Enhancement of seal life through carbon composite back-up rings under shock loading conditions in defence applications

The life of Nitrile Butadiene Rubber(NBR) O-ring seal having shore hardness of A70 and A90 under shock loading conditions was investigated by a specially designed pneumo-hydraulic shock test rig. Shock tests have been carried out on bare seals, seal with conventional polytetrafluoroethylene(PTFE) back-up rings and seal with newly developed carbon composite back-up rings to study its behaviour under different operating conditions until failure. Experiments were conducted by varying annular gap ranging from 0.3 to 0.5 mm, oil temperature from 30 ℃ to 70 ℃ and rate of pressure rise from 600 to 2400 MPa/s. Significant enhancement in seal life was observed with carbon composite back-up ring at reduced annular clearances compared to seal life with conventional PTFE back-up ring and without back-up rings.

Sonochemically assisted synthesis of nano HMX

Nanotechnology has played an influential role in improving the energetic content without subsiding the performance of high energy materials in the current era.In this work,HMX(octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)nanoparticles were prepared by sonochemically assisted solvent-antisolvent spray technique focussing the reduction in its size so as to improve its energetic properties.In order to fabricate nano HMX various parameters such as different solvents and temperature were investigated.Sonication is one of the strategies recently explored in this regard;so time dependent study of sonication using probe sonicator was performed.It has been postulated that bubble formed during sonication when collapses generate high temperature and many nucleation sites which leads to the formation of uniform spherical particles with small size and fast transition phase.XRD studies depicted phase transformation from a toβas a result of sonication.The TEM images revealed that the rise in the sonication time resulted into decrease in the particle size from 300 to 10 nm.Differential scanning calorimetry(DSC)was employed to determine the heat release of the samples and enhancement in the heat release with the decrease in the particle size.A decrease in the spark sensitivity was observed from 2 J(regular HMX)to 50 mJ(nano HMX).

Effect of pH on Mechanical, Physical and Tribological Properties of Electroless Ni-P-Al2〇 3 Composite Deposits for Marine Applications

Successful co-deposition of fine particulate matter within an Electroless Nickel-Phosphorous(ENi-P) matrix is dependent on various factors like bath composition, particle compatibility with metallic matrix, bath reactivity(pH), particle size and their distribution. ENi-P deposits incorporating Al_2O_3/Alumina in a disperse phase have varied effects on properties and attributes like surface roughness(Ra), microhardness, wear resistance, corrosion resistance and surface morphology of the deposits obtained. This paper experimentally investigates the effect of alumina(1.55 g/L) on Ra, microhardness, surface morphology, deposition rate, wettability, wear resistance and corrosion resistance of ENi-P-Al_2O_3 composite deposits on mild steel substrates at bath pH 5, 7 and 9. Study reveals that optimum deposit parameters and deposition rates are achieved with bath pH. However, not much study has been undertaken concerning composite deposits obtained from higher bath pH or basic bath. This is attributable to the fact that at higher bath pH or alkaline baths, the bath gets unstable and eventually degrades or decomposes, thereby resulting in sub optimal or poor deposition. Hence, experimental investigations carried out by preparing suitable baths, operating under optimum conditions, and enabling successful composite deposition in acidic and alkaline baths have revealed that there is a significant improvement in the above mentioned properties of the as-deposited composite deposits, as the pH is increased from pH 5 to pH 9. This aspect can therefore be advantageously utilized for preparing various marine components like fasteners, nuts, bolts, washers, pipes, cables, components having relative motion etc.

Investigation and Analysis of High Temperature Corrosion and Degradation of Marine Boiler Combustion Swirler

现在的纸调查了并且分析了 swirler 材料由在 30 MW 水兵锅炉为一年的时期受到服务的低碳钢组成。由于在结合的炉子的高温度的存在，腐蚀剂水兵环境 swirler 材料显示出加速的降级和材料消耗量。调查进与交替的材料或涂层生产存在 swirler 的可行性有热障碍涂层的 swirler 材料被承担。基于他们的性质和表演， SS 304 和 SS 316 为 swirler 作为代替材料被建议。有在提高的温度在他们的表演为任何改进观察的热障碍涂层也是的一种形式的存在 swirlers 测试了的涂层的另外的选择。钨铬钴合金，它是一个 Ni 公司基于涂层，在 MS 样品上被执行，一样暴露于上面提及的一样的温度。可得到的选择的表演关于材料的谷物结构被评估，在提高的温度的材料和恶化的坚硬价值。调查证明象 SS 304， SS 316 和钨铬钴合金涂层一样的建议材料 / 涂层表明 SS 316 是适合高温度申请的材料最好。

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.

Polymer composite for antistatic application in aerospace

The pheno menon of static electricity is unpredictable,particulariy when an aircraft flying at high altitude that causes the accumulation of static charges beyond a threshold value leading to the failure of its parts and systems including severe explosion and radio communication failure.The accumulation of static charges on aircraft is generated by the virtue of interaction between the outer surface of aircraft and the external environmental attributes encompasses air particles,ice,hail,dust,volcanic ash in addition to its triboelectric charging.In the recent years,advanced polymer-based composites or nanocomposites are preferred structural constituents for aircrafts due to their light weight and comparable mechanical properties,but such composite systems do not render low impedance path for charge flow and are subsequently vulnerable to effect of lightning strike and precipitation static.In this context,it is essential to develop conductive composite systems from non-co nductive polymer natrix by nano fillerembodime nts.The advent of carbon-based nanocomposite/nano materials have adequately addressed such issues related to the nonco nductive polymer matrix and further turned into an avant-garde genre of materials.The current review envisioned to illustrate the detailed exploitation of various polymer nanocomposites in addition to especially mentioned epoxy composites based on carbon fillers like carbon black,carbon nanotube(single walled carbon nanotube and multi walled carbon nanotube) and graphene the development of antistatic application in aircra ft in addition to the static charge phenomenon and condition for its prevalence in avionic systems.