Evaluation of effects of geometrical parameters on density distribution in compaction of PM gears

Khodaee, Alireza; Melander, Arne

doi:10.1063/1.5008051

Cited by 2 publications

(7 citation statements)

References 5 publications

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“…In the pressing step, where two punches are used to press the powder, a density gradient is obtained along the gear axial direction with the minimum densities located on the middle of gear axial direction. After the first sintering step of the PM gear the density in the neutral zone remains at the lowest levels while on the outer surfaces of the two ends of the face width the highest densities are observed [15]. This behavior remains in the PM gear through the second pressing and second sintering as well.…”

Section: Introductionmentioning

confidence: 88%

“…Validated FE simulation results can enable us to propose a predictive model to follow the component density developing during the process route in Figure 1. The present authors have previously evaluated the effects of gear geometry on the pressing of PM gears and they have shown that different gear parameters could result in different density gradients in the PM gear [15]. In the present paper, the influence of two parameters, which are defining the gear size, are considered for the analysis.…”

Section: Introductionmentioning

confidence: 99%

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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

Khodaee

Melander

2018

JMMP

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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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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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

Khodaee

Melander

2018

JMMP

Self Cite

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“…In order to define CAP parameters, an initial estimate based on the previous work is made [28,29]. The ring compaction tests were performed on the specimen as shown in Fig.…”

Section: Model Parametersmentioning

confidence: 99%

“…This region with lower density at the middle will have open pores which are not possible to be closed after capsule-free HIP. Meanwhile, the neutral zone arises after first pressing and dominant in the gear specimen [15,29]. In order to map the regions where the presence of pores is evident in the samples, the samples were sectioned exactly at the neutral zone and prepared for analysing the porosity.…”

Section: Effect Of Dpds and Hip Process On Densificationmentioning

confidence: 99%

“…The results show that the used simulation model is precise in predicting the material response during the process and necessary for further development of the process route. Khodaee et al [29] have shown, by using the same material model and modifying the gear geometry, the density gradient can be eliminated by having lower gear width and higher gear module. The formation of neutral zone is predicted well by the FE simulations for the geometry studied in this work.…”

Section: Fem Simulationsmentioning

confidence: 99%

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Experimental and finite element simulation study of capsule-free hot isostatic pressing of sintered gears

Sundaram

Khodaee

Andersson

et al. 2018

Int J Adv Manuf Technol

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A novel approach to reach full density in powder metallurgy (PM) components is demonstrated in this work. Water-atomised Moprealloyed 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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Evaluation of effects of geometrical parameters on density distribution in compaction of PM gears

Cited by 2 publications

References 5 publications

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

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

Experimental and finite element simulation study of capsule-free hot isostatic pressing of sintered gears

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