Unraveling the simultaneous shock magnetization and demagnetization of rocks

International audienceIn the natural case of an hypervelocity impact on a planetary or asteroidal surface, two competing phenomena occur: partial or complete shock demagnetization of pre-existing remanence and acquisition of shock remanent magnetization (SRM). In this paper, to better understand the effects of shock on the magnetic history of rocks, we simulate this natural case through laser shock experiments in controlled magnetic field. As previously shown, SRM is strictly proportional to the ambient field at the time of impact and parallel to the ambient field. Moreover, there is no directional or intensity heterogeneity of the SRM down to the scale of ∼0.2mm. We also show that the intensity of SRM is independent of the initial remanence state of the rock. Shock demagnetization and magnetization appear to be distinct phenomena that do not necessarily affect identical populations of grains. As such, shock demagnetization is not a limiting case of shock magnetization in zero field

LAser Shock Adhesion Test (LASAT), an innovation dedicated to industry

NonWOSAvailable online for free at http://www.ila.org.in/kiran/kiran_19_2.pdfInternational audienc

Laser Shock Adhesion Test (LASAT) of electron beam physical vapor deposited thermal barrier coatings (EB-PVD TBCs)

International audienceDamage prediction, adhesion strength and remaining lifetime of TBC are highly important data for understanding and preventing TBC spallation on blades. LAser Shock Adhesion Test (LASAT) is a powerful method to measure adhesion of coating due to its rapidity, simplicity and capabilities to distinguish different strength levels and the easy damage observation in case of TBCs. A new protocol of LASAT has been introduced in order to measure the adhesion level of the ceramic coating from the exploitation of the two-dimensional effects that promotes a shock wave pressure-dependent size of the damage. Finite element modeling, taking into account the TBCs dimensions, showed the edges effect on interfacial stress applied by laser shock

Adhesive Bond Testing By Laser Induced Shock Waves

Peer reviewed: YesNRC publication: Ye

Study of plant fibre composites with damage induced by laser and mechanical impacts

Polymer composite materials provide good strength to weight ratio and tailored mechanical properties thanks to the reinforcing fibres. Until recently, the need for taking into account the whole life cycle of a composite structure was neglected and only the service aspects were important. Today, the designers of a new composite structure have to take into account the environmental aspects from the sustainability of raw materials to the management of end life products. There are recycling issues related to the most popular composites. A solution for the recycling issue can be sought in green composites with reinforcing fibre originating from plants. The behaviour of eco-composites, when subjected to laser or mechanical impact loadings, is not well known yet. Short fibre composites were made with spruce fibres. Another set of samples was made of flax fibres. Also a woven hemp fabric-based eco-composite was investigated. A fully synthetic woven composite was used for comparison with green composites. Mechanical impacts were performed by means of a falling dart impact testing machine. Laser impacts were made with high power laser source. Four assessment techniques were employed in order to analyse and compare impact damage. Damage detection thresholds for each material and technique were obtained

Diversity and Functional Traits of Lichens in Ultramafic Areas: A Literature Based Worldwide Analysis Integrated by Field Data at the Regional Scale

While higher plant communities found on ultramafics are known to display peculiar characteristics, the distinguishability of any peculiarity in lichen communities is still a matter of contention. Other biotic or abiotic factors, rather than substrate chemistry, may contribute to differences in species composition reported for lichens on adjacent ultramafic and non-ultramafic areas. This work examines the lichen biota of ultramafics, at global and regional scales, with reference to species-specific functional traits. An updated world list of lichens on ultramafic substrates was analyzed to verify potential relationships between diversity and functional traits of lichens in different Köppen–Geiger climate zones. Moreover, a survey of diversity and functional traits in saxicolous communities on ultramafic and non-ultramafic substrates was conducted in Valle d’Aosta (North-West Italy) to verify whether a relationship can be detected between substrate and functional traits that cannot be explained by other environmental factors related to altitude. Analyses (unweighted pair group mean average clustering, canonical correspondence analysis, similarity-difference-replacement simplex approach) of global lichen diversity on ultramafic substrates (2314 reports of 881 taxa from 43 areas) displayed a zonal species distribution in different climate zones rather than an azonal distribution driven by the shared substrate. Accordingly, variations in the frequency of functional attributes reflected reported adaptations to the climate conditions of the different geographic areas. At the regional scale, higher similarity and lower species replacement were detected at each altitude, independent from the substrate, suggesting that altitude-related climate factors prevail over putative substrate–factors in driving community assemblages. In conclusion, data do not reveal peculiarities in lichen diversity or the frequency of functional traits in ultramafic areas