• Geomechanics and Engineering
• /
• v.24 no.6
• /
• pp.545-557
• /
• 2021

Since the functionally graded materials (FGMs) are used extensively as thermal barriers in many of applications. Therefore, the current article focuses on studying and presenting dynamic responses of multilayer functionally graded (FG) deep beams placed in a thermal environment that is not addressed elsewhere. The material properties of each layer are proposed to be temperature-dependent and vary continuously through the height direction based on the Power-Law function. The deep layered beam is exposed to harmonic sinusoidal load and temperature rising. In the modelling of the multilayered FG deep beam, the two-dimensional (2D) plane stress continuum model is used. Equations of motion of deep composite beam with the associated boundary conditions are presented. In the frame of finite element method (FEM), the 2D twelve-node plane element is exploited to discretize the space domain through the length-thickness plane of the beam. In the solution of the dynamic problem, Newmark average acceleration method is used to solve the time domain incrementally. The developed procedure is verified and compared, and an excellent agreement is observed. In numerical examples, effects of graduation parameter, geometrical dimension and stacking sequence of layers on the time response of deep multilayer FG beams are investigated with temperature effects.

• Coupled systems mechanics
• /
• v.13 no.2
• /
• pp.95-113
• /
• 2024

In this paper, we will analyse the thermo-elastic behavior of the plate element of a structure arranged in a climatically aggressive environment (extreme temperature), we use a refined four-variable thick plate theory to take the shear effect into consideration, the proposed theory less computationally expensive and more accurate so that it incorporates the shear effect into the formulation. The plate is assumed to be simply supported on its four edges, so exact (closed-form) solutions are found according to the Navier expansion, and the governing stability equations and associated boundary conditions of the problem are obtained via the virtual works principle. The plate studied ismade of laminated composite materials, so a parametric study is needed to see the effect of different types of parameters and coupling on the critical temperature value causing thermo-elastic instability of the plate and also on the natural frequency of free vibration, as well as for other parameters such as anisotropy, slenderness and aspect ratio of the plate and finally the lamination angle. Numerical results are obtained for specially orthotropic and antisymmetrical plates and are compared with those obtained by othertheoriesin the literature to validate the analysis approach used.

• Korean Journal of Materials Research
• /
• v.34 no.9
• /
• pp.422-431
• /
• 2024

Hydrothermal and ultrasonic processes were used in this study to synthesize a single-atom Cu anchored on t-BaTiO₃. The resulting material effectively employs vibration energy for the piezoelectric (PE) catalytic degradation of pollutants. The phase and microstructure of the sample were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and it was found that the sample had a tetragonal perovskite structure with uniform grain size. The nanomaterial achieved a considerable increase in tetracycline degradation rate (approximately 95 % within 7 h) when subjected to mechanical vibration. In contrast, pure BaTiO₃ demonstrated a degradation rate of 56.7 %. A significant number of piezo-induced negative charge carriers, electrons, can leak out to the Cu-doped BaTiO₃ interface due to Cu's exceptional conductivity. As a result, a single-atom Cu catalyst can facilitate the separation of these electrons, resulting in synergistic catalysis. By demonstrating a viable approach for improving ultrasonic and PE materials this research highlights the benefits of combining ultrasonic technology and the PE effect.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.2
• /
• pp.442-458
• /
• 2014

Wave induced vibrations increase the fatigue and extreme loading, but this is normally neglected in design. The industry view on this is changing. Wave induced vibrations are often divided into springing and whipping, and their relative contribution to fatigue and extreme loading varies depending on ship design. When it comes to displacement vessels, the contribution from whipping on fatigue and extreme loading is particularly high for certain container vessels. A large modern design container vessel with high bow flare angle and high service speed has been considered. The container vessel was equipped with a hull monitoring system from a recognized supplier of HMON systems. The vessel has been operating between Asia and Europe for a few years and valuable data has been collected. Also model tests have been carried out of this vessel to investigate fatigue and extreme loading, but model tests are often limited to head seas. For the full scale measurements, the correlation between stress data and wind data has been investigated. The wave and vibration damage are shown versus heading and Beaufort strength to indicate general trends. The wind data has also been compared to North Atlantic design environment. Even though it has been shown that the encountered wind data has been much less severe than in North Atlantic, the extreme loading defined by IACS URS11 is significantly exceeded when whipping is included. If whipping may contribute to collapse, then proper seamanship may be useful in order to limit the extreme loading. The vibration damage is also observed to be high from head to beam seas, and even present in stern seas, but fatigue damage in general is low on this East Asia to Europe trade.

• 한국HCI학회:학술대회논문집
• /
• 2008.02a
• /
• pp.130-134
• /
• 2008

Touch screen phone which is expected to play a big part of the mobile market for the next few years, has many merits but demerits of inaccurate feedback. It offers audio and tactile feedback to strengthen the weak point. This study aims to see if audio feedback and vibration feedback react upon each other under realistic conditions. We had a qualitative research in perception after using touch screen phone feedback. The result showed that with any feedback users were satisfied more than without any feedback and there was diversity in response. We ran the study again to see the performance level and the projective workload between the kind of feedback and interrupting feedback environment Performance rates were faster with audio feedback and according to the projective workload assessment users felt that task was easier and less annoying with audio-vibration feedback. The results suggest that audio feedback could be more effective than vibration feedback. A future study will figure out the relationship between the factors of qualitative-controlled feedback and learning time and the performance, and the main cause to make people prefer one feedback over another in a realistic world.

• Aerospace Engineering and Technology
• /
• v.2 no.2
• /
• pp.105-114
• /
• 2003

It is conducted to analyze vibration loads on the 1st stage of KSR-III(KSR : Korea Sounding Rocket) during their ground transportation and various handling process. These loads may be different from the real flight environment. Inadequate assessment of these loads can cause not only local damages on the rocket system but also the critical problem like flight mission failure. Therefore, transportation and handling loads must be considered during design and attenuated to ensure that the rocket structural damage does not occur. This work is concerned with the generation of criteria and prediction of transportation and handling loads for KSR-III. The results show that the shipping container is well designed to satisfy the design requirements. The maximum vibration level recorded during whole transportation and handling for KSR-III is less than 2g, the criteria of KSR-III movement condition.

• Journal of Energy Engineering
• /
• v.15 no.3 s.47
• /
• pp.202-208
• /
• 2006

Although the importance of good conservation of historic sites including ancient royal tombs is well aware, still not much attention has been paid for the facilities and systems to preserve those historic sites, which includes precious artifacts as wall paints and carved works, etc. Even the general understanding about the environment of the underground space or tombs is not satisfactory. In the present study, vibration levels due to the operation of an HVAC system to maintain the desired indoor temperature and humidity are investigated experimentally. According to the measured data, the level of vibration inside the present model tomb with the indoor unit inside, showed order of magnitude less values than the Swiss Standards, but still higher than the value suggested by German standards, which is, zero. Further study will be pursued for cases including different ways of installation, because the vibration level depends not only on the system design, but also on the installation methods.

• International Journal of Highway Engineering
• /
• v.16 no.5
• /
• pp.155-164
• /
• 2014

PURPOSES : The purpose of this article is to compare and evaluate the riding comfort of a passenger in tunnels depending on different surface textures of concrete pavement. METHODS : Evaluation of riding comfort is conducted at 17 sections, which have different surface texture such as transverse tinned(TT), longitudinal tinned(LT) and diamond grinded(DG). A triaxial accelerometer was set up on the passenger seat surface of the test vehicle to measure vibrations of an occupant, then the effects of vibration on comfort and health were evaluated by ISO 2631. And microphones were installed at passenger's ears height to measure sound pressure level(SPL) in the test vehicle. Additionally, a surface microphone was installed on the inside of wheel arch to evaluate noise between tire and pavement by NCPX method. All tests were conducted cruising at 100km/h. RESULTS : The results of all tests are as follows. First, both vibration magnitudes for comfort and for health in LT and DG sections are almost same and they represent lower than those in TT sections. Second, the average SPL of DG shows the lowest decibels among them. And third, it is founded that interior noise is significantly affected by noise between tire and pavement. CONCLUSIONS : It may be concluded that DG can provide more excellent riding comfort to passenger than LT or TT. Therefore, it is necessary to consider applying DG to existing pavement surface to improve surface condition when the driving environment especially requires riding comfort like a long tunnel.

• Explosives and Blasting
• /
• v.30 no.1
• /
• pp.9-16
• /
• 2012

With the deterioration and functional loss of structures, there is an increasing demand for demolition and various demolition technologies have been developed. In case of a large-scale concrete foundation, application of some mechanical demolition techniques is limited because of the structural characteristics, and explosive demolition or explosive demolition combined with mechanical demolition is applied recently due to the effect to the surrounding environment by the ground vibration. In this study, we compared peak particle velocity of ground vibration depending on average fragment size in case of explosive demolition design for large-scale concrete foundation using the relation among specific charge, charge constant and transmitting medium constant as well as the relation between average concrete fragment size and specific charge.

• Explosives and Blasting
• /
• v.30 no.1
• /
• pp.37-51
• /
• 2012

In this case of "Seongnam~Yeoju double-lanes railroad construction", there were safety facilities which were concerned about damages from vibration and noise. In the project design stage, the rock-splitter method was designed to prevent them. The electronic blasting was considered to improve construction speed and economic value as an alternative tunnelling method, complying with the site's vibration criteria(cowhouse : 0.09cm/sec, residence : 0.2cm/sec). In the environment evaluation report of the eDev, tunnel electronic blasting systems, the blasting pollutions can be managed by the electronic blasting method. The results were successfully conducted with high speed construction without any damages to adjacent facilities.