Defect Assessment Methods Research Articles

Solder Defect Assessment Method for Power Electronic Devices Based on Mechanical Stress Wave Signals

The health of a power electronic device is closely related to the mechanical stress waves released at the moment when the device is turned on and off. Research has shown the potential of mechanical stress waves in power electronic device health monitoring. However, the correlation between power device defect severity and mechanical stress wave signal characteristics has not been fully established and an effective evaluation method is currently lacking. This article uses finite element simulation methods to explore the impact of void defects in the chip solder and base plate solder of insulated gate bipolar transistor (IGBT) devices on mechanical stress wave signals. By analyzing the mechanical stress wave curves of cavity defects of multiple sizes, a method for assessing the health status of power devices based on principal component analysis (PCA) is proposed. By calculating the projection of the mechanical stress wave signal on the principal component, the characteristic quantity representing the severity of the defect is obtained. Simulation results indicate that for chip soldering defects, as the severity of defects increases, the feature values gradually decrease. Therefore, this method exhibits good evaluation performance for defects throughout the entire lifecycle. In the case of plate solder defects, this approach can effectively identify mid-to-late-stage defects in devices and can also be utilized for reliability prediction before device failure.

Modeling of multiple atrial septal defects with inferior vena cava rim deficiency: Three-dimensional visualization of the rim based on transthoracic echocardiographic imaging.

The morphologic features of the multiple atrial septal defects assessed by TTE-based 3D imaging were similar to those by 3D-TEE. TTE-based 3D model had excellent visibility, allowing observation of 3D structure of the rims of the defects. It may be useful method for assessment of the multiple atrial septal defects.

Parametric image-based concrete defect assessment method

Structural health monitoring aims to ensure the integrity of infrastructure. Assessing structural integrity through image classification techniques based on human perception is often challenging. Incorporating a morphological image-based crack detection algorithm can mitigate these limitations. This study proposes a parametric approach for concrete crack analysis using digital image processing techniques. The objective is to detect damage to the concrete surface of infrastructures, potentially exacerbating structural deterioration. The research justifies the utilization of digital parametric image processing techniques, including a weighted median filter, grayscale, Otsu filter, and other methods. These techniques were applied to evaluate different concrete images for crack detection. The findings were validated through Image Quality Assessment (IQA), determining the condition of the studied images and statistical properties using metrics such as Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Index (SSIM), Blind/Referenceless Image Spatial Quality Evaluator (BRISQUE), Natural Image Quality Evaluator (NIQE), and Perceptual Image Quality Evaluator (PIQE). Additionally, uncontrollable factors such as variations in lighting effects under different conditions, testing setups, and different textures of the concrete were considered in this study. The comprehensive experimental results demonstrated that the Otsu filter outperforms other filtering techniques. Overall, the study achieved remarkable accuracy, approximately 95%, in detecting cracks on building infrastructure. The proposed method holds potential for integration with advanced techniques in practical applications for the maintenance and safety of infrastructure. This research not only contributes to technological advancements in concrete defect assessment but also carries significant implications for the future of automated and reliable structural health monitoring.

Detection and Characterization of Endplate Structural Defects on CT: A Diagnostic Accuracy Study.

Diagnostic test study. To determine the reliability and validity or diagnostic accuracy of two previously described endplate structural defect (EPSD) assessment methods. Studies of EPSD may further the understanding of pathoanatomic mechanisms underlying back pain. However, clinical imaging methods used to document EPSD have not been validated, leaving uncertainty about what the observations represent. Using an evaluation manual, 418 endplates on CT sagittal slices obtained from 19 embalmed cadavers (9 men and 10 women, aged 62-91yr) were independently assessed by two experienced radiologists and a novice for EPSD using the two methods. The corresponding micro-CT (µCT) from the harvested T7-S1 spines were assessed by another independent rater with excellent intra-rater reliability (k=0.96). Inter-rater reliability was good for the presence (k=0.60-0.69) and fair for specific phenotypes (k=0.43-0.58) of EPSD. Erosion, for which the Brayda-Bruno classification lacked a category, was mainly (82.8%) classified as wavy/irregular, while many notched defects (n=15, 46.9%) and Schmorl's nodes (n=45, 79%) were recorded as focal defects using Feng's classification. When compared to µCT, endplate fractures (n=53) and corner defects (n=28) were routinely missed on CT. Endplates classified as wavy/irregular on CT corresponded to erosion (n=29, 21.2%), jagged defects (n=21, 15.3%), calcification (n=19, 13.9%), and other phenotypes on µCT. Some focal defects on CT represented endplate fractures (n=21, 27.6%) on µCT. Overall, with respect to the presence of an EPSD, there was a sensitivity of 70.9% and a specificity of 79.1% using Feng's method, and 79.5% and 57.5% using Brayda-Bruno's method. Poor to fair inter-rater reliability (k=0.26-0.47) was observed for defect dimensions. There was good inter-rater reliability and evidence of criterion validity supporting assessments of EPSD presence using both methods. However, neither method contained all needed EPSD phenotypes for optimal sensitivity, and specific phenotypes were often misclassified.

A constraint-based approach for notch cleavage fracture toughness estimations

A stress-based approach is used to evaluate the role of notch sharpness on effective toughness of S355J2 + N steel samples. A notch corrected constraint method based on a J-Q approach is proposed for the first time. The approach is calibrated using experimental fracture data of pre-cracked and notched SEN(B) samples and validated using notched C(T) data from open literature for the same material. A two-parameter Weibull model is used to describe the probability of failure to incorporate confidence levels into the analysis. The methodology shows to be a promising method for assessment of non-sharp defects where benefit may be taken from resolving non-sharp defects acuity.

Effect of weld geometry on the limit load of a cracked specimen under tension

The accuracy of the defect assessment methods strongly depends on the accuracy of limit load solutions. Usually, many parameters classify welded structures. Therefore, parametric analysis of such structures may be time-consuming. The upper bound theorem supplies an efficient method for reducing lengthy calculations. The mathematical features of this theorem allow for accurate estimations of the limit load to be found using rather simple kinematically admissible velocity fields. In the case of highly undermatched welded joints, the known singular velocity behavior near the bi-material interface can be taken into account to choose a kinematically admissible velocity field satisfying some features of the real velocity field. The present article provides such a solution for V-bevel butt welds containing a crack of quite an arbitrary shape. The welded joint is subject to tension. The solution consists of two steps. The first step determines the limit load of the specimen with no crack. This step requires the numerical minimization of a function of one variable. The second step accounts for the crack, assuming that the solution for the uncracked specimen is known. This step is purely analytical. The accuracy of the solution is confirmed by comparison with a solution for a particular geometry of the weld found using Riemann’s method. The effect of the weld geometry on the limit load is revealed.

Real-Time Instance Segmentation of Metal Screw Defects Based on Deep Learning Approach

Abstract In general, manual methods are often used to inspect defects in the production of metal screws. As deep learning shines in the field of visual detection, this study employs the You Only Look At CoefficienTs (YOLACT) algorithm to detect the surface defects of the metal screw heads. The raw images with different defects are collected by an automated microscopic camera scanning system to build the training and validation datasets. The experimental results demonstrate that the trained YOLACT is sufficient to achieve a mean average accuracy of 92.8 % with low missing and false rates. The processing speed of the trained YOLACT reaches 30 frames per second. Compared with other segmentation methods, the proposed model provides excellent performance in both segmentation and detection accuracy. Our efficient deep learning-based system may support the advancement of non-contact defect assessment methods for quality control of the screw manufacture.

Pipeline volumetric defect assessment method based on multi risk factors and in-line inspection data

Volumetric defects in pipeline is one of the main factors causing pipeline leakage accidents. Once an accident occurs, it will cause huge economic and environmental loss. At present, the assessment of pipeline volumetric defects in existing standards is only calculate the residual strength of pipeline by defect size (length, width, depth), without considering the influence of other external risk factors. Therefore, defect-related risk factors were introduced when calculating the residual strength of defects using in-line inspection data. Due to the massive data resources produced during the construction and the operation period, a risk factor correlation analysis model for extracting the risk factors related to the pipeline safety was established. The weight of each factor is obtained by using analytic hierarchy process algorithm, and a new defect risk index was put forward. Therefore, the volumetric defect assessment method based on multiple risk factors of defects and in-line inspection data is proposed. The result of on-site examples shows that the defect assessment method proposed in this paper can reflect the true safety status of the defects, it can also provide support for scientific and reasonable pipeline maintenance decision.

Quick Method for Presurgical Volumetric Analysis of Alveolar Cleft Defects.

Presurgical evaluation of the alveolar cleft defect is an essential and crucial step for procedural success. This study proposes a method for rapid and precise volumetric assessment of alveolar cleft defects using computed tomography data and computer-aided engineering (CAE) software. For comparison, 3-dimensional-printed models of the alveolar bone were also made. A simulated graft was used on the models and the graft volume was measured using the water displacement technique. We then compared the CAE software-derived volumes with the actual volumes of the simulated grafts. The intraclass correlation coefficient ranged from 0.95 to 0.97 (intraobserver) and 0.94 to 0.98 (interobserver), indicating a high level of reliability and reproducibility of the CAE measurements. The mean time spent to calculate an alveolar cleft defect volume was 8.4 minutes. The average volume of the simulated bone grafts of 3-dimensional-printed models was 1.39 mL, which was lower than the mean volume of 1.42 mL calculated using the CAE software. The paired Student t-test showed no statistically significant difference between the volumes derived from the 2 methods. This study demonstrates that this quick assessment method is a useful adjunct to busy clinical practice.

Method for quantitative assessment of acetabular bone defects.

ABSTRACTThe objective of the study was to suggest a novel quantitative assessment of acetabular bone defects based on a statistical shape model, validate the method, and present preliminary results. Two exemplary CT‐data sets with acetabular bone defects were segmented to obtain a solid model of each defect pelvis. The pathological areas around the acetabulum were excluded and a statistical shape model was fitted to the remaining healthy bone structures. The excluded areas were extrapolated such that a solid model of the native pelvis per specimen resulted (i.e., each pelvis without defect). The validity of the reconstruction was tested by a leave‐one‐out study. Validation results showed median reconstruction errors of 3.0 mm for center of rotation, 1.7 mm for acetabulum diameter, 2.1° for inclination, 2.5° for anteversion, and 3.3 mm3 for bone volume around the acetabulum. By applying Boolean operations on the solid models of defect and native pelvis, bone loss and bone formation in four different sectors were assessed. For both analyzed specimens, bone loss and bone formation per sector were calculated and were consistent with the visual impression. In specimen_1 bone loss was predominant in the medial wall (10.8 ml; 79%), in specimen_2 in the posterior column (15.6 ml; 46%). This study showed the feasibility of a quantitative assessment of acetabular bone defects using a statistical shape model‐based reconstruction method. Validation results showed acceptable reconstruction accuracy, also when less healthy bone remains. The method could potentially be used for implant development, pre‐clinical testing, pre‐operative planning, and intra‐operative navigation. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 9999:1–9, 2018.

Strength Assessment of Corroded Pipelines — Finite Element Simulations and Parametric Studies

Pipelines are one of the most efficient means for transporting hydrocarbons from one point to the other. However, there is a great risk of pipelines operation failure due to the detrimental effects of corrosion. At the point of corrosion, the pipe wall becomes thinner and loses its mechanical resistance. In such cases, reliable defect assessment methods are necessary to decide whether to resume continual operation or to shut down for maintenance or replacement. However, the available assessment methods are over-conservative, which enforce either unnecessary maintenance or premature replacement. Furthermore, the defect assessment methods should not only ensure safe operation, but also optimized operation cost. Therefore, a new assessment method was developed based on the nonlinear finite element (FE) analysis and a parametric study of geometric parameters related to the corrosion defect. The new method was validated with burst test database, which can predict the burst pressure of corroded pipelines with better accuracy and consistency.

Application of State of the Art Assessment for Pipeline Girth Weld

In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructural heterogeneities. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes have been applied in this field, there are many differences among them. In this paper, the application of weld defect assessment methods was extensively studied. The key points of ECA applications, such as the pipeline axial stress and toughness, have been introduced. Furthermore, some suggestions were given on the application of girth weld ECA assessment.

Assessment of MOF's Quality: Quantifying Defect Content in Crystalline Porous Materials.

A quantitative method for assessment of defects in metal-organic framework (MOF) is presented based on isotherms calculated using Grand Canonical Monte Carlo (GCMC) simulations. Defects in MOF structures generated during the synthesis and sample preparation can lead to large variations in experimentally measured adsorption isotherms but are difficult to quantify. We use as a case study CO2 adsorption on Cu3(BTC)2 MOF (BTC = benzene-1,3,5-tricarboxylic acid) to show that different samples reported in the literature have various proportions of principal pores blocked or side pores blocked, resulting in isotherms with different capacity and affinity toward CO2. The approach presented is easily generalized to other materials, showing that simulation results combined with experimentally measured gas adsorption isotherms can be used to quantitatively identify key defective features of the material.

Engineering Critical Assessment for the Flaws in the Pipeline Steel Girth Weld

In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructure. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes are used in this field, there are many differences among them. In this paper, the welding defect assessment methods, such as API 1104 and BS7910, were studied. The results show the key factors that affect the result of these assessment methods. The application of these methods was also discussed. The results indicate that API 1104 level1 has the highest conservatism, while API 1104 level 2 is next.

Defects Characterization in CFRP Using X-ray Computed Tomography

Although carbon fiber reinforced plastic (CFRP) is ideally high mechanical performance, manufacturing induced defects are hardly avoidable and their appearances generally result in a loss of mechanical properties. To accurately characterize this kind of defects is a foundation to estimate mechanical performance of a CFRP structure. Compared to the traditional defect assessment methods, X-ray computed tomography (CT) has been approved a promising method due to its ability to provide spatial information of defect. In this study, the effect of resolution on the accuracy of defects estimation was investigated in details. Scanning data obtained by using two different resolutions were comparatively studied based on delamination characterization. In addition, an image processing based method for porosity estimation was discussed as well. It is concluded that it is possible for us to enlarge our region of interest by selecting a reasonable resolution not at cost of losing too much desired details.

Three-dimensional reciprocal space mapping with a two-dimensional detector as a low-latency tool for investigating the influence of growth parameters on defects in semipolar GaN

A rapid nondestructive defect assessment and quantification method based on X-ray diffraction and three-dimensional reciprocal-space mapping has been established. A fast read-out two-dimensional detector with a high dynamic range of 20 bits, in combination with a powerful data analysis software package, is set up to provide fast feedback to crystal growers with the goal of supporting the development of reduced defect density GaN growth techniques. This would contribute strongly to the improvement of the crystal quality of epitaxial structures and therefore of optoelectronic properties. The method of normalized three-dimensional reciprocal-space mapping is found to be a reliable tool which shows clearly the influence of the parameters of the metal–organic vapour phase epitaxial and hydride vapour phase epitaxial (HVPE) growth methods on the extent of the diffuse scattering streak. This method enables determination of the basal stacking faults and an exploration of the presence of other types of defect such as partial dislocations and prismatic stacking faults. Three-dimensional reciprocal-space mapping is specifically used in the manuscript to determine basal stacking faults quantitatively and to discuss the presence of partial dislocations. This newly developed method has been applied to semipolar GaN structures grown on patterned sapphire substrates (PSSs). The fitting of the diffuse scattering intensity profiles along the stacking fault streaks with simulations based on a Monte Carlo approach has delivered an accurate determination of the basal plane stacking fault density. Three-dimensional reciprocal-space mapping is shown to be a method sensitive to the influence of crystallographic surface orientation on basal stacking fault densities during investigation of semipolar (11{\overline 2}2) GaN grown on an r-plane (1{\overline 1}02) PSS and semipolar (10{\overline 1}1) GaN grown on an n-plane (11{\overline 2}3) PSS. Moreover, the influence of HVPE overgrowth at reduced temperature on the quality of semipolar (11{\overline 2}2) GaN has been studied.

Non-probabilistic defect assessment for structures with cracks based on interval model

Traditional defect assessment methods conservatively treat uncertainty of parameters as safety factors, while the probabilistic method is based on the clear understanding of detailed statistical information of parameters. In this paper, the non-probabilistic approach is introduced to the failure assessment diagram (FAD) to propose a non-probabilistic defect assessment method for structures with cracks. This novel defect assessment method contains three critical processes: establishment of the interval failure assessment curve (IFAC), determination of the assessment rectangle, and solution of the non-probabilistic reliability degree. Based on the interval theory, uncertain parameters such as crack sizes, material properties and loads are considered as interval variables. As a result, the failure assessment curve (FAC) will vary in a certain range, which is defined as IFAC. And the assessment point will vary within a rectangle zone which is defined as an assessment rectangle. Based on the interval model, the establishment of IFAC and the determination of the assessment rectangle are presented. Then according to the interval possibility degree method, the non-probabilistic reliability degree of IFAC can be determined. Meanwhile, in order to clearly introduce the non-probabilistic defect assessment method, a numerical example for the assessment of a pipe with crack is given. In addition, the assessment result of the proposed method is compared with that of the traditional probabilistic method, which confirms that this non-probabilistic defect assessment can reasonably resolve the practical problem with interval variables.

Nano-volume drop patterning for rapid on-chip neuronal connect-ability assays

The ability of neurons to extend projections and to form physical connections among them (i.e., "connect-ability") is altered in several neuropathologies. The quantification of these alterations is an important read-out to investigate pathogenic mechanisms and for research and development of neuropharmacological therapies, however current morphological analysis methods are very time-intensive. Here, we present and characterize a novel on-chip approach that we propose as a rapid assay. Our approach is based on the definition on a neuronal cell culture substrate of discrete patterns of adhesion protein spots (poly-d-lysine, 23 ± 5 μm in diameter) characterized by controlled inter-spot separations of increasing distance (from 40 μm to 100 μm), locally adsorbed in an adhesion-repulsive agarose layer. Under these conditions, the connect-ability of wild type primary neurons from rodents is shown to be strictly dependent on the inter-spot distance, and can be rapidly documented by simple optical read-outs. Moreover, we applied our approach to identify connect-ability defects in neurons from a mouse model of 22q11.2 deletion syndrome/DiGeorge syndrome, by comparative trials with wild type preparations. The presented results demonstrate the sensitivity and reliability of this novel on-chip-based connect-ability approach and validate the use of this method for the rapid assessment of neuronal connect-ability defects in neuropathologies.

A three dimensional limit load solution for highly undermatched single edge cracked specimens in pure bending

ABSTRACTThe accuracy of defect assessment methods for cracked structures depends on the accuracy of limit load solutions. The present paper focuses on a new method to construct simple three‐dimensional kinematically admissible velocity fields for highly undermatched welded joints with edge cracks and its application to single edge cracked specimens in pure bending. The objective is to take into account specific features of flow pattern in highly undermatched joints to propose three‐dimensional kinematically admissible velocity fields whose level of complexity as well as accuracy of limit load predictions are comparable with plane strain fields. The three‐dimensional solution found for single edge cracked specimens in pure bending is compared to available semi‐analytical plane strain solutions. Several feasible ways to improve the solution found are proposed.

An engineering assessment methodology for non-sharp defects in steel structures – Part II: Procedure validation and constraint analysis

This Part II paper validates a new engineering methodology for assessing non-sharp defects in ferritic steel structures. The new approach, presented in the companion Part I paper, is based on a modification of the Failure Assessment Diagram for notches. A series of worked examples is presented based on a large dataset of U-notched SE(B) specimens machined from a heat-treated structural steel grade S690. Failure predictions of notched specimens using the modified approach result in significantly reduced conservatism compared to the standard Failure Assessment Diagram assessment method. The new methodology is also combined with the existing constraint-modified approach in the R6 defect assessment method to predict cleavage fracture in shallow, blunt-notched SE(B) specimens with a small degree of conservatism.