On the fatigue properties of a third generation aluminium-steel butt weld made by hybrid metal extrusion & bonding (HYB)

The paper informs about the research devoted to load–carrying capacity, fatigue strength and life–time of welded steel structures. The experimental programme comprises fatigue tests of constructional steel S380 (QStE 380 TM). In the first stage 35 specimens were tested: 9 without any weld connection, 14 with transverse milled butt weld and 12 with transverse rough butt weld. The applied loading in this stage was harmonic with constant stress range. All tests ended by fatigue failure. The second part of the research comprised the tests with block simulated loading with variable stress range. The third part applied continuous recording of stresses and strains in critical sections, that gave information about the local failure development in time. Data sets have allowed to define fatigue properties of investigated steel and degradation effects of used welds including the initiation time of remarkable changes in stress-strain stage expressed through the total kinetic energy. The degradation effects of welds on fatigue strength of structural steels were confirmed, especially it was the case of rough welds - without additional milling. Additionally, the differences in the fatigue curves inclinations were indicated that can depend on the level of fatigue strength. The applied approach gives an opportunity to analyse the effects of actual loading process and improve the methodology of judgement of fatigue strength and life-time of steel elements. Reasonable fatigue properties of this steel suggest it for using also in severe technology structures.

Download Full-text

Extremely-Low-Cycle Fatigue Damage for Beam-to-Column Welded Joints Using Structural Details

Materials ◽

10.3390/ma13071768 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1768

Author(s):

Lizhen Huang ◽

Weilian Qu ◽

Ernian Zhao

Keyword(s):

Fatigue Damage ◽

Welded Joints ◽

Low Cycle Fatigue ◽

Damage Model ◽

Multiaxial Fatigue ◽

Fatigue Properties ◽

Cycle Fatigue ◽

Butt Weld ◽

Damage Models ◽

Structural Details

The multiaxial fatigue critical plane method can be used to evaluate the extremely-low-cycle fatigue (ELCF) damage of beam-to-column welded joints in steel frameworks subjected to strong seismic activity. In this paper, fatigue damage models using structural detail parameters are studied. Firstly, the fatigue properties obtained from experiments are adopted to assess ELCF life for steel frameworks. In these experiments, two types of welded specimens, namely, plate butt weld (PB) and cruciform load-carrying groove weld (CLG), are designed according to the structural details of steel beam and box column joints, in which both structural details and welded factors are taken into account. Secondly, experiments are performed on three full-scale steel welded beam-to-column joints to determine the contribution of stress and/or strain to damage parameters. Finally, we introduce a modification of the most popular fatigue damage model of Fatemi and Socie (FS), modified by us in a previous study, for damage evaluation, and compare this with Shang and Wang (SW) in order to examine the applicability of the fatigue properties of PB and CLG. This study shows that the modified FS model using the fatigue properties of CLG can predict the crack initiation life and evaluate the damage of beam-to-column welded joints, and can be subsequently used for further investigation of the damage evolution law.

Download Full-text

Fatigue properties of AA6060‐T6 butt welds made by hybrid metal extrusion & bonding

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1111/ffe.13302 ◽

2020 ◽

Vol 43 (10) ◽

pp. 2349-2358

Author(s):

Lise Sandnes ◽

Øystein Grong ◽

Torgeir Welo ◽

Filippo Berto

Keyword(s):

Fatigue Properties ◽

Butt Welds ◽

Metal Extrusion

Download Full-text

Assessment of the Mechanical Integrity of a 2 mm AA6060-T6 Butt Weld Produced Using the Hybrid Metal Extrusion & Bonding (HYB) Process – Part I: Bend Test Results

Procedia Manufacturing ◽

10.1016/j.promfg.2019.06.132 ◽

2019 ◽

Vol 34 ◽

pp. 147-153 ◽

Cited By ~ 2

Author(s):

Lise Sandnes ◽

Luca Romere ◽

Filippo Berto ◽

Torgeir Welo ◽

Øystein Grong

Keyword(s):

Bend Test ◽

Test Results ◽

Butt Weld ◽

Mechanical Integrity ◽

Metal Extrusion

Download Full-text

An Experimental Study for Fatigue Performance of 7% Nickel Steels for Type B LNG Carriers

Volume 5: Materials Technology; Petroleum Technology ◽

10.1115/omae2014-23885 ◽

2014 ◽

Cited By ~ 1

Author(s):

Young Woo Kim ◽

Jae Myung Lee ◽

Myung Hyun Kim ◽

Byeong Jae Noh ◽

Hee Joon Sung ◽

...

Keyword(s):

Cryogenic Temperature ◽

Storage Systems ◽

Nickel Content ◽

Fatigue Performance ◽

Structural Safety ◽

Fatigue Properties ◽

High Price ◽

Nickel Steel ◽

Type B ◽

Butt Weld

The most important issue associated with liquefied natural gas storage systems, such as LNG carriers, LNG FPSO and FLNG, is the structural safety. One of the most common materials for the LNG storage systems has been 9% nickel steel over the last 50 years as it has excellent mechanical properties under cryogenic temperature. Recently, the consideration for lowering the nickel content becomes necessary due to the increase of the nickel price and the high price of nickel based welding consumables. In this respect, 7% nickel steels are developed for cryogenic applications. Nippon Steel and Sumitomo Metals Corporation have developed 7% nickel steels with improved toughness comparable to that of 9% nickel steels by TMCP and micro-alloying technology. The major objective of this study is to evaluate the fatigue performance of 7% nickel steels with a special attention to Type B LNG carrier applications. Cyclic fatigue and fatigue crack growth rate (FCGR) tests for 7% nickel steels were conducted at room and cryogenic temperature. Fatigue tests were carried out with three types of specimens such as base metal, butt weld and fillet weld to characterize the fatigue properties. Also FCGR tests were carried out using compact tension specimens. The difference of FCGR characteristics among base, weld and HAZ (Heat Affected Zone) are investigated for three types of specimens. The results of 7% nickel steels are evaluated and compared with those of 9% nickel steels.

Download Full-text