Investigating the effects of hardening of aluminium alloys on equal-channel angular pressing-A finite-element study

Equal-channel angular pressing (ECAP) is a promising severe plastic deformation method for production of ultrafine-grained bulk metals and alloys with considerably improved mechanical properties. In this study, numerical experiments were carried out to investigate the effect of strain hardening of aluminum alloys on the process performance of ECAP via finite element modeling. In the constitutive model, isothermal-plane strain, frictionless condition was assumed. The numerical results showed that strain hardening behavior strongly affects the deformation homogeneity and process performance, mainly due to corner gap formation in the workpiece

Comparison of the deep drawability of aluminum and steel using numerical simulation experiments

Sheet metal forming processes, especially deep drawing processes give diverse results by various materials. Extreme differences occur between steel sheets and aluminum sheets. The main causes of these differences are variances in micro- and macroscopic material properties, such as anisotropy. In this study, the behavior of two distinct materials, steel and aluminum alloy, during an axisymmetrical cup drawing operation has been studied numerically. For this purpose, finite element (FE) simulations of a simple cup drawing process, which was studied in the benchmarks of the NUMISHEET 2002 have been conducted using a commercial dynamic-explicit FE-analysis package. The materials analyzed have been 6111-T4 aluminum alloy and mild steel graded as deep drawing quality. Basic process parameters, which are the blank holding force and the lubrication condition, have been varied to obtain a "successful" product and the process windows for these two materials have been compared and investigated. Thickness distributions in the blank, force requirements for the process and product quality have been used for the basis of comparison. The results are also compared with an analytical model developed by Ramaekers

Comparison of the Deep Drawability of Aluminum and Steel using Numerical Simulation Experiments

Abstract. Sheet metal forming processes, especially deep drawing processes give diverse results by various materials. Extreme differences occur between steel sheets and aluminum sheets. The main causes of these differences are variances in micro-and macroscopic material properties, such as anisotropy. In this study, the behavior of two distinct materials, steel and aluminum alloy, during an axisymmetrical cup drawing operation has been studied numerically. For this purpose, finite element (FE) simulations of a simple cup drawing process, which was studied in the benchmarks of the NUMISHEET 2002 have been conducted using a commercial dynamic-explicit FE-analysis package. The materials analyzed have been 6111-T4 aluminum alloy and mild steel graded as deep drawing quality. Basic process parameters, which are the blank holding force and the lubrication condition, have been varied to obtain a "successful" product and the process windows for these two materials have been compared and investigated. Thickness distributions in the blank, force requirements for the process and product quality have been used for the basis of comparison. The results are also compared with an analytical model developed by Ramaekers

Metallurgical influence on quench distortion of SAE 52100 long cylinders

Quenching of steel components results in complex and hard-to-predict dimensional and shape changes (distortion). Even the components manufactured from different parts of the same semifinished product may show significantly different distortion behaviours during quenching. The reason is thought to be non-uniform distribution of distortion potential carriers in the final component (i.e. alloying elements, segregations, residual stresses and phases) which are accumulated throughout the whole manufacturing chain. This study focuses on the effects of alloying element distribution and segregation on quench distortion. For this aim, long cylinders of various diameters were machined from 45 mm diameter SAE 52100 steel bars, and marked to define their exact positions in the initial bar. Then the cylinders were austenitised in a vertical furnace under nitrogen atmosphere and quenched in a gas nozzle field. The coordinate measurement results show that dimensional changes deviate significantly with machining position; however, the bending magnitudes and directions do not exhibit a distinct correlation with machining position and the cylinder diameter

Alüminyum alaşımlarının aşırı plastik deformasyon işlemleriyle üretilmesi

TÜBİTAK MAG01.09.2008Yüksek dayançlı alüminyum alaşımından mühendislik parçalarının üretimi, kapsamlı yatırım gerektiren büyük tesislerde termo-mekanik işlemlerle mümkün olmaktadır. Bu işlemlerin tane boyutunu ancak 10 mikrona kadar düşürebilmesi ve işlem parametrelerinin her alaşım için yeniden ayarlanma gerekliliği dezavantaj olarak değerlendirilmektedir. Bu nedenle, Al alaşımları için alternatif imalat tekniklerinin geliştirilmesi için son zamanlarda çok sayıda araştırma yapılmıştır. Çalışmalar, aşırı plastik deformasyon ile çok ince taneli iç yapı elde edilerek, Al- alaşımlarının mukavemetinde önemli artış sağlanabildiğini göstermiştir. Bu projenin konusu, alüminyum alaşımları için laboratuar ölçekli aşırı plastik deformasyon sistemleri tasarlayıp imal etmek ve elde edilen numuneleri karakterize etmektir. Projede gerçekleşenler aşağıda aşamalı olarak özetlenmiştir: ■ Önce, imal edilecek deformasyon düzeneklerinin tasarıma yardımcı olmak ve deformasyona etki eden faktörleri irdelemek için sonlu eleman analizi yöntemiyle modelleme çalışmaları yapılmıştır. İşlem parametrelerinin (kalıp geometrisi, sürtünme katsayısı) ve deforme edilen malzeme özelliklerinin (deformasyon pekleşmesi parametreleri/mekanizmaları ve deformasyon hızı hassasiyeti) işlem performansına etkileri incelenmiştir. Ayrıca malzeme sertleşme mekanizmaları ve hasar oluşumunun deformasyona uğrayan malzeme üzerine etkileri tartışılmıştır. ■ İkinci aşamada, çubuk şeklinde hacimli parçaları deforme eden Eş Kanallı Açısal Presleme (ECAP) sistemi tasarımlanıp imal edilmiştir. ECAP sistemi kullanılarak deforme edilen çeşitli alüminyum alaşımlarının mekanik özelliklerindeki ve mikroyapısındaki değişimler incelenmiştir. ■ Son aşamada, elde edilen tecrübeler ışığında, yassı mamulleri kesintisiz deforme edebilen Değişken Kanallı Açısal Presleme (DCAP) sistemi tasarımlanıp imal edilmiştir. Farklı sayıda pasodan geçirilen 6061 Al-alaşımı numunelere sertlik ve çekme deneyleri uygulanarak, DCAP paso sayısına bağlı olarak yüksek mukavemetli, ince taneli alüminyum levha üretilebilirliği incelenmiştir.Industrial products of high-strength Al-alloys are currently manufactured by thermo-mechanical processes, which are only applicable in the integrated plants requiring high investment cost. Moreover, reduction of the average grain size not less than 10 μm and re-adjustment of process parameters for each alloy type is evaluated as disadvantage. Therefore, recently there have been many research studies for development of alternative manufacturing techniques for aluminum alloys. Research activities have shown that it is possible to improve the strength of Al-alloys remarkably by severe plastic deformation which results in ultra-fine grain size. This project aims to design and manufacture the laboratory scale set-ups for severe plastic deformation of aluminum alloys, and to characterize the severely deformed samples. The stages of the project are summarized below: ■ First, for optimization of die design and investigation of parameters effecting the deformation finite element modeling simulations were performed. The effects of process parameters (die geometry, friction coefficient) and material properties (strain hardening, strain-rate sensitivity) were investigated. Beside, the effects of strain hardening and failure mechanisms on the severely deformed samples were discussed. ■ Next, Equal Channel Angular Pressing (ECAP) system that can severely deform the rod shaped samples were designed and manufactured. The variations in the microstructure and mechanical properties of 2024 Al-alloy rods deformed by ECAP were investigated. ■ Finally, based on the experience gained, a Dissimilar Channel Angular Pressing (DCAP) system for severe plastic deformation of flat products was designed and manufactured; then, 6061 Al-alloy strips were deformed. By performing hardness and tension tests on the strips that were deformed by various passes, the capability of the DCAP set-up for production of ultra-fine grain sized high-strength aluminum flat samples were investigated

Microstructural characterization of SiC reinforced aluminum matrix composites

TÜBİTAK MAG Proje30.10.200

Nondestructive determination of curing state of rubbers during vulcanization process

EPDM (ethylene-propylene-diene monomer) elastomer is one of the most widely used synthetic rubbers in several industries ranging from automotive to heating, ventilation, and air conditioning. Gaskets, bumpers, auto parts, auto brake systems, electrical installation, dust covers, weather stripping and conveyor belts are typical application examples. Quality control is important to ensure the rubber compound products meet the requested mechanical properties. Satisfactory properties can be obtained only by proper compounding and by appropriate vulcanization. Vulcanization is a chemical process that converts natural rubber and other polydiene elastomers into cross-linked polymers which have much improved mechanical properties. The aim of this study is to develop a non-destructive quality control method to determine the curing state, and thus the mechanical properties of elastomers by measuring ultrasonic wave velocity. A series of samples were prepared by curing the EPDM compound at 125oC for different periods ranging from 5 to 90 minutes. The results of the mechanical tests and ultrasonic measurements showed that ultrasonic wave velocity, hardness, and the maximum force increase with increasing curing time, in contrast to the tangent delta values