Non-destructive testing of interfacial stiffness based on spring model for diffusion bonding interface of titanium alloy components with complex surface.

Ultrasonic testing is an important non-destructive testing method, which is sensitive to the defects in the diffusion bonding interface. Ultrasonic testing of diffusion bonding interfaces in complex-surface components is a challenge due to the geometry and the weak echo signal of the diffusion bonding defects. This paper proposes an interfacial stiffness characterization method based on the spring model for the ultrasonic testing of the diffusion bonding interface of titanium alloy complex-surface component.

High-precision automatic identification method for dicentric chromosome images using two-stage convolutional neural network.

Dicentric chromosome analysis is the gold standard for biological dose assessment. To enhance the efficiency of biological dose assessment in large-scale radiation catastrophes, automatic identification of dicentric chromosome images is a promising and objective method. In this paper, an automatic identification method for dicentric chromosome images using two-stage convolutional neural network is proposed based on Giemsa-stained automatic microscopic imaging.

A novel non-destructive testing method for turbine disks using dual array ultrasonic transducer.

A novel dual array inspection method for detecting the diffusion bonding defects of superalloy turbine disk has been proposed in this study. The influence of relative position between the planar defect and acoustic source has been analysed, and based on which, the transmission and reception algorithm for the dual array method has been proposed. The time delay law of the dual array transducer for the complex turbine disk structure has been investigated.

Detailed characterisation and evaluation of composite stiffener R-zones based on mono-pulse ultrasonic reflection behavior.

R-zones are important part of the skin-stiffener joint in composite panels. Owing to their complex geometric shapes, defect behaviour, and poor accessibility, it is difficult to perform non-destructive testing and evaluation of their defects. A new method based on reflection behaviour generated by mono-pulse ultrasonic (MU) waves in R-zones for characterising and evaluating their defects was developed.

A Method for Prediction of Ultrasonic Detectability of Interface Gap Defects on TC4 Diffusion-Bonded Joints.

An analysis method for the detectability of defects on the TC4 (Ti-6Al-4V) diffusion bonding interface was proposed in this study. First, a semi-analytical model of the liquid-solid coupling acoustic field with attenuation characteristics was constructed. Based on this, a method for the selection of transducer parameters was investigated for effective focus on the diffusion bonding interface.

Rapid and automatic detection of micronuclei in binucleated lymphocytes image.

Cytokinesis block micronucleus (CBMN) assay is a widely used radiation biological dose estimation method. However, the subjectivity and the time-consuming nature of manual detection limits CBMN for rapid standard assay. The CBMN analysis is combined with a convolutional neural network to create a software for rapid standard automated detection of micronuclei in Giemsa stained binucleated lymphocytes images in this study.

Inspection of disbonds in titanium alloy honeycomb sandwich structures with different skin thicknesses using linear frequency-modulated thermography.

This paper reports the linear frequency-modulated thermography inspection of disbonds in titanium alloy honeycomb sandwich structures with different skin thicknesses. A three-dimensional finite element model of a titanium alloy honeycomb sandwich structure is built. The maximum value of the phase difference between the disbond defect region and the nondefective region is used to optimize the heating duration and frequency bandwidth.

Application of Ultrasonic Array Method for the Inspection of TC18 Addictive Manufacturing Titanium Alloy.

Ultrasonic arrays have been investigated for inspecting the quality of special materials. Unfortunately, non-destructive testing and evaluation (NDT&E) of internal defects in additive manufacturing (AM) materials are difficult due to the anisotropy and the coarse grain. To solve the problem, this paper brings forward research on the inspection of TC18 AM titanium alloy products using an ultrasonic array.

Numerical Simulation and Experimental Study of Fluid-Solid Coupling-Based Air-Coupled Ultrasonic Detection of Stomata Defect of Lithium-Ion Battery.

Aiming at the characteristics of the periodic stacking structure of a lithium-ion battery core and the corresponding relationship between the air-coupled ultrasonic transmission initial wave and the wave propagation mode in each layer medium of a lithium-ion battery, the homogenized finite element model of a lithium-ion battery was developed based on the theory of pressure acoustics and solid mechanics. This model provided a reliable method and basis for solving the visualization of ultrasonic propagation in a lithium-ion battery and the analysis of ultrasonic time-frequency domain characteristics. The finite element simulation analysis and experimental verification of a lithium-ion battery with a near-surface stomata defect, near-bottom stomata defect and middle-layer stomata defect were performed.

Inspection of butt welds for complex surface parts using ultrasonic phased array.

Detection of weld defects for complex surface parts has always been a difficult point in ultrasonic testing because the geometry complexity makes it difficult to arrange transducers and determine the propagation paths of acoustic beams. In this paper, the linear friction weld of the engine blade is taken as an example of the butt weld in complex surface parts, and the application of the ultrasonic array testing method is carried out. Firstly, the propagation properties of acoustic waves in the inspection area are analysed based on both the Snell's law and the acoustic pressure reciprocating transmittance (APRT).

A dicentric chromosome identification method based on clustering and watershed algorithm.

Aiming at the problem of low efficiency of dicentric chromosome identification counting under the microscope, this paper presents a joint processing algorithm combining clustering and watershed. The method first uses clustering and watershed algorithm to segment the original chromosome image, and then identifies the individual chromosomes. The results show that when the equivalent width Y parameter is selected m = 1, n = 1, the true positive rate of dicentric chromosome identification is 76.

Detection of disbonds in multi-layer bonded structures using the laser ultrasonic pulse-echo mode.

The laser ultrasonic technique with a pulse-echo mode has been investigated to detect disbonds in a multi-layer bonded structure and a quantitative method has been proposed to evaluate the defect sizes. The simulations were carried out to analyze influences of spot sizes on the characteristics of laser ultrasonic reflected waves, the interaction of laser ultrasonic reflected waves with disbonds, and quantitative characterization on disbonds. A noncontact laser ultrasonic inspection system has been established to perform a series of experiments to verify the theoretical results.

Application of P4 Polyphase codes pulse compression method to air-coupled ultrasonic testing systems.

Air-coupled ultrasonic testing systems are usually restricted by low signal-to-noise ratios (SNR). The use of pulse compression techniques based on P4 Polyphase codes can improve the ultrasound SNR. This type of codes can generate higher Peak Side Lobe (PSL) ratio and lower noise of compressed signal.

Step-heating infrared thermographic inspection of steel structures by applying least-squares regression.

This paper reports the application of the least-squares regression method in the step-heating thermographic inspection of steel structures. The surface temperature variation of a slab with finite thickness during both the step-heating phase and the cooling-down phase is presented. A mild steel slab with holes of various depths and diameters is chosen as the specimen.

Inspection of disbonds in multilayer dissimilar metal structure using lock-in thermography.

This paper reports the characterization of disbonds between a steel plate and a lead plate on the surface of the lead using lock-in thermography. Based on the photothermal model, the excitation frequency of the bonding specimen with the steel plate and the lead plate is optimized. A lock-in thermography testing system is established to inspect the specimen.

Application of laser ultrasonic method for on-line monitoring of friction stir spot welding process.

Application of a laser ultrasonic method is developed for on-line monitoring of the friction stir spot welding (FSSW) process. Based on the technology of FSSW, laser-generated ultrasonic waves in a good weld and nonweld area are simulated by a finite element method. The reflected and transmitted waves are analyzed to disclose the properties of the welded interface.

Detection of drilling-induced delamination in aeronautical composites by noncontact laser ultrasonic method.

A novel application of the laser ultrasonic technique for the detection of drilling-induced delamination in composite components of aircrafts is proposed. Numerous key components of aircrafts are made of composite materials, and drilling is often a final operation during assembly. Drilling-induced delamination significantly reduces the structural reliability, and it is rather difficult to be detected effectively and automatically.

Ultrasonic characterization of delamination in aeronautical composites using noncontact laser generation and detection.

The characterization of delamination in composite plates with ultrasonic waves generated and detected by lasers is presented. Composite materials have become one of the most important structural materials in the aviation industry because of their excellent mechanical properties, such as high specific stiffness and antifatigue. This paper reports a new application of the laser ultrasonic technique to perform nondestructive detection of carbon-fiber-reinforced plastic (CFRP) and continuous-fiber-reinforced ceramic matrix composites (CFCCs) containing artificial internal defects, based on propagation characteristic of ultrasonic waves generated by pulse laser with a wavelength of 1064 nm and pulse duration of 10 ns.

Effects of experimental variables on the nonlinear harmonic generation technique.

Harmonic generation is a promising technique for measuring small changes in the microstructure of components. Its extreme sensitivity is a benefit for detection, but results in a high degree of variability in any measurements taken. This paper characterizes the effects of experimental variables throughout the measurement signal path, establishing their relative importance and making suggestions for the best way to take measurements using harmonic generation.