Three-dimensional Dynamic Finite Element Model Research Articles

Analysis of transient energy conversion performance improvement of thermoelectric generator with penetrating crack under pulsed heat source

To simulate the performance of a thermoelectric generator (TEG) in practical applications more accurately and comprehensively analyse the influence of transient heat source and crack on such devices, it is necessary to examine the transient performance of TEGs with cracks under periodic pulsed heat source. In this study, a three-dimensional nonlinear dynamic finite element model with thermal, electrical, and mechanical coupling was established, and the laws describing the macroscopic electrical energy output and thermal stress distribution were derived. The position of the maximum thermal stress changed as the crack size varied. When the crack field axis was increased from 0.2 mm to 1.8 mm, the total output energy increased by 14.4 %, whereas the thermal stress increased to 447 MPa. The total energy growth rate under pulsed heat source conditions reached 52.3 % (from 62.71 J to 95.52 J) compared with that of the steady-state heat source. However, the maximum thermal stress increased by 173.6 % (from 91 MPa to 249 MPa). The results show that the crack and pulsed heat source can effectively improve the electrical output performance of TEGs; however, their mechanical properties deteriorated. This study is useful in terms of predicting the performance of TEGs in practical applications more accurately.

Assessment of Thermal Osteonecrosis during Bone Drilling Using a Three-Dimensional Finite Element Model.

Bone drilling is a common procedure used to create pilot holes for inserting screws to secure implants for fracture fixation. However, this process can increase bone temperature and the excessive heat can lead to cell death and thermal osteonecrosis, potentially causing early fixation failure or complications. We applied a three-dimensional dynamic elastoplastic finite element model to evaluate the propagation and distribution of heat during bone drilling and assess the thermally affected zone (TAZ) that may lead to thermal necrosis. This model investigates the parameters influencing bone temperature during bone drilling, including drill diameter, rotational speed, feed force, and predrilled hole. The results indicate that our FE model is sufficiently accurate in predicting the temperature rise effect during bone drilling. The maximum temperature decreases exponentially with radial distance. When the feed forces are 40 and 60 N, the maximum temperature does not exceed 45 °C. However, with feed forces of 10 and 20 N, both the maximum temperatures exceed 45 °C within a radial distance of 0.2 mm, indicating a high-risk zone for potential thermal osteonecrosis. With the two-stage drilling procedure, where a 2.5 mm pilot hole is predrilled, the maximum temperature can be reduced by 14 °C. This suggests that higher feed force and rotational speed and/or using a two-stage drilling process could mitigate bone temperature elevation and reduce the risk of thermal osteonecrosis during bone drilling.

Accuracy prediction of wearable flexible smart gloves

Abstract This article aimed at providing a new biomechanical three-dimensional dynamic finite element model of the hand–glove combination for exploring the distribution of the overall continuous dynamic contact pressure of the hand with the flexible glove in the state of grabbing an object, and further predicting the accuracy of sensors of wearable smart gloves. The model was validated by garment pressure experiments at eight muscle points. The results showed that the pressure value measured with three flexible gloves was highly consistent with the finite element simulation value. Based on the model, the distribution of dynamic pressure between the soft tissue of the hand and the fabric in the process of flexing the fingers and grabbing external objects were predicted accurately and effectively, which indicated that the model with high accuracy could be applied to evaluate the accuracy of the pressure value collected by sensors of smart gloves. In addition, the model had been confirmed that it has a certain application value. The findings could help to provide a reference for dynamic continuous monitoring equipment or other intelligent wearable devices, and promote the development of the intelligent clothing industry in the future.

Study on vibration characteristics of fine breccia soil subgrade reinforced with a new prestressed structure under train cyclic loading

Train cyclic loading generally results in significant dynamic responses of the breccia soil subgrade, resulting in a series of subgrade problems. A new prestressed reinforcement structure (PRS) is proposed to reinforce subgrade structures. However, characteristics of the prestressed subgrade under dynamic loading have not been investigated. This study investigates the vibration characteristics of a new prestressed subgrade structure under train cyclic loading. The acceleration responses of the subgrade surface under different train axle loads and prestress levels are measured and discussed by developing a 1:5 scale dynamic model test on a prestressed fine breccia soil subgrade structure. Subsequently, a three-dimensional dynamic finite element model of the prestressed subgrade is constructed for an in-depth analysis of the internal acceleration of the prestressed subgrade. The results showed that a periodic acceleration response of the subgrade should be observed, and its mean crest and mean trough are used to characterize the long-term vibration degree of the subgrade. The peak vertical acceleration of the subgrade is significantly affected by the prestress level, and the dynamic response of the subgrade around the lateral pressure plate (LPP) is reduced more obviously by the prestress than that of the subgrade’s inner region. The peak vertical acceleration at the subgrade shoulder presents linear increase and exponential attenuation with the rise in the train axle load and prestress level, respectively. In addition, an empirical model describing the relationships among the peak acceleration, train axle load, and prestress is proposed. The vertical dynamic displacement and dynamic stress decrease with the increase of the prestress. The average elastic deformation and peak dynamic stress of the subgrade under a prestress level of 100 kPa are found to be 95.8% and 87.22–90.07% of that with the absence of prestress, respectively. The vertical vibration of the prestressed subgrade structure can be reduced by taking measures such as adjusting the prestress magnitude and increasing the subgrade slope ratio, thereby achieving an effective prestress reinforcement effect.

Pile group in clay subjected to cyclic lateral load: Numerical modelling and design recommendation

Major structures like offshore platforms, wind turbines, transport infrastructure, tall buildings, etc., resting on soft compressible clays, are often supported by pile foundations. Apart from usual vertical loading (dead load, live load, etc.), these piles are subjected to significant cyclic loads arising from actions of waves, ship impacts, winds or moving vehicles. Under such circumstances, the lateral mode of cyclic loading is predominant and affects the overall foundation stability. Such repetitive loading leads to stress reversal in adjacent soft clay initiating progressive degradation in soil strength and stiffness, deteriorating the pile capacity with unacceptable displacements. Although several past studies investigated the response of single pile under lateral cyclic loading, a detailed investigation on pile group in clay subjected to cyclic lateral loading, which is of immense practical interest to field engineers, is yet to be carried out. In this paper, in-depth study has been carried out by developing a three-dimensional dynamic finite element model. Comparison of the computed results with available test data validates the numerical model. Extensive parametric studies with field data indicate that both the axial and lateral pile capacities and displacements have been significantly influenced by the cyclic loading parameters. Relevant design curves are also constructed.

Influence of Environmental Vibration Caused by Three Lines Overlapping in Subway Tunnel Operations

Taking the six-hole overlapped tunnel area of Tianjin Metro Lines Z1, 5, and 6 as the research object, the universal finite element software ABAQUS is used to establish a three-dimensional dynamic finite element model of the overlapped tunnel area, and the vibration load of the subway train is applied. The environmental vibration response law of the overlapped tunnel area under different load combinations and different orders of tunnel construction conditions is analyzed, and some suggestions for the assessment and control of the environmental vibration of the overlapped tunnel area are put forward. The research results can provide a reference for subway line planning, design, construction, and operation management in the complex spatial tunnel area with multiple overlapped lines under similar conditions.

Research on collapse failure characteristics and theoretical prediction formulas of Solid expandable tubular

Solid expandable tubular (SET) is plastically formed in the well, it needs to undergo the double test of internal and external pressure. The collapse resistance of the SET after expansion is an important guarantee for the wellbore structural integrity reconstruction. In addition, due to the diversity of the material of the SET and the complexity of plastic forming, there is no unified formula for calculating the collapse strength of the SET. Aiming at the above problems, this paper builds a three-dimensional dynamic collapse strength calculation Finite element model (FEM) based on the collapse experiment of SET, and analyzes the influence of expansion rate, wall thickness and eccentricity on the collapse strength of expansion pipes, and fits the theoretical calculation formula of collapse strength. The research results show that: the expansion rate causes the collapse performance of the pipe after expansion to be reduced by 15% to 30%; the wall thickness has almost a linear effect on the collapse performance; the greater the eccentricity, the lower the collapse strength, the more likely it is to “ Concave ”. Through data fitting, a theoretical prediction formula for the collapse strength of SET with a material of 20G and a diameter-to-thickness ratio of less than 30 is obtained. The formula is simple and easy to calculate using parameters. The research results in this paper provide theoretical guidance and methods for the study of the collapse strength of SET.

Settlement simulation of soft clay in the subway under dynamic load based on Midas GTS NX

The subway has become the main way for people to travel nowadays. The saturated soft clay area has a large population and subway construction is the most extensively distributed. The saturated soft clay foundation will settle under the dynamic load of the subway train, which will affect the service life and structural safety. To study the settlement characteristics of soft clay under the dynamic load of the subway, a three-dimensional dynamic finite element model was established based on the finite element software Midas GTS NX, and the soft clay under the normal design speed (80 km/h) and the high-speed (120 km/h) were compared and analyzed. The research results show that the higher the train speed, the larger the lateral influence range of the surface settlement trough, but the settlement decreases with the increase of the subway running speed. The settlement of the subway line after one year of operation is about 45mm, and the settlement after 20 years is about 58mm. The growth rate of the settlement prediction curve decreases gradually, and the settlement increment is very small for a long time in the later period of operation.

Assessment of heat generation and risk of thermal necrosis during bone burring by means of three-dimensional dynamic elastoplastic finite element modelling

During bone burring, the heat generated due to friction at the bone-burr interface may cause thermal damage to the bone. Therefore, it is necessary to assess bone temperature distribution around a burring site and identify high-risk regions for thermal necrosis due to bone burring. In this study, a three-dimensional (3-D) dynamic elastoplastic finite element model for the burring process was developed and experimentally validated to investigate the influence of burring parameters (rotational speeds: 3,000, 10,000, 15,000 and 60,000 rpm; feed rates: 0.5, 0.9, 1.5 and 3.0 mm/s) on heat generation and evaluate the risk region for thermal necrosis. Calculated bone temperatures were compared with experimental values and found to be in good agreement with them. The analytical results demonstrated a linear relationship between the burring time and friction energy. In addition, the friction energy increased with the bone temperature. The high-risk thermal necrosis zone was measured from the edge of burring (y-direction) at feed rates of 0.5, 0.9, 1.5 and 3.0 mm/s and was found to be 7.8, 7.3, 6.6 and 5.5 mm, respectively. When the burr rotational speed increased from 3,000 to 60,000 rpm, the high-risk zone for thermal necrosis increased from 4.5 to 8.1 mm. We concluded that both the friction energy and the bone temperature increased in proportion with the burr rotational speed. Reducing burr rotational speeds and/or increasing feed rates may decrease the rise in bone temperature, thus decreasing the potential for thermal necrosis near the burring site. Our model can be used to select the optimal surgery parameters to minimise the risk of thermal necrosis due to bone burring and to assist in the design of optimal orthopaedic drill handpieces.

Effects of deep knee flexion on skin pressure profile with lower limb device: A computational study

Knee flexion behavior alters the contact pressure distribution exerted by compression devices during exercise. This study aimed to develop a three-dimensional dynamic finite element model of the lower limb with detailed bony structures, wearing a compression device with higher pressure over the calf, and then to quantify and compare the garment–body interface contact pressure and the cross-section pressure gradient deviation in standing and deep knee flexion postures (30°, 60°, 90°, and 120° of knee flexion). Contact pressure experiment on seven muscle points was applied to validate the model. The cross-section pressure gradient deviation was calculated on landmarks based on deviation along the four axial pathways from the average cross-section pressure gradients. In general, the results demonstrated that the whole pressure profile gradually decreased from the ankle to the thigh with higher compression on the calf in a standing position. Cross-section pressure gradient deviation resulted in a dramatic increase of ∼100% and ∼110% on positions B1 and D on the anterior of calf at 60° flexion, respectively, which resembled an M shape. This phenomenon was caused by the combination of the stretch of clothing during knee flexion, high compression over the calf, and the shape of the lower limb. This finite element model and its findings together could help us to understand the compression effects of sports lower limb devices and garments to enhance walking and running performance, and help to improve the design concepts.

Effect of Track Irregularities on the Response of Two-Way Railway Tracks

In predicting the response of track from a moving train only one track is generally considered. However, the effect of ground vibrations from one track and its effect on the nearby tracks has not been studied completely. Therefore, in the present paper, the effect of track irregularities and speed on the prediction of two-way tracks response is investigated. For this purpose, a three-dimensional dynamic finite element (FE) model capable of simulating interactions between the train and track by using a nonlinear hertz contact method was developed. The model uses tensionless stiffness between the wheel and rail to couple them. The model components including the sleeper, ballast, and soil domain are represented by solid brick elements. The rails are modeled as 3D Euler–Bernoulli beam elements. An iterative numerical algorithm was established for the integrations of the train and track interface. A comparative analysis was performed at various speeds and rail surface irregularity wavelengths. With the increase in speed, the results showed a significant increase in the adjacent tracks response and can induce much larger track vibrations at high frequency.

Three-dimensional (3D) dynamic finite element modeling of the effects of a geological fault on the seismic response of underground caverns

Faults generally have detrimental effects on the stability of underground caverns. During earthquakes these destructive effects are magnified. In this paper, a fully three-dimensional (3D) dynamic finite element model is developed to assess the effects of a fault on the seismic behaviors of underground caverns. A nonlinear thin-layer element model is developed to describe the complex mechanical properties of the fault. The developed model is first verified by two traditional shear experiments. Then the effects of fault parameters (e.g. the intersection angle, fault thickness, fault shear strength), in situ stress states and the intensity of earthquake on seismic response of underground cavern are analyzed. The predicted results show that when the fault strike is parallel to the longitudinal axis of the cavern and the intersection angle between the fault and the vertical axis in the cavern cross section is approximately 40°, the cavern is in the most unstable state. In addition, the cavern is likely to suffer a collapse when critical peak ground acceleration (PGA) is around 0.3 g under the cases studied in this work.

Comparative Study of Tunnel Blast-Induced Vibration on Tunnel Surfaces and Inside Surrounding Rock

In tunnel blast applications, vibration monitors are typically placed on tunnel surfaces to measure the responses of rock to explosion loads for statutory compliance. Few publications in the open literature have focused on the differences between the blasting vibration on tunnel surfaces and inside the surrounding rock. During blasting excavation of the experimental tunnels in the China Jinping Underground Laboratory, velocity sensors were arranged both on the tunnel walls and inside the surrounding rock to monitor far-field vibrations. In this paper, the vibration characteristics on the tunnel surfaces and inside the surrounding rock are presented based on the recorded field data. Corresponding empirical formulae for peak particle velocity (PPV) attenuation and dominant frequency variation are derived from these data. A three-dimensional dynamic finite-element model is used to verify the site survey results. The field and numerical studies show that compared with the inside vibration, the tunnel surface vibration has a higher, more readily attenuated PPV and a lower frequency with a slower rate of decline in the dominant frequency. The mechanisms that cause the differences between the surface and inside vibration are discussed in detail. The tunnel surface vibration in the far field is dominated by surface waves, which occupy more than 75% of the total vibrational energy. For this reason, the results presented in this paper do not apply to vibration in the near field, where body waves are expected to be dominant.

Nonlinear Seismic Response of a Hydraulic Tunnel Considering Fluid-Solid Coupling

The seismic response of hydraulic tunnels is a complex nonlinear process. What makes the case even more interesting is that the large amount of water in hydraulic tunnels which is likely to induce considerable hydrodynamic pressure acted on tunnel structures during earthquakes. In this work, a full three-dimensional (3D) dynamic finite element model is adopted to conduct a comprehensive assessment of the seismic behaviors of a hydraulic tunnel system. In this analysis, the plastic-damage model is employed to reflect the nonlinear mechanical behaviors of the concrete lining, and a fluid-solid coupling method based on an explicit weighted residual approach is proposed to consider the effects of the hydrodynamic pressures on the seismic response of the hydraulic tunnel. The numerical results indicate that the hydrodynamic pressure contributes to a greater seismic response of the tunnel structure. When the hydrodynamic pressure is considered, the magnitudes of the maximum principal stresses are likely to increase by 50% and the displacement amplitudes are approximately 2 cm more than that of without hydrodynamic pressure. The hydrodynamic pressure exacerbates the damage degree of the tunnel structure, and the waist suffers the most severe damage.

Experimental study on dynamic response of model shield tunnel induced by moving-axle loads of subway train

A new testing method was introduced to apply moving-axle loads of a subway train on a track structure. In order to investigate the dynamic responses of the shield tunnel subjected to moving-axle loads, a series of laboratory model tests were conducted in a 1/40 scale model tunnel. The influences of the axle load, the wheel speed, and the cover depth of the shield tunnel on the vertical displacement and acceleration of the lining were presented and discussed. Parametric studies revealed that the vertical displacement–time history of the lining presents a “W” shape due to the combined action of two axles of a bogie. The peak value of the vertical displacement increased with the axle load linearly, while it decreased with the increase in the cover depth. Moreover, response time of the displacement decreased with the increase in the wheel speed, but the peak values remained stable at the same level. Finally, a three-dimensional dynamic finite element model was adopted to simulate the movement of the axle loads and calculate the responses of the lining. The numerical results analysis agrees well with experimental results.

Seismic damage assessment and mechanism analysis of underground powerhouse of the Yingxiuwan Hydropower Station under the Wenchuan earthquake

The Yingxiuwan underground powerhouse is one of the closest large-scale underground structures from the epicenter of the Wenchuan earthquake and suffered significant damage during this earthquake. What makes this case even more interesting is that the seismic damage is mainly distributed in the upper part of the concrete structure in the underground powerhouse. A full three-dimensional dynamic finite element model of the underground structure and rock system is adopted to make a reasonable assessment for the seismic damage observed in the field and to study the damage characteristics and mechanisms of the underground powerhouse. Additionally, to approximate actual field conditions, the oblique incidence of seismic waves and the rock-structure interaction (RSI) are both considered in this study, and their effects on the seismic response are evaluated. The numerical results indicate that the oblique incidence of the seismic wave and the RSI both contribute to a larger seismic response, and the results compare well with the field observations when the two are considered. The damage distribution of the concrete structure is mainly dominated by the structure feature itself. The main cause of the severe damage in the upper structure is due to the lack of sufficient constraints on it, which leads to a large deformation in the upper structure.

Assessment of thermal necrosis risk regions for different bone qualities as a function of drilling parameters

Background and objectiveDuring bone drilling, the heat generated by friction depends directly on bone quality and surgical parameters. Excessive bone temperatures may cause thermal necrosis around the pilot hole, weaken the purchase of inserted screws, and in turn reduce the stability of screw fixation. A few studies have addressed the key parameters of drilling, such as the rotation speed of the drill-bit, feed force (axial force), feed rate, tool type, and tip geometry of drill-bits. Nevertheless, in the literature, information on the relationship between bone quality and thermally affected regions is still lacking. This study employed a three-dimensional dynamic elastoplastic finite element model to evaluate the influence of surgical parameters on the bone temperature elevation and assess the risk region of thermal necrosis for different bone qualities as a function of drilling parameters. MethodsTo ascertain the heat generation rate and the high-risk region of thermal necrosis, the effects of bone quality, feed rate, feed force, and drill-bit diameter on the bone temperature elevation were explained using a three-dimensional dynamic elastoplastic finite element model, which was validated through experimental measurements. ResultsThe bone temperature was affected by the drilling parameters; the maximum temperature was attained at the junction of cancellous and cortical bones. The bone temperature increased with cortical bone thickness, bone density, and drill-bit diameter, and it decreased with the drilling speed and feed force. ConclusionsThe present model could assess the risk region of thermal necrosis by accurately analyzing the bone temperature elevation for various bone qualities, feed forces, and feed rates. The bone temperature increased with the bone mineral density and cortical bone thickness. The highest bone temperature and maximum necrosis region were found near the junction of cortical and cancellous bones. Increasing the drilling speed or feed force can minimize the bone temperature elevation and the risk range of thermal necrosis.

Mechanical response of a lined pipe under dynamic impact

Abstract An experimental and numerical investigation on the mechanical response of a lined pipe (compound pipe) under a dynamic impact is presented. The influence of the impact energy has been studied in terms of the depth of the dent formed, and of the strains and residual stresses. To this end, a three-dimensional explicit dynamic non-linear finite element model has been developed and successfully validated against the results of impact-test experiments conducted on pipes made of AISI 10305 steel, with and without the AISI304 stainless steel liner. The validation was made by comparing numerically computed strains with those measured by strain gauges, as well as in terms of permanent deformation. The model is then utilized to evaluate the residual stresses, the amount of energy dissipation and the velocity of impact process as a function of different pipes (i.e. with or without liner) and of the free drop heights.

Design and Simulation Analysis of Lightweight HDPE Milk Bottle

A lightweight design is proposed for a 2800 ml HDPE milk bottle. In designing the bottle, a three-dimensional elastic-plastic dynamic finite element model is first constructed to explore the effect of the bottle thickness on the critical load and stress distribution. The validity of the proposed model is confirmed by comparing the numerical results for the load-displacement response of the bottle with the experimental results. A parametric analysis is then performed to examine the effects of the body thickness and bottom thickness on the critical load and weight of the HDPE bottle. The results show that the critical load increases with an increasing body thickness, but is insensitive to the bottom thickness. Finally, a lightweight design is proposed in which the structural shape of the original bottle is retained, but the thickness is varied in different regions of the body in order to reduce the weight. It is shown that the redesigned bottle achieves the same maximum top-load 315 N, but reduces the weight by 21.4% compared to the reference design obtained in the parametric analysis.

Investigation of three-dimensional moisture diffusion modeling and mechanical degradation of carbon/bismaleimide composites under seawater conditioning

The effect of moisture diffusion on the mechanical properties of carbon/bismaleimide composites exposed to seawater conditioning at elevated temperatures was investigated in this study. Carbon/bismaleimide composites with two stacking sequences (unidirectional and cross-ply) were fabricated using out-of-autoclave process. Testing coupons were immersed in the seawater at two elevated temperatures (50℃ and 90℃) for approximately 3 months. Moisture diffusivities and solubility for each type of carbon/bismaleimide specimen were characterized using the experimental data. A three-dimensional dynamic finite element model was developed using these parameters to predict the moisture diffusion behavior in the carbon/bismaleimide laminates. The degradation of mechanical properties due to hygrothermal aging was assessed by short-beam shear and three-point bending tests. It was found that flexural strength and interlaminar shear strength reductions are higher at 90℃ aging than that at 50℃ aging. The reduction in mechanical properties for bismaleimide laminates can be attributed to the fiber/matrix interfacial cracks observed by scanning electron microscopy.