Search

Heat treatment of steel is a common industrial procedure to alter the microstructure of a component locally. Often, only the surface of a component is heat-treated to a certain thickness such that it benefits from the high durability provided by a hardened microstructure, while the core microstructure remains ductile. The nondestructive determination of this thickness, the case-hardened depth, can be performed by evaluating the slight differences of the ultrasonic backscatter from the grains of changing size in different layers. However, current methods require a small transition zone from the hardened to the core microstructure for accurate results. In this work, a different approach for the determination of the case-hardened depth of components with a large transition zone is described. This approach utilizes ultrasonic frequencies about 20 MHz in contact technique. The ultrasound is introduced in an oblique setup with a wedge and is mode converted to the transverse mode. The statistical evaluation of the backscattering shows promising results for the determination of the case-hardened depth of hardened components with a smooth decrease of the hardness over the depth.

We are currently experiencing the next industrial revolution (industry 4.0). Production facilities and product parts communicate during manufacturing process. The properties of products can now be simulated before production using modeling which creates digital twins. But even under these advanced manufacturing conditions natural variability and “scatter” in material properties and occurrence of material defects cannot be completely ruled out. To provide advanced material characterization (or material state awareness) requires a new kind of cyber-based NDE where inspection processes are planned and optimized virtually using digital twins. The optimized inspection process has to be integrated into the cyber-controlled process and inspection results for individual parts have to be evaluated. Such NDE data is stored to and insights used to improve reliability and enable both forecasting and lifecycle management (prognostics). We call this NDE 4.0 where NDE data become a valuable resource. This contrasts with classical NDE approaches where the ability and experience of an inspector is required to perform and evaluate the NDE results, all in the context of a procedure where there has been a statistical POD assessment developed. Techniques developed in the past are now being viewed under a new light and are gaining in importance. The paper will present the IRMS, Inspection and Revision Management System, an approach that is supporting all necessary processing steps related to inspection and needed responses to better manage system life cycle at power plants, chemical plants, and in other industries based on a modular design beyond process limits. The use of IRMS creates a database of all inspections and component data, it supports inspection planning, and is a tool for prognostics and life-cycle management of components.

Fiber-reinforced polymer composite materials have become materials of choice for manufacturing application due to their high specific stiffness, strength and fatigue life, low density and thermal expansion coefficient. However, there are some types of defects such as porosity that form during the manufacturing processes of composites and alter their mechanical behavior and material properties. In his study, hand lay-up was conducted to fabricate samples of carbon fiber-reinforced polymer composites with three different vacuum levels in order to vary porosity content. Nondestructive evaluation, destructive techniques and mechanical testing were conducted. Nondestructive evaluation results showed the trend in percentages of porosity through-thickness. Serial sectioning images revealed significant details about the composite’s internal structure such as the volume, morphology and distribution of porosity. Mechanical testing results showed that porosity led to a decrease in both Mode I static interlaminar fracture toughness and Mode I cyclic strain energy release rate fatigue life. The fractographic micrographs showed that porosity content increased as the vacuum decreased, and it drew a relationship between fracture mechanisms and mechanical properties of the composite under different modes of loading as a result of the porosity effects. Finally, in order to accurately quantify porosity percentages included in the samples of different vacuum levels, a comparison was made between the parameters and percentages resulted from the nondestructive evaluation and mechanical testing and the features resulted from fractography and serial sectioning.

Condition based maintenance is now routinely applied to rotating machinery, with data transmitted wirelessly and reviewed automatically, to give a prognostic or remaining life estimate. The challenge is implementing integrated NDE/SHM strategies for structural assessment. However, advances in computer and communications technology, the internet of things and management of big data are starting to offer the digital infrastructure which can be combined with new sensor systems to enable SHM/prognostics to be applied to structural materials. Some challenges and opportunities which assess and demonstrate how NDE and SHM can potentially be revolutionized in the age of Industry 4.0 are outlined.

The smartphones of today have come a long way from its first inception. Technologically they are highly advanced and can be put to various uses that could not be dreamt of, a decade back. There are instruments now out in the market which when combined with smartphones can become a powerful tool to conduct nondestructive evaluations. Yes, that’s right, NDE. These instruments can be applied to solve simple household issues. For example, detecting heat leaks using a detachable Infrared camera with the cellphone. In this presentation, results from android adaptable NDE devices and from standard NDE devices will be compared. The devices to be used are: • Eddy Smart - a transducer is attached to the phone that makes eddy current measurement on the specimen and stores data on the phone. • FLIR ONE Thermal Imaging - an Infrared camera that is attached to a smartphone through USB jack and relay The devices to be used are: • Eddy Smart - a transducer is attached to the phone that makes eddy current measurement on the specimen and stores data on the phone. • FLIR ONE Thermal Imaging - an Infrared camera that is attached to a smartphone through USB jack and relays heat images to the phone. • PCUS Pocket – This device is the size of a hard disk but makes accurate ultrasonic measurements at par with the standard devices, when connected to a laptop/PC. Test samples will be developed to quantify the performance of these low-cost systems. A comparison of the results from standard and smart, portable devices validate the performance of the new devices. It determines the areas where the technology needs to be further developed. Advantages and limitations of the android adaptable systems with respect to nondestructive testing will be discussed. Acknowledgement: The authors greatly acknowledge the support from Fraunhofer IKTS, Berlin and the staff and faculty at Centre for Nondestructive Evaluation (CNDE), Ames. References: 1. https://walabot.com/ 2. http://www.flir.com/flirone/content/?id=81730 3. http://www.eddycation.de/41265.html

The manufacturing process of carbon fiber reinforced polymer (CFRP) components is gaining a more and more significant role when looking at the increasing amount of CFRPs used in industries today. The monitoring of the manufacturing process and hence the reliability of the manufactured products, is one of the major challenges we need to face in the near future. Common defects which arise during manufacturing process are e.g. porosity and voids which may lead to delaminations during operation and under load. To find irregularities and classify them as possible defects in an early stage of the manufacturing process is of high importance for the safety and reliability of the finished products, as well as of significant impact from an economical point of view. In this study we compare various NDT methods which were applied to similar CFRP laminate samples in order to detect and characterize regions of defective volume. Besides ultrasound, thermography and eddy current, different X-ray methods like radiography, laminography and computed tomography are used to investigate the samples. These methods are compared with the intention to evaluate their capability to reliably detect and characterize defective volume. Beyond the detection and evaluation of defects, we also investigate possibilities to combine various NDT methods within a smart manufacturing process in which the decision which method shall be applied is inherent within the process. Is it possible to design an in-line or at-line testing process which can recognize defects reliably and reduce testing time and costs? This study aims to show up opportunities of designing a smart NDT process synchronized to the production based on the concepts of smart production (Industry 4.0). A set of defective CFRP laminate samples and different NDT methods were used to demonstrate how effective defects are recognized and how communication between interconnected NDT sensors and the manufacturing process could be organized.

Modern aerospace industry is migrating from reactive to proactive and predictive maintenance to increase platform operational availability and efficiency, extend its useful life cycle and reduce its life cycle cost. Multiphysics modeling together with data-driven analytics generate a new paradigm called “Digital Twin.” The digital twin is actually a living model of the physical asset or system, which continually adapts to operational changes based on the collected online data and information, and can forecast the future of the corresponding physical counterpart. This paper reviews the overall framework to develop a digital twin coupled with the industrial Internet of Things technology to advance aerospace platforms autonomy. Data fusion techniques particularly play a significant role in the digital twin framework. The flow of information from raw data to high-level decision making is propelled by sensor-to-sensor, sensor-to-model, and model-to-model fusion. This paper further discusses and identifies the role of data fusion in the digital twin framework for aircraft predictive maintenance.Modern aerospace industry is migrating from reactive to proactive and predictive maintenance to increase platform operational availability and efficiency, extend its useful life cycle and reduce its life cycle cost. Multiphysics modeling together with data-driven analytics generate a new paradigm called “Digital Twin.” The digital twin is actually a living model of the physical asset or system, which continually adapts to operational changes based on the collected online data and information, and can forecast the future of the corresponding physical counterpart. This paper reviews the overall framework to develop a digital twin coupled with the industrial Internet of Things technology to advance aerospace platforms autonomy. Data fusion techniques particularly play a significant role in the digital twin framework. The flow of information from raw data to high-level decision making is propelled by sensor-to-sensor, sensor-to-model, and model-to-model fusion. This paper further discusses and identifies the ...

A composite material is a combination of two or more materials with very different mechanical, thermal and electrical properties. The various forms of composite materials, due to their high material properties, are widely used as structural materials in the aviation, space, marine, automobile, and sports industries. However, some defects like voids, delamination, or inhomogeneous fiber distribution that form during the fabricating processes of composites can seriously affect the mechanical properties of the composite material. In this study, several imaging NDE techniques such as: thermography, high frequency eddy current, ultrasonic, x-ray radiography, x-ray laminography, and high resolution x-ray CT were conducted to characterize the microstructure of carbon fiber composites. Then, a 3D analysis was implemented by the destructive technique of serial sectioning for the same sample tested by the NDE methods. To better analyze the results of this work and extract a clear volume image for all features and defects contained in the composite material, an intensive comparison was conducted among hundreds of 3D-NDE and multi serial sections’ scan images showing the microstructure variation.

Industry 4.0 stands for the fourth industrial revolution that is ongoing at present. Industry 4.0 is a terminology preferred used in Europe to characterize the integration of production and communication technologies, the so called “smart factory”. The first industrial revolution was the mechanization of work. The second was mass production and the assembly line. While the third revolution was the computer integrated manufacturing. Industry 4.0 encompasses the complete networking of all industrial areas. Lowering costs and efficient in-time production will be possible also for low numbers of very unique parts for example by additive manufacturing (3D printing). A significant aspect is also quality and maintainability of these sometimes unique structures and components. NDE has to follow these trends, not only by adapting NDE techniques to the new technologies, but also introducing the capability of cyber systems into the inspection and maintenance processes. The requirements and challenges for this new technological area will be discussed. Chances for applications of new technologies and systems for NDE will be demonstrated online.

Carbon fiber composites have been increasingly used in aerospace, military, sports, automotive and other fields due to their excellent properties, including high specific strength, high specific modulus, corrosion resistance, fatigue resistance, and low thermal expansion coefficient. Interlaminar fracture is a serious failure mode leading to a loss in composite stiffness and strength. Discontinuities formed during manufacturing process degrade the fatigue life and interlaminar fracture resistance of the composite. In his study, three approaches were implemented and their results were correlated to quantify discontinuities effecting static and fatigue interlaminar fracture behavior of carbon fiber composites. Samples were fabricated by hand layup vacuum bagging manufacturing process under three different vacuum levels, indicated High (-686 mmHg), Moderate (-330 mmHg) and Poor (0 mmHg). Discontinuity content was quantified through-thickness by destructive and nondestructive techniques. Eight different NDE m...

Lightweight components for transportation and aerospace applications are designed for an estimated lifecycle, taking expected mechanical and environmental loads into account. The main reason for catastrophic failure of components within the expected lifecycle are material inhomogeneities, like pores and inclusions as origin for fatigue cracks, that have not been detected by NDE. However, material degradation by designed or unexpected loading conditions or environmental impacts can accelerate the crack initiation or growth. Conventional NDE methods are usually able to detect cracks that are formed at the end of the degradation process, but methods for early detection of fatigue, creep, and corrosion are still a matter of research. For conventional materials ultrasonic, electromagnetic, or thermographic methods have been demonstrated as promising. Other approaches are focused to surface damage by using optical methods or characterization of the residual surface stresses that can significantly affect the cre...

On the present work, samples of carbon fiber/epoxy composites with different void levels were fabricated using hand layup vacuum bagging process by varying the pressure. Thermal nondestructive methods: thermal conductivity measurement, pulse thermography, pulse phase thermography and lock-in-thermography, and mechanical testing: modes I and II interlaminar fracture toughness were conducted. Comparing the parameters resulted from the thermal nondestructive testing revealed that voids lead to reductions in thermal properties in all directions of composites. The results of mode I and mode II interlaminar fracture toughness showed that voids lead to reductions in interlaminar fracture toughness. The parameters resulted from thermal nondestructive testing were correlated to the results of mode I and mode II interlaminar fracture toughness and voids were quantified.

During thermo-inductive inspection, an eddy current of high intensity is induced into the inspected material and the thermal response is detected using an infrared camera. Anomalies in the surface temperature during and after inductive heating correspond to inhomogeneities in the material. A finite element simulation of the surface crack detection process using active thermography with inductive heating has been developed. The simulation tool was tested and used for investigations on austenitic steel components with different longitudinal orientated cracks. The shape of the crack varies in the crack opening and the depth. The simulation model was based on the finite element programming software ANSYS. The suitability of the developed simulation of the inductive excited thermography for crack detection will be demonstrated by calculations and experiments. This paper focuses on longitudinal orientated cracks in austenitic steel, which are opened to the surface. The result s show that depending on the shape of the crack the temperature distribution of the material under test made of austenitic steel is different. It will be shown how the crack size affects the temperature difference between the crack and the surrounding surface.

In this paper an assembly concept of the radiation resistant, direct converting X-ray line detector is presented. In addition to efforts on radiation protection of sensitive electronics, realization of arranging several sensor modules is discussed. Furthermore, the electrical behavior of the designed and manufactured GaAs sensors is explained.

Carbon fiber materials become more and more important for many applications. Unlike metal the technological parameters and certified quality control mechanisms for Raw Carbon Fiber Materials (RCF) have not yet been developed. There is no efficient and reliable testing system for in-line inspections and consecutive manual inspections of RCF and post laminated Carbon Fiber Reinforced Plastics (CFRP). Based upon the multi-frequency eddy current system developed at Fraunhofer IZFP, structural and hidden defects such as missing carbon fiber bundles, lanes, suspensions, fringes, missing sewing threads, and angle errors can be detected. Using an optimized sensor array and intelligent image pre-processing algorithms, the complex impedance signal can be allocated to different carbon fiber layers. This technique enables the detection of defects in depths of up to 5 layers, including the option of free scale measuring resolution and testing frequency. Appropriate parameter lists for optimal error classifications are available. The dimensions of the smallest detectable flaws are in the range of a few millimeters. Algorithms and basic Eddy Current C-Scan processing techniques for carbon fiber material testing are described in this paper.

Kurzfassung Die Lebensdauer von Flugzeugturbinen-Komponenten kann verlängert werden, indem zusätzliche Druckspannungen in die Materialoberfläche eingebracht werden. Typische Flugzeugturbinen-Legierungen wie Nickelbasis-Superlegierungen werden hierzu mittels Kugelstrahlen oberflächenbehandelt. Durch die zusätzlichen Druckeigenspannungen wird der Rissbildung in den Bauteilen vorgebeugt, womit die Lebensdauer der Komponenten verlängert werden kann. Da durch die hohen thermischen und mechanischen Belastungen während des Turbinenbetriebs die Druckspannungen relaxieren können, müssen regelmäßig zerstörungsfreie, quantitative Untersuchungen der Spannungsgradienten in der Materialoberfläche durchgeführt werden. In dieser Veröffentlichung werden Arbeiten präsentiert, bei denen solche Verfestigungs-Tiefenprofile mit hochpräzisen Wirbelstrommessungen im hochfrequenten Bereich bis 100MHz durchgeführt wurden. Entsprechende Testkörper aus IN178 wurden in unterschiedlichen Intensitäten kugelgestrahlt und konnten mittels Wirbelstrommessungen gut voneinander separiert werden. Indem Messfrequenzen zwischen 100 kHz und 100 MHz hintereinander durchgeschaltet werden, kann ein Tiefenprofil der elektrischen Leitfähigkeit in Tiefen von 50 bis 500 μm erreicht werden. Das ermittelte Leitfähigkeitsprofil ist ein gemischtes Signal bestehend aus Informationen von den Eigenspannungen, der Kaltverfestigung, der Oberflächenrauigkeit und dem Gefüge des Materials. Zusätzlich werden in dieser Veröffentlichung erste Ergebnisse von Spannungsprofilen präsentiert, die mit einem industriell applizierbaren NDT-Gerät ermittelt worden sind.

The opening width of fatigue crack was very small, and conventional Bobbin probe was very difficult to detect it in steam generator tubes. Different sizes of 8 fatigue cracks were inspected using bobbin probe rotating probe. The analysis results showed that, bobbin probe was not sensitive for fatigue crack even for small through wall crack mixed with denting signal. On the other hand, the rotating probe was easily to detect all cracks. Finally, the OD phase to depth curve for fatigue crack using rotating probe was established and the results agreed very well with the true crack size.

This paper discusses a new methodology for characterizing the magnetic properties of ferromagnetic materials. The method uses an alternating electric current to periodically magnetize ferromagnetic materials. The periodic magnetization generates a high-frequency electric potential noise between two electrodes within the excitation circuit. The magnetically induced electric potential noise (MIPN) is related to the discontinuous processes that occur during magnetization similar to magnetic Barkhausen noise. This paper discusses the results of several experiments that measured both electric potential noise and Barkhausen noise signal. A comparison of the results showed that the MIPN correlates directly to magnetic Barkhausen noise. The MIPN signal is small when compared to Barkhausen noise, but it is still easy to measure under laboratory conditions. Therefore, MIPN could be an efficient technique for materials characterization and sensor technology, for example, as fiber stress sensors in a composi...

The magnetic Barkhausen Noise technique is a well suited method for the characterization of ferromagnetic materials. The Barkhausen effect results in an interaction between the magnetic structure and the microstructure of materials, and is sensitive to the stresses and microstructure related mechanical properties. Barkhausen noise is a complex signal that provides a large amount of information, for example frequency spectrum, amplitude, RMS value, dependence of magnetic field strength, magnetization frequency and fractal behavior. Although this technique has a lot potentials, it is not commonly used in nondestructive material testing. Large sensors and complex calibration procedures made the method impractical for many applications. However, research has progressed in recent years; new sensor designs were developed and evaluated, new algorithms to simplify the calibration and measurement procedures were developed as well as analysis of additional material properties have been introduced.

The magnetic Barkhausen Noise (BN) is well suited to evaluate the effects of mechanical stresses of ferromagnetic materials, e.g. the indirect detection of residual stress states. The most common causes for the occurrence of residual stresses are manufacturing processes, such as casting, welding, machining, forming, heat treatment, etc., consecutive repairs and design changes, and installation or assembly and overloads during the operating life of a construction. A significant calibration effort based on a set of reference values and/or test samples is needed for these measurements, which require a great deal of time and material resources. Additionally, it is impossible to determine the stress states of different components (σxx and σyy) at the surface. Therefore, a new auto-calibration method was developed to analyze two-dimensional stresses. A fixed calibration function based on defined parameters (determined experimentally) was applied. To adjust the auto-calibration function to the experimental refer...

The magnetic Barkhausen Noise technique is a well suited method for the characterization of ferromagnetic materials. Most sensors are composed of a magnetic yoke that excites the electromagnetic field in the material, and a coil or Hall-Element, which is located between both feet of the yoke to record the Barkhausen Noise. Due to both factors, the overall size of the sensors and the spot size at the material are relatively large. For some applications, Barkhausen Noise Sensors for miniaturized samples with complex geometries are needed, for example for small mass-production components or measurements inside of boreholes. Therefore, a new design for a Barkhausen Noise sensor was developed. The principle of exciting the Magnetic Field changes from a magnetic yoke to a thin tip. The alternating current flows through the tip into the material and induces a magnetic field, which in turn generates the Barkhausen Noise. A small coil wounded around the tip, records the Barkhausen Noise signal. With this design, the contact point between sensor and material is very small and it is possible to apply the sensor to very small samples or inside boreholes.

The 34 papers in this special issue focus on sensor systems for structural health monitoring.

Multi energy radioscopy using normalization to a reference material is a method which can easy be performed using standard radioscopy equipment. The identification of different materials is possible by comparison of two or more projection images taken for different kV Experiments and simulations have shown that the identification of materials is also possible in layed stuctures using the proposed method.

The developed direct converting X-ray line detectors offer a number of advantages in comparison to other X-ray sensor concepts. Direct converting X-ray detectors are based on absorption of X-rays in semiconductor material, which leads to a generation of charge carriers. By applying high bias voltage charge carriers can be separated and with this the arising current pulse can be assessed by suitable readout integrated circuits (ICs) subsequently. The X-ray absorber itself is implemented as a diode based on GaAs to use it in the reverse direction. It exhibits low dark currents and can therefore be used at room temperatures. The GaAs absorber has a structured top electrode designed on variable bonding and high breakdown voltages. The implemented GaAs absorber exhibits a pixel size of 100 μm while the readout IC features fast dead-time-free readout, energy discrimination by two individually adjustable thresholds with 20 bit deep counters and radiation-hard design on chip level. These properties guarantee the application as fast and thus sensitive line detector for imaging processes. Another advantage of the imaging line detector is the cascadability of several sensor modules with 1024 pixels each. This property ensures that the 102.4 mm long sensor modules can be concatenated virtually with arbitrary length gaplessly. The readout ICs hitting radiation dose can be further minimized by implementing constructive steps to ensure longer lifetime of the sensor module. Furthermore, first results using the introduced sensor module for solid state X-ray detection are discussed.

Embedding of discrete passives or functional chips as bare dies has been successfully proven in the last years. The embedding technology provides multiple advantages when compared to conventional surface mount technology. As of today multiple possibilities to embed active devices in the substrate exist. One method has been selected here and a fully parameterized finite-element framework has been created to assess its reliability potential. It is shown how it is possible to represent even very complex geometries with features spanning over multiple orders of magnitude, while fulfilling the requirement of reasonable simulation time effort and the possibility to still extracting all necessary local simulation result information. Special attention has been given to the simulation sequence used for the proposed model. Because the embedding technology involves multiple temperature critical production process steps it is advised to transfer the residual stresses of the previous step into the following. This ensures simulation results with high quality. Furthermore it is proposed to update the geometries according to the process calculations. In this work a feasible modeling approach for the underfill curing process is given. With the proposed framework the structural behavior of an embedded IC component both during the manufacturing stage and under environmental loading conditions can be investigated. This will facilitate future design choices and help expose the reliability potential of the novel embedding technology compared to conventional SMT.

The paper presents an approach to bring numerical simulation and electronic design engineering closer together. In focus is the development of a design support tool, based on Finite Element Analysis as an automated running system behind an engineer adapted Graphical User Interface platform. The Quick Predict tool will have the capability to fast calculated mechanical stresses on PCB and electronic components, which are loaded by vibration. Vibration loading usually occurs in mobile transportation systems or mechanical motion systems. The paper presents the solution of the easy and quick input of geometry variations, material variation and different vibration scenarios reflected on the example of an Electronic Control Unit (ECU). The automated generation of the virtual model is based on the available general design parameter. A set of material data was determined experimentally. A suitable way to insert material data variations for PCB with low effort on measurements was developed and integrated. The engineers target to achieve, with the approach, is to improve vibration resistivity of electronic components or to design new configurations of PCB with vibration critical components with very low time consumption.