بررسي عوامل ايجاد عيوب شكلي در فرآيند نورد ورق و اثرات آن روي كيفيت محصول

چكيده انگليسي :

Investigations on the Development of Shape Defects in Sheet Rolling and Its Influence on Product Quality Babak Moazeni b moazeni@me iut ac ir Date of Submission 2012 02 05 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Mahmoud Salimi salimi@cc iut ac ir Alireza Shahidi shahidi@cc iut ac irAbstractRolling process is one of the most popular processes in manufacturing industries such that almost 80 percent ofmetallic equipment has been exposed to rolling at least one time in their production period Among all kinds ofrolling processes flat rolling is the most practical In industrial countries about 40 60 percent of rollingproducts are produced with this type of rolling Increasing demand for thin flat products with high quality andwithout any shape defects has led to high importance of rolling process During the rolling process of thin atproduct i e long metal strips the development of residual stresses acting predominantly in the axial directionof the strip are hardly to avoid They are originated by even very small differences in the opening of the rollinggap along the width of the plate leading to small variations in the thickness reduction and as a consequence ofthe incompressibility of plastic deformations to axial stresses The problem of excessive residual stress in coldrolled at products represents an important source of production loss Thin plates are prone to buckle even undersmall compressive membrane forces Hence it happens frequently that during the release of the global tensileforce buckling and post buckling can be observed leading to wavy plates Certainly the best way to achievebetter efficiency and accuracy and also control of every process including rolling process is identification of thebasic parameters governing the process and the relations between them in order to study the effect of eachparameter on the whole process In this project after studying various types of shape defects and the cause offormation of waves in rolling process a model of flat rolling process employing ABAQUS software is createdin order to recognize the factors affecting the non uniform deformation of plates After modeling andverification of the model with theoretical results the deformation of the rolled plate in the roll gap for the caseof the uniform entry and exit profile and the effect of rolling parameter on the variation of longitudinal residualstresses is studied In this case it is found that in addition to uneven geometrical factor influencing the platequality variation of forming condition along the plate width as a result of different boundary condition lead toheterogeneity of deformation despite the fact that variation in residual stresses may be very low It is shown thatthis condition plays an important role in buckling of thin flat rolled products To examine the relation betweensheet thickness profile changes and the final plate shape metal flow in deformation area for different crownplate models is studied The results of simulation show that transversal flow of metal in roll gap has greatinfluence on residual stress for different crown shapes It is shown that the transition from flatness to bad shapefor specific ratio of output thickness to the width of plate occur as a result of thickness profile changes and alsoit has shown that critical crown ratio changes for long edge shape is smaller than long middle shape Keywords Flat Rolling Shape Defects Residual Stress Finite Element Method

موذني، بابك

بررسي عوامل ايجاد عيوب شكلي در فرآيند نورد ورق و اثرات آن روي كيفيت محصول

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