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Background: Carbon fiber composites were chosen because of their advantages in terms of high strength, light weight, and resistance to high temperatures. The sound dampening on go-karts functions to reduce disturbances produced by the engine, and the use of carbon fiber composite material is expected to improve acoustic performance and reduce the overall weight of the vehicle. Purpose: This research aims to analyze the mechanical strength characteristics of carbon fiber composites used as dampening materials in go-karts. Methode: The research method involves making test specimens from carbon fiber composites with an epoxy resin matrix. Variations in fiber presentation and layer orientation were tested to determine the optimal configuration. Tests carried out include bending tests, impact tests and Vickers hardness tests to measure the modulus of elasticity and resistance to dynamic loads. Result: The test results showed that the ratio of carbon to resin 85/15 resulted in the highest bending strength (0.712 N/mm²), while the ratio of 90/10 yielded the lowest strength (0.529 N/mm²). Specimen C with a ratio of 80/20 has a moderate strength (0.662 N/mm²) and the highest impact value (0.751 joule/mm²). The lowest impact value was obtained in specimen A with a ratio of 90/10 (0.445 joule/mm²). For the Vickers hardness test, specimen B with a ratio of 85/15 had the highest hardness (84.09 HVN), while specimen A with a ratio of 90/10 showed the lowest hardness (10.4 HVN). Specimen C with a ratio of 80/20 has a moderate hardness (46.65 HVN). Conclusion: Based on the results of the study, carbon fiber composites with a ratio of carbon to resin 85/15 show optimal mechanical strength characteristics for use as a silencer material in go-karts. [ABSTRACT FROM AUTHOR]

Thermal and mechanical cutting processes are commonly applied in manufacturing industries for making a specific size and shape of samples. The material properties of the heat-affected metal at the cut edge might be different from those of the parent metal. Hardness as a very important parameter for the assessment of material properties has been widely used in the design procedure. The Vickers hardness test is a versatile method to measure material hardness in practice. In this study, a comparison of cut-edge hardness between the thermal and mechanical cutting processes was performed on the structural steels S355 and S1100 by using the Vickers hardness test method with a small angle at cut edges to widen the heat-affected zone (HAZ). Based on the measurements, the influence of the Vickers test load on the magnitude and distribution of cut-edge hardness for laser-cut samples of steels S355 and S1100 was clarified. Furthermore, the effects of cutting processes on the hardness were illustrated. Finally, a comparison between the distribution characteristics of the cut-edge hardness of steels S355 and S1100 was made. For structural steel, it is recommended to apply the Vickers hardness testing method with a test load of 1 kpf and with a small angle at cut edges to widen the HAZ and to get reasonable results. The hardness distribution and the maximum for laser- and plasma-cut edges are similar, depending on the material, with a maximum of 450 HV1 for S355N and of 550 HV1 for S1100M. [ABSTRACT FROM AUTHOR]

Курган № 1 раннесакского периода в могильнике Кызылжартас (Карагандинская обл., Республика Казахстан) исследован в 2020 году. В основании округлой насыпи диаметром 37 м находилась крепида из крупных камней. Насыпь окружала ограда диаметром 56 м. Под насыпью находились три каменных изваяния (два мужских и одно женское), а ещё одно (мужское) было установлено в дромосе могилы. Захоронение ограблено в древности. Возле могильной ямы найден железный топор длиной 21,3 см и весом 1,7 кг. В могиле находились часть костей скелета человека, возле которых найдено свыше 300 мелких золотых украшений. Весной 2023 г. по образцам кости человека (из могилы) и кости животного (из грабительского хода в насыпи) в лаборатории Vilnius Radiocarbon (Литва) получены две радиоуглеродные даты. На основании археологических данных и радиоуглеродной даты по кости человека погребение датируется VIII в. до н.э. К этому же периоду относится, по-видимому, и массивный железный топор архаического облика, изготовленный из куска железа. Это первая находка железного топора раннесакского периода в Казахстане. В 2022—2023 гг. проведены металлографический и химический анализы топора, и их результаты публикуются здесь впервые. Оба лезвия специально цементированы для придания им твёрдости, что подтверждается результатами измерений твёрдости по шкале Виккерса в зонах лезвий и в центральной части топора.

Featured Application: Feature Applications: This paper proposes a data-driven approach based on convolutional neural networks to measure the Vickers hardness value directly from the image of the specimen to get rid of the requirement of the manually generation of indentations for measurement. Hardness testing is an essential test in the metal manufacturing industry, and Vickers hardness is one of the most widely used hardness measurements today. The computer-assisted Vickers hardness test requires manually generating indentations for measurement, but the process is tedious and the measured results may depend on the operator's experience. In light of this, this paper proposes a data-driven approach based on convolutional neural networks to measure the Vickers hardness value directly from the image of the specimen to get rid of the aforementioned limitations. Multi-task learning is introduced in the proposed network to improve the accuracy of Vickers hardness measurement. The metal material used in this paper is medium-carbon chromium-molybdenum alloy steel (SCM 440), which is commonly utilized in automotive industries because of its corrosion resistance, high temperature, and tensile strength. However, the limited samples of SCM 440 and the tedious manual measurement procedure represent the main challenge to collect sufficient data for training and evaluation of the proposed methods. In this regard, this study introduces a new image mixing method to augment the dataset. The experimental results show that the mean absolute error between the Vickers hardness value output by the proposed network architecture can be 10.2 and the value can be further improved to 7.6 if the multi-task learning method is applied. Furthermore, the robustness of the proposed method is confirmed by evaluating the developed models with an additional 59 unseen images provided by specialists for testing, and the experimental results provide evidence to support the reliability and usability of the proposed methods. [ABSTRACT FROM AUTHOR]

Aluminium samples are irradiated using a continuous-wave diode laser in a laboratory environment to study the effect on its surface, structural, and mechanical properties. The exposed samples are investigated by scanning electron microscopy and x-ray diffractometer for the surface and structural morphology, respectively. The scanning electron microscopic analysis unveils the realization of micrometer grain size, exfoliational sputtering, and crater production. The diffractometric x-ray analysis reveals the grain size, d-spacing, and dislocation line density of the targeted samples. The hardness of the samples as a function of exposure time is investigated using the micro Vickers hardness tester to perceive the mechanical properties. An increase in micro-hardness is observed with the increase in the exposure time.

Introduction: New generation composite resin materials have revolutionized the art of aesthetic dentistry. The clinical success is dependent on effective polymerisation and surface hardness which in turn are dependent on the performance of Light Curing Units (LCU). This study utilises surface hardness as a measure of degree of polymerisation of composite resins achieved by LCUs. Aim: To evaluate the difference in surface hardness of nanohybrid and microhybrid resin composites cured by light curing systems, Light Emitting Diode (LED) and Quartz Tungsten Halogen (QTH). Materials and Methods: In this invitro experimental study, two types of hybrid composites (Nanohybrid and Microhybrid) were tested for surface hardness by using two different light curing systems (LED and QTH). All the Nanohybrid and Microhybrid specimens were cured using LED and QTH LCUs, thus giving four combinations. A total of 60 specimens (6 mm diameter and 2 mm depth) were prepared using Teflon mould with 15 samples for each combination. Surface hardness was measured on upper and lower surface after 24 hours and hardness ratio was calculated. Data was analysed using independent t-test for intergroup comparison. Level of significance was kept at 5%. Results: Surface hardness of resin composites cured by LED LCU was greater than those cured by QTH LCU. Additionally, the hardness value was greater for the upper surface. Nanohybrids showed better surface hardness than Microhybrids for both the LCUs. Conclusion: Nanohybrid composite resins and LED system were found to be more effective in terms of surface hardness as compared to their counterparts.

Hardness testing is an essential test in the metal manufacturing industry, and Vickers hardness is one of the most widely used hardness measurements today. The computer-assisted Vickers hardness test requires manually generating indentations for measurement, but the process is tedious and the measured results may depend on the operator’s experience. In light of this, this paper proposes a data-driven approach based on convolutional neural networks to measure the Vickers hardness value directly from the image of the specimen to get rid of the aforementioned limitations. Multi-task learning is introduced in the proposed network to improve the accuracy of Vickers hardness measurement. The metal material used in this paper is medium-carbon chromium-molybdenum alloy steel (SCM 440), which is commonly utilized in automotive industries because of its corrosion resistance, high temperature, and tensile strength. However, the limited samples of SCM 440 and the tedious manual measurement procedure represent the main challenge to collect sufficient data for training and evaluation of the proposed methods. In this regard, this study introduces a new image mixing method to augment the dataset. The experimental results show that the mean absolute error between the Vickers hardness value output by the proposed network architecture can be 10.2 and the value can be further improved to 7.6 if the multi-task learning method is applied. Furthermore, the robustness of the proposed method is confirmed by evaluating the developed models with an additional 59 unseen images provided by specialists for testing, and the experimental results provide evidence to support the reliability and usability of the proposed methods.

Aluminium samples are irradiated using a continuous-wave diode laser in a laboratory environment to study the effect on its surface, structural, and mechanical properties. The exposed samples are investigated by scanning electron microscopy and x-ray diffractometer for the surface and structural morphology, respectively. The scanning electron microscopic analysis unveils the realization of micrometer grain size, exfoliational sputtering, and crater production. The diffractometric x-ray analysis reveals the grain size, d-spacing, and dislocation line density of the targeted samples. The hardness of the samples as a function of exposure time is investigated using the micro Vickers hardness tester to perceive the mechanical properties. An increase in micro-hardness is observed with the increase in the exposure time. [ABSTRACT FROM AUTHOR]

Welding is a technique of fusion joining the material involving a process of inter-molecular diffusion adhesion. Polymer welding is an assembly method among several known assembly techniques such as gluing. This welding process applies to thermoplastics; they have the rheological or softening characteristics during melting. This process is fast and controlled in order to obtain a solid and durable mechanical connection on the series parts. This study focuses on the weldability of high density polyethylene (HDPE) using the friction stir welding technique. A parametric choice was made to optimize the operating parameters namely the shape of the welding tool, the speed of rotation and the speed of advance of the tool. Monotonic tensile tests were used to compare the mechanical characteristics between a HDPE test specimen and a specimen taken from an FSW weldment. It emerges from this study that the FSW welding introduces a weakening of the joints characterized by a clear decrease of the deformation at break.

Introduction: Restorative resins during their prolonged use are exposed to variety foods and beverages are subjected to wear, degradation, and staining resulting in failure of restoration and require replacement. This study is aimed to evaluate surface roughness and hardness of five commercially available posterior resin composites following exposure to various food-simulating liquids (FSLs). Materials and Methods: Specimens were immersed in distilled water, ethanol, citric acid, and air and later examined using a profilometer, scanning electron microscope for the surface profiles. Hardness was measured by Vickers Hardness test. Statistical Analysis: Results were subjected to two-way ANOVA and Tukey's multiple Post hoc test. Results: There were significant differences in results among the composite resin tested. Inter comparison between materials after treating with FSLs, clear fill majesty (CFM) and Z350 showed better hardness values under the influence of ethanol, followed by Ever X, Tetric Evo Ceram and Sure fill SDR. None of the composites were unaffected by air compared to FSLs. Citric acid had reduced the hardness of CFM and had caused surface roughness on Sure fill SDR and Tetric Evo Ceram. Distilled water reduced hardness of CFM and SureFil SDR. EverX was not affected by any of the FSL either in hardness or surface roughness properties. All composites showed surface irregularities in all media. Ethanol and water had almost similar effect on all composites. Conclusions: Differences in hardness and surface roughness are due to different composition of resin matrix and different filler particles in all composite resin material tested.

Introduction: Dental caries is a multifactorial microbial infectious disease characterised by demineralisation of the inorganic and destruction of the organic substance of the tooth. To combat dental caries the application of nanotechnology includes the inhibition of formation of biofilm and regulating the balance of demineralisation-remineralisation processes, ensuring a possible mechanism that can aid in prevention and treatment of tooth decay. Initial caries progression may be prevented by suitable surface treatment, by applying surface remineralising agents. Aim: To evaluate and compare the efficacy of remineralising potential of Acidulated Phosphate Fluoride (APF) gel, Chitosan nanoparticles and Silver Diamine Fluoride (SDF) on microhardness of artificial carious lesions created on extracted teeth. Materials and Methods: This was an in-vitro experimental study associated with Krishna Institute of Medical Sciences, Karad conducted during a period of two months (October and November 2019) at Mechanical Department of Rajarambapu Institute of Technology, Islampur, Maharashtra. The total sample size was 30 premolar teeth. In this in-vitro study, test materials Chitosan nanoparticles, Silver Diamine Fluoride (SDF) and Acidulated Phosphate Fluoride gel (APF) varnishes were manipulated and applied (10 in each group) in accordance with manufacturer’s instructions. Artificial carious lesions were created in the enamel. This was achieved by suspending the teeth in an artificial caries system. Baseline microhardness was then recorded using Vickers Hardness Test and varnish application was carried out. Samples were then placed separately in a demineralisation solution for three hours. Thereafter, samples were placed in a remineralisation solution. Any change in microhardness was determined by evaluating the Vickers Hardness Test at the end of 28 days. The data was then recorded, tabulated and statistically analysed using KruskalWallis Test and Wilcoxon Signed Test for inter and intra groups comparisons to find out if there was a significant difference. Results: All the three varnishes i.e., Chitosan nanoparticle, silver diamine fluoride and APF gel in intragroup comparison after intervention showed significant differences with Chitosan nanoparticle showing the highest increase in microhardness with p-value of 0.001 followed by SDF with p-value of 0.005 and APF gel with p-value of 0.005. Conclusion: All the three varnishes increased enamel microhardness significantly. Chitosan nanoparticle showed highest increase in remineralisation followed by SDF and APF gel. Hence, varnish application is a good method in remineralising the tooth.

Introduction: Disinfection of root canals can be done using intracanal irrigants. Sodium hypochlorite or NaOCL is amongst the most commonly used endodontic irrigants. Due to disadvantages of NaOCl, there is a need to identify a more biocompatible irrigant. Aim: To evaluate the antibacterial efficacy, depth of penetration into dentinal tubules and effect on microhardness of root dentin when NaOCl, Neem extract, Gau ark and Normal saline used as an irrigant against Enterococcus faecalis. Materials and Methods: Prepared Neem leaf extract, 3% NaOCl, Gau ark, Normal saline, Brain Heart Infusion (BHI) broth and BHI Agar were used in the present in-vitro study conducted from August-October 2019. Antimicrobial efficacy was measured by agar well diffusion method on 10 petriplates. After access opening and biomechanical preparation, each tooth sample was irrigated with 5 mL of irrigant. Samples were decoronated and roots were split along the longitudinal axis to check penetration depth of irrigants under stereomicroscope for 40 teeth samples. After preparation of 40 teeth sample, 2 mm dentin discs prepared were embedded in acrylic resin. Microhardness was checked under Vickers Microhardness (VHN) tester after samples were irrigated. Statistical Analysis of Variance and Tukey post-hoc test were used. Results: Zones of inhibition were highest with NaOCl (7.66 mm). Irrigants penetration depth into dentinal tubules was significant with NaOCl with average value 0.35 mm. Microhardness of root dentin of saline was 145.90 VHN, followed by Neem 136.59 VHN which was then followed by Gau ark 123.05 VHN hence, Neem has lesser effect on microhardness value as compared to NaOCl and Gau ark. There was statistically significant difference among four groups regarding antimicrobial efficacy, depth of penetration into dentinal tubules and microhardness of root dentin. Conclusion: Neem extract showed significant antimicrobial property as compared to Gau ark and normal saline, good penetration depth and less effect on microhardness of root dentin. Herbal irrigant like Neem extract can be used as a root canal irrigant.

Introduction: Dental caries is a multifactorial microbial infectious disease characterised by demineralisation of the inorganic and destruction of the organic substance of the tooth. To combat dental caries the application of nanotechnology includes the inhibition of formation of biofilm and regulating the balance of demineralisation-remineralisation processes, ensuring a possible mechanism that can aid in prevention and treatment of tooth decay. Initial caries progression may be prevented by suitable surface treatment, by applying surface remineralising agents. Aim: To evaluate and compare the efficacy of remineralising potential of Acidulated Phosphate Fluoride (APF) gel, Chitosan nanoparticles and Silver Diamine Fluoride (SDF) on microhardness of artificial carious lesions created on extracted teeth. Materials and Methods: This was an in-vitro experimental study associated with Krishna Institute of Medical Sciences, Karad conducted during a period of two months (October and November 2019) at Mechanical Department of Rajarambapu Institute of Technology, Islampur, Maharashtra. The total sample size was 30 premolar teeth. In this in-vitro study, test materials Chitosan nanoparticles, Silver Diamine Fluoride (SDF) and Acidulated Phosphate Fluoride gel (APF) varnishes were manipulated and applied (10 in each group) in accordance with manufacturer’s instructions. Artificial carious lesions were created in the enamel. This was achieved by suspending the teeth in an artificial caries system. Baseline microhardness was then recorded using Vickers Hardness Test and varnish application was carried out. Samples were then placed separately in a demineralisation solution for three hours. Thereafter, samples were placed in a remineralisation solution. Any change in microhardness was determined by evaluating the Vickers Hardness Test at the end of 28 days. The data was then recorded, tabulated and statistically analysed using KruskalWallis Test and Wilcoxon Signed Test for inter and intra groups comparisons to find out if there was a significant difference. Results: All the three varnishes i.e., Chitosan nanoparticle, silver diamine fluoride and APF gel in intragroup comparison after intervention showed significant differences with Chitosan nanoparticle showing the highest increase in microhardness with p-value of 0.001 followed by SDF with p-value of 0.005 and APF gel with p-value of 0.005. Conclusion: All the three varnishes increased enamel microhardness significantly. Chitosan nanoparticle showed highest increase in remineralisation followed by SDF and APF gel. Hence, varnish application is a good method in remineralising the tooth. [ABSTRACT FROM AUTHOR]

Introduction: Disinfection of root canals can be done using intracanal irrigants. Sodium hypochlorite or NaOCL is amongst the most commonly used endodontic irrigants. Due to disadvantages of NaOCl, there is a need to identify a more biocompatible irrigant. Aim: To evaluate the antibacterial efficacy, depth of penetration into dentinal tubules and effect on microhardness of root dentin when NaOCl, Neem extract, Gau ark and Normal saline used as an irrigant against Enterococcus faecalis. Materials and Methods: Prepared Neem leaf extract, 3% NaOCl, Gau ark, Normal saline, Brain Heart Infusion (BHI) broth and BHI Agar were used in the present in-vitro study conducted from August 2019- October 2019. Antimicrobial efficacy was measured by agar well diffusion method on ten petriplates. After access opening and biomechanical preparation, each tooth sample was irrigated with 5ml of irrigant. Samples were decoronated and roots were split along the longitudinal axis to check penetration depth of irrigants under stereomicroscope for 40 teeth samples. After preparation of 40 teeth sample, 2 mm dentin discs prepared were embedded in acrylic resin. Microhardness was checked under Vickers microhardness tester after samples were irrigated. Statistical Analysis of Variance and Tukey post-hoc test were used. Results: Zones of inhibition were highest with NaOCl (7.66 mm). Irrigants penetration depth into dentinal tubules was significant with NaOCl with average value 0.35 mm. Microhardness of root dentin of saline was 145.90 VHN, followed by Neem 136.59 VHN which was then followed by Gau ark 123.05 VHN hence, Neem has lesser effect on microhardness value as compared to NaOCl and Gau ark. There was statistically significant difference among four groups regarding antimicrobial efficacy, depth of penetration into dentinal tubules and microhardness of root dentin. Conclusion: Neem extract showed significant antimicrobial property as compared to Gau ark and normal saline, good penetration depth and less effect on microhardness of root dentin. Herbal irrigant like Neem extract can be used as a root canal irrigant. [ABSTRACT FROM AUTHOR]

In this research, four specimens of hypo‐eutectic Al–7Si–0.35Mg–0.2Ti–xZr (x = 0, 0.1, 0.2, 0.3 wt%) cast alloys were fabricated via a traditional casting method. The effect of different concentrations of Zr on the microstructure and mechanical properties of cast alloys was investigated through metallographic observation, SEM analysis, TEM observations, tensile strength testing, and Vickers hardness test. The results show that the plate‐like shape eutectic Si phase is gradually transformed into fine fibrous eutectic Si phase, and is more evenly distributed as the content of Zr increased. The α‐Al matrix grains are transformed from dendrites to isometric grains, of which the grains sizes became smaller. The results of the tensile test show that with the addition of 0.2% Zr, Al–7Si–0.35Mg–0.2Ti alloys obtain the best tensile properties. The ultimate tensile strength and elongation values are 221 MPa and 11%, the number of which is increased by 14.5 and 71.9% than base alloy, respectively. Additionally, the alloy's yield strength, Vickers hardness, and other comprehensive mechanical properties have also improved significantly. [ABSTRACT FROM AUTHOR]

Introduction: New generation composite resin materials have revolutionised the art of aesthetic dentistry. The clinical success is dependent on effective polymerisation and surface hardness which in turn are dependent on the performance of Light Curing Units (LCU). This study utilises surface hardness as a measure of degree of polymerisation of composite resins achieved by LCUs. Aim: To evaluate the difference in surface hardness of nanohybrid and microhybrid resin composites cured by light curing systems, Light Emitting Diode (LED) and Quartz Tungsten Halogen (QTH). Materials and Methods: In this invitro experimental study, two types of hybrid composites (Nanohybrid and Microhybrid) were tested for surface hardness by using two different light curing systems (LED and QTH). All the Nanohybrid and Microhybrid specimens were cured using LED and QTH LCUs, thus giving four combinations. A total of 60 specimens (6 mm diameter and 2 mm depth) were prepared using Teflon mould with 15 samples for each combination. Surface hardness was measured on upper and lower surface after 24 hours and hardness ratio was calculated. Data was analysed using independent t-test for intergroup comparison. Level of significance was kept at 5%. Results: Surface hardness of resin composites cured by LED LCU was greater than those cured by QTH LCU. Additionally, the hardness value was greater for the upper surface. Nanohybrids showed better surface hardness than Microhybrids for both the LCUs. Conclusion: Nanohybrid composite resins and LED system were found to be more effective in terms of surface hardness as compared to their counterparts. [ABSTRACT FROM AUTHOR]

Welding is a technique of fusion joining the material involving a process of inter-molecular diffusion adhesion. Polymer welding is an assembly method among several known assembly techniques such as gluing. This welding process applies to thermoplastics; they have the rheological or softening characteristics during melting. This process is fast and controlled in order to obtain a solid and durable mechanical connection on the series parts. This study focuses on the weldability of high density polyethylene (HDPE) using the friction stir welding technique. A parametric choice was made to optimize the operating parameters namely the shape of the welding tool, the speed of rotation and the speed of advance of the tool. Monotonic tensile tests were used to compare the mechanical characteristics between a HDPE test specimen and a specimen taken from an FSW weldment. It emerges from this study that the FSW welding introduces a weakening of the joints characterized by a clear decrease of the deformation at break.

In this work, the experimental method and the calculation model for the determination of indentation moduli, indentation work, and indentation creep of metallic materials, by means of macroscale-level forces provided by a primary hardness standard machine at the National Institute of Metrological Research (INRIM) at the at room temperature were described. Indentation moduli were accurately determined from measurements of indentation load, displacement, contact stiffness and hardness indentation imaging and from the slope of the indentation unloading curve by applying the Doerner-Nix linear model; indentation work, representing the mechanical work spent during the force application of the indentation procedure, was determined by calculating the areas under the loading–unloading indentation curve, through fitting experimental data with a polynomial law. Measurements were performed with a pyramidal indenter (Vickers test). The applied force was provided by a deadweight machine, and the related displacement was measured by a laser interferometric system. Applied forces and the occurring indentation depths were simultaneously measured: the resulting loading–unloading indentation curve was achieved. Illustrative tests were performed on metals and alloy samples. Discussion and comments on the suitability of the proposed method and analysis were reported.

Aim: To assess the effect of coca cola and diet coca cola on surface enamel roughness. Materials and Method: In this vitro study, there were 8 teeth extracted and these specimens were prepared with 4 teeth immersed with coca cola and 4 teeth in diet Coca Cola of 40ml at room temperature for 5 minutes each. The enamel micro hardness of enamel was tested using Vickers hardness test. On each specimen, one indentation of 100 μm were made using a load of 25 gf for 5 s in a micro durometer and it was done as a single-blind test and the final results were further compared using t-test. Results: There has been considerable reduction in enamel hardness when the teeth are dipped in coca cola and slight and negligible reduction in hardness when dipped in diet coca cola. Mean Difference in Coca Cola - 84.05 and DIET Coca Cola - 16.725. All the teeth except those exposed to Coca Cola showed a statistically significant decrease in the surface VHN (p < 0.05). Conclusion: The results of this study showed significant reduction in the enamel hardness after treating with coca cola, whereas very minimal reduction in enamel hardness when treated with diet coca cola. [ABSTRACT FROM AUTHOR]

• Teeth of many mammals do not grow further after they have emerged, nor are repaired. • These species are expected to die when all its dental crown tissue has been depleted. • Tooth hardness does not differ between sexes in red deer. • The amount of tooth depleted can be used to assess sex differences in life expectancy. Teeth of many mammalian species do not grow further after they have emerged, nor are they replaced or repaired if they break or wear. These dental properties have been used to test evolutionary hypotheses on life expectancy relative to actual age (senescence, aging), as the animal is expected to die when all its dental crown tissue has been depleted due to the wearing effect of mastication. Females of polygynous mammals with small litter size are expected to live longer than males of the same species, as female reproductive fitness is maximised by having a long reproductive life. In contrast, maleś reproductive success is limited to the short period when they are in prime condition, as it is in this period that they are most successful in intra-sexual competition for mating opportunities. Consequently, it has been predicted that femaleś teeth should be more durable and so wear more slowly than maleś teeth. However, these predictions are affected by potential sex differences in the hardness of dental tissues, which have not been assessed in depth in the literature. I tested sexual differences in the hardness of enamel and dentine on a balanced, by sex and age, sample of 156 lower first molars of Scottish red deer of known age using Vickers micro-hardness indentation measures as a proxy of the resilience of the tooth to wear. My results clearly indicate that there are no sexual differences in enamel and dentine hardness, and that tooth hardness has a negligible effect on predicting tooth wear, which supports the use of tooth wear relative to body size as a convenient proxy for assessing sexual differences in senescence in polygynous ungulates. I warn on making conclusions from comparisons between populations or species in tooth wear when tooth hardness was controlled for. [ABSTRACT FROM AUTHOR]

Introduction: Restorative resins during their prolonged use are exposed to variety foods and beverages are subjected to wear, degradation, and staining resulting in failure of restoration and require replacement. This study is aimed to evaluate surface roughness and hardness of five commercially available posterior resin composites following exposure to various food-simulating liquids (FSLs). Materials and Methods: Specimens were immersed in distilled water, ethanol, citric acid, and air and later examined using a profilometer, scanning electron microscope for the surface profiles. Hardness was measured by Vickers Hardness test. Statistical Analysis: Results were subjected to two-way ANOVA and Tukey's multiple Post hoc test. Results: There were significant differences in results among the composite resin tested. Inter comparison between materials after treating with FSLs, clear fill majesty (CFM) and Z350 showed better hardness values under the influence of ethanol, followed by Ever X, Tetric Evo Ceram and Sure fill SDR. None of the composites were unaffected by air compared to FSLs. Citric acid had reduced the hardness of CFM and had caused surface roughness on Sure fill SDR and Tetric Evo Ceram. Distilled water reduced hardness of CFM and SureFil SDR. EverX was not affected by any of the FSL either in hardness or surface roughness properties. All composites showed surface irregularities in all media. Ethanol and water had almost similar effect on all composites. Conclusions: Differences in hardness and surface roughness are due to different composition of resin matrix and different filler particles in all composite resin material tested. [ABSTRACT FROM AUTHOR]

Abstract In this study, welding effects on the tensile strength of high strength steel butt joints were investigated experimentally and numerically. Two butt joints were fabricated by joining two 8 mm thick reheated, quenched and tempered S690Q high strength steel (HSS) plates together using Shielded Metal Arc Welding with different welding heat inputs. In the experimental study, post-welding microstructure and micro-hardness tests performed for the butt joints confirmed the existence of a soft layer within the heat-affected zone. The size of this soft layer increased when higher heat input was adopted. Subsequent coupon tensile tests showed that the tensile strength of the butt joints deteriorated with the increase of the welding heat input. In numerical study, a finite element (FE) simulation considering the non-uniform material properties heat-affected zone was implemented to complement the experimental study. Comparisons between experimental and numerical results were carried out for the temperature history curves, failure modes and stress-strain curves for the coupons manufactured from the butt joints. It was found that the proposed simulation method could reflect the influence of welding process on the tensile strength of the S690Q HSS butt joints tested in this study. Highlights • Microstructure study, hardness and tensile tests conducted on S690Q butt joints • Test results revealed the existence of soft layer in HAZ of S690Q butt joints • S690Q butt joint strength deteriorated after welding as heat input increased • A FE model considering the non-uniform material properties of HAZ is developed [ABSTRACT FROM AUTHOR]

Welding is a technique of fusion joining the material involving a process of inter-molecular diffusion adhesion. Polymer welding is an assembly method among several known assembly techniques such as gluing. This welding process applies to thermoplastics; they have the rheological or softening characteristics during melting. This process is fast and controlled in order to obtain a solid and durable mechanical connection on the series parts. This study focuses on the weldability of high density polyethylene (HDPE) using the friction stir welding technique. A parametric choice was made to optimize the operating parameters namely the shape of the welding tool, the speed of rotation and the speed of advance of the tool. Monotonic tensile tests were used to compare the mechanical characteristics between a HDPE test specimen and a specimen taken from an FSW weldment. It emerges from this study that the FSW welding introduces a weakening of the joints characterized by a clear decrease of the deformation at break. [ABSTRACT FROM AUTHOR]