Local Stress Effects on MFL Signals

2000 ◽  
Author(s):  
L. Clapham ◽  
A. Plotnikov ◽  
D. L. Atherton
Keyword(s):  
Stress Responses ◽  
Local Stress ◽  
Magnetic Behaviour ◽  
Stress Distributions ◽  
Stress Concentrations ◽  
Stress Effects ◽  
Local Stresses ◽  
The Difference ◽  
Hole Defects ◽  
As Stress

Of these various factors that influence the Magnetic Flux Leakage (MFL) signal, stress is the most complex and the least understood. Pipe wall operating stresses may exceed 70% of the yield strength, but much higher local stress levels are present around defects because of stress concentrations. Understanding how these stresses affect MFL signals is crucial to accurate defect depth predictions. We have conducted a number of studies that investigate the effects of bulk and local stresses on magnetic behaviour and MFL signals. Both single defects and interacting (2-hole) defects have been investigated. In addition to MFL studies, we have used a Magnetic Barkhausen Noise (MBN) measurement technique to characterize magnetic behaviour of the sample in response both to local and bulk stresses. In general we find that, for typical inspection geometry (axial magnetizing field and hoop stress) the MFL signal decreases as stress increases. At high flux densities stress effects diminish, but are still significant. Although the general trends described above are common to all defects, different types of defects (through wall hole, blind hole, interacting defects) all display uniquely different MFL stress responses. We attribute this to the difference in local stress distributions (stress concentrations) around these defects.

Experimental and Numerical Analysis of Traditional Column Connections with the Possible Retrofit Concept

2010 ◽  
Vol 133-134 ◽  
pp. 479-484 ◽  
Author(s):  
Damir Lazarević ◽  
Josip Atalić ◽  
Joško Krolo ◽  
Mario Uroš ◽  
Marta Šavor
Keyword(s):  
Numerical Analysis ◽  
Strain Diagram ◽  
Stress Distributions ◽  
Construction Process ◽  
Structural System ◽  
Rotational Stiffness ◽  
Stress Concentrations ◽  
Real Nature ◽  
Load Carrying ◽  
Local Stresses

Several historical constructions in Croatia have permanent column problems, particularly at connections with capitals and bases, characterized by specific fractures. Experimental and numerical analysis of traditional column connections were conducted. Distinct fractures concentrated around the connections, as well as the traces of previous restorations noted by the chronicles, intrigued us to conduct research of the possible fundamental deficiency of the structural system. Traditional connections can be described as carefully smoothed stone contact areas, joined with centrally placed iron dowel fixed with a lead infill in a slightly larger hole. The comprehensive numerical and experimental efforts have shown that even a small imperfection in the construction process or a disturbance of bearing system have consequence, the contact leans to one side. As the joint has a very limited ability to compensate rotations, the relative rotation between column elements causes high local stresses at the edge of a column, which eventually results in numerous fractures. Ignoring or not fully appreciating the real nature of connections leads to significantly different stress distributions and orientations of thrust lines which may grossly overestimate the safety factor. This usually leads to inadequate rehabilitation, but also if no action is taken continuous fracture propagation can endanger local or global stability of the structure. Laboratory tests were performed on stone samples provided from traditional quarries and we tried to restore a rather similar level of stress and stress distribution caused by eccentric forces. Although some results will be presented, final objective will be to obtain the value of rotational stiffness and stress – strain diagram for connections, which is crucial for understanding of the load carrying mechanism, numerical treatment of connections and adequate retrofit strategies. In order to ensure serviceability and durability, we have started to test the possible retrofit concept with a layer of lead placed between two connected areas. The material such as lead enables small rotations and protects connected areas from large stress concentrations. Lead has already been used to fill the dowel holes and the additional horizontal thin layer appears to be an appropriate and almost invisible intervention.

Machining of simulated defects in pipeline steels: A neutron diffraction study of local stress effects

1997 ◽  
Vol 32 (5) ◽  
pp. 325-334 ◽  
Author(s):  
L Clapham ◽  
T W Krause ◽  
R Sabet-Sharghi ◽  
D Micke ◽  
D L Atherton ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Local Stress ◽  
Uniaxial Stress ◽  
Neutron Diffraction Study ◽  
Residual Stress Field ◽  
Pipeline Inspection ◽  
Stress Effects ◽  
Electrochemical Drilling ◽  
Local Stresses ◽  
Stressed Sample

The most commonly used in-line pipeline inspection tools utilize the magnetic flux leakage (MFL) technique, which is sensitive to the stress state of the pipe wall. Calibration of these MFL tools is often carried out using unstressed pipeline sections containing simulated defects, usually produced by mechanical drilling. There is also strong interest in creating simulated defects in stressed pipe walls, thus simulating corrosion in the field. In this study, neutron diffraction is used to map the local stresses surrounding mechanically and electrochemically drilled holes in a steel plate sample. Holes were drilled in unstressed samples, as well as samples held at a constant 80 MPa uniaxial stress. Mechanical drilling into a stressed sample was found to induce considerable residual stresses around the hole. Conversely, electrochemical drilling did not create a residual stress field in the vicinity of the hole.

Influence of Microstructure on Small Crack Behavior

2005 ◽  
Vol 297-300 ◽  
pp. 1165-1171
Author(s):  
Masayuki Kamaya ◽  
Takayuki Kitamura
Keyword(s):  
Crystal Orientation ◽  
Crack Tip ◽  
Circular Crack ◽  
Local Stress ◽  
Crack Size ◽  
Polycrystalline Materials ◽  
Element Analysis ◽  
Crystal Model ◽  
The Difference ◽  
As Stress

Averaging the anisotropy of each crystal, the macroscopic behavior of polycrystalline materials is isotropic and homogenous in terms of elastic deformation. However, the anisotropic property of each crystal influences on the local stress field ahead of a crack tip if the crack size is not large enough in comparison with the grain diameter. This brings about the change in the crack driving force (CDF) such as stress intensity factors. In the present study, in order to investigate the cause and magnitude of the change in the CDF, the finite element analysis is performed. The calculations are carried out for a single crystal model, a bi-crystal model, and a polycrystal model containing a transgranular or an intergranular semi-circular crack. The results implied that the magnitude of CDF is dependent not only on the crystal orientation but also on the deformation-constraint caused by the difference in elastic modulus of grains near the crack tip. The statistical scatter of CDF due to the random crystal orientation in a polycrystal is examined by a Monte Carlo simulation. The variation in the SIF becomes small as the crack size increases.

Strengthening Analysis on Tenon-Mortise Joint of a Face Beam in Tai-He Palace in the Forbidden City in China

2011 ◽  
Vol 255-260 ◽  
pp. 1597-1602
Author(s):  
Qian Zhou ◽  
Wei Ming Yan
Keyword(s):  
Finite Element ◽  
Composite System ◽  
Finite Element Models ◽  
Wood Composite ◽  
Stress Distributions ◽  
Element Simulation ◽  
The Face ◽  
As Stress ◽  
Strengthening Method ◽  
Cultural Relics

To protect Chinese ancient building,by theoretical calculation and finite element simulation sinkage as well as strengthening method on tenon-mortise joint of a face beam in Tai-He Palace in the Forbidden City were studied.2 strengthening methods were considered,by which calculation diagrams as well as finite element models for the beam were built and static analysis were carried out.Based on analysis results,displacement as well as stress distributions of the face beam before strengthened were obtained;Based on laws of cultural relics protection,the 2 strengthening methods were discussed and the more suitable one was selected.Results show that the main cause of sinkage of the face beam tenon relates closely to over great values of bending,tension as well as shearing stress values at the tenon-mortise joint position;The method that strengthening tenon-mortise joint by additional columns under the face beam may bring adverse effects to the substructure,however the method of using steel-wood composite system to strengthen the joint is more suitable which meets the demand of cultural relics protection.

Influence of Magnetoelastic Anisotropy on Properties of Nanostructured Microwires

2013 ◽  
Vol 646 ◽  
pp. 59-66 ◽  
Author(s):  
Arcady Zhukov ◽  
Margarita Churyukanova ◽  
Lorena Gonzalez-Legarreta ◽  
Ahmed Talaat ◽  
Valentina Zhukova ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Hysteresis Loops ◽  
Magnetic Behaviour ◽  
Soft Magnetic ◽  
Magnetoelastic Anisotropy ◽  
Thermal Expansion Coefficients ◽  
Magnetoelastic Energy ◽  
Expansion Coefficients ◽  
The Difference ◽  
Magneto Resistance

We studied the effect ofthe magnetoelastic ansitropy on properties of nanostructured glass-coated microwires with soft magnetic behaviour (Finemet-type microwires of Fe70.8Cu1Nb3.1Si14.5B10.6, Fe71.8Cu1Nb3.1Si15B9.1 and Fe73.8Cu1Nb3.1Si13B9.1 compositions) and with granular structure (Cu based Co-Cu microwires). The magnetoelastic energy originated from the difference in thermal expansion coefficients of the glass and metallic alloy during the microwires fabrication, affected the hysteresis loops, coercivity and heat capacity of Finemet-type microwires. Hysteresis loops of all as-prepared microwires showed rectangular shape, typical for Fe-rich microwires. As expected, coercivity, HC, of as-prepared microwires increases with decreasing of the ratio ρ defined as the ratio between the metallic nucleus diameter, d to total microwire diameter, D. On the other hand we observed change of heat capacity in microwires with different ratio ρ. In the case of Co-Cu microwires ρ- ratio affected the structure and the giant magneto-resistance of obtained microwires.

Comparative study of hemodynamic effects, quality of extubation and emergence - agitation response of the patients with dexmedetomidine versus lignocaine during and following the endotracheal extubation

2021 ◽  
Vol 19 (3) ◽  
pp. 91-95
Author(s):  
Manasi Panat ◽  
Keyword(s):  
Comparative Study ◽  
Stress Responses ◽  
Tracheal Extubation ◽  
Emergence Agitation ◽  
Quality Of Recovery ◽  
Group 12 ◽  
The Difference ◽  
Group D ◽  
Endotracheal Extubation

Background: Endotracheal extubation is the translaryngeal removal of a tube from the trachea via the nose or mouth. It is associated with hemodynamic changes because of reflex sympathetic discharge caused by epipharyngeal and laryngopharyngeal stimulation. Various drugs and techniques have been tried to attenuate the airway and stress responses during tracheal extubation. In present study, we have compared the effects of dexmedetomidine and intravenous lignocaine on the hemodynamic and recovery profiles during endotracheal extubation. Material and Methods: Present study was prospective randomised comparative study, conducted in patients from age group of 18-45 years, ASA grade I/II, scheduled for elective abdominal surgeries. The patients were categorised into two different groups using the sealed envelope method as Group D and group L. Results: In present study, patients were divided in following 2 groups with 50 patients in each group as group D (Dexmedetomidine) and group L (Lignocaine). Age, gender, mean BMI were comparable in both groups and difference was not significant statistically. The difference between mean heart rate, systolic BP, diastolic BP and mean arterial BP during extubation, after extubation at 1, 3, 5, 10, 15, 20, 25, 30 minutes in dexmedetomidine group and lignocaine group was statistically significant. In Dexmedetomidine group, 12% of the patients had no cough during extubation, 72% of the patients had smooth extubation with minimal cough while in Lignocaine group, 22% of the patients had smooth extubation with minimal cough, 74 % of the patients had moderate cough during extubation. Statistical analysis of the Emergence agitation score shows better results in group D. Conclusion: Administration of Dexmedetomidine before tracheal extubation was more effective in maintaining the hemodynamic stability, facilitated smooth tracheal extubation and had a better quality of recovery as compared to Lignocaine.

Low Cycle Fatigue Analysis of Marine Structures

2006 ◽  
Author(s):  
Xiaozhi Wang ◽  
Joong-Kyoo Kang ◽  
Yooil Kim ◽  
Paul H. Wirsching
Keyword(s):  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Prediction Method ◽  
Local Stress ◽  
Cyclic Plasticity ◽  
Cycle Fatigue ◽  
Stress Concentrations ◽  
Damage Prediction ◽  
Marine Structure ◽  
Number Of Cycles

There are situations where a marine structure is subjected to stress cycles of such large magnitude that small, but significant, parts of the structural component in question experiences cyclic plasticity. Welded joints are particularly vulnerable because of high local stress concentrations. Fatigue caused by oscillating strain in the plastic range is called “low cycle fatigue”. Cycles to failure are typically below 104. Traditional welded joint S-N curves do not describe the fatigue strength in the low cycle region (< 104 number of cycles). Typical Class Society Rules do not directly address the low cycle fatigue problem. It is therefore the objective of this paper to present a credible fatigue damage prediction method of welded joints in the low cycle fatigue regime.

scholarly journals ANALISIS PENGARUH BENTUK DAN LOKASI BUKAAN PADA BALOK TINGGI MENGGUNAKAN METODE ELEMEN HINGGA

2020 ◽  
Vol 3 (4) ◽  
pp. 1209
Author(s):  
Anthony Fariman ◽  
Leo S. Tedianto
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Wall Structure ◽  
Deep Beam ◽  
Stress Distributions ◽  
Stress Concentrations ◽  
Offshore Structure ◽  
Deep Beams ◽  
Concentrated Load ◽  
Cable Networks

ABSTRAKBalok tinggi beton bertulang merupakan salah satu struktur khusus yang dapat memikul beban cukup besar dan umumnya digunakan sebagai transfer girder, struktur lepas pantai, struktur dinding, dan pondasi. Kehadiran bukaan pada balok tinggi dapat memfasilitasi jalur saluran AC, saluran pipa, jaringan kabel dan lain-lain. Dengan adanya bukaan pada balok tinggi dapat memberikan beberapa efek samping yaitu terjadinya diskontinuitas geometri, tegangan terdistribusi non-linier pada balok tinggi, berkurangnya kekuatan dari balok, dan timbulnya konsentrasi tegangan di sekitar bukaan. Penelitian ini bertujuan untuk menganalisis efek dari kehadiran bukaan pada balok tinggi di atas dua perletakan (sendi-rol) dan dibebani beban terpusat di tengah bentang balok lalu memvariasikan bentuk bukaan (persegi, persegi panjang, dan lingkaran) dan lokasi bukaan. Tegangan lentur pada balok tinggi dan konsentrasi tegangan yang terjadi di sekitar bukaan merupakan hal yang akan dibahas dalam penelitian. Analisis akan dibantu dengan Midas FEA yang merupakan program berbasis elemen hingga dan  pemodelan dilakukan dengan elemen solid tiga dimensi. Hasil dari analisis ini menunjukkan bahwa kehadiran bukaan pada balok tinggi menyebabkan kenaikan tegangan secara signifikan. Lokasi dari bukaan yang mendekati daerah tengah bentang balok juga sangat mempengaruhi besarnya tegangan yang terjadi.ABSTRACTReinforced concrete deep beam is one of the special structures that can carry quite a big load and generally used as a transfer girder, offshore structure, wall structure, and foundation. The appearance of openings in deep beams can facilitate AC pipelines, plumbing pipes, cable networks, etc. The existence of openings in deep beams can provide a few side effects such as geometric discontinuity, non-linear stress distributions over the deep beams, reduced strength of the deep beams, and stresses concentration will emerged around the openings. The purpose of this research is to analyze the effects from the existence of openings in deep beams on two supports (hinge and roller) and loaded by concentrated load in mid-span then variate the shape of openings (square, rectangle, and circle) and location of the openings. Flexural stresses in deep beams and the stress concentrations that occur around the openings are discussed in this research. The analysis will be assisted by Midas FEA which is a finite element based program and modelling will be executed in three dimensional solid elements. The result of this analysis showed that the existence of the openings in deep beams can cause stresses to increase significantly high. The location of the openings close to the mid-span of the deep beams also affect the amount of the stresses that occurs.

Interfacial Fracture Strength of Micro-Scale Si/Cu Components with Different Free-Edge Shape

2015 ◽  
Vol 665 ◽  
pp. 169-172
Author(s):  
Yoshimasa Takahashi ◽  
Hikaru Kondo ◽  
Kazuya Aihara ◽  
Masanori Takuma ◽  
Kenichi Saitoh ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Stress Singularity ◽  
Fracture Initiation ◽  
Interfacial Fracture ◽  
Free Edge ◽  
Stress Distributions ◽  
Micro Scale ◽  
Transmission Electron ◽  
The Difference

The strength against interfacial fracture initiation from a free-edge of Si/Cu micro-components was evaluated. The micro-scale cantilever specimens containing dissimilar interfaces were fabricated with a focused-ion-beam (FIB) technique, and they were loaded with a quantitative nanoindenter holder operated in a transmission electron microscope (TEM). The specimens were successfully fractured along the Si/Cu interface, and the critical loads at fracture were measured. The critical stress distribution near the free-edge was evaluated with the finite element method (FEM). The near-edge stress distributions of 90°/90°-shaped specimens were scattered while those of 135°/135°-shaped specimens were in good agreement despite the difference in specimen dimensions. Such a difference was discussed in terms of the relation between the magnitude of stress singularity and the microstructures of material.

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