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一、引言在工业生产中,经常遇到受弯受扭的构件。这些构件内的应力分布是不均匀的。应力分布不均匀对流动极限有何影响及其原因,仍需进一步研究。这个问题,无论在理论上,还是在实践上都具有一定的意义。例如,在锅炉强度计算中,拉杆和烟管受拉伸作用,而端盖板受弯曲作用。试验与计算可知,弯曲应力比较大。对同一种材料,如何选取这两种受力情况下的流动极限呢?据有关资料介绍,弯曲由于应力分布不均匀能提高试件外层纤维拉压流动极限10～20%,对于碳钢圆截面试件将提高60%。此外,圆轴扭转也能提高表层材料剪切流动极限20～30%。但对部分材料的弯曲试验表明,根据 Nadai 弹塑性弯曲公式计算表层纤维拉压流动极限 S_(0.2)~b 和拉伸时的口σ_(0.2)接近。
I. INTRODUCTION In industrial production, often encountered torsion bending member. The stress distribution within these components is not uniform. The impact of uneven stress distribution on the flow limit and its causes still need further study. This question has some significance both in theory and in practice. For example, in the calculation of boiler strength, the drawbar and the smoke pipe are stretched, while the end cover is bent. Test and calculation shows that bending stress is relatively large. According to the relevant information, due to the uneven distribution of stress, the flow limit of tension and compression of the outer layer of the test piece can be increased by 10-20%. For the carbon steel circle Section test pieces will be increased by 60%. In addition, the torsion of the circular shaft can also increase the shear flow limit of the surface layer by 20-30%. However, the bending tests on some materials show that the flow-stress limit S_ (0.2) ~ b is close to σ_ (0.2) at the time of drawing according to Nadai’s elasto-plastic bending formula.