Defect Shape Research Articles

ГРАНУЛИРОВАННЫЕ КОСТНОПЛАСТИЧЕСКИЕ МАТЕРИАЛЫ НА ОСНОВЕ ТРИКАЛЬЦИЯ ФОСФАТА И ВОЛЛАСТОНИТА

An important area of modern materials science is the development of synthetic materials for bone grafting, providing gradual restoration of damaged hard tissues. In this work, a series of ceramic granular materials with varying contents of tricalcium phosphate and wollastonite were obtained using emulsion technology. It is shown that the synthesized particles have a spherical shape, polydisperse composition (0.1 – 4 mm) and open porosity in the range of 50 – 56%. These characteristics will make it possible to use the developed materials in maxillofacial surgery, traumatology and orthopedics to restore bone defects of any complex shape and location.

Ferroelectric nematic droplets in their isotropic melt.

The isotropic to ferroelectric nematic liquid transition was theoretically studied over one hundred years ago, but its experimental studies are rare. Here we present experimental results and theoretical considerations of novel electromechanical effects of ferroelectric nematic liquid crystal droplets coexisting with the isotropic melt. We find that the droplets have flat pancake-like shapes that are thinner than the sample thickness as long as there is room to increase the lateral droplet size. In the center of the droplets a wing-shaped defect with low birefringence is present that moves perpendicular to a weak in-plane electric field, and then extends and splits in two at higher fields. Parallel to the defect motion and extension, the entire droplet drifts along the electric field with a speed that is independent of the size of the droplet and is proportional to the amplitude of the electric field. After the field is increased above 1 mV μm-1 the entire droplet gets deformed and oscillates with the field. These observations led us to determine the polarization field and revealed the presence of a pair of positive and negative bound electric charges due to divergences of polarization around the defect volume.

Detection of subsurface defects in silicon carbide bulk materials with photothermal radiometry

<sec>With excellent physical, mechanical and processing properties, silicon carbide (SiC) has gradually become a preferred lightweight optical material for primary mirrors of large space optical systems. The subsurface defects generated during the preparation and processing procedures of SiC will affect the optical quality of the primary mirrors and the imaging performance of the corresponding optical systems employing the SiC primary mirror as well. In this work, photothermal radiation (PTR), a powerful nondestructive testing technique for detecting sub-surface defects of solid materials, is employed to characterize the subsurface defects of bulk SiC material for primary mirrors.</sec><sec>Theoretically, three-dimensional one-layer and three-layer PTR theoretical models are developed to describe the defect-free and defect regions of an SiC bulk material. By analyzing the frequency dependence of PTR phase of the SiC bulk material with different defect depths, an empirical formula for estimating the defect depth via a characteristic frequency (appearing at the minimum of the PTR phase-frequency curve) defined thermal diffusion length is proposed, and simulation results show reasonably good agreement between the estimated and simulated defect depths in a depth range of 0.05–0.50 mm. Experimentally, an SiC bulk sample with a subsurface defect region is tested by the PTR via position scanning and modulation frequency scanning to obtain the position and frequency dependent PTR amplitude and phase. From the spatial distributions of PTR amplitude and phase measured at different frequencies and the phase difference frequency curves of measurement positions in the defect region, the depth and shape of the defect region are estimated and found to be in good agreement with the actual shape of the defect region, which is destructively measured via a depth profiler. The experimental and calculated results demonstrate that the PTR is capable of detecting non-destructively the subsurface defects of SiC bulk material. In addition, for subsurface defects with relatively flat interface, the defect depth can be determined accurately by the developed empirical formula.</sec>

RESTORATION OF "LEMKEN" PLOUGHSHARE KNIVES BY THE METHOD OF HEAT-STRENGTHENED COMPENSATING ELEMENTS

The constructive and technological design of the "Lemken's" ploughshares knives allows providing a resource of up to 35-40 hectares when plowing heavy soils. Complex manufacturing technology, high market price (up to 8 thousand rubles per unit) and a certain shortage of branded knives in the spare parts market necessitates the restoration of these parts. However, the information about wear, their numerical value and geometry available in the public domain is insufficient and does not allow a reasonable approach to the development of technology to eliminate shape defects. There is no information about the use of the repair dimensions method when using technologies based on the method of heat-strengthened compensating elements. (Research purpose) The research purpose is analyzing the linear wear of the knives of the "Lemken" composite ploughshares to determine the possibility of their restoration by the method of heat-strengthened compensating elements using repair groups. (Materials and methods) It was noted that the technical condition of the knives after their operation was assessed by the residual dimensions: the width of the part in several sections; the distance from the first mounting hole to the toe; the thickness at several points of the part in accordance with the developed scheme. (Results and discussion) It was revealed that the maximum wear of the toe of the knives does not exclude the possibility of their further use. The maximum wear of knives in thickness also cannot be a reason for their decommissioning. The reason for the extreme condition of the knives is wear in width. (Conclusions) Proposed to divide worn knives into three repair groups. The use of the repair size method allows us to obtain a number of positive solutions that simplify the technology.

A Deep Detection Model based on Multi-task Learning for Appearance Defect of Solid Propellants

Solid propellants (SPs), as a high-energy material, are commonly used in military and industrial power systems, such as solid rocket and missiles. The SPs, however, confronts severe difficulties of inevitable defects while being made, thus bringing about the significance of inspection. However, the literatures before typically tackled this problem separately, which subsequently combines different models for the variety of defect patterns. Despite of the effectiveness, this act of matters usually brings excessive complexity and additionally computational burden. In this article, we managed to solve this problem in an integrated framework, which unite both the size detection task and shape detection task at the same time, but with different training strategies. To be specific, our framework is mostly consisted of two stage. Firstly, the SPs region is output using a semantic segmentation network, and size measurements are completed with traditional image processing to determine the size defects of the SPs. Then, the depth features of the segmentation network are combined with the semantic segmentation map to make a spatial attention mechanism, which is input to the deep classifier to complete the shape defect detection. The focus of model is gradually shifted from the segmentation task to the classification task as the number of training sessions increases by introducing dynamic balancing factors. The experimental results show that the multi-task learning approach can greatly improve the generalization and robustness of the model, and the accuracy and speed are improved for appearance defect detection of SPs.

Temporal and spatial laser intensification within nodular defects overcoated with multilayer dielectric mirrors over a wide range of defect geometries.

The nodular defect shape and the laser incidence angle have a dramatic impact on the spatial distribution of light intensification within the nodule as well as how the laser light is drained from the defect. Nodular defect geometries unique to ion beam sputtering, ion-assisted deposition, and electron-beam (e-beam) deposition, respectively, are modeled in this parametric study over a wide range of nodular inclusion diameters and layer count for optical interference mirror coatings constructed with quarter-wave thicknesses and capped with a half wave of the low index material. It was found for hafnia (n=1.9) and silica (n=1.45) multilayer mirrors that the light intensification in nodular defects with a C factor of 8, typical of e-beam deposited coatings deposited with a wide range of deposition angles, was maximized for a 24-layer design. For intermediate size inclusion diameters, increasing the layer count for normal incidence multilayer mirrors reduced the light intensification within the nodular defect. A second parametric study explored the impact of the nodule shape on the light intensification for a fixed number of layers. In this case, there is a strong temporal trend for the different nodule shapes. Narrow nodules tend to drain more laser energy through the bottom of the nodule into the substrate while wide nodules tend to drain more laser energy through the top of the nodule when irradiated at normal incidence. At a 45° incidence angle, waveguiding is an additional method to drain laser energy from the nodular defect. Finally, laser light resonates within nodular defects longer than within the adjacent nondefective multilayer structure.

Human globozoospermia-related genes and their role in acrosome biogenesis.

The mammalian acrosome is a secretory vesicle attached to the sperm nucleus whose fusion with the overlying plasma membrane is required to achieve fertilization. Acrosome biogenesis starts during meiosis, but it lasts through the entire process of haploid cell differentiation (spermiogenesis). Acrosome biogenesis is a stepwise process that involves membrane traffic from the Golgi apparatus, but it also seems that the lysosome/endosome system participates in this process. Defective sperm head morphology is accompanied by defective acrosome shape and function, and patients with these characteristics are infertile or subfertile. The most extreme case of acrosome biogenesis failure is globozoospermia syndrome, which is primarily characterized by the presence of round-headed spermatozoa without acrosomes with cytoskeleton defects around the nucleus and infertility. Several genes participating in acrosome biogenesis have been uncovered using genetic deletions in mice, but only a few of them have been found to be deleted or modified in patients with globozoospermia. Understanding acrosome biogenesis is crucial to uncovering the molecular basis of male infertility and developing new diagnostic tools and assisted reproductive technologies that may help infertile patients through more effective treatment techniques. This article is categorized under: Reproductive System Diseases > Environmental Factors Infectious Diseases > Stem Cells and Development Reproductive System Diseases > Molecular and Cellular Physiology.

Fast and high-resolution laser-ultrasonic imaging for visualizing subsurface defects in additive manufacturing components

Additive manufacturing (AM) is an emerging technique for efficient fabrication of individually tailored and complex geometry parts. The fabrication process is prone to induce various defects that can have detrimental effects on the AM components. Therefore, a reliable technique that enables monitoring the integrity of AM components and in return helping to optimize the fabrication parameters in mission-critical structures is highly demanded. This work presents a fast and high-resolution damage visualization method using laser-ultrasonic (LU) imaging technique for accurately detecting and quantifying the subsurface defects in printed AM components. Specifically, a fully noncontact LU scanning system is implemented to generate and detect high signal-to-noise ratio laser ultrasonic waves using a pulsed laser and laser Doppler vibrometer, respectively. A strategy for fast defect localization using Rayleigh waves with circular scans is firstly proposed. The high-resolution 3D synthetic aperture focusing technique (SAFT) imaging with raster scans is subsequently performed focusing around the located damage areas to stereoscopically visualize and quantify the subsurface defects. The reconstructed images are further processed and improved using Gaussian filter algorithm to obtain accurate defect shapes, sizes, and positions. The feasibility of the proposed method is eventually verified on AlSi10Mg and stainless steel (316L) components containing subsurface defects with various types and dimensions. The measured sizes are well consistent with the designed values, suggesting that it is a reliable inspection method for AM parts to ensure quality control and feedback.

CONCEPT FOR AN ADVANCED TRIBOLOGICAL SYSTEMS RESEARCH METHODOLOGY

The conduct of research on advanced tribological systems in order to determine the best solutions in terms of the durability and reliability of technical objects containing these systems requires a multifaceted and comprehensive approach due to the complexity of tribological processes occurring during operation. Observation of these processes is complicated and limited due to the inaccessibility of the friction zone. Therefore, progress in improving tribological characteristics is mainly determined by developing laboratory test methods. From the point of view of describing the tribological properties of the surface layer, the geometric structure of the surface (shape, waviness, roughness and surface defects), the structure of the physicochemical zones (microstructure, mechanical properties, physicochemical properties), and the ability to properly interact with the lubricant should be taken into account. Studies of advanced tribological systems should therefore include two complementary test methods, i.e., friction wear tests and surface layer tests (as manufactured and as operated). This paper presents a concept for research on advanced tribological systems and a justification for conducting complementary research on these systems, referring to selected examples (processing tools, joint implants, and dental implants). The research results are examples which illustrate the essence of conducting complementary research.

A Novel Study on the Effect of Tool Offset in Friction Stir Processing for Mg-NiTi Composite

Mg-NiTi-based metal matrix composites are appropriate solutions for the two most important goals of material engineers in the present day, i.e., imparting functional behaviour and the light weighting of metallic structures. In recent years, due to its solid-state nature, the development of Mg-based metal matrix composites has largely benefited from friction stir processing. Despite the great effort of researchers in the domain of friction stir welding and processing, finding optimum process parameters for efficient material mixing and consolidation remains a rigorous and exhaustive challenge. Tool offset variation has been seen to aid the integrity and strength of friction stir welds; however, its effect upon the stir zone structure, material flow, particle distribution, and defect formation has not been investigated for friction stir processing. Therefore, the authors employed Mg as the base metal and NiTi shape memory alloy as the reinforcement to the targeted metal matrix composite. The tool offset was linearly varied by tilting the slotted length with respect to the traverse direction. Friction stir processing performed at a rotational speed of 560 rpm and traverse speed of 80 mm/min revealed crucial changes in defect morphology and area, which has been explicated with the quantified variation in tool offset from the advancing side to the retreating side. For the positive offset conditions, i.e., tool offset towards the advancing side, the shape of the tunnelling defect was chiefly convex from the outward direction. Meanwhile, for the negative offset conditions, i.e., tool offset towards the retreating side, the tunnelling defect exhibited a concave outward shape. A transition from rectangular to triangular morphology was also observed as the tool moved from an offset of 1.75 mm in the advancing side to 1.75 mm in the retreating side.

Wheel hub defect detection based on the DS-Cascade RCNN

At present, object detection methods based on machine vision have been widely used in the field of industrial defect detection. Wheel hub defects are characterized by multiple scales and complex types. The location, size and affiliation of different defect marks are different, so it is difficult to establish an accurate wheel hub defect detection model. Therefore, a wheel nuclear hub defect detection method based on the DS-Cascade RCNN was proposed. To effectively locate multiscale s, a spatial attention mechanism was added as a wheel hub defect location enhancement module. Then deformable convolution is added, and the position and size of the convolution kernel are adjusted dynamically according to the shape of wheel defects. Finally, the pruning algorithm is used to optimize the improved model and compress the model space without losing the accuracy. The model was evaluated under the wheel dataset. Experimental results show that the proposed method can effectively detect six kinds of wheel hub defects, and the mean Average Precision (mAP) is 95.49%. Multiscale defect location and defect category estimation are realized, which meets the requirements of wheel hub detection in actual production.

Verification of a Technique for Reconstructing the Shape of Defects in Soft Magnetic Ferromagnets Using MFL Data

Verification of a Technique for Reconstructing the Shape of Defects in Soft Magnetic Ferromagnets Using MFL Data

Therapeutic potential of adipose tissue-derivatives in modern dermatology.

Stem cell-mediated therapies in combination with biomaterial and growth factor-based approaches in regenerative medicine are rapidly evolving with increasing application beyond the dermatologic field. Adipose-derived stem cells (ADSCs) are the more frequently used adult stem cells due to their abundance and easy access. In the case of volumetric defects, adipose tissue can take the shape of defects, restoring the volume and enhancing the regeneration of receiving tissue. When regenerative purposes prevail on volume restoration, the stromal vascular fraction (SVF) rich in staminal cells, purified mesenchymal stem cells (MSCs) or their cell-free derivatives grafting are favoured. The therapeutic efficacy of acellular approaches is explained by the fact that a significant part of the natural propensity of stem cells to repair damaged tissue is ascribable to their secretory activity that combines mitogenic factors, cytokines, chemokines and extracellular matrix components. Therefore, the secretome's ability to modulate multiple targets simultaneously demonstrated preclinical and clinical efficacy in reversing pathological mechanisms of complex conditions such atopic dermatitis (AD), vitiligo, psoriasis, acne and Lichen sclerosus (LS), non-resolving wounds and alopecia. This review analysing bothin vivoandin vitromodels gives an overview of the clinical relevance of adipose tissue-derivatives such as autologous fat graft, stromal vascular fraction, purified stem cells and secretome for skin disorders application. Finally, we highlighted the major disease-specific limitations and the future perspective in this field.

Optimization of the modular reinforced bone scaffold for customized alveolar bone defects

A modular reinforced bone scaffold with enhanced mechanical properties has recently been developed by our group. It includes: 1) A load-bearing module: a skeleton which is made of a slowly degradable material, undertaking mechanical necessities of the scaffold, and 2) A bio-reactive module: a porous and biodegradable component undertaking biological necessities of the scaffold. The load-bearing module is placed into the bio-reactive module to reinforce it. This paper is dedicated to optimizing the load-bearing module for a certain customized alveolar bone defect. More specifically, a 3D-printed skeleton, made of polycaprolactone (PCL), is optimized based on the boundary conditions of the defect shape using the finite element method (FEM) to minimize the weight (to minimize the amount of PCL) and maximize the mechanical properties and porosity of the skeleton. Gelatin foam has been incorporated into the optimized skeleton through the aminolysis process to form the bio-reactive module. The mechanical characterization confirmed that the optimized load-bearing module has a bridge-like shape and can significantly improve the mechanical properties of the scaffold. Also, in vitro studies showed that the fabricated scaffold can improve cell proliferation and osteogenesis. This kind of scaffold can be useful for the treatment of critical-sized defects.

Plate shape recognition based on Gaussian function and particle swarm optimization for roller quenching process

Plate shape recognition in the roller quenching process provides effective feedback signals for plate shape control. Its accuracy directly affects the control effect. Most studies have obtained the high recognition accuracy of the plate shape defects by neural networks or parameter identification methods, but cannot provide a sufficiently detailed feedback signal with controllable accuracy for plate shape control, limiting the further improvement of the control effect. For these problems, a plate shape recognition method for roller quenching process is proposed. Firstly, the roller quenching process and the representation of the plate shape are introduced, and the structure of the plate shape recognition method is designed. Secondly, the Gaussian function is used to describe the plate shape defects, and the physical significance of each parameter in the Gaussian function is analyzed. Based on the Gaussian function, a plate shape fitting method with iterative structure and controllable fitting accuracy is designed to extract the detailed information about each defect. Thirdly, according to the actual production experience, the expert rules are designed for plate shape classification and to evaluate the quality. Finally, the method is verified by industrial production data. The results verify the correctness and effectiveness of our method, indicating that the method can provide important guidance for the improvement of plate shape quality and lays an important foundation for plate shape control.

Parametric reduced-order modeling enhancement for a geometrically imperfect component via hyper-reduction

In this paper, an improved nonlinear reduced-order modeling technique capable of describing the parameterized shape defect is presented. In the proposed framework, a set of defect-shapes are pre-determined based on a nominal configuration. Then, the reduced-order representation is created in a polynomial form comprising a set of reduced-tensor coefficients of defect and physical displacement fields. However, constructing reduced tensors using a large number of discretized elements usually requires enormous amounts of computational resources. Therefore, to reduce the computational expense, a quadratic-manifold-based energy-conserving sampling and weighting approach was employed to obtain the reduced tensors concerning only a few optimally selected elements. This approach can be used to conduct both time-transient and frequency response analyses on rotating mechanical components. It was found that the proposed approach can accurately estimate the broad defect-parametric variation. In particular, its computational efficiency demonstrated a significant improvement over that of existing approaches.

Depth classification of defects in composite materials by long-pulsed thermography and blind linear unmixing

This paper presents the automatic analysis of surface thermograms in response to a long-pulsed thermography inspection to classify buried defects in composite materials. Time-dependent thermal contrasts, captured from the sample surface by an infrared thermal camera, are linearly unmixed at the pixel scale to produce results independent of the in-plane defect shapes in the training dataset. The extended blind end-member and abundance extraction (EBEAE) method unmix the thermograms to compute feature vectors carrying information about the internal structure of the composite. The estimated abundances fed an optimized support vector machine (SVM) classifier, which learns a model from the data and labels the defects accordingly to their depths. The inspection of a calibrated glass fiber reinforced polymer proves the ability of EBEAE and SVM in defect classification with an average balanced accuracy of 96.18% in testing. This methodology clearly improves the current state of the art, even without the need for inspections with different source excitations. Furthermore, the estimated end-members automatically model the thermal response of the surface, providing crucial feedback for experimental optimization.

Coil shape defects prediction algorithm for hot strip rolling based on Siamese semi-supervised DAE-CNN model

Purpose Coil shape quality is the external representation of strip product quality, and it is also a direct reflection of strip production process level. This paper aims to predict the coil shape results in advance based on the real-time data through the designed algorithm. Design/methodology/approach Aiming at the strip production scale and coil shape application requirements, this paper proposes a strip coil shape defects prediction algorithm based on Siamese semi-supervised denoising auto-encoder (DAE)-convolutional neural networks. The prediction algorithm first reconstructs the information eigenvectors using DAE, then combines the convolutional neural networks and skip connection to further process the eigenvectors and finally compares the eigenvectors with the full connect neural network and predicts the strip coil shape condition. Findings The performance of the model is further verified by using the coil shape data of a steel mill, and the results show that the overall prediction accuracy, recall rate and F-measure of the model are significantly better than other commonly used classification models, with each index exceeding 88%. In addition, the prediction results of the model for different steel grades strip coil shape are also very stable, and the model has strong generalization ability. Originality/value This research provides technical support for the adjustment and optimization of strip coil shape process based on the data-driven level, which helps to improve the production quality and intelligence level of hot strip continuous rolling.

OC-089 STANDARDIZED SUTURING OF MEDIAN INCISIONS AND DEFECTS CAN REDUCE SUTURE SLACKENING AND BURST RATES

Abstract Aim Has standardization of criteria of a small-stitch-small-bite suture (SSSB) a significant influence on its durability? Material and Methods Porcine abdominal walls and bovine flanks were used as model tissues. We cut a median 15 cm long incision into the tissues. Then we punched an additional round (5–10 cm wide) or rhomboid (5×15 cm) defect in the middle of the incision. Monomax® and Maxon® USP 1 and 2–0 sutures were used in a running technique with a suture to incison lengths above 4:1. The mesh-tissue compounds were investigated on our self-built hydraulic bench test simulating coughs. Cyclic pressure impacts were repeatedly delivered peaking around 210 mmHg. In each of twenty experimental series, ten preparations were loaded 425 times. Results Standardized SSSB sutures using 2–0 Monomax® with a suture-incision-ratio of 4.5 : 1 can give a durable closure of a large defect in thin, elastic tissues. Under other conditions, suture lines can reopen. Standardization of the suturing technique significantly increased the durability (p = 0.00008). Defect shape is important since the larger rhomboid defects were easier to close compared to the smaller, 5 cm wide, round defects (SSSB: p = 0.00018; LSLB: p = 0.00906). Discussion After standardization, insignificant influences on the durability were exerted by the suture material and diameter, the bite and stitch size (small versus large), the surgeon, the tissue elasticity and tension and the defect size. Conclusions A standardized suturing technique was developed. The standardization improved the durability of a suture repair significantly.

Non-local volumetric approach to analysis defect's shape influence on specimens durability subjected to bending and torsion

The influence of defect features on fatigue behaviour is a complex trivial issue. Although the important advances over the last decades, the dialectical relationship between the defect orientation and durability is not clearly understood. The paper aims at studying the influence of the orientation of elliptical defects on the durability of samples made of C45 steel. Three types of samples with elliptical defects were subjected to cyclic bending and torsion (R = -1) in the form of a one-sided notch oriented at various angles, namely 45, 60 and 90°. The stress analysis was performed using local and non-local methods in order to determine an equivalent stress amplitude. The stress fields surrounding the defects were evaluated via three-dimensional numerical models. Then, the results were compared with the results obtained for smooth samples. The results show that the defect orientation has a higher effect under bending loading than under torsion and that the defects oriented perpendicularly to the longitudinal axis of the specimen are more detrimental.