Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Numerical Simulations of Canted Nozzle and Scarfed Nozzle Flow Fields

Abstract: Computational fluid dynamics (CFD) techniques are used for the analysis of issues concerning non-conventional (canted and scarfed) nozzle flow fields. Numerical simulations are carried out for the quality of flow in terms of axisymmetric nature at the inlet of canted nozzles of a rocket motor. Two different nozzle geometries are examined. The analysis of these simulation results shows that the flow field at the entry of the nozzles is non axisymmetric at the start of the motor. With time this asymmetry diminishes, also the flow becomes symmetric before the nozzle throat, indicating no misalignment of thrust vector with the nozzle axis. The qualitative flow fields at the inlet of the nozzles are used in selecting the geometry with lesser flow asymmetry. Further CFD methodology is used to analyse flow field of a scarfed nozzle for the evaluation of thrust developed and its direction. This work demonstrates the capability of the CFD based methods for the nozzle analysis problems which were earlier solved only approximately by making simplifying assumptions and semi empirical methods.

Nondestructive Testing Method for Finding out the Defects in a Composite Liner

Abstract: A composite liner of carbon phenolic has been inspected by ultrasonic, X-ray radiography andX-ray computed tomography (CT) to find defects like delaminations, debonds, voids, foreign inclusions, etc.The geometry, detection of multiple defects and porosity of the liner make ultrasonic testing (pulse-echo anddrycoupling) difficult for inspection. X-ray radiography being a non-contact technique finds multiple defectsbut compresses the structural information of 3-D volume into a 2-D image and interferes with overlyingand underlying areas of the object. X-ray CT generates an image of a thin and cross-sectional slice ofan object. R e linear attenuation coefficients in terms of Hounsfield values have been measured, comparedand correlated with CT images at the contrasts observed. 3-D images can be generated by stacking2-D cross-sectional images of the slices. These 3-D images can be cut at any angle of choice for mappingthe extent of delaminated/debonded areas. This type of information is difficult to obtain with conventionalnon-destructive testing techniques.

Environment-Induced Degradation in Maraging Steel Grade 18Ni1700

Abstract: A high degree of cold working is involved in forming C18Ni1700 maraging steel into products such as flow formed tubes. After the standard aging treatment of 3.5 h at 480 °C, such heavily deformed material acquires a very high strength level with relatively low value of ductility. Such high strength condition, it is apprehended, is also associated with poor resistance to environment-induced degradation. Efforts were made to modify the aging treatment of cold worked C18Ni1700 to arrive at better strength-ductility combination, while still meeting AMS 6520 requirements, and reduced susceptibility to environment-induced damage. The results were found to be encouraging. In addition to normal tensile testing, slow strain rate testing was carried out to assess the susceptibility of the material to environment-induced degradation after different aging treatments. Distinctly lower ductility values were obtained when tested at lower strain rate, strongly suggesting that the material is prone to hydrogen induced damage. Potentiodynamic testing revealed that increasing the aging temperature resulted in major reduction in corrosion rate. Increasing both aging temperature and time resulted in formation of substantial amount of austenite, having an adverse effect on the corrosion rate.