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Highlights • Structural sound insulation effect is introduced to EFEA for extruded structures. • Interior noise is predicted based on modified EFEA theory. • Predicted responses are validated by on-site test results. • Energy contribution of exterior excitation sources is calculated by prediction models. • Sound quality of interior noise is reduced by excitation optimizations. Abstract Compared with traditional finite element analysis and statistical energy analysis, the energy finite element analysis (EFEA) has the advantages of small computations and solving local responses in large-scale complex structures. In this paper, the structural sound insulation effect is introduced to EFEA for predicting and analyzing interior noise responses of extruded structures in a high-speed train. Firstly, the carriage structure and cavity models are established based on EFEA theory, and model parameters are obtained through experiments and effective simulations. Mechanical and acoustic excitation sources of the high-speed train are extracted through multi-body dynamic simulation, acoustic finite element method and nonlinear acoustic solution. The reliability of predicted excitations is validated by verifying the amplitude peak frequency bands. The interior noise responses at several observations are obtained and in good agreement with on-site test results, and the EFEA prediction model of interior noise is verified accurately. Secondly, the energy contribution of exterior excitation sources to interior noise responses is analyzed based on EFEA model. The results indicate that acoustic excitations dominate the acoustic energy in the frequency bands above 800 Hz, and the energy contribution of mechanical excitations and acoustic excitations is relatively close in the frequency bands below 600 Hz. The contribution of aerodynamic noise excitations is predominantly concentrated in the frequency bands below 500 Hz, while that of wheel-rail noise excitations is concentrated in the frequency bands above 800 Hz. In the frequency bands below 1250 Hz, the energy contribution of rail noise excitations is much more important than that of wheel noise excitations, while their contribution gets gradually close in the frequency bands above 1600 Hz. Besides, the acoustic excitations at the bottom of the carriage are quite important sources. Finally, wheel-rail noise excitations are optimized with spoke-shielding damping wheels and dynamic vibration absorbers, and the sound pressure level in the amplitude peak bands is reduced by about 8 dB. The interior noise responses are reduced by about 3–5 dB in the frequency bands above 800 Hz, and total loudness, sharpness and roughness at different locations are decreasing by more than 1 sone, 0.05 acum and 0.03 asper respectively. Therefore, wheel-rail noise optimizations have good reduction effects on interior noise responses in the high frequency bands. [ABSTRACT FROM AUTHOR]

High-speed-railway-train interior noise at low, medium, and high frequencies could be simulated by finite element analysis (FEA) or boundary element analysis (BEA), hybrid finite element analysis–statistical energy analysis (FEA–SEA) and statistical energy analysis (SEA), respectively. First, a new method named statistical acoustic energy flow (SAEF) is proposed, which can be applied to the full-spectrum HST interior noise simulation (including low, medium, and high frequencies) with only one model. In an SAEF model, the corresponding multi-physical-field coupling excitations are firstly fully considered and coupled to excite the interior noise. The interior noise attenuated by sound insulation panels of carriage is simulated through modeling the inflow acoustic energy from the exterior excitations into the interior acoustic cavities. Rigid multi-body dynamics, fast multi-pole BEA, and large-eddy simulation with indirect boundary element analysis are first employed to extract the multi-physical-field excitations, which include the wheel–rail interaction forces/secondary suspension forces, the wheel–rail rolling noise, and aerodynamic noise, respectively. All the peak values and their frequency bands of the simulated acoustic excitations are validated with those from the noise source identification test. Besides, the measured equipment noise inside equipment compartment is used as one of the excitation sources which contribute to the interior noise. Second, a full-trimmed FE carriage model is firstly constructed, and the simulated modal shapes and frequencies agree well with the measured ones, which has validated the global FE carriage model as well as the local FE models of the aluminum alloy–trim composite panel. Thus, the sound transmission loss model of any composite panel has indirectly been validated. Finally, the SAEF model of the carriage is constructed based on the accurate FE model and stimulated by the multi-physical-field excitations. The results show that the trend of the simulated 1/3 octave band sound pressure spectrum agrees well with that of the on-site-measured one. The deviation between the simulated and measured overall sound pressure level (SPL) is 2.6 dB(A) and well controlled below the engineering tolerance limit, which has validated the SAEF model in the full-spectrum analysis of the high speed train interior noise. [ABSTRACT FROM AUTHOR]

• The laser strain sensor was used to obtain accurate experimental data. • The actual working temperature and relaxation have profound effects on sealing performance of rubber. • The main failure mechanism caused by temperature and relaxation have been discussed. • Temperature safety factor and stress relaxation safety factor were put forward. In the last few decades, rubber seal elements have been extensively used in the oil and gas industry. However, mechanical properties of rubber decrease at high temperatures, and stress relaxation can lead to sealing performance degradation, even sealing element failure. Therefore, how high temperature and stress relaxation affect the sealing performance of rubber is an important issue in oil and gas production. According to the oilfield feedback information, hydrogenated nitrile butadiene rubber (HNBR) was chosen for sample tension test at different temperature (20 °C and 120 °C) and the stress relaxation tests at 120 °C. The constitutive model of rubber was fitted by the test data. At the setting pressure of 14 MPa, the influence of temperature and stress relaxation on the packer rubber seal system was investigated by finite element analysis (FEA) software. The results indicated that temperature and stress relaxation had an appreciable impact on the sealing performance of packer rubber seal system. The average contact stress at 120 °C between the rubber and the borehole wall, compared with the calculation results at 20 °C, decreased by more than 15% and the maximum contact stress decreased by 20%. Similarly, the average contact stress before the relaxation decreased by more than 35% after stress relaxation behavior at 120 °C. In addition, the maximum contact stress decreased by 50% due to the stress relaxation. Our experimental results and discussion enable us to provide some advice to improve the sealing performance of a packer seal system, and present a basic experimental and theoretical foundation for future research into the optimum design of a packer sealing system. [ABSTRACT FROM AUTHOR]

• The finite element analysis based on the blocked force test method was developed. • The frequency resolution of the vibration source was improved by signal processing. • The effectiveness of the numerical calculation was verified with high accuracy. In the continuous development of automotive technology, source characterization is becoming a significant and challenging step in the research of vehicle vibration and noise. Compared to classical transfer path analysis (CTPA), blocked force-transfer path analysis (BF-TPA) method is introduced as a more effective technique to characterize the intrinsic properties of the vibration source without disconnecting the source and receiver. This paper focused on the vibration of a brake booster with a short duration and conducted the rig test to obtain the internal excitation based on BF-TPA combined with signal processing methods of zero-padding, periodic extension and symmetric extension, respectively. The vibration response of dash panel on which the booster installed was calculated by the three proposed signal processing methods. The comparison showed that more accurate simulation results can be obtained with the periodic extension of the data than with the zero-padding, while the results of the symmetric extension are almost the same as the periodic extension. The good agreement between the results of the calculation and the corresponding vibration test verified that the blocked force obtained by the modified BF-TPA method can be applied in the numerical calculation of the coupled assembly composed of the vibration source and receiver. [ABSTRACT FROM AUTHOR]

A dash panel is a plate that separates the engine compartment from the cabin and mainly serves to block engine noise. The effect of automotive lightweight design on sound insulation performance of the dash panel needs to be studied. In this paper, the study of acoustic characteristics of automotive magnesium composite dash panel was conducted in four steps. Firstly, the sound insulation performance of a basic magnesium alloy plate was investigated using finite element method/indirect boundary element method (FEM/IBEM) and was verified with corresponding sound insulation test. The result proved that the structural-acoustic coupling based FEM/IBEM was feasible for calculating the sound insulation. Secondly, finite element models of two bare (steel and magnesium alloy) dash panels were created and the FE model of the steel dash panel was verified with a constrained modal test. The sound insulation performance of the two bare dash panels of different materials was then predicted by developing their FEM/IBEM models, and the modal contribution was examined based on the partially-coupled modal assumption. It was found that although the weight was lightened the sound insulation performance did not deteriorate, and the performance was even better in some frequency bands after replacing steel with magnesium alloy. Thirdly, the sound insulation performance of composite dash panel applied with acoustic packages was studied. It was found that the sound insulation performance deteriorated in a low frequency band (0–1000 Hz) for certain acoustic packaging materials, and it was not always true that the thicker the acoustic package, the better the sound absorbing performance. Finally, the finite element-statistical energy analysis (FE-SEA) method was used to extend the sound insulation research of the composite dash panel to the full-frequency band. The results showed that acoustic packaging design of key areas could have significant acoustic optimization effects. Relevant discussions on the results were provided and conclusions were made. [ABSTRACT FROM AUTHOR]

As the researches of electric impedance tomography (EIT) applications in medical examinations deepen, we attempt to produce the visualization of 3D images of human bladder. In this paper, a planar electrode array systemwill be introduced as the measuring platform and a series of feasible methods are proposed to evaluate the simulated volume of bladder to avoid overfilling. The combined regularization algorithm enhances the spatial resolution and presents distinguishable sketch of disturbances from the background, which provides us with reliable data from inverse problem to carry on to the three-dimensional reconstruction. By detecting the edge elements and tracking down the lost information, we extract quantitative morphological features of the object from the noises and background. Preliminary measurements were conducted and the results showed that the proposed algorithm overcomes the defects of holes, protrusions, and debris in reconstruction. In addition, the targets' location in space and roughly volume could be calculated according to the grid of finite element of the model, and this feature was never achievable for the previous 2D imaging. [ABSTRACT FROM AUTHOR]

Elasticity is of profound significance to evaluating the function of a biological soft tissue. When the elasticity of a tissue is macroscopically changed, it means that the biological function of the tissue is abnormal and some disease or injury may occur. In the present work, an elastometer is developed to measure the elasticity of biological soft tissues. The measurement is based on the indentation method and the force is measured by the bending of the cantilever. The force-indentation data of the soft tissue is experimentally measured by this elastometer and Young's modulus of the tissue is calculated using the Hertz—Sneddon model. For comparison, a numerical model for the indentation method is established using the finite element method. The difference between the actual modulus and the measured modulus is discussed. The effect of the thickness of the specimen on the measurement is investigated. Young's moduli of beef, porcine liver and porcine kidney are experimentally measured. The results indicate that our elastometer is effective in measuring Young's modulus of a soft tissue quantitatively. [ABSTRACT FROM AUTHOR]

Abstract: High sound quality and low radiated noise are two dominant demands for the vibro-acoustic performance of internal combustion engines. Such engines with high acoustic quality will greatly improve the acoustic environment both inside and outside of the passenger compartment of an automobile. In this paper, this performance of the block of a four-cylinder diesel engine was simulated and bench-tested. Then the vibro-acoustic problems were diagnosed and optimized. The finite element analysis method was adopted to numerically analyze the natural modes of the block. The finite-element model of the block was verified by the experimental modal analysis utilizing the single-input and multiple-output technology. The results indicate that the modal frequency errors from the simulation and experiment are permissible in respect of engineering and the accuracy of the finite-element model highly matching the real one is validated. Then, the flexible multi-body dynamics model of the diesel engine was constructed and excited by the boundary conditions comprised of in-cylinder gas pressures, cylinder liner-piston contact induced lateral forces and valve system motion induced impact forces. The simulated vibration velocity levels from the block surface were obtained under the rated condition (75kW/3600rpm) and well verified by the bench test. Boundary element analysis method was employed to acquire the radiated acoustic pressures from the block surface in the frequency range of interest. Optimized schemes are implemented to the block surface in order to reduce the radiated noise and enhance the sound quality of the diesel engine. Finally, the optimal block was cast. And the bench-test results indicate that the sound quality of the new-block engine is substantially improved. The research achievements validate the feasibility and reliability of the optimal design for the block. [Copyright &y& Elsevier]

The article discusses a study which examines the ability of quantitative computed tomography-based (QCT) structural assessment techniques to predict vertebral strength in anterior bending. It aims to compare the abilities of QCT-based bone mineral density mechanics of solids models. Results suggest that the poor clinical performance of noninvasive structural measures may be due to their inability to predict vertebral strength.