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Direct stiffness method
About: Direct stiffness method is a research topic. Over the lifetime, 2584 publications have been published within this topic receiving 53131 citations.
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TL;DR: In this paper, a method of creating the stiffness matrix of a hexahedral eight-node finite element with a single, non-propagating, transverse, one-edge crack at half of its length is presented.
19 citations
TL;DR: In this paper, an algorithm is presented for the evaluation of the stiffness matrices of higher-order elements on the CDC STAR-100 computer, where the organization of the computation and the mode of storage of different arrays to take advantage of the STAR pipeline (streaming) capability are discussed.
19 citations
TL;DR: The proposed approach presents an effective design tool for evaluation and limitation of stiffness of machines and robots.
Abstract: New stiffness performance indices using the collinear stiffness value (CSV) associated with a given configuration of the machine are proposed. The minimal CSV (MinCSV) is applied to stiffness evaluation for all types of configurations. Similar to the determinant, the MinCSV equals zero in singular configurations. In regular configurations, the MinCSV is applied to evaluation of local stiffness for a given configuration and global stiffness in the workspace, wherein stiffness limitations are satisfied. A screw stiffness value, i.e., the CSV during a screw displacement, presents the general case of the CSV. There are two important special cases: rotational and translational stiffness values. Procedures for evaluation of the MinCSV are developed in natural and dimensionless forms. The CSV of the hexapod are simulated and compared with those of serial-type mechanisms. The proposed approach presents an effective design tool for evaluation and limitation of stiffness of machines and robots.
19 citations
TL;DR: In this article, a dynamic analysis of a stiffened cylindrical shell using the Dynamic Stiffness Method, also known as the Continuous Element Method, is presented, which is based on the determination of the dynamic stiffness matrix of an unmeshed structure.
19 citations
01 May 1996
TL;DR: In this article, an innovative concept for an axial strut mechanism was discovered as part of research into variable stiffness, which employs SMA springs (specifically Ni-Ti) in a way that reduces overall stiffness when the SMA spring gains stiffness.
Abstract: Variable stiffness is a new branch of smart structures development with several applications related to aircraft. Previous research indicates that temporarily reducing the stiffness of an airplane wing can decrease control actuator sizing and improve aeroelastic roll performance. Some smart materials like shape memory alloys (SMA) can change their material stiffness properties, but they tend to gain stiffness in their `power on' state. An alternative is to integrate mechanisms into a structure and change stiffness by altering boundary conditions and structural load paths. An innovative concept for an axial strut mechanism was discovered as part of research into variable stiffness. It employs SMA springs (specifically Ni-Ti) in a way that reduces overall stiffness when the SMA springs gain stiffness. A simplified mathematical model for static analysis was developed, and a 70% reduction in stiffness was obtained for a particular selection of springs. The small force capacity of commercially available SMA springs limits the practicality of this concept for large load applications. However, smart material technology is still immature, and future advances may permit development of a heavy-duty, variable stiffness strut that is small and light enough for use in aircraft structures.
19 citations