•An systematic experimental investigation is conducted to identify the failure modes of the lubricated PEEK gears under different loading conditions through the enclosed power flow test rig, ...supplemented with the measurements on wear, vibration and the surface micro-topography.•S evere thermal damage occurs on the tooth surface of the PEEK gear under dry contact operation, while the no thermal damages are observed under the lubrication condition due to the fact that the heat accumulation on the tooth surface is dissipated effectively.•Experimental results reveal that the pitting-induced tooth breakage occurs under light and moderate loading conditions, while the tooth root breakage dominates under the heavy duty loading conditions.
An experimental investigation is conducted to identify the failure modes of the lubricated PEEK gears under different loading conditions through the enclosed power flow test rig, supplemented with the measurements on wear, vibration and the surface micro-topography. The FZG C type gear pair is selected while the mating driving gear is chosen with the material of C45. Experimental results reveal that the pitting-induced tooth breakage occurs under light and moderate loading conditions, while the tooth root breakage dominates under heavy duty loading conditions. The measurement of the wear and the tooth surface micro-topography help to identify that the micro-pits near the pitch line lead to the final tooth breakage under moderate loading conditions. Meanwhile, the insufficiency of the bending strength under heavy loading conditions is the cause of the tooth root fracture.
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•A high-power-density design method via adaptive NSGA-III and surrogate sub-models for polymer gear systems is outlined.•The key factors affecting the operating performance of polymer ...accessory gearbox are explained.•Compared with metallic design scheme, the polymer scheme achieves a 49 % weight reduction and power density with 22.5 kW/kg.
There is a growing and prevalent trend in the power transmission field of high-performance polymers replacing metallic materials given the strict light-weight requirement. Polymer gears exhibit a low elasticity modulus, high-temperature sensitivity, and increased geometric design flexibility, presenting technical challenges to the straightforward application of metallic design methods to polymer gear systems. This study is centred on the development of a high-power-density polymer gear transmission system for the accessory unit of a gas turbine engine, utilising an adaptive NSGA-III algorithm and surrogate sub-models. A comprehensive assessment indicator for the operating performance of the transmission system is suggested, encompassing gear strength, bearing temperature, and shaft torsional stiffness. The model made it possible to simultaneously optimise forty-six structural parameters, including gear tooth module, web thickness, and bearing clearance. In contrast to the original steel design scheme, the optimised polymer gear transmission system indicated a 49% reduction in weight and a 1.96-fold increase in power density. This presents a method for substituting steel with polymers for effective power transmission.
•The injection molding lunker defect is detected by X-ray CT and the polymer gear fatigue model considering lunker is established considering the thermal-elastic-plastic constitutive behavior.•The ...effects of loading condition and the lunker defect on the POM gear fatigue life are studied numerically and experimentally.•The failure mode competitive mechanism of POM gears reveals that the final failure mode is more sensitive to the loading condition, but the presence of injection molding lunker rises the possibility of tooth root breakage.
Polymer gears manufactured with injection molding have been widely used in many industries, but the unavoidable injection molding lunker defects limit the loading capacity and the further use of polymer gears in power transmissions. In this work, injection molding lunker defects are detected by X-ray CT and a polymer gear fatigue model with lunker defect is established considering the thermal-elastic-plastic constitutive material behavior. Durability tests are also conducted, and the fatigue lives correspond well with simulation results. Results reveal that the lunker defect jeopardizes the loading capacity of tooth root under medium or heavy loading conditions, while the tooth flank failure is significantly influenced by the loading condition.
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This study presents the results of detailed wear process examination on polyformaldehyde gears under both dry and lubricated conditions. A multi-purpose durability test rig was employed to study the ...wear performance of polyformaldehyde gear pairs. The wear behaviors of polyformaldehyde gears under dry and oil-lubricated operating conditions were characterized via measurements of gear tooth surface micro-topography and tooth profile deviation. Under the dry running condition, a hump and a gully appear on the tooth surface in the pitch line area of the driving gear and the driven wheel, respectively. The largest amount of wear was observed around the tooth root of the driving gear. However, the gear tooth wear pattern with lubrication is different from that under the dry running condition.
Acetal gears are the most widely applied type among these polymer gears. Acetal gears may suffer from many failure forms such as severe wear, tooth breakage or tooth surface cracks depending on the ...loading conditions and the lubrication and temperature environment. The contact fatigue performance of acetal gear relates to many factors including temperature and load, however, their influences on the mechanical properties and fatigue parameters of the acetal material are still not fully understood. In this work, the thermo-elastic-plastic constitutive equations are derived to describe the acetal material behavior during gear meshing process, and the modified Brown-Miller multi-axial fatigue criterion is proposed to estimate the polymer gear contact fatigue life. Durability tests of acetal gear against steel gear are conducted based upon a developed test rig. Results reveal that the temperature rise could significantly reduce the contact pressure of acetal gear due to the decay of the modulus, but still jeopardize the fatigue life on tooth flank because the fatigue properties are also affected by the temperature rise. The predicted location of fatigue failure zone on the tooth and the lifespan agree well with experimental observation.
•Temperature effect on fatigue life of acetal gear is considered.•Thermo-elastic-plastic constitutive equations of acetal gear is derived.•The predicted fatigue lifespan agree well with test results.
Highlights
Optimizing the current collectors with rGO and the addition of CNT in PPy, and the structural pulverization is prevented significantly.
Areal capacitances of 65.9 to 70 mF cm
−2
are ...achieved for PPy-CNT@rGO microsupercapacitors (MSCs) with 79% capacitance retention after 10,000 cycles.
The MSC-derived capacitive micro-strain sensor is capable of biosignals detection.
The micro strain sensor is capable of detecting wide levels of applied strain with short response/recovery time and excellent reliability.
Conducting polymers have achieved remarkable attentions owing to their exclusive characteristics, for instance, electrical conductivity, high ionic conductivity, visual transparency, and mechanical tractability. Surface and nanostructure engineering of conjugated conducting polymers offers an exceptional pathway to facilitate their implementation in a variety of scientific claims, comprising energy storage and production devices, flexible and wearable optoelectronic devices. A two-step tactic to assemble high-performance polypyrrole (PPy)-based microsupercapacitor (MSC) is utilized by transforming the current collectors to suppress structural pulverization and increase the adhesion of PPy, and then electrochemical co-deposition of PPy-CNT nanostructures on rGO@Au current collectors is performed. The resulting fine patterned MSC conveyed a high areal capacitance of 65.9 mF cm
−2
(at a current density of 0.1 mA cm
−2
), an exceptional cycling performance of retaining 79% capacitance after 10,000 charge/discharge cycles at 5 mA cm
−2
. Benefiting from the intermediate graphene, current collector free PPy-CNT@rGO flexible MSC is produced by a facile transfer method on a flexible substrate, which delivered an areal capacitance of 70.25 mF cm
−2
at 0.1 mA cm
−2
and retained 46% of the initial capacitance at a current density of 1.0 mA cm
−2
. The flexible MSC is utilized as a skin compatible capacitive micro-strain sensor with excellent electromechanochemical characteristics.
The purpose of this study was to investigate the clinical utility of three-dimension (3D) high-resolution inversion recovery (IR)-prepared fast spoiled gradient-recalled (SPGR) magnetic resonance ...imaging (MRI) in the diagnosis of cranial nerve meningeal carcinomatosis (MC).
A total of 114 patients with MC from January 2015 to March 2020 were enrolled and their MRIs were analyzed retrospectively. All patients underwent MRIs before being administered a contrast agent. Both a 2D conventional MRI sequence and a 3D IR-prepared fast SPGR high-resolution T1-weighted (BRAVO) scan sequence were measured after contrast agent administration. The characteristics of MC and the involved cranial nerves were then examined.
Among the 114 MC patients, 81 (71.05%) had cranial nerve enhancement on contrast-enhanced 3D-BRAVO imaging, while only 41 (35.96%) had image enhancement on conventional MRI. The contrast-enhanced 3D-BRAVO displayed stronger image contrast enhancement of the cranial nerves than the conventional MRI (P < 0.001). Furthermore, detection rates for the facial and auditory nerves, trigeminal nerve, oculomotor nerve, sublingual nerve, optic nerve, glossopharyngeal/vagal/accessory nerve, and abductor nerve on contrast-enhanced 3D-BRAVO imaging were 58.77%, 47.37%, 9.65%, 8.77%, 5.26%, 3.51%, and 0.88%, respectively. We found a statistically significant difference between the affected facial and auditory nerves, as well as the trigeminal nerve, oculomotor nerve, sublingual nerve, and optic nerve.
In MC, contrast-enhanced 3D-BRAVO imaging displayed the cranial nerves more effectively than 2D conventional enhanced MRI. The facial, auditory, and trigeminal nerves are the primary nerves involved in MC, and improved scanning of these nerves would aid in the early detection and treatment of MC.
Gears fabricated using powder metallurgy technique (PMT) have the potential to replace traditional wrought gears due to their very high forming efficiency and relatively low cost. However, their ...practical applications are restricted due to the lack of understanding of their fatigue properties and failure mechanisms. This work investigates the contact fatigue performance and corresponding failure mechanism of a typical Fe-based small-module gears fabricated by PMT. The fatigue tests were conducted under grease lubrication condition, using a power-opened small-module gear testing rig. The experimental results show that the current PMT fabricated small-module gears exhibit contact fatigue properties comparable to those of traditional wrought steel gears. It has been found that the subsurface cracks induced from pores are the dominant cause of spalling of PMT fabricated small-module gears during rolling contact. The cracks tend to propagate between adjacent pores, playing a vital role in the overall fatigue life. Thus, this study suggests that PMT can be a successful method for fabricating Fe-based small-module gears with excellent contact fatigue property if formation of pores during fabrication is well inhibited.
Abstract
The advancement in materials and lubrication has significantly improved the load-carrying capability of polymer gears, making them ideal for replacing metal gears in power transmission. ...However, this conversion is not as simple as substituting steel with polymer; it requires a thorough redesign of the structural parameters specific to polymer gears. To enable the metal-to-polymer conversion of gear in power transmission, a model for optimizing polymer gear systems was developed. An investigation of the accessory transmission system of a low-thrust turbofan aeroengine was conducted. A comprehensive performance index for the accessory transmission was developed using combined weighting coefficients to achieve the optimization goals including total mass, transmission efficiency, maximum transmission error and so on. The polymer gear system developed using the proposed optimization model demonstrated a 70.4% reduction in total mass compared to the metal gear system, as well as a transmission error decrease of over 29% when compared to polymer gear systems with standard tooth profiles. The contribution analysis results demonstrated that optimizing the tooth width, pressure angle, and addendum height of polymer gears can significantly enhance the load-carrying capacity of the polymer gear system while maximizing tooth profile flexibility.
Loading capacity of POM gear under oil lubrication ZHONG, Bingbing; SONG, Hailan; LIU, Huaiju ...
Journal of Advanced Mechanical Design, Systems, and Manufacturing,
2022, 2022-00-00, 20220101, 2022-01-01, Letnik:
16, Številka:
1
Journal Article
Recenzirano
Odprti dostop
As one of the most common polymer materials, POM gear has been widely applied in automatic transmission boxes, intelligent house devices, etc. Though the mechanical properties of POM material have ...been extensively studied, the loading capacity and failure mechanism of POM gear still require to be explored. This paper experimentally investigates the loading capacity of medium-module POM gears based upon the durability test under various loading conditions. The POM gears are mated with 18CrNiMo7-6 steel pinions. The tooth wear, surface roughness, and tooth profile evolution are recorded. In the experimental results, the contact fatigue failure was observed in tooth flank of the POM gear with medium modulus under oil lubrication conditions, including tooth surface pitting and fatigue cracks. And according to the experimental durability life data, the contact fatigue S-N curve of POM gear is fitted.
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