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The effects of laser beam welding (LBW) process parameters on the characteristics of Nd:YAG laser butt welding 1.5 mm thick 2205 duplex stainless steel. Specifically, the study focuses on the depth of penetration, bead width, ultimate tensile strength (UTS) and elongation. To achieve this, a parametric study is conducted using a central composite design (CCD) with response surface methodology (RSM) to establish mathematical regression equations that identify the key process parameters and their effects on the responses. The investigations showed that the size of the meltpool at the fusion zone (FZ) increases as the laser power increases. This leads to the formation of wider and deeper weld beads, ultimately leading to stronger and more flexible joints. Similarly, pulse width and scanning speed have a significant impact on the weld bead geometry, UTS, and elongation. It is observed that the FZ is free of any visible cracks, voids, or porosity. The LBW process parameters have been optimized to reduce operating costs by lowering the line energy, without compromising the welding quality. The optimal UTS value for the welded joint is around 865 MPa, which is almost equivalent to 99% of the UTS of the 2205 duplex stainless steel base material (BM). To obtain high-quality welded joints, it is recommended to use a laser power ranging from 423 to 425 W, scanning speed of 5.3 mm/s and pulse width of 5.4 ms. [ABSTRACT FROM AUTHOR]

Aim: The aim of the study was to evaluate and compare the depth of penetration of adhesive resin in resin-modified glass ionomer cement (RMGIC) after different surface pretreatment methods using a confocal laser scanning microscope (CLSM). Methods: Class I cavity preparation was done in 45 freshly extracted premolars and divided into three groups, according to the surface pretreatment of RMGIC which was placed in a thickness of 1 mm in the cavity. In the control group, no pretreatment was done, and other two groups were pretreated with acid etching and air abrasion (AA). The fifth-generation dentin bonding agent mixed with rhodamine B dye 0.1% was applied on RMGIC in all the samples and cured for 15 s. Samples were restored using composite resin and sectioned longitudinally. The depth of penetration of adhesive resin was evaluated using CLSM. Results: Depth of penetration of adhesive resin was highest with AA (153.70 ± 10.23), followed by acid etching (122.71 ± 12.25) and control group (77.12 ± 6.37). Conclusion: Based on the findings of this research, AA enhances the depth of penetration of adhesive resin in the RMGIC surface. Thus, AA before placement of composite resin on the RMGIC can be effective in a clinical scenario. [ABSTRACT FROM AUTHOR]

Based on numerical simulation within the framework of a two-dimensional axisymmetric problem of continuum mechanics, an analysis has been made of penetration into a semi-infinite barrier by dummy strikers with diameters of 14 and 18 mm and an initial velocity of 1200 m/s with and without account for the effects of the detachable sabot used for accelerating the dummies in the barrel of a ballistic installation. In simulating the penetration by dummy strikers in a sabot, a reduction was registered in the depth of penetration by a little over 10% with increase in the maximum overload compared to the case of penetration in the absence of a sabot. A cause has been identified for the sabot′s negative effects on dummy strikers′ penetration, lying in an increase of tangential stresses acting on the surface of the dummies′ contact with the adjacent layer of loosened concrete due to precompression of this layer by the sabot until the sabot′s complete detachment from the dummy striker. [ABSTRACT FROM AUTHOR]

This study was conducted on a linear shaped charge with a double-angle liner. The double-angle liner has a large inner apex angle and a small outer liner angle. Experiments and numerical analysis were performed in a penetration performance study, and it was confirmed that the experimental results and numerical analysis results matched well. As a result of the numerical analysis, at the standoff distance of 1.5 CD, the penetration performance of the double-angle linear shaped charge was improved by 14.5% compared to the conventional linear shaped charge, and at the standoff distance of 2.5 CD, the penetration performance was improved by 12.5%. For miniaturization, numerical analysis was performed by reducing the height of the explosive and the standoff distance. As a result of the numerical analysis, the penetration performance of the double-angle linear shaped charge was improved by 14.6% compared to the conventional linear shaped charge. Double-angle liners are effective in improving the penetration performance of linear shaped charges. [ABSTRACT FROM AUTHOR]

Using GTAW, or tungsten inert gas (TIG) welding, weld penetration is usually lesser than the other arc welding processes. ATIG (Activated-flux TIG) welding can be a good alternative to provide deep penetration, and hence, improved productivity. In this work, 304L SS plate of 8 mm thickness was used as base plate, and a flux with a mixture of SiO2, MnO2 and MoO3 was used as a ternary flux in the ratio of 1:1:2. A 2-factor 3-level response surface methodology of central composite design was considered for designing experimental runs. Back Propagation (BP) type Artificial Neural Networks (ANN) model was developed to assess penetration in ATIG welding by using heat input and pulse frequency as the two process parameters. The ANN chosen has 2-10-1 network structure. Results show that the predicted values through ANN are conforming quite well to the experimentally obtained penetration, and hence, the applicability of ANN. [ABSTRACT FROM AUTHOR]

In this study, high velocity impact behaviour of friction stir welded AA7075-T651 25 mm thick plates were investigated using a 7.62 mm × 51 mm lead core and 7.62 mm × 39 mm steel core projectiles. Prior to ballistic trails, mechanical and metallurgical properties of friction stir welded AA 7075-T651 25 mm thick plates were studied. Microstructural and hardness studies revealed that friction stir welds constituted three distinct regions namely Weld Nugget (WN), Thermo-Mechanically Affected Zone (TMAZ) and Heat Affected Zone (HAZ). Base Material (BM) and all three weld regions were ballistically tested as per military standard NIJ.0108.01 using lead and steel core bullets at maximum permissible velocities of 830 ± 20 and 700 ± 30 m/s, respectively. It has been found that base material (AA7075-T651) and all three weld regions of 25 mm thick plates were able to resist perforation by both types of projectiles used. However depth of penetration has been found to increase from BM to WN, HAZ and TMAZ for both types of projectiles. In all cases steel core projectiles caused higher depth of penetration compared to those caused by lead core projectiles. TMAZs of the friction stir welds were found to be the weakest zone. The fracture that occurred in the base material was spall fragmentation indicating brittle failure, whereas all zones of friction stir welded AA7075-T651 targets with a front petalling, indicating ductile failure. The post-ballistic tested samples showed no significant change in the microstructure of the BM and WN. On the other hand, TMAZ and HAZ showed severe grain deformation in the direction of projectile penetration, and the formation of adiabatic shear bands (ASB). This work showed that 25 mm thick friction stir welded AA7075-T651 joints responded well to ballistic impact loads, making them a good choice for light combat vehicles.

In this study, high velocity impact behaviour of friction stir welded AA7075-T651 25 mm thick plates were investigated using a 7.62 mm ( 51 mm lead core and 7.62 mm ( 39 mm steel core projectiles. Prior to ballistic trails, mechanical and metallurgical properties of friction stir welded AA 7075-T651 25 mm thick plates were studied. Microstructural and hardness studies revealed that friction stir welds constituted three distinct regions namely Weld Nugget (WN), Thermo-Mechanically Affected Zone (TMAZ) and Heat Affected Zone (HAZ). Base Material (BM) and all three weld regions were ballistically tested as per military standard NIJ.0108.01 using lead and steel core bullets at maximum permissible velocities of 830 ± 20 and 700 ± 30 m/s, respectively. It has been found that base material (AA7075-T651) and all three weld regions of 25 mm thick plates were able to resist perforation by both types of projectiles used. However depth of penetration has been found to increase from BM to WN, HAZ and TMAZ for both types of projectiles. In all cases steel core projectiles caused higher depth of penetration compared to those caused by lead core projectiles. TMAZs of the friction stir welds were found to be the weakest zone. The fracture that occurred in the base material was spall fragmentation indicating brittle failure, whereas all zones of friction stir welded AA7075-T651 targets with a front petalling, indicating ductile failure. The post-ballistic tested samples showed no significant change in the microstructure of the BM and WN. On the other hand, TMAZ and HAZ showed severe grain deformation in the direction of projectile penetration, and the formation of adiabatic shear bands (ASB). This work showed that 25 mm thick friction stir welded AA7075-T651 joints responded well to ballistic impact loads, making them a good choice for light combat vehicles. [ABSTRACT FROM AUTHOR]

This study was conducted on a linear shaped charge with a double-angle liner. The double-angle liner has a large inner apex angle and a small outer liner angle. Experiments and numerical analysis were performed in a penetration performance study, and it was confirmed that the experimental results and numerical analysis results matched well. As a result of the numerical analysis, at the standoff distance of 1.5 CD, the penetration performance of the double-angle linear shaped charge was improved by 14.5% compared to the conventional linear shaped charge, and at the standoff distance of 2.5 CD, the penetration performance was improved by 12.5%. For miniaturization, numerical analysis was performed by reducing the height of the explosive and the standoff distance. As a result of the numerical analysis, the penetration performance of the double-angle linear shaped charge was improved by 14.6% compared to the conventional linear shaped charge. Double-angle liners are effective in improving the penetration performance of linear shaped charges.

In this work, a comparative study on the ballistic behaviour of friction stir processed AL6061 targets had been made. Base Metal AL6061 (BM) plates with 25 mm thickness were friction stir processed by adding Multi Walled Carbon Nano Tubes (MWCNT) and Graphene (G), producing AL6061-MWCNT and AL6061-G surface composites. Optical microscopy and microhardness test on BM, AL6061-MWCNT and AL6061-G samples were performed as per the standard procedure. It was noticed that uniform dispersion of ceramic particles and refined grains were obtained for the friction stir processed surface composites. From the microhardness test, it was perceived that friction stir processing had induced strengthening of surface composites, hence increasing the microhardness of AL6061-MWCNT and AL6061-G by ~60.3% and ~73.6% respectively. Also, ballistic experiments were conducted at 680±10 m/s by impacting Ø7.62×51 mm projectiles. AL6063 backing plates were placed to compare the ballistic behaviours AL6061-MWCNT and AL6061-G targets by depth of penetration. It was noted that the depth of penetration of AL6061-MWCNT and AL6061-G targets were 37.81% and 65.84% lesser than the BM target. Further, from the results of Post ballistic microscopy it was observed that the microstructure near and away from the penetration channel edge looks unchanged in BM target. However, the AL6061-MWCNT and AL6061-G targets showed considerable change in their morphology, by forming Adiabatic Shear Bands.

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Successful endodontic treatment requires advanced materials to eliminate biofilm This study aims to assess the penetration depth and the effectiveness of Boswellia sacra as a novel intracanal medicament compared with calcium hydroxide against Enterococcus faecalis biofilm. 60 single‐rooted teeth were decoronated, prepared and sterilised. Fifty teeth were contaminated with a culture of E. faecalis (ATCC 19433) for 21 days. Two teeth were used to confirm the biofilm using scanning electron microscope. For colony‐forming unit (CFU), 40 samples were divided into one control group (calcium hydroxide) and the other experimental group (B. sacra). Each group was divided into two subgroups to be tested at 3 and 7 days. The minimum inhibitory concentration (MIC) of B. sacra was determined, and the B. sacra's ethanolic extract medicament was prepared. Eight discs divided into groups similar to CFU were used to evaluate live/dead bacteria using confocal laser scanning microscopy (CLSM). Ten teeth were selected for penetration depth using CLSM. The intracanal medicaments were mixed with 0.1% rhodamine B. were inserted into the root canals 0.2 slices were dissected and viewed under CLSM. The MIC of B. sacra was 1.25 mg/ml. The CFU evaluation proved that B. sacra are more effective than calcium hydroxide in the 3 days groups. However, it was statistically insignificant compared with calcium hydroxide after 7 days. The depth of penetration of B. sacra exceeds that of calcium hydroxide. B. sacra is an effective intracanal medicament. [ABSTRACT FROM AUTHOR]

Today, more and more importance is given to the improvement of polymer materials' wear resistance, i.e., their micro-mechanical and tribological properties, which could widen their application in practice. The properties of materials can be modified by several methods, among them exposure to electron radiation. This study focuses on the effect of varying radiation intensity (15 kGy to 99 kGy), depth of penetration, and subsequent structure modification of injection-molded polypropylene on tribological and micro-mechanical properties. Electron radiation influences the structure of individual layers, thus improving or degrading their properties. Hence, the depth of penetration can be examined by instrumented hardness tests and scratch tests. Due to irradiation, surface properties and wear resistance increased by up to 105% (from 38 MPa to 78 MPa). As the results show, an increase in mechanical properties was recorded in the direction towards the center of the sample (from 72 MPa to 82 MPa). Micro-mechanical tests were also confirmed by the observation of cross-linking changes (gel test) as well as crystallinity increases (wide-angle X-ray diffraction and microtome cuts). This finding could have a significant effect on the manufacturing and subsequent modification of injection-molded polypropylene parts, which opens new possibilities in practice for this material. The increased surface wear resistance enables the use of parts for which the durability and abrasion resistance of the surface are demanded, especially in applications facing exposure to long-term cyclical loads (e.g., gears). [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper deals with pulsed mode laser beam welding (LBW) on 2 mm thick Ti-6Al-4V alloy sheets. ANSYS Fluent 16.0 version is utilized to develop a generic model with Vc++ code. The model is validated with test results. The optimal LBW parameters are obtained by maximizing the depth of penetration (DP) and minimizing the weld bead width (BW). To minimise the number of numerical simulations, Taguchi approach is adopted. The LBW parameters considered are pulse frequency, pulse width and welding speed, the absorbed power is kept as constant. The performance indicators are width of fusion zone, depth of penetration, heat affected zone and maximum temperature. The optimal LBW parameters are found to be dependent on the process indicators. A simple reliable modified Taguchi approach is followed to get a set of optimal LBW parameters for maximum DP and minimum BW.

Calibration of the non-destructive testing (NDT) methods for pipeline inspections is commonly done via machined defects with simple shapes and known sizes. However, such defects do not represent, e.g. an actual pit morphology observed in the field, which could lead to the unreliable interpretation of the inspection results. This work proposed a systematic approach to create and characterise real pits in stainless steel pipe specimens to assess the sensitivity of selected NDT methods. Pipe samples with three different diameters and thicknesses were used. Pits of different geometries and dimensions were generated by electrochemical methods, and immersion in an acidic ferric chloride solution filled in pre-drilled holes on the external surface of the specimens. NDT methods including radiography, Eddy current and dye penetrant testing were used for detecting and sizing the pits. The results were then compared with true pit depths obtained from cross-section analysis. Radiography and Eddy current methods failed to detect small pits with depths less than 70 µm. The porous metal cover on the pit mouth affected the detectability of radiography, while it had little impact on Eddy current testing. The findings of this investigation could be used to design training and calibration blocks for NDT methods. [ABSTRACT FROM AUTHOR]

In this paper, the ballistic performance of AA6061-B4C surface composite targets fabricated by Friction Stir Processing (FSP) technique has been investigated. The paper is divided into two stages. Stage I identifies the suitable process parameters namely, the rotational speed and feed to produce defect free surface composite targets. Standard tests such as tensile test, microhardness and macroscopic examination are carried on FSPed AA6061-B4C surface composite to identify the best process parameters. In stage II, ballistic experiments are conducted on FSPed AA6061-B4C targets for both single and multiple hit conditions. The ballistic performances of the targets are measured in by Depth of Penetration (DoP) method. It is seen that, in both single and multiple impact conditions, radial cracks are observed near the crater region of BM AA6061 targets. Especially in multiple hit, severe cracking occurred around the craters present near the edges of BM AA6061 target. On the other hand, no cracks are observed in FSPed AA6061-B4C targets after both single and multiple hit conditions. A 13%–20% DoP is observed in FSPed AA6061 target compared to BM target. It is inferred that, improvement in microhardness and frictional characteristics offered by B4C particles have played a vital role in improving the ballistic performance of FSPed AA6061-B4C targets. [ABSTRACT FROM AUTHOR]

Activated flux gas tungsten arc welding of 316L austenitic stainless steel plates was carried out using different multicomponent fluxes composed of various oxides. The performance of these fluxes was further compared with SiO2 flux for different weld characteristics such as macro and microstructure. Hardness and residual stress analysis on weld beads were carried out. Electrochemical corrosion tests were conducted, to study the corrosion behaviors of the weld. Tool wear pattern and mechanism were analyzed. Among all used multicomponent fluxes, flux composed of 40% SiO2, 35% TiO2, 15% MoO3, and 10% NiO named Flux-3 provided better weld quality. A better depth of penetration with fine dendritic grain structure was obtained using a Flux-3. Better conceived residual stress from higher depth-to-width ratio of weld using Flux-3 is supported by XRD stress analysis. A lower corrosion rate was observed in the welds using Flux-3. Tool wear in welding with Flux-3 was higher compared with welding without any flux. [ABSTRACT FROM AUTHOR]

Analysis of depth of penetration (DoP) experimental data of Dyneema® HB26 hard ballistic laminates is presented using an energy approach. Several DoP experimental parameters have been identified and calculated including the threshold velocity of penetration ( V T H ), the characteristic time ( τ D o P ), the DoP damping coefficient ( c D o P ), and the dynamic pressure per unit impact speed ( Σ D o P H ). For the first time, a simple penetration model is developed from the energy approach to predict the projectile motion and penetration resistance force during depth of penetration experiments. [ABSTRACT FROM AUTHOR]

In this work, a comparative study on the ballistic behaviour of friction stir processed AL6061 targets had been made. Base Metal AL6061 (BM) plates with 25 mm thickness were friction stir processed by adding Multi Walled Carbon Nano Tubes (MWCNT) and Graphene (G), producing AL6061-MWCNT and AL6061-G surface composites. Optical microscopy and microhardness test on BM, AL6061-MWCNT and AL6061-G samples were performed as per the standard procedure. It was noticed that uniform dispersion of ceramic particles and refined grains were obtained for the friction stir processed surface composites. From the microhardness test, it was perceived that friction stir processing had induced strengthening of surface composites, hence increasing the microhardness of AL6061-MWCNT and AL6061-G by ~60.3% and ~73.6% respectively. Also, ballistic experiments were conducted at 680±10 m/s by impacting Ø7.62×51 mm projectiles. AL6063 backing plates were placed to compare the ballistic behaviours AL6061-MWCNT and AL6061-G targets by depth of penetration. It was noted that the depth of penetration of AL6061-MWCNT and AL6061-G targets were 37.81% and 65.84% lesser than the BM target. Further, from the results of Post ballistic microscopy it was observed that the microstructure near and away from the penetration channel edge looks unchanged in BM target. However, the AL6061-MWCNT and AL6061-G targets showed considerable change in their morphology, by forming Adiabatic Shear Bands. [ABSTRACT FROM AUTHOR]

Carnoy's solution, a chemical cauterisation agent, has been indicated as one of the adjuvant treatment modalities for odontogenic keratocyst. In 2000, after the ban of chloroform many surgeons adopted the use of Modified Carnoy's solution. The purpose of this study is to compare the depth of penetration and amount of bone necrosis of Carnoy's versus Modified Carnoy's solution on the mandible of Wistar rats at different time intervals. Twenty-six male Wistar rats of six to eight weeks old, weighing approximately 150–200 grams, were allocated for this study. The predictor variables were type of solution and application time. The outcome variable was depth of penetration and amount of bone necrosis. Carnoy's solution was applied on the defect on the right side of the mandible and Modified Carnoy's solution on the left side for five minutes on eight rats, eight minutes on eight rats, and 10 minutes on eight rats. All specimens were subjected to histomorphometric analysis done using Mia image AR software. Univariate ANOVA test, and paired sample t test was done to compare the results. The depth of penetration for Carnoy's solution was more than Modified Carnoy's solution in the three different exposure times. Statistically significant results were observed at five minutes and eight minutes. The amount of bone necrosis was more in Modified Carnoy's solution. The results were not statistically significant at the three different exposure times. To conclude, when one wants to use Modified Carnoy's solution, the minimum exposure time should be 10 minutes to achieve similar results as those of Carnoy's solution. [ABSTRACT FROM AUTHOR]

In this study, a relation between the quasi-static, dynamic compressive and ballistic impact of 7055 and 7075 Al alloys was made. The results showed that the ultimate tensile strength, hardness and absorption capacity were considerably higher in 7055 Al alloy compared to 7075 Al alloy. Consequently, 7055 Al alloy exhibited superior ballistic impact resistance (low depth of penetration) against different shapes of 7.62 mm soft steel core projectiles. The microstructure evolution after ballistic impact revealed gradient variation of strain rate away from the crater which assists in the nucleation of different deformation zones, i.e., fine grain zone (FGZ), high-density deformation zone (HDZ) and low-density deformation zone (LDZ). These zones were confirmed through optical micrographs, hardness, stress-strain and XRD analysis. The strong texture {111} component was changed to the {111} and {200} component in HDZ and LDZ, which also assists in understanding that the deformation was more complex in these regions. Therefore, a model was proposed for the nucleation of fine grains near the crater. In addition, fracture morphology was different under each loading condition and a transitional effect is observed from quasi-static loading to ballistic impact loading. These interesting features can further enhance the understanding and the development of Al alloys in aerospace and military applications.

An initial boundary value problem has been formulated within the A. V. Luikov theory for calculating temperature and moisture content fields in a homogeneous halfspace whose boundary is in a state of heat and mass exchange with an air medium. The halfspace material is made up of a hard substrate (a capillary-porous body) and water, the heat transfer between the halfspace boundary and the air medium occurs according to the Newton law, and the mass transfer occurs according to the Dalton law. In the initial state, the air medium and the material have an identical temperature, and the densities of the heat and moisture flows on the boundary separating them are equal to zero. At the instant of time assumed as the computing origin, the air temperature begins to make minor harmonic oscillations near its original value. It has been shown that with the passage of time, a heat and mass transfer regime will set in inside the material, under which temperature and moisture content fields have the form of decaying harmonic waves. For a mathematical model of partial-type heat and mass transfer (the movement of moisture of the surface only occurs due to a moisture content differential, and the transformation of water into steam only occurs on the surface), a dependence of the penetration depth and phase velocity of these waves on the values assigned under the problem conditions and determining the process has been obtained. The constructed solution and the resulting conclusions are the extension of Fourier′s investigations described in the literature, that refer to a situation when the halfspace material does not contain moisture and, according to a harmonic law, there is variation in the temperature of the material′s surface rather than in the air temperature. The results of the investigation can be used in geocryology as a theoretical tool in simulating daily and annual oscillations in the soil′s thermophysical state, which is an important task for planning economic activity in the frozen rock areas. [ABSTRACT FROM AUTHOR]

In the current experiment, the fiber laser parameters were optimized for welding P91 steel using the Box–Behnken design (BBD). Bead-on-plate welds were produced with an 8000 W fiber laser welding machine, with the focal point, power, and welding speed of the laser varied under various shielding atmospheres. The input parameters were optimised to achieve the desired depth of penetration (Dp), underfill (U), top bead width (Tw), and heat-affected zone width (Hw), and their impact on output responses were analyzed using the analysis of variance (ANOVA). The results of bead-on-plate trial welds and analysis of variance demonstrated that welding speed has the most decisive influence on the depth of penetration (Dp), the width of top bead (Tw), and HAZ (Hw), while laser power has the most significant influence on underfill (U). The optimal solution for argon shielding resulted in a weld with a penetration depth of 5.5 mm, compared to full penetration weld with a narrow top bead and heat affected zone achieved in CO2 shielding atmosphere. The results of validation trials utilising the optimal parametric combination were found to be highly correlated with the expected values, confirming the mathematical model's adequacy. The high laser intensity used in CO2 shielding resulted in the formation of underfill with a depth of 0.456 mm. In both shielding atmospheres, the fusion zone microstructure exhibited untempered martensite in as-welded condition with a columnar lath structure and was devoid of δ-ferrite. [ABSTRACT FROM AUTHOR]

A candidate for an armor material should present a lower density, a suitable ballistic performance, and low cost. Porcelain tiles might be an alternative considering their outstanding technical properties and availability. To the best of our knowledge, the use of porcelain tiles was explored for the first time as an armor material. The tests were carried out with reference and chemical-tempered samples. A chemical tempering procedure was applied to improve the impact and mechanical properties. The procedure consists of a cation exchange of sodium and potassium ions, as confirmed by chemical analysis (EDX). Mechanical properties, hardness, and flexural strength were measured. The depth of penetration (DOP) test was used to verify the ballistic protection offered by porcelain tiles. A projectile was fired into a ceramic tile backed by a semi-infinite block in the test. The residual penetration into the backing material was measured and compared to the penetration of the projectile into a monolithic block of the backing material. The test was carried out with 7.62 × 51 mm NATO-FMJ (North Atlantic Treaty Organization - Full Metal Jacket) ammunition specified for NIJ (National Institute of Justice – USA) level III body armor. After chemical tempering, the potassium concentration on the material surface increases. Chemical tempered samples showed an increase in mechanical properties and ballistic performance when compared to untreated ceramic tiles. The flexural strength was 129 ± 8 MPa for the reference material and 143 ± 14 MPa for the chemical tempered material, an increase of 10%; the hardness was HV 8.5 ± 0.9 MPa and 12.7 ± 0.5 MPa respectively, an increase of 49%; and the ballistic efficiency factor (q2) was 2.74 ± 0.72 and 3.22 ± 0.5 respectively, an increase of 17%. [ABSTRACT FROM AUTHOR]

Optimization of target thickness and influence of heat treatment condition on the high velocity impact response of aluminium alloy 7075 targets have been determined. Both experimental and numerical studies were conducted using a 7.62 mm hard steel core projectile. The numerical simulation used a 7.62 mm Ogival nose shaped projectile with a target thickness ranging from 20 to 26 mm. High velocity impact experiments on T651 and solution treated targets, with rolled plate thicknesses ranging from 21 to 25 mm were carried out to validate the numerical findings. The microhardness of the targets was measured using Vicker's microhardness tester and fractographs were examined using a scanning electron microscope. The projectile penetrated regions were analyzed using light microscopy. A good correlation between the numerical and experimental ballistic behaviour of aluminium alloy 7075 targets was observed and an optimum target thickness of 21 and 24 mm was observed for the T651 and solution treated targets to prevent the projectile's penetration. It was also noted that, after the projectile's impact, solution treated targets had higher microhardness compared to T651 condition targets. This is due to higher work hardening of solution treated targets near the penetration channel. Even though T651 targets have a lower depth of penetration compared to solution treated targets, 'splintering' failure of the T651 targets is observed. In contrast, 'petalling' and 'plugging' kinds of failures were noticed on the solution treated targets. Thus, solution treatment of ballistic targets may enhance the ballistic limit of armoured vehicles. [ABSTRACT FROM AUTHOR]

High velocity ballistic impact deformation behaviour of Titanium/GFRP Fiber Metal Laminates (FML) has been explored. Both single and multiple projectiles impact conditions were considered. Ti/GFRP FML targets were fabricated with addition of 5% and 10% weight percentage of boron carbide (B4C) particles. Mechanical properties of Ti/GFRP FML targets were determined as per ASTM standards. High velocity ballistic experiments were conducted using Armour Piercing Projectile (APP) of diameter 7.62 mm and velocity ranging between 350 and 450 m/s. Depth of penetration of the projectile into the target was measured. The deformation behaviour of Ti/GFRP targets with and without the presence of ceramic powder (B4C) was investigated. “Ductile hole growth” failure mode was observed for pure GFRP target when subjected to single projectile impact whereas “plugging” failure mode was noted for Ti/GFRP targets. The presence of B4C (5% by weight) particles has significantly improved the ballistic resistance of the Ti/GFRP FML target by offering frictional resistance to the projectile penetration. Further addition (10% by weight) of B4C has reduced the ballistic performance due to agglomeration. None of the targets showed ‘brittle cracking’ or ‘fragmentation’ failures. When compared to the published results of Aluminium (Al 1100/GFRP and Al 6061/GFRP) FMLs, Ti/GFRP FML showed lesser DoP which increases its potential application to aerospace industry.

Ti6Al4V titanium alloys are widely used in a variety of scientific and industrial fields. Laser beam welding is one of the most effective techniques for the joining of titanium plates. The main objective of this study was to investigate the influence of the most important laser parameters on welding performance of titanium alloy in two different physical environments such as air and water (i.e., serum) media. Specifically, the laser beam welding of 2 mm thick Ti6Al4V samples was applied using an Nd:YAG laser in open-air welding using argon as a shielding gas, and in wet welding using a serum environment. The deepest penetration was achieved at −3 mm focal position with 11 J of laser energy in both investigated media (i.e., air and serum). The maximum hardness (1130 HV) was achieved for the focal position of −4 mm in serum medium while it was 795 HV for a focal position of −5 mm in air medium. The minimum (1200 μm and 800 μm) and maximum (1960 μm and 1900 μm) weld widths were observed for air and serum medium, respectively. After the welding process, martensite, massif martensite, and transformed martensite were observed in the microstructure of Ti6Al4V. To the best of our knowledge, the underwater wet welding of titanium alloy was carried out and reported for the first time in this study. [ABSTRACT FROM AUTHOR]

The influence of shot peening (SP) on the ballistic performance of base metal (BM) and friction stir welded (FSWed) AZ31B magnesium alloy joints has been investigated. The defect-free welded joints of AZ31B magnesium alloy were prepared by using the optimum weld parameters, and the joints were shot peened by using steel balls of 2 mm in diameter. In order to investigate the effect of SP on the microstructure, SEM analyses were done at several regions of the top and bottom surfaces of the BM and stir zone (SZ) regions of the FSWed joints. Improved microhardness values of 75 and 70 HV were observed at the top surface of SP-treated BM and SZ regions. The effect of SP on the ballistic performance of AZ31B magnesium alloy joints was determined by conducting high velocity ballistic experiments. Steel core projectiles of 7.62 mm in diameter were used to impact the welded joints. Aluminium alloy AA6062 plates of 25 mm thickness were used as a back plate along with the target. The depth of penetration of the projectile into the target and the back plate was measured to determine the ballistic performance. Among the various regions tested, the SP-treated BM target offered improved ballistic performance compared to the SZ of the SP target. Post investigation of the projectile penetrated regions of the SP targets indicated the absence of voids and micro-cracks compared to non-treated targets. [ABSTRACT FROM AUTHOR]

Microorganisms are the major cause for the failure of root canal treatment, due to the penetration ability within the root anatomy. However, irrigation regimens have at times failed due to the biofilm mode of bacterial growth. Liposomes are vesicular structures of the phospholipids which might help in better penetration efficiency into dentinal tubules and in increasing the antibacterial efficacy. Methods: In the present work, chlorhexidine liposomes were formulated. Liposomal chlorhexidine was characterized by size, zeta potential, and cryo-electron microscope (Cryo-EM). Twenty-one single-rooted premolars were extracted and irrigated with liposomal chlorhexidine and 2% chlorhexidine solution to evaluate the depth of penetration. In vitro cytotoxicity study was performed for liposomal chlorhexidine on the L929 mouse fibroblast cell line. Results: The average particle size of liposomes ranged from 48 ± 4.52 nm to 223 ± 3.63 nm with a polydispersity index value of <0.4. Cryo-EM microscopic images showed spherical vesicular structures. Depth of penetration of liposomal chlorhexidine was higher in the coronal, middle, and apical thirds of roots compared with plain chlorhexidine in human extracted teeth when observed under the confocal laser scanning microscope. The pure drug exhibited a cytotoxic concentration at which 50% of the cells are dead after a drug exposure (IC50) value of 12.32 ± 3.65 µg/mL and 29.04 ± 2.14 µg/mL (on L929 and 3T3 cells, respectively) and liposomal chlorhexidine exhibited an IC50 value of 37.9 ± 1.05 µg/mL and 85.24 ± 3.22 µg/mL (on L929 and 3T3 cells, respectively). Discussion: Antimicrobial analysis showed a decrease in colony counts of bacteria when treated with liposomal chlorhexidine compared with 2% chlorhexidine solution. Nano-liposomal novel chlorhexidine was less cytotoxic when treated on mouse fibroblast L929 cells and more effective as an antimicrobial agent along with higher penetration ability. [ABSTRACT FROM AUTHOR]

In this paper, an attempt was made to study the ballistic resistance of Friction Stir Welded (FSW) AZ31B magnesium alloy. The base metal AZ31B plates were sliced to required size and FSW was carried out using a non-consumable taper pin tool made up of HCHCr steel. Samples were taken out from the FSW plates to study the microstructure and microhardness. The FSW AZ31B contain refined grains and tiny Mg17Al12 precipitates which were formed because of severe plastic deformation during FSW. The FSW AZ31B targets also showed ∼7.47% increase in microhardness compared to BM target. Further, ballistic test was conducted by impacting Ø7.62 × 39 mm hard steel core projectiles at an initial velocity of 420 m/s. AA6062 material of 25 mm was used as backing plate to measure the Depth of Penetration (DOP) of the projectile. The failure mechanism and the ballistic resistance of BM and FSW AZ31B samples were studied and compared. Finally, post ballistic analysis was made to study the failure modes of the target at microscopic level. Through various experimental results, it was identified that the increase in ballistic resistance of FSW AZ31B target was mainly due to two reasons; the refinement of grain size and small strengthening precipitates. [ABSTRACT FROM AUTHOR]

Introduction and Objective: The proper performance of a sealer in root canal treatment depends on its physical properties. The aim of this study was to investigate the effect of two bioceramic and epoxy resin sealers in terms of marginal adaptation and tubular penetration depth in different obturation methods of human premolar teeth. Materials and Methods: A total of 82 premolar teeth extracted due to caries and gum disease were used in the present in vitro experimental study. Two types of sealers, epoxy resin (AH-Plus, Dentsply, Germany) and bioceramic (Endosequence BC sealer, Brasseler, Savannah, GA, USA), were used in this research. Lateral compaction and single-cone techniques were used for filling the teeth. Marginal adaptation and tubular penetration depth were measured by scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM), respectively. Statistical analysis of data was performed by repeated-measures ANOVA. The significance level was considered as P < 0.05. Results: The marginal adaptation and tubular penetration depth in all three coronal, middle, and apical regions were better in bioceramic sealer (P < 0.001). The marginal adaptation and tubular penetration depth in all regions were not affected by the filling method and the interaction between the sealer type and the obturation technique. Conclusion: Based on the results of this study, the use of bioceramic sealer caused better depth of tubular penetration and marginal adaptation compared to epoxy resin. Further studies and the use of different filling techniques are necessary to achieve a three-dimensional sealing in curved root canals.

Today, more and more importance is given to the improvement of polymer materials’ wear resistance, i.e., their micro-mechanical and tribological properties, which could widen their application in practice. The properties of materials can be modified by several methods, among them exposure to electron radiation. This study focuses on the effect of varying radiation intensity (15 kGy to 99 kGy), depth of penetration, and subsequent structure modification of injection-molded polypropylene on tribological and micro-mechanical properties. Electron radiation influences the structure of individual layers, thus improving or degrading their properties. Hence, the depth of penetration can be examined by instrumented hardness tests and scratch tests. Due to irradiation, surface properties and wear resistance increased by up to 105% (from 38 MPa to 78 MPa). As the results show, an increase in mechanical properties was recorded in the direction towards the center of the sample (from 72 MPa to 82 MPa). Micro-mechanical tests were also confirmed by the observation of cross-linking changes (gel test) as well as crystallinity increases (wide-angle X-ray diffraction and microtome cuts). This finding could have a significant effect on the manufacturing and subsequent modification of injection-molded polypropylene parts, which opens new possibilities in practice for this material. The increased surface wear resistance enables the use of parts for which the durability and abrasion resistance of the surface are demanded, especially in applications facing exposure to long-term cyclical loads (e.g., gears).

The present work analyses the effect of five types of oxide fluxes – SiO2, TiO2, CrO3, MnO2 and MoO3 – on the depth of penetration and pitting corrosion behaviour of UNS S32205 duplex stainless steel produced with the activated tungsten inert gas welding (A-TIG) process. Five bead-on-plate (BoP) weld samples prepared autogenously with constant weld parameters. Depth of penetration (DP), depth-to-width (D/W) ratio and weld bead width (BW) were measured and compared with reference to the weld thermal cycle. The test results of ferrite measurement and micro-hardness were compared with normal – without flux added TIG-welded sample. Macro analysis of all samples indicates that SiO2 and TiO2 flux offer enhanced penetration depth and D/W ratio, in contrast, to use of other fluxes. Possibly, under the effect of either reversed Marangoni or arc constriction or both, however, all TIG BoP weld samples exhibited poor pitting corrosion resistance. Enhanced heat input due to flux and thus resultant unbalanced ferrite austenite proportion affected pitting corrosion resistance. ASTM A 923 microstructures did not show any presence of nitride formation. Results of energy-dispersive X-ray spectroscopy and scanning electron microscopy analysis of corrosion pits showed no abnormality with the chemistry of standard 2205 DSS. [ABSTRACT FROM AUTHOR]

Influence of post weld cryogenic treatment conditions (deep and shallow) on the ballistic resistance of friction stir welded (FSW) AZ31B magnesium alloy has been investigated. AZ31B welded joints which were prepared by using friction stir welding process were subjected to two types of cryogenic treatment conditions. The microstructural investigation of cryogenic treated joints showed the formation of Mg17Al12 precipitates and conversion of coarse eutectic phase into thin discontinues phase along with halos. In addition, superior microhardness values were noticed for the cryogenically treated joints compared with non-treated joints and base metal. High velocity ballistic experiments were conducted on cryogenically treated and non-treated weld targets using 7.62 mm deformable projectiles at an initial velocity of 450 ± 10 m/s. At the stir zone, the depth of penetration (DOP) of the projectile into the deep cryogenic treated (DCT) target was observed to be 11% and 34 % lesser than the shallow cryogenic treated (SCT) and FSW targets. Thus increase in the ballistic resistance was observed for the post-weld cryogenic treated FSW joints compared to non-treated FSW joints. SEM investigation of the projectile impacted DCT targets showed the formation of cracks, dimples and micro voids at the crater region. It is also noticed that, the Stir Zone (SZ) and Heat Affected Zones (HAZ) of the DCT target has effectively absorbed the ballistic impact energy of the projectile by a ductile fracture and hence DCT can be used to improve the ballistic penetration resistance of the FSW joints at the SZ and HAZ regions. [ABSTRACT FROM AUTHOR]

The intent of the present study is to investigate the effect of heat input on the bead geometry by the combined action of both metal inert gas welding (MIG) and submerged arc welding (SAW). The focus of this study is to evaluate the effect of preheating the welding specimen with MIG welding to improve weldment properties. Preheating the welding sample using MIG welding is the first time to be used in welding process. Mild steel of IS 2062 grade B was used for the same and the welding processes were carried out consequently one after the other on 16 samples. The samples were cut at 5 mm thickness followed by fine polishing and etching prior to the measurement of bead geometry. Bead geometry for each sample was measured separately and then compared with 16 other samples welded by only submerged welding at similar parametric condition. The results show improved weldment properties for the combined welding in comparison to only submerged arc welding. Microstructure analysis reveals that increase in heat input results in formation of coarse grain structure both for combined welding and only SAW. Thus, MIG welding can be effectively used as prehating process in welding. [ABSTRACT FROM AUTHOR]

Day by day laser welding (LW) is gaining industrial importance. Good quality of weld joints can be realized through this process. Because this process yields low distortion and small weld bead. Aerospace, nuclear, automotive, and biomedical industries are opting for the lightweight and corrosion resistance titanium alloys. This paper deals with the generation of optimal weld bead profiles in the conduction mode laser beam welding (LBW) of thin Ti–6Al–4V alloy sheets. Laser beam diameter, power and welding speed are the 3 LBW parameters, whereas, bead width, depth of penetration, heat affected zone and maximum temperature are the performance indicators (PIs). 3 levels are set for each LBW parameter. Taguchi's L9 OA (orthogonal array) is selected to minimize the numerical simulations. ANSYS Fluent V16.0 with Vc++ code is used to develop a generic model. %Contribution of each process variable on the PIs is assessed performing ANOVA analysis. The range of PIs is assessed adopting the modified Taguchi approach. A set of optimal LBW parameters are identified considering a multi-objective optimization technique. For these optimal LBW parameters weld bead width is minimum, and the depth of penetration is maximum. Empirical relations for PIs are developed and validated with simulations. Utilizing the Taguchi's design of experiments, empirical relations are developed for the performance indicators in laser beam welding (LBW) simulations performing few trial runs and identified the optimal LBW process parameters.

Prediction of fusion zone in numerical modelling of welds using a modified heat transfer model requires experimental results for validation. Primarily, the modified heat transfer models are developed from the point and disc source heat models which can be assumed to be a semi-circle or spherical shape. In this study, a simple relationship between melt areas, the depth of penetration and weld width was proposed for point and disc source profiles to represent the actual weld profile. The results obtained for focused and defocused laser beams indicate that the actual weld profile is closer to a point source than the disc source. The transition between the conduction and keyhole regimes was achieved when the actual weld depth of penetration is below that of the point source.