Investigating local orientation methods to segment microstructure with 3D solid texture

Historically, the ideal nasolabial angle (NLA) ranges from 90° to 120°. This study was conducted to evaluate the current preferences of NLA of laypeople and clinicians based on 3D female textured and 3D male textured images. Three-dimensional software (Di3DView) was used to create a 3D facial image with a NLA of 70°. The colour images of one male and female adult were remapped onto the generated 3D image, resulting in a colour textured 3D male, and 3D female image, both with the same facial shape and a 70° NLA. This process was repeated for NLA’s of 80°, 90°, 100°, and 110°. Based on a 7-point Likert scale, seventy-two laypeople and fifty clinicians were asked to evaluate the NLA of each rotating 3D image and give a facial attractiveness score. Clinicians and laypeople showed good intra-rater reliability (ICC 0.75 to 0.89). A 90° NLA was found to be most attractive for 3D male textured images (p=0.001). Whilst for 3D female textured images, an 80° and 90° NLA was found to be the most attractive (p=0.001). Laypeople were more critical than clinicians. Both groups would seek treatment for NLA of 70°, 100°, and 110°. We were able to show that 90° NLA’s were preferred for males and 80°–90° NLA’s for females. Laypeople were more critical of obtuse nasolabial angles, and less critical of acute nasolabial angles than clinicians. Obtuse NLA’s angles greater than 90° are no longer considered acceptable.

Dynamic crack propagation and bifurcation phenomena are investigated analytically by utilizing the strain energy density fracture criterion in the framework of catastrophe theory. The effect of biaxial stress, loading imperfections (mixed-mode loading), Poisson's ratio, state of stress as well as crack tip propagation speed on the crack path directional stability is analyzed. Special crack path stability charts for (un)stably propagating cracks are obtained, and their connection with the experimentally recorded crack tip stress field is addressed. It is shown that a slight change of the normal stress acting parallel to a crack at its tip (crack-parallel stress) may be able to affect the crack surface roughening and/or branching velocity considerably. It is also indicated that under small tensile crack-parallel stress, the crack propagation is stable only when the crack propagation speed is less than about 30% of the relevant shear wave speed. The crack becomes unstable, and its surfaces roughen severely at a higher speed, and the crack bifurcates at the highest propagation speed, some 45% of the shear wave speed. It is suggested that superimposing mode-II (shear) loading will enhance the dynamic crack path stability while increasing crack propagation speed will reduce the stability of crack propagation. It is expected that under compressive crack-parallel stress no crack surface roughening will occur before the crack stably bifurcates.

We have developed a three-dimensional (3D) dynamic integral-imaging (InIm)-system-based optical see-through augmented reality display with enhanced depth range of a 3D augmented image. A focus-tunable lens is adopted in the 3D display unit to relay the elemental images with various positions to the micro lens array. Based on resolution priority integral imaging, multiple lenslet image planes are generated to enhance the depth range of the 3D image. The depth range is further increased by utilizing both the real and virtual 3D imaging fields. The 3D reconstructed image and the real-world scene are overlaid using an optical see-through display for augmented reality. The proposed system can significantly enhance the depth range of a 3D reconstructed image with high image quality in the micro InIm unit. This approach provides enhanced functionality for augmented information and adjusts the vergence-accommodation conflict of a traditional augmented reality display.

In the case of a severe accident scenario of a pressurized water reactor which includes cracking of the vessel bottom head, it is crucial to predict the leak rate and hence the crack size for the ex-vessel accident management. We present an experimental framework to analyze the crack propagation under such severe conditions for different 16MND5 French nuclear steel grades. An original experimental setup has been designed in order to perform bi-axial tests (tensile load independent of internal pressure) at high temperatures (1180K – 1280K) on tubular test specimens. The temperature loading and the mechanical loading can be set to reproduce the stress distribution of the hemispherical vessel bottom head submitted to an internal pressure. Moreover, the test was designed to be easily transposable to the real structure in terms of crack propagation and depressurization thanks to an energy based scaling methodology. We observed the crack initiation and propagation with two high speed digital cameras. Force, internal pressure, displacement and temperature fields were also measured and synchronized with the optical measurements. The different creep stages are observed and characterized. The crack propagation and opening history have been measured. During crack initiation and propagation stages, the depressurization can be correlated with the crack geometry. Finally, the setup has been designed in order to validate future numerical analysis.

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Pavement texture is an important surface characteristic for safety evaluation. Through a series of laboratory and field testing, this study presents an automatic non-contact method using high resolution 3D images for accurate and efficient pavement texture evaluation. Firstly, a 3D laser device was applied to capture pavement texture. Subsequently, the 3D texture images were denoised using image processing methods. Then, the 3D seed filling algorithm was developed to calculate mean texture depth (MTD) and mean profile depth (MPD). The computed MTD and MPD values from 3D images showed a good correlation with results of sand patch testing and high repeatability. Further, through the follow-up field testing, the proposed method using 3D images showed better performance in texture evaluation than the 2D texture profiler or sand patch testing. The results indicate it is accurate and efficient to evaluate pavement texture using high resolution 3D images in a non-contact and automatic manner.

The effect of LPSO phases on the crack propagation in different microstructures modified by heat treatment is investigated. Solution heat treatment on a hot-extruded Mg–Dy–Nd–Zn–Zr alloy (RESOLOY) is done to change the initial fine-grained microstructure, consisting of lamellar LPSO structures within the matrix, into coarser grains of less lamellae but blocky LPSO phases. C-Ring compression tests were done with the focus on crack initiation and propagation. The blocky LPSO phases clearly hinder crack growth, either by increasing the energy to pass through the phases or along its interface. LPSO phases are found to be responsible for crack initiation: by the interface or the softer Mg-matrix in between LPSO lamellae. The softer Mg-matrix layer is providing the possibility for slip band cracking. In the coarser-grained microstructure, the crack propagation is also influenced by twins. The microstructural features were characterized by micro and nanohardness, as well as the amount and location of LPSO phases, in dependence on the heat treatment condition. Blocky LPSO phases show a higher hardness than the grains with or without lamellar LPSO phases— more specific by nanoindentation.

IT has been known for more than 10 years that titanium alloys suffer from intergranular stress corrosion cracking if they are in contact with chlorides at elevated temperatures (> 250° C), but it was only 18 months ago that Brown1 discovered that stress corrosion failures could occur at room temperature in a 3 per cent solution of sodium chloride. Titanium alloys are highly resistant to pitting attack in chloride solutions, and in order to investigate crack propagation rather than crack initiation, Brown used specimens of titanium alloy in the form of notched rectangular bars which had been fatigued in air until fine cracks had formed at the base of the notch. He found with static load tests that under plain strain conditions a 3 per cent solution of sodium chloride caused a decrease in the resistance of the alloy to the further propagation of the crack. This was a very important result, as it indicated that the stress corrosion resistance of titanium alloys under marine conditions depended on the resistance of the surface oxide on the alloy to the solution and not on the intrinsic resistance of the alloy lattice to the propagation of a stress corrosion crack which is the only really safe criterion.

The real 3D stereoscopic display system is based on the light field scanning, which is realized by reconstructing the spatial distribution of object light intensity and reducing information redundancy. The entire system is designed with a high-speed projector, a directional scattering mirror, a circular stainless steel carrying disk, a rotating shaft and a micro electric motor. In this paper, the feasibility of developing the display system is discussed in detail by analyzing the principle of 3D display of light field, and the working principle of the system, and the system architecture, and the principle of stereo imaging. The experiment proves that the projection rate of the image matches the rotating circle of the rotating mirror and the rotating speed of the motor, which can be generated a stable 3D image. The accuracy of the image depends on the angle and quantity of the selected pictures. The smaller the angle of the selected pictures, the more number of pictures, and the more realistic 3D image will be presented.

Investigating the impact toughness properties and influential factors of titanium alloy joints

Reconstruction of sub‐mm 3D pavement images using recursive generative adversarial network for faster texture measurement

The change in crystallographic orientation distribution during deformation by deep drawing in mild steel has been investigated in order to understand their role in initiation and propagation of crack. The results show that the change of grain orientation from the initial recrystallization texture component of {111}<112> to deformation orientation {111}<110> incites the initiation and propagation of transgranular cracking in the region of {111}<112> small grains. Moreover, the transgranular misorientation and local orientation are analyzed in detail to discuss the change from {111}<112> to {111}<110>. The SEM-EBSD technique was used to reveal that change of orientationm, XRD was performed for the characterization of the global evolution of texture for deformed samples.

Synthesizing solid particle textures via a visual hull algorithm

Two-dimensional and three-dimensional image correlation methods have been developed and used successfully to measure the surface displacement and strain fields during crack propagation in aerospace structures. Initial testing focused on obtaining experimental data for both the surface strain fields and the critical Crack Tip Opening Displacement (CTOD) in thin sheet 2024-T3 aluminum under predominantly tensile loads. This work was then expanded to include CTOD measurements under mixed mode loading, the study of crack closure effects, the study of buckling in large center-cracked specimens and the effect of multi-site damage on various aerospace materials.In this work, a brief background for both the two-dimensional and the three-dimensional image correlation methods is provided. Results from two projects, one using 2-D image correlation for crack closure measurements during fatigue and another using 3-D image correlation to measure surface deformations in large cracked panels, are presented.KeywordsDigital Image CorrelationCrack ClosureImage CorrelationCrack Opening DisplacementSensor PlaneThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Titanium alloy has the advantages of low thermal conductivity, a small expansion coefficient and being non-magnetic, making it an ideal low-temperature structural material. In this paper, the typical TC4 titanium alloy in industrial titanium alloy is selected as the research object. The microstructure deformation law and mechanical behavior of TC4 titanium alloy at liquid nitrogen temperature are mainly investigated, and compared with the microstructure and properties at room temperature. The macroscopic and microscopic deformation mechanism of the simultaneous increase in elongation and hardening index of titanium alloy at low temperature is revealed, which provides a basic basis for the low-temperature deformation mechanism and strengthening and toughening design of titanium alloy. Based on the uniaxial tensile tests at room temperature (298 K) and low temperature (77 K), the effects of low temperature on the yield strength, elongation, tensile strength and work hardening curve of titanium alloy were compared and analyzed. The strength/plasticity synergistic improvement of TC4 titanium alloy under low-temperature deformation was found. At low temperature, the yield strength, tensile strength and elongation of TC4 titanium alloy are improved compared with room temperature. The tensile strength increases from 847.93 MPa at 298 K to 1318.70 MPa at 77 K, and the elongation increases from 21.8% at 298 K to 24.9% at 77 K. The grain morphology, grain orientation, dislocation density and fracture morphology of titanium alloy under room temperature and low-temperature tensile conditions were studied by SEM and EBSD. The results of fracture morphology characterization at room temperature and low temperature show that TC4 titanium alloy exhibits ductile fracture characteristics and a large number of dimples are formed on the fracture surface. The dimple depth at low temperature is shallower than that at room temperature and the overall surface is more flat. Compared with room temperature deformation, the deformation process of TC4 titanium alloy in a low-temperature environment produces stronger dislocation pile-up and forms a large number of twins, but the grain rotation is more significant, which effectively alleviates the stress concentration and delays the initiation and propagation of cracks at grain boundaries.