Theoretical research of the technology of finishing cylinders with antifriction materials

The article analyzes the research aimed at the use of various materials, additives and additives to oils. It is established that their application is mainly limited to the stages of operation, bench and operational running-in. The use of antifriction materials at the stage of processing the parts of internal combustion engines, limiting the resource, is small, despite the fact that such treatment reduces the running-in time and improves the finish of the friction surfaces. Theoretical calculation of the parameters of the working surface of the engine cylinder liner during their finishing using special antifriction materials showed a 2-fold increase in the bearing surface (from 0.2 to 0.4 of the nominal surface area at the level of the middle line of the profile) and a roughness of 0.27 μm, which is close to the values after the bench run-in. This proves the possibility of using this treatment in order to reduce the time of preparation of CNG and improve the characteristics of the surfaces to be worked. It is established that the finishing of engine cylinder liners with antifriction materials should be carried out at the contact pressure of the working tool (brass bars) on the surface of the sleeve 3 MPa, the speed of the working tool 5.5 m/s, the processing time of the sleeve 20 min. Finishing of sleeves with use of compositions TSK-B100 + SURM-KV, SURM-UO and RVS allows to reduce mechanical losses on friction in TsPG by 5-19% at the beginning of process of running in after processing in comparison with mechanical losses at the end of cold running in without finishing sleeves; to obtain the roughness parameters after finishing the same as after cold running in without additional processing of the sleeves; increase the bearing surface by 2 - 2.5 times (from 0.2 - 0.25 to 0.4 - 0.5 of the nominal surface area at the level of the middle line of the profile), which confirms the calculated data. The final treatment of sleeves with compositions based on antifriction materials TSK-B100 + SURM-KV, SURM-UO and RVS allows to provide values of parameters of a working surface of sleeves (reduction of roughness, increase of a basic surface) approaching their values after cold running in, therefore allows to increase contact loadings. in the connection "sleeve - piston ring" after this treatment and reduce the time of the bench run-in (to the values required for the attachment of other engine connections).

A solution considering elastic-plastic deformation of asperities for contact between rough cylindrical surfaces

Purpose This paper aims to study the contact between rough cylindrical surfaces considering the elastic-plastic deformation of asperities. Design/methodology/approach The elastic deformation of the nominal surface of the curved surface is considered, the contact area is discretized by the calculus thought and then the nominal distance between two surfaces is obtained by iteration after the pressure distribution is assumed. On the basis of the Zhao, Maietta and Chang elastic-plastic model, the contact area and the contact pressure of the rough cylindrical surfaces are calculated by the integral method, and then the solution for the contact between rough cylindrical surfaces is obtained. Findings The contact characteristic parameters of smooth surface Hertz contact, elastic contact and elastic-plastic contact between rough cylindrical surfaces are calculated under different plastic indexes and loads, and the calculation results are compared and analyzed. The analysis shows that the solution considering the elastic-plastic deformation of asperities for the contact between rough cylindrical surfaces is scientific and rational. Originality/value This paper provides a new effective method for the calculation of the contact between rough cylindrical surfaces.

Influence of Process Parameters on Geometric Precision of Machined Surface after WEDM

Geometrical precision machined surface is generally understood as mainly precision shape, orientation, location and run-out. As a rule, it is measuring the appropriate deviations from the nominal surface. The geometric size of this deviation from the nominal surface can in practice affect the conventionally measured value for the dimension and the dimension whilst maintaining the required tolerance. Because the WEDM technology is among the most accurate technology, the small final geometric accuracy deviation has also a negative impact on the final quality of the machined surface. The paper aimed to describe errors geometrical precision of machined surface which occurs in wire electrical discharge machining (WEDM) and quantify their scope.

Chemical analysis of sea ice vein μ-environments using Raman spectroscopy

ABSTRACTSea ice is a unique environment providing a vast habitat for a variety of life, including microscopic organisms. It accounts for roughly 5–6% of the surface area of the oceans. It is a complex porous structure of crystalline water, gas bubbles, and pockets of brine, as well as a connected structure composed of macro- and micro-porosity filled with concentrated aqueous liquids. Using micro-Raman spectroscopy, it is possible to characterise features of ice at a spatial resolution of a few to tens of micrometers, the scale of relevance to trapped microorganisms, by providing information concerning the presence and amount of molecular species present in the trapped liquids. We have applied this technique to determine the spatial distribution of sulphate, phosphate and carbonate anions in sea-ice veins using ice obtained from the vicinity of the Palmer Station, Antarctica. The observed sulphate concentrations were approximately 20–30% higher than nominal surface seawater concentrations, consistent with the concentration of brine in vein and inclusion liquids during the ice formation process. This concentration was lower than that in veins present in laboratory-prepared ice. Carbonate and dibasic phosphate anions were also observed in the sea ice. This speciation is consistent with an alkaline environment in the sea-ice aqueous system. The mean dibasic phosphate concentration found throughout the sample was 648 mM, while, for carbonate, it was 485 mM. However, these anions showed extremely high spatial variability. The high phosphate and carbonate enhancements observed relative to sulphate point to the influence of processes other than brine formation controlling the chemistry of these anions in sea ice.

A Differentiated Registration Method for Complex Surfaces

Different error requirements on different surfaces are necessary in many situations. If the registration between the measured dataset and the nominal surface is performed ignoring these differences, an inaccurate result could occur due to the surfaces which have low precision. An improper registration even results in false verdict. So the differentiated registration is of significance in precision engineering. In this paper, a new registration method taking into consideration of the different error requirements is proposed. Firstly surfaces are classified based on different error requirement. Then, appropriate weight factors are iteratively given to these surfaces. Based on the change relationship of error and weight factors, the algorithm controls the error distribution by optimizing the weighted least squares. Our method has the great flexibility in distributing the error, which is suitable for engineering applications. The experiment demonstrates the validity.

CFD Challenge: Solutions Using the In-House Finite-Element-Based Solver NEWTETR

Briefly, this Challenge aims to test the sensitivity of steady and pulsatile pressure drops as predicted by different CFD solvers or groups, and ultimately against in vitro pressure measurements. The current study focuses on the Phase I of the Challenge. We simulated steady state and pulsatile pressure drops based on the nominal surface geometry and specific inlet flow rates on a giant cerebral aneurysm with proximal stenosis.

Process Signature Modeling for Tolerance Analysis

Many well-known approaches exist in the literature for tolerance analysis. All the methods proposed in the literature consider the dimensional and the geometric tolerances applied to some critical points (contact points among profiles belonging to couples of parts) on the surface of the assembly components. These points are generally considered uncorrelated since the nominal surface is considered. Therefore, the methods proposed in the literature do not consider the actual surface due to a manufacturing process. Every manufacturing process leaves on the surface a signature, i.e., a systematic pattern that characterizes all the features machined with that process. The aim of the present work is to investigate the effects of considering the manufacturing signature in solving a tolerance stack-up function. A case study involving three parts has been defined and solved by means of a method of the literature, the variational method, with and without considering the correlation among the points of the same surface due to the manufacturing signature. This work represents a first step toward the integration of the design and the manufacturing in a concurrent engineering approach.

EXPERIMENTAL ANALYSIS OF POOL BOILING HEAT TRANSFER ON EXTENDED SURFACES AT NEAR VACUUM PRESSURES

This research paper presents a study of boiling heat transfer from longitudinal rectangular and square pin finned surfaces immersed in saturated water at low vapor pressures of 2 and 9 kPa. Conventional boiling analysis, which is based on the nominal surface area of the heater, was compared with a boiling analysis that considers the total "wetted" surface area.

Regular Surface Texture Generated by Special Grinding Process

Most of the methods for generating regular surface texture (RST) consist of shaping a set of regular grooves (cavities) arranged in a regular way. This paper presents possibilities for regular surface texture generation by so-called “pattern grinding” with the wheel prepared in a special way. The simple variant of the method involves grinding with the wheel having helical grooves. The grooves shaped on the work material are the result of specific wheel surface reproduction. The ratio between work-material feed and wheel speed is an important factor, determining the layout of the grooves generated on the work-material and the shape of the groove sides. Surface texture consists of two components: deterministic, resulting from the nominal wheel active surface, and random, resulting from the random shape and arrangement of abrasive grains. The limited contribution of the random component of surface texture is discussed based on the ratio between the undeformed chip thickness and the sizes of the grooves. Kinematical analysis of the wheel reproduction process is performed for description of nominal surface texture. Experimental results of flat and cylindrical surfaces, obtained with pattern grinding are also provided. Two critical values of the ratio between work-material feed and wheel speed were derived, and three ranges of this ratio are discussed. The kinematical approach provided relationships between input data of the process (wheel shape and grinding parameters) and nominal groove dimensions and groove layout. The geometrical characteristics of the work-material nominal surface texture are presented for each of the three types of surface texture. It is important to ensure that the work feeds are greater than the lower critical value. For achievable work feeds the shape of the sides of the grooves is cycloid. Experiments revealed the limited contribution of the random component of the surface structure of the work material. Random arrangement of abrasive grains is important only at local (micro-) level and affects the roughness of groove bottoms, while the dimensions and arrangement of the grooves are affected only to a minimal degree.