Papers by Author: Jin Cheng Wang

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Authors: Zhong Ming Zhang, Bo Hu, Feng Tao Gao, Jin Cheng Wang
Abstract: MMCs can be usually fabricated by powder metallurgy, stir casting and spray co-deposition, etc. Al2O3/Al composites were produced by means of reciprocating extrusion with alumina and pure aluminum particulates in the present study. The microstructure was analyzed by scanning electronic microscope, and the mechanical properties were measured by hardness tester and universal testing machine, respectively. The results showed that Al2O3/Al composites with as high as 20 vol.% alumina can be successfully produced by reciprocating extrusion. During reciprocating extrusion process, the reinforced alumina particles can be fragmentized and uniformly distributed in the aluminum matrix. The tensile strength and hardness of the composites increase as volume fraction of alumina particles increases, whereas the elongation decreases. Compared with the pure aluminum compact, the tensile strength and hardness of the composite with 20 vol.% alumina particles is 29.3% and 93.5% higher, respectively; whereas the elongation decreases 66.6%, and the fracture mechanism of the composites is attributed to ductile rupture.
Authors: Jin Cheng Wang, Zhong Ming Zhang, Gen Cang Yang
Abstract: Experiments have been carried out to investigate the damping behaviors of commercially pure aluminum (L2) prepared by equal-channel angular pressing (ECAP). The damping characterization was conducted on a DMTA-V apparatus. The internal friction was measured at frequencies of 0.1, 0.3, 1.0, 4.0 and 8.0 Hz over the temperature range of 20~150°C. The measured damping capacity shows that ultra-fine grained structure pure Al (L2) prepared by ECAP has a damping capacity that is enhanced in comparison with coarse one, especially when the temperature is higher than 60°C. The dependence of the damping capacity at room temperature on the strain amplitude shows a nonlinear characteristic, and increases rapidly with the strain amplitude (0) when 0 is comparatively low. While the strain amplitude is higher than certain value, the damping capacity will become saturated slowly. The high damping capacity of the pure Al prepared by ECAP was attributed to the high density of dislocations and ultra-fine grained structure.
Authors: Jin Cheng Wang, M. Osawa, Tadaharu Yokokawa, Hiroshi Harada, Masato Enomoto
Abstract: A calculation of the interface energy for the Ni-Al binary alloy, including the inter-phase boundary (IPB) energy and the anti-phase boundary (APB) energy, has been performed using the Cluster Variation Method (CVM) with the tetrahedron approximation within the temperature range of 600°C~1300°C. The calculated IPB energies range between 8 and 13 mJ/m2, while the APB energies range between 24 and 46 mJ/m2. Additionally, the dependence of the average composition and the order parameter on distance with the compositionally diffuse interfacial regions has been computed. The calculation also shows the width of the diffuse IPB increases with the temperature linearly.
Authors: Di Qing Wan, Bo Lin He, Jin Cheng Wang, Gen Cang Yang
Abstract: An investigation on low frequency strain amplitude dependence damping characteristic of as-cast high damping Mg-based alloys continuously extending to microplastic strain was carried out. Two-stage damping behavior via strain amplitude was particularly reported. The first is the strain amplitude strongly dependent part due to breakaway loss and the second is the strain amplitude weakly dependent part due to microplastic deformation loss, which is also frequency dependent. The damping mechanism is discussed in detail.
Authors: Jin Cheng Wang, Si Hao Chen, Shan Zhong Xu, Ye Xue, Jian Zhong Lou
Abstract: With polylactic acid (PLA) resin as walls and capsaicin as core substances, microcapsules were prepared based on diphase emulsion method. The microcapsule characteristics such as the particle size, inner structure and properties were investigated. The morphology and size distribution of the microcapsules were analyzed by laser particle size analyzer and scanning electron microscopy (SEM). The microcapsules had a mean diameter of about 60~120 µm. In addition, their thermal properties were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was demonstrated that the melting point and thermal stability were improved or changed compared with that of the pure capsaicin. These phenomena were caused by the encapsulated PLA resin over the surface.
Authors: Zhong Ming Zhang, Jin Cheng Wang, Chun Jie Xu, Wei Ming Li, Gang Wang
Abstract: Damping capacities of the annealed nodular cast iron dense bar produced by horizontal continuous casting were measured by Dynamic Mechanical Analyzer. The relation of damping capacities with vibration amplitude, frequency and temperature was analyzed to investigate the damping mechanism of the alloy. The results show that the damping capacities increase with increasing temperature and frequency. The internal friction spectra exhibits two internal friction peaks at about 40°C and 150°C and caused by Snoek relaxation and Snoek-Köster relaxation, respectively. The maximum damping capacity can be obtained at about 63Hz. The damping is positive amplitude-dependent, whereas critical amplitude exists where the damping increases dramatically. The temperature-dependent damping results from the superposition effect of point-defect damping, grain boundary damping and interface damping, while dislocation damping is predominant in the frequency dependent damping. The amplitude dependent damping can be interpreted by G-L theory.
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