Bernard Masserey

School of Engineering and Architecture of Fribourg · Department of Mechanical Engineering

Background The purpose of this study is to optimize conservative treatment of distal radius and scaphoid fracture, in terms of comfort, fracture stabilization, and prevention of cast complications. Description of Technique Advances in additive manufacturing have allowed the development of patient-specific anatomical braces (PSABs) which have the po...

Thin monocrystalline silicon wafers are employed for the manufacture of solar cells with high conversion efficiency. Micro-cracks can be induced by the wafer cutting process, leading to breakage of the fragile wafers. High frequency guided waves allow for the monitoring of wafers and detection and characterization of surface defects. The material a...

Corrosion thickness loss due to adverse environmental conditions of pipelines and marine structures can cause degradation of structural health. Monitoring in difficult to access areas can be achieved using high frequency guided waves propagating along the structure, selectively excited using standard ultrasonic angle beam transducers with single si...

Adverse environmental conditions result in corrosion during the life cycle of marine structures such as pipelines, offshore oil platforms, and ships. Generalized corrosion leading to wall thickness loss can cause the degradation of the integrity, strength, and load bearing capacity of the structure. Nondestructive detection and monitoring of corros...

Monocrystalline silicon wafers are employed in the photovoltaic industry for the manufacture of solar panels with high conversion efficiency. Micro-cracks can be induced in the thin wafer surfaces during the cutting process. High frequency guided waves are considered for the testing of the wafers and the nondestructive characterization of the micro...

Micro-cracks can be induced in thin monocrystalline silicon wafers during the manufacture of solar panels. High frequency guided waves allow for the monitoring of wafers and characterization of defects. Selective excitation of the first anti-symmetric A0 guided wave mode was achieved experimentally using a custom-made wedge transducer. The Lamb wav...

In the photovoltaic industry, monocrystalline silicon wafers are employed for solar cells with high conversion efficiency. Micro-cracks induced by the cutting process in the thin wafers can lead to brittle wafer fracture. Guided ultrasonic waves would offer an efficient methodology for the in-process non-destructive testing of wafers to assess micr...

In the photovoltaic industry monocrystalline silicon wafers are employed for the manufacture of solar panels with high conversion efficiency. The cutting process induces micro-cracks on the thin wafer surface. High frequency guided ultrasonic waves are considered for the structural monitoring of the wafers and the nondestructive characterization of...

Monocrystalline silicon wafers are widely used in the photovoltaic industry for solar panels with high conversion efficiency. Guided ultrasonic waves offer the potential to efficiently detect micro-cracks in the thin wafers. Previous studies of ultrasonic wave propagation in silicon focused on effects of material anisotropy on bulk ultrasonic waves...

Aerospace structures often contain multi-layered metallic components where hidden defects such as localized disbonds can develop, necessitating non-destructive testing. Model structures consisting of two adhesively bonded aluminium plates and artificial defects in the bond layer were manufactured. Immersion ultrasonic C-scans were used to check the...

Monocrystalline silicon wafers are widely used in the photovoltaic industry for solar panels with high conversion efficiency. The cutting process can introduce micro-cracks in the thin wafers and lead to varying thickness. High frequency guided ultrasonic waves are considered for the structural monitoring of the wafers. The anisotropy of the monocr...

Corrosion due to adverse environmental conditions can occur for a range of industrial structures, e.g., ships and offshore oil platforms. Pitting corrosion and generalized corrosion can lead to the reduction of the strength and thus degradation of the structural integrity. The nondestructive detection and monitoring of corrosion damage in difficult...

The mechanical properties of reinforced plastic components are not only influenced by the orientation of the fibers during the injection process but also by the wall thickness of the component. Rigidity deviations in a range up to 20% are seen with wall thicknesses of 1 to 4 mm. Comparing the results of numeric simulations and experimental tests sh...

The scattering of high frequency guided ultrasonic waves by a fatigue crack at the side of a fastener hole has been studied. The guided wave pulse consists of the superposition of the two fundamental Lamb modes A0 and S0 above the cut-off frequencies of the higher modes. The scattered field was simulated using a three-dimensional finite difference...

The development of fatigue cracks at fastener holes represents a common maintenance problem for aircraft. High frequency guided ultrasonic waves allow for the monitoring of critical areas without direct access to the defect location. During cyclic loading of tensile, aluminum specimens fatigue crack growth at the side of a fastener hole was monitor...

Varying loading conditions of aircraft structures result in streß concentration at fastener holes, where multi-layered components are connected, potentially leading to the development of hidden fatigue cracks in inacceßible layers. High frequency guided waves propagating along the structure allow for the structural health monitoring (SHM) of such c...

Especially for ageing aircraft the development of fatigue cracks at fastener holes due to stress concentration and varying loading conditions constitutes a significant maintenance problem. High frequency guided waves offer a potential compromise between the capabilities of local bulk ultrasonic measurements with proven defect detection sensitivity...

Aerospace structures contain multi-layer components subjected to cyclic loading conditions; fatigue cracks and disbonds can develop, often at fastener holes. High-frequency guided waves have the potential for non-destructive damage detection at critical and difficult to access locations from a stand-off distance. Using commercially available ultras...

Aerospace structures often contain multi-layered metallic components where hidden defects such as fatigue cracks and localized disbonds can develop, necessitating non-destructive testing. Employing standard wedge transducers, high frequency guided ultrasonic waves that penetrate through the complete thickness were generated in a model structure con...

The development of fatigue cracks at fastener holes due to stress concentration is a common problem in aircraft maintenance. This contribution investigates the use of high frequency guided waves for the non-contact monitoring of fatigue crack growth in tensile, aluminium specimens. High frequency guided ultrasonic waves have a good sensitivity for...

The development of fatigue cracks at fastener holes due to stress concentration is a common problem in aircraft maintenance. This contribution investigates the use of high frequency guided waves for the non-contact monitoring of fatigue crack growth in tensile, aluminium specimens. High frequency guided ultrasonic waves have a good sensitivity for...

A common problem in aircraft maintenance is the development of fatigue cracks at fastener holes due to stress concentration. High-frequency guided ultrasonic waves allow for the structural health monitoring of critical areas of a structure and can be measured with high accuracy using a noncontact laser interferometer. The use of a specific type of...

High-frequency guided ultrasonic waves allow for the non-destructive testing of aerospace structures. This type of structure often contains multi-layer components subjected to cyclic loading conditions, where fatigue cracks and localized disbonds can develop. Using standard ultrasonic transducers, high frequency guided wave modes were generated in...

Aircraft structures contain multi‐layered components connected by fasteners, where fatigue cracks and disbonds can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along the structure allow for the efficient non‐destructive testing of components, such as aircraft wings. However, the sensitiv...

Aerospace structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds or localized lack of sealant can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along such a structure allow for the efficient non-destructive testing of large components, such a...

Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi layer components are connected, possibly leading to the development of fatigue cracks. Guided ultrasonic waves propagating along a structure allow in principle for the efficient non-destructive testing of large plate-like structures, such...

A common problem in aircraft maintenance is the development of fatigue cracks at fasteners due to stress concentration. The use of Rayleigh‐like waves for the monitoring of fatigue crack growth at a fastener hole in tensile, aluminum specimens is investigated. Rayleigh‐like waves can propagate along the structure and have good sensitivity for the d...

The use of a special type of high-frequency guided ultrasonic wave (coupled Rayleigh-like waves) has been investigated with a view towards applications for the non-destructive testing of aircraft structures. Rayleigh-like waves tran, fer energy between the plate sides and have good sensitivity for the detection and localisation of small defects oil...

This contribution deals with the use of coupled Rayleigh-like waves for the remote detection of defects in stiffened plates similar to aerospace structures, where access is restricted by regularly spaced features such as stiffeners or stringers. Selecting appropriate excitation frequency and position, it is shown experimentally that a significant p...

The use of coupled Rayleigh‐like waves has been investigated for the nondestructive inspection of aircraft structures. Rayleigh‐like waves transfer energy between the plate surfaces and have good sensitivity for the detection and localization of small defects on both surfaces. The beating phenomenon allows for the remote detection of defects in are...

The use of coupled Rayleigh-like waves in aluminum plates has been investigated with a view towards applications for the non-destructive inspection of aircraft structures. Such waves can be generated using standard Rayleigh wave transducers at frequencies, so that the Rayleigh wavelength corresponds to approximately half the plate thickness. The Ra...

The use of coupled Rayleigh‐like waves in aluminum plates with a view towards the non‐destructive inspection of aircraft structures has been investigated experimentally and theoretically. Rayleigh‐like waves transfer energy between both plate surfaces with a characteristic distance called the beatlength. A simple, analytical model and finite differ...

The development of fatigue cracks at fastener holes is a common problem in aircraft maintenance. This contribution investigates the use of Rayleigh-like waves for the in-situ monitoring of fatigue crack growth in tensile, aluminum specimens. Experimentally the Rayleigh-like wave is excited using standard angle beam transducers and measured using ei...

The reflection of coupled Rayleigh-like waves from surface defects in elastic plates is investigated experimentally and analyzed on the basis of an analytical model and finite difference simulations. The propagation of Rayleigh-like waves in plates is characterized by an energy transfer to the opposite plate side and back over a distance called the...

This paper presents a method for ultrasonic sizing of surface cracks based on time domain and frequency domain Rayleigh wave near-field analysis. The procedure allows for the entire range of ratio of crack depth to Rayleigh wavelength a/lambda to be covered with one single measurement. In the time domain the time-of-flight method was extended to cr...

The characterization of surface cracks on complex geometries using surface waves is investigated numerically and experimentally. The specimen geometry is implemented in a finite difference code by approximation of the contour using a Cartesian grid. In the experiments the out-of-plane surface displacement is measured by means of a heterodyne laser...

The near-field scattering of a Rayleigh wave at a surface crack is analyzed with analytical and numerical calculations complemented by detailed experimental observations. These investigations are directed towards the development of inversion schemes for surface crack sizing in mechanical components. The near-field analysis is based on a procedure t...

The characterization of surface cracks in steel plates using surface acoustic waves is investigated. In the experiments Rayleigh wave is generated by a standard wedge technique and the surface displacement is measured pointwise by means of a heterodyne laser interferometer. The presence of a crack in the acoustic field leads to an amplitude increas...

Service-like thermomechanical fatigue tests have been performed in order to characterize the endurance of 1% CrMoV rotor steel under such transient thermal conditions. The key features of these tests are low strain rates (≤10−5 s−1) and longer hold periods. In all testpieces, ratcheting with progressive section reduction is observed in the central...

A key requirement for modern power generation turbines is a flexible operating capability. One of the main objectives in the design optimization of modern plant is to reduce the time required to reach rated values of power generation during turbine start-up. Significant transient thermal stresses can lead to a complex creep-fatigue damage condition...

The nondestructive detection of fatigue cracks at fastener holes in aircraft structures employing guided waves is studied. Experimentally the first antisymmetric Lamb wave mode A0 is excited using piezoelectric transducers and the scattered field is measured by means of a heterodyne laser interferometer. The detectability of small defects is invest...

Thermo-mechanical fatigue tests have been performed to determine the cyclic constitutive behaviour of a 1%CrMoV rotor steel. The mechanical strain and temperature control profiles adopted in these tests were selected to represent loading conditions which could occur at critical rotor locations in a high temperature turbine rotor in service. The cyc...