Material Specimens Research Articles

TMIC-01. STAT3 EXPRESSION IN BRAIN METASTASES FROM BREAST CANCER: CORRELATIONS WITH DIFFERENT MOLECULAR SUBTYPES AND CLINICAL OUTCOME

Abstract BACKGROUND STAT3 expression in peritumoral reactive astrocytes (RA) of brain metastases (BM) from breast cancer (BC) may favor a pro-metastatic environment. MATERIAL AND METHODS Eighty-five BM specimens from BC were identified from the biobank of Pathology Unit of University of Turin and Spanish national BrM network (RENACER). pSTAT3 expression was scored in RA of peritumoral tissue according to Priego et al. (Nat Med 2018). Clinical, molecular data, and intracranial progression (i-PFS) were retrospectively retrieved. RESULTS Median age was of 54 years (range 30–81). Immunohistochemistry for GFAP and pSTAT3 was feasible in 68/85 (80%). 15/68 patients (21.1%) had BM from luminal BC, 27/68 (39.7%) from HER2-positive BC, and 26/68 (39.2%) from TNBC. 56/68 (82.4%) showed positive staining of pSTAT3, of which 9/68 (13.3%) scored with 3, 26/68 (38.2%) with 2, 21/68 (30.9%%) with 1, and 12/68 (17.6%) with 0 (negative). High pSTAT3 expression (score 2-3) was observed in 17/27 (62.9%) BM from HER2-positive BC and in 15/26 (57.7%) BM from TNBC, while most of BM from luminal BC (12/15 – 80%) had low or absent pSTAT3 (score 0-1) (p=0.021). Overall i-PFS was 16 months (range 7-41): low pSTAT3 BM (score 0-1) had a median i-PFS of 21 months versus 12 months for high pSTAT3 BM (score 2-3). A shorter median i-PFS was observed in high pSTAT3 BM from TNBC (4 months) as compared with low pSTAT3 BM (11 months). Conversely, i-PFS of high pSTAT3 BM (7 months) was similar to low pSTAT3 BM (6 months) in HER2-positive BC. CONCLUSION pSTAT3 expression in RA of peritumoral tissue of BM from TNBC and HER2-positive BC is higher than in BM from luminal BC. Of note, patients with high pSTAT3 BM from TNBC progressed earlier in comparison with those with low pSTAT3, suggesting that pSTAT3 expression has an influence on the outcome.

The evaluation of hydrogen embrittlement threshold force using the Small punch test

This study aims at developing a methodology for assessing the hydrogen embrittlement threshold force (Pth) in high strength steels using the Small Punch Test (SPT) technique and the ASTM F1624 standard recommendations. This methodology is based on material specimen stiffness and aims to test steels with hardness lower than 33HRC. In the methodology development phase, non-notched specimens made of four high strength steels (AISI 4137 M − 32HRC and AISI 4130 M − 25, 40, 44HRC), widely used in the oil and gas offshore industry, were tested according to the ASTM F1624 standard. Based on the literature, hold times of 20 min for the first 10 and 40 min for the last 10 steps were adopted. The tests were performed in a cathodic protection environment, consisting of a 3.5 wt% NaCl aqueous solution for hydrogen embrittlement (HE). The threshold force values (Pth-SPT) for the Incremental Small Punch Test (ISPT) were measured based on the specimen stiffness. In order to validate the proposed methodology, the ISPT and the incremental step loading (ISL) techniques were applied to test notched specimens manufactured from AISI 4130 M − 25 HRC and AISI 4137 M − 32HRC. The Pth-SPT values showed a systematic error of -4.0 % and 2.2 %, respectively, in relation to the ISL method, indicating an excellent accuracy. The Pth-SPT values provided by the ISPT under the experimental conditions investigated are adequate and quite promising. These values corroborate that the proposed methodology for the measuring of the Pth-SPT, based on material specimen stiffness, proved to be robust, efficient, and of easy implementation.

Multi-Point Interaction of Partially Conductive Cracks with Sweep Frequency Eddy Currents in Electromagnetic Non-Destructive Evaluation

An investigation of real corrosion cracks that can be partially conductive in electromagnetic non-destructive evaluation using sweep-frequency eddy-current frequency-response analysis is carried out in this study. A new approach incorporating innovative solutions is proposed. The goal was to increase the probability of detection of real corrosion cracks in contrast to the conventional sweep-frequency method that is based on single-point signal detection. The proposed procedure was tested on real material specimens where differential responses were gained from real corrosion cracks. Seven austenitic steel plate specimens having corrosion cracks were inspected. Eddy-current responses due to the material cracks were sensed, while a multi-point approach was used for this purpose. The presented unique results clearly showed that the detection ability of a fixed probe driven with sweep-frequency excitation signal could be increased when the multi-point detection is used, and the gained signals are further mathematically processed.

Characterisation of mortarless refractory masonry joints under elevated temperatures

Refractory linings are commonly employed in Industrial vessels used in high-temperature processes to protect them against extreme working environments. The working lining of an industrial steel ladle frequently employs mortarless refractory masonry to contain the molten steel and limit heat losses. Such masonry lining undergoes high thermomechanical loads, primarily due to thermal expansion arising from thermal and mechanical boundary conditions. Dry joints, described as a physical break in the continuum, reduce some of these effects. Therefore, understanding dry joints is an essential factor for developing numerical constitutive models that employ a meso or macro modelling approach. This work aims to experimentally investigate the normal compressive behaviour of dry joints in refractory masonry. For this purpose, various refractory specimens of alumina-spinel material are tested from ambient temperature to 1200 °C. The results obtained from these experiments are then used to identify critical joint parameters with different mathematical models for the interface. The outcome describes exponential joint closing behaviour with respect to the force applied. It was observed that the pressure required to close a joint reduces with an increase in temperature. The exponential model was then used to numerically simulate the joint closure of mortarless refractory masonry. Finally, numerical and experimental results were compared.

Optimization of the dimension of computer numerical control–milled polyetheretherketone clasps: An in vitro evaluation of accuracy

Statement of problemThe accuracy and optimal dimensions of computer numerical control (CNC)-milled polyetheretherketone (PEEK) removable partial denture (RPD) clasps are unclear. PurposeThe purpose of this in vitro study was to investigate the trueness and precision of CNC-milled PEEK clasps with different thicknesses and lengths. Material and methodsLadder-shaped specimens of 2 thicknesses with 5 lengths of clasps were designed and milled with PEEK and commercially pure titanium (CP Ti) (n=6). All milled specimens were scanned and superimposed onto the design data. Three-dimensional and 2-dimensional deviation analyses were carried out to evaluate the trueness of milled PEEK clasps. The scanning data of each group were superimposed pairwise, and the 3-dimensional deviations were analyzed to evaluate the precision. Nonparametric tests, ANOVA, the Pearson correlation, and univariate linear regression were used for statistical analysis (α=.05). ResultsThe deviation of trueness of the PEEK clasps (0.047 to 0.164 mm) was higher than that of the CP Ti clasps (0.037 to 0.060 mm) (P<.001). Increasing the length of the clasps increased the deviations (P<.001). Deviation in the 2 thicknesses was not significantly different (P=.210). The correlation coefficients of 1.0-mm-thick and 1.5-mm-thick PEEK and CP Ti clasps were 0.843, 0.794, 0.638, and 0.405. The positive correlation coefficients of PEEK were higher than those of CP Ti and those of 1.0-mm-thick clasps was higher than those of 1.5-mm-thick clasps. The deviations were evenly distributed in the 9-mm length of the clasp for CP Ti and in the 6-mm length of the clasp for PEEK. Beyond these lengths, deviations increased with increased length. The increasing amplitude of CP Ti was smaller than that of the PEEK group, and that of the 1.5-mm-thick clasp was smaller than that of the1.0-mm-thick clasp. The measured range of precision of PEEK clasps was 0.079 to 0.152 mm, while that of CP Ti clasps was 0.036 to 0.096 mm. CP Ti clasps tended to have better precision than PEEK clasps, except for the 1.0-mm-thick clasps with a length greater than 9 mm and the 1.5-mm-thick clasp with a 12-mm length. The correlation of the clasp length with precision showed that the lengths of 1.0-mm-thick clasps strongly influenced precision (PEEK, P=.020; CP Ti, P<.001); this correlation decreased sharply when the thickness of clasps was 1.5 mm (PEEK, P=.199; CP Ti, P=.107). ConclusionsGreater elasticity increased the deviations of milled clasps. The increased thickness helped the clasp remain stable during the milling process. The 1.5-mm-thick PEEK clasps in the 3-mm and 6-mm lengths were the optimal design tested.

Thermal diffusivity from Fourier’s inverse problem supervised by an optimization model: Theoretical analysis and experimental validation

An original experimental device coupled with an optimization technique, for determining the thermal diffusivity (αdiff) of solid materials, has been devised and experimentally validated. The inverse problem of the classical Fourier heat equation in transient condition is numerically supervised by an optimization procedure for the initial and boundary conditions from measurements. Imperfect adiabaticity on the insulated lateral surfaces is explained by modeling heat loss correction functions with additional time dependent Robin conditions. The optimization model identifies the optimal values of the heat transfer coefficients and of αdiff by minimizing the residual function between the model predictions and the experimental data. Incorporating the heat loss corrections in the solution of the heat equation significantly improves the estimation of the αdiff. Indeed, the time profile of the surface temperatures measured for a specimen of PPMA material is well reflected by the simulated curves. The estimated αdiff is in good agreement with an experimental inter-comparison of eleven laboratories equipped with Laser Flash, hot disk, and hot bridge certified devices. Our results reveal a reliable capability of the model to identify the αdiff value that explains the functional dependence underlying the experimental observations. The error lies in the range 5% or 34%, depending on whether the heat losses are accounted or not.

Synthesis of carbon energized materials with directed regulation of specific surface and pore structure as potential adsorbent for methane mitigation

In this study, nanoporous carbon material (NCM) specimens were synthesized from polymer raw materials (a mixture of furfural, hydroquinone, and urotropine). The influence of the conditions and parameters of the synthesis method (temperature, weight ratio of the activating agent to the precursor and contact time) on the NCM structure was examined. The effect of the weight ratio of the initial components on the properties of the resulting NCM was investigated, and the optimal composition of the ternary system of furfural, hydroquinone and urotropine was found. The results of nitrogen adsorption-desorption showed that NCM specimens obtained by varying the activation temperature were microporous but with different micropore volumes and the same pore size distribution. Varying the weight ratio of the activating agent (KOH) to the precursor made it possible to obtain microporous, micromesoporous, and mesoporous NCMs. NCM specimens with different pore hierarchy and different specific surface area were also obtained, including microporous NCMs (SBET: 1546–3030 m3/g; Vmic/Vt: 76.0–100%), micro- mesoporous NCMs (SBET: 3204–3516 m3/g; Vmic/Vt: 41.2–57.4% Vmes/Vt: 42.6–58.8%) and mesoporous NCMs (SBET: 3641–3649 m3/g; Vmes/Vt: 74.0–83.8%). Further, a mechanism for the development of pores during KOH activation of polymeric carbon precursor was proposed. The outcomes of this study signify that the NCM5/750/1 has a high adsorption capacity for CH4 and has good prospects for monitoring CH4 emissions and reducing greenhouse gas emissions.

Comb-based multispectral LiDAR providing reflectance and distance spectra.

Multispectral LiDAR enables joint observations of the 3D geometry and material properties of natural targets by combining ToF-based distance measurements with remote spectroscopy. Established multispectral LiDAR solutions provide mm-level range resolution and reflectance estimates of the target material over some tens of spectral channels. We propose a novel multispectral LiDAR approach based on an ultra-broadband frequency comb that enables enhanced remote spectroscopy by resolving relative delays in addition to reflectance. The spectrally-resolved delay and power measurements are transformed into distance and reflectance spectra by differential observations to a common reference object and adequate system calibration. These distance and reflectance spectra encode material information related to the surface and sub-surface composition and small-scale geometry. We develop the proposed comb-based multispectral LiDAR on an implementation covering the spectral range between 580 nm and 900 nm on 2 different spectral configurations with 7 and 33 channels of different spectral width. The performance assessment of the implemented system demonstrates a distance measurement precision better than 0.1 mm on most channels. Table-top probing results on five material specimens show that both the distance and the reflectance spectra alone enable discrimination of material specimens, while the novel distance signature particularly complements reflectance and increases classification accuracy when the material surface exhibits significant reflectance inhomogeneity. Material classification results using a support vector machine with radial basis function kernel demonstrate the potential of this approach for enhanced material classification by combining both signature dimensions.

Genomic Characterization of a Multidrug-Resistant Escherichia coli Isolate Co-Carrying bla NDM-5 and bla CTX-M-14 Genes Recovered from a Pediatric Patient in China.

Public health is seriously threatened by the rise of carbapenem-resistant Enterobacterales (CRE). However, the genomic characteristics of CRE detected in pediatric patients are largely unknown. Here, we reported the genomic characteristics of a multidrug-resistant Escherichia coli strain containing the plasmid-borne bla NDM-5 and bla CTX-M-14 genes recovered from a Chinese pediatric patient. The genome sequence of E. coli strain B379 was determined using Illumina NovaSeq 6000 and Oxford Nanopore MinION. Multiple bioinformatics tools were used to annotate the genome sequence, identify antimicrobial resistance genes and plasmid replicons and perform the in silico multilocus sequence typing (MLST) analysis. Using BacWGSTdb 2.0 server, a core genome MLST (cgMLST) comparison was made between E. coli B379 and all ST746 E. coli strains downloaded from the public database. The E. coli B379 genome sequence is comprised of six contigs totaling 5,152,502 bp, including one chromosome and five plasmids. Nineteen antimicrobial resistance genes were predicted. The bla NDM-5, which is located on a 46,161 bp IncX3 plasmid and the bla CTX-M-14 gene which is located on a 147,204 bp IncFII/IncFIA/IncFIB plasmid are two examples of these 19 genes. E. coli B379 was resistant to ampicillin, ampicillin/sulbactam, ceftriaxone, ceftazidime, imipenem, cefepime, ciprofloxacin, ertapenem, trimethoprim-sulfamethoxazole. This isolate belonged to ST746 and the closest relative was another one originating from a human material specimen in Denmark, which differed by 273 cgMLST alleles. Our study reports the emergence of a multidrug-resistant E. coli strain co-carrying bla NDM-5 and bla CTX-M-14 recovered from a pediatric patient in China. These data would help us better understand the prevalence, genetic characteristics, and mechanisms of antimicrobial resistance of this recently identified multidrug-resistant bacteria in children.

Electron diffraction characterization of nanocrystalline materials using a Rietveld-based approach. Part II. Application to microstructural analysis

This is the second in a two-paper series concerning the quantitative characterization of nanocrystalline materials using an electron-diffraction-based approach, in which a full-pattern fitting Rietveld-based refinement is applied to electron powder diffraction data in transmission electron microscopy (TEM). Part I [Sinha et al. (2022). J. Appl. Cryst. 55, 953–965] established a standard calibration protocol to determine the instrumental effects, with special emphasis on the camera length and the diameter of the selected area apertures. Possible application cases are now considered to demonstrate the capabilities of the approach, including the evaluation of the phase composition of TEM specimens, an operation that reveals new application fields for this powerful materials characterization technique. In this regard, different types of material specimen are examined: nanocrystalline yttrium oxide, silicon, titanium dioxide and debris from disc brake wear, each one featuring specific aspects to be tackled with the proposed methodology. To demonstrate the limits of the proposed approach as concerns the material characteristics, an analysis of a hematite sample obtained from the heat treatment of natural goethite, displaying a relatively coarse crystallite size, is performed and a critical discussion of the results is given.

Influence of Surface Type with Coffee Immersion on Surface Topography and Optical and Mechanical Properties of Selected Ceramic Materials.

BACKGROUND The aim of this study was to assess and compare the effect of surface type (glazed or polished) with coffee immersion and aging on surface topography (Ra), optical properties (TP, OP), and mechanical properties (fracture forces and modes) of zirconia-reinforced lithium silicate (Vita Suprinity), hybrid polymer-infiltrated-feldspathic ceramic network material (Vita Enamic), and leucite-containing feldspathic glass (Vitablocs® Mark II) made by computer-aided design and computer-aided manufactured (CAD/CAM) ceramic materials. MATERIAL AND METHODS Fifty-four specimens were assembled out of the above 3 CAD/CAMs ceramic materials. Each group was divided into glazed or polished surfaces, having 9 specimens of every type and stained in coffee for 15 days. Ra and color of specimens in the form of TP and OP were recorded before and after immersion in staining material. Fracture forces and modes were analyzed after the 90-day aging. Data were analyzed using ANOVA, then post hoc analysis and Bonferroni tests. RESULTS Our study found significant differences in Ra, TP, and Op before and after coffee immersion between glazed and polished specimens, with higher values in the polished surfaces among the 3 ceramic materials. The highest values of fracture resistance were noted in Vita Suprinity, and Vita Enamic had the lowest values, without significant differences among groups. CONCLUSIONS Most of the TP and OP values were in acceptable clinical range, and Vita Suprinity had superior TP than the other groups. Reparable fracture types were observed in Vita Suprinity, whereas semi-reparable and non-reparable were predominant in other groups.

The Experimental Investigation on Mechanics and Damage Characteristics of the Aeolian Sand Paste-like Backfill Materials Based on Acoustic Emission.

With the wide application of the filling mining method, it is necessary to consider the influence of rock activity on the filling body, reflected in the laboratory, that is, the influence of loading rate. Therefore, to explore the response characteristics of loading rate on the mechanical and damage characteristics of aeolian sand paste filling body, DNS100 electronic universal testing machine and DS5-16B acoustic emission (AE) monitoring system were used to monitor the stress–strain changes and AE characteristic parameters changes of aeolian sand paste filling body during uniaxial compression, and the theoretical model of filling sample damage considering loading rate was established based on AE parameters. The experimental results show that: (1) With the increase in loading rate, the uniaxial compressive strength and elastic modulus of aeolian sand paste-like materials (ASPM) specimens are significantly improved. ASPM specimens have ductile failure characteristics, and the failure mode is unidirectional shear failure → tensile failure → bidirectional shear failure. (2) When the loading rate is low, the AE event points of ASPM specimens are more dispersed, and the large energy points are less. At high loading rates, the AE large energy events are more concentrated in the upper part, and the lower part is more distributed. (3) The proportion of the initial active stage is negatively correlated with the loading rate, and the proportion of the active stage is positively correlated with the loading rate. The total number of AE cumulative ringing decreases with the increase in loading rate. (4) Taking time as an intermediate variable, the coupling relationship between ASPM strain considering loading rate and the AE cumulative ringing count is constructed, and the damage and stress coupling model of ASPM specimen considering loading rate is further deduced. Comparing the theoretical model with the experimental results shows that the model can effectively reflect the damage evolution process of ASPM specimens during loading, especially at high loading rates. The research results have significant reference value for subsequent strength design of filling material, selection of laboratory loading rate and quality monitoring, and early warning of filling body in goaf.

Suggestion of Practical Application of Discrete Element Method for Long-Term Wear of Metallic Materials

This study presents a simulation procedure for the wear of metallic materials exposed to long-term cumulative contact forces and introduces a numerical analysis procedure using the discrete element method (DEM) to predict the wear damage. Since the DEM can calculate the motion and contact load of each particle and the interaction between particles for each dynamic collision of particles, it was possible to analyze the motion of the particles causing metal wear. A method to reflect particle size, material properties, and long-term cumulative friction distance required by the DEM was proposed so that the collision and friction load between particles can be predicted practically. Considering the feature of wear suggested by Archard, it was shown that the wear amount can be predicted efficiently by converting the long-term load into an equivalent material constant. In addition, it was suggested that it is reasonable to determine the size of the particles in consideration of the size of the surface mesh of the metal surface. The accuracy of the analysis results obtained using the procedure proposed in this study was compared with that of the wear test results of metal material specimens presented by former studies. The numerical analysis was also performed in the reference study, but inaccurate results were derived compared to the analysis results. The reason for the inaccuracy of the numerical model performed in the previous study was found to be environmental factors that cannot be considered in a numerical analysis. In this study, it was determined that it was because the behavior of particles and the load transferred to the specimen were not well simulated, which remains a problem for future research. As a result, it was confirmed that it is possible to compute a worn shape similar to the measured shape of experiments. Thereafter, the change in the contact load predicted by simulation is discussed in terms of wear shape and cross-sectional area loss ratio.

Epinephelusrankini Whitley, 1945, a valid species of grouper (Teleostei, Perciformes, Epinephelidae) from Western Australia and southeast Indonesia.

The grouper Epinephelusrankini, described from the waters off Western Australia, has long been regarded as a junior synonym of Epinephelusmultinotatus. However, the two species are discernible as distinct species on the basis of their morphological characteristics and genetic differences by the holotype material and non-type of specimens. In this study, Epinephelusrankini is considered as a valid species and re-described based on the examination of the holotype and additional specimens. Epinephelusrankini can be distinguished from the closely-related species E.multinotatus by the following combination of characters: body dark greyish-brown to chocolate with irregular white blotches (vs. body pale brownish-grey with irregular and small white blotches in E.multinotatus), absence of small dark brown spots (vs. numerous small dark brown spots in E.multinotatus). Furthermore, genetic differences between the two species strongly support the validity of both species based on molecular analysis (mtDNA, COI gene). In addition based on the sampling range, E.rankini was observed range from the Abrolhos Islands of Western Australia to south-eastern Indonesia, while E.multinotatus ranges from the Persian Gulf to southern Mozambique.

A Study on the Reliability of Mass, Density, and Fire Performance of Recycled Wastepaper Building Finishing Material Made with Large Wet Cellulose 3D Printers

The impact of non-face-to-face contact following the COVID-19 pandemic has emerged as a social problem and has increased the amount of wastepaper, mainly in home delivery boxes. The appropriate recycling of paper waste is an area where sustainable growth is required in terms of the net environment system and carbon neutrality practice. Therefore, in this study, a specimen of building finishing material using wastepaper was produced using a custom-made large wet cellulose (LWC) 3D printer, and the site applicability of the fire performance was evaluated. The specimen of the building finish material was a mixture of wastepaper and ceramic binder, and the molding of the specimen was uniformly produced by a cylinder injection-type LWC 3D printer. The production reliability of the 3D printer was analyzed by measuring the mass and density of the specimen. The uniformity of the mass and density of the manufactured building finishes were confirmed to have standard deviations of ±0.05 g and ±0.01 g/cm3, respectively. The uniformity of the fire performance of specimens was confirmed by checking the relative standard deviation (RSD) value of ±3% under the same ceramic addition conditions from ISO 5660-1. Through the mass and density analysis and fire performance analysis of the building finishing materials, it was confirmed that the same mass, density, and fire performance can be produced simultaneously, and manufacturing using LWC 3D printers has been confirmed to be effective in developing uniform semi-non-combustible and retardant building materials.

Prestressed concrete bridge tested to failure: the Alveo Vecchio viaduct case study

The number of bridges approaching or exceeding their initial design life has been increasing dramatically. Meanwhile, bridges are withstanding an ever-increasing traffic volume, both in number and weight of vehicles. Analytical and numerical models can predict bridges’ response to traffic loads and their ultimate capacity with low uncertainties; however, such uncertainties increase as bridges age due to deterioration mechanisms. Non-destructive tests of material specimens and full-scale load tests allow for updating structural models and predicting bridges’ responses with higher accuracy. On-site load tests with different load levels provide different information on the bridge behaviour (e.g., elastic response, first-crack load, and ultimate capacity), which impact the model updating differently. This paper compares the observed response of the Alveo Vecchio viaduct, a prestressed concrete (PC) bridge subjected to a controlled load test up to its failure, with its predicted response provided by four structural models. The observed response is measured by an extensive structural health monitoring system, while the structural models are developed with different levels of refinement and uncertainty in the input parameters. This study gives an insight into the ultimate load-carrying capacity of existing PC bridges and their behaviour during a whole load test to failure. The results show that the load-carry capacity of the Alveo Vecchio viaduct is almost four times higher than the design load; likely, many other Italian highway bridges with similar structural characteristics have a similar capacity.

Damage evolution and fracture behavior of different materials specimens containing a central hole subjected to local loading

The strength of the different materials specimens containing a central hole subjected to varying loading areas constitutes lots of underground engineering such as entry arrangement and mining process. In this study, the failure resulted from micro-fracturing in the specimen, which can be characterized by the crack propagation path if the damage events are monitored by using Digital Image Correlation (DIC), infrared thermal imager and high-speed camera. The experimental results demonstrate that there are three different types of typical failure modes for specimens with central holes according to the loading areas. The evolution of the temperature field is shown for various loading areas, the smaller loading area, the greater the stress concentration, and the more pronounced the thermodynamic features. The temperature field can also be associated with material properties in addition to loading area. Additionally, failure around the hole with redistributed stress has been observed, and strain energy density (SED) can help explain the failure mechanisms. The progressive damage process, which takes into account the heterogeneity in elastic modulus and rock strength characteristic, is demonstrated by developing a constitutive model that uses the uniaxial compression and Brazilian disc tests to parameterize it. By comparison with plastic zone, the proposed constitutive model is used to quantitatively evaluate the accumulation of damage. Failure mechanisms are established based on this work and are anticipated to be extensively utilized in engineering applications.

Mechanical Properties Evaluation of Three Different Materials for Implant Supported Overdenture: An In-Vitro Study.

Aim: the aim of this study was to compare the flexural strength and elastic modulus of three-dimensionally (3D) printed, conventional heat-cured, and high-impact implant-supported overdenture materials specimens. Materials and Methods: Thirty implant-supported overdenture materials specimens (bar-shaped, 65.0 × 10.2 × 5.1 ± 0.2 mm3) with one central hole were fabricated using 3D-printed, heat-cured conventional, and high-impact denture base resins (n = 10/group). Autopolymerizing acrylic resin was used to attach titanium matrix housings to the central holes of the specimens. A three-point bending test was conducted using a universal testing machine and a model analog with a crosshead speed of 5 mm/min. The indicative flexural strength and elastic modulus were recorded. Data were statistically analyzed using analysis of variance (ANOVA) and the Tukey tests at α = 0.05. Results: One-way ANOVA revealed a significant effect of denture base material on the flexural strength (p < 0.001) but not on the elastic modulus (p = 0.451) of the evaluated materials. The flexural strength of the 3D-printed specimens (95.99 ± 9.87 MPa) was significantly higher than the conventional (77.18 ± 9.69 MPa; p < 0.001) and high-impact ones (82.74 ± 7.73 MPa; p = 0.002). Conclusions: The maximum flexural strength was observed in the 3D-printed implant-supported overdenture material specimens, which might indicate their suitability as an alternative to the conventionally fabricated ones. Flexural strength and elastic modulus of conventional and high-impact heat-cured implant-supported overdenture materials specimens were comparable.

Towards standardizing the preparation of test specimens made with material extrusion: Review of current techniques for tensile testing

Researchers and industries rely heavily on standardized testing methods to ensure products are designed and manufactured with high quality. With increasing use of additive manufacturing processes, such as material extrusion (MEX), there is a significant gap in material testing standards tailored for such components, and a lack of guidance on preparing appropriate test specimens with mesostructures that best represent the final part being analyzed. This paper aims to support the standardization of MEX material testing by reviewing the current methods used for preparing test specimens for tensile testing and proposing guidelines for implementation in a new standard. The need for standardization of MEX specimen preparation is addressed by analyzing the effects of slicing parameters on resulting tensile properties of the specimen. It is suggested that a standard should acknowledge these parameters, in addition to specimen geometry, toolpath optimization, printer and material specifications, so that they are appropriately selected for the test specimen by regarding the final part structure. Consideration of the proposed guidelines in a standardized method may enable comparisons between published results and support the development of MEX technology for use in advanced applications. • Material testing standards are incomplete for specimens made by material extrusion. • Test specimen preparation procedures found in literature are inconsistent. • Process parameters greatly influence tensile strength and stiffness. • Guidelines for a standard test specimen preparation procedure are proposed.

Evolution mechanism of compression deformation of carbon black reinforced epoxy resin composites

AbstractIn this paper, the double‐element composites were developed, which contained the epoxy resin as matrix phase and carbon black rubber powder as toughening materials. Quasi‐static compression tests on epoxy resin and different mass fractions carbon black rubber powder‐epoxy resin composites were performed in room temperature to test their compression properties. The energy absorption performance and the energy absorption efficiency of the composites were calculated according to the compression curve. The fracture characteristics of the micro appearance of the compressed material specimen were observed by scanning electron microscope. The deformation mode of the composite was analyzed. By systematically analyzing the effects of carbon black rubber powder content on the mechanical properties of carbon black rubber powder‐epoxy resin, it was found that carbon black rubber powder as a reinforced material could effectively improve the brittleness of epoxy resin, the yield strength and the adsorption properties and efficiency of composites. With the mass fraction of carbon black rubber powder increasing, the energy absorption performance of carbon black rubber powder‐epoxy resin first increases and then decreases. The most significant performance observed was at a mass fraction of 5 % in carbon black rubber powder‐epoxy resin composites.