Impact-Induced Fracture

Numerical simulation of a complex dynamic fracture application can be illustrated by calculations of impact induced damage in a ceramic cylinder. The computer model used was originally developed for oil shale explosive fragmentation (Grady and Kipp, 1980), with various extended applications considered by Boade et al. (1981) and Chen et al. (1983). In this model, stress and strain are related through... 

A low velocity impact induces various types of damage in fiber reinforced laminated composite structures. In addition to the visible or barely visible indentation on the impacted surface and cracking on the back surface, the most prevalent damage inside a laminated composite includes delamination, matrix cracking, fiber/matrix interfacial debonding, and fiber fracture (see Figure 1.1) [3]. 

Figure 1.4 Low velocity impact induced delamination, debonding, and shear fracture in the laminated skin and balsa wood core...

In addition to speed, a number of other factors could impact the fracture strength of solder joints, including surface finish, pad size, ball diameter, ball metallurgy, and pad construction. All these need to be taken into account when comparing ball shear data across different packages. Another important factor that could impact the force-to-failure and the failure modes induced is the time after reflow. It is preferable to perform the test as early as possible after reflow. ... 

The preliminary impact test results are shown in Figure 4a. The plots show the evolution of impact-induced damage with time (i.e. plastic deformation, fatigue wear and fracture) throughout the test. The height of the surface is recorded with sub-nm precision when the probe is on the surface. 

A cube corner indenter was used to test these observations and to more easily induce fractures. The cube comer indenter is sharper (higher contact pressure) and the 90 degree angle means that the instantaneous contact strain under the probe on impact is much greater than for the spherical probe. 

PARTICLE IMPACT DAMAGE AND POINT LOAD-INDUCED FRACTURE BEHAVIOR IN ZIRCONIA PLASMA SPRAY COATING FILM... 

Particle Impact Damage and Point Load-Induced Fracture Behavior... 

Chang, K.H. and Siddique, Z., "Re-Engineering and Fast Manufacturing for Impact-Induced Fatigue and Fracture Problems in Aging Aircrafts," Final Report, AFOSR Grant F49620-02-1-0336, January 31, 2006. 

Jansen, J.-D., van den Hoek, P.J., Zwarts, D., Ai-Masfry, R., Hustedt, B., and van Schijndei, L. 2008. Behaviour and impact of Dynamic induced Fractures in Waterflooding and EOR. Paper 08-135 presented at the 42nd U.S. Rock Mechanics Symposium (USRMS), San Francisco, 29 June-2 July. 

Irradiation-induced embrittlement, modifications of impact, and fracture toughness properties... 

Mechanical treatment alone may be sufficient to induce significant decomposition such processes are termed mechanochemical or tribo-chemical reactions and the topic has been reviewed [385,386]. In some brittle crystalline solids, for example sodium and lead azides [387], fracture can result in some chemical change of the substance. An extreme case of such behaviour is detonation by impact [232,388]. Fox [389] has provided evidence of a fracture initiation mechanism in the explosions of lead and thallium azide crystals, rather than the participation of a liquid or gas phase intermediate. The processes occurring in solids during the action of powerful shock waves have been reviewed by Dremin and Breusov [390]. 

Osteoporosis is currently defined as a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Bone strength reflects the integration of two main features bone density and bone quality (NIH Consensus 2001). Thus, osteoporosis is a debilitating condition of the skeleton that propends to fractures and is associated with advanced age. The disease has a high prevalence in western countries, as it is a condition associated with advanced age, and it is on the rise since fife expectancy has risen dramatically in the last several decades. It is, therefore, a major public health problem because it not only induces morbidity (fractures and chronic sequelae) with a substantial impact on health-related quality of life, but is also associated with increased mortality (Badia et al. 2001, 2004). 

Impact modifiers for PET are generally elastomeric compounds that increase impact strength and elongation while usually decreasing modulus. An effective way to enhance the impact strength and to induce a brittle/ductile transition of the fracture mode, is by the dispersion of a rubber phase within the PET matrix. The... 

Brief History. B.W., a 75-year-old woman, fell at home and experienced a sudden sharp pain in her left hip. She was unable to walk and was taken to a nearby hospital where x-ray examination showed an impacted fracture of the left hip. The patient was alert and oriented at the time of admission. She had a history of arteriosclerotic cardiovascular disease and diabetes mellitus, but her medical condition was stable. The patient was relatively obese, and a considerable amount of osteoarthritis was present in both hips. Two days after admission, a total hip arthroplasty was performed under general anesthesia. Meperidine (Demerol) was given intramuscularly as a preoperative sedative. General anesthesia was induced by intravenous administration of thiopental (Pentothal) and sustained by inhalation of halothane (Fluothane). The surgery was completed successfully, and physical therapy was initiated at the patient s bedside on the subsequent day. 

Table 3. The toughness improvement induced by the -modification, rationalized in terms of the ratio Gt0t(/ -nuclcalcd)/Gtot (non-nucleated), is markedly stronger for the series tested under biaxial conditions. As both sets of investigated samples were injection molded, the skin-core structure (discussed in Sect. 3.2.3) could be inferred to be at least partly responsible for this feature. This was, however, confirmed in a recent work, where impacted /3-PP samples (tested at 5 ms-1, T = 23 °C and - 20 °C) with or without skin layers showed the same fracture performance within the limits of the experimental error [116].

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