喷丸处理的锆合金残余应力场分布规律

目的通过不同的喷丸处理工艺,探索适用于锆合金包壳管的喷丸处理参数。方法对锆合金包壳管采取9种不同的喷丸处理工艺且编号(1—9号),采用XRD残余应力检测技术,对处理后的包壳管试样分别进行轴向和切向的残余应力场测定。结果未喷丸处理的试样表面轴向、切向残余应力分别为-277 MPa和-250 MPa,最大应力在最外表层。喷丸处理试样表面轴向残余压应力比未喷丸处理的大,只有9号工艺对应的表面轴向残余应力比未喷丸的小,这很有可能是因为喷丸强度过大,在表面形成了微裂纹,残余应力得以释放,所以锆合金包壳管的喷丸强度不宜超过0.40 mm A。对于强度较高的5—9号喷丸工艺,喷丸强度达到0.15 mm A以上,包壳管压应力影响层的厚度均超过460μm,几乎达到了喷丸处理后包壳管的整个壁厚。在相同喷丸强度和相同弹丸直径条件下,玻璃丸的表面压应力和最大压应力与不锈钢丸的相近,不锈钢丸处理的压应力影响层比玻璃丸处理的压应力影响层厚约80μm。结论在相同喷丸强度和相同弹丸材料下,改变弹丸直径对锆合金两个方向上的表面残余应力和最大残余应力的大小影响不大;直径较小的弹丸对应轴向最大残余应力的位置更深,直径较大的弹丸对应切向最大残余应力的位置更深。随着锆合金喷丸强度的增加(没有出现过喷),表面两个方向上的残余应力都增加,两个方向上的最大残余应力也有所增加。

Distribution Rule of Residual Stress Field of Zirconium Alloy Induced by Shot Peening

The work aims to explore shot peening parameters applicable to zirconium alloy cladding tubes by means of dif-ferent shot peening process. Zirconium alloy cladding tubes were treated by 9 different shot peening processes and numbered (from 1—9). Besides, residual stress fields of the treated cladding tube specimens were measured in both axial and transversal direction by adopting XRD residual stress measurement technique. The residual stress of untreated specimen in axial and trans-versal direction was -277 MPa and -250 MPa, respectively, and the maximum stress appeared in the outermost layer. Axial re-sidual compressive stress on the specimens subject to shot peening treatment (number 2—8) was higher than that on untreated specimen, while the residual compressive stress on the surface subject to 9# treatment was lower than that on untreated speci-men. This was probably because the shot peening intensity was too high, thus microcrack formed on the surface and then the re-sidual stress was released, shot peening intensity of the zirconium alloy cladding tubes should not exceed 0.40 mmA. For the higher intensity (above 0.15 mmA) shot peening process, such as 5—9 shot blasting process, the thickness of compressive stress affected layer was over 460 μm, almost the whole wall thickness of the cladding tubes subject to shot peening. Provided with same shot peening intensity and same projectile diameter, the surface compressive stress and the maximum compressive stress of glass projectile were close to those of stainless steel projectile. Thickness of compressive stress affected layer treated by glass projectile was nearly 80 μm thicker than that of compressive stress affected layer treated by stainless steel projectile. Provided with same shot peening intensity and the same projectile material, change in projectile diameter has little influence on surface residual stress and maximum residual stress in both axial and transversal direction. Meanwhile, the smaller the projectile diame-ter is, the deeper the maximum residual stress position in axial direction is; the larger the projectile diameter is, the deeper the maximum residual stress position in transversal direction is. As shot peening intensity on zirconium alloy increases (no over peening), the surface residual stress and the maximum residual stress increase in both directions.