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Predicting ductile fracture in steel connections.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Predicting ductile fracture in steel connections./
Author:	Wen, Huajie.
Description:	1 online resource (236 pages)
Notes:	Source: Dissertation Abstracts International, Volume: 78-03(E), Section: B.
Contained By:	Dissertation Abstracts International78-03B(E).
Subject:	Civil engineering. -
Online resource:	click for full text (PQDT)
ISBN:	9781369050394

Predicting ductile fracture in steel connections.
Wen, Huajie.

Predicting ductile fracture in steel connections. - 1 online resource (236 pages)

Source: Dissertation Abstracts International, Volume: 78-03(E), Section: B.

Thesis (Ph.D.)

Includes bibliographical references

This item is not available from ProQuest Dissertations & Theses.

Separation of material, known as fracture, is one of the ultimate failure phenomena in steel elements. Preventing or delaying fracture is therefore essential for ensuring structural robustness under extreme demands. Despite the importance of fracture as the final stage during inelastic response of elements, the underlying mechanisms and the factors influencing the onset and progression of fracture have not been fully investigated. This is particularly the case for ductile fracture where significant pre-crack deformations are present. Existing approaches geared at predicting brittle fracture, marked by little to no plastic deformation, have been proven inadequate for capturing ductile fracture. Ductile fracture is dependent on two stress state parameters, the stress triaxiality and Lode parameter, which correspond, respectively, to two kinds of work hardening damage -- that is hydrostatic and deviatoric stress components. The role of stress triaxiality on ductile fracture has been well defined and implemented in various models over the past several decades. Only until recently, however, has the role of Lode parameter been identified as an important factor for accurate prediction of ductile fracture. In general, no reliable fracture prediction methods are present that are consistent throughout the whole range of stress states, where the stresses are dominated by either tension loading, shear loading, or a combination of both.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9781369050394Subjects--Topical Terms:

561339
Civil engineering.
Index Terms--Genre/Form:

554714
Electronic books.

Predicting ductile fracture in steel connections.
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100 1 $a Wen, Huajie. $3 1180243
245 1 0 $a Predicting ductile fracture in steel connections.
264 0 $c 2016
300 $a 1 online resource (236 pages)
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500 $a Source: Dissertation Abstracts International, Volume: 78-03(E), Section: B.
500 $a Adviser: Hussam N. Mahmoud.
502 $a Thesis (Ph.D.) $c Colorado State University $d 2016.
504 $a Includes bibliographical references
506 $a This item is not available from ProQuest Dissertations & Theses.
520 $a Separation of material, known as fracture, is one of the ultimate failure phenomena in steel elements. Preventing or delaying fracture is therefore essential for ensuring structural robustness under extreme demands. Despite the importance of fracture as the final stage during inelastic response of elements, the underlying mechanisms and the factors influencing the onset and progression of fracture have not been fully investigated. This is particularly the case for ductile fracture where significant pre-crack deformations are present. Existing approaches geared at predicting brittle fracture, marked by little to no plastic deformation, have been proven inadequate for capturing ductile fracture. Ductile fracture is dependent on two stress state parameters, the stress triaxiality and Lode parameter, which correspond, respectively, to two kinds of work hardening damage -- that is hydrostatic and deviatoric stress components. The role of stress triaxiality on ductile fracture has been well defined and implemented in various models over the past several decades. Only until recently, however, has the role of Lode parameter been identified as an important factor for accurate prediction of ductile fracture. In general, no reliable fracture prediction methods are present that are consistent throughout the whole range of stress states, where the stresses are dominated by either tension loading, shear loading, or a combination of both.
520 $a In this study, a new ductile fracture criterion based on monotonic loading conditions is first developed based on analysis and definitions of the two stress state parameters and subsequently extended to the reverse/cyclic loading conditions. The extension from monotonic to cyclic loading is based fundamentally on the fact that as long as large pre-crack plastic strain fields exist, the inherent mechanism in both loading cases can be viewed to be the same. Although the inherent mechanism is the same for both loading cases, extending the model to the reverse loading conditions required the inclusion of the effects of nonlinearity of the damage evolution rule as well as the loading history. The two criteria, monotonic and cyclic, are then validated on the coupon specimen level through comparisons between predicted fracture strains and their experimental equivalents for various metal types and steel grades that are available in the literature. The newly developed models offer improvements to existing known ductile fracture criteria in terms of both accuracy and practicality.
520 $a Following the validation of the fracture model on the coupon specimen level, the model is employed on the connection level, up to and including failure, to evaluate block shear failure for gusset plate and coped beam connections under monotonic loading and shear links under cyclic loading. The chosen connection types are dependent on stress triaxiality (tension) and Lode parameter (shear) and are therefore appropriate for the validation of the ductile fracture model. For the block shear failure, prediction accuracy is verified through comparisons with results from corresponding laboratory tests, in the perspective of load versus displacement curves, fracture profiles, and fracture sequences. Some underlying mechanism of block shear is also explored and explained for the first time. Following the same modeling procedure, parametric studies on geometric effects on block shear failure is conducted. Three different block-shear failure modes and one bolt hole tear out mode are captured in the simulations and suggestions on design code changes are provided. For the shear links, which are typically employed in Eccentric Braced Frames, simulation of fracture under reverse/cyclic loading is also conducted and verifications are performed through comparisons with their previous experimental results. The fracture-associated variables are included in the cyclic loading analysis through deriving an implicit integration algorithm for the material constitutive equations with combined hardening, which was integrated in the simulation using a user-defined material subroutine VUMAT.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
650 4 $a Civil engineering. $3 561339
650 4 $a Mechanical engineering. $3 557493
655 7 $a Electronic books. $2 local $3 554714
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690 $a 0548
710 2 $a ProQuest Information and Learning Co. $3 1178819
710 2 $a Colorado State University. $b Civil and Environmental Engineering. $3 1178865
773 0 $t Dissertation Abstracts International $g 78-03B(E).
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10149943 $z click for full text (PQDT)