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Incoloy 800, which is used within steam generator tubes, is a heat resistant material since it is an iron-nickel-chromium alloy. However, construction of a systematic database is needed to receive integrity data defecting insurance of specific data about room and elevated temperature fretting fatigue behavior for Incoloy 800. Accordingly, this study investigates the specific change in fatigue limitations under the condition of the fretting fatigue as compared to that under the condition of the plain fatigue by performing plain and fretting fatigue tests on Incoloy 800 at 320°C, real operating temperature and at room-temperature, respectively. The change in the frictional force is measured during the fretting fatigue testing against the repeated cycle, and the mechanism of fretting fatigue is investigated through the observation of the fatigue-fracture surface.

In orthodontic treatment, the efficiency of tooth movement is affected by the frictional force between the archwire and bracket slot. This study evaluated the static and kinetic frictional forces produced in different combinations of orthodontic archwires and brackets. Three types of archwires [stainless steel, nickel-titanium (NiTi) alloy, and beta-titanium (TMA) alloy] and two types of brackets (stainless steel and self-ligating) were tested. Both static and kinetic frictional forces of each archwire–bracket combination were measured 25 times using a custom-designed apparatus. The surface topography and hardness of the archwires were also evaluated. All data were statistically analyzed using two-way analysis of variance and Tukey's test. The experiments indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire–bracket combinations not involving TMA wire. TMA wire had the highest friction, followed by NiTi wire, and then stainless steel wire when using the stainless steel bracket. However, there was no difference between NiTi and stainless steel archwires when using the self-ligating bracket. For TMA wire, the friction was higher when using the stainless steel bracket than when using the self-ligating bracket. Scanning electron microscopy indicated that stainless steel wire exhibited the smoothest surface topography. The hardness decreased in the order of stainless steel wire > TMA wire > NiTi wire. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire. The reported data will be useful to orthodontists.

A numerical study is presented to examine the peristaltic transport of fractional bio-fluids (viscoelastic fluids with fractional Oldroyd-B model) through the channel. Analysis is carried out under the assumptions of long wavelength and low Reynolds number. Numerical and analytical approximate solutions of problem are obtained by using homotopy analysis method. It is assumed that the cross section of the channel varies sinusoidally along the length of channel. The effects of fractional parameters, material constants (relaxation time and retardation time), time and amplitude on the pressure and frictional force across one wavelength are studied with particular emphasis. The computational results are presented in graphical form. It is found that the effect of both fractional parameters on pressure is opposite to each other i.e., pressure reduces with increasing magnitude of the first fractional parameter whereas it increases with increasing magnitude of the second fractional parameter. The effects of relaxation time and retardation time on pressure are similar to that of first and second fractional parameters, respectively.

Colonoscopy is common procedure frequently carried out. It is not without its problems, which include looping formation. Looping formation prevents the tip of the colonoscope itself from advancing, thus further probing induces a risk of perforation, significant patient discomfort, and failure of colonoscopy. During colonoscopy, the manipulated colonoscope for intubation in the colon goes through the friction between the colonoscope and the colon. Due to major frictional force, the sigmoidal colon forms looping with the scope during intubation. The interactive frictional force between the colon and the colonoscope is highly complex because of frictional contact between two deformable objects. In this paper, contact force computation was formulated into a linear complementarity problem (LCP) by linearizing Signorini's problem, which was adapted into non-interpenetration with unilateral constraints. Frictional force was computed by the mechanical compliance of finite element method (FEM) models with the consideration of dynamic friction between the colonoscope and the intestinal wall. Furthermore, we presented a mathematical model of the elongation of the colon that predicts the motion of scope relative to the intestinal wall in colonoscopy.

In this study, we investigate the special type of magnetic trajectories associated with a magnetic field ${ℬ}$ defined on a 3D Riemannian manifold. First, we consider a moving charged particle under the action of a frictional force, $f$, in the magnetic field ${ℬ}$. Then, we assume that trajectories of the particle associated with the magnetic field ${ℬ}$ correspond to frictional magnetic curves ($f$-magnetic curves$)$ of magnetic vector field ${ℬ}$ on the 3D Riemannian manifold. Thus, we are able to investigate some geometrical properties and physical consequences of the particle under the action of frictional force in the magnetic field ${ℬ}$ on the 3D Riemannian manifold.

If one rolls a vertically standing hula hoop forward with backspin applied, it moves once far away and then eventually back to hand. In this paper, we study such a motion of a rolling hula hoop from both theoretical and experimental aspects. The hula hoop is rolling with slipping immediately after it leaves the hand, and its motion will transit to that of without slipping due to the transition of the frictional force from kinetic friction to static friction. We show that the experimental results analyzed by Tracker software can be well described by equations of motion that take into account the deformation of the hula hoop. Theoretical and experimental studies in this paper are suitable for university students in physics courses. The video analyzed in this paper can be viewed at https://youtu.be/i4j1lDhCI2os.