Kod Yardımı İle Çekme Testinden Akış Gerilmesi ve Hasar Modeli Parametre Katsayılarının Tahmini

Öz

Sadece sınır şartlarının kusursuz verilmesi değil, metal şekillendirme, imalat, çarpışma vb. simülasyonlarda en önemli diğer bir girdi de kullanılan malzemeye ait özellikleridir. Bu özelliklerinin doğru tanımlanması, simülasyonun sonuçlarının uygulamada kullanımına olan güveni artırır. Simulasyon programlarında farklı sıcaklıklarda ve şekil değiştirme hızlarında stress-strain ilişkisini temsil eden parametrik modellerin en çok tanınmışlarından biri Johnson-Cook gerilme akışı ve sünek hasar modelidir. Ancak malzemeye ait JC parametrelerinin elde edilmesi süreci oldukça uzun ve yorucudur. Çok sayıda testin ve simülasyon sonuçlarının beraber değerlendirilmesi, eğri uydurma, regresyon ve optimizasyon prosedürleri, organize bir matematiksel işlem uygulama sürecini zorunlu kılar. Yaptığımız program ile farklı yapıdaki testler, test cihazı sonuç ve simülasyon rapor format girdileri, hiyerarşiye uygun bir düzende girilerek, parametre katsayıları otomatik elde edilmektedir. Kullanıcı testlere ve sonuçlara ait ortak grafiklerle görsel olarak kontrol edebilmekte, gerekli durumlarda testlere ait kritik noktaların bulunmasına müdahale edebilmektedir. Farklı eğri uydurma algoritmaları kullanılarak en uygun parametrelerin bulunması sağlanmaktadır.

Anahtar Kelimeler

• Akma gerilmesi modeli
• Sünek hasar modeli
• JC parametreleri
• Eğri uydurma
• Optimizasyon

Estimate of The Flow Stress and Damage Model Parameter Coefficients from Tensile Test with The Help of Code

Abstract

Metal forming, machining, crashing, etc. in simulations, not only the boundary conditions are given perfectly, but also another important input is the properties of the material used. Defining these properties correctly increases the confidence in using the results of the simulation in practice. One of the most well-known parametric models representing the stress-strain relationship at different temperatures and strain rates in simulation programs is the Johnson-Cook flow stress model and ductile damage model. However, the process of obtaining JC parameters for the material is quite long and tiring. Combined evaluation of multiple tests and simulation results, curve fitting, regression and optimization procedures necessitate an organized mathematical operation process. With the program written, it was tried to get both fast and accurate parameter results by using different mathematical solution methods. Parameter constants are obtained automatically by entering different test types, test device result format and simulation report format entries in a hierarchical order using the written program. The user can visually check the tests and results with on the same graphics and intervene in the detection of critical points of the tests when necessary. By using different curve fitting algorithms, finding the most suitable parameters is provided.

Keywords

• Flow Sress Model
• Ductile damage model
• JC parameters
• Curve fitting
• Optimization

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