Bu çalışmada, Yld2000 akma fonksiyonunun katsayılarının belirlenmesinde nümerik optimizasyon tekniklerinden ardışık kuadratik programlama ve aktif-set metotlarının performansları değerlendirilmiştir. Çalışmada iki alüminyum alaşımı (AA6111-T4, AA6181-T4) ve bir yüksek mukavemetli sac malzeme (DP980) seçilmiştir. Yöntemler, hata fonksiyonunu yakınsama hızlarına ve minimizasyon sırasında inceledikleri fonksiyon sayısına göre değerlendirilmiş olup, üç malzeme için de aktif-set metodunun ardışık kuadratik programlamaya göre daha başarılı olduğu belirlenmiştir. Metodu doğrulamak için, belirlenmiş katsayılara göre malzemelerin akma gerilmesi oranları, Lankford katsayılarının sac düzlemi içerisindeki değişimleri ve akma yüzeylerinin pozitif bölgeleri tahmin edilmiş ve teorik sonuçlar deneysel sonuçlarla karşılaştırılmıştır. Yapılan karşılaştırmalardan malzemelerin düzlemsel anizotropilerinin ve pozitif bölgede akma yüzeylerinin başarılı bir şekilde tahmin edilebildiği görülmüştür.

In this study, performances of sequential quadratic programming and active-set methods from numerical optimization techniques were investigated in the determination of Yld2000 yield function coefficients. Two aluminum alloys (AA6111-T4, AA6181-T4) and a high strength steel sheet material (DP980) were selected in the study. Methods were examined according to their convergence rate and the number of function evaluations that occurred during the minimization and it was determined that active-set method was more successful than sequential quadratic programming for three materials. The variations of the yield stress ratios and Lankford coefficients in the sheet plane and positive regions of yield surfaces of the materials were predicted and theoretical results were compared with experimental results to validate the method. It is seen from the comparisons that planar anisotropy and yield surfaces of the materials in the positive regions could be successfully predicted.

Natural stones have taken place in all areas of our lives from ancient times to the present. In theearly days of humanity, they were used in daily life such as cutting, drilling, and agricultural tools, and their usagearea increased in parallel with the development of humanity. Especially, natural stones, which hold an importantplace in the field of construction, appear as monumental structures that express power, authority, and longevityfrom defense structures to grand magnificent structures. As well as being durable, natural stones were also usedfor their decorative features such as color and texture properties. Dusty rose-colored natural stones (andesite)which are used locally as building materials in İncesu (Seydişehir) and its surroundings were examined in termsof geological, geochemical, petrographical, physico-mechanical, and weathering indices. Geologically, in thechemical analysis results of the samples taken from the natural stones (andesite) observed in the district of İncesuand its surroundings, all of the rocks are located "andesite" area in the total alkaline versus silica (TAS) diagram,"sub alkaline" area in the alkaline-sub alkaline separation diagram and "calc-alkaline" area in the AFM diagram.The physico-mechanical test results of andesites, which are resistant to weathering under atmospheric conditionsfor many years and known for their high strength, were also evaluated according to standards. It was found thatthe abrasion resistance and bending strength (flexural strength) remained within the limit values. According tothe weathering indices, it was found to be slightly weathered.