Computational modelling of impact damage in brittle materials

Electrical discharge machining (EDM) is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and die making process to a micro-scale application machining alternative attracting a significant amount of research interests. In recent years, EDM researchers have explored a number of ways to improve the sparking efficiency including some unique experimental concepts that depart from the EDM traditional sparking phenomenon. Despite a range of different approaches, this new research shares the same objectives of achieving more efficient metal removal coupled with a reduction in tool wear and improved surface quality. This paper reviews the research work carried out from the inception to the development of die-sinking EDM within the past decade. It reports on the EDM research relating to improving performance measures, optimising the process variables, monitoring and control the sparking process, simplifying the electrode design and manufacture. A range of EDM applications are highlighted together with the development of hybrid machining processes. The final part of the paper discusses these developments and outlines the trends for future EDM research.

http://zclient.persiangig.com/ScienceDirect/M02.pdf

State of the art electrical discharge machining (EDM)

Introduction Metal forming process Analysis and technology in metal forming Plasticity and viscoplasticity Methods of analysis The finite element method (1) The finite element method (2) Plane-strain problems Axisymmetric isothermal forging Steady state processes of extrusion and drawing Sheet metal forming Thermo-viscoplastic analysis Compaction and forging of porous metals Three dimensional problems Preform design in metal forming Solid formulation, comparison of two formulations, and concluding remarks Index.

/pdf/metal-forming-and-the-finite-element-method-5ev6lca5h5.pdf

Metal Forming and the Finite-Element Method

http://digitalknowledge.cput.ac.za/bitstream/11189/4942/3/Makinde_Oluwole_D_Aziz_A_Eng_2011.pdf

Boundary layer flow of a nanofluid past a stretching sheet with a convective boundary condition

An account is given of the development of the idea of a yield stress for solids, soft solids and structured liquids from the beginning of this century to the present time. Originally, it was accepted that the yield stress of a solid was essentially the point at which, when the applied stress was increased, the deforming solid first began to show liquid-like behaviour, i.e. continual deformation. In the same way, the yield stress of a structured liquid was originally seen as the point at which, when decreasing the applied stress, solid-like behaviour was first noticed, i.e. no continual deformation. However as time went on, and experimental capabilities increased, it became clear, first for solids and lately for soft solids and structured liquids, that although there is usually a small range of stress over which the mechanical properties change dramatically (an apparent yield stress), these materials nevertheless show slow but continual steady deformation when stressed for a long time below this level, having shown an initial linear elastic response to the applied stress. At the lowest stresses, this creep behaviour for solids, soft solids and structured liquids can be described by a Newtonian-plateau viscosity. As the stress is increased the flow behaviour usually changes into a power-law dependence of steady-state shear rate on shear stress. For structured liquids and soft solids, this behaviour generally gives way to Newtonian behaviour at the highest stresses. For structured liquids this transition from very high (creep) viscosity (>106 Pa.s) to mobile liquid (

The yield stress—a review or ‘παντα ρει’—everything flows?

Application of a rigid—plastic finite-element method to some metalforming operations☆

This paper reviews the status of CAD/CAM applications in forging and the significant variables of the forging process, which must be considered in developing and applying computer technology in forging In addition, the principles of CAD/CAM for design and manufacture of finisher and blocker dies are reviewed Examples are given to illustrate the computer simulation of metal flow to design blocker shapes for forging applications Finally, the paper discusses the present status of CAD/CAM in forging, the immediate economic and practical applications of this technology, and the expected future research and development

Computer aided design and manufacturing (CAD/CAM) of hot forging dies

In this study, the estimation of shear force for blind shear ram type blowout preventer was investigated by using Finite Element Method (FEM). So, the effect of the blowout preventer working condition on shear force requirement for shear operation could be accurately approximated by simulating the entire process, and ram geometry could be optimized to reduce force and energy used to shear the tube by plastic deformation. The results of FEM analyzes was compared with blowout preventer manufacturer shear force information. Comparisons show that forces evaluated by using FEM (Deform 3D) simulations provided fairly accurate results for actual shear force. Also, it was found that by using Finite Element simulations the effect of the blowout preventer working condition on shearing operation can be estimated and ram geometries can be optimized. Therefore, FEM analyses could be used to design more reliable and efficient ram type blowout preventers.

/pdf/estimation-of-shear-force-for-blind-shear-ram-blowout-539b9xhfag.pdf

Estimation of shear force for blind shear ram blowout preventers

Computer-Aided Process Modelling of Hot Forging and Extrusion of Aluminum Alloys

Lubricants are necessary to avoid adhesion, galling, and scratching in aluminum stamping processes. In this study, various lubricants, including dry lubes and wet lubes, were evaluated using cup drawing test (CDT) for stamping of Al 5182-O aluminum sheets. The effects of surface texturing, with electro-discharge texturing (EDT) and mill finish (MF), on the friction behavior were also investigated. Furthermore, the methodology to evaluate the performance of lubricants was established based on (a) maximum applicable blank holder force (BHF) and (b) draw-in length in flange or flange perimeter of formed cups. Finite element (FE) simulations were carried out to determine the coefficient of friction (CoF) at tool–workpiece interface during deep drawing under different lubrication conditions. Flow stress data of Al 5182-O material were obtained using viscous pressure bulge (VPB) and tensile tests. In this study, it was confirmed that, in forming Al 5182-O, dry film lubricants have better lubricity than wet lubricants. A better lubrication condition was found with EDT surface texture. [DOI: 10.1115/1.4030750]

Taylan Altan

Papers

Application of a rigid—plastic finite-element method to some metalforming operations☆

Computer aided design and manufacturing (CAD/CAM) of hot forging dies

Estimation of shear force for blind shear ram blowout preventers

Computer-Aided Process Modelling of Hot Forging and Extrusion of Aluminum Alloys

Evaluation of Lubricants for Stamping of Al 5182-O Aluminum Sheet Using Cup Drawing Test