Buckle Fractures

Compressive forces in children can result in cortical bone buckling. These fractures, which are commonly also referred to as buckle or torus injuries, are incomplete and the cortex is intact (Fig. 8.6a,b). Torus is derived from the Latin meaning a protuberance or knot and typically involves both cortical surfaces, while a buckle fracture may only involve a... 

Fig. 8.6a,b. Torus or buckle fracture of the distal radial metaphysis... 

Overall, the fifth metatarsal is the most frequently injured but patterns are age dependent. Children under 5 years age have a higher proportion of first metatarsal fractures (Owen et al. 1995). A buckle fracture of the first metatarsal in young children is commonly known as the bunk bed fracture because of its frequent occurrence in children who have sustained a fall from an upper bunk (Oesterich and Crawford 1985). 

Fig. 19.21. A 7-year-old boy punched his brother, sustaining a transverse buckle fracture of the index metacarpal neck...

Fig. 19.33. Scaphoid views of the wrist performed in a 12-year-old boy show a dorsal buckle fracture of the radius...

Torus (or buckle) fractures can be managed with either a padded bandage or a wrist splint. A cast is... 

Recall from discussion of the structural design process in Section 7.2 that reconfiguration of the structure is an essential step. Reconfiguration occurs either to increase the capability or to decrease the weight because the structure has more than adequate capability. The term ca-pabi/ity s meant to include margin of safety relative to fracture, adequate resistance to buckling, sufficient difference of excitation frequency from resonant frequencies, etc. 

The most common conditions of possible failure are elastic deflection, inelastic deformation, and fracture. During elastic deflection a product fails because the loads applied produce too large a deflection. In deformation, if it is too great it may cause other parts of an assembly to become misaligned or overstressed. Dynamic deflection can produce unacceptable vibration and noise. When a stable structure is required, the amount of deflection can set the limit for buckling loads or fractures. 

In many cases, a product fails when the material begins to yield plastically. In a few cases, one may tolerate a small dimensional change and permit a static load that exceeds the yield strength. Actual fracture at the ultimate strength of the material would then constitute failure. The criterion for failure may be based on normal or shear stress in either case. Impact, creep and fatigue failures are the most common mode of failures. Other modes of failure include excessive elastic deflection or buckling. The actual failure mechanism may be quite complicated each failure theory is only an attempt to explain the failure mechanism for a given class of materials. In each case a safety factor is employed to eliminate failure. 

In unidirectional cloth specimens the fracture mode was essentially compressive there was compressive shear at lower temperatures and buckling after the peak, but tensile fracture apparently became dominant at moderate temperatures. For bidirectional cloth specimens the fracture is almost controlled by tension but it shifts to compressive shear and then to buckling at higher temperatures. 

Kgure 10.2. Schematic view of the three regions of the force-displacement curve of a typical cellular solid I, small deformation of the intact structure II, buckling and fracture of cell walls and III, compaction of what is increasingly collapsed cell wall material. 

Even if the Al Oj interlayer accelerates the activation of the transverse cracking, it seems to have the opposite effect on adhesion failure. Indeed, we observe for both systems with an Al Oj interlayer (B and E) that the debonding and buckling are delayed. Therefore, the adhesion of the films is improved. The presence of this thermally grown Al Oj interlayer increases the interfacial fracture energy values to about 15 J.m in both systems. Two qualitative explanations can be proposed for the adhesion improvement. First, the Al Oj certainly permits an increase in the number of 0-Si bonds between the interlayer and the film. Second, prior to the... 

Interfacial fracture energy determination associated with the decohesion and buckling process. 

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