A new non-destructive evaluation technique to detect cracks emanating from the inner surface (inner cracks) of a high-pressure hydrogen storage cylinder was developed by means of mechanoluminescence (ML) sensor consisting of SrAl 2 O 4 :EuML material and epoxy resin. To visualize the inner crack,a sheet ML sensor was attached onto the outer surface of the storage cylinder subjected to hydraulic pressure cycling with the maximum pressure of 45 MPa. The ML pattern was changed with an increase in the cycle number and the ML sensor could visualize the inner crack. The stress analysis by the finite element method clarified that the ML sensor provided unique equivalent strain distribution associated with stress concentration at the crack tip, i.e. the distance between two points having high equivalent strains was inversely proportional to the crack depth;consequently, the growth behavior of the inner crack was non-destructively quantified with the ML sensor attached on the outer surface.

We have found that phosphorescence intensity of CaZnOS:Cu decreased visibly under an applied load. This mechanical quenching (MQ) of phosphorescence in CaZnOS:Cu corresponded to the mechanical stimuli. We have thus demonstrated that the MQ of CaZnOS:Cu could be used for visualizing stress distributions in practical applications. We propose that MQ arises from non-radiative recombination due to electron-transfer from trap levels to non-radiative centers as a result of the mechanical load.

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Here, a mechanoluminescence-assisted double cantilever beam (DCB) test was proposed and its effectiveness was demonstrated. Based on mechanoluminescence, a crack tip was clearly distinguished and successfully tracked during crack propagation and delamination in the DCB test, which helped overcome the difficulty associated with the conventional DCB test. The crack length could be easily determined and used to evaluate the fracture toughness. In addition, mechanoluminescence sensing using the top image of the DCB specimen provided valuable information on the fracture and adhesive frontline to determine the distribution of fracture toughness and adhesive strength under the surface treatment and adhesion curing conditions in the DCB test.

In this study, we investigated a behavior of cuprous ion (denoted as Cu(I)) in the copper sulfate plating solution and effects of the Cu(I) on a quality of Cu plating film. Through spectroscopic method, two kinds of holding structure of Cu(I) in the plating solution were firstly indicated by analyzing the kinetics of complex forming reaction between the Cu (I) and bathocuproinedisulfonic acid, disodium salt (BCS). One component is ignited from Cu(I) probably incorporated into deep inside of polyethylene glycol (PEG), and the Cu(I) must have steric hindrance of PEG to be interacted with the BCS in plating solution. Another one is a component for Cu(I) which can be instantaneously reacts to the BCS to be complex. In addition, interestingly, it has been shown that instantaneous component is affecting the roughness of Cu plating film. These results indicate that spectroscopic measurement and analysis is effective for the management and evaluation of the plating solution for high quality production.