http://nopr.niscpr.res.in/handle/123456789/32140 2026-10-12T20:56:51Z http://nopr.niscpr.res.in/handle/123456789/32181 Title: Impact damage assessment in composite structures based on multiwavelet analysis of modal shapes Authors: Katunin, A Abstract: The low-velocity impact damage of composite structures is an important problem in various industrial branches, especially in the aircraft and aerospace industriess. Due to the nature of impact damage initiation and propagation and its poor ability of detection based on surface inspection, the appropriate non-destructive damage assessment methods need to be developed. One of the extensively developed groups of methods is the technique based on modal testing and further processing of modal shapes using wavelet analysis. <span style="mso-ansi-language:EN-US" lang="EN-US">Since the wavelet analysis is very sensitive to even small abrupt changes in an analyzed signal, this approach is chosen for extraction of diagnostic information. In the following study, the novel approach based on multiwavelet analysis of modal shapes, achieved from measurements using a laser vibrometer, is applied to the composite plates damaged <span style="mso-ansi-language:EN-US" lang="EN-US">following various scenarios. Based on the comparative study, the Donovan-Geronimo-Hardin-Massopust multiwavelet is selected as the best for evaluation of damage sites. The proposed algorithm makes possible detection and localization of cracks and accompanying delaminations, resulted from the impact loading, with high precision, which is verified by comparison with ultrasonic C-scans of the analyzed plates. The obtained results allow for application of the presented method in the industrial non-destructive testing as well. </span></span> Page(s): 451-459 2015-08-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/32180 Title: Machinability of NdFeB magnet via wire and sinking EDM methods Authors: Li, Li; Cheng, Xiang; Sima, Zhongwen; Niu, Zongwei Abstract: NdFeB magnet is widely used in many industries due to their powerful magnetic properties. However, it belongs to hard-to-machine material because of its mechanical characteristics. Electrical discharge machining (EDM) is an alternative competitive process to machine any material with high hardness and low flexural strength. Machinability and surface characteristics of EDMed NdFeB magnet surfaces are poorly understood. Wire EDM and sinking EDM with Cu-SiC electrode are explored the machining characteristics. Surface roughness, surface topography, surface alloying, and material removal efficiency have been characterized. Results show that EDM is an effective method to machine NdFeB magnet. The machined quality could be modified with the multiple cuts at reduced discharge energy in wire EDM. Six-sigma distribution of <i>R</i>_a in rough cut mode is different from that of trim cut modes. Electrode alloying to the work-piece can be negligible by using low discharge energy. The low toughness of NdFeB magnet would be the major contributing factor to the appearance of microcracks. The fabricated Cu-SiC electrode has better performance in terms of MRR and surface roughness. Page(s): 407-413 2015-08-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/32179 Title: Development of composites for dental implants obtained by ultrasonic mixture of TiH₂ powder and colloidal calcium phosphate Authors: Gemelli, Enori; Nery, Fabio; Camargo, Nelson Heriberto Almeida; Henriques, Vinicius André Rodrigues; Junior, Nelson Levandowski; Silva, Daiara Floriano da Abstract: <span style="mso-ansi-language:EN-US" lang="EN-US">Titanium-based composites with calcium and phosphor phases are prepared by ultrasound and powder metallurgy processing with TiH₂ and hydrated calcium phosphate powders. The mixtures are performed by ultrasound in water, dried by atomization process in flame, pressed at 600 MPa and vacuum-sintered at 1200°C for 2 h. Crystal phases of the as-fabricated composites are found to be α<span style="mso-ansi-language:EN-US" lang="EN-US">-Ti, CaTiO₃ and Ti_xP_y phase(s). The Ti_xP_y and CaTiO₃ phases resulted from the reaction between titanium and tricalcium phosphate at about 1130°C. The as-fabricated composites presented higher compressive strength than the yield stress of pure cast titanium and lower contact angles than vacuum-sintered TiH₂. Contact angles are further decreased by a chemical treatment. </span></span> Page(s): 443-450 2015-08-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/32178 Title: Effects of stacking fault energy on the deformation mechanisms and mechanical properties of Cu and Cu alloys processed by rolling at different temperatures Authors: Cai, Baozhuang; Ren, Shiying; Zhou, Shitong; Li, Peng; Lv, Weiwei; Tao, Jingmei; Zhu, Xinkun Abstract: The effects of stacking fault energy (SFE) on the deformation mechanisms and mechanical properties of Cu, Cu-2.5 at.% Al-2.5 at.% Zn, and Cu-12.1 at.% Al-4.1 at.% Zn alloys processed by different rolling temperatures have been systematically investigated. Tensile tests at room temperature indicate that, as SFE decreased, strength and ductility increased, and at constant SFE the samples deformed via rolling at liquid nitrogen temperature (77 K) exhibit higher strength and better ductility than those deformed via rolling at room temperature (293 K). With lowering SFE, the crystallite size decreases while the microstrain, dislocations and twin densities increase. With decreasing temperature, there is a transition of deformation mechanism from that dominate by dislocation activities to that dominate by deformation twinning. The results indicate that decreasing SFE is an optimum method for improving the ductility of Cu and Cu alloys without loss of strength, and that temperature plays a key role in the rolling process. Page(s): 399-406 2015-08-01T00:00:00Z