NONDESTRUCTIVE TESTING USING ROTATIONAL AE SENSORS

Authors: Liu, Cheng Kung; Latona, Nicholas - Nick; Dimaio, Gary; GODINEZ, VALERY - PHYSICAL ACOUSTICS CORP; FINLAYSON, RICHARD - PHYSICAL ACOUSTICS CORP; HANSON, MARJORIE - SETON COMPANY

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2005
Publication Date: 11/10/2005
Citation: Liu, C., Latona, N.P., Dimaio, G.L., Godinez, V., Finlayson, R.D., Hanson, M. 2005. Nondestructive testing using rotational ae sensors. Journal of American Leather Chemists Association. 100(11):438-446.

Interpretive Summary: The current test method for measuring the mechanical properties of leather is a destructive process, wherein a sample has to be cut out of the leather. Besides being very time-consuming, these destructive tests are wasteful of leather. Therefore, there is a great incentive to develop a nondestructive test that will save time and materials. Under a cooperative R&D agreement, we have developed an automated on-line nondestructive acoustic emission (AE) testing method that uses a rotational sensor. This novel sensor allows dynamic measurements that cannot be made by traditional static sensors. This research showed that the softness, grain wrinkle patterns and mechanical strength of leather could be measured nondestructively. The significance of this finding is profound, especially as a quality control/quality assurance method for manufacturing and the potential for becoming a standard testing method. This cooperative R&D effort will hopefully produce an on-line AE instrument, providing the industry with a nondestructive device for monitoring the quality of product at each intermediate leather-making stage without damaging the leather.

Technical Abstract: At the present time, testing the mechanical properties of leather is a destructive process, wherein cutouts are taken off the tannery floor for mechanical testing. Under a cooperative R&D agreement (CRADA), we recently investigated the feasibility of using the acoustic emission (AE) technique to dynamically and nondestructively measure the mechanical properties of leather. The long-range goal of this collaborative effort is the production of an AE instrument, which will provide the leather industry with a nondestructive way in which to monitor the quality of leather at each of the leather-making stages. In this investigation, a rotational acoustic sensor was rolled across the leather samples to collect their AE quantities such as waveforms, frequency, hits, counts and energy. The software AE-Win was utilized to capture and record the data, and the neural network software 'NOESIS' was subsequently used for data analysis. Observations showed an excellent correlation between the softness of leather and the corresponding cumulative acoustic counts. We also used this dynamic method to characterize the grain break of leather. Results showed that the difference in grain break could be determined from the amount of acoustic energy collected from moving the AE sensor over a leather sample laid inside a half pipe. The grain break decreased as the AE energy increased. The higher AE energy is an indication of stiffer leather; therefore, the results revealed that stiffer leather is prone to bad grain break. Data also demonstrated that thicker samples tended to have poorer grain break. We derived a predictive model that could be very useful for nondestructively testing grain break using the AE method described in this report. Results also showed a close relationship between the tensile strength and AE energy or duration obtained from testing. In short, this study demonstrated that the softness, tensile strength and grain break could be nondestructively determined by measuring the acoustic quantities with a rotational sensor rolling over the leather.