scholarly journals Experimental studies of the energy dissipation processes at the tops of fatigue cracks in the elements of bridge structures

2021 ◽  
Vol 8 (3) ◽  
Author(s):  
Leonid Solovyev ◽  
Vladislav Fedorenko
Keyword(s):  
Control Method ◽  
Fatigue Cracks ◽  
Experimental Studies ◽  
Thermal Control ◽  
Sample Surface ◽  
Fatigue Tests ◽  
Heating Zone ◽  
Bridge Structures ◽  
Thermal Imagers ◽  
Loading Procedure

In the article, the authors investigated the possibility of using the thermal control method for diagnosing fatigue cracks in the metal superstructure, determined the necessary parameters for that control method. The studies were conducted during cantilevered steel samples fatigue tests simulating the superstructure beam wall operation, reinforced with stiffening ribs. To carry out the experiments were developed a test setup and a loading procedure at the various intensity of exposure. An electric motor with eccentrics is used as a loading device. The sample surface heating was recorded by thermal imagers with 0.03 K and 0.05 K temperature sensitivities and 60 frames/s and 9 frames/s shooting speed, respectively. Was confirmed the possibility of determining crack presence before its emergence to the surface namely at the stage of its initiation, and also were determined the self-heating zone dimensions at the tip of a crack. The conducting a laboratory experiment technique on the dissipative processes study in the metal superstructure elements is described.

scholarly journals POSSIBILITY USING THERMOGRAPHIC CONTROL METHOD TO DETECT CRACKS IN REINFORCED CONCRETE STRUCTURES

2021 ◽  
pp. 32-38
Author(s):  
Ye.V. Klymenko ◽  
◽  
S.V. Kolesnichenko ◽  
K.V. Polianskyi ◽  
A.O. Popadenko ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Thermal Field ◽  
Control Method ◽  
Concrete Structures ◽  
Thermal Control ◽  
Qualitative Assessment ◽  
Reinforced Concrete Structures ◽  
Thermal Imager ◽  
Thermal Imagers ◽  
Non Destructive

Abstract. The article presents the study results of the possibility of using thermographic non-destructive testing to search for cracks in reinforced concrete structures. The basis of non-destructive thermal control is the registration of changes in the thermal field that occurs when the thermodynamic equilibrium of object with the environment is disturbed, which appears on the surface, and the nature of which allows obtaining the necessary information. The thermal control method is based on the interaction of the object's thermal field with thermodynamic sensitive elements (thermocouple, photodetector, liquid crystal element, bolometer), which convert the field parameters (intensity, temperature gradient, contrast, radiance) into an electrical signal of the recording device. As a result of the experiment, it was confirmed that the thermographic control method can be used when examining reinforced concrete structures for a qualitative assessment of hidden defects and damages. Thermal imagers with different resolution of the IR image matrix, an infrared thermo hygrometer, and a luxmeter were used as measuring instruments for the experiment. During the experiment, no fundamental difference in the use of thermal imagers with different types of IR matrices was revealed. When using the more accurate Flir E8 thermal imager, the thermogram had a clearer definition of the surface temperature compared to the Flir C2. This feature can be useful for quantifying defects, for example, the depth and size of a crack under a layer of paint, but fundamentally, for high-quality detection of defects and damage, the use of more accurate equipment is not a prerequisite. The authors conclude that the method of thermographic control can be used when examining reinforced concrete structures for a qualitative assessment of the presence of cracks.

Notch Effects in High Cycle Fatigue of Ti-6Al-4V

2013 ◽  
Vol 750 ◽  
pp. 232-235 ◽  
Author(s):  
Kenji Shojima ◽  
Sabine Weldle ◽  
Saburo Okazaki ◽  
Masahiro Endo ◽  
Dietmar Eifler ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Cycle Fatigue ◽  
Notch Root ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Experimental Studies ◽  
Fatigue Tests ◽  
Different Depths ◽  
Fatigue Characteristics ◽  
Circumferential Notch

In this study, a series of experimental studies was conducted to investigate the fatigue behavior of Ti-6Al-4V alloy at room temperature. Specifically, by inspecting the cylindrical specimens with a circumferential notch of different depths (20-200µm) and notch root radii (20-100µm), the notch effect was systematically investigated with tension-compression fatigue tests (R = –1). To quantify the effects of small notch, the -parameter model was adopted and its applicability for Ti-6Al-4V alloy was examined. Finally, the fatigue characteristics are discussed in conjunction with the behavior of small fatigue cracks at notches.

Analysis of the results of medium-energy electrons on the protective and thermoregulatory coatings of high-orbit satellites

2018 ◽  
pp. 156-171
Author(s):  
A. M. Shamayev ◽  
M. D. Ozersky
Keyword(s):  
Structural Changes ◽  
Protective Coatings ◽  
Experimental Studies ◽  
Thermal Control ◽  
Space Vehicles ◽  
Medium Energy ◽  
Electrostatic Discharges ◽  
High Orbit ◽  
Thermal Control Coatings ◽  
Solar Batteries

The results of experimental studies of the effect of electron irradiation on K-208 and CMG glasses used for manufacturing protective coatings of solar batteries and thermal control coatings of space vehicles are analyzed. It is shown that the caused electrostatic discharges lead to structural changes in the surfaces of the glasses studied. The goals of further studies of the influence of proton and electronproton effects on the properties of such coatings are outlined. 

scholarly journals The Influence of Genetics in Myopia Control: A Pilot Study

2021 ◽  
Vol 10 (4) ◽  
pp. 808
Author(s):  
Cristina Alvarez-Peregrina ◽  
Miguel Ángel Sánchez-Tena ◽  
Clara Martinez-Perez ◽  
Catalina Santiago-Dorrego ◽  
Thomas Yvert ◽  
...  
Keyword(s):  
Pilot Study ◽  
Treatment Response ◽  
Axial Length ◽  
Contact Lenses ◽  
Control Method ◽  
Saliva Sample ◽  
Experimental Studies ◽  
Strong Linkage Disequilibrium ◽  
Student’S T ◽  
Myopia Control

Background: Many epidemiological and experimental studies have established that myopia is caused by a complex interaction between common genetic and environmental factors. The objective of this study was to describe and compare the allelic and genotypic frequencies of the rs524952 (GJD2), rs8000973 (ZIC2), rs1881492 (CHRNG), rs1656404 (PRSS56), rs235770 (BMP2), and rs7744813 (KCNQ5) SNPs (single-nucleotide polymorphism) between responder and nonresponder patients who had undergone a two-year treatment with lenses for myopia control. Method: Twenty-eight participants from the MiSight Assessment Study Spain (MASS), who had received treatment for myopia control for two years with MiSight contact lenses, were examined. The criteria for better/worse treatment response was the change in the axial length (< / ≥ 0.22 mm two years after the treatment). The clinical procedure consisted of the extraction of a saliva sample, and the participants also underwent an optometric examination. Genetic data were analyzed using SNPStats software (Catalan Institute of Oncology, Barcelona, Spain), and statistical analysis was performed using SPSS v.25 (SPSS Inc., Chicago, IL, USA). Demographic variables were analyzed using the Student’s t-test. Results: The T allele, the one with the lowest frequency, of the “rs235770” SNP was associated with a better treatment response [AL/CR (axial length/corneal radius): OR = 3.37; CI = 1.079–10.886; SE (spherical equivalent): OR = 1.26; CI: = 0.519–57.169; p = 0.019). By performing haplotype analysis, significant differences were found between the rs235770…rs1881492 and rs235770–rs1656404 polymorphisms. The latter presented a strong linkage disequilibrium with each other (r2 ≥ 0.54). Conclusion: The result of lens therapies for myopia control could vary depending on genetic variants. Studies with a larger sample are needed to confirm the results presented in this pilot study.

scholarly journals Extended-State-Observer-Based Super Twisting Control for Pneumatic Muscle Actuators

Actuators ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 35
Author(s):  
Yu Cao ◽  
Zhongzheng Fu ◽  
Mengshi Zhang ◽  
Jian Huang
Keyword(s):  
Control Method ◽  
Experimental Studies ◽  
State Observer ◽  
Extended State Observer ◽  
Extended State ◽  
Pneumatic Muscle ◽  
System States ◽  
The Stability ◽  
Twisting Control ◽  
Muscle Actuators

This paper presents a tracking control method for pneumatic muscle actuators (PMAs). Considering that the PMA platform only feedbacks position, and the velocity and disturbances cannot be observed directly, we use the extended-state-observer (ESO) for simultaneously estimating the system states and disturbances by using measurable variables. Integrated with the ESO, a super twisting controller (STC) is design based on estimated states to realize the high-precision tracking. According to the Lyapunov theorem, the stability of the closed-loop system is ensured. Simulation and experimental studies are conducted, and the results show the convergence of the ESO and the effectiveness of the proposed method.

The York-Arup cable experiments: Implications for the fire design of cable-supported bridges

2021 ◽  
Author(s):  
Benjamin Nicoletta ◽  
John Gales ◽  
Panagiotis Kotsovinos
Keyword(s):  
Thermal Strain ◽  
Experimental Studies ◽  
Thermal Response ◽  
Structural Response ◽  
Fire Performance ◽  
Stay Cable ◽  
Stay Cables ◽  
Bridge Structures ◽  
Recent Trends ◽  
High Level

<p>Recent trends towards performance-based fire designs for complex and critical structures have posed questions about the fire resilience of bridge infrastructure. There are little-to-no code requirements for bridge fire resistance and practitioner guidance on the subject is limited. Research on the fire performance of cable-supported bridge structures is scarce and knowledge gaps persist that inhibit more informed fire protection designs in a variety of bridge types. There have been few numerical or experimental studies that investigate the fire performance of steel stay-cables for use in cable-supported bridges. The thermal response of these members is critical as cable systems are highly dependent on the response of individual members, such as in the case of an anchor cable for example. The study herein examines the thermal response of several varieties of unloaded steel- stay cable during exposure to a non-standard methanol pool fire and the implications for the structural response of a cable-supported bridge. Experimental thermal strain data from fire tests of various stay-cables is used to inform high-level insights for the global response of a cable-supported bridge. Namely, the effects of cable thermal expansion on the overall cable system is approximated.</p>

On the Direction of Fatigue Cracks in Polycrystalline Ingot Iron

1952 ◽  
Vol 19 (1) ◽  
pp. 54-56
Author(s):  
F. A. McClintock
Keyword(s):  
Statistical Analysis ◽  
Shear Failure ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Tensile Failure ◽  
Bending Fatigue ◽  
Polycrystalline Iron

Abstract A statistical analysis is developed to show how a microscopic shear failure can result in the apparent tensile failure of polycrystalline iron in rotary bending fatigue tests.

Slowest heating zone migration for heterophase baby food system

2021 ◽  
pp. 49-53
Author(s):  
Владимир Владимирович Кондратенко ◽  
Борис Львович Каневский ◽  
Галина Петровна Покудина ◽  
Вячеслав Иванович Сенкевич ◽  
Лидия Алексеевна Борченкова
Keyword(s):  
Young Children ◽  
Food Systems ◽  
Food System ◽  
Experimental Studies ◽  
Baby Food ◽  
Dispersed Phase ◽  
Heating Zone ◽  
Heterophase System ◽  
Thermal Sterilization ◽  
Slowest Heating Zone

В работе приведены результаты исследования миграции зоны наименьшего прогревания (Slowest Heating Zone, далее SHZ) в упаковке при термической стерилизации мелкодисперсной гетерофазной пищевой системы для питания детей раннего возраста. Локализация SHZ является основным параметром, на основе которого производится разработка режимов термической стерилизации для пищевых систем с конвективным теплообменом. В качестве объекта исследования использовали сок яблочный с мякотью для детского питания отечественного производства, который представляет собой гетерофазную систему с жидкой дисперсионной средой и равномерно распределенной в ней высокодисперсной фазой в виде частиц мякоти с плотностью, близкой к плотности жидкой среды. Продукт был расфасован в стеклянные банки III-52-190. Прогрев проводили в термостате при температурах греющей среды 75, 80, 85, 90 и 95 °C, которые поддерживали и регистрировали автоматически, что обеспечивало равномерность температурного поля воды в термостате. Кривые прогрева снимали с помощью термопары, рабочий спай которой размещался по оси банки на высоте 6, 12, 18, 24, 30, 36, 40, 42 и 48 мм от дна. В результате экспериментальных исследований процесса стерилизации установлено, что в подобной пищевой системе локализация SHZ и кинетика ее миграции аналогичны этим параметрам в гомофазных пищевых системах, но различаются важными особенностями, вызванными как наличием дисперсной фазы, так и различиями в теплофизических параметрах продуктов. Отмечено влияние обязательной для питания детей раннего возраста гомогенизации сока с мякотью на вязкость продукта из-за упорядоченности ориентации частиц мякоти, вызывающей миграцию SHZ при изменении температуры сока при нагреве и охлаждении. The paper presents the results of researches of Slowest Heating Zone (SHZ) migration in packaging during thermal sterilization of fine heterophasic food system for feeding young children. Localization of SHZ is the main parameter on the basis of which the development of thermal sterilization modes for food systems with convective heat exchange is made. As the object of the study, we used apple juice with pulp for baby food of domestic production, which is a heterophase system with a liquid dispersion medium and a highly dispersed phase uniformly distributed in it in the form of pulp particles with a density close to the density of the liquid medium. The product was packaged in glass jars III-52-190. Warming up was carried out in a thermostat at temperatures of the heating medium of 75, 80, 85, 90, and 95 °C, which were maintained and recorded automatically, which ensured the uniformity of the temperature field of water in the thermostat. The heating curves were recorded using a thermocouple, the working junction of which was located along the can axis at heights of 6, 12, 18, 24, 30, 36, 40, 42, and 48 mm from the bottom. As a result of experimental studies of the sterilization process, it was found that in such a food system, the localization of SHZ and the kinetics of its migration are similar to these parameters in homophase food systems, but differ in important features caused by both the presence of a dispersed phase and differences in the thermophysical parameters of products. The effect of homogenization of juice with pulp, obligatory for feeding young children, on the viscosity of the product due to the regularity of the orientation of pulp particles, which causes migration of SHZ when the temperature of the juice changes during heating and cooling, has been noted.

Effect of Blade Aspiration Slot Configuration on the Aerodynamic Performance of a Highly Loaded Aspirated Compressor Cascade

2017 ◽  
Author(s):  
Longxin Zhang ◽  
Le Cai ◽  
Bao Liu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Flow Control ◽  
Flow Rate ◽  
Control Method ◽  
Active Flow Control ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Flow Path ◽  
Compressor Cascade ◽  
Flow Loss ◽  
Highly Loaded

As a promising active flow control method, boundary layer suction (BLS) can be used to enhance the aerodynamic performance of the highly-loaded compressor effectively, and due to this reason, extensive studies have been carried out on it. However, contrast to those abundant studies focusing on the flow control effects of BLS, little attention has been paid on the design method of the aspiration flow path. This work presents a 3-D steady numerical simulation on a highly-loaded aspirated compressor cascade. The aspiration slot is implemented at its best location based on the previous experimental studies and the aspiration flow rate is fix to 1.5% of the inlet massflow. The plenum configuration follows the blade shape and remains unchanged. One-side-aspiration manner is adopted to simplify the aspiration devices. Two critical geometry parameters, slot angle and slot width, are varied to study the effects of blade aspiration slot configuration on the cascade loss, radial distribution of the aspiration flow rate and inner flow structures within the aspiration flow path. Results show that the slot configuration does affect the cascade performance. In comparison with the throughflow performance, it is especially true once the flow loss caused by the aspiration flow path is also taken into account, and higher flow loss will be generated within the aspiration flow path if an inappropriate scheme is adopted. In the present investigation, apart from the cases with larger negative slot angle, a wider slot is more preferable to a narrower one, since it could enhance the aspiration capacity near the endwall regions and lower the dissipation loss within the aspiration flow path. In terms of the slot angle, a larger negative value, i.e., the slot direction more aligned with the incoming flow, is not beneficial to improve the throughflow performance, while concerning the flow loss yield by the aspiration flow path, a proper negative slot angle is always optimal.

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