Relationships between tensile and fracture mechanics properties and fatigue properties of large plastic mold steel

presentazione oral

Relationships between tensile and fracture mechanics properties and fatigue properties of large plastic mold steel

presentazione oral

Heat treatment and failure risk of large automotive plastic molds: a fracture mechanics approach and property assessment

Molds for plastic automotive components such as bumpers and dashboards are usually machinedfrom large pre-hardened steel blocks. Due to the dimension of the blooms, the heat treatment producesmixed microstructures, continuously varying with the distance from the quenched surface,at which fracture toughnesses lower than those appropriate for a fully quenched and temperedmetallurgical condition are usually associated. Furthermore, final fabrication machining exposes, in partof the mold's surface, the steel that was at heart during both ingot casting and bloom heat treatment.The response of the mold to defects (for example, microcracks from weld bed deposition) or events(for example, incomplete formed plastic object extraction) that can conceivably cause failureduring service (and in a few cases actually did), depends on the steel properties, that in turn dependupon the heat treatment and the microstructure. A pointwise survey of the mechanical properties of somecommercial blooms, actually used to machine bumper molds, has shown usual and expected valuesof hardness and of tensile properties, but, indeed, a low range of fracture toughness, suggestingthat the latter is a critical characteristic of this steel and that fracture mechanics verifications,already usual in other fields of industry, should dutifully be applied to the molds' design.The relationship between the mechanical properties, the morphology of the fracture surfacesand the microstructure has been also investigated

Advanced high-strength steels for car-body manufacturing

Presentazione oral

Belle II Vertex Detector Performance

The Belle II experiment at the SuperKEKB accelerator (KEK, Tsukuba, Japan) collected its first e+e− collision data in the spring 2019. The aim of accumulating a 50 times larger data sample than Belle at KEKB, a first generation B-Factory, presents substantial challenges to both the collider and the detector, requiring not only state-of-the-art hardware, but also modern software algorithms for tracking and alignment. The broad physics program requires excellent performance of the vertex detector, which is composed of two layers of DEPFET pixels and four layers of double sided-strip sensors. In this contribution, an overview of the vertex detector of Belle II and our methods to ensure its optimal performance, are described, and the first results and experiences from the first physics run are presented