Conflict and Sensitivity Analysis of Articulated Vehicle Lateral Stability Based on Single-Track Model

Lateral stability is quite essential for the vehicle. For the vehicle with an articulated steering system, the vehicle load and steering system performance is quite different from the passenger car with the Ackman steering system. To investigate the influence of the tire characteristics and vehicle parameters on lateral stability, a single-track dynamic model is established based on the vehicle dynamic theory. The accuracy of the built model is validated by the field test result. The investigated parameters include the tire cornering stiffness, vehicle load, wheelbase, and speed. Based on the snaking steering maneuver, the lateral stability criteria including the yaw rate, vehicle sideslip angle, tire sideslip angle, and lateral force are calculated and compared. The sensitivity analysis of the tire and vehicle parameters on the lateral stability indicators is initiated. The results demonstrated that the parameters that affect the lateral vehicle stability the most are the load on the rear part and the tire cornering stiffness. The findings also lay a foundation for the optimization of the vehicle’s lateral stability.

Justification of a rational option of development of the highspeed railway according to technical, technological and economic criteria

When a new high-speed railway is designed on the routes with the existing mixed(freight and passenger) traffic, part of the trains can be relocated from the existing railway to thenew one. This will have an additional effect of the increasing current capacity of the existing railway. A method is proposed for justification of a rational option for the development of a high-speedrail on the basis of technical, technological and economic criteria. It is proposed to solve the problemof determining the rational option for the development of a high-speed railway as the problem ofoptimal distribution of resources among the components of the railway, taking into account technical,technological and economic criteria. The result is a set of solutions consisting of options for thedevelopment of each component of the railway, which will provide the maximum systemic effect forthe railway as a whole. Each jth option of the development of the ith component of a high-speed railwaycan be described by three main indicators: the travel time of a high-speed train; capital investmentsrequired to implement this option; and the available traffic capacity of the component. Depending onthe problem being solved, each of the listed parameters can act both as a criterion and as a limitation.Depending on the purposes of the design, it is proposed to consider the problem of determiningthe rational option for the railway development either in the direct or inverse setting. In the first case,the systemic effect is expressed by an objective function that minimizes the amount of necessarycapital investments in the railway infrastructure while ensuring the stipulated travel time of a highspeed train. In the second case, the purpose is to minimize the travel time of the train withoutexceeding the specified amount of capital investment in the development of all components of therailway.The results obtained can be used to justify decisions on the use of single-track components andto determine the rational configuration of single-track lines when high-speed traffic is organized.

Selective Laser Melting of Pre-Alloyed NiTi Powder: Single-Track Study and FE Modeling with Heat Source Calibration

Unique functional properties such as the low stiffness, superelasticity, and biocompatibility of nickel–titanium shape-memory alloys provide many applications for such materials. Selective laser melting of NiTi enables low-cost customization of devices and the manufacturing of highly complex geometries without subsequent machining. However, the technology requires optimization of process parameters in order to guarantee high mass density and to avoid deterioration of functional properties. In this work, the melt pool geometry, surface morphology, formation mode, and thermal behavior were studied. Multiple combinations of laser power and scanning speed were used for single-track preparation from pre-alloyed NiTi powder on a nitinol substrate. The experimental results show the influence of laser power and scanning speed on the depth, width, and depth-to-width aspect ratio. Additionally, a transient 3D FE model was employed to predict thermal behavior in the melt pool for different regimes. In this paper, the coefficients for a volumetric double-ellipsoid heat source were calibrated with bound optimization by a quadratic approximation algorithm, the design of experiments technique, and experimentally obtained data. The results of the simulation reveal the necessary conditions of transition from conduction to keyhole mode welding. Finally, by combining experimental and FE modeling results, the optimal SLM process parameters were evaluated as P = 77 W, V = 400 mm/s, h = 70 μm, and t = 50 μm, without printing of 3D samples.

Selection of effective manufacturing conditions for directed energy deposition process using machine learning methods

In the directed energy deposition (DED) process, significant empirical testing is required to select the optimal process parameters. In this study, single-track experiments were conducted using laser power and scan speed as parameters in the DED process for titanium alloys. The results of the experiment confirmed that the deposited surface color appeared differently depending on the process parameters. Cross-sectional view, hardness, microstructure, and component analyses were performed according to the color data, and a color suitable for additive manufacturing was selected. Random forest (RF) and support vector machine multi-classification models were constructed by collecting surface color data from a titanium alloy deposited on a single track; the accuracies of the multi-classification models were compared. Validation experiments were performed under conditions that each model predicted differently. According to the results of the validation experiments, the RF multi-classification model was the most accurate.

Single-Track Bike Trails in the Moravian Karst as Part of Forest Recreation

Recently, cycling has become a popular recreation activity, and mountain biking provides an experience that is sought by an increasing number of people. Bike trails constructed for mountain bikers in access areas lead mostly through the forest and provide not only an extraordinary riding experience but the opportunity to admire the surrounding nature. The reason for constructing such trails from a landowner’s point of view is to help keep bikers’ movements within a defined access area and to ensure adjacent areas are left free for other forest functions. It also helps distribute groups of visitors with other interests to other parts of the forest. This is what we call “controlled recreation”. In this example, it means that if cyclists come to the locality to use the bike trails, they should ride only along the designated trails; however, they may leave these trails and ride on the surrounding land. This article studied the movements of bikers in an accessible area of the Moravian Karst and the regulation of their movements by controlled recreation. Attendance in the area was measured using automatic counters. These were placed at the entry points to the accessible area and just behind the routes where the trails branch off. The results showed that bikers mostly stayed on the formal routes and that the trails were effective, i.e., there was no uncontrolled movement of bikers into the surrounding forest stands. We also noted the time of day that cyclists were active. These results can be used to better plan work in the forest, for example, harvesting and logging. To further the suitable development of accessible areas of the forest, we also compared the usual size of trail areas in two other European countries and the increasing width of bike trails due to the transverse slope of the terrain.

Effect of Powder Feeding Rate on the Forming Quality of Alloy by Laser Melting Deposition

12CrNi2 alloy steel was prepared by Laser Melting Deposition (LMD) technology, and the effect of powder feeding rate on surface quality, internal defects, microstructure, and microhardness of the single track and manufactured part were investigated. The results show that the metallurgical bonding of the single track deteriorates, the surface quality of the manufactured part is improved, the average microhardness of the manufactured part increases, and the number of pores first decreases and then increases with the increase of powder feeding rate. At the lower powder feeding rate, the manufactured parts have larger pore defects, while at the higher powder feeding rate, the manufactured parts have poor fusion defects. The main phase composition of the manufactured parts is ferrite(F), granular bainite (GB), and pearlite(P), and the manufactured part has finer grains at the higher powder feeding rate.