Papers by Keyword: Spring Back

Abstract: Roll forming is a continuous profile production process to form sheet metal progressively into the desired shape with closer tolerances. The process offers several advantages such as complex geometrical shapes, high strength, dimensional accuracy, closer tolerances, better quality and consistency, high production rate, improved conformity, and good surface finish. Several parts of automobile body are produced with this process. Nowadays roll forming technology draws more attentions than before in the automotive industry. In this paper, A Finite Element Method applied to study von mises stress, equivalent plastic strain, thickness, plastic strain, longitudinal strain and spring back of the metal sheet with ribs formed by roll forming process. The thickness variation was almost -6.144%.

Abstract: Roll forming is a kind of plastic forming process in which a steel strip is bent by several sets of rolls gradually into the desired shape. The products are cold roll forming steels with various sections. Roll forming is one of the most widely used processes in the world for forming metal. Roll forming is a complex deformation process, which involves large displacement, finite strain and the problems of contact and friction between strip and rolls. This process exhibits obvious geometry, physical and boundary nonliterary. The complex processes contain many aspects such as geometry, kinematics and dynamics, etc. The forming process involves not only transverse bending, but also other additional deformations. In this paper, a group of simulations have been established with ABAQUS software to studying about the spring back and bow defect in the roll forming process. At last, experiments have been accomplished to verify the simulation results. The simulations based on the ABAQUS software calculate the spring back angles and bow displacements. The bow displacement of the roll forming process is considered relate to many factors include inner distance between stands, gaps of the rolls, channel width, the material of the sheet, sheet thickness and so on.To verify the bow displacement in roll forming process, 9 groups of simulations were set up use Taguchi method to figure out the influence on bow displacement of every factor. The longitudinal strain also has been learned in the present study.

Abstract: Inner vessel in reactor assembly of sodium cooled fast reactor separates hot and cold pool sodium. The shape of inner vessel is optimized with reduced upper & lower shell diameters and toroidal redan for future Fast Breeder Reactor (FBR). This results in higher buckling strength and reduced thickness and hence reduced weight. To achieve the intricate toroidal shape with specified dimensional tolerances, a comprehensive technology development exercise was carried out successfully for the manufacture of inner vessel 30° sector. The achieved profile of the redan meets the specified dimensions and other design requirements. Spring-back observed in the sector was small. To verify the developmental exercise results, a finite element analysis (FEA) of forming of inner vessel sector was performed on finite element software ABAQUS. In this paper, FEA results and spring back are discussed. Spring back assessed is maximum at the center and relatively lower towards the edges for the redan with the chosen radius of 5980 mm.

Abstract: The effects of Al₂O₃ sol on the mechanical, morphological, and water sorption properties of rice husk were studied by means of compression-strain tester, and scanning electron microscopy (SEM) associated with the energy spectrum analysis. The results showed that the spring back of materials is found to decrease with increasing coating concentration. With the increase in Al₂O₃ sol concentration, the gaining of mass fraction of the materials increased proportionally, while the water absorption, which measured at ambient temperature, was gradually decreased with increasing Al₂O₃ sol concentrations. The gaining of mass fraction, lowest water absorption and lowest of compressive recovery ratio of 10.15%, 34.5% and 16.58%, respectively, were obtained when Al₂O₃ sol solid content was 8%, and resulted mainly from an increase in the rigidity increase. The Al₂O₃ sol had a positive effect on the morphology stabilization of rice husk.

Abstract: To compare mechanical properties of three commercial NiTi orthodontic round wires, three commercial brands of NiTi round wire (Nic-China, Ormco-USA, and Smart-Thailand) with sizes 0.014’’, 0.016’’, and 0.018’’were studied. Five specimens each size of each brand were used to test mechanical properties; unloading force (N), spring back (mm), and yield strength (N/mm) with three-point bend test using an Instron Universal Testing Machine. Kolmogorov-Smirnov test and one-way ANOVA were employed to test the differences among groups with statistical difference at p<0.05.The average unloading force from lowest to highest were Ormco, Smart and Nic with 0.014”, Smart, Ormco and Nic with 0.016”and Smart, Nic and Ormco with 0.018”, respectively. The Nic brand had the highest value of unloading force, spring back, and yield strength in all wire sizes, except unloading force 0.018” Ormco and spring back 0.018” Smart. There were no statistically significant differences in unloading forces among all wire sizes. The three brands of commercial orthodontic NiTi wires presented similar unloading force, spring back, and yield strength properties. These mechanical properties are related to lower rates of deformation and are appropriate to be used in the initial phase of orthodontic treatment.