冷成型不锈钢部件力学性能的精确预测(英文)

Accurate Prediction of Mechanical Properties for Cold-formed Stainless Steel Sections

冷加工截面构件的制作过程导致材料的力学性能和强度有明显的改变.本文提出了精确预测不锈钢材料和冷加工材料力学性能的研究结果.首先,本文对不锈钢材料提出了一种新的应力-应变关系模型,这种模型可以精确预测全范围内的拉应变和压应变.新的应力-应变模型采用3个基本的Ram-berg-Osgood参数,并基于对已有试验数据的详细分析来定义.在论文的第二部分,提出了预测冷加工材料的应力-应变性能的有限元模型.该方法中,通过对压弯成形截面制作过程的数值模拟,以及在随后对Coupon测试的有限元模拟中以加工过程中所导致的残余应力和等效塑性应变作为初始状态,解释了冷加工材料的应力-应变性能.这种方法能够预测冷加工材料的拉伸和压缩的应力-应变性能.新提出的应力-应变模型以及有限元方法的精度通过和试验得到的应力-应变曲线的对比进行了验证.所提出的有限元方法和新的应力-应变模型可以在将来应用到原始材料和冷加工材料的关系中.

The cold work from the manufacturing process of cold-formed sections causes a significant change in the mechanical behaviour and enhances the strength of the material. This paper presents the results of a study on the accurate prediction of the mechanical properties of both virgin stainless sheet materials and cold-worked materials of cold-formed stainless steel sections. This paper first presents a new stress-strain model for stainless steels, which is capable of accurate predictions over the full ranges of both tensile and compressive strains. The new stress-strain model is defined using the three basic Ramberg-Osgood parameters and is based on a careful interpretation of existing experimental data. In the second part of the paper, a finite element method is then presented for predicting the stress-strain behaviour of cold-worked materials, including corner materials and fiat materials, in press-braked stainless steel sections. In this method, the effect of cold working on the stress-strain behaviour of cold-worked materials is account for by means of a numerical simulation of the manufacturing process of the press-braked section, with the resulting residual stresses and equivalent plastic strains specified as the initial state in a subsequent finite element simulation of coupon tests. This method is capable of predicting both tensile and compressive stress-strain behaviour of cold-worked materials. The accuracies of both the new stress-strain model and the finite element method are demonstrated by comparing its predictions with experi- mental stress-strain curves. The proposed finite element method together with the new stress-strain model can be applied in the future in a development of a direct relationship between the virgin material properties and cold- worked material ones.