Variation Of Mechanical Characteristics Research Articles

Effects of Graphene Reinforcement on Static Bending, Free Vibration, and Torsion of Wind Turbine Blades.

Renewable energy markets, particularly wind energy, have experienced remarkable growth, predominantly driven by the urgent need for decarbonization in the face of accelerating global warming. As the wind energy sector expands and turbines increase in size, there is a growing demand for advanced composite materials that offer both high strength and low density. Among these materials, graphene stands out for its excellent mechanical properties and low density. Incorporating graphene reinforcement into wind turbine blades has the potential to enhance generation efficiency and reduce the construction costs of foundation structures. As a pilot study of graphene reinforcement on wind turbine blades, this study aims to investigate the variations of mechanical characteristics and weights between traditional fiberglass-based blades and those reinforced with graphene platelets (GPLs). A finite element model of the SNL 61.5 m horizontal wind turbine blade is used and validated by comparing the analysis results with those presented in the existing literature. Case studies are conducted to explore the effects of graphene reinforcement on wind turbine blades in terms of mechanical characteristics, such as free vibration, bending, and torsional deformation. Furthermore, the masses and fabrication costs are compared among fiberglass, CNTRC, and GPLRC-based wind turbine blades. Finally, the results obtained from this study demonstrate the effectiveness of graphene reinforcement on wind turbine blades in terms of both their mechanical performance and weight reduction.

Multi-stimuli-responsive Hydrogels for Therapeutic Systems: An Overview on Emerging Materials, Devices, and Drugs.

The rising interest in hydrogels nowadays is due to their usefulness in physiological conditions as multi-stimuli-responsive hydrogels. To reply to the prearranged stimuli, including chemical triggers, light, magnetic field, electric field, ionic strength, temperature, pH, and glucose levels, dual/multi-stimuli-sensitive gels/hydrogels display controllable variations in mechanical characteristics and swelling. Recent attention has focused on injectable hydrogel-based drug delivery systems (DDS) because of its promise to offer regulated, controlled, and targeted medication release to the tumor site. These technologies have great potential to improve treatment outcomes and lessen side effects from prolonged chemotherapy exposure.

Effects of Weld Heat Input on Mechanical Characteristics of Low Carbon Sheet Steels

This study focuses on examining the variation in mechanical characteristics of low-carbon sheet steels when they are subjected to heat input from Tungsten Inert Gas (TIG) welding. The weld heat input parameters, such as welding speed and current, were controlled through the TIG welding process. A finite element analysis was performed to evaluate the couple field thermomechanical effects of the weld heat line, using the Gauss heat flux approach for thermal heat variation across the weld heat-affected zone. The numerical study yielded results for weld heat-affected deflection, residual stress, and modal analysis through the finite element model. It was found that the ductility decreased and hardness increased in the fusion zone, as a function of weld current and speed. The residual stresses and their zone of influence, as determined by weld line parameters, were found to be key factors affecting deflection and natural frequencies in structural aspects of low carbon sheet steels.

Evolution of microstructure and mechanical characteristics of friction stir welded ultrafine‐grained aluminum alloy 6082

AbstractBulk production of ultrafine‐grained material is in great demand presently. Ultrafine‐grained material can be synthesized using accumulative roll bonding, which is a prominent severe plastic deformation technique to develop such materials in bulk. There are further challenges in the fabrication of ultrafine‐grained material. Friction stir welding is a potential technique to join the ultrafine‐grained material while maintaining its mechanical and microstructural characteristics stability as no fusion is required. The present research work demonstrates the microstructural and mechanical characteristics of various welding zone after friction stir welding of ultrafine‐grained aluminum alloy 6082. The microstructural features were examined using optical microscopy and the electron back‐scattered diffraction technique. The variation in mechanical characteristics was observed using tensile and microhardness tests. The fractography of tensile specimens was studied to identify the mode of failure. The present study demonstrates the viability of friction stir welding to join ultrafine‐grained aluminum alloy 6082 developed by accumulative roll bonding. The ultrafine grain size of 0.52 μm was achieved after four accumulative roll bonding cycles. The microhardness of accumulative roll bonding processed samples and the tensile strength of the weld joint were increased about two times and 1.6 times respectively compared to the annealed sample.

Mechanical characteristics analysis of horizontal lifting of subsea pipeline with different burial depths

Different burial depths have different effects on the mechanical characteristics of the horizontal lifting of subsea pipelines. With the consideration of the soil resistance to subsea pipelines, combined with the specific sea condition parameters of a certain sea area, and based on the lumped mass method, the subsea pipeline is discretized into a lumped mass model, the dynamic analysis model of the three-point horizontal lifting of subsea pipelines with different burial depths is established. The stress and bending of the pipelines with different burial depths are analyzed. The calculation results with different burial depths are compared. The variation of mechanical characteristics of the process of lifting horizontal pipelines with different buried depths is obtained. The results show that the change of burial depth has a significant influence on the effective tension of the pipeline. With the increase of the burial depth, the maximum degree of stretching of the pipeline first decreases and then increases. Within a certain depth range, burying the pipeline in the seabed can reduce both the effective tension and the intensity of the fluctuation of the effective tension when the pipeline is lifted. The change of burial depths for the shear action is mainly reflected in the numerical values of the shear force. There is no significant impact on the degree and variation fluctuation of the shear force. The conclusions can provide a certain theoretical reference for the design of the process of horizontal pipeline lifting.

Compound influence of topological defects and heteroatomic inclusions on the mechanical properties of SWCNTs

Abstract The utility of carbon nanotubes as the reinforcement agents in polymer and metal matrix composites has opened up a new avenue in the development of novel composite materials with exceptional strength and stiffness to weight ratios. Such exploitation of superior mechanical properties of carbon nanotubes depends on their inherent irregularities and structural integration. The nanotubular structures of carbon are prone to topological defects and heteroatom dopants due to the inevitable complexities in nano-synthesis. The objective of this article is to quantify the compound influence of such inherent structural irregularities (such as single vacancy defects and nanopores) and foreign atom inclusions (such as nitrogen and boron atoms) on the mechanical characteristics (like constitutive relation, fracture strength, failure strain and Young’s moduli) of single-walled carbon nanotubes (SWCNT) under various multi-physical influences (such as temperature, strain rate, diameter and chirality) based on molecular dynamics (MD) simulations. The current investigation also includes a detailed analysis on the variation in mechanical characteristics of CNTs under different spatial distributions of defects and doping.

Mechanical Characteristics and Optimum Design of SMW Construction Method for a Comprehensive Pipe Gallery in a Water-Rich Weak Stratum

The K0+080-K0+275 bid section of the underground comprehensive pipe corridor on Wanxin Road in Binhai New City located in Fuzhou was considered in this work. The mechanical properties and optimal design of the soil mixing wall (SMW) construction method piles (steel-cement mixing piles) in the comprehensive pipe corridor in the water-rich, weak stratum were studied. In the K0+080-K0+275 bid section of the comprehensive pipe gallery, different construction parameters of the steel-cement-soil mixing piles were tested through pile tests. The construction parameters of the SMW construction piles were as follows: water-cement ratio of 1.3 and cement content of 20%. The finite element software MIDAS-GTS NX was used to establish a mechanical model of the SMW construction method piles. The variations in mechanical characteristics, such as the horizontal displacement of SMW construction method piles under different supporting pile diameters, steel layouts, steel sizes, and supporting axial forces, were analyzed. The optimal design of the SMW construction method piles was also determined. Results revealed that when the pile diameter of the SMW construction method increased from 0.55 m to 0.85 m, the horizontal displacement of the pile body decreased by 28.9%. The horizontal displacement of the pile body could be effectively controlled by increasing the pile diameter. Increasing the size of the flange and web of the section steel had little effect on the deformation of the foundation pit. The flange was sensitive to the deformation of the supporting structure because it was on the stressed side. The different layout forms of the steel section exerted a great influence on the deformation of the foundation pit. The maximum horizontal displacement of the pile body for the type of steel close insertion was 18.4% less than that for the plug-one-jump-one insertion type. Increasing the supporting pre-added axial force effectively reduced the deformation of the envelope structure, and adopting the value of 50%-80% of the designed axial force was reasonable. The K0+080-K0+275 bid section of the Wanxin Road underground comprehensive corridor was determined to be supported by φ650@450 cement-soil five-axis mixing pile interpolated with HM500×300×11×18 section steel, and the layout of the section steel adopts the plug-one-hop-one type. The on-site monitoring data of the optimal construction plan were in accordance with the change law of the numerical simulation and were successfully used in the underground comprehensive pipe corridor project. Ideal results were achieved.

Energetic analysis of fatigue hysteresis by thermographic and digital image correlation methodologies

AbstractA hysteresis cycle can define the variation in mechanical characteristics of fatigue life and failure response. Traditional analysis is performed using force‐displacement signals derived from the testing equipment, but this approach is prone to large errors due to clearances and slips in the measuring chain. For this reason, the authors here propose a novel setup able to assess accurately the strain status of specimens by digital image correlation (DIC) and a procedure to calculate the hysteresis energy by thermographic analysis in order to measure the damping energy with precision. The results obtained by an experimental investigation on a common austenitic steel (AISI 304) highlight that the hysteresis areas defined by the DIC displacements, and those found by the testing machine outputs have substantial differences in value. The thermal variations and the areas of the hysteresis loops, both linked to the plastic energy, were also compared, showing a reliable correlation.

Variation of Mechanical Characteristics of Polyurethane Foam: Effect of Test Method.

Polyurethane foam (PUF), a representative insulation material, not only prevents heat conduction but can also support a load. Particular interest in rigid PUF proliferated over the past several years in fields where extreme environments are applied. A closed-cell structure which forms the interior of rigid PUF serves to maximize the utilization of these polymeric foams. Rigid PUF is more sensitive to external conditions such as temperature or restraint than other structural materials such as steel. Depending on the market trends in which utilization of a cryogenic environment is expanding, the tendency of material behavior resulting from the binding effect also needs to be investigated. However, most conventional compression test method standards applicable to rigid PUF do not adequately reflect the restraints. Therefore, this study proposes a method for evaluating the mechanical performance of materials in a more reliable manner than that of conventional tests. Experimental observation and analysis validated this compression evaluation method in which constraints are considered. Consequently, the compressive strength of rigid PUF compared to the results of the conventional test showed a difference of up to 0.47 MPa (approximately 23%) at cryogenic temperatures. This result suggests that there are important factors to consider when assessing performance from a material perspective in an environment where rigid PUF insulation is utilized. It is believed that the test methods newly proposed in this study will provide an experimental framework that can be applied to the evaluation criteria of material properties and reflected in structural design.

UDM processed superior acrylic resin based ZrO2 nanoparticle reinforced composite for dental application

Acrylic based ZrO2 nanoparticle reinforced composite has been studied to improve its properties for biomedical dental application. Practically cluster free ZrO2 nanoparticles have been homogeneously introduced into the acrylic resin (PMMA) at varying amount of 5–15 wt% by ultrasonic dual mixing. The cluster size and distribution of ZrO2 nanoparticles in PMMA matrix have been studied using filed emission scanning electron microscopy (FESEM) analysis on the PMMA composites containing different amount of nano powder. The EDAX analysis of the PMMA composites confirms the presence of different amount of ZrO2 in the matrix. Viscoelastic properties of the ZrO2-PMMA composite have been studied with the help of dynamic mechanical analyzer in terms of storage modulus and tanδ value and variation in mechanical characteristics of the matrix as a function of particle reinforcement has been studied by its fractographic analysis. Particle-matrix bonding in the composite has been studied by FTIR analysis. Degradation temperature of the composite has been identified using thermogravimetric analysis (TGA). Hardness of the ZrO2-PMMA nano filler composites has been studied using micro hardness tester. The ZrO2-PMMA composite with 10 wt% reinforcement of particle produced best results in the response of storage modulus enhancement (35% at 35 °C) and glass temperature (23%). PMMA composites with 10 wt% ZrO2 also shown considerable improvement in TGA and hardness.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ДЛЯ КОМПЬЮТЕРНОЙ ОБРАБОТКИ СКАНИРОВАНИЯ ТВЕРДЫХ ДЕФОРМИРУЕМЫХ ТЕЛ ПРИ ПОСТРОЕНИИ И АНАЛИЗЕ ИХ КОНЕЧНО-ЭЛЕМЕНТНЫХ МОДЕЛЕЙ

PURPOSE. The modern practice of engineering calculations of part material strength uses averaged mechanical characteristics obtained through the standard tests of samples. In real conditions, it is strongly advised to avoid this averaging in order to minimize the errors when constructing the mathematical models of deformable solids using a finite element method. METHODS. In this paper, we propose a new approach based on the scanning of deformable solids using computed tomography. However, a series problem hinders the implementation of this approach: accurate identification of the scanned deformable solid relative to a real object by geometry and mechanical properties of material require an extremely large amount of data (information). RESULTS AND THEIR DISCUSSION. This problem is solved through the use of mathematical modeling and an algorithm for processing bitmap images of deformable solid sections enabling to construct the variations of mechanical characteristics of its material and geometry. The key algorithm of the presented mathematical modeling is the use of pixel characteristics of computed tomography images. Also, the necessary component of the algorithm is the use of data obtained via full-scale testing of samples. Assuming the wide use of computed tomography for medical purposes the fragments of human femur and jaw have been chosen as the objects of the study. This choice is determined by the specificity of their geometry and explicit heterogeneity of the bone material. CONCLUSION. A finite element model of a deformable solid with a real distribution of mechanical characteristics of material and individual geometry has been developed. The stress-strain state has been analyzed on the basis of the model.

Circumferential variation in mechanical characteristics of porcine descending aorta

Arterial characterization of healthy descending thoracic aorta (DTA) is indispensable in determining stress distributions across wall thickness and different regions that may be responsible for aorta inhomogeneous dilation, rupture, and dissection when aneurysm occurs. Few studies have shown the inhomogeneity of DTA along the aorta tree considering changes in circumferential direction. The present study aims to clarify the circumferential regional characterization of DTA. Porcine DTA tissues were tested according to region and orientation using uniaxial tension. For axial test, results show that the difference in circumferential direction was mainly in collagen fiber modulus, where the anterior collagen fiber modulus was significantly lower than the posterior quadrant. For circumferential test, the difference in circumferential direction was mainly in the recruitment parameter, where the circumferential stiffness is significantly higher in the posterior region at physiological maximum stress. The proximal posterior quadrant and left quadrant showed significantly lower axial collagen fiber stiffness than the right and anterior quadrants, which may be a factor in aneurysm development. Furthermore, the constitutive parameters for similar detailed regions can be used by biomedical engineers to investigate improved therapies and thoroughly understand the initial stage of aneurysm development. The regional collagen fiber modulus can help improve our understanding of the mechanisms of arterial dilation and aortic dissection.

Analysis of Sampled-data Open-loop Characteristics on Magnetic-Head Positioning System in HDDs

Abstract In the magnetic-head positioning system in hard disk drives (HDDs), it is hard to analyze the effect of mechanical resonances beyond the Nyquist frequency after the HDDs were assembled. However, unexpected variations of mechanical characteristics often happen in actual HDDs because HHDs are mass-produced products. To solve such a problem, this paper proposed the analysis method of the sensitivity characteristics including the intersampling oscillations for the magnetic-head positioning control system of HDDs. This method enables us to analyze the performance of the magnetic-head positioning control system beyond the Nyquist frequency by using measurable open-loop characteristics. To show the validity of the proposed method, this study conducted simulation analyses on the magnetic-head positioning control system. The simulation results show that proposed sensitivity characteristics are good approximated solutions.

Variation of Mechanical Characteristics and Microstructural Evolution in AISI 316 Austenitic Stainless Steel Subjected to Long-Term Thermal Aging at Elevated Temperature*

The objective of this study was to investigate the mechanical degradation of AISI 316 austenite stainless steel as light-water reactor pressure vessel materials in the primary system of nuclear power plants. The influences of long-term aging on the microstructural and mechanical characteristics were studied. The long-term aging tests were interrupted at various stages to obtain different levels of degraded specimens. The test specimens were heat-treated and exposed to an acceleration heat-treatment at 600°C for up to 10,000 hours. AISI 316 steel showed polygonalshaped grains with many annealing twins, and these tended to become gradually more circularshaped grains during long-term aging. In the initial material degradation, twins were distributed uniformly within most grains, but they all recovered and disappeared after a prolonged 10,000-hour aging time. Delta ferrite along austenitic grain boundaries transformed into sigma phases and Cr23C6 precipitates during long-term aging, and the area fraction on the grain boundary increased. The peak strength appeared at a 100-hour aging time and then decreased up to 1000 hours. With further aging time, the strength increased to a higher level than the initial state. However, the elongation and toughness decreased continuously, demonstrating the material embrittlement during long-term thermal aging.

Structural and mechanical stability of the nano-crystalline Ni–Ti (50.9 at.% Ni) shape memory alloy during short-term heat treatments

In this study, the nano-crystalline Nitinol (50.9 at.% Ni) was prepared by 40% cold deformation. Subsequently it was subjected to 15-min-heat treatments at 300–550 °C. Changes of the structure and mechanical properties were studied by transmission electron microscopy, micro X-ray diffraction, differential scanning calorimetry, Vickers hardness measurements, tensile and bend-type fatigue testing. It was shown that the cold drawn material contains textured nano-crystalline B2 grains of 50 nm in thickness and a high concentration of lattice defects. Its tensile strength, hardness and fatigue life were 1521 MPa, 421 HV0.05 and 2435 bending cycles to fracture, respectively. After heat-treatment up to 450 °C/15 min the material underwent Ni4Ti3 precipitation and partial recovery processes. Heat-treatments at above 450 °C induced recrystallization, grain and precipitate growth. Hardness and fatigue lives showed maxima of 692 HV0.05 and 5883 cycles, respectively, after heat-treatments at 450 °C/15 min. In contrast, both tensile strength and B2 → B19′ transformation stress decreased with increasing heat-treatment temperature, but a decrease of the tensile strength after heat-treatments at 300–450 °C was slow (tensile strength after heat-treatment at 450 °C/15 min was 1486 MPa). The observed variations of mechanical characteristics were discussed in relation to structural changes observed.

Effect of moisture content on the mechanical characteristics of rammed earth

Abstract In this paper, influence of moisture content on the mechanical characteristics of rammed-earth has been studied. Samples from different soils (sandy, clayey, stabilised) were manufactured and tested in unconfined compression at several moisture contents. Compressive strength, elastic modulus and Poisson's ratio were determined. A simplified method to measure the suction within rammed earth samples has been developed and validated. The variation of mechanical characteristics related to moisture content and suction are presented. This paper shows that a slight increase in the moisture content of dry rammed-earth is not followed by sudden drop in wall strength. Qualitative explanations at the nano-scale are presented.

Structure and mechanical characteristics of preliminarily deformed welded joints of the 40KKhNM alloy

The results of investigating the structural state and the variation in mechanical characteristics during the static and cyclic loading of deformed welded joints of the 40KKhNM alloy are presented. It is shown that quenching eliminates structural-and-mechanical nonuniformity. The formation of ɛ martensite can introduce an essential contribution to alloy hardening because of the development of the γ → ɛ transformation during tensile static deformation. It is established that the fatigue characteristics vary insignificantly depending on the degree of preliminary deformation. Production modes that provide the maximal fatigue strength with a minimal accumulation intensity of cyclic damages of welded joints are determined.

Influence Mechanism of Grouting on Mechanical Characteristics of Rock Mass

Grouting technology has been widely used in all fields of geotechnical and civil engineering. Prospective engineering objectives including reinforcement of rock mass and groundwater leakage treatment can be achieved by grouting which will change the mechanical parameters of rock mass such as strength, elastic modulus, and coefficient of permeability. In this paper, rock mass is assumed as a composite material consisting of rock particles and random microcracks initially. Since part or all of the cracks will be filled with cement slurry after grouting, rock mass consists of rock particles, grout condensate, and some or no random microcracks after grouting. The damage constitutional law of the mesoscopic element is established based on the theory of mesoscopic damage mechanics. With the heterogeneity of the components of rock mass considered, the variation of mechanical characteristics of rock mass is studied before and after grouting. And the influence mechanism of grouting on rock mass is investigated at mesoscale level.

Mechanical properties with high temperature and the microstructure of carbon/phenolic ablative composites

Carbon fiber reinforced phenolic based composites were prepared by laminating molding. The variation in mechanical characteristics of composites was evaluated with heating temperature and procedure. The microstructures of composites at different temperatures were observed by optical microscope and scanning electron microscope, respectively. The results showed that the main weight loss range of carbon/phenolic is from 300 to 800 °, before 700 ° the weight loss was resulted from pyrolysis and after that the weight loss was mainly by oxidation in the fiber phase; with the heat treatment temperature rising, the bonding at the interface of carbon fibers and resin matrix weakened; in the pyrolysis temperature range, the interlaminar shear strength(ILSS) of carbon/phenolic showed a rapid drop with temperature rising, and then decrease in the rate of ILSS became relatively slower; the fiber oxidation had little influence on the ILSS.

A study of optimization of injection molding process parameters for SGF and PTFE reinforced PC composites using neural network and response surface methodology

This study analyzed variations of mechanical characteristics that depend on the injection molding techniques during the blending of short glass fiber and polytetrafluoroethylene reinforced polycarbonate composites. A hybrid method including back-propagation neural network (BPNN), genetic algorithm (GA), and response surface methodology (RSM) are proposed to determine an optimal parameter setting of the injection molding process. The specimens are prepared under different injection molding processing conditions based on a Taguchi orthogonal array table. The results of 18 experimental runs were utilized to train the BPNN predicting ultimate strength, flexural strength, and impact resistance. Simultaneously, the RSM and GA approaches were individually applied to search for an optimal setting. In addition, the analysis of variance was implemented to identify significant factors for the injection molding process parameters and the result of BPNN integrating GA was also compared with RSM approach. The results show that the RSM and BPNN/GA methods are both effective tools for the optimization of injection molding process parameters.