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A deep-drawing grade AKDQ steel sheet was tested to determine the Forming Limit Diagrams (FLDs) using two different forming methods to identify points where the incipient necking started. With the conventional out-of-plane spherical forming test, incipient necking points were determined from the formed dome samples at areas diametrically opposite to the necked and fractured locations. With the Marciniak in-plane forming test, incipient necking points were determined from real-time video images obtained during the experiment. These images were analyzed with strain-measurement software to determine the strain distributions in the samples. Various data plotting schemes were explored to produce meaningful results for the flat-bottom in-plane tests. These methods included “best fit” line analysis and strain vs. time plots. The final outcome is reasonably consistent with published FLD data.

In this study, a piezo disk was used to generate a cloud of n-decane fuel drops, which were mixed with air, then carried into a combustion chamber and ignited by a platinum wire. Microgravity data obtained at the Japan Microgravity Center (JAMIC) were compared to normal gravity data, all at 1Atm pressure and 20+/-1°C initial temperature. Under normal gravity the lean limit was found to be 7.6x106/mm3 (Φ = 1.0), and from this point the flame front speed steadily increased from 20cm/s up to a maximum flame front speed of 210cm/s at a fuel drop density of about 14x106/mm3 (Φ = 1.85). Microgravity data showed a much richer lean limit - about 14.5x106/mm3 (Φ = 1.9), and the flame front speed did not gradually rise to a peak value. Instead, the measurements indicated a peak value of about 250cm/s, with a steep increase followed by a gradual decrease at richer fuel air ratios. A cellular flame structure appeared, and the cell size decreased as the mixture density increased.

Aluminum alloy sheets of 2010-T4 of 0.831 mm and 2.590 mm thicknesses and 6111-T4 of 1.029 mm thickness were tested to determine the Forming Limit Diagrams (FLDs). The forming limit curves were obtained from both rolling and transverse samples. Due to the large scatter observed in the experimental data, exact identification of the forming limit based on incipient necking was not an easy task. Two alternate methods of determining the equivalent FLDs were explored and tested. The resulting forming limit curves based on the two methods are reasonably consistent with trends indicated by previous forming limit diagram determinations.

A methodology is presented for springback analysis and control in forming two-step rail-shaped sheet metal parts. A computer system for bending and springback analysis of two-step rails is developed and described. Effects of tool corner radii, material properties and process variables on the springback behavior of two-step rails is investigated using the analysis system, and conclusions are drawn based on the sensitivity analysis result. An example of springback control is provided in obtaining an accurate shape of a given part in the design stage by changing some of the variables.

A bending and springback analysis method for 2D-draw bending parts has been developed based on a new mathematical model. The main feature of the new model is described and the analysis results obtained from this model are compared with those from other methods. These results show consistent springback behavior for the selected cases. Roles of blankholder force and friction are investigated using the new method, as well as the effect of material properties on springback behavior, e.g., strain hardening index, Young's modulus, plastic anisotropy, etc. The trends are illustrated graphically and some conclusions are drawn based on the analysis.

A recently developed automated method for measuring surface strains on a deformed three dimensional part is compared with a careful manual measurement method and the differences are discussed. The overall experimental procedure consisted of marking the sheet steel surface with square grids, forming them into different shapes, and measuring surface strains by the two different methods. The manual method involved measuring the distances in each square using a traveling microscope. The automated method is based on digital image processing techniques and is capable of measuring strain distributions over an area of interest. The measured results from both methods agree reasonably well, but some discrepancies are observed at locations where strains are localized.