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.

An investigation of the failure process of maraging steel grade X3NiCoTi18-9-5 produced by the SLM method that is subjected to various three-dimensional stress-states has been carried out. In this paper, deformations and damage evolution are analysed experimentally and numerically. Three microstructures of the SLM steel were obtained after the appropriate heat treatment. Tensile tests of smooth specimens and axisymmetric notched specimens have been performed. Numerical models of the samples with ring notches were made in order to determine the stress state and displacement field in the notch area at the moment of the sample’s breakage as well as to compare the experimentally determined effective strain in the notch after the sample’s breakage with the deformation being calculated on the basis of the numerical solution. As a result of the research, it was found that the type of fracture of samples obtained from X3NiCoTi18-9-5 steel powder by the SLM method depends on the size of the ring notch’s radius. Based on the performed numerical calculations and experimental tests, it was found that, for each of the analysed variants of heat treatment, it was possible to indicate the approximate limit value of triaxiality factor T_f, above which there is a scrap of brittle X3NiCoTi18-9-5 steel produced by the SLM method. This value is determined by the characteristic bending of the function that determines the relationship between triaxiality factor T_f and effective strain e_eff.