Life Prediction Based on Transient Dynamics Analysis of Van Semi-trailer with Air Suspension System

The early fatigue damage in the van-body of the semi-trailer is often caused by the unique mechanical characteristics and the dynamic impact of the loads.The traditional finite element method with static strength analysis cannot support the fatigue design of van-body;thus,the dynamics analysis should be adopted for the endurance performance.The accurate dynamics model to describe the transient impacts of all kinds of uneven road and the proper system transfer functions to calculate the load transfer effects from tire to van-body are two critical factors for transient dynamics analysis.In order to evaluate the dynamic performance,the dynamics model of the trailer with the air suspension is brought forward.Then the analysis method of the power spectral density （PSD） is set up to study the transient responses of the road dynamic impacts.The transient responses transferred from axles to van-body are calculated,such as dynamic stress,dynamic RMS acceleration,and dynamic load factors.Based on the above dynamic responses,the fatigue life of van-body is predicted with the finite element analysis （FEA） method.Applying the test parameters of the trailer with air suspension,the simulation system with Matlab/Simulink is constructed to describe the dynamic responses of the impacts of the tested PSD of the vehicle axles,and then the fatigue life is predicted with FEA method.The simulated results show that the vibration level of the van-body with air suspension is reduced and the fatigue life is improved.The real vehicle tests on different roads are carried out,and the test results validate the accuracy of the simulation system.The proposed fatigue life prediction method is effective for the virtual design of auto-body.

Complex transient dynamics of hidden attractors in a simple 4D system

A simple four-dimensional system with only one control parameter is proposed in this paper. The novel system has a line or no equilibrium for the global control parameter and exhibits complex transient transition behaviors of hyperchaotic attractors, periodic orbits, and unstable sinks. Especially, for the nonzero-valued control parameter, there exists no equilibrium in the proposed system, leading to the formation of various hidden attractors with complex transient dynamics. The research results indicate that the dynamics of the system shows weak chaotic robustness and depends greatly on the initial states.

Stability and dispersion analysis of reproducing kernel collocation method for transient dynamics

A reproducing kernel collocation method based on strong formulation is introduced for transient dynamics. To study the stability property of this method, an algorithm based on the von Neumann hypothesis is proposed to predict the critical time step. A numerical test is conducted to validate the algorithm. The numerical critical time step and the predicted critical time step are in good agreement. The results are compared with those obtained based on the radial basis collocation method, and they axe in good agreement. Several important conclusions for choosing a proper support size of the reproducing kernel shape function are given to improve the stability condition.

Research of transient rotor dynamic characteristic of magnetic liquid double suspension bearing in double collision state

During the operation of magnetic liquid double suspension bearing(MLDSB),due to rotor resonance,assembly error and other factor,the vibration amplitude of the rotor in resonance state exceeds the original design clearance,resulting in the collision damage between the rotor and the stator,the rotor and the casing.This paper presents a method to simulate the influence of different factors on the dynamic characteristics of 5 degrees of freedom(DOF)rotor based on the dynamic model of MLDSB.Firstly,according to the second Lagrange equation,the dynamic equation of 5 DOF rotor is derived,and the mathematical model is established.Then,based on 5 DOF rotor dynamic equation,the rotor transient dynamic equation under collision state is obtained,and the rotor transient collision dynamic simulation model is established.Finally,the key influencing factors of rotor dynamic characteristics are extracted,and the influence mapping relationship of rotor displacement,axis locus and stress distribution under different factors is simulated by using ANSYS Workbench software.The experimental results show that this method can effectively reflect the influence of various factors on the dynamic characteristics of the rotor.This method can provide theoretical reference for the design and control of MLDSB.

Transient Dynamics of Fluoride-Based High Concentration Erbium/Cerium Co-Doped Fiber Amplifier

We designed and evaluated a fluoride-based high concentration erbium/ cerium co-doped fiber amplifier. It is suitable for Metropolitan Area Networks due to faster transient, flatter (unfiltered) gain, smaller footprint and gain excursion than its silica-based counterpart.

Dynamic Response of Foundations during Startup of High-Frequency Tunnel Equipment

The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional,and complex orientations.The vibration caused by the high-frequency units during regular operation is supported by the foundation of the units,and the magnitude of vibration and the operating frequency fluctuate in different engineering contexts,leading to variations in the dynamic response of the foundation.The high-frequency units yield significantly diverse outcomes under different startup conditions and times,resulting in failure to meet operational requirements,influencing the normal function of the tunnel,and causing harm to the foundation structure,personnel,and property in severe cases.This article formulates a finite element numerical computation model for solid elements using three-dimensional elastic body theory and integrates field measurements to substantiate and ascertain the crucial parameter configurations of the finite element model.By proposing a comprehensive startup timing function for high-frequency dynamic machines under different startup conditions,simulating the frequency andmagnitude variations during the startup process,and suggesting functions for changes in frequency and magnitude,a simulated startup schedule function for high-frequency machines is created through coupling.Taking into account the selection of the transient dynamic analysis step length,the dynamic response results for the lower dynamic foundation during its fundamental frequency crossing process are obtained.The validation checks if the structural magnitude surpasses the safety threshold during the critical phase of unit startup traversing the structural resonance region.The design recommendations for high-frequency units’dynamic foundations are provided,taking into account the startup process of the machine and ensuring the safe operation of the tunnel.

Extreme parameter sensitivity of transient persistence in spatially coupled ecological systems

This paper investigates persistence of transient dynamics depending on parameters in spatially coupled ecological systems. We emphasis that the persistence time can be obtained by populations of species or Lyapunov exponents of transient dynamics. It is found that extreme sensitive dependence of persistence on parameters occurs commonly in ecological models. A non-zero uncertainty exponent is used to characterize the high sensitivity in a reasonable parameter region. The result of a small uncertainty exponent indicates a fractal structure of transient persistence in the two-dimensional parameter space. In spite of different methods of measurement, the fractal dimensions have a good consistency. Since populations of natural communities with many coupled oscillators are often affected by disturbance of migration rates, the large probability of error in estimating persistence of transients should be concerned.

Tunnel effect of fractal fault and transient S-wave velocity rupture (TSVR) of in-plane shear fault

Transient S wave velocity rupture (TSVR) means the velocity of fault rupture propagation is between S wave velocity α and P wave velocity β . Its existing in the rupture of in plane ( i.e . strike slip) fault has been proved, but in 2 dimensional classical model, there are two difficulties in transient S wave velocity rupture, i.e ., initialization difficulty and divergence difficulty in interpreting the realization of TSVR. The initialization difficulty means, when v ↑ v R (Rayleigh wave velocity), the dynamic stress strength factor K 2(t) →+0, and changes from positive into negative in the interval ( v R, β ). How v transit the forbidden of ( v R, β )? The divergence difficulty means K 2(t) →+∞ when v ↓ β . Here we introduce the concept of fractal and tunnel effect that exist everywhere in fault. The structure of all the faults is fractal with multiple cracks. The velocity of fault rupture is differentiate of the length of the fault respect to time, so the rupture velocity is also fractal. The tunnel effect means the dynamic rupture crosses over the interval of the cracks, and the coalescence of the intervals is slower than the propagation of disturbance. Suppose the area of earthquake nucleation is critical or sub critical propagation everywhere, the arriving of disturbance triggers or accelerates the propagation of cracks tip at once, and the observation system cannot distinguish the front of disturbance and the tip of fracture. Then the speed of disturbance may be identified as fracture velocity, and the phenomenon of TSVR appears, which is an apparent velocity. The real reason of apparent velocity is that the mathematics model of shear rupture is simplified of complex process originally. The dual character of rupture velocity means that the apparent velocity of fault and the real velocity of micro crack extending, which are different in physics, but are unified in rupture criterion. Introducing the above mentioned concept to the calculation of K 2 (t) , the difficulty of initialization can be overcome, and the integral equation of triggering the initialization of TSVR is given quantitatively. By solving this integral equation, the lower limit of TSVR is 1.105 3 β , not β , and the divergence difficulty is overcome. TSVR is unstable solution, and may degenerate to sub Rayleigh wave velocity rupture immediately where the non critical condition can be measured. The results of this paper show that the initialization and continuum depends on the condition of earthquake nucleation in seismogenic area.

Low Velocity Impact Response on GFRP and GF-SMP Panels in Structural and High Frequency Bands

A low velocity impact response study has been carried out on glass fibre composite laminates, made up of regular aircraft grade epoxy (GFRP) and shape memory polymer (GF-SMP). Under various impact loading intensities (4J, 6J, 12J), the responses are measured by a network of PZT (Lead Zirconate Titanate) sensors. A signal analysis methodology is subsequently developed to process the very high frequency (60 MHz) sampled data. In two frequency bands, namely 0 - 2000 Hz and 0 - 100 KHz, the results are examined and the transient dynamic behaviours of the composite laminates are evaluated. It is observed that both the laminates have generated the high frequency structural waves (0 - 100 KHz), which can be exploited to examine the BVID. However, GF-SMP laminate has shown some advantage in terms of energy dissipation in the structural frequency band (<2000 Hz). Further, the GF-SMP laminate has demonstrated its capability to generate very high frequency structural waves, which could carry the damage information like BVID due to impact event to nearby sensors for impact event monitoring and health assessment.

Effects of Unbalance Location on Dynamic Characteristics of High-speed Gasoline Engine Turbocharger with Floating Ring Bearings

For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings（FRBs）, the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.

Effects of Floating Ring Bearing Manufacturing Tolerance Clearances on the Dynamic Characteristics for Turbocharger

The inner and outer oil film dynamic characteristic coefficients of floating ring bearings（FRBs） change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger＇s vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.

Assessment of ship manoeuvrability by using a coupling between a nonlinear transient manoeuvring model and mathematical programming techniques

In this paper, a numerical method based on a coupling between a mathematical model of nonlinear transient ship manoeuvring motion in the horizontal plane and Mathematical Programming （MP） techniques is proposed. The aim of the proposed procedure is an efficient estimation of optimal ship hydrodynamic parameters in a dynamic model at the early design stage. The proposed procedure has been validated through turning circle and zigzag manoeuvres based on experimental data of sea trials of the 190 000- dwt oil tanker. Comparisons between experimental and computed data show a good agreement of overall tendency in manoeuvring traiectories.

Investigation on Transient Dynamic Behaviors of Low-Tension Undersea Cables

This paper presents a numerical analysis of the dynamic transient behaviors of undersea cables.In this numerical study,the governing equations based on Euler-Bernoulli beam theory are adopted,and they can satisfy many applications no matter what the magnitude of the cable tension is.The nonlinear coupled equations are solved by a popular central finite difference method,and the numerical results of transient behaviors are presented when several kinds of surrounding conditions,such as different towing speeds of surface vessel,different currents and waves with various frequencies and amplitudes,are exerted.Then a detailed comparison of the results,including the upper end tension and cable shape in time-domain,is made under the above external excitations,and finally the possible reasons for these are further explained.

Numerical approach to the modelling of transient interaction of prospective combustor concepts and conventional high pressure turbines

The Institute of Gas Turbines and Aerospace Propulsion at Technische Universitait Damstaxlt conducts research projects in the field of“combustor turbine interaction”(CTI).This paper presents numerical studies on the interaction between novel combustion concepts and conventional“high pressure turbine”(HPT)stages.In order to obtain higher efficiency and reduce emissions of jet engines,it is necessary to apply innovative and revolutionary technologies.The most promising technical solutions are based on the cycle processes,employing“pressure gain combustion”(PGC)methods PGC methods provide a significant thermal efficiency enhancement and low NO_(x)-emission rates at the same time.The investigations presented in this paper give information on the integrability of revolutionary combustion concepts into conventional engine architecture.This paper aims at providing insight into the numerical modelling of the transient behaviour of prospective combustion outflow and its influence on the operation of HPTs,especially on the first stage.The focus is on the aerodynamic effects and loss mechanisms within the blade passage.The interaction between the two components plays an important role.To study the performance under new conditions,an engine-like HPT geometry is used.This study reveals a decrease in turbine efficiency with transient inflow conditions compared to a steady-state inflow case.The decrease is primarily due to the interation between transient inflow and the loss mechanisms in the turbine.The presented research was done as part of the project“Technologien fir REVolutionire Arbeits Prozesse”(TREVAP)

Airborne transmission during short-term events: Direct route over indirect route

Numerous short-term exposure events in public spaces were reported during the COVID-19 pandemic,especially during the spread of Delta and Omicron.However,the currently used exposure risk assessment models and mitigation measures are mostly based on the assumption of steady-state and complete-mixing conditions.The present study investigates the dynamics of airborne transmission in short-term events when a steady state is not reached before the end of the events.Large-eddy simulation(LES)is performed to predict the airborne transmission in short-term events,and three representative physical distances between two occupants are examined.Both time-averaged and phase-averaged exposure indices are used to evaluate the exposure risk.The results present that the exposure index in the short-term events constantly varies over time,especially within the first 1/ACH(air changes per hour)hour of exposure between occupants in close proximity,posing high uncertainty to the spatial and temporal evolutions of the risk of cross-infection.The decoupling analysis of the direct and indirect airborne transmission routes indicates that the direct airborne transmission is the predominated route in short-term events.It suggests also that the general dilution ventilation has a relatively limited efficiency in mitigating the risk of direct airborne transmission,but determines largely the occurrence time of the indirect one.Given the randomness,discreteness,localization,and high-risk characteristics of direct airborne transmission,a localized method that has a direct interference on the respiratory flows would be better than dilution ventilation for short-term events,in terms of both efficiency and cost.