Comparative study of destructive, nondestructive, and numerical procedures for the determination of moisture dependent shear moduli in Scots pine wood

In this study, moisture dependent shear moduli in Scots pine (Pinus sylvestris L.) wood were determined by a 45° off-axis (longitudinal, radial, and tangential) compression test and ultrasonic transverse wave propagation. Finite element modeling was performed to ascertain how the results agree with the numerical method. Ultrasonic transverse wave velocities on the LR, LT, and RT planes were decreased from 1347, 1323, and 589 m × s-1 to 1286, 1269, and 561 m × s-1 when relative humidity increased from 45 % to 85 % at a constant temperature of 20 ± 1 °C, respectively. The dynamic and static shear modulus on the LR, LT, and RT planes were decreased from 988, 953, and 189, and 966, 914, and 182 MPa to 927, 903, and 176, and 845, 784, and 154 MPa when relative humidity increased from 45 % to 85 % at a constant temperature of 20 ± 1 °C, respectively. Therefore, both velocity and modulus values at all principal axes and planes were decreased with an increase in moisture. Maximum (15.2 %) and minimum (2.3 %) differences between dynamic and the static shear modulus were observed for GLT at 85 % and GLR at 45 % relative humidity, respectively. Coefficients of determinations between the dynamic and static shear moduli were ranged from 0.68 (GLR at 65 % RH) to 0.97 (GLR at 85 % RH). Finite element analysis, only for 65 % RH values, was performed using Solid 45 element, and, according to results, load-deformation curves created by linear orthotropic material properties, are well-matched with the static curves.

Study on Field Test and Seismic Performance of MJS Joint Microdisturbance Reinforcement on Existing Tunnel

Metro Jet System (MJS) joint microdisturbance reinforcement is often adopted to strengthen and remediate existing tunnels that are severely deformed by under-construction peripheral works, but analysis related to the reinforcement system of tunnel under consideration of seismic effects is insufficient at present. In this work, a field test of MJS joint microdisturbance reinforcement system of existing tunnels was conducted on the basis of a subway tunnel deformation reinforcement project. Then, a numerical simulation study of the seismic dynamic response of reinforcement system was performed in combination with seismic wave direction and intensity. Results show that the MJS joint microdisturbance reinforcement measures can effectively reduce the settlement and horizontal radial convergence deformation of the tunnel. The seismic longitudinal wave significantly affects the vertical displacement of the tunnel, and the seismic-induced vertical displacement of the tunnel increases with the rise in seismic intensity. The seismic transverse wave significantly affects the horizontal radial convergence deformation of the tunnel, and the seismic-induced horizontal radial convergence deformation of the tunnel increases with the rise in seismic intensity. The antiseismic property of MJS joint microdisturbance reinforcement measures on the existing tunnel is not obvious.

Propagation of Transverse Wave for the Piezoelectric Radial Phononic Crystal Annular Plate in a Fibonacci Order

Based on the previous conventional phononic crystal (PC) structures infinitely periodic in Cartesian coordinates, this paper addresses a new radial phononic crystal annular plate (RPCAP) modeled in a Fibonacci order along the radial direction. In this study, piezoelectric material PZT4 is simultaneously inserted into this RPCAP model to investigate the stop band behaviors. In order to clearly show the transmission characteristics of transverse wave, in cylindrical coordinates, the transfer matrix is deduced through combining the general solutions, piezoelectric governing equations, and continuity conditions. Compared with conventional PC structures, transmission response of transverse vibration for the Fibonacci RPCAP model is calculated theoretically to analyze the stop band phenomenon. Finite element simulation method (FEM) is conducted here to verify the theoretical results. The results show that the Fibonacci RPCAP model presents two newly emerging resonance frequencies while the radial periodic order is disorganized. To thoroughly understand the RPCAP, the effects of structural parameters, material parameters, and piezoelectric parameters on the stop band are discussed in detail. The proposed Fibonacci RPCAP can be employed in many engineering applications, such as in rotating parts which are often coupled with transverse vibration (like gear driving systems).

Desain Rancang Bangun Trainer Kit untuk Menentukan Pengaruh Jenis Bahan Tali Terhadap Cepat Rambat Gelombang

The aim of the research is to establish the design of the trainer kit project to determine the effect of the rope material type toward the rope wave velocity and the effect of the type of nylon, raffia, polyester, hemp and chinnese satin rope materials on the velocity of rope wave propagation. The research method used is the Research and Development method using Nieveen design. The development of trainer kit uses an Arduino UNO microcontroller equipped with a proximity sensor HC-SR04 for measuring the rope wavelength. One point of the rope is tied with a timer ticker and the other is tied to a hanging load which is resting on a pulley. When the power supply is turned on, the timer ticker will vibrate to move the rope that has been tied. The rope will form a transverse wave. The result of this research, the design of trainer kit is development by using micro-controlled Arduino UNO and a proximity sensor HC-SR04 can be declared as a valid result. There are mass convention impacts of the type of rope likely nylon, polyester, raffia, hemp and chinese satin toward the rope wave velocity.

Transverse motions in sunspot super-penumbral fibrils

Sunspots have played a key role in aiding our understanding of magnetohydrodynamic (MHD) wave phenomena in the Sun’s atmosphere, and it is well known they demonstrate a number of wave phenomena associated with slow MHD modes. Recent studies have shown that transverse wave modes are present throughout the majority of the chromosphere. Using high-resolution Ca II 8542 Å observations from the Swedish Solar Telescope, we provide the first demonstration that the chromospheric super-penumbral fibrils, which span out from the sunspot, also show ubiquitous transverse motions. We interpret these motions as transverse waves, in particular the MHD kink mode. We compile the statistical properties of over 2000 transverse motions to find distributions for periods and amplitudes, finding they are broadly consistent with previous observations of chromospheric transverse waves in quiet Sun fibrils. The very presence of the waves in super-penumbral fibrils raises important questions about how they are generated, and could have implications for our understanding of how MHD wave energy is transferred through the atmosphere of a sunspot. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

Numerical simulation of the pier geometry effects on forming the transverse wave in converged spillways

Investigating the effect of the geometrical characteristics of the piers, i.e. increase in the length of the pier end, could reduce the transverse wave height and help to achieve the optimal design for the converging chute walls height and reducing the construction costs. In this paper, FLOW-3D is used for three-dimensional simulations of the Khair-Abad dam spillway and investigating the spillway piers geometry effects on forming the transverse waves. The simulation results show that the heights of the second and third waves increase by increasing the length of the pier end which is located adjacent to the chute walls due to the superiority of the effect of the chute convergence on the piers end length changes. It is shown that the suitable way to reduce the transverse wave height is increasing the length of the middle pier end. The simulation results demonstrated that the third wave height does not significantly change by increasing the length of the middle pier end more than a specific value and increasing the end length to more than this value to just increases the construction costs. Consequently, a specific length could be recommended for the spillway piers end optimum length to reduce the possibility of generation of the second and third waves and also to reduce the chute walls height.