Gererek bükme proses parametrelerinin sonlu elemanlar yöntemi ile incelenmesi
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Tarih
2022
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info:eu-repo/semantics/openAccess
Özet
Otomotiv sektöründe soğuk sac şekillendirme yöntemlerinden biri olan gererek bükme prosesi genellikle rollforming prosesinden sonra uygulanan, seri üretimlerde yüksek mukavemetli parçaların üretimine imkân tanıyan yaygın yaklaşımlardandır. Ticari araç kayar kapılarının güvenlik bileşenlerinden biri olan ray profilleri de rollforming prosesinden sonra gererek bükme ile şekillendirilmektedir. Söz konusu mekanizmaların hassas boyutsal ölçülere sahip olması gerektiğinden, gererek bükme prosesinin tasarımının da özenle yapılması zaruridir. Kayar kapı rayı için imalat prosesinin tasarlanmasında kesit geometrisi, büküm açısı ve kullanılacak malzeme parametreleri etkili parametreler arasında başta gelmektedir. Profilin kesit geometrisi, profilin kaç eksende gererek bükülmesi gerektiğini ve büküm için referans alınması gereken bölgelerin belirlenmesi açısından büyük önem taşımaktadır. Büküm açısı tasarlanacak kalıbı belirleyeceği için önemlidir. Profilde kullanılacak malzeme türü ise proses sırasında gererek bükme için uygulanacak kuvvetlerin belirlenmesinde ve profil geometrisinin oluşturulması için gerekli bükme açılarının malzemenin mekanik özellikleri ile ne ölçüde uyumlu olduğunun belirlenmesi açısından önem arz etmektedir. Son yıllarda ağırlık azaltma yaklaşımlarının yaygınlaşması ile yüksek dayanımlı yeni nesil malzemelerin kullanımını gerektirmektedir. MS1500 çeliği de bu doğrultuda kullanımı giderek yaygınlaşmakta olan malzemeler arasında gelmektedir. Bu çalışmada MS1500'den üretilmiş araç kayar kapısı üst rayının gererek bükülmesinde etkili parametrelerin parça geometrisi üzerindeki etkileri incelenmiştir. Bu kapsamda kalıbın dönme merkezi, profilde uygulanacak çekme oranının aldığı farklı değerlerin profil kesitinde neden olduğu deformasyonlar araştırıldı. Bu çerçevede, MS1500 malzemenin mekanik özelliklerinin karakterizasyonundan elde edilen veriler kullanılarak bir malzeme kartı oluşturuldu. Profilin gererek bükülmesi ile analizler MSC Marc/Mentat sonlu elemanlar programında doğrulanarak tasarım geliştirilmeleri yapılmıştır. Farklı dönme merkezine göre yapılan analizlerde dönme merkezi sabit tutulup çekme oranı değiştirildiğinde bükülemeyen, bükülen ama çökme olan, bükülen ama alttan burkulma olan ve tamamen bükülen profillerin olduğu görüldü. Alınan sonuçlar incelendiğinde profil kesitinin bükme sırasındaki çökmesinin en düşük seviyede tutulacağı bir merkezin seçilmesi için izlenebilecek bir yaklaşım ortaya konulmuştur. Bu yaklaşım dahilinde, plastik deformasyon baskın şekilde kesitteki çökmenin en az seviyede meydana geldiği nokta profil doğrultusunda araştırılmıştır. Profilin plastik deformasyon bölgesinde şekillenmesi için de çekme oranlarının alacağı değerler araştırılarak optimum proses koşulları belirlenmiştir.
Stretch bending process, which is one of the cold sheet forming methods in the automotive industry, is one of the common approaches that is generally applied after the rollforming process and allows the production of high-strength parts in mass production.Rail profiles, one of the safety components of commercial vehicle sliding doors, are also shaped by stretching and bending after the rollforming process. The design of the stretch bending process must be done with elaboration, as the mechanisms in question must have precise dimensional measurements. Section geometry, bending angle and material parameters to be used are among the most effective parameters in the design of the manufacturing process for the sliding door rail. The section geometry of the profile has major importance in terms of determining how many axes the profile have to be bent by stretching and the regions that have to be referenced for bending. The bending angle is important as it will determine the mold to be designed. As for the type of material to be used in the profile is important in determining the forces to be applied for stretch bending during the process and determining to what extent the bending angles required for the forming of the profile geometry are compatible with the mechanical properties of the material. With the widespread use of weight reduction approaches in recent years, it requires the use of high-strength new generation materials. MS1500 steel is among the materials that are becoming increasingly common in this direction. In this study, the effects of the parameters effective on the tension bending of the vehicle sliding door upper rail made of MS1500 on the geometry of the part were examined. In this context, the deformations caused by the center of rotation of the mold and the different values of the tensile ratio to be applied in the profile were investigated. A material card was created using data from the characterization of the mechanical properties for MS1500 material. By stretching the profile, analyzes were verified in MSC Marc/Mentat finite element program, and design improvements were done. In the analyzes taken according to different rotation centers, it was observed that when the center of rotation was kept constant and the tensile ratio was changed, there were profiles that could not be fully bent, twisted but collapsed, bent but buckled from the bottom, and completely bent. When the results are examined, an approach has been put forward to select a center where the collapse of the profile section during bending will be kept at the lowest level. Within this approach, the point where the collapse in the section occurs at the lowest level, with plastic deformation dominant, is investigated in the profile direction. Optimum process conditions were determined by investigating the values of the shrinkage ratios for the profile to be shaped in the plastic deformation zone.
Stretch bending process, which is one of the cold sheet forming methods in the automotive industry, is one of the common approaches that is generally applied after the rollforming process and allows the production of high-strength parts in mass production.Rail profiles, one of the safety components of commercial vehicle sliding doors, are also shaped by stretching and bending after the rollforming process. The design of the stretch bending process must be done with elaboration, as the mechanisms in question must have precise dimensional measurements. Section geometry, bending angle and material parameters to be used are among the most effective parameters in the design of the manufacturing process for the sliding door rail. The section geometry of the profile has major importance in terms of determining how many axes the profile have to be bent by stretching and the regions that have to be referenced for bending. The bending angle is important as it will determine the mold to be designed. As for the type of material to be used in the profile is important in determining the forces to be applied for stretch bending during the process and determining to what extent the bending angles required for the forming of the profile geometry are compatible with the mechanical properties of the material. With the widespread use of weight reduction approaches in recent years, it requires the use of high-strength new generation materials. MS1500 steel is among the materials that are becoming increasingly common in this direction. In this study, the effects of the parameters effective on the tension bending of the vehicle sliding door upper rail made of MS1500 on the geometry of the part were examined. In this context, the deformations caused by the center of rotation of the mold and the different values of the tensile ratio to be applied in the profile were investigated. A material card was created using data from the characterization of the mechanical properties for MS1500 material. By stretching the profile, analyzes were verified in MSC Marc/Mentat finite element program, and design improvements were done. In the analyzes taken according to different rotation centers, it was observed that when the center of rotation was kept constant and the tensile ratio was changed, there were profiles that could not be fully bent, twisted but collapsed, bent but buckled from the bottom, and completely bent. When the results are examined, an approach has been put forward to select a center where the collapse of the profile section during bending will be kept at the lowest level. Within this approach, the point where the collapse in the section occurs at the lowest level, with plastic deformation dominant, is investigated in the profile direction. Optimum process conditions were determined by investigating the values of the shrinkage ratios for the profile to be shaped in the plastic deformation zone.
Açıklama
Anahtar Kelimeler
Gererek bükme prosesi, ray, ticari araç kayar kapıları, sonlu elemanlar analizleri, MS1500, Stretch bending process, rail, commercial sliding doors, MS1500, finite element analysis
