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Tuesday, July 14, 2020 | History

2 edition of Micro-mechanisms of fracture in transition welds found in the catalog.

Micro-mechanisms of fracture in transition welds

Su-Jun Wu

Micro-mechanisms of fracture in transition welds

by Su-Jun Wu

  • 18 Want to read
  • 28 Currently reading

Published by University of Birmingham in Birmingham .
Written in English


Edition Notes

Thesis (Ph.D) - University of Birmingham, School of Metallurgy and Materials, Faculty of Engineering.

Statementby Su-Jun Wu.
ID Numbers
Open LibraryOL17873294M

In the present study, the crack opening displacement (COD) tests of specimens of C-Mn base and weld steel were carried out in the ductile-brittle transition temperature region. The majority of the specimens were fractured and others were unloaded prior to fracture after ductile fracture initiated and extended. Engineers must also consider the feasibility of fabricating the structural hardware in the material selection process. During the past few decades, fracture mechanics has become a necessary discipline for the solution of many structural problems in which the survivability of structure containing pre-existing flaws is of great interest.

It has been found that fracture appearance transition temperature of the weld metal depends on the size of intragranular bainite (acicular ferrite) nucleated on oxide inclusions and that the upper shelf energy is affected by the density of dispersive oxides inclusions. Topics Covered: Basic fracture mechanics, atomic view of fracture, Griffith energy criterion, energy release rate R and driving force curves, stress analysis, crack tip plasticity, mixed mode fracture, crack tip opening displacement, J Integral, J-CTOD relationships, crack growth resistance curves, J controlled fracture,dynamic fracture, rapid crack propagation/arrest, .

@article{osti_, title = {Effect of weld metal mismatch on fracture mechanics parameters}, author = {Lee, M M.K. and Luxmoore, A R}, abstractNote = {This paper presents the results of a combined experimental and numerical investigation into the effect of weld metal mismatch on the fracture behavior of single edge notch bend specimens. Brittle fracture, due to the loss of plasticity, was first studied as early as the second half of the 19 th century. With the development of welding and its application to the construction of large-scale structures, a certain number of spectacular, often catastrophic, failures have occurred.


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Micro-mechanisms of fracture in transition welds by Su-Jun Wu Download PDF EPUB FB2

The majority of research activities in fracture mechanics involve welding of structures. The discipline does not only provide a means for selecting steels suited for welding, but also serves a useful purpose in quality control.

It can characterize the influence of micro-alloy and carbon-manganese steel weld joints in fracture toughness. Generally, the fracture mechanics assessment procedure assumes that the crack is located in an homogeneous material of uniform tensile and toughness properties, adopting either the weld metal properties, or the lowest tensile properties and the lowest toughness value of the base metal or the weld metal.

This book provides a comprehensive and thorough guide to those readers who are lost in the often-confusing context of weld fatigue. It presents straightforward information on the fracture mechanics and material background of weld fatigue, starting with fatigue crack initiation and short cracks, before moving on to long cracks, crack closure, crack growth and threshold, residual.

Constraint Effects and Fracture of Micro-mechanisms of fracture in transition welds book the effects of constraint, including crack-front stress fields, plane-strain fracture toughness/constraint to predict the applied stress-intensity factor/constraint, the location around the perimeter where crack growth initiation will occur, and T-stress in analyses of fracture toughness data.

Similar transition of failure location has been reported in for testing at room temperature. The only one fracture at HAZ of 9%Cr is incidental due to a large welding-related pore being the crack nucleation site, which will be discussed by: 7. There was a transition from the ductile tear to quasi-cleavage from the middle to the top of the weld fracture surface.

This is consistent with Zadpoor et al. [20] where brittle regions were formed in the top of the sheet which underwent severe plastic deformation when in contact with the rotating tool shoulder. Besides the weld imperfections there are additional possible sites of cracks initiation in welded joints.

These are the weld toe transition in fillet and butt welds, the root gap of fillet welds and the weld bead itself. Stress analysis for fracture mechanics. Fracture Definition • Theessence offast fracture is that it is a failure mechanismthat involves the unstable propagation ofa crackina structure.

• This is sometimes described as brittle fracture, althoughthe micro mechanisms bywhich cracks propagate maybeanything from low-straincleavage to fully ductile shear separation.

Fatigue and fracture are significant failure modes of ships as history and recent service experience have shown. Associated failures have to be avoided or at least controlled to exclude costly repairs and catastrophic events.

Fatigue and fracture became significant in the middle of the twentieth century. Introduction to Fracture Mechanics David Roylance Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 2.

The Micro-Mechanisms of Fracture in Steels Used for High Integrity Structural Components 3. Welds, Their Quality and Inspection Ability for High Integrity Structures and Components 4. Material Conditions That Lead to Crack Arrest 5.

Fracture Toughness - A Measurable Materials Parameter 6. Microstructural Development in RPV Steels 7. The German guideline “Fracture Mechanics Proof of Strength for Engineering Components” has been released in as a result of activities sponsored by the Research Committee on Mechanical Engineering (FKM), task group “Component Strength”.

The guideline describes basics for the integrity assessment of cracked components subjected to static or cyclic loading and. assessment techniques to weld fracture.

In the first study, the fracture behavior of an overmatched butt weld containing a buried, lack-of-penetration defect was predicted and verified experimentally. The second study examined computationally the effect of residual stresses on constraint conditions and subsequent fracture in a cracked weld.

The weld deposited with controlled levels of Nb and V was further tested in different joint configurations and base plate thickness. The fracture toughness was evaluated by CTOD testing of the weld in two different thicknesses (50 mm and 70 mm).

Increased specimen thickness resulted in lower CTOD values. This work examines the fracture behavior of ferritic steel welds in the transition temperature regime, where failure can occur either by ductile tearing or cleavage fracture.

A computational and probabilistic-based mechanistic approach to cleavage fracture and ductile crack growth is adopted to model the fracture processes. brittle fracture initiation character­ istics of the bond and the weld metal is shown in Fig. Likewise shown are the edge preparations of test specimen for the bond in the case of manual welding with a heat input of 13, joules/cm; the automatic welding or the submerged-arc welding, 35, joules/cm; and the automatic.

For ceramics, this type of transition occurs at much higher temperatures than for metals. The ductile-to-brittle transition can be measured by impact testing: the impact energy needed for fracture drops suddenly over a relatively narrow temperature range – temperature of the ductile-to-brittle transition.

Ductile-to-brittle transition. Most of the fracture toughness tests gave reasonably high values of CTOD (above mm for the GMAW welds tested at °C, and above mm for the SMAW welds tested at °C). However, a number of specimens did give very low fracture toughness values (below mm) in both welds; either due to pop-ins or critical fracture events.

In the bcc transition metals such as iron and carbon steel, brittle and improper welding can lead to brittlen ess both by alt While there are a number of books on fracture mechanics, most.

Ductile-brittle transition region In this region, micro-mechanisms of cleavage fracture cause that the cleavage toughness data tend to be highly scattered when compared to the lower shelf region, and thus a statistical analysis must be performed as shown in Table 3.

nuclear pressure vessels. Additionally, KIcvalues for steels tested at various temperatures and loading rates are required for correlation with small-scale production control tests (such as the Charpy V-notch test) for setting material specifications and fracture-safe design procedures.[Show full abstract] the different fracture modes of DP weld.

Experimental results show that the model is effective on mm and mm DP welds and is also better than other evaluation.This talk will explain fracture mechanisms, the use of the ductile-to-brittle transition curve, and also describe how materials and welding engineers are involved in controlling the fracture performance of steel structures.

Bio. Doug holds BS, MS, and PhD degrees in Welding .