The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Zohre Ahmadi - One of the best experts on this subject based on the ideXlab platform.
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optimization of effective parameters on thermal shock resistance of zrb2 sic based composites prepared by sps using taguchi design
Materials Chemistry and Physics, 2017Co-Authors: Zohre Balak, M Azizieh, Hosein Kafashan, Zohre AhmadiAbstract:Abstract Thermal shock optimization of ZrB2-SiC-based composites is the main goal of this research. Different additives such SiC, Cf, MoSi2, HfB2 and ZrC, SPS conditions (temperature, time and pressure) and milling time of Cf were chosen as survey factors. Each of these factors was examined on four levels to obtain the optimum levels. So, according to very high experimental runs (49), Taguchi design was applied. Spark plasma sintering (SPS) was used for sintering. Repeated thermal shock test was carried out on all composites. One cycle consisted of heating up to 1500C, holding for 15 min in this temperature and quenching to water. This cycle was conducted for each composite till the Initiation of Crack was observed by optical microscopy. Then, Taguchi design was applied to determine the effect of each factor and their optimum level on thermal shock resistance.
Meng Zhang - One of the best experts on this subject based on the ideXlab platform.
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high cycle fatigue and ratcheting interaction of laser powder bed fusion stainless steel 316l fracture behaviour and stress based modelling
International Journal of Fatigue, 2019Co-Authors: Meng Zhang, Xiang Zhang, Ju Wei, David HardacreAbstract:Abstract Variations in the physical and mechanical properties of parts made by laser power bed fusion (L-PBF) could be affected by the choice of processing or post-processing strategies. This work examined the influence of build orientation and post-processing treatments (annealing or hot isostatic pressing) on the fatigue and fracture behaviours of L-PBF stainless steel 316L in the high cycle fatigue region, i.e. 104–106 cycles. Experimental results show that both factors introduce significant changes in the plastic deformation properties, which affect fatigue strength via the mechanism of fatigue-ratcheting interaction. Cyclic plasticity is characterised by hardening, which promotes mean stress insensitivity and improved fatigue resistance. Fatigue activities, involving the Initiation of Crack at defects and microstructural heterogeneities, are of greater relevance to the longer life region where the global deformation mode is elastic. As the simultaneous actions of ratcheting and fatigue generate complex nonlinear interactions between the alternating stress amplitude and mean stress, the fatigue properties could not be effectively predicted using traditional stress-based models. A modification to the Goodman relation was proposed to account for the added effects of cyclic plasticity and was demonstrated to produce good agreement with experimental results for both cyclic hardening and softening materials.
Konstantin Y. Volokh - One of the best experts on this subject based on the ideXlab platform.
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Cracks in rubber
International Journal of Solids and Structures, 2008Co-Authors: Pavel A. Trapper, Konstantin Y. VolokhAbstract:The onset of Crack propagation in rubber is studied computationally by using the softening hyperelasticity approach. The basic idea underlying the approach is to limit the capability of a material model to accumulate energy without failure. The latter is done by introducing a limiter for the strain energy density, which results from atomic/molecular considerations and can be interpreted as the average bond energy or the failure energy. Including the energy limiter in a constitutive description of material it is possible to enforce softening and, consequently, allow tracking the onset of structural instability corresponding to the onset of material failure. Specifically, Initiation of Crack propagation is studied in the case of a thin sheet of a rubber-like solid under the hydrostatic tension. The large deformation neo-Hookean material model enhanced with the energy limiter is used for finding the critical tension corresponding to the onset of static instability of the sheet, i.e. the onset of fracture propagation. The influence of the Crack sharpness and length on the critical load is analyzed. It is found that material is sensitive to the Crack sharpness when the shear modulus is significantly greater than the average bond energy. The sensitivity declines when the value of the shear modulus approaches the value of the failure energy. Roughly speaking, softer materials are less sensitive to Cracks than more brittle materials where the brittleness is defined as a ratio of the shear modulus to the failure energy. It is also found that the critical tension is proportional to the inverse square root of the Crack length for more brittle materials. The latter means that the Griffith theory based on the linearized elasticity is also applicable to softer materials undergoing large deformations. Unfortunately, the applicability of the Griffith theory is restricted to Cracks with equivalent sharpness only.
Zohre Balak - One of the best experts on this subject based on the ideXlab platform.
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optimization of effective parameters on thermal shock resistance of zrb2 sic based composites prepared by sps using taguchi design
Materials Chemistry and Physics, 2017Co-Authors: Zohre Balak, M Azizieh, Hosein Kafashan, Zohre AhmadiAbstract:Abstract Thermal shock optimization of ZrB2-SiC-based composites is the main goal of this research. Different additives such SiC, Cf, MoSi2, HfB2 and ZrC, SPS conditions (temperature, time and pressure) and milling time of Cf were chosen as survey factors. Each of these factors was examined on four levels to obtain the optimum levels. So, according to very high experimental runs (49), Taguchi design was applied. Spark plasma sintering (SPS) was used for sintering. Repeated thermal shock test was carried out on all composites. One cycle consisted of heating up to 1500C, holding for 15 min in this temperature and quenching to water. This cycle was conducted for each composite till the Initiation of Crack was observed by optical microscopy. Then, Taguchi design was applied to determine the effect of each factor and their optimum level on thermal shock resistance.
David Hardacre - One of the best experts on this subject based on the ideXlab platform.
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high cycle fatigue and ratcheting interaction of laser powder bed fusion stainless steel 316l fracture behaviour and stress based modelling
International Journal of Fatigue, 2019Co-Authors: Meng Zhang, Xiang Zhang, Ju Wei, David HardacreAbstract:Abstract Variations in the physical and mechanical properties of parts made by laser power bed fusion (L-PBF) could be affected by the choice of processing or post-processing strategies. This work examined the influence of build orientation and post-processing treatments (annealing or hot isostatic pressing) on the fatigue and fracture behaviours of L-PBF stainless steel 316L in the high cycle fatigue region, i.e. 104–106 cycles. Experimental results show that both factors introduce significant changes in the plastic deformation properties, which affect fatigue strength via the mechanism of fatigue-ratcheting interaction. Cyclic plasticity is characterised by hardening, which promotes mean stress insensitivity and improved fatigue resistance. Fatigue activities, involving the Initiation of Crack at defects and microstructural heterogeneities, are of greater relevance to the longer life region where the global deformation mode is elastic. As the simultaneous actions of ratcheting and fatigue generate complex nonlinear interactions between the alternating stress amplitude and mean stress, the fatigue properties could not be effectively predicted using traditional stress-based models. A modification to the Goodman relation was proposed to account for the added effects of cyclic plasticity and was demonstrated to produce good agreement with experimental results for both cyclic hardening and softening materials.