SHOTVISUAL: A Software to Visualize Shot Dynamics

Author:  E. Guyot, E. Rouhaud, M. Micoulaut, Y. Colaitis
Source:  ICSP-13
Doc ID:  2017085
Year of Publication:  2017
Introduction: Cold working processes such as mechanical pre-stressing treatments are widely used in automobile, aeronautic and biomedical industries, and lead to a substantial improvement of mechanical parts and structures. A rather conventional method is shot peening, air blast or ultrasonic [1]-[4], which uses projected spherical media in order to create surface compressive residual stresses. The impact produces surface hardening which protects the structure from fracture as fatigue cracks propagates mostly from surfaces during operation. The gain in strength and fatigue life observed after such a treatment can be spectacular while offering the advantage of being relatively easy to perform technically. However, the relationship between the operating conditions (chamber and part geometry, shot weight,…) and the impact properties (velocity, coverage, impact angle,…) is partially if not entirely unknown. The situation becomes even worse for the case of ultrasonic shot peening in which the spheres are propelled by an ultrasonic vibrating wall (a sonotrode), and bounce around in a blind peening chamber [5]-[6]. While the determination of the velocity of a single steel sphere bouncing on a plate is relatively straightforward, the description of a collection of spheres needs, indeed, an adapted framework typical of many body problems. The absence of such operating parameter/impact property relationships is clearly a major drawback of the technology since such impacts must obviously affect the targeted mechanical properties, and might influence the design of adapted peening chambers. Therefore, in order to make additional progress and bring the technology to the next level, there is need to understand how shot behaves collectively inside the peening chamber, and how it is influenced by the operating parameters. In addition, a direct visualization of the shot could provide an interesting added value to the problem posed because one might be able to detect the dynamics of the shot with time. This might lead to an increased rationale for the choice of process parameters given that most of them remain largely empirical at this stage, making it costly, time consuming and only partially optimized, the situation being also more problematic when complex industrial parts are to be considered.

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