Effect of Mineral Oil on the Mechanical Properties and Fractographs of Fe_3(Al,Cr,Zr) Intermetallic Alloy

The effect of mineral oil on the mechanical properties and fractographs of Fe3(Al,Cr,Zr) in termetallic alloy has been investigated. The results show that the tensile ductility of the Fe3(Al,Cr,Zr) alloy tested in oil is comparable with the results obtained in oxygen and is in sensitive to strain rate. The fracture mode of the Fe3(Al,Cr,Zr) alloy treated at 700℃/1.5 h and tested in oil, is cleavage and with dimples in some areas.

Spalling fracture mechanism of granite subjected to dynamic tensile loading

Rocks are likely to undergo spalling failure under dynamic loading.The fracture development and rock failure behaviours were investigated during dynamic tensile loading.Tests were conducted with a split-Hopkinson pressure bar(SHPB)in four different impact loading conditions.Thin sections near failure surfaces were also made to evaluate the growth patterns of fractures observed by polarizing microscope.Scanning electron microscopy(SEM)was used to observe mineral grains on failure surfaces and to evaluate their response to loading and failure.The results indicate that the number of spalling cracks increases with increase in peak impact loads and that quartz sustains abundant intergranular fracturing.Cleavage planes and their direction relative to loading play a vital role in rock strength and fracturing.Separation along cleavage planes perpendicular to loading without the movement of micaceous minerals parallel to loading appears to be unique to the rock spalling process.

Influence of mineral fillers on the rheological response of polymer-modified bitumens and mastics

The rheological properties of the bituminous components （bitumen and bituminous mastic） within asphalt mixtures contribute significantly to the major distresses of flexible pavements （i.e. rutting, fatigue and low temperature cracking）. Asphalt mixtures are usually composed of mastic-coated aggregates rather than pure bitumen-coated aggre- gates. The purpose of this study is to investigate the effects of mineral fillers on the theological behaviour of several polymer-modified bitumens （PMBs） through laboratory mixing. A neat bitumen and two types of polymers （elastomeric and plastomeric） were used to produce PMBs, and two fillers with different minerals （limestone and basalt） were selected to obtain mastics. The dynamic shear rheometer （DSR） and bending beam rheometer （BBR） were used to characterize the theological properties of PMBs and mastics. In particular, multiple stress creep recovery （MSCR） tests were performed to evaluate the rutting potential at high temperatures, whereas BBR tests were carried out to investigate the low temperature behaviour of these materials. BBR results for unmodified mastics show that the increase of stiffness is similar regardless of the filler type, whereas results for polymer-modified mastics indicate that the degree of stiffening depends on the combi- nation of filler/polymer types. MSCR results show that adding filler leads to a reduced susceptibility of permanent deformation and an enhanced elastic response, depending on the combination of filler/polymer types. Overall results suggest that a physical-chemical interaction between the filler and bitumen occurs, and that the interaction level is highly dependent on the type of polymer modification.