Miroslaw Rucki

Plastic Deformations of Measured Object Surface in Contact with Undeformable Surface of Measuring Tool

Abstract Measuring errors caused by deformation (flattening) of a measured object appear under the influence of pressure force and weight of the measured object. Plastic strain, arising at the contact of a measured object and an undeformable contact tip of a measuring device, can be calculated by applying the Hertz plastic solution and the hypothesis of plastic strain. In a small area of contact between two bodies pressing against one another with force F, there appears the so-called contact stress. It can sometime reach very high values, exceeding the yield point, even when the contact pressure is relatively small. In the present work, the authors describe a theoretical solution to the problem of plastic strain between two bodies. The derived relationships enable to calculate force F during measurements of a deformable object by means of an instrument with an undeformable, spherical measuring tip. By applying the τmax hypothesis, a solution was obtained for the force F in an inexplicit form. The theoretical solution was verified with the digital simulation and experimental measurement. With the FEM method, the limit length gage was modeled in interaction with the measured shaft of a diameter d larger than the nominal one of Δl value.

Metallurgical quality evaluation of the wind turbine main shaft 42CrMo4 steel: microscopic and Mössbauer studies

Abstract In this paper, the results of the complex examination of the 42CrMo4 steel samples are presented. The samples were taken from the metallurgical forging prepared for the production of the wind turbine main shaft. The samples underwent Mössbauer spectroscopic analysis, as well as the measurement of its mechanical characteristics such as hardness and strength are analysed. Conversion electron Mössbauer spectrometry confirmed phase purity and isotropy of the investigated 42CrMo4 steel. The method provided accurate results, proving Mössbauer spectrometry to be an effective tool for the wind turbine main shaft analysis.

Air Gauge Characteristics Linearity Improvement

This paper discusses calibration uncertainty and linearity issues of the typical back-pressure air gauge. In this sort of air gauge, the correlation between the measured dimension represented by the slot width and the air pressure in the measuring chamber is used in a proportional range. However, when high linearity is required e.g., nonlinearity less than 1%, the measuring range should be shortened. In the proposed method, based on knowledge of the static characteristics of air gauges, the measuring range is kept unchanged but the nonlinearity is decreased. The static characteristics may be separated into two sections, each of them approximated with a different linear function. As a result, the nonlinearity is reduced from 5% down to 1% and even below.

Internal Stresses Analysis in the Shrink-Fitted Joints of the Assembled Crankshafts

The paper describes investigation results aimed to the assessment of the shrink-fitting of the marine diesel crankshaft elements. Since the crankshafts are of the large size (above 20 m) and weight (above 300 tons), the models were made in scale 1:5, keeping the same technical conditions. The measurement of internal stresses was made by a non-destructive ultrasonic method. The obtained results confirmed the existence of the zones where stresses had crossed the yield points, which meant the plastic deformation and weakening of the interference fit.

Influence of the Inlet Nozzle Diameter on the Air Gauge Dynamics

In the paper, the experimental results of the study on the dynamic characteristics of the air gauges are presented. Dynamical properties of the air gauge are dependent mainly on the pressure transducer type and also on the geometry of its flow-through elements. The present investigations focused on the diameter of the inlet nozzle and its impact on the time constant and the frequency at which the dynamic error would not exceed 5%. It was proved that in the most common configurations of the air gauges, those two parameters may vary up to 100%, and the dynamics of the air gauges worsened with smaller inlet nozzles. The results are of high practical importance in industrial measurement systems where the air gauges are applied, because the multiplication of the air gauge is typically set by the adjustment or replacement of the inlet nozzle.

Application of the microscopic and Mössbauer studies to the analysis of a marine diesel engine crankshaft

ABSTRACT In the paper, the issue of the material quality of the large-size crankshaft is discussed. In order to ensure the reliability and wear resistance of the crankshaft, its chemical composition was checked in detail, revealing also the presence of trace elements omitted in Standards. The mechanical characteristics of the material were measured using the samples taken from the upper and lower parts of the forging. The novelty of the quality analysis was the additional measurement with the conversion electron Mössbauer spectrometry method. High phase purity, homogeneity and isotropy of the investigated material were confirmed. The carbon-saturated ferrite was detected as dominating phase of about 95% content. The observed martensite structure appeared to be correct, and the material met the specification requirement. Only slight differences in atomic ordering of alloying elements in ferrite structure were observed between the upper and lower part region, which was not considered a threat. It was assumed that the confirmed chemical purity and homogeneity contributed to the high straightness of the tested material.