6th Youth Symposium on Experimental Solid Mechanics May, 9-12 2007 Vrnjaka Banja, Serbia A. 1. 1 DESIGN OF AN HEEL TESTING MACHINE FOR IMPACT AND IMPACT FATIGUE LOADING C. Fragassa, V. Pezzotta, G. Minak * * DIEM, Alma Mater Studiorum – Università di Bologna, Italia, e-mail: giangiacomo.minak@unibo.it ABSTRACT Experimental test methods for the evaluation of the resistance of heels of ladies’ shoes in impact and impact fatigue loading are well-defined by ISO standard procedures that indicate all the conditions of experiment. A first Standard specifies the test method for determining the impact strength of the heels [1]. The result provides an assessment of the liability to failure under the occasional heavy blows. A second Standard [2] specifies a test method for determining the ability of heels of ladies’ shoes to withstand the repeated small impacts provoked by normal walking. These Standards strictly define the features for two different devices (with specific materials, geometries, weights, etc.) and all the experimental procedures to be followed during the tests. This paper describes the technical solutions used to design one single experimental machine able to perform impact testing of heels in both conditions. Joining the accuracy of mechanic movements with the speed of an electronic control system, a new and versatile equipment for the complete experimental characterization of heels was developed. KEY WORDS: Impact test, Characterization, Heels, Shoe 1. INTRODUCTION An equipment for the complete evaluation of the resistance of heels of ladies’ shoes for single impact and impact fatigue according to ISO standard procedures is proposed. Technical solutions were adopted to design a single experimental equipment able to perform on heels two different genres of tests: - a single strong impact provoked by an individual knock - the repeated small impacts provoked by normal walking. FEM analysis of the heel under static and dynamic loads joined with an experimental acquisition of stress curve during normal use of the shoes (ex. walking, climbing stairs, etc.) supported the design phase. 2. APPLICABLE STANDARDS The design was realized according to ISO standard procedures that indicate all the testing conditions for experiments on heels of shoes and that strictly define all the main characteristics (geometries, materials, etc.) for the equipments. In particular: 1. ISO 19953 [1] describes the lateral impact tester as an apparatus that includes:  Pendulum, consisting in a circular steel bob fixed by a circular steel shaft to a hub, on the bearing axle. The moment of the pendulum when it is held horizontally is (17,3 ± 0,2) N·m.  Striker head, consisting of a strip of metal with a rounded striking edge. The head is fixed rigidly to the pendulum bob so that the striker tip and centre of the bob lie on the same circle of swing of the pendulum. Energy scale for the pendulum, calibrated in increment of 0,68 J, from 0 J to 18,3 J. A marker attached to the pendulum moves over this scale and enables the pendulum to be set up to the desired impact energy.  Base clamp, for holding the metal mounting tray and for adjusting it vertically and horizontally to achieve correct alignment of the heel tip.