Abstract
We designed a high-pressure chamber that can sustain up to 1500 PSI, to study the crumpling process of a thin sheet under an ambient pressure. Special attention is devoted to the following four aspects: (1) having confirmed the power-law behavior in our previous efforts, we study the mechanical response of the thin sheet in the so-called jammed region, where the power-law behavior ceases. Upon the application of our highest pressure 1500 PSI, we confirm the internal structure of HDPE is polycrystalline instead of a single crystal. (2) We use a precrumpled or shredded sheet as the sample. Part of our motivation is to study (a) how these conditions affect the power-law behavior, (b) determine the percentage of work into the ridge formation. (3) Study the properties of crackling noises generated during the crumpling process. We confirm that the probability and energy of the noises obey the power-law relation. However, when the samples are preprocessed as in (2), the noises deviate from such a simple universal behavior. (4) A simple model is proposed to explain why the exponent of the power-law relation is sample-dependent, as opposed to the predictions of existing computer simulations..