Preliminary Experimental Investigation Research Articles

A preliminary experimental investigation on the biotribocorrosion of a metal-on-polyethylene hip prosthesis in a hip simulator

Corrosion at the taper/trunnion interface of total hip replacement (THR) often results in severe complications. However, the underlying mechanisms of biotribocorrosion at the taper/trunnion interface during the long-term walking gait cycles remain to be fully understood. In this study, a hip joint simulator was therefore instrumented with an electrochemical cell for in-situ monitoring of the tribocorrosion evolution in a metal-on-polyethylene (MoP) THR during a typical long-term walking gait. In addition, the biotribocorrosion mechanism was investigated via surface and chemical characterizations. The experimental results confirmed that the taper/trunnion interface dominated the contemporary MoP hip joint corrosion. Three cyclic variations in the open circuit potential (OCP) were observed throughout the long-term electrochemical measurements, attributed to the formation and disruption of the adsorbed protein layer. The corrosion exhibited an initial increase at each period, peaking at approximately 0.125 million cycles, followed by a subsequent gradual reduction. Surface and chemical analyses revealed the formation of a tribochemical reaction layer (tribolayer) on the worn surface of the taper/trunnion interface. The surface/chemical characterizations and the electrochemical measurements indicated that the adhesion force of the adsorbed protein layer was weaker than that of the tribolayer. In contrast, the opposite was true for the corrosion resistance. Based on the observations from this study, the tribocorrosion mechanism of the taper/trunnion interface under the long-term walking gait cycles is deduced.

Development of a novel magnet system for a 1 kg Planck balance

Abstract The following paper presents the development of a novel magnet system for use in a 1 kg Planck balance. For this purpose, several preliminary theoretical and experimental investigations were carried out and an optimized prototype magnetic system was modeled, designed and built based on the results. Initial measurements showed that the magnet system with an outer diameter of 104mm and a height of 50mm achieved a constant average value of 85.25NA−1 at a range of motion of ±0.6mm.

Modeling nonequilibrium thermoviscoelastic material behaviors of glass in nonisothermal glass molding

AbstractNonisothermal glass molding (NGM) is developed aiming to satisfy the fabrication of complex and precision optical elements at high production volumes. The technology, however, was encountered by the high form deviation of manufactured glass optics. During the nonisothermal compression molding, glass undergoes a rapid temperature change making it a transition from equilibrium to nonequilibrium nature of matter. Owing to this characteristic, viscoelastic material behaviors of glass depend on not only temperature but also thermal history. Understanding the nature of nonequilibrium thermoviscoelasticity, the central importance to control the final shape and optical characteristics of the manufactured glass optics is the focus of this research. First, this study presents preliminary experimental investigations indicating the difference in viscoelastic deformation responses under the equilibrated and nonequilibrated glass specimens. In the following, modeling the temperature‐dependent viscoelasticity over a wide temperature range in glass transition region is described, where temperature is directly coupled in each parameter of a rheological constitutive model. This concept allows us to bypass the thermorheologically simple assumption used to tolerate the description of thermoviscoelastic responses in most of the earlier works. Finally, we propose a modeling method that incorporates temperature and thermal history into the rheological model parameters, each of which is described by employing the Mauro–Allan–Potuzak viscosity equation. Viscoelastic experiments were carried out to validate the model. The results show that the time‐dependent responses varying with temperature are well predicted in both equilibrium and nonequilibrium regimes of glass‐forming systems. The benefit of this research is that a unique material model is entirely applicable for numerical studies of various hot forming processes such as annealing when glass undergoes pure thermal loads, as well as precision glass molding and NGM when glass is deformed by fully coupled thermal–mechanical loads under either its equilibrium or nonequilibrium state of materials, respectively.

Natural Rubber Latex for Improving Ductility Characteristics of Soil: A Preliminary Experimental Investigation

Natural Rubber Latex for Improving Ductility Characteristics of Soil: A Preliminary Experimental Investigation

Seismic performance of self-centering beam-column joints reinforced with superelastic shape memory alloy bars and engineering cementitious composites materials

This paper presents a preliminary experimental investigation of a self-centering beam-column joint reinforced with superelastic Ni-Ti SMA bars and ECC materials. As an alternative to the longitudinal bars in the beam plastic hinge, SMA is used to reduce the residual deformations and dissipate energy, whereas the ECC materials used in the critical region of the joints can improve the ductility of the structural member. Five 1/2 scale frame joints were designed and manufactured. The failure phenomenon, bearing capacity, energy dissipation capacity, displacement ductility, residual deformation, and self-centering performance of the joints were comparatively analyzed through a low cyclic loading experiment. A finite element model of SMA-ECC joints was established, and the influence of the SMA and ECC on the seismic behavior of the joints was investigated. The study results show that SMA bars can dramatically enhance their self-centering capability, enabling self-retrofitting damage. The ECC material is helpful for optimizing the development of the plastic hinge at the end of the beam and improving the ductility and energy dissipation capacity of the structure. The SMA-ECC composite materials exhibit good supplement to significantly improve the ductility, energy dissipation, and self-centering capabilities and delay the stiffness degradation of the structure under extreme events.

Preliminary Experimental Investigation of Loading Sequence Effects on Low-Cycle Bending Fatigue

AbstractBending fatigue, as one of the impact factors to reduce a metal’s service life, could play a critical role in fatigue life estimation of aerospace components and civil infrastructures, such...

Development of a Compact Multivariable Sensor Probe for Two-Phase Detection in High Temperature PbLi–argon Vertical Columns

Liquid gas two phase flow is a common occurrence in various industrial applications. For nuclear fusion applications with a Li based breeder, existence of two phase flow may lead to critical issues including decreased tritium breeding ratio, generation of hot spots and improper nuclear shielding. Additionally, a very large density ratio of liquid metal to gas mandates relevant experiments towards development and validation of software tools. PbLi has gained immense focus for its various advantages and is utilized in several breeding blanket concepts. In view of above mentioned requirements, a two phase detection tool is imperative for liquid PbLi environment. For liquid metal applications, electrical conductivity based probes are most suitable in terms of ruggedness, fabrication ease and operational simplicity. However, corrosive nature and high operational temperature for PbLi put severe demands on electrical insulation, a foremost requirement for electrical conductivity based schemes. In this study, a multivariable probe based on electrical conductivity and temperature measurement schemes is developed using Al2O3 coating as electrical insulation. Developed probe is validated in PbLi/Ar vertical column with bulk PbLi temperature upto 400 degC and time averaged void fraction upto 0.95 covering flow regimes from dispersed bubbly flow upto in box loss of coolant accident. Developed probe provides high reliability and excellent temporal resolution towards individual bubble detection through electrical conductivity based principle alongwith simultaneous two phase temperature trends. Present paper provides details about sensor probe fabrication, calibration, two phase test facility, void fraction estimations, bubble frequency and bubble residence time estimations alongwith critical observations from preliminary experimental investigations.

Far-field pressure measurements of elliptic jets discharged close to a wing

This paper presents a preliminary experimental investigation into the acoustics of two elliptical jet nozzles installed close to a wing model. Acoustic pressure data is obtained for a range of observer polar angles mounted in the far field of the jets. Three nominal jet Mach numbers, namely 0.4, 0.6 and 0.8 are studied. Results suggest that the elliptic jets surveyed provide a noise reduction of the jet-surface installation noise source. The noise reduction is maximum in the forward arc and in the order of 1 dB for the fully-corrected overall sound pressure level data. Additionally, the noise benefit exists only when the minor axis of the elliptical nozzle is mounted parallel to the wing trailing edge. It is hypothesised that the reduction in the jet plume cross-section width limits the scattering of the near pressure field by the wing trailing edge to a lower frequency range. The jet mixing noise source, however, is seen to increase with decreasing nozzle exit-plane aspect ratio. The three jet velocities surveyed suggest the consistency of the key results discussed in the paper. Investigation of the jet turbulent flow structures and jet near pressure field is under way.

Investigation of engineering properties of sun-dried bottom ash based eco clay blocks

Eco blocks can be produced by using engineering and agricultural wastes to protect ecology. Thermal power plant wastes namely fly ash and bottom ash will be a major predicament for the environment Arenas et al. (2013) [1], Aggarwal et al. (2007) [2], Datta et al. (2019) [8]. So globally, research work is being focused to find various options for using these waste materials, and making use of them in the construction industry is one of the effective methods of exploitation. In India, presently about 710 million tonnes of fly ash and bottom ash are generated every year. India's coal consumption gives two-thirds of electricity generation with 35% fly ash in India. Cement's fly ash requirement is about 151 MT will be required in 2030, but 128MT of fly ash will be remaining as unutilized. This needs an additional 2300 ha of land and 1.30 billion cubic meters of water for ash ponds exacerbates the problems of disposal of fly ash only. Bottom ash about 60MT disposal will make us miserable Asokan et al. (2005) [3]. Making use of bottom ash in equal proportion to fly ash is done in this research. A small proportion of the Natural clay has been used as a significant proportion. Coconut shells collected locally were used as reinforcing materials. The preliminary experimental investigation was done to observe the effect of fly ash, bottom ash and clay as partial replacement of cement to act as supplementary cementitious material. The compressive strength at 28 days of testing revealed that a replacement of 15% of clay, bottom ash and fly ash with equal proportions has achieved the optimum strength.

Preliminary Experimental Investigation of the Design-Overloaded Stage in Two-Stage Axial Turbine Test Rig

The article deals with the issue of experimental research of the so-called design overloaded stage. A new experimental device enabling measurements on two-stage axial turbine is advantageously used in this research task. The experimental setup is designed so that a preparatory stage is included in front of the examined stage. The stage design introduces some aerodynamic overload already in the flow path design phase. This research program is focused primarily on the effect of leakage flows and their mixing with the mainstream. This paper describes the verification measurements on a newly introduced two-stage arrangement and reveals the first data obtained.

A PRELIMINARY EXPERIMENTAL INVESTIGATION INTO AMMONIA OXIDATION IN A FIXED-BED

This paper reports the findings of a preliminary experimental investigation into NH3 oxidation in a quartz fixed-bed reactor. The reactor was filled with quartz sand of a size fraction of 1.0 ~ 2.0 mm to a bed height of 430 mm. NH3 and O2 were diluted with Ar, mixed and passed through the reactor at a constant total gas flowrate of 818 mL·min-1. The experiments were carried out at various reaction temperatures between 700 and 1450 K, corresponding to residence times ranging from 0.68 to 2.07 s and equivalence ratios of 0.5, 1.0, and 1.5. The reactor exit stream was sampled and analysed using a gas chromatograph (Shimadzu 2014) and an electrochemical analyser (Testo 340) for the concentrations of N2, O2, NO, and NO2. A set of comparative experiments without bed material (considered as an ‘empty bed reactor’) at identical residence times were also performed in order to appreciate the effect of quartz surface on NH3 oxidation and NOx formation. It was revealed that the lowest temperature to initiate noticeable NH3 oxidation was reduced from 1300-1350 K in the empty bed reactor, to 1050-1350 K in the quartz sand filled fixed-bed reactor. The presence of quartz sand significantly reduced NOx formation during NH3 oxidation. Additionally, the peak NO concentrations and the temperature to reach the peak were reduced from 578 to 191 ppm and ~1350 to ~1050 K, respectively. It is speculated that the active radicals such as NH* produced from the heterogeneous decomposition reaction of NH3 on the quartz surface may have promoted NH3 oxidation and NOx reduction.

Proposal and preliminary experimental investigation on a novel efficient integrated system of combined refrigeration, heating, and hot water supply

Poly-generation systems with high integration can meet various needs of users. Therefore, design and efficient operation have always been the focus of attention. In this paper, a novel multi-functional system with R410A as the working fluid is proposed. Cooling, heat, and hot water can be provided under five kinds of operation modes. The most prominent advantages of the system lie in the high integration of multiple functions and high effectiveness in the combined cooling/hot water mode. The feasibility of system integration and mode switching is firstly analyzed and validated. The variation regulations of determining variables and performance indicator, including compressor inlet and outlet pressure, valve opening, and coefficient of performance, are revealed based on the self-built experiment rig. Research results exhibit that, an increase in the water tank temperature can promote the compressor outlet pressure. The average difference of inlet pressure between water tank temperatures of 50 °C and 40 °C is 30 kPa, while that of outlet pressure is 611 kPa. The larger the charge amount, the smaller the valve opening. Besides, under typical operating conditions, the total COP of the combined refrigeration/hot water mode can reach up to 8.25, and it is 51% more efficient than that of the hot water mode.

Safety considerations for SPIcDER: Spacesuit integrated carbon nanotube dust ejection/removal system

This paper presents a multi-tier safe implementation of the Spacesuit Integrated Carbon Nanotube Dust Ejection/Removal (SPIcDER) system. SPIcDER mitigates dust contamination of spacesuits and flexible surfaces during surface exploration of Moon and Mars. SPIcDER has Carbon nanotube (CNT) fibers embedded within the spacesuit outerlayer. These are energized using high voltage, low power, Alternating Current (AC) signals (∼350–1000 V). Laboratory experiments show the time-varying electric fields produced by SPIcDER repel the dust.This system mitigates astronaut exposures to lunar dust, and protects spacesuits and flexible surfaces from dust abrasion, wear and tear, and reduction in thermal performance. The adherence of lunar dust, and its entry into the habitable volume of habitats/landers, which was a major problem during Apollo missions, is also minimized.In this study, we review the primary health and safety aspects of SPIcDER for astronauts operating in these spacesuits. Simulation using ANSYS Maxwell® and preliminary experimental investigations were performed to conduct safety analysis and provide recommendations for implementation of SPIcDER for lunar mission operations.

Laboratory tests of a prototypical user-centric radiant cooling solution

Radiant cooling systems are being increasingly promoted because of their energy efficient operation as well as their potential to improve occupants’ thermal comfort due to a draft-free cooling process. This paper focuses on a specific radiant cooling approach, which was introduced in previous contributions. This approach involves the positioning of relatively small-sized vertical radiant panels in the close proximity to occupants. Furthermore, the panels incorporate drainage systems or collection elements to accommodate, if needed, water vapour condensation. Consequently, the surface temperature of the radiant panels does not need to stay above the dew point temperature. We present the outcome of a preliminary experimental investigation of such a personal radiant cooling system. In this context, prototypical radiant panels were installed in a laboratory and multiple experiments were conducted. The uniformity level of the panels’ surface temperature distribution was documented. Moreover, near-panel air flow velocities were measured at several positions. Likewise, the formation of condensed water on panels was observed for different panel surface temperatures, room temperatures, and room humidity levels. The results of the preliminary laboratory investigation do not point to any risk of draft or turbulence discomfort.

Reinforced Concrete Slab with Added Steel Fibers for Engineering Application: Preliminary Experimental Investigations

The application of steel fiber as added materials in a plain concrete shows many potential benefits in improving structural properties namely tensile and flexural strength. The plain concrete with steel fibers added is said to be effective for both short and long terms duration based on its characteristics mainly size, shape, volume, and distribution. Such potentials have made it a material worthy to be further studied. This research was conducted to assess the strength of a plain concrete with the addition of steel fibers in the conventional concrete slab. Several testings were conducted to determine the strength characteristic (compressive and flexural) of the control sample; conventional reinforced concrete (RC) and reinforced concrete with steel fibers added (RCSF). In this study, the commercial steel fibers taken from Dramix which is categorised under 5D-Type was added during the concrete mixing processes according to the three different percentages of 0.5%, 0.75% and 1.0%. Obtained result shows that the concrete with steel fibers added (0.5%) had the highest compressive strength while both reinforced concrete and concrete with 0.75% addition of steel fibers showed almost similar flexural strength value. Deflection testing was conducted on both RC slab and RCSF slab via Three-point bending test. It is found that the RC slab showed a higher mid-span deflection rate. Furthermore, result from the physical observation and measurement for crack propagation evaluation shows that RC slab had a wider cracking gap compared to RCSF. In a nutshell, steel fibers in plain concrete gives several advantages and provide an alternative for the construction practitioner in minimizing the construction cost while maintaining the quality and reducing the cracking problem mainly due to the structural properties of concrete.

Preliminary experimental investigation on the inundating-induced collapse in collapsible soils improved by encased sand column

ABSTRACT The present research aims to explore experimentally the performance and modes of failure of the wetting-induced collapse of fully penetrating reinforced and unreinforced models of a short single sand column in a collapsible soil subjected to partial inundation through a series of model tests under high constant total stress of more than 200 kPa. A specific loading frame and a test container were designed to apply vertical pressure and measure vertical movements of the columns . The experimental test results demonstrated that providing only sand columns in collapsing soil have no significant contribution in reducing the large volume change and sudden collapse when wet. In contrast, geosynthetic-encased columns prevented the occurrence of wetting-induced collapse and highly reduced the sudden vertical movements to a gradual process under relatively high applied pressure. Additionally, a slight change in the dry density of the soil had a dramatic influence on the behaviour of the wetting-induced collapse and modes of failure. In this study, the experimental test results and theoretical results from different analytical approaches in the literature have confirmed that it is practically possible to apply high total stress of more than 300 kPa on a single footing on collapsible soils subjected to wetting condition.

Anchor Plates Bonded on Reinforced Concrete: A Preliminary Experimental Investigation

During the last decades, different technologies to anchor steel elements in concrete were proposed. The present work presents the results of a preliminary investigation of a new connection characterized by single steel plates that are directly bonded on concrete surfaces. The anchor response was experimentally investigated under both tension and shear actions. Specific conditions influencing the behavior of the bonded assembly were discussed, with particular reference to the presence of cracks and crack cycling in concrete.

Preliminary Experimental Investigation of Cut-Resistant Materials: A Biomimetic Perspective

Abstract The objective of the work was the preliminary experimental investigation of cut-resistant materials including a biomimetic perspective. The effects of the cutting were expressed as static and dynamic cut resistance of the following materials: knitted fabrics, woven fabrics, continuously coated knitted fabrics, and dot-coated knitted fabrics. The cutting process gives rise to frictional forces, but the current test methods for cut-resistant gloves are not designed to measure them. Therefore additionally, the cut resistance of the material was evaluated using a modified procedure based on the standard EN 1082-1, taking into consideration grip strength tests to assess if there is a potential correlation between cut resistance and anti-slip properties.

Биофизическая модель процесса распознавания картин ответной реакции кожного покрова на оптическую активацию

This paper presents a biophysical model of the recognition process of glow patterns (response) of the skin in the area of biologically active zones to external optical activation. The model was developed to increase the efficiency of the process of identifying the causes of differences in glow patterns. The structures of glow patterns are described and their differences are described. A rationale for the use of forced radiation of skin cells in current studies is given (recognition of weak signals of spontaneous radiation is technically difficult). Forced radiation of biological objects appears as a result of excitation of the biological environment by an external action and is much higher than spontaneous radiation. Spontaneous optical radiation of skin cells under certain conditions is one of the characteristic features of the skin. This radiation can be caused by a field form of intercellular interaction, which causes biochemiluminescence in the form of spontaneous weak signals ensuring intercellular communication. The model uses a biotechnical system related to the human physical state, its characteristics, type of meridian and external conditions. We have identified subsystems (biological and technical), the main elements of the system, determined the links between them, necessary and sufficient for drawing conclusions, formulated the main requirements for the system, determined the initial data. The results of the preliminary experimental investigations with the use of the developed model are presented in which some dependence of the luminescence patterns on the meridian type is revealed. It is noted that final conclusions on the causes of skin glow patterns differences in certain points of biologically active zones will be made when more extensive statistical data is collected using the developed model.

The use of the empirical crack orientation tensor to characterize the damage anisotropy

In practice, a dominant failure mode of brittle materials, such as fiber-reinforced thermosets is the initiation and propagation of cracks under cyclic loading. In general, the damage in composites with irregular microstructure do not occur in regular patterns. There are several state-of-the-art continuum mechanical models which take the anisotropic damage for predicting the material behavior into account. Since damage generally occurs in an anisotropic way, methods that experimentally characterize the damage anisotropy are needed.Micro-Computed Tomography systems (μCT) acquire volumetric images in a non-destructive way. By combining μCT scanning and mechanical in-situ testing, detailed microstructure data of specimens under load are generated. Based on image processing methods, the damage propagation from crack initiation to fracture is analyzed. In practice, cyclic load is a common load case for many components. Consequently, fatigue and cycle load tests are essential for a comprehensive material characterization.In this contribution interrupted in-situ μCT tests with cyclic tensile load are performed on Sheet Molding Compounds (SMC), a discontinuous glass fiber-reinforced thermset composite. Image processing methods are introduced for the experimental determination of the anisotropic damage characteristic based on volumetric images. The methods enable analyzing the spatial crack orientation distribution. In order to quantify the damage anisotropy, empirical formulations of the crack density distribution and second-order crack orientation tensor are applied. The presented work in this contribution extends the results of preliminary experimental damage investigations. In addition to previous studies, the damage anisotropy is quantified and analyzed.