Low-Cost Measurement Technique of Poisson’s Ratio of Thin, Solvent-Sensitive Polymer Membranes

This paper investigates a low-cost testing procedure that measures Poisson’s ratio of thin membranes whose properties may be affected by traditional speckle patterns which are solvent-based. The shear modulus, a key indicator of how materials will fail — especially for thin membranes subjected to interfacial stresses — is a function of Young’s modulus and Poisson’s ratio, which can be determined by tensile testing. The precision of using Digital Image Correlation (DIC) to measure Poisson’s ratio coupled with a solvent-free speckle pattern of fused silica on polyimide film specimen is investigated. DIC processes for thin membranes are currently under development. As such, spraying a conventional speckle pattern may be unfeasible for thin polymer membranes whose properties are a function of solvent content. Experimental factors’ effects, such as vibration and area to which DIC is applied, were also studied in a design of experiments. It was determined that using fused silica as a solvent-free speckle pattern, as opposed to a traditional solvent pattern, does not significantly affect the measurements of Poisson’s Ratio of the polyimide film. Furthermore, it was found that the experimental factors noted above can play a significant role in fused silica-speckled Poisson’s ratio specimen.

Analysis of Symmetric Angle-Ply Laminated Composite Skew Plates Using Hybrid Trefftz Finite Element

Analysis of symmetric angle-ply skew laminated composite plates has been presented in the study using a newly developed hybrid Trefftz finite element (hTFE). Mindlin’s plate theory has been used to develop the present hTFE. The forms of displacement are assumed such that governing partial differential equations are satisfied a priori inside the element domain. Particular solutions of the governing equations have been ignored and Trefftz functions are derived using the homogenous solutions only. Inter-element continuity has been established by employing another displacement field along the edges of the hTFEs. The transverse shear stresses have been ignored at the top and bottom surfaces of the laminate. The angle of inclination of the width of the plate with the y-axis has been taken as the skew angle and different forms of skew plates are obtained by varying the skew angle. Sinusoidally distributed load (SDL), uniformly distributed load (UDL), and point load (PL) have been subjected to the top surface of the laminate and the non-dimensionalized center point deflection have been evaluated to assess the performance of the present hTFE. The observation from the present study further reinforce the versatility of the hTFE method for analysis of composite structures with complex shapes or geometries.

Evaluation of Thermal Effects in Turning Processes: Numerical and Experimental Approach

The 3D Finite element method (FEM) is an efficient tool to predict the variables in the cutting process, which is otherwise challenging to obtain with the experimental methods alone. The present study combines both experimental findings and finite element simulation outcomes to investigate the effect of tool material on output process variables, such as vibrations, cutting temperature distribution and tool wear mechanism. Machining of popular aerospace materials like Ti-6Al-4V and Al7075 turned with coated and uncoated tools are part of the investigation. The authors choose the orthogonal test, measured vibrations and cutting temperatures and used FE simulations to carry out the subsequent validations. This study includes the influence of the predicted heat flux and temperature distribution on the tool wear mechanism. The main aim of this study is to investigate the performance quality of uncoated and coated carbide tools along with its thermal aspects. Comparison of experiment and simulation outcomes shows good agreement with a maximum error of 9.02%. It has been noted that the increase of cutting temperature is proportional to its cutting speed. As the cutting speed increases, it is observed that vibration parameter and flank wear value also increases. Overall, coated carbide turning insert tool is the best method for metal turning with higher rotational speeds of the spindle.

Numerical Study on the Interfacial Modification Effects of Soy Protein on Poly(Vinylidene Fluoride)

The application of bio-degradable green materials is a rising global trend during the past decades for the sake of environment protection and sustainable development. Soy protein-based biomaterial is a promising candidate to replace the petroleum-based synthetic materials and was proved to be an effective functional modifier for polymers from our previous studies. Molecular dynamic (MD) simulation is implemented in this study to provide insights in understanding the underlying mechanisms. 11S molecule is chosen as a representative of soy protein, and three different denaturation processes are applied, including heat denaturation at two temperatures and the breaking of disulfide bonds. It is observed that by controlling the denaturation conditions, the hydrophobicity of the protein molecule is manipulated: high temperature denaturation can increase the exposed area of hydrophilic residues; whereas, by breaking the disulfide bonds, the hydrophobic residues of the molecules can be largely exposed. Besides, the mechanisms of using protein as functional modifier to tune the structures of the hydrophobic Poly(vinylidene fluoride) (PVDF) polymer (amorphous and β-crystal phases) are studied. S-S debond protein is found to favor the formation of amorphous PVDF; whereas, high temperature denatured one has stronger interactions with β phase.

Enhancing the Frictional Behaviour of H-BN Reinforced Nanocomposites Through Laser Shock Peening

In this research work, LM6 Aluminum alloy based metal matrix composites reinforced with varying amounts (0.2, 0.4, 0.6 and 0.8 wt%) of boron nitride (BN) having 10 to 30 nanometers average size were developed by using powder metallurgy and squeeze casting routes. The mechanical and tribological properties are analyzed for the samples developed through the two different routes and the influence of the process on the properties is discussed. Thus developed nano composite is studied for the effect of weight percentage addition of nano H-BN particle on the bulk and surface properties. Mechanical testing and advanced characterization methods are used to study the effect of the nano H-BN addition to the matrix material and to evaluate the composite for its suitability as a potential friction material used in strategic sectors. It has been inferred that the presence of nano H-BN have improved the bulk and surface properties. Further, it has been established that the powder metallurgy route has some favorable results when compared to squeeze casting in terms of certain properties. Thus fabricated composites were subjected to laser shock peening process to study its impact on the surface and wear characteristics. The 0.6 wt% H-BN reinforced composites fabricated separately by Powder metallurgy and Squeeze casting method are exposed to laser shock peening process and it was inferred that there is a significant improvement on the surface and wear properties when compared to normal specimen.

A Systematic Material Design Approach to Develop Self-Lubricating Ceramic-Composite Tool Inserts for Dry Cutting Conditions

A systematic approach is the focus of the current work in order to design and develop ceramic composites for cutting tool inserts with a balanced combination of structural and thermal properties together with enhanced antifriction characteristics. In the material design stage, various combinations of ceramic materials and inclusions with optimum self-lubricating attributes are selected based on predictions of mechanical and thermal properties using in-house built codes. A mean-field homogenization scheme is used to predict the constitutive behavior while J-integral based fracture toughness model is used to predict the effective fracture toughness of the ceramic composites. An effective medium approximation is used to predict the potential optimum thermal properties. The current strategy incorporates thermal and structural properties of composites as a constraint on the design process together with self-lubrication property. Among various metallic and carbon-based fillers, silicon carbide (SiC) together with titanium oxide (TiO2) and graphite are found the most suitable candidate fillers in alumina (Al2O3) matrix to produce cutting inserts with best combinations of thermal, structural and tribological properties. As a validation, various combinations of Al2O3-SiC-TiO2 and Al2O3-SiC-TiO2 composites are developed in line with the designed range of filler size and volume fraction using Spark Plasma Sintering (SPS) process to complement the material design.

Ionic Liquid As Cutting Fluid Additive Using Minimum Quantity Lubricant (MQL) in Titanium-Ceramic Contact

Titanium alloys have a wide range of application in the field of automotive, biomedical and the civil industry due to its excellent material properties such as high thermal resistance, high load bearing capacity and high corrosion resistance. However, the high cost of machining titanium limits its application in aerospace and shipbuilding industry. Minimum quantity lubrication (MQL) has emerged as a new lubrication technique to achieve sustainable and profitable machining, but multiple studies show that conventional cutting fluid in MQL is not sufficient to reduce the friction and the associated effects. Recently, ionic liquids have shown a great potential in reducing the friction and wear of materials in contact. This study focuses on using an environment-friendly protic ionic liquid (PIL) tri-[bis (2-hydroxyethylammonium)] citrate (DCi) as an additive to a biodegradable oil (BO) used as lubricant in a ball-on-flat reciprocating tribometer in the titanium-ceramic contact at three different frequencies (3Hz, 4Hz and 5 Hz) under different loads. Results show a maximum 50% reduction in friction coefficient and 23% wear reduction at a frequency of 5 Hz under a normal load of 2 N by using 1 wt% DCi as an additive to BO as compared to using neat BO as the lubricant.

Design of a Deformable Smart Tire Using Soft Actuator

The unique functional properties of nickel-titanium Shape Memory Alloys (SMA) enable them to be used as actuators. This research paper demonstrates theoretically and experimentally the feasibility of using SMA in smart tires for a mobile robot. The design procedure for SMA as a coil spring actuator for a soft deformable wheel is described. The primary focus is the mechanical modeling, manufacturing, and system dynamics of a soft deformable wheel. The 3D printed soft tire exploits the capabilities of the SMA actuation using a voltage signal. The printed components are activated and integrated with electromechanical circuit for wireless communication system. The performance of the force feedback control system is evaluated at different operating conditions to demonstrate the shape-changing characteristic of the smart tire. The developed prototype is designed to propel forward and backward on flat and uneven surface. The experimental results obtained demonstrate the potential of SMA as soft actuators, its benefits and limitations as flexible systems.

Influence of the Applied Load on the Creep Behaviour of Tin-Silver-Copper Solder

During the life cycle of an electronic printed circuit boards (PCBs), the cold solder joints formation between the component and PCB are a failure mode that happen commonly. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. In this way, once as fatigue life decreases with increasing plastic strain, it is important to study creep occurrence, especially during thermal cycles. In this work, a dynamic mechanical analyser (DMA) was used to study the influence of different applied load and temperature on the creep behaviour of the solder during a sequence of cycles. For these tests, different SAC405 alloy samples were produced, all in the same processing conditions. Creep tests were made on three-point-bending clamp configuration, isothermally at 303, 323 and 348 K, under three separate applied load of 3, 5 and 9 MPa. The results show that creep rate has an important decrease from the 1st to the following applied creep cycles. This behaviour occurs for all the tested loads and temperatures. Results, also, show that the main creep mechanisms changes, from a diffusion base type, for low load and different temperatures, to a dislocation glide-climb type for an applied load of 9 MPa and temperatures from 303 to 348 K. Experimental determined n exponent for the tested conditions allows the correlation between creep mechanisms and experimental parameters (applied load and temperature).

Investigating Density Functional Theory’s Effectiveness in Studying Metal-Organic Frameworks Structures

In combatting human induced climate change, carbon capture provides the potential to more slowly ease away from the dependence on hydrocarbon fuel sources, while mitigating the amount of CO2 released into the atmosphere. One promising material to use is metal-organic frameworks (MOF’s). MOF’s offer an immense variety in potential exceptionally porous structures, a property important in separation. As a result of practical experimental measurements being expensive and time consuming, interest in accomplishing the same goal through modeling has also increased. Using density functional theory to optimize the approximate experimentally measured atomic geometries has been shown to have sufficient accuracy. A previous study by Nazarian et al. was performed to optimize structures on the CoRE MOF Database using a supercomputer. The purpose of this study was to attempt to replicate their work done with a single MOF using computational resources more commonly available. Furthermore, as time tends to be the limiting factor in conducting these studies, the use of a smearing function was adjusted for two optimizations to see if any considerable improvement on the efficiency of the optimizations could be made. Our results show both optimizations improved the bond length accuracy relative to the raw data compared with the optimization from Nazarian, et al. The optimization with a more present smearing effect was able to converge the electron field in roughly half the time, while still showing nearly the same results, except for slightly more variability in the bond lengths involving transition metals. Unfortunately, the improvement in bond length, did not correspond in consistent improvement of the larger cell defining metrics. This shows that either a different energy minimum was found or the relationship between the larger cell parameters, with the more local parameters such as bond length is too complex for the method to effectively solve.