Papers by Keyword: Nonlinear

Abstract: By dint of nonlinear mechanics theory and method, and based on rock creep characters, do some analysis to the model of rock mechanics, so we can get conclusions and stability about rock system’s stationary state under the action of uniaxial compress. It has some directed senses to the underground rock project under mining effects.

Abstract: With the application of ANSYS finite element analysis software and environmental data in ChengDao oil field, a nonlinear finite element model of suspended submarine pipeline coupled with sea-floor soil is developed. Discarding the traditional and imprecise pipeline model with double clamped or simply supported ends, the model is founded on the theory of elastic foundation beam, in which the nonlinear effect between pipeline and sea-floor soil is considered. Base on the model we developed, the influences of span length and shear strength of soil at the ends of span on the span’s natural frequency are discussed. And the effects of span length, shear strength of soil and current velocity on the dynamic response of span are also analyzed in this paper. The model we developed in this paper fits the actual structure better, and the analysis is instructive for preventing and controlling the suspending of submarine pipeline.

Abstract: The machine joint surfaces are necessary to form the functions of the complex mechanical system. Because the macro or micro relative motions may appear in the machine joint surfaces, the vibration and friction phenomena will be excited, then the singularities, disturbances and faults of the mechanical system may be appeared when the machine equipments in the running process. These undesired phenomena will have adverse effect on the efficiency, precision, reliability and lifetime of the mechanical equipment. In order to ensure the functions and properties of the mechanical system, more attentions should be paid to mechanism of vibration and friction during the process of designing and manufacturing the modern machine. In this paper, machine joint surfaces are classified by different classification standards: the macro relative motions and micro contact styles between the joint surfaces. The theories and methods for researching vibration and friction mechanism are inducted and summarized and the view of non-linear should be advocated for the future research. The point of precisely quantifying for machine assembly accuracy design while considered the relevancies between the macro and micro-scale of mechanical system indicates that new directions and methods for studying vibration and friction mechanism in machine joint surfaces should be put forward.

Abstract: According to the requirements and characteristics of air compressor control systems in the process of air separation, an intelligent control method based on the fuzzy PID was proposed. Through simulating the designed control method, it is concluded that the control effect was extraordinarily satisfactory. It can offer a certain meaning of guidance and reference for the control of other equipment in air separation systems.

Abstract: The output of Terfenol-D is nonlinear and hysteretic under the effect of magnetic field and prestress. The nonlinear constitutive relation between magnetostriction and magnetization with magneto-stress coupling was built in consideration of the magnetostriction saturation and the prestress correlation. Then, the hysteresis behavior of Terfenol-D was modeled based on the Jiles-Atherton model. The error of magnetostriction between simulations and experimental data is less than 6%. This result indicates that the model can adequately predict the nonlinear hysteresis and magneto-stress coupling character of Terfenol-D.

Abstract: A coupled constitutive model of viscoplasticity and ductile damage for penetration problems has been deduced. The model proposed by Lemaitre was based on the continuum damage mechanics. In the model, large strain, high strain-rate, thermal softening and damage evolution were taken into account. At the meanwhile, Von Mises yield criterion, Johnson-Cook hardening model and Johnson-Cook fracture strain model were adopted. The model was implemented in the explicit finite element code Abaqus\Explicit through the Vumat subroutine by using an efficient explicit time integration algorithm. Based on the model, the rotating band’s engraving process was simulated, at the same time the influence of the stress state on damage evolution and the thermal softening effect was discussed. An effective way to simulate the fire process of gun was afforded.

Abstract: A nonlinear method was applied in the stability study of landslides due to the highly nonlinear feature of landslides stability. Based on the data collected as research samples, we selected six influence factors as the indicators of slope stability, including the average slope, slope of the invading front, sliding surface slope, the maximum annual average daily rainfall, the recent slide situation and human engineering activities. Through the comprehensive analysis of landslides stability with BP neural network method, we established a novel nonlinear analysis model. And from the work we may conclude that the landslide stability analysis model is of profound technical meaning with accuracy over 95%.

Abstract: The nonlinear constitutive relations of clay are investigated with different initial stress conditions. Two series of triaxial compression tests are performed, respectively after consolidation and isotropic consolidation. On the basis of the framework of ~ model, a uniform nonlinear constitutive model is proposed by fitting of the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison of the experimental stress-strain curves with the predicted results by the constitutive model is made. It is shown that the model prediction is reasonable, which can reflect the stress-strain behavior of the soil under the consolidation and isotropic consolidation conditions.

Abstract: Based on researches in material properties of reinforced concrete under high temperature, and combined with the whole process of fire, the fire-resistance test curve of building components suggested by ISO834 instead of the actual heating-up process. nonlinear transient temperature field simulates and analyses under fire of concrete frame columns based on Abaqus in this study. And temperature field distribution laws of column section are obtained. Conclusions of the paper are helpful to further understand of the mechanical properties of frame column under high temperature, and provide theoretical support for safety evaluation and reinforcement techniques of the structure after fire.

Abstract: In this paper, semi active control of non-ideal mechanical system with Magneto-Rheological (MR) damper is presented. The setup composed of a motor operating on a structure with mass M connected to a fixed frame by a non-linear spring and with a linear viscous damper. From the investigations carried out it is possible to observe the DC motor influence on the vibrating system along with non-periodic motions with chaotic characteristic. To control this system linear viscose damper is substituted by MR damper. A semi-active control method, sky-hook control is used in this study. Our results suggest that the addition of a MR damper turns the phase space smoother and it is so effective to suppress chaos.