Evaluation of strain and stress states in the single point incremental forming process

Single point incremental forming (SPIF) is a promising manufacturing process suitable for small batch production. Furthermore, the material formability is enhanced in comparison with the conventional sheet metal forming processes, resulting from the small plastic zone and the incremental nature. Nevertheless, the further development of the SPIF process requires the full understanding of the material deformation mechanism, which is of great importance for the effective process optimization. In this study, a comprehensive finite element model has been developed to analyse the state of strain and stress in the vicinity of the contact area, where the plastic deformation increases by means of the forming tool action. The numerical model is firstly validated with experimental results from a simple truncated cone of AA7075-O aluminium alloy, namely, the forming force evolution, the final thickness and the plastic strain distributions. In order to evaluate accurately the through-thickness gradients, the blank is modelled with solid finite elements. The small contact area between the forming tool and the sheet produces a negative mean stress under the tool, postponing the ductile fracture occurrence. On the other hand, the residual stresses in both circumferential and meridional directions are positive in the inner skin of the cone and negative in the outer skin. They arise predominantly along the circumferential direction due to the geometrical restrictions in this direction.The authors would like to gratefully acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) under project PTDC/EMS-TEC/1805/2012. The first author is also grateful to the FCT for the postdoctoral grant SFRH/BPD/101334/2014.info:eu-repo/semantics/publishedVersio

Incremental deformation: A literature review

Nowadays the customer requirements are in permanent changing and according with them the tendencies in the modern industry is to implement flexible manufacturing processes. In the last decades, metal forming gained attention of the researchers and considerable changes has occurred. Because for a small number of parts, the conventional metal forming processes are expensive and time-consuming in terms of designing and manufacturing preparation, the manufacturers and researchers became interested in flexible processes. One of the most investigated flexible processes in metal forming is incremental sheet forming (ISF). ISF is an advanced flexible manufacturing process which allows to manufacture complex 3D products without expensive dedicated tools. In most of the cases it is needed for an ISF process the following: a simple tool, a fixing device for sheet metal blank and a universal CNC machine. Using this process it can be manufactured axis-symmetric parts, usually using a CNC lathe but also complex asymmetrical parts using CNC milling machines, robots or dedicated equipment. This paper aim to present the current status of incremental sheet forming technologies in terms of process parameters and their influences, wall thickness distribution, springback effect, formability, surface quality and the current main research directions

Force Analysis for single point incremental forming

Single point incremental forming is a new forming process for small batch production and rapid prototyping of sheet metal parts. The forces induced during single point incremental forming are unknown process parameters the magnitude of which is of importance for the development of process models. The purpose of the current study is to develop a method for predicting forces for complex part geometries based on the measured forces for parts with uniform wall angles. Firstly, a set of experiments, planned applying techniques for design of experiments, was performed with the aim of establishing a relation between the forces and the main process parameters for uniform angle parts. A regression equation of the forces was then obtained in terms of four parameters: the vertical step size between consecutive contours, the diameter of the tool, the wall angle of the part and the thickness of the sheet metal. In a second step, a technique of assembling the force curves obtained from the regression equation was employed to predict the forces for other shapes with varying wall angles.status: publishe

Force reduction in bending of thick steel plates by localized preheating

A trend towards higher tonnage press brakes, suitable for processing thick plates, can be observed. In this paper a dynamic method for preheating of thick steel plates, limited to the bending area, is presented, facilitating bending with a significantly reduced total force. The dynamic heating method thus allows to substantially extend the process window of press brakes. The method was experimentally tested on low carbon steel plates, characterised by a relatively high required temperature rise in order to achieve a favourable yield behaviour. A prototype setup developed for this purpose is described. Reported test results include achievable temperature distributions, force measurements as a function of temperature and spring back measurements. A derived simulation model allows to extrapolate the results to higher thickness plates.status: publishe

Perbedaan Kualitatif dan Kuantitatif Semen Segar pada Berbagai Bangsa Sapi potong

Penelitian ini dilaksanakan di BBIB Singosari yang berada di Desa Toyomarto Kecamatan Singosari Kabupetan Malang, Jawa Timur pada tanggal 11 Juni 2012 sampai dengan 11 Juli 2012. Penelitian ini bertujuan untuk mengetahui perbedaan kuantitatatif dan kualitastatif semen segar pada sapi Limousin, Simental, Brahman, Ongole dan Bali. Penelitian ini diharapkan dapat digunakan sebagai pedoman BBIB untuk penggunaan pejantan Sapi potong sebagai penghasil semen berdasarkan bangsa ternak yang dapat digunakan sebagai salah satu kriteria dalam produksi semen beku. Materi yang digunakan di dalam penelitian ini adalah bangsa sapi potong. Metode penelitian yang digunakan yaitu percobaan, yaitu 2 ekor sapi Limousin, 2 ekor sapi Simental, 2 ekor sapi Brahman, 2 ekor sapi Ongole dan 2 ekor sapi Bali. Parameter yang diamati adalah volume semen segar, warna, konsentrasi, konsistensi, pH, motilitas massa dan individu, jumlah spermatozoa motil. Data yang diperoleh selama penelitian kemudian dianalisis menggunakan Rancangan Acak Kelompok (RAK) dengan bantuan program SPSS, apabila terdapat perbedaan dilakukan uji lanjut yaitu dengan uji jarak berganda duncan. Hasil penelitian menunjukkan bahwa kualitas semen segar pada kelima kelompak bangsa (Limousin, Simental, Brahman, Ongole, Bali) secara berturut-turut adalah Warna : putih susu, pH: 6,5 ± 0,14 (10 6 /ml); 6.4 ± 0.14 (10 6 /ml); 6.4± 0.35 (10 6 /ml); 6.5 ± 0.147 (10 6 /ml) dan 6.5 ± 0.33 (10 6 /ml), konsistensi: pekat; pekat; pekat; pekat dan sedang, motilitas massa: 2+, volume: 6.308 ± 1.386; 6.238 ± 1.566; 5.174 ± 1.719; 6.748 ± 3.441 dan 7.358 ± 1.478 ml, konsentrasi: 1403.366 ± 409.2; 1845.556 ± 421.3; 1651.884 ± 540.3; 1263.934 ± 621.6 dan (1361.33 ± 316.3) juta/ml, motilitas individu: 69.9 ± 6.67 (%); 70.4 ± 4.56 (%); 58 ± 14.46 (%); 65.2 ± 12.9 (%) dan 68.7 ± 6.77 (%), jumlah spermatozoa motil: 6273± 2703 (10 6 ); 8197 ± 2955 (10 6 ); 5135 ± 2769 (10 6 ); 4913 ± 2718 (10 6 ) dan 6801 ± 1936 (10 6 ). Hasil penelitian menunjukkan bahwa terdapat perbedaan pada kualitatif dan kuantitatif semen segar pada berbagai bangsa sapi potong. Kualitas dan kuantitas semen segar bangsa sapi Simental lebih baik dibandingkan bangsa sapi Limousin, Brahman, Ongole dan Bali

La lymphoscintigraphie dans la prise en charge thérapeutique des œdèmes des membres par les soins de santé en Belgiq

Limbedemas of lymphatic origin, either primary, or secondary, represent a chronic disease sometimes heavy to bear by patients who suffer from them. These lymphedemas imply specific care by physical therapists trained to the use of different therapeutic approaches. Until a few years, only the treatments of secondary lymphedemas after radiotherapy and/or complete nodal dissection for cancer were reimbursed by the national health insurance system in Belgium. The introduction of the primary congenital lymphedemas as a disease also reimbursed raised several problems and led to a redefinition of these situations and of their cares. The definition and classification of the lymphedemas in view of the reimbursement of their treatments by the national health insurance system are now officially based (not only on the sole clinical history but) mainly on their clinical severity and/or also on the result of their lymphoscintigraphic investigation (according to a methodological protocol and to diagnostic criteria adopted at the national level). The reimbursements of the treatments by the physical therapists were also adapted and improved. The lymphocintigraphic investigations of the limbedemas became so essential in the management of the lymphedematous situations and in the reimbursement of their physical treatments in Belgium. © 2010 Elsevier Masson SAS.SCOPUS: ar.jinfo:eu-repo/semantics/publishe