GH4169材料小阻尼精确测试方法研究
Study on Accurate Measurement Method of Small Material Damping of GH4169
闫松 1张志伟 1李芙东2
作者信息
- 1. 航天液体动力全国重点实验室 西安,710100
- 2. 西安交通大学机械工程学院 西安,710049
- 折叠
摘要
针对高温合金材料小阻尼的精确测试问题,设计了基于非接触测试的试验方案,通过激光测振获取悬臂梁的自由衰减时域响应,采用控制力矩的方式消除固支端可能引入的摩擦阻尼.首先,在时域对自由衰减响应信号进行带通滤波,采用自由衰减法计算悬臂梁的前 3阶阻尼比;其次,在频域根据采样率和采样时长做快速傅里叶变换(fast Fourier transform,简称FFT)全景谱,分别对频谱曲线第1、第2和第3阶峰值±5 Hz频率范围采用线性调频Z变换方法(chirp Z transform,简称CZT)进行频谱细化,获得该频带范围内极高分辨率的共振峰频谱;最后,利用半功率带宽法获得材料的阻尼比.结果表明:基于带通滤波的自由衰减法可以从时域衰减曲线获得GH4169悬臂梁的前3阶模态阻尼比,基于CZT变换的频域阻尼识别方法在不增加采样分辨率和数据样本点的情况下,可以识别阻尼比为10-5量级的高温合金的材料阻尼.本测试分析方法可以为整体式涡轮颤振和受迫响应计算提供精确的材料阻尼数据.
Abstract
In order to obtain accurate damping data of super alloy materials,a test scheme based on non-contact measurement is designed.Free attenuation time-domain response of cantilever beam is obtained by laser vibra-tion measurement,and the friction damping that might be introduced by the fixed end is eliminated by control-ling the torque.In the time domain,the free decay response signal is first band-pass filtered,and then the free decay method is used to calculate the first 3-order damping ratios of the cantilever beam.In the frequency do-main,the fast Fourier transform(FFT)spectrum is made according to the sampling rate and sampling time.The first,second and third-order peak frequency ranges of the spectrum curve are respectively refined by chirp Z transform(CZT)to obtain the very high-resolution formant spectrum within±5 Hz frequency range,and the damping ratio of the material is obtained by half power band width method.The results show that the free attenu-ation method based on band-pass filtering can obtain the first three order modal damping ratio of GH4169 cantile-ver beam from the time-domain attenuation curve.The frequency-domain damping identification method based on CZT transformation can identify the material damping of superalloy with a damping ratio of the order of 10-5,and does not need to increase the sampling resolution and data sample points.This test analysis method provides accurate material damping data for integral turbine flutter and forced response calculations.
关键词
涡轮颤振/材料阻尼/GH4169材料/半功率带宽法/线性调频Z变换方法Key words
turbine flutter/material damping/GH4169 material/half power bandwidth method/chirp Z trans-form引用本文复制引用
基金项目
国家重点实验室基金资助项目(HTKJ2021KL011004)
出版年
2024
NETL
NSTL
万方数据