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| 2. |
- Khodaee, Alireza, 1984-, et al.
(författare)
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Evaluation of effects of geometrical parameters on density distribution in compaction of PM gears
- 2017
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Ingår i: AIP Conference Proceedings. - : Author(s). - 0094-243X. - 9780735415805
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Konferensbidrag (refereegranskat)abstract
- The usage of powder metallurgy (PM) for manufacturing of transmission components in automotive industries has been studied by many researchers. PM components have become of interest in recent years due to advancements in post processing possibilities such as hot isostatic pressing (HIP). Still in many of the forming process routes for making components from PM materials, the compaction of the powder into green component is the first step. Compaction is required to put the powder into the near net shape of the desired component and it causes a density gradient in the body of the green component. Basically the friction between powder particles and between the powder particles and die walls are the well-known roots for such density gradients in the compacted component. Looking at forming of PM gears, the gradient in density is one of the most important roots of problems in the processing of PM gears as well. That is because making a gear with full density and no pores will be very costly if large density gradients exist in the green component. The purpose of this study is to find the possible relations between the gear geometry and the density gradients in the green component after compaction in addition to the friction effects. For this purpose several gears should be tested. To reduce the research costs, the finite element (FE) method is used. First a FE model of the compaction process is developed and verified. To investigate the relations between the density gradients and the gear parameters such as addendum diameter (da) and the face width (b) several gear geometries have been studied. The compaction of selected gears is simulated using the FE model. The simulations results which are the distribution of density in the green component are evaluated and discussed and conclusion are made based on them. © 2017 Author(s).
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| 3. |
- Khodaee, Alireza, 1984-, et al.
(författare)
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Finite Element Simulation as a Tool to Evaluate Gear Quality after Gear Rolling
- 2013
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Ingår i: Current State-Of-The-Art On Material Forming. - : Trans Tech Publications Inc.. - 9783037857199 ; , s. 300-306
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Konferensbidrag (refereegranskat)abstract
- Gear rolling is a manufacturing technique for gears with many advantages like reducedmaterial consumption, reduced scrap generation, fast cycle times, good surface quality andimproved final properties of the gear wheels compared to conventional production technology basedon machining. In order to make use of all these advantages it is desired to reach the final shape ofthe gear wheel already after rolling. This means that post treatments like grinding should beavoided. This puts high requirements on the shape accuracy after gear rolling.In this paper it was studied if finite element simulation could be used to evaluate the shape accuracyafter gear rolling. The measurement of shape accuracy of gear wheels is specified in standards likeISO1328-1. The allowed deviations from nominal shape are often of the order of 10-30 μm for verygood qualities. So if such evaluation shall be possible from a finite element simulation the accuracymust be of the same order.In order to have sufficient accuracy of the finite element simulation 2D simulations were performedon a spur gear. The FE code DEFORM was utilized. The shape accuracy was evaluated for gearrolling of two cases. One case had gears with the module of 1 mm. The other case involved gearswith a significantly larger module of 4 mm. This was an interesting case since it is known that it ismore difficult to roll the gear with good accuracy in large modules.
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| 4. |
- Khodaee, Alireza, 1984-
(författare)
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Innovative Manufacturing Method for Gears for Heavy Vehicle Application
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis is a summary of research result on an innovative manufacturing method for production of PM gears for application in heavy vehicle. The method uses a powder metal densifications process route to ensure full density. The thesis addresses an innovative processing route where loosely packed powder goes through a double pressing followed by double sintering combined with hot isostatic pressing at the end of the chain in order to reach the full density for the PM gear. The thesis addresses three research questions. First the feasibility of reaching full density for a gear constructed of standard modules relevant for heavy vehicles is investigated. Then the effect of gear geometry on the PM processing is studied. It is revealed that gear geometry influences the density distributions hence the final result. Therefore, the part of the research focusing on the relationship between gear dimensions and the densification results is conducted. It is shown that specific gear geometrical parameters could be more suitable to reach full density. Finally, a prediction model is proposed which can be used in order to measure the density before HIP and exclude risky geometries. A combined numerical and experimental research methodology is implemented in order to address the research questions in the thesis. A verified hardening model for one sample powder mixture is developed in ABAQUS using experimental densification tests. The model helps us to simulate the first pressing and follow the density gradients generated during the first pressing step. The density gradient will be stored in the green component and modified after first sintering and then is used as the input for the second pressing simulation. The result of the second pressing simulation is then modified to include the second sintering effects and finally it is used as the input for HIP simulation. This chain of simulations helps us to understand the gear geometry influence on the density gradients and neutral zone formation during the pressing process. It also ensures that the transition of open pores to closed pores occurs before HIP as a requirement to reach fully density in the analysis. Physical experiments were performed in order to validate FE simulations predictions. Density measurement and dimensional measurement are used to compare the results of FE simulations and physical trial results in order to validate and support the final conclusions based on FE model. Using the validated FE model, a methodology to predict the density before HIP is designed where different gear geometries are modelled and then a regression model is extracted which can predict the minimum RD in neutral zone of the gear before performing costly experiments for a specific material and gear dimensions.
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| 5. |
- Khodaee, Alireza, 1984-, et al.
(författare)
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Numerical and Experimental Analysis of the Gear Size Influence on Density Variations and Distortions during the Manufacturing of PM Gears with an Innovative Powder Processing Route Incorporating HIP
- 2018
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Ingår i: Journal of manufacturing and material processing. - : MDPI AG. - 2504-4494. ; 2:3, s. 49-
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Tidskriftsartikel (refereegranskat)abstract
- The paper is the result of research intended to develop a process route for the manufacturing of powder metallurgical (PM) gears for application in transmissions units for heavy duty powertrain applications. The main problem of PM for such applications is that the generated pores that occur through conventional pressing and sintering processes reduce the gear strength, which reduces the capacity for power transmission by the gear. In prior work, removing the pores and reaching 100% density by adding Hot Iso-static Pressing (HIP) after two times pressing and two times sintering steps in the process route was suggested to solve the mentioned problem. During the investigations of this work it was revealed that the gear dimensions could influence the process results with respect to geometrical distortions. In this paper we have presented a finite element (FE) model based analysis on how the gear geometrical parameters influenced the distortions occurring in HIP. The simulation model is validated with experiments. Furthermore, the simulation model is used to create a prediction model for further investigations. The research showed that PM gears with different sizes during the proposed process route behaved differently in terms of distortions. This was illustrated with a series of simulations with different gear geometries. A regression model was developed based on the FE results for further practical predictive use. The distortions caused by HIP should be considered in the process design to prevent expensive post processes afterwards to reach the gear with accurate geometry and keep the costs of manufacturing low. It is concluded that it is possible to use the innovative process route including HIP to reach the full density and close all the open pores but not for all kind of gear geometries.
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| 6. |
- Khodaee, Alireza, 1984-, et al.
(författare)
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The Effects of Blank Geometry on Gear Rolling for Large Gear Modules : Experiments and Finite Element Simulations
- 2018
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Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 6, s. 33344-33352
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Tidskriftsartikel (refereegranskat)abstract
- Gear rolling is a forming process to produce gear wheels by plastic deformation. The advantage of the process is to eliminate the chip formation during production and also to improve the product properties since the non-metallic inclusions will be oriented along the cog surface and not perpendicular to it. The method has been developed in the past years for gear production for automobile application with modules up to 3 mm. The successful application of gear rolling in those cases raises the question regarding the feasibility of using cold rolling to manufacture gears with larger modules which can be used for heavy vehicles. In this paper, a gear wheel with normal module of 4 mm has been studied in order to investigate if such large modules can be manufactured by gear rolling. One of the issues in rolling of gears is the design of the blank geometry in order to obtain the right gear geometry after the rolling process. Blank shape modifications are necessary to control and to reduce the undesired shape deviations caused by the large plastic deformations in rolling. The blank modifications also help the process designer to control the forming force and torque. In this paper, the process has been modeled by finite element simulation and the influence of different blanks has been simulated. The validity of the FE model has been checked through several experiments. Both the numerical and experimental results revealed favorable blank modifications to apply for further developments of the gear rolling process.
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| 7. |
- Strondl, Annika, et al.
(författare)
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Innovative powder based manufacturing of high performance gears
- 2016
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Ingår i: World PM 2016 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- There are strong driving forces towards high-performance gear wheels which can handle higher engine outputs, or allow more compact designs of transmissions. Today the performance and life of conventionally manufactured gear wheels are limited by factors such as inhomogeneous microstructure and distribution of inclusions. Powder metallurgy (PM) can solve some of these problems but has so far had limitations caused by porosity. In this paper a cost effective way to eliminate porosity by HIP-ing without canister has been evaluated with encouraging results. Parameters such as powder particle size, lubricant and double pressing have been evaluated in the PM route in order to get a gas tight surface enabling effective post HIP-ing. So far double pressing has given promising results. Challenges such as open porosity, surface porosity and inclusions are addressed in the paper.
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| 8. |
- Vattur Sundaram, Maheswaran, 1987, et al.
(författare)
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Experimental and finite element simulation study of capsule-free hot isostatic pressing of sintered gears
- 2018
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 99:5-8, s. 1725-1733
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Tidskriftsartikel (refereegranskat)abstract
- A novel approach to reach full density in powder metallurgy (PM) components is demonstrated in this work. Water-atomised Mo-prealloyed steel powder is utilised for manufacturing cylindrical and gear samples through double pressing and double sintering (DPDS) process route. The effect of sample geometry and powder size fraction on densification is investigated and it is found that the DPDS route enables a density level of > 95% which is sufficient to eliminate the surface open pores. Reaching such high density is necessary, in order to perform capsule-free hot isostatic pressing (HIP). After HIP, full densification is achieved for the cylindrical samples and only near full density is realised for the gears resulting in neutral zone formation due to the density gradient. In order to predict the densification behaviour during the compaction, FEM simulations considering the gear geometry are performed for both the pressing stages and HIP. The simulation predicted a similar densification behaviour with the formation of the neutral zone. The proposed DPDS route with capsule-free HIP in combination with FEM simulation is demonstrated as a potential route for manufacturing full-density PM steel components, e.g. gears, suitable for high-performance applications.
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