Vibratory Test Research Articles

Non-destructive Evaluation of Cavitation Erosion Behavior of Alumina-based Ceramic Samples

Numerous industrial parts, devices, and processes are designed to withstand the conditions that lead to cavitation erosion. Metallic, ceramic, and composite materials used for these conditions must achieve specific mechanical characteristics required to resist cavitation erosion. When molten metal or alloy flows and comes into contact with refractory material or coated furnace linings, cavitation erosion can occur. This phenomenon is particularly expected in metallurgy, especially in casting operations. Alumina-based refractories, specifically low cement castable (ALCC), are often used in furnace lining applications due to their superior properties, such as high refractoriness, thermal stability, and mechanical characteristics. Mullite is another refractory material frequently used in foundry lining applications. It can be utilized as a coating in casting processes, such as the Lost Foam process, which is a novel method for producing high-quality, cost-effective castings. These two refractory materials were chosen to study their behavior under cavitation conditions. An ultrasonic vibratory test with a stationary specimen (ASTM G-32) was used for experimental cavitation determination. The results of mass loss and surface morphological parameters of degradation revealed that ALCC samples eroded predominantly at the surface, while the mullite samples exhibited more significant degradation by depth.

Phenomenological Model of Cavitation Erosion of Nitrogen ION Implanted Hiped Stellite 6

Abstract Stellites are a group of Co-Cr-C-W/Mo-containing alloys showing outstanding behavior under cavitation erosion (CE) operational conditions. The process of ion implantation can improve the CE resistance of metal alloys. This work presents the elaborated original phenomenological model of CE of nitrogen ion implanted HIP-consolidated (Hot Isostatically Pressed) cobalt alloy grade Stellite 6. The ultrasonic vibratory test rig was used for CE testing. The nitrogen ion implantation with 120 keV and fluence of 5 × 1016 N+/cm−2 improves HIPed Stellite 6 cavitation erosion resistance two times. Ion-implanted HIPed Stellite 6 has more than ten times higher CE resistance than the reference AISI 304 stainless steel sample. Comparative analysis of AFM, SEM and XRD results done at different test intervals reveals the kinetic of CE process. The model includes the surface roughness development and clarifies the meaning of cobalt-based matrix phase transformations under the nitrogen ion implantation and cavitation loads. Ion implantation modifies the cavitation erosion mechanisms of HIPed Stellite 6. The CE of unimplanted alloy starts on material loss initiated at the carbides/matrix interfaces. Deterioration starts with cobalt matrix plastic deformation, weakening the carbides restraint in the metallic matrix. Then, the cobalt-based matrix and further hard carbides are removed. Finally, a deformed cobalt matrix undergoes cracking, accelerating material removal and formation of pits and craters’ growth. The nitrogen ion implantation facilitates ɛ (hcp—hexagonal close-packed)) → γ (fcc—face-centered cubic) phase transformation, which further is reversed due to cavitation loads, i.e., CE induces the γ → ɛ martensitic phase transformation of the cobalt-based matrix. This phenomenon successfully limits carbide removal by consuming the cavitation loads for martensitic transformation at the initial stages of erosion. The CE incubation stage for ion implanted HIPed Stellite 6 lasts longer than for unimplanted due to the higher initial content of γ phase. Moreover, this phase slows the erosion rate by restraining carbides in cobalt-based matrix, facilitating strain-induced martensitic transformation and preventing the surface from severe material loss.

Three-Dimensional Printing of Ultrasoft Silicone with a Functional Stiffness Gradient.

A methodology for three-dimensionally printing ultrasoft silicone with a functional stiffness gradient is presented. Ultraviolet-cure silicone was deposited via two independently controlled extruders into a thixotropic, gel-like, silicone oil-based support matrix. Each extruder contained a different liquid silicone formulation. The extrusion rates were independently varied during printing such that the combined selectively deposited material contained different ratios of the two silicones, resulting in localized control of material stiffness. Tests to validate the process are reported, including tensile testing of homogeneous cubic specimens to quantify the range of material stiffness that could be printed, indentation testing of cuboid specimens to characterize printed stiffness gradients, and vibratory testing of synthetic multilayer vocal fold (VF) models to demonstrate that the method may be applied to the fabrication of biomechanical models for voice production research. The cubic specimens exhibited linear stress-strain data with tensile elasticity modulus values between 1.11 and 27.1 kPa, more than a factor of 20 in stiffness variation. The cuboid specimens exhibited material variations that were visually recognizable and quantifiable via indentation testing. The VF models withstood rigorous phonatory flow-induced vibration and exhibited vibratory characteristics comparable to those of previous models. Overall, while process refinements are needed, the results of these tests demonstrate the ability to print ultrasoft silicone with stiffness gradients.

SURFACE MODIFICATION OF SS-316 TO ENHANCE CAVITATION RESISTANCE THROUGH COMPOSITE MICROWAVE CLADS

Microwave cladding is one of the latest surface engineering techniques, which has been used to improve the surface properties of a material. This technique overcomes almost all limitations of the existing methods. In this study, Ni-based+10% Cr3C2 composite clads have been developed in domestic microwave oven of 2.45-GHz frequency and 900-W power. The developed composite clads have been characterized using various standard mechanical and metallurgical techniques like SEM/EDS, XRD and Vickers microhardness tester. Cavitation erosion resistance of developed composite clads has also been examined at different parametric conditions. The microstructure analysis exhibits that the developed composite clads of 730-[Formula: see text]m thickness are free of cracks (solidification and interfacial) and less porous. The presence of various intermetallic and hard carbide phases like FeNi3, CrSi2, Cr3Ni2SiC, SiC and NiC is confirmed from the XRD analysis. The Vickers microhardness study reveals that the average microhardness of clad region is [Formula: see text] HV[Formula: see text]. The cavitation erosion study (at different parametric conditions using vibratory cavitation erosion testing) reveals that the developed composite clads perform much better under cavitation erosion environment than the SS-316 substrate. The stand-off distance is found to be the most dominating factor followed by amplitude and immersion depth.

Development of a Thermographic Vibratory Test Bench for Predictive Maintenance in Asynchronous Motors

The predictive philosophy contributes to improving productivity, reducing system failures and reducing unplanned downtime in a non-invasive way to the machine, for which the test bench is based on the German standard VDI2221, using mathematical models to select the materials and the design of the final prototype. The development of the project consists of applying vibration analysis, thermographic analysis and the quality of energy in which each measurement and the correlation that exist between them is shown; in addition, the inverse Fourier transform was used to demonstrate the amplitude and frequency ranges according to the theoretical equation proposed in the Matlab program, it can also be seen the higher order vibrations of 22.1 is located at the same critical point of the SP7 measurement with a temperature of 34.6 ° C and an emissivity of 0.95, likewise the Power quality measurements are within the allowable limits according to ISO 50001; On the other hand, this analysis made it possible to determine the existence of a positive linear correlation between thermography and vibration analyzes with a correlation coefficient equal to 0.828.

Comparative Analysis of Cavitation Resistance of Deposited/Sprayed Layers of Carbides, Stainless Steels and Metastable Austenite

The cavitation erosion resistance of deposited/sprayed layers prepared by thermal spraying and welding processes was evaluated using a new principle of ultrasonic vibratory testing [1]. A high velocity air fuel thermal spraying process (HVAF), gas tungsten arc welding (GTAW or TIG), and shielded metal arc welding (SMAW) were used to prepare the deposit deposited/sprayed layers. The WC-10Co4Cr powder was deposited on 20X13 stainless steel, while E308L-17 welding filler electrode, 06X19H9T welding solid wire, and Fe-Cr-Al-Ti cored wire (known as PPM-6) were deposited on AISI 316L stainless steel. For all materials, the curves of volume loss as a function of testing time were plotted. The obtained results showed that the deposited layers of PPM-6 metastable austenite steel prepared by TIG welding process was exhibited a higher resistance to cavitation erosion than the others. The maximum volume loss of PPM-6 steel was about 0.31 mm1, whereas the volume loss for the other materials was of 5-20 times high.

Influence of low temperature plasma carbonitriding on cavitation erosion resistance of the Stellite 250 alloy – A preliminary evaluation

Superalloys are a potential material class for selection in some tribological systems, particularly those subjected to wear. When subject to cavitation erosion, the cobalt-based alloys are often applied. Surface treatments have been employed to improve the tribological resistance without loss of corrosion performance for several class of materials. In this context, the thermochemical treatment of low temperature plasma carbonitriding was carried out in a superalloy of the Co-Cr-Fe system in order to improve cavitation erosion resistance. The carbonitriding treatments were performed at temperature of 380 °C over a period of 3, 9 and 15 h. The gas mixture was composed of 72.5% H2, 25% N2 and 2.5% CH4. After the thermochemical treatment, phases formation was identified by X-ray diffraction and the glow discharge optical emission spectroscopy was used for mass concentration depth profiling of carbon and nitrogen. Cavitation erosion resistance of specimens were evaluated by a vibratory test. Mass losses were periodically measured as a function of exposure time during test. Specimens were evaluated in terms of mean depth of erosion, incubation time and mass loss. In addition, the cavitation erosion mechanism was investigated by scanning electron microscopy observation of damaged surfaces. S-phase formation was observed for all treatments. Results showed that low temperature plasma carbonitriding and the formation of expanded phase are effective to increase cavitation erosion resistance of the studied cobalt-based alloy when treatment was carried out during 3 and 9 h.

Effect of technological modes of stampings on strength properties of rocket and space equipment parts

The reasons for premature failure during vibratory tests and tensile tests of highly loaded parts of the locking mechanism made by stamping from AISI 5140 steel bars and used in rocket and space technology are studied. It is determined that destruction is caused by the microlaminations in metal formed during heat treatment. Recommendations for adjusting of the deformation processing modes of forgings, ensuring the exclusion of premature destruction cases, are developed.

Investigation on cavitation erosion of diamond-like carbon films with heterogeneous multilayer structure

Cavitation tests of three heterogeneous multilayer diamond-like carbon (DLC) films (Ti/DLC, TiCx/DLC and Ti-TiCx/DLC) were performed using a vibratory test rig to evaluate their cavitation erosion resistance. Results indicated that the cavitation erosion of multilayer DLC films resulted from flexural cracks in the bending regions, then fatigue failures were developed along the uplifted regions of the films. Comparing to TiCx/DLC film and Ti-TiCx/DLC film, Ti/DLC film had the lowest average erosion area. It was concluded that multilayer structure with titanium as adhesion layer improved the adhesion strength and reduced the plastic deformations of the DLC films in the incubation phase; these Ti layers also decreased the residual stress of the DLC films and reduced the cracks within the films in the attenuation phase; lower ID/IG ratio could improve the fatigue resistance of the multilayer films in the steady phase.

Vibratory testing with the 64 Hz Rydel-Seiffer tuning fork and its relation to the sural nerve action potential.

Despite its widespread use, little is known regarding the ability of the semi-quantitative Rydel-Seiffer tuning fork to designate peripheral nerve function. We sought to determine in a large sample of normal and abnormal nerves the relationship between vibration sense and compound sensory nerve action potential (SNAP) parameters recorded in a corresponding innervation area. Vibratory thresholds were determined on a scale of 0 to 8 with a 64 Hz Rydel-Seiffer tuning fork placed on the lateral malleolus of 303 subjects. Sural nerve sensory neurography was employed to derive SNAP parameters, which were related to vibration sense by means of multiple linear regression. ROC curve analysis was performed to determine the classification efficacy of the tuning fork in distinguishing normal from abnormal sural nerve responses. SNAP amplitude was the most significant predictor in the whole subjects group and in the subgroup of subjects with normal SNAPs, whereas conduction velocity played a major role in subjects with abnormal SNAPs. Age was significantly associated with vibration perception, particularly in subjects with normal SNAPs. With an area under the curve of 0.730, vibration sense was a fair classifier for decreased SNAP amplitudes. The optimal vibratory cutoff was 4.2. Age is a major determinant of vibratory test results, highlighting the importance of aging of central and peripheral pathways in mediating vibration sense. Hence, neurophysiological testing cannot be omitted in the context of polyneuropathy work-up, since even at the optimal cutoff threshold, vibratory examination still displays 40% false negative test results.

Audiovestibulograma: una forma práctica de ver todos los resultados

RESUMEN Introducción y objetivo: El oído (órgano cócleovestibular) es un órgano multifrecuen-ciaL. Por lo tanto, debe verse a este órgano como lo que es: una unidad embriológica, anatómica, fisiológica y clínica. Objetivo: desarrollar una cartilla audiovestibular don-de se puedan volcar los resultados obtenidos en los diferentes estudios que valoran al oído como un todo. Método: Se tomó como base la cartilla audiométrica y su sim-bología clásica, extendiendo su rango frecuencial y colocando los diferentes estu-dios a documentar: audiometría tonal liminal, impedanciometría, reflejo estapedial, electrococleografía, potenciales miogénicos vestibulares, test vibracional, video head impulse test, prueba rotatoria, prueba calórica y comandos oculomotores centrales. Discusión: Esta forma de presentación de datos, si bien no es completa, otorga la mayoría de los estudios de diagnóstico audiovestibulares. A primera vista genera sobrecarga de información al especialista, requiriendo un mínimo de entrenamiento. Conclusiones: Se trata de una cartilla de documentación única de los principales estudios cócleovestibulares, con sus respectivas referencias de normalidad, para ser presentada ante el especialista en una sola imagen requiriendo un mínimo de entre-namiento.

Multimodal Evaluation of Functional Nerve Regeneration in Transgender Individuals After Phalloplasty With a Free Radial Forearm Flap

BackgroundConstructing a sensitive phallus is a key objective in sex affirmation surgery, but still there is a major lack of evidence in outcome analysis of postoperative sensibility of the newly constructed body part. AimTo evaluate the innervation and sensibility of a forearm free-flap neophallus with nerve coaptation by a broad-spectrum follow-up. MethodsThe phallic sensibility of 20 transgender individuals who underwent phalloplasty with a free radial forearm flap was evaluated by a standardized multimodal approach, examining 5 main sensory modalities. Measurements were performed in defined areas at the phallus and at the unoperated forearm as a control area. Additionally, all patients were asked to complete a questionnaire about their subjective quality of life and ability to orgasm. OutcomeThis study evaluated the following parameters: perception of pressure (Semmes-Weinstein monofilaments) and vibration (C64 Hz tuning fork), static two-point discrimination, sharp-blunt and hot-cold discrimination at the phallus and the forearm, sum score of calculated life satisfaction, and ability to orgasm. ResultsMost of the patients (n = 14) were able to perceive 2 or more sensory modalities tested at the newly constructed phallus. 2 patients did not develop any sensibility. Interestingly, the median values for vibration perception were similar for the phallus and the unoperated forearm. Pressure sensibility was present at the phallus, but less than at the forearm. Moreover, sharp-blunt sensibility was present in 11 patients. In contrast, clear cold-warm discrimination could not be achieved, although the majority of patients detected the cold stimulus. A two-point discrimination of up to 23 mm could not be detected in either body part. 15 patients experienced orgasms without difficulty after 23 months (n = 20 after 54 months). Clinical ImplicationsWe observed successful recovery of sensibility at the phalli for the majority of patients, including the preservation of orgasm. Strengths & LimitationsOur institution is one of the few centers regularly performing phalloplasties in transgender patients, especially preferring the technique of Gottlieb and Levine. This study contributes to the few studies that perform sensory testing at the phallus and is unique in its kind in that it uses a multimodal approach. A limitation of this study is the limited number of cases and the limited validity of vibratory testing. ConclusionConfirming a promising tactile sensibility after phalloplasty with a neurovascular radial forearm flap, the next step would be to identify whether this reinnervation effectively develops due to nerve coaptation or spontaneous sprouting.Küenzlen L, Nasim S, van Neerven S, et al. Multimodal Evaluation of Functional Nerve Regeneration in Transgender Individuals After Phalloplasty With a Free Radial Forearm Flap. J Sex Med 2020;17:1012–1024.

Cavitation Erosion-Corrosion Resistance of Deposited Austenitic Stainless Steel/E308L-17 Electrode

The ultrasonic vibratory test was carried out to evaluate the cavitation erosion/corrosion resistance of welded-deposited austenitic stainless steel/E308L-17. Three layers of the E308L-17 electrode were deposited onto AISI 1040 substrate utilizing Shielded Metal Arc Welding (SMAW) process. The eroded surfaces of the E308L welded deposit/coating and AISI 1040 substrate steel have been analyzed by evaluating surface topography, as well as scanning electron microscope (SEM) micrographs. In addition, the cumulative weight loss and erosion rate curves were attained to evaluate the cavitation resistance of the tested materials. The cavitation results showed that the E308L-17 deposited stainless steel has lost about 15 mg as a cumulative weight, while the loss of AISI 1040 substrate was about 123 mg. This is equal to 0.12% and 1.0% of the original test specimen weight for the E308L-17 and AISI 1040, respectively. Consequently, E308L-17 austenitic stainless steel can be effectively used as a protective material for surfaces exposed to cavitation wear, since the AISI 1040 substrate has been enhanced by 8 times using E308L stainless steel.

Bi-Modal Failure Mechanism of Rolling Contact Bearings

The theory of failure of rolling contact bearings is based on fluctuating high level loading and material fatigue. This theory is unimodal, considering only the solid components of the bearing, and ignoring the liquid phase, which is the lubricant. Bearing life is rather dispersed, reaching a ratio of 20 between the extreme values. Since this theory was established, several exceptional phenomena were detected that could not be explained by it, such as: 1) Pitting damage beyond the contact path; 2) Detrimental effect of a minute quantity of water in the lubricant on bearing life. 25 ppm of water in the lubricant brought about shorter bearing life by over than 30%. The bimodal failure theory considers both solid and liquid bearing components. The damaging process of the lubricant evolves from its cavitation. During this process vapor filled cavities are formed in low pressure zones. When these cavities reach high pressure zones they implode exothermally. These implosions cause local high pressure pulses reaching 30,000 at accompanied by a temperature rise of about 2000 degrees K [1]. This paper includes cavitation erosion test results on stainless steel samples by vibratory and water tunnel test rigs. Various methods of lubricant dehydration are presented and evaluated. The main conclusion from this analysis is the use of water-free lubricants, for long life of RC bearings and more uniform service life thereof.

Introduction to the Examination of Thin-Walled Structures Using the Vibrodiagnostic Method

Abstract The article presents a methodology of non-destructive diagnostic vibratory tests of welded plates with geometrical parameters that classify them into a group of thin-walled panels. On the basis of such plates, most ship constructions are created. In previous works, the authors dealt with the study of welded joints in plates with significant thicknesses and developed for them a number of methods for assessing the quality of welded joints. Vibrodiagnostics is a NDT method that allows the use of a variety of techniques and tools. It enables measurements to be made in both a contact and non-contact way depending on the requirements of the structure and the environment. Vibrodiagnostic method is one of the most modern NDT methods, which uses modern measurement tools and computer analysis of data. On the basis of the developed methods, the authors intend to verify their application to plates from real welded constructions, which will be performed in typical shipyard conditions by welders. Such tests are important due to their use for the construction of a real SHM ship construction monitoring system. These methods allow for the examination of the condition of ships’ structural plates and can detect defects in welded joints that prevent ships from operating under severe sea conditions. The article presents the laboratory stand, the sensor layout, results, and their initial analysis.

Bubble–bubble interaction effects on multiple bubbles dynamics in an ultrasonic cavitation field

A vibratory erosion test rig is used to study the cavitation erosion of 6061 alloy. Some craters and material fracture are found on the specimen surface at the beginning of test. A cavitation model in an ultrasonic field is developed by applying the bubble–bubble interaction effect into Keller–Miksis equation to obtain the bubbles dynamic characteristics. The results reveal that the bubble cloud configuration is suitable for the explanation of cavitation erosion, and the erosion surfaces of the specimen were subjected to the effect of both massive bubbles collapsing, occurring in the thin liquid layer between the horn and the specimen. It is concluded that the optimal coupling strength of bubbles increases with the decrease of the bubble initial radius, and stable cavitation only occurs when the acoustic pressure amplitude is higher than a threshold value, which can well predict the experimental results.

Influence of TiO2 Additives on Cavitation Erosion Resistance of Al-Mg Alloy Micro-Arc Oxidation Coating

Four ceramic coatings are fabricated on 6061 aluminum alloy substrates with a micro-arc oxidation technique in silicate electrolytes with different TiO2 nano-additive concentrations. To explore the cavitation erosion resistance of the micro-arc oxidation (MAO) coating, cavitation tests are performed using a vibratory test rig. After cavitation tests lasting 10 min, the mass losses, surface morphologies, and chemical compositions of the samples after cavitation tests are examined using a digital balance, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), respectively. The results indicate that, in contrast to the aluminum alloy, the MAO coatings, by adjusting TiO2 nano-additive concentration, can decrease the mean depth of erosion rate (MDER) due to the cavitation damage, and lead to an excellent cavitation erosion resistance. The results also show that: In contrast to aluminum alloy, MAO coatings can decrease the MDER due to the cavitation damage in a short period of time by adjusting TiO2 nano-additive concentration. With the increase of TiO2 nano-additive concentration, the compactness and the surface hardness of MAO coatings decrease, which can easily lead to larger erosion pits.

Influence of adhesion strength on cavitation erosion resistance of diamond-like carbon coating

Purpose The disbonding of DLC coating is a main failure mode in the high-speed cavitation condition, which shortens the service life of the bearing. This study aims to investigate influence of adhesion strength on cavitation erosion resistance of DLC coating. Design/methodology/approach Three DLC coatings with different adhesion strengths were grown on the 304 steel surfaces by using a cathodic arc plasma deposition method. Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of a DLC coating. The cavitation mechanism of the substrate-coating systems was further discussed by means of surface analyses. Findings The results indicated that, the residual stress decreased and then increased with the increasing DLC coating thickness from 1 µm to 2.9 µm, and the lower residual stress can improve the adhesion strength of the DLC coating to the substrate. It was also concluded that, the plastic deformation as well as the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion strength. However, lower residual stress and better adhesion strength could help resist the occurrence of the coating fracture. Originality/value Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of the DLC coating. The plastic deformation and the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion of coating. Lower residual stress and better adhesion of coating could resist the occurrence of the DLC coating fracture.

Choosing a Vibratory Test to Pair With Semmes Weinstein Monofilament Testing for Evaluating Lower Extremity Sensation in Patients With Diabetes: A Comparison of Three Vibratory Methodologies.

Numerous guidelines recommend pairing Semmes-Weinstein monofilament (SWM) testing with a secondary clinical test when screening for diabetic peripheral neuropathy, yet time is very limited in clinical practice. This study compared the time to complete and the diagnostic agreement of three vibratory sensation tests. Sixty-five individuals (42% male; aged: 61 ± 12 years) were recruited. A single investigator administered the following tests bilaterally: 10-site SWM, traditional tuning fork (TTF), electronic tuning fork (ETF), and vibration perception threshold (VPT) via biothesiometer. Times to physically administer the tests were compared with a one-way repeated measures ANOVA. Cochran's Q test was used to compare the varied tests' diagnostic agreement. The ANOVA indicated there were significant (P < .001, partial eta squared = .442) differences in time to complete the varied tests. Sidak post hoc comparisons indicated the VPT (21.2 ± 14.3) testing took an intermediate time to complete, while the ETF (9.7 ± 6.5) and TTF (10.1 ± 7.5) tests took the least amount of time, and the SWM (28.6 ± 8.4) test took the longest time. There were also numerous significant differences (P ≤ .001) between the different tests in regards to neuropathy diagnoses. Tuning fork methods required 11 seconds less to administer than VPT testing. Although that may seem trivial, it is worth noting peripheral neuropathy screening often fails to occur in the precious few minutes clinicians are allotted per patient. Considering ETF's intrinsic control of stimulus amplitude and its ease of use with an embedded timer, the ETF is recommended over the TTF. Clinicians should also be mindful that different tests yield different diagnostic conclusions.

Fatigue strength of S355JC steel under harmonic and random bending-torsion loading by a tri-axis shaker: Preliminary experimental results

A new testing system for applying coupled/uncoupled bending-torsion loading in vibratory tests by a tri-axis shaker has been recently developed at the Department of Engineering of University of Ferrara. The system is composed of a cylindrical specimen with eccentric tip masses, excited by horizontal and/or vertical base accelerations. A special design of the gripping system for specimen constraint allows torsional and bending deformations to be produced and controlled independently, when vertical and horizontal base accelerations are applied simultaneously by the shaker. The values of accelerations and strains in the tested specimens can be monitored continuously. This paper presents a first set of experimental results under harmonic bending and torsion, and under narrow-band combined random loading. Estimations from two frequency-domain approaches are also discussed.