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Solid powder lubricants provide distinct advantages over conventional coolants in machining applications. Various novel approaches have been used over the years for delivering these lubricants to the machining zone. This work employs air-assisted approach using air as carrier medium and reports on the effects of “lubricant/air mixture ratio,” powder particle size,” and “lubricant laden airflow rate” on surface roughness, microhardness, and residual stresses when AISI 1045 steel is ground with boric acid as lubricant. Nested-factorial mixed model design of experiment is used for structured inquiry; two levels (25 and 96.5 μm) of lubricant “powder particle size” are in factorial arrangement with three levels (1:1/2, 1:1, 1:2) of “lubricant/air mixture ratio.” Three distinct levels of “lubricant laden airflow rate” are nested within the levels of “lubricant/air mixture ratio.” Results show that coarse particles and concentrated mixture give favorable results in general, except for residual stresses. Balanced analysis of variance (ANOVA) reveals that “powder particle size” is statistically significant (95% confidence) for all three response measures whereas “lubricant/air mixture ratio” is significant for microhardness and residual stresses. Further, interaction of “powder particle size” with “lubricant laden airflow rate” is significant for surface roughness and residual stresses. Values obtained with 96.5 μm particle size, 1:1/2 mixture ratio and 0.74 g/s flow rate are within 2% and 22% for microhardness and surface roughness respectively w.r.t. “grinding with conventional coolant”; 7% better microhardness, 48% less surface roughness, and 75% less residual stresses are obtained w.r.t “dry grinding.”

The use of advanced brittle composites in engineering systems has necessitated robotic rotary ultrasonic machining to attain high precision with minimal machining defects such as delamination, burrs, and cracks. Longitudinal–torsional coupled (LTC) vibrations are created by introducing helical slots to a horn’s profile to enhance the quality of ultrasonic machining. In this investigative research, modified ultrasonic horns were designed for a giant magnetostrictive transducer by generating helical slots in catenoidal and cubic polynomial profiles to attain a high amplitude ratio (TA/LA) and low stress concentrations. Novel ultrasonic horns with a giant magnetostrictive transducer were modelled to compute impedances and harmonic excitation responses. A structural dynamic analysis was conducted to investigate the effect of the location, width, depth and angle of helical slots on the Eigenfrequencies, torsional vibration amplitude, longitudinal vibration amplitude, stresses and amplitude ratio in novel LTC ultrasonic horns for different materials using the finite element method (FEM) based on the block Lanczos and full-solution methods. The newly designed horns achieved a higher amplitude ratio and lower stresses in comparison to the Bezier and industrial stepped LTC horns with the same length, end diameters and operating conditions. The novel cubic polynomial LTC ultrasonic horn was found superior to its catenoidal counterpart as a result of an 8.45% higher amplitude ratio. However, the catenoidal LTC ultrasonic horn exhibited 1.87% lower stress levels. The position of the helical slots was found to have the most significant influence on the vibration characteristics of LTC ultrasonic horns followed by the width, depth and angle. This high amplitude ratio will contribute to the improved vibration characteristics that will help realize good surface morphology when machining advanced materials.

This paper reports on the effects of spindle attributed forced vibrations on machinability characteristics of vertical milling process. The effects of three levels of spindle attributed forced vibrations along with feed rate and axial depth of cut are evaluated on surface roughness, dimensional accuracy, and tool wear under constant conditions of radial depth of cut and cutting speed. AISI P20 and solid carbide cutter are used as workpiece material and tool, respectively. Taguchi L 9 standard orthogonal array is used for experiments followed by analysis of variance (ANOVA) for identifying significant parameters that affect surface roughness and dimensional accuracy. Tool wear in terms of crater wear (Kt) and tool flank wear (VB max ) is measured along with an analysis of chipping and built-up edges for accessing the influence of forced vibrations. It is found that machine tool vibration amplitude and axial depth of cut are statistically significant at 95 % confidence level for surface roughness, with vibration amplitude being the most contributing factor (83.4 %) followed by axial depth of cut (12.39 %). The dimensional accuracy is found to be insensitive to the parameters at stated confidence level. Higher values of vibration amplitude and feed rate are found to be resulting into excessive tool wear with vibration amplitude of 0.185929 mm/min combined along with a feed rate of 600 mm/min and an axial depth of cut of 0.15 mm resulting in catastrophic tool failure.

Aramid fiber–reinforced polymer composite (AFRPC) is popular in aerospace and defense industries owing to its superior thermal and mechanical properties. However, its intricate hexagonal cellular structure and the material’s heterogeneous, soft, and brittle characteristics lead to significant surface defects, such as burr formation, wall tearing, roughness, dimensional inaccuracies, and uncut fibers during traditional machining. Such poor machining quality issues notably affect the operational lifespan and functional performance of its sandwich structural components. To address these issues, the rotary ultrasonic assisted machining (RUSAM) process has been introduced. To thoroughly investigate the RUSAM of AFRPC using various cutting tools, a 3D finite element model was developed and validated. This paper mainly investigates the effect of various machining parameters such as vibration amplitude (VA), cutting width (CW), feed rate (FR), and spindle speed (SS) on the cutting force, surface morphology, burr formation, and burr height during RUSAM of AFRPC structure by plane and toothed disc cutters. The burr height was found to decrease with the increase of spindle speed (60.82% and 71.00%) and vibration amplitude (78.15% and 82.32%), whereas increase with cutting width ( 149.81 % and 321.16%) and feed rate (156.53% and 314.83%) during RUSAM by plane and toothed disc cutters, respectively. The pattern of variation of burr height with machining parameters was found similar to that of the cutting force. Significance analysis based on 4 levels, 4 factors orthogonal L 16 ( 4 4 ) experiments revealed the cutting width to be the most influential parameter on the burr height and cutting force followed by the spindle speed, feed rate, and vibration amplitude during RUSAM of the AFRPC core by the disc cutters. Up to 62.54 % reduction in burr height was realized by rotary ultrasonic assisted machining compared to the conventional machining. Under specified operating conditions, the disc cutter generates a higher but less number of burr as compared to the toothed disc cutter without any tearing defects. 3–10% and 5–20% burrs were observed during rotary ultrasonic assisted machining compared to 20–50% and 40–70% burrs during conventional machining of AFRPC structure by plane and toothed disc cutters, respectively. This experimental research will be extremely useful to comprehend the burr formation mechanism and optimize the machining parameters for enhanced surface morphology of AFRPC structures.

The applications of Nomex honeycomb composite (NHC) structures in aerospace, automotive and defence sectors have been significantly increasing due to their high compressive strength, hexagonal thin-walled structure, ultra-light weight and excellent thermal resistance. Specific applications include composite sandwich structures in helicopter propellers, satellite cabins, aeroplane floors, engine cowls, wings and nacelles. Accuracy of the machined surface of NHC structures is required for adhesive bonding with face-sheets. Conventional machining processes generate machining defects in terms of tearing, damaged cell walls, burr formation, delamination and poor surface quality that result in reduction of strengths of the core structure and its bond with face sheet. Ultrasonic machining is a proven technique to overcome such machining defects and improve the surface quality of NHC structures. Novelty of this research includes the development of a three-dimensional (3D) finite element model to analyse cutting forces, chip formation and machining quality of NHC structures using disc cutter through both ultrasonic and conventional machining processes by providing feed to the workpiece instead of the cutting tool. The significant influence of machining parameters such as depth of cut, feed rate, ultrasonic amplitude and spindle speed on cutting forces was investigated numerically followed by experimental validation. Numerical model in support with experimental results show that cutting forces decrease by increasing ultrasonic amplitude and spindle speed (up to 54.74% and 62.71%, respectively), and increase with the increase of depth of cut and feed rate (up to 60% and 60.48%, respectively). It was also found that the ultrasonic machining reduces the magnitude of cutting forces as compared to conventional machining (up to 42.74%). Surface morphology analysis through scanning electron microscope also indicated improved machining quality achieved by ultrasonic machining at NHC structures’ hexagonal cells, triple points and walls. A burr formation of 5% was observed during ultrasonic machining of NHC structures for Fy≤3N, while it was found up to 10% if Fy>3N, compared to at least 30% burr during conventional machining. To sum up, the employed methodology can be effectively applied for determining the effect of various machining parameters on cutting forces as well as surface quality, chip formation, structural integrity and dimensional accuracy of machined NHC structures during ultrasonic machining process.

Purpose Utilization of advanced hard and brittle materials in engineering applications has led to the need of non-conventional machining techniques such as rotary ultrasonic machining (RUM) to achieve high dimensional accuracy and low machining defects (delamination, burr and cracks formation, etc.). RUM performance greatly depends on vibration amplitude at tool end which is achieved through appropriate ultrasonic horn design. Longitudinal–torsional coupled (LTC) vibrations, generated by incorporating helical slots in horn design, improve ultrasonic machining quality of hard and brittle materials. In present investigative work, modified ultrasonic horns were designed and analyzed for RUM by producing helical slots in quadratic and cubic Bezier horn profiles to achieve high amplitude ratio ( T A / L A ) within safe stress limits. Methods Modal and harmonic analyses were performed to investigate the influence of depth ( D s ), width ( W s ), angle ( θ s ) and location ( L sp ) of helical slots on the modal frequencies, vibration amplitudes, torsional to longitudinal amplitude ratio and stresses in ultrasonic LTC Bezier horns using FEM. Modified ultrasonic horns were tested for three different materials: steel, aluminum, and titanium after validation with available literature. Results Presently designed horns were found to attain high amplitude ratio and low stresses as compared to the commercial step LTC horn for same end diameters and length. Different stresses (shear, von Mises, radial, tangential and axial) were also computed and plotted along horn axial length for optimum designs and were found well below the endurance limit. Conclusions For the same end conditions and length, cubic Bezier LTC ultrasonic horn is preferable to its quadratic counterpart due to 19.91 % higher amplitude ratio. However, stresses are 24.78 % less in quadratic Bezier LTC ultrasonic horn. The amplitude ratio attained by both types of LTC Bezier horns was found to be significantly greater than that in the commercial LTC step horn, with additional advantage of low stresses. Achievement of high amplitude ratio will help in reduced cutting force and improved surface quality of advanced hard and brittle materials as compared to standard LTC horn design.

Glass fiber reinforced polymer (GFRP) composite sections, manufactured through pultrusion process, are known for their high strength-to-weight ratio, corrosion resistance, low thermal conductivity, electric and magnetic transparency, low life cycle cost and ease of fabrication. They are being widely applied in infrastructure systems. The load response of thin-walled GFRP composite sections is different from that of isotropic slender members. For instance, stress variation exists across the wall thickness and the FRP members are more prone to warping and local buckling including shear-lag. The literature survey revealed that the response of pultruded GFRP sections under combined bending and torsion has not yet been studied both in terms of the strength and stiffness. Thru this research, the behavior of full scale sections was investigated under bending, torsion and combined bending and torsion. The shapes under investigation include circular, square and wide-flange with dimensions from 2” to 6” and lengths from 24” to 144”. The analytical part is based on modified flexural and torsional theories for anisotropic materials. Due to the absence of any formulation on combined bending and torsion of orthotropic sections, the formulae for isotropic sections were extended for orthotropic ones. Some finite element analysis models were also included to make a comparison. The experimental work consists of (i) determining the laminate properties at coupon level through tension-tests, shear-tests, burnout-tests and microscopy, and (ii) investigating the behavior of full-length samples under 3-point bending, pure torsion and combined bending and torsion. Under torsion and combined loading, a dedicated apparatus was designed, fabricated, instrumented and calibrated at WVU-CFC Major Units laboratory. This apparatus is capable of incorporating samples of cross-sections up to 6”×6” and lengths up to 144”; with the angle of twist measurement ranging from +60° to -60°. It was found from coupon tests that strength and modulus values are measurable with a reasonable range of accuracy, but fiber alignment and fiber volume fraction may vary along the cross-section. The bending behavior of full-length closed-sections was controlled by strength and that of wide-flange sections was due to flange-buckling. The torsional behavior of closed sections was also strength controlled, while the wide-flange section practically showed no torsional strength. The behavior under combined bending and torsion was influenced by principal stresses and maximum shear stresses under the effect of compressive bending and torsional shear stresses. On the T/Tmax - M/Mmax interaction curve, some of the data-points agreed-well with the ideal curve, while the others lay beyond that. The reasons of deviation were investigated to be load rate, variations in fiber content and different types of losses in the apparatus.

The existing literature on internal branding has often adopted a managerial-based approach and seldom considered employees’ perceptions. Therefore, there is a need to understand the perspective of frontline and non-managerial employees. In this context, the current study investigates the impact of internal brand management on brand commitment, brand citizenship behavior, and sustainable competitive advantage for the hotel industry. A survey-based quantitative data was gathered from 390 non-managerial frontline staff working in 3-, 4-, and 5-star hotels of Pakistan. The results revealed that internal brand management positively impacts brand commitment, brand citizenship behavior, and sustainable competitive advantage. Besides, brand commitment has a positive impact on brand citizenship behavior and sustainable competitive advantage. Moreover, brand citizenship behavior has a positive impact on sustainable competitive advantage. In addition, the mediating roles of brand commitment and brand citizenship behavior exist between internal brand management and sustainable competitive advantage. The research implications, together with research limitations, have also been discussed.

In the modern era, the demand for lightweight and high-strength aluminium matrix composites (AMCs) has significantly grown as a result of their structural applications in various sectors. The distinctive characteristics of AMCs are intricately impacted by variables like the type and weight percentage (wt.%) of reinforcement, the selection of processing techniques, and the matrix employed. Fabricating hybrid AMCs poses several challenges, including achieving desired geometrical shapes, homogeneous mixing of reinforcements, addressing porosity, and ensuring strong interfacial bonding of reinforcement-matrix interfaces. Stir-squeeze casting has emerged as a non-traditional casting technique with the potential to address these challenges effectively. This study intends to look into the impacts of the distinct reinforcement particles (Al 2 O 3 , SiC, Si 3 N 4 , and BN) with varying wt.% on the development of different configurations of hybrid AMCs based on AA2024. The key properties that have been examined include porosity, ultimate tensile strength (UTS), elongation percentage (EL%), hardness, and impact energy of developed hybrid AMCs. The results reveal that UTS (235.6 to 377.8 MPa) and hardness (51.5 to 85.1 HRB) significantly increased with the addition of reinforcement particles, while EL% (11.6 to 7.9%) and impact energy (6.62 to 5.61 J) decreased. AA2024/2%Al 2 O 3 /2%SiC/2%Si 3 N 4 /2%BN outperformed in terms of UTS and hardness and gave 60.36% and 65.24%, respectively; however, the porosity, EL%, and impact energy have been compromised from the matrix material (AA2024) by 1.61%, 31.89%, and 15.26%, respectively. Fractography analysis of UTS and Charpy impact fractured samples depicts that a dimple fracture has been observed for the AA2024 without any reinforcement. However, with the inclusion of particles for reinforcing (Al 2 O 3 , SiC), the fabricated AMC AA2024/2%Al 2 O 3 /2%SiC provided the cleavage fracture, while transgranular cleavage fractures have been observed in the fractured surfaces of the third and fourth configurations (AA2024/2%Al 2 O 3 /2%SiC/2%Si 3 N 4 , AA2024/2%Al 2 O 3 /2%SiC/2%BN). Moreover, the brittle fracture has been depicted in the broken sample of AA2024/2%Al 2 O 3 /2%SiC/2%Si 3 N 4 /2%BN.

A novel N,N methylene-bis-acrylamide (MBA) crosslinked tamarind gum and β-cyclodextrin graft- poly(methacrylic acid) (TG/β-CG- g -MAA) hydrogel was formulated for colon targeting. The swelling capability, mechanical strength, sol–gel fraction (%), in vitro release and in vivo toxicological screening were estimated experimentally. The effect of polymers, monomer and crosslinker on percentage drug loading, swelling and drug release was determined. TG/β-CD-g-MAA hydrogel was characterized by FTIR, thermal analysis, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Swelling was significant at pH 7.4 as compared to pH 1.2. Drug release studies showed that release was significant at pH 7.4 as compared to pH 1.2. Developed hydrogels were porous, thermally stable, offered uniform distribution of amorphous drug and pH-dependent capecitabine release in controlled fashion. Kinetic modelling revealed zero-order drug release and Korsmeyer-Peppas model mechanism of release. Lastly, TG/β-CD-g-MAA hydrogel (F11) can act as prospective pH-responsive carrier for colon targeting. Graphical abstract