重庆时时彩0_9数字规律|重庆时时彩的规律

折弯板材英文文献和中文翻译

时间:2017-09-19 20:48来源:毕业论文
Air-bending of sheet metal is one of the widely used industrial processes. This single-step air-bending processing is suitable for simple structure pares. However, large parts with complex surfaces could not be bent by the single-step air-be
Air-bending of sheet metal is one of the widely used industrial processes. This single-step
air-bending processing is suitable for simple structure pares. However, large parts with
complex surfaces could not be bent by the single-step air-bending. To solve this problem,
a multi-step incremental air-bending forming could be utilised. Sheet incremental
air-bending forming system with significant flexibility uses the principles of stepped
manufacturing. It transforms the complicated geometry information into a series of
parameters of single-step, and then the plastic deformation is carried out step by step
through the computer numerical controlled movements of the punch and sheet feed to get
the desired part. Just like the traditional stamping, springback is unavoidable in the
incremental air-bending forming. Due to the existence of springback, the precision of
products and subsequent assembly operations were severely affected. How to effectively
control springback has been the key issue to precision forming.13521
  In the past, sheet metal multi-step air-bending processes are dependent on the
designer’s experience and involve trails and errors to obtain the desired result. Trail and
error can involve adjustments made to the machine tools and process control to
compensate for springback by experiment iteration. This practice would consume high
cost, much time as well as labour cost. We note that numerous fundamental studies have
been conducted over the years in an attempt to predict and control springback on
single-step air-bending processes of sheet metal (Kurtaran, 2008; Narayanasamy and
Padmanabhan, 2009; Gardiner, 1957). With the advent of computation technology, sheet
metal bending processes can be analysed prior to experiments using the finite element
method (Heller and Kleiner, 2006; Streppel et al., 2001; Singh et al., 2004). However,
most of these researches are only limited to single-step air-bending forming, relatively 本文来源:http://www.mamitama.com/a/www.cwikids.org/

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little has been devoted to the detailed analysis on the numerical simulation of the
multi-step incremental air-bending forming. Therefore, in order to reduce the number of
practical forming experiments, the authors think that it is of great worth to study
multi-step incremental air-bending forming with finite element simulation method to
obtain the optimised process parameters of large workpiece forming.
     It should be noted that the yield criterion is the key factor influencing the result of the
finite element simulation. As literature (Ming and Li, 1999) mentioned, the Hill’48
anisotropic yield criterion was better able to describe steel sheet material yield behaviour
(Hill, 1984), while Barlat’s 89 anisotropic yield criterion could provide favourable
agreement with the experimental value of aluminum alloy sheet forming (Barlat and
Lian, 1989). Therefore, this study intends to simulate multi-step incremental air-bending
forming process of anisotropic steel sheet with Hill’s quadratic yield criterion.
     In the present paper, the FE simulation is performed by ABAQUS/Explicit and
Standard modules. Plane strain element CPE8R (namely the eight-node biquadratic plane
strain quadrilateral, reduced integration elements), exponent hardening material, Hill’48
anisotropic yield function are applied to the simulation. Then, shape curves and plastic
strain distributions along geometry neutral layer of the simulated workpieces formed with
three different tool parameters are compared with practical CAD data. Finally, a large
workpiece is manufactured with the optimised simulation results. As will be shown
through subsequent manufacturing example of workpiece, finite-element simulation
method offers several advantages, including excellent convergence rate, ease of 折弯板材英文文献和中文翻译:重庆时时彩的规律/a/fanyi/20170919/13768.html
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