Force analysis of the stress-strain state of the surface layer of Al 2O3‒TiCceramics with AlN and TiN coatings

Regularities of stress-strain state of surface layer of Al2O3‒TiC-ceramics with AlN and TiN coatings under the action of force load are established using the methodology of computer engineering. The features of influence of AlN and TiN coatings on the nature of changes in the stress intensity in the surfaces of structural elements forming the surface layer of Al2O3‒TiC ceramics are determined. The formation of microstructural stress concentrators at the boundary of the AlN and TiN coatings with the initial ceramics is revealed.

The Existence of Stilt Houses Post-Disaster

Stilt houses are one of the architectural identities of the archipelago that are still commonly found in Indonesia. Stilt houses have proven to be sustainable products because they still exist today after going through various natural disasters. This is inseparable from the stilts house building techniques, including the process of finding and determining the form and implementation of adat (philosophy). So, this research aims to show the existence of post-disaster stilt houses which include tsunami disasters in Aceh and Palu. This research is a case study that uses a comparativeanalysis method to show the influence factors of the existence of stilts houses after disaster in Aceh dan Palu. Based on the results of the study, it is known that the stilt houses in Aceh and Palu have stilt buildings that are sturdy and stable in accepting the force load when a disaster occurs. The key of building sturdiness lies on building structures such as connection systems, foundation type, material type, and the buildings proportion. These factors caused the stilts houses to not suffer severe damage, and in some cases did not show any damage to the buildings after being affected by natural disasters.

Eggs With Trilobite Larvae in a Cambrian Community. Modeling the Hydrodynamics

Background: Reproductive behaviors include mating, pregnancy, birth, and ulterior brood care. Fossil records (eggs, nests, etc.) provide a glimpse into the reproductive sequences of ancient animals. Here, we show putative trilobite egg clusters from the middle Cambrian (Miaolingian, Wuliuan Stage) that were found in the Kaili Formation, South China. The arrangement of these egg clusters would ensure efficient oxygen diffusion from the water into cells.Results: We applied a computational fluid mechanics simulation method to understand the behavior of Kaili trilobite eggs in Cambrian seawater under different flow patterns. The drag force and lift force load on the eggs increased rapidly when current speeds exceeded 0.2 m/s. Moreover, the drag coefficient of the single egg model was 1.8–2 times larger than that of each egg in the egg cluster model. The trilobite larva within the egg cluster (ca. 0.5 mm in size) are smaller than the eggs (ca. 0.6 mm), which indicates that they had recently hatched.Conclusions: We suggest that not all trilobites had an unmineralized preliminary stage in their ontogeny and that some protaspis shield may have been formed before hatching. Moreover, we hypothesize that aquatic animals can use egg clustering to effectively reduce the effects of drag and lift forces from the surrounding water.

Influence of Deformations on the Filtration Coefficient of Materials

This article is devoted to the study of the filtration coefficient depending on the loads applied to the material. In filtration theory, it is classical to solve problems with a constant filtration coefficient. Moreover, due to the conditionality of the filtration coefficient value by various physical and chemical processes, both in the solid fraction and in the liquid, its value is usually determined empirically. However, it is obvious that depending on the loads applied to the material, the pore space and filtration coefficient will change. This is especially true when using various filter materials, such as concrete. The latter, depending on the brand, can absorb the liquid quite well. Therefore, assuming that the pore space is a collection of capillary tubes, the paper shows the relationship between the filtration coefficient and the average pore diameter of the material. The dependence of the material filtration coefficient on the first invariant of the stress tensor arising in the medium is found. The change in the filtration coefficient of a concrete slab at different points is shown when a force load is applied to its upper surface.

Double-Helix Linear Actuators

Many robotic systems require linear actuation with high forces, large displacements, and compact profiles. This article presents a series of mechanisms, termed double-helix linear actuators (DHLAs), designed for this purpose. By rotating the fixed end of a double-helix linear actuator, its helix angle changes, displacing at the free end. This article proposes two concepts for DHLA designs, differing in their supporting structure, and derives kinematic and geometric models for both. Prototypes of each concept are presented, and for the more promising “continuous-rails” design, hardware tests are conducted that validate the actuator's kinematic model and characterize its force transmission properties. The final prototypes can exert both tension and compression forces, can displace up to 75% of their total length, and show consistent trends for torque vs. force load. These designs have the potential to overcome the force and displacement limitations of other linear actuators while simultaneously reducing size and weight.

COMPARATIVE ANALYSIS OF MONOCORTICAL AND BICORTICAL METHODS OF INSTALLING MINI-IMPLANTS

The aim of the study. Carry out a comparative analysis of the support ability of human jaw bone tissue in monocortical and bicortical installation of a mini-implant of own design OMG. Research methods. In order to study biomechanical characteristics of developed OMG mini-implant and bone tissue capacity during monocortical and bicortical installation, the finite element method (MSE) was used. The scheme and finite element 2-D model of bicortical installation of OMG mini-implant (length 8 mm, diameter 1.8 mm) provided full penetration through one layer of cortical bone equal to 1 mm, the entire cancellous bone and immersion in the second layer of cortical bone by 0, 5 mm. No implantation was immersed in the second cortical layer of bone during monocortical installation. A single force load of 1 N was applied in the horizontal direction parallel to the cortical plate of the bone. Results of the study. One of the most important factors leading to the success of the use of a mini-implant is its stability in the process of orthodontic treatment. Quite a high level of failure in the monocortical installation of mini-screws has led to the search for better methods to ensure the stability of their use. This was a bicortical method of fixation, based on the placement of the minig screw in the thickness of the two cortical plates of the jaws. Area for such installation of mini-screws can be a site of a palate and alveolar sprouts at installation of miniimplants through all its thickness. As shown by our data on the use of the finite element method under the force load of the biomechanical system "bone - mini-implant", the stress concentration zone is located in the area of the cortical bone of the jaw. The results of the calculation of the maximum stresses (σmax, MPa) and the maximum possible displacements (umax, mm) of the mini-implant in the biomechanical system "bone - mini-implant" in monocortical installation were, respectively, 8.27 MPa and 0.300 * 10-8 mm and in bicortical installation 6.00 MPa and 0.201 * 10-8 mm. The bicortical method of fixing the mini-implant in the jaw bones significantly increases the ability to resist deformation of this type of biomechanical system under force loads of the mini-implant. In the bicortical method of mini-implant placement, the extreme values of equivalent according to Mises stresses in the upper part of the cortical bone of the jaw are reduced by 27%. This can be explained by a significant increase in the area of contact due to the two layers of the cortical bone of the jaw with the surface of the mini-implant. Conclusion. The bicortical method of installing mini-implants is a more effective and reliable way to provide skeletal support during orthodontic treatment.

Development of turning process digital twin based on machine learning

Today, manufacturing technologies are developing within the Industry 4.0 concept, which is the information technologies introduction in manufacturing. One of the most promising digital technologies finding more and more application in manufacturing is a digital twin. A digital twin is an ensemble of mathematical models of technological process, which exchanges information with its physical prototype in real-time. The paper considers an example of the formation of several interconnected predictive modules, which are a part of the structure of the turning process digital twin and designed to predict the quality of processing, the chip formation nature, and the cutting force. The authors carried out a three-factor experiment on the hard turning of 105WCr6 steel hardened to 55 HRC. Used an example of the conducted experiment, the authors described the process of development of the digital twin diagnostic module based on artificial neural networks. When developing a mathematical model for predicting and diagnosing the cutting process, the authors revealed higher accuracy, adaptability, and versatility of artificial neural networks. The developed mathematical model of online diagnostics of the cutting process for determining the surface quality and chip type during processing uses the actual value of the cutting depth determined indirectly by the force load on the drive. In this case, the model uses only the signals of the sensors included in the diagnostic subsystem on the CNC machine. As an informative feature reflecting the force load on the machine’s main motion drive, the authors selected the value of the energy of the current signal of the spindle drive motor. The study identified that the development of a digital twin is possible due to the development of additional modules predicting the accuracy of dimensions, geometric profile, tool wear.

Modeling the process of force load generation at the initial periodic change in pressure (a plane problem)

The article deals with modeling the process of force load generation at an initial periodic change in pressure (a plane problem). The subject of research is a pulsating flow in a flat channel at an initial periodic pressure change. The determination of flow parameters with a periodic change in the inlet pressure; the changes in the structure of the working fluid associated with the release of various particles from the pipe walls, the addition of impurities to prevent leaks, and the high-speed modes, are given in the article considering the law of molecular and molar transfer between layers. Research methods are based on Newton’s rheological law, according to which molecular transfer is described by the law of proportionality of stresses to the derivative of the normal velocity; on the method of accounting for molar transfer by proportionality of stresses to the derivative of normal acceleration; on the method of mathematical modeling and the analytical method for their solutions, based on the provisions of operational calculus. An analytical solution to the problem of pulsating fluid motion in a plane-parallel channel is obtained with allowance for single and group transfer of molecules in the flow. The application of the analytical expressions obtained for the velocities is not limited to the critical Reynolds number, i.e. they are applied for any values of this number. Analytical expressions are obtained for the transverse and longitudinal components of the flow velocity. The resulting solution describes two zones of flow: in the first zone, two types of transfer occur, depending on the flow pattern, either molecular or molar transfer of fluid volumes between the layers prevails. In the second zone, only molecular transfer occurs.

Computational engineering of surface layer ground Al2O3‒TiC ceramic. Combined analysis

The main regularities of the stress state of the surface layer of ground Al2O3‒TiC ceramic under the combined load are determined. It is revealed that the force load compensates for thermal elastic deformations, but at the same time complicates the stress state in comparison with the action of loads of the same type. The role of the combination of structural elements that formed the surface of Al2O3‒TiC ceramic in the formation of unfavorable microstructural stress concentrators is established.