State of art of impact tensile test (ITT): Its historical development as a simulated crash test of industrial materials and presentation of new 'ductile/brittle' transition diagrams

摘要

The purpose of the Charpy test is to determine the impact resistance of materials. It makes it possible to measure their impact strength. It consists of breaking a standard notched bar using a pendulum hammer. The notch can take various forms: out of U or, generally, out of V. The power consumption to break the bar is measured by making the difference between the drop height of the hammer and that to which it goes up after having broken the bar. If this last were completely brittle, the hammer would go up with the same height as that from where it fell. If it were on the contrary extremely tough, it would not be broken and the pendulum would not go up at all. The fracture energy thus determined is called impact strength. More it is raised, more the material is tough. Today, this test is identified by measuring of the impact force in accordance with ISO 148-1 and largely used for industrial materials. However, with technological evolution of industrial materials used in manufacturing engineering, other test methods have been developed, in time and complexity, to characterise particularly thin sheet welded pieces (tailored blanks) used in automotive industry. However, one may see a little development in this domain for thin plates regarding to thick plates. This paper reports the early history of instrumented impact testing, started from Augustin Georges Albert CHARPY (1865-1945) up to now, and gives a comparative study on the recent results of experiments obtained on the different welded steel grades by means of the new developed machine called impact tensile crash test or simulated crash test and presents of new "ductile/brittle" transition diagrams concerning different welding techniques. This concerns dynamic testing of the welded pieces used in automotive industry.