A comprehensive analysis of literature pertaining to ecological trends in machining processes of difficult-to-cut materials (e.g. hard steels, Ti-based alloys, Ni-based alloys) has been performed. ...The paper focuses on the improvement of machining processes with a balanced attention onthe reduction of pollution generated by coolants and emulsions. Here, the specific areas of interest are: Dry cutting; Minimum Quantity Lubrication/Minimum Quantity Cooling Lubrication; Cryogenic Cooling; High-Pressure Coolant and Biodegradable Vegetable Oils. The proposed approach of sustainable and cleaner production for the above-mentioned areas involves the minimized use of coolant/lubricants, employment of appropriate cutting tool's grade and machining conditions that leads to the reduction of total cost, cutting force, energy consumption, temperature but improvements of surface quality, volume of material removed, as well as the prolongation of tool life. In addition, the qualitative judgments like impact on human operator's health, atmospheric air, chip removal from machining area etc. are taken into account. The study presented in the paper is such a vast compendium of knowledgeregarding multi-directional critical analysis of machined parts, tools, chips under state-of-art cooling/lubrication systems that it will help the next generation scientists to find recent advances as well as future avenues of research on ecological aspects of machining for sustainability.
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•Review of ecological trends in machining of hard to-cut-materials.•Discussion on improvement of machining, regarding the reduction of pollution.•Development of ring of sustainable machining.•Implementation of discussed methods in cleaner and effective production.
This study focuses on the prediction of cutting forces during micro end milling using a novel approach that takes into account the chip thickness accumulation phenomenon. The proposed original force ...model considers the micro end milling kinematics, geometric errors of the machine tool–toolholder–mill system, elastic and plastic deformations of workpiece correlated with the minimum uncut chip thickness, and flexibility of the slender micro end mill. It also includes a novel analytical approach for the instantaneous area of cut. The chip thickness accumulation phenomenon can be manifested as chip thickness variations in the current tool rotation, resulting from material burnishing and elastic recovery in all previous tool rotations. The predicted forces consider the minimum uncut chip thickness value, which has been estimated directly from the micromilling process of AISI 1045 steel based on an original analytic–experimental approach that applies the identification of a stagnant point in the milling process. The results obtained show that the instantaneous and average micromilling forces determined using the proposed model have considerably better conformity with the experimental forces than those predicted using the commonly used rigid micro end milling model. Moreover, the non-linearity of the cutting forces as a function of feed per tooth is strongly affected by multiple cutting mechanism transitions observed during micromilling with uncut chip thicknesses close to the minimum uncut chip thickness value.
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•Novel concept of chip thickness accumulation in burnishing-dominant regime.•Minimum uncut chip thickness model for micromilling considering the stagnant point.•Comprehensive micromilling force model considering effective uncut chip thickness.•High accuracy of predicted forces in cutting- and burnishing-dominant regimes.•Influential effect of chip thickness accumulation on micromilling force variations.
Laser cladding technology enables the regeneration or manufacturing of machine parts with the improved surface layer properties. The materials applied during the laser cladding processes very often ...contain hard and wear-resistant tungsten carbide (WC) particles. However, the parts obtained after the laser cladding have usually unsatisfactory surface quality and thus require post-process finishing. In addition, the content of WC particles causes that clad layers are difficult to cut. Therefore, in order to improve their machinability, the laser-assisted machining (LAM) technology can be applied. Nevertheless, the material removal mechanisms during LAM of WC/NiCr clad layers are not recognized. Thus, this study is focused on the estimation of minimum uncut chip thickness and analysis of cutting forces which are important factors describing the chip decohesion process. The proposed method is based on the novel approach dedicated directly to the oblique cutting, considering the zeroth tangential force increment located onto rounded cutting edge. The experimental procedure involves cutting force component (
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) measurements in the range of variable cutting conditions, as well as the cutting tool’s micro-geometry inspection. On the basis of the measurements carried out, the force regression equations are formulated and subsequently applied to the determination of tangential force expression. Subsequently, the minimum uncut chip thickness is calculated on the basis of the equation derived from the zero tangential force increment condition and presented in function of cutting speed. The obtained results enable the effective selection of the cutting parameters during LAM of WC/NiCr clad layers.
Abstract Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid derived from Cannabis sativa . It has therapeutic effects in different paradigms of brain injury, acting as a neuroprotectant. As ...oxidative stress is a primary risk factor for brain damage after neonatal hypoxia, we tested the effect of CBD on oxidative status and non-protein-bound iron accumulation in the immature brain after hypoxia. Moreover, we tested whether cannabidiol affects the accumulation of hypoxia-inducible factor-1 alpha (HIF-1α) which plays a key role in the regulation of cellular adaptation to hypoxia and oxidative stress. We used 7-day-old mice randomly assigned to hypoxic or control groups. Immediately after hypoxia or control exposure, pups were randomly assigned to a vehicle or CBD treatment. 24 h later, they were decapitated and the brains were immediately removed and stored for further biochemical analyses. We found that CBD reduced lipid peroxidation and prevented antioxidant depletion. For the first time, we also demonstrated that CBD upregulated HIF-1α protein level. This study indicates that CBD may effective agent in attenuating the detrimental consequences of perinatal asphyxia.
•Evaluation of relations between tool displacements and surface profile formation.•Novel method for measurement of ball end mill’s working part displacements.•Two distinct mechanisms of surface ...profile formation depended on tool overhang.•High effect of cutting speed on surface roughness in milling with flexible tool.
The study presents an analysis of relations between the instantaneous tool displacements and surface roughness formed during ball end milling of surface with inclination towards the tool’s axis. A novel experimental method for the estimation of ball end mill’s working part vibrations, considering displacements correlated with the geometrical errors of tool-toolholder-spindle system and deflections caused by milling forces has been proposed. The experiments have been conducted on hard-to-cut low carbon hardened alloy steel. Milling tests involved the use of monolithic ball end mills varied in terms of overhang l values. In the first stage, the finishing machining of inclined surface with variable cutting speeds vc was carried out. During the experiment, the instantaneous tool’s joining part displacements have been measured with the application of laser displacements sensor. Subsequently, in order to obtain the tool’s tip instantaneous displacements, the analytical extrapolation method has been proposed. In the next stage, the machined surface roughness has been measured with the application of stylus and optical profile meters. The investigations show that the value of tool’s overhang significantly affects the mechanisms of surface roughness generation during finishing ball end milling. In case of milling with the rigid tool (l = 35 mm), the surface roughness is strongly correlated with kinematic-geometric model, as well as with geometrical errors of machining system. Nevertheless, in case of milling with the slender tool (l = 85 mm), the surface roughness formation is mainly affected by the tool’s working part dynamic deflections caused by milling forces.
This paper presents the study on the formation of surface layer in A359/20SiCP metal matrix composite (MMC) during laser assisted turning, with the consideration of SiC particles’ sedimentation in a ...liquid matrix. The developed model includes the effect of gravity, buoyancy, resistive force of liquid matrix and centrifugal force of the rotating work material. On the basis of the proposed approach the instantaneous sedimentation speed, as well as the depth of sedimented SiC particles are calculated. Consequently, the applied model enables the selection of the effective depth of cut and tool’s angular distance from the laser beam, which can improve the machined surface quality and composite’s exploitation properties. The experiments confirm that sedimentation phenomenon plays an important role during the surface layer formation in laser heating conditions. Furthermore, the laser assisted turning with the selection of the recommended cutting conditions affects the improvement of surface quality, and composite’s wear resistance.
The theory of delayed life history effects assumes that phenotype of adult individual results from environmental conditions experienced at birth and as juvenile. In seasonal environments, being born ...late in the reproductive season affects timing of puberty, body condition, longevity, and fitness. We hypothesized that late-born individuals are more prone to respond to short photoperiod (SP) than early born ones. We used Siberian hamsters Phodopus sungorus, a model species characterized by high polymorphism of winter phenotype. We experimentally distinguished the effect of litter order (first or third) from the effect of exposure to long photoperiod (LP) before winter (3 months or 5 months) by manipulating the duration of LP acclimation in both litters. We predicted that, irrespective of the litter order, individuals exposed to long photoperiod for a short time have less time to gather energy resources and consequently are more prone to developing energy-conserving phenotypes. To assess effect of litter order, duration of acclimation to long days, and phenotype on basal cost of living we measured basal metabolic rate (BMR) of hamsters.
Individuals born in third litters had faster growth rates and were bigger than individuals from first litters, but these differences vanished before transfer to SP. Litter order or duration of LP acclimation had no effects on torpor use or seasonal body mass changes, but prolonged acclimation to LP inhibited winter molting both in first and third litters. Moreover, individuals that did not molt had significantly higher BMR in SP than those which molted to white fur. Although one phenotype usually predominated within a litter, littermates were often heterogeneous. We also found that over 10% of individuals presented late response to short photoperiod.
Our data indicate that duration of postnatal exposure to LP may define propensity to photoresponsiveness, regardless of the litter in which animal was born. Existence of littermates presenting different phenotypes suggests a prudent reproductive strategy of investing into offspring of varied phenotypes, that might be favored depending on environmental conditions. This strategy could have evolved in response to living in stochastic environment.
•Parametric description of differences in the surface topography.•Parametric changes in the surface topography for different cooling conditions.•Nonparametric description of the surface ...topography.•Analysis of geometric product specifications.•Analysis of material ratio of the profile and distribution of ordinates of the surface texture.
This paper focuses on the parametric and nonparametric description of surface topography after turning in the dry and MQCL conditions. The carried out research involved the longitudinal turning tests of duplex stainless steel, conducted in a range of variable cutting speeds vc and feeds f. Surface topography measurements were conducted with the application of Infinite Focus G4 microscope. In the first stage of research, the parametric analysis of the machined surfaces has been conducted. It included the evaluation of amplitude surface roughness parameters. In the next stage the nonparametric description of machined surfaces was carried out. This analysis has been focused on the presentation of machined surfaces in the form of contour maps and isometric images. The last stage of experiment involved the evaluation of surface isotropy and formulation of material ratio charts. The conducted research shows that the application of MQCL method can lead to the reduction of 3D surface roughness parameters compared to values reached after the dry machining. Moreover, the better distribution of irregularity peaks and pits under the MQCL method, comparing to that obtained after dry cutting implies that surfaces machined with the use of MQCL technique can be characterized by a high wear resistance.
Anthropogenic land use changes, such as deforestation and commercial forestry, have substantially reduced natural roost sites for European bats. A common conservation solution is to provide ...artificial roosts (i.e. bat boxes), but there are concerns that these can become hotter than natural roosts in summer and could be death traps during heat waves. Nevertheless, females of several bat species form maternity colonies in these boxes, thus occupying hotter and more humid microclimates than solitarily roosting males. We tested if cooling efficiency and heat tolerance differ between sexes in European bats, and estimated the evaporative water requirements for bats living in bat boxes during hot summer days.
We used indirect calorimetry and thermometry to quantify thermoregulation at high air temperatures (Ta) in four species of verspitilionid bats that regularly occupy artificial roosts. We measured resting metabolic heat production, evaporative water loss rates (EWL) and body temperature (Tb) at Ta between 28°C and 48°C during summer. We predicted that females have higher evaporative cooling efficiency (evaporative heat loss/metabolic heat production) than males, allowing them to reach their heat tolerance limit at higher Ta.
We found no sex differences in maximum evaporative cooling efficiency, maximum Tb, and maximum Ta tolerated. However, the patterns of increasing EWL with Ta differed between sexes. Females tolerated higher Ta before increasing EWL than males and then rapidly increased EWL to higher values than males at the maximum Ta tolerated. These sex differences in heat dissipation strategies may reflect varying ecological and physiological constraints associated with different summer roosting habits.
Synthesis and applications. Our study revealed that some small European bat species are already at risk of succumbing to lethal dehydration during present‐day heat waves, with daytime evaporative water requirements equivalent to ~30% of body mass in sun‐exposed boxes. For conservation managers working with common European bat species, particularly those in monoculture forests with woodcrete bat‐boxes, our physiologically informed recommendations include positioning boxes in diverse locations varying in aspect and sun exposure. This will ensure thermal heterogeneity of roost sites and provide a wide gradient of microclimate conditions, allowing for roost switching when necessary.
Our study revealed that some small European bat species are already at risk of succumbing to lethal dehydration during present‐day heat waves, with daytime evaporative water requirements equivalent to ~30% of body mass in sun‐exposed boxes. For conservation managers working with common European bat species, particularly those in monoculture forests with woodcrete bat‐boxes, our physiologically informed recommendations include positioning boxes in diverse locations varying in aspect and sun exposure. This will ensure thermal heterogeneity of roost sites and provide a wide gradient of microclimate conditions, allowing for roost switching when necessary.
Synopsis White-nose syndrome (WNS) has caused alarming declines of North American bat populations in the 5 years since its discovery. Affected bats appear to starve during hibernation, possibly ...because of disruption of normal cycles of torpor and arousal. The importance of hydration state and evaporative water loss (EWL) for influencing the duration of torpor bouts in hibernating mammals recently led to "the dehydration hypothesis," that cutaneous infection of the wing membranes of bats with the fungus Geomyces destructans causes dehydration which in turn, increases arousal frequency during hibernation. This hypothesis predicts that uninfected individuals of species most susceptible to WNS, like little brown bats (Myotis lucifugus), exhibit high rates of EWL compared to less susceptible species. We tested the feasibility of this prediction using data from the literature and new data quantifying EWL in Natterer's bats (Myotis nattereri), a species that is, like other European bats, sympatric with G. destructans but does not appear to suffer significant mortality from WNS. We found that little brown bats exhibited significantly higher rates of normothermic EWL than did other bat species for which comparable EWL data are available. We also found that Natterer's bats exhibited significantly lower rates of EWL, in both wet and dry air, compared with values predicted for little brown bats exposed to identical relative humidity (RH). We used a population model to show that the increase in EWL required to cause the pattern of mortality observed for WNS-affected little brown bats was small, equivalent to a solitary bat hibernating exposed to RH of ∼95%, or clusters hibernating in ∼87% RH, as opposed to typical near-saturation conditions. Both of these results suggest the dehydration hypothesis is plausible and worth pursuing as a possible explanation for mortality of bats from WNS.
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