Nithyanandan Ramakrishnan

Dubai Health Authority | DHA · Physician

Springback remains a major concern in sheet metal bending in fabricating any final product within the permissible tolerance. Apart from the geometrical and material parameters, springback is significantly affected by the forming load also and the present study is focused on it. Sheet metal bending process involves large rotation and strain as well...

The analytical model for springback in arc bending of sheet metal can serve as an excellent design support. The amount of springback is considerably influenced by the geometrical and the material parameters associated with the sheet metal. In addition, the applied load during the bending also has a significant influence. Although a number of numeri...

Electromagnetic forming (EMF) is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils are generally used for electromagnetic forming of sheet metals. However, with this type of coil the central portion of the workpiece ex...

Among several other definitions, the crack initiation fracture toughness (Ji) based on critical stretch zone width (SZWc), called JSZWc, is being considered as a geometry independent material property. The problem in SZWc experimental evaluation is in identifying the size of stretch zone on a blunted crack front as this requires a high degree of pr...

In this study, die profiles of the rod extrusion processes are optimised to produce products of desirable microstructure at maximum production speed and minimum left out material in the die. The design problem is formulated as a non-linear programming problem which is solved using genetic algorithm. Selection of the processing parameters is carried...

Using large deformation FEM analyses in SA333Gr.6 carbon steel material, the present study demonstrated the assessment of SZWc value that leads to JSZWc and finally compares with the respective experimental results. It also includes numerical prediction of specimen J–R curve using Gurson–Tvergaard–Needleman parameters obtain from tensile specimen t...

The present study demonstrates the numerical prediction of experimental specimen J-R curve using Gurson–Tvergaard–Needleman phenomenologically based material model. The predicted specimen J-R curve is used to determine the geometric independent initiation fracture toughness (JSZWc) value that compares well with experimental result. Using the experi...

This study is related to material modeling and die and process design of tube extrusion of γ iron. Strain dependent rate power law is used for material modeling whose coefficients are arrived at through genetic algorithm (GA). Die profile of the tube extrusion process is optimized to produce microstructurally sound product at maximum production spe...

The need of a generalised flow curves considering strain (ε), strain rate ([(e)\dot] \dot{\varepsilon } ) and temperature (T) is a primary requirement for material modelling related to several conventional and strategic mechanical processing to meet critical and non-critical engineering applications. The realistic coefficients of flow curves need t...

Springback remains a major concern in sheet metal forming process. Springback, shape discrepancy between fully loaded and unloaded configuration due to elastic recovery of material, is mainly affected by geometrical parameters, material properties of sheet and lubrication condition between the blank and the tool. A total-elastic–incremental-plastic...

ABSTRACT There is an increasing effort to use critical stretch zone width (SZW) for the evaluation of initiation fracture toughness that is considered as geometry independent material property. The existing numerical SZW evaluation method is based on crack tip opening displacement measurement, which is evaluated using various definitions. This nume...

The current investigation essentially comprises a number of 3D non-linear FEM simulations to study and correlate crack tip blunting with experimental results. The study attempts to establish a physically tangible procedure for numerical determination of stretch zone width (SZW). The proposed methodology explains the mechanism involved in the creati...

In piping components, for the stability assessment it is important to calculate the point of initiation of the crack and to monitor the subsequent crack propagation behaviour. The objective of this paper is to use the finite element method backed up with experimental results to determine the crack initiation stage and to subsequently predict the cr...

The study addresses numerical determination of stretch zone width and its critical value. The proposed method is based on the highly deformed stretch zone that is defined as stretch zone width, expected to be better than the half of the crack tip opening distance which inturn determined using 45° line method. The investigation essentially comprises...

Cenospheres in the range of 30–50 vol.% were used as space holders for making syntactic aluminum foam having density 1.5–1.9gm/cc using stir-casting technique. The synthesized syntactic foam (SF) was characterized in terms of microstructures, hardness and compressive deformation behaviour. It was noted that the SF behaves like a high strength alumi...

Ductile fracture assessments of circumferentially through-wall cracked elbows based on the elastic–plastic J-integral concept are discussed with particular interest in its ability and accuracy to predict experimental results corresponding to initiation of stable crack growth and instability. 3D non-linear finite element analyses were performed cons...

In the present study, an attempt was made to examine the synergic effect of SiC particle reinforcement and heat treatment on the two body abrasive wear behavior of an Al–Si alloy (BS: LM13) under varying loads and abrasive sizes. Silicon carbide particles with size 50–80μm were reinforced in Al–Si alloy, in varying concentration (10wt% and 15wt%),...

Selection of processing and geometrical parameters is a crucial step in the extrusion process design. Optimized parameters may result in desirable microstructure at minimum load. To achieve this goal, dynamic material modeling (DMM) and genetic algorithms (GA) are used in this study. Selection of strain rate and temperature is done by DMM which ins...

The objective of the work is to predict elbow behaviour under monotonic and cyclic loadings using finite element method (FEM). The 3D non-linear FEM analysis results predictions are backed up with experimental results. Non-linear finite element analyses were performed considering both material and geometrical non-linearity using two advanced FEM an...

The moduli of porous materials have been extensively studied analytically as well as experimentally. Several empirical and analytical equations were proposed to express the effective moduli of porous solids. In the present investigation, a few of these relations were checked for experimental validity in the case of closed-cell aluminum foams. Also,...

2014 Al alloy and 2014 Al alloy-10wt% SiCp composite foams are prepared by melt route. The structural parameters namely cell size, cell wall thickness, shape of the cell and anisotropy ratios are found out along the length of the cylindrical foam casting. The results show that the cell wall thickness is more in 2014 Al alloy-10wt% SiC composite foa...

The age hardening behavior of solid Al-alloy–SiCp composite and closed cell Al-alloy–SiCp composite cellular materials has been examined and compared. The peak aging period of these materials were also compared with that of the solid unreinforced alloy. The effect of SiCp content on the peak aging time has been examined. It was found that the compo...

Ductile fracture assessments of circumferentially through-wall cracked elbows, based on the elastic–plastic J-integral concept, are discussed with particular interest in its ability and accuracy to predict experimental results corresponding to the initiation of stable crack growth. 3D non-linear finite element analysis is backed up with experimenta...

One of the important features of flanging process is elastic recovery during unloading leading to springback. The elastic recovery is associated with various tool and material parameters. It is difficult to analytically predict the elastic recovery accurately owing to the complex material deformation behavior. In this investigation, a commercially...

Compressive deformation of 2014 Al-alloy–SiCp composite has been compared with that of 2014 Al-alloy in as-cast and peak aged condition. In as-cast condition, the strength, elastic modulus and strain-hardening exponent of the alloy were improved significantly at the expense of its ductility due to reinforcement of SiC particles. After peak aging, t...

A large deformation algorithm based on Total-Elastic-Incremental-Plastic Strain (TEIP) was used for modeling a typical sheet metal bending process. The bending process involves large strain, rotation as well as springback due to elastic recovery of the material. A finite element method (FEM) software based on TEIP strain that is capable of handling...

Several methods are available to understand the process of crack initiation and propagation in ductile materials. In an attempt to achieve an overall understanding, some of these techniques were studied using a large deformation based finite element method (FEM). In the current investigation, typical crack tip blunting prior to ductile fracture beh...

The interface in a metal matrix composite (MMC) is modeled using finite element method (FEM) to study the deformation behavior of MMCs as a function of interface characteristics such as the interface stiffness and thickness as well as the volume fraction of the reinforcing phase. The interface is modeled as a thin layer of artificial material. The...

The compressive deformation behaviour of 2014Al-SiCp composites containing varying amount of SiCp has been studied at different strain rates (10−3 to 10−1s−1). The composite materials were prepared through stir-casting (vortex) method. The yield stress, Young's modulus, percentage elongation and fracture stress were measured from the true stress–tr...

The solutions of cracked elbow are shown to be excessively conservative and on occasion, non-applicable to the cases for which they are intended. The objective of the work described in this paper is to use the 3D non-linear finite element method (FEM) backed up with experimental results to determine the collapse limit load. Non-linear finite elemen...

Ductile fracture is initiated by void nucleation at a characteristic distance (lc) from the crack tip and propagated by void growth followed by coalescence with the tip. The earlier concepts expressed l c in terms of grain size or inter-particle distance because grain and particle boundaries form potential sites for void nucleation. However, Sriniv...

The sheet metal bending is an important form of sheet metal forming process, widely used in various industrial applications like aircraft, automobiles, household items, power industries, etc. This study predicts the responses of the sheet metal bending process using artificial neural network. Based on44 cases analysedusing finite element method, a...

This study is related to reverse engineering solution of friction and yield stress in a hot ring compression test using finite element method (FEM). Ring material is steel and test temperature is 800°C. Load deflection curve and the deformed geometry, obtained from the test, are considered as the benchmark parameters for the reverse engineering. Th...

Several methods are in vogue to understand the process of crack initiation and propagation in ductile materials. In an attempt to achieve a unified understanding of these methods, a large deformation finite element analysis has been carried out. An attempt has been made to understand ductile fracture by numerically determining the ductile fracture...