3D Dynamic Finite Element Model Research Articles

Numerical Simulation on Dynamic Response of Existing Tunnel to Moving-Axle Loads under the Influence of Oblique Shield Crossing the Intersection Area

A 3D dynamic finite element model is developed to study the response of the existing tunnels’ concrete structure under the influence of different train speeds and undercrossing with fixed shield excavation. The intersection area of Metro Line 3 in Guangzhou and the intercity railway between Foshan and Dongguan is used as the case study. A programming idea simulating oblique moving-axle loads in the numerical model by using function expressions to constrain activity area is proposed. The Hilber–Hughes–Taylor time-integration scheme is used to calculate the dynamic response parameters of the double-channel rectangular cross section tunnels. Considering fixed excavation steps in the process of shield crossing, acceleration and deformation of the existing tunnels were analyzed under the moving-axle loads of trains at different speeds. From the perspective of the vibration and deformation of existing tunnels, shield excavation and moving speed have their own emphasis on the dynamic influence of the existing tunnel. In addition, the calculation results of the numerical simulation are in good agreement with the data obtained from some field tests, which further verifies the reliability of the calculation method of the numerical model. The results of this research can guide the arrangements for reinforcement measures for existing tunnels in the later stage.

Investigation on impact pressure and residual stress of water jet peening on AL6061-T6 with an inclined surface

Water jet peening (WJP) is a surface enhancement technique that can use the impact pressure to induce compressive residual stress in the narrow concave area of metal components. For WJP on the inclined surface, this research reveals the impact pressure evolution and the forming mechanism of compressive residual stress field (CRSF). Mathematical models of predicting the critical inclined angle θc and the maximum water hammer pressure Pm are developed. Besides, a 3D dynamic finite element model of WJP is developed. Then, the simulation model is verified by the experimental results of the inclined surface. Moreover, the influence of parameters such as inclined angle θ, jet velocity v, and jet diameter d on θc, Pm, and CRSF is investigated by simulation. The results indicate that Pm essentially determines the CRSF, and WJP parameters indirectly affect the CRSF by changing Pm. v determines θc, and θc increases with increasing v. θ and v determine Pm, and Pm decreases with increasing θ while increases with increasing v. The magnitude and depth of CRSF decrease with increasing θ while increases with increasing v. But d only affects the depth of CRSF, which increases with increasing d.

Multiphysics analysis of a hybrid suspension system for middle-low-speed maglev trains

The suspension force − a critical factor in the operation of middle-low-speed maglev trains − is provided by electromagnets. However, the eddy current effect produced by the relative motion between electromagnets and the steel track causes a reduction of the suspension force, especially under high speed. A novel type of permanent-electro-magnetic suspension system is proposed to improve performance by considering the variation of material characteristics with temperature. A 3D dynamic finite element model of this hybrid system − accounting for the influence of temperature − has been created to study the variation of magnetic flux distribution, suspension force and guiding force under different operational speeds of the train, in comparison with the electromagnetic version. Verified by simulations, the hybrid system has superior performance offering a powerful suspension force and a reliable guidance force even at high speeds of the train.

Identifying damage in a bridge by analysing rotation response to a moving load

This article proposes a bridge damage detection method using direct rotation measurements. Initially, numerical analyses are carried out on a one-dimensional (1D) simply supported beam model loaded with a single moving point load to investigate the sensitivity of rotation as a main parameter for damage identification. As a result of this study, the difference in rotation measurements due to a single moving point load obtained for healthy and damaged states is proposed as a damage indicator. A relatively simple laboratory experiment is conducted on a 3-m long simply supported beam structure to validate the results obtained from the numerical analysis. The case of multi-axle vehicles is investigated through numerical analyses of a 1D bridge model and a theoretical basis for damage detection is presented. Finally, a sophisticated 3D dynamic finite element model of a 20-m long simply supported bridge structure is developed by an independent team of researchers and used to test the robustness of the proposed damage detection methodology in a series of blind tests. Rotations from an extensive range of damage scenarios were provided to the main team who applied their methods without prior knowledge of the extent or location of the damage. Results from the blind test simulations demonstrate that the proposed methodology provides a reasonable indication of the bridge condition for all test scenarios.

Blast response of a thin oriented strand board wall

There has been a remarkable increase in the worldwide number of suicide bombing attacks in recent years. These attacks have left numerous victims as well as economic and psychological impacts on targeted locations. Developing new approaches to designing and constructing blast protection wall systems is an ever pressing need to partially mitigate the damaging effects of blast loadings. Several applications of simple blast protection wall systems have been considered for military purposes, but far fewer studies exist for non-military applications. The current study evaluates the overall performance of a thin oriented strand board (OSB) cantilever wall in response to the blast energy from explosive detonations. The study presents the results of open-space blast tests to measure the blast wave pressure in free air (without wall), and blast pressure (behind wall) at specified standoff distances. For the OSB response, a 3D dynamic finite element model was created using ABAQUS/Explicit software combined with the ConWep blast model to represent wall-blast wave interactions in free air to compare with the blast test results. Reductions in blast pressure behind the OSB wall of over 20 percent were observed. Good agreement between the test results and the numerical predictions was also found. The results of this work indicate the potential of using simple blast walls to partially mitigate blast loading at extremely low cost and minimal installation effort.

Random distribution characteristics of peak dynamic stress on the subgrade surface of heavy-haul railways considering track irregularities

The dynamic response of the subgrade surface under moving train loads provides information for subgrade settlement prediction, condition evaluation and so forth. In this paper, a 3D dynamic finite element (FE) model that considers the interactions among the wagon, track and subgrade was built. Then, the irregular vertical track spectrum of the three major lines in China was applied to simulate track irregularity. Through numerical calculation, the influence of vertical track irregularity on the dynamic stress of subgrade surface was investigated. The distributions of peak dynamic stresses at three subgrade surface locations (under each of the two rails and at the track center) along the track under the passage of trains with various axle loads were statistically acquired. The normal distributions of the peak dynamic stresses on the subgrade surface were verified. The maximum peak dynamic stresses were forecasted. The results indicated that the dynamic stresses on the subgrade surface were asymmetric along the center of subgrade surface due to the random distribution of track irregularities, and the peak dynamic stresses were found to follow a normal distribution. With the increase of axle load, the dispersion of peak dynamic stresses increased gradually, and the distribution curve of peak dynamic stresses gradually became steeper. The computed peak dynamic stresses aligned well with the field test data, indicating that the 3D dynamic FE model and statistical analysis method were reasonable. The research results will provide a basis for the reliability analysis of the dynamic deformation and accumulated settlement of subgrade surface.

Numerical analysis of influence factors on low-velocity impact damage of stitched composite laminates

A 3D dynamic finite-element model is proposed in this paper to simulate the damage development process of stitched laminates subjected to low-velocity impact. The strain-based Hashin criteria and a sudden degradation scheme are employed to determine the intra-laminar damage initiation and evolution; a mix-mode bilinear constitutive model is adopted to evaluate the inter-laminar delamination damage. The predicted numerical results agree well with the available experimental data, thus validating the proposed damage analysis model. Moreover, the influence factors, including the thickness of laminates, stitching density, diameter of stitching thread and strength of stitching thread, are analyzed and discussed in detail.

Effects of implant drilling parameters for pilot and twist drills on temperature rise in bone analog and alveolar bones

This study concerns the effects of different drilling parameters of pilot drills and twist drills on the temperature rise of alveolar bones during dental implant procedures. The drilling parameters studied here include the feed rate and rotation speed of the drill. The bone temperature distribution was analyzed through experiments and numerical simulations of the drilling process. In this study, a three dimensional (3D) elasto-plastic dynamic finite element model (DFEM) was proposed to investigate the effects of drilling parameters on the bone temperature rise. In addition, the FE model is validated with drilling experiments on artificial human bones and porcine alveolar bones. The results indicate that 3D DFEM can effectively simulate the bone temperature rise during the drilling process. During the drilling process with pilot drills or twist drills, the maximum bone temperature occurred in the region of the cancellous bones close to the cortical bones. The feed rate was one of the important factors affecting the time when the maximum bone temperature occurred. Our results also demonstrate that the elevation of bone temperature was reduced as the feed rate increased and the drill speed decreased, which also effectively reduced the risk region of osteonecrosis. These findings can serve as a reference for dentists in choosing drilling parameters for dental implant surgeries.

Research on Impact Process of Lander Footpad against Simulant Lunar Soils

The safe landing of a Moon lander and the performance of the precise instruments it carries may be affected by too heavy impact on touchdown. Accordingly, landing characteristics have become an important research focus. Described in this paper are model tests carried out using simulated lunar soils of different relative densities (called “simulant” lunar soils below), with a scale reduction factor of 1/6 to consider the relative gravities of the Earth and Moon. In the model tests, the lander was simplified as an impact column with a saucer-shaped footpad with various impact landing masses and velocities. Based on the test results, the relationships between the footpad peak feature responses and impact kinetic energy have been analyzed. Numerical simulation analyses were also conducted to simulate the vertical impact process. A 3D dynamic finite element model was built for which the material parameters were obtained from laboratory test data. When compared with the model tests, the numerical model proved able to effectively simulate the dynamic characteristics of the axial forces, accelerations, and penetration depths of the impact column during landing. This numerical model can be further used as required for simulating oblique landing impacts.

Vibration Analysis and Human Comfort Evaluation of Underground Hydropower House

Human comfort is of great importance to main powerhouse and vibration level should be controlled below the human comfort limit. Comparison of ISO2631/1-1985 and ISO2631/1-1997 was performed firstly in this study. It points out that weighted root-mean-square acceleration is basic variable for vibration evaluation. The reduced comfort boundary of 2 hours (0.260m/s2) in 1985 version is very close to the comfort threshold (0.315m/s2) in 1997 version. Above two values were selected as human comfort standard in this paper. After that, 3D dynamic finite element model of HongPing pumped storage station was established and vibration analysis under pressure fluctuations was conducted using time history method. The calculation results indicated that vibration of generator floor was mainly caused by the multiples of runner blade number frequency. Vibration level of generator floor would not lead to human discomfort.

Investigation on Dynamics of Ultrasonic Surface Rolling Process

Ultrasonic surface rolling processing (USRP) is a surface nanocrystallization method developed recently, which can bring metal surface with superior properties. In order to obtain the motion state of the processing tip during USRP, a 3D dynamic finite element model was adopted to simulate the response of processing tip. The model parameters were provided by piezoelectric force sensor test system. Simulated results indicate that the peak value of impact force forms at the time of 25μ̓ and the maximum speed of working tip forms at the time of ̃̀μ̓.

Study on Ultrasonic Surface Rolling Process Using FEM Analysis

Ultrasonic surface rolling processing (USRP) is a surface nanocrystallization method developed recently, which can bring metal surface with superior properties. In order to obtain the material response during USRP, a 3D dynamic finite element model was adopted to study the effects of parameters. This model was validated by experimental results of residual stress. Simulated results indicate that large ultrasonic vibration parameters generate high stress and strain, where static pressure plays a more important role than vibration amplitude. Yet high spindle speed leads to small stress and strain.