Dynamic Stress Analysis Research Articles

Development of a biomechanical model for dynamic occlusal stress analysis

The use of traditional finite element method (FEM) in occlusal stress analysis is limited due to the complexity of musculature simulation. The present purpose was to develop a displacement boundary condition (DBC)-FEM, which evaded the muscle factor, to predict the dynamic occlusal stress. The geometry of the DBC-FEM was developed based on the scanned plastic casts obtained from a volunteer. The electrognathographic and video recorded jaw positional messages were adopted to analyze the dynamic occlusal stress. The volunteer exhibited asymmetrical lateral movements, so that the occlusal stress was further analyzed by using the parameters obtained from the right-side eccentric movement, which was 6.9 mm long, in the stress task of the left-side eccentric movement, which was 4.1 mm long. Further, virtual occlusion modification was performed by using the carving tool software aiming to improve the occlusal morphology at the loading sites. T-Scan Occlusal System was used as a control of the in vivo detection for the location and strength of the occlusal contacts. Data obtained from the calculation using the present developed DBC-FEM indicated that the stress distribution on the dental surface changed dynamically with the occlusal contacts. Consistent with the T-Scan recordings, the right-side molars always showed contacts and higher levels of stress. Replacing the left-side eccentric movement trace by the right-side one enhanced the simulated stress on the right-side molars while modification of the right-side molars reduced the simulated stress. The present DBC-FEM offers a creative approach for pragmatic occlusion stress prediction.

Understanding and treatment of brake pipe fracture of metro vehicle bogie

In a railway vehicle air brake system, a brake pipe is used to connect all related elements, for example, the air source system, brake control device, and brake valve. The brake pipe has a significant impact on the safety and reliability of trains. This paper presents a fracture analysis of a brake pipe installed on the bogie of a metro train running on one metro line in China. The analysis was conducted using a brake pipe modal test in a depot, a bogie vibration test, and a brake pipe dynamic stress measurement applied at the field site. The field experiment results indicate that the main cause of a brake pipe fracture is the coupling resonance between the first-order lateral bending eigenmode of the brake pipe (74 Hz) and the eigenmode of the reverse yawing of two side beams of the bogie frame (73 Hz). The wheel out-of-roundness is the main excitation source. To solve the pipe fracture problem, a dynamic stress analysis method that considers the frequency and time domains is presented to assess the possible measures. The measures investigated in this study are the pipe wall thickness, pipe clamp stiffness (elastic modulus), and pipe clamp numbers. The simulation results and on-track tests show that doubling the pipe wall thickness and decreasing the elastic modulus of the pipe clamp by 5.67 fold can reduce the dynamic stress amplitude of the pipe by approximately 60%. If a pipe clamp is added at the middle position between the two pipe clamps on the pipe, the dynamic stress amplitude of the pipe will decrease by 94% compared to the present pipe structure. This is because the additional pipe clamp alters the frequency of the first-order lateral bending eigenmode of the brake pipe to avoid being equal to the eigenfrequency of the reverse yawing of the two side beams of the bogie frame. After the metro corporation added a pipe clamp and applied a regular wheel re-profiling, no brake pipe fracture occurred on the investigated metro line.

Wetting mechanism and interfacial bonding performance of bamboo fiber reinforced epoxy resin composites

A polyacrylate-based wetting agent, BYK-358N, was used to improve the interfacial bonding between the bamboo fibers and epoxy matrix. Fourier transform infrared spectrometer and differential scanning calorimetry were used to study the curing process of epoxy resin. The wettability of the treated bamboo fiber, which by the untreated and wetting agent treated epoxy, was studied using the surface tension of epoxy and bamboo fiber. The analysis of dynamic contact angle and interfacial shear stress confirmed that the composite interface was improved. Finally, Vacuum-assisted resin transfer molding was used to prepare bamboo fiber reinforced epoxy resin (BF/EP) composites, and the tensile properties were measured. The results showed that the addition of the wetting agent could effectively improve the interface compatibility of BF/EP composites. The interfacial shear stress of BF/EP composites treated with 1% wetting agent was 24.36 MPa, tensile strength was 111.54 MPa, and Young's modulus was 3.90 GPa, which was 165.7%, 99.7%, and 66.7% higher than that of untreated BF/EP composites.

Analysis of Subgrade Vibration and Dynamic Stress of Heavy Haul Railway with High Embankment based on ZL-TNTLM Program

Aiming at the high embankment section of heavy-load Railway, a finite element model of dynamic response of subgrade structure under train load is established, and ZL-TNTLM program is used to apply load excitation. The results show that the dynamic stress on the top of the roadbed is a single peak curve under heavy train load, and the peak value of the vertical acceleration vibration changes obviously under heavy train load, and presents a periodic change With the increase of the train speed, the dynamic pressure stress of the track bed and the foundation bed does not increase obviously with the increase of the train speed, but fluctuates and changes slowly; the dynamic stress and the vertical acceleration in the roadbed attenuate non-linearly along the depth direction The attenuation of acceleration is greater than dynamic stress along the direction of subgrade depth. The results are of theoretical and engineering significance for revealing the dynamic stress and vertical acceleration mechanism of heavy-haul railway subgrade under the change of high-speed train speed.

Accurate and efficient analysis of dynamic runner stresses considering hydrodynamic damping effects

Safe and reliable dynamic designs of Francis and pump turbine runners require an accurate and efficient prediction of the dynamic response during operation including dynamic stresses. If resonance phenomena cause significant dynamic amplifications, response amplitudes strongly depend on damping effects, and numerical simulations have to include realistic damping behavior. For submerged components like turbine runners, hydrodynamic (flow-induced) damping and hydro-acoustic radiation are much greater than structural or material damping, but cannot be assessed sufficiently accurate by simple assumptions. Therefore, a newly developed fluid-structure interaction (FSI) methodology is presented which offers accurate and efficient harmonic response analyses of submerged structures not only accounting for added-mass effects but also for flow-induced damping and acoustic radiation. The acoustic FSI approach, widely used to consider added-mass effects, is enhanced by convective terms to include fluid forces caused by the deflection of the mean flow due to structural motion. Only a stationary flow solution, obtained from standard computational fluid dynamics analyses, is required as additional input. The linearized second-order system with non-proportional damping matrix is solved in frequency domain using a Krylov subspace based model order reduction technique. The methodology is validated using experimental damping data from an elastic hydrofoil in a cavitation tunnel. A first application to a prototype Francis runner, being excited close to resonance by rotor-stator interaction, reveals a significant influence of the operating condition on hydrodynamic damping and dynamic stresses. The numerical results for both part load and full load agree very well with measured prototype strains. Meanwhile, the automated methodology is applied as a standard tool within the hydro-mechanical runner design process ensuring dynamically safe and reliable runner designs.

Analysis of Dynamic Stresses of Pump-Turbine Runner during Load Rejection Process in Turbine Mode

During load rejection process, the rotation rate, head and discharge change a lot and the internal flow of the runner is complex, leading to fatigue cyclic loads on the runner. In some cases, fatigue cracks appear at the stress concentration location of the runner. This paper studied the dynamic stresses of a pump-turbine runner during load rejection process in turbine mode using finite element method. The hydraulic loads were obtained from CFD analysis, and the clearance flow was taken into consideration in the CFD simulation. The variation of performance characteristics was calculated through the one-dimensional method of characteristic (1D-MOC). The results show that the pressure on outer surfaces of runner changed the stress of the runner, and the rotation rate had a great influence on the dynamic stresses of the runner.

Seismic Response Characteristics of Liquefiable Sites with and without Sediment Ejecta Manifestation

Dynamic nonlinear effective stress analysis of 45 well-documented liquefaction field case histories provides insights on the seismic response of sites where simplified liquefaction triggering procedures indicated liquefaction effects would be severe but either surface manifestations were not observed or inconsistent amounts of sediment ejecta were observed. The occurrence of sediment ejecta and its severity depend significantly on hydraulic processes after strong ground shaking ceases, which the simplified procedures do not consider. Postshaking advection processes govern the amount of upward seepage–induced artesian flow that determines ejecta severity. The ejecta potential index (EPI) captures these key aspects of the hydraulic processes of liquefaction manifestation. EPI can be sensitive to variables such as hydraulic conductivity, groundwater level, and input ground motions. However, it proves to be a useful index that correlates well to the severity of ejecta manifestation observed in the field case histories. Sites with severe ejecta have high EPI values, and sites without ejecta have low EPI values.

Investigation of Structural Stress Monitoring System on Excavator under Impact Loads

Displacement and pressure sensors were used to measure the displacement and pressure variations of the hydraulic cylinders in an excavator under impact loads. Taking the measured cylinder displacement as a driven boundary condition, the kinematics simulation is completed in the LMS Virtual Lab. Taking the measured cylinder thrust and the simulation results of the kinematics as driven boundary conditions, the dynamic simulation of the excavator is carried out. The CAE dynamic stress analysis of the boom and arm of the excavator is performed using ABAQUS inertial release approach under the loads on the sub-structure obtained from the above multi-body dynamic simulation and the measured data, it provides a reference for the material selection of each part of excavator boom. The good agreement between the analytical and testing results demonstrates that the present method is accurate, efficient, cost effective, and able to monitor the stress status and access the health of an excavator instead of using field testing techniques.

Assessing the seismic effect of quarry blasting at surface mineral workings on the state of underground mines using PRESS 3D URAL software

Relevance. The development of numerical and analytical methods of assessing ore in place dynamic overload from quarry blasting impact is due to the need to improve the reliability of underground mines stability analysis. Research aim is to assess the effect of blasting at surface mineral workings on underground mines stability and safety. Research methodology includes the numerical and analytical analysis of dynamic stress within ore in place containing underground mines based on the boundary integral equations method in spatial formulation. Research results. Under conditions of dynamic impact made by quarry blasting, the stability of underground mines may be preserved by means of strengthening the support through bolting with reinforced concrete roof bolts. Summary. The proposed method makes it possible to adjust the value of underground mines factor of safety with the account of the dynamic impact made by quarry blasts.

Dynamic Stress Analysis of Exposed Pipes Subjected to a Moving In-Line Inspection Tool

AbstractIn-line inspection (ILI) is a non-destructive assessment method commonly used for defect assessment and for pipeline monitoring. Passing an ILI tool through an excavated or exposed section of a pipe during an integrity assessment can excite vibrations. The ILI tool’s weight and speed can exert substantial forces, stresses, and deflections on the pipe section. When the excitation frequency from the ILI tool’s movement is close to the pipe’s natural frequency, the dynamic stress generated within the pipe can become great enough that it creates integrity concerns on the pipeline. This research aims to study the effects of an ILI tool’s passage through exposed and partially supported pipes under a variety of boundary and loading conditions. A finite element model of an exposed pipe section is developed based on the Timoshenko beam theory to predict the pipe’s displacement, strain, stress, and frequency responses under a wide range of excitation frequencies. The model is further validated using a lab-scale experimental setup with a mass that moves at different speeds. A comparison between the simulation and the experimental results shows that the proposed model can effectively predict the pipe’s dynamics.

Analysis of Dynamic Stresses during Acceleration and Deceleration of a Conveyor Belt (Maxwell Element Model)

Analysis of Dynamic Stresses during Acceleration and Deceleration of a Conveyor Belt (Maxwell Element Model)

Dynamic Stress Analysis and Structural Optimization of Braking Pipeline of Metro Vehicle

Dynamic Stress Analysis and Structural Optimization of Braking Pipeline of Metro Vehicle

Analysis of Rock Dynamic Stresses During the Drilling by Polycrystalline Diamond Compact Bits

In view of shortening the development period of polycrystalline diamond compact (PDC) bits, the finite element method was adopted to simulate the dynamic stress of rocks. By employing drilling related theories, the three dynamic principal stresses of rock were analysed and the dynamic rock-breaking criterion was established. Second, the drilling model of PDC core bit was constructed, and the stress was simulated and calculated. Finally, laboratory tests were carried out to verify the simulation results. The analytical results demonstrate that the two obvious stages in the rock-breaking process are the initial rock-breaking stage and the normal one. The dynamic rock-breaking stress in the normal drilling stage varies from 66.3 to 99.6 MPa, which is lower than 278.4 MPa in the initial rock-breaking stage. During spud drilling, the axial force and the tangential force are 1.85 and 1.60 kN, respectively. During normal drilling, the axial force ranges from 0.2 to 0.9 kN, and the tangential force from 0.15 to 0.6 kN. The load of normal drilling is lower than the spudding load, and the bit is more likely to be damaged during spudding. The bit is normally worn during normal drilling.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

Fatigue life evaluation of spindle of rolling mill using ADINA structure and WINLIFE

The fatigue life prediction method using numerical analysis is the latest evaluation technology to predict the fatigue life using the stress data obtained from the structural analysis in order to reduce the evaluation time and cost. A rolling mill is a machine that produces a coil by rolling the material by a roller and the spindle of the rolling mill device serves to transmit the power to the rollers by periodically rotating by the motor. These spindles consist of universal joints, shafts and bearings to deliver power to the rollers. The spindle of the rolling mill is always exposed to the environment subjected to the fatigue load due to the rotation moment by the periodic rotation and there is possibility of the breakage accident due to this. It is very important to prevent breakage by predicting the fatigue life of the spindle in a dynamic operating environment. Therefore, in this study, dynamic stress analysis is performed considering the actual rotating environment conditions using ADINA. Based on the results of stress analysis, we want to predict fatigue life considering dynamic operating environment using WINLIFE that is used for the evaluation of the fatigue life of single shafts, multi-shafts, and gear bearings. Fatigue life analysis of the spindle of the rolling mill using linear cumulative damage theory using S-N curve and equivalent stress was performed in order to evaluate the fatigue life. Stress-life fatigue theory is a method of calculating the lifetime by the minimum input showing the fatigue characteristics of the material.

Recycled tire granular for playground in hot regions: technical assessment

Scrap tire granulation used for crumb rubber tiles and poured-in-place rubber surfaces are waste management strategy for the overgrowing tire stockpiling. However, limited technical studies have been done assessing how these surfaces perform during their usage particular in hot climate region. In this work, the serviceability of the rubber tile is assessed on numerous field samples collected from different playgrounds in UAE. They are subjected to structural and thermal analytical techniques, i.e., ball-drop test, static and dynamic stress analyses, frictional coefficient, microscopic analysis (ESM), thermogravimetric and emission. Results show that tiles rather disintegrate relatively fast and attain unsafe user condition. The ball-drop and stress tests detected increase in stiffness and stress over 25% to initiate earlier tile failure. Friction results in drastic reduction in the needed traction. The SEM analysis suggests deterioration of the binding agent, elemental analysis showed an excess sulfur content per the detected SK compound in the aged sample and surface erosion, while TGA revealed higher thermal degradation and potential formation of hazardous polymers. Finally, PAHs study confirm rubber volatilization in the vapor phase and their partial contaminant leaching at toxic concentration. These observations do not favor using rubber granules for surfaces in hot regions and seeking alternative recycling is strongly recommended.

Field Test and Numerical Analysis of Dynamic Stress of High-Speed Railway Tunnel Invert in Mudstone

In order to obtain the dynamic stress of invert and its filling in the high-speed railway tunnel under the vibration load of the train, this paper uses the field measurement method to arrange the resistance strain gauge inside the invert of the Lanzhou–Urumqi high-speed railway Fuchuan tunnel. The dynamic stress of the invert and its filling was measured, and the measurement results were verified by numerical analysis, the results obtained by the two were consistent. The results show that under the action of CRH5 electric multiple units, the dynamic stress time history curve of the invert and its filling has 16 peaks, with V-shape on both sides and W-shape in the middle. When the train load speed is constant, the dynamic stress in the tunnel invert and invert filling decreases with the increase of the depth. The dynamic stress at 0.5 m below the track bed is attenuated by about 23.1% compared to 0.2 m, the dynamic stress at 2.0 m below the track bed is attenuated by 67.5% compared to 0.2 m. Tunnel invert and its filling are the main carriers of train vibration load. The dynamic stress attenuation law of the invert and its filling conforms to the exponential function distribution. Through the data fitting, the calculation formula of the dynamic stress in different depths is given. The research results provide a new method for obtaining the dynamic stress of the invert and its filling in high-speed railway tunnel.

Dynamic stress analysis on nonlinear vibration of a stiffened plate with initial stresses and geometric imperfections considering different resonance conditions

PurposeStiffened plates have been widely used in civil, marine, aerospace engineering. As a kind of thin-walled structure operating in complex environment, stiffened plates mostly undergo a variety of dynamic loads, which may sometimes result in large-amplitude vibration. Additionally, initial stresses and geometric imperfections are widespread in this type of structure. Furthermore, it is universally known that initial stresses and geometric imperfections may affect mechanical behavior of structures severely, particularly in dynamic analysis. Thus, the purpose of this paper is to study the stress variation rule of a stiffened plate during large-amplitude vibration considering initial stresses and geometric imperfections.Design/methodology/approachThe initial stresses are represented in the form of initial bending moments applying to the stiffened plate, while the initial geometric imperfections are considered by means of trigonometric series, and they are assumed existing in the plate along the z-direction exclusively. Then, the dynamic equilibrium equations of the stiffened plate are established using Lagrange’s equation as well as aforementioned conditions. The nonlinear differential equations of motion are simplified as a two-degree-of-freedom system by considering 1:2 and 1:3 internal resonances, respectively, and the multiscale method is applied to solve the equations.FindingsThe influence of initial stresses on the plate, stresses during internal resonance is remarkable, while that is moderate for initial geometric imperfections. (Upon considering the existence of initial stresses or geometric imperfections, the stresses of motivated modes are less than the primary mode for both and internal resonances). The influence of bidirectional initial stresses on the plate’s stresses during internal resonance is more remarkable than that of unidirectional initial stresses. The coupled vibration in 1%3A2 internal resonance is fiercer than that in internal resonance.Originality/valueStiffened plates are widely used in engineering structures. However, as a type of thin-walled structure, stiffened plates vibrate with large amplitude in most cases owning to their complicated operation circumstance. In addition, stiffened plates usually contain initial stresses and geometric imperfections, which may result in the variation of their mechanical behavior, especially dynamical behavior. Based on the above consideration, this paper studies the nonlinear dynamical behavior of stiffened plates with initial stresses and geometrical imperfections under different internal resonances, which is the originality of this work. Furthermore, the research findings can provide references for engineering design and application.

Study on Building Digital-Twin of Face-Milled Hypoid Gear From Measured Tooth Surface Topographical Data

AbstractA highly accurate digital-twin spiral bevel gear or hypoid gear is often required for dynamic analysis or stress analysis for gear transmission. However, a highly accurate digital-twin solid model is not always available because the final hypoid gear is completed by the gear manufacturer. This study constructs a digital-twin from a sample hypoid gear. The tooth surface of sample gear is digitized as topographical grids using a coordinate measuring machine (CMM) or a gear measurement center. The geometric parameters (the surface position vector, the normal vector, the principal curvatures, and the corresponding principal directions) for the measured tooth surface (MTS) are then extracted using numerical differential geometry (NDG). The machine settings and the cutter parameters for the sample hypoid gear are obtained by minimizing the topographical error between the replicated digital-twin and the sample gear using optimization software. The initial estimation for the machine settings and the cutter parameters is calculated using an explicit form of the modified-roll motion (MRM), which decreases numerical divergence and time that is required for calculation. The machine settings, the cutting tool parameters, and the auxiliary flank modification (AFM) motion are used as the design variables. A numerical example is presented to verify the proposed methodology. The numerical results show that the replicated digital-twin that is developed using the proposed method is sufficiently accurate for industrial applications.

A liquefaction potential integral index based on pore pressure build-up

The increased attention paid to the effects of liquefaction on the built environment has led over time to the introduction of vulnerability integral parameters that somehow quantify for a given site and a given seismic shaking the severity of the potential liquefaction damage induced at ground level. If the vulnerability parameter is properly calibrated and effective, it should somehow correlate to the observed damage datasets, increasing as the severity of liquefaction effects increase.In some cases, as for instance for the Canterbury earthquakes (New Zealand, 2010–2011) and for the 2012 Emilia Romagna seismic sequence, the existing vulnerability parameters for the assessment of liquefaction potential were not able to capture the observed damages induced by liquefaction, highlighting that further progress remains to be made in the current state-of-practice. The potentiality of a new index (Induced dAmage paraMeter- IAM), strictly related to the free-field post-volumetric consolidation settlement and therefore based on the estimate of liquefaction induced excess pore pressure, has been verified for a reference site located in the area struck by the 2012 Emilia seismic sequence by means of simplified and 1D effective stress dynamic analyses. The results were compared with those obtained by using one of the most convincing parameters existing in literature (Liquefaction Severity Number, LSN), showing the robustness of IAM, as well as the possibility to calculate it at different levels of complexity (via either coupled, simplified or super simplified and conservative analyses). The outcomes of the analyses allowed to define a simplified procedure for defining liquefaction microzonation maps, then representing a step forward towards the definition of a sound but easy-to-implement procedure to assess the resilience to liquefaction of urban centres.