Acoustic Emission from Breaking a Bamboo Chopstick

Abstract

The acoustic emission from breaking a bamboo chopstick or a bundle of spaghetti is found to exhibit similar behavior as the famous seismic laws of Gutenberg-Richter, Omori, and Båth. By use of a force-sensing detector, we establish a positive correlation between the statistics of sound intensity and the magnitude of tremor. We also manage to derive these laws analytically without invoking the concept of phase transition, self-organized criticality, or fractal. Our model is deterministic and relies on the existence of a structured cross section, either fibrous or layered. This success at explaining the power-law behavior supports the proposal that geometry is sometimes more important than mechanics. PACS numbers: 62.20.mt, 91.30.Px, 43.50.+y Fracture[1] is a complex phenomenon with many interesting properties, such as crack propagation[2], breakdown [3], and self-affine fractals in the crack surface morphology [4]. This kind of studies started in seismology and attracted the attention of physicists and material scientists. Crackling noise [5,6] in the acoustic emission from fracturing wood plate [7], paper [8,9], rock[10], concrete [11], and charcoal [12] has been found to exhibit similar statistical properties as earthquake [13,14]. On the other hand, the slow growth of a single crack in a fibrous sheet has been studied by the lattice model [9] which incorporates thermodynamics to describe the temperature dependence. To understand the failure process, the fiber bundle model [15] has also been extended [16] by introducing time-dependent damage accumulation of fibers to capture the stochastic nature of fracture.In contrast to 2-and 3-D samples in previous fracture experiments, we shall adopt the 1-D like chopstick because it rarely fractures in multiple places at the same time, which makes the interpretation of data easier. Chopsticks are easily accessible because they are indispensable implements for most Asian families and carry special cultural meanings [17] in Chinese tradition. They are usually made by bamboo in Taiwan and China. Bamboo exhibits a fibrous cross section. Its excellent compressive strength, endowed from the vascular bundles scattered throughout the stem in the cross section instead of in a cylindrical arrangement, enables us to collect about 400 crackling sounds from breaking one chopstick, as opposed to just one sound from a chalk or twig.Our main sample is the cheap and omnipresent bamboo chopstick of diameter 0.67cm and length 20.5cm. Sticks are also taken directly from the bamboo tree to make sure our conclusions are independent of the length, freshness, and processing to turn them into chopsticks. A bundle of spaghetti [18] is also used to check the generality of our model because it shares similar cross section as bamboo (see Fig.1). The fracture machine in Fig.2 is placed inside a soundproof chamber with foam rubber plank on the interior to avoid echo. A Sony ECM166BC microphone that is connected to a Sony ICD-PX333 recorder picks up fracture sound. By tight- ening the screw, the mov...

Non-trivial avalanches triggered by shear banding in compression of metallic glass foams

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Collapsing minerals: Crackling noise of sandstone and coal, and the predictability of mining accidents

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Avalanches and force drops in displacement-driven compression of porous glasses

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