Technological features of the production of welded beds from prefabricated base parts

The work is devoted to the problem of fatigue strength of welded-cast joints as applied to the operating conditions of body parts of machines. Such operating conditions are characterized by non-uniformity of intensity and concentration of the load on parts and assemblies during the operation of the equipment. This heterogeneity of the load actualizes production of precisely welded-cast base parts for metalworking equipment beds. This is of considerable technological and economic interest. The aim of the work is to study the strength of welded-cast bearing structures in relation to the work of beds of heavy lathes. Unalloyed medium-carbon structural steel 35L and steel of ordinary quality MCT3 in the form of rolled products were used as the main materials for research. The research methods are presented. The study of the structure and properties of the welded joint made it possible to assess the technical feasibility of using the studied metals in the manufacture of welded-cast bearing structures. It has been established that welding of steel castings with rolled steel causes significant structural and mechanical heterogeneity. The influence of processing technology on the nature of formation of the structure of welded-cast joints is presented. The influence of heat treatment on the value of the hardness of the welded seam and the heat-affected zone was investigated. The study of the fatigue resistance of welded-cast specimens was carried out in relation to the operating conditions of joints undergoing vibration loads at normal temperatures, which can be classified as fatigue with a symmetric load cycle. It was found that the use of heat treatment of welded-cast specimens significantly reduces the mechanical heterogeneity of the joint along the seam and the heat-affected zone. Based on the results of studying mechanical characteristics, the choice of technology for the production of welded-cast joints is justified.

Biomechanical Effects on Lower Extremities in Human-Robot Collaborative Agricultural Tasks

The present study pertains to a key aspect of human-robot collaborative systems which is usually underestimated, namely occupational health prolepsis. The aim of this investigation was to assess the biomechanical effects of manual symmetric load lifting related to a synergistic agricultural task that utilizes an unmanned ground vehicle to undertake the carriage of loads. Towards that goal, kinetic and kinematic data were collected from the lower extremities of thirteen experienced workers, by testing three different deposit heights (70, 80, 90 cm) corresponding to possible adjustments of the available agricultural robot. Moreover, the muscle activation levels of three lower extremity muscles and one trunk muscle were evaluated via a wireless electromyography system. Overall, the experimental findings revealed that the lower examined load height was associated with larger knee flexion moments and hip extension moments. Nevertheless, this height was related to lower activation mainly of the erectus spinae muscles. Finally, insignificant alterations were observed for the ankle joint as well as the activation levels of the other muscles. Consequently, a height equal to 90 cm is suggested, however, by avoiding extreme lumbar postures. The current results can be exploited for possible ergonomic interventions concerning the optimal deposit height of a robotic platform when a similar case is designed.

Carrying Asymmetric Loads While Walking on a Treadmill Interferes with Lower Limb Coordination

The purpose of this study was to investigate the effect of different load carriage modes on coordinative patterns in the lower extremities during walking. Twenty-five university students walked on a treadmill at their preferred pace under three different load conditions: symmetric load (5% of body mass in messenger bags on each shoulder hanging vertically and against the hips), asymmetric load 1 (10% of body mass in a messenger bag on one shoulder hanging vertically against the ipsilateral hip), and asymmetric load 2 (10% of body mass in a messenger bag on one shoulder with the bag draped across the trunk to the contralateral hip). Altered thigh-shank and shank-foot couplings were found for the loaded side during the stance of gait when comparing the asymmetric 1 and 2 to the symmetric load. In addition, thigh-thigh coupling was changed during gait when comparing the asymmetric load 2 and symmetric load. However, we did not find any significant differences in intralimb and interlimb couplings between the two different asymmetric load conditions. The results suggest potential benefits when carrying symmetrical loads in order to decrease abnormal limb coordination in daily activities. Thus, it may be advisable to distribute load more symmetrically to avoid abnormal gait.

THE FLEXURE OF COMBINED PLATES WITH PIECEWISE VARIABLE THICKNESS. THE SOLUTIONS IN TERMS OF LEGENDRE FUNCTIONS

The work considers the problems of flexure of plates of circular form and consisting of separate parts with different laws of thickness variation. The each part of this plate has the form of a ring. The mentioned separate sections may be made from the same or from the different materials. The material of the piece-wise variable plate parts can be isotropic or orthotropic, homogeneous or nonhomogeneous. In the places of the separate parts conjugation the plate’s thickness can be continuous or discontinuous. The action of symmetric load on piece-wise variable plate is studied. The analytical approach is used, the solutions are obtained in the closed forms in terms of Legendre functions and Legendre polynomials. Rather wide set of plates’ profiles is determined. For the satisfaction of the conditions of the separate sections conjugation the special auxiliary functions are introduced. The computation of the plate, consisting of three sections and subjected to an action of discontinuous loads, is considered as an example.

THIN-WALLED BARRELL SHELL DEFLECTIVE MODE ANALYSIS

The paper deals with the deflective mode of steel rotary shell with different form of outer surface that are loaded with axially symmetric load. The results show solution of shell voltage and strain equation under the load that is described by exponential law and based on efforts from temperature differentials. Besides, the paper represents design formulas for deflection analysis, running bending moments and running transverse forces in shells with different abutment to the basis. It was shown the basic function of deflection and maximum value of relevant parameters of the reaction. The analysis of aspects about efficiency of using corrugated wall for steel barrel shell is done. The results in analytical and graphical form are shown. According to resulting formulas, it was made comparative calculations of shells with constant and variable wall thickness.

10Ghz Charge Pump PLL for Low Jitter Applica-tions

This paper presents design and simulation of charge pump architectures for 10GHz Charge Pump Phase locked Loop. Differential delay cell VCO with symmetric load and Programmable frequency divider are efficiently implemented in loop. Able to achieve Peak jitter of the Divider 10ns, Peak jitter of VCO 205ps at 1GHz.Charge pump is analysed in loop by reduced current mismatch using improved high swing cascode structure including start up circuitand it has low turn ON voltage and high ouput impedance to provide stable voltage.Charge pump results current mismatch less than 0.05%.10GHz DPLL is simulated with 65nm techonology, 1.2V and tsmc foundary model files

Calculation of a beam on an inhomogeneous basis

The questions of analytical calculating the beam on the base with the modulus of deformation (modulus of elasticity), which is changed by thickness of the layer by power law, was deals in the article. The purpose of work was receiving finite expressions for reactive pressure of the basе on a beam and internal efforts in a beam when using model of the base with two characteristics (coefficient of subgrade resistance). A system of differential equations second-order with respect to the displacements of points the surface of a layer with a continuously changing modulus of elasticity was obtained based on the minimum of the total potential strain energy. The calculation of the rigid beam on the base on the action of the symmetric load was performed and the formulas for the reactive pressures of the base were got. Numerical calculation is executed and the analysis of influence of change of the module of deformation of a layer by the amount of reactive pressure and the bending moment in a beam was given. It is shown that with increase in the module of deformation on layer thickness the basе with two characteristics on nature of work is approaching vinklerovsky.