Claus-Peter Fritzen

• Prof. Dr.
• University of Siegen

Piezoelectric wafer active sensors are very sensitive to changes of loads in structures, which makes them useful for the load monitoring. Unfortunately, these transducers are also sensitive to environmental effects such as a change of the ambient temperature. These effects can mask the information about the load in the recorded measurement data of...

Das FOSTA‐Forschungsprojekt P 1403 „Detektion von Vorspannkraftverlusten in Schrauben auf Basis elektromechanischer Impedanzspektren“ zielt auf die Entwicklung eines statistisch abgesicherten Verfahrens ab, welches im Rahmen eines Structural Health Monitorings (SHM) eine kostengünstige, kontinuierliche Überwachung von Schraubenkräften in vorgespann...

Bolted connections are one of the most widely used types of joints in various fields of applications. Their functionality depends on the conservation of the preload in the bolt’s shaft, which implies the need to monitor it. This paper addresses a monitoring procedure of the preload. Therefore, two measurement techniques for the preload are compared...

Fatigue crack growth is one of the most common damage mechanisms of structural components and can result in a sudden and unexpected abrupt fracture which can cause catastrophic failure. Thus, monitoring of crack propagation is an important topic of structural health monitoring. For that reason, this work aims at the detection of crack propagation b...

The functionality of bolted connections depends significantly on the conservation of the bolt’s preload, which entails the necessity to monitor these components. Traditional monitoring techniques using electro-mechanical impedance spectra are based on the observation of the structural resonances and antiresonances. The change of structural resonanc...

Common industrial procedures for the preload measurement of bolted joints are for example conducted by means of strain gauges (applied directly on the structure or employed in a force washer) or acousto ultrasonics (observing the time of flight-TOF- or wave propagation). A new method is introduced by the observation of the electro-mechanical impeda...

Many recent investigations in the context of graphene nanoplatelets (GNPs) coatings report surface strain measurements by using piezoresistive sensing capabilities. An often underestimated problem is that the strain field is unknown and the principal strain components as well as their orientations must be determined. Herein, GNP films subjected to...

Within a research project carried out at the Department of Civil Engineering and the Department of Mechanical Engineering of the University of Siegen, a new monitoring method for non-destructive damage detection on bolts was developed and tested according to its applicability on real life structures. The so-called EMI-method is based on the measure...

Herein, a short crack propagation in a martensitic spring steel by means of in situ fatigue tests in a confocal laser microscope and additional electron back‐scattered diffraction analyses to link the local crystallographic orientation of the hierarchical martensitic microstructure with the short crack propagation behavior are investigated. For thi...

Since stringers are often applied in engineering constructions to improve thin-walled structures’ strength, methods for damage detection at the joints between the stringer and the thin-walled structure are necessary. A 2D mathematical model was employed to simulate Lamb wave excitation and sensing via rectangular piezoelectric-wafer active transduc...

To show the effectiveness and sensitivity of SHM systems, proof of concept-experiments have been state of the art for quite some time. For the detailed analysis of SHM systems, frequently numerical modeling is used. Its quality is shown with a comparison to experimental data. Deviations are often called to be caused by the influence of environmenta...

Experimental and theoretical investigations of Lamb waves excitation and sensing by rectangular piezoelectric transducers perfectly and imperfectly mounted on the surface of a plate are presented in this study. Out-of-plane velocities measurements via laser Doppler vibrometry and voltage signal measurements by the piezoelectric transducers are comp...

Inhalt Vorwort ..... 1 Plenarvortrag Verbesserter Systementwurf durch KI-Methoden . . . . . 3 Condition Monitoring und KI-Methoden Stand und Tendenzen der Normung zum Thema Schwingungsüberwachung . . . . . . . . . . . . . 15 Praxiserfahrungen mit der Schwingungsbewertung von Industriegetrieben nach DIN ISO 10816-3 und DIN ISO 20816-9. . . . . 29 Fl...

In total knee arthroplasty (TKA), force is transmitted into the tibia by a combined plate-stem device along with cemented or cementless stem fixation. The present work analyzes this force transmission in finite element simulations with the main aim to avoid reported postsurgical bone density reduction as a consequence of a reduced tibial bone loadi...

Residual stresses (RSs) in the very high cycle fatigue regime have to be evaluated, as in some cases they are comparable with the applied stress, affecting the fatigue behaviour. In this work, the evolution of RSs in terms of types I, II, and III was investigated for a duplex stainless steel (DSS) during cyclic loading in high and very high cycle f...

Axles are widely used mechanical components in rotating machines. In many applications, axles are exposed to varying environmental and operational conditions, including for example, temperature, load and rotational speed. To apply acousto-ultrasonics–based structural health monitoring for axles, it is in some cases not economically feasible to coll...

Investigation on the cyclic response of metallic materials in very high cycle fatigue (VHCF) is a challenging problem, which hinders the development of fatigue theories. To overcome this difficulty, we initially applied several sensible techniques, e.g., High-energy X-ray diffraction (HEXRD), confocal laser scanning microscope (CLSM), nanoindentati...

Objective The rupture of abdominal aortic aneurysms (AAAs) is associated with high mortality despite surgical developments. The determination of aneurysm diameter allows for follow up of aneurysm growth but fails in precisely predicting aneurysm rupture. In this study, time resolved three dimensional ultrasound (4D ultrasound) based wall motion ind...

This article presents the results of theoretical and experimental investigations of characteristic changes of Lamb wave excitation and scattering by a strip-like horizontal delamination in a layered elastic waveguide for Lamb waves induced by a piezoelectric wafer active sensor. The boundary integral equation method is used to describe wave propaga...

The third dataset dedicated to the Open Guided Waves platform aims at carbon fiber composite plates with an additional omega stringer at constant temperature conditions. The two structures used in this work are representative for real aircraft components. Comprehensive measurements were recorded in order to study (I) the impact of the omega stringe...

Im Rahmen eines kooperativen Forschungsprojekts der Universität Siegen zwischen der Arbeitsgruppe Technische Mechanik (ATM) des Departments Maschinenbau und des Lehrstuhls Stahlbau und Stahlverbundbau des Departments Bauingenieurwesen wurde eine Methode zur zerstörungsfreien Schadensdetektion an Schrauben und Bolzen entwickelt und auf ihre grundsät...

The paper proposes a new hybrid approach technique to simulate acousto-ultrasonic wave excitation and propagation due to operation of the partially debonded piezoelectric transducer attached to a plate-like structure. The semi-analytical boundary integral equation method is applied to calculate guided waves propagation in the unbounded structures a...

Highlights • Force decomposition into plate and stem parts is an indicator for post-surgery tibial bone loss. • Force transfer mainly through the tibial plate (stem) reduces (increases) stress-shielding. • Strong activation of the plate in force transfer by sliding friction at the stem-bone interface. • Stress-shielding can be overcome even for...

Background Manual skull drilling is an old but in modern neurosurgery still established procedure which can be applied quickly and universally in emergency situations. Electrical drilling requires more complex equipment and is usually reserved to the Operating Room (OR). It also seems desirable to apply an electrical drill for bedside usage but a s...

Single values of all drilling parameters, manual drilling (E 5–8). (XLSX)

Single values of all drilling paramaters, electrical drilling (E 1–4). (XLSX)

In total knee arthroplasty (TKA) force is transmitted into the tibia by a combined plate-stem device along with a fully or partially cemented fixation. The present work analyzes this force transmission in finite element simulations with the main aim to avoid reported post-surgical bone density loss as a consequence of reduced tibial bone loading. I...

Detektions- und Lokalisationsalgorithmen auf der Basis des Laufzeitverhaltens von piezoelektrisch (aktiv) oder durch den Schaden selbst (passiv) angeregten Lamb-Wellen in Plattenstrukturen sind auf akkurate Kenntnisse über die Wellenausbreitung innerhalb der Platte sowie oft unerwünschten Vorgängen innerhalb der Messkette angewiesen. Zwischen der G...

Time-resolved three-dimensional ultrasound combined with speckle tracking algorithms (4D ultrasound) is a non-invasive medical imaging technique that provides full field displacement data of aortic and aneu-rysmal wall motion in vivo. Combined with inverse techniques to identify the parameters of an orthotropic and nonlinear elastic constitutive eq...

Ultrasonic guided waves have been used successfully in structural health monitoring systems to detect damage in isotropic and composite materials with simple and complex geometry. A limitation of current research is given by a lack of freely available benchmark measurements to comparatively evaluate existing methods. This article introduces the ext...

Hydrogen can substantially increase the material degradation under cyclic loading. During short fatigue crack growth, which is often the dominating stage during crack propagation, the crack growth rate is highly influenced by microstructural characteristics such as grain boundaries, the formation of slip bands and the local concentration of hydroge...

Abdominal aortic aneurysms (AAA) are a degenerative disease of the aorta with high associated mortality. Currently, there is a lack of in vivo information, which allows to characterise the individual aneurysmal wall with regard to wall strength or rupture risk. We have used 4D ultrasound strain imaging to compute the spatially resolved distribution...

The use of two-dimensional graphene, with its inherent low thickness and weight, provides high potential for large-area application and building smart structures without changing their properties. Nanocomposites and films with graphene nanoplatelets promote the formation of electrical conductive networks with piezoresistive sensing capabilities for...

Background: Hallux valgus disease is a common deformity of the forefoot. There are currently more than 100 surgical approaches for operative treatment. Because hypermobility of the first tarsometatarsal joint is considered to be causal for hallux valgus disease, fusion of the tarsometatarsal joint is an upcoming surgical procedure. Despite the dev...

In the present study, the influence of hydrogen on the fatigue behaviour of the high strength martensitic stainless steel X3CrNiMo13-4 and the metastable austenitic stainless steels X2Crni19-11 with various nickel contents was examined in the low and high cycle fatigue regime. The focus of the investigations was the changes in the mechanisms of sho...

In the present study, the influence of hydrogen on the fatigue behavior of the high strength martensitic stainless steel X3CrNiMo13-4 and the metastable austenitic stainless steels X2Crni19-11 with various nickel contents was examined in the low and high cycle fatigue regime. The focus of the investigations were the changes in the mechanisms of sho...

The increased usage of carbon fiber reinforced plastics (CFRP) for primary aerospace structures involves dealing with the susceptibility of composite laminates to impact loads as well as the occurrence of barely visible impact damages. One special case among impact sources is the so-called blunt impact, which may cause damage primarily to the inter...

Two-dimensional (2D) layered materials are ideal for micro- and nanoelectromechanical systems (MEMS/NEMS) due to their ultimate thinness. Platinum diselenide (PtSe$_{2}$), an exciting and unexplored 2D transition metal dichalcogenides (TMD) material, is particularly interesting because its scalable and low temperature growth process is compatible w...

Two-dimensional (2D) layered materials are ideal for micro- and nanoelectromechanical systems (MEMS/NEMS) due to their ultimate thinness. Platinum diselenide (PtSe$_{2}$), an exciting and unexplored 2D transition metal dichalcogenides (TMD) material, is particularly interesting because its scalable and low temperature growth process is compatible w...

Purpose: Opening wedge high tibial osteotomy (HTO) as a treatment in unicompartimental osteoarthritis of the knee can significantly relieve pain and prevent or at least delay an early joint replacement. The fixation of the osteotomy has undergone development and refinements during the last years. The angle-stable plate fixator is currently one of...

The experimentally observed short fatigue crack growth rate of an uncharged specimen tested in air is compared with results obtained from specimens tested in 10 MPa hydrogen atmosphere and specimens previously charged with hydrogen. To further discuss the hydrogen related short propagation mechanisms, a simulation approach for predicting short fati...

By means of high frequency (about 20 kHz) fatigue testing techniques, the fatigue behavior of an austenitic-ferritic duplex stainless steel was experimentally investigated up to one billion load cycles. Additional fatigue tests were performed by means of conventional fatigue testing techniques at 30 Hz in order to characterize the influence of the...

In the context of a project cooperation – consisting of an experimental part (see previous article of this book) and a modelling and simulation part – the characterisation of the cyclic deformation behaviour of austenitic stainless steels during very high cycle fatigue (VHCF) was carried out. Experimental observations indicated clear differences be...

The focus of this work lies on the investigation of the fatigue properties of austenitic Cr-Ni steels in the HCF and VHCF regime. This class of steels is characterized by low stacking fault energies which determine the main characteristics of deformation mechanisms (dislocation gliding, phase transformation). Three austenitic stainless steels, havi...

The two-dimensional material graphene promises a broad variety of sensing activities. Based on its low weight and high versatility, the sensor density can significantly be increased on a structure, which can improve reliability and reduce fluctuation in damage detection strategies such as structural health monitoring (SHM). Moreover; it initializes...

Two austenitic stainless steels of strongly different stacking fault energies (SFEs) and correspondingly different stabilities of the austenite phase were studied with respect to their very high cycle fatigue (VHCF) behavior. The metastable austenitic stainless steel 304L shows a very pronounced transient behavior and a fatigue limit in the VHCF re...

Abdominal aortic aneurysms (AAA) are a degenerative disease of the human aortic wall that may lead to weakening and eventually rupture of the wall with high mortality rates. Since the currently established criterion for surgical or endovascular treatment of the disease is imprecise in the individual case and treatment is not free of complications,...

The use of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) purposes is state of the art for acousto-ultrasonic-based methods. For system reliability, detailed information about the PWAS itself is necessary. This paper gives an overview on frequent PWAS faults and presents the effects of these faults on the wave prop...

Recent experiments in the very high cycle fatigue (VHCF) regime showed that the traditional differentiation regarding the existence of a fatigue limit based on the crystal structure of the material is unsustainable. On the one hand it was proved that bcc materials can show fracture even after ten million load cycles, which is contrary to former ass...

The exploration of fatigue mechanisms in the VHCF regime is gaining importance since many components have to withstand a very high number of loading cycles due to high frequency or long product life. In this regime, the period of fatigue crack initiation and thus the localization of plastic deformation play an important role. The material that was...

The aim of this study was to measure, characterize, and compare the time-resolved three-dimensional wall kinematics of the ascending and the abdominal aorta. Comprehensive description of aortic wall kinematics is an important issue for understanding its physiological functioning and early detection of adverse changes. Data on the three-dimensional,...

A two-dimensional model for stage I short crack propagation on multiple slip planes under the influence of hydrogen is presented. It considers elastic-plastic material behaviour by allowing sliding on the active slip planes in the corresponding slip directions. A crack propagation law based on the crack tip sliding displacement is used to simulate...

Load monitoring and damage identification are important tasks in the field of Structural Health Monitoring and are necessary for assessing the structural integrity and predicting the remaining useful life time. Reconstructing unknown force inputs or system parameters usually involves the solution of an inverse problem which is mostly ill-posed and...

Monitoring of impact loads is a very important technique in the field of structural health monitoring (SHM). However, in most cases it is not possible to measure impact events directly, so they need to be reconstructed. Impact load reconstruction refers to the problem of estimating an input to a dynamic system when the system output and the impulse...

Bogies are the core part of railway vehicles. The primary function is to carry the structure of the car body and to lead the railway vehicle on the track. Thus, it has a high impact on the dynamics of the whole train and due to its complex technical structure a huge number of failure cases can occur. Beside safety also economic motivations cause an...

A stable (AISI 316L) and a metastable (AISI 304L) austenitic stainless steel were investigated with respect to their VHCF behavior. The focus of the paper lies on the investigation of the cyclic deformation behavior of the two materials at very low stress amplitudes. The 304L steel is characterized by a pronounced cyclic softening during its initia...

In Part I - Experimental study, the cyclic deformation behavior of two austenitic stainless steel grades (AISI 304, AISI 316 L) were experimentally investigated at low stress amplitudes in the very high cycle fatigue (VHCF) regime. The observations indicate that during VHCF the metastable austenitic stainless steel (304 grade) performs a pronounced...

Probability-based methods for the consideration of detection rates and associated damage sizes have been state of the art in NDT. For structural health monitoring (SHM) systems, the quantification of detection capabilities needs to be addressed to enable the industrial implementation. Due to the fixed mounting of SHM systems on structures, experime...

Elektrische Fahrzeugantriebe auf Basis von FEM-Simulationen Bei der Entwicklung von elektrischen Maschinen spielt das Thema akustisches Verhalten eine immer wichtigere Rolle. Neben der Erhöhung von Leistungsdichten und Performance gilt es, die strukturdynamischen Anregungskräfte zu reduzieren. Mit Hilfe der FinitenElementen-Methode (FEM) und des Ei...

Using heterogeneous strain fields, it is feasible to identify the parameters of an anisotropic, nonlinear elastic constitutive equation based on the observation of just two load cases, even though the load free geometry is unknown. These data are available from in vivo observation of deformed configurations of the aorta by the use of non-invasive 4...

High frequency push-pull fatigue experiments on the austenitic-ferritic duplex stainless steel X2CrNiMoN22-5-3 (318LN) revealed that crack nucleation and crack propagation through the first grain determine significantly the lifetime of the material. Only in very few cases it was observed that fatigue samples which endured one billion load cycles wi...

The experimental observation of the microstructural deformation behavior of a metastable austenitic stainless steel tested at the real VHCF limit indicates that plastic deformation is localized and accumulated in shear bands and martensite formation occurs at grain boundaries and intersecting shear bands. Based on these observations a microstructur...

This paper presents a new procedure to evaluate a method for piezoelectric wafer active sensor (PWAS) inspection, when it is combined with a given structural health monitoring (SHM) system for structural damage detection. A data-driven method is used, applying a damage indicator DIPWAS based on the electro-mechanical impedance spectrum (EMI), to di...

Objective/background: Ultrasound measurement of aortic diameter for aneurysm screening allows supervision of aneurysm growth. Additional biomechanical analysis of wall motion and aneurysm deformation can supply information about individual elastic properties and the pathological state of the aortic wall. Local aortic wall motion was analyzed throu...

Computational analysis of the biomechanics of the vascular system aims at a better understanding of its physiology and pathophysiology and eventually at diagnostic clinical use. Because of great inter-individual variations, such computational models have to be patient-specific with regard to geometry, material properties and applied loads and bound...

The development of acousto ultrasonics (AU)-based methods in the area of structural health monitoring (SHM) within the scientific community has been enormous within the last years. A variety of methods and procedures to monitor diverse structures have been investigated. Following fundamental studies, the examination of distinct influences on these...

The decision on endovascular or surgical repair of abdominal aortic aneurysms (AAA) most commonly is taken according to two statistical criteria: a diameter exceeding 5.5 cm and a growth rate exceeding 1 cm/year. In order to obtain additional rupture risk predictors such as peak wall stress and derived indices computational biomechanical models of...

The present study documents how the irreversible fraction of cyclic plastic strain, induced by loading amplitudes close to the durability limit, causes fatigue damage such as (i) slip band development, (ii) fatigue crack initiation and (iii) short fatigue crack propagation. The damage evolution of the austenitic-ferritic duplex stainless steel X2Cr...

The information of the external loads is of great interest in many fields of structural analysis, such as structural health monitoring (SHM) systems or assessment of damage after extreme events. However, in most cases it is not possible to measure the external forces directly, so they need to be reconstructed. Load reconstruction refers to the prob...

Die Einschätzung des Rupturrisikos von Abdominellen Aorten Aneurysem (AAA) wird meist nach dem Durchmesserkriterium (> 5,5 cm) vorgenommen. Da zum einen kleinere AAA rupturieren, größere AAA aber lange Zeit intakt bleiben [1], zum anderen die Mortalität nach einer Operation nach wie vor hoch ist [2], ist es notwendig zusätzliche Indikatoren für das...

The actual wind load information is helpful in evaluating the health status of high-rise structures. However, as a type of distributed load, the wind load is very difficult to be measured directly. A possible solution is to reconstruct it from the structural response measurements. This is often an ill-posed inverse problem. In this article, such il...

During VHCF loading of duplex steels fatigue damage starts within the softer austenite phase. Depending on the spatial mismatch between the slip systems of neighboring grains, intergranular or transgranular fatigue cracks are initiated. If these cracks can propagate or are blocked depends on the interactions with the local microstructure. These int...

Damage assessment can be considered as the main task within the context of structural health monitoring (SHM) systems. This task is not only confined to the detection of damages in its basic algorithms but also in the generation of early warnings to prevent possible catastrophes in the daily use of the structures ensuring their proper functioning....

In the very high cycle fatigue (VHCF) regime, fatigue damage starts by the formation of slip bands within the softer austenite phase. By high energy X-ray diffraction it was shown that local austenite plasticity due to elastic/plastic anisotropy results in the gradual formation of residual stresses within the ferrite grains. Consequently, cracks ar...

The present paper deals with experimental results on the fatigue damage of grade SAE 318 LN austenitic-ferritic duplex steel and a modified SAE 4150 tempering steel in the very high cycle fatigue (VHCF) regime. Particular attention was paid to the relation- ship between the crystallographic orientation of individual grains and grain patches that ex...

The Structural Health Monitoring (SHM) technique Acousto Ultrasonics is based on a permanently installed piezoelectric transducer network. A reliable and effective transducer installation procedure shall be developed so that SHM represents a feasible alternative to the currently used Non-Destructive Testing (NDT) in Aircraft. A co-bonding procedure...

The exploration of fatigue mechanisms in the VHCF regime is gaining importance since many components have to withstand a very high number of loading cycles due to high frequency or long product life. In this regime, particular attention is paid to the period of fatigue crack initiation and thus the localization of plastic deformation. The resonant...

A microstructural simulation model is proposed which accounts for damage accumulation in shear bands and deformation-induced martensite formation in a metastable austenitic stainless steel (AISI304). The model is numerically solved using the two-dimensional (2-D) boundary element method. By using this method, sliding displacements can be directly e...

In order to obtain a sound data basis for the development of a physically oriented modeling approach towards crack initiation and propagation in the VHCF regime, detailed mechanical experiments were carried out in the present investigation. The focus of the study was put on the systematic analysis of local microstructure influences on the crack ini...

High frequency push-pull fatigue experiments on the austenitic-ferritic duplex stainless steel X2CrNiMoN22-5-3 (318LN) revealed that crack nucleation and crack propagation through the first grain determine significantly the lifetime of the material. Only in very few cases it was observed that fatigue samples which endured one billion load cycles wi...

In the present study the damage mechanisms of a metastable austenitic stainless steel (AISI304) are modeled and investigated starting from an initially purely austenitic condition. Microscopic examinations of the damage behavior of AISI304 tested at the real VHCF limit indicate that plastic deformation is localized in shear bands and is accompanied...

The aim of the present work is the development of mathematical models for simulation and analysis of elastic waveguides with piezoelectric wafer active sensors (PWASs) generating Lamb waves, taking into account the partial debonding. The continuous wavelet transformation is applied to the recorded signal in order to identify the debonded part of th...

The monitored resonant behavior of fatigue specimens of metastable austenitic stainless steel (AISI304) is correlated with its damage accumulation in the very high cycle fatigue (VHCF) regime. The resonant behavior is studied experimentally and shows a distinct transient characteristic. Microscopic examinations indicate that during VHCF a localized...

High performance and reliability are required for floating wind turbines due to the fact that they operate under hard conditions with minimum access for maintenance and high cost of repair. Therefore, the assessment of the severity of possible faults on the floating turbine structure will provide good guidelines once they occur either to employ the...