Impact of Wedge Effect on Outcomes of Intertrochanteric Fractures Treated with Intramedullary Proximal Femoral Nail

The purpose of this study is to investigate the risk factors for wedge effect and its relevance between blade cut-out in patients with intertrochanteric fractures (ITF) treated with proximal femoral nail antirotation II (PFNA-II). A total of 113 patients with ITF treated with PFNA-II between 2012 and 2016 were retrospectively analyzed. Radiographic variables including preoperative fracture pattern, fracture classification, lateral wall fracture, and postoperative neck–shaft angle (NSA), femoral offset (FO), blade cut-out, and Parker’s ratio were measured for analysis. An average of 4.16° of varus malalignment in NSA and 5.5 mm of femoral shaft lateralization in FO was found post-operatively. The presence of lateral wall fracture was significantly related to post-operative varus change of NSA (p < 0.05). After at least one year of follow up, the blade cut-out rate was 2.65% (3/113), and Parker’s ratio was significantly higher in patients with blade cut-out (p = 0.0118). This study concluded that patients with ITF-present preoperative lateral wall fracture and postoperative higher Parker’s ratio in AP radiography showed higher incidence of wedge effect that might increase risk of blade cut out.

Using FEM to Assess the Effect of Orthodontic Forces on Affected Periodontium

Orthodontic treatment in patients with no periodontal tissue breakdown vs. horizontal bone loss should be approached with caution even though it can bring significant benefits in terms of periodontal recovery and long-term success. We used the finite element method (FEM) to simulate various clinical scenarios regarding the periodontal involvement: healthy with no horizontal bone loss, moderate periodontal damage (33%) and severe horizontal bone loss (66%). Afterwards, forces of different magnitudes (0.25 N, 1 N, 3 N, and 5 N) were applied in order to observe the behavioral patterns. Through mathematical modeling, we recorded the maximum equivalent stresses (σ ech), the stresses on the direction of force application (σ c) and the displacements produced (f) in the whole tooth–periodontal ligament–alveolar bone complex with various degrees of periodontal damage. The magnitude of lingualization forces in the lower anterior teeth influences primarily the values of equivalent tension, then those of the tensions in the direction in which the force is applied, and lastly those of the displacement of the lower central incisor. However, in the case of the lower lateral incisor, it influences primarily the values of the tensions in the direction in which the force is applied, then those of equivalent tensions, and lastly those of displacement. Anatomical particularities should also be considered since they may contribute to increased periodontal risk in case of lingualization of the LLI compared to that of the LCI, with a potential emergence of the “wedge effect”. To minimize periodontal hazards, the orthodontic force applied on anterior teeth with affected periodontium should not exceed 1 N.

Effect of angular speed of cam on oil film variation in the line contact thermal EHL of a cam-tappet pair

Purpose The influence of the cam angular speed on the pressure, film thickness and temperature profiles at some selected angular positions together with the oil characteristics are investigated. Design/methodology/approach A high-order polynomial cam is used, and thermal elastohydrodynamic lubrication (EHL) calculations are carried out by the multi-grid method and line-line scanning technique. Findings It is found that the film thickness decreases with a decrease in angular speed. The depth of the dimple that occurred in the reverse motion is also reduced because of the recession in the “temperature–viscosity wedge” effect. Originality/value It is revealed that the reduction in the cam angular speed makes the classical big surface dimple evolve into a small centralized dimple during the opposite sliding motion. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0327

CONTROLLABLE TEMPERATURE AND VISCOSITY WEDGE EFFECT IN FLUID FRICTION BEARINGS: RESULTS OF PHYSICAL EXPERIMENTS AND DESIGN OF A DIGITAL TWIN

The paper considers the use of lubricants with different temperatures and multi-zone supply of liquid for lubrication. The best lubrication combinations were identified, and graphical images of sensors were presented for better analysis. A simulation model of the rotary support system is designed, which also includes models of motion sensors and converters.

Investigation on the Strain Distribution in Tube High-Pressure Shearing

The Finite-element method (FEM) and experiments were used to investigate the geometric factors and material parameter on the strain distribution during tube high-pressure shearing (t-HPS). The results show that t-HPS could be realized successfully either by pressurizing on both ends of the tube, or by pressurizing using the wedge effect; and in both cases, the “dead metal zone” could be found at both ends of the tube. The grain size distribution from the experiment confirmed this strain distribution feature. In the case of t-HPS pressurized using the wedge effect, the half cone angle has little effect on the strain distribution. Decreasing the strain-hardening exponent leads to increased deformation inhomogeneity in both the ideal t-HPS described by theoretical equations and the close to practical t-HPS described by FEM. This feature of t-HPS stands out from other SPD processes like HPT, and makes practical t-HPS behavior more predictable using the analytical formation than any other SPD processes, and places it an advantageous position in understanding the basics of deformation physics through the coupling between practical experiments and theoretical approaches.