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Author: American Concrete Institute. Committee 446
Publisher:
ISBN: 9780870311529
Category : Concrete
Languages : en
Pages : 29
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Book Description
Author: American Concrete Institute. Committee 446
Publisher:
ISBN: 9780870311529
Category : Concrete
Languages : en
Pages : 29
Get Book Here
Book Description
Author: Jung-Heum Yon
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 368
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Book Description
Author: Jung H. Yon
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 142
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Book Description
A displacement controlled dynamic test system and instrumentation for dynamic fracture testing of concrete specimens, was developed. Also a hybrid experimental-numerical procedure for evaluating the dynamic fracture data thus generated was developed. The experimental data consisted of the applied load and transient strains in single edge notched, three point bend specimens which were subjected to controlled displacement loading. In addition, moire interferometry data was obtained in three point bend specimens subjected drop weight loading. Also the applied load, transient strains and crack opening displacement were measured in crack-line wedge-loaded, double cantilever beam specimens which were subjected to controlled wedge displacement loading. These test systems and the hybrid analysis were used to determine the strain rate sensitivity of the elastic properties and the fracture process zone of rapidly fracturing concrete specimens. The increase in both tensile and compressive moduli of elasticity and the tensile strength with increasing strain rate were quantified. The fracture process zone decreased in magnitude with increasing strain rate but the tensile strength necessary to propagated the tip of the fracture process zone under a tensile strength criterion increased substantially with the strain rate. The net effect was that dynamic fracture responses of a rapidly propagating crack in concrete resembled that of linear elasto-dynamic fracture mechanics with influence of the fracture process zone decreasing with increasing strain rate of loading. (sdw).
Author: Jiaji Du
Publisher:
ISBN:
Category :
Languages : en
Pages : 295
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Book Description
Static and dynamic analyses of concrete failure based on fracture mechanics were conducted using crack-line wedge-loaded, double cantilever beam (CLWL-DCB) and edge-cracked, three point bend specimens under Mode I loading conditions, aimed at developing a mathematical model which describes the tensile failure process of concrete materials at the macro-level. The fracture process zone associated with a stably growing crack in concrete was determined by a hybrid experimental-numerical technique where a crack closure stress versus crack opening displacement (COD) relation of a finite element model of the specimen was optimized to fit the COD data, obtained by Moire interferometry with real reference grating, and other experimental measurements. For the first time, the crack closure stress versus COD relation of a fracture process zone in concrete was determined directly and was found to be similar to those obtained by others using inverse procedures. The crack closure stress versus COD relation for the two CLWL-DCB and edge-cracked, three point bend specimens were identical thus implying that this relation is a specimen-independent but material-dependent constitutive relation. The above static constitutive relation, with modifications to account for the differences in tensile strengths and aggregate sizes, were used to simulate the recorded dynamic crack propagation in large scale, impacted three point bend specimens (unnotched) by Mindess and the Charpy type impact tests by Shah. In both cases, dynamic finite element modeling with the adjusted constitutive equations for the fracture process zones simulated the measured crack propagation histories within the experimental accuracies. (kr).
Author: Nadarajah Somaskanthan
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 248
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Book Description
Author: Arun Shukla
Publisher: World Scientific
ISBN: 9812773320
Category : Technology & Engineering
Languages : en
Pages : 374
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Book Description
Covering a wide variety of topics in dynamic fracture mechanics, this volume presents state-of-the-art experimental techniques and theoretical analysis on dynamic fracture in standard and exotic materials. Written by world renowned researchers, this valuable compendium contains eleven chapters on crack initiation, crack propagation, crack arrest, crack-stress wave interactions, and experimental, analytical and numerical methods in dynamic fracture mechanics. Contents: Modeling Dynamic Fracture Using Large-Scale Atomistic Simulations (H-J Gao & M J Buehler); Dynamic Crack Initiation Toughness (D Rittel); The Dynamics of Rapidly Moving Tensile Cracks in Brittle Amorphous Material (J Fineberg); Optical Methods for Dynamic Fracture Mechanics (H V Tippur); On the Use of Strain Gages in Dynamic Fracture (V Parameswaran & A Shukla); Dynamic and Crack Arrest Fracture Toughness (R E Link & R Chona); Dynamic Fracture in Graded Materials (A Shukla & N Jain); Dynamic Fracture Initiation Toughness at Elevated Temperatures with Application to the New Generation of Titanium Aluminides Alloys (M Shazly et al.); Dynamic Fracture of Nanocomposite Materials (A Shukla et al.). Readership: Researchers, practitioners, and graduate students in fracture mechanics and materials science.
Author: NM. Hawkins
Publisher:
ISBN:
Category : Concrete fracture
Languages : en
Pages : 11
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Book Description
Fifteen identical three-point bend concrete specimens with an offset precrack were subjected to the same impact load to failure and the transient moire interferometric fringes associated with the diagonally propagating crack were recorded. The crack opening displacement (COD) and the crack sliding displacement (CSD) were derived from the moire fringe patterns and used together with the measured impact load to drive a dynamic finite element code in the propagation mode. The result of an inverse analysis using this hybrid experimental-numerical procedure showed that contrary to other findings, the crack shearing stress (CSS) in the presence of the COD was negligible but increased the crack closing stress (CCS) in the CCS versus COD relation over that of mode I fracture.
Author: K. Ravi-Chandar
Publisher: Elsevier
ISBN: 0080472559
Category : Science
Languages : en
Pages : 265
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Book Description
Dynamic fracture in solids has attracted much attention for over a century from engineers as well as physicists due both to its technological interest and to inherent scientific curiosity. Rapidly applied loads are encountered in a number of technical applications. In some cases such loads might be applied deliberately, as for example in problems of blasting, mining, and comminution or fragmentation; in other cases, such dynamic loads might arise from accidental conditions. Regardless of the origin of the rapid loading, it is necessary to understand the mechanisms and mechanics of fracture under dynamic loading conditions in order to design suitable procedures for assessing the susceptibility to fracture. Quite apart from its repercussions in the area of structural integrity, fundamental scientific curiosity has continued to play a large role in engendering interest in dynamic fracture problems In-depth coverage of the mechanics, experimental methods, practical applications Summary of material response of different materials Discussion of unresolved issues in dynamic fracture
Author: T. Belytschko
Publisher:
ISBN:
Category :
Languages : en
Pages : 33
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Book Description
Closed form solutions have been developed for wave propagation problems in materials which have a constitutive equation with strain softening (SS). These solutions have been useful in assessing the performance of finite element programs and in examining the validity of SS models from physical grounds. The salient characteristics of these wave propagation solutions with SS is that the strain softening localizes into a domain of one-dimension smaller than the space of the problem: for example, in a one-dimensional wave propagation problem, the strain softening localizes to a single point where strain softening is first initiated. Furthermore, if the stress goes to zero as the strain increases in the SS discontinuity is introduced in the displacement. A more serious shortcoming is the absence of energy dissipation in the SS part of the continuum. This absence is due to the extreme localization of the SS phenomenon. Since strain-softening models are usually intended to model dissipative processes such as microcracking or crushing of material, the absence of dissipation is quite troublesome. To overcome this drawback of the SS continuum model, a nonlocal theory was examined. In a non-local theory, the stresses depend on an average of the strain in a volume about the point at which the stress is being computed. In this type of theory, the localization which is characteristic of strain softening solutions can be limited and a finite amount of energy dissipation which is relatively insensitive to element size, can be achieved. Keywords: Concrete; Structures; Failures; Size effects.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 93
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Book Description
A hybrid experimental-numerical procedure was used to analyze the micro-mechanics of the mixed-mode, static and dynamic fracture of a concrete three-point bend specimen with an offset precrack. Four/two beam moire interferometry was used to record simultaneously separating horizontal and vertical displacements associated with stable/rapid growth. An elasto-static/ elasto-dynamic finite element code was execute in its propagation mode with assumed crack closure stress (CCS) versus crack opening displacement (COD) and crack shearing stress (CSS) versus crack sliding displacement (CSD) relations which were adjusted to match the computed and measured COD's and CSD's. The resultant CCS versus COD and the CSS versus CSD relations were then used to compute the dissipated energy in the FPZ. This energy dissipation rate in the FPZ accounted for about 80% of the total energy release rate throughout the dynamic fracture process. This study also showed that the strain energy released at the crack tip and the dissipated energy in the fracture process zone after crack kinking are due mainly to mode I crack tip) deformation.
