FEM Simulation Analysis of Ring Compression Test Using Stationary and Rotating Die under Constant Shear Friction

The main objective of this research was to investigate the effect of friction on the behaviour of the metal flow and ring geometry, using comparisons from a stationary and rotating bottom die. This was carried out using friction calibration curves, compressive force analysis, stress and strain relationships and the reduction ratio of the ring specimen. The ring compression test (RCT) is considered one of the most reliable ways to obtain the friction factor existing in a plastic deformation process. This technique utilizes the dimensional changes of a test specimen to determine the magnitude of the friction factor. The variation of the calibration curve for the stationary die, with a range of m=0.0 to 0.9, and for the rotating die a range of m=0.1, 0.5 and 0.9. The frictional factor is calculated using FEM analysis, friction calibration and reduction ratio curves were generated from the compressive force using the DEFORM software package. The results indicated that the change in the inner diameter is related to the friction conditions and angular velocities at the die-workpiece interface.

Lubrication efficiency of vegetable oil nano-lubricants and solid powder lubricants

Reducing crude oil reserves and also environmental pollution caused by its excessive use has led to numerous researches to find alternatives to petroleum-based oils. Thus, owing to lower pollution and higher lubrication efficiency, the use of vegetable base lubricants has been widely considered. Due to the unique properties of different nanoparticles such as sphericality and high surface area besides low environmental risk, the subjected nanoparticles can be applied as additives to the base lubricants and create optimal tribological properties. In this study, in order to improve the lubricating efficiency of vegetable base lubricants, SiO2nanoparticles with different weight concentrations were used in the cold forging process of aluminum alloy. Then, the lubrication proficiency of both nano-lubricants and conventional solid powder lubricants in the forging industry was evaluated. Friction coefficient was determined by standard compression test and friction calibration curves. In order to evaluate the lubricants’ efficiency, two key parameters, namely shear friction coefficient and surface roughness have been considered. Experimental results showed that the presence of SiO2nanoparticles in the base lubricants significantly increased the lubrication efficiency of the base lubricants and notably reduced both the friction coefficient and surface roughness.

Observations on the Use of Friction Factor Maps in Metal Forming

In metal forming simulation the right definition of friction conditions at the tool-workpiece interface is a key matter, in order to obtain reliable results. The aim of the present work is the determination of friction factor maps by using the RCT with different alloys which are commonly used in the metal forming practice; and the subsequent comparison of the curves to probe if there are important deviations among different materials, which will lead to prevent the use of a unique and general map of friction curves for all materials. Results confirm the necessity of using a friction calibration map for each material. Furthermore the differences and similarities in the behaviour observed are evaluated for all materials.

A Method for Determination of Friction Coefficient in Sheet Metal Forming of Magnesium Alloy

A new method for determination of friction coefficient in sheet metal forming of Mg alloy AZ31B is presented in this paper. The method is based on the bulging test of sheet metal in which the specimen is processed with a hole at the center. The diameter of the hole will increase along the stroke of the punch and the dimensional change of the hole has a certain relationship with the friction coefficient at the punch/specimen interface. Thus, the friction coefficient can be determined indirectly according to the dimension of the hole in the bulging process. The bulging process of the sheet is simulated using FE code DEFORM-2D. The analysis model is set up according to the experiment of the bulging and the friction calibration curves are generated from the simulations of the bulging by setting different coefficients of friction. The friction coefficient can be determined by measuring the hole dimension during the bulging process and comparing it with the friction calibration curves.

Analysis of Ring Compression Test for Determination of Friction Circumstances in Forging Process

Friction is a major factor in determining the characteristics ofmetals as they are forged.Regularand efficient lubrication is one of the best ways in controlling friction and wear in this process.One of the best ways of testing the lubricant is the ringCompression test. In this research the effect of mixed graphite in water and also the effect of the amount of graphite in the lubricant in the reduction of friction between the sample-die are calculated using the ring test. Friction behavior is changed fromsticking friction to sliding frictionby using the lubricant; but the changes in the amount of graphite in water didnot have a great effect on the reduction of the friction coefficient. Furthermore, after viewing differences in the friction coefficients calculated by the means of FE analysis and the friction calibration curves, it is concluded that the sole calibration curves could not be used for hot working conditions.

Development of Lubricants Evaluation for Different Friction Laws by Using Rigid-Plastic Finite Element Method

A simulator based on rigid-plastic finite element method is developed with two common friction law: Coulomb friction law and constant shear friction law are imposed. This project is to develop a simple method to identify tribological properties of various lubricants by metal forming method. In this project, the influence of different lubricants was studied by using ring compression test. The deformation of the ring compression test was measured to obtain an experimental friction calibration curves under different lubricants. To model the friction effect, theoretical friction calibration curves for Coulomb friction law and shear friction law are generated under various parameter of μ, coefficient of friction (Coulomb friction law) and m, shear factor (constant shear friction law). The experimental and theoretical friction calibration curves were compared and the result shows corresponding. The friction of the lubricants was further verified by using a common method: pulling a block on flat surface with load sensor yields the friction force, F in the basic equation F=μN where N is the normal force. The results match the calibration curves too.

Determination of Friction Coefficient by Employing the Ring Compression Test

The main objective of this research was to investigate the effect of material properties, strain-rate sensitivity, and barreling on the behavior of friction calibration curves. The compression tests were conducted to obtain the necessary material properties for the finite element analysis. A series of ring compression tests were then conducted in order to determine the magnitude of the friction coefficient, μ. The experiments were first conducted for the modeling materials, namely, white and black plasticine and later on, for aluminum, copper, bronze, and brass. The experiments were then simulated via an elastic-plastic finite element code (ABAQUS). Contrary to the results available in the literature, where the same friction calibration curves are recommended for all types of materials and test conditions, the results of this investigation showed that friction calibration curves are indeed affected by the material properties and test conditions.

An Approximate Model to Calculate Foldover and Strains During Cold Upsetting of Cylinders Part II: Use of the Foldover Model to Estimate Friction

This paper addresses an approach to calculate the friction coefficient during nonuniform compression of cylinders. The approach combines new friction-calibration curves (prepared using the finite-element analysis) that relate friction to workpiece shape and the foldover model from Part I. Foldover in upsetting is used in the same way that the change in internal diameter is used in the ring test to determine friction. However, the new approach has the advantage that measurements are taken directly from the workpiece. Comparisons of friction values calculated from the ring test and the new approach showed good agreement.