Unbalanced Vector Research Articles

An Approach on V-Shaped Milling for Rotor Balancing of Armatures

In order to improve the dynamic balancing accuracy of the micromotor armature, a method of V-shaped milling based on a discrete vector model for unbalance correction is proposed. The discrete vector model is fitted according to the parameters of the milling cutter and rotor, and then all the unit unbalance vectors in the discrete vector model are added to the milling center. The numerical relationship between the milling depth and the removal of the mass unbalance vector is obtained, and the accuracy of the model is verified via comparison with the data of the simulation experiments. The complexity of the integral formula of the numerical milling model makes it difficult to apply in practice. The discrete vector model does not require integration of the numerical formula and only considers the milling area as being composed of countless discrete blocks, which greatly simplifies the process of solving the unbalance vector. In view of the different thicknesses of the tooth surface of the armature, in order to avoid damage to the armature during milling, the unbalanced vector is decomposed at the center of the tooth surface by force decomposition. The experimental results show that this proposed method can effectively improve the dynamic balancing accuracy of the micromotor armature.

Analysis of the similarity design and vibration transmission characteristics of typical support structures of an aero-engine

In the vibration test of an entire aero-engine, the magnitude and phase of the unbalanced vector of the internal rotor must be identified based on the vibration signal of the measuring point on the casing. Therefore, in addition to understanding the vibration transmission law between the high- and low-pressure rotors under unbalanced excitation, the vibration transmission law of the support structure must be studied urgently. However, few studies have investigated the vibration transfer characteristics of typical support structures. In this study, the similarity design of typical support structures was first performed, and the structural parameters of the core member squirrel cage were determined using theoretical calculations. Subsequently, the bush and spring elements were used to establish the connection between the inner and outer rings of the bearing to realise the equivalent simulation of the bearing stiffness. Using this method, refined finite element models of elastic and rigid support structures were established, and the accuracy of the model was verified based on low-speed rotating vibration and hammering tests. Furthermore, the unbalanced vibration transmission law of typical support structures was studied, and the vertical vibration transmission law from an aero-engine bearing pedestal to the panel was established with the vibration transmission rate as the quantitative index. Finally, considering the vital role of the squirrel cage, the influence of the local stiffness degradation of the squirrel cage on the unbalanced vibration transmission of the elastic support structure was studied. The research methods and results of this study can provide a basis for aero-engine assembly as well as manufacturing and structural performance evaluation.

A new dynamic balancing method of spindle based on the identification energy transfer coefficient

A new vector matching balance method (VMBM) based on the identification of energy transfer coefficient of spindle rotor system (ETCSRS) is proposed in this paper. This method only needs to extract the original vibration signal of the spindle to compute the spindle rotor system unbalanced vector, and the calculation accuracy depends on the identification precision of ETCSRS. The initial parameters of bearings were calculated by applying Newton-Raphson algorithm based on the quasi-static mechanics analysis of rolling bearings. Through establishing the FEA model of spindle, the structural parameters of the rotor shaft system are obtained and modified by modal correction method. First, the principle of VMBM is verified on a Bentley rotor test bench at different rotating speeds. Second, the verification experiment of VMBM on a high-speed spindle is carried out. Furthermore, the VMBM has a better performance than the influence coefficient method (ICM). The method proposed in this paper is very suitable for on-line dynamic balancing, since it greatly improves the balance efficiency.

A solution strategy for non-linear implicit BEM formulation using a unified constitutive modelling framework

A new solution strategy for the non-linear Implicit Formulation of the Boundary Element Method is presented. Such strategy is based on a decomposition of the strain increment variation vector in two parts: one associated to the cumulative external loads and another associated to the current unbalanced vector, obtained from the difference of the first part and the calculated internal strain field distribution, during the iterative process. This approach makes the algorithm generic enough to deal with different control methods that governs the progression of the non-linear analysis. Also, a unified constitutive modelling framework for a single loading function is used to provide the material constitutive informations required by the solution strategy, which permits the implementation of a very comprehensive series of models in an independent way. However, only local models were treated. To demonstrate the efficiency and versatility of the methodology, some numerical examples are presented.

Relationship between fundamental and realized ecological niches

Since species are formed in course of evolutionary process, their ecological niches are formed in the evolutionary process, too. Species exist in a state of evolutionary stasis diring hundreds of thousands and millions years. Stasis in sustained mainly by counterbalance of vectors of directional selection. Niche can be viewed as a multidimensional structure. Multitude of environmental factors acts upon every population, which cause elimination and, by that, selection for adaptation to each eliminating factor. Different directions of these vectors of selection lead to their counteractions; selection in one direction is interfered by selection in an opposite direction. The counterbalance of vectors of selection interferes with progressive evolution thus supporting stasis. During species existence in a stasis condition it endures a whole set of various deterioration of environment. Such deteriorations lead to imbalance of selective processes. Unbalanced vectors of selection form adaptations to extreme conditions of existence. Such adaptations are superfluous as for usual conditions; but they define fitness borders and, by that, borders of a fundamental niche. Realized niche, as well as fundamental one, is a multidimensional structure. Each population occupies a subniche of the specific realized niche. Thus, it occupies habitats where conditions are as close to an ecological optimum as can be admitted by the conditions in the given part of the areal. The sum of all subniches of populations--the specific realized niche--coincides with a part of fundamental niche because only the part of adaptive possibilities of a species sufficient for existence in the given environment is used. Interspecific competition, even when it is capable to restrict consumption of limiting resources, is not the reason of the realized niche limitation. Restriction of one or two of niche parameters does not influece all others parameters of its multidimensional space.

Nuances of the Composite Face-lift Technique

The composite face-lift is a well-described, comprehensive facial rejuvenation technique that results in harmonious repositioning of all components of the aging face. It is distinguished by the superior-medial movement of the cheek and the septal reset maneuver. The composite rhytidectomy reverses the unbalanced vectors of the traditional face-lift in patients with the lateral sweep and may reestablish the youthful convexity in patients with hollow eyes.