Applied Mechanics and Materials Vols. 80-81

Abstract: A support vector machine (SVM) optimized by particle swarm optimization (PSO)-based damage identification method is proposed in this paper. The classification accuracy of the damage localization and the detection accuracy of severity are used as the fitness function, respectively. The best and can be obtained through velocity and position updating of PSO. A simply supported beam bridge with five girders is provided as numerical example, damage cases with single and multiple suspicious damage elements are established to verify the feasibility of the proposed method. Numerical results indicate that the SVM optimized by PSO method can effectively identify the damage locations and severity.

Abstract: According to the new profiling characteristic of carbide pinion cutter with convex curved rake face, the machining process of convex curved rake face is designed, the special grinding equipment is designed and developed. Tool presetting and detecting equipment is developed by using laser sensor. It can be used to locate the initial location of grinding wheel precisely when convex curved rake face is machining. The tool path for CNC machining is solved. The grinding experiment is done for convex curved rake face of pinion cutter with 21teeth and 5modulus , different process parameters are established. The ideal surface roughness is obtained. The experiment result shows that the grinding equipment and tool presetting equipment are proper for machining requirements of convex curved rake face of pinion cutter.

Abstract: The cutting of inner helical surfaces within the parts of screw machine is an important manufacturing technique. According to the principle of inner helicoid which is formed under specific processing conditions using an especial disk milling cutter, a design algorithm for the profile of the forming cutter which is based on coordinate transformation is proposed by the paper. The article introduces the detailed steps of the algorithm and realizes the smooth interpolation of the cross-section of the workpiece’s contour curve and the disk cutter’s contour curve using a method of step-shaped and low-order interpolation. The work provides a theoretical basis to the cutting for this kind of helical surface.

Abstract: In combination with a certain road tunnel instance Ningwu Highway，a working face rock ahead of forecast model is established. The prediction criterions include the Working face of rock radar images coefficient factor rock tunnel face conditions and the tunnel observation and analysis of geological factors are determined in the article. Their evaluation indexes are determined by the principle of which degree comes close and judged by experts. Finally the prediction results are came up through the fuzzy comprehensive evaluation and compared with the indexes of the degree of stability. Then it can make the prediction conclusion. The result shows that the model is convenient to use in practice very well. So it is proved that this prediction model is reliable.

Abstract: Simulation modeling VV&A is verification, validation and accreditation. In the field of petrochemical industry, focus of VV&A still lays on the model validation, and people always do appropriate model verification, validation work after model development. It does not yet formed a complete hierarchy or framework for effective implementation of life cycle VV&A. This paper referenced the research achievement of military simulation modeling and test-driven software development technology, introduced the modeling VV&A technology into the whole life of the model development. Simulation modeling process based on validation discussed in this paper is totally based on validation, and it is carried out closely around VV&A from appearance of the first idea to the final application. As a result, people can completely control the whole process of model development. At the same time of improving model accuracy, reliability and credibility, such process could greatly improve the efficiency of model development and effectively reduce the model development period. And this process can be also applied to system-level, complex object.

Abstract: Slope stability is the key to ensuring the safety of foundation pit construction. This paper is on the background of metro foundation pit monitoring of the West Railway Station in Changchun City. Through the time series analysis of the pit slope deformation data, the Auto Regressive Moving Average Model (ARMA) of pit slope deformation is established. Then the orders of the model are determined by the Akaike Information Criterion (AIC). Further, the deformation prediction of pit slope is finished using the ARMA model. By the comparison of the predictive value and the true monitoring value, it shows that using time series to analyze the deformation of foundation pit slope is reasonable and reliable. At the same time, this method is providing a new way to estimate the stability of pit slope.

Abstract: The geometry and the arrangement of a brake pad for railway vehicles are the important influencing factors for distribution of the temperature and the thermal stress in a brake disc，and closely related to the thermal fatigue damage of the brake disc. The conception of structure function is presented with the view that friction strength on the brake disc is related to the geometry and the arrangement of the pad. Non-uniform heat sources model are suggested based on the structure function, and the temperature and the thermal stress of the brake disc are simulated with FEA software ABAQUS for four difference arrangements brake pads. The results show that changing patterns of the temperature and the thermal stress on brake disc surfaces are coincided with that of structure function. While the peak value of structure function is smaller and the distribution uniformity is better, the temperature and the thermal stress on the corresponding brake disc surface are lower, and distribution is more uniform. Structure function connects the geometry and the arrangement of the brake pad with the friction contact relationship of the brake disc, reflects distribution law of the temperature and the thermal stress and solves the problem of creating a heat source model.

Abstract: Pipe crack identification method based on vibration has been researched by many people in recent years. The natural frequency plays an important role in the method. The natural frequency will change due to the appearance of the crack, so the crack may be identified according to the change law of the natural frequency with the size and location of crack. The dynamic model of cracked pipe is established by dispersing the pipe into a series of nested thin-walled pipes in this paper, and then the change law of the first three natural frequencies of the pipe is discussed.

Abstract: Second generation wavelet (SGW) provides diversity and agility for constructing wavelet besides the multiresolution property. By introducing SGW into finite element method, a series sequence of finite element approximation spaces which are nested and hierarchically expanded can be constructed. The method has high calculation speed and precision and is suited for constructing adaptive algorithm. In this paper, the beam element based SEW is constructed, which set up a basis for the adaptive finite element method based on multiresolution analysis.

Abstract: Advanced aircraft and spacecraft structures are exposed to increasingly severe operating environments, including a combination of mechanical, aerodynamic, acoustic and thermal loads. Such loading conditions can cause thin-walled structures to respond in a nonlinear fashion and exhibit complex response characteristics. This paper investigates the dynamic response of pre/post buckled thin-walled structure under high level random acoustic loading. Firstly, different orders of critical buckling temperatures and modal frequencies under alternative temperatures are obtained using Finite Element Method (FEM), and the modal frequency changes in a disorder fashion are discussed in detail. Then with coupled BEM/FEM method, the dynamic responses including transverse displacement, strain and stress of a stiffened rectangular plate under thermo-acoustic loading are simulated. By comparing the response characteristics of the plate in pre/post buckled conditions, some valuable conclusions are derived, which can be used to explain the response behaviours of thin-walled structures.