Toe-in and toe-out gait modifications have received increasing attention as an effective, conservative treatment for individuals without severe osteoarthritis because of its potential for improving knee adduction moment (KAM) and knee flexion moment (KFM). Although toe-in and toe-out gaits have positive effects on tibiofemoral (TF) joint pain in the short term, negative impacts on other joints of the lower extremity may arise. The main purpose of this study was to quantitatively compare the effects of foot progression angle (FPA) gait modification with normal walking speeds in healthy individuals on lower-extremity joint, ground reaction force (GRF), muscle electromyography, joint moment, and TF contact force. Experimental measurements using the Vicon system and multi-body dynamics musculoskeletal modelling using OpenSim were conducted in this study. Gait analysis of 12 subjects (n = 12) was conducted with natural gait, toe-in gait, and toe-out gait. One-way repeated measures of ANOVA (p < 0.05) with Tukey’s test was used for statistical analysis. Results showed that the toe-in and toe-out gait modifications decreased the max angle of knee flexion by 8.8 and 12.18 degrees respectively (p < 0.05) and the max angle of hip adduction by 1.28 and 0.99 degrees respectively (p < 0.05) compared to the natural gait. Changes of TF contact forces caused by FPA gait modifications were not statistically significant; however, the effect on KAM and KFM were significant (p < 0.05). KAM or combination of KAM and KFM can be used as surrogate measures for TF medial contact force. Toe-in and toe-out gait modifications could relieve knee joint pain probably due to redistribution of TF contact forces on medial and lateral condylar through changing lateral contact centers and shifting bilateral contact locations.

Indentation size effect (ISE) is a critical feature for investigating the local properties of materials using the indentation test method. Although there are numerous works on the indentation response, there is a lack of data in the literature on the association between nanoindentation and uniaxial compression. Herein this study, uniaxial compression tests combined with Digital Image Correlation Technique are conducted on Ti6Al4V alloy with a focus on investigating the elastic–plastic properties and obtaining the accurately constitutive relation. Then, an ISE model of Ti6Al4V is established based on this constitutive relation and strain gradient theory. Indentation hardness, predicted by this proposed model, agrees well with the measurement by nanoindentation experimental techniques. This model can be used to bridge the gap between the uniaxial stress–strain and the depth‐dependent hardness, and clarifies the effect of the strain hardening on indentation hardness. The significance of this model is that it provides a direct and reasonable theory foundation to investigate ISE by uniaxial compression, and promotes the potential application of nanoindentation.

Indentation pop‐in behavior of CoCrFeNiAl0.1, CoCrFeNiAl0.3, and CoCrFeNiAl0.6 high‐entropy alloys (HEAs) at different loading rates is investigated using instrumental nanoindentation. Experimental results show that the increase in either loading rate or the aluminum atomic content (Alx) of the alloy all have a reducing effect on the pop‐in behavior on the load–displacement curve. Meanwhile, both conditions exert a lagging effect on the triggered depth of the first pop‐in event and significantly affect the bursting width. The first pop‐in event is characterized using the previous phenomenological model and the effects of loading rate and Alx are quantitatively analyzed through combining the elastic deformation energy prior to the first pop‐in and the energy dissipation during the indentation process. In addition, the activation volumes for pop‐in event are evaluated to be about 4–13 Ω much higher than that in pure metal, revealing the multiatom‐coordinated migration process in HEAs.

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