Strain concentration effects in large structures

1965 ◽  
Vol 285 (1400) ◽  
pp. 46-57 ◽  
Keyword(s):  
Steel Structures ◽  
Fracture Initiation ◽  
Simple Calculation ◽  
Crack Arrest ◽  
Stress Concentrations ◽  
Concentration Effects ◽  
Large Structures ◽  
Inclusion Distribution ◽  
Large Sections

When a large structure is subject to a temperature lower than the crack-arrest temperature of the particular steel from which it is built, the problem of fracture initiation at stress concentrations becomes of paramount importance. On the basis of the attainment of a critical local displacement as the criterion for fracture initiation, a theoretical analysis has been undertaken on some aspects of the fracture of large sections. In particular a simple calculation has been made for the fracture stress of a large plate containing a notch, and it has been shown that the results are identical for small stresses with those given by the fracture mechanics approach, which was developed from energetic considerations. If a steel is very brittle, then inclusions or small defects may act as the cracks from which final fracture is initiated; consideration has been given to the role of inclusion distribution on the behaviour of steel structures.

Argumentation theory: competition between modern research approaches

2018 ◽  
pp. 77-87
Author(s):  
Анатолий Мигунов ◽  
Anatoliy Migunov ◽  
Елена Лисанюк ◽  
Elena Lisanyuk
Keyword(s):  
Social Life ◽  
Critical Discussion ◽  
Procedural Semantics ◽  
Social Success ◽  
Large Structures ◽  
Criteria Importance ◽  
Practical Argumentation ◽  
Argumentative Structure ◽  
Theory Competition

To overcome the crisis in the sphere of argumentation studies, the project proposes a logical-cognitive concept of argumentation which is a compound formalized theory that includes formalisms for modeling argumentation of different types, a relevant conceptual framework and a methodology for the use of scientific research in the practice. Three types of argumentation are defined: theoretical (two types) and practical. Theoretical argumentation is a critical discussion of the agents’ knowledge and opinions about facts aimed to substantiate a certain view or to change it – i.e. persuasion. Practical argumentation is a critical discussion of opinions about actions which includes, in addition to the statements about knowledge and opinions, statements of a non-descriptive nature about the agents’ values and intentions to adhere to a certain line of behavior. The study of argumentation needs to focus on the large structures that reflect specifics of the criticism and defense of the positions of the parties. An atom unit of such study is the argument as a statement of reason, while its molecular elements are the argumentative structure of a dispute (frame), a multitude of arguments that express the parties’ positions, a multitude of the agents’ knowledge and opinions that act as the bases for the formation of positions, lines of behavior, etc. Within the framework of this trend, both indefeasible (deductive) and defeasible argumentations can be studied. The argumentation effectiveness can be assessed based on the procedural semantics and using analogues of such logical notions as consistency and completeness. Modern approaches to the argumentation, including those claiming the compound status, can be classified using two methods: based on the substantive and practical criteria. Importance of the research outcomes amounts to the theoretical and methodological role of the new conception of argumentation and the general “umbrella” term argumentation that allows systematizing the manifold research and educational approaches and concepts in this field and is associated with communicative nature of modern social life where efficiency and social success rely on argumentative and narrative competences.

scholarly journals A Simplified Method for the Design of Steel Beam-to-column Connections

2017 ◽  
Vol 48 (2) ◽  
pp. 79-86
Author(s):  
Imola Kristóf ◽  
Zsanett Novák ◽  
Dezső Hegyi
Keyword(s):  
Failure Modes ◽  
Steel Structures ◽  
Simple Calculation ◽  
Geometric Parameters ◽  
End Plate ◽  
Simplified Method ◽  
Eurocode 3 ◽  
Steel Sections ◽  
The Moment ◽  
Hot Rolled

The moment resistance of beam-to-column connections is frequently utilised in steel structures. Eurocode 3 suggests the component method to analyse such connections, and it implements the equivalent T-stub method to determine the resistance of the end plate of the beam. The latter method requires tedious and concentrated work. A simplified method is suggested to reduce the number of calculations and enable the designer to focus on construction aspects in the pre-design phase, or in education.The resistance of the T-stub covers three possible failure modes: the yield of the plate, the failure of the of the bolt and simultaneous yield. The yield of the plate and simultaneous yield depend on numerous parameters, and they are verified by multiple equations. The failure of the bolts are more easily checked.In the present paper, requirements for geometric ratios are defined for the widely used steel sections to assure failure of the bolts at a lower level of the load than the yield of the plate. These parameters facilitate the simple calculation of the resistance of the bolts instead of the tedious work needed for the end plate resistance.The paper presents a proper explanation for the design rules and the effect of the geometric parameters on the resistance of the end plate. Geometric parameters are suggested for the widely used hot rolled and typical welded beam sections. All the parameters fulfil the requirements of the equivalent T-stub method of Eurocode 3.

Role of Stress Concentrations on the Electrochemical Response of a Li-Ion Battery Anode Particle

2019 ◽  
Vol 166 (12) ◽  
pp. A2574-A2588 ◽  
Author(s):  
Mohammad Ayub Ansari ◽  
Pramod Yallappa Kumbhar ◽  
Narasimhan Swaminathan
Keyword(s):  
Li Ion Battery ◽  
Stress Concentrations ◽  
Electrochemical Response ◽  
Li Ion ◽  
Battery Anode

Dimensioning against fatigue - stress-based approach or fracture mechanics?

2006 ◽  
Vol 220 (8) ◽  
pp. 1109-1120
Author(s):  
H-P Gänser ◽  
K Glinsner ◽  
W Eichlseder
Keyword(s):  
Crack Length ◽  
Crack Arrest ◽  
Accurate Estimate ◽  
Formal Structure ◽  
Structural Stress ◽  
Propagation Condition ◽  
Stress Concentrations ◽  
Notch Radius ◽  
Sharp Crack ◽  
Limiting Case

The non-propagation condition of a sharp crack introduced in the root of a generic notch is investigated. Thus, pre-existing flaws near structural stress concentrations are advantageously treated in a unified manner, giving in the limit of vanishing notch radius the case of a crack in an unnotched component, and in the limit of vanishing crack length the classical engineering case of a notched, crack-free component. Particular focus is put on the limiting case of vanishing crack length. The results are compared with the classical engineering strength estimate following the nominal stress concept. It is shown that both concepts may, with minor differences, be brought into the same formal structure. The transition between notch-like and crack-like behaviour of notches is investigated in some detail, giving an accurate estimate for the transition between both regimes as well as reliable lower bounds for the fatigue strength in both regimes with special consideration of crack arrest effects in flawed components.

Role of Deformable Fine Spinel Particles in High-Strain-Rate Superplastic Flow of Tetragonal ZrO2

2004 ◽  
Vol 821 ◽  
Author(s):  
Koji Morita ◽  
Keijiro Hiraga ◽  
Byung-Nam Kim ◽  
Yoshio Sakka
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Flow Behavior ◽  
Grain Boundary Sliding ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
Stress Concentrations ◽  
Tensile Direction

AbstractThe role of MgAl2O4 spinel particle dispersion in high-strain-rate superplasticity (HSRS) of tetragonal ZrO2 was examined by characterizing microstructural changes during deformation. The dispersed spinel particles elongate with strain along tensile direction and the elongation tends to be pronounced with increasing strain rate. In the elongated spinel particles, intragranular dislocations lying along the elongated direction were observed, suggesting that the elongation relates to the dislocation motion. The flow behavior characterized by a stress exponent of ≈ 2.0 suggests that grain boundary sliding (GBS) is the predominant flow mechanism. The dislocation-induced plasticity in the spinel particles may assist the relaxation of stress concentrations exerted by GBS, leading to HSRS in tetragonal ZrO2.

Evaluation of Experiments on Semi-Large Scale Specimens With Underclad Cracks With Focus on Constraint Evaluation

2008 ◽  
Author(s):  
Dana Lauerova ◽  
Milan Brumovsky
Keyword(s):  
Large Scale ◽  
Failure Process ◽  
Fracture Initiation ◽  
Pressure Vessels ◽  
Experimental Results ◽  
Elastic Plastic ◽  
T Stress ◽  
The Moment ◽  
Embedded Crack

During years 2005–2006, a series of semi-large scale experiments on specimens containing underclad (embedded) crack were performed in NRI Rez. The experiments were performed in the frame of EU PHARE project EUROPAID/116529/D/SV/CZ, in cooperation with VTT, FNS, TVONS (Finland) and Tecnatom (Spain). The aim of the project was to investigate fracture mechanics properties of cladding, in particular, to establish the role of cladding in the fracture/failure process of the specimens, and to exploit the obtained knowledge in the procedure for evaluation of integrity of WWER reactor pressure vessels. Experimental results of the project are described in details in parallel paper [1]. In the present paper, brief summary of experimental results is provided, and FE evaluation of the experiments is described, with focus on constraint evaluation. FE evaluation covers, among others, evaluation of J-integral in the moment of cleavage fracture initiation (1st pop-in or sudden fracture through) for both upper and lower crack fronts, and evaluation of some type of constraint parameter. Three types of constraint parameter were calculated: T-stress based on elastic calculation, T-stress based on elastic-plastic calculation and Q-parameter. In the paper, detailed development of elastic-plastic T-stress as well as Q-parameter with loading is presented for one specimen that sustained the highest load. Besides of that, the approach of effective stress intensity factor KIeff is examined in the paper, and results of sensitivity analysis with respect to uncertainty concerning the way in which the effect of constraint is included into the KIeff approach are presented.

Yielding and Plastic Flow in Stainless Steel: A TEM Study of the Evolution of Microstructure Associated with the Stress-Strain Diagram

1980 ◽  
Vol 38 ◽  
pp. 386-387
Author(s):  
L.E. Murr ◽  
S-H. Wang
Keyword(s):  
Grain Boundaries ◽  
Elastic Stress ◽  
Metals And Alloys ◽  
Strain Diagram ◽  
Stress Concentrations ◽  
Polycrystalline Metals ◽  
Pile Up ◽  
Local Slip ◽  
Evolution Of Microstructure

In spite of the fascination with dislocation pile-ups and the description of flow in metals and alloys based upon pile-up models, evidence has existed for decades suggesting that slip often if not always starts at grain boundaries in polycrystalline metals and alloys. Hook and Hirth showed that elastic incompatibility could result in local slip at the boundary between bicrystals, and their contention that local elastic stress concentrations at grain boundaries would aid slip nucleation was confirmed by Carrington, etal. Ashby has also described polycrystalline metals and alloys as plastically non-homogeneous because gradients of plastic deformation are imposed by the grain boundaries, and Murr has discussed the role of grain boundary ledges as initial sources for dislocations when polycrystalline metals and alloys are deformed. Brentnall and Rostoker earlier concluded that grain boundaries are both sources of early dislocations and barriers limiting their movement at higher stresses, and that slip is confined to grains in which it was initiated until the yield point is reached.

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