Effects of tool positioning on joint interface microstructure and fracture strength of friction stir lap Al-to-steel welds

Friction stir lap welding (FSLW) experiments have been conducted to study the effects of tool positioning on microstructures formed in the Al-to-steel interface region and on joint strength, defined as maximum applied force over the width (F m/w s) of the test sample, of the welds. Various pin positioning and speed conditions were used in the FSLW experiments followed by microstructure examination on the interface regions and tensile-shear testing on the welds, including an examination on crack propagation in mixed stir zone. It was found that when the pin was close to the bottom steel piece, Al-to-steel reaction occurred resulting in intermetallic outbursts formed along the interface. This represents the case of incomplete metallurgical joint. When the pin was lowered to just reach the steel, a thin and continued interface intermetallic layer formed. Evidences and consideration on growth kinetics have suggested that the layer could only remain thin (≤2.5 μm) during FSLW. This layer could bear a high load during tensile-shear testing and the adjacent aluminium deformed and fractured instead. The resulting F m/w s was high. When the pin penetrated to steel, F m/w s reduced due to brittle fracture being dominant inside mixed stir zone. Evidences have shown that the amount of penetration and speed condition during FSLW do not have large effects on F m/w s.

Quantification of sensitization in AA5083-H131 via imaging Ga-embrittled fracture surfaces

Sensitization of 5xxx series Al alloys involving precipitation of β phase (Mg2Al3) at grain boundaries was studied for different exposure times at 100°C upon AA5083-H131 (UNS A95083). In this work, we reveal that fracture surfaces prepared by liquid gallium embrittlement can yield a quantification of grain boundary β phase with significant statistics on β phase size and spacing. This information is a necessary first step toward development of quantitative damage models to describe inter-granular corrosion (IGC) and stress corrosion (IGSCC).

Osteopaenia - a marker of low bone mass and fracture risk

Areal bone mineral density is commonly categorised into normal bone mineral density, osteopaenia and osteoporosis on the basis of nominal thresholds recommended by the World Health Organization. However, bone mineral density is a continuous variable and there is a strong association between lower bone mineral density and greater risk for fracture. Fracture risk is not negligible in persons with moderate deficits in bone mineral density. Although absolute fracture risk is greatest for individuals with osteoporosis, more than half of the fractures arise from those with osteopaenia, and even normal bone mineral density, a probable consequence of greater numbers of individuals at risk in these categories. However, areal bone mineral density measurements used commonly in clinical practice do not detect differences in bone tissue properties, geometry and microarchitecture, which contribute to bone strength. Newer technologies such as high-resolution peripheral computed tomography have the advantage of assessing trabecular and cortical components of bone separately, in addition to geometric characteristics of the skeleton. Quantifying these parameters and considering clinical risk factors that affect fracture risk independent of bone quantity and quality, may better discriminate between high- and low-risk individuals. This would improve the decision-making for targeting appropriate interventions, either lifestyle or medication, to reduce thepublic health burden of fractures.

Personal and psychosocial impacts of clinical fracture in men

Background : Little is known about the personal burden of fracture across the age spectrum, particularly in men. This study aimed to document the impact of clinical fracture on men's participation in employment, sports and outdoor recreation, mobility, handiwork, activities of daily living, home modification, and utilisation of community and health services.

Methods : This prospective study followed 196 men with incident fracture identified from radiology reports at the Geelong Hospital during the period July 2006 to December 2007 and examined personal and psychosocial impacts 12 months post-fracture, using a self-report questionnaire.

Results : Of all men identified with fracture, 40% took time off work. All fractures, except those to the upper limbs, had considerable impact on mobility. Inability to drive was associated with all fractures, but was most common with ankle fractures and most prolonged with hip fractures. Loss of confidence was reported by over one-third of all fracture cases, even 12 months after the fracture event. All fractures affected activities of daily living, and this was generally most prolonged for fractures of the hip. Similarly, all men with fracture utilised community and health services, even for the relatively minor fractures of the finger/thumb.

Conclusions : This study supports previous reports of the personal impact of hip fracture, and presents data about the consequences of upper and lower limb fractures and the generally poorly described sequelae of fractures of the finger/thumb and foot/toe. These observations have important implications for post-fracture care and rehabilitation in men.

Polyalanine repeat polymorphism in RUNX2 is associated with site-specific fracture in post-menopausal femals

Runt related transcription factor 2 (RUNX2) is a key regulator of osteoblast differentiation. Several variations within the RUNX2 gene have been found to be associated with significant changes in BMD, which is a major risk factor for fracture. In this study we report that an 18 bp deletion within the polyalanine tract (17A>11A) of RUNX2 is significantly associated with fracture. Carriers of the 11A allele were found to be nearly twice as likely to have sustained fracture. Within the fracture category, there was a significant tendency of 11A carriers to present with fractures of distal radius and bones of intramembranous origin compared to bones of endochondral origin (p = 0.0001). In a population of random subjects, the 11A allele was associated with decreased levels of serum collagen cross links (CTx, p = 0.01), suggesting decreased bone turnover. The transactivation function of the 11A allele showed a minor quantitative decrease. Interestingly, we found no effect of the 11A allele on BMD at multiple skeletal sites. These findings suggest that the 11A allele is a biologically relevant polymorphism that influences serum CTx and confers enhanced fracture risk in a site-selective manner related to intramembranous bone ossification.

Direct comparison of eight national FRAX® tools for fracture prediction and treatment qualification in Canadian women

The authors compared the calibration of FRAX tools from Canada, the US (white), UK, Sweden, France, Australia, New Zealand, and China when used to assess fracture risk in 36,730 Canadian women. Their data underscores the importance of applying country-specific FRAX tools that are based upon high-quality national fracture epidemiology.