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 anal...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.展开更多
The turbulence structure in the stirred tank with a deep hollow blade(semi-ellispe) disc turbine(HEDT) was investigated by using time-resolved particle image velocimetry(TRPIV) and traditional PIV.In the stirred tank,...The turbulence structure in the stirred tank with a deep hollow blade(semi-ellispe) disc turbine(HEDT) was investigated by using time-resolved particle image velocimetry(TRPIV) and traditional PIV.In the stirred tank,the turbulence generated by blade passage includes the periodic components and the random turbulent ones.Traditional PIV with angle-resolved measurement and TRPIV with wavelet analysis were both used to obtain the random turbulent kinetic energy as a comparison.The wavelet analysis method was successfully used in this work to separate the random turbulent kinetic energy.The distributions of the periodic kinetic energy and the random turbulent kinetic energy were obtained.In the impeller region,the averaged random turbulent kinetic energy was about 2.6 times of the averaged periodic one.The kinetic energies at different wavelet scales from a6 to d1 were also calculated and compared.TRPIV was used to record the sequence of instantaneous velocity in the impeller stream.The evolution of the impeller stream was observed clearly and the sequence of the vorticity field was also obtained for the identification of vortices.The slope of the energy spectrum was approximately-5/3 in high frequency representing the existence of inertial subrange and some isotropic properties in stirred tank.From the power spectral density(PSD) ,one peak existed evidently,which was located at f0(blade passage frequency) generated by the blade passage.展开更多
The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP(cathode arc ion plating), the surface morphologies and phases were analyzed with FESEM(field emission scanning electron micr...The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP(cathode arc ion plating), the surface morphologies and phases were analyzed with FESEM(field emission scanning electron microscopy), and XRD(X-ray diffraction), respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM(atomic force microscope). The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN+TiAlN, TiN+Si_3N_4+TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength(102-103 nm), the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength(〉103 nm).展开更多
The main research motive is to analysis and to veiny the inherent nonlinear character of MPEG-4 video. The power spectral density estimation of the video trafiic describes its 1/f^β and periodic characteristics.The p...The main research motive is to analysis and to veiny the inherent nonlinear character of MPEG-4 video. The power spectral density estimation of the video trafiic describes its 1/f^β and periodic characteristics.The priraeipal compohems analysis of the reconstructed space dimension shows only several principal components can be the representation of all dimensions. The correlation dimension analysis proves its fractal characteristic. To accurately compute the largest Lyapunov exponent, the video traffic is divided into many parts.So the largest Lyapunov exponent spectrum is separately calculated using the small data sets method. The largest Lyapunov exponent spectrum shows there exists abundant nonlinear chaos in MPEG-4 video traffic. The conclusion can be made that MPEG-4 video traffic have complex nonlinear be havior and can be characterized by its power spectral density,principal components, correlation dimension and the largest Lyapunov exponent besides its common statistics.展开更多
This paper is the second step of our work. The first step presents a set of parametric studies performed on automotive radiators by designing different heat exchanger models. The analysis focuses on the cooling perfor...This paper is the second step of our work. The first step presents a set of parametric studies performed on automotive radiators by designing different heat exchanger models. The analysis focuses on the cooling performance for automobile radiator by changing several dimensions of the radiator fin phase (P2.5, P2.4, P2.3, P2.2, and P2.1) as well as the importance of coolant flow lay-out on the radiator global performance [1]. The second step consists on the study of the vibration fatigue of the sample with the best heat dissipation performance we design (radiator P2.1). We use Hyper Mesh to proceed with the finite element model. Frequency response analysis is solved by using MSC. Nastran (MSC. MD. Nastran. v2010.1.3-MAGNiTUDE), fatigue durability ana-lysis by using MSC Fatigue. In this experiment, the frequency response of the unit load (the unit load is 1 g) is analyzed. Based on the analysis of the frequency response of the unit load, the fatigue life of the radiator is analyzed by the PSD (power spectral density) curve and the S-N curve. From our experiments results, we observe that the radiator we design meets the international requirements of fatigue vibration under automobile normal working condition.展开更多
This paper presents a new idea for an a lyzing the complicated shock signal.Based on this kind of analysis,an equivale nt power spectral density(PSD) chart is drawn for vibration environmental test,which is carried to...This paper presents a new idea for an a lyzing the complicated shock signal.Based on this kind of analysis,an equivale nt power spectral density(PSD) chart is drawn for vibration environmental test,which is carried to test the vehicle loading instrument's vibration behavior.T he environment test is equivalent to the condition under which the vehicle and t he instrument is experiencing a firing period.Exactly speaking,the short time vibration during the firing period is a complicated shock event.The paper point s out the deficiency of the commonly used half sine equivalence for the shock an d vibration environment test and gives the procedure of how to draw the PSD char t through the actual acceleration data.展开更多
In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncer...In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncertainties. This model employs upper and lower bounds instead of precise probability distributions to quantify uncertainty in a parameter at any given time point. It is anticipated to complement the conventional stochastic process model in the coming years owing to its relatively low dependence on experimental samples and ease of understanding for engineers. Building on our previous work, this paper proposes a spectrum analysis method to describe the frequency domain characteristics of an interval process, further strengthening the theoretical foundation of the interval process model and enhancing its applicability for complex engineering problems. In this approach, we first define the zero midpoint function interval process and its auto/cross-power spectral density(PSD) functions. We also deduce the relationship between the auto-PSD function and the auto-covariance function of the stationary zero midpoint function interval process. Next, the auto/cross-PSD function matrices of a general interval process are defined, followed by the introduction of the concepts of PSD function matrix and cross-PSD function matrix for interval process vectors. The spectrum analysis method is then applied to random vibration problems, leading to the creation of a spectrum-analysis-based interval vibration analysis method that determines the PSD function for the system displacement response under stationary interval process excitations. Finally, the effectiveness of the formulated spectrum-analysis-based interval vibration analysis approach is verified through two numerical examples.展开更多
With the continuous incorporation of renewable energy and new loads into the electric power grid,random factors that induce general forced oscillations(GFOs)gradually become risks that affect the power system's se...With the continuous incorporation of renewable energy and new loads into the electric power grid,random factors that induce general forced oscillations(GFOs)gradually become risks that affect the power system's security and stability.T his research conducts a comparative analysis of the generation mechanisms of GFOs versus the traditional special forced oscillations(SFOs),specifically,from the perspective of frequency domain.Similarities and differences in en-oscillating conditions,occurrence probabilities,and the influencing factors of GFO and SFO are compared to better understand and recognize the GFO theory and the response characteristics of the power system under random excitations.A series of simulations in the lO-generator,39-bus New England Test System is carried out to verify the analysis.展开更多
为了研究响应谱估计误差及其传递对振动响应功率谱密度传递比(Power Spectrum Density Transmissibility,PSDT)估计的影响,基于摄动理论和统计矩定义,推导了两个变量比例函数的均值和方差近似表达式;将响应谱估计统计矩代入,可以推导出...为了研究响应谱估计误差及其传递对振动响应功率谱密度传递比(Power Spectrum Density Transmissibility,PSDT)估计的影响,基于摄动理论和统计矩定义,推导了两个变量比例函数的均值和方差近似表达式;将响应谱估计统计矩代入,可以推导出由响应相干函数、谱估计中信号平均分段数,近似表征的PSDT估计幅值的均值和方差解析公式.基于此,揭示了共振频率处PSDT估计幅值误差规律,并实现了模态振型幅值的精度度量.研究发现,共振频率处PSDT幅值方差存在极小值,且变异系数小于相关响应谱.通过数值框架数据验证了文中误差公式的准确性.此外,还研究了参考响应的选择、响应时长、窗函数类型对PSDT和模态振型估计的影响.结果表明,以PSDT两组响应作为参考响应,能得到较好PSDT和模态分析结果;同时模态振型估计标准差随测试数据时长的增加,也随之降低至一定水平.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50905092)
文摘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.
基金Supported by the National Natural Science Foundation of China(20776008 20821004 20990224) the National Basic Research Program of China(2007CB714300)
文摘The turbulence structure in the stirred tank with a deep hollow blade(semi-ellispe) disc turbine(HEDT) was investigated by using time-resolved particle image velocimetry(TRPIV) and traditional PIV.In the stirred tank,the turbulence generated by blade passage includes the periodic components and the random turbulent ones.Traditional PIV with angle-resolved measurement and TRPIV with wavelet analysis were both used to obtain the random turbulent kinetic energy as a comparison.The wavelet analysis method was successfully used in this work to separate the random turbulent kinetic energy.The distributions of the periodic kinetic energy and the random turbulent kinetic energy were obtained.In the impeller region,the averaged random turbulent kinetic energy was about 2.6 times of the averaged periodic one.The kinetic energies at different wavelet scales from a6 to d1 were also calculated and compared.TRPIV was used to record the sequence of instantaneous velocity in the impeller stream.The evolution of the impeller stream was observed clearly and the sequence of the vorticity field was also obtained for the identification of vortices.The slope of the energy spectrum was approximately-5/3 in high frequency representing the existence of inertial subrange and some isotropic properties in stirred tank.From the power spectral density(PSD) ,one peak existed evidently,which was located at f0(blade passage frequency) generated by the blade passage.
基金Funded by the Jiangsu Province Science and Technology Support Program(Industry)(No.BE2014818)
文摘The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP(cathode arc ion plating), the surface morphologies and phases were analyzed with FESEM(field emission scanning electron microscopy), and XRD(X-ray diffraction), respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM(atomic force microscope). The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN+TiAlN, TiN+Si_3N_4+TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength(102-103 nm), the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength(〉103 nm).
基金Supported by the National Natural Science Founda-tion of China (60132030)
文摘The main research motive is to analysis and to veiny the inherent nonlinear character of MPEG-4 video. The power spectral density estimation of the video trafiic describes its 1/f^β and periodic characteristics.The priraeipal compohems analysis of the reconstructed space dimension shows only several principal components can be the representation of all dimensions. The correlation dimension analysis proves its fractal characteristic. To accurately compute the largest Lyapunov exponent, the video traffic is divided into many parts.So the largest Lyapunov exponent spectrum is separately calculated using the small data sets method. The largest Lyapunov exponent spectrum shows there exists abundant nonlinear chaos in MPEG-4 video traffic. The conclusion can be made that MPEG-4 video traffic have complex nonlinear be havior and can be characterized by its power spectral density,principal components, correlation dimension and the largest Lyapunov exponent besides its common statistics.
文摘This paper is the second step of our work. The first step presents a set of parametric studies performed on automotive radiators by designing different heat exchanger models. The analysis focuses on the cooling performance for automobile radiator by changing several dimensions of the radiator fin phase (P2.5, P2.4, P2.3, P2.2, and P2.1) as well as the importance of coolant flow lay-out on the radiator global performance [1]. The second step consists on the study of the vibration fatigue of the sample with the best heat dissipation performance we design (radiator P2.1). We use Hyper Mesh to proceed with the finite element model. Frequency response analysis is solved by using MSC. Nastran (MSC. MD. Nastran. v2010.1.3-MAGNiTUDE), fatigue durability ana-lysis by using MSC Fatigue. In this experiment, the frequency response of the unit load (the unit load is 1 g) is analyzed. Based on the analysis of the frequency response of the unit load, the fatigue life of the radiator is analyzed by the PSD (power spectral density) curve and the S-N curve. From our experiments results, we observe that the radiator we design meets the international requirements of fatigue vibration under automobile normal working condition.
文摘This paper presents a new idea for an a lyzing the complicated shock signal.Based on this kind of analysis,an equivale nt power spectral density(PSD) chart is drawn for vibration environmental test,which is carried to test the vehicle loading instrument's vibration behavior.T he environment test is equivalent to the condition under which the vehicle and t he instrument is experiencing a firing period.Exactly speaking,the short time vibration during the firing period is a complicated shock event.The paper point s out the deficiency of the commonly used half sine equivalence for the shock an d vibration environment test and gives the procedure of how to draw the PSD char t through the actual acceleration data.
基金supported by the National Natural Science Foundation of China (Grant No. 52105253)the State Key Program of National Science Foundation of China (Grant No.52235005)。
文摘In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncertainties. This model employs upper and lower bounds instead of precise probability distributions to quantify uncertainty in a parameter at any given time point. It is anticipated to complement the conventional stochastic process model in the coming years owing to its relatively low dependence on experimental samples and ease of understanding for engineers. Building on our previous work, this paper proposes a spectrum analysis method to describe the frequency domain characteristics of an interval process, further strengthening the theoretical foundation of the interval process model and enhancing its applicability for complex engineering problems. In this approach, we first define the zero midpoint function interval process and its auto/cross-power spectral density(PSD) functions. We also deduce the relationship between the auto-PSD function and the auto-covariance function of the stationary zero midpoint function interval process. Next, the auto/cross-PSD function matrices of a general interval process are defined, followed by the introduction of the concepts of PSD function matrix and cross-PSD function matrix for interval process vectors. The spectrum analysis method is then applied to random vibration problems, leading to the creation of a spectrum-analysis-based interval vibration analysis method that determines the PSD function for the system displacement response under stationary interval process excitations. Finally, the effectiveness of the formulated spectrum-analysis-based interval vibration analysis approach is verified through two numerical examples.
基金supported by the National Key Basic Research Program of China(973 Program)(2013CB228204)the National Natural Science Foundation of China(51137002,51190102).
文摘With the continuous incorporation of renewable energy and new loads into the electric power grid,random factors that induce general forced oscillations(GFOs)gradually become risks that affect the power system's security and stability.T his research conducts a comparative analysis of the generation mechanisms of GFOs versus the traditional special forced oscillations(SFOs),specifically,from the perspective of frequency domain.Similarities and differences in en-oscillating conditions,occurrence probabilities,and the influencing factors of GFO and SFO are compared to better understand and recognize the GFO theory and the response characteristics of the power system under random excitations.A series of simulations in the lO-generator,39-bus New England Test System is carried out to verify the analysis.
文摘为了研究响应谱估计误差及其传递对振动响应功率谱密度传递比(Power Spectrum Density Transmissibility,PSDT)估计的影响,基于摄动理论和统计矩定义,推导了两个变量比例函数的均值和方差近似表达式;将响应谱估计统计矩代入,可以推导出由响应相干函数、谱估计中信号平均分段数,近似表征的PSDT估计幅值的均值和方差解析公式.基于此,揭示了共振频率处PSDT估计幅值误差规律,并实现了模态振型幅值的精度度量.研究发现,共振频率处PSDT幅值方差存在极小值,且变异系数小于相关响应谱.通过数值框架数据验证了文中误差公式的准确性.此外,还研究了参考响应的选择、响应时长、窗函数类型对PSDT和模态振型估计的影响.结果表明,以PSDT两组响应作为参考响应,能得到较好PSDT和模态分析结果;同时模态振型估计标准差随测试数据时长的增加,也随之降低至一定水平.