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Impact Load (impact + load)

Distribution by Scientific Domains

Polymers and Materials Science	37%
Engineering	37%

Selected Abstracts

Nondestructive Evaluation of Elastic Properties of Concrete Using Simulation of Surface Waves

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2008
Jae Hong Kim
In this study, to evaluate information of a surface waveform beyond the simple wave velocity, artificial intelligence engines are employed to estimate simulation parameters, that is, the properties of elastic materials. The developed artificial neural networks are trained with a numerical database having secured its stability. In the process, the appropriate shape of the force,time function for an impact load is assumed so as to avoid Gibbs phenomenon, and the proposed principal wavelet-component analysis accomplishes a feature extraction with a wavelet transformed signal. The results of estimation are validated with experiments focused on concrete materials. [source]

High-pressure short time behavior of traction fluids

LUBRICATION SCIENCE, Issue 1 2006
Nobuyoshi Ohno
Abstract The squeeze film formation ability of traction fluids is studied under impact load by dropping a steel ball-bearing against a flat anvil made of mild steel. The effect of the pressure,viscosity coefficient and of the viscosity is investigated for plastic impact. The depth difference between the lubricated surface dent and the dry dent increases linearly with the product ,, of the pressure,viscosity coefficient , and the viscosity ,. The importance of the lubricant parameter ,, is observed under the squeeze film formation ability from contact voltage or elastohydrodynamic lubrication central film thickness measurement at rolling condition. The intensity of each impact collision is measured by means of an acoustic emission (AE) sensor. The high-pressure short-time solidification of traction fluids was confirmed by dent analysis after the impact tests and AE analysis under impact loads. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Microabrasion of Coatings Investigated by the Inclined Impact Test at Various Loads under Dry and Lubricated Conditions

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Konstantinos-Dionysios Bouzakis
Abstract The impact test has clearly emerged as an important technology for the prediction of cohesive, adhesive, and fatigue failure of coatings, further enabling the establishment of Smith and Woehler diagrams of PVD films. In the present paper, the abrasive wear of a well-adherent (Ti46Al54)N coating was investigated by the inclined impact test, at impact loads higher, equal to or lower than the fatigue critical impact load of the applied film. These investigations were conducted for few thousands up to several millions of impacts both under dry and lubricated conditions. The obtained results suggest that the inclined impact test is a very efficient method for detecting coating resistance against impact microabrasion, with or without lubrication and according to the test conditions for the synchronous contribution of fatigue phenomena to the film wear. [source]

Calcium signaling leads to mitochondrial depolarization in impact-induced chondrocyte death in equine articular cartilage explants

ARTHRITIS & RHEUMATISM, Issue 7 2007
C. A. M. Huser
Objective Chondrocyte apoptosis is an important factor in the progression of osteoarthritis. This study aimed to elucidate the mechanisms involved upstream of caspase 9 activation and, in particular, calcium signaling and mitochondrial depolarization. Methods Articular cartilage explants obtained from healthy horses were subjected to a single impact load (500-gm weight dropped from a height of 50 mm) and cultured in vitro for up to 48 hours. Chondrocyte death was quantified by the TUNEL method. Release of proteoglycans was determined by the dimethylmethylene blue assay. Weight change was measured, and mitochondrial depolarization was determined using JC-1 staining. To assess the role of calcium signaling in impact-induced chondrocyte death, explants were preincubated in culture medium containing various concentrations of calcium. Inhibitors were used to assess the role of individual signaling components in impact-induced chondrocyte death. Results Calcium quenching, inhibitors of calpains, calcium/calmodulin-regulated kinase II (CaMKII), and mitochondrial depolarization reduced impact-induced chondrocyte death after 48 hours in culture. Transient mitochondrial depolarization was observed 3,6 hours following a single impact load. Mitochondrial depolarization was prevented by calcium quenching, inhibitors of calpain, CaMKII, permeability transition pore formation, ryanodine receptor, and the mitochondrial uniport transporter. Cathepsin B did not appear to be involved in impact-induced chondrocyte death. The calpain inhibitor prevented proteoglycan loss, but the percentage weight gain and proteoglycan loss were unaffected by all treatments used. Conclusion Following a single impact load, calcium is released from the endoplasmic reticulum via the ryanodine receptor and is taken up by the mitochondria via the uniport transporter, causing mitochondrial depolarization and caspase 9 activation. In addition, calpains and CaMKII play important roles in causing mitochondrial depolarization. [source]

Experimental and numerical studies on dynamic crack growth in layered slate rock under wedge impact loads: part II , non-plane strain problem

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2007
M. R. ALAM
ABSTRACT Dynamic crack propagation in non-plane strain (or 3D) slate blocks under wedge impact loads was investigated numerically in this part of the paper. A parabolic-shaped crack trajectory was taken into consideration to model the crack propagation in slate blocks for analyzing the impact splitting of layered slate rock. Major and minor axes of the parabola were determined from the condition of equal mode I stress intensity factors (SIFs) along the crack front. Mode I SIFs were determined for experimental breaking loads for each increment of crack growth in a manner similar to that mentioned in part I of this paper. These values were compared with the plane strain material fracture toughness value obtained from experimental studies and very good agreement was obtained between them, for the case of actual load applied on the specimen. Numerical analysis of a field problem, i.e., separation of a large-sized slate slab from the rock strata in a slate quarry using wedge impacting, was also carried out in this paper. It can be observed that a large magnitude of load is required to break large-sized slate blocks; but this load is applied through a number of smaller load-capacity actuators-in-parallel, requiring large power capacity for the hydraulic pumps. However, this required power could be reduced considerably if the load applied on the line of hydraulic actuators is cascaded across the (line of) actuators (starting from centrally placed actuators) with a small time delay (equal to the initial crushing time in slate rock). [source]

Generation of bioaerosols during manual mail unpacking and sorting

JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2005
H. Brandl
Abstract Aims:, The dynamics of bioaerosol generation in specific occupational environments where mail is manually unpacked and sorted was investigated. Methods and Results:, Total number of airborne particles was determined in four different size classes (0·3,0·5, 0·5,1, 1,5 and >5 ,m) by laser particle counting. Time dependent formation of bioaerosols was monitored by culturing methods and by specific staining followed by flow cytometry. Besides handling of regular mail, specially prepared letters (,spiked letters') were added to the mailbags to deliberately release powdered materials from letters and to simulate high impact loads. These letters contained various dry powdered biological and nonbiological materials such as milk powder, mushrooms, herbs and cat litter. Regarding the four size classes, particulate aerosol composition before mail handling was determined as 83·2 ± 1·0, 15·2 ± 0·7, 1·7 ± 0·4 and 0·04 ± 0·02%, respectively, whereas the composition changed during sorting to 66·8 ± 7·9, 22·3 ± 3·6, 10·4 ± 4·0 and 0·57 ± 0·27%, respectively. Mail processing resulted in an increase in culturable airborne bacteria and fungi. Maximum concentrations of bacteria reached 450 CFU m,3, whereas 270 CFU of fungi were detected. Conclusions:, Indoor particle concentrations steadily increased during mail handling mostly associated with particles of diameters >1 ,m. However, it was not possible to distinguish spiked letters from nonspiked by simple particle counting and CFU determinations. Significance and Impact of Study:, The dynamics of bioaerosol generation have to be addressed when monitoring specific occupational environments (such as mail sorting facilities) regarding the occurrence of biological particles. [source]