THE MICROMECHANICAL AND TRIBOLOGICAL FEATURE OF MILD MOTTLED ENAMEL

2014 ◽  
Vol 14 (04) ◽  
pp. 1450050 ◽  
Author(s):  
HONGYI FAN ◽  
SHANSHAN GAO ◽  
YANG LIU ◽  
ZHUOLI ZHU ◽  
HAIYANG YU
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Elastic Modulus ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Normal Load ◽  
Artificial Saliva ◽  
Wear Properties ◽  
Constant Normal Load

The relationships between the basic mechanical and wear properties of mottled enamel, especially during the mastication process, are important factors and must be explored. This study evaluated mottled enamel's micro-tribological behavior under artificial saliva conditions in vitro. The basic mechanical properties were determined by nanoindentiation testing. A conical diamond nanoindenter tip was used to scratch mottled enamel and normal enamel. The scratches were sliding with a constant normal load of 2 mN, with different cycles during the tests. The hardness, elastic modulus and friction coefficient were obtained to analyze the mechanical properties. The results showed that the hardness and elastic modulus of mottled enamel were 10% and 14.6% less, respectively, than those of normal enamel. Mottled enamel showed a lower friction coefficient and a higher wear rate, compared to normal enamel. The friction coefficient did not appear to be related to the wear rate for either type of enamel. The wear mechanism for normal enamel was plastic deformation for early wear, while the combination of plastic deformation and delamination was the main damage feature of mottled enamel.

scholarly journals Mechanical Properties of Thermoplastic Polymers for Aligner Manufacturing: In Vitro Study

2020 ◽  
Vol 8 (2) ◽  
pp. 47 ◽  
Author(s):  
Francesco Tamburrino ◽  
Vincenzo D’Antò ◽  
Rosaria Bucci ◽  
Giulio Alessandri-Bonetti ◽  
Sandro Barone ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Stress ◽  
Artificial Saliva ◽  
In Vitro Study ◽  
Tensile Tests ◽  
Operating Conditions ◽  
Thermoplastic Polymers ◽  
The Impact

The use of metal-free thermoplastic materials plays a key role in the orthodontic digital workflow due to the increasing demand for clear aligner treatments. Three thermoplastic polymers commonly used to fabricate clear aligners, namely Duran®, Biolon® and Zendura®, were investigated to evaluate the effect of thermoforming (T.), storage in artificial saliva (S.A.S.) and their combination on their mechanical properties. Elastic modulus and yield stress of the specimens were characterized. Each material was characterized for each condition through tensile tests (ISO527-1). The results showed that thermoforming does not lead to a significant decrease in yield stress, except for Zendura® that showed about a 30% decrease. An increase of the elastic modulus of Duran® and Zendura®, instead, was observed after thermoforming. The same increase was noticed for the yield stress of Duran®. For S.A.S. specimens, the elastic modulus generally decreases compared to supplier condition (A.S.) and simply thermoformed material. A decrease of yield stress, instead, is significant for Zendura®. The results demonstrated that the impact of the operating conditions on the mechanical properties can vary according to the specific polymer. To design reliable and effective orthodontic treatments, the materials should be selected after their mechanical properties are characterized in the simulated intraoral environment.

High-Temperature Wear Mechanisms of a Severely Plastic Deformed Al/Mg2Si Composite

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Mahsa Ebrahimi ◽  
Abbas Zarei-Hanzaki ◽  
A. H. Shafieizad ◽  
Michaela Šlapáková ◽  
Parya Teymoory
Keyword(s):  
Plastic Deformation ◽  
Room Temperature ◽  
Wear Behavior ◽  
Normal Load ◽  
Aluminum Matrix ◽  
Hardened Layer ◽  
Dry Sliding Wear ◽  
Wear Properties ◽  
Wear Performance ◽  
Processed Material

The present work was primarily conducted to study the wear behavior of as-received and severely deformed Al-15%Mg2Si in situ composites. The severe plastic deformation was applied using accumulative back extrusion (ABE) technique (one and three passes). The continuous dynamic recrystallization (CDRX) was recognized as the main strain accommodation and grain refinement mechanism within aluminum matrix during ABE cycles. To investigate the wear properties of the processed material, the dry sliding wear tests were carried out on both the as-received and processed samples under normal load of 10 and 20 N at room temperature, 100 °C, and 200 °C. The results indicated a better wear resistance of processed specimens in comparison to the as-received ones at room temperature. In addition, the wear performance was improved as the ABE pass numbers increased. These were related to the presence of oxide tribolayer. At 100 °C, the as-received material exhibited a better wear performance compared to the processed material; this was attributed to the formation of a work-hardened layer on the worn surface. At 200 °C, both the as-received and processed composites experienced a severe wear condition. In general, elevating the temperature changed the dominant wear mechanism from oxidation and delamination at room temperature to severe adhesion and plastic deformation at 200 °C.

Water Absorption, Friction and Wear Behaviors of Polypropylene Composites Filled with Hydroxyapatite

2017 ◽  
Vol 733 ◽  
pp. 60-64
Author(s):  
Munir Tasdemir ◽  
Ozkan Gulsoy
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Water Absorption ◽  
Polymer Composites ◽  
Friction And Wear ◽  
Wear Properties ◽  
Polypropylene Composites ◽  
Friction And Wear Properties

In the present work, the friction and wear properties of Polypropylene (PP) based composites filled with Hydroxyapatite (HA) particles were studied. Fillers contents in the PP were 10, 20, and 30 wt%. The effects of hydroxyapatite ratio on the water absorption, friction and wear properties of the polymer composites is presented. The result showed that the addition of HA to the composite changed the water absorption, friction coefficient and wear rate.

scholarly journals Fabrication and Tribological Properties of Copper Matrix Solid Self-Lubricant Composites Reinforced with Ni/NbSe2 Composites

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1854
Author(s):  
Fei-xia Zhang ◽  
Yan-qiu Chu ◽  
Chang-sheng Li
Keyword(s):  
Powder Metallurgy ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Tribological Properties ◽  
Friction And Wear ◽  
Copper Matrix ◽  
Wear Properties ◽  
Disk Friction ◽  
Friction Reducing ◽  
Properties Of Composites

This paper presents a facile and effective method for preparing Ni/NbSe2 composites in order to improve the wettability of NbSe2 and copper matrix, which is helpful in enhancing the friction-reducing and anti-wear properties of copper-based composites. The powder metallurgy (P/M) technique was used to fabricate copper-based composites with different weight fractions of Ni/NbSe2, and tribological properties of composites were evaluated by using a ball-on-disk friction-and-wear tester. Results indicated that tribological properties of copper-based composites were improved by the addition of Ni/NbSe2. In particular, copper-based composites containing 15 wt.% Ni/NbSe2 showed the lowest friction coefficient (0.16) and wear rate (4.1 × 10−5 mm3·N−1·m−1) among all composites.

Friction Coefficient and Wear Rate of Different Materials Sliding Against Stainless Steel

2013 ◽  
Vol 1 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Dewan Muhammad Nuruzzaman ◽  
Mohammad Asaduzzaman Chowdhury
Keyword(s):  
Stainless Steel ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Normal Load ◽  
304 Stainless Steel ◽  
Sliding Velocity ◽  
Stainless Steel 304 ◽  
Different Types ◽  
Pin On Disc ◽  
Ss 304

This paper examines the relation between friction/wear and different types of steel materials under different normal loads and sliding velocities and to explore the possibility of adding controlled normal load and sliding velocity to a mechanical process. In order to do so, a pin on disc apparatus is designed and fabricated. Experiments are carried out when different types of disc materials such as stainless steel 304 (SS 304), stainless steel 316 (SS 316) and mild steel slide against stainless steel 304 (SS 304) pin. Variations of friction coefficient with the duration of rubbing at different normal loads and sliding velocities are investigated. Results show that friction coefficient varies with duration of rubbing, normal load and sliding velocity. In general, friction coefficient increases for a certain duration of rubbing and after that it remains constant for the rest of the experimental time. The obtained results reveal that friction coefficient decreases with the increase in normal load for all the tested materials. It is also found that friction coefficient increases with the increase in sliding velocity for all the materials investigated. Moreover, wear rate increases with the increase in normal load and sliding velocity. At identical operating condition, the magnitudes of friction coefficient and wear rate are different for different materials depending on sliding velocity and normal load.

Wear Properties of Y-TZP Ceramics Dispersed with Second Phase Particles

2008 ◽  
Vol 368-372 ◽  
pp. 744-747
Author(s):  
Xiao Ping Liang ◽  
Shao Bo Xin ◽  
Xiao Hui Wang ◽  
Zheng Fang Yang
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Mass Fraction ◽  
Normal Load ◽  
Roller Bearing ◽  
Second Phase ◽  
Wear Properties ◽  
Wear Rates ◽  
Second Phase Particles ◽  
Better Than

The wear properties of ADZ (alumina dispersed in Y-TZP) and MDZ (mullite dispersed in Y-TZP) were investigated by using a ring-on-block tribometer. The results showed that for Y-TZP ceramic, the addition of alumina phase (with 10-20% in mass fraction) leads to an improved wear resistance. With the increase of the normal load, the wear rates of ADZ ceramics increase. Under low and medium normal load (100N and 300N), the wear resistance is controlled by the hardness of ceramics, and under high normal load (500N) the fracture toughness is obviously contributed to the wear resistance of the ceramics. For MDZ ceramic, the wear resistance of 15MDZ (15wt% mullite dispersed in Y-TZP) is better than that of 20 MDZ (20wt% mullite) under the normal load from 100 N to 500 N. The mechanical properties of 15MDZ are worse than that of Y-TZP ceramic, but the wear resistance is enhanced due to the action of “needle roller bearing” of the fractured rod-like mullite particles.

Effects of potassium titanate whisker and glass fiber on tribological and mechanical properties of PTFE/PEEK blend

2017 ◽  
Vol 30 (6) ◽  
pp. 752-764 ◽  
Author(s):  
Xue Teng ◽  
Lefei Wen ◽  
Yunxia Lv ◽  
Wenge Tang ◽  
Xiaogang Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Glass Fiber ◽  
Tribological Properties ◽  
Reinforcing Effect ◽  
Potassium Titanate ◽  
Polyether Ether Ketone ◽  
Ether Ketone

Two series of 10% polytetrafluoroethylene (PTFE)/polyether ether ketone (PEEK) composites reinforced with potassium titanate whisker (PTW/PTFE/PEEK) and chopped glass fiber (GF/PTFE/PEEK) were prepared and characterized. We investigated the effects of the additives on thermal stability, tribological properties, mechanical properties, and rheological behavior. The results illustrated that the mechanical properties of 10% PTFE/PEEK blend can be dramatically improved by incorporating either PTW or GF; however, the reinforcing effect of GF was found to be superior. It was found that 1% additive resulted in blends with the best tribological properties. Compared to the unmodified blend, the friction coefficient and wear rate of the 1% PTW blend decreased by 7.2% and 21%, respectively, while the corresponding values of 1% GF blend decreased by 0.66% and 51%, respectively.

Friction Characteristics and Adhesion Force Under Low Normal Load

1995 ◽  
Vol 117 (4) ◽  
pp. 569-574 ◽  
Author(s):  
Yasuhisa Ando ◽  
Yuichi Ishikawa ◽  
Tokio Kitahara
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Adhesion Force ◽  
Normal Load ◽  
Adhesion Forces ◽  
Test Pieces ◽  
Before And After ◽  
Constant Normal Load ◽  
The Mean ◽  
Steel Balls

The friction coefficient and adhesion force between steel balls and flat test pieces were measured during friction under low normal load in order to examine the tribological characteristics. First, the friction coefficients were measured under a constant normal load of 0.8 to 2350 μN, and the adhesion forces were measured before and after each friction. The result showed that the friction coefficient was highest at low normal loads, while the friction force divided by the sum of the normal load and the mean adhesion force was almost constant over the whole range of loads. Second, when the normal load was reduced gradually during friction, friction still acted when the normal load became negative and a pulling off force was applied to the surface. Thus an adhesion force acts during friction and this adhesion force affects the friction force in the same way as the normal load.

Wear Properties of DLC and Plasma Sprayed WC Structure Coating

2007 ◽  
Vol 127 ◽  
pp. 245-250 ◽  
Author(s):  
Mitsuyasu Yatsuzuka ◽  
Yoshihiro Oka ◽  
Akifumi Tomita ◽  
Noritaka Murata ◽  
Mitsuaki Hirota
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Testing Machine ◽  
Carbon Film ◽  
Wear Testing ◽  
Wear Properties ◽  
Dlc Film ◽  
Coated Metal ◽  
Hydrocarbon Gas ◽  
Plasma Sprayed

Diamond-like carbon film (DLC) with an interlayer of plasma sprayed tungsten-carbide (WC) was prepared on an aluminum alloy substrate (A5052) by a hybrid process of plasma-based ion implantation and deposition using hydrocarbon gas. Typical thicknesses of DLC and WC films were 1 μm and 100 μm, respectively. The hardness and friction coefficient of DLC were typically 15 GPa and 0.15, respectively. The durability of DLC/WC/A5052 system was evaluated from the measurement of the friction coefficient by a ball-on-disk friction tester in which the loaded ball was drawn repeatedly across a sample and the load was increased with each traverse. For the DLC/A5052 system, which has no WC interlayer, the DLC film was broken quickly because of distortion of the substrate. For the DLC/WC/A5052 system, on the other hand, the DLC film was excellent in durability for long running. The wear rate of rubber rotor to the metal rotor was measured by a roller-pitching-type wear testing machine, showing large reduction in wear rate using DLC-coated metal rotor.

Experimental Investigation into the Influences of Weathering on the Mechanical Properties of Sedimentary Rocks

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiaoshuang Li ◽  
Yingchun Li ◽  
Saisai Wu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Friction Coefficient ◽  
Uniaxial Compression ◽  
Sedimentary Rocks ◽  
Uniaxial Tensile ◽  
Mechanical Parameters ◽  
Uniaxial Tensile Strength ◽  
Weathering Grades

The time-dependent behaviors of the sedimentary rocks which refer to the altering of the mechanical and deformable properties of rock elements in the long-term period are of increasing importance in the investigation of the failure mechanism of the rock strata in underground coal mines. In order to obtain the accurate and reliable mechanical parameters of the sedimentary rocks at different weathering grades, the extensive experimental programs including the Brazilian splitting test, uniaxial compression tests, and direct shear tests have been carried out on the specimens that exposed to the nature environments at different durations. The correlation between the weathering grades and mechanical parameters including uniaxial tensile strength, uniaxial compression strength, elastic modulus, Poisson’s ratio, cohesion, and friction coefficient was proposed. The obtained results suggested that uniaxial tensile strength, uniaxial compressive strength, elastic modulus, and cohesion dramatically decreased with increasing weathering time, characterized as the negative exponential relationship in general. The influences of various weathering grades on fracture behavior of the rock specimens were discussed. The cumulative damage of the rock by the weathering time decreased the friction coefficient of the specimens which led to the initiation and propagation of microcrack within the rock at lower stress conditions. The obtained results improved the understanding of the roles of weathering on the mechanical properties of sedimentary rocks, which is helpful in the design of the underground geotechnical structures.

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