A Multi-Station Rolling/Sliding Tribotester for Knee Bearing Materials

2004 ◽  
Vol 126 (2) ◽  
pp. 380-385 ◽  
Author(s):  
Douglas W. Van Citters ◽  
Francis E. Kennedy ◽  
John H. Currier ◽  
John P. Collier ◽  
Thomas D. Nichols
Keyword(s):  
Material Properties ◽  
Normal Load ◽  
Fatigue Behavior ◽  
Water Environment ◽  
Fatigue Tests ◽  
Test Environment ◽  
Normal Contact ◽  
Bearing Materials ◽  
Number Of Cycles

Total joint replacements traditionally employ ultra high molecular weight polyethylene (UHMWPE) as a bearing material due to its desirable material properties and biocompatibility. Failure of these polyethylene bearings can lead to expensive and risky revision surgery, necessitating a better understanding of UHMWPE’s tribological properties. A six-station rolling/sliding machine was developed to study the behavior of accelerated-aged UHMWPE in cylinder-on-cylinder contact. The normal load and sliding/rolling ratio in the oscillatory contacts can be controlled separately for each test station, as can the liquid test environment. Fatigue tests were run on the machine with UHMWPE versus cobalt-chrome cylinders in a distilled water environment at normal contact pressures of approximately 20 MPa. All specimens failed by subsurface cracking during tribotesting on the machine, and the failures were similar to those that occur in-vivo. The fatigue behavior of the polymer was analyzed to determine its relationship to oxidation and stress state in the rolling/sliding cylinder. At the 20 MPa test load, the number of cycles to fatigue failure by subsurface cracking was inversely proportional to the oxidation level. Analysis of the stress levels through the bulk of the polyethylene specimens and their relationship to the material properties provide insight as to why cracks initiate and propagate subsurface.

Fatigue Damage Evaluation in CFRP Woven Fabric Composites Through Dynamic Modulus Measurements

2004 ◽  
Author(s):  
Hideaki Kasano ◽  
Osamu Hasegawa ◽  
Chiaki Miyasaka
Keyword(s):  
Fatigue Damage ◽  
Material Properties ◽  
Elastic Moduli ◽  
Fatigue Loading ◽  
Damage Function ◽  
Fatigue Tests ◽  
Woven Fabric ◽  
Damage Development ◽  
Dynamic Elastic Moduli ◽  
Number Of Cycles

Advanced fiber reinforced composite materials offer substantial advantages over metallic materials for the structural applications subjected to fatigue loading. With the increasing use of these composites, it is required to understand their mechanical response to cyclic loading [1–4]. Our major concern in this work is to macroscopically evaluate the damage development in composites during fatigue loading. For this purpose, we examine what effect the fatigue damage may have on the material properties and how they can be related mathematically to each other. In general, as the damage initiates in composite materials and grows during cyclic loading, material properties such as modulus, residual strength and strain would vary and, in many cases, they may be significantly reduced because of the progressive accumulation of cracks. Therefore, the damage can be characterized by the change in material properties, which is expected to be available for non-destructive evaluation of the fatigue damage development in composites. Here, the tensiontension fatigue tests are firstly conducted on the plain woven fabric carbon fiber composites for different loading levels. In the fatigue tests, the dynamic elastic moduli are measured on real-time, which will decrease with an increasing number of cycles due to the degradation of stiffness. Then, the damage fimction presenting the damage development during fatigue loading is determined from the dynamic elastic moduli thus obtained, from which the damage function is formulated in terms of a number of cycles and an applied loading level. Finally, the damage function is shown to be applied for predicting the remaining fifetime of the CFRP composites subjected to two-stress level fatigue loading.

Effect of Roller-Working on Fatigue Strength Improvement of Notched Structural Stainless Steel

2006 ◽  
Vol 306-308 ◽  
pp. 151-156
Author(s):  
Priyo Tri Iswanto ◽  
Shinichi Nishida ◽  
Nobusuke Hattori ◽  
Yuji Kawakami
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Fatigue Limit ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Increase With Increase ◽  
Fatigue Strength Improvement ◽  
Rolled Specimen ◽  
Number Of Cycles

In order to study the effect of plastic deformation on fatigue behaviors of plastically deformed specimen, bending fatigue tests had been performed on notched deformed stainless steel specimens. Also pulsating fatigue tests were done on notched non-deformed specimens to evaluate the influence of mean stress on fatigue behavior of notched non-deformed specimens. The result showed that according to increase of deformation value, the fatigue limits of these specimens also significantly increase. Fatigue limit of rolled specimen does not linearly increase with increase in plastic deformation value. Based on fatigue limit diagram, the effect of compressive residual stress on fatigue limit improvement of stainless steel is higher than that of work-hardening. In case of non-deformed specimen, when the compressive mean stress increases, the fatigue limit and the number of cycles to failure increase. In case of tensile mean stress, this kind of mean stress decreases the fatigue limit.

Evaluation of Low-Cycle Fatigue in Simulated PWR Environment

2006 ◽  
Vol 326-328 ◽  
pp. 1011-1014 ◽  
Author(s):  
Ill Seok Jeong ◽  
Sang Jai Kim ◽  
Taek Ho Song ◽  
Sung Yull Hong
Keyword(s):  
Fatigue Life ◽  
Nuclear Power ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Water Environment ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Number Of Cycles ◽  
Measured Length

For developing fatigue design curve of cast stainless steel that is used in piping material of nuclear power plants, a low-cycle fatigue test rig was built. It is capable of performing tests in pressurized high temperature water environment of PWR. Cylindrical solid fatigue specimens of CF8M were used for the strain-controlled environmental fatigue tests. Fatigue life was measured in terms of the number of cycles with the variation of strain amplitude at 0.04%/s strain rates. The disparity between target length and measured length of specimens was corrected by using finite element method. The corrected test results showed similar fatigue life trend with other previous results.

Experimental fatigue behavior of carbon/flax hybrid composites under tensile loading

2020 ◽  
pp. 002199832095490
Author(s):  
Mariem Ben Ameur ◽  
Abderrahim El Mahi ◽  
Jean-Luc Rebiere ◽  
Moez Beyaoui ◽  
Moez Abdennadher ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Hybrid Composites ◽  
Fatigue Behavior ◽  
Damping Ratio ◽  
Hysteresis Loops ◽  
Tensile Loading ◽  
Fatigue Tests ◽  
Dissipated Energy ◽  
Fiber Volume ◽  
Number Of Cycles

The aim of the present study is to investigate the mechanical behavior of carbon/flax hybrid composites under static and fatigue tensile loading. The failure characteristics and parameters used in the fatigue tests were deduced from the static ones. The effect of the applied stress level, hybridization and stacking sequences on the stiffness, hysteresis loops, dissipated energy and damping, were studied for a various number of cycles during fatigue tests. The Wohler S-N curves were constructed to investigate the effect of hybridization on the fatigue behavior. The results obtained show that the fatigue performance as well as the fatigue resistance increase with the increase of the volume fraction of carbon fiber. Nevertheless, the damping ratio and the fatigue life increase with the increase of the flax fiber volume fraction.

Importance of the Roughness and Residual Stresses of Dental Implants on Fatigue and Osseointegration Behavior. In Vivo Study in Rabbits

2016 ◽  
Vol 42 (6) ◽  
pp. 469-476 ◽  
Author(s):  
Eugenio Velasco ◽  
Loreto Monsalve-Guil ◽  
Alvaro Jimenez ◽  
Iván Ortiz ◽  
Jesús Moreno-Muñoz ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Dental Implants ◽  
Bone Growth ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Bone Tissue Regeneration ◽  
Time Behavior ◽  
Pull Out ◽  
Long Time

This study focuses on the fatigue behavior and bone-implant attachment for the more usual surfaces of the different CP-titanium dental implants. The implants studied were: as-received (CTR), acid etching (AE), spark-anodization (SA), and with a grit-blasted surface (GB). Residual stresses were determined by means of X-ray diffraction. The fatigue tests were carried out at 37°C on 160 dental implants, and the stress-failure (S-N) curve was determined. The fatigue tests showed that the grit-blasting process improved fatigue life. This is a consequence of the layer of compressive residual stresses that the treatment generates in titanium surfaces. Further, our aim was to assess and compare the short- and midterm bone regenerative potential and mechanical retention of the implants in bone of New Zealand rabbits. The mechanical retention after 4 and 10 weeks of implantation was evaluated with histometric and pull-out tests, respectively, as a measure of the osseointegration of the implants. The results demonstrated that the GB treatment produced microrough that accelerated bone tissue regeneration and increased mechanical retention in the bone bed at short periods of implantation in comparison with all other implants tested. The GB surface produced an improvement in mechanical long-time behavior and improved bone growth. These types of treated implants can have great potential in clinical applications, as evidenced by the outcomes of the current study.

Mechanical Damage to the Intervertebral Disc Annulus Fibrosus Subjected to Cyclic Tensile Loading

2003 ◽  
Author(s):  
David A. Ryan ◽  
Jeffrey J. MacLean ◽  
James C. Iatridis
Keyword(s):  
Cyclic Loading ◽  
Material Properties ◽  
Annulus Fibrosus ◽  
Permanent Deformation ◽  
Mechanical Damage ◽  
Quantitative Relationship ◽  
Peak Stress ◽  
Tensile Loading ◽  
Number Of Cycles

Damage progression in the circumferential direction of the disc annulus is likely to occur in vivo in response to cyclic loading with associated degradation in tensile material properties, yet this information is not available in the literature. We hypothesize that damage of the annulus will be increased by the number of cycles and magnitude of strain applied to the tissue. Therefore, the objective of this study is to obtain a quantitative relationship between number of cycles and magnitude of tensile strain and damage on the annulus fibrosus. Damage to the annulus is assessed through measurement of permanent deformation (% elongation) and peak stress in the tissue under cyclic loading conditions.

Study on Effects of Non-Isothermal Condition and Strain Holding on Environmentally Assisted Fatigue in PWR Primary Water Environment

2016 ◽  
Author(s):  
Seiji Asada ◽  
Yuichi Fukuta ◽  
Kawaljit Ahluwalia ◽  
David Steininger
Keyword(s):  
Fatigue Behavior ◽  
Hold Time ◽  
Water Environment ◽  
Isothermal Condition ◽  
Austenitic Stainless Steels ◽  
Strain Range ◽  
Fatigue Tests ◽  
Test Material ◽  
Strain Rate Change ◽  
Primary Water

To understand the fatigue behavior of austenitic stainless steels in a simulated PWR primary water environment, the patterns were studied. Austenitic stainless steel Type 316 plate was used as the test material. Regarding non-isothermal testing: isothermal and non-isothermal fatigue tests were carried out for several patterns of temperature change and strain rate change. Typically, fatigue lives for non-isothermal tests with an out-of-phase strain change pattern were longer than those for isothermal tests. Regarding strain holding testing: multiple groups of strain range cycles were separated by a long hold time and several test cases were carried out. Testing shows there is little difference in fatigue life for strain holding tests with high strain amplitude.

scholarly journals IN VITRO MECHANICAL EVALUATION OF SPINAL FIXATION ROD CONNECTORS

2021 ◽  
Vol 20 (3) ◽  
pp. 156-160
Author(s):  
CARLOS RODRIGO DE MELLO ROESLER ◽  
RÔMULO PEDROZA PINHEIRO ◽  
ANDRÉ LUÍS ALMEIDA PIZZOLATTI ◽  
VALERIA ROMERO ◽  
HELTON LUIZ APARECIDO DEFINO
Keyword(s):  
Fatigue Behavior ◽  
Bending Moment ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Mechanical Resistance ◽  
Yield Limit ◽  
Cobalt Chromium ◽  
Level Of Evidence

ABSTRACT Objective Evaluate and compare the mechanical resistance and the fatigue behavior associated with the use of three different modalities of vertebral fixation system rod connectors through in vitro pre-clinical mechanical tests developed specifically for this application (linear, lateral with square connector and lateral with oblique connector). Methods Cobalt chromium rods 5.5 mm in diameter were used and coupled with three types of connectors: a) side rod with oblique connector, b) side rod with square connector, and c) rod and linear connectors. Quasi-static mechanical four-point bending and fatigue tests were performed. The variables measured were (I) the bending moment at the yield limit, (II) the displacement at the yield limit, (III) the rigidity of the system in flexion and (IV) the number of cycles until system failure. Results The linear system presented the greatest force and the greatest moment at the yield limit, as well as the greatest stiffness equivalent to bending. All specimens with square and oblique connectors endured 2.5 million cycles in the minimum and maximum conditions of applied moment. The specimens with linear connector endured 2.5 million cycles with fractions of 40.14% of the bending moment at the yield limit, but failed with levels of 60.17% and 80.27%. Conclusions Systems with linear connectors showed greater mechanical resistance when compared to systems with square and oblique connectors. All systems supported cyclic loads that mimic in vivo demands. Level of evidence V; In vitro research.

scholarly journals Fatigue Behavior of Al 7075-T6 Plates Repaired with Composite Patch under the Effect of Overload

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2025
Author(s):  
Bel Abbes Bachir Bouiadjra ◽  
S. M. A. K. Mohammed ◽  
Faycal Benyahia ◽  
Abdulmohsen Albedah
Keyword(s):  
Crack Growth ◽  
Fatigue Behavior ◽  
Adhesive Layer ◽  
Fatigue Tests ◽  
Thin Plates ◽  
Composite Patch ◽  
Al 7075 ◽  
Number Of Cycles ◽  
Aluminum Alloy 7075 ◽  
Cycles To Failure

Repair of aeronautical structures by composite patch bonding has shown its effectiveness in several studies during the last few decades. This repair technique leads to a retardation in the propagation of repaired cracks via load bridging across the patch throughout the adhesive layer, interfacing it with the repaired structure. The purpose of this study is to analyze the behavior of patch-repaired cracks present in thin plates made of aluminum alloy 7075-T6 and subjected to a single tensile overload. The sequence of application of overload on the fatigue behavior was also studied. Fatigue tests were conducted on Al 7075-T6 notched specimens where crack growth and number of cycles to failure were monitored for different patching/overload scenarios. A detailed fractographic study was performed on failed specimens to analyze the micromechanical behavior of the crack growth related to each scenario. The obtained results showed that the application of the overload before bonding the patch leads to an almost infinite fatigue life of the repaired plates.

scholarly journals Fatigue Crack Behavior of Stainless Steel 304 by the Addition of Carbon Nanotubes

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Rizwanulhaque Syed ◽  
Wei Jiang
Keyword(s):  
Carbon Nanotubes ◽  
Stainless Steel ◽  
Fatigue Life ◽  
Fatigue Behavior ◽  
Crack Tip ◽  
Cyclic Fatigue ◽  
Compact Tension ◽  
Fatigue Tests ◽  
Stainless Steel 304 ◽  
Number Of Cycles

Fatigue is the main source of almost half of whole mechanical failures. This research investigated the effect on cyclic fatigue behavior of stainless steel 304 (SS304) when including carbon nanotubes (CNTs) at the crack tip. The cyclic fatigue tests were conducted on compact tension (CT) specimens to establish the relationship between crack growth and the number of cycles (a-N). It is found that the incorporation of a small amount of CNTs increased the fatigue life of the SS304/metal. Micrographs showed that the enhancement in fatigue life is caused by CNTs dense arrangement around the crack tip, entangled with each other, and finer grain size. Smooth bonding at the interface of the CNTs and SS304 grains is also observed.

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