EFFECT OF GMAW TWIN WIRE TANDEM PARAMETERS ON MECHANICAL PROPERTIES OF WELDED JOINTS

Tandem welding has the advantage of higher productivity over a limitation considering narrow groove joints. Tandem has higher deposition and heat input. To study the effect of variation in robotic tandem parameters on fatigue properties of welded joints, the following parameters were investigated, viz. first case root & the second pass using a single wire, subsequent run tandem twin and second case using root pass using a single wire, subsequent run using tandem twin wire welding. Butt joint samples were subjected to ultrasonic testing, mechanical & metallurgical testing, and fatigue testing. Found Group 1 tensile strength, yield strength, % elongation & impact value to be 12 %, 9 %, 23 % & 14 %, respectively, higher than Group 2. Explained variations in microhardness & better fatigue life were observed for Group 1. This investigation will help manufacturers in decision-making while selecting tandem parameters considering productivity or reliability

RELATIONSHIP OF DEW POINT AND AMBIENT TEMPERATURE VARIATION ON WELD QUALITY

This investigation deals with the study of the effect of environmental parameters viz dew point temperature, relative humidity, ambient air temperature, and job surface temperature on robotic MAG (Metal active gas) welded joint quality. Weld samples taken were mass manufacturing welded structures of a heavy-large scale industry, which were further subjected to semi-automatic ultrasonic testing to assess defects within welded joints. The trend of defects observed and recorded after ultrasonic testing of weld joints was co-related with the trend of atmospheric parameters for a span of four years to establish a linear empirical relationship. It has been established that variations in atmospheric parameters resulted in variations in the trend of weld defects. These variations were studied to get the empirical relationship to establish the effect of variation in atmospheric parameters on weld quality or defects in joints. It has been observed that whenever there was a drop in the "difference in ambient air temperature & dew point temperature, especially less than 5", a drop in ultrasonic testing straight pass % was observed than the average value

Development of Estimation Procedure of Population Mean in Two-Phase Stratified Sampling

This article describes the problem of estimation of finite population mean in two-phase stratified random sampling. Using information on two auxiliary variables, a class of product to regression chain type estimators has been proposed and its characteristic is discussed. The unbiased version of the proposed class of estimators has been constructed and the optimality condition for the proposed class of estimators is derived. The efficacy of the proposed methodology has been justified through empirical investigations carried over the data set of natural population as well as the data set of artificially generated population. The survey statistician may be suggested to use it

EFFECT OF PURITY LEVEL OF CO2 SHIELDING ON METAL ACTIVE GAS WELDED JOINT QUALITY

The investigation deals with the study of the effect of the purity level of carbon dioxide shielding gas on the metal active gas weld quality. Studied 99.78 %, 99.95 %, and 99.97 % purity levels of carbon dioxide shielding gas. Factors considered were related to shielding gas purity, moisture, Sulphur, and oxygen content. Welded samples were subjected to ultrasonic testing to assess weld quality. With the reduction in purity level below 99.9 %, it was observed that the weld defect percentage increased in both lab trials and mass manufacturing jobs. The defects recorded were 5% higher when jobs were welded using carbon dioxide supplied from a gas cylinder than that supplied from liquid cryogenic bullets; this established that a higher purity level could be maintained in cryogenic storage and transport of shielding gases. This states helpful references to manufacturing industries for selecting the purity level of shielding gas, with the objective of rework reduction

Tribological and Corrosion Behavior of Vacuum Plasma Sprayed Ti-Zr-Ni Quasicrystalline Coatings

This investigation deals with a study of the friction, wear, and corrosion behavior of vacuum plasma sprayed quasicrystalline (QC) Ti41.5Zr41.5Ni17 coatings. During pin on disc experiments, a change in the mode of wear has been found to occur with corresponding changes in normal load and sliding velocity. The low thermal conductivity of quasicrystals and its brittleness play a vital role in determining the friction and wear behavior of such materials. When these coatings are subjected to rubbing for a longer period of time, wear occurs by subsurface crack propagation, and subsequent delamination within the coated layer. By comparing the QC to its polycrystalline counterpart during potentiodynamic measurements according to ASTM G 31, higher currents were found over the whole range of potentials for QC when immersed in 1M HCl solutio

Seven new combinations in Phanera (Fabaceae: Caesalpinioideae: Cercideae)

Seven new combinations in Phanera Lour. are made for species which were either described in Lasiobema (Korth.) Miq. or later transferred to Lasiobema from Bauhinia L

Water quality improvement of Penaeus monodon culture pond for higher productivity through biomediation

Intensive culturing of Penaeus monodon generates considerable amount of wastes leading to the deterioration of water quality, disease outbreaks and lower yields. Recently, the application of biocontrol agents were started in ponds in order to improve yield through bioremediation. Analytical investigation of a biocontrol product (PROFS), an extensively used product of Biostadt India Ltd. was performed to determine its accuracy and applicability. It was found that four different types of Bacillus species (69×10 9 cfu/g) were present in the product. Amylase, phytase and protease activities in the product were 3.078, 4.584 and 84.154 U/g, respectively. The biocontrol treatment was applied in the ponds five times during the cultivation (120 days) of P. monodon at a dose of 1 kg/ha. The amount of total ammonia, nitrate and nitrite of the treated ponds varied from 0.418 ± 0.039 to 0.079 ± 0.028 ppm, 0.029 ± 0.008 to 0.014 ± 0.004 ppm and 0.0127 ± 0.0008 to 0.0098 ± 0.00007 ppm, respectively, which were significantly lower than the values measured for untreated ponds. The product showed antimicrobial activity against Vibrio harveyi MTCC 7954 (inhibition zone: 4.89 mm) and Vibrio vulnificus MTCC 1145 (6.41 mm). Average body weight of shrimps in treated ponds was 33 ± 2.42 g, which was 39.5% higher than the values measured from control ponds. The Vibrio count was negligible (0.12×10 5 cfu/ml) and the survival rate was 93% in treated ponds