Abstract
Using a finite element package software DEFORMTM, this study simulated plastic deformation of the sheet at the roll-gap during sheet rolling processes. Rigid-plastic model of material is adopted. The rolls are assumed to be perfectly rigid and the sheets are isotropic. This study consists of three parts¡G(1) analysis of asymmetrical sheet rolling ; the effects of rolls speed ratios, roll radii ratios, friction factor ratios between sheet and rolls surface, upon the curvature of the rolled product and rolling force were systematically discussed. The larger the roll radius and the roll speed ratios are, the smaller the rolling force is and the larger the curvature of the sheet analytically. (2) Closing behavior, the deformation mechanism and stress-strain distributions around internal voids inside the sheet during sheet rolling was discussed numerically. The influences of various rolling conditions, such as the thickness reduction, the dimension of the internal void, friction factor, cross-sectional area of the void, etc., on the dimension of the void at the exit were discussed. The critical thickness reductions, over which the void would close completely, were also investigated. It is known that the critical reduction decreases with increasing roll radius. That is because the rolling pressure at the roll gap increases with increasing roll radius, accordingly, it takes smaller reductions to make the void closed completely. The critical thickness reduction decreases with increasing roll radius and decreasing voids dimension-thickness ratios. (3) The possibility of voids occurred at the front and back of the inclusion was investigated. The effects of various rolling conditions, such as the thickness reduction, the diameter of the inclusions, the roll diameter, friction factor, etc., on the generation and development of voids anticipated to occur in the front and rear of the inclusions were discussed. The critical thickness reductions under which void generation can be avoided were also examined. On the other hand, the effect of friction factor on between roll and sheet upon the void lengths in the front and rear of the inclusion is greater than that of friction factor on between inclusions and sheet. It is known that it decreases with increasing inclusions dimension, whereas the critical reduction decreases with decreasing roll radius. The analytical results showed a steady trend for 0.1mm< voids and inclusions dimension < 2.5mm.
To verify the validity of the models, a series of experiments on the sheet rolling using aluminum (A1050, A6061) sheet as specimen were carried out. The experiments on sheet rolling with an internal void inside the sheet were conducted by micro-drill. The inclusions used ¡§SUS HSS¡¨ steel. The void length in the front of the inclusion is larger than that in the rear of the inclusion for both simulated and experimental results. The simulated results were compared with experimental results, and good agreement is found. Therefore, this numerical model using DEFORM software can offer useful knowledge for designing the pass-schedule in sheet rolling processes.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0112103-112313 |
| Date | 12 January 2003 |
| Creators | Chen, Dyi-Cheng |
| Contributors | Fuk-Kuo Chen, Yeong-Maw Hwang, Rong-Tsong Lee, Ray-Quan Hsu, Chinghua Hung, You-Min Huang, Jao-Hwa Kuang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0112103-112313 |
| Rights | unrestricted, Copyright information available at source archive |
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