The paper presents the microscopic and mechanoacoustic study of degradation processes of the porcelain material C 130 type.
This kind of material is used in the production of the most durable and reliable electrotechnical elements. Raw material composition of the studied porcelain was modified. This had an impact on the inner properties, cohesion and – in consequence – on operational properties of the material.
Using mechanical-acoustic and microscopic methods of testing of small-size samples that were subjected to compression, it was possible to distinguish successive stages of degradation of the porcelain structure. These stages were generally typical of the porcelain materials. In the authors’ opinion, they are connected to the ageing process happening over many years of work under operating conditions.
Optimization of composition and technological properties – important during technological processes – resulted in a slight decrease in inner cohesion of the porcelain. When compared to the reference material – typical domestic C 130 material, mechanical strength was somewhat lower. Carried out investigations proved that resistance of the investigated material to the ageing degradation process – during long term operation – also decreased. The improvement of technological parameters and the reduction in the number of defective elements occurred simultaneously with some decrease in the operational parameters of the material. To restore their initial high level, further work is needed to optimize the raw material composition of the porcelain.
Safety and reliability are primary concerns in launch vehicle performance due to the involved costs and risk. Pressure vessels are one of the significant subsystems of launch vehicles. In order to have minimal weight, high strength material viz. maraging steel M250 grade is used in realizing the pressure vessel casing hardware. Despite the best efforts in design methodology, quality evaluation in production and effective structural integrity assessment is still a farfetched goal. The evolution of such a system requires, first, identification of an appropriate technique and next its adoption to meet the challenges posed by advanced materials like maraging steels. In fact, a quick survey of the available Non-Destructive Evaluation (NDE) techniques suggests Acoustic Emission (AE) as an effective structural integrity assessment tool capable of identifying any impending failure or degradation at an earlier stage. Experience shows that the longitudinal welds in the pressure vessels are quite vulnerable to failure due to the fact that they experience the maximum stress (i.e. hoop stress). Loading welded tensile samples are quite synonymous to the hoop stress experienced by longitudinal welds. An attempt is made to compare the Acoustic Emission data acquired during tensile deformation of maraging steel welded specimens. A total of 16 welded specimen’s with known defects were studied for their tensile behaviour is in connection with Acoustic Emission data. The lowest failure load was 70.5 kN and the highest being 84.8 kN. AE activity graphs viz. cumulative AE activity, hit rate, energy rate, count rate, AE amplitude history, AE count history, AE energy history, amplitude-count correlation and hit amplitude distribution have been investigated and salient features with respect to the data have been critically studied and relevant correlations are arrived at.