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Long-term outcomes of open treatment of condylar head fractures using cannulated headless bone screws—a retrospective analysis

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International Journal of Oral and Maxillofacial Surgery 2025年第7期54卷 598-606页

作者： Franke, A. Matschke, J.B. Sembdner, P. Seidler, A. McLeod, N.M.H. Leonhardt, H. Department of Oral and Maxillofacial Surgery University Hospital Carl Gustav Carus Dresden Technische Universität Dresden Dresden Germany Virtual Product Development Institute of Machine Elements and Machine Design TU Dresden Dresden Germany Oral and Maxillofacial Surgery University Hospitals Coventry and Warwickshire NHS Trust Coventry United Kingdom

The treatment of mandibular fractures affecting the condylar head (CHF) can be either closed or open. In the case of an open approach, the headless bone screw (HBS) is an option. This study was performed to investigate the efficacy of osteosynthesis with HBS using three-dimensional radiographic imaging and clinical evaluation over long-term follow-up. This was a single-centre retrospective study. Clinical parameters and three-dimensional radiographic scans were collected during follow-up, DICOM datasets were segmented, and model analysis was conducted. Forty-five patients who received a HBS and met the eligibility criteria were included. There were significant improvements in all clinical parameters (mouth opening, protrusion, laterotrusion;all P < 0.05) except for the laterotrusion of the unaffected side (P = 0.071). Mean volume and surface area changes (from postoperative (mean 1.9 days) to final follow-up (mean 1675 days)) were 127.2 mm³ and −22.4 mm², respectively, and were not statistically significant (P = 0.18 and P = 0.51). There were radiographic signs of condylar remodelling. Nine HBS in nine patients required removal due to the screw penetrating the articular surface of the healing condylar head. This single-centre retrospective study found good functional outcomes using HBS for CHF, with a screw removal rate of 20%. © 2025 The Authors

关键词： Bone screws Internal fracture fixation Mandibular condyle Mandibular fractures Open fracture reduction Three-dimensional imaging Traumatology

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Simulation of mild wear in spur gears

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WEAR 1997年第1-2期207卷 16-23页

作者： Flodin, A Andersson, S Machine Elements Department of Machine Design Royal Institute of Technology S-100 44 Stockholm Sweden

Mild wear in gears is in most cases a smooth process giving initially improved contact conditions followed by a very slow and mild wear process. In some cases the mild wear may cause unfavorable changes of the surface topography, giving non-uniform gear rate, increasing dynamic effects and perhaps more severe forms of tooth failures. The knowledge about the interactions between mild wear, dynamic effects and other severe failures is rather limited. This paper therefore treats mild wear of spur gears, how it can be simulated and the effects of the same on contact conditions. A numerical model for wear prediction of spur gears is developed. The model can adopt any wear model although in this paper the wear simulations are based on a generalized Archard's wear equation. The running conditions for gear tooth surfaces are particularly considered and the contact between the surfaces are modelled by Winkler's elastic foundation model. (C) 1997 Elsevier Science S.A.

关键词： gears mild wear simulation

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A NUMERICAL-METHOD FOR REAL ELASTIC CONTACTS SUBJECTED TO NORMAL AND TANGENTIAL LOADING

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WEAR 1994年第1-2期179卷 117-122页

作者： BJORKLUND, S ANDERSSON, S [a]Machine Elements Department of Machine Design The Royal Institute of Technology S-100 44 Stockholm Sweden

A numerical model has been developed for studies of the micro-slip phenomenon. Micro-slip is the local tangential displacements that appear in contacts subjected to normal and tangential loading. The model simulates three-dimensional elastic contacts between rough surfaces using Coulomb's law of friction as a condition for local sliding. The numerical solution uses small rectangular traction elements in which the tractions are assumed to be constant. General expressions for the surface displacements due to uniform tractions (in three directions) over such a rectangle are derived. The numerical results are compared with existing analytical theories for a smooth ball-plane contact. Simulation results for contacts between balls with rough surfaces and smooth planes are also presented. It is concluded that the surface roughness increases the tangential deformation compared with a smooth contact.

关键词： MICRO-SLIP ELASTIC CONTACTS ROUGHNESS

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THE INFLUENCE OF SURFACE-ROUGHNESS AND OIL VISCOSITY ON THE TRANSITION IN MIXED LUBRICATED SLIDING STEEL CONTACTS

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WEAR 1994年第1-2期174卷 71-79页

作者： ANDERSSON, S SALASRUSSO, E [a]Machine Elements Department of Machine Design Royal Institute of Technology S-100 44 Stockholm Sweden

The moving surfaces in all high performance machines are functionally potential critical points, which rely on mild running conditions with low friction and no or insignificant wear. However, sometimes a transformation from a mild to a severe state may occur which will lead to a rise in friction and a catastrophic increase in wear. This severe situation is often known as scoring, galling, scuffing or seizure depending on the appearance of the surfaces. In this study the influence of surface roughness and oil viscosity on the transition from the mild to the severe sliding condition is studied. It is found that the transition in lubricated sliding steel contacts running under mixed conditions is strongly dependent on surface roughness. The loading capability of a sliding contact may be increased considerably by smoothing the surface. Even marginal flattening of the asperities may give considerable effects. However, single scratches may change the situation, since a scratch on a smooth surface will increase the risk for transition to a local seizure or scoring sometimes ending in a total seizure.

关键词： Tribology

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SIMULATING FOLLOWER WEAR IN A CAM-FOLLOWER CONTACT

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WEAR 1994年第1-2期179卷 101-107页

作者： HUGNELL, A ANDERSSON, S [a]Machine Elements Department of Machine Design The Royal Institute of Technology S-100 44 Stockholm Sweden

Mild wear in a rolling-sliding contact may gradually worsen the contact conditions. The probability for surface fatigue will then increase due to changes in the surface topography. This phenomenon has been observed for cam-follower contacts in automotive engines. A simulation model of the wear of a follower based on the principal of single point observation has been developed. The wear is simulated using a modified version of Archard's wear equation. The simulation is carried out in steps, recalculating the pressures as the surface topography gradually changes. The results show good agreement with corresponding worn surfaces. It can be concluded that the simulation method presented here, using a modified Archard's wear equation, can be used to simulate the mild wear in a rolling-sliding contact. This work highlights the importance of including follower rotation in the wear simulation and the use of the single point observation method in the derivation of a wear simulation model.

关键词： CONTACT CAMS FOLLOWERS SIMULATED WEAR

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Simulation of the mild wear in a cam-follower contact with follower rotation

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WEAR 1996年第2期199卷 202-210页

作者： Hugnell, ABJ Bjorklund, S Andersson, S Machine Elements Department of Machine Design The Royal Institute of Technology S-100 44 Stockholm Sweden

Mild wear may have damaging effects on contacting components, when the material removal distorts component geometry. Surface pressures can then be redistributed in an unfavourable way which increases the probability for surface fatigue. Phenomena like this have been observed in an ordinary automotive cam-follower contact, The purpose of this work is to derive a simulation model for the mild wear in a cam-follower contact with follower rotation, The mild wear in such a contact is simulated using the principle of single point observation, The simulation model is based on a modified Archard's wear equation, After each simulation step the pressures are recalculated using the topographically changed surfaces. Three cases are studied: one where only follower wear is considered, one where only the cam wear is simulated and finally the case where both cam and follower wear is simulated, An FEM analysis of the follower was used to verify the infinite half plane assumption in the pressure calculations, The present work highlights the importance of including follower rotation in the wear simulation and the use of the single point observation method in the derivation of a wear simulation model. The results show that the case where only the cam is worn gives the lowest contact pressures, The case where only follower wear is considered is the most unfavourable when it comes tt, contact pressures and wear.

关键词： simulated wear contact mechanics cams followers

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Online instantaneous angular speed estimation from vibration on low-power embedded systems evaluated on a gas foil bearing use case

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Measurement: Sensors 2025年

作者： Kliemank, Martin Leonhard Rupprecht, Bernhard Ahmadzadeh, Majid Brederlow, Ralf Stahl, Karsten Liebich, Robert Vogel-Heuser, Birgit Gühmann, Clemens Chair of Electronic Measurement and Diagnostic Technology Technische Universität Berlin Germany Institute of Automation and Information Systems TUM School of Engineering and Design Technical University of Munich Germany Chair of Engineering Design & Product Reliability Technische Universität Berlin Germany Chair of Circuit Design TUM School of Computation Information and Technology Technical University of Munich Germany Institute of Machine Elements TUM School of Engineering and Design Technical University of Munich Germany

This study presents an algorithm for estimating the instantaneous angular speed (IAS) from vibrations in low-power embedded systems, evaluated on the use-case of a gas foil bearing. While there are numerous methods for IAS estimation, they have thus far only been evaluated using industrial-grade sensors and data acquisition systems with high computational resources. To boost the application of IAS estimation methods in embedded applications, like sensor-integrating machine elements, this paper highlights and evaluates an algorithm for low-power embedded systems. Theoretical analysis and benchmarks on various low-power microcontrollers demonstrate its feasibility for real-time application. Furthermore, evaluation with lower sampling rates and ADC resolutions confirms compatibility with small-scale sensors typical in embedded systems. For good performance, a typical Cortex-M4-based MCU (e.g. 1.12 ms estimation time using 1024 data points) and a sensor with 8-bit resolution and 6400 Hz sampling rate would suffice. These findings establish the algorithm's readiness for diverse embedded applications. © 2024

关键词： Microcontrollers

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Characterisation of wear in boundary lubricated spherical roller thrust bearings

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WEAR 1997年第1-2期208卷 194-203页

作者： Olofsson, U Machine Elements Department of Machine Design Royal Institute of Technology S-100 44 Stockholm Sweden

Wear of boundary lubricated spherical roller thrust bearings has been characterised qualitatively as well as quantitatively with 3-d surface measurements and 2-d form measurements respectively. Due to the curved contact surface in a spherical roller thrust bearing, the rollers will undergo sliding in the contact. For an unskewed roller there will be two points along each contact where the sliding velocity is zero. At all other points along the contact, sliding is present. The experimental results from the form measurements show that outside the zero-sliding points there is a significant change in surface profile due to wear. The results from 3-d surface measurements show that there are different wear mechanisms involved. Mild wear dominates at the start but for the long term tests, wear particles, presumably removed from the contacting surfaces, clearly influence the amount of wear. (C) 1997 Elsevier Science S.A.

关键词： wear boundary-lubrication spherical roller thrust bearing

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Wear simulation with the winkler surface model

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WEAR 1997年第1-2期207卷 79-85页

作者： Podra, P Andersson, S Machine Elements Department of Machine Design Royal Institute of Technology KTH S-10044 Stockholm Sweden

Recurrent calculations of contact pressure distribution are often the major difficulty in wear simulations of rubbing contacts. The pressure distribution changes with time, as a result of the wear and plastic deformation of the interacting surfaces. To calculate the pressure distribution in a contact, it is often necessary to use advanced numerical methods. One of the most powerful tools is the finite element method (FEM). However, the FEM-as is also the case with most other numerical methods used for contact problems-has the disadvantage of being quite time consuming. Therefore, the advantages and disadvantages of using the simple Winkler surface model in wear simulations have been studied. The Winkler model can be seen as a mattress with many springs with no lateral effects between them. The stiffness of the springs is a critical parameter, which is evaluated for different boundary conditions and cases. It is shown that the sum of the springs' volume deformations, called the 'deformed volume', can be used to simplify the determination of the contact pressure distribution in a contact. Wear simulations have been made with a Winkler surface model and compared with simulations made previously with an FEM model. The results show a very good agreement. (C) 1997 Elsevier Science S.A.

关键词： wear simulation contact pressure winkler surface model

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Fatigue life reduction due to wear in boundary lubricated spherical roller thrust bearings

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WEAR 1997年第1-2期207卷 74-78页

作者： Olofsson, U Machine Elements Department of Machine Design Royal Institute of Technology S-100 44 Stockholm Sweden

Due to the curved contact surface in a boundary lubricated spherical roller thrust bearing the rollers will undergo sliding in the contact. For an unskewed roller there will be at most two points along each contact where the sliding velocity is zero. At all other points along the contact sliding is present. Experimental results from measurements of the contacting surfaces show that outside the zero sliding points there is a significant change in the washer surface profile due to wear. An analytical method is used to determine how the surface profile change due to wear affects the fatigue life of the bearings. Fatigue life as predicted by this method shows a reduction of up to 80% for a bearing that was run 480 000 rev. (C) 1997 Elsevier Science S.A.

关键词： fatigue life spherical roller thrust bearings wear

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