A Chord Vibration Method in Measuring the Deformation of Member Bodies

一对细金属弦被拉伸在两个桥件上，这两个桥件被固定在要测量变形或应力的构件体上。弦的基振频率与张力、跨和线密度有明显的关系，因此弦的跨的变化，即杆体的变形，可以随时由频率数换算出来。在光电位置传感器和相移电路的帮助下，将电流输入弦中，产生连续的振动。弦在这种长时间的紧拉伸下的蠕变，将是今后需要考虑的问题之一。暴露在露天的弦的腐蚀也应考虑在内。

A couple of fine metal chords are stretched across the two bridge pieces which have been fixed onto the member body where the deformation or the stress is to be measured. Frequency of fundamental vibration of the chord is obviously related to the tension, span and linear density, so that the change of span of the chord, that is the deformation of member body, can be translated from the frequency number at any time. An electric current is fed into the chord, and it results in a continual vibration with the aid of an opto- electronic position sensor, together with a phase shifting circuitry.The creep of the chord under such the tight stretch for long term, will be one of the problem to be considered in the future. Corrosion of the chord exposed in open air should also be considered.