Mahmut Gülesin

A part recognition based computer aided assembly system

In this paper, a new approach has been developed to recognize the CAD models through their face adjacency relations and attributes and to automatically assemble the recognized parts in a CAD environment. Adjacent faces and the face attributes belonging to each face of parts designed in a CAD platform are derived by using of standard for the exchange of product data (STEP) file. They are represented in a square matrix format named face oriented relation matrix (FORM). An expert system was developed and embedded within the system. A knowledge base of the expert system is generated using a text editor. Reasoning the face adjacency relations and the face attributes in the knowledge base and FORM, the parts are recognized. Then, a reference face belonging to recognized parts is determined and they are positioned and assembled in assembly file through their reference faces. Part recognition approach developed in this study is applied to a computer aided assembly system. But it may be useful and practical for different CAD/CAM applications such as process planning and group technology too. The algorithm has been applied to a diesel automobile engine which has complex parts to demonstrate its efficiency and capability.

The machinability of Al/B4C composites produced by hot pressing based on reinforcing the element ratio

Abstract In this study, the effects of the particle reinforcement ratio on cutting forces and surface roughness were investigated when milling particle-reinforced metal matrix composite (MMCp) produced by hot pressing with different cutting tools. Alumix 123 alloy as the matrix material and B4C particles with an average size of 27 μm and 5%, 10% and 15% ratio as reinforcing elements were used for the manufacture of composite materials. The experiments were carried out in dry cutting conditions with four different cutting speeds, constant feed rate and depth of cut. Changes depending on the increased reinforcement ratio in cutting forces and surface roughness values were investigated; the effects of 10% B4C reinforced composite on tool wear were also examined. It was observed that cutting forces increased with the increase in cutting speed and particle ratio with carbide cutting tools, and it was seen that the cutting forces on the cutting tools decreased when cutting speed decreased and the cutting forces increased as the reinforcement ratios increased. In addition, with increasing the cutting speed, the surface roughness of the machined surfaces of composite samples increased with the carbide tools, while the cubic boron nitride (CBN) tools have the opposite effect. While it was seen that flank and crater wear occurred on the cemented carbide cutting tools, abrasive, adhesive and other wear mechanism tools in addition to the main wear mechanism, no remarkable flank and crater wear occurred on CBN cutting tools.

Mechanical and fracture behavior of B4C reinforced Al composites produced by hot pressing

Abstract In this study, the effects of particle addition on the microstructure, mechanical properties and fracture behaviors of Al/B4C particle reinforced composite produced by hot pressing method were investigated. After the production of 5, 10 and 15 wt.-% of B4C reinforced composites, T6 heat treatment was applied. It was specified that a strong interface bond occurred between the matrix and particles, and during the fracturing of composites, this effect increased the particle fracture. It was observed that particles were fractured parallel to the fracture surface and to each other fracture surface of MMCp. In general, cavity of particle separated from the matrix was not seen. In the production of MMCp, it was also observed that hot pressing provided a density higher than 99 %. After the heat treatment the maximum hardness value of 173 HB was reached with 15 wt.-% B4C reinforced sample. The transverse rupture strength (TRS) decreased with the increase of reinforcement ratio. The highest TRS was 510 MPa with the 5 wt.-% reinforced material, whereas the lowest value was obtained to be 387 MPa with the 15 wt.-% B4C reinforced material.

BİLGİSAYAR DESTEKLİ PARÇA TANIMA SİSTEMİNİN GELİŞTİRİLMESİ VE MOTOR MONTAJINA UYGULANMASI

Bu calismada, dizel motor parcalarinin yuz bitisiklik iliskileri ve nitelikleri kullanilarak taninmasi ve taninanparcalarin bilgisayar destekli tasarim (BDT) ortaminda montajinin yapilmasi icin bir yaklasim gelistirilmistir.Tanima isleminde uzman sistem teknigi kullanilmistir. Motor parcalarinin BDT modellerinin otomatik olarakSTEP donusumu yapilmis ve olusturulan STEP dosyasi yorumlanarak parca uzerindeki her bir yuzun komsuyuzleri ve nitelikleri cikarilmistir. Ayni zamanda, bir yazim editoru kullanilarak bir veri tabani olusturulmustur.Veri tabani ve parca tanima isleminden elde edilen yuz bitisiklik iliskileri ve nitelikleri karsilastirilarak parcalarbilgisayar tarafindan taninmaktadir. Parca modeli, parca ismi ile veri tabanina kaydedilmekte ve modele ait yuzkomsuluk iliski matrisi ile temsil edilmektedir. Montaj asamasinda, taninan parcalarin referans yuzeylerbelirlenmis ve referans yuzeyler vasitasiyla parcalar montaj dosyasina tasinarak BDT ortaminda montajiyapilmistir.

BDT/BDİ UYGULAMALARI İÇİN BİLGİSAYAR DESTEKLİ PARÇA TANIMA YAKLAŞIMININ GELİŞTİRİLMESİ

3 boyutlu BDT (Bilgisayar Destekli Tasarim) modellerinden imalat bilgilerinin otomatik cikarimi BDT/BDI(Bilgisayar Destekli Imalat)’in entegrasyonu icin onemli bir calisma alanidir. Bu makalede, BDT/BDIentegrasyonunu desteklemek icin uzman sistem tabanli bir parca tanima yaklasimi gelistirilmistir. Sisteme girdiolarak 3 boyutlu BDT modellerinin STEP (Standard for the Exchange of Product Model Data) dosyasikullanilmistir. Her bir yuzeye ait komsu yuzeyler ve nitelikler STEP dosyasindan cikarilarak matematiksel birmodelde (YKIM- Yuzey Komsuluk Iliski Matrisi) temsil edilmistir. Ayni zamanda, Windows tabanli bir yazimeditoru kullanilarak bilgi tabani olusturulmus ve bilgi tabani icin bir kural yazma formati gelistirilmistir. YKIMve bilgi tabaninda temsil edilen geometrik ve topolojik bilgi karsilastirilarak parcalar taninmistir. Parca tanimaalgoritmasi islem planlama, grup teknolojisi gibi bircok BDT/BDI uygulamasi icin uygulanabilirdir.Algoritmanin verimliligi ve kapasitesini gostermek icin yaklasim karmasik parcalara sahip olan otomobil motorparcalarina uygulanmistir.