scholarly journals Effect of head size and rotation on taper corrosion in a hip simulator

2021 ◽  
Vol 2 (11) ◽  
pp. 1004-1016
Author(s):  
Christian M. Wight ◽  
Cari M. Whyne ◽  
Earl R. Bogoch ◽  
Radovan Zdero ◽  
Ryan M. Chapman ◽  
...  
Keyword(s):  
Flexural Rigidity ◽  
Alternative Hypothesis ◽  
Head Size ◽  
Wear Testing ◽  
Frictional Torque ◽  
Linear Wear ◽  
Wear Depth ◽  
Joint Movement ◽  
Hip Simulator ◽  
Significant Difference

Aims This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads. Methods In all, six 28 mm and six 36 mm titanium stem-cobalt chrome head pairs with polyethylene sockets were tested in a novel instrumented hip simulator. Samples were tested using simulated gait data with incremental increasing loads to determine corrosion onset load and electrochemical activity. Half of each head size group were then cycled with simulated gait and the other half with gait compression only. Damage was measured by area and maximum linear wear depth. Results Overall, 36 mm heads had lower corrosion onset load (p = 0.009) and change in open circuit potential (OCP) during simulated gait with (p = 0.006) and without joint movement (p = 0.004). Discontinuing gait’s joint movement decreased corrosion currents (p = 0.042); however, wear testing showed no significant effect of joint movement on taper damage. In addition, 36 mm heads had greater corrosion area (p = 0.050), but no significant difference was found for maximum linear wear depth (p = 0.155). Conclusion Larger heads are more susceptible to taper corrosion; however, not due to frictional torque as hypothesized. An alternative hypothesis of taper flexural rigidity differential is proposed. Further studies are necessary to investigate the clinical significance and underlying mechanism of this finding. Cite this article: Bone Jt Open 2021;2(11):1004–1016.

Effect of Wear of Bearing Surfaces on Elastohydrodynamic Lubrication of Metal-on-Metal Hip Implants

2005 ◽  
Vol 219 (5) ◽  
pp. 319-328 ◽  
Author(s):  
F Liu ◽  
Z M Jin ◽  
F Hirt ◽  
C Rieker ◽  
P Roberts ◽  
...  
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Linear Wear ◽  
Wear Depth ◽  
Hip Implants ◽  
Bearing Surface ◽  
Lubricant Film Thickness ◽  
Hip Simulator ◽  
Metal On Metal

The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul™ bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul™ bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 μm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul™ bearing to achieve a fluid film lubrication regime during this period, and this was consistent with the minimal wear observed between 1 and 5 million cycles. However, under adverse in vivo conditions associated with start-up and stopping and depleted lubrication, wear of the bearing surfaces can still occur. An increase in the wear depth beyond a certain limit was shown to lead to the constriction of the lubricant film around the edge of the contact conjunction and consequently to a decrease in the lubricant film thickness. Continuous cycles of a running-in wear period followed by a steady state wear period may be inevitable in MOM hip implants. This highlights the importance of minimizing the wear in these devices during the initial running-in period, particularly from design and manufacturing points of view.

Study of Wear Prediction on Total Ankle Replacement

2013 ◽  
Vol 845 ◽  
pp. 311-315 ◽  
Author(s):  
A.M.S. Putra ◽  
Muhamad Noor Harun ◽  
Syahrom Ardiyansyah
Keyword(s):  
Early Stage ◽  
Computational Simulation ◽  
Reaction Force ◽  
Total Ankle Replacement ◽  
Wear Testing ◽  
Linear Wear ◽  
Wear Depth ◽  
Joint Reaction Force ◽  
Ankle Replacement

Pre-clinical experimental wear testing is very effective to evaluate new ankle replacement in the aspect of design and material used. However, both cost and time can be one of the constraints factors, particularly in the early stage of design or analysis. Numerical method has been addressed as an alternative to predict wear on ankle replacement. The computational wear simulation has been widely used on the hip and knee but very less found in study related to wear analysis of the ankle. The purpose of this research is to develop computational simulation to predict wear on total ankle replacement (TAR). Three dimensional (3D) models of the right ankle TAR were developed using BOX total ankle replacement model. Mobile bearing device was developed consisting of three components tibial, bearing and talar. Each component has different design and purposes representing its physiological behaviour of the ankle. The ankle load applied was based on the joint reaction force profile at the ankle joint. This is to determine the distribution of contact stress on the meniscal bearing surfaces contact with talar component for 25 discrete instant during stance phase of gait cycle. The sliding distance was obtained from predominates motion of plantar/dorsi flexion. The computed linear wear depth and cumulative volumetric wear were 0.01614 mm per million cycles and 30.5 mm3, respectively. The values obtained were proven to be consistent with the previous in vitro result.

Wear Characteristics of Conventional and Squeeze-Film Artificial Hip Joints

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
S. Boedo ◽  
S. A. Coots
Keyword(s):  
Implant Design ◽  
Squeeze Film ◽  
Linear Wear ◽  
Wear Depth ◽  
Element Analysis ◽  
Wear Characteristics ◽  
Wear Rates ◽  
Cycle Loading ◽  
Artificial Hip Joints ◽  
Elastic Elements

This paper investigates the wear characteristics of a novel squeeze-film hip implant design. Key features of the design are elastic elements attached to the cup which provide a mechanical means for ball separation during the swing phase of the gait loading cycle. An Archard-based wear formulation was implemented utilizing the ansys finite element analysis program which relates contact pressure and sliding distance to linear wear depth. It is found that low-modulus elastic elements with bonded high-modulus metal coatings offer significant predicted improvement in linear and volumetric wear rates when compared with conventional implant geometries for gait cycle loading and kinematic conditions found in practice.

Hip simulator wear testing according to the newly introduced standard ISO 14242

2005 ◽  
Vol 38 (3) ◽  
pp. 641-642
Author(s):  
V. Saikko ◽  
O. Calonius
Keyword(s):  
Wear Testing ◽  
Hip Simulator

scholarly journals Text-based Character in Teaching Reading: Do Students Can Achieve Significant Result in Reading Test?

2021 ◽  
Vol 3 (1) ◽  
pp. 21-28
Author(s):  
Hasan Hasan ◽  
Andi Sadapotto ◽  
Muhammad Hanafi ◽  
Usman Usman
Keyword(s):  
Alternative Hypothesis ◽  
T Test ◽  
Reading Test ◽  
Control Group ◽  
Significant Difference ◽  
Good Classification ◽  
Post Test ◽  
The Mean ◽  
And Control ◽  
Experimental Group

This quasi-experimental study involves the experimental and control group which consist of 60 students in first year of SMA Muhammadiyah Sidenreng Rappang   2019/2020 academic year.  The reading test is used to collect data to find out do the students can achieve significant result in reading test using Text-based Character. Based on the result the mean score of the experimental group pre-test was 72.67 and classified into good classification, while the control group was 69.63 classified into good. The mean score of the post-test after treatment for the experimental group was 82.43 (very good) while the control group was 76.53, (good) classification still.  The researcher found that the T-table is higher than the t-test (α) (1.659<2.021). It means that there is a significant difference in the pre-test of the control and experimental group, while in post-test of an experimental and control group, the researcher finds that the T-test is higher than the alpha and previous score in the the pre-test (α) (3.089>2.021). The degree of freedom is 58. This study reveals that the alternative hypothesis (H1) was accepted, and the null hypothesis (H0) was rejected. This is means that the use of Text-based Characters can improves students' reading skills in significant way.

scholarly journals THE USE OF INSTAGRAM TO DEVELOP STUDENTS’ WRITING ABILITY

Akademika ◽  
2020 ◽  
Vol 9 (01) ◽  
pp. 97-107
Author(s):  
Amelia Nurdiansyah ◽  
Tryanti R. Abdulrahman
Keyword(s):  
Teaching And Learning ◽  
Alternative Hypothesis ◽  
Sampling Technique ◽  
T Test ◽  
Control Group ◽  
Discrimination Power ◽  
Control Group Design ◽  
Writing Ability ◽  
Significant Difference ◽  
Difficulty Index

The research consists of two variables, namely the independent variable (Instagram) and the dependent variable (writing ability). The aim of this research is to find out whether or not the use of Instagram is effective in teaching writing Descriptive Text. The population of this research was all grade ten students at SMAN 3 Bekasi, consisted of 370 students divided into 10 classes. The sample of this research was 74 students divided into 2 classes, taken from the population using Cluster Random Sampling Technique. This research used the Quasi Experimental Method, and the design was randomized post-test only control group design. To collect the data, the writers used instrument. The instrument consists of 10 question items in an essay. They were developed from the indicators of writing as specified in BluePrint. To get a good instrument, it was tried out to other classes outside the sample classes, and the instrument was analyzed in the item of its validity, reliability, difficulty index, and discrimination power by using Ms. Excel 2010. After it has been analyzed, it gained 5 items which were used to collect data for the research. The writers used a T-test to find out whether the alternative hypothesis (Ha) was accepted or rejected. The result of this research presented that there was a significant difference of Instagram on students’ writing ability at SMAN 3 Bekasi. The significance (Sig.) score of T-test 0.000 is lower than (<) 0.05. Therefore, the research had a significant difference in Instagram on Grade Ten Students’ Writing Ability at SMAN 3 Bekasi. In addition, Instagram helped the students to develop their writing, and also, it can ease the teaching and learning process.

scholarly journals THE EFFECT OF HERRINGBONE TECHNIQUE ON THE STUDENTS’ ABILITY IN READING COMPREHENSION ON RECOUNT TEXT

2020 ◽  
Vol 3 (2) ◽  
pp. 91-100
Author(s):  
Sam Roberto Andre Hasian Lumbantobing ◽  
Hilman Pardede ◽  
Herman Herman
Keyword(s):  
Reading Comprehension ◽  
Reading Ability ◽  
Test Score ◽  
Alternative Hypothesis ◽  
Average Score ◽  
Control Group ◽  
Significant Difference ◽  
Tenth Grade ◽  
Post Test ◽  
Experimental Group

This research is a study of improving students’ ability in reading comprehension. The aim was to find out whether the use of Herringbone technique would bring a significant difference in teaching reading comprehension through Recount text, compared with the result before the students being treated. The study was conducted in the tenth grade students of SMA N 4 Pematangsiantar. The research method used was the experimental design, where the Experimental group was the PMIA 3 class, and the PMIA 2 class as the control class. Both of the classes had 34 students in each of it. The data were obtained through pre-test, treatment and post test. The pre-test was held to know the students’ basic ability or score before treatment was given. Meanwhile, the post test was held to know the students’ achievement and significant effect after the students were taught using Herringbone technique. Finding of the research showed that both groups had a significant improvement in their reading ability after being treated and passed the KKM. The Control group, which the pre-test score was 60, made an improvement shown in their post-test score in amount of 70,44. The experimental group, the group which the researcher treated the Herringbone technique to them, had a higher improvement than the control group. The average score of pre-test in this group was about 54,41 where then being improved up to 78,97. The score of t-test (3,981) was higher than t-table (1,668) at the level of significance 5% for two tailed test, so Null Hypothesis is rejected and Alternative Hypothesis is accepted.

scholarly journals THE EFFECT OF BLINDFOLD GAME ON STUDENTS’ VOCABULARY ACHIEVEMENT AT SMP NEGERI 13 KENDARI

2020 ◽  
Vol 5 (3) ◽  
pp. 200
Author(s):  
Andi An-Nisaa Arfin ◽  
Kamaluddin Kamaluddin ◽  
Wa Ode Fatmawati
Keyword(s):  
Junior High School ◽  
Alternative Hypothesis ◽  
First Grade ◽  
First Year ◽  
First Year Students ◽  
Comparison Research ◽  
Significant Difference ◽  
Post Test ◽  
The Difference ◽  
Vocabulary Achievement

The purpose of conducting this research is to examine the difference NGain scores between students who learn vocabulary with Blindfold Game and students who learn vocabulary without Blindfold Game at the first year students of SMP Negeri 13 Kendari. The samples of this research are the first grade four (VII-4) and the first grade three (VII-3) which consists of 27 students for each class. This research is conducted in comparison research design that consists of experimental class (VII-4) and controll class (VII-3). The data of this research are collected by giving pre-test and post-test in two classes (VII-4 & VII-3). The result shows that there is an improvement of the students’ vocabulary achievement. Independent samples t-test shows that, there is a significant difference in the Ngain scores for experimental class ( M = 60.08,  SD = 9.36 ) and controll class ( M = 20.41, SD = 14.56 ), t (52) = 11.904, p (0.000) < 0.05. Therefore, it can be concluded that the value of Sig (2 tailed) is lower than the significance α value (0.000 < 0.05). In other words, alternative hypothesis (H1) is accepted and the null hypothesis (H0) is rejected. It means that the Blindfold game can enrich students’ vocabulary achievement for Junior High School Student.

scholarly journals Improving Students’ Writing Skill by Using Wholesome Scattering Game

2021 ◽  
Vol 1 (1) ◽  
pp. 39-47
Author(s):  
Dina Novrieta ◽  
Sopi Nurisa
Keyword(s):  
Null Hypothesis ◽  
Alternative Hypothesis ◽  
Writing Skills ◽  
Sampling Technique ◽  
T Test ◽  
Control Group ◽  
Paired Sample ◽  
Significant Difference ◽  
Writing Skill ◽  
Academic Year

The aim of this research is to describe the implementation of Wholesome Scattering Game in improving students’ writing skills on descriptive text and to find out whether there is a significant difference between students who were taught by using Wholesome Scattering Game and the students who were not. This research used quantitative approach focusing on experimental research which was conducted at SMAN 2 Sungaiselan in academic year 2019/2020. The researcher used purposive sampling technique and two classes were taken as samples, with 69 students (35 students for the control group and 34 students for the  experimental). The result of the test was analyzed by using statistical analysis of Paired sample t-test and Independent sample t-test. The finding showed that the students who were taught by using Wholesome Scattering Game got higher score than those who were taught by using non-Wholesome Scattering Game. It means that the alternative hypothesis (Ha) was accepted, while the null hypothesis (Ho) was rejected. It could be concluded that there was a significant difference between students who were taught by using Wholesome Scattering Game and the students who were taught without using Wholesome Scattering Game.

Effect of substrate surface roughness on the wear of molybdenum disulphate coated rolling contact bearings

2021 ◽  
Vol 63 (9) ◽  
pp. 848-854
Author(s):  
Bahar Gokce ◽  
Necdet Geren ◽  
Mahmut Izciler
Keyword(s):  
High Temperature ◽  
Molybdenum Disulfide ◽  
Substrate Surface ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Wear Testing ◽  
Wear Depth ◽  
Phosphate Coating ◽  
Depth Measurement ◽  
Friction Moment

Abstract The objective of the present experimental work is to investigate the influence of subsurface roughness on the friction and wear performance of high-temperature ball bearing. Bearings, which are used in high-temperature applications, are affected by several operating conditions. Some factors under high-temperature conditions such as short grease life, thin-film thickness at low speed, and insufficient internal clearance can drastically reduce bearing service life due to an increase in surface friction. For this reason, rolling contact bearings are coated with molybdenum disulfide. Before the molybdenum disulfide (MoS2) coating, phosphatization is applied to the bearings. Because the phosphate layer is micro-porous, it assures that molybdenum disulfide is entrapped in the interstitials between the phosphates. Also, phosphate coating provides a much larger surface area for the lubricant to attach to. In this study, several process steps, sandblasting, manganese phosphate coating, molybdenum disulfide coating, friction moment testing, wear testing, wear depth measurement, SEM, and XRD analyses were carried out. Wear tests and friction moment tests were applied to the rings of bearings of varied raceway roughness. This process ultimately provides molybdenum disulfide coated bearings optimum raceway roughness parameters for good wear resistance and optimum boundary lubrication.

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