Microstructural Characterization and Corrosion Behavior of Similar and Dissimilar Welded Advanced High-Strength Steels (AHSS) by Rotary Friction Welding.

Advanced high-strength steels (AHSSs) are designed for meeting strict requirements, especially in the automotive industry, as a means to directly influence the reduction in the carbon footprint. As rotary friction welding (RFW) has many important advantages over other welding technologies, it plays an important role in the automotive sector. On the above basis, in this work, combinations of the first (complex phase (CP)), second (TWIP (TW)), and third (quenched and partitioned (Q&P)) generations of similar and dissimilar high-alloyed advanced steels have been joined by the RFW process. Having a specific microstructure, rods of CP/CP, Q&P/Q&P, CP/TW, and Q&P/TW steels were welded by employing a homemade adaptation machine under fixed parameters. Microstructural characterization has allowed us to corroborate the metallic bonding of all the tested advanced steels and to identify the different zones formed after welding. Results indicate that the welding zone widens in the center of the workpiece, and under the current friction action, the intermixing region shows the redistribution of solute elements, mostly in the dissimilarly welded steels. Furthermore, because of their complex chemistry and the different mechanical properties of the used steels, dissimilarly welded steels present the most noticeable differences in hardness. The TWIP steel has the lower hardness values, whilst the CP and Q&P steels have the higher ones. As a direct effect of the viscoplastic behavior of the steels established by the thermomechanical processing, interlayers and oxidation products were identified, as well as some typical RFW defects. The electrochemical response of the welded steels has shown that the compositional and microstructural condition mostly affect the corrosion trend. This means that the dissimilarly welded steels are more susceptible to corrosion, especially at the TWIP-steel interface, which is attributed to the energy that is stored in the distorted microstructure of each steel plate as a consequence of the thermomechanical processing during RFW.

Dataset on critical angular clamping speeds of fasteners.

This article reports on an experiment that studied the critical angular clamping speeds for fasteners using the Design of Experiments (DOE) methodology and Analysis of Variance (ANOVA). The study aimed to investigate the stick-slip phenomenon, a critical factor limiting the angular speed. The stick-slip was measured using the stick-slip factor, which is defined as the ratio of stick-slip chattering amplitude to frequency. The investigation focused on the factors that affect the stick-slip factor, torque, and clamping force (preload): friction coefficient, clamping angular velocity, cathodic electrodeposition, and hardness of the bolthead bearing plate. Automated predictive algorithms can utilize the data collected from this study to prevent the occurrence of the stick-slip phenomenon in screw clamping processes.

Effect of Recycled Polyvinyl Butyral (rPVB) Addition on the Tribological Performance of Glass-Fiber Reinforced Polyamide (PAGF) during Reciprocating Sliding Wear Conditions.

Plastic recycling in the automotive industry is a priority. In this study, the effect of adding recycled polyvinyl butyral (rPVB) from automotive windshields on the coefficient of friction (CoF) and specific wear rate (k) of a glass-fiber reinforced polyamide (PAGF) is investigated. It was found that, at 15 and 20 wt.% of rPVB, it acts as a solid lubricant, reducing CoF and k up to 27% and 70%, respectively. Microscopical analysis of the wear tracks showed that rPVB spreads over the worn tracks, forming a lubricant layer, which protects the fibers from damage. However, at lower rPVB content, fiber damage cannot be prevented as the protective lubricant layer is not formed.

Thermomechanical Simulation of Orthogonal Metal Cutting with PFEM and SPH Using a Temperature-Dependent Friction Coefficient: A Comparative Study.

In this work, we apply the Particle Finite Element Method (PFEM) and Smoothed Particle Hydrodynamics (SPH) to simulate the orthogonal cutting chip formation of two workpiece materials, i.e., AISI 1045 steel and Ti6Al4V titanium alloy. A modified Johnson-Cook constitutive model is used to model the plastic behavior of the two workpiece materials. No damage or strain softening is included in the model. The friction between the workpiece and the tool is modeled following Coulomb's law with a temperature-dependent coefficient. The accuracy of PFEM and SPH in predicting thermomechanical loads at various cutting speeds and depths against the experimental data are compared. The results show that both numerical methods can predict the rake face temperature of AISI 1045 with errors less than 34%. For Ti6Al4V, however, the temperature prediction errors are significantly higher than those of the steel alloy. Errors in force prediction were in the range of 10% to 76% for both methods, which compare very well with those reported in the literature. This investigation infers that the Ti6Al4V behavior under machining conditions is difficult to model on the cutting scale irrespective of the choice of numerical method.

Does the initial surface roughness of different CuNiTi wires affect the frictional resistance?

Abstract This study aimed to assess and correlate initial surface roughness and frictional resistance of rectangular CuNiTi wires inserted in different self-ligating brackets. The sample consisted of 40 bracket-wire sets (rectangular CuNiTi wires of 0.017" x 0.025" and passive self-ligating brackets) divided into four groups (n=10): metallic self-ligating bracket and metallic CuNiTi wire (G1); metallic self-ligating bracket and rhodium-coated CuNiTi wire (G2); esthetic self-ligating bracket and metallic wire (G3); esthetic self-ligating bracket and rhodium-coated CuNiTi wire (G4). The initial surface roughness of the wires was examined with a Surfcorder roughness meter, model SE1700. Later, frictional resistance was assessed in an Instron 4411 universal testing machine at a speed of 5 mm/min, in an aqueous medium at 35°C. Microscopic analyses of surface morphology were performed with scanning electron microscopy, using an LEO 1430, with magnifications of 1000X. Generalized linear models were applied, considering the 2 x 2 factorial (bracket type x wire type), at a 5% significance level. Regardless of bracket type, the groups with esthetic wires presented higher initial surface roughness than the groups with metallic wires (p<0.05). There was no significant difference between the different bracket-wire sets for frictional resistance and no significant correlation between frictional resistance and initial surface roughness in the environment studied. It is concluded that esthetic wires presented higher initial surface roughness but did not interfere with the frictional resistance between brackets and wires.

Resumo O objetivo deste estudo foi avaliar e correlacionar a rugosidade superficial inicial e a resistência a fricção dos fios CuNiTi retangulares inseridos em diferentes bráquetes autoligados. A amostra foi composta por 40 conjuntos bráquetes-fios (fios retangulares CuNiTi de 0.017" x 0.025" e braquetes autoligados passivos), divididos em 4 grupos (n=10): bráquete autoligado metálico e fio CuNiti metálico (G1); braquete autoligado metálico e fio CuNiti com revestimento de rhodium (G2); bráquete autoligado estético e fio metálico (G3); bráquete autoligado estético e fio CuNiti com revestimento de rhodium (G4). A rugosidade superficial inicial do fio foi examinada com um rugosímetro Surfcorder modelo SE1700. Posteriormente, a resistência a fricção foi avaliada em uma máquina de ensaios universal Instron 4411, a uma velocidade de 5mm/min em meio aquoso à 35oC. Análises microscópicas da morfologia de superfície foram realizadas por microscopia eletrônica de varredura, utilizando um LEO 1430, com ampliações de 1000X. Foram aplicados modelos lineares generalizados, considerando o fatorial 2 x 2 (tipo de bráquete x tipo de fio), com o nível de significância de 5%. Independentemente do tipo de bráquete, os grupos com fios estéticos apresentaram maior rugosidade superficial inicial que os grupos com fios metálicos (p<0,05). Não houve diferença significativa entre os diferentes conjuntos bráquetes-fios quanto a resistência à fricção e não houve correlação significativa entre a resistência a fricção e a rugosidade superficial inicial no ambiente estudado. Conclui-se que os fios estéticos apresentaram maior rugosidade superficial inicial porém não interferiram na resistência a fricção entre os braquetes e os fios.

Perspectives of 2D MXene Tribology.

The large and rapidly growing family of 2D early transition metal carbides, nitrides, and carbonitrides (MXenes) raises significant interest in the materials science and chemistry of materials communities. Discovered a little more than a decade ago, MXenes have already demonstrated outstanding potential in various applications ranging from energy storage to biology and medicine. The past two years have witnessed increased experimental and theoretical efforts toward studying MXenes' mechanical and tribological properties when used as lubricant additives, reinforcement phases in composites, or solid lubricant coatings. Although research on the understanding of the friction and wear performance of MXenes under dry and lubricated conditions is still in its early stages, it has experienced rapid growth due to the excellent mechanical properties and chemical reactivities offered by MXenes that make them adaptable to being combined with other materials, thus boosting their tribological performance. In this perspective, the most promising results in the area of MXene tribology are summarized, future important problems to be pursued further are outlined, and methodological recommendations that could be useful for experts as well as newcomers to MXenes research, in particular, to the emerging area of MXene tribology, are provided.

Soft tissue and incisor position changes in class I bimaxillary subjects after retraction using friction and frictionless mechanics

Aim: Bimaxillary protrusion is a common condition observed irrespective of race and ethnicity and is a chief concern for patients who seek orthodontic treatment. The aim of this study was to compare and evaluate changes in soft tissue structures and incisor positions in class I bimaxillary protrusion subjects undergoing orthodontic therapy when friction and frictionless mechanics were used. Methods: Two groups with a total of 40 patients aged 18­30 years diagnosed with class I bimaxillary protrusion treated by extracting first premolars were considered for this study. Patients treated with friction mechanics were included in Group 1 and those treated with frictionless mechanics in Group 2. The digital lateral cephalograms were calibrated and analyzed using Nemoceph software. Selected landmarks were marked on pre- and post-treatment cephalograms and assessed for intra- and inter-group soft tissue and incisor position changes. Student's t-test was used to analyze the collected data using SPSS 20 software. Result: Intragroup comparison revealed significant changes in both groups. Inter-group comparison of the selected parameters between groups 1 and 2 showed differences but without any statistical significance, except for the inter-incisal angle. Conclusion: Pre- and post-treatment comparison analysis revealed significant soft tissue changes in both groups. However, the comparison between friction and frictionless mechanics showed no statistically significant changes

Influência da pressão dos alicates na rugosidade superficial de fios ortodônticos / Influence of gripping with pliers on the surface rugosity of orthodontic wires

Resumo Proposição: avaliar in vitro a rugosidade superficial de fios ortodônticos antes e após a compressão com pinças ortodônticas. Material E Métodos: 30 fios 0,014" de níckel-titânio termoativados (Neosentalloy, GAC) e 30 fios 0,019 x 0,025" de aço foram usados nos experimentos. Avaliou-se a rugosidade superficial com rugosímetro (NewViewTM 7100, Zygo), antes e após a compressão com alicate Weingart do lado esquerdo e pinça Mathieu do lado direito (Dentaurum). Foram determinados os parâmetros de rugosidade Ra (µm), Rq (µm), PV (µm), Srmax Iso (nm). Testes estat´siticos Wilcoxon foram realizados para analisar a variação dos parâmetros da rugosidade com nível de confiança de 95% e p<0,05. Resultados: Os fios redondos de NiTi apresentaram diferenças significaticas dos parâmetros Ra e Rq antes e após a compressão com pinça Mathieu. O emprego do alicate Weingart não alterou a rugosidade dos fios redondos. Os fios retangulares apresentaram diferenças significativas em todos os parâmetros com uso das duas pinças. As médias das diferenças dos parâmetros entre o alicate Weingart e a pinça Mathieu nos fios redondos, não foram estatisticamente significativos. Os fios retangulares apresentaram maior rugosidade com o emprego do alicate Weingart, com diferenças significativas. Conclusão: O uso do alicate tipo Weingart e da pinça tipo Mathieu aumentam a rugosidade dos fios de NiTi e de aço (AU)

Abstract Proposition: the surface roughness of orthodontic wires was evaluated in vitro before and after gripping with two different orthodontic pliers. Material And Methods: Units were made of 30 round heat-activated Nickel Titanium alloy wires 0,014" (Neosentalloy, GAC), and another group with 30 rectangular steel wires 0,019 x 0,025". The surface roughness was evaluated with a rugosimeter (NewViewTM 7100, Zygo), before and after gripping with Weingart plier on the left side and Mathieu plier on the right side (Dentaurum), in addition to the average difference in roughness between groups of the same types of wires with parameters Ra (µm), Rq (µm), PV (µm), Srmax Iso (nm). The variation of parameters with different clamps was evaluated (Wilcoxon test); different alloys by the same clamp, 95% confidence level and p<0.05. Results: The round wires showed significant differences (Ra and Rq) before and after being gripped with Mathieu plier. The roughness was higher after being gripped. Weingart pliers and round wires obtained the same results, with greater roughness after being clamped. Rectangular wires showed significant differences in all parameters, with both clamps. The means of the differences in the parameters between the Weingart pliers and the Mathieu forceps on the round wires were not statistically significant. In the rectangular wire, the values between the tweezers showed greater roughness with the grip of the Weingart pliers, with significant differences.Conclusion: After securing the orthodontic wires, the Weingart pliers and the Mathieu tweezers increased the roughness parameters (AU)

Soft Tribology and Its Relationship With the Sensory Perception in Dairy Products: A Review.

Nowadays, dairy products, especially fermented products such as yogurt, fromage frais, sour cream and custard, are among the most studied foods through tribological analysis due to their semi-solid appearance and close relationship with attributes like smoothness, creaminess and astringency. In tribology, dairy products are used to provide information about the friction coefficient (CoF) generated between tongue, palate, and teeth through the construction of a Stribeck curve. This provides important information about the relationship between friction, food composition, and sensory attributes and can be influenced by many factors, such as the type of surface, tribometer, and whether saliva interaction is contemplated. This work will review the most recent and relevant information on tribological studies, challenges, opportunity areas, saliva interactions with dairy proteins, and their relation to dairy product sensory.

Comparison of the friction forces delivered by different elastomeric patterns and metal ligature on conventional metal brackets with a NiTi arch wire versus a self-ligating system: An in vitro study.

OBJECTIVES: The aim of this study was to measure the frictional resistance of different types of ligatures used on conventional and self-ligating brackets. MATERIALS AND METHODS: Monoblock (conventional) and Portia (self-ligating) brackets were used and the archwire used was nickel-titanium. On conventional brackets the ligatures tested were the Elastomeric type and steel 0.30 tie-wire. The groups were divided according to the ligature types (n=8): (1) conventional elastomeric ligature; (2) relaxed conventional elastomeric ligature; (3) elastomeric ligature in shape-8; (4) double vertical elastomeric ligatures; (5) double-crossed elastomeric ligatures; (6) crossed ligature; (7) steel wire ligature; and (8) self-ligating ligature (self-ligating bracket). A segment of five brackets, each ligature types, was mounted. The archwire, between the bracket and the ligature, was connected on Instron® Universal test machine to simulate the frictional resistance. The maximum frictional resistance was obtained, and the mean values were submitted to the analysis of variance (ANOVA) and the Tukey's post-hoc test (α=0.05). RESULTS: The elastomeric ligature in shape-8 showed the highest value compared with other groups (P<0.05). Although the crossed elastomeric ligature presented the lowest mean value and it was not statistically different regarding relaxed conventional elastomeric ligature, steel wire ligature and self-ligating (P≥0.05). CONCLUSIONS: The frictional resistance was influenced by ligature types. Elastomeric Ligature in shape-8 showed the highest frictional force. Crossed Elastomeric Ligature had the lowest frictional force value.

CFD modeling of different mass transfer coefficients on hydrogen sulfide emission in a flux chamber.

Hydrogen sulfide (H2S) is commonly used as an indicator for odorous gas emission monitoring in wastewater treatment plants. The H2S emission estimations can be performed using algebraic mathematical models or carrying out measurements at the source, with the dynamic flux chamber, for example. This work brings together these two methodologies in a computational fluid dynamics analysis. Fifteen liquid-phase mass transfer coefficient ([Formula: see text]) models were initially evaluated in establishing, at the liquid-gas interface in a flux chamber, an H2S emission flux based on the friction velocity field from three different inlet flows (2, 5, and 10 L min-1). Ten [Formula: see text] models were fully simulated, and the numerical results were compared with available experimental data. The higher the inlet flow, the higher the friction velocity at the interface, and the higher the H2S emission. The H2S emission was also strongly dependent on the constant coefficients of the existing [Formula: see text] models. Small variability on those coefficients generates considerable changes in emissions at the interface. Few and different models performed well in describing the available concentration data at the outlet sampling probe for different inlet flows, which shows there is still no single model capable of representing all simulated friction velocity ranges (0.005 to 0.017 m s-1).

Braquetes cerâmicos impressos em 3D: ensaio mecânico de coeficiente de atrito / Ceramic brackets printed on 3D: mechanical essay on the friction coefficient

Objetivo: Avaliar e comparar o atrito entre braquetes ortodônticos (convencional e impressos) e fio de aço. A hipótese nula (H0) é que a média de forças de atrito sejam iguais entre os grupos. Material e Método: O ensaio mecânico foi realizado com 3 grupos de braquetes distintos. Sendo eles: Grupo de braquetes convencional como referência o ClarityTM Advanced (3M Unitek), comparado com dois grupos de braquetes impressos em impressora 3D o Lightforce White (Lightforce Orthodontics) e Lightforce Translucent (Lightforce Orthodontics). As amostras de cada grupo possuem um N=10; os braquetes usados são referentes ao dente 23 (U23) com slot 0.022 e prescrição MBT. O fio ortodôntico foi o de aço inoxidável (CrNi) com calibre de 0.019"x 0.025". O conjunto braquete/fio, unido por ligadura elastomérica, foi colado ao dispositivo de teste, desenvolvido em CAD e impresso em 3D com resina sensível a luz UV, totalizando 30 amostras. Cada amostra foi adaptada a máquina universal de ensaio (EMIC DL ­ 2000) com deslocamento de 2,0mm e velocidade de 1,0mm/min, para mensurar o atrito causado pelo deslize. A força (N) representada pelo pico de cada amostra e, então, realizados a média e o desvio padrão. A comparação foi realizada em nível de significância α = 0,05. A análise de variância ANOVA foi usada para determinar se houve diferenças entre as amostras e o teste post-hoc Tukey. Resultados: µ=0,121N para o Clarity, µ=0,173N para o Lightforce White e µ=0,189N para o Lightforce Translucent. Conclusão: Os braquetes impressos não apresentaram diferença significativa entre eles, porém houve uma pequena diferença para os braquetes do grupo controle que apresentaram uma resistência menor ao deslize do arco (AU)

Purpose: To evaluate and compare the friction between orthodontic brackets (conventional and imprinted) and steel wire. The null hypothesis (H0) is that the average friction forces between the groups are equal. Material and method: The mechanical test was performed with 3 different groups of brackets. These are: Conventional bracket group as reference, ClarityTM Advanced (3M Unitek), compared to two groups of 3D printer printed brackets, Lightforce White (Lightforce Orthodontics) and Lightforce Translucent (Lightforce Orthodontics). The samples from each group have an N=10, and the brackets used are for tooth 23 (U23) with slot 0.022 and MBT prescription. The orthodontic wire was stainless steel (CrNi) with a thickness of 0.019" x 0.025". The bracket/wire set, connected by an elastic ligature, was bonded to the test fixture, which was designed in CAD and 3D printed with UV light-sensitive resin. A total of 30 specimens were fabricated. Each specimen was mounted on a universal testing machine (EMIC DL - 2000) with a displacement of 2.0 mm and a speed of 1.0 mm/min to measure the friction caused by the slide. The force (N) represented by the peak value of each sample, mean and standard deviation were calculated. The comparison was performed with a significance level of α = 0.05. The ANOVA analysis of variance was used to determine if there were differences between samples, and the Tukey test was performed post hoc. Results: µ=0.121N for Clarity, µ=0.173N for Lightforce White, and µ=0.189N for Lightforce Translucent. Conclusion: The printed brackets did not show significant differences. However, there was a small difference in the brackets of the control group, which showed less resistance to arch wire slippage (AU)

Lesão por fricção em idosos / Skin tears in the elderly / Skin tears en los ancianos

Objetivos:identificar na literatura científica o conhecimento produzido sobre lesões por fricção em idosos. Métodos: trata-se de uma revisão integrativa de literatura (2014-2019), realizada a partir de busca nas bases de dados/plataformas National Library of Medicine, Biomedical Answers e Biblioteca Virtual em Saúde, com descritores e os operadores booleanos "and" e "or". Resultados: a partir da busca bibliográfica, seleção e análise, oito artigos compuseram a amostra. Para lesão por fricção em idosos emergiram quatro pilares do cuidado: manutenção da homeostase orgânica e tissular com foco na nutrição e hidratação apropriada; evitar traumas na pele senil, proporcionando um ambiente seguro com dispositivos adequados; e a sistematização da assistência e educação em saúde do cuidado com a pele do idoso. Conclusão: como mecanismos de prevenção, encontram-se a realização da prevenção primária por meio de um plano de cuidados singular e as atividades de educação em saúde, focadas nos fatores de risco e nas vulnerabilidades, minimizando danos e complicações

Objectives:to identify in the scientific literature the knowledge produced about skin tears injuries in the elderly. Methods: it is an integrative literature review (2014-2019), carried out by searching the databases/platforms National Library of Medicine, Biomedical Answers and Biblioteca Virtual em Saúde, with descriptors and the Boolean operators "and" and "or ". Results: from the bibliographic search, selection and analysis, eight articles made up the sample. For skin tears injuries in the elderly, four pillars of care emerged: maintenance of organic and tissue homeostasis with a focus on proper nutrition and hydration; avoid trauma to senile skin, providing a safe environment with suitable devices; and the systematization of health care and education for elderly skin care. Conclusion: as prevention mechanisms, primary prevention is achieved through a unique care plan and health education activities, focused on risk factors and vulnerabilities, minimizing damage and complications

Objetivos:identificar em la literatura científica El conocimiento producido sobre las lesiones skin tears en el anciano. Métodos: Se trata de una revisión integradora de la literatura (2014-2019), realizada em las plataformas/bases de datos de la National Library of Medicine, Biomedical Answersy Virtual Health Library, com descriptores y operadores booleanos "and" y "or". Resultados: Tras la búsqueda, selección y análisis previo de los artículos, se seleccionaron ocho para componer la muestra. Para las lesiones por desgarro de la piel en los ancianos, surgieron cuatro pilares de atención: mantener la homeostasis orgánica y tisular común enfoque en una nutrición e hidratación adecuadas; evitar traumatismos em la piel senil, proporcionando un entorno seguro con dispositivos adecuados; y la sistematización de la atención a la salud y la educación para el cuidado de la piel del anciano. Conclusión: Como mecanismos de prevención, la prevención primaria se puede encontrar a través de um plan de atención único y actividades de educación para la salud enfocadas em lós factores de riesgo y vulnerabilidades, minimizando daños y complicaciones

On the Tribological and Oxidation Study of Xanthophylls as Natural Additives in Castor Oil for Green Lubrication.

The present study focuses on an introductory analysis of the use of three xanthophylls as additives for green lubricant applications. For this purpose, the additives were characterized by FTIR and 1H-NMR techniques, and the bio-lubricants were described by their physical properties. The effect of the natural compounds on the friction and wear properties of bio-lubricants were evaluated by sliding friction tests under boundary conditions, as confirmed by an analysis of the lubricating film thickness. The antioxidant capacity was analyzed by FTIR spectroscopy. It was observed better wear protection in castor oil with xanthophylls than without these additives. The wear rate was reduced up to 50% compared with neat oil. Lesser beneficial effects were appreciated in friction coefficient since it was increased 25%. The best contribution was observed with astaxanthin as an additive. In addition, a significant improvement in the oxidation of castor oil, complemented with this additive, was exhibited by FTIR analysis. It was found that xanthophylls could be employed as additives for totally biodegradable lubricant applications since they have better tribological and antioxidant behavior than current additives.

Influence of Contact Plateaus Characteristics Formed on the Surface of Brake Friction Materials in Braking Performance through Experimental Tests.

This work applies a procedure for analysis and characterization of the surface of brake friction materials, correlating them with the tribological and thermal properties achieved in different vehicle braking conditions. Experiments were performed in a vehicle under two real conditions of braking operation, simulated flat track descent and emergency braking. Characteristics of the plates formed on the surfaces of the friction materials were analyzed by scanning electron microscopy (SEM) and correlated with the performance during braking, as measured by the coefficient of friction at the interface of the friction pair and temperature. As a result, the formation of the primary and secondary plateaus in these two different braking operating conditions was observed, and the relationship between the characteristics of the plateaus formed on the surface and the surface roughness parameters and performance measurements during braking.

Phototribology: Control of Friction by Light.

In dry sliding, the coefficient of friction depends on the material pair and contact conditions. If the material and operating conditions remain unchanged, the coefficient of friction is constant. Obviously, we can tune friction by surface treatments, but it is a nonreversible process. Here, we report active control of friction forces on TiO2 thin films under UV light. It is reversible and stable and can be tuned/controlled with the light wavelength. The analysis of atomic force microscopy signals by wavelet spectrograms reveals different mechanisms acting in the darkness and under UV. Ab initio simulations on UV light-exposed TiO2 show a lower atomic orbital overlapping on the surface, which leads to a friction reduction of up to 60%. We suggest that photocontrol of friction is due to the modification of atomic orbital interactions from both surfaces at the sliding interface.

Study of Friction and Wear Effects in Aluminum Parts Manufactured via Single Point Incremental Forming Process Using Petroleum and Vegetable Oil-Based Lubricants.

This paper focuses on studying how mineral oil, sunflower, soybean, and corn lubricants influence friction and wear effects during the manufacturing of aluminum parts via the single point incremental forming (SPIF) process. To identify how friction, surface roughness, and wear change during the SPIF of aluminum parts, Stribeck curves were plotted as a function of the SPIF process parameters such as vertical step size, wall angle, and tool tip semi-spherical diameter. Furthermore, lubricant effects on the surface of the formed parts are examined by energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) images, the Alicona optical 3D measurement system, and Fourier-transform infrared spectroscopy (FTIR). Results show that during the SPIF process of the metallic specimens, soybean and corn oils attained the highest friction, along forces, roughness, and wear values. Based on the surface roughness measurements, it can be observed that soybean oil produces the worst surface roughness finish in the direction perpendicular to the tool passes (Ra =1.45 µm) considering a vertical step size of 0.25 mm with a 5 mm tool tip diameter. These findings are confirmed through plotting SPIFed Stribeck curves for the soybean and corn oils that show small hydrodynamic span regime changes for an increasing sample step-size forming process. This article elucidates the effects caused by mineral and vegetable oils on the surface of aluminum parts produced as a function of Single Point Incremental Sheet Forming process parameters.

Another Solution to the Schrödinger-Langevin Equation / Una Solución Alterna a la Ecuación de Schrödinger-Langevin / Uma Solução Alternativa para a Equação Schrödinger-Langevin

Abstract Introduction: an alternative solution to the Schrödinger-Langevin equation is presented, where the temporal dependence is explained, assuming a Coulomb potential. Finally, the trajectory equations are found. Objective: in this paper we contribute by presenting a detailed and simple solution of the Schrödinger-Langevin equation for a Coulomb potential. Materials and Methods: using an appropriate ansatz, we solve the Schrödinger-Langevin equation, finding the expected values of position and moment. Results: a simple method was presented to find the expected position and moment values in the Schrödinger-Langevin equation, the ansatz used to find these solutions allows the model to be generalized in a certain way to electric potentials and harmonic oscillators. Conclusions: the model used to solve the Schrödinger-Langevin equation, allowed to find the expected values of position and moment of a particle in a Coulomb potential, the temporal dependence of such solutions is made explicit, which allows finding the path equations of the particles.

Resumen Introducción: se presenta una solución alternativa a la ecuación de Schrödinger-Langevin, donde se explica la dependencia temporal, asumiendo un potencial de Coulomb. Finalmente, se encuentran las ecuaciones de trayectoria. Objetivo: en este trabajo hacemos una contribución presentando una solución detallada y sencilla de la ecuación de Schrödinger-Langevin para un potencial de Coulomb. Materiales y Métodos: usando un ansatz apropiado, solucionamos la ecuación de Schrödinger-Langevin, encontrando los valores esperados de posición y momento. Resultados: se presentó un método sencillo para hallar los valores esperados de posición y momento en la ecuación de Schrödinger-Langevin, el ansatz utilizado para encontrar estas soluciones permite generalizar en cierta forma el modelo a potenciales eléctricos y osciladores armónicos. Conclusiones: el modelo utilizado para solucionar la ecuación de Schrödinger-Langevin, permitió encontrar los valores esperados de posición y momento de una partícula en un potencial de Coulomb, se explicita la dependencia temporal de tales soluciones lo que permite encontrar las ecuaciones de trayectoria de las partículas.

Resumo Introdução: uma solução alternativa para a equação de Schrödinger-Langevin é apresentada, onde a dependência temporal é explicada, assumindo um potencial de Coulomb. Finalmente, existem as equações de caminho. Objetivo: neste trabalho fazemos uma contribuição apresentando uma solução simples e detalhada da equação de Schrödinger-Langevin para um potencial de Coulomb. Materiais e métodos: usando um ansatz apropriado, resolvemos a equação de Schrödinger-Langevin, encontrando os valores esperados de posição e momento. Resultados: foi apresentado um método simples para encontrar os valores esperados de posição e momento na equação de Schrödinger-Langevin, o ansatz utilizado para encontrar essas soluções permite que o modelo seja generalizado de certa forma para potenciais elétricos e osciladores harmônicos. Conclusões: o modelo utilizado para resolver a equação de Schrödinger-Langevin, permitiu encontrar os valores esperados de posição e momento de uma partícula em um potencial de Coulomb, sendo explicitada a dependência temporal de tais soluções, o que permite encontrar as equações de caminho das partículas.

Evaluation of tensile strength after insertions andremovals of abutments on frictional Morse taper implants / Evaluación de la Resistencia a la Tracción Después de la Inserción y Extracción de Pilares en Implantes de Cono de Fricción Morse

This study aimed to evaluate possible changes in final retention after nine sequences of insertion and removal (SIR) of a frictional Morse taper implant/abutment system, evaluating the force required for dissociating this set between sequences, and verifying possible deformations in the implant heads. Ten implants, 13 mm long and 3.3 mm in diameter, were coupled to a universal mechanical testing machine. Ten anti-rotational abutments, 13 mm long and 3.5 mm in diameter, were connected to the implants parallel to the long axis, using an instrument called beat-connection, and subjected to tensile tests and SEM analysis. The results were analyzed using the Kruskal-Wallis test with Dunn's post-test, and the significance level was set at 5 %. There was no statistically significant difference in final retention among the nine SIRs evaluated. The force needed to uncouple the abutment from the implant increased as SIRs were performed on all ten implants, and an increase of 29.03 % was observed in the ninth SIR compared to the first SIR. After SEM analysis, no significant deformations, fractures, or cracks were observed in the implant heads.

Este estudio tuvo como objetivo evaluar los posibles cambios en la retención final después de nueve secuencias de inserción y extracción (SIR) de un sistema de implante / pilar de cono de fricción Morse, evaluando la fuerza necesaria para disociar este conjunto entre secuencias y verificando posibles deformaciones en las cabezas de los implantes. Se acoplaron diez implantes, de 13 mm de largo y 3,3 mm de diámetro, a una máquina universal de ensayos mecánicos. Se conectaron a los implantes en paralelo al eje largo diez pilares antirrotacionales, de 13 mm de largo y 3,5 mm de diámetro, mediante un instrumento llamado beat-connection, y se sometieron a pruebas de tracción y análisis SEM. Los resultados se analizaron mediante la prueba de Kruskal-Wallis con la prueba posterior de Dunn, y el nivel de significancia se estableció en 5 %. No hubo diferencias estadísticamente significativas en la retención final entre los nueve SIR evaluados. La fuerza necesaria para desacoplar el pilar del implante aumentó a medida que se realizaban SIR en los diez implantes, y se observó un aumento del 29,03 % en el noveno SIR en comparación con el primer SIR. Después del análisis SEM, no se observaron deformaciones, fracturas o grietas significativas en las cabezas de los implantes.