Editorial

3 pages, 138 KiB

Open AccessEditorial

Advanced Non-Destructive Testing in Steels

by Evangelos Hristoforou

Metals 2018, 8(7), 492; https://doi.org/10.3390/met8070492 - 28 Jun 2018

Cited by 6 | Viewed by 2391

The quality of steel and its corresponding products depends on the distribution and level of stress on the steel’s volume and surface, since the stress gradient is responsible for steel cracking generation and failure[...] Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

Research

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15 pages, 8597 KiB

Open AccessArticle

Characteristics of Metal Magnetic Memory Testing of 35CrMo Steel during Fatigue Loading

by Zhibin Hu, Jianchun Fan, Shengnan Wu, Haoyuan Dai and Shujie Liu

Metals 2018, 8(2), 119; https://doi.org/10.3390/met8020119 - 08 Feb 2018

Cited by 25 | Viewed by 4829

Abstract

The fatigue fracture of a drillstring could cause drilling disturbances and some negative impacts (e.g., economic loss) will be brought when restoring the drillstring to functionality. In order to evaluate the effects of the fatigue damage of the drillstring during drilling, a new [...] Read more.

The fatigue fracture of a drillstring could cause drilling disturbances and some negative impacts (e.g., economic loss) will be brought when restoring the drillstring to functionality. In order to evaluate the effects of the fatigue damage of the drillstring during drilling, a new apparatus, which could monitor the load level in real-time, was built to perform the four-point bending fatigue test on 35CrMo steel, a typical material of drillstrings. Such an apparatus is based on metal magnetic memory (MMM) technology and can acquire the tangential and normal components of MMM signals. Based on the analysis of the change of surface morphology and MMM signals, it was concluded that the variation of MMM signals could be divided into four stages, which are used to accurately describe the fatigue damage process of the drillstring. Additionally, the MMM signal characteristics are introduced to especially evaluate the fatigue damage of the drillstring, including crack initiation. Furthermore, the scanning electron microscopy (SEM) results demonstrated that morphologies of fatigue fracture were related to the variation of MMM signals. Linear fitting results indicated that fatigue crack length had a good linear relationship with the characteristics, so it is feasible to monitor fatigue damage and predict the residual life of a drillstring by using MMM technology. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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5126 KiB

Open AccessArticle

Nondestructive Evaluation of Strain-Induced Phase Transformation and Damage Accumulation in Austenitic Stainless Steel Subjected to Cyclic Loading

by Chungseok Kim

Metals 2018, 8(1), 14; https://doi.org/10.3390/met8010014 - 29 Dec 2017

Cited by 8 | Viewed by 4222

Abstract

Strain-induced phase transformation and damage accumulation in austenitic stainless steel subjected to cyclic loading were investigated by nondestructive evaluation. The cyclic loading test was performed at various strain amplitudes at the same strain rate. The volume fraction of the strain-induced phase transformation (α′-martensite) [...] Read more.

Strain-induced phase transformation and damage accumulation in austenitic stainless steel subjected to cyclic loading were investigated by nondestructive evaluation. The cyclic loading test was performed at various strain amplitudes at the same strain rate. The volume fraction of the strain-induced phase transformation (α′-martensite) was determined by ferrite scope and magnetic coercivity measurement. The damage accumulation and microstructure of cyclic loading specimens were characterized by microstructural observation. The cyclic hardening and cyclic softening behavior are discussed in terms of the generation of strain-induced martensite phases and a dislocation substructure at each strain amplitude. The volume fraction of the strain-induced phase increased with the strain amplitude. The increase in α′-martensite was evaluated by measuring the ultrasonic nonlinearity parameter. The presence of α′-martensite is sufficient to distort the austenitic matrix due to an interface misfit between the austenite matrix and α′-martensite, resulting in wave distortion of the longitudinal wave. From this wave distortion, super-harmonics may be generated with nucleation of the strain-induced martensite, a process that strongly depends on the strain amplitude. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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3875 KiB

Open AccessArticle

Development of Amplifier Circuit by Active-Dummy Method for Atmospheric Corrosion Monitoring in Steel Based on Strain Measurement

by Nining Purwasih, Naoya Kasai, Shinji Okazaki and Hiroshi Kihira

Metals 2018, 8(1), 5; https://doi.org/10.3390/met8010005 - 22 Dec 2017

Cited by 8 | Viewed by 4076

Abstract

This paper describes an amplifier circuit fabricated by the active-dummy method for atmospheric corrosion monitoring based on strain measurement. The circuit was used to determine the relationship between the voltage and strain. Experiments involving the thickness reduction of low-carbon steel test pieces induced [...] Read more.

This paper describes an amplifier circuit fabricated by the active-dummy method for atmospheric corrosion monitoring based on strain measurement. The circuit was used to determine the relationship between the voltage and strain. Experiments involving the thickness reduction of low-carbon steel test pieces induced by galvanostatic electrolysis were carried out with the amplifier circuit. The circuit was capable of accurately measuring signals induced by the thickness reduction of the test piece. Moreover, the circuit was assessed for the effects of environmental temperature drift, and was found to exhibit a high tolerance. The proposed amplifier circuit would be suitable for atmospheric corrosion monitoring in many types of infrastructure. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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4177 KiB

Open AccessArticle

Magnetic Investigations of Steel Degradation Using a Magnetic Hysteresis Scaling Technique

by Satoru Kobayashi, Kodai Miura, Yuki Narita and Seiki Takahashi

Metals 2018, 8(1), 2; https://doi.org/10.3390/met8010002 - 21 Dec 2017

Cited by 2 | Viewed by 4436

Abstract

We report the results of magnetic measurements on austenitic stainless steels and duplex stainless steels using a magnetic hysteresis scaling technique. Unlike saturation hysteresis loops, this scaling technique, which uses a set of minor hysteresis loops, can be used in low measurement fields. [...] Read more.

We report the results of magnetic measurements on austenitic stainless steels and duplex stainless steels using a magnetic hysteresis scaling technique. Unlike saturation hysteresis loops, this scaling technique, which uses a set of minor hysteresis loops, can be used in low measurement fields. We show that there is a universal scaling power law between minor-loop parameters, which is independent from the level of deformation. The behavior of a coefficient deduced from the scaling law was explained from the viewpoint of the morphology of a ferromagnetic phase. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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10298 KiB

Open AccessArticle

A Numerical Study on the Excitation of Guided Waves in Rectangular Plates Using Multiple Point Sources

by Wenbo Duan, Xudong Niu, Tat-Hean Gan, Jamil Kanfoud and Hua-Peng Chen

Metals 2017, 7(12), 552; https://doi.org/10.3390/met7120552 - 08 Dec 2017

Cited by 11 | Viewed by 4736

Abstract

Ultrasonic guided waves are widely used to inspect and monitor the structural integrity of plates and plate-like structures, such as ship hulls and large storage-tank floors. Recently, ultrasonic guided waves have also been used to remove ice and fouling from ship hulls, wind-turbine [...] Read more.

Ultrasonic guided waves are widely used to inspect and monitor the structural integrity of plates and plate-like structures, such as ship hulls and large storage-tank floors. Recently, ultrasonic guided waves have also been used to remove ice and fouling from ship hulls, wind-turbine blades and aeroplane wings. In these applications, the strength of the sound source must be high for scanning a large area, or to break the bond between ice, fouling and plate substrate. More than one transducer may be used to achieve maximum sound power output. However, multiple sources can interact with each other, and form a sound field in the structure with local constructive and destructive regions. Destructive regions are weak regions and shall be avoided. When multiple transducers are used it is important that they are arranged in a particular way so that the desired wave modes can be excited to cover the whole structure. The objective of this paper is to provide a theoretical basis for generating particular wave mode patterns in finite-width rectangular plates whose length is assumed to be infinitely long with respect to its width and thickness. The wave modes have displacements in both width and thickness directions, and are thus different from the classical Lamb-type wave modes. A two-dimensional semi-analytical finite element (SAFE) method was used to study dispersion characteristics and mode shapes in the plate up to ultrasonic frequencies. The modal analysis provided information on the generation of modes suitable for a particular application. The number of point sources and direction of loading for the excitation of a few representative modes was investigated. Based on the SAFE analysis, a standard finite element modelling package, Abaqus, was used to excite the designed modes in a three-dimensional plate. The generated wave patterns in Abaqus were then compared with mode shapes predicted in the SAFE model. Good agreement was observed between the intended modes calculated in SAFE and the actual, excited modes in Abaqus. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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6471 KiB

Open AccessArticle

RBF-Neural Network Applied to the Quality Classification of Tempered 100Cr6 Steel Cams by the Multi-Frequency Nondestructive Eddy Current Testing

by Víctor Martínez-Martínez, Javier Garcia-Martin and Jaime Gomez-Gil

Metals 2017, 7(10), 385; https://doi.org/10.3390/met7100385 - 21 Sep 2017

Cited by 3 | Viewed by 3581

Abstract

This article proposes a Radial Basis Function Artificial Neural Network (RBF-ANN) to classify tempered steel cams as correctly or incorrectly treated pieces by using multi-frequency nondestructive eddy current testing. Impedances at five frequencies between 10 kHz and 300 kHz were employed to perform [...] Read more.

This article proposes a Radial Basis Function Artificial Neural Network (RBF-ANN) to classify tempered steel cams as correctly or incorrectly treated pieces by using multi-frequency nondestructive eddy current testing. Impedances at five frequencies between 10 kHz and 300 kHz were employed to perform the binary sorting. The ANalysis Of VAriance (ANOVA) test was employed to check the significance of the differences between the impedance samples for the two classification groups. Afterwards, eleven classifiers were implemented and compared with one RBF-ANN classifier: ten linear discriminant analysis classifiers and one Euclidean distance classifier. When employing the proposed RBF-ANN, the best performance was achieved with a precision of 95% and an area under the Receiver Operating Characteristic (ROC) curve of 0.98. The obtained results suggest RBF-ANN classifiers processing multi-frequency impedance data could be employed to classify tempered steel DIN 100Cr6 cams with a better performance than other classical classifiers. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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7037 KiB

Open AccessArticle

Acoustic Emission Signatures of Fatigue Damage in Idealized Bevel Gear Spline for Localized Sensing

by Lu Zhang, Didem Ozevin, William Hardman and Alan Timmons

Metals 2017, 7(7), 242; https://doi.org/10.3390/met7070242 - 30 Jun 2017

Cited by 15 | Viewed by 5181

Abstract

In many rotating machinery applications, such as helicopters, the splines of an externally-splined steel shaft that emerges from the gearbox engage with the reverse geometry of an internally splined driven shaft for the delivery of power. The splined section of the shaft is [...] Read more.

In many rotating machinery applications, such as helicopters, the splines of an externally-splined steel shaft that emerges from the gearbox engage with the reverse geometry of an internally splined driven shaft for the delivery of power. The splined section of the shaft is a critical and non-redundant element which is prone to cracking due to complex loading conditions. Thus, early detection of flaws is required to prevent catastrophic failures. The acoustic emission (AE) method is a direct way of detecting such active flaws, but its application to detect flaws in a splined shaft in a gearbox is difficult due to the interference of background noise and uncertainty about the effects of the wave propagation path on the received AE signature. Here, to model how AE may detect fault propagation in a hollow cylindrical splined shaft, the splined section is essentially unrolled into a metal plate of the same thickness as the cylinder wall. Spline ridges are cut into this plate, a through-notch is cut perpendicular to the spline to model fatigue crack initiation, and tensile cyclic loading is applied parallel to the spline to propagate the crack. In this paper, the new piezoelectric sensor array is introduced with the purpose of placing them within the gearbox to minimize the wave propagation path. The fatigue crack growth of a notched and flattened gearbox spline component is monitored using a new piezoelectric sensor array and conventional sensors in a laboratory environment with the purpose of developing source models and testing the new sensor performance. The AE data is continuously collected together with strain gauges strategically positioned on the structure. A significant amount of continuous emission due to the plastic deformation accompanied with the crack growth is observed. The frequency spectra of continuous emissions and burst emissions are compared to understand the differences of plastic deformation and sudden crack jump. The correlation of the cumulative AE events at the notch tip and the strain data is used to predict crack growth. The performance of the new sensor array is compared with the conventional AE sensors in terms of signal to noise ratio and the ability to detect fatigue cracking. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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Review

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5630 KiB

Open AccessReview

Magnetic Hysteresis and Barkausen Noise in Plastically Deformed Steel Sheets

by Fausto Fiorillo, Michaela Küpferling and Carlo Appino

Metals 2018, 8(1), 15; https://doi.org/10.3390/met8010015 - 30 Dec 2017

Cited by 17 | Viewed by 8297

Abstract

The magnetic properties of steels are affected by plastic deformation, because the domain wall processes magnetoelastically interact with the dislocations and the residual stresses. The evolution of the magnetic hysteresis loop and its parameters with the type and degree of straining can thus [...] Read more.

The magnetic properties of steels are affected by plastic deformation, because the domain wall processes magnetoelastically interact with the dislocations and the residual stresses. The evolution of the magnetic hysteresis loop and its parameters with the type and degree of straining can thus provide a macroscopic signature of the underlying the mechanical and structural properties. Additional information can be achieved at a microscopic level through analysis of the Barkhausen noise, the signal generated by the stochastic flux variations associated with the discontinuous motion of the domain walls. Nondestructive methods for the structural evaluation of magnetic steels, devoted, in particular, to the investigation of work-hardening and state of internal stress following plastic straining, have therefore been developed in the literature, either through magnetic hysteresis or Barkhausen noise measurements. In this paper, we summarize significant results regarding the relationship between magnetic properties and plastic deformation in steel samples and the related experimental methods. Attention will be devoted, in particular, to the measurement and analysis of the Barkhausen noise spectral density and the way it relates to the macroscopic magnetic behavior and the structural properties. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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