摘要
对挤压后的铝合金孔边残余应力分布进行了X射线测定,发现残余压应力在近表层有陡降。扫描电镜观测表明孔的内表层存在机械损伤,其深度约与应力陡降范围相当。说明表面损伤不仅本身可能影响疲劳抗力,而且使有益的残余压应力在挤压后即发生较大程度的松弛。 增大挤压量可增大残余压应力分布深度及数值,但须注意挤压后存在尺寸反弹有可能影响构件的装配精度。在固定挤压量的条件下,将挤压棒由锥形改为糖葫芦形,可使残余压应办的分布深度及数值得到进一步提高。这是由于后者属非连续挤压方式,后一台阶的挤压总是在前一台阶挤压的基础上进行,材料的组织预先经过一定程度的形变强化,并且变形材料受相邻两台阶的几何约束难以充分恢复。
X-ray stress measurements on cold-expansion holes of aluminum alloy show a dramatic dropping of compressiveresidual stresses in an out-surface layer. This is attributed to geometry-dependent stress relaxation, since SEM examination on deformed surface reveals mechanical damage which has nearly the same depth as that of the reduced stresses. More attention should be paid to the surface damge for its possible effect on fatigue, strength as well as the effect on the stability of residual stresses in very surface layer. For an improvement of cold-expansion quality, a taper-like could be. roplacced by a new one with special shape like a stick with sugarcoated haws. Both the depth and the magnitute of compressive residual stress can be enhanced further. The reason lies in the fact that the expanded material undergoes a loading and un-loading process and the deformation hardening have been introduced when next expansion is made with the following collar flange.
出处
《兵器材料科学与工程》
CAS
CSCD
北大核心
1993年第2期7-13,共7页
Ordnance Material Science and Engineering
关键词
挤压强化
铝合金
残余应力
cold-expansion,aluminum alloy,residual stress
