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In this paper, in order to reduce the indentation rolling resistance of a belt conveyor and improve its operation efficiency, the indentation rolling resistance of a belt conveyor is studied. Firstly, the theoretical calculation of the indentation rolling resistance caused by the contact between a conveyor belt and an idler is studied. Additionally, the expression of the indentation rolling resistance including the multi-element Maxwell relaxation modulus is simplified and deduced using the assumption of small deformation, and the steps of iterative calculation of the indentation rolling resistance through setting the initial values are designed. Then, the multi-component Maxwell relaxation modulus function of the conveyor belt tested in the previous work of the authors is substituted into COMSOL 5.6 finite element software, and the stress distribution caused by the contact between the conveyor belt and the idler under different working conditions is analyzed. Also, a series of measures to reduce the indentation rolling resistance are found through the laws presented by the simulation results. Finally, the experimental study of the indentation rolling resistance is carried out using the indentation rolling resistance testing device from our research group. By comparing the experimental results for the indentation rolling resistance under different working conditions with the theoretical calculation results for the indentation rolling resistance, it was found that the relative error was less than 13%, which proved the feasibility of the indentation rolling resistance and relaxation modulus testing method, as well as the theoretical calculation method for indentation rolling resistance. [ABSTRACT FROM AUTHOR]

Viscoelastic materials are applied in several fields, and their relaxation characteristics are intricately related to the failure mechanism of sealing components and the generation of indentation rolling resistance in belt conveyors. Therefore, it is imperative to explore the relaxation characteristics of viscoelastic materials using characterization models. This article focuses on exploring these characterization models and the indentation rolling resistance of viscoelastic materials. The research comprises the following aspects: (1) A 2N + 2 element generalized Maxwell constitutive model is proposed for the relaxation behavior of viscoelastic materials to address the limitations of conventional relaxation models. (2) We conducted numerical calculations based on the relaxation modulus to solve the relaxation spectrum using several relaxation spectrum models. The findings showed that the model parameters were dependent on the testing time range. (3) The relationship between the indentation rolling resistance and relaxation model parameters was evaluated based on the theoretical foundation of the indentation rolling resistance calculation. [ABSTRACT FROM AUTHOR]

Viscoelastic parameters of viscoelastic materials should be measured to ensure their effective use. Unfortunately, devices for effective and accurate measurement of the relaxation modulus of materials are not currently available. In this study, we designed a mechanical device that can control the spherical indenter to press on the material at a uniform speed to allow measurement of the relaxation modulus of a viscoelastic material. The results showed that the device is accurate and easy to operate. The load expressions of ramp loading (the motion of the indenter is a uniform velocity) and ramp-constant loading (the motion of the indenter is stationary after uniform velocity) were derived for the spherical indenter. The relaxation modulus function of the material was calculated by measuring the displacement and load of the indenter and fitting it using the non-negative least square method. The relaxation modulus expression of viscoelastic materials calculated using the ramp loading experiment was substituted into the derived load expression of ramp-constant loading. The values were compared with the load values obtained using the ramp-constant loading experiment and the error was evaluated. The error was less than 2.5%, indicating high feasibility and practicability of the experimental device designed in this study. [ABSTRACT FROM AUTHOR]

Viscoelastic materials are widely used in various fields. In order to better use viscoelastic materials in various working conditions, it is necessary to master the material properties of viscoelastic materials. Relaxation modulus is a characterization method of viscoelastic material properties. In this paper, by analyzing that viscoelastic materials are time-domain related parameters, the load-time curves are obtained by using the spherical indentation instrument to carry out the ramp loading indentation test at different speeds. According to the law of ramp strain history loading, the data at different velocities are summarized and a method for judging the linear viscoelastic boundary of viscoelastic materials in spherical indentation tests is obtained. Aggregate the load-time data at different speeds to obtain a set of valid data for a longer period of time. A method of measuring the relaxation modulus using the ramp-constant strain history is proposed. Compared with the ramp loading test method, it is simple and easy to operate, and it can make up for the short time period of the measured data in the ramp loading test. The experiment verifies the feasibility of the method of ramp-constant strain history. [ABSTRACT FROM AUTHOR]

A novel chemo-photodynamic combined therapeutic self-assembly polymeric platform (MPEG-Hyd-Br2-BODIPY) was constructed based on 2,6-diBr-BODIPY as the photosensitizer core and MPEG as the hydrophilic side chain through hydrazone bond linkage which can successfully encapsulate DOX and exhibited an accelerated release rate with decreasing pH value from 7.4 to 5.0 which results in considerable time/dose-dependent cytotoxicity. In addition, the photosensitizer moieties embedded in MPEG-Hyd-Br2-BODIPY could generate singlet oxygen (1O2) effectively under light irradiation, which was expected to realize the synchronization therapy of chemo- and photodynamic therapy (PDT). [ABSTRACT FROM AUTHOR]

A formula based on Winkler foundation and generalized viscoelastic Maxwell model of belt backing material has been given by Thomas J Rudolphi to determine the indentation rolling resistance. However, this formula must be solved by the iteration. As a result, the influence of some common working conditions can be reflected indirectly on this formula that results in the formula not being useful practically. On the other hand, the formula which is developed by Jonkers can reflect firstly the effect of working condition directly except for belt speed, but this formula has an inherent deficiency where Jonkers assumes that the indentation depth is independent of the belt speed. However, if the vertical load is assumed to be constant then the indentation depth and the contact will decrease with increasing belt speed in nature. Therefore, it offers an advantageous reference for simplifying the Rudolphi’s formula to get an analytic formula which can exhibit the influence of working condition on the rolling resistance. In this paper, author analyzes the effect of common working conditions on rolling resistance with the help of Rudolphi’s formula firstly. Then, in the premise of satisfying the suitable precision, author simplifies the Rudolphi’s formula to get an analytic formula. Finally, a verification example based on experiment is given to validate the rationality of analytic formula which may be of interest to belt-conveyor designers. [ABSTRACT FROM AUTHOR]

Contact stiffness is an important parameter for describing the contact behavior of rough surfaces. In this study, to more accurately describe the contact stiffness between grinding surfaces of steel materials, a novel microcontact stiffness model is proposed. In this model, the novel cosine curve-shaped asperity and the conventional Gauss distribution are used to develop a simulated rough surface. Based on this simulated rough surface, the analytical expression of the microcontact stiffness model is obtained using contact mechanics theory and statistical theory. Finally, an experimental study of the contact stiffness of rough surfaces was conducted on different steel materials of various levels of roughness. The comparison results reveal that the prediction results of the present model show the same trend as that of the experimental results; the contact stiffness increases with increasing contact pressure. Under the same contact pressure, the present model is closer to the experimental results than the already existing elastic–plastic contact (CEB) and finite-element microcontact stiffness (KE) models, whose hypothesis of a single asperity is hemispherical. In addition, under the same contact pressure, the contact stiffness of the same steel material decreases with increasing roughness, whereas the contact stiffness values of different steel materials under the same roughness show only small differences. The correctness and accuracy of the present model can be demonstrated by analyzing the measured asperity geometry of steel materials and experimental results. [ABSTRACT FROM AUTHOR]

A novel near-infrared fluorescent probe TM2 based on a rhodamine-bearing framework was disclosed with a large Stokes shift (100 nm). TM2 exhibits highly selective recognition for Cu 2+ in EtOH/H 2 O (1 : 1, v/v) solution with a low detection limit (2.3 μM) and a wide detection range (0-50 μM). Detection of Cu 2+ is undisturbed at physiological pH levels of 5-9. This recognition mechanism is attributed to the formation of a 1 : 1 complex between TM2 and Cu 2+ , validated by Job's plot, 1 H NMR titration, and LC-MS experiments. Moreover, the successful fluorescence imaging of Cu 2+ both in vitro and in vivo was also accomplished.