Low velocity impact studies of E-glass/epoxy composite laminates at different thicknesses and temperatures

Low velocity impact experiments were carried out on E-glass/epoxy composite laminates having varying thicknesses at sub zero and elevated temperatures using hemi spherical steel impactor of 16 mm diameter with impact energies in the rage of 50-150 J.The performance of the laminates was assessed in terms of energy absorption,maximum displacement,peak force and failure behaviour.Results indicated that the effect of temperature on energy absorption of the laminate is negligible although the laminates are embrittling at sub zero temperatures.However it has influence on failure behaviour and displacement.Peak force has increased linearly with increase in laminate thickness from 5 to 10 mm.However it got reduced by 25% when temperature was increased from-20℃ to 100℃,Based on experimental results,laminate perforation energies were predicted using curve fitting equations.Statistical analysis was carried out using Taguchi method to identify the global effects of various parameters on laminate performance and confirmed that the laminate thickness has significant influence as compared to temperature,for the studied range.

Influence of welding consumables on tensile and impact properties of multi-pass SMAW Armox 500T steel joints vis-a-vis base metal

In this investigation, comparative study of tensile and impact properties of multi-pass SMAW Armox500 T steel joints fabricated by austenitic stainless steel(ASS) and low hydrogen ferritic steel(LHF)consumables vis-a-vis base metal was carried out. The tensile tests were conducted on computer controlled Walter t Bai Ag UTM at a nominal strain rate of 10à3 sà1. Subsequently, charpy impact tests were carried out on an instrumented Zwick-Roell test setup to obtain load vs. displacement and maximum energy absorbed vs. displacement of the specimen. It was observed that, the joint efficiency of weldment processed by LHF consumable was 41.7% and weldment processed by ASS was 30.6% of its base metal indicating the influence of electrode consumable on tensile properties of the joints. On the contrary, impact toughness of weldment processed by ASS was 20% more and weldment processed by LHF was 12% less than that of base metal. Microstructural studies also revealed that, ASS can be considered as a candidate welding consumable for good strain hardening and toughness of the welding joint in impact applications. However, LHF steel consumable is recommended for welding joints that requires higher joint efficiency under tensile loading conditions.

Hot deformation behavior and processing maps of Ti-15Al-12Nb alloy

The isothermal hot compression tests of Ti-15Al-12Nb alloy under wide range of strain rates(0.01-10.00 s^(-1)and deformation temperatures(950,1000,1050,and 1100℃)were carried out using Gleeble-3500 thermo-simulation machine.A constitutive equation represented as a function of temperature,strain rate and true strain was developed,and the hot deformation appar-ent activation energy is calculated to be about 453 kJ·mol^(-1).By employing dynamic material model(DMM),the processing maps of Ti-15Al-12Nb alloy at various strains were established.Maximum efficiency of about 57%for power dissipation is obtained at high temperature and low strain rate.Owing to the high power dissipation efficiency and excellent processing ability in dynamic recrystallization(DRX)zone for metal material,the optimum processing conditions are selected as the temperature range of 1050-1100℃and the strain rate range of 0.01-0.10 s^(-1).Using transmission electron microscopy(TEM)studies,it is found that the dislocation density is directly associated with the value of processing efficiency.It is observed that when the processing effi-ciency is about 22%,the dislocation density is reasonably large.The flow instability region occurs at strain rate of 10.00 s^(-1)with cracks,which should be avoided during hot processing to obtain the required mechanical properties.