Wedge Test Research Articles

Streamlines behind curved shock waves in axisymmetric flow fields

Streamlines behind axisymmetric curved shock waves were used to predict the internal surfaces that produced them. Axisymmetric ring wedge models with varying internal radii of curvature and leading-edge angles were used to produce numerical results. Said numerical simulations were validated using experimental shadowgraph results for a series of ring wedge test pieces. The streamlines behind curved shock waves for lower leading-edge angles are examined at Mach 3.4, whereas the highest leading-edge angle cases are explored at Mach 2.8 and 3.4. Numerical and theoretical streamlines are compared for the highest leading-edge angle cases at Mach 3.6. It was found that wall-bounding theoretical streamlines did not match the internal curved surface. This was due to extreme streamline curvature curving the streamlines when the shock angle approached the Mach angle at lower leading-edge angles. Increased Mach number and internal radius of curvature produced more reasonable results. Very good agreement was found between the theoretical and numerical streamlines at lower curvatures before the influence of the trailing edge expansion fan.

Evaluation of the interfacial strength for adhesive joint of dissimilar materials by wedge testing method

Evaluation of the interfacial strength for adhesive joint of dissimilar materials by wedge testing method

Asymmetric inner wedge group sequential tests with applications to verifying whether effective drug concentrations are similar in adults and children.

Extrapolating from information available on one patient group to support conclusions about another is common in clinical research. For example, the findings of clinical trials, often conducted in highly selective patient cohorts, are routinely extrapolated to wider populations by policy makers. Meanwhile, the results of adult trials may be used to support conclusions about the effects of a medicine in children. For example, if the effective concentration of a drug can be assumed to be similar in adults and children, an appropriate paediatric dosing rule may be found by 'bridging', that is, by matching the adult effective concentration. However, this strategy may result in children receiving an ineffective or hazardous dose if, in fact, effective concentrations differ between adults and children. When there is uncertainty about the equality of effective concentrations, some pharmacokinetic-pharmacodynamic data may be needed in children to verify that differences are small. In this paper, we derive optimal group sequential tests that can be used to verify this assumption efficiently. Asymmetric inner wedge tests are constructed that permit early stopping to accept or reject an assumption of similar effective drug concentrations in adults and children. Asymmetry arises because the consequences of under- and over-dosing may differ. We show how confidence intervals can be obtained on termination of these tests and illustrate the small sample operating characteristics of designs using simulation. Copyright © 2016 John Wiley & Sons, Ltd.

Passive twin-layer spatial-temporal phase-interference compensator for improved transcranial ultrasound propagation

Transcranial ultrasound wave degradation created by variations in both thickness and tissue composition is a significant impediment to diagnostic and therapeutic interventions of the brain. The current “active” solution is to vary the transmission delay of ultrasound pulses, inherently necessitating electronic control of each individual transducer element. By applying the sonic-ray concept of ultrasound wave propagation, it was hypothesised that wave degradation can be significantly reduced if both the transit-time and propagation path-length for all sonic-rays are made constant. A computer simulation study was performed to investigate the implications of zero, partial and full spatial-temporal matching. Considering ultrasound propagation through a 20-step acrylic wedge test sample, only full spatial-temporal matching removed phase-interference. A “passive” physical ultrasound phase-interference compensator (UPIC), consisting of two layered materials of variable thickness, was developed and experimentally evaluated using acrylic step-wedge test samples exhibiting varying degrees of transit-time heterogeneity induced phase-interference. Time- and frequency-domain analysis demonstrated that incorporation of the UPIC successfully removed phase-interference in all cases. It is further hypothesised that the UPIC concept may be applied to both pulse-echo mode diagnostic imaging and transmission mode therapeutic interventions, incorporating either a single-element or a multi-element array transducer, of any practicable dimension.

How chimpanzees integrate sensory information to select figs.

Figs are keystone resources that sustain chimpanzees when preferred fruits are scarce. Many figs retain a green(ish) colour throughout development, a pattern that causes chimpanzees to evaluate edibility on the basis of achromatic accessory cues. Such behaviour is conspicuous because it entails a succession of discrete sensory assessments, including the deliberate palpation of individual figs, a task that requires advanced visuomotor control. These actions are strongly suggestive of domain-specific information processing and decision-making, and they call attention to a potential selective force on the origin of advanced manual prehension and digital dexterity during primate evolution. To explore this concept, we report on the foraging behaviours of chimpanzees and the spectral, chemical and mechanical properties of figs, with cutting tests revealing ease of fracture in the mouth. By integrating the ability of different sensory cues to predict fructose content in a Bayesian updating framework, we quantified the amount of information gained when a chimpanzee successively observes, palpates and bites the green figs of Ficus sansibarica. We found that the cue eliciting ingestion was not colour or size, but fig mechanics (including toughness estimates from wedge tests), which relays higher-quality information on fructose concentrations than colour vision. This result explains why chimpanzees evaluate green figs by palpation and dental incision, actions that could explain the adaptive origins of advanced manual prehension.

Testing and modelling of DIARC plasma coated elastic–plastic steel wedge specimens

The stability and durability of DIARC vacuum plasma surface treatment was tested for structural bonding with elastic–plastic steel wedge test specimens. In the treatment nanostructured DIARC Bindo coating is deposited on the substrates in a vacuum chamber. The DIARC-treated surface is ready for bonding and does not require any additional treatments, chemicals or primers containing hazardous CrVI chromium. The tests were performed at hot and wet exposure. Virtual Crack Closure Technique (VCCT) was successfully used in the design of test specimens and in the analyses of the results. Five-year-old DIARC coating performed equally with the freshly-bonded DIARC specimens. The results were also comparable with the best results achieved with existing grit-blast silane and grit-blast Sol–Gel primer methods with aluminium and titanium.

Benchmarking numerical models of brittle thrust wedges

We report quantitative results from three brittle thrust wedge experiments, comparing numerical results directly with each other and with corresponding analogue results. We first test whether the participating codes reproduce predictions from analytical critical taper theory. Eleven codes pass the stable wedge test, showing negligible internal deformation and maintaining the initial surface slope upon horizontal translation over a frictional interface. Eight codes participated in the unstable wedge test that examines the evolution of a wedge by thrust formation from a subcritical state to the critical taper geometry. The critical taper is recovered, but the models show two deformation modes characterised by either mainly forward dipping thrusts or a series of thrust pop-ups. We speculate that the two modes are caused by differences in effective basal boundary friction related to different algorithms for modelling boundary friction. The third experiment examines stacking of forward thrusts that are translated upward along a backward thrust. The results of the seven codes that run this experiment show variability in deformation style, number of thrusts, thrust dip angles and surface slope. Overall, our experiments show that numerical models run with different numerical techniques can successfully simulate laboratory brittle thrust wedge models at the cm-scale. In more detail, however, we find that it is challenging to reproduce sandbox-type setups numerically, because of frictional boundary conditions and velocity discontinuities. We recommend that future numerical-analogue comparisons use simple boundary conditions and that the numerical Earth Science community defines a plasticity test to resolve the variability in model shear zones.

The methods for the surgical correction of pareses, paralyses of the superiorinferior oblique muscle in the children

Aim. The objective of the present study was to estimate the effectiveness of the surgical correction of hyperfunction of the inferior oblique muscle in the children depending on the degree of overaction. Materials and methods. We undertook the analysis of hyperactivity of the inferior oblique muscle in 78 children (128 eyes) at the age varying from 4 to 15 years. All the patients were followed up for 9 years. The ophthalmological examination included the determination of vertical deviation with the use of the Hirschberg test and prisms, the study of eyeball movements in 8 gaze directions, the Bielschowsky darkening wedge test, the assessment of the character of vision by means of the Worth's four-dot test, visiometry, dioptos copy, and ophthalmoscopy. Results. The patients underwent myotomy, anterior transposition or myoectomy of the inferior oblique muscle with recession taking into consideration the degree of hyperfunction. Conclusion. Myotomy eliminates vertical deviation only in case of grade 1 overaction. Anterior transposition of the inferior oblique muscle provides an efficient tool for the surgical treatment of the condition being considered because it permits to rapidly correct the large angle of vertical strabismus in the patients presenting with grade 2 or 3 hyperfunction of the inferior oblique muscle. It is recommended to treat grade 4 overaction my means of myoectomy with a recession of up to 10 mm.

Light-induced cracking and abrasion of inkjet prints: Damage and mitigation

This study is part of a larger research project at the Image Permanence Institute dedicated to digital print preservation issues – the Digital Print Preservation Portal (DP3). Previous DP3 studies determined that certain digital print types are prone to cracking and/or abrasion, and that factors such as low relative humidity, pollutants, and light increase the brittleness of the ink-receiving layer of some inkjet papers. The purpose of this investigation was to explore if light also increases the propensity of inkjet prints to abrade, and to examine the potential of framing glazings to mitigate light-induced physical damage (cracking and abrasion) by attenuating some portion of the UV spectrum. Inkjet papers and prints were subjected to xenon lighting (to simulate daylight through window glass) without glazing, or in sealed framing packages with plain framing glass (soda-lime) or UV filtering glass. Before and after light exposure, brittleness, and abrasion resistance were evaluated independently using two tests: ISO 18907 (Imaging materials – Photographic films and papers – Wedge test for brittleness) and a rub test utilizing a Sutherland® Rub Tester. In this study, exposure to light increased the cracking and/or abrasion tendency of some specimens. The use of UV filtering glass reduced this light-induced propensity in all cases. Plain glass protected all samples from at least one of these two types of surface damage, but was less effective than UV glass. Light-induced brittleness and sensitivity to abrasion were mostly, though not exclusively, caused by UV radiation. It was also seen that some prints may become brittle and/or prone to abrasion in the absence of image fade. Budgeting the amount of light these objects can be exposed to, protecting them from UV radiation, and handling prints with caution especially after exhibition, is essential in order to limit physical damage.

Influence of roughness on mechanical strength of direct bonded silica and Zerodur® glasses

Direct bonding is of particular interest for optical system manufacturing for spatial application. This process requires very precise physical and chemical preparations of surface, especially roughness controls. Thus, this paper proposes to understand and discuss the roughness influence on mechanical strength and bonding energy of an elementary mechanical structure after a room temperature bonding and an annealing at optimal temperature. First, surfaces are characterized and roughness is measured. At the same time, the performances of fused silica and Zerodur® glasses are compared. Then interface properties are measured using double shear and wedge tests. At the end of the paper, a discussion, based on literature models, is proposed to explain the existence of an optimum of roughness put in evidence in experimental results.

Food mechanical properties and dietary ecology.

Interdisciplinary research has benefitted the fields of anthropology and engineering for decades: a classic example being the application of material science to the field of feeding biomechanics. However, after decades of research, discordances have developed in how mechanical properties are defined, measured, calculated, and used due to disharmonies between and within fields. This is highlighted by "toughness," or energy release rate, the comparison of incomparable tests (i.e., the scissors and wedge tests), and the comparison of incomparable metrics (i.e., the stress and displacement-limited indices). Furthermore, while material scientists report on a myriad of mechanical properties, it is common for feeding biomechanics studies to report on just one (energy release rate) or two (energy release rate and Young's modulus), which may or may not be the most appropriate for understanding feeding mechanics. Here, I review portions of materials science important to feeding biomechanists, discussing some of the basic assumptions, tests, and measurements. Next, I provide an overview of what is mechanically important during feeding, and discuss the application of mechanical property tests to feeding biomechanics. I also explain how 1) toughness measures gathered with the scissors, wedge, razor, and/or punch and die tests on non-linearly elastic brittle materials are not mechanical properties, 2) scissors and wedge tests are not comparable and 3) the stress and displacement-limited indices are not comparable. Finally, I discuss what data gathered thus far can be best used for, and discuss the future of the field, urging researchers to challenge underlying assumptions in currently used methods to gain a better understanding between primate masticatory morphology and diet.

Inoculation Enhancing Effects on Chill Tendency in the Mould Inoculated Grey Cast Iron

Inoculation is a treatment applied to the liquid base iron, to supply one or more elements, such as Al, Ba, Ca, Zr, Sr, Ce, La etc. with active roles in developing graphite nucleation sites. The efficiency of inoculants is directly dependent on the sulphur level: lower sulphur, lower inoculating power or unpredictable results. The objective of this paper is to examine the effects of a S and O containing inoculant enhancer [S,O,Al,Ca-FeSi alloy] to conventional Ca,Ba-FeSi alloy, in the mold treatment of electrically melted grey iron at 0.035%S, 0.002%Al, 0.0005%Zr, (%Mn) x (%S) < 0.02. The wedge test samples [W3 – ASTM A367] were used to evaluate the influence of the cooling rate and inoculation on the carbides formation. It was re-confirmed that for above mentioned critical chemistry conditions, this iron is sensitive to chill formation, despite the carbon equivalent level at 3.8%. Inoculation enhancement increased the effectiveness of the Ca,Ba-FeSi standard inoculant.

A model for patterned interfaces debonding – Application to adhesion tests

Patterned interfaces are widely used in the industries of microelectronics and micro-electromechanical systems and are of general interest for obtaining specific interface properties by playing on geometry as an additional parameter influencing physical processes (interface engineering). In this paper, a novel analytical model is proposed to characterize the debonding of patterned interfaces. This model is accounting for both stretching and rotation of the finite width bond lines composing a patterning between two plain substrates. The model highlights how the choice of pattern periodicity and line width allows for controlling the interface mechanical behavior during debonding: presence of stable and unstable crack growth regimes. It is shown that models considering a continuum interface are to be used with care when dealing with patterned interfaces. The model proposed here, used in conjunction with an experimental procedure providing the sample bending profile during a wedge test (or a DCB test) should provide valuable guidance for determining the interface fracture energy Gc (mode I) for a patterned interface.

Probing Lithium-Ion Battery Safety in Mining Environments

Lithium-ion batteries are increasingly ubiquitous in portable consumer electronic devices, including laptop computers, cellular phones, and tablet computers. Lithium-ion batteries are also finding widespread deployment in many additional applications and settings, including underground mining environments, where lithium-ion batteries are used as electrochemical power sources for cap lamps, and in tracking and communications equipment.1,2 Battery safety is of paramount importance in any portable electronic device regardless of setting, and is particularly significant in enclosed and isolated areas such as passenger aircraft, or in underground mining environments, where potentially explosive methane/air mixtures can be ignited by a simple spark, which can be caused by shorting and thermal runaway of lithium-ion batteries. This presentation will summarize systematic abuse testing of different lithium-ion batteries used in underground mining safety and communication equipment, including lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (NMC), and lithium iron phosphate (LiFePO4) based cathode chemistries. Prismatic and cylindrical 18650 lithium-ion batteries were obtained from commercial vendors and subjected to both wedge and flat plate crush tests, in order to determine the relative safety of each cathode chemistry under two crush speeds and various states-of-charge (SOC). Battery voltage, case temperature and applied load were recorded for each crush test. Video recording of each crush test was also collected. In some cases, hard or soft electrical short circuits were caused by crushing the battery, resulting in thermal runaway, rapid temperature increases, and explosions or fires. Correlations will be drawn between choice of cathode chemistry, state-of-charge, type of crush test, and choice of atmosphere (air or methane/air mixtures), in order to determine the most suitable lithium-ion battery chemistry for underground mining applications. References 1) Dubaniewicz, T. H. Jr.; DuCarme, J. P. Journal of Loss Prevention in the Process Industries. 2014, 32, 165. 2) Dubaniewicz, T. H. Jr.; DuCarme, J. P. IEEE Transactions on Industry Applications. 2013, 6, 2451-2460.

Volumetric Testing Parallel to the Boundary Surface for a Nonconforming Discretization of the Electric-Field Integral Equation

The volumetric monopolar-RWG discretization of the electric-field integral equation (EFIE) imposes no continuity constraint across edges in the surface discretization around a closed conductor. The current is expanded with the monopolar-RWG set and the electric field is tested over a set of tetrahedral elements attached to the boundary surface. This scheme is facet-oriented and therefore, well suited for the scattering analysis of nonconformal meshes or composite objects. The observed accuracy, though, is only competitive with respect to the RWG-discretization for a restricted range of heights of the tetrahedral elements. In this communication, we introduce a novel implementation of the volumetric monopolar-RWG discretization of the EFIE with testing over a set of wedges. We show with RCS and near-field results that this scheme offers improved accuracy for a wider range of heights than the approach with tetrahedral testing. The application of the wedge testing to the even-surface odd-volumetric monopolar-RWG discretization of the EFIE, edge-oriented and therefore less versatile, shows similar accuracy as with tetrahedral testing, which is a sign of robustness.

Original test device for crack propagation in the weld nugget of advanced high strength steels

Advanced High-Strength Steels are ever increasingly used in industry, and unlike mild steels the crack propagates through the weld nugget. At the present time, any method to measure the strength of the fusion zone is unavailable.Therefore a new test setup enforcing crack propagation through the weld nugget was developed. In the wedge test proposed, this device provides stable crack growth as the wedge is displaced. Thus, along with in situ observations, this device, without any prior assumptions is able to measure energy dissipation rate as well as crack opening angle. This is very significant because from these two data, a mechanical modeled was established to predict the cohesive energy and strength in the weld nuggets of AHSS. This method: the experimental setup and mechanical model were then applied to commercial alloys and synthetic grades successfully. This indicates that this methodology can be applied to any type of alloy.

The association between systolic blood pressure and positional changes of the main renal venous blood flow

Objective. To assess the impact of the position-dependent changes of the main renal venous blood flow on systolic blood pressure (SBP). Design and methods. We measured blood pressure, blood flow in the renal veins, and resistance index in patients with pathological kidney mobility (PKM). Based on the difference between the maximum and minimum velocity of renal venous blood flow several groups were identified, namely, groups with normal venous blood flow, with borderline and severe alterations of venous outflow. Based on the sum of the rotation angles (according to the excretory urogram and ultrasonography wedge and tilt test in three planes), patients were divided into three groups: I rotation degree — sum of rotation angles 40°, II — from 40° to 70°, III — 70° and above. Results. We found a relation between SBP and both velocity and resistance indices in both renal vessels. There is an increase in the incidence and amplitude of SBP fluctuations in patients with all rotation degrees with the direct association with the severity of PKM. The classification of PKM patients based on the sum of rotation angles measured by ultrasound and Doppler examinations is highly efficient, and the accuracy was 89,13%. Conclusions. The changes in renal veins seem to contribute to the SBP elevation. The measurement of BP in six static states can enable new insight on the physiological BP changes and will help early diagnostics and verification of pathogenic factors responsible for the development of hypertension in patients with PKM and position-dependent changes of the main renal venous flow.

Thermal Analysis—Theory and Applications in Metalcasting

Monitoring and adjusting the chemical composition and the nucleation potential of casting alloys melts is critical to the production of castings of consistent high quality. While other methods such as fractured test samples (e.g., the wedge test for gray iron) and spectrographic chemical analysis deliver useful information, thermal analysis (TA) (also called cooling curve analysis, CCA) can provide a more complete insight in the dynamic changes occurring upon melting and during melt treatment of casting alloys. Initially TA was used for the rapid evaluation of the carbon equivalent (CE) in cast iron, or the silicon content in Al-Si alloys. Extensive research then extended the capabilities of TA to the understanding of the solidification changes induced by compositional variations such as the Mn/S ratio, Ce and Mg additions. With the advent of ever faster computers, the first derivative of the cooling curve, which is the cooling rate, was added to the arsenal of data provided by TA, and a new technique, Computer Aided Cooling Curve Analysis (CA-CCA), was born. This technique evolved then into Differential Thermal Analysis (DTA) without a reference sample. With this tool in hand the metallurgist ventured to predict not only the chemistry of the melt but also the nucleation potential (degree of inoculation), the shrinkage propensity, the dendrite arm spacing and the grain size, the graphite shape, the solidification microstructure, and even the room temperature microstructure. Currently, different TA techniques are used worldwide in the daily production of all grades of cast iron, as well as in monitoring the melting of aluminum and steel alloys. From this short introduction it should be obvious that the story of DTA/CCA is a long and exciting one. This paper will try to summarize the fascinating development and extraordinary success of this technique in the casting industry.

Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al) in comparison to an anodizing process (NaTESi process). The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO) as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

Relation of various GFA indicators to the critical diameter of Zr-based BMGs

In the face of a large number of glass forming ability (GFA) thermal indicators that can be found in the literature, the authors have made an attempt to order a variety of them by their correlation with the critical diameters (Dc) of four various Zr-based alloys. Dcs were determined by the wedge test and varied from 4.5 to 10.4mm. Characteristic temperatures, determined by the DTA, were used to calculate some GFA thermal indicators: ΔTxg, Trg, Kgl, α, β1, β2, γ, γm, δ and ξ. The data were used to built plots: GFA indicator versus Dc. Using the logarithmic fitting, the R2 correlation coefficient was determined for each indicator. Ordering the GFA indicators by the R2 ascending values allowed both qualitative as well as quantitative comparisons. It was revealed that the ΔTxg indicator exhibited weak correlation (R2=0.019) with the Dc in contrast to β1, γ, γm and ξ. It was also proven that the solidus temperature should not be used in a formula of a GFA indicator in order to achieve high correlation with the Dc.The authors also made an attempt to modify the formula of the γm indicator in order to improve the R2 value. It was possible to raise it to the level of 0.882 – a new GFA indicator ω was proposed.