A study on Al 2219 alloy precipitate growth rates by non-linear ultrasonic technique

A non-linear ultrasonic study has been carried out to characterise the variation in precipitation phase. An age-hardenable aluminium alloy (2219) has been taken as a model alloy for the present investigation. It is shown that there is a strong correlation between the change in the non-linear coefficient and the change in the precipitated phase. The observed variations in the non-linear ultrasonic parameter have been explained by modifying an existing dislocation-coherent precipitate interaction model for the generation of harmonics in order to account for a weaker dislocation-semicoherent precipitate interaction. In general, the model proposed can be applicable to all precipitation-hardenable alloy systems undergoing coherent to incoherent precipitate phase transition.

Monitoring damage in composite plates from crack initiation to macro-crack propagation combining linear and nonlinear ultrasonic techniques

In this article, a holistic technique for sensing damage initiation, as well as damage progression in composite plates, is presented combining linear and nonlinear ultrasonic techniques. For this investigation, multiple sets of composite plate specimens made of two different composite materials were fabricated to check if the proposed technique works for different types of specimens. The specimens were damaged by impact loading and then inspected by propagating Lamb waves through them. Different failure mechanisms, such as fiber breaks, matrix cracking, debonding, and delamination, cause composite damage. Two groups of composite specimens that were fabricated and damaged were glass fiber–reinforced polymer composite and basalt fiber–reinforced polymer composite. A chirp signal excited by PZT (lead zirconate titanate) transducer was propagated through undamaged and damaged specimens to investigate the effects of varying degrees of damage on the recorded signals. Both linear and nonlinear ultrasonic parameters were extracted from the recorded signals and analyzed. The change in the linear ultrasonic parameters such as the wave speed and attenuation with damage progression were recorded. A new nonlinear ultrasonic parameter, the sideband peak count or sideband peak count-index, is also introduced and calculated from the recorded signals. It is observed that the nonlinear ultrasonic parameter can monitor the early stage of damage progression better than the linear ultrasonic parameters, while some linear ultrasonic parameters are more effective than the nonlinear ultrasonic parameter for monitoring the advanced stage of damage. Therefore, a combination of linear ultrasonic and nonlinear ultrasonic analyses is ideal for the holistic monitoring of the composite panels from the crack nucleation stage to the structural failure stage.

Association of Menstrual Extension and Surgery Effectiveness with Ultrasound Parameters of Cesarean Section Scar Diverticulum in Patients Undergoing Transvaginal Uterine Diverticulum Repair

The association of residual myometrium thickness (RMT) and scar defect depth (D) with menstrual abnormalities and the effectiveness of vaginal repair remain to be determined in patients with cesarean section scar diverticulum (CSD). To assess the value of ultrasound to predict vaginal repair effectiveness. This was a retrospective study of patients with CSD treated with vaginal repair between 01/2014 and 02/2016 at Shanghai First Maternity and Infant Hospital (Tongji University). Transvaginal ultrasound was performed before and 3 months after surgical repair. RMT, D, scar defect length (L), and scar defect width (W) were measured. Width (W), D, and L increased along the duration of menstrual period (P<0.05). When the menstrual extension time was ≥15 days, RMT/D and RMT/RMT+D were smaller than in patients with period <15 days (P<0.05). L was the most positively correlated ultrasonic parameter with menstrual prolongation (r=0.492). RMT/D and RMT/RMT+D were negatively correlated with prolonged menstruation (r=‐0.304 and -0.305, respectively). RMT/D and RMT/RMT+D were associated with the disappearance of CSD after vaginal repair (P<0.05). The cutoff value of RMT/RMT+D was 0.496, with sensitivity of 53.0% and specificity of 61.4%. L of CSD is closely correlated with menstrual extension but has no relationship with the effectiveness of surgery. RMT/RMT+D is correlated with menstrual extension time ≥15 days and the effectiveness of vaginal repair.

Comparison of Linear and Nonlinear Ultrasonic Parameters in Characterizing Grain Size and Mechanical Properties of 304L Stainless Steel

Ultrasonic nondestructive techniques can be used to characterize grain size and to evaluate mechanical properties of metals more practically than conventional destructive optical metallography and tensile tests. Typical ultrasonic parameters that can be correlated with material properties include ultrasonic velocity, ultrasonic attenuation coefficient, and nonlinear ultrasonic parameters. In this work, the abilities of these ultrasonic parameters to characterize the grain size and the mechanical properties of 304L stainless steel were evaluated and compared. Heat-treated specimens with different grain sizes were prepared and tested, where grain size ranged from approximately 40 to 300 μm. The measurements of ultrasonic velocity and ultrasonic attenuation coefficient were based on a pulse-echo mode, and the nonlinear ultrasonic parameter was measured based on a through-transmission mode. Grain size, elastic modulus, yield strength, and hardness were measured using conventional destructive methods, and their results were correlated with the results of ultrasonic measurements. The experimental results showed that all the measured ultrasonic parameters correlated well with the average grain size and the mechanical properties of the specimens. The nonlinear ultrasonic parameter provided better sensitivity than the ultrasonic velocity and the ultrasonic attenuation coefficient, which suggests that the nonlinear ultrasonic measurement would be more effective in characterizing grain size and mechanical properties than linear ultrasonic measurements.