In this investigation an attempt has been made to establish a criterion to forecast the possible crack initiation region (toe or root) in double fillet welded load carrying cruciform joints and also to know the probable failure mode. Cruciform joints were fabricated from pressure vessel grade (ASTM 517 'F' grade) steel using shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) processes. Fatigue crack growth experiments were carried out in a mechanical resonance vertical pulsator (SCHENCK 200 kN capacity) with a frequency of 30 Hz under constant amplitude loading (R=0). It was found that the fatigue crack initiation lives (root crack or toe crack) were relatively lower in the joints fabricated by FCAW process than the joints fabricated by SMAW process. © 2004 Elsevier Ltd. All rights reserved.

Bimalendu Guha

FAILURE ANALYSIS

Joints (structural components)

Loads (forces)

Pressure vessels

Steel

Welding

AMPLITUDE LOADING

Failure modes

MECHANICAL RESONANCE

TOE CRACKING

Crack initiation

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Engineering Failure Analysis

The fatigue crack growth behaviours of two weld metals deposited by shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) processes have been compared. Load carrying cruciform joints, with a lack of penetration (LOP) defect, were fabricated from high strength, quenched and tempered steel of ASTM 517 'F'' grade. Fatigue crack growth experiments were carried out in a vertical pulsator (Schenck 200 kN capacity) with a frequency of 30 Hz under constant amplitude loading (stress ratio R = 0). It was found that the fatigue crack growth resistance of the weld metal deposited by the SMAW process is superior, compared to the weld metal deposited by the FCAW process. The high heat input involved in the FCAW process probably contributes to the changes in weld metal properties, which result in a change in fatigue crack growth behaviour.

Science and Technology of Welding and Joining

Effect of welding process on fatigue crack growth behaviour of ASTM 517 'F' grade steel weld metals

New fracture mechanics equations have been developed to predict the fatigue life of shielded metal arc welded (SMAW) cruciform joints of ASTM 517 'F' Grade steels, containing lack of penetration (LOP) defects. These equations have been developed by combining the Paris law with the ΔK(i)-endurance equation The initiation life (N(i)) and the propagation life (N(p)) of the joints were accounted for, to obtain the total fatigue life (N(f)). The initiation life was obtained experimentally using crack initiation criteria. The propagation life was evaluated using the numerically developed equations. The accuracy of the developed equations were tested by comparing the predicted data with the experimental data and it was found that the correlation is quite good. Further, the effect of L/T(p) ratio (weld size) on fatigue life prediction was analysed in detail.New fracture mechanics equations have been developed to predict the fatigue life of shielded metal arc welded (SMAW) cruciform joints of ASTM 517 `F' Grade steels, containing lack of penetration (LOP) defects. These equations have been developed by combining the Paris law with the ΔKi-endurance equation. The initiation life (Ni) and the propagation life (Np) of the joints were accounted for, to obtain the total fatigue life (Nf). The initiation life was obtained experimentally using crack initiation criteria. The propagation life was evaluated using the numerically developed equations. The accuracy of the developed equations were tested by comparing the predicted data with the experimental data and it was found that the correlation is quite good. Further, the effect of L/Tp ratio (weld size) on fatigue life prediction was analyzed in detail.

International Journal of Pressure Vessels and Piping

Effect of L/T(p) ratio on fatigue life prediction of SMAW cruciform joints of ASTM 517 'F' Grade steels

The fatigue life of a manual metal arc welded cruciform joint failing from a root lack of the penetration region is estimated by the application of crack growth relations. A two-parameter relation was used. The initiation life and propagation life of the joint were taken into account to obtain the total fatigue life of the joint from the crack growth parameters. To test the accuracy of the method, the predicted data was compared with the experimental data for a CMn type steel welded joints. The results were in good agreement with the experimental data. © 1994.

Theoretical and Applied Fracture Mechanics

Fatigue life estimate of CMn steel welded cruciform joints

Fatigue Strength of Welded Structures

Significance of weld imperfections

International Journal of Fatigue

Importance of toe irregularity for fatigue resistance of automatic welds

Establishing criteria for root and toe cracking of load carrying cruciform joints of pressure vessel grade steel

Journal	Engineering Failure Analysis
ISSN	13506307
Open Access	No