Titanium Screw Head With Fretting Structure at Contact Area With Plate Hole

Recently, magnesium alloys have gained a significant amount of recognition as potential biomaterials for degradable implants for craniofacial bone screws. Purpose: The aim of this work was to compare screws made specifically for mandibular head osteosynthesis from different materials. Materials and Methods: Screws measuring 14 mm made by one manufacturer specifically for mandibular head osteosynthesis out of the following materials were selected: magnesium (MgYREZr), titanium (Ti6Al7Nb), and polymer (PLGA). The axial pull-out strength and torsional properties were investigated. Results: Each type of screw presented different pull-out forces (Kruskal–Wallis test, p < 0.001). The magnesium screw had the highest pull-out force of 399 N (cracked without the screw out being pulled out), followed by the titanium screw, with a force of 340 N, and the PLGA screw, with a force of 138 N (always cracked at the base of the screw head without the screw being pulled out). ANOVA was performed for the maximal torques before damage to the screw (torsional properties), revealing that the maximal torque of the magnesium screw was 16 N·cm, while that of the titanium screw was 19 N·cm. The magnesium screw was significantly weaker than the titanium screw (p < 0.05). The measured torque and pull-out force were not related to each other (p > 0.05). Conclusion: Among the screws compared, the metal biodegradable magnesium screw seems to be the most suitable material for multiscrew mandibular head osteosynthesis, considering the condition of the fragile screwdriver socket.

Download Full-text

An In Vitro Analysis of Ligament Reconstruction or Extension Osteotomy on Trapeziometacarpal Joint Stability and Contact Area

Yearbook of Hand and Upper Limb Surgery ◽

10.1016/s1551-7977(08)70357-1 ◽

2007 ◽

Vol 2007 ◽

pp. 214-215 ◽

Cited By ~ 1

Author(s):

B. Wilhelmi

Keyword(s):

Contact Area ◽

Ligament Reconstruction ◽

Joint Stability ◽

Trapeziometacarpal Joint ◽

Vitro Analysis ◽

In Vitro Analysis

Download Full-text

Load-Bearing in the Ovine Medial Tibial Condyle: Effect of Meniscectomy

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.1055/s-0038-1633027 ◽

1993 ◽

Vol 06 (02) ◽

pp. 100-104 ◽

Cited By ~ 8

Author(s):

D. M. Pickles ◽

C. R. Bellenger

Keyword(s):

Knee Joint ◽

Contact Area ◽

Mammalian Species ◽

Total Removal ◽

Load Bearing ◽

Human Knee ◽

Biochemical Effects ◽

Pressure Sensitive ◽

Medial Meniscectomy ◽

Tibial Condyle

SummaryTotal removal of a knee joint meniscus is followed by osteoarthritis in many mammalian species. Altered load-bearing has been observed in the human knee following meniscectomy but less is known about biochemical effects of meniscectomy in other species. Using pressure sensitive paper in sheep knee (stifle) joints it was found that, for comparable loads, the load-bearing area on the medial tibial condyle was significantly reduced following medial meniscectomy. Also, for loads of between 50 N and 500 N applied to the whole joint, the slope of the regression of contact area against load was much smaller. Following medial meniscectomy, the ability to increase contact area as load increased was markedly reduced.The load bearing area on the medial tibial condyle was reduced following meniscectomy.

Download Full-text

An Analytical Thermodynamic Approach to Friction of Rubber on Ice

Tire Science and Technology ◽

10.2346/1945-5852-40.2.124 ◽

2012 ◽

Vol 40 (2) ◽

pp. 124-150

Author(s):

Klaus Wiese ◽

Thiemo M. Kessel ◽

Reinhard Mundl ◽

Burkhard Wies

Keyword(s):

Coefficient Of Friction ◽

Liquid Layer ◽

Contact Area ◽

Leading Edge ◽

Viscous Friction ◽

Analytical Approximation ◽

Real Contact Area ◽

Length Scales ◽

Real Contact ◽

Ice Surface

ABSTRACT The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.

Download Full-text

Measurement and Visualization of the Contact Pressure Distribution of Rubber Disks and Tires

Tire Science and Technology ◽

10.2346/1.2137506 ◽

1995 ◽

Vol 23 (4) ◽

pp. 238-255 ◽

Cited By ~ 16

Author(s):

E. H. Sakai

Keyword(s):

Pressure Distribution ◽

Contact Pressure ◽

Contact Area ◽

Light Absorption ◽

Lateral Force ◽

Contact Pressure Distribution ◽

High Definition ◽

The Road ◽

Close Relationship ◽

Processing Techniques

Abstract The contact conditions of a tire with the road surface have a close relationship to various properties of the tire and are among the most important characteristics in evaluating the performance of the tire. In this research, a new measurement device was developed that allows the contact stress distribution to be quantified and visualized. The measuring principle of this device is that the light absorption at the interface between an optical prism and an evenly ground or worn rubber surface is a function of contact pressure. The light absorption can be measured at a number of points on the surface to obtain the pressure distribution. Using this device, the contact pressure distribution of a rubber disk loaded against a plate was measured. It was found that the pressure distribution was not flat but varied greatly depending upon the height and diameter of the rubber disk. The variation can be explained by a “spring” effect, a “liquid” effect, and an “edge” effect of the rubber disk. Next, the measurement and image processing techniques were applied to a loaded tire. A very high definition image was obtained that displayed the true contact area, the shape of the area, and the pressure distribution from which irregular wear was easily detected. Finally, the deformation of the contact area and changes in the pressure distribution in the tread rubber block were measured when a lateral force was applied to the loaded tire.

Download Full-text

Issues on Design of Piled Raft Foundation

JOURNAL OF ADVANCES IN CHEMISTRY ◽

10.24297/jac.v14i1.5905 ◽

2018 ◽

Vol 14 (1) ◽

pp. 6057-6061 ◽

Cited By ~ 1

Author(s):

Padmanaban M S ◽

J Sreerambabu

Keyword(s):

Contact Area ◽

Concrete Slab ◽

Design Procedure ◽

Bending Moment ◽

Foundation Design ◽

Detailed Review ◽

Piled Raft ◽

Piled Raft Foundation ◽

Raft Foundation ◽

Influencing Parameters

A piled raft foundation consists of a thick concrete slab reinforced with steel which covers the entire contact area of the structure, in which the raft is supported by a group of piles or a number of individual piles. Bending moment on raft, differential and average settlement, pile and raft geometries are the influencing parameters of the piled raft foundation system. In this paper, a detailed review has been carried out on the issues on the raft foundation design. Also, the existing design procedure was explained.

Download Full-text

Cytomorphometric characteristics of imprints of the contact area between the gingiva and the dental implant after one-step implantation

Nauchno-prakticheskii zhurnal «Patogenez» ◽

10.25557/gm.2017.2.7306 ◽

2017 ◽

pp. 77-82

Author(s):

А.С. Рыбалко ◽

А.С. Григорьян ◽

А.А. Орлов

Keyword(s):

Dental Implants ◽

Dental Implant ◽

Contact Area ◽

Inflammatory Reactions ◽

Diagnosis And Prognosis ◽

Dental Implantation ◽

Data Points ◽

One Step ◽

Cytological Method ◽

Clinical Pictures

Цель исследования состояла в разработке неинвазивного метода диагностики состояния тканей периимплантационной зоны после постановки дентальных имплантатов, а также прогноза течения послеоперационного периода и ранней диагностики послеоперационных осложнений, таких, как мукозит и периимплантит, при одноэтапном методе дентальной имплантации. Методы. В исследовании представлена цитологическая характеристика отпечатков из области контакта имплантата с десной, в которых оценивали состояние эпителиальных клеток при различных проявлениях цитопатологии. Определяли индекс деструкции (ИД) и воспалительно-деструктивный индекс (ВДИ) в клетках воспалительного инфильтрата, которые сопоставляли с клинической картиной течения послеоперационного периода. Сроки забора цитологического материала 1, 5, 15, 25, 30, 60, 120 дней после постановки имплантатов. Количество исследованных цитограмм - 442 от 11 пациентов (по 1-2 имплантата). Общий массив использованных для вычисления интегральных показателей составил »2550. Результаты. Было установлено, что в сроки 1-5 дней после постановки дентальных имплантатов происходит резкое повышение показателей ИД (до 7500 ± 15) и ВДИ (до 80 ± 20), что отражает процесс развития в области имплантатов острых воспалительных реакций. В отдаленные сроки наблюдений отмечалось 2 варианта развития событий. Первый из них характеризовался сохранением во все сроки высоких показателей ИД и ВДИ. Для второго варианта динамики показателей было характерно их падение, что соответствовало развитию процесса остеоинтеграции дентальных имплантатов. The objectives of the investigation were to develop protocols evaluating the validity and effectiveness of the cytological method for diagnosis and prognosis of tissue conditions adjacent to a dental implant. Methods. This study examined the cytological characteristics of imprints of the gingiva-implant contact area, a. the correlation of quantitative ratios of epithelial cells either with or without hystopathological manifestations (an index of destruction, ID); b. ratio of cells of the inflammatory infiltrate (an inflammatory and destructive index, IDI); these data were researched in relation with dynamics of the clinical pictures during a postoperative period.The cytological material was obtained 1, 5, 15, 25, 30, 60, 120 days after dental implantation. Totally 442 cytogramme from 11 patients (1-2 implant per a patient) were assayed. The data array for computation of integrated indicators was composed of ca. 2550 data points. Results. A significant increase of ID (7500 ± 15) and IDI (80 ± 20) indicators, which reflects the development of acute inflammatory reactions in tissues neighboring an implant, was observed within 1-5 days following the insertion of dental implants. Long-term observations revealed two scenarios. The first scenario was characterized by the retention of high levels of ID and IDI over the period of observations. The second scenario featured the reduction of ID and IDI indices, which corresponded to the development of the osseointegration of dental implants.

Download Full-text

Bottom Hole Assembly Design Enhancement Successfully Eliminate Hole Problems and Reduce Significant Drilling Time : South S Field Case Study

Proc. Indon. Petrol. Assoc., Digital Technical Conference, 2020 ◽

10.29118/ipa20-e-71 ◽

2020 ◽

Author(s):

Y. D. Mulia

Keyword(s):

Contact Area ◽

Cost Savings ◽

Assembly Design ◽

Drilling Performance ◽

Bottom Hole ◽

Unconsolidated Sand ◽

Bottom Hole Assembly ◽

Drilling Parameter ◽

Drilling Time

For S-15 and S-14 wells at South S Field, drilling of the 12-1/4” hole section became the longest tangent hole section interval of both wells. There were several challenges identified where hole problems can occur. The hole problems often occur in the unconsolidated sand layers and porous limestone formation sections of the hole during tripping in/out operations. Most of the hole problems are closely related to the design of the Bottom Hole Assembly (BHA). In many instances, hole problems resulted in significant additional drilling time. As an effort to resolve this issue, a new BHA setup was then designed to enhance the BHA drilling performance and eventually eliminate hole problems while drilling. The basic idea of the enhanced BHA is to provide more annulus clearance and limber BHA. The purpose is to reduce the Equivalent Circulating Density (ECD,) less contact area with formation, and reduce packoff risk while drilling through an unconsolidated section of the rocks. Engineering simulations were conducted to ensure that the enhanced BHA were able to deliver a good drilling performance. As a results, improved drilling performance can be seen on S-14 well which applied the enhanced BHA design. The enhanced BHA was able to drill the 12-1/4” tangent hole section to total depth (TD) with certain drilling parameter. Hole problems were no longer an issue during tripping out/in operation. This improvement led to significant rig time and cost savings of intermediate hole section drilling compared to S-15 well. The new enhanced BHA design has become one of the company’s benchmarks for drilling directional wells in South S Field.

Download Full-text