NAMRC 49 Fast-Tracked Research Papers to Journal of Manufacturing Systems and Journal of Manufacturing Processes

n/

Experimental and finite element investigation of springback of aerospaceautomotive sheet metal products

Springback is a phenomenon that occurs when nonhomogeneous elastic and plastic deformation occurs throughout a component during forming processes. Since the elastic deformation is recovered when the forming load is removed, geometrical changes occur. Springback is particularly important in sheet forming; therefore, in order to provide formed parts of close tolerances it is essential to first have a good understanding of the factors which affect springback and to be able to determine the extent those factors have. It is also important to be able to predict springback under different conditions so that it can either be minimized or properly accounted for in the process design. This research presents work done thus far on understanding and predicting springback in sheet metal forming of stainless steel 410 and inconel 718, which have a wide range of usage in the aerospace industry as well as dual-phase steels 6001300 and 600/400 which are used in the automotive sector.The role that the anisotropy plays in the springback is assessed in this work. The effect of normal anisotropy on springback for the aerospace materials is considered while the automotive materials were considered perfectly isotropic and only the effect of forming conditions was studied. In order to characterize the materials and their anisotropic behaviour, a series of mechanical tests is conducted. These tests include standard uniaxial tension and uniaxial tension-compression tests. Moreover, a series of simple multiplebending experiments were conducted on the aerospace materials (steel and Ni based alloys) to examine the effect of specimen orientation on the springback in simple bending.Furthermore, since process conditions have an obvious effect on springback and one of the most important of these is the blank holding force, 2D draw bending experiments are conducted with varying blank holding force to assess its role in springback of the formed part. The combined effect of anisotropy and blank holding force was also studied for the aerospace materials.Finite element simulations that include only either classical isotropic hardening or kinematic hardening did not show close agreement with the experimental findings especially for springback prediction. Therefore, to properly simulate springback a material model that combines both hardening effects, along with the material anisotropy, has been developed in this work. The developed finite element model implements isotropic hardening as well as kinematic hardening based on the Mroz multiple-yield surface formulation. Hill's 1948 yield function with normal anisotropy is considered. The developed material model has been tested by simulating the tension-compression experiments and a good agreement was reached.Furthermore, to demonstrate the model capability, bending experiments were simulated. Springback angles predicted by the model reflected those obtained experimentally for the simple multiple-bending experiments. Moreover, draw-bending experiments were simulated with the developed material model, which showed good agreement with the experiments.Finally, the capability of the model can be readily extended to cover real forming operations, which will reduce cost and enhance the quality of the formed parts

Preface

n/

Special Issue of Journal of Manufacturing Processes on New Trends in Manufacturing Processes Research

Special issue of journal of manufacturing processes on new trends in manufacturing processes researc

special issue of journal of manufacturing systems on new trends in manufacturing systems research

n/

Preface

n/

A Review of Electrically-Assisted Manufacturing With Emphasis on Modeling and Understanding of the Electroplastic Effect

Increasingly strict fuel efficiency standards have driven the aerospace and automotive industries to improve the fuel economy of their fleets. A key method for feasibly improving the fuel economy is by decreasing the weight, which requires the introduction of materials with high strength to weight ratios into airplane and vehicle designs. Many of these materials are not as formable or machinable as conventional low carbon steels, making production difficult when using traditional forming and machining strategies and capital. Electrical augmentation offers a potential solution to this dilemma through enhancing process capabilities and allowing for continued use of existing equipment. The use of electricity to aid in deformation of metallic materials is termed as electrically assisted manufacturing (EAM). The direct effect of electricity on the deformation of metallic materials is termed as electroplastic effect. This paper presents a summary of the current state-of-the-art in using electric current to augment existing manufacturing processes for processing of higher-strength materials. Advantages of this process include flow stress and forming force reduction, increased formability, decreased elastic recovery, fracture mode transformation from brittle to ductile, decreased overall process energy, and decreased cutting forces in machining. There is currently a lack of agreement as to the underlying mechanisms of the electroplastic effect. Therefore, this paper presents the four main existing theories and the experimental understanding of these theories, along with modeling approaches for understanding and predicting the electroplastic effect