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Purpose: To investigate whether toothpastes with diamond powder vs those with traditional abrasives abrade dentin and enamel differently and to determine the relative dentin abrasivity (RDA) and relative enamel abrasivity (REA) values of those toothpastes.Materials and Methods: Dentin and enamel samples of bovine permanent incisors were randomly allocated into groups of eight, brushed with 20 different toothpastes (three of which contained diamond powder) and analysed for their RDA and REA values.Results: Toothpastes with diamond powder exhibit low RDA values but high REA values. Some RDA values exceeded the ones declared by the manufacturer.Conclusion: Diamond powder as an abrasive might have a mild action on dentin, but it is highly abrasive on enamel. [ABSTRACT FROM AUTHOR]

The focus of this study was to evaluate the effect of heat treatment and increasing confining pressure on the CERCHAR abrasiveness index (CAI) and Sievers' J-value (SJ-value) on selected granitic rocks from Garam Chashma Pluton (GCP) and Kafiristan Pluton (KP) formations. The results of SJ-value test were further utilized for the computation of specific energy (S.E) for rotary drilling. Moreover, petrographic analyses were also performed to observe the behaviour of the creation of cracks introduced in rock fabric due to progressive heat treatment. Results show that for GCP and KP granites, CAI values decreased with an increase in temperature up to 500 °C while at 600 °C an increase in CAI values is observed which is attributed to a α–β quartz crystal transition, whereas SJ values (or penetration) kept on increasing despite an increase in the CAI value. Specific Energy (S.E.) values decreased with increasing temperature due to the thermal degradation of rocks. Further CAI and S.E. values have an increasing relationship with confining pressure, while SJ values have a decreasing relationship with confining pressure. It can be established from the findings of this study that overheating of the granitic rocks increases their abrasivity after a certain temperature. Therefore, using a combined thermo-mechanical drilling technique for the exploitation of deep geothermal reservoirs, thermal treatment may be provided in such a way as to avoid the occurrence of α–β quartz crystals transition limit. Highlights: Selected granite samples from Garam Chashma Region, Chitral Pakistan were heat treated. The heat-treated granite samples were subjected to CERCHAR abrasivity and Siever's J-value tests at ambient pressure. The heat-treated granite samples were subjected to CERCHAR abrasivity and Siever's J-value tests at elevated confining pressures to simulate in-situ pressure conditions. Effects of increasing temperatures and confining pressures on both the CERCHAR abrasivity test and Siever's J-value tests were analysed to develop meaningful statistical relationships. [ABSTRACT FROM AUTHOR]

In this study, we have established and demonstrated the relationships between petrographic and fabric features of igneous rocks and their engineering properties experimentally. To meet this purpose, we have examined several igneous rock specimens and have investigated their engineering properties, including their drillability (drilling rate index (DRI)), abrasivity (Cerchar abrasivity index (CAI)), mechanical features (uniaxial compressive strength (UCS), point load strength index (IS50), Brazilian test strength (BTS)), and their physical properties (dry density, porosity (N), and wave velocity (VP)). Then, we have investigated their petrographic features, including shape descriptors, size descriptors, rock fabric features, and mineralogical indexes. We tested 16 types of igneous rocks from 8 various locations in the Gelas tunnel route in Naghadeh City, west Azerbaijan, Iran. The Pearson correlation coefficient indicated a low drillability potential of fine-grained rocks compared to that of coarse-grained rocks. UCS displayed the best Pearson correlation with heterogeneity (H) and texture coefficient (TC) (R = − 0.88 and R = 0.86, respectively). Although the results obtained from multilinear regression (MLR) and multilinear log-linear regression (MLLR) models proved the efficiency of such models in predicting CAI, TC, H, index of interlocking (g), and Feldspathic index (IF). Their determination coefficient (R2) was 0.84 and R2 = 0.87, respectively. Nevertheless, in comparison, the artificial neural network (ANN) analysis is apparently more efficient than both MLR and MLLR (R2 = 0.90). The results revealed rock fabric features have a higher capability in identifying the engineering properties of igneous rocks than their mineralogical composition. [ABSTRACT FROM AUTHOR]

Objectives: Very little data are known about charcoal toothpastes. The aim of this study was to counteract the missing data by determining the relative dentin abrasivity (RDA) and relative enamel abrasivity (REA) values of charcoal toothpastes. Methods: Radioactively charged dentin and enamel samples were randomly divided into groups of eight specimens. Each group was brushed with two of total 12 charcoal toothpaste slurries and with a standard abrasive with a known RDA and REA value. The measured radioactivity in counts per minute within the slurries corresponds to the amount of dentin or enamel abraded. RDA and REA values of the charcoal toothpastes were expressed relative to the known value of the standard slurry. Results: The RDA and REA values of the charcoal toothpastes have a broad range of 24–166 and 0–14, respectively. Conclusions: The RDA and REA values do not differ significantly from previously tested commercially available toothpastes. However, the lack of fluoride compounds in many of the investigated charcoal toothpastes can have a less beneficial effect for the consumers. It is very important to educate patients accordingly. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to investigate the resulting abrasive dentin wear using abrasive slurries with different RDA values and applying increasing brushing forces. Methods: Forty‐five bovine incisors were randomly allocated in three groups (A, B, C, n = 15). One hundred and eighty dentin samples were prepared from these incisors and allocated to twelve groups (A1‐A4, B1‐B4, C1‐C4; n = 15). The groups were subjected to a brushing cycle (120 strokes/min, 25 min) as follows: groups A1 to A4 with an abrasive slurry (RDA = 71) applying increasing brushing forces (1, 2, 3 and 4 N). Groups B1 to B4 were brushed using an abrasive slurry (RDA = 85) and C1 to C4 (RDA = 133) applying the same above‐mentioned brushing forces. Abrasive dentin wear was recorded using a stylus profilometer and compared amongst the groups using robust models. Pairwise comparisons in each model were tested and corrected after Tukey's method (α = 0.05). Results: Applying 1‐N brushing force resulted in the same amount of abrasive dentin wear in all groups regardless of the abrasivity of the used slurry. Increasing the brushing force to 2 N resulted in statistically significantly higher abrasive wear in all groups. This increase in abrasive wear was much higher when the slurry with high abrasivity was used (RDA = 133) compared with the lower abrasive slurry (RDA = 71). Conclusion: The abrasivity of the used slurry does not add to the resulting abrasive wear when the brushing force is kept at 1 N. It seems better to advise and help the patients (showing signs of non‐carious cervical lesions) calibrating their brushing force to 1 N, than only to advise them to use toothpastes with lower abrasivities. [ABSTRACT FROM AUTHOR]

Objective: This study aims to evaluate extrinsic tooth stain removal and whitening efficacy of two experimental dentifrices containing (i) 5% sodium tripolyphosphate (STP)/1% micronized alumina or (ii) 5% STP/1% micronized alumina with abrasive silica (ED2) compared to a regular fluoride dentifrice (RFD) following 8 weeks of use., Materials and Methods: This was a single-center, randomized, controlled, blind, three-arm, stratified, parallel-group study. Eligible participants underwent clinical assessment of stain on the facial/lingual surfaces of maxillary and mandibular teeth using the modified Lobene stain index (MLSI), and shade of the facial surfaces of the central and lateral maxillary incisors using the VITA Bleachedguide 3D-Master (VITA) shade guide. Participants brushed twice daily with their assigned dentifrice and returned to the clinic for clinical assessments at weeks 4 and 8., Results: A total of 272 participants completed the study (281 screened, 279 randomized). Both experimental dentifrices demonstrated statistically significant reduction from baseline and significant differences compared to RFD for MLSI and VITA shade scores at 4 and 8 weeks. 10 treatment-related treatment-emergent adverse events were reported in seven participants. All were resolved at the end of the study., Conclusions: This study demonstrated that dentifrices containing 5% STP/1% micronized alumina provide enhanced stain removal and shade improvements compared to a regular dentifrice. Study treatments were generally well tolerated., Clinical Significance: A low-abrasion daily-use fluoride dentifrice containing 1% micronized alumina and 5% STP, suitable for people at risk of erosive toothwear and/or dentin hypersensitivity, can provide clinically meaningful superior reductions in tooth stain, which translates into a visibly noticeable improvement in tooth shade., (© 2025 The Author(s). Journal of Esthetic and Restorative Dentistry published by Wiley Periodicals LLC.)

The Bukit Timah Granite (BTG) formation is widely distributed in the central and northern parts of Singapore Island. The BTG rocks in the formation vary from granite to granodiorite. Several hybrid rocks and dykes are also present in the BTG. The granite is in various states of fracturing and weathering, ranging from residual soils to intact, unweathered fresh rock. This paper presents some mechanical and physical properties of Singapore BTG rocks, based on data from the Factual Geotechnical Reports of more than 200 boreholes from Downtown Line stage II (DTL2) sites of Cashew, Hillview, Bukit Panjang and Beauty World. The variations of the parameters, including the unconfined compressive strength (UCS), the point-load strength index (Is50), the Cerchar abrasivity index (CAI), and the slake-durability index are derived from laboratory tests on samples from borelogs of different depths. The empirical correlations between the UCS and Is50 and between the CAI and the strength parameters (UCS and Is50) are derived and validated against the commonly adopted equations. Statistical information, including the average values, the standard deviations, and the coefficients of variation, are provided for these parameters. These statistics provide a useful reference for numerical simulations and future projects involving BTG rocks.

Assessment of drillability of rocks is vital in the selection, operation, and performance evaluation of cutting tools used in various excavation machinery deployed in mining and tunneling. The commonly used rock drillability prediction methods, namely, drilling rate index (DRI) and Cerchar hardness index (CHI) have limitations in predicting the penetration rate due to differential wear of the cutting tool in rocks with varied hardness and abrasivity. Since cutting tools get blunt differently in different rocks, the stress beneath the tip of the bit decreases until it reaches a threshold value beyond which the penetration rate becomes constant. In this research, a new composite penetration rate index (CPRI) is suggested based on the investigations on four metamorphic rocks viz. quartzite, gneiss, schist and phyllite with varied hardness-abrasivity values. The penetration-time behavior was classified into active, moderate, passive, and dormant phases based on the reduction in penetration rate at different stages of drilling. A comparison of predicted penetration rate values using DRI and CPRI with actual penetration rate values clearly establishes the supremacy of CPRI. Micro-structure and hardness-based index was also developed and correlated with CPRI. The new indices can help predict cutting tool penetration and its consumption more accurately.

This study is a part of an overall research project on the effects of microwave (MW) irradiation on rocks for assisted rock breaking systems as well as mineral processing at McGill University. For the first time, this paper highlights a comprehensive investigation on the effects of microwave irradiation on Canadian kimberlites. Potential contribution to the continuous rock excavation and rock weakening effect prior to implementation of mechanical techniques was explored. Two different kimberlite rocks, i.e. volcaniclastic kimberlite (VK) and hypabyssal kimberlite (HK), and granite samples were studied. Some important physical properties of the rock samples were measured including rock quality designation (RQD), specific gravity, porosity, and specific heat capacity. Rock samples were treated for various exposure times using a multi-mode MW unit at different power levels ranging from 2 kW to 15 kW. The effect of MW irradiation on rock samples was investigated. The results indicate that the mechanical properties including unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) were significantly dropped as a result of MW irradiation. Finally, the effect on rock abrasivity using the Cerchar abrasivity index (CAI) has also been discussed.

The Qixia Formation of Shuangyushi structure in northwestern Sichuan Basin is an important strata for increasing reserve and production of natural gas in the Sichuan Basin. However, the difficult drilling strata represented by Xujiahe Formation in this block were faced with the bottleneck problems such as difficult rock breaking, fast wear, low rate of penetration(ROP) and short footage of a single bit, which seriously restricts the drilling speed and the overall exploration process of Qixia Formation gas reservoir. The outcrop rock samples and cuttings from the lower Xujiahe Formation (X2 and X1) were selected to carry out the analysis experiments of rock drillability, abrasivity and anti-drilling mechanism. The results show that the average drillability grade of the tested rock sample are 8. 45, while all the sample of X1 Formation reach the highest grade 10. In addition, the average grinding amount of the standard bar are 16. 26 mg, showing extremely strong drill resistance. Analysis considered that the low porosity and permeability, high quartz content, high cementation strength, compressive strength and hardness in the lower Xujiahe Formation are not conducive to rock breaking with impact and cutting of bit and hydraulic assisted, which is the main reason for the low ROP. Macroscopically high strength and hardness, as well as the strong abrasion of drilling cuttings in micro scales are not only the key factors leading to the impact failure and grinding failure of the bit teeth, but also the key direction of the subsequent research and selection of drill bits. [ABSTRACT FROM AUTHOR]

Determination of rock abrasivity using the LCPC test – Recommendation No. 24 of the Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society) is compiling instructions for rock testing in laboratory and in situ and for monitoring of rock masses and civil engineering structures. This recommendation No. 24 deals with the LCPC test for investigating hard rock samples in order to determine the abrasivity and the crushability of hard rock. The requirements for the test facility and sample preparation as well as the procedure for carrying out and evaluating LCPC tests are specified. The LCPC test was developed by the Laboratoire Central des Ponts et Chaussées and is used to classify the abrasivity and crushability of rock. This recommendation takes into account the French standard NF P 18‐579: 2013‐02 [1], but goes beyond it in terms of testing procedure and evaluation. The abrasivity index is determined by exposing a defined steel test plate to a granular sample at a defined speed of rotation for a defined amount of time. The material loss of the test plate is measured and applied for the calculation of an index value for the abrasivity of the original hard rock sample. In addition, an index value for the crushability can be determined from the change in grain size compared to the initial sample. [ABSTRACT FROM AUTHOR]

The equivalent quartz content – historic review and its future application in abrasivity prediction The assessment of the abrasion resistance of minerals and their influence is an important aspect in engineering geology and rock mechanics. Questions with regard to rock excavation and the expected wear parameters play a decisive role. Various test methods have been developed over the decades to assess the hardness properties and abrasiveness of minerals and rocks. These include direct tests on rock samples, hardness tests but also parameters derived from mineralogical and petrographic data, such as the equivalent quartz content FEQ. The values used today for determining the FEQu exist since more than 100 years, and are named after August Rosiwal (1860–1923), the pioneer in the field of grinding tests, referred to as Rosiwal factors. The present work deals with this approach, compiles the factors of various authors, and establishes correlations with other hardness parameters. Using laboratory data, the FEQu are calculated and compared amongst the different sources. It is also shown how the FEQu can be directly related to the widely used cerchar test, on the basis of cerchar abrasivity index (CAI) values of selected reference minerals. The FEQu cannot record structural influences, but quartz as a common reference in the cerchar test and FEQu offers the possibility of directly linking the two parameters. [ABSTRACT FROM AUTHOR]

Replacing worn disc cutters in a tunnel boring machine (TBM) operation is a time-consuming and expensive process. This article presents the study of disc cutter wear rate during the excavation of 36 km Naqadeh water conveyance tunnel with a diameter of 6.325 m. The construction of this tunnel in northwest Iran has been recently completed. The geological setting of the tunnel consists of variable lithology, including limestone, shale, granite, and granodiorite units. Field data were collected and analyzed from TBM tunneling of 9.5 km of the tunnel. The analysis was performed by incorporating the types of wear and comparing the accuracy of traditional cutter wear prediction models. The new model was developed using statistical analysis of the observed cutter wear in this project. The validity of the proposed model was evaluated using the excavation data for the following 2 km of the tunnel. The model developed in this study allows estimating wear rate and cutter life using common rock characterization parameters such as the Cerchar abrasivity index (CAI) and the uniaxial compressive strength (UCS). [ABSTRACT FROM AUTHOR]

Objective Charcoal-containing dentifrices are gaining popularity, but scientific information on their effect on oral health is scarce. This study investigated properties of dentifrices that may affect dentine abrasivity, as well as their ability to adsorb fluoride, their pH and the presence of harmful substances. Materials and methods The dentifrices NAO and COCO were subjected to the following analyses: abrasivity, expressed as mean abraded depth and relative dentin abrasivity (RDA), and surface roughness of extracted human molars (n = 30) after simulated brushing; fluoride adsorption measured as concentration change; pH measurements; detection of polycyclic aromatic hydrocarbons by gas chromatography–mass spectrometry. The products were compared to a reference dentifrice (Colgate® MaxWhite), positive controls (ISO dentifrice slurry, activated charcoal for laboratory use) and a negative control (distilled water). Results The mean abraded depths of NAO and COCO were not different (p > .05), but higher than the reference dentifrice and the negative control (p .05). Both NAO and COCO were alkaline (pH > 7). Analysis of NAO revealed the presence of naphthalene (112.8 ± 2.0 ng/mL). Conclusion The charcoal-containing dentifrices were abrasive within acceptable limits set by ISO and did not adsorb fluoride. The presence of naphthalene in one product is a cause for concern.

Objective: To explore the use of 3D intraoral scanner/image analysis for the detection and monitoring of simulated non-carious cervical lesions (NCCLs) in vitro. Materials and methods: A total of 288 NCCLs of different severities and simulated using a laboratorial model associating toothbrush stiffness (soft, medium, and hard) and toothpaste abrasivity (low, medium, high, and negative control) were analyzed. Dental impressions were taken from specimens before and after 35K and 65K brushing strokes, and then scanned with a CEREC Omnicam scanner. 3D models were analyzed for volumetric tooth loss. 3D optical profilometry was considered as the gold standard. Data were analyzed using ANOVA and Fisher's PLSD tests (alpha = 0.05), and agreement between methods by using intraclass correlation coefficient. Results: Toothbrushes of hard and mid stiffness caused higher tooth loss than soft when associated with the highest abrasive, at 35K and 65K strokes (p < 0.001). Variation in slurry abrasivity led to differences in tooth loss (with control < low < medium < high, p < 0.0001) after both 35K and 65K strokes, regardless of the type of toothbrush used, except at 35K, wherein control = low (p = 0.55). 35K strokes caused less tooth loss than 65K for all abrasive slurries (p < 0.0001) except controls. The intraclass correlation coefficient for agreement between the test and gold standard methods was 0.85. Conclusions: Analysis of 3D images from intraoral scanner could detect and monitor NCCL progression, although this ability was limited on incipient lesions. Overall good agreement was found between the test method and optical profilometry. Clinical relevance: The suggested method may be applicable to detect and monitor NCCLs clinically. [ABSTRACT FROM AUTHOR]

Determination of rock abrasivity using mineralogical‐petrographical methods – Recommendation No. 25 of the Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society) is compiling suggestions for rock testing in laboratory and in‐situ and for performing monitoring of rock masses and civil engineering structures. Recommendation No. 25 deals with the determination of mineralogical‐petrographic parameters from hardrock samples in order to assess hardrock abrasivity. It specifies the requirements for testing equipment and test specimen, the procedures to perform and to evaluate thin‐section and powder X‐ray diffractometer analysis and the methods for deriving various index values for abrasivity assessment. Petrographical analysis provides information about the type and amount of a rock's mineral composition as well as on its structural properties. This information can be applied for the characterization of rock abrasivity either by use of direct values (for instance quartz content) or in the form of index values (for instance Equivalent Quartz Content, Schimazek Index or Rock Abrasivity Index). [ABSTRACT FROM AUTHOR]

Abrasivity of rock and soil causes tool wear in excavation or drilling operations, and the presence of sandy gravels stratum also plays a significant role in causing serious damage to the cutting tools. Understanding the wear mechanism is important for the cost estimation and planning of projects. Abrasivity of cobbles and boulders present within soil matrix may vary from negligible in some cases to severe under certain conditions depending upon the volume and characteristics of those cobbles and boulders being encountered. Several methods have been proposed to assess the abrasivity of rock. In the present research, LCPC rock abrasivity tests were performed on 14 gravel samples collected from different river deposits of Pakistan. Practical extensions to the standard LCPC abrasivity test were used and fraction larger than 6.3 mm was incorporated in accordance with the method proposed by Thuro et al. (2007). Moreover, in order to observe the effect of increasing grain size on LCPC abrasivity coefficient (LAC g/t), 3 river gravel samples (out of initially selected 14 samples) were chosen and evaluated along with the computation of brittleness coefficient (LBC, %). Correlations were developed with LAC values of originally rounded grains against crushed/angular grains. XRD analysis was incorporated in order to determine the mineralogical composition of each sample and the possible correlation of LAC (g/t) with abrasive mineral content (AMC, %) for both modes of testing (rounded and crushed samples) were developed. Moreover, the correlations of LAC (g/t) with quartz content, equivalent quartz content, and mass-weighted average Moh's hardness were also discussed. [ABSTRACT FROM AUTHOR]

Keywords: Cobalt-rich crust; Compressive strength; Abrasivity; Friability; Cutting test EN Cobalt-rich crust Compressive strength Abrasivity Friability Cutting test 2929 2934 6 06/05/20 20200601 NES 200601 Introduction Hydrogenetic cobalt-rich ferromanganese crusts (cobalt-rich crusts, CRCs) are expected as potential mineral deposits for rare earth elements and platinum group elements as well as cobalt, nickel, and manganese (Manheim [8]; Rona [13]). Thereafter, Yamazaki et al. ([17]) reported the compressive strength of CRCs and substrate rocks, and then Wu and Chen ([16]) reported the shear strength of CRCs. 1 Porosity, P-wave velocity, and uniaxial compressive strength of the cobalt-rich crusts (CRCs) and substrate rocks. a Relation between porosity and uniaxial compressive strength. The curves for the CRCs are located on the left side of those for the substrate rocks; that is, the debris of the CRCs is smaller than that of the substrate rocks after crushed. [Extracted from the article]

Background: Toothbrushing with toothpaste is a major contributor to dental abrasion. A number of factors such as abrasivity and concentration of the toothpaste, brushing frequency, brushing duration, force of brushing, and toothbrush bristle stiffness have a potential impact on the abrasion process of dental hard tissue. However, the abrasivity of the toothpaste is the most important parameter that affects the abrasion process of dental hard tissue. Aims: This study aims to evaluate the maximum and mean enamel abrasivity of commercially available dentifrices such as Colgate total®, Pepsodent whitening®, Vicco vajradanti®, Dabur red® in primary and permanent teeth. Materials and Methods: Human extracted 60 primary and 60 permanent teeth were randomly selected based on the inclusion criteria. Teeth were sectioned at cementoenamel junction using diamond disc and mounted in an acrylic resin blocks. Baseline profilometric measurements were recorded for all the samples. Four commonly used dentifrices were selected and labeled as Group A (Colgate Total®), B (Pepsodent Whitening®), C (Vicco Vajradanti®), and D (Dabur Red®). Toothpaste slurry was prepared. Tooth specimens were brushed in vitro using a customized brushing machine. After toothbrushing, profilometric measurements were obtained, and the differences in readings served as proxy measure to assess surface abrasion. Data were collected and analyzed using student t-test and ANOVA test. Student t-test was used to compare the enamel abrasivity prebrushing and postbrushing, and ANOVA was used to compare the enamel abrasivity among the four different commercially available toothpastes. Results: In permanent teeth, all the toothpastes were found to cause significant enamel abrasion (P = 0.000) and a significant variation was observed when maximum (P = 0.008) and mean (P = 0.036) enamel abrasivity of these toothpastes were compared. In primary teeth also, all the toothpastes caused significant abrasion (P = 0.000); however, when the maximum and mean abrasivity of these toothpastes were compared, no significant variation was observed (P = 0.438 and 0.163). Conclusions: All the commercially available toothpastes cause significant enamel abrasion. Colgate group caused more enamel abrasion whereas pepsodent caused the least enamel abrasion in permanent teeth.

Objective: Charcoal-containing dentifrices are gaining popularity, but scientific information on their effect on oral health is scarce. This study investigated properties of dentifrices that may affect dentine abrasivity, as well as their ability to adsorb fluoride, their pH and the presence of harmful substances. Materials and methods: The dentifrices NAO and COCO were subjected to the following analyses: abrasivity, expressed as mean abraded depth and relative dentin abrasivity (RDA), and surface roughness of extracted human molars (n=30) after simulated brushing; fluoride adsorption measured as concentration change; pH measurements; detection of polycyclic aromatic hydrocarbons by gas chromatography-mass spectrometry. The products were compared to a reference dentifrice (Colgate® MaxWhite), positive controls (ISO dentifrice slurry, activated charcoal for laboratory use) and a negative control (distilled water). Results: The mean abraded depths of NAO and COCO were not different (p>.05), but higher than the reference dentifrice and the negative control (p<.05). The RDA values of NAO, COCO and the ISO dentifrice slurry were higher than the reference dentifrice value (p<.05) by up to 10 times. The dentine surface roughness was higher after brushing with NAO, COCO and ISO dentifrice slurry compared to distilled water (p<.05). No change in mean adsorbed fluoride concentration was observed after 24 h (p>.05). Both NAO and COCO were alkaline (pH > 7). Analysis of NAO revealed the presence of naphthalene (112.8 ± 2.0 ng/mL). Conclusion: The charcoal-containing dentifrices were abrasive within acceptable limits set by ISO and did not adsorb fluoride. The presence of naphthalene in one product is a cause for concern. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the effect of toothbrush stiffness and dentifrice slurry abrasivity on the development and progression of simulated non-carious cervical lesions (NCCLs). Materials and methods: Human maxillary premolars were allocated to 12 groups generated by the association between toothbrushes, soft, medium, and hard stiffness, and simulated dentifrice slurries, lower, medium, and higher; deionized water (DI) served as negative control. Teeth were mounted on acrylic blocks, and their root surfaces partially covered with acrylic resin to simulate gingiva, leaving a 2-mm area apical to the cemento-enamel junction exposed to toothbrushing. Specimens were brushed with the test slurries for 35,000 and 65,000 double strokes. Impressions taken at baseline and after both brushing periods were scanned by a 3D optical profilometer. Dentin volume loss (mm3) was calculated by image subtraction. Data were analyzed using three-way ANOVA and Fisher's PLSD tests. Results: All toothbrushes caused higher volume loss when associated to higher abrasive slurry, compared to medium- and lower-abrasive slurries. Medium caused more volume loss than lower-abrasive slurry, which led to more volume loss than DI. Hard and medium toothbrushes were not different when used with medium- or higher-abrasive slurries. There were no differences among toothbrushes when used with DI and lower-abrasive slurry. Overall, 35,000 brushing strokes resulted in significantly less volume loss than 65,000. Conclusions: Toothbrush stiffness was an important factor on NCCL development, especially when brushing with medium- and higher-abrasive slurries. Clinical relevance: Medium and hard toothbrushes associated with medium- and high-abrasive toothpastes can yield more severe NCCLs. [ABSTRACT FROM AUTHOR]

Results of a round robin test referring to DGGT testing recommendation no. 23: Cerchar test. At least since its reference in the General Technical Terms of Contract (VOB/C), the Cerchar scratch test can be regarded as standard procedure for the determination of hardrock abrasivity in Germany. The test is usually carried out with reference to testing recommendation no. 23 of the national Commission on Rock Testing (working group 3.3) of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society), which was published in 2016. In order to verify the aim of this recommendation, i.e. the standardization of the test procedure, a round robin test was organized as part of a master thesis at TU Darmstadt. In total, a number of 17 rock mechanical laboratories from Germany and Austria participated in the test and test results were evaluated according to DIN ISO 5725 in order to analyze their precision. An evaluation of the test and its results shows, that the Cerchar method, based on recommendation no. 23 can be considered as a generally suitable testing method for the assessment of hardrock abrasivity. However, the results emphasize, that an appropriate interpretation of CAI test results should always take into account the specific variation of measured values, which significantly depends on the composition and microstructure of the tested rock material. Regarding the quantification of variability, the Cerchar round robin test is able to provide valuable baselines. In addition, some recommendations for further optimization of the testing procedure were derived. [ABSTRACT FROM AUTHOR]

• Drilling performance of a PDC bit was experimentally evaluated in a laboratory. • Drilling parameters changed reasonably according to the rock properties. • The wear of PDC cutters was associated with some of the indexes for rock abrasivity. A high-performance drilling bit for geothermal well drilling is expected to be developed to reduce the drilling duration and cost. The application of polycrystalline diamond compact (PDC) bits to geothermal well drilling has been considered worldwide. In this study, drilling tests on several types of rock were performed in a laboratory using a PDC bit. The drilling parameters changed reasonably in the tests according to the rock properties. The progress of the wear of PDC cutters was quantitatively observed and was found to be associated with some of the indexes of rock abrasivity. [ABSTRACT FROM AUTHOR]

Highlights • A new technic for the application of stress levels on abrasive soil samples was developed. • The effect of water content and effective stress level on the soil abrasivity was investigated. • Water drainage during abrasivity test has a considerable effect on the recorded wears. • The theory of soil compaction can be used to describe the abrasive behavior of granular soils. • The effect of stress levels and rotation speed on the obtained wear is different under different moistures. Abstract The development of mechanized tunneling technology and the extent of its application in the soft grounds have revealed the importance of soil abrasivity studies more. As one of the first methods of soil abrasivity assessment, LCPC test is widely used in predicting the wear of cutting tools in soft grounds. In this study, the effect of water content, rotation speed, and applied stress on the abrasivity of crushed silica particles are investigated with the LCPC tests. The results showed that water content has a considerable effect on the abrasive behavior of silica particles. The occurrence of drainage during the tests considerably changed the dominant conditions of moisture and affected the observed wear rates. The obtained correlation between the effective stress levels and recorded wears showed that the theory of granular soils compaction can be used to describe the variations of soil abrasivity with water content changes. Moreover, the results showed a direct linear correlation between the rotation speed of steel propellers and measured wears. The same correlation was also found between effective stress levels and wear amounts. However, in the samples with higher water content than 10 percent, the effect of stress on the wear rates increases with the increase of propeller rotation speed. [ABSTRACT FROM AUTHOR]

Ten potentially abrasive rock samples selected from various locations of Pakistan covering igneous, metamorphic and sedimentary rocks were subjected to a comprehensive laboratory testing program. The experimental work includes the NTNU/SINTEF abrasion value steel (AVS) and Sievers' J-miniature drill (SJ) tests accompanied by CERCHAR and LCPC rock abrasivity tests. The results of SJ tests and AVS tests were further utilized to compute the cutter life index (CLI), which estimates the life of tunnel boring machine (TBM) disc cutter rings in boring hours. In this research, a comparative study was performed on an NTNU/SINTEF rock abrasivity device by varying the particle size of rock abrasion powder and rotational test speed of the steel disc. The NTNU/SINTEF AVS test results showed a gradual decrease in abrasivity with the corresponding decrease in grain size of test fractions. An increase in the wear of the test piece was observed at a test speed of 10 rpm as compared to the standard test speed of 20 rpm. Relevant correlations of CLI, SJ-value and AVS with CERCHAR abrasivity index (CAI) and LCPC abrasivity coefficient (ABR, g/t) were also discussed. [ABSTRACT FROM AUTHOR]

In the CERCHAR abrasivity test for rocks, to understand the wear process of styli is important for the appropriate setting of test conditions and for the estimation of bit wear in in-situ rock excavation. In this study, the wear process of a stylus was estimated from both the stylus vertical displacement measured during the test and the groove depth measured after the test. The results showed that the stylus wear during the test can be traced with a simple calculation of the measured values for the two high abrasive rocks, Inada granite and Iwaki sandstone. In those tests, the styli were worn flatly. The calculation was corrected for the other medium to low abrasive eight rocks, because the measured groove depth was not thought to be completely consistent with the penetration depth of the stylus. Comparing the results of the nine rocks with the exception of the granite, the stylus wear continued for longer sliding distance in the tests for higher abrasive rock. It was found from the results of the granite that the mineral constitution affected the wear process of the stylus. In addition, this paper discussed the relation of the CAI (CERCHAR Abrasivity Index) and its variation to the stylus wear process and the rock hardness. On the basis of the results, points of attention in the CERCHAR test were described.

Abstract Cerchar abrasivity index (CAI) test is widely used to estimate the tool life and wear in various excavation equipment in mining and tunneling projects. The aim of this study is to analyze the effect of various factors related to the CAI testing procedure. Particularly, sensitivity of CAI results is investigated due to variation of certain testing parameters, including the type of apparatus used, wear flat measurement methods, specimen surface conditions and stylus hardness. Relationship between CAI and certain testing parameters, and its repeatability are also investigated through statistical analyses of a series of CAI tests results obtained from twenty-one selected rock specimens. Results show little variation between the type of apparatus used and between the selected wear flat measurement methods. Nevertheless, there is a significant large variation in CAI values according to the changes in specimen surface conditions and the hardness of stylus used. The results show that with an increase in the hardness of the steel stylus the CAI values decrease differently in accordance with the rock type tested. Highlights • Cerchar abrasivity index (CAI) test is widely used for determination of rock abrasiveness. • CAI was found to vary with changes in certain testing preferences; • hardness of the stylus used in testing. • Surface condition of the rock specimens (rough vs. saw-cut). • Wear flat measurement methods. • CAI values for both testing preferences (measurement methods and type of apparatus used) were highly reliable and accurate. • A significantly variation found between CAI values of saw-cut and rough specimen surfaces. • CAI values exhibit a wide variation with changes in the stylus hardness, rock type, and geological origin of rock. • HRC55 steel stylus produce the best reliable result among HRC41, HRC45, HRC49, HRC51, HRC55, and HRC59 styli. [ABSTRACT FROM AUTHOR]

During soft ground tunnel construction, the presence of sandy gravel stratum often causes serious wear and tear of cutting tools. In this paper, an experimental study to assess abrasivity of sand-gravel materials with different gravel content (GC) and gravel size (GS) was carried out with a horizontally oriented mechanical mixing device. The abrasive characteristics of testing materials were quantitatively assessed through the measurement of weight loss on the testing steel cube, with a focus on the influence of GC and GS of the mixtures. Experimental testing results indicate that GC and GS have significant impact on soil abrasion and tool wear, through affecting the packing density of the sand-gravel mixtures, breakage resistance of particles, and the soil-tool wear mechanisms. The torque required to drive the propeller in the sand-gravel mixtures during the abrasivity test was measured and provided more insights into the abrasivity of mixtures and the associated soil-tool wear mechanisms. In addition, potential relationships between coefficient of uniformity ( C u ) and coefficient of curvature ( C c ) of the sand-gravel mixtures and the tool wear were sought. [ABSTRACT FROM AUTHOR]

The physical and physicochemical properties of thermal muds (peloids) from 20 spas in Turkey were defined and compared with those of naturally pure clay minerals, smectite, illite, sepiolite, and kaolinite, to define the suitability of their use in pastes, masks, creams, and/or mud baths. The liquid and plastic limit values of the peloids show medium to high plasticity. The values of the pure clay minerals vary from 110 to 369 and 60 to 130, respectively, being higher than those of the peloid samples except for illite and kaolinite. The peloid samples show very soft, soft, semihard, hard, and fluid properties according to the consistency index. The CEC values of the peloids vary from 10.11 to 36.01 meq/100 g. The abrasivity of the peloids and clay minerals ranges from 0.58 to 3.12 mg/m2. and 0.05 to 0.37 mg/m2., respectively. The viscosity values of the peloid samples are variable and the thixotropic values are considerably higher in some peloid samples. In the pure clay minerals, sepiolite shows high values. The oil absorption capacity of sepiolite is higher than that of the other clay minerals. The peloids with high CEC, swelling, and absorption capacity may be suitable for the removal of oils, toxins, and contaminants from the skin. [ABSTRACT FROM AUTHOR]

The paper reports selected results of a study on tool wear for mechanized tunnelling in coarse soil. Several laboratory soil abrasion tests were performed and the results correlated with mineralogical composition, shape and surface roughness of the grains and the grain size curve of the soils. The analysis of the results clearly confirms the well-known correlation between soil abrasivity and quartz content and, for the soils tested, can quantify the relevant influence of grain size and grain roughness. We also report and discuss results useful for quantifying the positive effect of the addition of different chemical agents, injected as foams in a process known as soil conditioning, commonly performed in mechanized tunnel excavation using tunnel boring machines whit earth pressure technology to minimise tool consumption. [ABSTRACT FROM AUTHOR]

The efficiency of a tunneling project is mainly associated with the abrasivity of the acting soil and the wear resistance of the cutting tools. Heavy wear can dull the cutting tool, which negatively affects the penetration rate and therefore the efficiency of a tunneling process. Completely worn tools with a short service life have to be replaced by newer ones. This circumstance results in unplanned machine shutdowns and higher maintenance costs. It is thus of high economic as well as technical interest to obtain a deeper understanding of soil/cutting tool interactions during tunneling. To meet this challenge, a large number of different testing devices to estimate the abrasivity of soils have been developed within the last two decades. An innovative and promising experimental setup is presented in this work. A horizontal implementation offers the possibility of simulating a tunneling process as well as the tribological system of a TBM tool. The interactions between all system components can be mapped and analyzed in detail. This method offers a unique setup, which allows wear prediction of TBM tools in a homogeneous soil with project-specific parameters (soil composition/condition, soil mechanics, tool material and machine/tunneling data). [ABSTRACT FROM AUTHOR]

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Der Arbeitskreis AK 3.3 “Versuchstechnik Fels” der Deutschen Gesellschaft für Geotechnik e. V. erarbeitet Empfehlungen für felsmechanische Labor‐ und Feldversuche sowie Messungen im Gebirge und an Bauwerken. Die vorliegende Empfehlung Nr. 23 behandelt den CERCHAR‐Versuch an Gesteinsprobekörpern. Es werden die Anforderungen an die Prüfeinrichtung und die Probekörper sowie die Vorgehensweisen für die Durchführung und Auswertung von CERCHAR‐Versuchen festgelegt. Der CERCHAR‐Versuch wurde vom Centre d'Études et des Recherches de Charbonnages de France entwickelt und hat sich seitdem zur Bestimmung der Abrasivität von Festgesteinen weltweit etabliert. Die vorliegende Empfehlung berücksichtigt die internationalen Normen AFNOR NF P 94‐430‐1 [1] sowie ASTM D 7625‐10 [2], geht jedoch hinsichtlich Versuchsdurchführung und ‐auswertung über diese hinaus. Die Empfehlung ist hinsichtlich Versuchsdurchführung und der Klassifikation konform mit den Angaben in der Empfehlung der International Society for Rock Mechanics [3]. Beim CERCHAR‐Versuch wird ein Indexwert für die Abrasivität eines Festgesteins bestimmt, indem ein definierter Prüfstift aus Stahl entlang einer definierten Prüfstrecke unter konstanter Auflast über die Oberfläche eines Probekörpers gezogen wird. Als Maß für die Abrasivität des Probekörpers wird die idealisiert kegelstumpfförmige Abnutzung des Prüfstifts gemessen. In dieser Empfehlung werden der Zweck, die Begriffe, die Prüfeinrichtung, die Anforderungen an den Probekörper sowie die Versuchsdurchführung und ‐auswertung behandelt. Recommendation No. 23 of the Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society) – “Determining the abrasivity of rock using the CERCHAR test” The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e.V. (German Geotechnical Society) is compiling instructions for rock tests in laboratory and in‐situ and for performing monitoring of rock masses and civil engineering structures. The recommendation No. 23 deals with the CERCHAR test for determining the abrasivity of rocks. The CERCHAR test was developed by the Centre d'Études et Recherches des Charbonnages de France and is established worldwide for determining the abrasivity of rocks. This recommendation considers the international standards AFNOR NF P 94‐430‐1 [1] as well as ASTM D 7625‐10 [2], but is more specific regarding the testing procedure and evaluation. It is compliant to the given testing procedures and classification in the recommendation of the International Society for Rock Mechanics [3]. The CERCHAR Abrasivity Index (CAI) is determined in a CERCHAR test by scratching a defined steel stylus for a distinct length and under defined load over the surface of a rock specimen. The measure of the abrasivity is defined by the idealized shape of the wear flat of the steel pin. In this recommendation the scope of the test, the terms, the requirements on the testing apparatus and the specimen are described as well as the testing procedure and evaluation. [ABSTRACT FROM AUTHOR]

Drilling, blasting and mechanical methods using road headers or tunnel boring machines (TBMs) are among the methods used for underground excavation of rock and soil. The interaction between the tools used and the ground leads to fragmentation of rocks and soil grains as well as tool wear. Wear is defined as the loss of tool material as a result of the interaction between rocks (or soil) and the drilling tools. The LCPC abrasivity test is a quick and easy procedure used widely to assess the abrasivity of soil and rock for predicting the rate of wear of cutting and drilling tools. The LCPC test device is designed to measure the abrasivity of particles as small as fine gravel. Various parameters can affect the LCPC abrasivity coefficient (LAC). In this paper, equations relating the index properties and the LAC were applied to 27 different samples. The derivation of models predicting the engineering geological properties of rocks and soils is useful because providing specimens of rocks at depth is difficult and expensive in the preliminary design of underground projects. Regression analysis was applied in developing some models for the LAC based on indirect methods including the equivalent quartz content (EQC), grain shape, grain size, grain angularity and water saturation applied to data from rock and soil samples in Iran. The results showed that EQC is the most important parameter affecting the LAC, with the other parameters having lower levels of importance. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to correlate patient-reported reactions with in vitro analyses of the pH, abrasive quality, and cytotoxicity of four toothpastes. Materials and Methods: One hundred twenty-one patients received non-identified samples of toothpaste to be used for 6 days and answered a questionnaire about their sensations. In vitro analysis: the pH of toothpastes was measured with a pH meter. The abrasivity of toothpastes was evaluated against composite resin specimens ( n = 10). A toothbrushing machine was used to simulate wear, which was indirectly measured by mass loss using a scale. Cell culture media conditioned with toothpaste were used to assess the cytotoxicity. Confluent cells were kept in contact with the conditioned media or control for 24 h. The cell viability was measured using the 3-(bromide, 4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium (MTT)-reduction assay. The obtained data on the pH, weight loss, and cell viability were compared by ANOVA/Tukey's tests ( p < 0.05). Results: With the exception of the bleaching effect paste, the Oral B® paste produced the highest frequencies of irritation reports, tooth sensitivity, taste discomfort, and texture discomfort in the clinical study; patients also reported rougher teeth, soft tissue peeling, dry mouth, thrush, tingling, and taste changes in response to this paste. The in vitro analysis demonstrated that Oral B® had the lowest pH, the highest abrasivity, and produced the lowest cell viability ( p < 0.01). Conclusion: Results suggest that low pH toothpastes that are highly abrasive and cytotoxic may cause undesirable reactions in patients. Clinical relevance: Toothpaste's properties should be well known for indication to patient therefore minimizing discomfort reports. [ABSTRACT FROM AUTHOR]

Accurate estimation of rate of penetration (ROP), daily rate of advance (AR), and cutter cost/life is necessary for the justification and successful use of a TBM on any tunneling project. Various models have been introduced over the years to provide such estimates. In many cases, these models have been successful with pin point accuracy, and in other instances off by a wide margin. Improving the accuracy of performance prediction models for hard rock TBMs has been the subject of many studies, some yielding project-based models and some more universal models that can be used elsewhere. This paper will discuss the latest version of a new empirical model for estimating penetration rate and disc cutter life for hard rock TBM tunneling based on recent tunneling projects, constructed during the period 2002-2009. The new model was then applied to predict TBM performance and disc cutter wear in different mechanized tunneling projects under construction since 2009. Accuracy and validity of the model for prediction of ROP were checked by comparing predicted and measured values of TBM performance in 24 km of newly bored tunnel. The results indicate that despite some minor deviations in estimates in some tunnel sections, reasonable agreement can be observed between predicted and actual ROP of TBMs. [ABSTRACT FROM AUTHOR]

The abrasiveness of crushed rock is determined in the design phase of a tunnelling project to estimate the wear on excavation and boring tools, using for example the LCPC abrasiveness test. Considered from the point of view of material science, there are problems with the validity of such an index value since important tribological factors, like for example the internal structure of the sample impeller (size, phase composition) are not considered in the current testing standard (AFNOR P18-579). In this investigation, LCPC tests were performed with impellers of various steels of the same and different hardnesses against two abrasives (Mohs hardness 7, 9) in order to determine the influence of the internal structure and the associated tribo-mechanical properties on the LCPC index value (ABR). In addition to the material hardness required by the standard (60 to 75 HRB ≈ 105 to 140 HV 10 according to DIN EN ISO 18265-2013), sample materials with higher hardness values were also used in order to extend the basis of the LCPC abrasiveness index to these practically applicable material groups. The results make clear that awareness has to be raised regarding the materials used for the LCPC test. An abrasive can be classified differently just by using various materials of the same hardness. In order to obtain reliable and reproducible index values for the abrasiveness of crushed rock, it is necessary to consider the influence of materials in future recommendations for the LCPC. Die Abrasivität von Lockergestein wird im Rahmen der Planungsphase eines Tunnelbauprojekts zur Abschätzung des Verschleißes an Abbau- und Bohrwerkzeugen bestimmt, beispielsweise durch den LCPC-Abrasivitätstest. Aus werkstofftechnischer Sicht ergeben sich Schwierigkeiten in Bezug auf die Aussagekraft eines solchen Indexwertes, da wichtige tribologische Einflussfaktoren wie z. B. das Gefüge des Prüfflügels (Größe, Phasenzusammensetzung) in der aktuellen Prüfnorm (AFNOR P18-579) nicht berücksichtigt werden. Im Rahmen dieser Untersuchung wurden LCPC-Versuche mit Drehflügeln aus verschiedenen Stählen gleicher und unterschiedlicher Härte gegen zwei Abrasive (Mohshärte 7, 9) durchgeführt, um den Einfluss des Gefüges und den damit verbundenen tribo-mechanischen Eigenschaften der Prüfflügelwerkstoffe auf den LCPC-Indexwert (ABR) zu ermitteln. Neben Werkstoffhärten, die nach Norm gefordert werden (60 bis 75 HRB ≈ 105 bis 140 HV 10 nach DIN EN ISO 18265-2013), fanden auch Prüfwerkstoffe mit höheren Härtewerten Anwendung, um die Datenbasis des LCPC-Abrasivitätsindex auf diese anwendungsnahen Werkstoffgruppen auszuweiten. Die Ergebnisse verdeutlichen, dass eine Sensibilisierung im Umgang mit dem LCPC-Versuch in Bezug auf die verwendeten Werkstoffe erforderlich ist. Ein Abrasiv lässt sich unterschiedlich klassifizieren, nur durch die Nutzung von verschiedenen Werkstoffen derselben Härte. Um aussagekräftige und reproduzierbare Indexwerte für die Abrasivität von Lockergestein bestimmen zu können, ist es notwendig, werkstofftechnische Einflüsse in zukünftigen Empfehlungen für den LCPC-Versuch zu berücksichtigen. [ABSTRACT FROM AUTHOR]

Aim: A lot of herbal and medicated toothpastes having natural and antisensitivity properties are creating niches for themselves in the market. However, toothpaste containing high content of abrasives can be harmful to the teeth. The present in vitro study was conducted to assess the abrasiveness of three commercially available dentifrices on human-extracted anterior teeth on sound and demineralized enamel., Materials and Methods: A total of 42 freshly extracted teeth were mounted on acrylic resin and randomly divided into three groups (group I, Colgate; II, Glister; and III, Dant Kanti). Each group consisted of one test tooth (partially) and one control tooth (completely) covered with nail varnish. The study had two phases. Phase 1-baseline average roughness (Ra) value was assessed with a profilometer of all the samples. Phase 2-further, teeth were immersed in the demineralizing solution for 4 days to allow the formation of an artificial carious lesion. Tooth brushing was performed by a customized automated toothbrushing model on all the teeth for 28 days. Ra value was again evaluated with Profilometer., Result: Data were analyzed, and a statistically significant result was observed with demineralized teeth in all three groups ( p = 0.005). The intragroup comparison showed a significant difference with demineralized teeth of Colgate and Dant Kanti, ( p =0.018) and ( p =0.027), respectively. However, there was no significant difference in demineralized teeth of glister and sound teeth of all three groups., Conclusion: Glister was found to be the least abrasive of all three toothpastes, followed by Dant Kanti and Colgate., Clinical Relevance: The particle size of the ingredients used in manufacturing toothpaste can lead to abrasion of the teeth.This, in combination with the hard bristles, can cause more harm to the teeth than good. The current study has compared the abrasive potential of three commercially available kinds of toothpaste. Hence daily use of these commercially available dental products should be used cautiously., How to Cite This Article: Priyam S, Sankeshwari R, Jalihal S, et al. Comparative Evaluation of Abrasiveness among Three Dentifrices: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(2):264-269., Competing Interests: Source of support: Nil Conflict of interest: None, (Copyright © 2023; The Author(s).)

The main problems associated with the operation of microspherical treating-type chromia-alumina catalysts with increased strength during isoparaffin dehydrogenation are discussed. The erosive wear of the walls of overflow pipelines when using a mixture of treating-type KDI and conventional IM-2201S catalysts and ways of solving the problem are emphasized. It is found that the main reason for an increase in erosive wear is the greater momentum of catalyst particles due to a higher mean particle size and gas transport rate; upon transitioning from IM-2201S to a mixture of IM-2201S and KDM (70 : 30), the mean particle size of the equilibrium catalyst grows from 68 to 74 μm. The optimum size range of a high-strength catalytic system in which the activity does not increase over time is calculated with a lower rate of transport gas injection while keeping the number of particles 20-40 μm in size at 20-30 wt %. Pilot batch production of high-strength catalyst in the optimum size range is recommended in order to shift units for the industrial dehydrogenation of isobutane to the use of treating-type KDI catalyst without the addition of IM-2201S. [ABSTRACT FROM AUTHOR]

The correlation between the type of abrasive in the brake friction composite and the braking induced emission was studied. Brake pads with four different abrasives; silicon carbide, alumina, zircon, and magnesia, were evaluated using a reduced scale dynamometer with an airborne particle counter. The results indicated that the particle abrasivity, comprising aspects such as hardness, fracture toughness, and angularity, strongly affected the disc wear and airborne particle emission, whereas the pad wear was more influenced by the strength of the friction film that was changed by the iron moved from the grey iron disc. The fracture toughness of the abrasives had a significant effect on the disc wear rate and mass concentration of airborne wear particles emitted during brake application. In contrast, the number concentration was considerably influenced by the wear mode of the abrasives against the grey iron disc. • Type of abrasives in the friction composite affected wear and brake emission. • Pad wear increased by the iron transferred from the grey iron disc. • Fracture toughness of abrasives strongly affected the brake emission. • Abrasive wear mode causes a discrepancy between number and mass concentrations. [ABSTRACT FROM AUTHOR]

Abstract: The increase of urbanization constantly demands more infrastructure, which often requires to utilize the underground. The complex functioning of Tunnel Boring Machines (TBM) and the complexity of their working environment make arriving at wear predictability a challenging affair. The economic consequence of tool wear is, on the other hand, significant. There are several methods and approaches to estimate geo-material's abrasion properties in tunnelling with TBMs. The methods are mainly based on using empirical observations and experiences from completed tunnelling projects correlated with simplified laboratory test results. The simplified laboratory tests means that the soil's in-situ properties such as the cohesion, density, adhesion, water content and original grain size distribution are lacking or is disturbed. The intention of this research paper is to give a brief overview the respective test procedures of the different approaches and their pros and cons. In light of these, we assess a new methodological approach and examine the extent to which it is capable of advancing the understanding of predicting wear on TBMs with respect to general tribological experiences such as the influence of hard minerals or particles, grain shape and grain size. The applicability of the laboratory experiments from a practitioner's point of view is equally briefly discussed. [Copyright &y& Elsevier]

This paper presents an experimental study of tool wear and abrasivity of granular soils using a testing system specifically designed for the evaluation of wear on earth-moving machines, especially soft ground tunneling applications where the impact of soil abrasion on the operation is significant. In the testing system, a propeller fitted with steel covers of different hardnesses is rotated at 60 rpm in granular soil samples in a chamber under ambient pressures of up to 10 bar. The developed system can quantitatively assess the abrasive characteristics of soils through the measurement of weight loss on the special covers of the propeller, accounting for soil gradation, mineral composition, sphericity and roundness, water content, and tool hardness. Preliminary test results indicate that water content, particle angularity, and relative hardness between the tool and soil have significant impact on tool wear and soil abrasion. For the tests conducted, it is observed that angular sands produce significantly higher tool wear than round sands in dry condition. Tool wear first increases with water content until the water content reaches approximately 7-10%; beyond this range, higher water content reduces tool wear. An increase in hardness ratio (tool/mineral), corresponding to an increase in tool hardness and/or a decrease in mineral hardness, results in a decrease in tool wear in dry sand mixtures, but this trend is not monotonic for sand mixtures with high water content. [ABSTRACT FROM AUTHOR]