Air Blast Test Research Articles

Comparative evaluation of neodymium-doped yttrium aluminum garnet laser with nanocrystalline hydroxyapatite dentifrices and herbal dentifrices in the treatment of dentinal hypersensitivity.

Background:The aim of this study was to compare and evaluate the efficacy of neodymium-doped yttrium aluminum garnet laser with and without herbal and nanohydroxyapatite dentifrices in management of dentinal hypersensitivity (DH).Materials and Methods:A total of 180 patients who responded to air-blast test and cold-water test using verbal rating scale (VRS) were included in this study. The patients were randomly assigned to six groups (n = 30): control group (CG), scaling and root planning (SRP) + nanocrystalline hydroxyapatite dentifrices, SRP + nanocrystalline hydroxyapatite dentifrices + laser, SRP + herbal dentifrices, SRP + herbal dentifrices + laser, and SRP + laser. Each group was evaluated at baseline, 1 week, 1 month, and 6 months. In every visit of each patient, their clinical examination was done.Results:Among all groups’, repeated ANOVA measures and Kruskal–Wallis test was performed in which laser groups showed maximum reduction in DH in all indices while the CG showed minimum reduction in DH. The VRS values showed maximum reduction in SRP + nanocrystalline hydroxyapatite dentifrices + laser group with mean of 0.3 ± 0.5 and minimum reduction in CG with mean of 3.0 ± 0.5 (P < 0.001).Conclusion:Among all the groups, SRP + Nanocrystalline hydroxyapatite + Laser can be an effective treatment modality for DH.

The effects of foam filling on the dynamic response of metallic corrugated core sandwich panel under air blast loading – Experimental investigations

This research aims to elucidate the effects of foam filling on the dynamic response of metallic corrugated core sandwich panels by conducting air blast testing. The panels were designed to investigate the influences of specific parameters, like the foam filler density, the core configuration and the filling material, on the blast performance from the aspects of permanent deformation, failure modes and associated mechanisms. Experimental results demonstrate that foam filling is an effective way to improve blast resistance of sandwich panels. The benefits from foam filler for the reduction of the levels of the failure damage and plastic deformation of panels would be improved with the increase of foam density. Comparisons of panels with different core configurations verify that the foam-filled sandwich panel performed the best under low intensity blast loading. The superiority of foam-filled sandwich panel over the foam core sandwich panel would be swallowed up with the increase of blast loading intensity. The panels filled with PVC foams displayed a superior blast resistance over the ones filled with aluminum foams of almost same density. Moreover, the difference in blast resistance would increase with the decrease of blast intensity.

Effectiveness of desensitizing dentifrice and mouthwash on dentin hypersensitivity and tooth remineralization

Background:Over many years, numerous products have been suggested for the relief of dentin hypersensitivity (DH). Calcium sodium phosphosilicate is one desensitizing agent that has remineralizing potential. Available in toothpaste and mouthwash delivery vehicle, this study was carried out to compare the effectiveness on dentinal hypersensitivity (using the Airblast test and Cold test) and on tooth remineralization (using DIAGNOdent pen) in a 4-week period.Materials and Methods:Out of the 45 patients screened, 28 patients who fulfilled the inclusion criteria and who willingly signed the consent form were selected and were randomly allocated into two groups – toothpaste and mouthwash. The tooth numbers and specific site of dentinal hypersensitivity for every patient were noted and the air blast test, cold test, and DIAGNOdent scores were recorded at baseline visit. The patients were instructed about the use of the product and were asked to come on the 30th day for re-evaluation.Results:Within-group comparison showed a significant reduction (P < 0.05) in the air blast score (toothpaste – 68.53% and mouth rinse – 48.52%), cold test score (toothpaste – 56.38% and mouth rinse – 38.87%), and DIAGNOdent score (toothpaste – 20.35% and mouth rinse – 9.49%). In-between group comparison showed no statistically significant difference (P > 0.05).Conclusion:Desensitizing mouthwash is as effective as toothpaste in reducing DH with a fair remineralization potential comparable with that of the toothpaste.

Behavior of Steel Rectangular Hollow Sections Subject to Blast Loading

AbstractLarge-scale far-field air-blast testing of cold-formed steel rectangular hollow sections (RHS) in flexure has been performed for the first time. These arena trials illustrated the excellent...

Evaluation of dentin hypersensitivity treatment with glass ionomer cements: A randomized clinical trial.

A randomized, double-blind, split-mouth clinical trial was performed compared the desensitizing efficacy of the resin-modified glass ionomer cement (GIC) ClinproTM XT (3M ESPE, Minnesota, USA) and the conventional GIC Vidrion R (SS White, Gloucester, UK) in a 6-month follow-up. Subjects were required to have at least two teeth with dentin hypersensitivity. Teeth were divided at random into 2 groups, one group received Clinpro XT and the other conventional GIC Vidrion R. Treatments were assessed by tactile and air blast tests using Visual Analogue Scale (VAS) at baseline, after 20 minutes, and at 7, 15, 21, 30, 90 and 180 days post-treatment. Twenty subjects (152 teeth) were included. Both tests (tactile and air blast) showed a significant reduction of dentin hypersensitivity immediately after the application of Vidrion R and Clinpro XT (20 min). VAS scores obtained along the 6-month follow-up were statistically lower when compared to initial rates (p < 0.05). Both GIC were able to reduce dentin hypersensitivity up to 6-month post-treatment period without statistically significant differences among them (p > 0.05). Both cements provided satisfactory results in long-term dental sensitivity reduction.

Comparative clinical evaluation of gallium-aluminum-arsenide diode laser and potassium nitrate in treating dentinal hypersensitivity.

Context:Dentinal hypersensitivity (DH) is a chronic disorder in which patients report sharp and acute pain to a variety of stimuli. Till date, a standardized procedure to treat DH is missing, though several alternative treatment strategies have been designed, including laser therapies.Aim:The aim of the study was to treat DH with minimum chemical concentration and least laser energy level with longer follow-up period.Materials and Methods:One hundred and twenty patients were randomly divided into four groups: (i) Group 1-5% potassium nitrate (KNO3); (ii) Group 2 - gallium-aluminum-arsenide diode laser (62.2 J/cm2, wavelength - 980 nm, noncontact pulse mode, and power wattage - 0.5 W); (iii) Group 3 - combined 5% KNO3 and the diode laser; and (iv) Group 4 - placebo (control). The visual analog scale (VAS) scores were recorded, analyzed, and compared to tactile stimuli, cold water, and air blast tests at different intervals for 6 weeks.Results:Synergistic use of 5% KNO3 and diode laser (Group 3) significantly reduced the DH pain, which was almost negligible after 6th week (97%–99% of the pain was reported to be relieved) and showed promising results than any other studied groups. Further, the diode laser (Group 2) showed better results than 5% KNO3 (Group 1). One-way ANOVA and Bonferroni correction post hoc test revealed the combination of groups with significant differences in the mean VAS scores at the different interval of time (P < 0.01).Conclusions:Convincingly, the combined application of 5% KNO3 with the diode laser can be recommended for treating DH patients.

Experimental Investigation on Shock Wave Characteristics of Aluminized Explosives in Air Blast

To investigate the shock wave characteristics of RDX-based aluminized explosives, air blast tests were conducted for measuring the parameters of 10.kg aluminized explosives which contained 0-40% aluminum. The results showed that with the increasing of aluminum content, the overpressures and impulses increase at first and then decrease within 7 m or 5 m, which reached the maximum when aluminum content was 20% or 30%. Power exponential formulas are used to fit the shock wave parameters vs scaled distance, where an equal weight of TNT is used to calculate the scaled distance. The overpressures of HL0 and TNT in tested locations not only conform to the similar law, but also conform to the same attenuation law after gaining the scaled distances of equal TNT mass. The pre-exponential factors of overpressure and impulse, kp and kI, decrease along with the increasing of Al content and keep the same pace as the calculated PCJ. The attenuation coefficients aP and aI increase at first and decrease later with the increasing of aluminum content, and they reached the maximal values with 30% Al containing, which keeps the same pace as the calculated QV.

Blast Performance of Composite Sandwich Structures

A range of composite sandwich panels with different polymeric foam cores and face-sheets were subjected to full-scale air and underwater blast testing. The air blast panels had glass fiber reinforced polymer (GFRP) face-sheets with three different polymeric foam cores: styrene acrylonitrile (SAN), polyvinylchloride (PVC) and polymethacrylimide (PMI). The panels were subjected to 100kg TNT equivalent charge from a stand-off of 15 m. The SAN panel had the lowest deflection and suffered from the least damage. The underwater blast panels had either a single density or graded density SAN foam core and either glass fiber reinforced polymer or carbon fiber reinforced polymer (CFRP) face-sheets. The research revealed that there is a trade-off between reduced panel deflection and damage. All the blast research that has been performed is part of a program sponsored by the Office of Naval Research (ONR).

Comparative Evaluation of Effect of Nano-hydroxyapatite and 8% Arginine Containing Toothpastes in Managing Dentin Hypersensitivity: Double Blind Randomized Clinical Trial.

This double blind randomized clinical trial was conducted with the purpose of evaluating the effects of Nano-hydroxyapatite toothpaste as compared to 8% Arginine containing toothpaste in the management of Dentin hypersensitivity (DH). Patients (30 in each group) suffering from DH and eliciting a VAS score higher than 2 in air blast and tactile test were randomly allocated (block randomization) into either a group 1 (arginine toothpaste) or group 2 (nHA toothpaste). The primary outcome evaluated was the reduction of DH as measured by the electrical stimulus reading on the digital pulp tester. Current required for eliciting a VAS score of 2 was recorded before application of dentifrice. 1 cm of toothpaste was then expressed on the tooth surface for two minutes in each group and rinsed off. The electrical stimulus required to elicit a VAS score of 2 was recorded after 5 minutes, 1 week and 4 weeks. The desensitizing paste containing arginine provided a statistically significant reduction in DH and so did the paste containing nHA. Mean increase in amperage value (reduction in DH) was higher for nHA based than the arginine containing dentifrice. This difference was not statistically significant showing that both toothpastes are equally effective. The findings of the present study encourage the use of Nano-hydroxyapatite and arginine containing dentifrice as an effective desensitizing agent providing relief from symptoms 5 minutes after application and after 1 and 4 weeks.

Effect of fibre-matrix interfacial strength on the explosive blast resistance of carbon fibre laminates

The influence of the fibre-polymer matrix interfacial bond strength on the explosive blast response of carbon fibre laminates is experimentally investigated. Air blast tests were performed on laminate target panels containing woven carbon fabric treated with a fibre-sizing agent that promoted either weak or strong bonding with the polymer matrix. The laminates were subjected to increasing shock wave impulse loads by increasing the mass or reducing the stand-off distance of the plastic explosive charge. High-speed digital image correlation photography (DIC) during explosive blast testing revealed the dynamic deformation responses and surface strains of the laminate targets were not influenced significantly by the type of fibre-sizing agent, except at high shock wave impulse levels. However, non-destructive testing using ultrasonics and X-ray computed tomography revealed that the initiation and growth of blast-induced damage (e.g. delamination cracks, matrix cracks, fibre fracture) was dependent to the interfacial bond strength. Damage occurred at a high shock impulse level in the laminate with strong fibre-matrix interfacial bonding, and this is attributed to higher flexural and interlaminar fracture toughness properties compared to the composite with weak interfacial bonding. The post-blast mechanical properties were also higher for the laminate with strong interfacial bonding. This study reveals that the fibre-sizing agent has a substantial influence on the explosive blast resistance and post-blast properties of laminates, and it is essential that an agent having high chemical compatibility with the polymer matrix is used to promote strong bonding.

Desensitizing effect of stannous fluoride-containing toothpaste for patients with dentine hypersensitivity: a Meta-analysis

This study aims to assess the effects of desensitizing toothpaste containing stannous fluoride on dentine hypersensitivity by performing Meta-analysis of randomized controlled trials (RCT) involving the treatment of dentine hypersensitivity with stannous fluoride-containing toothpaste. The study was developed based on the Cochrane handbook for systematic reviews of interventions (Version 5.1.0) and included the following: search strategy, selection criteria, data extraction, and risk of bias assessment. We searched electronic databases such as CNKI, CBM, PubMed, Embase, and Cochrane Library up to January 2015. RCT of treating dentine hypersensitivity with stannous fluoride-containing toothpaste were included. Data extraction and domain-based risk of bias assessment were independently performed by two reviewers. Meta-analysis was performed with RevMan 5.3 software. Six RCT with 494 patients (247 in the experimental group and 247 in the control group) were included. The results of Meta-analysis showed that the desensitizing effect of stannous fluoride-containing toothpaste was significantly better than that of control in tactile sensitivity test (SMD=1.41, 95% confidence interval 0.74-2.09, P<0.00001) and air blast test (SMD = -1.16, 95% confidence interval -1.84--0.48, P<0.000 01). Current evidence shows that stannous fluoride-containing toothpaste is effective in treating dentine hypersensitivity in clinic. However, due to limited sample size and lower quality of the included studies, more high quality and large-sample RCT are needed to further verify the evidence.

Arginine-containing desensitizing toothpaste for the treatment of dentin hypersensitivity: a meta-analysis.

ObjectiveTo estimate the effect of arginine-containing desensitizing toothpaste on dentin hypersensitivity (DH).MethodsDatabases including China National Knowledge Infrastructure, VIP Database for Chinese Technical Periodicals, China Biology Medicine disc, Wangfang Data, PubMed, Web of Science, and Cochrane Trials Register were searched, and Google was used as a supplementary tool to search for information through February 2014. Randomized controlled trials (RCTs) of the treatment of DH with arginine-containing toothpaste were included. Relevant information was extracted, and a quality evaluation was performed. Meta-analyses were performed using RevMan 5.2 software.ResultsEighteen RCTs with 1,423 patients were included. The results of the meta-analyses demonstrated that at days 0 and 3; weeks 2, 4, and 8; and more than 12 weeks, arginine-containing toothpaste led to significantly improved results on the tactile sensitivity test (standardized mean difference [SMD] =1.95, 95% confidence interval [CI] [1.14, 2.76]) and the air-blast test (SMD =−1.60, 95% CI [−2.14, −1.05]) at 4 weeks and the tactile sensitivity test (SMD =2.01, 95% CI [1.41, 2.61]) and the air-blast test (SMD =−1.41, 95% CI [−1.83, −0.98]) at 8 weeks compared to toothpastes containing other desensitizing components, thus indicating a superior therapeutic effect of arginine-containing desensitizing toothpaste. However, no significant differences between arginine-containing toothpaste and toothpastes containing other desensitizing components were observed in the air-blast test at days 0 and 3 and week 2 and in the tactile sensitivity and air-blast tests at more than 12 weeks.ConclusionThe current evidence indicates that arginine-containing toothpaste is effective for DH. However, further high-quality, large-sample RCTs are needed.

Comparative Evaluation of Efficacy of Two New Commercially Available Desensitizing Agents: An in vivo Study

ABSTRACT Objective To compare the clinical efficacy of two commercially available desensitizing agents, Fluorprotector vivampuole and GLUMA comfort bond plus desensitizer in the treatment of dentinal hypersensitivity. Materials and methods A total of 203 teeth were selected for study. Patients who presented with a history of sensitivity to hot/cold, sweet, and sour food were examined using light tactile response along the cervical margin of the teeth. The assessment methods used to quantify sensitivity were tactile test, air blast test, and cold water test. The subjects were randomly divided into two groups. Group 1: GLUMA comfort bond plus desensitizer; group 2: Fluorprotector vivampuole (newly introduced by Ivoclar). The patients were evaluated for sensitivity at five appointments: at baseline, immediately after application of the agent, 1 day after application, after 1 week, and after 1 month. Results Patients belonging to group 2 showed significantly better results compared with patients of group 1 at 4 weeks. Conclusion Both the desensitizing agents showed significant reduction in sensitivity at all time intervals compared with baseline. However, Fluorprotector vivampuole appeared to be more effective in providing long-term relief against all the three test stimuli. Clinical Significance Fluorprotector vivampuole is a newly introduced fluoride varnish which is clear and colorless. It can be used in cases of dentinal hypersensitivity without affecting the aesthetics of the patient, particularly in case of anterior teeth. How to cite this article Maroli S. Comparative Evaluation of Efficacy of Two New Commercially Available Desensitizing Agents: An in vivo Study. Int J Experiment Dent Sci 2016;5(1):40-44.

Comparative efficacy of application of three different desensitizing agents with iontophoresis in the treatment of hypersensitive teeth

Background: The purpose of this study was to compare the efficacy of sodium fluoride, strontium chloride, methyl prednisolone, and distilled water (control) with iontophoresis in treating hypersensitivity. Materials and Methods: The study recruited 64 subjects fulfilling inclusion and exclusion criteria who were evaluated for hypersensitivity using tactile, air blast, and cold water tests. The subjects were randomly divided into four groups - group A: 2% sodium fluoride, group B: 10% strontium chloride, group C: 0.125% methyl prednisolone, and group D: distilled water (control). The subjects were evaluated for 6 weeks and their responses were recorded on the verbal rating scale. All the reagents were administered through iontophoresis. In the in vitro study, a total of 32 dentin specimens were obtained, which were randomly divided into four groups. The above mentioned reagents were applied onto the dentin specimens through iontophoresis, the unit of which was available in the department, and were evaluated under a scanning electron microscope (SEM). Results: After the statistical analysis, it was found that comparison between group A and group B was nonsignificant, whereas comparison between groups A and C, groups A and D, groups B and C, groups B and D, and groups C and D were significant. In SEM analysis, maximum numbers of occluded tubules were seen with sodium fluoride. Conclusions: Clinically, a single application of iontophoresis with 2% sodium fluoride, 10% strontium chloride, and 0.125% methyl prednisolone proved to be a better therapeutic agent in comparison with distilled water. The SEM results also related with clinical finding in that reduction in the patency of tubules was associated with improvement in treatment efficacy.

Investigation on Behavior of Glazing System with Elastomeric Interlayers under Blast Effects

The purpose of this study is to develop mitigation systems suitable for use in preventing casualties and injury due to glass window and glass façade failure in public facilities, such as mass transportation terminals, government, sport arenas or hotel buildings, etc. A series of air-blast tests are conducted to validate the blast resistance of laminated glazing system of new elastomeric urethane interlayers. The tests are conducted in a shock tube capable of achieving reflective impulses up to 250 psi-msec which does not have negative phase contribution to the mitigation system performance. Two aspects of mitigation systems are examined, blast resistant glazing utilizing a new elastomeric urethane interlayer and attachment methods. The attachment systems vary in order to determine the influence of deflection and ductility that yields the best results of reducing the loading to the structural elements.

Explosive driven shock tube loading of aluminium plates: experimental study

To accurately identify the material characteristics in material testing, the control of the initial and boundary conditions is very important. Among these conditions, obtaining a repeatable and known loading is a sensitive point especially for tests in the dynamic and impulsional range. Several techniques are used to generate blast wave loads. This paper focuses on the use of an explosive driven shock tube (EDST). The results of a series of tests using an EDST are discussed, with regard to the pressure, the impulse, the wave planarity and the repeatability of the loading. The EDST and free air blast are used to generate blast loading on fully clamped square aluminium plates. The response from both loads is measured with a high-speed 3D digital image correlation (DIC) system and compared to each other. The DIC measurements are compared to strain gauge measurement for validation purposes. It is found that EDST allows to reach higher levels of pressure and impulse than the free air blast leading to higher deformations and strain rates. It is also observed that the EDST tests show a higher repeatability and symmetry relative to the free air blast tests.

Sandwich Panel Cores for Blast Applications: Materials and Graded Density

Sandwich composites are of interest in marine applications due to their high strength-to-weight ratio and tailorable mechanical properties, but their resistance to air blast loading is not well understood. Full-scale 100 kg TNT equivalent air blast testing at a 15 m stand-off distance was performed on glass-fibre reinforced polymer (GFRP) sandwich panels with polyvinyl chloride (PVC); polymethacrylimid (PMI); and styrene acrylonitrile (SAN) foam cores, all possessing the same thickness and density. Further testing was performed to assess the blast resistance of a sandwich panel containing a stepwise graded density SAN foam core, increasing in density away from the blast facing side. Finally a sandwich panel containing compliant polypropylene (PP) fibres within the GFRP front face-sheet, was subjected to blast loading with the intention of preventing front face-sheet cracking during blast. Measurements of the sandwich panel responses were made using high-speed digital image correlation (DIC), and post-blast damage was assessed by sectioning the sandwich panels and mapping the damage observed. It was concluded that all cores are effective in improving blast tolerance and that the SAN core was the most blast tolerant out of the three foam polymer types, with the DIC results showing a lower deflection measured during blast, and post-blast visual inspections showing less damage suffered. By grading the density of the core it was found that through thickness crack propagation was mitigated, as well as damage in the higher density foam layers, thus resulting in a smoother back face-sheet deflection profile. By incorporating compliant PP fibres into the front face-sheet, cracking was prevented in the GFRP, despite damage being present in the core and the interfaces between the core and face-sheets.

Long duration blast loading of cylindrical shell structures with variable fill level

This paper investigates the effect of long-duration blast loads on the structural response of aluminium cylindrical shell structures containing varying fluid levels. A detailed non-linear numerical model comprising remapped Lagrangian analysis examines localised plate buckling and deformation. The relative computational accuracy of an uncoupled numerical model developed in this paper is compared with experimental results obtained at one of the worlds׳ most powerful air blast testing facilities. Evaluating structural response for blast loads with an extended dynamic pressure phase is exceptionally difficult using only Eulerian controlled CFD methods; due to domain constraints incorporating restrictive cell sizes engulfing the target structure before remapping. The further complexity of shock transmission through a structure damped by an internal fluid is examined experimentally. Fibre optic controlled instrumentation and high speed photography provide a vital insight towards coupled flow-field behaviour of the shell structure. Surface mounted pressure gauges on the cylindrical wall accurately record the pressure time history throughout the passage of the shock wave. This paper highlights the key influence on blast response due to varying internal fluid levels and the relative importance pertaining to a conservative design solution for varying operational states. Numerical modelling in this paper demonstrates the robust accuracy achievable for a remapped Lagrangian solution. The routine analytical assumption of uniform drag forces acting on the structural body was shown to be both misleading and inaccurate by comparison. This research will be of direct interest to both practitioners and researchers considering high power explosive blasts from sources such as hydrocarbon vapour cloud ignition.

The Comparison of Various Foam Polymer Types in Composite Sandwich Panels Subjected to Full Scale Air Blast Loading

Abstract Full scale air blast testing has been performed on a range of polymeric foam composite panels. These panels employed glass fibre reinforced polymer (GFRP) face-sheets with different polymer foam cores, namely: Styrene acrylonitrile (SAN); Polyvinylchloride (PVC) and Polymethacrylimide (PMI). The three sandwich panels were all subjected to 100 kg TNT equivalent blast loading at a stand-off distance of 15 m, and the responses of the panels were measured using Digital Image Correlation (DIC). The extent of damage in the sandwich panels was then inspected via post-blast sectioning, and it was found that the SAN core suffered the least damage, and the PMI suffered the most. The DIC showed that the deflection of the SAN core sandwich panel was much less than the other two foam polymer cores, due to less damage meaning a greater stiffness was retained. All blast research to date is part of a programme sponsored by the Office of Naval Research (ONR).

Non-linear long duration blast loading of cylindrical shell structures

This paper investigates the influence of long-duration blast loads on the structural response of aluminium cylindrical shell structures. Full scale coupled non-linear dynamics are examined experimentally at one of the worlds’ most powerful air blast testing facilities. Evaluating structural response to blast loads of this magnitude is exceptionally difficult using only computational fluid dynamics; typically not achievable without incurring unmanageable solution domains. Clearing, diffraction and exhaust of a long-duration blast wave across any comparatively small structure imposes constraints leading to the use of approximated drag coefficients, designed primarily to expedite the calculation of net translational forces. In this research, detailed pressure histories measured experimentally on the surface of the cylindrical shell are used to accurately configure a computational analysis dispensing with the requirement to utilise approximated drag forces. When further combined with accurate material test data, fibre optic controlled strain gauge instrumentation and high-speed video photography, a full comparative model was possible. This paper shows that without exact knowledge of long-duration flow-field effects a priori, it is very difficult to reliably determine the mode of structural response and degree of blast resistance. Preliminary modelling predicted a global sway and localised plate buckling; however, subsequent experimental testing showed a crushing failure of the shell before any translational movement occurred. Results in this paper will be of direct interest to both practitioners and researchers considering the dynamic response of cylindrical shell structures subject to high power explosive blasts from sources such as hydrocarbon vapour cloud ignition.