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Characteristics of porous implant steel 316L for orthopedic applications
Get PDFThe porous materials are recently considered to be the prospective biomaterials for restorative medicine. The Young’s modulus of porous metallic biomaterials is much lower than those of non-porous and comparable to modulus of hard tissues, which can improve the conditions of bone remodeling and heading. The porous structure is also interesting from tribological point of view. The usage of porous material for friction elements of joint endoprostheses changes the wear mechanisms and causes decrease of resistance to motion and material wear loss. The aim of present research was to analyze the structure of porous 316L implant steel and its influence on main functional properties of sinters. Samples with porosity of 26, 33, and 41% were made of the 316 stainless steel by the powder metallurgy method. Microstructure was described using conventional image analysis techniques. The mechanical properties were determined in static compressing tests. Fatigue tests were conducted under the fully reversed strain controlled mode. A good correlation has been found between structural parameters and tribological as well as mechanical properties. The low-cyclic fatigue investigations confirm the steady properties of porous materials in the certain range of strai
Measurement of sportsman‘s jump psychomotoric reaction
Get PDFFor representatives of sport games are very important components of physical abilities – spring and rate of psychomotoric reaction. For the following sportsman’s especially important is the rate of psychomotoric reaction, which defines reaction to the constantly changing ambience, similar to the sport action. Testing system, which simulates the situation of sports game, was created in the department of Informatics and biomechanics of LKKA. This system allows estimating the physical capabilities of player – spring and the speed of psychomotoric reaction. The speed of psychomotoric reaction is evaluated by making the jump-up. The influence of the height of jump-up on the spring and speed of reaction of sportsman is investigated. Considering the results of experiments and statistical analysis some recommendations are given and conclusions withdraw
Development of smart membrane valve based on geometric moiré interferometry
Get PDFNovel smart membrane valve which functionality is based on optical interference effects caused by moiré interferometry is proposed in this paper. The membrane is comprised from two steel gratings. Geometrical adjustment between adjacent holes in both membranes results in zero flow rate through the valve when no control signal is activated. Rotation of the control membrane generates moiré interference effects which are exploited for flow control. Relationships between the shape and geometric locations of the moiré circles and the control parameters of the second membrane are determined what helps to implement optimal valve control strategie
Modeling and design optimization of butterfly type piezoelectric actuator
Get PDFA study of a novel design miniature butterfly type piezoelectric actuator is proposed and analyzed in the paper. Actuator consists of butterfly type oscillator and two piezoceramic elements. Operating principle of the actuator is based on exciting electrodes of the piezoceramic elements using input voltage of the same frequency but different phases. Elliptic trajectory of the contact point movement is achieving when phases of the voltage differ by ?/2 on different electrodes. Numerical modelling and simulation of the piezoelectric actuator was performed using finite element method. Natural frequencies, modal shapes and actuator response to the different input voltage sets were analyzed. Optimization of actuator boundary conditions was carried out. Experimental prototype of the piezoelectric actuator was built and measurements of driven tip movements were performed. The results of numerical and experimental studies are discusse
Development of mortar simulator with shell-in-shell system – problem of internal ballistics
Get PDFThe shell-in-shell system used in the mortar simulator raises a number of non-standard technical and computational problems starting from the requirement to distribute the propelling blast energy between the warhead and the ballistic barrel, finishing with the requirement that the length of warhead’s flight path must be scaled to combat shell firing tables. The design problem of the simulator is split into two parts – the problem of external ballistics where the initial velocities of the warhead must be determined, and the problem of internal ballistics – where the design of the cartridge and the ballistic barrel must be performed. Initial velocities of the warhead determined in the problem of external ballistics form the set of initial data for the problem of internal ballistics of mortar simulator with shell-in-shell system. The ballistic barrel (reusable component of the mimicking shell) must be ejected from the mortar tube and its flight path must be only few meters. Moreover, the propelling charge can be located only in the warhead and the blast energy must be distributed between the warhead and the ballistic barrel. That turns the problem of internal ballistics into a complex nonlinear dynamical problem. Its solution involves building of the numerical model, optimisation of system parameters and experimental investigations. Presented mortar simulator proved its effectiveness in combat training exercises and is fully adopted in Lithuanian Army training facilitie
Concept and methods of adaptive vibration protection and stabilization
Get PDFThe concept, the general formulation of problems and the algorithms of adaptive real-time control of multivariate vibration protection and stabilization of multi-axis chassis body position in space, which in the general case provide in general case the solution of the problems of oscillations moderation and motion stability, are considere
Development of electropneumatic servo system with reference model based signal adaptive force controller
Get PDFDue to pneumo-mechanical power conversion process nonlinearities and process parameters (volumes and initial pressures of pneumatical cylinder working chambers) on line change it is problematic to ensure satisfactory control quality of pneumatic proportional servo drive. Considering that all nonlinearities are concentrated in the force generation stage, application of adaptive force control mode is suggested. Electropneumatic servo drive with reference model based signal adaptive force controller is developed and investigated in this paper. It is presented the strategies of reference model choice and are given control quality investigation results of electropneumatic servo syste
The evaluation of resonant frequencies of rotary system with adaptive segmental sliding bearings by orbits of rotor rotation axis
Get PDFThis paper is based on research of work parameters of rotary systems with segmental sliding bearings, working system in the resonant regime. Primary signals are given doing experimental researches, they are analyzed with special programmable pockets and different formats of data are given. Evaluation of work state of rotary system is done in the resonant and in the normal regime by getting orbits of rotor rotation. The principal scheme of researching system is given in this work and its technical characteristics and principle of working are described. Methodology of experimental researches is given. The gained results are described in graphs and a comparison of obtaining results and its discussio
Evaluation components of the heart rate kinetics for assessment cardiac adaptation during rehabilitation
Get PDF"The purpose of the study was assessment of the cardiovascular adaptation to the workload and physical training by analysis of the heart rate kinetics and dynamics of power spectrum components in healthy subjects and ischemic heart disease patients during rehabilitation. The contingent of study was 20 healthy subjects and 97 patients post-myocardial infarction (74 without chronic heart failure and 23 with chronic heart failure symptoms). Multistage bicycle ergometry or spiroergometry and computerized analysis of heart rate variability during active orthostatic, symptom-limited workload tests and recovery period after test were performed. The rhythmogram at 50W of the workload, and during bicycle (Kettler) training and recovery period was analyzed and the time constant (?) of the exponential function (by using Proni method), coefficients of amplification, rapidity as well as heart rate (HR) power spectral components (?VLF, ?LF, ?HF) were evaluated. Heart rate kinetics response time constant to the low-level (?50W) workload (30.3 vs. 19.3 s) and during recovery period (40 vs. 45.6 s) was delay in post-myocardial infarction patients, especially in those with CHF and low physical capacity as compared with healthy subjects. Heart rate responses (?50W) correlated with baseline HR autonomic control components (?LF, r=-0.25, ?RRB%, r=-0.24, RRB, r=0.23,) and with physical capacity (r=-0.30). In CHF patients the delay HR response to the workload and during recovery correlated with expressed ventilatory response (VE/VCO2, r=0.60) in this group. Positive dynamic of HR kinetics components (?=37.1 vs. 34.6 s) and power spectrum characteristics after low intensity bicycle training procedure and during recovery (?=42.4 vs. 39.9 s) period was observed. The faster HR reaction to the physical stressor after 3-weeks bicycle training correlated with positive dynamics of ?HF (r=-0.35). The HR power spectrum components during bicycle training changed favorably (?VLF, 15.2 vs. 16.3 ms; ?LF, 8.2 vs. 9.4 ms; ?HF, 8.8 vs. 9.4 ms) too. Conclusions. Analysis of the heart rate kinetics components and power spectrum data during exercise provides a new possibility evaluation of the cardiac adaptation to the workload and physical training procedures in ischemic heart disease patients during rehabilitation
Surgical treatment of equinus foot deformity in cerebral palsy patients
Get PDFSince 1997 thirty seven spastic cerebral palsy children (54 feet) with shortening m. triceps surae (soleus and gastocnemius portions) underwent heel cord advancement by simplified technique of Murphy procedure. Good correction of the deformity and gait improvement was obtained in 52 cases (96%). No patient had a recurrence of equines. All patients and his parents are satisfied with results of treatment. It study has documented that heel cord advancement is biomechanicaly- and pathophysiologicaly- grounded procedure for adequate correction and following prevention of equinus deformity. Proposed technique of heel cord advancement is relatively simple minimal invasive and can use for treatment as single or(and) with combination in multilevel operations. Best results of surgical treatment obtained in young child who has non-formed rigid deformation and has no stable pathological gait patterns ye