Janis Rudzitis

Influence of Flexible Body Contact Deformation on the Linear Dimension Measurement Precision

The common measurement error when measuring the component geometrical dimensions using universal contact measurement instruments is caused by different factors, such as error of the measurement instrument, personal reading errors, effect of surface roughness on the measuring line deviation, influence of contact deformation measurement force, and others. The present article examines one of these factors, i.e. contact deformations under the influence of measurement force. To make precise measurements it is essential to find out the effect of roughness of measured components. High roughness creates additional measurement errors. It is particularly important in the measurement of thin components, flexible materials and films, as well as for components with nanocoating. Flexible bodies in the meaning of this article are components of different shape and sizes made of rubber or soft plastic. This article studies principles of error formation based on the deformation of surface roughness and basic material.

Microtopography Model of Rough Surface

For perfect surface roughness description is not enough to know characteristics of surface profile. It is necessary to use topography methods, so called microtopography. Thereby, surface roughness in microtopographycal understanding must be described with three coordinates, whose in Cartesian coordinates system compose point under consideration height h, abscissa and ordinate, determines point position in the plane. Most efficient methods in irregular surface roughness research are random function theory methods. Therefore, microtopography, analogically to profile, may consider as random function, but two dimensional function, i.e. two variable x and y random field h(x,y). From analogy with random process, random field can be normal – ordinates are distributed by normal (Gaussian) distribution. Moreover, random field can be homogeneous and heterogeneous. Random field is deemed homogeneous if its mean value is discretionary and correlation function depends only from distance between surface points. Important characteristic of random field is correlation function, whose depends of two variables t1 and t2 – orthogonal Cartesian coordinates of vector t. Random field is homogeneous and isotropic when its characteristics are equivalent in any direction. There are three types of surface anisotropy: • General event of surface anisotropy. Characteristics of this event roughness parameters are depend of surface split direction. • Surface roughness with direct anisotropy. Those surfaces are with typical traces of tool and they proper two mutually perpendicular surface roughness directions. • Extended anisotropy area – special event of anisotropy roughness. Of analytical opinion, gainfully anisotropy roughness see as extended occasional isotropy area. This let easy cross from anisotropy surface to isotropy and contrariwise, thereby embrace amount class of surface roughness. Let’s formulate microtopography model of rough surface [1]. Surface roughness is described with homogeneous normal random field h(x,y) that has uninterrupted correlation function and uninterrupted deriviates. We may consider that E{h(x,y)}=0. The mean random field value is plane called mean plane. For describing random field we must know mathematical expectation and field correlation function, what in fact reduces on determining dispersion and rationed correlation function r(t1, t2). Homogeneous random field dispersion D{h} doesn’t depends of direction and can be founded in any surface split. Given model of rough surface let inspect surfaces produced by abrasive instruments and friction surfaces after wear-in period.

Measurement Accuracy Problems of the Surface Texture Parameters

In this scientific article the recommendations for a three-dimensional surface roughness parameters determination of mechatronics elements are developed. First of all, the measurements for surface with irregular roughness were made, what led to the determination of a 3D roughness correlation function. On that basis correlation interval in two perpendicular treatment directions was calculated and associated with number of surface roughness uncorrelated points. Secondly, the surface roughness step parameters evaluation precision in two mutually perpendicular directions was analysed. Particular attention was paid to the roughness average step RSm in the treatment longitudinal direction. As a result, the recommendations for a 3D roughness parameters determination were prepared.

The Effect of the Cutting Parameters on the Machined Surface Roughness

From the invention of turning machine or lathe, some engineers are trying to increase the turning productivity. The increase of productivity is following after the breakout in instrumental area, such as the hard alloy instrument and resistance to wear cutting surfaces. The potential of cutting speed has a certain limit. New steel marks and cutting surfaces types allow significantly increase cutting and turning speeds. For the most operation types the productivity increase begins from the feeding increase. But the increase of feeding goes together with machined surface result decreasement. Metal cutting with high feeding is one of the most actual problems in the increasing of manufacturing volume but there are some problems one of them is the cutting forces increasement and larger metal removal rate, which decrease the cutting tool life significantly. Increasing of manufacturing volume, going together with the cutting instrument technology and material evolution, such as the invention of the carbide cutting materials and wear resistant coatings such as TiC and Ti(C,N). Each of these coating have its own properties and functions in the metal cutting process. Together with this evolution the cutting tool geometry and machining parameters dependencies are researched. Traditionally for the decreasing the machining time of one part, the cutting parameters were increased, decreasing by this way the machining operation quantity. In our days the wear resistance of the cutting tools increasing and it is mostly used one or two machining operations (medium and fine finishing). The purpose of the topic is to represent the experimental results of the stainless steel turning process, using increased cutting speeds and feeding values, to develop advanced processing technology, using new modern coated cutting tools by CVD and PVD methods. After investigation of the machined surface roughness results, develop the mathematical model of the cutting process using higher values of the cutting parameters.

Theoretical Approach of Wear for Slide-Friction Pairs

A number of different mechanisms and devices in mechatronic systems may involve sliding-friction surfaces. The issues of service life and its prediction for the details of such surfaces have always been of particular importance. Having studied the wear process prediction theories that have been developed in the course of time, which can be classified by dividing them in definite groups based on similar theoretical approach one can state that each of them has different shortcomings, which might affect the result precision, when essential basic parameters have been disregarded, as well as create a need for useless additional practical experiments, as a result of which theoretical calculation becomes unnecessary. [4] The article determines the most suitable wear calculation model that allows considering the set of parameters necessary for calculating slide-friction pair. Wearing usually proceeds in three stages: the running-in stage, the normal wear stage, and the intensive wear stage. The proposed model is provided for normal wear stage calculations. The proposed model for wear calculation is based on the application of theories from several branches of science to the description of 3D surface micro-topography in accordance with random field theory, assessing the material’s physical and mechanical characteristic quantities, substantiating the regularities in creation of material particles separated during the wear process and taking into consideration definite service conditions of fittings. Since the wear process is variable and many-sided, it is influenced by numerous different parameters, for example, surface geometry (roughness, waviness, form deviation, etc.), physical and mechanical conditions of the upper layer, material components, wear regime, wear temperature, etc. Based on the regularities stated in the article one can propose the following wear calculation sequence [4]:1) Initial data should be stated which will be further necessary in calculations: constructive-kinematic characteristic quantities (rated area Aa of wearing component, load P, gliding movement speed v, movement time t), fatigue characteristic of friction component material (friction coefficient f (f≤0,1) and material fatigue destruction parameters (m, σ-1, N0), mechanical characteristic quantities of material (E, μ);2) Parameters should be stated after attachment: surface roughness parameters (Sa, Sm1, Sm2, Sm2a), initial wear Up and corresponding time Tp, tolerated wear Umax.

Friction and Slip Property Investigation of Nanostructured Metal Surface Coatings

In this study authors tests whether on inclined plane principle based simple experimental slip property estimation device which is modified with optical sensors for sample sliding time measurements can be effectively used for surface static sliding friction coefficient (COF) and dynamic slip property investigation. Parameters measured with the device allows to compare how different types of surface treatments (including nanostructured coatings) influence surface tribological parameters thus allowing to determine most efficient treatment technology. In order to verify slip property estimation device effectiveness in real life situation prototype was fabricated and experiments with 5 samples (1 polished stainless steel sample and 4 titanium-containing nanocoatings sputtered on same polished stainless steel substrates) were formed. Collected experiment data approved that such device can be effectively used for both COF and dynamic slip property investigation.

Titanium Compound Erosion-Resistant Nano-Coatings

The main objective of this paper is to offer ion-plasma technology for production of Ti (titanium) and titanium nitride (TiN) erosion-resistant nanocoatings for the machine building products, which ensures the coatings with optimum and stable properties. As a result of experiments and processing experimental data the optimum composition of ion-plasma titanium and titanium nitride nanocoatings was obtained and offered.The approbation of the developed technology on the existing machine building products (compressor blade of the helicopter gas turbine; base material: Incoloy 800) was carried out. The comparative study on the influence of the coating on the surface quality, coefficient of friction, adhesion strength and erosion resistance was done. For evaluation of the obtained nanocoating surface’s quality 2D and 3D surface description approaches were applied. Achieved results prove the effectiveness of offered ion-plasma technology for production of titanium and titanium nitride erosion-resistant nanocoatings with appropriate and stable properties.

Wear Problems of Slide-Friction Pair

A number of different mechanisms and devices may involve sliding-friction surfaces. The issues of service life and its prediction for the details of such surfaces have always been of particular importance. The article determines the most suitable wear calculation model that allows considering the set of parameters necessary for calculating slide-friction pair. The offered model is based on the application of the theories of several branches of sciences. Since the wear process is variable and many-sided, it is influenced by numerous different parameters, for example, surface geometry (roughness, waviness, form deviation, etc.), physical and mechanical conditions of the upper layer, material components, wear regime, wear temperature, etc.

Determining the Number of Peaks of Rough Surfaces Necessary for Wear Calculation

The problem of evaluating the life period of different mechanisms is of great importance nowadays. This could be explained by the fact that the wear process is very complex and very many factors take place simultaneously. During the history a variety of theories that offered different methods of wear calculation models were developed. However still there is no exact wear calculation model that could be applied to all cases of wear processes. The offered method is dealing with the calculation of rough surface peaks that make the contact between two surfaces. Taking into account the number of these peaks and applying fatigue wear model based on 3D surface micro-topography, assessing the materials physical and mechanical characteristic quantities and considering definite service conditions of sliding friction pair it is possible to make the wear calculation of friction pair under definite working conditions.

Precision Assessment of Surface Coating Roughness Height 3D Parameter St

One of the main surface coating quality indexes of details of mechatronic systems is surface roughness. And the surface roughness is described by surface roughness parameters. Nowadays characterization of surface roughness using three-dimension (3D) methods and parameters become more and more important. This type of surface quality characterization, unlike the two-dimension (2D) methods, provide a more complete view on the surface qualities, since the surface roughness is viewed as a spatial object. Within the last ten years intensive work is being carried out on the development of 3D roughness standards, therefore it is necessary to agree on a unified approach in the assessment of surface roughness 3D parameters. To make possible application of the ISO/DIS 25178 standard being developed one needs information on the determination of 3D surface roughness parameter precision, such as number of measurements, dimensions of measurement areas and their disposition on the measured surface.