Effect Of Mechanical Impact Research Articles

Effect of mechanical impact on the microstructure and IR spectra of cohesive soil

The aim of the study is to determine the correlations between mechanical impacts on clay soil samples and resulting changes in the microstructure of the samples and their IR spectra. For research, soil from a railway subgrade under construction in the Azov-Black Sea region was used. The soil was examined by traditional and modern physical methods and classified as light clay. Clay properties were modified by adding alabaster to the soil, after which the samples with different amounts of alabaster were subjected to mechanical load. A cyclic mechanical impact by the compression method was applied to a clay sample without alabaster, an equivalent to the passage of 400 freight trains along the railway track. The microstructure of samples was studied by electron microscopy which allowed determining the microstructure parameters of the fragments of samples before and after the mechanical action. Samples of clay and clay with the addition of alabaster were subjected to a semi-quantitative express analysis by IR spectroscopy, as a result of which the concentrations of minerals were determined with an accuracy of no worse than 10%. Clay and clay samples with the addition of alabaster were subjected to static uniaxial compression, after which the samples were examined by IR spectroscopy. Comparison of the results of spectral and compression studies made it possible to investigate the correlations between changes in the peak intensities of the IR spectra bands and the concentration of alabaster, as well as the strength properties of the soil.

Nucleation in supercooled water triggered by mechanical impact: Experimental and theoretical analyses

Supercooling is one of the major drawbacks that hinder the wide application of phase change thermal storage technology, where supercooling needs to be suppressed, or nucleation triggered at desired supercooling or time. The disturbance of mechanical impact can effectively promote nucleation. However, up to now, its nucleation mechanism has not been well explained, and the corresponding nucleation triggering technology has not been reasonably developed. In this paper, the effect of mechanical impact in supercooled water on nucleation is investigated experimentally by impact rod falling freely to hit the bottom of container. The nucleation temperature under impact at different heights of free fall are measured. The results show that 80% supercooling reduction can be achieved by a low impact energy of 0.007 J. In addition, we modify the existing model based on the experimental data to develop a revised model, which can estimate the impact stimulus required to trigger nucleation at desired supercooling. Moreover, the nucleation mechanism under impact based on classical nucleation theory is analyzed. By comparing the changes in pre-exponential factor and nucleation barrier with and without impact, the enhancement in nucleation rate under impact can be explained as a reduction on the free energy barrier for nucleation. Our experimental and theoretical analysis results preliminarily reveal the impact nucleation mechanism, which are expected to promote more in-depth research on the related topics. These results could also better serve to predict whether nucleation will occur in the supercooled water under mechanical impact, and to actively trigger nucleation or suppress supercooling as needed through mechanical impact.

Calcaneal quantitative ultrasound analysis in korean and japanese elite female athletes

The relationships between bone properties and cumulative mechanical impact were examined in elite female athletes (N=70) and age, gender matched non-athlete controls (N=64). The athletes were divided into 3 groups, namely, high-impact (HI: body weight bearing with high mechanical loading, N=18), medium-impact (MI: body weight bearing with medium load, N=36), and low-impact (LI: body weight bearing with low load, N=16). Effects of mechanical impact on quantitative ultrasonography (QUS) parameters, including speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI), were assessed using a multiple linear regression model adjusted for age, body weight, height, body mass index, and impact. We found that BUA was positively influenced by MI (P < 0.05). SOS was negatively influenced by LI (P < 0.05). SI was positively influenced by MI (P < 0.05). In conclusion, the bone qualities in elite female athletes differ depending on their cumulative impacts.

Effect of mechanical impact and friction treatment on the microstructure of TIG welding surface

Effect of mechanical impact and friction treatment on the microstructure of TIG welding surface

Cryomilling-induced solid dispersion of poor glass forming/poorly water-soluble mefenamic acid with polyvinylpyrrolidone K12

The effect of mechanical impact on the polymorphic transformation of mefenamic acid (MFA) and the formation of a solid dispersion of mefenamic acid, a poor glass forming/poorly-water soluble compound, with polyvinylpyrrolidone (PVP) K12 was investigated. The implication of solid dispersion formation on solubility enhancement of MFA, prepared by cryomilling, was investigated. Solid state characterization was conducted using powder X-ray diffraction (PXRD) and Fourier-transform infrared (FTIR) spectroscopy combined with crystal structure analysis. Apparent solubility of the mixtures in pH 7.4 buffer was measured. A calculation to compare the powder patterns and FTIR spectra of solid dispersions with the corresponding physical mixtures was conducted. Solid state characterization showed that (1) MFA I transformed to MFA II when pure MFA I was cryogenically milled (CM); and (2) MFA forms a solid dispersion when MFA was cryogenically milled with PVP K12. FTIR spectral analysis showed that hydrogen bonding facilitated by mechanical impact played a major role in forming solid dispersions. The apparent solubility of MFA was significantly improved by making a solid dispersion with PVP K12 via cryomilling. This study highlights the importance of cryomilling with a good hydrogen bond forming excipient as a technique to prepare solid dispersion, especially when a compound shows a poor glass forming ability and therefore, is not easy to form amorphous forms by conventional method.

Failure Mechanism Analysis of Electromagnetic Relay under Mechanical Impact

The aim was to analyze failure mechanism of electromagnetic relay caused by mechanical impact. The principle of electromagnetic relays was studied and the effect of mechanical impact on electromagnetic relays was analyzed in this paper. Based on the established magnetic circuit model, the relationship of the magnetic field strength, the electromagnetic attraction and the impact damage degree was studied. Then, the damage intensity of mechanical impact on magnetic circuit was decided. Afterwards, the structure of electromagnetic relays was improved, and the mechanical impact simulation was studied by ANSYS. The results show that the uncontrollability of electromagnetic relay is mainly caused by air gap, which is aroused by mechanical impact; in addition, the size of air gap is inversely proportional to electromagnetic attraction force. Moreover, the improved structure of relays can increase impact resistance and broaden the scope of engineering application of electromagnetic relay.

Electromagnetoelastic behavior induced by a crack under antiplane mechanical and inplane electric impacts

Based on the piezoelectromagnetism theory, the dynamic problem of a crack of finite length embedded in a polarized ceramic under the action of antiplane mechanical impact and inplane electric impact is considered. The basic equations are simplified to two decoupled wave equations. Integral transform techniques are employed to reduce the associated initial-boundary value problem to integral equations. By using numerical methods, the resulting integral equations are solved and dynamic field intensity factors are presented graphically. A comparison of the dynamic results and the quasi-static results for dynamic field intensity factors near the crack tips is made, and the effect of mechanical impact on the dynamic magnetic field intensity factor is examined.

The thermal effect of piezoelectric medium for anti-plane problem under high electrical impact loading

In present paper, the anti-plane problem of thermal effect near crack tip region of piezoelectric material subjected to electrical impact loading is investigated by means of the integral transforms and the singular integral equations. By introducing the thermal power, the temperature field near crack tip is finally obtained on the basis of the hypotheses of the uncoupling between the thermal field and the electro-mechanical fields and the adiabatic approximation. The numerical results indicate that a high temperature field of small region near crack tip is deduced when high electrical impact load is applied. Moreover, the results show that the temperature field strongly depends on crack size. However, the thermal effect of mechanical impact comparing with electrical impact may almost be neglected.

The influence of mechanical impact and storage conditions on subsurface hardening in pre-peeled potatoes (Solanum tuberosum L.)

In investigating the effect of mechanical impact and storage conditions on subsurface hardening in boiled pre-peeled potatoes, potatoes (cv. Sava) were peeled using an industrial peeler, a laboratory knife peeler or a hand knife peeler, packed in polymer bags and stored at 4 to 18 °C for 6 days. Industrially peeled potatoes were significantly harder than potatoes peeled by hand or using a laboratory knife peeler. Potato hardening was not related to pectin methyl esterase activity (EC 3.1.1.11.). However, it was significantly correlated with mechanical impact from the peeler knives and by treatment in a damage barrel. Blunt knives resulted in harder potatoes than when sharp knives were used. An increase in storage temperature from 4 to 18 °C also increased subsurface hardening significantly. Maximum hardness was found below the wounded surface at a depth of 2–8 mm (average 4 mm).