Stress Induced Self Magnetic Flux Leakage at Stress Concentration Zone

PurposeA tower crane mainly ensures the success or efficiency of building construction. Fatigue crack analysis is important for tower crane components to prevent any accidents to workers in construction sites caused by component failure and to ease the maintenance or replacement of failed components. This work aimed to characterise the damage of failed components, analyse the relationship between the metal magnetic memory (MMM) result and the damage of failed components, and to validate the relationship between MMM and finite element analysis (FEA).Design/methodology/approachMMM was used in this work to detect any irregularities or early failure on the basis of the high stress concentration zone of ferromagnetic steel using magnetic flux leakage. Magnetic flux leakage was used on the MMM device to achieve the first objective using the MMM system by detecting the irregularities. The results of MMM analysis were validated through comparison with FEA results by determining their relationship.FindingsMMM results show that the position of defects on the tower crane pulley is within the stress area shown on FEA.Originality/valueHence, MMM method is a potential tool in monitoring failure mechanism in construction site.

Download Full-text

Magnetic Memory Inspection of an Overhead Crane Girder – Experimental Verification

Journal of KONES ◽

10.2478/kones-2019-0034 ◽

2019 ◽

Vol 26 (2) ◽

pp. 69-76

Author(s):

Agnieszka Kosoń-Schab ◽

Jarosław Smoczek ◽

Janusz Szpytko

Keyword(s):

Stress Concentration ◽

Magnetic Flux ◽

Material Handling ◽

Impact Load ◽

Ferromagnetic Material ◽

The Self ◽

Magnetic Flux Leakage ◽

Magnetic Memory ◽

Earth Magnetic Field ◽

Flux Leakage

Abstract The safety and efficiency of material handling systems involve periodical inspections and evaluation of transportation device technical conditions. That is particularly important in case of industrial cranes, since they are subjected to a large impact load and mechanical stresses acting on the crane's structure and equipment. The paper considers the possibility of a crane structure inspection using the metal magnetic memory (MMM) method. As an advanced non-destructive technique, this method can be employed for inspection of crane structure during operation, which leads to reduce the down time costs and increase the safety confidence in the monitoring process. The MMM technique is effective for early identification of the possible defect location and detecting the micro-damage in ferromagnetic structures through detecting the stress concentration areas. The basic principle of MMM method is the self-magnetic flux leakage signal that correlates with the degree of stress concentration. This method allows detecting early damage of ferromagnetic material through performing measurement in the earth magnetic field, without the use of a special magnetizing device. The paper presents the experimental results carried out on the double-girder overhead travelling crane with hoisting capacity 1000 kg. The influence of the load variation and duration time on the intensity of the self-magnetic flux leakage signal is analysed and discussed.

Download Full-text

DETECTION OF CRACKED POSITION DUE TO CYCLIC LOADING FOR FERROMAGNETIC MATERIALS BASED ON MAGNETIC MEMORY METHOD

Jurnal Teknologi ◽

10.11113/jt.v75.5175 ◽

2015 ◽

Vol 75 (7) ◽

Cited By ~ 3

Author(s):

Azli Ariffin ◽

Meor Iqram Meor Ahmad ◽

Shahrum Abdullah ◽

Wan Zulhelmi Wan Jusoh

Keyword(s):

Stress Concentration ◽

Magnetic Flux ◽

Testing Machine ◽

Ferromagnetic Material ◽

Magnetic Flux Leakage ◽

Magnetic Memory ◽

Tensile Testing Machine ◽

Potential Possibility ◽

Crack Position ◽

Flux Leakage

In this paper, metal magnetic memory (MMM) method is used to detect the micro-crack position on the ferromagnetic material due to the fatigue process by determining to the stress concentration zones in the metal surfaces. The MMM method was carried out on mild steel using Instron 8874 universal tensile testing machine with different values of the ultimate tensile strength (UTS) varies from 75%, 80% and 85% until the specimens fails. An equipment of stress concentration indicator was used to measure the magnetic flux leakage, Hp patterns in the specimens. The results indicated that the position of a crack on the specimen that failed due to fatigue test was correlated with the scanning interval from the magnetic flux leakage signals. Therefore, the MMM method provides the potential possibility to detect the position of fatigue damage or defect in the metal components.

Download Full-text

Effect of Stress Concentration on Magnetic Flux Leakage Signals from Blind-Hole Defects in Stressed Pipeline Steel

Research in Nondestructive Evaluation ◽

10.1080/09349849608968108 ◽

1996 ◽

Vol 8 (1) ◽

pp. 83-100 ◽

Cited By ~ 1

Author(s):

T. W. Krause ◽

R. W. Little ◽

R. Barnes ◽

R. M. Donaldson ◽

B. Ma ◽

...

Keyword(s):

Stress Concentration ◽

Magnetic Flux ◽

Pipeline Steel ◽

Magnetic Flux Leakage ◽

Blind Hole ◽

Hole Defects ◽

Flux Leakage

Download Full-text

Effect of Stress Concentration on Magnetic Flux Leakage Signals from Blind-Hole Defects in Stressed Pipeline Steel

Research in Nondestructive Evaluation ◽

10.1080/09349849609409591 ◽

1996 ◽

Vol 8 (2) ◽

pp. 83-100 ◽

Cited By ~ 8

Author(s):

T. W. Krause ◽

R. W. Little ◽

R. Barnes ◽

R. M. Donaldson ◽

B. Ma ◽

...

Keyword(s):

Stress Concentration ◽

Magnetic Flux ◽

Pipeline Steel ◽

Magnetic Flux Leakage ◽

Blind Hole ◽

Hole Defects ◽

Flux Leakage

Download Full-text

Metal Magnetic Memory Testing of Welded Joints under Fatigue Load

Materials Science Forum ◽

10.4028/www.scientific.net/msf.898.1069 ◽

2017 ◽

Vol 898 ◽

pp. 1069-1078

Author(s):

Ning Qiao ◽

Mu Xiao Shan ◽

Ye Zheng Li

Keyword(s):

Stress Concentration ◽

Magnetic Flux ◽

Crack Propagation ◽

Normal Component ◽

Fatigue Loading ◽

Fracture Morphology ◽

Magnetic Flux Leakage ◽

Magnetic Memory ◽

Metal Magnetic Memory ◽

Flux Leakage

To investigate the influence of stress concentration, crack propagation and types of fatigue loading on metal magnetic memory signals, two groups of fatigue experiments with different types of fatigue loading were carried out on Q235B steel welded joint. The normal components of magnetic flux leakage were measured by metal magnetic memory tester in the course of fatigue test, and the fracture surfaces of specimens were observed by scanning electron microscopy after fatigue tests. The experimental results showed that the normal components of magnetic flux leakage filed, as well as the metal magnetic memory signal, changed polarity and their gradients have peak values at stress concentration zones. The zero position of the normal component of magnetic flux leakage changed gradually with increasing cycle numbers. In addition, the metal magnetic memory signal feature of fatigue crack propagation was affected by the loading type clearly. Moreover, a combination of brittle rupture and ductile rupture was obtained in the fracture morphology figure.

Download Full-text