Comparison of regression and artificial neural network model for the prediction of springback during air bending process of interstitial free steel sheet

This paper compares the regression and neural network modeling for predicting springback of interstial free steel sheet during air bending process. In this investigation, punch travel, strain hardening exponent, punch radius, punch velocity and width of the sheet were considered as input variables and springback as response variable. It has been observed that the ANN modeling process has been able to predict the springback with higher accuracy when compared with regression model.     

Studies on buckling behavior of honeycomb sandwich panel

In the present work, an avant-garde study on Buckling of honeycomb sandwich panel of hexagonal cell has been carried out by considering simply supported boundary constraints explicitly. A novel theoretical formulation has been developed for the buckling of honeycomb panel as per Mil Standard (MIL-HDBK-23A). The laminate element type has been considered for linear static analysis using Lanczos Method (finite element method (FEM)). The buckling analysis carried out by FEM has been compared and validated with theoretical and experimental investigation for different panel aspect ratio under static load.     

Some study on wrinkling behaviour of commercially pure aluminium sheet metals of different grades when drawn through conical and tractrix dies

This paper deals with some aspects of wrinkling behaviour of annealed three different grades of commercially pure aluminium sheets namely ISS 19000, ISS 19600 and ISS 19660 having thickness of 2.00 mm when deep drawing into cylindrical cups through conical and tractrix dies using a flat bottomed punch. It is well established that, the use of either a conical die or a tractrix die can enhance the limiting draw ratio compared with that obtainable in a conventional drawing operation. When a conical or a tractrix die is employed the need for a hold down or clamping ring is eliminated. However, this enhances the propensity of the blank to fail by wrinkling or buckling, particularly in the early stages of a drawing process in which thin sheet blanks are used. It is proved by these researchers that the onset of wrinkling can be studied with help of the ratio of strain increments (dε_r/dε_θ) value during the drawing process. This value which could be determined experimentally over which the wrinkling takes place has been shown in the form of wrinkling diagrams for the above three different grades. An attempt is also made to rank the aluminium grade that appear to suppress the wrinkling based on results obtained in the form of wrinkling diagrams, established for the above three different grades, in terms of the strain increments ratio and the stress ratio parameters. Further it is observed that the Aluminium grade ISS 19660 having high strain hardening index value, low ratio of tensile to yield (σ_u/σ_y) and fairly good value of high normalized hardening rate shows better resistance against wrinkling. Drawing through the tractrix die shows better resistance against wrinkling comparing with the conical die.     

Effect of geometric work-hardening and matrix work-hardening on workability and densification of aluminium–3.5% alumina composite during cold upsetting

The densification is a measure of deformation in upset forming of Powder Metallurgy (P/M) processes. A complete experimental investigation on the deformation behaviour of aluminium–3.5% alumina powder composite has been discussed for the case of triaxial stress state condition. Cold upsetting of aluminium–3.5% alumina composite with and with no annealing having different initial preform relative density and with different aspect ratio was carried out and the densification behaviour of the preform under triaxial stress state condition was determined. A new true strain considering the effect of bulging was taken into account for the case of determination of the hoop strain. Plots made for different preforms were analyzed for the densification behaviour of preforms considering the effect of both geometrical work-hardening (GWH) and the matrix work-hardening (MWH).     

Effect of annealing temperature on void coalescence in 5086 aluminium alloy formed under different stress conditions

In this paper, the influence of annealing temperature on formability, fracture behavior, void nucleation, its growth, and coalescence are studied. The voids and fracture behavior are studied as a function of various void parameters, namely δd-factor (ligament thickness between consecutive voids), d factor (ratio of δd and radius of the void), void area fraction (V_a) and L/W ratio (ratio of length to width of the void). The L/W ratio of the oblate or prolate voids at fracture is correlated with the mechanical properties, microstructure, minor strain at fracture (ε₂), Mohr’s circle shear strains, stress, and strain triaxiality factors. The Lode factor (θ) is determined and correlated with the Stress triaxiality factor (T), which is the ratio of mean stress (σ_m) to effective stress (σ_e). In addition, the Void area fraction (V_a), which is the ratio of void area to the representative sample area, is determined correlated with the Strain triaxiality factor (T_o). It is found that the sheets annealed at 300°C, possesses better formability due to lower d-factor, higher and -values, greater void area fraction and lower L/W ratio of void accommodating more plastic deformation.     

Workability studies on powder metallurgy pure iron preforms during hot forging under triaxial stress state condition

An experimental research work was performed for the understanding of the workability behavior of pure iron preforms produced through powder metallurgy route during hot forging under triaxial stress state condition. Relationship was established between the formability stress index and the axial strain. A relationship between the relative density and the axial strain was also established. Various stress ratio parameter under triaxial stress state condition which indicates the workability behavior of the material namely, , and were studied. An attempt has also been made to relate the stress ratio parameters with the relative density (R).     

Effect of glass in aluminum matrix on workability and strain hardening behavior of powder metallurgy composite

A complete experimental investigation on workability behavior of the Al–Glass has been carried out during cold upsetting. The present study has been performed to evaluate the effect of different percentage of Glass addition in Powder metallurgy (P/M) preforms of Al–Glass composite on workability behavior. The material studied in this paper is aluminum with glass as reinforcement. Glass content has been varied from 0% to 8% with particle size of 60 μm. The experimental results were analyzed for workability under triaxial stress state condition as a function of the relative density. The formability stress index (β), stress ratio parameters (σ_θ/σ_eff) were obtained for each percentage addition of Glass. It is found that as percent content of Glass increases, the workability parameter also increases. The addition of glass in Aluminum matrix affects the strain hardening index (n) of the composite.     

Some Aspects of Cold Upset Forming of Sintered Aluminum Preforms Using Different Lubricants

Cold upset forming and densification features in sintered aluminum preforms using different lubricants were investigated. Cylindrical preforms with initial density 91% of the theoretical one and aspect radio 0.75 were prepared on a 0.1 MN capacity universal testing machine. The preforms were covered with dry fine silica sand and sintered at 520±10°C for 1 h. Cold deformation experiments were carried out in several steps. In general, each compact was subjected to compressive loading in steps of 0.01 MN until fine cracks appeared on its free surface. The experimental data showed that grease exhibits enhanced densification compared to that for MoS₂ or graphite lubricants, provided that the initial preform density and aspect ratio are kept constant. The instantaneous strain hardening exponent and strength coefficient of the preforms were calculated and found to reach a peak value when the deformation or packing density were low. Further, they decreased and became constant. The initial geometry of the P/M preforms was shown to play a predominant role in influencing them.     

Impedance and Magnetization Studies of Ultrafine Ni-Zn Ferrite

Ultrafine Ni0.5Zn0.5 Fe2O4 powder was prepared by PVA aided chemical method. The powder and sintered pellets were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and complex impedance (Cl) analysis. The particles are found to be in the size range of 15 to 26 nm for various annealing temperatures. The coercivity, saturation magnetisation, Neel temperature and electrical conductivity are found to vary with sintering time at 800℃ for the pellet samples. The variations in the above intrinsic properties are explained qualitatively