Indentation Machine Research Articles

Effect of Herbal Intracanal Medicaments on Microhardness of Root Dentin: An In Vitro Study.

The use of intracanal medicaments (ICM) is crucial toreduce the microbial load in root canals. However, its application may negatively affect the physical properties of root dentine. Thus, this in vitro study was performed to investigate the effects of different herbalICM on the microhardness ofroot dentin. A total of 100 mid-root discs were randomly divided into five groups (n = 20) and treated with Aloe vera, Aloe vera + chitosan, curcumin, curcumin + chitosan, and control for 14 days. A Vickers hardness indentation machine (Laizhou Laihua Testing Instrument Factory, Yantai, China) with a load of 200 g and a dwell time of 15 seconds was used for microhardness testing before andafter treatment. The results were analyzed usingStatistical Product and Service Solutions (SPSS, version 26.0; IBM SPSS Statistics for Windows, Armonk, NY). Intragroup comparisons were executed using paired t-tests, while intergroup comparisons employed ANOVA, followed by post-hoc Tukey's tests. The Aloe vera + chitosan and curcumin + chitosan groups showed a statistically significant reduction in dentin microhardness (p < 0.05). The decrease in dentin microhardness ofthe Aloe vera and curcumin groups was non-significant (p > 0.05) and similar to that of the control. Aloe vera or curcumin alone as ICM did not affect the root dentin microhardness. The addition of0.2% chitosan to either Aloe vera or curcumin negatively affected the root dentin microhardness.

Non-equibiaxial residual stress evaluation methodology using simulated indentation behavior and machine learning

Measuring the residual stress in the components in nuclear power plants is crucial to their safety evaluation. The instrumented indentation technique is a minimally invasive approach that can be conveniently used to determine the residual stress in structural materials in service. Because the indentation behavior of a structure with residual stresses is closely related to the elastic-plastic behavior of the indented material, an accurate understanding of the elastic-plastic behavior of the material is essential for evaluation of the residual stresses in the structures. However, due to the analytical problems associated with solving the elastic-plastic behavior, empirical equations with limited applicability have been used. In the present study, the impact of the non-equibiaxial residual stress state on indentation behavior was investigated using finite element analysis. In addition, a new nonequibiaxial residual-stress prediction methodology is proposed using a convolutional neural network, and the performance was validated. A more accurate residual-stress measurement will be possible by applying the proposed residual-stress prediction methodology in the future.

Effect of specimen size and crystallographic orientation on the nano/microscale mechanical properties and deformation behavior of CrCoNi medium-entropy alloy

CrCoNi medium-entropy alloy (MEA) shows an exceptional combination of macroscale mechanical properties, however, knowledge of its mechanical properties at nano/microscale is lacking. In this paper, nano/microscale single crystal MEA pillars with orientation of 〈116〉, 〈014〉, 〈102〉 were fabricated using focused ion beam milling, and the compressive strength was determined with micropillar compression testing using a flat-end tip in an indentation machine. Results showed that the yield and flow strength of these MEA pillars were orientation-dependent, i.e., the lower the Schmid factor, the higher the strength. At the same time the strength of the pillars was dependent on the pillar’s size, the strength increasing as the pillar diameter reduced. From the results of the micropillar compression testing, the bulk critical resolved shear stress (CRSS) was determined to be 92 MPa, which is the highest value of the group of CrCoNi-based medium and high-entropy alloys. Analysis of transmission electron microscope images and large-scale molecular dynamics simulations revealed a group of complimentary deformation mechanisms, including dislocation slides, dislocation annihilation, dislocation-slip band interaction, formation of nanoscale stacking-faulting networks, and deformation nanotwins.

Investigation of the Microstructure of Sintered Ti-Al-C Composite Powder Materials under High-Voltage Electrical Discharge.

Dispersion-hardened materials based on TiC-AlnCn are alloys with high heat resistance, strength, and durability that can be used in aircraft and rocket technology as a hard lubricant. The titanium-rich composites of the Ti-Al-C system were synthesized via the spark plasma sintering process. Composite powder with 85% of Ti, 15% of Al, and MAX-phases was processed using high-voltage electrical discharge in kerosene at a specific energy of 25 MJ kg-1 to obtain nanosized particles. This method allows us to analyze the most efficient, energy saving, and less waste-generating technological processes producing materials with improved mechanical and physical properties. An Innova test indentation machine was used to determine the hardness of the synthesized composites. The microhardness of Ti-Al-C system samples was determined as approximately 500-600 HV. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were performed to identify the hard titanium matrix reinforced by intermetallic phases and the clusters of carbides. Three types of reinforcing phases were detected existing in the composites-TiC, Al4C3, and Al3Ti, as well as a matrix consisting of α- and β-titanium. The lattice parameters of all phases detected in the composites were calculated using Rietveld analysis. It was determined that by increasing the temperature of sintering, the amount of aluminum and carbon increases in the carbides and intermetallic phases, while the amount of titanium decreases.

Effect of Propolis on Root Dentine Microhardness When Used as an Intracanal Medicament: An In Vitro Study.

Application of intracanal medicaments may affect the physical properties of root dentine. Calcium hydroxide (CH), a gold standard intracanal medicament, has proven to decrease root dentine microhardness. A natural extract, propolis, has been shown to be superior to CH in eradicating endodontic microbes, but its effect on the microhardness of root dentine is still not known. This investigation aims to evaluate the effect of propolis on root dentine microhardness compared to calcium hydroxide. Ninety root discs were randomly divided into three groups and treated with CH, propolis, and a control. A Vickers hardness indentation machine with a load of 200 g and dwell time of 15 s at 24 h, 3, and 7 days was used for microhardness testing. ANOVA and Tukey's post hoc test were used for statistical analysis. A progressive decrease in microhardness values was observed in CH (p < 0.01), whereas a progressive increase was observed in the propolis group (p < 0.01). At 7 days, propolis demonstrated the highest microhardness value (64.43 ± 1.69), whereas CH demonstrated the lowest value (48.46 ± 1.60). The root dentine microhardness increased over time when propolis was applied, while it decreased over time after application of CH on root dentine sections.

압입 시험과 머신러닝을 통한 초탄성 소재 모델 계수 예측 기법 개발

압입 시험과 머신러닝을 통한 초탄성 소재 모델 계수 예측 기법 개발

Influence of geochemical reactions on the creep behavior of Mt. Simon sandstone

The capture and subsurface storage of carbon dioxide is a sustainable option that is currently pursued worldwide to mitigate greenhouse gas effect. However, predicting the long-term mechanical integrity of CO2 underground storage systems remains a challenge. To address that question, it is essential to understand the influence of fluid-rock chemo-mechanical interactions on the long-term and on the time-dependent mechanical properties. In turn, the long-term mechanical response and the time-dependent mechanical behavior can be represented by the creep response. We investigate the impact of CO2-induced geochemical reactions on the creep response of Mt. Simon sandstone with a 50–400 μm grain size. We perform static and dynamic flow experiments on Mt. Simon sandstone specimens under geological conditions, at a temperature of T=50–53 °C and for CO2 pressures of P=8.62, 17.2 MPa under both static flow and dynamic flow-through conditions. After aging, we employ creep indentation testing, high-resolution SEM-EDS, computer vision, machine learning, and micromechanics modeling to probe changes on the microstructure and mechanical properties. Following both static and dynamic flow-through experiments, we observe a 10–22% decrease in quartz volume fraction and an increase in both the microporosity (7–28%) and nanoporosity (60–65%). Additional CO2-induced microstructural changes include an enlargement of pore throats and the formation of channels. These observations point to the presence of CO2-induced K-feldspar dissolution and clay dissolution reactions. The macroscopic creep behavior is logarithmic and the macroscopic creep modulus varies depending on the microporosity and the relative quartz and feldspar content. As a result of these geochemical reactions and of the related microstructural changes, a 55–60% decrease in the macroscopic logarithmic creep modulus is predicted.

Evaluation of the antibacterial efficacy of two herbals and their effect on dentin microhardness (A comparative in vitro study)

Objectives: The aim of the study was to compare the antibacterial efficacy and the effect on dentin microhardness of turmeric extract, thymus vulgaris oil, sodium hypochlorite and chlorhexidine when used as root canal irrigants. Material and methods: Sixty four permanent mandibular single rooted premolars were classified into 4 groups of 16 teeth each according to the final irrigant used. For the antibacterial test, 11 teeth per group (n=11), and the microhardness test, 5 specimens per group (n=5): Group I: 2% Turmeric extract. Group II: 2% Thymus vulgaris oil. Group III: 5.25% NaOCl. Group IV: 2% CHX. Forty four Samples were inoculated with E. faecalis, incubated then chemo-mechanically prepared according to the assigned group, sampled and incubated for 24 hours then Colony Forming Units were counted. Twenty samples were used to create dentin blocks, then were kept in airtight containers saturated with 5 ml of each irrigant for 5 minutes. Microhardness test was performed at different time intervals; After 24 hours, 3 days and 7 days using Vickers hardness indentation machine. Results: The highest antibacterial efficacy against E. faecalis was in 2% CHX followed by 5.25% NaOCl, 2% Thymus vulgaris oil and finally 2% Turmeric extract. In microhardness test 2% CHX showed the highest statistically significant value of dentin microhardness, followed by 2% Turmeric extract, 2% Thymus and finally 5.25% NaOCl. Conclusion: Herbals may serve as alternatives to conventional root canal irrigants as they possess antibacterial properties and cause minimal alteration in dentin microhardness when compared to chemical irrigants.

Metallurgical investigation of a heat-exchanger tube of 70/30 cupronickel failed by fretting corrosion

The present paper describes a failure investigation of a tube that had shown leakage in a shell and tube type heat-exchanger with 70/30 cupronickel tubes and mild steel baffles (13 nos.). Corrosion damage or thinning of the failed tube was found to have occurred from the outer surface at all the baffle locations. Further examination of the failed tube was done using an optical microscope, a scanning electron microscope equipped with energy dispersive spectroscopy, Raman spectroscopy and an instrumented microhardness indentation machine for hardness measurement. Based on the results, it was concluded that the failure and the loss in wall-thickness of the tube at locations where it was in contact with the mild steel baffles were caused by fretting corrosion. The focus of this investigation is to bring out the metallurgical changes and the surface conditions (including changes in microstructure and microhardness, mode of corrosion attack and type of oxides/corrosion products) of the tube material undergoing fretting corrosion at micro level. Recommendations to avoid such a failure are also suggested.

Characterization of the ageing of an epoxy resin using high temperature nanoindentation

This article aims to understand better the mechanical properties and behavior of organic matrix composite materials under elevated temperature conditions. Two specific specimens of cured RTM6 epoxy resin are tested with DMA analysis: one being unaged and the other one aged for 5000 h at 130 °C under ambient air. Anti-plasticization effects seem to occur on aged resin. Series of nano-indentation tests are carried out from the surface to the core of the sample so as to measure gradient properties of the resin, at temperatures up to 150 °C using a high temperature indentation machine prototype. Thermo-oxidation phenomena involve oxidized layer formation during thermal ageing of the epoxy resin which is characterized through measurements of indentation Young’s modulus. After aged treatment, the variation of Young’s modulus of the oxidized layer at the surface of the sample is not clearly affected by the increasing test temperature whereas Young’s modulus of the core of the sample is decreasing significantly with the temperature test as on unaged epoxy resin. Thus, asymptotic growing of the oxidized layer is then confirmed.

Effect of Water Immersion on Interfacial Strength of a Metal/Epoxy Joint

Metal/resin joints have been widely used for automotive, electrical device and others. The degradation of interfacial strength of the joints through the effects of moisture is one of the important deterioration mechanisms in their structure applications. In this study, the interfacial strength of an aluminum-alloy/epoxy-resin joint was evaluated by the indentation test using of the instrumented indentation machine developed by ourselves. The in-situ observations of delamination cracking were carried out during the indentation test. The interfacial fracture toughness of the joint was evaluated from the relationship between the indentation load and the crack length. The effect of immersion into service water on the evaluated interfacial strength of the joint was discussed.

파일-업 재료에 대한 나노 압입 시험기의 경도 측정값 교정

Measurements of the elastic modulus and hardness using a nano indentation machine rely on the equation for the fitted contact area, which is valid for only sink-in materials. For most soft engineering materials that involve pile-up behavior rather than sink-in, the contact area equation underestimates the contact area and thus overestimates the elastic modulus and hardness. This study proposes a correction method to amend erroneous hardness measurements in pile-up situations. The method is a supplemental derivation to the original hardness measurement with the known value of the elastic modulus. The method was examined for soft engineering metals, Al 6061 T6 and C 12200, via tensile tests, nano indentation tests, impression observations, and finite element analysis. The proposed technique shows reasonable agreement with the analytical results accounting for strain gradient plasticity from a previous study.

Orientation-dependent nanoscratch resistance of zirconium diboride ceramic grains

The orientation dependence of scratch resistance of zirconium diboride (ZrB2) grains was investigated during nanoscratch testing. The experimental material was produced by spark plasma sintering (SPS) and the crystal orientation of ZrB2 grains was determined by electron backscatter diffraction (EBSD) technique. Scratches were prepared on a previously mapped surface area by an instrumented indentation machine using Berkovich tip with constant loads of 50, 100 and 150mN along lengths of 200μm. The generated surface topography was studied by scanning electron microscopy (SEM), confocal and atomic force microscopy (AFM). Micro-plasticity was observed in the form of slip-lines and microcracking along the scratch tracks. The analysis of experimental data revealed significant anisotropy in residual scratch depth with the lowest resistance corresponding to the tilt angle of around Φ=50°–60°. Anisotropic crack initiation was observed, which depends on the load and crystal orientation. The orientation dependence of scratch resistance showed a proportional tendency with hardness, yield and rupture stress anisotropies reported recently by the present authors.

Comparison of Antibacterial Efficacy of Calcium Hydroxide Paste, 2% Chlorhexidine Gel and Turmeric Extract as an Intracanal Medicament and their Effect on Microhardness of Root Dentin: An in vitro Study.

ABSTRACTAim: To evaluate and compare the antibacterial efficacy of turmeric extract as an intracanal medicament against E. faecalis and its effect on the microhardness of root dentin in comparison with calcium hydroxide and 2% chlorhexidine gel.Materials and methods: One hundred and fourty dentin blocks were prepared from 70 extracted human single-rooted teeth and standardized. For antibacterial assessment, 120 blocks were infected for 21 days with E. faecalis (n = 24/group). Dentin blocks were treated with group I (Ca(OH)2), group II (2% chlorhexidine gel), group III (turmeric extract), group IV (saline) and group V (negative control). Dentin shavings were obtained in TSB at depth of 400 μm and plated to count CFUs at 24 hours, 3 and 7 days (n = 8/day). For microhardness assessment, eight samples of 2 mm thickness were prepared form four dentin blocks (n = 8/group). Following treatment with medicaments, microhardness test was performed at 24 hours, 3 and 7 days using Vickers hardness indentation machine at 400 μm from canal lumen.Results: Complete inhibition of E. faecalis was observed with group II, followed by 64% with group I and 54% with group III which was statistically highly significant (p < 0.001). Highest effect on microhardness of root dentin was shown by group I, followed by group II and no effect was seen with group III which was statistically highly significant (p < 0.001).Conclusion: Turmeric extract has substantial antibacterial activity with no effect on microhardness of root dentine and hence has a potential to be used as intracanal medicament if its antibacterial activity could be enhanced.How to cite this article: Prabhakar AR, Swapnil T, Savita H, Sugandhan S. Comparison of Antibacterial Efficacy of Calcium Hydroxide Paste, 2% Chlorhexidine Gel and Turmeric Extract as an Intracanal Medicament and their Effect on Microhardness of Root Dentin: An in vitro Study. Int J Clin Pediatr Dent 2013;6(2):171-177.

Design and Application of the Motor Driven Book Lateral Indentation Machine

Comply with the binding of books and the development trend of automation, the single process mechanization is the real road for some small binding enterprises and characteristics of binding enterprises. The structure principle and characteristics about the motor driven book lateral indentation machine were introduced aiming at the high quality requirements for binding book. This paper analyzes the working program of the motor driven book lateral indentation machine and its adjustment principle. We provide the evidence to choose the reliable auxiliary tool for binding correctly. Further, providing the basis to ensure the quality of modern book binding appearance

Introduction

Although studies of indentation hardness of solids have been carried out for more than a century, it is only during the last 30–40 years that researchers started to develop and use instrumented indentation machines with which both the indenter load and indenter displacement are recorded simultaneously and accurately. Since the availability of commercial instrumented indentation machines in the 1980s, their use has been extended to almost all branches of materials sciences and even some aspects of biological sciences. Mechanical properties of materials can now be measured from the macro-scale down to the nano-scale. These mechanical properties include hardness, Young’s modulus, equivalent uni-axial yield stress, fracture toughness, elasticity of biological cells, viscoelasticity and residual stresses. The instrumented indentation machine has indeed become an essential aid to universal material characterization and modeling.

Stored elastic energy influence on the elastic–plastic transition of GaAs structures

Abstract

104 円錐圧子を用いたシングルセンサ式押込み試験機によるヤング率評価(ナノインデンテーション試験の新展開)

104 円錐圧子を用いたシングルセンサ式押込み試験機によるヤング率評価(ナノインデンテーション試験の新展開)

Regenerated spider silk as a new biomaterial for MEMS

Spider drag-line silk is introduced for the first time as a new biomaterial for Micro-Electro-Mechanical Systems (MEMS). The tasks accomplished in this paper were focused on mechanical characterization of regenerated spider silk under two conditions: (1) spin-coated thin film formed onto a silicon substrate; and (2) formation of a free-standing microbridge (800 x 800 x 40 microm3) obtained by a surface micromachining process. Micromechanical tests using a nano indentation machine showed the spider silk film having an elastic modulus of 7.3 GPa, a loss tangent of 0.044 and an UTS (Ultimate Tensile Strength) of 85.1 MPa.

Indentation of elastic solids with a rigid Vickers pyramidal indenter

Experimental investigations of the normal loading of a rigid Vickers pyramidal indenter on to several blocks of elastic solids, namely neoprene, rubber, and optically clear polydimethylsiloxane (PDMS) containing 10%, 5%, and 2.5% by volume of the curing agent have been described. An instrumented indentation machine was used and several types of measurement were made. These included (1) indentation load versus indenter penetration behaviour, (2) in situ photography of the contact area between the indenter and the substrate, (3) the depth of the points of contact where a plane going through an indenter diagonal and containing the indenter tip intersects the surface of the specimen, and the depth of the contact points lying along a direction at an angle of 45° to the planes containing the diagonals. The measurements were compared with the predictions of the theory of a rigid cone indenting an elastic half space and by assuming that the rigid pyramid could be likened to a cone of a semi-included angle of 70.3°. It is shown that in all cases there were significant discrepancies between the predictions of the theory and the experimental measurements. It is concluded that a rigid pyramidal indenter normally loading on to an elastic solid cannot be likened to a conical indenter for such studies. It is suggested that it is the high friction at the ridges of the indenting pyramid, which gives rise to the discrepancies between the experimental data and the theory for a frictionless indentation with a rigid cone. This conclusion has very significant implications for a commonly used method of nanoindentation data analysis. These implications are also discussed.