Polyether ether ketone (PEEK) with its high glass transition temperature, low friction coefficient, high heat resistance and good machinability is a promising material to meet the growing demand for ...lightweight, durable components.
In this study, radial PEEK bearings were produced by lathe machining and their rolling contact fatigue behavior under dry condition was investigated. Under low (<80N) and high (>100N) radial loads PEEK bearings failed under 5×105 cycles by adhesion and seizure, respectively, however under medium loads, the bearings achieved relatively long lives, as well as a unique feature of self-lubrication. An optimum load range to assure the longest possible service life of PEEK components was established.
► For this research we produced PEEK (polyether ether ketone) polymer radial bearing by lathe machining. ► We performed rolling contact fatigue tests under dry conditions. ► We found that PEEK self-lubrication occurs during bearing work in contact with alumina balls. ► PEEK bearings achieved long bearing life through self-lubrication. ► We managed to determine the optimal load range for PEEK polymer radial bearing work.
Reciprocating fatigue tests were performed for five kinds of stainless steels, induction heated 13Cr-2Ni-2Mo, non-treated SUS304, hard chromium plated SUS304, soft nitrided SUS304 and SUS630. We ...observed material microstructure, hardness distribution, wear track depth and crack propagation in these materials. It is concluded that the 13Cr-2Ni-2Mo stainless steel was successfully heat treated and had high wear resistance.
Cyclic stresses around welding joint part affect the strength of mechanical components. In order to understand the fatigue phenomena caused by the cyclic stresses, non-destructive methods that can be ...related to number of stress cycles are necessary. In the present work, we used a newly developed scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor and observed three-dimensional magnetic fields of the specimen before and after four-point fatigue testing at room temperature in air. Low carbon steel plates (JIS SS400) were used in the experiments. It was found that the intensity of the magnet field in a direction perpendicular to the specimen surface was strongly affected by the fatigue cycles. This result means that we can evaluate the fatigue in welding joint area using quantitative magnetic field measurements. Furthermore, it was discovered that the key factor to evaluate the fatigue is the range between 'S' and 'N' ('peak to bottom' values) of the magnetic fields. The three-dimensional magnetic fields decrease before the dislocation does not accumulate enough to generate a small crack at the early stage of the fatigue.
Machine elements in humanoid robots for our life support require light weight, high accuracy and high output torque. In order to achieve low transmission error of the humanoid robot joints, wear of ...reinforced poly-ether-ether-ketone (PEEK) bushes against the 7075 aluminium alloy cam plates is investigated. Sliding fatigue wear tests of PEEK bushes in the humanoid robot leg joint were performed under various load torques. In the case of the bush under 127 Nm load torque at 5·7 mm s
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sliding velosity, the backlash values were stable after the running process in fatigue wear test. PEEK film was formed by the friction between PEEK bush and 7075 cam plate under compression load. The oscillation angle of the output axis in the robot joint was stable after early stage because of the solid lublication caused by the film. This means the backlash value was stable and decreased due to the PEEK film between the bush and the cam plate.
Superscript textThe influence of gas nitriding on commercial pure titanium and Ti-6Al-4V (Ti64) alloy bearings by using a Q-sw laser on the wear loss during rolling contact fatigue is investigated. ...By optimizing the laser processing parameters, such as laser scanning speed, power and beam diameter thin TiN coats of 0.5 to 3 µm were produced. Non-coated and coated bearings made of pure Titanium and Ti-6Al-4V alloy were tested in equal conditions and it was found that the titanium nitride layers significantly improve the rolling contact fatigue performance of titanium components. For tests up to 106 cycles the wear loss of the coated samples was at least ten fold lower than that of the uncoated ones and for 7.76 x 106 cycles, the wear resistance improved almost 100-fold.
The influence of gas nitriding of commercial pure titanium and Ti-6Al-4V (Ti64) alloy by using a Q-sw laser on the wear loss during rolling contact fatigue is investigated. Despite very good ...biocompatibility, high strength to weight ratio and corrosion resistance, the tribological properties of titanium alloys are inferior to those of other metal alloys, such as steel. Fretting and wear related aspects become important issues when titanium alloys are used in rolling contact applications. Titanium bearings are employed in applications requiring high strength, light weight, and minimum maintenance (for example, aerospace and defense industries). In this work, a Q-sw laser was used to coat pure commercial titanium and Ti-6Al-4V bearings with TiN in a closed chamber in nitrogen atmosphere. The samples were tested under water by using a thrust-type rolling contact fatigue machine. The microstructure, morphology and crystallographic texture of the layers were observed by laser confocal microscope, scanning electron microscope and electron backscatter diffraction (EBSD). By optimizing the laser processing parameters, such as laser scanning speed, power and beam diameter, thin TiN coats of 1 to 3 mm were produced. The wear loss of the coated samples was at least ten times lower than that of the uncoated bearings.
In this work, wear of reinforced poly-ether-ether-ketone (PEEK containing PTFE, graphite and carbon fibres) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order ...to establish the application possibilities in transmission parts in humanoid robot joints. The PEEK bush surface conditions as well as the input axis-output axis transmission error (backlash) require close examination. Sliding wear tests were performed on bushes under 900 kgfcm loaded torque, while the cam plate oscillated. Based on the wear observation, it was found that PEEK wear fragments in the interface between PEEK bush and aluminium alloy cam plate formed a PEEK film.
Due to constant exposure to high torque and loads toughness, compressive durability and light weight of joint parts are crucial factors for biped walking humanoid robot parts. When polymer ...transmission parts are used for the manufacture of humanoid robot joint, wear becomes an important factor in terms of transmission error (backlash) between the input and output axes, ex. between the motor and the robot's leg joint. In such joint system, a polymer bushes is directly connected to a cam plate, playing an important role in the robot's movement ability. In this work, the influence of wear of reinforced poly-ether-ether-ketone (PEEK) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order to establish the application possibilities in transmission parts in humanoid robot's joint. The PEEK bush surface conditions as well as the input axis-output axis backlash require close examination, so that efficient systems can be built. Sliding wear tests were performed on bushes under 0-50kgfcm loaded torque while the cam plate oscillated. Based on the wear observation, it was found that in a high load range the backlash increased along with number of cycles due to PEEK bush wear. The bush surface roughness also increased during testing. Roughness of PEEK bush surface and the loaded torque for output axis were significantly related to backlash of output axis in robot joint.
An innovative type of one-point rolling contact fatigue (RCF) machine was developed in order to investigate crack initiation and propagation in metals. The microstructural changes and propagation of ...subsurface cracks during rolling contact in specimens tested by using the new device were studied by laser confocal microscope and X-ray diffraction. It was shown that this new method presents several important advantages compared to the conventional thrust type RCF machines.
The structural gene for phospholipase D (PLD) of an actinomycete, Streptoverticillium cinnamoneum, together with its promoter region was introduced into Streptomyces lividans using a shuttle ...vector--pUC702--for Escherichia coli and S. lividans. The transformant was found to secrete a large amount of PLD (about 2.0x10⁴ U/l, 42 mg/l) when cultured in a jar fermentor. Both an initial glucose concentration of 17.5 g/l and the feeding of carbon and nitrogen sources are effective for efficient secretion of PLD; under these culture conditions, the amount of PLD secreted reached a maximum level (about 5.5 x10⁴ U/l, 118 mg/l) after about 60 h. In contrast to the original producer, Stv. cinnamoneum, which secretes only a small amount of PLD (about 1.1x10³ U/l, 2 mg/l) along with other extracellular proteins, this heterologous expression system is markedly more efficient in production of secretory PLD.
