Papers by Author: Yang Wang

Abstract: The compressive behavior of ME20M alloy along rolling direction (RD) at a wide strain rates under low temperatures is investigated in this paper. Compressive stress-strain results reveal that the effect of strain rate on yield strength and flow stress is not obvious, especially at low temperatures. Moreover, the temperature plays an important role in compressive responses. SEM observations indicate that brittle fracture is the main fracture mode at low strain rate, and ductile fracture occurs in the failure of the alloy at high strain rate.

Abstract: The mechanical responses of Ti-5Al-2.5Sn alloy at low temperatures were investigated under quasi-static and dynamic tensile loads using MTS system and SHTB system, respectively. Tensile stress-strain curves were obtained over the temperature range of 153 to 298K and the rate range of 0.001 to 1050 s^-1. Experimental results indicate that the tensile behavior of Ti-5Al-2.5Sn alloy is dependent on strain rate and temperature. Yield stress and flow stress increase with increasing strain rate and decrease with increasing temperature. Results also indicate that strain hardening rate of Ti-5Al-2.5Sn alloy is lower at high strain rate, while strain hardening rate varies little with testing temperature. The Khan-Huang-Liang constitutive model was chosen to characterize the tensile responses of Ti-5Al-2.5Sn alloy at low temperatures and different strain rates. The model results coincide well with the experimental results within the tested temperature and rate ranges.

Abstract: Uniaxial tension tests for filled silicone rubber were performed at high strain rates using a split Hopkinson tension bar system. Quasi-static tension tests were carried out using an Instron-E3000 material test system. The grip fixture was designed to reliably connect the tensile specimen with the incident/transmitted bars. The method to increase the signal-noise ratio of the stress pulse in the transmitted bar was proposed. The effect of specimen gage length-to-width ratio on the stress-strain responses was experimentally studied. The suitable specimen geometry was determined by means of experimental investigation and finite element analysis. The automated grid method was used to capture the deformation information of the tensile specimen. Experiments indicate that the tension responses of silicone rubber exhibit the apparent hyper-elastic and rate-dependent characteristics. The values of tensile modulus increase with the increase of strain rate. The stress at a given elongation increases with the increase of strain rate.

Abstract: Titanium alloys have received great interest in the engineering applications requiring light weight and high impact resistance components. It is necessary to understand the mechanical properties of titanium alloys at high strain rates and various temperatures in the structural design. In the present paper, uniaxial tension tests at strain rates of 190, 500 and 1150s^-1 and temperatures of 20, 150, 300°C are carried out using a modified split hopkinson tension bar system to investigate the effects of strain rate and temperature on tension behavior of the Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy. Experimental results indicate that the alloy has the rate and temperature sensitivity and still keeps high strengths and toughness at temperature up to 300°C under high strain rate. SEM observations reveal that ductile fracture is the major fracture mode when the alloy is deformed at high strain rates.

Abstract: In penetration problems, the heterogeneity of the concrete would affect the ballistic responses. The presented paper studied the influence by numerical method. During the analysis, the concrete was defined as “numerical concrete”, which was composed with different size aggregates randomly included in the mortar. In the numerical concrete, the ITZ (interfacial transition zone) was replaced with the connected strength (tensile strength and shear strength). Based on the validation of the mesh, the ballistic responses were studied. From the study, it was concluded that: the randomly-distributed aggregates affected the stress symmetry which changed the missile trace, which couldn’t be alternated by concrete in the homogeneous model, and that the residual velocity of the missile decreased with the increase of the connected strength of the interfaces.

Abstract: The effect of temperature and strain rate on the mechanical behavior and microstructure evolution of Near Gamma Ti-46.5Al-2Nb-2Cr (NG TiAl) was investigated at temperatures ranging from room temperatures to 840 under strain rates of 0.001, 320, 800 and 1350s-1. The TEM analysis indicated that deformation twinning and stacking fault are the main deformation modes under dynamic loadings and dislocation slip is another important deformation mode under quasi-static loadings. The density of deformation twinning and/or stacking fault increases with the increased temperature and strain rate.