Request Expert

The expert is most experienced in the subset of surface science related to mathematics and mechanics of surface irregularities on micro- and macro scales and their contact interaction. In addition he has experience in the field of surface metrology and assessment of surface undulations using profilometric methods. Study of the actual profiles of the cylinder bores (of engines, compressors…) which deviate from the ideal round shape due to manufacturing, assembly and operational factors, led Val to become involved in a topic of the conformability of the of the piston rings to the bores. He explains that conformability is a major factor in seal ability of the piston rings (and correspondingly in the related to it oil consumption, emissions, blow-by, etc.) and wear of the rings and bores, the properties that make ring/bore conformability an important engineering subject.

The expert selected tribology as a primary concept because a subset of tribology, mathematical description of the surface texture and contact interaction of rough surfaces was a subject of his Ph.D. dissertation. The expert considers that understanding and utilization of this subject is very important to properly address many engineering factors and procedures including design specifications of machine components, contact stiffness/contact stress analysis, friction, wear, heat transfer and temperature generation, estimation of the minimum required oil film thickness in the sliding and rolling bearings, cost of the machining, noise and vibration of the sliding units, optical properties, resistance to fluid flow, etc. During his professional career, the expert was able to efficiently utilize knowledge of this subject in connection with some of the mentioned engineering areas.

The expert comments that wear typically results in change of micro-and macrogeometrical parameters of the contacting surfaces, modification of their physico/chemical structure and generation of wear debris. Depending on a function of a wearing unit, operational conditions and service time, a beneficial run-in wear may transfer into objectionable wear pronounced in reduction of reliability of the unit and the correspondent mechanism or machine and degradation of their performance. To combat the wear effect, various engineering means exist. These include construction of the unit in such a way as to reduce or prevent wear through selection of certain designs, geometries, materials, coatings, lubricants and operating conditions. Important part in reduction of wear is a proper maintenance. For example infringement on the required oil change intervals of the engine may result in degradation of the motor oil to the level that it cannot prevent separation of the interacting surfaces. As a result, wear of the piston rings, cylinder bore, piston and bearings will ensue. The expert came up with an ingenious wear proof design of a mechanism in scroll compressors (see his patent). In this wear design the difference between both the shear strength of an elastomeric shim and friction force at the interface of two contacting metallic surfaces is successfully employed to eliminate a relative motion of the metallic surfaces (and thus eliminate their wear) and to transfer it in the shear deformations of the elastomeric shim.

The expert knows that one of the purposes of wear modeling is to identify different manifestations of wear with their underlying mechanisms in order to successfully combat, predict or estimate wear. He adds that in a number of occasions wear demonstrates itself through single forms like abrasive, adhesive, corrosive, erosive, and fatigue wear. However, in many actual situations these forms of wear are often intermingled and wear occurs as a complex process. This complicates prediction of wear analytically and advances wear testing to the front of activities related to a proper selection of materials and design for a potential wear reduction. The expert cautions that one should consider also that wear demonstrates large variability and statistical methods are often employed to analyze wear data. One of the unfortunate phenomena of wear is that it has a low rate of reproducibility, that is results of wear studied on small samples may not be represented in the actual machine. Accordingly, full-scale friction/wear tests of a developed mechanism are needed to justify estimation of wear for this mechanism. These tests are often performed as durability tests. For better familiarities with wear prediction one can be referred to the expert’s articles.

The expert mentioned that wear resistant material and coatings are intuitively associated with hard surfaces. He cautions however that this view is in general incorrect. Wear resistance is often achieved by using special coatings having a property of self-lubrication. An example of this type of coatings is a so-called Tuffram produced by Magnaplate Corp. in NJ. The coating represents a layer of hard anodized aluminum infiltrated by self-lubricants like PTFE and MoS2. This coating gives a slippery feel and absence of adhesion between the mating surfaces during the operation. The expert believes that these properties are attained due to presence of large and inert fluorine atoms in the structure of PTFE and transfer of the PTFE from the coating onto the counter surface. Despite its good anti-adhesion/anti-wear properties, coefficient of friction of the assemblies with PTFE coatings is not necessarily small.

The expert has experience in dealing with friction and wears in different machines and mechanisms including components of the IC engines, railroad and automotive brakes and components of the refrigeration and air compressors. He feels that experience accumulated in fighting wear in these products, and his tribological background in general, is in many ways transferable to other big and small industrial products including magnetic media devices, robotics, MEMS, medical devices. He noted that wear is associated not only with materials, but it substantially depends on design properties of the unit or machine as a whole. Depending on a type of a mechanism, reduction or minimization of wear may require completely different approaches. For example, in the non-lubricated units, a relative motion between some wearing components needs to be constricted to prevent their wear. At the same time in the lubricated mechanisms, the related components need to be provided with freedom of motion to ensure good lubrication.

During his employment at WABCO, Copeland and Bendix he often was considered as consultant.

Based on in-depth tribological understanding of the friction squeal, proposed a concept of a low noise friction material which was implemented.Developed precision software for prediction of the braking temperatures in single and multiple braking events in the railroad and automotive brakes.Developed concepts and design of a variety of friction/wear testers for simulation of wear of the components of scroll compressors. He is probably one of the first in the engineering community who understood the effect of three-dimensional distortions of the piston rings on their conformability. Subsequently he spearheaded development of the analytical methods for analysis of the ring distortion/conformability effect and obtained (in collaboration with S. Alexandrov) a computer code for estimation of this effect.Based on understanding of the interaction between the surface texture height of the honed cylinder bore and rigidity/distortion of the cylinder block, proposed design of a clamping fixture of the block that minimized bore distortions.