Hardening and softening mechanisms of pearlitic steel wire under torsion

The mechanical behaviors and microstructure evolution of pearlitic steel wires under monotonic shear deformation have been investigated by a torsion test and a number of electron microscopy techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an aim to reveal the softening and hardening mechanisms of a randomly oriented pearlitic structure during a monotonic stain path. Significantly different from the remarkable strain hardening in cold wire drawing, the strain hardening rate during torsion drops to zero quickly after a short hardening stage. The microstructure observations indicate that the inter-lamellar spacing (ILS) decreases and the dislocations accumulate with strain, which leads to hardening of the material. Meanwhile, when the strain is larger than 0.154, the enhancement of dynamic recovery, shear bands (SBs) and cementite fragmentations results in the softening and balances the strain hardening. A microstructure based analytical flow stress model with considering the influence of ILS on the mean free path of dislocations and the softening caused by SBs and cementite fragmentations, has been established and the predicted flow shear curve meets well with the measured curve in the torsion test.     

造纸成形网技术进展及发展趋势

综述了造纸成形网的发展过程,对成形网用材料、结构和编织方法等方面的发展现状进行了详细介绍,并讨论了适应高速纸机用成形网的研究发展趋势.     

成形网对夹网造纸机的脱水和留着的影响

该文通过对夹网纸机的脱水原理和影响因素的介绍,讨论了造纸成形网在夹网脱水过程中所发挥的作用。除此之外,还以生活用纸为例阐述了成形网的表面特征与夹网纸机网部纤维留着间的微妙关系。