Biotribology

One way of controlling friction and associated energy losses is to engineer a deterministic structural pattern on the surface of the rubbing parts (i.e., texture engineering). Custom texturing enhances the quality of lubrication, reduces friction, and alloows the use of lubricants of lower viscosity. To date, a standardized procedure to generate deterministic texture constructs is virtually non-existent. Many engineers, therefore, study natural species to explore surface construction and to probe the role surface topography assumes in friction control. Snakes offer rich examples of surfaces where topological features allow the optimization and control of frictional behavior. In this paper we investigate the frictional behavior of a constrictor type reptile, Python regius. The study employed a specially designed tribo-acoustic probe capable of measuring the coefficient of friction and detecting the acoustical behavior of the skin in vivo. The results confirm the anisotropy of the frictional response of snakeskin. The coefficient of friction depends on the direction of sliding: the value in forward motion is lower than that in the converse direction. Detailed analysis of the surface metrological feature reveal that tuning frictional response in snakes originates from the hierarchical nature of surface topology combined to the profile asymmetry of surface micro-features, and the variation of the curvature of the contacting scales at different body regions. Such a combination affords the reptile the ability to optimize the frictional response.

In the framework of green materials, in recent years, natural fiber composites attracted great attention of academia and industry. Their mechanical and tribological characteristics, such as high strength, elasticity, friction, and wear resistance, make them suitable for a wide range of industrial applications in which issues regarding a large amount of disposal are to be considered since their environmental friendliness gives them an advantage over conventional synthetic materials. Based on the recent and relevant investigations found in the scientific literature, an overview focused on the tribological characteristics of composite materials reinforced with different types of natural fibers is presented. The aim is to introduce the reader to the issues, exploring the actual knowledge of the friction and wear characteristics of the composites under the influence of different operating parameters, as well as the chemical treatment of fibers. The main experimental tribological techniques and the main used apparatus are also discussed, with the aim of highlighting the most appropriate future research directions to achieve a complete framework on the tribological behavior of many possible natural fiber composite materials.

Tribology phenomena are obviously present and have significant importance in most of human activities, processes and actions. This paper presents an attempt in this direction dealing with study of tribology aspects in ballroom dancing. Analysing a couple of Standard and Latin ballroom dances, idea is to make approximate
calculation of friction forces and torques and their influence on foot floor interface. Authors take Viennese waltz with couple of other typical dances, where the concept and methodology of friction calculation has been performed. Besides the approximate calculation of friction, this paper attends to measure and analyse complete energy consumption during the dance as a human activity. This has been done by making several experiments where total energy loss in ballroom dance used to be measured. In combination with friction loss calculations, those experiments reach some conclusions, among others that impact of friction losses in total energy consumption is not dominant for quick dances. This topic could be interesting for some further investigations such also for floors and shoes manufacturers
aimed to make an optimum product for requested activity. Clear objective is to reduce energy consumption from one side, but also to prevent possible undesirable slips from another side.

ABSTRACT Deterministic surfaces are constructs of which profile, topography and textures are integral to the function of the system they enclose. They are designed to yield a predetermined tribological response. Developing such entities relies on controlling the structure of the rubbing interface so that, not only the surface is of optimized topography, but also is able to self-adjust its tribological behaviour according to the evolution of sliding conditions. In seeking inspirations for such designs, many engineers are turning toward the biological world to study the construction and behaviour of bio-analogues, and to probe the role surface topography assumes in conditioning of frictional response. That is how a bio-analogue can self-adjust its tribological response to adapt to habitat constraints. From a tribological point of view, Squamate Reptiles, offer diverse examples where surface texturing, submicron and nano-scale features, achieves frictional regulation. In this paper, we study the frictional response of shed skin obtained from a snake (Python regius). The study employed a specially designed tribo-acoustic probe capable of measuring the coefficient of friction and detecting the acoustical behavior of the skin in vivo. The results confirm the anisotropy of the frictional response of snakes. The coefficient of friction depends on the direction of sliding: the value in forward motion is lower than that in the backward direction. Diagonal and side winding motion induces a different value of the friction coefficient. We discuss the origin of such a phenomenon in relation to surface texturing and study the energy constraints, implied by anisotropic friction, on the motion of the reptile.

This investigation aims to wear analyze of acetabular cup on metal-on-metal total hip arthroplasty with and without dimple addition. Our contribution that present in this paper is to explore the effect of surface texturing application to reduce wear that important for implant's survival. Finite element method is using with 3D human's hip joint loading under normal walking conditions. Updating geometry also consider for more realistic simulation result. Wear prediction performed for one year from using implant that equal to 1x10 6 gait cycle. Textured surface in total hip arthroplasty found have to reduce cumulative linear wear and cumulative volumetric wear by around 24% compared untextured surface.

Laser texturing is one of the leading technologies applied to modify surface topography.
To date, however, a standardized procedure to generate deterministic textures is virtually
non-existent. In nature, especially in squamata, there are many examples of deterministic
structured textures that allow species to control friction and condition their tribological
response for efficient function. In this work, we draw a comparison between industrial
surfaces and reptilian surfaces. We chose the Python regius species as a bio-analogue with a
deterministic surface. We first study the structural make up of the ventral scales of the snake
(both construction and metrology). We further compare the metrological features of the ventral
scales to experimentally recommended performance indicators of industrial surfaces extracted
from open literature. The results indicate the feasibility of engineering a laser textured surface
based on the reptilian ornamentation constructs. It is shown that the metrological features, key
to efficient function of a rubbing deterministic surface, are already optimized in the reptile. We
further show that optimization in reptilian surfaces is based on synchronizing surface form,
textures and aspects to condition the frictional response. Mimicking reptilian surfaces, we
argue, may form a design methodology potentially capable of generating advanced
deterministic surface constructs capable of efficient tribological function.

Kajian ini bertujuan untuk menganalisa tekanan kontak pada permukaan acetabular cup dengan dan tanpa paplikasi permukaan bertekstur. Kontribusi utama dari studi ini adalah mempelajari efek penambahan dimple terhadap tekanan kontak yang berkorelasi terhadap keausan yang terjadi. Pendekatan dengan menggunakan perangkat lunak dilakukan dengan melakukan pemuatan fisiologis sambungan tulang pinggul secara 3D dalam kondisi berjalan normal. Analisa tekanan kontak dilakukan secara kontak langsung dan deskritasi elemen hingga dengan metode dua kutub dilakukan untuk memberikan hasil tekanan kontak yang akurat. Hasil menunjukkan bahwa model total hip arthroplasty dengan penambahan dimple dapat mengurangi tekanan kontak untuk seluruh fase dalam satu siklus penuh yang menjelaskan bahwa penambahan dimple pada permukaan acetabular cup di total hip artroplasti dapat mengurangi tekanan kontak dan mengurangi keausan.

Wear and wear-induced debris is a significant factor in causing failure in implants. Reducing contact pressure by using a textured surface between the femoral head and acetabular cup is crucial to improving the implant’s life. This study presented the effect of surface texturing as dimples on the wear evolution of total hip arthroplasty. It was implemented by developing finite element analysis from the prediction model without dimples and with bottom profile dimples of flat, drill,
and ball types. Simulations were carried out by performing 3D physiological loading of the hip joint under normal walking conditions. A geometry update was initiated based on the patient’s daily routine activities. Our results showed that the addition of dimples reduced contact pressure and wear. The bottom profile dimples of the ball type had the best ability to reduce wear relative to the other types, reducing cumulative linear wear by 24.3% and cumulative volumetric wear by 31%
compared to no dimples. The findings demonstrated that surface texturing with appropriate dimple bottom geometry on a bearing surface is able to extend the lifetime of hip implants.

This research analyzed the effect of applied surface texturing on bearing component of the artificial hip joint due to lubrication performance. The main contribution of the paper was explaining the significant role of adding dimples in artificial hip joint surface bearing who can probably decrease friction interaction on the acetabular liner and femoral head that impact on improving wear resistance. This is achieved by analyzing the geometric variation (shape and diameter) of the dimple to the performance of lubricating metal-on-metal artificial hip joint bearings under normal walking conditions. The research method focused on numerical analysis using the Fluid-Structure Interaction (FSI) simulation method which reviewed the solid and fluid structure. From the simulation results, it can be seen that the variation of ellipse dimple with a diameter of 80 μm has the best lubrication performance, which is indicated by the largest hydrodynamic fluid pressure of 0.915 Pa, the smallest solid pressure is 0.433 Pa, and the largest lubricant thickness is 22.672 μm.