Press Fit Research Articles

SC-type multi-core optical-fiber connectors using a pressurization spring

Prototype standard-connector (SC)-type physical-contact connectors were designed and fabricated for a seven-core fiber. The ferrule in the connector has a capillary inserted into a pipe, which fits into a flange with freedom to slide. After the capillary (with the seven-core fiber) and the flange are aligned and adhered, a pressurization spring is used to press fit the flange to a plug frame in a housing. Several prototype connectors have been used to achieve a low attenuation (less than 0.5 dB) and high return loss (40 dB or more). These coupling characteristics indicate that these SC-type physical-contact connectors will be one of the key devices for achieving space division multiplexing (SDM).

Investigation into the causes of fracture in railway freight car axle

Railway axles are vital parts of railway. Their failure in the form of dynamic fracture is commonly of disastrous outcomes for railway vehicles. Accordingly, railway axles are designed to be highly reliable, while the maintenance system requires regular inspection in terms of crack initiation. However, due to complex exploitation conditions, complex stress state and multiple stress concentration, railway axles often experience fatigue failures. This occurrence has been studied in a large number of papers. This paper too sheds light on the causes of fracture occurrence in the axle of railway freight car for coal transport in a thermal power plant. Detailed analyses were conducted on the axle fracture surface and mechanical properties. Also, microstructure of the axle material, as well as on exploitation conditions and stress state was examined. Calculations indicated that, apart from working load impact, the influence of press fit joints, especially of the one between the labyrinth seal and the axle is of crucial importance for the analysis of railway axle stress state. The entire numerical–experimental analysis has shown that the considered axle failure was caused by inadequate maintenance, insufficient axle strength and adverse stress state in the railway axle critical cross-sections.

Moovis prosthesis for osteoarthritis of CMC joint of the thumb

The idea to create a new prosthesis was born in the year 2012 with the innovation ofa double mobility cup, as our orthopaedic colleagues were using for the hip. However, the challenge was to obtain the same mobility as the Elektra metal-on-metal prosthesis: 120° in all directions. This new prosthesis is composed of 3 parts: - An anatomic stem in titanium covered with Hydroxyapatite(HAP). - A head covered by an insert of polyethylenewith 4 sizes of neck, - A cup which is in 2 designs, press fit or screwed with a HAP coating.The diameter of the cup in titanium is 9.5mm. The technique of implantation is almost the same as for the Elektra prosthesis. 3 important factors need to be adhered to. ○ Approach with care, especially with the branch of the dorsal sensory radial nerve, which is very close to the space between Abductor PollicisLongus and Extensor PollicisBrevis. ○ Freeing the base of the metacarpal is very importantin order to obtain a good view of the distal surface of the trapezium, because after an adequate resection of the base of the metacarpal and of the palmar beak it’s possible to dislocatethe metacarpalpalmarly. ○ To find the centre of the trapezium is easy, but extremely important, because of the size and final placement of the cup. Our first implantation of the Moovis prosthesis was done in March 2013.

High-resolution measurements of shock behavior across frictional Be/Cu interfaces

A longstanding question in the field of multi-material behavior pertains to the treatment of interfaces possessing finite frictional strength under high dynamic pressures and shear. Here, we examine the effects of constrained interface sliding on local deformation near the boundary using new, high-resolution measurements combined with simulations to infer friction strength. The experiments use laser driven plate impacts at the Los Alamos National Laboratory TRIDENT Laser Facility to launch a shock wave into a target consisting of a central cylindrical plate of Be and an outer ring of Cu oriented, such that the shock propagates at nearly a 90° angle to the interface normal producing a large velocity gradient across the material boundary. Impact experiments were performed on targets that underwent diffusion bonding of the two materials and on targets that were only press fit together. Friction-induced surface deformation was diagnosed using line-imaging velocity interferometry and surface Transient Imaging Displacement Interferometry in the immediate region of the interface. In these studies, we observed a significant behavioral change in both simulations and experiments between targets with diffusion bonded interfaces and those that were press fit. Bonded targets exhibited a mutual dragging between the Be and Cu parts throughout the entire experiment, whereas unbonded targets displayed a surface slope reversal on the Cu side of the interface, which simulations suggest arise due to altered wave interactions from a 3× lower frictional force compared to the bonded interface.

Small diameter acetabulum and femoral head in total hip arthroplasty for developmental dysplasia of the hip, with no femoral osteotomy.

We present the results of 66 total hip arthroplasties in 62 patients of mean age 46 years (24-74 years), with developmental dysplasia of the hip. In all cases the centre of rotation of the new hip was positioned at the site of the true acetabulum. In all patients cementless press fit acetabular components of small diameter (42-44 mm) were used, articulating exclusively with a 22.25 mm modular metal femoral head, without the use of bone grafts or shortening osteotomies of the femur. Despite the use of small diameter femoral heads the rate of dislocation was 3%. After an average follow-up period of 9 years (4-18 years), no revisions were required for infection, loosening or wear or implant migration. Osteolytic lesions were seen in the periacetabular region in 3 patients who were symptom free. A total of 2 revisions were required for instability and 2 patients had the wires of their trochanteric osteotomy removed because of bursitis. Leg length inequality was improved in 55% of the patients and one postoperative transient sciatic nerve lesion settled within 4 months. We believe that in patients with painful dysplastic hips, the use of small diameter implants with the centre of rotation at the true acetabulum, can give very satisfactory results, without any supplementary procedures.

Revision Total Ankle Replacement.

The technique for revision total ankle replacement described in this article addresses the subsidence and loosening that occur when an Agility total ankle replacement fails. The main indications for revision total ankle arthroplasty include loosening and subsidence of the talar component, with no limit to the extent of subsidence or loss of talar bone stock as neither precludes use of a revision system, particularly when a flat cut on the talus can be made. Make the incision employing the prior anterior midline incision, create full-thickness flaps of tissue to diminish the risk of wound dehiscence, and completely expose and debride the joint as this is critical to revising the total ankle replacement correctly. Remove the talar component, which is rarely difficult as it is usually loose. When removing the tibial component, it is critical to preserve as much of the anterior tibial cortex as possible to provide support for the revision tibial component. Tibial cuts can be made proximal or distal to tibial osseous defects. It is preferable to use a cutting block for the talus that attaches to the tibial guide. If there is substantial bone loss around the tibia after component removal, consider impaction bone-grafting, as better bone quality makes it is easier to obtain a press fit and allow immediate weight-bearing. Size the tibia and talus and subsequently insert the tibial and talar trials and polyethylene simultaneously. In revision settings, manual cement insertion is important because there is no medullary canal to work around. We previously reported the outcomes of revision of failed Agility total ankle replacements (DePuy, Warsaw, Indiana) in forty-one patients.Pitfalls & Challenges.

Adaptive Bone Remodeling of the Femoral Bone After Tumor Resection Arthroplasty With an Uncemented Proximally Hydroxyapatite-Coated Stem

Loss of bone stock and stress shielding is a significant challenge in limb salvage surgery. This study investigates the adaptive bone remodeling of the femoral bone after implantation of a tumor prosthesis with an uncemented press fit stem. We performed a prospective 1 yr follow-up of 6 patients (mean age: 55 (26–78) yr, female/male = 3/3) who underwent bone tumor resection surgery of the proximal femur (n = 3) or distal femur (n = 3). Reconstruction was done using a Global Modular Replacement System (Stryker® Orthopaedics, Mahwah, NJ) tumor prosthesis, and all patients received a straight-fluted 125-mm uncemented press-fit titanium alloy stem with hydroxyapatite coating of the proximal part of the stem. Measurements of bone mineral density (BMD; g/cm2) were done postoperatively and after 3, 6, and 12 mo in the part of the femur bone containing the Global Modular Replacement System stem using dual-energy X-ray absorptiometry. BMD was measured in 3 regions of interest (ROIs) in the femur bone. Nonparametric analysis of variance (Friedman test) for evaluation of changes in BMD over time. BMD decreased in all 3 ROIs with time. In ROI 1 (p = 0.01), BMD decreased by 10% after 3 mo and ended with a total decrease of 14% after 1 yr. In ROI 2 (p = 0.006), BMD was decreased by 6% after 3 and 6 mo; after 1 yr of follow-up, BMD was 9% below the postoperative value. In ROI 3 (p = 0.009), BMD decreased by 6% after 3 and 6 mo; after 1 yr of follow-up, BMD was 8% below the postoperative value. A bone loss of 8%–9% during the first postoperative year was seen along the femoral stem, but in the bone containing the hydroxyapatite-coated part of the stem, the decrease in BMD was 14%, thus indicating that stress shielding of this part of the bone may play a role for the adaptive bone remodeling.

An open-source spherical microphone array design

We present an open-source design for producing a spherically baffled, 32-channel microphone array having elements aligned with the vertices and face centers of a dodecahedron, and fabricated using additive manufacturing (3-D printing). The design approach emphasized low cost, assembly ease, and acoustic integrity. Mechanical, electrical, and acoustical design considerations are discussed, as are assembly and calibration details. The baffle is a 10-cm-radius sphere, built from separable hemispheres, and supported by a 2-cm-diameter cylindrical stand that serves as a conduit for the microphone signal cables. Microphone capsules are mounted on preamp boards, which provide balanced line level outputs, and press fit to the baffle. The performance of the array is characterized, and an example application to spatial room impulse response measurement is provided. Design documents, including the enclosure model and preamp electrical design and board layout, are provided at https://ccrma.stanford.edu/~granzow/sphericalmicarray/

Fixation performance of an ultrasonically fused, bioresorbable osteosynthesis implant: A biomechanical and biocompatibility study.

Bioresorbable implants may serve as an alternative option for the fixation of bone fractures. Because of their minor inherent mechanical properties and insufficient anchorage within bone bioresorbable implants have so far been limited to mechanically nondemanding fracture types. By briefly liquefying the surface of the biomaterial during insertion, bioresorbable implants can be ultrasonically fused with bone to improve their mechanical fixation. The objective of this study was to investigate the biomechanical fixation performance and in vivo biocompatibility of an ultrasonically fused bioresorbable polymeric pin (SonicPin). First, we biomechanically compared the fused pin with press fitted metallic and bioresorbable polymeric implants for quasi-static and fatigue strength under shear and tensile loading in a polyurethane foam model. Second, fused implants were inserted into cancellous bovine bone and tested biomechanically to verify the reproducibility of their fusion behavior. Finally, the fused pins were tested in a lapine model of femoral condyle osteotomies and were histologically examined by light and transmission electron microscopy. While comparable under static shear loads, fixation performance of ultrasonically fused pins was significantly (p = 0.001) stronger under tensile loading than press fit implants and showed no pull-out. Both bioresorbable implants withstood comparable fatigue shear strength, but less than the K-wire. In bovine bone the ultrasonic fusion process worked highly reproducible and provided consistent mechanical fixation. In vivo, the polymeric pin produced no notable foreign body reactions or resorption layers. Ultrasonic fusion of polymeric pins achieved adequate and consistent mechanical fixation with high reproducibility and exhibits good short-term resorption and biocompatibility.

S1160101 小型玉軸受の内輪と軸のクリープ力に及ぼす回転速度の影響

It is general that rotation axis has interference fit between the bearing when a bearing is installed into a machine. In inner ring rotation, interference fit is set between the internal diametrical surface and the rotating axis. In order to realize this, press fitting is required. In business and office machines, clearance fit is sometimes applied for sake of improvement of efficiency for assembly even if it is a case of inner ring rotation. However, if the clearance fit is applied between the axis and the inner ring, slip between them provokes damage called "creep". It will have a positive impact for avoiding creep that the inner rings should be pushed by an axial force larger than the force effecting creep. There is no report so far that investigates a measurement of the force effecting creep. Therefore, this research deals with the measurement of slipping force effecting between the rotating axis and the inner ring.

G1200102 「パラメータ設計」による圧入プロセス条件の最適化

G1200102 「パラメータ設計」による圧入プロセス条件の最適化

Total hip arthroplasty with minimal invasive surgery in elderly patients with neck of femur fractures: our institutional experience

The purpose of this study was to investigate whether minimal invasive surgery (MIS) in elderly patients with neck of femur fractures would reduce the peri-operative complications and improve the post-operative ambulation and length of hospital stay in his cohort of patients. Forty elderly patients were treated with either total hip arthroplasty (THA) or bipolar prosthesis using MIS transgluteal approach. A matched reference group treated with a conventional surgical approach formed the control group. All procedures were performed by the same surgeon. Selection of acetabular component included Novae® uncemented press fit dual mobility concept socket or Bipolar Hemi-Arthroplasty (BHA). The femoral implant was Corail® uncemented stem or Fjord® cemented stem when primary instability was encountered. The follow-up was done for all patients and its minimum length was more than thirty-six months.The average length of the skin incision was 7 (6–8) SD 0.7 cm. Eighteen THA, twenty-two BHA, thirty-seven uncemented femoral stems and three cemented stems were implemented. The length of the procedure was the same as those of the reference group. The operative and post-operative blood loss and analgesic use were significantly decreased in the MIS group. Radiographic implants positioning was similar amongst the two groups. No skin complication, no primary infection, no death within ninety days and no dislocations were observed. MIS approach for implanting THA after a femoral neck fracture in the elderly appears to be a reliable procedure.

Early Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty Implant Following Attempted Closed Reduction: A Case Report

Introduced in 1974 by Bousquet, the dual-mobility bearing for use in total hip arthroplasty (THA) confers increased jump distance and improved overall stability relative to conventional THA designs [1-3]. The dual-mobility bearing incorporates a relatively small (22-28mm) metal or ceramic femoral head press fit into a larger polyethylene liner which articulates with the acetabular component. Dissociation of the femoral head from the polyethylene liner (intraprosthetic dislocation) is a known late complication thought to be related to polyethylene liner wear and has been previously reported [2-7]. In a consecutive series of 384 primary THAs employing Bousquet’s original design, there were 14 intraprosthetic dislocations over 15 years (3.6%). The authors cited polyethylene wear as causative and mean time to intraprosthetic dislocation was 8.9 years [2].

Early Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty Implant Following Attempted Closed Reduction: A Case Report

Introduced in 1974 by Bousquet, the dual-mobility bearing for use in total hip arthroplasty (THA) confers increased jump distance and improved overall stability relative to conventional THA designs [1-3]. The dual-mobility bearing incorporates a relatively small (22-28mm) metal or ceramic femoral head press fit into a larger polyethylene liner which articulates with the acetabular component. Dissociation of the femoral head from the polyethylene liner (intraprosthetic dislocation) is a known late complication thought to be related to polyethylene liner wear and has been previously reported [2-7]. In a consecutive series of 384 primary THAs employing Bousquet’s original design, there were 14 intraprosthetic dislocations over 15 years (3.6%). The authors cited polyethylene wear as causative and mean time to intraprosthetic dislocation was 8.9 years [2].

Theoretical Model for Calculating the Rotation in Cementless Acetabular Cup Prosthesis Implanted by Press Fit into a Hip of Canines

The aseptic loosening of the cementless acetabular cup prosthesis implanted by press fit into a hip is a fault caused by the application of an excessive load, which creates the rotation of the cup on the hip [1]. This rotation of the cup on the hip disables the prosthesis, and a new surgical intervention to place correctly the cup in the hip housing is required. The aseptic loosening of the cementless acetabular cup has been studied during decades mainly through experiments and numerical methods [2,3,4]. This paper shows the development of a theoretical model for calculating the maximum load that the cup of the prosthesis can support as well as the angle and direction of the net load. The model proposed is based on the hertz laws [5], which considers the interface between the cup and hip as two spheres between which there is a coefficient of static friction (μ), and is applied on a acetabular cups [6] implanted in artificial bone [7].

Design and Automation in Back Plug Press Fitting Process of Ball Pen Assembly

In today’s era automation in the production is a key parameter of interest. Rise in the productivity is the main aim of every industry. To sustain in the global era many companies are switching their assembly line from manual to automatic. Consequently, assembly systems should be more flexible and efficient. Even which process needs the automation should be justified to make it automatic. The amount of automation and payback period plays an important role. On that basis authors identify the back plug process needs to be automate. So an attempt is made to design an Automatic Back Plug Press Fitting Process. The paper describes the design, modeling and manufacturing aspects of this process. In automation decisions, it is necessary to consider human resources, as well as mechanical technology and information flow. The paper also includes rise in the productivity along with payback period.

The Applicability of Computing Methods for Analysis of Press-Fit Assembly in Elasto-Plastic Field

It is important to choose an appropriate computing method to analyze stress of press fit in elasto-plastic field. If the selected computing method calculates only in elastic field, it is not in accord with practice when plastic deformation occurs. In this work, the analytical method was extended to two different materials, and stress analyses of press fits for different interference values were implemented by using analytical method and Finite Element Method (FEM). It was verified that results obtained from FEM were more consistent with practice than those obtained from the analytical method in elasto-plastic field. Diameter/interference ratio of press-fit assembly was calculated to estimate occurrence of the plastic deformation. The results show that the analytical method is applicable for simplified press fits of thick-walled cylinders in elastic field, and the ratio decides applicability of the analytical method. For the model that we studied, The plastic deformation began to appear on contact surface when the diameter/interference ratio was smaller than 231.

Stratégie chirurgicale dans les tumeurs osseuses « du genou »

Distal femur and proximal tibia are the main localization of primary malignant bone tumor. Osteosarcoma and Ewing sarcoma are the most frequent. New techniques in imaging, recent development in chemotherapy protocols and surgery sharpening led to major improvement in their management, which allowed to minimize amputation ratio. The complexity of their treatment and their rarity imply the involvement of multidisciplinary approach, in terms of both surgical and medical points of view. After resection, total knee arthroplasty has become the gold standard of reconstruction in such localizations. It uses press fit against healthy bone, thanks to long centromedullar stems, because of major soft tissues resection due to carcinologic surgery rules. The incision is usually antero-medial and the main difficulty is mostly linked to the care of vascular and nervous systems and the extensor apparatus. The conservation (or not) of the latter modifies the surgical technique. Articular invasion will impose to perform a one-piece-articular resection, which will complicate the conservation of the extensor apparatus. There are lots of different techniques and prosthesis. Arthrodesis indications are seldom because prosthesis reconstructions have made proof of their efficacy and their longevity. Functional and oncologic results of this excision and reconstructive surgery are now clearly established. However, this represents complex and risky interventions which will often lead to secondary surgical revision because of the young age of patients and their functional demands. This can only stress the necessity of addressing patients to specialized, network-organized sarcoma teams.

Parliamentary and press discourses on sustainable energy in Italy: No more hard paths, not yet soft paths

This article examines the way hard and soft energy paths are discussed by policy makers, key informants and the press in Italy. Adopting a psycho-social and constructivist perspective, we explored what representations of energy and users, and what technologies are associated with centralised and decentralised energy systems. A large textual corpus was gathered from the online archives of the Chamber of Deputies, using as search criteria the Italian keywords energ* and/or sostenibil* [sustainab*] for the period 2009–2012. Selected corpora (N=143 parliamentary debates and N=841 newspaper articles) were submitted to content analysis. Results show that contents related to hard paths prevail over those typical of soft paths. However, while the contents expressed by the press fit with the hard/soft path dichotomy, political discourse is largely polyphasic and mixes elements of the two systems. These traces of incoherence suggest that energy transition is far from being completed and that sustainable energy is still a contended object of representation.

Patellar clunk syndrome in fixed-bearing posterior-stabilised versus cruciate-substituting prostheses.

To compare the outcome of fixed-bearing posterior-stabilised versus cruciate-substituting prostheses in 46 patients who underwent primary bilateral total knee replacement (TKR). Records of 35 women and 11 men aged 54 to 78 (mean, 67) years who underwent primary bilateral TKR for osteoarthritis (n=44) and rheumatoid arthritis (n=2) were retrospectively reviewed. A fixed-bearing posterior-stabilised prosthesis (Zimmer NexGen Legacy flex [LPS-Flex]) was used in one knee, and a fixed-bearing cruciate-substituting prosthesis (Depuy Press Fit Condylar Sigma CS [PFC CS]) was used in the contralateral knee. The mean time interval between the 2 operations was 34 (range, 4-60) months. All operations were performed by the same group of surgeons using standardised techniques. The medial parapatellar approach was used, and the patella was resurfaced. Rehabilitation was also standardised. Outcome measures included the pre- and post-operative active range of movement and the American Knee Society Score. Postoperative complications were documented. At one year, the mean fixed flexion contracture, maximum flexion, and American Knee Society scores in knees with PFC CS and LPS-Flex prostheses were comparable. Three knees with the PFC CS prosthesis developed the patellar clunk syndrome, compared to none with the LPS-Flex prosthesis (p=0.24). The onset of the patellar clunk syndrome was around one year after surgery. Despite this, the axial alignment and rotation of the femoral and tibial components were good. Both prostheses produce good clinical outcome. The PFC CS prosthesis is more likely to be associated with the patellar clunk syndrome.