Study on the mechanism of dynamic slip-weakening for a rock material interface based on a vibration experiment

AbstractBlue organic light-emitting diodes require high triplet interlayer materials, which induce large energetic barriers at the interfaces resulting in high device voltages and reduced efficiencies. Here, we alleviate this issue by designing a low triplet energy hole transporting interlayer with high mobility, combined with an interface exciplex that confines excitons at the emissive layer/electron transporting material interface. As a result, blue thermally activated delay fluorescent organic light-emitting diodes with a below-bandgap turn-on voltage of 2.5 V and an external quantum efficiency (EQE) of 41.2% were successfully fabricated. These devices also showed suppressed efficiency roll-off maintaining an EQE of 34.8% at 1000 cd m−2. Our approach paves the way for further progress through exploring alternative device engineering approaches instead of only focusing on the demanding synthesis of organic compounds with complex structures.

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Partial Energy Transfer Model of Lamb Waves Scattering in Materially Isotropic Waveguides

Applied Sciences ◽

10.3390/app11104508 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4508

Author(s):

Pavel Šofer ◽

Michal Šofer ◽

Marek Raček ◽

Dawid Cekus ◽

Paweł Kwiatoń

Keyword(s):

Energy Transfer ◽

Lamb Waves ◽

Hybrid Approach ◽

Wave Mode ◽

Transfer Model ◽

Material Interface ◽

Modal Expansion ◽

Scattering Coefficients ◽

Expansion Technique ◽

Partial Energy

The scattering phenomena of the fundamental antisymmetric Lamb wave mode with a horizontal notch enabling the partial energy transfer (PET) option is addressed in this paper. The PET functionality for a given waveguide is realized using the material interface. The energy scattering coefficients are identified using two methods, namely, a hybrid approach, which utilizes the finite element method (FEM) and the general orthogonality relation, and the semi-analytical approach, which combines the modal expansion technique with the orthogonal property of Lamb waves. Using the stress and displacement continuity conditions on the present (sub)waveguide interfaces, one can explicitly derive the global scattering matrix, which allows detailed analysis of the scattering process across the considered interfaces. Both methods are then adopted on a simple representation of a surface breaking crack in the form of a vertical notch, of which a certain section enables not only the reflection of the incident energy, but also its nonzero transfer. The presented results show very good conformity between both utilized approaches, thus leading to further development of an alternative technique.

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Integrating a Smartphone-Based Vibration Experiment into an Engineering Course

2020 IEEE Integrated STEM Education Conference (ISEC) ◽

10.1109/isec49744.2020.9280731 ◽

2020 ◽

Author(s):

Musa K. Jouaneh

Keyword(s):

Vibration Experiment

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The durability of flexible eddy current array (FECA) sensors in harsh service environments

Scientific Reports ◽

10.1038/s41598-021-89750-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yujian Song ◽

Tao Chen ◽

Ronghong Cui ◽

Yuting He ◽

Xianghong Fan ◽

...

Keyword(s):

Eddy Current ◽

Fatigue Cracks ◽

Radiation Environment ◽

The Finite Element Method ◽

Integrated Sensor ◽

High Durability ◽

Vibration Experiment ◽

Service Environments ◽

Salt Fog Corrosion ◽

Salt Fog

AbstractSensors for structural health monitoring (SHM) need to be permanently integrated on structures and withstand the harsh service environments, which has been a big challenge for the application of SHM in aircrafts. This paper focuses on the durability of flexible eddy current array (FECA) sensors in harsh service environments of aircrafts, including vibration environment and several typical exposed environments. First, a kind of FECA sensor is illustrated and its integration method is proposed. Moreover, in order to study the durability of the sensor in vibration environment, the modal analysis is performed by the finite element method. According to the simulation results, the durability experiment in vibration environment is carried out under the fourth order vibration mode, which makes the sensor suffer the harshest vibration loads. During the vibration experiment, output signals of the sensor keep stable and the sensor is well bonded to the structure, which shows the integrated sensor has high durability in vibration environment. Finally, the durability of integrated sensors is separately tested in three exposed environments, including salt fog corrosion environment, fluid immersion environment, as well as hygrothermal and ultraviolet-radiation environment. After these environmental exposure experiments, all sensors are well bonded to structures and can effectively monitor fatigue cracks, which shows great durability. Therefore, FECA sensors can survive in harsh service environments of aircrafts, which provides important support for the engineering applications of FECA sensors.

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Interpretation of bi-material interface through the mechanical and microstructural possessions

Materials Today Proceedings ◽

10.1016/j.matpr.2021.05.699 ◽

2021 ◽

Author(s):

Arigela Surendranath ◽

P.V. Ramana

Keyword(s):

Material Interface

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Determination of Mechanical Properties of Altered Dacite by Laboratory Methods

Minerals ◽

10.3390/min11080813 ◽

2021 ◽

Vol 11 (8) ◽

pp. 813

Author(s):

Veljko Rupar ◽

Vladimir Čebašek ◽

Vladimir Milisavljević ◽

Dejan Stevanović ◽

Nikola Živanović

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Rock Mass ◽

Uniaxial Compressive Strength ◽

Rock Material ◽

Strength Parameter ◽

Gradual Transition ◽

Strength Parameters ◽

Triaxial Compressive Strength ◽

Heterogeneous Rock

This paper presents a methodology for determining the uniaxial and triaxial compressive strength of heterogeneous material composed of dacite (D) and altered dacite (AD). A zone of gradual transition from altered dacite to dacite was observed in the rock mass. The mechanical properties of the rock material in that zone were determined by laboratory tests of composite samples that consisted of rock material discs. However, the functional dependence on the strength parameter alteration of the rock material (UCS, intact UCS of the rock material, and mi) with an increase in the participation of “weaker” rock material was determined based on the test results of uniaxial and triaxial compressive strength. The participation of altered dacite directly affects the mode and mechanism of failure during testing. Uniaxial compressive strength (σciUCS) and intact uniaxial compressive strength (σciTX) decrease exponentially with increased AD volumetric participation. The critical ratio at which the uniaxial compressive strength of the composite sample equals the strength of the uniform AD sample was at a percentage of 30% AD. Comparison of the obtained exponential equation with practical suggestions shows a good correspondence. The suggested methodology for determining heterogeneous rock mass strength parameters allows us to determine the influence of rock material heterogeneity on the values σciUCS, σciTX, and constant mi. Obtained σciTX and constant mi dependences define more reliable rock material strength parameter values, which can be used, along with rock mass classification systems, as a basis for assessing rock mass parameters. Therefore, it is possible to predict the strength parameters of the heterogeneous rock mass at the transition of hard (D) and weak rock (AD) based on all calculated strength parameters for different participation of AD.

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Heat transfer, physiological responses, and subjective perceptions during short contact time with wood or other materials

Journal of Wood Science ◽

10.1186/s10086-021-01960-0 ◽

2021 ◽

Vol 67 (1) ◽

Author(s):

Yuko Tsunetsugu ◽

Masaki Sugiyama

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Blood Pressure ◽

Physiological Stress ◽

Physiological Responses ◽

Chamaecyparis Obtusa ◽

Material Interface ◽

Japanese Cypress ◽

Subjective Perceptions ◽

Short Contact Time

AbstractThis study investigates the physiological responses and subjective perceptions of touching wood. In particular, it focuses on their respective relationships with the amount of heat transfer across the hand–material interface during contact. The study participants included 55 university students (20 females and 35 males) who gave written informed consent. The participants’ blood pressure, pulse rate, and cerebral blood hemoglobin concentrations were measured continuously for 90 s while they gently held vertical bar-shaped specimens of Japanese cypress (Chamaecyparis obtusa), Japanese oak (Quercus crispula), polyethylene, and aluminum. The specimens also included wood with a surface coating. We measured subjective warmth and comfort as well as the heat flux between the palm and the surface of the material. The wooden materials were rated as significantly warmer compared to aluminum and polyethylene, regardless of the wood species (cypress or oak) or its coating; this result corresponds with smaller heat transfers in the wooden materials. Additionally, the wooden materials were more comfortable to hold as compared to the aluminum bar. Based on the changes in blood pressure, touching Japanese cypress and uncoated Japanese oak were interpreted to induce less physiological stress. Therefore, we can conclude that wood, with lower thermal conductivity, feels warm, and it causes relatively smaller physiological changes compared to other materials with higher thermal conductivity. Thus, they may present less physiological burdens when touched.

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Carbonization of Carbonates and Fractionation of Stable Carbon Isotopes in a Dynamic Slip Zone

Geochemistry International ◽

10.1134/s0016702920090062 ◽

2020 ◽

Vol 58 (9) ◽

pp. 981-993

Author(s):

Yu. A. Morozov ◽

V. S. Sevastianov ◽

A. Yu. Yurchenko ◽

O. V. Kuznetsova

Keyword(s):

Carbon Isotopes ◽

Stable Carbon Isotopes ◽

Slip Zone ◽

Stable Carbon ◽

Dynamic Slip

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Experimental and Theoretical Nonlinear Dynamic Response of Intact and Cracked Bone-Like Specimens With Various Boundary Conditions

Journal of Vibration and Acoustics ◽

10.1115/1.2731413 ◽

2007 ◽

Vol 129 (5) ◽

pp. 541-549 ◽

Cited By ~ 2

Author(s):

Erick Ogam ◽

Armand Wirgin ◽

Z. E. A. Fellah ◽

Yongzhi Xu

Keyword(s):

Boundary Conditions ◽

Duffing Oscillator ◽

Contact Friction ◽

Nonlinear Dynamic Response ◽

Various Boundary Conditions ◽

Vibration Data ◽

Element Simulation ◽

Resonance Frequencies ◽

Vibration Experiment ◽

Freely Suspended

The potentiality of employing nonlinear vibrations as a method for the detection of osteoporosis in human bones is assessed. We show that if the boundary conditions (BC), relative to the connection of the specimen to its surroundings, are not taken into account, the method is apparently unable to differentiate between defects (whose detection is the purpose of the method) and nonrelevant features (related to the boundary conditions). A simple nonlinear vibration experiment is described which employs piezoelectric transducers (PZT) and two idealized long bones in the form of nominally-identical drinking glasses, one intact, but in friction contact with a support, and the second cracked, but freely-suspended in air. The nonlinear dynamics of these specimens is described by the Duffing oscillator model. The nonlinear parameters recovered from vibration data coupled to the linear phenomena of mode splitting and shifting of resonance frequencies, show that, despite the similar soft spring behavior of the two dynamic systems, a crack is distinguishable from a contact friction BC. The frequency response of the intact glass with contact friction BC is modeled using a direct steady state finite element simulation with contact friction.

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