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H. Parameshwar , G. Krishna Mohan , B. Ravi Kumar , Y. Narsimha Reddy

Abstract

The hepatoprotective activity of methanolic extract of Borreria articularis ( L.F) F.N. W illams: ( Rubiaceae ) at doses of 250 mg/kg and 500 mg/kg were evaluated by carbon tetrachloride (CCl ₄ ) intoxication in rats. The toxic group which received 25% CCl ₄ in olive o il (1 ml/kg ) per oral (p.o), alone exhi bited significant incre ase in serum ALT , AS T , ALP , TB l evels. It also exhibited significant (P<0. 001) decre ase in TP and ALB l evels. The groups received pretreatment of Borreria articularis at a dose of 250 and 500 mg/kg b.w.p.o. had reduced the AST, ALT, ALP and TB levels and the effects were comp ar ed with standard drug (Silymarin 100 mg/kg b .w.p. o).The total protein (TP) and albumin (ALB) levels we re signifi cantly increased in the animals received pretre atment of the extract at the moderate and higher dose l evels and the histop athological studi es also supported the protective effect of the extract.

Keywords

Carbon Tetra Chloride, Silymarin, Borreria articularis, Biochemical Parameters and Histological Study.

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A. Seshu Kumar ¹, B. Ravi Kumar ¹, G. L. Datta ², V. R. Ranganath ²

Affiliations
1 National Metallurgical Laboratory, Jamshedpur 831007, IN
2 lndian Institute of Technology, Kharagpur 721302, IN

Abstract

Advances in welding technology and materials science have resulted in great improvements in the reliability of welded structures. However, catastrophic failures have not been uncommon. Most of the weld related failures have been attributed to have originated from the heat affected zone (HAZ), which is believed to be the weakest link in the heterogeneous welded joint comprising of weld metal, HAZ and the unaffected base material. One of the key requirements in the integrity assessment of welded joints is the availability of representative property data for the HAZ, which can be used for comparing with the applied stress and predict critical stress or the remaining life. The difficulties in estimating the properties of the HAZ are compounded by a microstructural gradient within a narrow zone. In this investigation, detailed experimental studies were carried out on the HAZ obtained in manual metal arc, submerged arc and gas metal arc welding processes. The properties evaluated include hardness, tensile data, CVN impact and fracture toughness. Inspite of placing the notch close to the fusion boundary, CVN impact tests do not provide the correct estimation of toughness because of irregular HAZ boundary and the finite ischolar_main radius of the CVN notch (0.25mm) which entails the crack to sample several heterogeneous grains. On the other hand, a sharp fatigue precrack narrows down the microstructural heterogeneity in the fracture toughness tests. Even so, the variation of the fracture toughness (CTOD) within the HAZ is as unpredictable as in CVN toughness. This depends on the crack tip encountering either a local brittle microstructure indicating pop-ins or the deviation of crack tip into adjacent softer microstructural regions resulting in an apparent increase of fracture toughness. Literature is lacking in proper validation criteria before the HAZ toughness test results can be applied for integrity assessment. The present paper systematically investigates the problems associated with evaluation of the properties of HAZ in typical C-Mn-Nb micro alloyed steel.

Keywords

HAZ, Microstructural Gradient, Tensile Data, Impact Toughness, Fracture Toughness, CTOD, Pop-Ins, C-Mn-Nb Micro Alloyed Steel.

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Sk. Abdul Khadeer ¹, P. Ramesh Babu ¹, B. Ravi Kumar ², A. Seshu Kumar ³

Affiliations
1 Department of Mechanical Engineering, Osmania University, Hyderabad - 500007, IN
2 National Metallurgical Laboratory, Jamshedpur - 831001, IN
3 Indian Institute of Chemical Technology (CSIR), Uppal Road, Tarnaka, Hyderabad - 500007, IN

Abstract

Friction welding is one of the most common methods employed in the joining of carbon and alloy steel tubular sections. In the present work, the analysis of the effect of upset pressure on mechanical and metallurgical properties of friction welded ASTM A 106 Gr. B low carbon steel pipes has been investigated. The test joints were made using continuous drive welding machine with upset pressures of 5 MPa to 8 MPa and evaluated for microstructure, hardness, tensile strength and impact toughness. The weld joints exhibited mostly ferrite and pearlite microstructure in both fully plastically deformed zone (FPDZ), partially deformed zone (PDZ) on the either side of the weld interface and a distinct dynamically recrystallized ferrite pearlite microstructure was observed in the FPDZ at the weld centre line. Better tensile properties were observed in case of the joints made with upset pressure of 6.4 MPa. It is observed that the weld region is stronger than base metal and the hardness has increased with the increase in the upset pressure. Marginal reduction in the toughness was noted with the increase in the upset pressure.

Keywords

Friction Welding, Upset Pressure, Fully Plastically Deformed Zone (FPDZ), Partially Deformed Zone (PDZ), Base Material (BM).

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B. Kishan ¹, B. Sudheer Prem Kumar ¹, S. Gajanana ², B. Ravi Kumar ², P. V. K. Chaitanya Kumar ²

Affiliations
1 Department of Mechanical Engineering, JNTUH College of Engineering, Hyderabad, Kukatpally, IN
2 Department of Mechanical Engineering, MVSR Engineering College, Nadergul, Hyderabad, IN

Abstract

Electrical Discharge Machining (EDM) is one of the electrical energy based Modern Machining Technique. where electrical energy is directly used to remove or cut the metals. In the present work experiments are conducted on EDM using Al6061+SiC(3%,6%,9%), Copper and Brass materials as electrodes and EN8 steel as work material. Discharge current (I_P), pulse on time (T_ON), pulse off time (T_OFF) are selected as process parameters, Surface Roughness (S_R), Tool Wear Rate (TWR) as response. Taguchi design of experiment is used to find the influence of process parameters on response and a mathematical model is developed. Percentage contribution of each factor is determined.

Keywords

Discharge Current(I_P), Pulse on Time (T_ON), Pulse Off Time (T_OFF), Surface Roughness, EDM.

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B. Ravi Kumar ¹, S. Gajanana ¹, Hemachandra Reddy ², P. V. K. Chaitanya Kumar ¹, A. Teja Vardhan ¹

Affiliations
1 Department of Mechanical Engineering, MVSR Engineering College, Nadergul, Hyderabad, IN
2 Andhra Pradesh State Council of Higher Education (APSCHE), Andhra Pradesh, IN

Abstract

Flow forming is an advanced, near net shape, chip less metal forming process, which employs an increment rotary point deformation technique for manufacturing seamless symmetrical products. Spinning is an advanced continuous and localized metal forming process, which is widely used in many fields due to its advantages of flexibility, high quality and low cost. It is frequently used for manufacturing axisymmetric shapes where press tooling might not be justified on grounds of size and production volumes. It is characteristic of this process that the deformation does not occur in an annular zone around the axis of rotation but that the tools act upon a much localized area in which plastic flow takes place. During spinning tools are moved relative to the rotating work piece. In this paper, a regression model showing the relation among input process parameters, Mandrel speed (rpm), Roller type and Thickness of sheet (mm) and output (response) as surface roughness (μm) is developed using Minitab Software. The experiments were conducted on Aluminium 2024 T-3 sheets with cylindrical mandrel using Taguchi orthogonal arrays (L9). Further Analysis of Variance was carried out to find the contribution of each parameter on the surface roughness.

Keywords

Mandrel Speed (rpm), Thickness of Sheet (mm), Surface Roughness (μm).

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B. Ravi Kumar ¹, S. Gajanana ¹, K. Hemachandra Reddy ², P. V. K. Chaitanya Kumar ¹

Affiliations
1 MVSR Engineering College, Hyderabad, Andhra Pradesh, IN
2 AP State Council for Higher Education, Vijayawada, Andhra Pradesh, IN

Abstract

Spinning is widely used metal forming process to fabricate components or products have rotational symmetry. It is a localized metal forming process which is mainly used due to its advantage of high quality associated with low cost for manufacture. In this process a tool is pressed against the rotating pre form of final product. The surface rough ness is one of the important parameters of spun product which are used in aerospace industry. In the present study an investigation is carried out on Al2024 material to get a conical product by adopting Taguchi OA methodology for experimentation. The experiment is carried out by using two different geometry rollers namely single roller and double radii roller at two different rotational speeds on different thickness of sheets as input parameters. The surface roughness is the target response in this investigation. Regression model for surface roughness is developed using MiniTAB software. Further Analysis of Variance was carried out to find the contribution of each parameter on the response.

Keywords

Conical Mandrel, Surface Roughness, Regression Model, Taguchi Method.

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