Aspects of creep buckling II. The effects of small deflexion approximations on predicted behaviour

In creep buckling analysis, small deflexion approximations generally influence the calculated displacement‒time relations and may also result in the prediction of different phenomena from those indicated by exact analyses. Part II examines the nature of these approximations and the effects of using them. As in Part I, much significance is attached to the link between a structure’s creep buckling behaviour at constant load and its instantaneous buckling and post-buckling behaviour under varying load. Analyses of simple single degree of freedom models are used for illustration. Some general conclusions are drawn which permit a better understanding of the relationships between the different types of analysis that have been used in previous creep buckling studies.

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The Response of Nonlinear Systems to Modulated High-Frequency Input

14th Biennial Conference on Mechanical Vibration and Noise: Dynamics and Vibration of Time-Varying Systems and Structures ◽

10.1115/detc1993-0130 ◽

1993 ◽

Author(s):

S. A. Nayfeh ◽

A. H. Nayfeh

Keyword(s):

Nonlinear Systems ◽

Natural Frequency ◽

Amplitude Modulation ◽

Carrier Frequency ◽

High Frequency ◽

Degree Of Freedom ◽

Resonant Excitation ◽

Single Degree Of Freedom ◽

Single Degree ◽

Different Types

Abstract We study the response of a single-degree-of-freedom system with cubic nonlinearities to an amplitude-modulated excitation whose carrier frequency is much higher than the natural frequency of the system. The only restriction on the amplitude modulation is that it contain frequencies much lower than the carrier frequency of the excitation. We apply the theory to different types of amplitude modulation and find that resonant excitation of the system may occur under some conditions.

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The Virtual Cam – Hexagon Method Authentication on Locating Key Instant Centers of All Planar Single Degree of Freedom Kinematically Indeterminate Linkages up to Ten-Bar

Volume 4A: Dynamics, Vibration, and Control ◽

10.1115/imece2018-87802 ◽

2018 ◽

Author(s):

Zhengqi Liu ◽

Yin-ping Chang

Keyword(s):

Degree Of Freedom ◽

Universal Method ◽

Single Degree Of Freedom ◽

Graphical Approach ◽

Single Degree ◽

Wide Range ◽

Different Types ◽

Limited Application ◽

Complete Sets ◽

Improved Technique

At this moment all the methods which had been proposed have extremely limited application to only several specific constructions of kinematically indeterminate linkages, i.e. their complete sets of instant centers cannot be obtained simply from Kennedy Theorem due to lack of enough four-bar loop information in their constructions. Planar single degree of freedom linkages up to ten-bar include two different types of mechanisms, i.e. pure bar linkages, such as four-, six-, eight-, and ten-bar; and geared-bar linkages, i.e. geared-five, seven, and nine-bar. The huge varieties of different types and constructions can serve as great testbeds for these methods. This research systematically investigates and modifies the graphical approach, i.e. virtual cam method, whose employment will show it to be an almost-universal method which can be compliantly applied on very wide range of kinematically indeterminate linkages. The procedures and criteria of the methodology are proposed and examined thoroughly to help locate key instant centers of all planar single degree of freedom kinematically indeterminate linkages up to ten-bar so that their complete sets of instant centers can be located successfully. We call this modified and improved technique as Virtual Cam – Hexagon Method. The results are verified carefully against traditional Kennedy Theorem approach and CAD modeling.

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Detection of Improper General Spatial Kinematic Chains With Different Types of Pairs

23rd Biennial Mechanisms Conference: Mechanism Synthesis and Analysis ◽

10.1115/detc1994-0210 ◽

1994 ◽

Author(s):

Xian-Wen Kong ◽

Ting-Li Yang

Keyword(s):

Unsolved Problem ◽

Degree Of Freedom ◽

Sufficient Condition ◽

Necessary And Sufficient Condition ◽

Single Degree Of Freedom ◽

Kinematic Chains ◽

Single Degree ◽

Different Types ◽

Necessary And Sufficient ◽

Topological Synthesis

Abstract Improper general spatial kinematic chains (GSKCs) due to the effect of pair types may be generated during the process of topological synthesis of GSKCs with different types of pairs. Thus, detection of improper GSKCs is necessary in topological synthesis of GSKCs with different types of pairs. Unfortunately, it is still an unsolved problem. In this paper, a method for detecting improper GSKCs is presented. Both a necessary and sufficient condition and a sufficient condition for proper GSKCs with R, P, H, T and C pairs are introduced at first. Based on these two conditions, an algorithm to detect improper GSKCs is then developed which is very efficient and suitable for topological synthesis of GSKCs with R, P, H, T and C pairs. The proposed algorithm has been applied to topological synthesis of 1- and 2-loop, single degree of freedom GSKCs with R, P, H, T and C pairs and the corresponding atlas is obtained.

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