The vibrostabilization optimization of a sorting arm structure

Vibration in the chip production process greatly limits the devices’working efficiency. There is a strong need to develop an optimization method to improve the structure vibrostabilization. In this paper, we studied an LED sorting arm and optimization the sorting arm in three steps. Firstly, a series of experiment are carried out to optimize the particle damping capsule distributionand filling ratio. Then, an improved level set optimization algorithm is adopted to carry out the shape and topology optimization of the arm with a damping capsule at the same time. At last, the virtual and real tests are carried out on three arms, the results proved that our optimize method can effectively suppress the vibration

Contact stiffness of bolted joint with different material combination in machine tools

Bolted joint is a commonly used complex flexible interface in machine tools. The stiffness influential factors-based dynamic model provides a high accuracy modeling method of bolted joints in machine tools. The key of wide application of this method is the database of the stiffness matrices of bolted joints under different conditions. This paper mainly concerns the contact stiffness of bolted joints with different material combination in machine tools and tries to establish the relationship of them. Using the stiffness influential factors-based dynamic modeling method, the contact stiffness of bolted joint is expressed as the stiffness matrix of the connection finite element. After impact modal tests were carried on the specimens, stiffness matrices of bolted joints with different material combinations are identified from the frequency response functions. The ratio of the stiffness matrices validates the effectiveness of the conclusion that the contact stiffness of bolted joints with different material combination is proportional to the corresponding equivalent elastic modulus deduced from Hertz contact theory. The reliable proportional relationship provides a great convenience to the wide application of the stiffness influential factors-based dynamic modeling method of bolted joint

An analytical method to select spindle speed variation parameters for chatter suppression in NC machining

Regenerative chatter vibrations may result in shortened tool life and poor surface finish, and hence should be avoided in practice. Since the Spindle Speed Variation (SSV) method has been certified as a feasible and effective way, the issue of speed variation parameters selection has yet to be solved. Based on the discussions of energy accumulation process in chatter and in vari-speed cutting, an analytical method was proposed to select spindle speed variation parameters. The variation of the phase delay between the inner and the outer modulations was regarded as an important argument that reflects the energy accumulation process. Two phase delay related coefficients were proposed for analyzing the mean energy accumulation process and regional energy accumulation enhancement. The importance of spindle acceleration for chatter suppression was also explained. The phase delay based analytical method was verified by numerical simulation and turning experiments

Extended Application Of Time-Varying Observer For Rigid Rotors Unbalance Estimation During Acceleration

Unbalance is one of essential problems for modern rotating machines. In this work, an improved time-varying observer is proposed to estimate the unbalance of rigid rotor during acceleration. In order to fitting different speed acceleration laws, the unbalance forces have been included in an new designed augmented states, meanwhile the state space model of rigid rotor has been also developed. The developed state space model is transformed to a canonical transformation and a new designed time-varying observer can be obtained. The estimated unbalances can be directly obtained by using this time-varying observer. This method would be very helpful for active balancing control strategy during acceleration

Simulational and experimental study of stress in bolts work-piece

In order to study the effect of different bolts tightening sequences on the stress of bolts work-piece, the finite element simulation and stress test experiments are adopted. Three types of bolt work-piece: two, five, and frame type bolts work-pieces are studied under different tightening sequences. The stress values and distribution are obtained under different tightening sequences by simulation. It is observed that the stress distribution tendency of bolts work-piece has little change under different tightening sequences. It also notices that the tightening sequences have no effect on two bolts work-piece due to the symmetry of work-piece. In five bolts work-piece, the variation range of stress under tightening from ends to middle is smaller than that under sequence tightening, which indicates that better stress uniformity is obtained under tightening from ends to middle in five bolts work-piece. Similarly, in frame bolts work-piece, the variation range of stress under symmetrical tightening is smaller than that under sequence tightening, which indicates that better stress uniformity is obtained under symmetrical tightening in frame type bolts work-piece. Furthermore, the experimental results are in good agreement with the simulation results. Moreover, the stress variation mechanism is revealed by analyzing residual preload variation under sequence tightening

Prediction of Residual Stress Field in Milling Planes by Establishing Bivariate Mathematical Models

The knowledge of the distribution of residual stresses in milling planes is of paramount importance to understand the surface qualities of engineering components, research on manufacturing processes and improve the assembly qualities of machines. For this purpose, a prediction method for the residual stress fields was proposed. Residual stresses of some surface discrete points of a rectangular specimen were measured. Based on the measurements, the residual stress field was predicted by establishing bivariate mathematical models. The obtained results are close to the experimental technique and superior to the previous average method. The predicted stress fields are almost symmetrical along the length or width. The proposed method avoids simulating the process of residual stresses generation and has a unique potential application for engineering components of which the generation process of residual stresses can hardly be simulated in detail

Prediction of Residual Stress Field in Milling Planes by Establishing Bivariate Mathematical Models

The knowledge of the distribution of residual stresses in milling planes is of paramount importance to understand the surface qualities of engineering components, research on manufacturing processes and improve the assembly qualities of machines. For this purpose, a prediction method for the residual stress fields was proposed. Residual stresses of some surface discrete points of a rectangular specimen were measured. Based on the measurements, the residual stress field was predicted by establishing bivariate mathematical models. The obtained results are close to the experimental technique and superior to the previous average method. The predicted stress fields are almost symmetrical along the length or width. The proposed method avoids simulating the process of residual stresses generation and has a unique potential application for engineering components of which the generation process of residual stresses can hardly be simulated in detail

Study on Dynamic Characteristics of the Disc Spring System in Vibration Screen

To avoid too large exciting force in traditional linear vibrating screen and unstable working state in resonance screen, the disc spring system is applied in the linear vibration screen. The model of the disc spring system in vibration screen is established by simulation and experiment. The characteristics of modal and amplitude of the disc spring system in vibration screen are studied. We found that the disc spring system vibrates in vertical direction at the third-order natural frequency, which is consistent with the direction of the vibration screen when screening particles. Moreover, the third-order natural frequencies in simulation and experiment are basically consistent. Furthermore, the maximum amplitude of the disc spring system appears at 960 r/min (16 Hz), which is in accord with the third-order natural frequency. Meanwhile, the amplitude increases proportionally with the increase of exciting force, while the amplification factors are the same under three different exciting forces. This indicates that the disc spring system has excellent linearity. The results of research provide guidance for design and application of elastic components on the vibration screen

A Three-Dimensional Transition Interface Model for Bolt Joint

Bolt connection is an important component in mechanical structure which significantly affects the dynamic property of the whole structure. In this paper, a three-dimensional transition interface model which contains geometric and physical parameters is proposed to model the bolted joint based on the contact analysis. The geometric parameters and the physical parameters are used to characterize the influence of contact area and contact pressure which are related to connection parameters such as material, roughness, connection thickness, and tightening force, respectively. After that, the geometric parameter identification method is proposed, and the geometric parameter database of bolt joints for machine tools is constructed based on the Kriging interpolation method. Then, the model updating method based on the combination of modal parameters and frequency response function is proposed to identify the physical parameters and thickness of the three-dimensional transition interface model. The database of the transition interface model is constructed after verifying the validity of the proposed model. Finally, an engineering example of an engraving machine tool is used to check the practicability of the proposed transition interface model and the usage of the constructed parameter database