Impact Coefficient Analysis of Curved Box Girder Bridge Based on Vehicle-Bridge Coupling

In the current vehicle-bridge dynamics research studies, displacement impact coefficients are often used to replace the moment and shear force impact coefficients, and the vehicle model is also simplified as a moving-load model without considering the contribution of vehicle stiffness and damping to the system in some concerned research studies, which cannot really reflect the mechanical behavior of the structures under vehicle dynamic loads. This paper presents a vehicle-bridge coupling model for the prediction of dynamic responses and impact coefficient of the long-span curved bending beam bridge. The element stiffness matrix and mass matrix of a curved box girder bridge with 9 freedom degrees are directly deduced based on the principle of virtual work and dynamic finite element theory. The vibration equations of vehicle-bridge coupling are established by introducing vehicle mode with 7 freedom degrees. The Newmark-β method is adopted to solve vibration response of the system under vehicle dynamic loads, and the influences of flatness of bridge surface, vehicle speed, load weight, and primary beam stiffness on the impact coefficient are comprehensively discussed. The results indicate that the impact coefficient presents a nonlinear increment as the flatness of bridge surface changes from good to terrible. The vehicle-bridge coupling system resonates when the vehicle speeds reach 60 km/h and 100 km/h. The moment design value will maximally increase by 2.89%, and the shear force design value will maximally decrease by 34.9% when replacing moment and shear force impact coefficients with the displacement impact coefficient for the section internal force design. The load weight has a little influence on the impact coefficient; the displacement and moment impact coefficients are decreased with an increase in primary beam stiffness, while the shear force impact coefficient is increased with an increase in primary beam stiffness. The theoretical results presented in this paper agree well with the ANSYS results.

Determination of natural frequencies of railway track elements under train load and selection of resilient shock absorbers

Objective: To outline the theoretical and methodological foundations of the railway track oscillation frequency analysis. To justify the need to assess the level of vibrodynamic impact of rolling stock on the elements of the track superstructure and the roadbed. To provide a methodology for calculating the oscillation parameters. To evaluate the effectiveness of the use of shock-absorbing elements. Methods: The modeling of the oscillatory process of the railway track elements and the analysis of physical models of oscillations were used. Results: The applicability of assessing the level of vibrodynamic impact of rolling stock on the elements of the track superstructure and the roadbed has been confirmed. A physical model of the vibrodynamic force impact of railway rolling stock and the responses of track infrastructure elements is described. The procedure for calculating the natural frequencies of the elements of the track superstructure and the roadbed and the characteristics of the shock-absorbing elements is given. Practical importance: The presented methods for calculating the natural frequencies of the elements of the track superstructure and the roadbed, as well as the characteristics of resilient shock-absorbing elements – rail shock pads and sleeper pads – make it possible to evaluate the effectiveness of their use to reduce the level of vibrodynamic impacts, to protect against resonance, and ensure the train traffic safety.

Carpometacarpal Dislocation with Third Metacarpal Fracture

Case Presentation: A 17-year-old male presented to the emergency department (ED) due to trauma to the right hand and wrist after punching a locker at school. He had significant soft tissue swelling. Radiographs demonstrated intra-articular metacarpal fractures with associated carpometacarpal dislocations. The dislocation was reduced bedside in the ED and ultimately underwent closed reduction surgical management with orthopedic surgery. Discussion: Metacarpal fractures result from high-force impact injuries and account for 30-40% of all hand injuries. The most common sites of second through fifth metacarpal fractures are at the neck and the shaft, with the majority involving the fifth metacarpal neck (commonly coined “boxer’s fractures”). Carpometacarpal (CMC) dislocations are a rare injury associated with high-force impact trauma to the wrist. These injuries account for as little as 1% of all acute hand and wrist injuries. Carpometacarpal dislocations are often difficult to diagnose on physical examination due to significant soft tissue swelling, and they can easily be missed on anterior-posterior views of the hand. Lateral and oblique plain radiograph views are essential in the diagnosis as they are more likely to show dislocations. Despite appropriate plain radiographic views, subtle CMC dislocations may be difficult to discern dependent on the level of dislocation or subluxation and overlapping of joints. These injuries are rare due to otherwise highly stable ligamentous and muscular attachments within the wrist. Because of these attachments, dislocations are often associated with concomitant metacarpal fractures.

Yoga instructions in Polish and Russian as directive speech acts: a cognitive linguistic perspective

abstract This paper offers an account of within- and between-language differences in the grammatical encoding of directive meaning as represented in yoga discourse in two cognate languages: Polish and Russian. Specifically, the focus is put on three constructions: the imperative and the imperfective non-past indicative in both languages, and the indicative past, which is utilised only in Russian. In the analysis, we make an eclectic selection of methodological tools, drawing on a few models of illocution which have been put forward within Cognitive Linguistics. As is shown, even if yoga instructions are generally assessed as relatively weak directives, there are fine-grained differences in some aspects of construal evoked by the examined constructions resulting in differences in the force impact among the respective patterns and in their distribution. In the analysis, we consider such aspects of construal as: (i) the actuality or virtuality of the event presented in the utterance; (ii) the presence or absence of the speaker in the onstage region; and (iii) the aspectual opposition between an ongoing or completed event. The analysis, which is both qualitative and quantitative, has been based on a corpus of 300 randomly selected instructions in each language (600 in total).

Coriolis force impact on lump kinematics in a grinder workspace

Research relevance. Currently produced rotary grinders are not efficient enough, while their efficiently is mainly characterized by the degree of fineness. This is due to sparse knowledge of the processes occurring in the counter-impact labyrinth rotor when the material is being ground, and therefore insufficient scientific substantiation of the design methods. The grinding member’s geometry and rotation speed have been set empirically according to the similarity principle, which inevitably results in grinding fineness and efficiency deviation from the set values. It seems impossible to improve the design and therefore the running efficiency of the equipment unless the kinematics of a lump in the channel of the grinder is analyzed. Particular attention should be paid to the Coriolis force impact on the kinematics of a lump. It will make it possible to scientifically substantiate the dependence between equipment design and technological parameters. Methods of research included the factor analysis, data synthesis, and methods of mathematical and physical modeling. Object of research is a rotary grinder preparing rocks for sampling. Subject of research is the workflow of the counter-impact rotary grinder. Research objective is to increase the efficiency of the ore rotary grinder by analyzing particles movement in the rotor channels. Methods of research includes the analysis of particles motion in the rotor channels using the provisions of theoretical mechanics and the theory of impact. The differential calculus acts as a mathematical apparatus. Results and summary. Based on the proposed particle motion theory analysis and qualitative representations of the processes in the rotor of the counter-impact grinder, it is essential to form the foundation to obtain quantitative dependencies for design calculations. This will improve the methods of design and construction of a new type of rotary grinder. It was found that the Coriolis force reduces the relative speed of a lump by not more than 20.3% depending on the assumptions made

Surface layer of 40Kh steel after electromechanical treatment with dynamic force impact

The paper presents the results of complex studies of the structure, microhardness and depth of the hardened surface layer of 40Kh steel formed as a result of electromechanical treatment with dynamic application of a deforming force (EMT with impact). The research was carried out using optical microscopy, X-ray diffraction analysis, and microhardness methods. The method of electromechanical treatment with dynamic force impact consisted in simultaneous transmission of electric current pulses and deforming force through the contact zone of the tool with the part. As a result of shock-thermal effects with different current densities (j = 100 A/mm2; 300 A/mm2; 600 A/mm2), segments of the hardened layer of different sizes and structure composition are formed on the steel surface in cross-section. Analysis of structural and phase transformations in the surface layer of 40Kh steel subjected to dynamic electromechanical treatment indicates the formation of a specific structure of the white layer, the structure and properties close to the amorphous state of the metal with a maximum hardness HV = 8.0 – 8.5 GPa. As you move away from the surface, a transition zone is formed behind the segment of the white layer with a structure that does not have the characteristic needle structure of martensite. It was found that with an increase in the current density during shock electromechanical treatment, the depth of hardening increases by 4 – 5 times with a simultaneous increase in the heterogeneity of strength properties; the level of micro-stresses increases by 25 %. Experimental data on the structural state, microhardness and depth of the surface layer of 40Kh steel show that electromechanical treatment with dynamic (shock) application of the deforming force causes deeper transformations in the steel structure compared to traditional static EMT. The results obtained show that as a result of electro-mechanical processing with impact, the intensity of the temperature-force effect on the steel surface layer increases, which allows you to open the internal reserves of 40Kh steel and control the process of forming its structure and phase states.

The small spacecraft with a magnetic sail on high-temperature superconductors

It is proposed to develop a small spacecraft for an experiment using high-temperature superconductors (HTS) and shape memory materials. The purpose of the experiment is to test a technological capability of creating a strong magnetic field on the small spacecraft using HTS and shape memory materials for deployed large-area structures, and study the magnetic field interaction with the solar wind plasma and the resulting force impact on the small spacecraft. This article is of a polemical character and makes it possible to take a fresh look at the applicability of new technologies in space-system engineering.

Laboratory studies of the impact of a roller sorting machine on potato tubers

Existing machines for sorting potatoes damage marketable products as a result of the interaction of potato tubers with each other, with working organs and soil clods. The greatest percentage of damage to potato tubers occurs as a result of their interaction with the working bodies of the machines for sorting. In order to determine the place of the greatest force impact of the working bodies of the sorting machines on the potato tuber and to carry out subsequent measures to eliminate negative effects in the design of these machines, laboratory studies were carried out using the "The TuberLog Electronic Potato" software tool. The article provides the results of comparative studies of the force impact of the sorting surface on the electronic potato tuber at various values of the forward speed of movement and interaction time of the working surface of roller-type machine for sorting potato tubers. Analysis of graphical dependencies showed that the greatest force impact (up to 22 N) on a potato tuber falls on the time interval of values from 8.5 to 9.5 s, while the standard deviation and coefficient of variation are σ = 5.7 and ν = 24.8 %, respectively. The analysis of the experimental data showed that the most "gentle" force impact of the working bodies of the sorting machine at the forward speed of the roller belt of 1.4 m / s throughout the entire technological process of sorting is the minimum force impact on the sorted products in the range from 3 to 6.5 N, which is 28-31% of the maximum force impact of working bodies at speeds of 1.8 and 2.2 m/s.