A.K. Jha

Forging of metal powder preforms

Abstract Metal powder technology is currently arousing interest in many parts of the world as an economic method of producing components from metal powders. Considering the process of the forging of metal powder preforms under axisymmetric and plane strain conditions, the problems of pressure distribution at the die-work piece interface and die load have been analysed. The correctness of the yield criterion and interfacial friction law used during the analysis have also been verified experimentally. The results so obtained are discussed critically to illustrate the interaction of various parameters involved and are presented graphically.

Deformation characteristics and fracture mechanisms during the cold forging of metal powder preforms

Abstract The paper reports on an investigation into the various aspects of cold forging of iron powder preforms which have been compacted and sintered from atomised iron powder. The influence of particle size, compacting pressure, sintering temperature and forging parameters on relative density of the preform was investigated. Experiments were conducted and measurements were made on the development of barrelling and strain variations at the free surface. Cracks were also observed at the free surface of the perform. The deformation characteristics and fracture mechanism is discussed critically to illustrate the interaction of various parameters involved and the results are presented graphically.

Production of sinter-forged components

Abstract The forging of sintered metal-powder preforms is currently arousing interest in many parts of the world as an economic method of producing components from metal powders. This paper reports on an investigation into the various technological aspects of the cold forging of sintered powder preforms. The influence of the powder particle size, the compacting pressure, the sintering temperature and other forging parameters on the relative density of the preform discs of atomised iron powder at room temperature under axisymmetric conditions. hallow discs of atomised iron powder at room temperature under axisymmetric conditions. Measurements were made on the development of barrelling and strain variations at the free surface. Crack formation at the free surface was observed. The deformation characteristics and fracture mechanisms are discussed critically, to illustrate the interaction of the various parameters involved, and the results are presented graphically. Powder preform design and techno-economic advantages are discussed briefly also.

Deformation characteristics and fracturing of sintered copper powder strips during cold forging

Abstract The industrial processing of sintered powder preforms has recently been developed for manufacturing various engineering components. The present investigation has been undertaken with a view to studying the deformation characteristics and fracture mechanism during the cold forging of sintered copper powder strips. The influence of compacting pressure, sintering temperature and forging parameters on the relative density of the copper powder strip is explored. Experiments have been conducted and measurements made on the development of barrelling and strain variations at the free surface. Crack formation at the free surface has also been examined. The theoretical and experimental results are analysed and discussed critically to explain the deformation characteristics and the fracturing of sintered copper powder strips during cold forging. Results are presented graphically.

Task-based design optimization of serial robot manipulators

In this article a direct search non-gradient design optimization method is proposed to determine the optimal task time and optimal parameters of serial robot manipulators. The design variables are treated as continuous variables associated with the motion trajectory profile and robots link lengths and masses. The method adopted in this study can be applied to any serial redundant or non-redundant manipulator that has rigid links and known kinematic and dynamic models with free motions or motions along specified paths. Trajectory can be planned in Cartesian or joint space under kinodynamic constraints. The cost function to be minimized is weighted terms of task time and joint torques quadratic average. Examples on 3-R planar and spatial serial robot manipulators are given to illustrate the method where the kinematic and dynamic models and the optimization method are developed in MATLAB®.

Cold forging of sintered iron-powder preforms

Abstract The paper reports on an investigation into various aspects of cold forging of iron-powder preforms which have been compacted and sintered from atomised iron powder. An upperbound solution is constructed for determining the die pressures developed during the cold forging of iron powder under axisymmetric and plane-strain condition. The results so obtained are discussed critically to illustrate the interaction of the various parameters involved and are presented graphically.

Investigations into the high-speed forging of sintered copper powder strips

Abstract The present paper reports on an investigation into the various technological aspects of the high-speed forging of sintered copper powder strips. Experiments were conducted and measurements were made in the development of barrelling, the strain variations at the free surface and densification during the high-speed forging of sintered copper powder strips at room temperature under dry and lubricated conditions. The theoretical relationship between the frictional stress at the interface and other process variables is also discussed and the results are analysed critically to illustrate the inter-action of various processing parameters involved during the high-speed forging of sintered copper powder strips, these results being presented graphically.

Effect of sintering on wear characteristics of Fe-Al2O3 metal matrix composites:

This article reports the results of investigation of tribological properties of 5 wt% Al2O3 reinforced iron-based metal matrix composite fabricated using powder metallurgy technique. Composition of the composite by weight was 95% Fe as a matrix material and 5% Al2O3 as reinforcement. Green compacts were sintered in an argon atmosphere in the temperature range of 900–1100  ℃ for 1 to 3 h. Dry sliding wear test were performed on the specimens using pin-on-disc wear and friction testing machine keeping the fixed sliding velocity as 4 m/s and sliding time as 60 min for loads of 0.5, 1.0 and 2.0 kg. Microstructure of weared specimens as studied by scanning electron microscope revealed that adhesive wear is more prominent at lower load where as abrasive wear is more prominent at higher load. Wear rate is also dependent on sintering temperature and time. This is explained in terms of densification, hardness and nature of wear occurring in the specimen.

Dynamic effects during a high-speed sinter-forging process

Abstract The paper reports on an investigation into the various technological aspects of a high-speed sinter-forging process. Experiments were conducted and measurements were made in the development of barrelling, strain variations at the free surface and densilication during dry and lubricated high-speed cold forging of sintered copper powder discs. The relationship between the frictional stress at the interface and other process variables is discussed and an analysis is given for the calculation of pressure distribution and die load by the solution of the equations of equilibrium taking barrelling into consideration for axial symmetry and plane strain sinter-forging conditions. Results are discussed critically to illustrate the interaction of various processing parameters involved during high-speed sinter-forging process and are presented graphically.

Hardness and Wear Behavior of CoO Doped Fe-Al2O3 Metal Matrix Composite (MMC) Synthesized via Powder Metallurgy (P/M) Technique

In the present paper results of investigations on addition of cobalt oxide in the Fe-Al2O3 Metal Matrix Composite (MMC) synthesized via Powder Metallurgy (P/M) technique on phase, microstructure and mechanical characteristics are reported. X-Ray Diffraction, Scanning Electron Microscopy, density, hardness and wear measurement were used for characterization. XRD and SEM reveal that addition of cobalt oxide addition retards the formation of iron aluminate phase. Mechanical properties investigated include hardness and wear respectively. The measurement of wear of the specimens was done at a constant sliding velocity of 4 m/sec and under a load of 0.5, 1.0, 1.5 and 2.0 Kg. A correlation behavior was set up between the hardness and wear behavior of the composite specimens. It was found that due to non reactive sintering the hardness of the specimens was low and wear was high in comparison to undoped Fe-Al2O3 MMC specimens. However, the ductility was improved and overall mechanical behavior of specimens was significantly improved.