Blade Test Research Articles

Evaluation of a substitute bird for engine fan blade impact tests considering the bird-slicing state

Bird ingestion is one of the major threats to aero engines. To evaluate airworthiness compliance in bird ingestion events, dynamic structural tests are the most straightforward and intuitive method. These tests can be conducted using either real birds or substitute birds, the latter offering enhanced repeatability and more convenient test management. In this study, an equivalent strategy is proposed aimed at developing a suitable substitute bird for impact tests on engine fan blades by evaluating the dynamic bird-slicing responses. Two gelatine recipes are adopted to manufacture the substitute birds and the impact responses are measured with a wedge-Hopkinson bar (WHB) system. It is found that the inertial force is the dominant factor in the impact load, and the gelatin resistance also has a certain influence. Generally, the impact responses of the gelatine birds show a constant distribution of the normalized peak impact force with good dispersion as velocity increases. The momentum transfer (MT) exhibits both a “velocity effect” and a “mass effect”, duplicating the responses observed in real bird tests. Besides, the temporal distribution of the force history for the gelatine birds closely matches that of the real birds. The results indicate that the equivalent strategy effectively evaluates the substitution, and the proposed gelatin recipe can be used for real bird alternatives in engine fan blade tests.

Water Turbine Guide Blades Effect of Quartz Sand on Abrasion Rate

Abstract Hydroelectric power plants with the aim of being used to generate electrical energy are mostly operated in areas with sedimentation content which can cause wear and tear on the components of the hydropower plant. This activity is emphasized to determine the effect of quartz sand on the rate of abrasion on the guide vanes of the Francis type water turbine. This activity was carried out using a water turbine guide blade abrasion test tool with a guide blade test object made of SUS 304 stainless steel material. The results are presented quantitatively and qualitatively, the greater the concentration and diameter of the quartz sand particles, the water pressure and the angle given at the same time, the greater the rate of abrasion that occurs in the francis type water turbine guide vane. The highest abrasion rate was 5.10 (g/cm2 x hour) in the angle variation test with a constant Q and a water: sand ratio of 70%: 30%.

Design, motion-planning, and manufacturing of custom-shaped tools for five-axis super abrasive machining of a turbomachinery blade type component

Free-form surfaces generated by non-uniform rational B-splines (NURBS) are evolving to face turbomachinery component requirements, such as turbine blades to enhanced efficiency. Super abrasive machining (SAM) is presented as a potential process for high-added value components using custom-shaped tools to be adapted to any surface. The adaptability and flexibility of these tool concepts are specifically designed to fit these complex surfaces. This paper presents an innovative manufacturing approach for blade type components using a custom-shaped tool designed through an optimization process that simultaneously optimizes both the shape of the tool and its motion. The proposed method with SAM finishing using a custom-shaped tool is compared against a standard tool and traditional machining process. The result obtained on the blade test case shows that the custom-shaped tools need fewer paths, yet produce more accurate surface finish.

A Full-Scale Tidal Blade Fatigue Test using the FastBlade Facility

Fatigue testing of tidal turbine blades requires the application of cyclic loads without the ability to match the natural frequency of the blade due to their high stiffness and the associated thermal issues of testing composite materials at those frequencies (i.e., 18–20 Hz). To solve this, loading the blades with an auxiliary system is necessary; in most cases, a conventional hydraulic system tends to be highly energy-demanding and inefficient. A regenerative digital displacement hydraulic pump system was employed in the FastBlade fatigue testing facility, which saved up to 75 % compared to a standard hydraulic system. A series of equivalent target loads were defined using Reynolds-Averaged Navier Stokes (RANS) simulations (based on on-site collected water velocity data) and utilised in FastBlade to demonstrate an efficient way to perform fatigue testing. During the test, a series of measurements were performed on the blade response and the Fastblade test structure itself, providing novel insights into the mechanical behaviour of a blade, and enabling improved testing practice for FastBlade. Without catastrophic failure, the blade withstood the principal tidal loading for 20 years (equivalent). This test data will enable FastBlade to identify improvements to the testing procedures, i.e., control strategies, load introduction, instrumentation layout, instrument calibration, and test design.

Durability Test of Microtome Blades with the High-Precision Tissue-Sectioning Machine

In this study, the durability of microtome blades, used for sectioning paraffin blocks, was evaluated with the goal of improving the quality of sections in pathology tests. First, for the durability test of microtome blades, a sectioning test device that realizes stable sectioning operations was developed. This device comprised precise stages supported by cross-roller guides, achieving sufficient rigidness. This device allowed automated repetitive sectioning and simultaneously measured the principal and thrust cutting forces. Samples embedding porcine kidney and rib tissues were used for the durability test. Two types of blades with different blade edge angles were used. Additionally, the rake face and cross-section of blades, as well as H&E-stained sections, were observed. In the durability test with porcine kidney tissue, good quality sections were obtained even after 100 times of sectioning with both microtome blades, showing sufficient durability. However, in sectioning porcine rib tissue, the microtome blade with a large blade edge angle produced good-quality sections in the initial phase of the durability test; however, defects such as overlapping of folds were observed after 100 times of sectioning. Meanwhile, the microtome blade with a small blade edge angle experienced blade damage from the early phase of the durability test, resulting in the production of unsuitable preparations for pathology tests. These results indicated that the microtome blade with a small blade edge angle lacked durability against hard tissues such as porcine ribs.

UJI PENGARUH VARIASI SUDU TURBIN PADA SUDUT KEMIRINGAN POROS 15 DERAJAT TERHADAP DAYA DAN EFISIENSI TURBIN ARCHIMEDES

The need for electrical energy sources increases along with the increasing population in Indonesia. While the electrical energy used today is sourced from fossils that are starting to run out. So there is a need for alternative energy sources to replace fossils. One of them is by utilizing the river flow which is converted into electrical energy which is called a screw turbine power plant. This study uses an Archimedes Screw Turbine, with a tilt angle of 15 degrees, at variations of blade 1,2 and blade 3 to test the electrical power and efficiency of the turbine. The results of the 1 blade test at an angle of 15 degrees obtained electrical power of 8.17 watts and turbine efficiency of 75.92655%. The results of the 2 blade test at an angle of 15 degrees obtained an electric power of 7.16 watts and a turbine efficiency of 66.54028%. The results of the 3 blade test at an angle of 15 degrees obtained an electric power of 7.45 watts and a turbine efficiency of 69.23534%. Thus the use of blade 3 at an angle of 15 degrees produces greater electrical power and efficiency for blade 1, the result is greater than blade 2 and blade 3

An efficient sparse surrogate model for aerodynamic characteristics of a supersonic compressor cascade with uncertain geometric deformations

The increasing demand for high-load compressors necessitates research and design of supersonic compressor blades. Geometric deformations of the blades resulting from manufacturing errors introduce uncertainties in their aerodynamic characteristics. For uncertainty analysis, Polynomial Chaos Expansion (PCE) has gained popularity among engineers in various disciplines. However, as the number of random variables used to describe uncertainties increases, the efficiency of the PCE method diminishes. To overcome this limitation, an Efficient Sparse Surrogate Model (ESSM) was first proposed. The ESSM combines PCE to approximate global characteristics and Gaussian process modeling to capture local variability, resulting in a highly accurate model. Additionally, by utilizing an iteratively diffeomorphic modulation under observable response preserving homotopy, important PCE basis functions are adaptively selected, leading to a sparse surrogate model that significantly reduces the required training samples. Then using the ESSM, efficient Uncertainty Quantification (UQ) and global sensitivity analysis were conducted to evaluate the impact of uncertain geometric deformations on the aerodynamic characteristics of a supersonic compressor cascade. Principal Component Analysis (PCA) was employed in conjunction with an Improved Class Shape Transformation (ICST) to characterize geometric deformations caused by manufacturing errors. The proposed ICST method exhibits enhanced accuracy in fitting near the leading and trailing edges compared to the CST method. PCA enables a 50% reduction in the number of random variables needed to describe geometric deformations. The UQ results establish a quantitative correlation between geometric deformations and supersonic aerodynamics, and the sensitivity analysis identifies some specific forms of geometric deformations that significantly impact the aerodynamics. Finally, the study investigated the flow mechanisms associated with typical geometric deformation forms, further providing recommendations for manufacturing and testing of supersonic blades to prevent performance deterioration.

A full-scale composite tidal blade fatigue test using single and multiple actuators

In order to perform fatigue testing on tidal turbine blades, it is necessary to apply cyclic loads that do not match the blade’s natural frequency. This is due to the high stiffness of the blades and the thermal challenges associated with testing composite materials at frequencies typically around 18–20 Hz. To overcome this challenge, auxiliary systems are used to load the blades. However, conventional hydraulic systems commonly used for this purpose are known to be energy-intensive and inefficient. In this work, we present results obtained at the FastBlade fatigue testing facility, which utilises a regenerative digital displacement hydraulic pump system to address these issues. This innovative system has proven to be highly efficient, resulting in up to 75% energy savings compared to standard hydraulic systems. To perform these tests, we first performed a series of Reynolds-Averaged Navier–Stokes (RANS) simulations using on-site water velocity data to determine equivalent target hydrodynamic loads. These target loads are applied to the blades using initially a single contact point and, later, three load contact points. The FastBlade facility showcases an effective approach to fatigue testing during these tests. Throughout the testing process, comprehensive measurements are taken to evaluate the response of the blades and the FastBlade test structure itself. These measurements provide valuable insights into the mechanical behaviour of the blades when a single or multi-actuator setup is used to match the root bending moment and contribute to the refinement of testing practices. Notably, the blades successfully endured the equivalent of 20 years of tides in an accelerated fatigue loading test without experiencing catastrophic failure. The data obtained from these tests will enable the identification of improvements in testing procedures, including control strategies, load introduction methods, instrumentation layout, instrument calibration, and test design. This knowledge will lead to enhanced performance and reliability of the FastBlade facility, further advancing the field of tidal turbine blade testing.

Application of 3D Digital Image Correlation Technique to Measurement of Wind Blade Properties from Coupon Test and Small-Sized-Blade Frequency Test

As a wind blade is getting larger, its structural behavior becomes more complex and thus the risk of blade structural failure becomes higher. Generally, structural integrity is proved through blade testing with contact measurement devices such as strain gauges. However, contact measurement can only measure the physical quantities from installation points and requires lengthy cables to transmit the electrical signals to a data acquisition system, which can cause signal noise and add unnecessary weight. Recently, noncontact measurement techniques such as digital image correlation (DIC) have been widely used in various industries to process images captured from cameras and generate full-field strains and displacements without any mechanical connections such as cables. In this study, the application of three-dimensional DIC to wind blades was investigated; in addition, the material properties of glass-fiber-reinforced plastics used in blades for the measurement of the first frequency were also studied. Tensile testing was performed using coupons equipped with strain gauges and speckle patterns. In addition, a small blade from a 10 kW wind turbine was utilized to measure the first flapwise frequency using DIC and modal tests; the results showed a 2.1% difference between the two different measurements. This research showed that the DIC technique could be an alternative replacement for the traditional measurement technique upon further validation tests.

Effects of Fibre-Reinforced Plastic Wedge-Stick Slope on the Performance of Wind-Turbine Blade Root Connections

Bushing-insert connections have emerged as efficient blade root connection designs. Bushing-insert connections with fibre-reinforced plastic (FRP) wedge-sticks enhance the strength and stability of the blade root, prevent stress concentration at the blade root, and improve the service life and reliability of the blade. However, studies on the failure mechanisms of the FRP wedge-sticks in bushing-insert connections are scarce. Hence, in this study, the influence of the FRP wedge-stick on the structural performance of the blade root was analysed by changing the slope of the FRP wedge-stick’s inclined surface at a constant thickness. The finite element method, sample testing, and full-size blade testing method were employed, and structural verification was conducted using an 84.5 m blade. The results reveal that the contact area of the inclined surface can be increased by reducing the slope of the FRP wedge-stick. This increase in area reduces the stress transmitted to each node of the FRP wedge-stick and blade root, prevents delamination of the FRP wedge-stick and blade root, and enhances the reliability of the blade root connection.

Nonlinear vibration characteristics of virtual mass systems for wind turbine blade fatigue testing

Abstract. The biaxial fatigue test of wind turbine blades is helpful to shorten the test time and is more suitable for the actual operating conditions. Adding tuning masses to the blade is a common method for blade uniaxial testing at present, and its purpose is to adjust the load distribution in one direction of the blade. However, the tuning masses on the blade will affect the load distribution in the direction of the blade flap-wise and edge-wise at the same time in the biaxial test, so the concept of “virtual masses” is proposed to realize the decoupling of the load distribution in the biaxial test. Due to the limitation of the size of the virtual mass mechanism and the complex motion trajectory of the blade, the actual inertial effect provided by the virtual masses is different from the ideal situation, which will affect the resonance characteristics of the test system and the load distribution of the blade. Therefore, in order to evaluate the effect of the nonlinear effect introduced by the virtual masses on the resonance characteristics of the test system and the blade load distribution, the equivalent dynamic model of the bladed virtual mass test system was established by using the Lagrange method. Then, the nonlinear effects of blade amplitude and virtual mass installation parameters on the test system are obtained by a numerical method. Then, based on the nonlinear vibration theory, the approximate nonlinear amplitude–frequency characteristics of the test system are obtained, that is, the resonance frequency of the test system will decrease with the increase in the blade amplitude. Through the simulation analysis of two blades over 80 m in length, the applicability of the theoretical method is verified. It can be seen from the simulation results of the simulated uniaxial test that larger amplitudes of the blade and shorter connection rods will reduce the resonance frequency of the test system. When the vibration amplitude at the excitation point is the same, a lower resonance frequency results in a smaller load distribution level, that is, the area which is actually fully tested will be reduced. In the biaxial simulation test, the resonance frequency of the test system will be further reduced because the virtual masses will be affected by the coupled motion in both directions at the same time. Furthermore, the introduction of an external mechanism of the virtual mass will also cause deformation of the envelope of the blade biaxial trajectory, which will further affect the load distribution of the blade. This work explores the nonlinear influence of virtual masses on the actual fatigue test. The theoretical analysis is helpful to provide the basis and reference for the preliminary preparation work of the test organization, including adjusting the tuning mass scheme, adjusting the load distribution and selecting the appropriate excitation equipment.

Assessment of performance properties of compressor blades made of EI961-Sh steel with nickel-cadmium and titanium-nitride coatings

Comparative tests of compressor blades made of EI961-SH steel were carried out for resistance to fatigue, abrasive wear and corrosion damage to the surface when applying electrolytic nickel-cadmium and vacuum plasma coating of titanium nitride.

(Second Best Student Paper Award) Blade Test in Atmospheric-Pressure Ar Gas to Characterize Bonded Interface Fabricated Using Atomic Diffusion Bonding

Atomic diffusion bonding (ADB) of wafers using thin films is a promising process to achieve room-temperature wafer bonding [1]. For ADB processing, thin oxide [2] and nitride [3] films are useful for bonding, as are thin metal films [1]. For blade testing, a conventional method to examine the surface free energy at the bonded interface γ, the debonding length L is measured after a thin blade is inserted between the bonded wafers. The value of γ is calculated using L values. For a bonded interface such as Si/SiO2 or SiO2/SiO2, stress corrosion caused by oxygen and water gases in air is well-known to affect the L value as does the bonding strength [4]. For this study, a blade test was applied in Ar gas at atmospheric pressure for wafers bonded using ADB processing. Bonded interfaces of two kinds were examined: interfaces bonded using thin metal films and those bonded using oxide films. Using Maszara’s equation for convenience, we assessed the variation of γ values calculated from L values.Figure 1 presents values of γ for quartz glass wafers bonded using Ti(0.7 nm) film on each side as a function of measurement time t. Two series of data are shown: those measured in Ar and in air. The blade-insertion speed was fixed at 100 μm/s. As t increased, γ measured in air decreased remarkably from the initial value γ0(air) of 3.1 J/m2. The values of γ measured in Ar were higher than those in air. γ in Ar maintained the initial value of γ0(Ar) until t=400 s; it then started decreasing. In fact, γ0(Ar) did not increase concomitantly with increasing blade-insertion speed. Results revealed that the gradual reduction of γ in Ar resulted from oxidation of Ti films with impurities of O2 and H2O in Ar gas. The value obtained without oxidation effects is γ0(Ar).Figure 2 presents values of γ for quartz glass wafers bonded using oxide thin films as a function of t: (A) using Al2O3(2 nm) films and (B) using ZrO2(0.5 nm) films. In both figures, the values of γ measured in Ar are much higher than those measured in air. Actually, γ in Ar for wafers bonded using Al2O3(2 nm) films maintained the initial value γ0(Ar) until t=150 s; then it started decreasing. This suggests that γ0(Ar) corresponds to the value obtained without the effects of water-stress corrosion. However, γ in Ar for wafers bonded using ZrO2(0.5 nm) films did not maintain the initial value γ0(Ar): γ decreased gradually as t increased, which indicates that the water–stress corrosion effects on the values of γ were not suppressed even in Ar. T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).T. Shimatsu, H. Yoshida, M. Uomoto, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. 51 (2021).M. Uomoto, H. Yoshida, T. Shimatsu, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. 45 (2021).F. Fournel, L. Continni, C. Morales, J. Da Fonseca, H. Moriceau, F. Rieutord, A. Barthelemy, and I. Radu, J. Appl. Phys., 111, 104907 (2012). Figure 1

Investigation of Anodic Bond Formation Process and Potential Use of the Results

Anodic bonding is a widely used process in research and industry for MEMS Applications. The main advantage is that it is a very reliable process, that results in a strong and hermetically sealed bond. The bonding process is also very stable to perform. These properties are due to the process sequence of heating the wafers, to be bonded, to a temperature in the range of 300 to 450°C. One of these two wafers has to be made of borosilicate glass (e.g., SCHOTT Borofloat33®). In such glasses, sodium ions (network modifier) are dissolved out of the glass network in the temperature range mentioned and thus become free and mobile. If now a negative voltage of typically 1000V is applied to the glass wafer, the free positively charged sodium ions will move away from the contact area of both wafers, the later bonding interface, under the influence of the electric field. This results in a displacement current, which decreases again after a maximum is reached, due to the limited available number of charge carriers (sodium ions). This ultimately leads to a depletion of the charge carriers in the glass. It is generally assumed that a linked effect occurs in the bond field, namely that oxygen ions migrate from the glass to the bond interface, where they cause the actual bond formation via anodic oxidation.Even though this basic concept of the anodic bonding corresponds to state of the knowledge of how the anodic bond is actually formed [1], it is difficult to prove in practice. In order to gain a deeper insight into the formation of anodic bonding and thus open up new applications and even wider utilization of anodic bonding, a first basic experiment was done as follows: A glass wafer was provided with a thin aluminum layer by a sputtering process and another glass wafer was anodically bonded to this aluminum layer. The typical bonding current (depletion and current drop) was observed and the resulting composite of two glass wafers with a very thin intermediate aluminum layer was examined and tested for bonding quality. First of all, it can be stated that bonding formation has taken place locally between the the 6" wafers. Unfortunately, particle contamination could not be completely avoided during processing leading to larger unbonded areas, especially in the center of the wafer. Nevertheless, the bonded areas allow for evaluation of bonding quality. The sputtered aluminum layer has a higher thickness in the center, due to the fact that the glass wafer was eccentrically rotated below a small sputter target. This inhomogeneity effect enables the characterization of different Aluminum layer thicknesses in one sample. The sputter time was set, that at the wafer center an untransparent Aluminum layer was deposited, while at the wafer edge just a few nanometers of aluminum forming a semitransparent layer. After the bonding experiment it was noticed that in all the bonded area the aluminum appears rather homogeneously transparent. According to that it can be concluded that the aluminum layer is oxidized during anodic bonding transforming into transparent Aluminum oxide. This finding is a clear confirmation of the general thesis, that during anodic bonding an anodic oxidation takes place at the bond interface. In further examinations the influence of the bonding parameters on this oxidation process will be investigated. It is expected that with higher temperature and bonding voltage the oxidation will be enhanced, ending up with an optically highly transparent layer of Aluminum oxide. This might be relevant for emerging optical applications requiring anodic bonding as reliable bonding process together with optical transparence for visual light. As blade tests have shown the bonding conditions in the first process are not yet optimal – the bonding strength was rather low, but darker spots in the crack opened area indicate a transfer of the aluminum oxide layer. By variating and improving bonding conditions, a deeper insight into the details of the oxidation process during anodic bonding will be available. So far it is known that easy to oxidize materials (Silicon and Aluminum) can be well anodically bonded while rather inert materials (Silicon Nitride) are hardly or not bondable with this procedure. For that reason, some materials like Platinum, Gold, and Titanium these predictions will be evaluated in practice. With this more profound knowledge it might be possible to predict the anodic bonding behavior of different materials in the future.Literature:[1] Lapadatu, A. C., & Jakobsen, H. (2015). Anodic bonding. In Handbook of Silicon Based MEMS Materials and Technologies (pp. 599-610). William Andrew Publishing. Figure 1

Oxide-Free SiC-SiC Direct Wafer Bonding and Its Characterization

There are different requirements for the production process and the final product of SiC-SiC wafer bonding. The manufacturing of devices that are sensitive to high temperature processing – due to broadened doping profiles and induced thermal stresses – requires room temperature bonding with high bond strength, while for electrical devices, it is mandatory that the bonding interface with a thin amorphous layer is oxide-free.[1] Reduced complexity of processes is also an important point for the final production. Hence, the goal of this work was to perform and characterize direct bonding of SiC-SiC without any added/deposited bonding layer. This type of bonded SiC wafers can be used for power electronics such as for the fabrication of traction inverter for automotive applications, DC/DC converter, on board charger or charging station.[2]For the wafer bonding processes standard 100 mm 4H SiC wafers were bonded with their Si-terminated faces in order to fabricate oxide-free bonds. The wafer bonding process was performed using the EVG ComBond® system: first the native oxides from both wafer surfaces were removed using an ion beam sputtering process, followed by the transfer of both wafers to the bonding process station operated in ultra-high vacuum (UHV) to significantly retard the oxidation process. Finally, the bonding process was performed at room temperature (RT).The goal of this study was to demonstrate the feasibility of the bonding process and to gain insight on the surface chemistry after activation. The investigations covered three areas: incoming inspection of the original wafer, characterization of activated single wafer and analysis of bonded wafer pairs. The focus was on compositional, chemical, mechanical and morphological analysis of the surfaces and of the bonded interfaces. In the case of single wafers, the focus of the incoming inspection was on whether the wafers fulfill the requirements of wafer bonding, and on the characterization of activated wafers to measure the surface modifications. Atomic force microscopy (AFM), white light interferometry (WLI) and spectroscopic ellipsometry (SE) were used to determine the surface roughness, the wafer topography and the surface layer structure, respectively. All three parameters are essential for successful RT SiC-SiC wafer bonding. The change of the surface chemistry was investigated by angle resolved x-ray photoelectron spectroscopy (AR-XPS). The quality of the bonded wafers and the bonding energy were verified using scanning acoustic microscopy (SAM) measurements (Fig. 1) as well as the Maszara blade test. Furthermore, cross-section transmission electron microscopy (X-TEM) showed a bonding interface with a thin amorphous layer and no noticeable additional oxygen containing layer (Fig. 2). In order to gain quantitative elemental distributions of oxygen and argon, energy dispersive x-ray spectroscopy (EDXS) was applied.The work reported is a demonstration of the capability of the different characterization methods regarding SiC-SiC wafer bonding. Future work will focus on the investigation of the bonded interface characteristics in the function of the bonding process parameters and the annealing conditions.[1] F. Mu, M. Fujino, T. Suga, Y. Takahashi, H. Nakazawa and K. Iguchi, "Wafer bonding of SiC-SiC and SiC-Si by modified surface activated bonding method" 2015 International Conference on Electronics Packaging and iMAPS All Asia Conference (ICEP-IAAC), Kyoto, Japan, 2015, pp. 542-545, doi: 10.1109/ICEP-IAAC.2015.7111073.[2] Tsunenobu Kimoto, "Material science and device physics in SiC technology for high-voltage power devices" Jpn. J. Appl. Phys. 54 040103 (2015), doi: 10.7567/JJAP.54.040103. Figure 1

Flutter Measurement of a Linear Turbine Blade Cascade with an Angular Position Deviation of One Blade

Abstract Experimental flutter testing of high-aspect ratio rotor blades is a mainstay of turbomachinery research. However, rotor blades are never identical, and geometrical errors between actual and nominal geometries exist due to limited machining precision or assembly imperfection. The paper presents the initial phase of the controlled flutter research of a linear turbine blade cascade with a geometric deviation in one blade position. A subsonic wind tunnel with four flexibly mounted blades in an otherwise rigid blade cascade is employed at one angle of incidence and three low reduced frequencies. Measurements are performed with an angular position deviation (±1.5°) of one blade in pure bending and torsion modes. A tangible effect of one blade’s slight incidence angle offset on the vibrating blade cascade aerodynamic stability is demonstrated, and this research effort opens the door to a more extensive testing campaign.

Acoustic signature of sUAS rotors undergoing edgewise forward flight

This presentation shares preliminary experimental results from a new sUAS rotor test rig installed in UNSW’s Anechoic Wind Tunnel (UAT). This new test rig allows acoustic and aerodynamic performance testing of small drone-scale rotor blades under edgewise forward flight conditions at a range of shaft angles. The study of sUAS rotors under edgewise forward flight presents asymmetric inflow to the rotor and unsteady loading on the blades themselves, with different flow conditions experienced by the advancing and retreating rotor blades. This means the acoustic signature of a rotor undergoing edgewise flight is significantly changed compared to static thrust or axial flight conditions of drone rotors or propellers. This presentation aims to outline changes to the acoustic signature of a collection of conventional off the shelf (COTS) rotor and propeller designs between static, axial flight and edgewise flight conditions, coupling this with rotor performance metrics.

Making use of Digital Image Correlation to identify the true character of the applied load

Digital Image Correlation became one of the dominant optical full-field techniques used in experimental mechanics. It does not require sophisticated equipment to evaluate the full displacement vector field of the specimen under test with great accuracy. In this paper, we would like to put the reader's attention to the DIC technique as a solution that may identify the genuine character of the load applied to the object under test. Our experience with testing wind turbine blades using DIC proves that possibility. Full Text: PDF References E.M.C Jones, M.A. Iadicola, "A good practises guide for digital image correlation" International Digital Image Correlation Society, (2018), CrossRef B. Pan, "Digital image correlation for surface deformation measurement: historical developments, recent advances and future goals", Meas. Sci. Technol. 29, 082001 (2018), CrossRef B. Pan, L.P. Yu, Q.B. Zhang, "Review of single-camera stereo-digital image correlation techniques for full-field 3D shape and deformation measurement", Sci. China Technol. Sci. 61, 2 (2018), CrossRef S. Sharma, N. Iniyan Thiruselvam, S.J. Subramanian, G.S. Kumar, "Computation of strains from stereo digital image correlation using principal component analysis", Meas. Sci. Technol. 32, 105201 (2021), CrossRef IEC 61400-5:2020 Wind energy generation systems - Part 5: Wind turbine, DirectLink IEC 61400-23:2014 Wind turbines - Part 23: Full-scale structural testing of rotor blades, DirectLink

Blade Test in Atmospheric-Pressure Ar Gas to Characterize Bonded Interface Fabricated Using Atomic Diffusion Bonding

A blade test was applied in atmospheric-pressure Ar gas for wafers bonded using atomic diffusion bonding processing. We assessed the variation of the values of surface free energy at the bonded interface γ calculated, for convenience, from the debonding length. For interfaces bonded using thin Zr and Ti films, γ measured in Ar maintained the initial value γ0(Ar) in the initial region of observation time t and started decreasing as t increased further. Results indicate that γ0(Ar) corresponds to the value without water stress corrosion effects. The initial value of γ measured in air with a higher blade insertion-speed was almost equal to γ0(Ar). Result obtained for wafers bonded using Al2O3 films were almost identical to those obtained using metal films. However, γ for wafers bonded using ZrO2 films did not maintain their initial values. They decreased gradually as t increased, even in Ar, suggesting high water stress corrosion effects.

Oxide-Free SiC-SiC Direct Wafer Bonding and Its Characterization

In this study, the feasibility of oxide-free room temperature wafer bonding process was demonstrated for 4H-SiC wafers with in situ surface oxide removal. The investigations covered three areas: incoming metrology of the original wafer, characterization of activated single wafer and analysis of bonded wafer pairs. The focus was on compositional, chemical, mechanical and morphological analysis of the surfaces and of the bonded interfaces. Incoming wafers were inspected whether they fulfill the requirements of wafer bonding, and activated wafers were characterized to measure the surface modifications. The quality of the bonded wafers and the bonding energy were verified using scanning acoustic microscopy measurements as well as the Maszara blade test. Furthermore, cross-section transmission electron microscopy was used to investigate the amorphous layer at the bonding interface. The work reported is a demonstration of the capability of different characterization methods regarding SiC-SiC wafer bonding.