Optimum shape design of incompressible hyperelastic structures with analytical sensitivity analysis

This paper is focused on the structural shape optimization of incompressible hyperelastic structures. An analytical sensitivity is developed for the rubber like materials. The whole shape optimization process is carried out by coupling a closed geometric shape in R² with boundaries, defined by B-splines curves, exact sensitivity analysis and mathematical programming method (S.Q.P: sequential quadratic programming). Design variables are the control points coordinate. The objective function is to minimize Von-Mises stress, constrained to the total material volume of the structure remains constant. In order to validate the exact Jacobian method, the sensitivity calculation is performed: numerically by an efficient finite difference scheme and by the exact Jacobian method. Numerical optimization examples are presented for elastic and hyperelastic materials using the proposed method.     

弧面分度凸轮机构的固有频率分析

以弧面分度凸轮机构为对象,建立了考虑其输入/输出轴的扭转、弯曲刚度及凸轮曲面与滚子间接触刚度等多种因素的动力学模型,在此基础上,重点分析接触刚度、凸轮与分度盘滚子啮合个数的变化、运动规律对系统固有频率的影响。实验结果表明,所建立的动力学模型具有较高的计算精度。     

Honeycomb damage detection in a reinforced concrete beam using frequency mode shape regression

The objective of the study was to propose a technique to determine the location and severity of honeycomb damage in a reinforced concrete beam using frequency mode shape regression focusing on minimal data. Simply supported reinforced concrete beams were constructed with two different volumes of honeycomb materials implanted at mid-span of the beams. The technique necessitated the performance of linear and eigen analyses on a control beam, and nonlinear analysis on the test beams with damage. Local stiffness indicators obtained from regression using the Levenberg–Marquardt algorithm and residuals from regression of the frequency mode shapes using the Chebyshev series rational and transformation and application into the fourth order centered finite divided difference formula were utilized. Both approaches were successful in determining the location of the honeycomb damage. The Chebyshev series rational method was unable to determine the severity of damage.     

Sliding mode control of I/O linearizable systems with uncertainty

In this paper we explore the application of sliding mode control to process control problems. Sliding mode control is presented as a natural tool for robust design of state feedback controllers for minimum phase input–output linearizable systems with uncertainty. An example is presented to illustrate some of the issues involved in the design of sliding mode robust controllers.     

Natural mode analysis of a telescopic boom system with multiple sections using the Rayleigh-Ritz method

Journal of Mechanical Science and Technology - A truck crane, a type of construction machine, contains a boom consisting of several strips with different cross-sectional data. A set of the overall...     

产品复杂表面形态结构的映射设计方法

为解决表面形态复杂、细节众多的产品在三维造型设计技术上的难题.以编织产品为例,分析了其组织结构的数学特征与造型规律,将其分为交织结构和缠绕结构两大基本类别.在织物结构三维设计的单元体技术基础上,增加了形态变量控制,实现了编织产品整体形态上的复杂细节高效造型设计方法.利用二次映射技术将非均匀有理B样条曲线曲面自动转化为细节丰富的编织结构,并根据用户输入的参数调整编织结构的组织样式、密度、粗细等细部结构形态.在藤椅等典型编织产品的设计中进行了应用实践,并探讨了三维图案结构的生成方法.将设计师的工作简化为一般的曲面造型概念设计,用软件工具完成复杂形态细节的自动化建模,促进了复杂形态产品的设计.     

薄膜蒸发器转子系统固有频率及稳态不平衡响应分析

薄膜蒸发器转子系统中的不平衡力易导致转子振幅加大,从而加剧刮板磨损,导致刮板失效.采用VB对ANSYS进行二次开发,对薄膜蒸发器转子系统进行模态分析,并对转子某些位置上的不平衡量进行了稳态不平衡响应分析,初步实现了薄膜蒸发器转子动力学分析,为薄膜蒸发器设计及安全运行提供依据.     

CMM uncertainty analysis with factorial design

The purpose of this research is to present a method to estimate the Coordinate Measuring Machine (CMM) measurement uncertainty. The approach is based on a performance test using a ball bar gauge and a factorial design technique. A factorial design was applied to carry out a performance test and to investigate CMM errors associated to orientation and length in the work volume. The CMM measurement uncertainty was estimated with components of variance obtained after statistical analysis of variance applied to volumetric measurement errors. An application was performed with a Moving Bridge CMM and the results were compared to the volumetric performance test proposed by ANSI/ASME B89.4.1 standard. The results showed that the proposed method is suitable to investigate CMM hardware performance and determine the contribution of machine variables to measurement uncertainty.     

Damping and mode shape modification for additively manufactured walls with captured powder

This paper describes the fabrication, modeling, and dynamic testing of laser powder bed fusion stainless steel walls with captured powder cores. The purpose of the study is to determine the increased structural damping, or energy dissipation, and mode shape modification caused by the inclusion of the unmelted powder core within the solid walls. It is shown experimentally that the damping increases with larger powder core width and that the damping addition is mode dependent. Damping increases over the solid wall values by factors of 2.9–225 are reported depending on the mode number and core width. It is also seen that the mode shapes are distorted relative to the solid wall results as the core width is increased and wall thickness is decreased. Comparisons with finite element models confirm this trend.     

Nonlinear modeling and dynamic analysis of flexible structures undergoing overall motions employing mode approximation method

This paper presents a nonlinear modeling method for dynamic analysis of flexible structures undergoing overall motions that employs the mode approximation method. This method, different from the naive nonlinear method that approximates only Cartesian deformation variables, approximates not only deformation variables but also strain variables. Geometric constraint relations between the strain variables and the deformation variables are introduced and incorporated into the formulation. Two numerical examples are solved and the reliability and the accuracy of the proposed formulation are examined through the numerical study.     

Pseudo-constructal theory for shape optimization of mechanical structures

This work gives some applications of a pseudo-constructal technique for shape optimization of mechanical structures. In the pseudo-constructal theory developed in this paper, the main objective of optimization is only the minimization of total potential energy. The other objectives usually used in mechanical structures optimization are treated like limitations or optimization constraints. Two applications are presented; the first one deals with the optimization of the shape of a drop of water by using a genetic algorithm with the pseudo-constructal technique, and the second one deals with the optimization of the shape of a hydraulic hammer’s rear bearing.     

Collapse mode transitions of thin tubes with wall thickness, end condition and shape eccentricity

Transition of deformation mode shapes of round aluminum tubes from axisymmetric concertina to non-axisymmetric diamond mode have been studied with varying tube wall thickness, boundary conditions and tube shape eccentricities. Quasi-static axial compression experiments were carried out on as received aluminum tubes and tubes with wall thickness eccentricity, incorporated by off center machining. Tubes were of D/t=29 and L/D=1.4. The numerical simulation of the collapse phenomenon has been undertaken using a static non-linear finite element analysis in ANSYS with a fine mesh discretization of the tube domain and small incremental displacements as load steps. Convergence studies for the finite element model with respect to load step size and mesh density have also been established. The numerical results are found to compare well with the experimental load compression and energy absorption responses both for the axisymmetric concertina and non-axisymmetric diamond collapse modes. Having validated the numerical model with experiments, it has been used to undertake a systematic study of the load–deformation characteristics, energy absorption response and collapse mode transition of the tubes in varying configurations of wall thickness, shape and inplane boundary condition eccentricities. Dependence of tube collapse characteristics and collapse mode transitions on such eccentricities have been discussed.     

矩形薄板通透开裂缝对固有频率和模态的影响分析

针对四边固支矩形板薄受到通透开裂影响,引起模态中固有频率和模态振型变化的问题,对两种开裂位置中不同开裂长度进行了研究。首先,应用ANSYS软件建立有限元模型;然后,对开裂裂缝平行于薄板短边且位于板中心(对称开裂)和不位于板中心(不对称开裂)的各25种裂缝长度进行了仿真计算,获得了薄板的固有频率和模态振型。分析结果表明,裂缝的长度和位置影响矩形薄板的固有频率和振型;开裂的缝长和开裂中心位于节线上或者附近是产生模态交叉的两个重要因素,可为板结构开裂的检测提供依据。     

Evaluation and uncertainty analysis of vectorial tolerances

Recently, the integration of coordinate measuring machines (CMMs) and computer-aided design (CAD) systems has promoted a new approach to the evaluation of workpiece geometry; namely, vectorial dimensioning and tolerancing. This new approach is promising, because it defines process-related dimensions and tolerances clearly and distinctly. Therefore, it enables proper manufacturing control and process diagnosis. However, current proposal of vectorial tolerancing has several limitations. First, the current orientation vector is inadequate for representing true three-dimensional (3D) orientation. As a result, the orientation of a free-form surface cannot be properly established. Second, there has been little discussion of vectorial tolerance evaluation. This paper proposes a new rotation vector that provides a more general mathematical basis for representing vectorial tolerances. A nonlinear, best-fit algorithm has been developed to evaluate vectorial tolerances for both analytical geometric elements and free-form surfaces. To study the uncertainty of the best-fit result caused by sampling strategy and dimensional errors, sensitivity analysis of the evaluated parameters was investigated. Simulation and experiment showed that the developed model can predict the uncertainty of the evaluated parameters accurately.     

Natural frequency analysis of tooth stability under various simulated types and degrees of alveolar vertical bone loss

The aim of this study was to test natural teeth stability under various simulated types and degrees of alveolar vertical bone loss, as well as to assess the role that the surrounding bone played for maintaining tooth stability. A three-dimensional finite element model of the human maxillary central incisor with surrounding tissue, including periodontal ligament, enamel, dentin, pulp, and alveolar bone, was established. One side and multiple vertical bone loss were simulated by means of decreasing the surrounding bone level apically from the cemento-enamel junction in 1 mm steps incrementally downward for 10 mm. Natural frequency values of the incisor model with various types and degrees of bone loss were then calculated. The results showed that, with one-sided bone resorption, the model with labial bone loss had the lowest natural frequency decreasing rates (8.2 per cent). On the other hand, in cases of multiple bone loss, vertical bone resorption at the mesial and distal sides had more negative effects on tooth stability compared to vertical bone losses on facial and lingual sides. These findings suggest that the natural frequency method may be a useful, auxiliary clinical tool for diagnosis of vertical periodontal diseases.     

Fundamental frequency and testing mode of complicated elastic clamped-plate vibration

Aimed at the modal analysis of complicated elastic clamped-plates, a trigonometric interpolation method of conformal mapping is applied to set up the mapping function between a complicated region and a unit dish region, and the fundamental frequency of the complicated vibrating region is analyzed with the help of the Galerkin method. Taking an elastic rectangle-plate with arc radius as an example, the testing mode frequency band of plates is determined by analyzing the fundamental frequency; meanwhile, according to hamming testing method of multi-point excitation to the single-point response, and by signal processing technology and its software programming, modal parameter recognition of the elastic clamped-plate is completed. Comparing the first order modal frequency with the theoretical fundament frequency, the validity of the testing mode method and theoretical analysis are verified.     

采用水焓值法的制冷量源及其不确定度分析

制冷量量值统一对促进空调器行业节能减排有基础性作用,采用水焓值法的制冷量源能够应用于制冷量的量值传递,提供数值可测、可控的制冷量量值。首先,提出了水焓值法制冷量源的装置原理,减少了输出制冷量测量参数;然后,设计并研制了制冷量源实验装置,并在平衡环境型量热计中进行了实验研究,实验结果显示,量热计测得值与冷量源输出制冷量最大相对偏差不超过±0.7%;最后,详细给出制冷量源的不确定度评定过程和结果:制冷量源重复性为11.4 W,源输出由1 660.8增大至5 810.4 W时,合成标准不确定度由12.3增大至18.2 W,对应相对扩展不确定度由1.5%(k=2)减小至0.6%(k=2)。采用水焓值法的制冷量源第1次从计量学角度实现了制冷量量值的溯源,输出量值可溯源至温度、压力、流量和功率单位,可作为校准制冷量测量装置的标准源使用。     

Fundamental frequency and testing mode of complicated elastic clamped-plate vibration

Aimed at the modal analysis of complicated elastic clamped-plates, a trigonometric interpolation method of conformal mapping is applied to set up the mapping function between a complicated region and a unit dish region, and the fundamental frequency of the complicated vibrating region is analyzed with the help of the Galerkin method. Taking an elastic rectangle-plate with arc radius as an example, the testing mode frequency band of plates is determined by analyzing the fundamental frequency; meanwhile, according to hamming testing method of multi-point excitation to the single-point response, and by signal processing technology and its software programming, modal parameter recognition of the elastic clamped-plate is completed. Comparing the first order modal frequency with the theoretical fundament frequency, the validity of the testing mode method and theoretical analysis are verified.     

钢锭模模样的机加工工艺分析

设计简单的夹具装置,可以在普通机床上完成具有部分圆锥体的零件的加工,效果良好,可以满足使用要求。