizing the governing scaling laws for collision analysis and evaluating the effect of the material strain rate on the plastic response of large scaled numerical models.

Seismic Retrofit and Repair of Circular Bridge Columns with Advanced Composite Materials

1999 ◽  
Vol 15 (4) ◽  
pp. 747-764 ◽  
Author(s):  
R. Ma ◽  
Yan Xiao
Keyword(s):  
Brittle Failure ◽  
Plastic Hinge ◽  
Plastic Region ◽  
Experimental Studies ◽  
Seismic Retrofit ◽  
Bridge Columns ◽  
Absorption Capacity ◽  
Scale Model ◽  
Dramatic Improvement ◽  
Lap Splice

Experimental studies on seismic retrofit and repair of typical circular bridge columns with poor lap splice details utilizing prefabricated glass fiber reinforced polymer (FRP) composite jackets and epoxy are presented in this paper. A total of seven tests on three 1/2-scale model columns were conducted. One column was tested under “as-built” condition and the other two columns were retrofitted with prefabricated composite individual and continuous jackets respectively. The jackets were applied in the potential plastic hinge region of the column to increase its lateral confinement. Brittle failure was observed in the “as-built” model column due to the bond deterioration of lap spliced longitudinal reinforcement. This brittle failure was prevented in the retrofitted columns. The repairing of failed “as-built” column by injecting epoxy into damaged plastic region resulted in significant stiffening of the portion and increase of capacity and ductility. The second repair of the specimen using both epoxy injection and prefabricated composite jacketing effectively improved its behavior further. The results of this study indicated that dramatic improvement in ductility and energy absorption capacity of columns can be achieved using these retrofit and repair methods.

scholarly journals Unraveling the Mechanics of Thermal Stress Weathering: Rate‐Effects, Size‐Effects, and Scaling Laws

2019 ◽  
Vol 124 (12) ◽  
pp. 3304-3328 ◽  
Author(s):  
Babak Ravaji ◽  
Víctor Alí‐Lagoa ◽  
Marco Delbo ◽  
Justin W. Wilkerson
Keyword(s):  
Thermal Stress ◽  
Size Effects ◽  
Scaling Laws ◽  
Weathering Rate ◽  
Rate Effects
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