Maraging steel (250) and 13-8 Mo stainless steel plates were joined by gas tungsten constricted arc welding(GTCAW) process in similar and dissimilar metal combinations using 13-8 Mo stainless steel filler wire. The si...Maraging steel (250) and 13-8 Mo stainless steel plates were joined by gas tungsten constricted arc welding(GTCAW) process in similar and dissimilar metal combinations using 13-8 Mo stainless steel filler wire. The similar and dissimilar metal welds made in solutionized condition were subjected to standard post weld hardening treatments direct ageing at 485 ℃, soaking for 31/2 hours followed by air cooling(ageing treatment of maraging steel) and direct ageing at 510 ℃, soaking for 4 h followed by air cooling(ageing treatment of 13-8 Mo stainless steel). The joint characterization studies include microstructure examination, microhardness survey across the weldments and transverse weld tensile test.Similar and dissimilar metal weldments responded to both the post weld ageing treatment. After post weld aging, increase in yield strength, UTS and slight reduction in % elongation of similar and dissimilar metal were observed. The observed tensile properties were correlated with microstructure and hardness distribution across the welds.展开更多
Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the...Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the load bearing capability of a weld joint, which in-turn decides the performance in real time service conditions. The present study introduces a novel approach of detecting a relationship between weld bead geometry and mechanical properties(e.g. tensile load) for the purpose of catering the best the process could offer. The significance of the proposed approach is demonstrated by a case of dissimilar aluminium alloy(AA2219 and AA5083) electron beam welds. A mathematical model of tensile braking load as a function of geometrical attributes of weld bead geometry is presented. The results of investigation suggests the effective thickness of weld-a geometric parameter of weld bead has the most significant influence on tensile breaking load of dissimilar weld joint. The observations on bead geometry and the mechanical properties(microhardness, ultimate tensile load and face bend angle) are correlated with detailed metallurgical analysis. The fusion zone of dissimilar electron beam weld has finer grain size with a moderate evaporation and segregation of alloying elements magnesium and copper respectively.The mechanical properties of weld joint are controlled by optimum bead geometry and HAZ softening in weaker AA5083 Al alloy.展开更多
The influence of different welding processes on the mechanical properties and the corresponding variation in the microstructural features have been investigated for the dissimilar weldments of 18% Ni maraging steel 25...The influence of different welding processes on the mechanical properties and the corresponding variation in the microstructural features have been investigated for the dissimilar weldments of 18% Ni maraging steel 250 and AISI 4130 steel. The weld joints are realized through two different fusion welding processes, tungsten inert arc welding(TIG) and laser beam welding(LBW), in this study. The dissimilar steel welds were characterized through optical microstructures, microhardness survey across the weldment and evaluation of tensile properties. The fiber laser beam welds have demonstrated superior mechanical properties and reduced heat affected zone as compared to the TIG weldments.展开更多
Sustained combustion and optimization of combustor are the two challenges being faced by combustion scientists working in the area of supersonic combustion.Thorough mixing,lower stagnation pressure losses,positive thr...Sustained combustion and optimization of combustor are the two challenges being faced by combustion scientists working in the area of supersonic combustion.Thorough mixing,lower stagnation pressure losses,positive thrust and sustained combustion are the key issues in the field of supersonic combustion.Special fluid mechanism is required to achieve good mixing.To induce such mechanisms in supersonic inflows,the fuel injectors should be critically shaped incurring less flow losses.Present investigations are focused on the effect of fuel injection scheme on a model scramjet combustor performance.Ramps at supersonic flow generate axial vortices that help in macro-mixing of fuel with air.Interaction of shocks generated by ramps with the fuel stream generates boro-clinic torque at the air&liquid fuel interface,enhancing micro-mixing.Recirculation zones present in cavities increase the residence time of the combustible mixture.Making use of the advantageous features of both,a ramp-cavity combustor is designed.The combustor has two sections.First,constant height section consists of a backward facing step followed by ramps and cavities on both the top and bottom walls.The ramps are located alternately on top and bottom walls.The complete combustor width is utilized for the cavities.The second section of the combustor is diverging area section.This is provided to avoid thermal choking.In the present work gaseous hydrogen is considered as fuel.This study was mainly focused on the mixing different fuel injection locations.It was found that injecting fuel upstream of the ramp was beneficial from fuel spread point of view.展开更多
基金Financial assistance from Defence Research and Development Organisation
文摘Maraging steel (250) and 13-8 Mo stainless steel plates were joined by gas tungsten constricted arc welding(GTCAW) process in similar and dissimilar metal combinations using 13-8 Mo stainless steel filler wire. The similar and dissimilar metal welds made in solutionized condition were subjected to standard post weld hardening treatments direct ageing at 485 ℃, soaking for 31/2 hours followed by air cooling(ageing treatment of maraging steel) and direct ageing at 510 ℃, soaking for 4 h followed by air cooling(ageing treatment of 13-8 Mo stainless steel). The joint characterization studies include microstructure examination, microhardness survey across the weldments and transverse weld tensile test.Similar and dissimilar metal weldments responded to both the post weld ageing treatment. After post weld aging, increase in yield strength, UTS and slight reduction in % elongation of similar and dissimilar metal were observed. The observed tensile properties were correlated with microstructure and hardness distribution across the welds.
基金financial support from Defence Research and Development Organisation(DRDO)
文摘Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the load bearing capability of a weld joint, which in-turn decides the performance in real time service conditions. The present study introduces a novel approach of detecting a relationship between weld bead geometry and mechanical properties(e.g. tensile load) for the purpose of catering the best the process could offer. The significance of the proposed approach is demonstrated by a case of dissimilar aluminium alloy(AA2219 and AA5083) electron beam welds. A mathematical model of tensile braking load as a function of geometrical attributes of weld bead geometry is presented. The results of investigation suggests the effective thickness of weld-a geometric parameter of weld bead has the most significant influence on tensile breaking load of dissimilar weld joint. The observations on bead geometry and the mechanical properties(microhardness, ultimate tensile load and face bend angle) are correlated with detailed metallurgical analysis. The fusion zone of dissimilar electron beam weld has finer grain size with a moderate evaporation and segregation of alloying elements magnesium and copper respectively.The mechanical properties of weld joint are controlled by optimum bead geometry and HAZ softening in weaker AA5083 Al alloy.
文摘The influence of different welding processes on the mechanical properties and the corresponding variation in the microstructural features have been investigated for the dissimilar weldments of 18% Ni maraging steel 250 and AISI 4130 steel. The weld joints are realized through two different fusion welding processes, tungsten inert arc welding(TIG) and laser beam welding(LBW), in this study. The dissimilar steel welds were characterized through optical microstructures, microhardness survey across the weldment and evaluation of tensile properties. The fiber laser beam welds have demonstrated superior mechanical properties and reduced heat affected zone as compared to the TIG weldments.
文摘Sustained combustion and optimization of combustor are the two challenges being faced by combustion scientists working in the area of supersonic combustion.Thorough mixing,lower stagnation pressure losses,positive thrust and sustained combustion are the key issues in the field of supersonic combustion.Special fluid mechanism is required to achieve good mixing.To induce such mechanisms in supersonic inflows,the fuel injectors should be critically shaped incurring less flow losses.Present investigations are focused on the effect of fuel injection scheme on a model scramjet combustor performance.Ramps at supersonic flow generate axial vortices that help in macro-mixing of fuel with air.Interaction of shocks generated by ramps with the fuel stream generates boro-clinic torque at the air&liquid fuel interface,enhancing micro-mixing.Recirculation zones present in cavities increase the residence time of the combustible mixture.Making use of the advantageous features of both,a ramp-cavity combustor is designed.The combustor has two sections.First,constant height section consists of a backward facing step followed by ramps and cavities on both the top and bottom walls.The ramps are located alternately on top and bottom walls.The complete combustor width is utilized for the cavities.The second section of the combustor is diverging area section.This is provided to avoid thermal choking.In the present work gaseous hydrogen is considered as fuel.This study was mainly focused on the mixing different fuel injection locations.It was found that injecting fuel upstream of the ramp was beneficial from fuel spread point of view.
