采用热模拟试验机对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行等温压缩试验,获得变形温度为750~900℃和应变速率为0.001~1 s 1时的真应力真应变曲线,并运用修正后的试验数据建立真应变为0.7的热加工图。通过显微组织观察,分析合金的变形机理,确定...采用热模拟试验机对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行等温压缩试验,获得变形温度为750~900℃和应变速率为0.001~1 s 1时的真应力真应变曲线,并运用修正后的试验数据建立真应变为0.7的热加工图。通过显微组织观察,分析合金的变形机理,确定热变形失稳区。研究结果表明：Ti-5Al-5Mo-5V-1Cr-1Fe合金加工温度范围较宽,当加工温度低于800℃且变形速率大于0.1 s 1时易发生绝热剪切,造成流变失稳;随着变形温度升高,功率耗散因子η有增大趋势,合金的流动软化机制由动态回复逐渐变为动态再结晶,显微组织也随之细化、均匀。展开更多
Magnetic resonance elastography (MRE) can visualize the shear wave propagation of in vivo tissues, which can be mapped into viscoelastic properties. No study has measured the biomechanical properties of the PM muscle ...Magnetic resonance elastography (MRE) can visualize the shear wave propagation of in vivo tissues, which can be mapped into viscoelastic properties. No study has measured the biomechanical properties of the PM muscle in vivo using MRE. In this study, we evaluated stiffness values calculated by local frequency estimate (LFE) and algebraic inversion of differential equation (AIDE) in PM-MRE. The PM muscles of 17 healthy male volunteers were scanned in supine position by MRE. The Laplacian-based estimate (LBE) phase wrapped image data were filtered by gaussian-bandpass filter (GBF), and by both directional and GBF. LFE (MREWave) and AIDE wave inversion methods were used to calculate the respective elastograms. The wave interferences were removed by directional filtering, and smooth wave fields were obtained. The stiffness values calculated by LFE of non-DF images were 1.39 ± 0.25 kPa and 1.33 ± 0.22 kPa for right and left PM respectively, whereas for DF images, they were 1.26 ± 0.20 kPa for right PM and 1.18 ± 0.28 kPa for left PM. The stiffness values calculated by AIDE of non-DF images were 0.78 ± 0.10 kPa and 0.78 ± 0.13 kPa for right and left PM respectively, whereas for DF images, they were 0.73 ± 0.12 kPa for right PM and 0.74 ± 0.11 kPa for left PM. There was no statistically significant difference in mean values of stiffness with/without applying directional filter whereas there was a statistically significant difference in mean values of stiffness between LFE and AIDE. Both LFE and AIDE could be used for psoas major MR Elastography.展开更多
文摘采用热模拟试验机对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行等温压缩试验,获得变形温度为750~900℃和应变速率为0.001~1 s 1时的真应力真应变曲线,并运用修正后的试验数据建立真应变为0.7的热加工图。通过显微组织观察,分析合金的变形机理,确定热变形失稳区。研究结果表明：Ti-5Al-5Mo-5V-1Cr-1Fe合金加工温度范围较宽,当加工温度低于800℃且变形速率大于0.1 s 1时易发生绝热剪切,造成流变失稳;随着变形温度升高,功率耗散因子η有增大趋势,合金的流动软化机制由动态回复逐渐变为动态再结晶,显微组织也随之细化、均匀。
文摘Magnetic resonance elastography (MRE) can visualize the shear wave propagation of in vivo tissues, which can be mapped into viscoelastic properties. No study has measured the biomechanical properties of the PM muscle in vivo using MRE. In this study, we evaluated stiffness values calculated by local frequency estimate (LFE) and algebraic inversion of differential equation (AIDE) in PM-MRE. The PM muscles of 17 healthy male volunteers were scanned in supine position by MRE. The Laplacian-based estimate (LBE) phase wrapped image data were filtered by gaussian-bandpass filter (GBF), and by both directional and GBF. LFE (MREWave) and AIDE wave inversion methods were used to calculate the respective elastograms. The wave interferences were removed by directional filtering, and smooth wave fields were obtained. The stiffness values calculated by LFE of non-DF images were 1.39 ± 0.25 kPa and 1.33 ± 0.22 kPa for right and left PM respectively, whereas for DF images, they were 1.26 ± 0.20 kPa for right PM and 1.18 ± 0.28 kPa for left PM. The stiffness values calculated by AIDE of non-DF images were 0.78 ± 0.10 kPa and 0.78 ± 0.13 kPa for right and left PM respectively, whereas for DF images, they were 0.73 ± 0.12 kPa for right PM and 0.74 ± 0.11 kPa for left PM. There was no statistically significant difference in mean values of stiffness with/without applying directional filter whereas there was a statistically significant difference in mean values of stiffness between LFE and AIDE. Both LFE and AIDE could be used for psoas major MR Elastography.
