Test Artifacts Research Articles

Multi-angle spatial compound imaging in ultrasonic immersion testing using a single transducer

A multi-angle spatial compound imaging method was developed to suppress the speckles and artifacts in ultrasonic immersion testing using a single transducer. The multi-angle echo signals were acquired by an ultrasonic immersion testing system with different incident angles. With consideration of the acoustic difference between water and the specimen, the deviation of the time of flight (TOF) and refraction were corrected. Then the corrected signals were superimposed to reconstruct a multi-angle spatial compound image. The performance of the proposed method is assessed with quantitative accuracy, signal to noise ratio (SNR) and contrast to noise ratio (CNR). Compared with the conventional B-scan imaging, the quantitative accuracy of the longitudinal and lateral sizes of the defect holes in proposed method are respectively improved by an average of 12.3% and 15.8%, and the SNR and CNR are increased by an average of 6.13 dB and 2.65 dB, respectively. The results show the advantage of the proposed multi-angle spatial compound imaging for ultrasonic immersion testing in terms of the less quantitative error and artifacts.

Impact of Hearing Loss and Amplification on Performance on a Cognitive Screening Test.

There have been numerous recent reports on the association between hearing impairment and cognitive function, such that the cognition of adults with hearing loss is poorer relative to the cognition of adults with normal hearing (NH), even when amplification is used. However, it is not clear the extent to which this is testing artifact due to the individual with hearing loss being unable to accurately hear the test stimuli. The primary purpose of this study was to examine whether use of amplification during cognitive screening with the Montreal Cognitive Assessment (MoCA) improves performance on the MoCA. Secondarily, we investigated the effects of hearing ability on MoCA performance, by comparing the performance of individuals with and without hearing impairment. Participants were 42 individuals with hearing impairment and 19 individuals with NH. Of the individuals with hearing impairment, 22 routinely used hearing aids; 20 did not use hearing aids. Following a written informec consent process, all participants completed pure tone audiometry, speech testing in quiet (Maryland consonant-nucleus-consonant [CNC] words) and in noise (Quick Speech in Noise [QuickSIN] test), and the MoCA. The speech testing and MoCA were completed twice. Individuals with hearing impairment completed testing once unaided and once with amplification, whereas individuals with NH completed unaided testing twice. The individuals with hearing impairment performed significantly less well on the MoCA than those without hearing impairment for unaided testing, and the use of amplification did not significantly change performance. This is despite the finding that amplification significantly improved the performance of the hearing aid users on the measures of speech in quiet and speech in noise. Furthermore, there were strong correlations between MoCA score and the four frequency pure tone average, Maryland CNC score and QuickSIN, which remain moderate to strong when the analyses were adjusted for age. It is concluded that the individuals with hearing loss here performed less well on the MoCA than individuals with NH and that the use of amplification did not compensate for this performance deficit. Nonetheless, this should not be taken to suggest the use of amplification during testing is unnecessary because it might be that other unmeasured factors, such as effort required to perform or fatigue, were decreased with the use of amplification.

Model-driven architecture based testing: A systematic literature review

ContextModel-driven architecture based testing (MDABT) adopts architectural models of a system under test and/or its environment to derive test artifacts. In the literature, different MDABT approaches have been provided together with the corresponding lessons results and lessons learned. ObjectiveThe overall objective of this paper is to identify the published concerns for applying MDABT, identify the proposed solutions, and describe the current research directions for MDABT. MethodTo this end we have provided a systematic literature review (SLR) that is conducted by a multi-phase study selection process using the published literature in major software engineering journals and conference proceedings. ResultsWe reviewed 739 papers that are discovered using a well-planned review protocol, and 31 of them were assessed as primary studies related to our research questions. Based on the analysis of the data extraction process, we discuss the primary trends and approaches and present the identified obstacles. ConclusionThis study shows that although a generic process the approaches different in various ways with different goals, modeling abstractions and results. Further, based on the synthesis process in the SLR we can state that the potential of MDABT has not been fully exploited yet.

Surface-specific additive manufacturing test artefacts

Many test artefact designs have been proposed for use with additive manufacturing (AM) systems. These test artefacts have primarily been designed for the evaluation of AM form and dimensional performance. A series of surface-specific measurement test artefacts designed for use in the verification of AM manufacturing processes are proposed here. Surface-specific test artefacts can be made more compact because they do not require the large dimensions needed for accurate dimensional and form measurements. The series of three test artefacts are designed to provide comprehensive information pertaining to the manufactured surface. Measurement possibilities include deviation analysis, surface texture parameter data generation, sub-surface analysis, layer step analysis and build resolution comparison. The test artefacts are designed to provide easy access for measurement using conventional surface measurement techniques, for example, focus variation microscopy, stylus profilometry, confocal microscopy and scanning electron microscopy. Additionally, the test artefacts may be simply visually inspected as a comparative tool, giving a fast indication of process variation between builds. The three test artefacts are small enough to be included in every build and include built-in manufacturing traceability information, making them a convenient physical record of the build.

Cross lifecycle variability analysis: Utilizing requirements and testing artifacts

Variability analysis is an essential activity that supports increasing and systemizing reuse across similar software products. Current studies use different types of artifacts for analyzing variability, most notably are architecture or design, requirements, and code. While architecture, design, and code help understand and model the differences in solutions and realizations, requirements enable capturing differences in a higher level of abstraction through the intended use of the software products or their behavior. However, analyzing variability based on requirements may result in inaccurate outcomes, due to the informal and incomplete nature of requirements. To tackle this deficiency, we call for augmenting requirements-based variability analysis with other behavior-related cross-lifecycle artifacts. Particularly, we extend an approach that compares and analyzes software behaviors based on requirements taking into account both ontological and semantic considerations. Using test cases and their relations to requirements, our extension, named SOVA R-TC, extract software behaviors more comprehensively, including their preconditions, post-conditions, and expected results. The outputs of SOVA R-TC are feature diagrams, which group similar behaviors and present variability of software products in a tree structure. Empirically evaluating outcomes of SOVA R-TC, they seem to be perceived as significantly better than outcomes generated based on requirements only.

Feature-Based Methodology for Design of Geometric Benchmark Test Artifacts for Additive Manufacturing Processes

The paper provides a systematic methodology for Geometric Benchmark Test Artifact (GBTA) design for evaluating the geometric behavior of Additive Manufacturing (AM) processes. The methodology is based on feature technology, a classification system based on geometric reasoning, and assembly considerations for part design. It includes dividing the complex geometries into generic implicit features (cubes, cylinders, prisms) with known geometric characteristics to facilitate feature selection depending on required output Geometric Dimensioning and Tolerancing (GD&T), fit for assembly evaluation and other geometric properties. Finally, a case study is presented to demonstrate the methodology for designing a GBTA specifically for an application product.

Conceptual approach for reuse of test automation artifacts on various architectural levels

When creating a test automation infrastructure, one of the main considerations for the buildup process is its efficiency. A main cause and method for improvement might come from reuse of test automation artifacts. Following that, one may ask ?To what extent can the test automation artifacts be re-used??. In this paper we present a model and test automation architecture for achieving such a goal. Repository Driven Test Automation (RDTA) is a conceptual approach for the buildup process of test automation infrastructure that employs reuse of testing artifacts. This paper discusses aspects of reuse of software test automation artifacts on various levels. Then, practical implications and adjustments arising from the implementation of this new paradigm are discussed. The proposed concept is documented by a case study in an international innovative computer hardware manufacturer, one of leaders in the market. The documented results are significant and confirm the validity of the concept.

Study on surface texture of Fused Deposition Modeling

Fused Deposition Modeling (FDM) is mostly used to develop functional prototypes and in some applications for end-use parts. It is important to study the surfaces produced by FDM to understand the certainty of process. Truncheon design test artefacts are printed at different print settings and surfaces are measured using stylus profilometer. Taguchi’s design of experiments, signal-to-noise ratio and multiple regression statistics are implemented to establish a concise study of the individual and combined effect of process variables on surface texture parameters. Further, a model is developed to predict the roughness parameters and is compared with experimental values. The results suggest significant roughness parameter values decrease with increase in build inclination and increases with increase in layer thickness except the roughness peak count.

Model-based optimisation of CT imaging parameters for dimensional measurements on multimaterial workpieces

The uncertainty of measurements with X-ray computed tomography (CT) depends on setup parameters that the operator must choose. Currently, there is no established model describing the relationship between setup parameters and measurement uncertainty. This paper presents an analytical method for optimising CT setup parameters for dimensional measurements on multimaterial workpieces. The method is based on defining and maximising scan quality. An experimental study proved the validity of the method by analysing the standard deviation of CT measurements on a multimaterial test artefact. An analysis of variance on the uncertainty contributions showed that the predicted parameters were globally optimal.

Effect of Build Angle on Surface Properties of Nickel Superalloys Processed by Selective Laser Melting

Aerospace, automotive, and medical industries use selective laser melting (SLM) to produce complex parts through solidifying successive layers of powder. This additive manufacturing technique has many advantages, but one of the biggest challenges facing this process is the resulting surface quality of the as-built parts. The purpose of this research was to study the surface properties of Inconel 718 alloys fabricated by SLM. The effect of build angle on the surface properties of as-built parts was investigated. Two sets of sample geometries including cube and rectangular artifacts were considered in the study. It was found that, for angles between 15° and 75°, theoretical calculations based on the “stair-step” effect were consistent with the experimental results. Downskin surfaces showed higher average roughness values compared to the upskin surfaces. No significant difference was found between the average roughness values measured from cube and rectangular test artifacts.

Automated Extraction of Function Knowledge From Text

This paper presents a method to automatically extract function knowledge from natural language text. The extraction method uses syntactic rules to acquire subject-verb-object (SVO) triplets from parsed text. Then, the functional basis taxonomy, WordNet, and word2vec are utilized to classify the triplets as artifact-function-energy flow knowledge. For evaluation, the function definitions associated with 30 most frequent artifacts compiled in a human-constructed knowledge base, Oregon State University's design repository (DR), were compared to the definitions identified by extraction the method from 4953 Wikipedia pages classified under the category “Machines.” The method found function definitions for 66% of the test artifacts. For those artifacts found, 50% of the function definitions identified were compiled in the DR. In addition, 75% of the most frequent function definitions found by the method were also defined in the DR. The results demonstrate the potential of the current work in enabling automated construction of function knowledge repositories.

From use case maps to executable test procedures: a scenario-based approach

Testing embedded systems software has become a costly activity as these systems become more complex to fulfill rising needs. Testing processes should be both effective and affordable. An ideal testing process should begin with validated requirements and begin as early as possible so that requirements defects can be fixed before they propagate and become more difficult to address. Furthermore, the testing process should facilitate test procedures creation and automate their execution. We propose a novel methodology for testing functional requirements. The methodology activities include standard notations, such as UCM for modeling scenarios derived from requirements, TDL for describing test cases and TTCN-3 for executing test procedures; other test scripting languages can also be used with our methodology. Furthermore, the automation of the methodology generates test artifacts through model transformation. The main goals of this test methodology are to leverage requirements represented as scenarios, to replace the natural language test case descriptions with test scenarios in TDL, and to generate executable test procedures. Demonstration of the feasibility of the proposed approach is based on a public case study. An empirical evaluation of our approach is given using a case study from the avionics domain.

Phononic Crystal Artifacts for Real-Time In Situ Quality Monitoring in Additive Manufacturing

Additive manufacturing (AM) is rapidly becoming a local manufacturing modality in fabricating complex, custom-designed parts, providing an unprecedented form-free flexibility for custom products. However, significant variability in part geometric quality and mechanical strength due to the shortcomings of AM processes has often been reported. Presently, AM generally lacks in situ quality inspection capability, which seriously hampers the realization of its full potential in delivering qualified practical parts. Here, we present a monitoring approach and a periodic structure design for developing test artifacts for in situ real-time monitoring of the material and bonding properties of a part at fiber/bond-scale. While the production method used in current work is filament based, the proposed approach is generic as defects are always due to materials in a bonding zone and their local bonding attributes in any production modality. The artifact design detailed here is based on ultrasonic wave propagation in phononic coupons consisting of repeating substructures to monitor and eventually to assess the bond quality and placement uniformity—not only for geometry but also for defect states. Periodicity in a structure leads to the dispersion of waves, which is sensitive to geometric/materials properties and irregularities. In this proof-of-concept study, an experimental setup and basic artifact designs are described and off-line/real-time monitoring data are presented. As a model problem, the effects of printing speed on the formation of stop bands, wave propagation speeds and fiber placement accuracy in samples are detected and reported.

In situ remote hot erosion scar measurement

When particles of grit, oxide or other contaminants get entrained in high speed gas or steam sections of power or aero turbines they can damage components through repeated impact of particles with the surface. This erosion in turn produces additional debris which can damage other surfaces further down-stream. An instrument to evaluate and quantify high temperature solid particulate erosion (HTSPE) is being designed and built at the National Physical Laboratory (UK). In order to speed up the measurement of the erosion scars, a system is required that can measure the shape and depth of scars on test coupons of materials without the need to remove them from the HTSPE system to perform the measurement. This paper deals with the optical technique that has been developed and validates its performance against a specially prepared test artefact containing ‘erosion pits’ of several different depths as well as on actual erosion scars produced with a particulate erosion system.

An integrative model for the filtration efficiencies in realistic tests with consideration of the filtration velocity profile and challenging particle size distribution

Many well-established models can be applied to calculate the filtration efficiencies. In these models the filtration velocity and challenging particle size are assumed to be known accurately. However, in realistic filtration tests, the filtration velocity has profiles dependent on the filter holder geometry and experimental conditions; the challenging particles have size distributions dependent on the instruments and operation conditions. These factors can potentially affect the measured filtration efficiency and lead to discrepancies with the models.This study aims to develop an integrative model to predict the filtration efficiencies in realistic tests by incorporating the effects of the filtration velocity profile and challenging particle size distribution classified by a differential mobility analyzer (DMA) into the existing filtration models. Face velocity profile is modeled with fluid mechanics simulations; the initial generated particle size distribution, the particle charging status and the DMA transfer function are modeled to obtain the challenging particle size distribution. These results are then fed into the filtration models. Simulated results are compared with experimental ones to verify the model accuracy. This model can be used to reduce filtration test artifacts and to improve the experimental procedure.The results reveal that the face velocity upstream the filter exhibits high degree of homogeneity not affecting the filtration efficiency if the filter pressure drop is not very low. The generated particle size distribution and the DMA selection size window could influence the challenging particle size distribution and therefore the measured filtration efficiency.Copyright © 2017 American Association for Aerosol Research

Geometric Element Test Targets (GETT™) for Determination of 3D Printers' Resolutions

This study presents a concept to address the dimensional and geometric viability of three-dimensional (3D) printers with test artifacts. These test artifacts we named as Geometric Element Test Targets (GETT™). GETT™ offers a simple method for quantitative appraisals of the dimensional performance of additive manufacturing processes. The design of GETT™ relies on logistically positioned and decreased feature dimensions. One characteristic of GETT™ is that the dimensional failures introduced may be inspected visually and quantitatively assessed through graphical analyses. We will illustrate the use of GETT™ to determine a printer's resolution through samples produced from fused deposition modeling (FDM) printers. Although the demonstration is from FDM systems, the concept is expected to hold for all 3D printing processes and can be process-specific. The potential applications of GETT™ include standardization, reference targets, in-line system control, and more.

An incremental method for extracting tests from object-oriented specification

ContextThe nature of the object-oriented development process is iterative and incremental, and through this process, software artifacts are refined and evolved continuously; however, most of proposed methods for deriving test cases from formal, object-oriented specifications have been adapted from previous structural techniques and are not aligned with such an incremental process. These methods are not adaptive with changes in the software specification, and there is no mechanism to evolve test artifacts respectively. Moreover, the existing methods do not cover all different object-oriented testing levels, i.e., intra-method, inter-method, intra-class and inter-class levels. ObjectiveThis paper presents an incremental method for extracting tests from formal, object-oriented specifications. Extracted tests are adaptive with changes in the class specification. In addition, the proposed method covers all different object-oriented testing levels. MethodWe first make a test machine (as a new notion introduced in this paper) for each class operation to cover the intra-method test level. With the combination of these test machines, new test machines covering the inter-method and intra-class test levels can be made. Extracted tests can be easily modified when the class specification is modified, and, in this way, our approach enables iterative and incremental test derivation. With test machines corresponding to a class hierarchy, this approach can also be used for deriving inter-class tests. ResultsAs a case study, we applied our method to the specification of a computer game. Results indicate that test machines can incrementally be extracted through a class hierarchy, and a parent test machine can be used to obtain its corresponding child test machines (by reusing test artifacts). Furthermore, by running extracted test cases on the implemented game, we discovered some real bugs. ConclusionThe proposed approach can incrementally extract tests and bring extendibility and reusability as two main advantages of the object- oriented paradigm to the test domain.

CT-based quality control of Laser Sintering of Polymers

Laser Sintering (LS) is an Additive Manufacturing (AM) technology for polymers processing which is increasingly being used to produce functional products with designs not achievable with traditional manufacturing technologies. Lightweight cellular structures are a good example of complex designs which are increasingly finding applications in AM parts. However, it is not yet clear how the LS process affects the porosity and geometrical characteristics of the cell structural elements. Getting this information allows to perform quality control of the LS process, gives insights into how to improve it, and might help to take into account manufacturing process variability during the design phase.In this work a test artifact containing cylindrical elements with diameters in the range typically used in lightweight cellular structures is used to investigate the influence of features' size and printing orientation on the porosity and shape deviation of each feature. In order to assess the reproducibility of the process, several replicas of the test object are produced in polyamide-12 (PA12) using the same LS process conditions. An X-ray Computed Tomography (CT)-based quality control approach, which uses both image processing of CT-slices and porosity analysis (porosity content, pores count and pores volume distributions) is used to gather the information.

Treatment of the Failed Modular Neck Stems: Tips and Tricks

BackgroundModular femoral components emerged because of the advantages of recreating limb length, offset, and native femoral version in total hip arthroplasty. Despite its potential benefits, the increase in modularity at the head-neck junction can lead to corrosion and subsequently failure of the implant. MethodsWe present 3 case examples of patients who underwent revision surgery secondary to corrosion of their modular femoral components. ResultsIssues addressed include understanding corrosion at the head-neck junction, presentations of adverse local tissue reactions, efficacy of metal ion testing and metal artifact reduction sequence magnetic resonance imaging, and approaches to revision surgery for failed modular neck stems. ConclusionsWhen revision surgery is indicated for failed modular neck stems, we recommend a thoughtful approach with contemporary extraction techniques and options to enhance stability. Furthermore, long-term follow-up is needed to define the growing effect of modularity in total hip arthroplasty.

Analysis of Glass-Filled Nylon in Laser Powder Bed Fusion Additive Manufacturing

At the Johns Hopkins University Applied Physics Laboratory (APL), glass bead-filled polyamide (a.k.a. nylon) (GFN) is being used frequently for functional parts and systems, built using a laser-based powder bed fusion (PBF) additive manufacturing (AM) system. Since these parts have performance requirements, it is important to understand the mechanical properties of the additively-made GFN as a function of build orientation and build parameters. In addition, the performance of the AM system used to manufacture these parts must be evaluated in order to understand its capabilities, especially in order to determine the dimensional precision and repeatability of features built with this system. This paper summarizes recent APL efforts to characterize the GFN powder, the mechanical properties of parts made with GFN, and the performance of the laser PBF machine while running GFN using an AM test artifact.