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One of the disadvantages of superplasticizers' use is that the concrete mixture modified by this kind of admixtures loses its workability very quickly. This paper summarizes the current state-of-the-art in the field concerning the effects of superplasticizer's SNF addition to the material cement, in particular its mechanisms and methods of addition. The paper presents the author's experimental investigation...
The paper focuses on the propagation of 1-D acoustic waves in an elastic isotropic material with the elastic potential proposed by Blatz and Ko [1]. Two special models and materials are described by this potential: foamed polyurethane elastomers and solid polyurethane rubbers. The problem of reflection and transmission of 1-D acoustic waves at the interface of two different media and the problem of...
The paper presents some problems connected with the topography of coated abrasives. Various classes of coating are discussed, ranging from conventional single-layer ones to modern engineered coatings of the TRIZAC type. Actual parameters of the active face for various makes are given. Principal in-service properties of abrasive belts are discussed: instantaneous grinding efficiency and variation in...
The thickness of the shear band mobilized on the pile shaft subjected to loading is practically the same for a small model and a large-diameter prototype. At the same normal stress applied to the shaft of the model and of the prototype pile, the normal stiffness of the interface and so the shear conditions are different for both cases. Lateral friction measured for the model and the prototype will...
In this paper, the problem of the kinematics and dynamics of two constructional conceptions of a two-wheeled mobile robot is considered. The wheeled mobile robot subjected to nonholonomic constraints moves over the inclined plane. Its trajectory consisting of the straight line and the curvilinear path described by the sinusoidal function is analyzed. The kinematic equations for arbitrarily chosen...
The final shape of the draw parts is seriously affected by the springback phenomenon. The present work deals with numerical simulation and experimental tests related to draw bending and springback of [omega]-shape parts manufactured from tailor welded stripes and it is trying to prove out the important role that the rolling direction of the joined steel sheets has on the springback intensity. The...
The thorough analysis of the accident situation in the Polish construction industry in years 1992÷2004 is presented. The accident situation, as a homogeneous phenomenon, is estimated by means of the accident rate of: minor, serious and fatal accidents and all the accidents jointly as well as by means of the accident seriousness index. However, the accident situation is not a homogeneous phenomenon...
The present paper focuses on the problem of the durability of bent RC beams strengthened with composite materials, subjected to cyclic loading. The theoretical model of determining fatigue life of the cross-section of the bent reinforced concrete beam strengthened with external, non-stressed CFRP strips is presented. The author's own propos al is to introduce the coefficient ofthe strip position effect...
A segment of a gravel column, I m high and 0.53 m in diameter, was modelled in a calibration chamber. The reconstituted sample was consolidated at a given confining pressure and then subjected to wdalload exerted by the upper and lower membranes. Volumetric changes in both membranes and in internal chamber were measured. Up to 2% vertical strain was reached and internal friction angle was evaluated...
The paper presents the method of analyzing static work of support zones in concrete composite structures. This method is based on MCFT (Modified Compression Field Theory). WhiJe designing composite beams, the author allows only such cases, where the appearance of the interface crack is precluded by the diagonal crack. The case of support zones with diagonal cracks and locally cracked interface has...
The paper presents the role of a bond layer in the repair process of concrete and reinforced concrete elements as well as the place of its laying. For the purpose of a detailed analysis of the above problems two series of tests were carried out. In the first series of the tests, the influence of the state of the surface under repair (wet, oiled) on the adhesion ofthe bond layer is taken into account...
The causes of failures in contemporary automatic diagnostic systems working with use of neural networks in industrial conditions are given. lt has been stated that one of the basic causes was the lack of opportunity to perform logical operations by the artificial neuron model of McCulloch and Pius which makes the core of artificial neural networks programs. A new method of data gathering and initial...
The problem of fitting the characteristic of the universal machine tool's main drive to anticipated machining tasks is considered. The power demand and the cutting torque demand for tuming and milling are analysed. It is shown that by employing a multiplying gear one can obtain a constant machining power in a wide range of spindle speeds whereby both steel and aluminium alloys can be efficiently machined.
Depending on fire duration, fire temperature (reaching several hundred degrees centigrade) leads to a damage (in varying degrees) to concrete. A structural damage assessment based on an inspection is highly unreliable, particularly when concrete heated up during a fire was rapidly cooled down with cold fire-fighting water. Because of this thermal shock the surface of concrete cracks heavily. The load-bearing...
This paper presents the results of thermovision temperature measurement in the contact zone of grinding wheel and workpiece during single-pass internal cylindrical grinding process. Such a kinematic form of grinding process is characterized by very difficult machining conditions. In order to control grinding temperature in this process, the authors developed a special measurement method which enables...
When designing assembly processes it is particularly difficult to determine the optimum automation level, i.e., the ratio of manual to automatic assembly operation times. This factor considerably affects the productivity since it determines product assembly labour intensity, the number of assemblers and the type and cost of equipment. The system module presented allows considerable flexibility in...
Flow curves enable to predict the response of material during metal forming processes. To establish properly the magnitude of flow stress, precise determination of the true stress from a tensile test is necessary. Calculation of true stress corresponding to the proof strength made it possible to determine the flow curves and select the appropriate flow stress equation for the tested drawn wires.
Conditions of arising cavitation and experimental investigations of this phenomenon by means of a special vacuum vessel are described. A simulation model of the piston-cylinder unit of a pump with an inclinable cylinder block was used to visualize cavitation in the pump. The results of tests aimed at showing a correlation between the onset of cavitation and an audible diagnostic signal are presented...
The aim was to determine the phase transformations temperatures of a specific IF steel grade, microalloyed by titanium, and quantify influence or phase composition on its deformation resistance in comparison with a common low carbon deep-drawing steel grade. In the case or the IF steel separate, sufficiently accurate, models describing mean equivalent stress after heating or the material directly...
This paper presents the results of critical, static loads calculations of three-Iayered, annular plates with a soft core. The plate with slidably clamped edges. uniformly loaded with compressive stress on the inner edges of outer layers and of the symmetric cross-section structure is the subject of consideration. In the description of deformation of layers, the assumption of the equal deflections...
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