Slip Propensity Research Articles

The Effects of 10% Front Load Carriage on the Likelihood of Slips and Falls

The objective of the present study was to evaluate if anterior load carriage would increase the likelihood of slips or falls while walking over a slippery floor surface. The study hypothesized that anterior load carriage may alter spatial-temporal characteristics, such as heel contact velocity, walking velocity (i.e., the whole body center-of-mass velocity), and step length, as well as friction demand characteristics at shoe-floor interface. Additionally, the study hypothesized that alterations in these gait parameters may influence slip initiation characteristics while ambulating over a slippery floor surface. Total of 10 subjects participated in the study: 5 younger (18-28 yr old) and 5 older adults (65 and older). A mixture was used to manipulate the coefficient of friction (COF) of the floor surface. All participants were unexpectedly introduced to a slippery surface while walking with and without a load. To evaluate slip severity, slip distance I and II were evaluated to assess whether a subject fell or not. Three-way repeated measure ANOVA (mix-factor design) was performed: Age factor: between-subject, Load and Floor factors: within-subject. Overall, older adults' heel contact velocity was slower while carrying a load. Additionally, all participants exhibited shorter SL while carrying a load. No significant friction demand characteristic differences were observed for all subjects while carrying a 10% front load. The results from the present study suggest that carrying 10% of the body weight in front should not intensify the slip propensity and severity although appears to influence spatial-temporal gait characteristics.

Influence of Localized Muscle Fatigue of the Knee Joint on Gait Parameters Related to Slip Propensity

Existing epidemiological evidence suggests that localized muscle fatigue might be considered as an intrinsic risk factor that causes lack of balance control leading to falls. The goal of the study was to examine how localized muscle fatigue of the knee joint (quadriceps) alters gait parameters that are related to slip propensity. Sixteen healthy young participants were recruited to walk across a vinyl floor surface in two different sessions (Fatigue and No fatigue). Kinematic and kinetic data were collected using a three-dimensional video analysis system and force plates during both sessions. The fatigue session results indicated a substantial increase in heel contact velocity (HCV) and required coefficient of friction (RCOF), as well as a decrease in the transitional acceleration of the whole body COM (TA), walking velocity (WV), and step length (SL). In addition, a positive correlation was observed between RCOF and HCV. These findings provide new insights into the biomechanical relationship between localized muscular fatigue and gait parameters linked with slip propensity. The study concluded that localized muscular fatigue affects gait parameters and hence can be considered as a potential risk factor for slip-induced falls.

Fatigue-crack growth in 2090 AlLi alloy

The fatigue-crack growth kinetics of the 12.7 mm thick 2090-T8E41 alloy plate vary significantly with plate thickness location. The apparent fatigue-crack growth rates in the midthickness location are substantially lower than those in the surface region at intermediate and high applied stress intensity ranges. The lower crack growth rates are related to the extraordinarily tortuous fatigue profile which induces high crack closure levels. Such a tortuous crack profile appears to be primarily a consequence of the alloy's intense crystallographic texture and its great propensity for planar slip.

Hydride habit planes in titanium-aluminum alloys

The habit plane of hydride precipitates in pure Ti has been previously reported as being predominantly the {10-10} prism plane, with precipitation also taking place on {10-11} planes, while habit planes in a Ti-3 pet Al alloy were {10-11} {11-21} and {10-12}. No habit planes near the basal plane have been reported in Ti alloys, although the {10-17} plane (14 deg from the basal plane) has been observed in certain zirconium alloys. In this work, Ti single crystals containing up to 6.6 wt pet Al were charged with hydrogen and the ef-fect of Al on hydride habit plane observed with both transmission and optical microscopy. Hydrides with a basal and near-basal habit plane were found in the higher Al content al-loys and it is suggested that the increased propensity for basal slip in these alloys is the reason for the change in habit plane. The implications of these observations in under-standing hydrogen induced fracture in Ti alloys are discussed, and possible modifica-tions to the conclusions of other investigators in this field suggested.

Slip character and the ductile to brittle transition of single-phase solids

Abstract A transition from brittle to ductile behaviour of single-phase polycrystals is shown experimentally to be a consequence of a change in slip character rather than of a change in yield stress. In the case of a b.c.c. Fe-Co alloy, deformation by planar glide induces brittleness, whereas the alloy is ductile if it deforms exclusively by wavy glide. For a series of copper-base solid solutions loaded in mercury, the degree of embrittlement increases with planarity of glide. The Cottrell-Petch equation can account for such behaviour provided the appropriate parameter, k y, is re-considered in terms of the number of operable slip systems and the propensity for cross slip.