Vertical Stiffness and Deformation Analysis Models of Rubber Isolators in Compression and Compression-Shear States

The vertical stiffness and deformation theories of rubber isolators in compression and compression-shear states are systemically researched in the paper, a series of basic concepts, such as origin compression stiffness, origin compression longitudinal elastic modulus, offset vertical stiffness, etc. are suggested with corresponding theoretical formula and experimental estimation method. Based on the basic concepts and newly suggested calculating theories, the deformation calculating theory related to pure compression state and compression-shear state of isolating bearing is established. The vertical stiffness, offset vertical stiffness and deformation tests are performed with nature rubber bearings and lead plug rubber bearings total 16 original specimens to verify the new concepts and computation model of rubber isolators. All test results show that the theories established in the paper are suitable for analyzing the vertical stiffness and deformation of rubber isolators.     

Analysis of the fatigue behaviour characterized by stiffness and permanent deformation for different distal volar radius compression plates

Fractures of the distal radius are with 10% the most frequent fractures of the human skeleton. In order to stabilize the fracture which is essential for succesful bone-healing, distal volar compression using dorsal compression plates is often used. Among the most important, but until now sparsely investigated criteria for implant-quality is the fatigue behaviour of the system of radius and stabilizing implant. Several types of implants were tested in combination with synthetic bones in the fatigue regime. The fatigue behaviour of samples was characterized using the parameters stiffness, tilting angle and reduction of the fracture gap which can be expressed by the permanent deformation of the system. The study of the evolution of these properties allows an interpretation of the mechanisms governing fatigue. Thus, a comparison of different implant types was obtained. Results show that the geometry of the implant as well as the positioning and type of the used screws has a profound effect on the characteristics of the system.     

A finite thin circular beam element for out-of-plane vibration analysis of curved beams

A finite thin circular beam element for the out-of-plane vibration analysis of curved beams is presented in this paper. Its stiffness matrix and mass matrix are derived, respectively, from the strain energy and the kinetic energy by using the natural shape functions derived from an integration of the differential equations in static equilibrium. The matrices are formulated with respect to the local polar coordinate system or to the global Cartesian coordinate system in consideration of the effects of shear deformation and rotary inertias. Some numerical examples are analyzed to confirm the validity of the element. It is shown that this kind of finite element can describe quite efficiently and accurately the out-of-plane motion of thin curved beams. This paper was recommended for publication in revised form by Associate Editor Seockhyun Kim Chang-Boo Kim received his B.S. degree in Mechanical Engineering from Seoul University, Korea in 1973. He then received his D.E.A., Dr.-Ing. and Dr.-es-Science degrees from Nantes University, France in 1979, 1981 and 1984, respectively. Dr. Kim is currently a Professor at the School of Mechanical Engineering at Inha University in Incheon, Korea. His research interests are in the area of vibrations, structural dynamics, and MEMS.     

Analysis of the transverse cracking in hybrid cross-ply composite laminates

A modified shear-lag analysis, taking into account the concept of interlaminar shear stress, is employed to evaluate the effect of transverse cracks on the stiffness reductions in different glass/epoxy and graphite/epoxy hybrid cross-ply laminates. The modified shear-lag model is proposed that assumes interlaminar adhesive layer between two neighbouring layers transferring not only interlaminar shear stress but also normal stress. The stress distribution is solved by the used model which rigorously satisfies the stress equilibrium equations, boundary conditions and the traction continuity at interfaces between layers.     

柔性多体动力学的建模与计算

本文在对柔性多体动力学发展略作回顾的基础上，采用ｄ＇Ａｌｅｍｂｅｒｔ－Ｌａｇｒａｎｓｅ原理，对由基座、（ｎ－１）个柔性连杆及端部负载组成、相互之间由柱铰联结的柔性链式多体系统进行理论建模；柔性杆模态取三维梁单元进行有限元离散；算法上选用Ｇｅａｒ算法克服柔体动力学微分方程的刚性（Ｓｔｉｆｆｎｅｓｓ）问题。成功地进行了一种工况的失重柔性机械臂的动力学数值计算，为在其上进一步实施控制打下了良好的基础。     

U形膨胀节刚度试验与分析

本文介绍了单层和多层U形膨胀节刚度的主要计算式和刚度测试结果,并将测试结果与有关理论公式计算结果进行了分析比较,评价了公式的准确性。     

Stiffness and Strength of Metal Bridge Deck Forms

Light gauge metal sheeting is often utilized in the building and bridge industries for concrete formwork. Although the in-plane stiffness and strength of the metal forms are commonly relied upon for stability bracing in buildings, the forms are generally not considered for bracing in steel bridge construction. The primary difference between the forming systems in the two industries is the method of connection between the forms and girders. In bridge construction, an eccentric support angle is incorporated into the connection details to achieve a uniform slab thickness along the girder length. While the eccentric connection is a benefit for slab construction, the flexible connection limits the amount of bracing provided by the forms. This paper presents results from the first phase of a research study investigating the bracing behavior of metal bridge deck forms. Shear diaphragm tests were conducted to determine the shear stiffness and strength of bridge deck forms, and modified connection details were developed that substantially improve the bracing behavior of the forms. The measured stiffness and strength of diaphragms with the modified connection often met or exceeded the values of diaphragms with conventional noneccentric connections. The experimental results for the diaphragms with the modified connection details dramatically improve the potential for bracing of steel bridge girders by metal deck forms.     

Force-Deformation Behavior of Isolation Bearings

The isolation bearings are widely used in earthquake prone areas to protect the structure from seismic forces. The isolation bearing consists of an isolator to increase the natural period of the structure away from the high-energy periods of the earthquake, and a damper to absorb energy in order to reduce the seismic force. The most common isolation bearings used are lead–rubber bearings. They combine the function of isolation and energy dissipation in a single compact unit, giving structural support, horizontal flexibility, damping, and a centering force in a single unit. The relation between the horizontal force and horizontal displacement of the isolation bearings is nonlinear; to calculate the stiffness and the damping constant, which correspond to effective design displacement, the nonlinear behavior is expressed by bilinear behavior. This technical note presents new relations to calculate yield force, horizontal displacement, and damping.     

Prediction of Creep Stiffness of Asphalt Mixture with Micromechanical Finite-Element and Discrete-Element Models

This study presents micromechanical finite-element (FE) and discrete-element (DE) models for the prediction of viscoelastic creep stiffness of asphalt mixture. Asphalt mixture is composed of graded aggregates bound with mastic (asphalt mixed with fines and fine aggregates) and air voids. The two-dimensional (2D) microstructure of asphalt mixture was obtained by optically scanning the smoothly sawn surface of superpave gyratory compacted asphalt mixture specimens. For the FE method, the micromechanical model of asphalt mixture uses an equivalent lattice network structure whereby interparticle load transfer is simulated through an effective asphalt mastic zone. The ABAQUS FE model integrates a user material subroutine that combines continuum elements with viscoelastic properties for the effective asphalt mastic and rigid body elements for each aggregate. An incremental FE algorithm was employed in an ABAQUS user material model for the asphalt mastic to predict global viscoelastic behavior of asphalt mixture. In regard to the DE model, the outlines of aggregates were converted into polygons based on a 2D scanned mixture microstructure. The polygons were then mapped onto a sheet of uniformly sized disks, and the intrinsic and interface properties of the aggregates and mastic were assigned for the simulation. An experimental program was developed to measure the properties of sand mastic for simulation inputs. The laboratory measurements of the mixture creep stiffness were compared with FE and DE model predictions over a reduced time. The results indicated both methods were applicable for mixture creep stiffness prediction.     

Static Stiffness Analysis of a New Type 6-DOF Micro-manipulation Robot

A 6-DOF micro-manipulation robot based on a 3-PPTTRS mechanism is proposed in this paper. Its static stiffness is an important index to evaluate load capacity and positioning accuracy. However, it is insufficient to consider the static stiffness only when the robot is in its initial pose. The stiffness in different positions and poses in its work space must be analyzed also. Thus a method to analyze the relationship between static stiffness and poses in the whole work space is presented. A static stiffness model is proposed first, and the relationship between structural parameters and static stiffness in different poses is discussed. The static stiffness analysis provides foundation for structural parameter design.