The investigation of effects of environmental conditions on fatigue strength and spring stiffness of rubber materials

2021 ◽  
pp. 009524432098816
Author(s):  
Berkan Tan ◽  
Erol Feyzullahoğlu
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Natural Rubber ◽  
Environmental Conditions ◽  
Dynamic Stiffness ◽  
Accelerated Aging ◽  
Working Environment ◽  
Spring Stiffness ◽  
Heated Oil ◽  
Before And After

Rubber materials are widely used in many applications. The most important applications of rubber materials are seals, tires, gaskets, hoses, hydraulic-pneumatic systems and vibration absorbers. Today, the working environment of rubbers varies. It has become important to see the responses of developed rubber materials to these challenging working conditions. Most rubber parts are subjected to fluctuating loads that can cause fatigue damage in their work environments. In this study, fatigue strength and spring stiffness of rubber materials under different environmental conditions is investigated. Three general factors that affect fatigue strength of rubber materials are the effects of mechanical loading, environmental effects and the effects of rubber formulation. In this study these factors are examined. For this purpose, fatigue strength and spring stiffness of natural rubber (NR), specially developed natural rubber (S-NR) and ethylene propylene diene monomer (EPDM) rubber were examined. The fatigue tests of rubber samples were performed before and after aging processes. During the study, the static and dynamic stiffness values of the rubber materials were examined before and after aging processes. As a result of experimental study, it was found that fatigue life decreases as a result of accelerated aging and annealing in heated oil processes for NR, EPDM and S-NR samples. Annealing in heated oil process is more effective in reducing fatigue life of rubber samples compared to accelerated aging. In this study, it is seen that S-NR rubber has the highest fatigue strength among rubber materials tested. It has been determined that production of samples with the semi-active vulcanization system is the most important parameter in increasing fatigue strength. In S-NR samples produced with the semi-active vulcanization system, the loss in spring stiffness occurring under different aging conditions is less compared to the loss in spring stiffness in conventional vulcanization system produced NR and EPDM samples.

Propagation of Contact Fatigue From Surface and Subsurface Origins

1966 ◽  
Vol 88 (3) ◽  
pp. 624-635 ◽  
Author(s):  
W. E. Littmann ◽  
R. L. Widner
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Failure ◽  
Contact Stress ◽  
Environmental Conditions ◽  
Failure Modes ◽  
Contact Fatigue ◽  
Initiation And Propagation ◽  
Tapered Roller ◽  
Tapered Roller Bearings

Fatigue life of tapered roller bearings and other elements subject to cyclic contact stress reflects the fatigue strength of the selected material under given environmental conditions. The various modes of contact-fatigue failure have been classified according to their appearance and the factors which promote their initiation and propagation. Illustrations of the various failure modes include rig test specimens and bearings representing normal catalog-rated life under laboratory and application environments. Evidence is presented for the propagation of contact fatigue from surface and subsurface origins.

Effect of Curing Systems on Fatigue of Natural Rubber Vulcanizates

1966 ◽  
Vol 39 (3) ◽  
pp. 785-797 ◽  
Author(s):  
W. L. Cox ◽  
C. R. Parks
Keyword(s):  
Fatigue Life ◽  
Natural Rubber ◽  
Main Chain ◽  
Accelerated Aging ◽  
Chain Scission ◽  
Rapid Loss ◽  
Effective Antioxidant ◽  
Natural Rubber Vulcanizates ◽  
Aging In Air ◽  
Oxidative Effect

Abstract The fatigue life of natural rubber-HAF black vulcanizates showed maxima when plotted as a function of crosslink concentration as did other properties related to a tearing process such as tensile strength, crack growth, and tear strength. Accelerated-sulfur vulcanizates were superior to peroxide and nonelemental-sulfur cures; this can be attributed to an exchange of polysulfide crosslinks under stress. An effective antioxidant was essential for maximum fatigue resistance. Accelerated-sulfur systems, although having a higher original fatigue life than peroxide or nonelemental-sulfur cures, showed a rapid loss on accelerated aging in air. This would indicate that an oxidative effect was involved. Sulfur group analyses of the flexed samples showed an increase in the concentration of RSSxSR linkages but a decrease in the total polysulfide sulfur, Sx, with no change in the crosslink densities. This suggests that the polysulfide linkages not only underwent exchange during the fatigue process but also homolytic cleavage to polythiyl radicals. These radicals can add to double bonds and in the presence of oxygen initiate oxidation chains which would lead to main chain scission.

scholarly journals Vigor evaluation of stored cotton seeds, including the Seed Vigor Imaging System (SVIS®)

2014 ◽  
Vol 36 (2) ◽  
pp. 222-230 ◽  
Author(s):  
Renata Oliveira Alvarenga ◽  
Julio Marcos-Filho
Keyword(s):  
Environmental Conditions ◽  
Cotton Seed ◽  
Imaging System ◽  
Seedling Emergence ◽  
Accelerated Aging ◽  
Automated Analysis ◽  
Seed Vigor ◽  
Vigor Index ◽  
Before And After ◽  
Cotton Seeds

This study aimed at evaluating efficiency of different tests to assess cotton seed vigor during storage, including the SVIS® software. Thereby, five cotton seed lots (cv. BRS 293) were stored under controlled environmental conditions of low temperature and relative humidity (10 ºC; 30% RH), and under non-controlled laboratory environmental conditions, for eight months. Evaluations of germination, first germination count, cool germination, accelerated aging test traditional and with saturated salt, field seedling emergence and seedling imaging automated analysis - SVIS® were performed before and after every two storage months. It was concluded that the cool germination, accelerated aging (traditional and with saturated salt), field seedling emergence and seedlings length (SVIS®) are adequate parameters for assessing vigor of cotton seeds during storage, and that both accelerated aging and SVIS® (vigor index and seedlings length) present enough sensitivity to identify changes on seed vigor during storage.

Assessment of Color Stability of Treated Leathers with Silicone Oil and Polyethylene Glycol

2014 ◽  
Vol 1 (1) ◽  
pp. 24-34
Author(s):  
Alireza K. ◽  
Hossein Ahmadi ◽  
Mohsen Mohammadi
Keyword(s):  
Ascorbic Acid ◽  
Polyethylene Glycol ◽  
Treatment Process ◽  
Color Change ◽  
Silicone Oil ◽  
Accelerated Aging ◽  
Color Stability ◽  
Antioxidant Additive ◽  
Before And After ◽  
Aesthetic Values

Lubricants and leather dressings are the most common treatments of dry and water logged historical leathers. Color change has a great importance during the time and treatment process, due to visual and aesthetic values of historic leather relics. Polyethylene glycol (PEG) and silicone oil (SiO) are frequently used leather dressings in the conservation procedures. Therefore, color stability of treated leathers with PEG and SiO were investigated before and after heat accelerated aging. Moreover, application of ascorbic acid was evaluated as an antioxidant additive for PEG (PEG+AA).Color change after treatment and aging were studied by colorimetry technique in the CIE *L*a*b system. Results indicated to severe color alteration in PEG treated and aged leathers with or without ascorbic acid. Whereas, SiO treated samples showed better stability and minimum color shift after aging. Silicone oil was characterized as the best dressing for historical leathers with compared to PEG and PEG+AA, due to its high stability and aesthetical properties.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

scholarly journals Wear and Friction Characteristics of 65Mn Steel for Spike-Tooth Harrow

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 319
Author(s):  
Zhiguo Lu ◽  
Chuanyu Du ◽  
Qingcai Chen ◽  
Tianying Niu ◽  
Na Wang ◽  
...  
Keyword(s):  
Friction And Wear ◽  
Working Environment ◽  
Manganese Steel ◽  
Wear Loss ◽  
Variable Parameters ◽  
Wear Characteristics ◽  
Before And After ◽  
Set Up ◽  
Worn Surface ◽  
Friction And Wear Characteristics

The friction and wear characteristics of spike-tooth material (65Mn steel) of Spike-Tooth Harrow in a two-stage peanut harvester were studied in this paper. The friction and wear tests of pin and disc on 65 manganese steel were carried out on the tribometer, then the wear loss and the friction coefficient were studied. The wear loss of the pin was acquired by calculating the mass of the pin before and after the experiment using an electronic balance. According to the actual working environment of peanut spring-finger, four variable parameters are set up: load, speed, soil moisture and soil type. The friction and wear characteristics of pins were studied under different loads, speeds and different soil environments. After wearing, the worn surface of the material was observed by scanning microscope and the wear mechanism was studied. The experimental results show that the wear of the pin increases with the increase of load and decreases with the increase of rotational speed in the same rotation number. Especially in the case of the sandy soil with 20% in moisture, a maximum wear loss of the pin is achieved.

Monitoring of Internal Damage of Glass Fibre Reinforced Composite Components Using Strain Measurements with Strain Gauges and Fibre Optic Sensors

2013 ◽  
Vol 486 ◽  
pp. 58-61 ◽  
Author(s):  
Ivo Černý
Keyword(s):  
Fatigue Strength ◽  
Glass Fibre ◽  
Shear Failure ◽  
Dynamic Stiffness ◽  
Strain Gauges ◽  
Shear Stresses ◽  
Fibre Optic ◽  
Internal Damage ◽  
Manufacture Process ◽  
Glass Fibre Reinforced

Glass fibre reinforced polymer (GRP) composites are perspective materials for manufacture of components in different machinery applications. Favourable characteristics of these materials include very high specific strength, ratio of static and dynamic stiffness, particularly beneficial in dynamically loaded structures, and potentially excellent fatigue strength provided that there are no latent internal imperfections, occurring usually in the manufacture process. Defects like insufficient wet-out of glass fibres by resin result in significant reduction of static and fatigue strength in shear. If the component thickness is high and it is loaded by bending, considerable shear stresses occur in the neutral plane, which can cause premature shear failure of the component. Results of static and fatigue tests in bending of full-scale models of longitudinal frames of railway freight vehicle bogies, manufactured from GRP polyester composites, are shown and analysed in the paper. Surface strains measured using strain gauges were monitored during the component loading, its continuous damage and were analysed. The results are in a good agreement with the subsurface strains evaluated using fibre optic sensors embedded in the component during the manufacture process. Asymmetry of strains, both internal and surface, was connected with internal defects and consequently reduced strength. On the contrary, very good fatigue resistance was characteristic for components, where strain values were symmetrical.

Fatigue Life Improvement of Welded Elements and Structures by Ultrasonic Impact Treatment

2011 ◽  
Author(s):  
Yuriy Kudryavtsev ◽  
Jacob Kleiman
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Highway Bridges ◽  
Surface Layers ◽  
Ultrasonic Impact Treatment ◽  
Stress Relieving ◽  
Life Improvement

The ultrasonic impact treatment (UIT) is relatively new and promising process for fatigue life improvement of welded elements and structures. In most industrial applications this process is known as ultrasonic peening (UP). The beneficial effect of UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of a material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The UP technique is based on the combined effect of high frequency impacts of special strikers and ultrasonic oscillations in treated material. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, heat treatment, hammer peening and application of LTT electrodes. The developed computerized complex for UP was successfully applied for increasing the fatigue life and corrosion resistance of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials. The UP could be effectively applied for fatigue life improvement during manufacturing, rehabilitation and repair of welded elements and structures. The areas/industries where the UP process was applied successfully include: Shipbuilding, Railway and Highway Bridges, Construction Equipment, Mining, Automotive, Aerospace. The results of fatigue testing of welded elements in as-welded condition and after application of UP are considered in this paper. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increasing of fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used.

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