A similar structure model has proposed for three-storey building structure based on similarity theory, thus differential equations are established for the 4-DOF vibration system. According to the vibration characteristics of resultant structures, the mass, stiffness and damping coefficient are obtained by using genetic optimum algorithm, and then an MRF absorber has been designed and fabricated based on the optimized absorber parameters obtained. Furthermore, a set of semi-active vibration control testing system for building structures is designed and a pilot study on the damping effect of the MRF absorber has been performed. By adjusting the shock absorber damping force, inertia force and movement frequency synchronously against the external excitation force, the installed MRF absorber could significantly reduce the vibration amplitude of the considered building structure, clearly evidencing the damping effect of the MRF absorber.

With the highest product performance, quality and reliability requirements, oil casing is the most demanding service conditions in the oil and gas fields. However, when solving with thin-walled seamless steel pipes by the existing straightening theory, the cross section distortion phenomenon shall not be considered, and when the proportion of diameter to wall thickness increases, an ideal straightening effect can't be obtained. With the elastic-plastic bending straightening theory, this paper analyzes straightening process of thin-walled seamless steel pipes, studies the relationship of the flattening rate, deflection and straightening force in thin-walled pipes straightening, deduces the best reduction calculation method in the practical six roller skew rolling straightening machine, and in the meantime, results of several steel pipes flattening rate are compared.

Due to the problems that the rolling force of seamless steel tube during tandem rolling process is affected by many factors, the calculation is complex and the accuracy is not enough. In order to improve the rolling force calculation accuracy of the tandem rolling mill, analyze the metal flow, stress distribution rules and cross section deformation characteristics during the rolling process of seamless steel tube, calculation of the rolling force was divided into the reduced-diameter area and the reduction of wall area, and a new calculation method was proposed, which concerns the rolling force in reduced-diameter area related to the material yield stress, friction coefficient and the crushing stress of the tube, while the rolling force in the reduction of wall area is only related to the material yield stress and the friction coefficient. The results show that the calculated rolling force is in agreement with the measured values with errors less than ±10%. The model satisfies the actual conditions and is applicable to engineering application.

Due to the influence of rolling force fluctuations, tube size changes and material uniformity and other factors, vibration and other phenomenon inevitably occur in the rolling process of tandem rolling mill. This vibration has a great impact on the dynamic stability of the mill and rolling reduction, and will significantly reduce the dimensional accuracy and surface quality of seamless steel pipe. In this paper, the non-linear finite element software ABAQUS is used to simulate the rolling process of seamless steel pipe. First, rolling force of the first frame with the maximum rolling force of PQF rolling mill is calculated. The reliability of rolling force calculated by the finite element method is verified by the test experiment. The dynamic response analysis of the roll is carried out to obtain the dynamic response curve of the roll in the rolling state and to provide technical support for the rolling schedule with the calculated rolling force being the load.