The blanking process has a wide range of usage in the sheet metal production industry.
Blanking is a major process and has a wide range of usage in manufacturing industry. The general concept of blanking seems a simple one but governing parameters are many and have a complex relationship which directly affect the quality of the produced parts (blanks) and also the energy efficiency of the process. The main problem is the lack of prediction capabilities of the effect of these parameters that lead to time, money and labor consuming trial and error procedures in experimental studies. Usage of FEM based programs to simulate blanking to obtain numerical results and observe the shearing mechanism is a cheap and a detailed way for industrial applications. In this study five different clearances (1%, 3%, 5%, 10% and 20%) and three different thicknesses (t = 2 mm, t = 3 mm and t = 4 mm) were used for simulation and experimental studies of the blanking process. Simulations were executed by using the FEM program, Deform 2-D. Investigations were made on the parameters related to crack progression like crack initiation and crack propagation angles, indentation angle, rollover angle and depth and also the related blanking energy values. The results of the present paper are in agreement with the results of experimental studies.
ÖZET Bu çalışmada; keten lifi, mısır sapı, ayçiçeği sapı, su kamışı, arpa samanı gibi beş farklı doğal destek malzemesi ile cam yünü ve karbon lifi gibi iki farklı sentetik destek malzemesi belirli oranlarda (2.5 g lif/72.5 g PE, 5 g lif/70 g PE, 7.5 g lif/67.5 g PE ve 10 g lif/65 g PE) yüksek yoğunluklu polietilen matris içerisine yerleştirilerek, lif takviyeli kompozit lamine levhalar üretilmiştir. Liflere ya da matrise herhangi bir ön kimyasal işlem uygulanmamıştır. Kompozit lamine levhalar presle kalıplama yöntemi ile üretilmiş, sonrasında ise çekme ve ısı testlerine tabi tutulmuşlardır. Sonuçlar; kompozit numunelerin çekme mukavemetlerinin desteklenmemiş polietilen numunelere göre daha düşük olduğunu fakat mısır sapı, ayçiçeği sapı ve su kamışı ile desteklenmiş kompozit numunelerin, cam yünü ve karbon lifi ile desteklenmiş kompozit numunelere çok yakın çekme mukavemetine sahip olduğunu göstermiştir. Ayrıca kompozit numuneler yüksek sıcaklığa karşı, desteklenmemiş polietilene göre daha az deformasyon göstermişlerdir.Production of different composite materials and determination of some technical properties Anahtar Sözcükler: Doğal lif Kompozit malzeme Sentetik lif Yüksek yoğunluklu polietilen ABSTRACT In this study, five different natural reinforce materials as flax fiber, corn stalk, sunflower stalk, reedmace, barley straw and two different synthetic reinforce materials as glass fibers and carbon fibers with different ratios (2.5 g fiber/72.5 g PE, 5 g fiber/70 g PE, 7.5 g fiber/67.5 g PE and 10 g fiber/65 g PE) were placed inside high density polyethylene matrix to produce fiber reinforced composite. No chemical pretreatment were made to the fibers or the matrix. Composite laminate sheets were produced by compression molding process, then tensile tests and heat tests were conducted. Results show that; tensile strengths of the composite samples are lower than unreinforced polyethylene but corn stalk, sunflower stalk and reedmace reinforced sample's tensile strengths are very close to the composite samples reinforced with glass and carbon fibers. Furthermore most composites show lower deformation against high temperature than unreinforced polyethylene.
The main goal of the blanking process is to shear the sheet metal with minimum energy consumption and to obtain a good surface quality on the sheared workpiece. The punch speed is one of the important process parameters which have effect on both surface quality and energy consumption. In the literature, investigations and experimental works contain a gap that includes the range of speed which the mentioned works were executed either at speeds which is below high speed (lower than 5m/s) or excessively high speeds (at ballistic level). Also, studies that investigate stainless steel sheets are scarce. The purpose of this study is to thermomechanically investigate the punch speed, cutting force, cutting energy and workpiece surface quality of a 2 mm thick AISI 304 stainless steel sheet that was blanked under a constant clearance value and three different punch speeds by using experimental and finite element methods. Theory and Methods:A 2 mm thick AISI 304 stainless steel sheet was used as the workpiece material. The die diameter was taken as 10 mm. The clearance were kept constant (5% of sheet thickness) and three different punch speeds (0.1 m/s, 1 m/s and 10 m/s) were used to execute the blanking process. A hydraulic press with 30 Tons capacity, a mechanical press with 100 Tons capacity and a powder actuated HERF hammer were used to obtain required speed values. On the other hand thermo-mechanical finite element analysis of the mentioned process were done by using Deform 2D. The maximum element number (10000) which is the highest value that can be defined was used and all mesh elements were compressed at the cutting zone to reach more realistic results. Surface roughnesses of the blanks were calculated by using a profilometer. Results:The strain hardening capability of AISI 304 is well known and results showed that the cutting force and cutting energy elevated with increasing punch speeds. But when the punch speed became 10 m/s, the cutting force and energy reached to lower values than expected. It was observed that the temperature values were elevated with increasing speed. There was 241% increase in temperature values between 1 m/s and 10 m/s punch speeds. Also, it was found out that the effective stresses got localized with increasing speed. The surface roughness values showed that the best quality was obtained at higher speeds. Conclusion:Cutting force and cutting energy increased due to AISI 304's tendency to strain harden but not to expected levels because of the thermal effects in the zone . Increase in the punch speed caused the effective strain rate to rise that resulted in a sudden heat emanation at the shear zone. This heat couldn't dissipate into the material and created an adiabatic shear zone with elevated temperature. Increase in temperature softened the material thermally by lowering the materials flow stress. There occurred a 53% loss in the expected cutting force. On the other hand, the localization of the effective stresses caused the material crack early, changing the distribution of zones espec...
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