Spin Test Research Articles

Effectiveness of auditory measures in the diagnosis of cochlear synaptopathy and noise-induced hidden hearing loss: a case–control study

BackgroundCochlear synaptopathy is a disorder where auditory perceptual impairments, such as speech perception in noise and tinnitus, may not be accurately reflected by audiometric thresholds, even if the audiogram appears normal. It is proposed that the connections between hair cells and the auditory nerve are more susceptible to sound and aging damage than the cochlea’s hair cells. Cochlear synaptopathy can be present in ears with normal audiograms and undamaged hair cells, leading to hidden hearing loss. This study aims to construct electrophysiological and behavioral auditory parameters associated with persons exposed to loudness and having normal audiograms and auditory complaints to identify hidden hearing loss.ResultsA case–control study was done with forty participants with a documented history of exposure to loud sounds and various auditory complaints, compared to a control group of forty persons who had all been confirmed to have normal audiograms. The chosen behavioral core tests comprised the speech intelligibility in noise test (SPIN), gaps detection in noise (GIN test), and pitch pattern sequence test (PPS). The electrophysiological measures utilized in the study were the auditory brainstem response test (ABR) and electrocochleography (ECochG). The SPIN, PPS, and GIN test results demonstrated statistically significant disparities between the control and case groups. The amplitude ratio of wave I to wave V in ABR and the ratio of EcochG AP to SP demonstrated a statistically significant variance between the two groups. The SPIN test exhibited the highest AUC, signifying its superior diagnostic capability in identifying hidden hearing loss.ConclusionThe present study has shown that the SPIN, as a behavioral test, and the EcochG AP amplitude measure, as an electrophysiological test, provide the greatest auditory diagnostic capability for identifying cochlear synaptopathy. Wave I amplitude in the auditory brainstem response (ABR) and the SP/AP ratio in electrocochleography (EcochG) are promising non-behavioral measures of cochlear synaptopathy or hidden hearing loss.

An Overview of the R&D of Flywheel Energy Storage Technologies in China

The literature written in Chinese mainly and in English with a small amount is reviewed to obtain the overall status of flywheel energy storage technologies in China. The theoretical exploration of flywheel energy storage (FES) started in the 1980s in China. The experimental FES system and its components, such as the flywheel, motor/generator, bearing, and power electronic devices, were researched around thirty years ago. About twenty organizations devote themselves to the R&D of FES technology, which is developing from theoretical and laboratory research to the stage of engineering demonstration and commercial application. After the research and accumulation in the past 30 years, the initial FES products were developed by some companies around 10 years ago. Today, the overall technical level of China’s flywheel energy storage is no longer lagging behind that of Western advanced countries that started FES R&D in the 1970s. The reported maximum tip speed of the new 2D woven fabric composite flywheel arrived at 900 m/s in the spin test. A steel alloy flywheel with an energy storage capacity of 125 kWh and a composite flywheel with an energy storage capacity of 10 kWh have been successfully developed. Permanent magnet (PM) motors with power of 250–1000 kW were designed, manufactured, and tested in many FES assemblies. The lower loss is carried out through innovative stator and rotor configuration, optimizing magnetic flux and winding arrangement for harmonic magnetic field suppression. Permanent magnetic bearings with high load ability up to 50–100 kN were developed both for a 1000 kW/16.7 kWh flywheel used for the drilling practice application in hybrid power of an oil well drilling rig and for 630 kW/125 kWh flywheels used in the 22 MW flywheel array applied to the flywheel and thermal power joint frequency modulation demonstration project. It is expected that the FES demonstration application power stations with a total cumulative capacity of 300 MW will be built in the next five years.

Bell inequality is violated in charmonium decays

The experimental data on the helicity amplitudes of charmonium decays allow us to measure entanglement in final state spin correlations and test possible violations of the Bell inequality. We find that the Bell inequality is violated with a significance of 5σ or more in the decays ηc,χc0,J/ψ→Λ+Λ¯, J/ψ→Ξ−+Ξ¯+,Ξ0+Ξ¯0,Σ−+Σ¯+,Σ0+Σ¯0, ψ(3686)→Ξ−+Ξ¯+,Σ−+Σ¯+,Σ0+Σ¯0, χc0,χc1→ϕ+ϕ. The decays ψ(3686)→Λ+Λ¯ and Ξ0+Ξ¯0 show the same violation but with less significance. The decay ψ(3686)→Ω−+Ω¯+ displays entanglement. These results firmly establish the presence of entanglement and quantum nonseparability at high energies, in a setting with particles of different spins and interacting through electroweak and strong interactions. In addition, the relatively long lifetime of some of the strange baryons produced in the decays provides a natural probe to test whether quantum spin correlations remain after the particles have interacted with the beam pipe and the first few layers of the detector. Published by the American Physical Society 2024

Experimental investigation on multiple-site fatigue failure of the hollow compressor impeller

This study conducts a systematic experimental investigation on multiple-site damage (MSD) in aero-engine hollow compressor impellers, focusing on MSD fatigue fracture growth and coalescence behaviors and mechanisms. Comparative analyses of literature research, standard specimen tests, and full-scale disk test experiences conclude that elevated cyclic radial stresses, especially in thin-walled disk webs, facilitate the occurrence of MSD fractures. Extending from previous numerical studies, a full-scale hollow impeller fatigue test on a high-speed spin tester revealed an over 153 mm circumferential through-wall MSD failure in the outlet web, accounting for 33 % of its circumference. Challenges in traditional nondestructive inspections for such complex structures emphasize the effectiveness of synergetic fractography analysis in investigating the MSD failure. Thousands of scanning electron microscope (SEM) images, examined at macro and micro levels with the assistance of metallography and stereomicroscopy, unfolded the MSD fracture features of crack initiation, propagation, coalescence, and interaction. Besides the well-known macroscopic rachet marks, this study is the first to identify and analyze various microscopic MSD merging features, such as terraces, plastic ridges, shear sliding surfaces, cliffs, plateaus, and lowlands. Differences in fracture merging and growth features enable us to distinguish MSD component cracks. Quantitative fractography analysis revealed that the crack initiation occurred 1126 test cycles earlier, and that the overall crack propagation life slightly surpassed 1646 cycles as new cracks merged and joined. Diverse crack growth durations and rates across 11 fracture paths indicate asynchronous initiations and confirm interactions among component cracks. Cracks initiate flatter near the central crack colony but appear bumpier and more pronounced plastic deformation at the periphery. The overall MSD fracture evolution process was backtracked through synergetic fracture assessments, detailing the merging process of varied component crack colonies, enhancing our understanding of the spatial–temporal evolvement of cracking scenarios in actual aero-engine impellers.

Influence of atlas-choice on age and time effects in large-scale brain networks in the context of healthy aging

Abstract Introduction: There is accumulating cross-sectional evidence of decreased within-network resting-state functional connectivity (RSFC) and increased between-network RSFC when comparing older to younger samples, but results from longitudinal studies with healthy aging samples are sparse and less consistent. Some of the variability might occur due to differences in network definition and the fact that most atlases were trained on young adult samples. Applying these atlases to older cohorts implies the generalizability of network definitions to older individuals. However, because age is linked to a less segregated network architecture, this assumption might not be valid. To account for this, the Atlas55+ (A55) was recently published. The A55 was trained on a sample of people over the age of 55, making the network solutions suitable for studies on the aging process. Here, we want to compare the A55 to the popular Yeo-Krienen atlas to investigate whether and to what extent differences in network definition influence longitudinal changes of RSFC. For this purpose, the following networks were investigated: the occipital network (ON, “visual network”), the pericentral network (PN, “somatomotor network”), the medial frontoparietal network (M-FPN, “default network”), the lateral frontoparietal network (L-FPN, “control network”), and the midcingulo-insular network (M-CIN, “salience network”). Methods: Analyses were performed using longitudinal data from cognitively healthy older adults (N = 228, mean age at baseline = 70.8 years) with five measurement points over 7 years. To define the five networks, we used different variants of the two atlases. The spatial overlap of the networks was quantified using the dice similarity coefficient (DSC). RSFC trajectories within networks were estimated with latent growth curve models. Models of varying complexity were calculated, ranging from a linear model without interindividual variability in intercept and slope to a quadratic model with variability in intercept and slope. In addition, regressions were calculated in the models to explain the potential variance in the latent factors by baseline age, sex, and education. Finally, the regional homogeneity and the silhouette coefficient were computed, and the spin test and Wilcoxon-Mann-Whitney test were used to evaluate how well the atlases fit the data. Results: Median DSC across all comparisons was 0.67 (range: 0.20–0.93). The spatial overlap was higher for primary processing networks in comparison to higher-order networks and for intra-atlas comparisons versus inter-atlas comparisons. Three networks (ON, PN, M-FPN) showed convergent shapes of trajectories (linear vs. quadratic), whereas the other two networks (L-FPN, M-CIN) showed differences in change over time depending on the atlas used. The 95% confidence intervals of the estimated time and age effects overlapped in most cases, so that differences were mainly evident regarding the p-value. The evaluation of the fit of the atlases to the data indicates that the Yeo-Krienen atlas is more suitable for our dataset, although it was not trained on a sample of older individuals. Conclusions: The atlas choice affects the estimated average RSFC in some networks, which highlights the importance of this methodological decision for future studies and calls for careful interpretation of already published results. Ultimately, there is no standard about how to operationalize networks. However, future studies may use and compare multiple atlases to assess the impact of network definition on outcomes. Ideally, the fit of the atlases to the data should be assessed, and heuristics such as “similar age range” or “frequently used” should be avoided when selecting atlases. Further, the validity of the networks should be evaluated by computing their associations with behavioral measures.

Multisensory effects of mask wearing on speech intelligibility and the benefit of multilingualism.

Due to the pandemic of the Covid-19 disease, it became common to wear masks on some public spaces. By covering mouth and nose, visual-related speech cues are greatly reduced, while the auditory signal is both distorted and attenuated. The present study aimed to analyze the multisensory effects of mask wearing on speech intelligibility and the differences in these effects between participants who spoke 1, 2 and 3 languages. The study consisted of the presentation of sentences from the SPIN test to 40 participants. Participants were asked to report the perceived sentences. There were four conditions: auditory with mask; audiovisual with mask; auditory without mask; audiovisual without mask. Two sessions were conducted, one week apart, each with the same stimuli but with a different signal-to-noise ratio. Results demonstrated that the use of the mask decreased speech intelligibility, both due to a decrease in the quality of auditory stimuli and due to the loss of visual information. Signal-to-noise ratio largely affects speech intelligibility and higher ratios are needed in mask-wearing conditions to obtain any degree of intelligibility. Those who speak more than one language are less affected by mask wearing, as are younger listeners. Wearing a facial mask reduces speech intelligibility, both due to visual and auditory factors. Older people and people who only speak one language are affected the most.

Analysis of Stem Assembly of Inflatable Aerodynamic Decelerator (IAD) that Failed During Spin Test

Analysis of Stem Assembly of Inflatable Aerodynamic Decelerator (IAD) that Failed During Spin Test

Infrared temperature measurements on fast moving targets: A novel calibration approach

In this study, an infrared system is developed for accurate measurements of surface temperature and heat transfer on fast moving targets. The system was designed for the Oxford Turbine Research Facility, a world-leading experimental facility delivering highly engine representative, scalable heat transfer results for aerospace research. Infrared thermography is employed to acquire temperature maps of high-pressure turbine blades, allowing assessment of surface thermal conditions including heat transfer coefficient, adiabatic wall temperature, Nusselt number, cooling effectiveness, and metal effectiveness.Achieving accurate infrared thermography measurements in rotating turbomachinery experimental conditions is arduous due to reflections from the surroundings, low emissivity of metallic parts, and motion blur resulting from high speed. To overcome these challenges, calibration procedures were developed against a traceable standard using a bespoke steady experimental facility. A method to determine the reflected temperature from surroundings was also validated. Correction for all measurement disturbances is demonstrated to within the accuracy of the primary measurement thermocouple.Finally, the developed calibration method was validated on a fast-moving rotating geometry demonstrating accurate correction for all measurement disturbances, without the need for an in situ calibration. A detailed uncertainty analysis for each calibration step is also presented.

Burst Speed Prediction of Impellers With Critical Strain Criteria

Abstract Accurate prediction of burst speed and critical location of a rotating disk is a great concern for turbomachinery designers and enables the reduction of test numbers required to show rotor integrity during turbo-engine certification. Existing burst methodologies mainly focused on axial disks with well-defined bore, web, and rim regions and mostly depended on correction factors that require previous test data of rotors with similar sizes and features. Furthermore, variation of radial and hoop stresses in a radial disk is less predictable than in axial disks due to the asymmetric nature of impellers, which results in uneven distribution of centrifugal and bending loads. This paper aims to explain the experimental and numerical effort dedicated to building an accurate burst methodology for impellers. Elastoplastic finite element analyses are performed by incorporating geometric and material nonlinearities. Analysis results allowed the prediction of failure locations and observation of redistribution of stresses due to material plasticity as rotor speed increases. An extensive test campaign is carried out to validate the numerical analysis. Critical strain criteria that correspond to the plastic strain of true ultimate tensile strength (UTS), are used to determine burst speeds before tests. Experimental results are compared with Robinson's average hoop stress criteria, Hallinan's criteria, and critical strain criteria to show the strong and weak sides of these methodologies for an impeller application. The numerical burst speeds and crack initiation locations associated with critical strain criteria are found to be in good agreement with the spin test results.

Functional Connectome Hierarchy Distortions in Female Nurses With Occupational Burnout and Its Gene Expression Signatures.

Burnout has become a serious public health issue worldwide, particularly during the COVID-19 pandemic. Functional connectome impairments associated with occupational burnout were widely distributed, involving both low-level sensorimotor cortices and high-level association cortices. To investigate whether there are hierarchical perturbations in the functional connectomes and if these perturbations are potentially influenced by genetic factors in nurses who feel "burned out." Prospective, case control. Thirty-three female nurses with occupational burnout (aged 27-40, 32.42 ± 3.37) and 32 matched nurses who were not feeling burned out (aged 27-42, 32.50 ± 4.21). 3.0 T, gradient-echo echo-planar imaging sequence (GE-EPI). Gradient-based techniques were used to depict the perturbations in the multi-dimensional hierarchical structure of the macroscale connectome. Gene expression data were acquired from the Allen Human Brain Atlas. Cortex-wide multivariate analyses were used for between-group differences in gradients as well as association analyses between the hierarchy distortions and the MBI score (FDR corrected). Partial least squares, spin test and bootstrapping were utilized together to select the gene sets (FDR corrected). Gene enrichment analyses (GO, KEGG and cell-type) were further performed. Significance level: P < 0.05. There were significant gradient distortions, with strong between-group effects in the somatosensory network and moderate effects in the higher-order default-mode network, which were significantly correlated with the gene expression profiles (r = 0.3171). The most related genes were broadly involved in the cellular response to minerals, neuronal plasticity, and the circadian rhythm pathway (q value < 0.01). Significant enrichments were found in excitatory (r = 0.2588), inhibitory neurons (r = 0.2610), and astrocytes cells (r = 0.2633). Regions affected by burnout severity were mainly distributed in the association and visual cortices. By connecting in vivo imaging to genes, cell classes, and clinical data, this study provides a framework to understand functional impairments in occupational burnout and how the microscopic genetic architecture drive macroscopic distortions. 1 TECHNICAL EFFICACY: Stage 2.

Qualification of Compressor Impeller for Aero-Engine Application

This paper presents the approach for qualification of indigenously developed compressor impeller for aero engine application. Indigenisation is understood to be the most important tool for effective technical empowerment of a developing nation. Indigenisation philosophy is adopted by several countries in various fields such as power, infrastructure, aerospace, military equipments and etc. Indigenous development fills the technical, financial and time frame gap between imports and ab-initio design and development. Hence, for a healthy technical growth of any developing nation, Indigenous development activities should go along with ab-initio design activities. Indigenous development has become an integral process of activities of Defence sectors due to its potential benefits. Indian defence imports stands at staggering 65 % of the total defence acquisition. In order to make the best use of indigenization opportunities in the defence sector, conservative figures would suggest an amount more than 100,000 crores. This gives an indication of the potential and benefits of indigenous development in defence sectors.&#x0D; In this paper a methodology for indigenous development of a military turboshaft engine compressor impeller is discussed. This activity has enabled uninterrupted supply of the component and a substantial Foreign Exchange savings. This paper specifies the various tests conducted over the forging. It also brings out the results of cyclic spin test on the component for 22500 cycles as life substantiation, 15% and 22% over speed test as structural integrity substantiation and 150 hours type test on engine for quality and assembly substantiation.&#x0D; This indigenous development procedure described in this paper can be readily extended to suitable critical aero engine component.

High-Speed Spin Testing of Bi-2212 Superconducting Wires for High-Field NMR Magnet Qualification: Final Progress Report

This paper summarizes an NIH-funded research project designed to study the strength of high temperature superconductors under high circumferential hoop stress, in order to qualify these materials for high-field (> 1 GHz-class) NMR magnets. The unique approach presented here is to spin test coils at high rotational speeds, approaching 50,000 rpm, in order to induce mechanical hoop stresses which are equivalent to the magnetic Lorentz stresses experienced by a high-field solenoid insert coil. Bi-2212 wires and coils were tested in sub-cooled nitrogen to determine if any mechanical damage was imparted by each spin test. These preliminary experimental results demonstrate that, with further development, this test could prove to be a simple method for qualifying superconducting wires for high-field insert magnets.

Recent Applications of System Identification Techniques at IPEV

This paper presents an overview of the system identification techniques developed and applied at the Flight Test and Research Institute during the last decade. System identification techniques have been used extensively to obtain aerodynamic models for a flight-test simulator, which was developed in house and specifically tailored for flight-test instruction and preparation for actual test flights. The methods applied were mostly the output error for data compatibility check and equation error in the time domain for model structure selection and parameter estimation. The most relevant applications are summarized in this paper, including identification of a high angle of attack model with compressibility effects for a jet trainer; estimation of drag polars at high subsonic regime for a jet fighter; identification of aerodynamic model in real-time for a propeller-driven fighter; application of flight-path reconstruction techniques to spin tests, in order to correct errors in the air data sensors; and identification of power effects on the longitudinal stability of a propeller-driven trainer. The examples show that system identification has become crucial to 1) obtain accurate aerodynamic models for training in the flight-test simulator and 2) develop more efficient flight-test techniques.

Situation analysis and blood transfusion strategy of Lewis antibodies in Hunan Province.

Detection rate, serological characteristics, and clinical data of patients with Lewis blood group antibodies in Hunan Province were analyzed through retrospective analysis. This was undertaken in order to optimize the detection methods and blood transfusion strategies of these patients. Blood typing, antibody screening, and cross-matching were performed by microcolumn gel, and Lewis antigen was detected by immediate spin test, antibody identification of positive and negative ABO samples, positive antibody screening, and cross-blood mismatch samples. Antibodies were identified by immediate spin test and microcolumn gel antiglobulin method, and the clinical data of the patients with Lewis antibody characteristics were analyzed. A total of 74 samples (15.91%) with Lewis antibodies were detected from 465 positive samples; cases were distributed in different cities of Hunan Province, with Changsha city being the most frequent (28%) one, with mostly non-O (66), anti-Lea (31; 41.89%), anti-Lea+anti-Leb (23; 31.08%), anti-Leb (5; 6.76%), anti-LebH and anti-Lea+anti-LebH (1+4; 6.76%), and antibody types immunoglobulin M (IgM) (51; 68.92%), immunoglobulin G (8; 10.81%), and IgG+IgM (4; 5.41%) cases. Patients included more females (67.57%) than males. The detection rate of gynecological diseases and patients with solid tumors was highest (44.59%). In all cases, the Lewis blood group was Le (a-b-); none of the 15 transfusion patients had hemolytic transfusion reaction. A variety of experimental methods must be adopted simultaneously to determine specificity and prevent the leakage of Lewis antibodies. The infusion of red blood cells matching with antiglobulin media at 37°C was recommended to ensure safe transfusion for recipients with Lewis antibodies.

Selective degradation of ceftriaxone sodium by surface molecularly imprinted BiOCl/Bi3NbO7 heterojunction photocatalyst

By using the surface molecular imprinting technique, BiOCl/Bi3NbO7 was used as the substrate photocatalyst and ceftriaxone sodium (CTRX) was used as the template. A molecularly imprinted photocatalyst with specific recognition and photocatalytic synergy for CTRX was synthesized. Due to the excellent photoelectric properties and the successful formation of CTRX-imprinted cavities on the imprinted layer surface. The characterization results showed that MIP-3 has the advantages of uniform particle size and high separation efficiency of photogenerated carriers. The molecularly imprinted photocatalyst MIP-3 showed remarkable synergy and selectivity in both adsorption-photocatalysis of CTRX. Further experimental results showed that MIP-3 exhibited high selective adsorption performance for both high and low concentrations of CTRX in the 30 min static adsorption experiment. About 92 % of CTRX was degraded in the 100 min light experiment, which was a large improvement compared with BiOCl/Bi3NbO7. The selectivity of MIP-BNO was evaluated by comparing the degradation efficiency of MIP-3 on CTRX and chloramphenicol (CIP). Compared to non-imprinted photocatalyst NIP-BNO, MIP-3 has a higher selectivity coefficient of 2.58 and a faster degradation kinetic rate of 0.0169 min−1. The stability experiments showed that MIP-3 has good recoverability and stability during photocatalytic degradation. The mechanism of selective photocatalytic degradation of CTRX by MIP-3 was investigated by UV–visible spectroscopy, radical capture experiments, and electron spin tests. The possible degradation pathway of CTRX was also analyzed by LC-MS. In conclusion, this study confirms that the combination of surface molecular imprinting and photocatalyst has great potential to provide a promising solution for the treatment of low-level, highly toxic target pollutants in mixed wastewater.

Working memory and listening fatigue in cochlear implantation

Background Hearing involves more than just the central auditory pathway’s operation and hearing threshold. Instead, the term ‘hearing’ encompasses a range of skills such as listening, comprehending, and communicating. As a result, a thorough assessment of the patient’s listening effort and working memory is critical. Methods Forty-four subjects with cochlear implantation were included in the study, 22 patients as a study group and 22 subjects as a control group. They were assessed by digit span test for working memory, speech in noise test at different SNR levels, Fatigue assessment scale and Effort assessment scale. Results There was a statistically significant difference in the Spin test between the study and control group. The study group showed a significant higher Spin scores at all SNR levels. There was a significant difference in both digit span forward and digit span backward tests between both the study and control group with a significant negative correlation between digit span and listening effort and fatigue scales. There was a significant statistical difference in the mean results of both the listening fatigue assessment scale and listening effort assessment scale between the study and control group where the study group showed a significant higher result in both scales. Conclusion Assessing the effort associated with recognising speech is very valuable. Scales for measuring listening effort and listening fatigue as well as working memory can be easily incorporated into the basic audiological evaluation providing valuable insights for further rehabilitation.

Fatigue crack propagation analysis in an aero-engine turbine disc using computational methods and spin test

This article presents a study on applying the fracture mechanics-based method to predict the fatigue crack growth (FCG) characteristics of the turbine disc in a turboshaft engine. According to the stress analysis results, the electric discharge machining (EDM) method introduced notches for initiating cracks of a specific size into the critical locations of the turbine disc. The FCG of these cracks under cyclic load was predicted utilising a three-dimensional (3D) numerical analysis method and a simplified rectangular plate model with relevant fracture mechanics properties. Meanwhile, the full-scale spin test was performed using a pre-flawed turbine disc under intentional loads at an isothermal temperature. After the test, the crack surface fractography and the quantitative fracture striation analysis revealed the practical crack propagation behaviour. There was a relatively small difference between the experimental results and the 3D finite element method, which indicated the good predictability of FEM for turbine disc crack growth. Furthermore, the rectangular plate models could predict the front stage of steady-state crack growth but were overall conservative due to their inability to precisely calculate the effects of crack growth and structure geometry on the stress intensity factor.

Influence of expertise level on techniques of applying top and back spins in cue sports

ABSTRACT This study compared the kinematics of upper body and cue stick among players of various skill levels when performing back spin and top spin shots. Twenty-eight male cue sports players were assigned to the novice (n = 10), intermediate (n = 9), or skilled groups (n = 9). The back spin and top spin tests were administrated while kinematic data were recorded using a 3D motion capture system. The results revealed greater upper limb joint ranges of motions (all p < 0.05), maximum angular velocities (all p < 0.05), and cue tip speed in the back spin than top spin shots (p < 0.001). None of joint kinematic or shot performance variables investigated was significantly different among the three skill levels (all p > 0.05). For the head movement, the novice group exhibited greater anteroposterior displacement than the skilled group (p = 0.020). In conclusion, except for the head movement, the upper body and cue stick kinematics did not significantly differ among players with varied skill levels. Greater joint ranges of motions and angular velocities were required to generate a faster cue tip speed for the back spin shots when compared with the top spin shots.

슈라우드 접촉에 따른 증기터빈 블레이드의 진동모드 해석과 실험적 검증

An integral shrouded blade with a gas turbine dovetail that is robust against the stress of the dovetail has been applied in large steam turbines to achieve high efficiency by minimizing the steam leakage of the tip. Further, the natural frequency of the blade has been calculated with high accuracy considering the contact condition of the shrouded blade for the avoidance design of resonance. This paper compares the analysis and measurement results for the shrouded blade with a gas turbine dovetail. To realize a valid analysis model, a full-scaled mock-up with blades and a rotor was manufactured and assembled, and a spin test was conducted in balancing shop up to 120 % overspeed of the rated speed. The spin test procedure was described, and a Campbell diagram was obtained as the test result. The FE model and boundary conditions of the shrouded blade were observed to agree well with the measured Campbell diagram. The model is expected to be applicable for the vibration design of the shrouded blade for gas turbine blades and steam turbines.

Effect of Residual Stress Induced by Different Cooling Methods in Heat Treatment on the Fatigue Crack Propagation Behaviour of GH4169 Disc.

In this study, the effects of residual stress induced by three different cooling methods during heat treatment on the crack propagation behaviour of the GH4169 disc were investigated. Different levels of stress fields were induced to the specially designed discs by using air cooling (AC), air jetting cooling (AJC) and water quenching (WQ) methods and were quantitated by numerical simulation. These discs were then subjected to prefabricated cracking, and crack propagation tests were conducted on a spin tester with two load spectrums. Crack growth behaviour was depicted via the surface replica technique and fracture morphology. Regarding the linear superposition of residual stress and centrifugal force, the crack propagation behaviour of different discs was simulated using the FRANC3D software. AJC and WQ introduced compressive residual stress (−259 MPa and −109 MPa, respectively) into the disc compared with the AC method (about −1.5 MPa). The AJC method increases the crack propagation life of the disc by introducing residual compressive stress into the area near the surface of the central hole to inhibit the opening of the crack surface. When the fatigue load was low, this inhibition effect was more significant.