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- Bergstedt, Edwin, 1986-
(författare)
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A Comparative Investigation of Gear Performance BetweenWrought and Sintered Powder Metallurgical Steel : Utilizing In-situ Surface Profile Measurements to Investigate theInitiation and Evolution of Micropitting and Pitting Damage
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vehicle electrification is a strong trend that introduces new challenges, such as increased input speed of the transmission and increased power density. Alsothe noise emittance of the gearbox is of increasing importance, as the sound of the gearbox is no longer masked by the internal combustion engine. Pressed and sintered powder metallurgical steel could be an interesting alternative towrought steel; the internal porosity has a dampening effect on the noise, and gears can be made in a fast and efficient process. However, current manufacturing of powder metallurgical steel has significant performance limitations. The Nanotechnology Enhanced Sintered Steel Processing project aims to reduce the gap in performance between conventional steel and powder metallurgical steel. One of the potential benefits is that with the inclusion of nano-powder the density can be increased. To validate the new material, its performance needs to be compared to the performance of current generation powder metallurgical materials and also to wrought steel. It is therefor crucial to be able to test and evaluate different materials and gears. This thesis has developed methods for testing, comparing, and evaluating the performance of gears. Powder metallurgical steel has been tested and compared to wrought steel; the efficiency as well as pitting life have been investigated in an FZG test rig. Also the effects of different surface finishing operations have been evaluated. The gear flanks were measured in-situ in the gearbox using a stylus instrument; an optimisation routine was created to fit the measurements to the theoretical involute profile. This enabled an in-depth analysis of surface wear and presented an opportunity to investigate micropitting initiation. It was found that the damage mechanisms of wrought steel and powder metallurgical steel are similar and related to the surface finishing method. However, the powder metallurgical steel was also susceptible to sub-surface cracks. Superfinished gears can be negatively influenced by the lack of tip relief as cracks initiate in the surface layer of the root, rapidly destroying the tooth.
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| 2. |
- Bergstedt, Edwin, et al.
(författare)
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Gear micropitting initiation of ground and superfinished gears : Wrought versus pressed and sintered steel
- 2021
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 160
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with CPT gears. The materials are wrought steel (16MnCr5) and a commercial powder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding and superfinishing. Experimental results show that the superfinishing prevented micropitting, but led to premature failure due to cracks in the root caused by tip-to-root interference. Micropitting was initiated at a higher load stage for the powder metallurgical steel compared to the ground wrought steel. The failure mechanisms were similar between materials with the same surface finish. The powder metallurgical steel showed subsurface initiated fatigue compared to the wrought ground steel having surface-initiated fatigue. Testing new finishing methods and materials, one has to be aware of the influence of the gear micro geometry.
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| 3. |
- Bergstedt, Edwin, 1986-, et al.
(författare)
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Gear Micropitting Initiation of Ground and Superfinished Gears: Wrought versus Pressed and Sintered Steel
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Ingår i: Tribology International. - 0301-679X .- 1879-2464.
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with C-PT gears. The materials are wrought steel (16MnCr5) and a commercialpowder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding andsuperfinishing. Experimental results show that the superfinishing prevented micropitting, but ledto premature failure due to cracks in the root caused by tip-to-root interference. Micropitting wasinitiated at load stage 8, and 9 for the ground wrought, and powder metallurgical steel respectively.The failure mechanisms were similar between materials with the same surface finish. The powdermetallurgical steel showed subsurface initiated fatigue compared to the wrought groundsteel having surface-initiated fatigue. Testing new finishing methods and materials, onehas to be aware of the influence of the gear micro geometry.
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| 4. |
- Bergstedt, Edwin, et al.
(författare)
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Influence of gear surface roughness on the pitting and micropitting life
- 2020
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Ingår i: Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science. - : SAGE Publications Ltd. - 0954-4062 .- 2041-2983. ; 234:24, s. 4953-4961
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Tidskriftsartikel (refereegranskat)abstract
- Pitting and micropitting are the two main gear rolling contact fatigue modes. It is widely accepted that micropitting will lead to pitting; however, the relationship between pitting and micropitting life needs further investigation. In this work, micropitting and pitting tests were performed on an FZG back-to-back test rig using standard FZG PT-C and GF-C gears. The gear tooth profile change due to micropitting and pitting damage was measured in situ in the gearbox using a profilometer after each test. The gear surface roughness parameters were calculated from the measured tooth profile. A Gaussian low pass filter with cut off length (Formula presented.) mm was applied to the measured tooth profile to obtain the waviness. The calculated roughness parameters and the obtained tooth profile with waviness for each test were imported into the KISSsoft software to calculate the contact stress and specific film thickness at the corresponding load stage. Experimental results show that smooth gear surface can reduce or even avoid micropitting damage, but could lead to a reduction in pitting life.
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| 5. |
- Bergstedt, Edwin, et al.
(författare)
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Influence of the DIN 3962 Quality Class on the Efficiency in Honed Powder Metal and Wrought Steel Gears
- 2020
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Ingår i: Tribology Transactions. - : Taylor and Francis Inc.. - 1040-2004 .- 1547-397X. ; 63:6, s. 1076-1084
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Tidskriftsartikel (refereegranskat)abstract
- To increase the efficiency of a gearbox, research on gear mesh loss is of importance. Britton et al. concluded that the surface finishing method affects the gear mesh efficiency. The efficiency benefits of superfinishing a surface and reducing the surface roughness have been reported by Kahraman. A novel method for calculating the bearing loss torque was proposed by Tu et al. Andersson et al. found that the efficiency can vary between 2 and 5% during repeated efficiency tests due to variations in the assembly process. This work investigates how the honing surface finishing process and DIN 3962 quality class affect the gear mesh efficiency by performing tests in an FZG back-to-back test rig. Two materials, a powder metal and a wrought steel, were tested. All gears were finished using a honing process and sorted according the measured quality class. Powder metal gears of class 6, 7, 8, and ≥9 and wrought steel gears of class 6, 7, and ≥9 were tested. The efficiency were calculated from measuring the torque required to maintain a constant velocity of the FZG test rig. The results from the efficiency tests showed no significant difference in efficiency between the wrought steel and powder metal steel gears. In addition, no obvious correlation between the DIN 3962 quality class and the gear mesh efficiency could be found. When examining the wrought steel material it was found that the reproducibility of the efficiency was comparable to the assembly error of the test rig, despite the variation in quality class.
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| 6. |
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| 7. |
- Lin, Jiachun, et al.
(författare)
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A quantitatively distributed wear-measurement method for spur gears during micro-pitting and pitting tests
- 2021
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- FZG gear testing is widely used to evaluate the performance of lubricants, gear materials, and gear-tooth geometries under different loads. During these tests, gear tooth wear results in the loss of gear profile in the form of micro-pitting, pitting and scuffing, can be observed. However, gear wear is usually measured by weighting. This method cannot be used to study the wear depth on a specific point on the gear-tooth surface. In this study, tooth profiles were measured via a profilometer during the FZG gear-pitting test. Moreover, an algorithm was developed to quantitatively evaluate the distributed cumulative wear and wear progress at a certain test stage. Simultaneously, the real tooth profile was obtained. Experiments were performed to validate the proposed method, and the results showed that gear-tooth-surface wear can be quantitatively determined. Thus, the proposed method can be used for further gear-failure-prediction experiments.
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| 8. |
- Lin, Jiachun, et al.
(författare)
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In situ measurement of gear tooth profile during FZG gear micropitting test
- 2019
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Ingår i: SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES. - : IOP PUBLISHING LTD. - 2051-672X. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- According to the GFKT-C/8.3/90 FZG gear micropitting test procedure, the average value of gear tooth profile deviation is used as the failure criterion. Typically, gear tooth profile deviation is measured using a gear measuring machine. In order to do that during the FZG gear test, the gears tested have to be disassembled from, and assembled to the test rig. This process is tedious, time-consuming and is likely to add uncertainty to the testing results. An in situ gear tooth profile measurement method has been developed and applied in FZG gear micropitting tests. The tooth profile of the tested gear was measured in-situ in the gearbox before, during and after each load stage of the gear micropitting test. An algorithm was developed to fit the measured profile to its theoretical shape. Furthermore, a tooth profile change evaluation algorithm was developed for monitoring the evolution of the tooth profile during the duration of the test. The whole methodology was exemplified with a wrought gear test case run to pitting damage.
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