Mikro derin çekme işleminde numune ve tribolojik boyut etkisinin sonlu eleman analiziyle incelenmesi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2013Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2013Bu çalışmada nümune boyut etkisi ve sürtünme katsayısının bir mikro derin çekme parçasının şekillendirilmesine etkisi sonlu eleman analizi yardımıyla incelenmiştir. Boyut etkisini incelemek amacıyla 0.1 , 0.2 ve 1 mm kalınlıklarında 3 farklı sac kullanılmış; kalıp ve zımbaya ait ölçüler de her bir işlemde aynı oranda arttırılarak 3 farklı sonlu eleman modeli oluşturulmuştur. Sac kalınlığının azaltılmasıyla eşdeğer von Mises gerilmesi değerlerinin arttığı tespit edilmiştir. Tribolojik boyut etkisinin belirlenmesi amacıyla yapılan analizlerde ise sürtünme katsayısının arttırılması durumunda eşdeğer gerilmelerde artış gözlenmiş ve 0.1 mm sac kalınlığı için en yüksek eşdeğer gerilme değeri elde edilmiştir.Effects of specimen size and coefficient of friction on micro-deep drawn part have been investigated by means of finite element analysis. To this goal, blanks with three different thicknesses, namely 0.1, 0.2, and 1 mm, have been used. Furthermore, dimensions for die and punch are increased by same factor in FE models. Results showed that, equivalent von Mises stress values are increased when thinner sheet gauges are used. Similarly, increased equivalent von Mises stress values are observed with increasing coefficient friction values, and the highest values are obtained for the smallest sheet thickness

Aa 6013 Alaşımının Halka Basma Testi Ve Sonlu Eleman Analizi

Konferans Bildirisi-- İstanbul Teknik Üniversitesi, Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2017Conference Paper -- İstanbul Technical University, Theoretical and Applied Mechanical Turkish National Committee, 2017Kalıp ve iş parçası arasındaki sürtünme, metal şekillendirme işlemlerinde deformasyon yükünü, metal akışını, yüzey kalitesini ve malzemenin iç yapısını etkileyen faktörlerdendir. Bu durum, kalıp ve iş parçası arasındaki sürtünmenin anlaşılmasını zorunlu kılmaktadır. Halka basma testi, ara yüzey sürtünmesini incelemek ve yağlayıcıları test etmek için yaygın olarak kullanılır. Bu çalışmada, özellikle otomotiv endüstrisi tarafından yoğun olarak kullanılan AA 6013 alaşımının sürtünme durumlarının incelenmesi amaçlanmıştır. Bu amaçla, ilgili alaşımdan halka şeklinde üretilen, standart boyut ölçülerine sahip (dış çap: iç çap: yükseklik = 6:3:2) numunelere oda şartlarında farklı deformasyon oranlarında basma testleri tatbik edilmiş ve sürtünme katsayısının belirlenmesi için yeni bir yöntem kullanılmıştır. Halka basma testleri gerçekleştirildikten sonra, bombeleşmeyen yüzey ile bombeleşen yüzey arasındaki akma yönündeki mesafe resim işleme (image processing) yöntemiyle ölçülmüştür. Daha sonra ise, halka basma testinin sonlu elemanlar modeli oluşturulmuştur. Modellemede, Coulomb sürtünme modeli kullanılmıştır ve farklı sürtünme katsayıları ile analizler gerçekleştirilmiştir. Bombeleşmeyen yüzey ile bombeleşen yüzey arasındaki akma yönündeki mesafenin deneysel verilerle uyum sağladığı durumdaki sürtünme katsayısı, o işlem için iş parçası ve kalıplar arasında oluşan sürtünme katsayısı olarak tanımlanmıştır.The interface friction between the workpiece and dies is among the factors that significantly affect deformation load, metal flow, surface quality and microstructure of the product. Therefore, it is crucially important to understand frictional conditions between the workpiece and dies. The ring compression test has been widely to analyze interface friction and for testing lubricants. This study, aimed for investigating the friction conditions of AA 6013 aluminum alloy which is commonly used in automotive industry. Standard ring shaped (Ratio of outer diameter: inner diameter: height = 6:3:2) specimens were compressed under different deformation ratios, and a novel approach was used to determine the coefficient of friction at the interface of die and workpiece. After experimental work, the distance between barreled and not barreled surfaces along material flow direction was measured by image processing. The finite element model was then established and constant friction coefficient (Coulomb friction coefficient) was used at interface. Several runs were performed along with different coefficient of friction values to match the experimental and numerical results, and consequently to determine the coefficient of friction experienced at die-workpiece interface

Ilık Hidromekanik Derin Çekme Prosesinin Sonlu Elemanlar Analizi Ve Parametrik Optimizasyonu

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Bu çalışmada otomotiv sanayiinde taşıt ağırlığını azaltmak için giderek artan şekilde kullanılan alüminyum alaşımlarının şekillendirilmesinde kullanılan geleneksel yöntemlerin yerini almaya başlayan ılık hidromekanik derin çekme prosesinin kapsamlı bir sonlu elemanlar modeli oluşturulmuştur. Farklı eleman sayıları ve eleman formülasyonları, temasta bulunan bileşenler için farklı sürtünme katsayıları ve malzeme modelleri sistematik bir şekilde denenerek sonlu eleman modeli için en uygun tercihler ve değerler belirlenmeye çalışılmıştır. Çalışmanın ikinci kısmında ise, oluşturulan sonlu elemanlar modeli ile ılık hidromekanik derin çekme işlemindeki takım sıcaklıklarının ve yükleme profillerinin (hidrolik basıncı ve baskı plakası kuvveti) en iyi şekillendirilebilirliği veren değerleri belirlenmeye çalışılmıştır. Bu çalışmalar neticesinde, malzeme davranışını en iyi elastik-viskoplastik-termal malzeme modelinin yansıttığı belirlenmiştir. Coulomb sürtünme katsayıları sac-kalıp ara yüzeyi için 0.05, sac-baskı plakası için 0.05 ve sac-zımba sürtünme yüzeyleri arasında 0.25 olarak tespit edilmiştir. En iyi şekillendirmenin sağlanabilmesi için kalıp ve zımbaya ait sıcaklık değerleri sırasıyla 300 ve 25 °C olarak belirlenmiştir. Hidrolik basıncın baskı plakasının kuvvetine göre daha etkin bir parametre olduğu görülmüştür.In current study, a comprehensive finite element modeling was established for warm hydromechanical deep drawing process which is a promising technique in forming of aluminum alloys that are expected to be increasingly exploited in automotive industry along with lightweighting efforts. Different number of elements and element formulations, coefficients of friction for contacting surfaces and material models were systematically tested and optimum choices and values were determined. In the second part of the study, optimum tool temperature, and loading profiles (hydraulic pressure and blank holder force) were obtained parametrically to achieve highest formability in warm hydromechanical deep drawing process by using established FE model. As a result, elastic-viscoplastic-thermal material model was found to be reflecting the material behavior better compared to other material models utilized. Coulomb friction coefficient for contacting surfaces blank-die, blank-blank holder and blank-punch were determined as 0.05, 0.05 and 0.25, respectively. Optimal temperatures values for die and punch were determined as 300 and 25°C, respectively when highest formability is taken into account. Hydraulic pressure was found to be more effective on formability than blank holder force

Defect types.

This chapter provides an overview of the common types of defects found in various structural materials and joints in aircraft. Materials manufacturing methods (including large-scale production) have been established in the aircraft industry. However, as will be seen in this chapter, manufacturing defects and defects during in-service conditions are very common across all material types. The structural material types include metals, composites, coatings, adhesively bonded and stir-welded joints. This chapter describes the defect types as a baseline for the description of their detection with the methods of Chap. 5 to 8. Based on the understanding of the defect types, there is great expectation for a technical breakthrough for the application of structural health monitoring (SHM) damage detection systems, where continuous monitoring and assessment with high throughput and yield will produce the desired structural integrity

Soğuk dövme işleminde sürtünme analizi.

Friction is one of the important parameters in metal forming processes since it affects metal flow in the die, forming load, strain distribution, tool and die life, surface quality of the product etc. The range of coefficient of friction in different metal forming applications is not well known and the factors affecting variation are ambiguous. Commercially available FEA packages input the coefficient of friction as constant among the whole process which is not a realistic approach. In this study, utility of user-subroutines is integrated into MSC SuperForm v.2004 and MSC Marc v.2003 FEA packages, to apply a variable coefficient of friction depending on the contact interface conditions. Instead of using comparatively simple friction models such as Coulomb, Shear (constant) models, friction models proposed by Wanheim-Bay and Levanov were used to simulate some cold forging operations. The FEA results are compared with the experimental results available in literature for cylinder upsetting. Results show that, large variation on the coefficient of friction is possible depending on the friction model used, the part geometry and the ratio of contact normal pressure to equivalent yield stress. For the ratio of contact normal pressure to equivalent yield stress values above 4, coefficient of friction values are approximately same for both friction models.M.S. - Master of Scienc

Comparative investigations on numerical modeling for warm hydroforming of AA5754-O aluminum sheet alloy

This study aimed to determine the proper combinations of numerical modeling conditions (e.g. solver, element type, material model) for warm hydroforming of AA5754-O aluminum alloy sheets. Assessment of finite element analyses (FEA) is based on comparison of numerical results and experimental measurements obtained from closed-die forming, hydraulic bulge and tensile tests at different temperature (25–300 °C) and strain rate (0.0013–0.013 1/sec) levels. Thinning (% t) and cavity filling ratios (CFR) on the formed parts were taken as comparison parameters. Several numerical analyses employing different element types, solution methods and material models were performed using the commercially available FEA package LS-Dyna to determine the best combination of modeling options to simulate the actual warm hydroforming operation as accurately as possible. Analyses showed that relatively better predictions were obtained using isotropic material model, shell elements and implicit solution technique when compared with experimental results

Effect of manufacturing process sequence on the corrosion resistance characteristics of coated metallic bipolar plates.

Metallic bipolar plate (BPP) with high corrosion and low contact resistance, durability, strength, low cost, volume, and weight requirements is one of the critical parts of the PEMFC. This study is dedicated to understand the effect of the process sequence (manufacturing then coating vs. coating then manufacturing) on the corrosion resistance of coated metallic bipolar plates. To this goal, three different PVD coatings (titanium nitride (TiN), chromium nitride (CrN), zirconium nitride (ZrN)), with three thicknesses, (0.1, 0.5, 1 μm) were applied on BPPs made of 316L stainless steel alloy before and after two types of manufacturing (i.e., stamping or hydroforming). Corrosion test results indicated that ZrN coating exhibited the best corrosion protection while the performance of TiN coating was the lowest among the tested coatings and thicknesses. For most of the cases tested, in which coating was applied before manufacturing, occurrence of corrosion was found to be more profound than the case where coating was applied after manufacturing. Increasing the coating thickness was found to improve the corrosion resistance. It was also revealed that hydroformed BPPs performed slightly better than stamped BPPs in terms of the corrosion behavior

EXPERIMENTAL INVESTIGATIONS ON DEVELOPMENT OF RAPID DIE WEAR TESTS FOR STAMPING OF ADVANCED HIGH STRENGTH STEELS

ABSTRACT In a quest to achieve low-mass vehicles (i.e., higher fuel economy and lower emission), the automotive industry has been actively investigating the use of lightweight materials for a wide range of body panels and structural parts. Among the lightweight materials considered, Advanced and Ultra High Strength Steels (A/UHSS) hold promise as a prominent choice for the near future due to their relatively high formability and low cost compared to Aluminum and Magnesium alloys. However, due to their significantly higher strength than mild steel, in addition to the springback, blanking and joining issues, serious problems with the die wear are expected to arise during manufacturing. Although the die wear literature for the forming of conventional steels is prevalent, tribological issues of high strength steels have not been understood well yet. This study aims to develop a new, rapid and automated wear test for the die materials used in sheet metal forming operations of high strength steels (mainly DP and TRIP steels) and to investigate the wear, friction, and lubrication issues. With this test, the actual stamping conditions such as contact pressure, temperature, and sliding velocity can be represented well. Our preliminary tests on two different extreme contact conditions (soft-soft, hard-hard

Die wear in stamping of advanced high strength steels-investigations on the effects of substrate material and hard-coatings

This study intended to investigate the wear performance of different coatings (two different PVD,a CVD, and a TD coating) applied onto variety of substrate materials (DC 53, SKD 11, DRM 3, DRM 51)against AHSS sheet blanks. A non-reciprocating, CNC-based, slider type of tester was employed in weartests. In effect of coating study, it was found that TD coated samples performed slight ly better than theother samples. The substrate material effect study, on the other hand, revealed that the TD coated DRM3 and DRM 51 die samples attained the lowest specific wear rate