scholarly journals Experimental Characterization of the Primary Stability of Acetabular Press-Fit Cups with Open-Porous Load-Bearing Structures on the Surface Layer

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 839 ◽  
Author(s):  
Volker Weißmann ◽  
Christian Boss ◽  
Christian Schulze ◽  
Harald Hansmann ◽  
Rainer Bader
Keyword(s):  
Primary Stability ◽  
Unit Cell ◽  
Artificial Bone ◽  
Load Bearing ◽  
Functional Relationships ◽  
Press Fit ◽  
Pull Out ◽  
Wide Range ◽  
The Press ◽  
Open Structures

Background: Nowadays, hip cups are being used in a wide range of design versions and in an increasing number of units. Their development is progressing steadily. In contrast to conventional methods of manufacturing acetabular cups, additive methods play an increasingly central role in the development progress. Method: A series of eight modified cups were developed on the basis of a standard press-fit cup with a pole flattening and in a reduced version. The surface structures consist of repetitive open-pore load-bearing textural elements aligned right-angled to the cup surface. We used three different types of unit cells (twisted, combined and combined open structures) for constructing of the surface structure. All cups were manufactured using selective laser melting (SLM) of titanium powder (Ti6Al4V). To evaluate the primary stability of the press fit cups in the artificial bone cavity, pull-out and lever-out tests were conducted. All tests were carried out under exact fit conditions. The closed-cell polyurethane (PU) foam, which was used as an artificial bone cavity, was characterized mechanically in order to preempt any potential impact on the test results. Results and conclusions: The pull-out forces as well as the lever moments of the examined cups differ significantly depending on the elementary cells used. The best results in pull-out forces and lever-out moments are shown by the press-fit cups with a combined structure. The results for the assessment of primary stability are related to the geometry used (unit cell), the dimensions of the unit cell, and the volume and porosity responsible for the press fit. Corresponding functional relationships could be identified. The findings show that the implementation of reduced cups in a press-fit design makes sense as part of the development work.

scholarly journals Influence of Synthetic Bone Substitutes on the Anchorage Behavior of Open-Porous Acetabular Cup

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1052 ◽  
Author(s):  
Volker Weißmann ◽  
Tim Ramskogler ◽  
Christian Schulze ◽  
Rainer Bader ◽  
Harald Hansmann
Keyword(s):  
Primary Stability ◽  
Bone Substitutes ◽  
Fixation Strength ◽  
Bone Stock ◽  
Structural Elements ◽  
Acetabular Cup ◽  
Load Bearing ◽  
Synthetic Bone ◽  
Press Fit ◽  
Pull Out

Background: The development in implants such as acetabular cups using additive manufacturing techniques is playing an increasingly important role in the healthcare industry. Method: This study compared the primary stability of four selectively laser-melted press-fit cups (Ti6Al4V) with open-porous, load-bearing structural elements on the surface. The aim was to assess whether the material of the artificial bone stock affects the primary stability of the acetabular cup. The surface structures consist of repeated open-porous, load-bearing elements orthogonal to the acetabular surface. Experimental pull-out and lever-out tests were performed on exact-fit and press-fit cups to evaluate the primary stability of the cups in different synthetic bone substitutes. The acetabular components were placed in three different commercially available synthetic materials (ROHACELL-IGF 110, SikaBlock M330, Sawbones Solid Rigid). Results & conclusions: Within the scope of the study, it was possible to show the differences in fixation strength between the tested acetabular cups depending on their design, the structural elements used, and the different bone substitute material. In addition, functional correlations could be found which provide a qualitative reference to the material density of the bone stock and the press-fit volume of the acetabular cups.

Auszugverhalten von Schaftfräsern*/Pull-out behavior of end mills – Experimental study on different clamping devices with various clamping mechanisms

2018 ◽  
Vol 108 (05) ◽  
pp. 353-358
Author(s):  
E. Abele ◽  
F. Ali ◽  
M. Berger
Keyword(s):  
Experimental Study ◽  
Test Bench ◽  
Mechanical Load ◽  
Mechanisms Of Action ◽  
Heavy Duty ◽  
Press Fit ◽  
Pull Out ◽  
The Press ◽  
End Mills ◽  
Tool Position

Aus Schwerzerspanung und Turbinenschaufelfertigung ist bekannt, dass Werkzeuge aus dem Spannfutter ausgezogen werden. Die veränderte Werkzeugposition führt zur Abweichung von den vorgegebenen Toleranzen und einer geringeren Fertigungsqualität oder Beschädigung des Werkstücks. Der Artikel untersucht das Auszugsverhalten verschiedener Spannfutter. Mit einem Prüfstand können die Einflüsse der mechanischen Belastung und der Klemmlänge auf die Haltekraft im Pressverband betrachtet und die Wirkmechanismen beim Auszug des Werkzeuges aus dem Spannfutter sensorisch ermittelt werden.   From heavy-duty cutting and turbine blade manufacturing it is known that tools pull out from chucks. A change in tool position leads to deviations from tolerance and decreases manufacturing quality or damages the workpiece. This article explores the extension behavior of different chucks on a specifically designed test bench. This allows determining how mechanical load and clamping length influence the holding force in the press fit and what mechanisms of action affect the extraction of the tool from the chuck.

scholarly journals Analysis of Interference-Fit Joints

2021 ◽  
Vol 11 (23) ◽  
pp. 11428
Author(s):  
Jerzy Madej ◽  
Mateusz Śliwka
Keyword(s):  
Bearing Capacity ◽  
Load Capacity ◽  
Fem Simulation ◽  
Load Bearing Capacity ◽  
Measuring Device ◽  
Plastic Deformations ◽  
Interference Fit ◽  
Load Bearing ◽  
Press Fit ◽  
The Press

Interference fit joints have been widely used in many engineering constructions, in particular in electric motors. It is of particular importance to calculate the load capacity of press-fit joints, especially in the overload ranges of construction to estimate the safety factor. The article presents a FEM numerical simulation of pressing the shaft into the hub, taking into account various types of fits. The results of numerical simulations presented in the article were positively verified with the MTS measuring device, which confirmed the correctness of the numerical model. So far, the load-bearing capacity of press-fit joints has been calculated from Lame’s formulas. The results of the load capacity of the joints obtained by the FEM simulation were compared with the results obtained from Lame’s formula. The comparison shows that when designing interference fit joints, attention should be paid to the fact that the press-in process, depending on the type of fit, may be elastic-plastic. Plastic deformations in the contact zone of the joint affect its load-bearing capacity. Therefore, the design of press-fit joints should not be based on Lame’s formulas, which do not take into account the range of plastic work of the material.

scholarly journals Estimation of the primary stability of the press-fit and screwed-in acetabular components after hip joint arthroplasty

2017 ◽  
Vol 0 (1) ◽  
pp. 92-97
Author(s):  
Oleg Loskutov ◽  
Nadiia Naumenko ◽  
Oleksandr Loskutov ◽  
Dmytro Syniehubov ◽  
Dmytro Gorobets ◽  
...  
Keyword(s):  
Hip Joint ◽  
Primary Stability ◽  
Joint Arthroplasty ◽  
Press Fit ◽  
The Press ◽  
Acetabular Components

Is there still a role for threaded acetabular cups?

2018 ◽  
Vol 28 (2_suppl) ◽  
pp. 15-20
Author(s):  
Luca Gala ◽  
Francesca Boisio ◽  
Filippo Calanna ◽  
Fiorello Lonati ◽  
Bruno M Marelli
Keyword(s):  
Bone Ingrowth ◽  
Primary Stability ◽  
Radiographic Evaluation ◽  
Main Concern ◽  
Consecutive Series ◽  
Press Fit ◽  
Track Record ◽  
The Press ◽  
Secondary Endpoints

Introduction: Total hip arthroplasty (THA) is 1 of the most common procedures in orthopaedic surgery. Different options and implants are currently available. Uncemented hip cups need primary stability for bone ingrowth, the use of screws is required when the desired stability is not achieved. Another option is the use of a hemispherical threaded cup with enhanced primary stability. The purpose of our study was to compare the results of a 3rd-generation threaded cup versus a press-fit cup with a long track record. Materials and methods: A consecutive series of 300 THAs performed by 2 surgeons was retrospectively reviewed, 150 press-fit cups and 150 screwed cups. Minimum follow-up 27 months; maximum 78 months (mean 52.5 months). The primary endpoint was a stable and painless THA, secondary endpoints included Hip disability and Osteoarthritis Outcome Score, Junior and radiographic evaluation. Results: Preliminary results showed no statistically significant differences between the 2 groups for all the evaluated parameters, the number of early mechanical loosening was higher for press-fit cups, but this value was not statistically significant. At a mean follow-up of 52.5 months 1 cup revision (0.3%) was seen in the screwed cup group and 2 (0.6%) in the press-fit cup; these results were not statistically significant. Discussion and conclusion: The main concern for screwed cups is the greater bone loss and possible removal difficulties during revision surgery. This study has some limitations, in particular regarding follow-up, but is still ongoing. Our results showed no difference between the 2 systems.

In Vitro Evaluation of the Acetabular Cup Primary Stability by Impact Analysis

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Adrien Michel ◽  
Romain Bosc ◽  
Romain Vayron ◽  
Guillaume Haiat
Keyword(s):  
Impact Analysis ◽  
Primary Stability ◽  
Bovine Bone ◽  
Acetabular Cup ◽  
Hip Prostheses ◽  
Press Fit ◽  
The Press ◽  
Force Signal ◽  
The Impact

The implant primary stability of the acetabular cup (AC) is an important parameter for the surgical success of press-fit procedures used for the insertion of cementless hip prostheses. In previous studies by our group (Mathieu, V., Michel, A., Lachaniette, C. H. F., Poignard, A., Hernigou, P., Allain, J., and Haiat, G., 2013, “Variation of the Impact Duration During the in vitro Insertion of Acetabular Cup Implants,” Med. Eng. Phys., 35(11), pp. 1558–1563) and (Michel, A., Bosc, R., Mathieu, V., Hernigou, P., and Haiat, G., 2014, “Monitoring the Press-Fit Insertion of an Acetabular Cup by Impact Measurements: Influence of Bone Abrasion,” Proc. Inst. Mech. Eng., Part H, 228(10), pp. 1027–1034), the impact momentum and duration were shown to carry information on the press-fit insertion of the AC within bone tissue. The aim of the present study is to relate the impact momentum recorded during the AC insertion to the AC biomechanical primary stability. The experimental protocol consisted in testing 13 bovine bone samples that underwent successively series of 15 reproducible mass falls impacts (5 kg, 5 cm) followed by tangential stability testing. Each bone sample was tested with different hole sizes in order to obtain different stability configurations. The impact momentum and the tangential primary stability reach a maximum value for an interference fit equal to around 1 mm. Moreover, a correlation between the impact momentum and the stability was obtained with all samples and all configuration (R2 = 0.65). The implant primary stability can be assessed through the measurement of the impact force signal analysis. This study opens new paths for the development of a medical device which could be used as a decision support system to assist the surgeon during the insertion of the AC implant.

scholarly journals Constructing a biomimetic robust bi-layered hydrophilic lubrication coating on surface of silicone elastomer

Friction ◽  
2021 ◽  
Author(s):  
Luyao Gao ◽  
Xiaoduo Zhao ◽  
Shuanhong Ma ◽  
Zhengfeng Ma ◽  
Meirong Cai ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Composite Layer ◽  
High Load ◽  
Silicone Elastomer ◽  
Aqueous Lubrication ◽  
Low Friction ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Lubrication Performance ◽  
Wide Range

AbstractSilicone elastomers-based materials have been extensively involved in the field of biomedical devices, while their use is extremely restricted due to the poor surface lubricity and inherent hydrophobicity. This paper describes a novel strategy for generating a robust layered soft matter lubrication coating on the surface of the polydimethylsiloxane (PDMS) silicone elastomer, by entangling thick polyzwitterionic polyelectrolyte brush of poly (sulfobetaine methacrylate) (PSBMA) into the sub-surface of the initiator-embedded stiff hydrogel coating layer of P(AAm-co-AA-co-HEMA-Br)/Fe, to achieve a unified low friction and high load-bearing properties. Meanwhile, the stiff hydrogel layer with controllable thickness is covalently anchored on the surface of PDMS by adding iron powder to provide catalytic sites through surface catalytically initiated radical polymerization (SCIRP) method and provides high load-bearing capacity, while the topmost brush/hydrogel composite layer is highly effective for aqueous lubrication. Their synergy effects are capable of attaining low friction coefficient (COFs) under wide range of loaded condition in water environment with steel ball as sliding pair. Furthermore, the influence of mechanical modulus of the stiff hydrogel layer on the lubrication performance of layered coating is investigated, for which the COF is the lowest only when the modulus of the stiff hydrogel layer well matches the PDMS substrate. Surprisingly, the COF of the modified PDMS could remain low friction (COF < 0.05) stably after encountering 50,000 sliding cycles under 10 N load. Finally, the surface wear characterizations prove the robustness of the layered lubricating coating. This work provides a new route for engineering lubricious silicon elastomer with low friction, high load-bearing capacity, and considerable durability.

scholarly journals Experimental & FEM Analysis of Orthodontic Mini-Implant Design on Primary Stability

2021 ◽  
Vol 11 (12) ◽  
pp. 5461
Author(s):  
Elmedin Mešić ◽  
Enis Muratović ◽  
Lejla Redžepagić-Vražalica ◽  
Nedim Pervan ◽  
Adis J. Muminović ◽  
...  
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Primary Stability ◽  
Fem Analysis ◽  
Implant Design ◽  
Special Focus ◽  
Engineering System ◽  
Mini Implants ◽  
Pull Out ◽  
Computer Aided

The main objective of this research is to establish a connection between orthodontic mini-implant design, pull-out force and primary stability by comparing two commercial mini-implants or temporary anchorage devices, Tomas®-pin and Perfect Anchor. Mini-implant geometric analysis and quantification of bone characteristics are performed, whereupon experimental in vitro pull-out test is conducted. With the use of the CATIA (Computer Aided Three-dimensional Interactive Application) CAD (Computer Aided Design)/CAM (Computer Aided Manufacturing)/CAE (Computer Aided Engineering) system, 3D (Three-dimensional) geometric models of mini-implants and bone segments are created. Afterwards, those same models are imported into Abaqus software, where finite element models are generated with a special focus on material properties, boundary conditions and interactions. FEM (Finite Element Method) analysis is used to simulate the pull-out test. Then, the results of the structural analysis are compared with the experimental results. The FEM analysis results contain information about maximum stresses on implant–bone system caused due to the pull-out force. It is determined that the core diameter of a screw thread and conicity are the main factors of the mini-implant design that have a direct impact on primary stability. Additionally, stresses generated on the Tomas®-pin model are lower than stresses on Perfect Anchor, even though Tomas®-pin endures greater pull-out forces, the implant system with implemented Tomas®-pin still represents a more stressed system due to the uniform distribution of stresses with bigger values.

scholarly journals Fabrication and Compressive Behavior of a Micro-Lattice Composite by High Resolution DLP Stereolithography

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 785
Author(s):  
Chow Shing Shin ◽  
Yu Chia Chang
Keyword(s):  
High Resolution ◽  
Lattice Structure ◽  
Low Cost ◽  
Hierarchical Structures ◽  
Dip Coating ◽  
Unit Cell ◽  
Digital Light Processing ◽  
Unit Cell Size ◽  
Wide Range ◽  
And Performance

Lattice structures are superior to stochastic foams in mechanical properties and are finding increasing applications. Their properties can be tailored in a wide range through adjusting the design and dimensions of the unit cell, changing the constituent materials as well as forming into hierarchical structures. In order to achieve more levels of hierarchy, the dimensions of the fundamental lattice have to be small enough. Although lattice size of several microns can be fabricated using the two-photon polymerization technique, sophisticated and costly equipment is required. To balance cost and performance, a low-cost high resolution micro-stereolithographic system has been developed in this work based on a commercial digital light processing (DLP) projector. Unit cell lengths as small as 100 μm have been successfully fabricated. Decreasing the unit cell size from 150 to 100 μm increased the compressive stiffness by 26%. Different pretreatments to facilitate the electroless plating of nickel on the lattice structure have been attempted. A pretreatment of dip coating in a graphene suspension is the most successful and increased the strength and stiffness by 5.3 and 3.6 times, respectively. Even a very light and incomplete nickel plating in the interior has increase the structural stiffness and strength by more than twofold.

New Approach for Versatile Self Piercing Riveting: Joining System and Auxiliary Part

2021 ◽  
Vol 883 ◽  
pp. 3-10
Author(s):  
Fabian Kappe ◽  
Mathias Bobbert ◽  
Gerson Meschut
Keyword(s):  
Boundary Conditions ◽  
Research Work ◽  
High Load ◽  
Continuous Increase ◽  
New Approach ◽  
Load Bearing ◽  
Mechanical Joining ◽  
Wide Range ◽  
Riveting Process

The increasing use of multi-material constructions lead to a continuous increase in the use of mechanical joining techniques due to the wide range of joining possibilities as well as the high load-bearing capacities of the joints. Nevertheless, the currently rigid tool systems are not able to react to changing boundary conditions, like changing the material-geometry-combination. Therefore research work is crucial with regard to versatile joining systems. In this paper, a new approach for a versatile self-piercing riveting process considering the joining system as well as the auxiliary joining part is presented.

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