High speed fracture

Burya, A. I., Kozlov, G. V., Sviridenok, A. I., Malamatov, A. Kh. (1999). The Fractal Characteristics of High Density Polyethylene in High-Speed Fracture Conditions. Dokla-dyNANBelarusi,43(i , 117-119. 

Bramuzzo, M. (1989) High speed fracture mechanics by photography of polypropylene copolymers. Polym. Eng. Sci., 29, 1077. 

Examination of oven-aged samples has demonstrated that substantial degradation is limited to the outer surface (34), ie, the oxidation process is diffusion limited. Consistent with this conclusion is the observation that oxidation rates are dependent on sample thickness (32). Impact property measurements by high speed puncture tests have shown that the critical thickness of the degraded layer at which surface fracture changes from ductile to brittle is about 0.2 mm. Removal of the degraded layer restores ductiHty (34). Effects of embrittled surface thickness on impact have been studied using ABS coated with styrene—acrylonitrile copolymer (35). 

The measurement of mechanical properties is a major part of the domain of characterisation. The tensile test is the key procedure, and this in turn is linked with the various tests to measure fracture toughness... crudely speaking, the capacity to withstand the weakening effects of defects. Elaborate test procedures have been developed to examine resistance to high-speed impact of projectiles, a property of civil (birdstrike on aircraft) as well as military importance. Another kind of lest is needed to measure the elastic moduli in different directions of an anisotropic crystal this is, for instance, vital for the proper exploitation of quartz crystal slices in quartz watches. 

Abstract The fracture properties and microdeformation behaviour and their correlation with structure in commercial bulk polyolefins are reviewed. Emphasis is on crack-tip deformation mechanisms and on regimes of direct practical interest, namely slow crack growth in polyethylene and high-speed ductile-brittle transitions in isotactic polypropylene. Recent fracture studies of reaction-bonded interfaces are also briefly considered, these representing promising model systems for the investigation of the relationship between the fundamental mechanisms of crack-tip deformation and fracture and molecular structure. 

Beguelin P, Kausch H-H (1995)Techniques for high speed testing. In Williams JG, Pavan A (eds) Impact and dynamic fracture of polymers and composites. Mechanical Engineering Publications, London... 

When extrusion is carried out at high speeds, distortion of extrudates may occur it may be attributable to melt fracture (known also as elastic... 

Percussion is a repetitive solid body impact, such as experienced by print hammers in high-speed electromechanical applications and high asperities of the surfaces in a gas bearing. Repeated impacts result in progressive loss of solid material. Percussive wear occurs by hybrid wear mechanisms, which combine several of the following mechanisms adhesive, abrasive, surface fatigue, fracture, and tribochemical wear.75... 

Photograph of brittle fracture from high speed movie (3,000 frames/sec).119... 

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