Visual Inspection of Highway Bridges

The Federal Highway Administration recently conducted an investigation to assess the reliability of visual inspection of highway bridges as implemented by state departments of transportation. The study focused on routine and in-depth inspection, the two most prevalent forms of visual inspection of bridges. Because visual inspection is a highly subjective nondestructive evaluation technique, the results of these bridge inspections can be highly variable and are dependent on many factors. This study included the completion of 10 bridge inspection tasks by 49 practicing state bridge inspectors. With regard to routine inspections, this study showed that condition ratings are assigned with significant variability. Specifically, approximately 68% of condition ratings are within 1 rating point of the average. The results of the in-depth superstructure inspections indicated that these inspections are not likely to detect and identify the specific types of defects for which this inspection procedure is sometimes prescribed. Specifically, widespread defects such as those normally noted during a routine inspection are likely to be noted; however, local deficiencies, such as crack indications, are unlikely to be detected. The results of the deck delamination survey indicate that the accuracy of this type of inspection is relatively poor, with few inspection teams providing results that could be considered to accurately portray the condition of the deck.     

铸钢拉伸试样的几种断口分析

对塑、韧性低的铸钢拉伸试样断口进行了宏、微观形貌观察，叙述了石状断口、贝壳状断口和结晶状断口的形貌、成因及影响材料塑、韧性的原因。     

ATTRIBUTES FOR EXPEDIENT COMPUTER VISION INSPECTION

The visual inspection of parts as they progress through die manufacturing process is an important task in all industries. Visual inspection, when performed by humans is a tedious task and is prone to error. This is precisely what makes it a good candidate for automation. Although computer vision systems have been around for over 30 years, die industrial applications of vision systems have become practical only in die last decade. Image processing and pattern recognition algorithms used in industrial vision systems are built upon a broad body of knowledge in vision research. But the use of computer vision systems in quality control has been limited to replicating die visual inspection tasks as they would be performed by a human operator. It is die contention of this study that when computerized inspection is employed, quality control inspection plans suitable for computerized inspection should also be employed to assure cost-effectiveness.

We study a simple gauging inspection task and propose a quality control plan that exploits die characteristics of computer vision systems in order to improve cost-effectiveness.     

Variable stage-independent double sampling plan with screening for acceptance quality loss limit inspection scheme

The quality loss suggested by Taguchi has been recognised as a new quality evaluation based on variable property instead of the quality evaluation based on traditional attribute property such as the proportion of nonconforming items. Some variable sampling inspection plans in order to assure the quality have been considered. As one of those sampling inspection plans, the single sampling plan with screening (SSPS) has been constructed for acceptance quality loss limit inspection scheme. Further, the repetitive group sampling plan with screening (RGSPS) has been developed for reducing the average total inspection (ATI). Although ATI by RGSPS has successfully been reduced in comparison with ATI by SSPS, RGSPS may sometimes increase the average sampling frequency (ASF) in return for reducing ATI. In this study, the stage-independent double sampling plan with screening (SIDSPS) based on the concept of the acceptance quality loss limit inspection scheme is proposed under the consideration of the trade-off between ATI and ASF. Through some numerical comparisons about ATI and ASF in SSPS, RGSPS, and SIDSPS, the usefulness of SIDSPS proposed in this study is confirmed.     

The Utility of Signal-Detection Theory in the Analysis of Industrial Inspector Accuracy

In an experimental study of inspector accuracy utilizing industrial electronics inspectors as subjects, a visual, subject-paced task requiring a “yes-no” response was used. The results are thought to be generally applicable to visual inspection tasks, but may not be applicable in an inspection task requiring measurement, as in machine parts inspection. The major conclusion of the research is that signal-detection measures are more useful in performance evaluation than are other available measures, because they not only relate performance to payoff, but indicate the magnitude and direction of improvement required.     

Visual inspection of components for mechanized assembly

Analyses (Boothroyd and Redford 1968) have indicated that a knowledge of the relationship between parts quality and cost is essential if the performance of a mechanized assembly machine is to be optimized. For mass-production parts, improvements in parts quality are invariably obtained by some form of inspection and a knowledge of the cost of and efficiency of inspection is therefore desirable.

Experiments have been carried out for visual inspection to determine the effect on inspection rate and efficiency of changing the quality of the part being inspected and the number, position and type of features of the part which can be inspected. The results of this work are presented in this paper and their significance is discussed.     

视觉检测技术及应用

视觉检测技术,尤其是基于三角法的主动和被动视觉检测技术具有非接触、速度快、柔性好等特点,是一种先进的检测手段,适合现代制造业的需要。文章论述了视觉检测技术原理,讨论了已经研制的多个实际视觉检测系统,从不同角度展示了视觉检测技术在现代制造业中广阔的应用前景。     

Three-color mixing for classifying agricultural products for safety and quality

A three-color mixing application for food safety inspection is presented. It is shown that the chromaticness of the visual signal resulting from the three-color mixing achieved through our device is directly related to the three-band ratio of light intensity at three selected wavebands. An optical visual device using three-color mixing to implement the three-band ratio criterion is presented. Inspection through human vision assisted by an optical device that implements the three-band ratio criterion would offer flexibility and significant cost savings as compared to inspection with a multispectral machine vision system that implements the same criterion. Example applications of this optical three-color mixing technique are given for the inspection of chicken carcasses with various diseases and for apples with fecal contamination. With proper selection of the three narrow wavebands, discrimination by chromaticness that has a direct relation with the three-band ratio can work very well. In particular, compared with the previously presented two-color mixing application, the conditions of chicken carcasses were more easily identified using the three-color mixing application. The novel three-color mixing technique for visual inspection can be implemented on visual devices for a variety of applications, ranging from target detection to food safety inspection.     

Minimum Cost 100% Inspection Systems with Inspection Error

A field failure in certain products has the potential to cause human suffering and/or loss of life. To the manufacturer, these failures will result in a significant external failure cost. In this paper, cost minimization models are developed to determine an optimal inspection system for multiple 100% attribute inspections with inspection error. An example involving the visual inspection of a braze joint in a cardiac biopsy device is presented to illustrate the use of the models. A key result is that a system requiring an item to pass every inspection in order to be shipped to a customer is not always the best alternative. Examples illustrating the sensitivity of the model results to key cost and operational parameters are shown.     

A Search Performance Test for Visual Lobe Size

Visual search is a very common form of inspection and monitoring activity. This paper reviews work by the author that demonstrates a relationship between visual lobe size and search performance. A card sorting task was found to correlate significantly with visual lobe dimensions and it is suggested that this relationship may be used as the basis of a test for screening individuals for certain types of inspection and monitoring activities. The test is considered to be a more useful measure of visual scanning ability than tests of foveal acuity.     

Application of fuzzy logic in the selection of part orientation and probe orientation sequencing for prismatic parts

With an increase in complex designs and tighter tolerances, the Coordinate Measuring Machine inspection process has become increasingly more advanced. By inspection planning, design data can be transferred to an inspection system and an entire inspection operation can be carried out with a minimum of time and with reduced uncertainty. The current need is to automate this process completely so that the inspection plan can be generated directly from the design information. Two modules of inspection planning, i.e. selection of part orientation and probe orientation sequencing, have not been dealt with properly. Also, some important factors for the selection of part orientation have been neglected and proper weights have not been given to the probe-orientation sequencing criteria. An attempt was made to overcome these limitations. Both problems have been approached as the ranking of a number of alternatives based on multiple criteria, where each criterion has unequal importance. To get the optimum probe-orientation sequence and stable part orientation, fuzzy logic was applied. Fuzzy sets were obtained and combined using a suitable methodology. To explain and validate the proposed methodology, an example part was taken. As a practical case, an engine block was considered and the results presented.     

Wind power research in Wikipedia: Does Wikipedia demonstrate direct influence of research publications and can it be used as adequate source in research evaluation?

Comparing 5 publications from China that described knockdowns of the human TPD52L2 gene in human cancer cell lines identified unexpected similarities between these publications, flaws in experimental design, and mis-matches between some described experiments and the reported results. Following communications with journal editors, two of these TPD52L2 publications have been retracted. One retraction notice stated that while the authors claimed that the data were original, the experiments had been out-sourced to a biotechnology company. Using search engine queries, automatic text-analysis, different similarity measures, and further visual inspection, we identified 48 examples of highly similar papers describing single gene knockdowns in 1–2 human cancer cell lines that were all published by investigators from China. The incorrect use of a particular TPD52L2 shRNA sequence as a negative or non-targeting control was identified in 30/48 (63%) of these publications, using a combination of Google Scholar searches and visual inspection. Overall, these results suggest that some publications describing the effects of single gene knockdowns in human cancer cell lines may include the results of experiments that were not performed by the authors. This has serious implications for the validity of such results, and for their application in future research.     

Two-color mixing for classifying agricultural products for safety and quality

We show that the chromaticness of the visual signal that results from the two-color mixing achieved through an optically enhanced binocular device is directly related to the band ratio of light intensity at the two selected wavebands. A technique that implements the band-ratio criterion in a visual device by using two-color mixing is presented here. The device will allow inspectors to identify targets visually in accordance with a two-wavelength band ratio. It is a method of inspection by human vision assisted by an optical device, which offers greater flexibility and better cost savings than a multispectral machine vision system that implements the band-ratio criterion. With proper selection of the two narrow wavebands, discrimination by chromaticness that is directly related to the band ratio can work well. An example application of this technique for the inspection of carcasses chickens of afficted with various diseases is given. An optimal pair of wavelengths of 454 and 578 nm was selected to optimize differences in saturation and hue in CIE LUV color space among different types of target. Another example application, for the detection of chilling injury in cucumbers, is given, here the selected wavelength pair was 504 and 652 nm. The novel two-color mixing technique for visual inspection can be included in visual devices for various applications, ranging from target detection to food safety inspection.     

An optimization model for selective inspection in serial manufacturing systems

This paper describes an optimization model for allocating inspection efforts at each stage in a serial multi-stage assembly line. The model explicitly considers the economic tradeoff between product yield and inspection accuracy. The paper also shows that the use of a heuristic solution method, simulated annealing, is effective and efficient for solving the inspection allocation model. Problem instances have been developed using real production and visual inspection data provided by a local high-volume electronics manufacturer. In addition, randomly generated problems are used to evaluate the performance of the proposed heuristic.     

Allocating solder-paste printing inspection in high-volume electronics manufacturing

The paper describes an optimization model for allocating solder-paste printing inspection that explicitly considers the economic tradeoff between board yield and inspection accuracy. The paper also shows that the use of a heuristic solution method for solving the post-printing inspection allocation model is effective and efficient for high-volume electronics manufacturing. The model has been developed using real production and visual inspection data provided by a high-volume electronics manufacturer located in Huntsville, AL. In addition, randomly generated problems are used to evaluate the performance of the proposed heuristic. Results from a large case study show that when compared with a full post-printing inspection, the heuristic approach provides a solution that can increase the total expected gains by 15%.     

Failure Analysis of Torsion Bar of Projectile Weaving Machine

Torsion bars are some of the most important elements used in projectile weaving machines. In this study, the fracture of a torsion bar for weaving machine produced from spring steel is investigated. Specimens prepared from the damaged torsion bars were subjected to visual inspection, hardness testing, chemical analysis, and metallurgical evaluations. The failed torsion bars had been fabricated from spring steel, and the calculated stress on the bars suggested that the steel did not have sufficient torsional strength. Examination of fractured parts showed that all fractures started at a shoulder radius due to high stress concentrations.     

Failures in inspection procedures: case studies

The most frequently used inspection methods, i.e., visual examination, dye penetrant examination, magnetic particle examination, eddy current examination, and ultrasonic examination, are, for the most part, effective and reliable. There have been instances, however, particularly in the aviation field, where the designated methods of inspection were not able to detect cracks, and as a result catastrophic failures occurred. In the aviation field, when major-accidents occur there is usually a thorough investigation to determine the cause. We are fortunate the accident reports concerning such events are made public, so that engineers can learn from the mistakes which led to an accident and take corrective action to prevent a recurrence of such accidents. The present paper discusses a number of cases wherein faulty inspection procedures resulted in accidents. These cases are based upon published reports as well as personal experiences, and will deal with the crashes which involved: a 707 freighter (visual examination), a DC-10 (dye penetrant), a small passenger plane (magnetic particle), a 737 (eddy currents), and a 747 freighter (ultrasonics).     

Adaptive optics and vision

It has long been recognised that the optical quality of the human eye is far from diffraction limited. This affects our visual acuity and severely limits the resolution at which images of the living retina can be obtained. Adaptive optics is a technique that can correct for the eye's aberrations and provide diffraction limited resolution. The origins of the technique lie in astronomy, but it was successfully adapted to the human eye just over 10 years ago. Since then there have been rapid developments in the field of adaptive optics and vision science. In vivo images of the retina can now be routinely achieved with unprecedented resolution. Sophisticated experiments can be performed to gain a deeper knowledge of the interaction of neural retinal architecture and visual perception. This article presents the theory behind adaptive optics for the human eye and reviews the developments in this field to date.     

Understanding Scribe Profile and Tool Type Effects on Visual Corrosion Assessments

Visual analysis is the most common evaluation of accelerated corrosion performance after exposure using a scribed protective coating on a metal substrate. Although the scribed-coating visual inspection is standardized, the specificity of initial conditions relative to the final performance has never been unified between laboratories, scribing tools, nor by published testing standards. To validate the initial state of the coating performance based on the selected tool, salt spray corrosion tests ASTM B117 and GM14872 were performed on 60 epoxy-amine primer coated UNS 10080/10100 steel test panels with nine different scribes (3 test panels each with 3 non-scribed control panels). The width of the initial scribe greatly impacted the visual corrosion assessment of the test results during ASTM B117, while the initial scribe width had little impact during GM14872. These results suggest that correlating the initial scribe with the final corrosion evaluation of the coating defect resulted in a better inter-comparable evaluation of coatings subjected to visual analysis by accelerated corrosion or electrolyte corrosion.     

Non-referential,self-compared shape defect inspection for bond pads with deformed shapes

Automated visual inspection algorithms for printed circuit boards have long been focused on geometric defects of conductive paths that comprise regularly straight line and circular arc segments. In this study, we aim at defect inspection of substrate bond pads consisting of rotated and deformed shapes. A non-referential, self-comparison machine vision scheme is proposed in this paper for shape defect detection of bond pads. It is invariant to translation and orientation, and is tolerable to shape deformation of faultless objects. A shape reconstruction technique based on Fourier transforms is first applied to restore an inspection object with varying smoothness. Two discrimination features are then extracted from the point-to-point distances between the original and reconstructed shapes. The first discrimination feature measures the global irregularity of the whole boundary of the inspection object, and the second feature measures the maximum local deviation of the object boundary. Experimental results of numerous real bond pad samples have shown that the proposed self-comparison scheme with the two discrimination features can well separate the clusters of faultless and defective samples.