Search

A previous perfect visco‐plastic constitutive formulation of the Perzyna type incorporating the concepts of prescribed stress increments and m‐AGC tangent operator (m‐Assumed algorithmic generalized compliance tangent operator) is extended to the case of Hardening/Softening (H/S). This extension is possible thanks to the closed‐form solution developed for the evolution of the loading function during a visco‐plastic time step. The formulation is then applied to constitutive modeling of zero‐thickness interfaces on the basis of a well‐established fracture‐based elasto‐plastic formulation, which in this manner is extended to visco‐plasticity. The resulting model is implemented in the finite element (FE) and small‐strain context by using both a standard Newton Raphson scheme for physical visco‐plasticity in which visco‐plastic time corresponds to physical time, and a Visco‐Plastic Relaxation (VPR) scheme, in which time corresponds to a fictitious time governing the transition from the elastic to the inviscid elasto‐plastic response. The numerical implementation is verified satisfactorily for common loading cases at interfaces such as pure tension (mode I) opening and shear‐compression (mixed‐mode) cracking/sliding, showing that the visco‐plastic results match the predictions of the fracture mechanics inviscid model in the long term. In addition, it is also shown that the VPR strategy developed is capable of providing temporary stability while the equilibrium path is recovered during instability events such as a snap‐back in the load‐displacement curve. This feature opens the door to a number of potential advanced applications of the formulation developed in the geomechanical context. [ABSTRACT FROM AUTHOR]

AbstractThe thermodynamics of mass transfer during gaseous carburization and its overall efficiency across various alloyed steels were investigated to discern the influence of alloy content. Quantitative analyses were conducted on the coefficients of mass transfer and carbon diffusivities for EN3, EN35, 20MnCr5, and EN353 steels at a carburization temperature of 930 °C. The study revealed distinct trends in mass transfer dynamics and carbon diffusion rates among the different alloyed steels. For instance, nickel majorly an austenite stabilizer, was found to enhance carbon diffusion in gamma iron, with observed coefficients of mass transfer ranging from 8.85 × 10−6 to 1.87 × 10−5 cm/s. However, EN35 steel exhibited slower mass transfer rates due to weaker atomic interactions, resulting in lower observed coefficients of mass transfer. Conversely, chromium and molybdenum, known carbide-forming elements, facilitated carbon transfer from the gaseous environment to the steel case in 20MnCr5 and EN353 steels, with observed coefficients of mass transfer ranging from 1.39 × 10−5 to 1.55 × 10−5 cm/s. Additionally, the study compared observed carbon diffusivities with those predicted by DICTRA (Diffusion Controlled TRAnsformation) kinetic and thermodynamic datasets, demonstrating excellent consistency. These findings underscore the significance of considering alloy content in achieving consistent carburizing outcomes and suggest potential modifications to existing carburizing methods to improve diffusion depth homogeneity. Overall, the study provides valuable insights into the impact of alloy elements on the carburization process and offers implications for optimizing carburizing practices in alloy steel manufacturing.

Numerical calculations were performed to study the vortex-induced vibration (VIV) of a circular cylinder, which was elastically supported by springs of linear and cubic terms. These simulations were conducted at high Reynolds numbers ranging from 4200 to 42,000. To simulate the cylinder's motion and the associated aerodynamic forces, Computational Fluid Dynamics were employed in conjunction with dynamic mesh capabilities. The numerical method was initially verified by testing it with various grid resolutions and time steps, and subsequently, it was validated using experimental data. The response of cubic nonlinearities was investigated using insights gained from a conventional linear vortex-induced vibration (VIV) system. This 2D study revealed that both the amplitude and frequency of vibrations are contingent on the flow velocity. The highest output was achieved within the frequency lock-in region, where internal resonance occurs. In the case of a hardening spring, the beating response was observed from the lower end of the initial branch to the upper end of the initial branch. The response displacement amplitude obtained for the linear spring case was 27 mm, whereas in the cubic nonlinear case, the value was 31.8 mm. More importantly, the results indicate that the inclusion of nonlinear springs can substantially extend the range of wind velocities in which significant energy extraction through vortex-induced vibration (VIV) is achievable. [ABSTRACT FROM AUTHOR]

We study a variational model for crack growth in elasto-plastic materials with hardening in the antiplane case. The main result is the existence of a solution to the initial value problem with prescribed time-dependent boundary conditions. [ABSTRACT FROM AUTHOR]

In order to raise the hardness and strength of the surface layer of mechanical components and induce favorable residual compressive stresses, case‐hardening procedures have become established in the heat treatment of steel. In this work, a calculation concept for the fatigue strength of components that have been case‐hardened through carburizing heat treatment is being developed. The residual stress and the load stresses in complex‐shaped, carburized materials are determined using a finite element (FE) model. The fatigue limit of the components is derived using probabilistic methods and taking into account hardness gradients, residual stresses, and non‐metallic inclusions. The model is validated with available axial bending fatigue test data and then used to predict the rotating bending fatigue limit of samples with various geometries and heat‐treatment conditions. This work demonstrates the capability of combining probabilistic and FE‐based modeling to represent complex interactions between variables that affect the fatigue of heat‐treated components, such as steel cleanliness, notch shape, case‐hardening depth, or loading conditions. Highlights: Combined FE‐based and probabilistic methods can predict fatigue strength accurately.Interplay of heat‐treatment output, geometry, load, and material is considered.Crack initiation position gets shifted by increased case‐hardness depth.Fatigue strength reduction due to defects in steel depends on load concentration. [ABSTRACT FROM AUTHOR]

As part of a comprehensive study on eco-friendly processing techniques, the influence of the heat treatment environment on the case hardening of AISI 1018 steel using pulverized cassava leaf was studied. The process was carried out at two different temperatures (850 °C and 950 °C) and under three environmental conditions: Process 1, the control experiment, was carried out in air only; in Process 2, the medium comprised pulverized cassava leaves; and in Process 3 a combination of pulverized cassava leaves plus barium carbonate (BaCO3) was used as an energizer (CBC mixture). Vickers microhardness testing and scanning electron microscopy were used to evaluate the effect of the processing environment on the case hardening of the steel. As expected, regardless of the processing temperature, Process 1 resulted in little or no hardening of the steel surface. However, notable case hardening occurred when the steel specimens were subjected to either Process 2 or Process 3. Furthermore, the inclusion of barium carbonate in Process 3 significantly enhanced the case hardening effectiveness of the cassava leaf in terms of the rate of and maximum hardness achieved. A maximum enhancement was observed at 950 °C. After 1 h, the increase in hardness was 160% and 280% for Process 2 and Process 3, respectively. Upon increasing the processing time to 5 h, the increase in hardness due to Process 2 was raised to 254%, while that of Process 3 remained at approximately 280%. The diffusivity of AISI 1018 was calculated using the microhardness data. The diffusivity was highest in Process 2 samples with values of 1.568 × 10−9 m2/s at 850 °C and 1.893 × 10−9 m2/s at 950 °C. Effective case hardening of AISI 1018 steel was carried out using the medium of cassava leaf, without the addition of barium carbonate (BaCO3) as an energizer. [ABSTRACT FROM AUTHOR]

To respond to the various issues of conventional drying (textural defects of collapse-shrinkage and case hardening, microbiological contamination, poor rehydrability, degradation of active molecules caused by high wet-bulb temperature, weak drying kinetics, and marketing difficulty), swell-drying has proven high relevance in combining conventional drying processes with the Instant Controlled Pressure Drop (D.I.C.). The international team of "Research & Engineering Platform for intensifying Drying Processes (REPID)" has studied phenomenological models and experimental trials combining D.I.C. with new Interval Hyper-Active Drying (IHAD) processes. Currently, IHAD includes interval starting accessibility drying (ISAD), interval infrared airflow drying (IIRAD), and interval microwave airflow drying (IMAD). All these "interval operations" are sandwiched into cycles, each comprising double separate independent mechanisms; a short, hyper-focused active period (that generates and sweeps out vapor to the surrounding environment) alternated by a passive period of internal water diffusion/moisture homogenization. Since surface evaporation is highly intensive, the wet-bulb temperature stays low, although highly effective drying kinetics. Thus, the operation results in avoiding biochemical damage risks. Coupled with the D.I.C. texturing-decontamination, these drying operations are very effective in terms of drying kinetics, energy consumption, and product quality of heat-sensitive solids. It has led to the manufacturing of effective drying equipment. [ABSTRACT FROM AUTHOR]

As part of a comprehensive study on eco-friendly processing techniques, the influence of the heat treatment environment on the case hardening of AISI 1018 steel using pulverized cassava leaf was studied. The process was carried out at two different temperatures (850 °C and 950 °C) and under three environmental conditions: Process 1, the control experiment, was carried out in air only; in Process 2, the medium comprised pulverized cassava leaves; and in Process 3 a combination of pulverized cassava leaves plus barium carbonate (BaCO3) was used as an energizer (CBC mixture). Vickers microhardness testing and scanning electron microscopy were used to evaluate the effect of the processing environment on the case hardening of the steel. As expected, regardless of the processing temperature, Process 1 resulted in little or no hardening of the steel surface. However, notable case hardening occurred when the steel specimens were subjected to either Process 2 or Process 3. Furthermore, the inclusion of barium carbonate in Process 3 significantly enhanced the case hardening effectiveness of the cassava leaf in terms of the rate of and maximum hardness achieved. A maximum enhancement was observed at 950 °C. After 1 h, the increase in hardness was 160% and 280% for Process 2 and Process 3, respectively. Upon increasing the processing time to 5 h, the increase in hardness due to Process 2 was raised to 254%, while that of Process 3 remained at approximately 280%. The diffusivity of AISI 1018 was calculated using the microhardness data. The diffusivity was highest in Process 2 samples with values of 1.568 × 10−9 m2/s at 850 °C and 1.893 × 10−9 m2/s at 950 °C. Effective case hardening of AISI 1018 steel was carried out using the medium of cassava leaf, without the addition of barium carbonate (BaCO3) as an energizer.

The thermodynamics of mass transfer during gaseous carburization and its overall efficiency across various alloyed steels were investigated to discern the influence of alloy content. Quantitative analyses were conducted on the coefficients of mass transfer and carbon diffusivities for EN3, EN35, 20MnCr5, and EN353 steels at a carburization temperature of 930 °C. The study revealed distinct trends in mass transfer dynamics and carbon diffusion rates among the different alloyed steels. For instance, nickel majorly an austenite stabilizer, was found to enhance carbon diffusion in gamma iron, with observed coefficients of mass transfer ranging from 8.85 x 10-6 to 1.87 x 10-5 cm/s. However, EN35 steel exhibited slower mass transfer rates due to weaker atomic interactions, resulting in lower observed coefficients of mass transfer. Conversely, chromium and molybdenum, known carbide-forming elements, facilitated carbon transfer from the gaseous environment to the steel case in 20MnCr5 and EN353 steels, with observed coefficients of mass transfer ranging from 1.39 x 10-5 to 1.55 x 10-5 cm/s. Additionally, the study compared observed carbon diffusivities with those predicted by DICTRA (Diffusion Controlled TRAnsformation) kinetic and thermodynamic datasets, demonstrating excellent consistency. These findings underscore the significance of considering alloy content in achieving consistent carburizing outcomes and suggest potential modifications to existing carburizing methods to improve diffusion depth homogeneity. Overall, the study provides valuable insights into the impact of alloy elements on the carburization process and offers implications for optimizing carburizing practices in alloy steel manufacturing. [ABSTRACT FROM AUTHOR]

Purpose: Numerous metals can be processed using the additive manufacturing process laser-based powder bed fusion of metals (PBF-LB/M, ISO/ASTM 52900). The main advantages of additive manufacturing technologies are the high degree of design freedom and the cost-effective implementation of lightweight structures. This could be profitable for gears with increased power density, combining reduced mass with considerable material strength. Current research on additively manufactured gears is focused on developing lightweight structures but is seldom accompanied by simulations and even less by mechanical testing. There has been very little research into the mechanical and material properties of additively manufactured gears. The purpose of this study is to investigate the behavior of lightweight structures in additively manufactured gears under static loads. Design/methodology/approach: This research identifies the static load-carrying capacity of helical gears with different lightweight structures produced by PBF-LB/M with the case hardening steel 16MnCr5. A static gear loading test rig with a maximum torque at the pinion of T1 = 1200 Nm is used. Further focus is set on analyzing material properties such as the relative density, microstructure, hardness depth profile and chemical composition. Findings: All additively manufactured gear variants show no failure or plastic deformation at the maximum test load. The shaft hub connection, the lightweight hub designs and the gearing itself are stable and intact regarding their form and function. The identified material characteristics are comparable to conventionally manufactured gears (wrought and machined), but also some particularities were observed. Originality/value: This research demonstrates the mechanical strength of lightweight structures in gears. Future research needs to consider the dynamic load-carrying capacity of additively manufactured gears. [ABSTRACT FROM AUTHOR]

Fairy chimneys of ignimbrite are well studied in Cappadocia in central Anatolia, Turkey. The ignimbrite landforms of Arizona's Basin and Range, USA, in contrast, remain relatively unexplored in geomorphic scholarship, despite decades of geological research on the characteristics of the ignimbrites themselves. This research focuses on the rock‐decay processes that modify Arizona's Basin and Range fair chimneys. Dissolution of glass and groundmass, measured along joints using digital image processing of back‐scattered electron microscope imagery, reveal a 3× higher porosity than inside the rock interior. This method also measured a 3‐4× increase in dissolution near the base of the chimney compared with the rock interior, leading to notch development that promotes chimney mass wasting and subsequent ballistic impacts. Epilithic organisms studied with electron microscopy both enhance rock decay and promote case hardening. These observations are consistent with prior understanding of how fairy chimneys evolve over time: columnar joints exposed on cliff faces experience enough decay to allow erosion of joint material, this erosion separates the chimney from the rock face and notch development near the chimney base promotes mass wasting. The rock‐decay processes studied here likely operate on very different timescales. Mass wasting events leading to ballistic impacts occur at observable timescales. Varnish microlamination dating, using ultrathin sections of rock varnish formed on fairy chimneys, indicates that the case hardening of the top of fairy chimneys are much more stable than the sides; the tops last experienced surface detachment during the early Holocene, as opposed to the sides that experienced flaking throughout the late Holocene. The timescale of basal notch development is not known, with the exception that the very surface of notches erode at rates too fast to accumulate rock varnish. The timescales of epilithic organisms enhancing rock decay and dissolution of columnar joints are not known. [ABSTRACT FROM AUTHOR]

Single-frequency thermal-wave radar (SF-TWR) imaging was used to produce dynamic images of effective case depths from phase image frequency scans in AISI 9310 and Pyrowear 53 steels. SF-TWR, as a fast non-destructive testing technique, was also compared with conventional photothermal radiometry measurements in these two types of steel samples using a three-layer theoretical thermal-wave model. In this paper, a novel approach of SF-TWR imaging, combining a three-distinct-layer thermal-wave model and radial phase profiles to image mean value case depths and their lateral non-uniform distributions, yielded quantitative images of case depths in the two hardened steels and exhibited very good correlation with standard Vickers measurements. The SF-TWR images further revealed strong inhomogeneities in the case depth thickness profiles to be used as important feedback to the heat treating manufacturing industry toward the optimization of their case depth hardening process. [ABSTRACT FROM AUTHOR]

The effect of temperature on the stability of anthocyanin extract from aronia as pigment and gallic acid as copigment was presented. The pigment:copigment system was investigated with different concentration from 1:1 to 1:50 molar ratio and at different temperatures at heating (from 25 to 80°C) and cooling (opposite to 25° The thermodynamic parameters of the system, ΔG, ΔH and ΔS were calculated as a function of temperature. Obtained results confirmed that the interaction between pigment: copigment complex was destroyed at heating to 80oC and at following cooling to 25°C reversibility of the copigmentation is observed. Keywords: cyaniding, gallic acid, copigmentation, thermodynamic parameters. [ABSTRACT FROM AUTHOR]

Recovery of cold worked metals is associated with a loss of strength due to the reduction of the defect density. However, already in the 1960s analytical models and few experiments suggested that this may not generally be the case and even a hardening rather than a softening might occur. With the availability of severe plastic deformation and deposition techniques this anneal hardening phenomenon has been observed frequently. In this overview we summarize early findings on this topic before focusing on general observations and potential origins, with a special focus to show the similarities for nanostructures across different grain size scales (i.e., structures prepared by deposition and severe plastic deformation techniques, respectively). Comparison of different results indicate a grain size dependent hardening increment that could be additionally affected by segregation or the processing variables. Considering the agreement of the peak hardening temperatures with that for dislocation annihilation at grain boundaries, anneal hardening can be rationalized by the loss of intragranular defects and grain boundary relaxation. Grain boundary diffusivity hence plays a crucial role and particular solutes could amplify the hardening process even further. As anneal hardening already occurs for grain sizes at the micron scale, its effect on properties is even of technological relevance. Beneficial effects on the fatigue strength are evident, but the strain softening of anneal hardened specimens drastically shorten ductility. Nevertheless, some strategies to overcome this adverse effect seem promising to create metallic structures with exceptional combinations of strength and ductility. [ABSTRACT FROM AUTHOR]

Thin‐layer drying of red beetroot having slice thicknesses of 0.5, 1, and 1.5 mm was carried out using a solar‐assisted continuous refractance window dryer at 75, 80, and 85°C drying temperatures for 30, 45, and 60 min. The drying kinetics including moisture ratio, drying rate, and moisture diffusivity was observed to understand the drying behavior of beetroot. The moisture ratio was fitted to the drying models for thin‐layer modeling of the beetroot drying. The drying operation reduced the firmness and water activity of the fresh beetroot; however, the antioxidant properties of dried beetroot increased with drying treatment. The minimum alteration was observed with a color difference and hue angle of dried slices. Process optimization was carried out to obtain the ideal drying conditions, which indicated the use of a dryer at 85°C temperature, 0.5 mm slice thickness, and 60 min exposure time with a desirability value of 0.874. Practical applications: Fourth‐generation drying technology refractance window drying dried the beet root slices without case hardening and improve its antioxidant properties. Dried beetroot contains carotenoids, vitamins, nitrates, flavonoids, and various minerals that have antioxidant, anti‐inflammatory, anticarcinogenic, and hepato‐protective activities. Dried beetroot flakes or powder is useful for the development of different functional foods that have anti‐diabetic, cardiovascular disease lowering, hypertensive, and wound healing benefits. [ABSTRACT FROM AUTHOR]

Medium manganese steels fall into the category of modern third-generation high-strength steels. Thanks to their alloying, they use a number of strengthening mechanisms, such as the TRIP and TWIP effects, to achieve their mechanical properties. The excellent combination of strength and ductility also makes them suitable for safety components in car shells, such as side reinforcements. Medium manganese steel with 0.2% C, 5% Mn, and 3% Al was used for the experimental program. Sheets with a thickness of 1.8 mm without surface treatment were formed in a press hardening tool. Side reinforcements require various mechanical properties in different parts. The change in mechanical properties was tested on the produced profiles. The changes in the tested regions were produced by local heating to an intercritical region. These results were compared with classically annealed specimens in a furnace. In the case of tool hardening, strength limits were over 1450 MPa with a ductility of about 15%. [ABSTRACT FROM AUTHOR]

Many Christian theologians believe in the existence of cases of divine hardening and divine election, where God either actively contributes to human evil or preordains it. God seems to act like a manipulator, who first covertly incites or determines people's evil actions and then condemns those actions and punishes the wrongdoers. I raise three questions regarding such cases: (1) how can humans be responsible for wrongdoings that are determined by God via either direct involvement or predestination; (2) is God justified in using covert manipulation to achieve his goals; (3) how can God judge human evil, if God predestines them or actively incites humans to commit evils? The article outlines two cases of supposed divine manipulation, discusses the general nature of manipulation and then examines each question outlined above. The argument is that the problems surrounding divine manipulation present significant challenges to especially those Christian theists that subscribe to divine determinism. Zusammenfassung: Viele christliche Theologen glauben an die Existenz von Fällen göttlicher Verhärtung und göttlicher Erwählung, in denen Gott entweder aktiv menschliches Übel herbeiführt oder es verurteilt. Gott scheint wie ein Manipulator zu handeln, der Menschen zu bösen Handlungen heimlich anstiftet oder vorherbestimmt und dann diese Handlungen verurteilt und den Übeltäter bestraft. Ich erhebe drei Anfrage an diese Fälle: (1) wie können Menschen für Fehlverhalten verantwortlich gemacht werden, die von Gott entweder durch direkte Einwirkung oder durch Prädestination determiniert sind; (2) ist Gott berechtigt, durch verdeckte Manipulation seine Ziele zu erreichen; (3) wie kann Gott menschliche Übeltaten verurteilen, wenn Gott diese vorherbestimmt hat oder aktiv Menschen angestiftet hat, Böses zu begehen? Der Beitrag skizziert zwei Fälle vermeintlicher göttlicher Manipulation, diskutiert die allgemeine Natur der Manipulation und untersucht dann jede der oben umrissenen Fragen. Es wird argumentiert, dass die Probleme im Zusammenhang mit der göttlichen Manipulation erhebliche Herausforderungen darstellen, insbesondere für jene christlichen Theisten, die sich dem göttlichen Determinismus verschrieben haben. [ABSTRACT FROM AUTHOR]

An attraction of the profilometry‐based indentation plastometry (PIP) procedure is that, while it involves interrogation of volumes sufficiently large to ensure that bulk properties are obtained, it still allows stress–strain curves to be inferred for relatively small regions, such that local properties can be mapped where they are changing over short distances. It is employed here to obtain these characteristics as a function of depth in samples that have been case hardened by the diffusional penetration of carbon, to a depth of just over a mm. This has been done for a grade of steel that is commonly treated in this way. The thickness of the layer characterized by the PIP test is around 200 μm. In addition, curvature measurements on strip samples, after incremental removal of thin layers, have been used to evaluate the (compressive) residual stresses in near‐surface regions. These range up to around 200 MPa. Such stresses have only a small effect on the PIP measurements. The carburization raises the peak yield stress from the base level of around 1000 MPa to about 1400 MPa, followed by considerable work hardening. The reliability of these PIP‐derived stress–strain relationships has been confirmed by comparing experimental outcomes of Vickers hardness tests with FEM predictions based on their use. [ABSTRACT FROM AUTHOR]

Purpose: Pulsed low-pressure carburizing (LPC) and omnidirectional high-pressure gas quenching (HPGQ) are innovative methods for quenching the surface layer. The thermochemical treatment carried out by this method reduces quenching geometric deformations, with detailed numerical values not available in the literature due to the short existence of this method. Design/methodology/approach: Sixteen toothed elements of EN 20MnCr5 steel were subjected to pulsed low-pressure carburising with omnidirectional jet quenching in 4 groups, varying the process temperature (920°C, 960°C) and in two groups performing a tempering treatment. The elements were tested before machining by measuring their internal hole diameters, radial runout, roundness and cylindricity. These values were tested again after treatment. The direction of change and the statistical significance of the effect of treatment and its parameters, temperature and tempering were analysed. Findings: Thermo-chemical treatment significantly affects geometric changes in diameters, roundness, cylindricity and radial runout compared to elements without heat treatment due to physical transformations occurring during this treatment (p<0.05). Changing the process temperature in the value range of 920°C-960°C affects the hole diameter (makes it smaller) (p<0.05), but does not affect radial runout, cylindricity and roundness. The observed dimensional changes in diameters have numerically small values (<0.005 mm). The tempering treatment can affect the values of average diameters. Its effect on roundness, cylindricity and radial runout was not observed. Research limitations/implications: In the temperature range studied, the method of pulsed low-pressure carburising + omnidirectional high-pressure gas quenching makes it possible to raise the temperature of the process and shorten its duration without significant geometric changes in the treated elements. Practical implications: The method of pulsed low-pressure carburising and omnidirectional high-pressure gas quenching (HPGQ) ensures the maintenance of reproducible quenching deformations at a level significantly lower than conventional processing methods. Originality/value: The method of pulsed low-pressure carburising together with omnidirectional high-pressure gas quenching (HPGQ) is a method that has been used briefly in the industry, and there are few reports on it to date. [ABSTRACT FROM AUTHOR]

The powder metallurgical manufacturing of gears offers a promising opportunity in terms of reducing the noise emission and increasing the power density. Sintered gears weigh less than conventional gears and potentially have a better noise-vibration-harshness behaviour, due to the remaining porosity. However, the potential of sintered gears for highly loaded applications is not fully utilised yet. Six variants of surface densified and case-hardened sintered gears from Astaloy Mo85 are tested to analyse the impact of the densification and case hardening depths on both the tooth root and flank load bearing capacities. Experimental investigations including metallography and computer tomography are carried out to characterise the microstructure. Furthermore, a simulation model is developed to quantitatively describe the residual stress and hardness profiles after the heat treatment. The load bearing capacity was improved by increasing the densification and case hardening depths, where the effect of the case hardening was identified to be predominant. [ABSTRACT FROM AUTHOR]

In the present study, crack propagation through the case hardened region of two different PM steels manufactured with different powder size distributions and sintered at different temperatures has been investigated. EBSD was used to study the microstructure before and after case hardening, revealing the relationship between powder particle grains after sintering and prior austenite grains after case hardening. A novel approach was used to achieve short cracks (10–20 µm) with high repeatability. The cracks were then analysed using EBSD and SEM, revealing detailed and novel information about the crack propagation route in the materials. Both tested materials show the same crack propagation behaviour. If a prior grain/prior austenite boundary is present within an angle from the crack initiation site, the cracks will follow the boundary and thus propagate intergranular, suggesting that the preferred route of crack propagation in case hardened sintered steel is along these boundaries. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the work is a complex review of methods applied industrially as case hardening. The paper contains an overview of scientific and development works on surface case hardening methods, especially carburising and quenching, described in the literature from 2001-2020. Design/methodology/approach: State-of-the-art was reviewed by a critical review of the world literature published in 2001-2022, including theoretical work, scientific research, and industry reports. An additional examination of the state of the art was conducted in terms of patent works. Findings: The period of 2001-2020 was a time of intensive work on the modernisation of case hardening techniques to improve the repeatability and uniformity of the produced layers and minimise deformations after hardening. Developing computing technologies have played a large part in this progress. New technologies have also been developed. Research limitations/implications: The review of papers and patent databases was limited to databases providing English-language content options. Practical implications: Case hardening is a crucial stage of steel heat treatment in almost every industrial branch: mechanical, tool, automotive, railway, and aviation. Originality/value: A synthetic review of case hardening methods was presented, particularly carburizing and quenching methods; it also analysed the possibilities and directions of their development. conducted in terms of patent works. Findings: The period of 2001-2020 was a time of intensive work on the modernisation of case hardening improve the repeatability and uniformity of the produced layers and minimise deformations after hardening. computing technologies have played a large part in this progress. New technologies have also been developed. Research limitations/implications: The review of papers and patent databases was limited to databases Englishlanguage content options. Practical implications: Case hardening is a crucial stage of steel heat treatment in almost every industrial tool, automotive, railway, and aviation. Originality/value: A synthetic review of case hardening methods was presented, particularly carburizing methods; it also analysed the possibilities and directions of their development. Keywords. Heat treatment, hardening, quenching, distortions, carburizing, simulation Reference to this paper should be given in the following way: E. Wołowiec-Korecka, Case hardening development review (2001-2020). [ABSTRACT FROM AUTHOR]

One of the most important challenge about using anthocyanin, is its low stability, especially against light and heat condition. Therefore, the main goal of this research was to increase the stability of the anthocyanin extract of the saffron petal in thermal and light condition. To reach this goal, encapsulation is the common method. Optimization of the anthocyanin encapsulation by Arabic gum, Persian gum, whey protein and maltodextrin was conducted to investigate the thermal stability in the model drink. Anthocyanin half- life during heat treatment (at 90 °C) was 100.8 min, which became the base of the heat treatment for the model drinks. Among the different wall material used in encapsulating of the anthocyanin extract, the highest total anthocyanin content was related to the maltodextrin microcapsule (191.7 mg cyaniding 3- glycoside/100g saffron petal powder). After that, there were the samples with two-part wall that one was maltodextrin. The lowest total anthocyanin was related to the microcapsules containing gum Arabic. After applying the microcapsule to the model drink, the highest anthocyanin retained (63.55%) was related to the microcapsule containing the combined maltodextrin and whey protein concentrate (at ratio of 1:1). Therefore the protein wall had the more positive effect on the retention of the anthocyanin in the model drink during thermal treatments. [ABSTRACT FROM AUTHOR]

The majority of wear-related problems are connected to crushing machines because hammer failure frequently causes machine failure which eventually leads to machine downtime. Therefore, improving the reliability of crushing materials is necessary for effective production. This research investigation focused on the development of crushing material with appropriate strength properties that can function in critical, impact-prone, corrosive, and abrasive conditions. The current study used palm kernel shell, coconut shell, and sawdust powder as the media for medium carbon steel in order to valorize the agro waste. Carburising media PKS-composition, CS-composition, and SD-composition were changed to 40%: 30%: 30%, PKS-composition 100%, CS-composition 100%, and SD-composition 100%. The process was carried out in 1 h (60 mims), 1 h:30 min (90 min), 2 h (120 min), 2 h:30 (150 min), and 3 h (180 min) soak period with varied carburising temperatures of 900, 950, 1000, and 1050 °C. However, several characterisation and mechanical tests were carried out using an optical microscope, a spark spectrometer, a scanning electron microscope coupled with an energy dispersive spectrometer, wear tester to explore their microstructural features. Vicker's hardness tester, sliding wear tester, and a thermal gravimetric analysis testing machine were also employed. In order to establish reasons for failure other than the cyclic loading on the materials, the results were compared with the properties of as-received un-failed, and carburised medium carbon steel. The results of carburisation show that PKS penetrates carbon at a rate that is noticeably higher than that of other materials at various temperatures and times, indicating that carbon diffuses deeply into the material. Hence, this enhances the wear resistance, and sample's hardness number but decreased its impact toughness respectively.

To reduce the processing time for in-line carburizing, we performed ultra-rapid carburizing and quenching using induction heating. Conventional gas carburizing and vacuum carburizing (low-pressure carburizing) are treated at 1203-1323 K, which is lower than the eutectic temperature. In contrast, in this study, the carburizing temperature of 1523K was higher than the eutectic temperature for speeding up this process. The SCM420 sample was rapidly heated to the treatment temperature by induction heating. CH4 and N2 were mixed and treated at atmospheric pressure at 5 vol% CH4 and 10 vol% CH4. For ultra-rapid carburizing, the total carburizing depth was proportional to the square root of the carburizing time, following the parabolic law, regardless of the CH4 concentration. We obtained that the amount of carbon penetrating the steel from the atmosphere was proportional to the carburizing time. In other words, the carbon penetration rate was approximately constant during the carburizing process. The processing time for the ultra-rapid carburizing and quenching at 1523K in this study was only 5% of that for the conventional gas carburizing at 1203 K. [ABSTRACT FROM AUTHOR]

In this article, is presented 3d visibility network using for analyzing complexity of microstructure of materials. A heat treating procedure called laser hardening, sometimes known as laser case hardening, is used to increase the tensile strength and longevity of component surfaces. High-powered diode lasers are used in this process to heat specific regions of the component surface. Fractal geometry is used for describe complexity of microstructure of robot laser hardened specimens. Topological properties of 3D visibility network is used to describe microstructure of robot laser hardened specimens. [ABSTRACT FROM AUTHOR]

The drying characteristics of a Japanese dry-cured ham model containing uniformly distributed brine were investigated. A higher effective moisture diffusivity was obtained at a lower relative humidity (RH) level. The activation energy of effective moisture diffusivity at 40 and 70% RH increased with decreasing moisture content, and was almost constant in the late stage of drying. Therefore, the moisture likely diffused without a large difference in the moisture distribution in the sample. In contrast, under low (10%) RH, the activation energy drastically increased with decreasing moisture content in the initial stage of drying. From the results of magnetic resonance imaging, the moisture content on the surface was drastically decreased; the surface was dried and hardened temporarily (i.e., case hardening) by the fast transfer of moisture. In the middle to late stages of drying, the activation energy gradually decreased to the similar values as at 40 and 70% RH in the late stage of drying. From the results of magnetic resonance imaging analysis after drying, the moisture distribution near the surface no longer exhibited a sharp difference in moisture concentration. The partly dried state of the surface could be alleviated by the transfer of moisture from the inside of the sample. Comparing the energy consumption for drying up to 175% dry basis, the drying condition of 35°C and 40% RH was the most efficient. [ABSTRACT FROM AUTHOR]

Physical hardening (PH) significantly affects bitumen's low-temperature performance. This paper investigates the effect of oxidative aging and wax structure on PH using 4-mm dynamic shear rheometer (4-mm DSR) and differential scanning calorimetry (DSC) tests. The results show that the wax chain length has a pronounced effect on the PH. Short-chain waxes, such as C18 and C24 affect the PH while longer-chain n-paraffins like C40 or Sasobit have almost no effect. In addition, the physical hardening index (PHI) is not linearly increasing with wax content but shows a maximum at a particular wax percentage. Wax-doped samples that crystallize before reaching the hardening temperatures typically show a reduced PHI compared to those with crystallization temperatures just below the hardening temperature. When crystallization and melting temperatures are not close to the hardening temperatures, the PHIs are typically reduced. Oxidative aging also influenced the PHI and in most cases the hardening decreased after aging. The highest PHI of almost all investigated samples occurs at 0 °C among the four typical temperatures. This investigation provides insights in the mechanism of PH and in the relations between wax contents, the hardening temperature, and the PHI. It also shows that while long-chain waxes used as warm mix additives, will not cause a PH risk, short-chain waxes present in pyrolyzed waste plastic, for example, should be handled with care. In addition, PH is also crucial for the intermediate service temperatures and not exclusively for thermal cracking at low temperatures. • Short chain waxes, like C18 and C24 will induce physical hardening in bitumen. • Long chain waxes, like C40 have little effect on the physical hardening in bitumen. • In wax-doped bitumen, the PHI shows a maximum at a particular wax concentration. • If waxes crystallize before reaching the PH temperature, their effect on PHI is lower. • After oxidative aging the PHIs of waxy and wax-doped samples typically reduces. [ABSTRACT FROM AUTHOR]

Counter-surfaces for radial shaft seals are usually finished by infeed grinding to avoid macro twist structures on the surface since they can impose a conveying action on the lubricant. This can lead to either leakage or starved lubrication and subsequent thermal damage depending on the direction of said conveying action. Turning processes can offer a more cost-effective surface finish, but conventional methods cause twist structures, which can impair the leakage prevention of the sealing system. An approach for the production of twist-free surfaces was developed based on new kinematics for turning. However, the surfaces produced with this approach using case hardened specimens made from the steel 16MnCr5 show deviating structural characteristics compared to the kinematic simulation. The causes of this and the resulting influence on the conveying value are the subjects of the research work. For this purpose, in addition to hardened steel, two other materials are considered: the steel 16MnCr5 in the unhardened hot rolled delivery condition and brass as a material with good machinability. The results clearly show that there is a deviation in the machining behavior of the steel materials compared to the kinematic surface simulations, especially in the repeatedly turned areas. This is mainly due to elastic–plastic deformation effects. Despite the actually twist-free surface profile, certain characteristics result in an anisotropic structure, which partially has an influence on the conveying value. [ABSTRACT FROM AUTHOR]

Smooth surfaces are conducive to improving the lubrication of gears in mechanical systems. In this study, chemical mechanical polishing (CMP) was used to process 18CrNiMo7-6 case hardening steel, a typical material for gears. The results reveal that compared with formic acid and oxalic acid, citric acid can be used as a suitable complexing agent without causing apparent corrosion, probably due to the fact of its relatively stable adsorption. A synergistic effect exists between citric acid and H2O2. At pH 3, with 0.067 M citric acid and 1 wt% H2O2, a satisfactory CMP performance (i.e., a 514 nm/min material removal rate (MRR) and a 0.85 nm surface roughness Sa) was achieved. After polishing, no observable defects were found on the surface, and no discernible processing damage occurred to the substrate. In terms of the CMP's mechanism, iron is first oxidized to Fe2+ and Fe3+, which then react with citric acid to form complexes. On the one hand, most of the complexes may stay on the surface to prevent further corrosion and, thus, the surface quality is excellent. On the other hand, the complexes may reduce the surface integrity and, thus, the MRR is high. The findings open new avenues for attaining ultra-smooth steel surfaces with CMP through controlling corrosive wear. [ABSTRACT FROM AUTHOR]

Deformation of the gear shaft in transmission is inevitable after case hardened heat treatment. Straightening is the normal way to ensure the straightness requirement. During the straightening process, cracks often appear and result in scrapped parts. Based on the situation of high rejection rate of straightening crack of the internal input shaft of a dual-clutch automobile transmission, this paper makes an in-depth analyses of the pressure straightening process theory, the crack generation mechanism, the working process of the automatic straightening machine and the crack detection system, etc., and establishes the relationship between the ram increment, the total displacement and the crack rate during multi-step progressive straightening, proposes a way to quickly judge the straightening performance of the parts. Finally, after optimizing the pressure position by finite element analysis, optimizing the straightening procedure by adjusting ram increment and adopting vector straightening method, optimizing the parts martial properties by heat treatment improvement, the straightening crack rate of internal input shaft was reduced from 1.95 % to 0.14 %. [ABSTRACT FROM AUTHOR]

Surface treatment methods are widely used in various industries to improve the material performance and change their physical properties. The methods can be categorised according to the nature of the operation as mechanical, chemical, electrochemical and case hardening processes. Mechanical surface treatment methods are mainly utilised to add compressive residual stresses in surface layers thus usually improving the life of engineering components. Among various mechanical surface treatment methods, peening process is common in treatment nature by treating the surface using mechanical means. Three peening processes, namely shot peening (SP), laser shock peening (LSP) and waterjet peening (WJP) are selected to be the focus of the present paper due to their similarity based on impulsive effect to the surface by the input force through unguided tools in repetitive irregular manner without any oscillating or vibrating movement of tools. A comprehensive review is presented to discuss each of the peening processes and their effects on the surface integrity in terms of the topography, mechanical properties and microstructural changes. The investigation includes the discussion on the existing advantages, disadvantages and technological barriers of peening technologies for industrial applications. Detailed examples of recent advances in the peening methods are also discussed. The results show that the SP method produces more roughness as compared to LSP and WJP methods. However, fatigue strength is better without considerable changes in roughness and corrosion after LSP and WJP treatments. It can be concluded that the peening processes can improve the material performance with acceptable qualities for in-service application in industries. [ABSTRACT FROM AUTHOR]

To explain the variance in core hardness of 18CrNi8 nozzle bodies after industrial heat treatment, several data sources, including steel melt composition, sensor process data, and measurement errors, of five years are aggregated. In order to predict hardness variations caused by alloy composition, traditional physical models by Maynier are compared with data‐driven machine learning models, which show no advantage due to low data variability. Neither method can fully explain the visible drifts, which are better tracked by an alternative (i. e., filter model) that uses past measurements. Machine learning on features from heat treatment is not successful in predicting hardness change, presumably because the process is too stable. Finally, a large part of the variance is caused by the HV 1 measurement error. [ABSTRACT FROM AUTHOR]

Cavernous weathering (honeycombs, tafoni) is a common weathering feature of both natural and artificial exposures. Honeycombs are known from various environments but are best developed in coastal areas. There are several theories as to their origin, with salt weathering currently being the most favoured by the geomorphological community. To test if the drying pattern of salt‐laden moisture results in honeycombs (the theory of Huinink et al., Earth Surface Processes and Landforms, 29(10), 1225–1233, 2004), coastal honeycombs in the metasandstone of Tuscany (Italy) were studied both in the field and with a laboratory evaporation experiment. The depth of the evaporation front was measured by the 'uranine‐probe' method in the honeycomb pits and lips. The evaporation rate was calculated from the depth of the evaporation front as well as the climatic conditions at the study site. Lastly, the amounts of precipitated salts were estimated based on the evaporation rate of seawater. In the evaporation experiment, the evaporation front retreated faster in the lips than in the pits, and the field measured evaporation front was closer to the surface in the pits (2 mm) than in the lips (7 mm). Thus, the calculated evaporation rate was higher in the pits than in the lips (16.1 and 4.6 mm/yr, respectively). Similarly, the amount of salts precipitated was also higher in the pits (0.7 kg/m2/yr compared to 0.2 kg/m2/yr in lips). Faster salt deposition in the pits as well as the evaporation front position fits well with the theory of Huinink et al. Based on surface tensile strength measurements, case hardening is not protecting the honeycomb lips. [ABSTRACT FROM AUTHOR]

• A novel approach is proposed for estimating broadband non-Gaussian fatigue damage. • The Johnson transformation model is employed to address the non-Gaussianity. • The proposed approach shows improved applicability for skewness and kurtosis. Estimating fatigue damage of marine structures using spectral methods under broadband random loadings is a complex and challenging task. In the presence of non-Gaussian loading, the spectral method typically employs the Hermite polynomial model (HPM) to address the non-Gaussianity. However, the applicability of HPM is limited in certain non-Gaussian cases due to the requirement of monotonicity. This paper adopts the Johnson transformation model (JTM) instead of HPM and integrates it with the non-Gaussian TB method (Ding and Chen, 2015) to overcome the constraints in broadband non-Gaussian fatigue estimation. To verify the performance of the new approach, this paper analyses the transformation accuracy of the two models. Additionally, taking the time-domain fatigue damage obtained by the rainflow counting method and the linear damage accumulation rule as a benchmark, this paper compares the fatigue damage estimates obtained from the spectral methods. The comparative assessment encompasses various spectra, S-N curves, and non-Gaussian characteristics. The results indicate the performance of JTM within the non-Gaussian TB method is comparable to HPM in most cases and even surpasses it in hardening non-Gaussian cases. Given the broader applicability of JTM across ranges of skewness and kurtosis, it emerges a superior option for the non-Gaussian TB method in estimating broadband non-Gaussian fatigue damage. Furthermore, the limitations of the proposed approach are discussed. [ABSTRACT FROM AUTHOR]