Methods for assessing the cushioning performance of free-stall dairy cow synthetic beds

Tierney, G. and Thomson, R.D. (2003) Methods for assessing the cushioning performance of free-stall dairy cow synthetic beds. Transactions of the ASAE, 46(1), pp. 147-153.

Abstract

Cushioning in dairy cow synthetic bed materials is quantifiable in terms of compression force attenuation and stability, but animal observation trials aimed at finding the best materials are expensive and time-consuming. Finite element analysis (FEA) is a computational technique used for engineering stress and deformation analysis. Accelerometric testing is used in sports engineering to test the cushioning offered by athletics tracks and synthetic sports surfaces. In the. current work, these two methods were used to study the cushioning performance of two of the most commonly used types of free-stall or cubicle synthetic bed, rubber-crumb mattresses and ethylene vinyl acetate (EVA) mats, both of which are classified in engineering terms as hyperfoams. That is, materials that can undergo large deformations under load and yet return to their original shape on unloading. FEA was used, in conjunction with quasi-static compression force tests, to assess free-stall bed cushioning during the getting-up movement of a cow (a quasi-static "push") and to predict, in a quick and cost-effective way; variation in performance in time or as a result of an altered bed specification. The force-deflection responses of the materials of the two bed types were closely matched in the ABAQUS FE code, giving confidence in the ability of the model to predict the effect of changes in, for example, bed thickness and density. Accelerometric testing was used for the assessment of two further performance criteria vital to a bed purchase decision: first, the impact absorption performance during. the lying down: movement of a cow (a dynamic "drop"), and second, variation in cushioning performance over time as a result of the bed being used by a herd for three years. The quasi-static testing and FEA showed that a new rubber-crumb bed was more compliant than a new EVA bed and would therefore be more likely to prevent knee pain during the getting-up movement. The peak acceleration results showed that the new-condition rubber-crumb bed cushioned a cow knee impact force from a lying down movement best. However, the test of the three-year-old rubber crumb bed showed it to be less compliant compared to the new condition (p lt 0.001). The EVA bed peak acceleration results also showed cushioning performance to be poorer after three years of use (p = 0.007), although the data showed a less stark-change compared to that for the rubber-crumb beds. The observed use-related reduction in cushioning performance of the rubber-crumb bed was simulated in ABAQUS by reducing the model thickness by 50% and looking at the force-deflection response.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Thomson, Dr Ronald
• Authors: Tierney, G., and Thomson, R.D.
• Subjects: S Agriculture > SF Animal culture
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: Transactions of the ASAE
• ISSN: 0001-2351