The work concerns the application of non-contact measurement 3D scanning techniques in conjunction with a study of the microstructure of a forging die (made of W360 steel) for the production of an ...engine valve (made of NCF 3015 steel) in a hot die forging process in order to analyse the changes in the working surface of the tools and identify the destructive mechanisms. The detailed analysis presented in this paper examines the possibility of using 3D reverse engineering techniques for a direct quality control and examination of the changes in the surface layer geometry of the forging dies, based on the measurement of the geometry changes for cyclically collected forgings. The selected area of the valve forgings cyclically retrieved from the forging process was scanned with the use of an intermediate scanning method - reverse 3D scanning. On this basis, an analysis of the progressive material growth on the selected surface of the forgings was made, which also meant a loss of material on the tools. The performed analyses showed a good agreement of the geometrical properties of the surfaces (of the selected forgings representing the proceeding wear of the tool) and the geometrical defect of the working impression of the tool, based on the direct measurements during the production process. The reverse 3D scanning method developed by the authors has been repeatedly verified by them, which is confirmed by numerous studies and applications. The obtained results combined with SEM analyses and microhardness measurements enable a fast analysis of the forging tool life with respect to the quality and quantity (of material defect), which, in consequence, leads to significant economical savings.
•Measurement of tool wear on the basis of the use reverse method of scanning 3D.•Identification of the destructive mechanisms and phenomena in different areas of die.•Use the combine results of SEM and microhardness measurements as well as FE modelling for a more complete analysis.•Practical knowledge for forging-engineers about the improvement of durability forging tools.
The slow afterhyperpolarization (sAHP) is a calcium-activated potassium conductance with critical roles in multiple physiological processes. Pharmacological and genetic data suggest that KCNQ ...channels partly mediate the sAHP. However, these channels are not typically open within the observed voltage range of the sAHP. Recent work has shown that the sAHP is gated by increased PIP2 levels, which are generated downstream of calcium binding by neuronal calcium sensors such as hippocalcin. Here, we examined whether changes in PIP2 levels could shift the voltage-activation range of KCNQ channels. In HEK293T cells, expression of the PIP5 kinase PIPKIγ90, which increases global PIP2 levels, shifted the KCNQ voltage activation to within the operating range of the sAHP. Further, the sensitivity of this effect on KCNQ3 channels appeared to be higher than that on KCNQ2. Therefore, we predict that KCNQ3 plays an essential role in maintaining the sAHP under low PIP2 conditions. In support of this notion, we find that sAHP inhibition by muscarinic receptors that increase phosphoinositide turnover in neurons is enhanced in Kcnq3-knockout mice. Likewise, the presence of KCNQ3 is essential for maintaining the sAHP when hippocalcin is ablated, a condition that likely impairs PIP2 generation. Together, our results establish the relationship between PIP2 and the voltage dependence of cortical KCNQ channels (KCNQ2/3, KCNQ3/5, and KCNQ5), and suggest a possible mechanism for the involvement of KCNQ channels in the sAHP.
The mechanisms of the degradation of hot forging tools and several mathematical models for the theoretical evaluation of them are described. Examples of abrasive wear, oxidization, thermomechanical ...fatigue and plastic deformation and the interdependences between them, based on the authors’ research, are provided. According to the presented research the commonly accepted view that abrasive wear is the dominant mechanism in the degradation of the dies in hot forging is highly dubious. The effect of each of the above phenomena on the life of forging dies is generally considered separately and there is no holistic description of the physical wear process, which would cover all the phenomena simultaneously. In reality, the degradation phenomena occur simultaneously and interact with each other.
The study discusses the issues of low durability of dies used in the first operation of producing a valve type forging from high nickel steel assigned for the application in motor truck engines. The ...analyzed process of manufacturing the exhaust valve forgings is realized in the coextrusion technology, followed by forging in closed dies. This process is difficult to master, mainly due to elevated adhesion of the charge material (high nickel steel – NCF3015) to the tool substrate as well as very high abrasive wear of the tool, most probably caused by the dissolution of hard carbide precipitates during the charge heating. A big temperature scatter of the charge during the heating and its short presence in the inductor prevents microstructure homogenization of the bearing roller and dissolution of hard precipitates. In effect, this causes an increase of the forging force and the pressures in the contact, which, in extreme cases, is the cause of the blocking of the forging already at the beginning of the process. In order to analyze this issue, complex investigations were conducted, which included: numerical modelling, dilatometric tests and hardness measurements. The microstructure examinations after the heating process pointed to lack of structure repeatability; the dilatometric tests determined the phase transformations, and the FEM results enabled an analysis of the process for different charge hardness values. On the basis of the conducted analyzes, it was found that the batch material heating process was not repeatable, because the collected samples showed a different amount of dissolved carbides in the microstructure, which translated into different hardnesses (from over 300 HV to 192 HV). Also, the results of numerical modeling showed that lower charge temperature translates into greater forces (by about 100 kN) and normal stresses (1000 MPa for the nominal process and 1500 MPa for a harder charge) and equivalent stresses in the tools (respectively: 1300 MPa and over 1800 MPa), as well as abrasive wear (3000 MPa mm; 4500 MPa mm). The obtained results determined the directions of further studies aiming at improvement of the production process and thus increase of tool durability.
The study presents the concept of physical modeling together with the characterization of model materials as well as the possibilities of applying this type of physical simulation methods for the ...analysis, design, and optimization of industrial metal forming processes. The method provides the possibility to define the stress and deformation distribution, to estimate force parameters of the given process, and to localize dead zones and material flow errors. It can also be an alternative or supplementation to finite element modeling. The paper discusses the crucial similarity conditions between the physical model and the real process, which is necessary to transform the results into industrial processes. The developed database of soft model materials was also presented, on the basis of which a model material can be selected for almost any metallic materials. The paper also proposes a new description of the plastic similarity condition, which was verified by the example of two semi-industrial processes (backward and forward extrusion). The study demonstrates the attempt and the results of the influence of the matching of the model materials for three metallic materials, which, at ambient temperature, represent three main types of metal forming processes: hot (lead), warm (reinforced aluminum) and cold working (annealed aluminum). The obtained results showed great usefulness of the proposed condition of plastic similarity, because, in the case of a low value of the similarity coefficient (close to zero), both the flow method and the strength parameters obtained in physical modeling are very similar to the industrial process. On this basis, it can be assumed that by selecting the appropriate model material for the actual metallic material, you can quickly and easily optimize the industrial process with low financial outlays.
The article presents the use of artificial neural networks (ANN) to build a system of analysis and forecasting of the durability of forging tools and the process of acquiring the source knowledge ...necessary for the network learning process. In particular, the study focuses on the prediction of the geometrical loss of the tool material after different surface treatment variants.The methodology of developing neural network models and their quality parameters is also presented. The standard single-layer MLP networks were used here; their quality parameters are at a high level and the results presented with their participation give satisfactory results in line with technological practice. The data used in the learning process come from extensive comprehensive performance tests of forging tools operating under extreme operating conditions (cyclic mechanical and thermal loads). The parameterization of the factors important for the selected forging process was made and a database was developed, including 900 knowledge vectors, each of which provided information on the size of the geometrical loss of the tool material (explained variables). The value of wear was determined for the set values of explanatory variables such as: number of forgings, pressure, temperature on selected tool surfaces, friction path and the variant of the applied surface treatment. The results presented in the study, confirmed by expert technologists, have a clear applicational character, because based on the presented solutions, the optimal treatment can be chosen and the appropriate preventive measures applied, which will extend the service life.
nema
Following paper is focused on experimental and numerical studies of the behavior and energy absorption for both: quasi-static and dynamic axial crushing of thin-walled cylindrical tubes filled with ...foam. The experiments were conducted on single walled and double walled tubes. Unfilled profiles were compared with tubes filled with various density polyurethane foam. All experiments were done in order to possibility of the safety of the elements absorbing collision energy which can applied in car body. The dynamic nonlinear simulations were carried out by means of PAM-CRASH™ explicit code, which is dedicated calculation package to modelling of crush. Computational crushing force, plastic hinges locations and specimens post-crushed geometry found to be convergent with the real experiments results. Conducted experiments allowed to draw conclusion, that crashworthiness ability is directly proportional to foam density. The investigation of the experimental data revealed, that double walled tubes have greater energy absorbing ability. A proposed investigation enable to analyze and chosen of optimal parameters of these elements, which can use in automotive industry as an absorption energy components.
Key points
Activation of spinally projecting sublaterodorsal nucleus (SLD) neurons inhibits motor activity, in part through spinal inhibitory interneurons, to produce muscle atonia during ...rapid‐eye‐movement (REM) sleep.
It has long been hypothesized that acetylcholine released during REM sleep contributes to REM sleep atonia through activation of SLD neurons.
We show, using whole‐cell recordings in brainstem slices, that acetylcholine directly excites spinally projecting SLD neurons via M1 and M3 muscarinic receptors, and increases afferent excitatory synaptic input to these neurons.
These results suggest that acetylcholine contributes to REM sleep muscle atonia through excitation of spinally projecting SLD neurons.
Considerable electrophysiological and pharmacological evidence has long suggested an important role for acetylcholine in the regulation of rapid‐eye‐movement (REM) sleep. For example, injection of the cholinergic agonist carbachol into the dorsomedial pons produces an REM sleep‐like state with muscle atonia and cortical activation, both of which are cardinal features of REM sleep. Located within this region of the pons is the sublaterodorsal nucleus (SLD), a structure thought to be both necessary and sufficient for generating REM sleep muscle atonia. Subsets of glutamatergic SLD neurons potently contribute to motor inhibition during REM sleep through descending projections to motor‐related glycinergic/GABAergic neurons in the spinal cord and ventromedial medulla. Prior electrophysiological and pharmacological studies examining the effects of acetylcholine on SLD neurons have, however, produced conflicting results. In the present study, we sought to clarify how acetylcholine influences the activity of spinally projecting SLD (SLDsp) neurons. We used retrograde tracing in combination with patch‐clamp recordings and recorded pre‐ and postsynaptic effects of carbachol on SLDsp neurons. Carbachol acted presynaptically by increasing the frequency of glutamatergic miniature excitatory postsynaptic currents. We also found that carbachol directly excited SLDsp neurons by activating an Na+–Ca2+ exchanger. Both pre‐ and postsynaptic effects were mediated by co‐activation of M1 and M3 muscarinic receptors. These observations suggest that acetylcholine produces synergistic, excitatory pre‐ and postsynaptic responses on SLDsp neurons that, in turn, probably serve to promote muscle atonia during REM sleep.
The article presents an analysis of the multi-operation hot die forging process, performed on a press, of producing a lever forging used in the motorcycles of a renowned producer by means of ...numerical simulations. The investigations were carried out in order to improve (perfect) the currently applied production technology, mainly due to the presence of forging defects during the industrial production process. The defects result mainly from the complicated shape of the forging (bent main axis, deep and thin protrusions, high surface diversity in the cross section along the length of the detail), which, during the filling of the die by the deformed material, causes the presence of laps, wraps and underfills on the forging. Through the determination of the key parameters/quantities during the forging process, which are difficult to establish directly during the industrial process or experimentally, a detailed and complex analysis was performed with the use of FEM as well as through microstructure examinations. The results of the performed numerical modelling made it possible to determine: the manner of the material flow and the correctness of the impression filling, as well as the distributions of temperature fields and plastic deformations in the forging, and also to detect the forging defects often observed in the industrial process. On this basis, changes into the process were introduced, making it possible to improve the currently realized technology and obtain forgings of the proper quality as well as shape and dimensions.
The paper presents a prototype semi-industrial cooling line developed by the authors, which makes it possible to design a thermal treatment of forgings with the use of the forging heat, together with ...exemplary test results for forgings forked type. The proposed method of heat treatment dedicated to these forgings was described and compared to traditionally used heat treatment method in chamber furnaces. Next, the original research stand was presented, which performs mechanical fatigue test on final products – forked-type forgings. Forgings after heat treatment and cooling on the prototype line were tested on this stand in condition of cyclically variable mechanical loads in order to resistance to mechanical fatigue was analyzed and the influence of performed exemplary heat treatment on mechanical properties. The presented preliminary investigations performed on the designed combined research standing, consisting of: the prototype controlled cooling line, as well as mechanical fatigue stand point to the possibility of implementing thermal treatment with the use of the heat generated during the forging process and determining its impact on the mechanical properties of forgings.
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