Fatigue Crack Growth Analysis of Mild Steel Plate Welded by Friction Stir Welding

2013 ◽  
Author(s):  
K. N. Pandey ◽  
Saurabh Kumar Gupta
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Friction Stir Welding ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Mild Steel ◽  
Crack Growth ◽  
Base Metal ◽  
Steel Plate ◽  
Friction Stir

Parts and structures are often welded together in different ways, as it is cost and weight effective in comparison to conventional bolted and riveted joints. Steel followed by aluminum alloys, are the most frequently welded metal. Welding results in inhomogeneous and different materials near the joint which may lead to defects. These defects may be the cause of initiation and development of cracks as a result of cyclic loading. In the present work fatigue crack growth rate of a mild steel plate welded by friction stir welding (FSW) has been studied under constant amplitude load with different values of R-ratio. Hardness in the base metal was found to be low in comparison to thermo-mechanically affected and weld nugget zone. Grain size of weld zone was much smaller to base metal and it was the same to heat affected zone and base metal. A C-T specimen with notch at welded and non welded region was tested to get the behavior of Fatigue Crack Growth (FCG) at different zones. It has been found that the fatigue crack growth rate in welded material is lower as compared to base material.

Fatigue Crack Growth Behavior of Friction Stir Welding of 6063-T5 Aluminum Alloys

2010 ◽  
Vol 146-147 ◽  
pp. 1498-1501
Author(s):  
Supachai Surapunt
Keyword(s):  
Fatigue Crack ◽  
Friction Stir Welding ◽  
Aluminum Alloys ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Base Metal ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Friction Stir

The microstructure and fatigue crack growth behavior of friction stir welding of 6063-T5 aluminum alloys were investigated. For this propose, fatigue crack growth curves were determined in four different locations of notch, which are base metal, middle of welded zone (parallel to weld line), near interface and interface (shoulder limits). The crack initiation and crack propagation of the base metal specimens presented slower than those of stir welded specimens. The microstructure observations show that the grain sizes in stir welded zone are finer than that in the unaffected base material and in the heat affected zone.

Fatigue Crack Growth on FSW AA2024-T3 Aluminum Joints

2012 ◽  
Vol 498 ◽  
pp. 126-138 ◽  
Author(s):  
Pedro Miguel Guimarães Pires Moreira ◽  
Paulo Manuel Salgado Tavares de Castro
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Solid State ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Base Material ◽  
Welding Process ◽  
Butt Joints ◽  
Friction Stir

Friction stir welding (FSW) is a solid-state joining process which emerged as an alternative technology to join high strength alloys that were difficult to weld with conventional techniques, [1]. Developments of this technique are being driven by aeronautic, aerospace and railway industries. An advantage of this joining technique is its low heat input when compared with arc welding processes. This feature allows the achievement of high mechanical properties, low distortion and low residual stresses, [2]. Also, since it is a solid-state welding process, hydrogen cracking or heat affected zone (HAZ) softening phenomena are limited. This paper presents a study of fatigue crack growth behaviour of friction stir welded butt joints of AA2024-T3, aluminium commonly used in riveted aeronautic fuselage structures. Crack growth studies are often carried out using uniform thickness joints, ASTM E647 [3]. Nevertheless, for some applications there is a need to join components with different thicknesses, which, under certain limits, can be welded using FSW. Crack growth tests on these joints are not standard. The present study concerns butt joints made using two plates with different thicknesses, 3.8mm and 4.0mm. The joints’ mechanical behaviour was studied performing static (tensile) and fatigue tests. The fatigue crack growth rate of cracks growing in different zones of the welded joint (nugget, heat affected zone - HAZ) and in base material was analysed. The microhardness profile was assessed in order to analyse the influence of the welding process in each weld zone. Further to higher static properties, welded joints present lower crack growth rate when compared with its base material.

scholarly journals High Temperature Fatigue Crack Growth Rate Studies in Stainless Steel 316L(N) Welds Processed by A-TIG and MP-TIG Welding.

2018 ◽  
Vol 165 ◽  
pp. 21014 ◽  
Author(s):  
Manuel Thomas ◽  
Raghu V. Prakash ◽  
S Ganesh Sundara Raman ◽  
M. Vasudevan
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
High Temperature ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Base Metal ◽  
Tig Welding ◽  
Weld Distortion

Welded stainless steel components used in power plants and chemical industries are subjected to mechanical load cycles at elevated temperatures which result in early fatigue failures. The presence of weld makes the component to be liable to failure in view of residual stresses at the weld region or in the neighboring heat affected zone apart from weld defects. Austenitic stainless steels are often welded using Tungsten Inert Gas (TIG) process. In case of single pass welding, there is a reduced weld penetration which results in a low depth-to-width ratio of weld bead). If the number of passes is increased (Multi-Pass TIG welding), it results in weld distortion and subsequent residual stress generation. The activated flux TIG welding, a variant of TIG welding developed by E.O. Paton Institute, is found to reduce the limitation of conventional TIG welding, resulting in a higher depth of penetration using a single pass, reduced weld distortion and higher welding speeds. This paper presents the fatigue crack growth rate characteristics at 823 K temperature in type 316LN stainless steel plates joined by conventional multi-pass TIG (MP-TIG) and Activated TIG (A-TIG) welding process. Fatigue tests were conducted to characterize the crack growth rates of base metal, HAZ and Weld Metal for A-TIG and MP-TIG configurations. Micro structural evaluation of 316LN base metal suggests a primary austenite phase, whereas, A-TIG weld joints show an equiaxed grain distribution along the weld center and complete penetration during welding (Fig. 1). MP-TIG microstructure shows a highly inhomogeneous microstructure, with grain orientation changing along the interface of each pass. This results in tortuous crack growth in case of MP-TIG welded specimens. Scanning electron microscopy studies have helped to better understand the fatigue crack propagation modes during high temperature testing.

Evaluation of Crack Growth of Ni-Base Alloys Under Long Term Cyclic Loading in BWR Environment

2015 ◽  
Author(s):  
Masao Itatani ◽  
Takuya Ogawa
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Weld Metal ◽  
Crack Growth ◽  
Base Metal ◽  
Test Data

Crack growth test data of Ni-base alloys under cyclic loading in simulated boiling water reactor (BWR) environment including the effects of load rising time (tr) were evaluated in the view points of both fatigue and stress corrosion cracking (SCC). When the test data were plotted in the relationship between da/dt and Kmax, da/dt monotonically decreased with increasing tr and the stress ratio (R). For alloy 182 weld metal under short tr and/or low R, the crack growth rate assuming SCC is much lower than those of the test data. For alloy 182 under tr = 30 and 1000 s at R = 0.8, the crack growth rate assuming SCC almost coincided with test data. For heat affected zone (HAZ) of alloy 600 base metal (600HAZ), the crack growth rate assuming SCC had much different slope of da/dN-ΔK relationship compared with the test data in the tested range of tr up to 3000 s. From these observations, the contribution of SCC is relatively small and the main mechanism of crack growth is thought to be fatigue for the tested range (tr=1 to 1000 s for weld metal, tr=1 to 3000 s for base metal and R = 0.1 to 0.8). It was assured that the fatigue crack growth formula proposed by the authors accounts the effect of SCC adequately at long tr. Additionally, the applicability of the fatigue crack growth rate formula for austenitic stainless steels to the long term cyclic load was investigated and it was found that the formula can be applied to tr=30000 s.

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