铸造不锈钢机匣R角区域的水浸超声相控阵检测技术

Ultrasonic water immersion phased array detection technology in R angle area of cast stainless steel casing

大型燃气涡轮发动机不锈钢机匣结构中包含大量R角区域,该区域因壁厚较大且是曲面结构,制造过程中容易出现微裂纹、气孔、夹杂等缺陷。射线检测因受到R角曲面的形状限制而无法布置射线底片,并且大厚度R角区域也很难被射线穿透,造成射线检测灵敏度下降、缺陷出现漏检。由此,提出大型不锈钢机匣R角区域内部缺陷的超声水浸相控阵检测技术。将相控阵探头布置于机匣内环曲面,通过修正曲面聚焦法则控制阵元发射超声波在R角区域形成聚焦声场;通过建立数值仿真模型分析聚焦法则修正前后的声场聚焦性能,同时分析了水距对聚焦声场的影响;最后,基于修正的聚焦法则和优化的水距开展机匣R焦区区域的超声相控阵检测试验。结果表明:通过曲面聚焦法则修正和水距优化可在R角区域形成聚焦声场,该区域扇形扫描图像质量得到明显改善;能够显示Φ1.5 mm当量尺寸的横孔缺陷并具有良好的检测分辨率,-6 dB法下定量相对误差低至6.7%。

The stainless steel casing structure of large gas turbine engine contains a large number of R angle regions,which are prone to micro-cracks,pores,inclusions and other defects in the manufacturing process because of its large wall thickness and curved surface structure.Due to the shape limitation of the curved surface of the R angle,the radiographic film cannot be arranged,and the R angle area with large thickness is difficult to be penetrated by the ray,so that the sensitivity of the radiographic testing is reduced,and defects are missed.Therefore,the ultrasonic immersion phased array testing for the internal defects in the R corner region of the large stainless steel case is proposed.The phased array probe is arranged on the inner ring curved surface of the casing,and the array element is controlled to transmit ultrasonic waves to form a focused sound field in the R angle area by modifying the curved surface focusing rule.The numerical simulation model is established to analyze the focusing performance of the sound field before and after the modification of the focusing law,and the influence of the water distance on the focusing sound field is also analyzed.Based on the modified focusing rule and the optimized water distance,the ultrasonic phased array testing of the R focal region of the casing is carried out.The results show that a focused sound field can be formed in the R angle region by modifying the curved surface focusing rule and optimizing the water distance,and the image quality of the sector scanning in this region is significantly improved;the transverse hole defect with the equivalent size ofΦ1.5 mm can be displayed with good resolution,and the quantitative relative error is as low as 6.7%by use of-6 dB quantitative method.