Evaluation and improvement of tire rolling resistance and grip performance based on test and simulation

In order to clarify the contradictory mechanism between tire rolling resistance and grip performance, ten (10) 205/55 R16 radial tires with different tread patterns were selected as the research objects. Using VIC-3D non-contact strain measurement system, the pattern deformation in the contact area under vertical load was tested and the relevant deformation parameters of the contact area were extracted. Correlation analysis was used to establish the relationship between the identified deformation parameters and tire performance indicators. Then the contradiction mechanism between tire rolling resistance and grip performance was identified. The mechanism is such that, in order to improve the grip performance of the tire, it is necessary to reduce the transverse tensile strain of the tread in the contact area and increase the longitudinal tensile strain of the tread, but with the increase of the longitudinal tensile strain, the rolling resistance of the tire will also increase, which leads to the contradiction between tire rolling resistance and grip performance. In order to better understand and solve this contradiction, a finite element model of 205/55R16 tire with complex pattern was established. The influence of the number and width of transverse grooves in outer shoulder area on tire rolling resistance and grip performance was analyzed by numerical simulation, where it was identified that, the longitudinal tensile deformation of the tread is the main cause of contradiction between the two performances. An optimized design of concave transverse groove with narrow groove in the middle and wide groove at both ends was proposed in the outer shoulder area to resolve the contradiction. Compared with the original scheme, the rolling resistance of the optimized scheme was reduced by 2.112 N, and the grip force saw an increase of 10.196 N, and thus delivering a cooperative improvement of tire rolling resistance and grip performance.

Acoustic Emission Analysis of Defective Radial Ball Bearings for Quality Control

The objective of this study is to capture and characterize the acoustic emissions of radial ball bearings in operation. A comparison is made between healthy bearings and defective ones. A precise 0.012” wide groove was cut into either a ball, the inner or outer race of test bearings. To reduce vibrational interference, the test shaft is isolated using a magnetic coupling and is supported by a thrust air bearing. The test bearing is acoustically insulated from its surrounding with mass loaded vinyl and acoustic reflections are dampened by wedge foam to improve the signal quality. The acoustic emissions are captured and digitized using a smartphone. Various signal processing techniques are used to characterize the signals and analyze defect modes. The results provide a comparison between the acoustic emissions of healthy and defective bearings operated at various speeds and provide methods for characterization.

Nueva especie de rana bromelícola del género Pristimantis (Amphibia: Craugastoridae), meseta de la Cordillera del Cóndor, Ecuador

We describe a small frog of the genus Pristimantis inhabiting bromeliads (snout-vent length 20.3‑23.3 mm in females, 16.1‑17.4 mm in males), from a remote sandstone plateau of the Cordillera del Condor, in southeastern Ecuador, with an altitudinal range of 2,045‑2,860 m. A phylogeny based on sequences of DNA (mitochondrial and nuclear genes) supports inclusion in the P. orestes group and suggests an undescribed Pristimantis from the southern slope of eastern Ecuador as the closest taxon. The new species differs from its congeners in Ecuador by having predominantly black dorsal and ventral coloration; comprehensive and robust palmar surface with stubby fingers; presence of a deep and wide groove from the anterior base of finger I to the rear base of the palmar tubercle; subarticular divided tubers, enlarged supernumerary small granules and tubercles. All individuals were found in terrestrial bromeliads. The calls are short, frequency modulated, comprising of a note 5‑15 ms in duration. Insects represented 80% of the diet of the new species.

Free-living nematodes from a colonisation experiment in the upwelling area of Arraial do Cabo, Rio de Janeiro, Brazil: Lavareda decraemerae gen. n., sp. n. and emended diagnosis of Cricolaimus Southern, 1914 (Plectida: Rhadinematidae)

Lavareda decraemerae gen. n., sp. n. is characterised by a cheilostom with a sclerotised ring bearing six anterior projections, a funnel-shaped to tubular stegostom, a large unispiral amphid with wide groove and males with a single precloacal setiform sensillum and 19 tubular supplements in a continuous series. The new species is similar to Cricolaimus coronatus in having the cheilostom consisting of a cuticularised ring with anterior projections. Re-examination of C. elongatus revealed clear differences to the new species, the former showing a bilateral symmetry anteriorly with a lateral axis: the lips are merged into one large dorsal and one large ventral lip with elongated inner and outer labial sensilla and the cheilostom has a cuticularised oblique ring, higher dorsally and ventrally than laterally, with two anteriorly directed claw-like projections, one mid-dorsal and one mid-ventral, whereas the new species has a radial symmetry with low lips with inner and outer labial papillae indistinct and a cheilostom with a cuticularised ring with six anteriorly directed projections, thereby justifying the proposal of Lavareda gen. n. to accommodate the new species from Brazil and L. coronatus comb. n. (= C. coronatus). An emended diagnosis of Cricolaimus is given. This is the first record of a species belonging to the Rhadinematidae colonising an artificial substrate.

The collapse of thick-walled metal tubes with wide external grooves as controllable energy-dissipating devices

This article focuses on the experimental and theoretical investigation of the axial crushing behaviour of thick-walled tubes with a number of wide grooves, cut from their outer surface, under both static and dynamic loading. While this structure is subjected to axial loading, plastic deformation occurs within the space of each wide groove, and thick portions (grooveless areas) control and stabilize the collapsing of grooved thick-walled tubes. Therefore, the kinetic energy is dissipated by the plastic collapsing of the structure between grooves. In the present study, quasi-static compression tests of specimens with various geometric parameters are performed. Dynamic tests of some specimens using a drop hammer apparatus are also carried out to study the dynamic effects on the collapsing and energy absorption behaviour of the shock absorber. Numerical simulations of axial crushing of the shock absorber under both quasi-static and impact loading, using LS-DYNA finite-element explicit code, are also carried out in this article, and their results are verified with experimental findings. Based on experimental studies, an analysis with consideration of strain hardening effects to predict mean crushing load and energy absorption of the structure under axial compression is developed. Through the performed experimental, numerical, and analytical studies, major parameters in the design of the shock absorber are characterized and possible collapse modes of deformation during axial crushing of the structure are identified. In the present study, experimental and theoretical studies show that the introduced structure can be considered as an efficient energy-dissipating device since it provides favourable crashworthiness characteristics.

Adhesion formation of primary human osteoblasts and the functional response of mesenchymal stem cells to 330 nm deep microgrooves

The surface microtexture of an orthopaedic device can regulate cellular adhesion, a process fundamental in the initiation of osteoinduction and osteogenesis. Advances in fabrication techniques have evolved to include the field of surface modification; in particular, nanotechnology has allowed for the development of experimental nanoscale substrates for investigation into cell nanofeature interactions. Here primary human osteoblasts (HOBs) were cultured on ordered nanoscale groove/ridge arrays fabricated by photolithography. Grooves were 330 nm deep and either 10, 25 or 100 μm in width. Adhesion subtypes in HOBs were quantified by immunofluorescent microscopy and cell–substrate interactions were investigated via immunocytochemistry with scanning electron microscopy. To further investigate the effects of these substrates on cellular function, 1.7 K gene microarray analysis was used to establish gene regulation profiles of mesenchymal stem cells cultured on these nanotopographies. Nanotopographies significantly affected the formation of focal complexes (FXs), focal adhesions (FAs) and supermature adhesions (SMAs). Planar control substrates induced widespread adhesion formation; 100 μm wide groove/ridge arrays did not significantly affect adhesion formation yet induced upregulation of genes involved in skeletal development and increased osteospecific function; 25 μm wide groove/ridge arrays were associated with a reduction in SMA and an increase in FX formation; and 10 μm wide groove/ridge arrays significantly reduced osteoblast adhesion and induced an interplay of up- and downregulation of gene expression. This study indicates that groove/ridge topographies are important modulators of both cellular adhesion and osteospecific function and, critically, that groove/ridge width is important in determining cellular response.

Effect of fiber flocculation and filling design on refiner loadability and refining characteristics

The loadability of a pulp refiner was studied using refiner data such as gap movement, total power, no-load power, and net refining power. Two different types of pulp and three different types of refiner filling were used in the study. The floc formation and floc size of each pulp was studied in a flow channel simulating filling grooves. The loadability of the pulp refiner was linked to refining effects such as fiber shortening, and internal and external fibrillation. The trapping point of the refiner, and therefore refiner loadability, was found to be more related to fiber characteristics such as fiber length and coarseness, while being less dependent on refining consistency in the range of 2.0-5.5%. The data on the formation of flocs and floc size was used to explain the trapping of fibers between refiner bars and the refiner gap width. Filling design characteristics such as groove width and cutting speed affect the gap width and trapping of flocs inside the refiner. Fillings with high cutting speed tend to break flocs composed of long and short fibers at the same rate and therefore both types of floc maintain the same gap width. On the other hand, wide-groove fillings with lower cutting speed have a gentler effect and the differences in fiber characteristics are easily reflected in the gap width and trapping point. Fillings with low cutting speed have a greater straightening effect than fiber cutting, whereas narrow-bar fillings have a more noticeable effect on fiber cutting, external fibrillation, and fiber swelling.

Neural Correlates for Roughness Choice in Monkey Second Somatosensory Cortex (SII)

This experiment explored the relationship between neural firing patterns in second somatosensory cortex (SII) and decisions about roughness of tactile gratings. Neural and behavioral data were acquired while monkeys made dichotomous roughness classifications of pairs of gratings that differed in groove width (1.07 vs. 1.90 and 1.42 vs. 2.53 mm). A computer-controlled device delivered the gratings to a single immobilized finger pad. In one set of experiments, three levels of contact force (30, 60, and 90 g) were assigned to these gratings at random. In another set of experiments, three levels of scanning speed (40, 80, and 120 mm/s) were assigned to these gratings at random. Groove width was the intended variable for roughness. Force variation disrupted the monkeys' groove-width (roughness) classifications more than did speed variation. A sample of 32 SII cells showed correlated changes in firing (positive or negative effects of both variables) when groove width and force increased. While these cells were recorded, the monkeys made roughness classification errors, confusing wide groove-width gratings at low force with narrow groove-width gratings at high force. Three-dimensional plots show how some combinations of groove width and force perturbed the monkeys' trial-wise classifications of grating roughness. Psychometric functions show that errors occurred when firing rates failed to distinguish gratings. A possible interpretation is that when asked to classify grating roughness, the monkeys based classifications on the firing rates of a subset of roughness-sensitive cells in SII. Results support human psychophysical data and extend the roughness range of a model of the effects of groove width and force on roughness. One monkey's SII neural sample (21 cells) showed significant correlation between firing rate response functions for groove width and speed (both correlations either positive or negative). Only that monkey showed a statistically significant interaction between groove width and speed on roughness classification performance. This additional finding adds weight to the argument that SII cell firing rates influenced monkey roughness classifications.

Computed Effect of Rub-Groove Size on Stepped Labyrinth Seal Performance

A numerical study was undertaken to explore the effects of the size of wear-in rub grooves that are typically cut into the abradable land of stepped labyrinth seals. The elliptic form of the 2-D axisymmetric Navier-Stokes equations for compressible turbulent flow were solved. The relationships among the friction coefficient, the leakage Reynolds number, the groove depth and width and the pre-rub radial clearance were examined. It was found that the standard k-ε turbulence model and wall functions are effective for computing the friction coefficient and leakage for labyrinth seals with honeycomb land surfaces, both with and without the presence of rub grooves. The so-called rub grooves are the result of labyrinth teeth cutting wear grooves into the abradable surface of the land (stationary housing of the seal). Furthermore, it was found that the case of a small pre-rub tooth radial clearance, a wide rub groove and an intermediate step height is the most sensitive to the presence of a rub groove, with a leakage increase over the no-groove case of about 100 percent and 194 percent for the shallow and deep grooves, respectively. It was also found, for example, that the leakage varied with pre-rub clearance and groove width, in order from lowest to highest leakage, as: (a) small clearance and narrow groove, (b) small clearance and wide groove, (c) large clearance and narrow groove and (d) large clearance and wide groove.