0000000000044281
AUTHOR
C. Cosenza
Controllo per il rilievo di difetti con tecnica ad ultrasuoni laser
Damage and fracture study of cold extrusion dies
Abstract In the present paper die fracture in cold extrusion was investigated considering a few different die reduction zone geometries. A former finite element method (FEM) analysis of the process was developed to obtain the contact pressure distribution at the workpiece–die interface for each of the investigated geometries; subsequently a stress and strain analysis utilizing the BEM code Franc3D was carried out, with the aim to evaluate the crack propagation at each loading cycle, i.e. at each extrusion process. In this way the die life for each of the investigated extrusion die geometries was compared utilizing the Paris law and the values assumed by the stress concentration coefficient …
Non-contact ultrasonic inspection of skin/core bond in honeycomb with lamb waves
The assessment of skin/core bond in honeycomb samples was carried out by a bistatic ultrasonic non-contact system. Lamb waves were generated by a Nd:YAG pulsed laser and detected by an air-coupled capacitance transducer located in pitch-catch configuration. Periodically spaced line sources, generated on the sample surface using a four element lenticular array, allowed generation of narrow-band directional Lamb waves. Changes in amplitude of the transmitted signal permitted detection of skin/core disbonds.
Experimental analysis of a continuously operated reverse electrodialysis unit fed with wastewaters
Reverse Electrodialysis (RED) is one of the most promising technologies to convert salinity gradient chemical energy into electricity. RED units are traditionally operated with natural streams as river water and seawater thereby limiting the spread of the technology in sites far from coastal areas. Aim of the present work is that of exploring and expanding feed possibilities for RED systems by employing waste streams. Thus, an experimental study was performed by testing, for the first time, a Reverse Electrodialysis (RED) unit fed with a high salinity wastewater originated in a fish canning factory, and a low salinity wastewater from a sewage treatment plant. Uninterrupted, long duration ex…
laser-based ultrasonic rail flaw inspection prototype: system overview and status
Generation of narrowband antisymmetric lamb waves using a formed laser source in the ablative regime
A formed laser source, using a four-element lenticular array, is used in the ablative regime to generate select, narrowband, acoustic plate waves. The arrangement of the array produces acoustical signals that have frequencies compatible with the response of the broadband capacitive air-coupled transducer used in this study. A simplified concept is presented to explain the effect of a line array source on the frequency content of acoustic waves. The analytical model for a point pulse surface displacement is derived from the point load solution to Lamb's problem. The point pulse displacement elements of a line array source are summed mathematically, taking into account all applicable propagat…