Powder Metal Gears Research Articles

Crack detection of powder metal and steel gears

The application of the Powder Metallurgy (PM) method is confirmed as a production technology for gears and other mechanical parts. The PM method offers lightweight, repeatability with high precision, maximum material use, freedom of design, cost efficiency, and sustainability. Condition Monitoring (CM) is an important strategy to adopt in different gear systems. The current paper studies the possibility of crack detection for steel and PM gears to investigate the effect of having different gear materials on fault detection possibility. Four different statistical indicators, namely the RMS, kurtosis, peak value and crest factor are studied. The study is based on calculating Tooth Varying Mesh Stiffness (TVMS) using a calculation model and generating the system dynamic response using a gear dynamic model. Different fault detection indicators are applied to examine the detection possibility with crack propagation. The paper concludes on how having different gear materials has an impact on the fault detection possibility.

Influence of the DIN 3962 Quality Class on the Efficiency in Honed Powder Metal and Wrought Steel Gears

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.

High-strength gears produced by powder metallurgical processes – KL500/93-2

Purpose The purpose of this study is to optimize high-strength gears produced by powder metallurgical process and to provide a material model to predict the tooth root bending fatigue strength. Powder metal (PM) technology offers great opportunities for the reduction of the carbon footprint and improvement of the cost efficiency of gear production. PM gears can achieve flank load-carrying capacities comparable to wrought steel gears if the loaded volume is fully densified. Still, the tooth root strength is of particular importance. Design/methodology/approach The tooth root stresses can be minimized by optimizing the tooth root geometry. This usually leads to a target conflict, as fully optimized tooth root geometries cannot be manufactured by generating processes such as hobbing, generating-grinding or rolling. To use the increase in tooth root load-carrying capacity of fully optimized root geometry on PM gears, a non-generating method for surface densifying is needed. The shot-peening process is used as an alternative densification process for PM gears. The properties of both shot peened and cold-rolled PM gears are analyzed and compared. To quantify the effect of both manufacturing processes, the tooth root bending fatigue strength will be evaluated and compared to wrought gears. Findings From the fatigue strength perspective, a material model is developed, which is able to predict local endurable stress amplitudes. The model is gained through regression varying carbon content, density and size effect on bending specimens. Originality/value It is transferable to PM gears of the same material using a load transfer coefficient.

Powder Metal Gears for Highly Loaded Powertrains: How Powder Metallurgy Supports Current Trends in Transmission Technology

Powder Metal Gears for Highly Loaded Powertrains: How Powder Metallurgy Supports Current Trends in Transmission Technology

The effect of elasticity in powder metal gears on tooth loading and mean coefficient of friction

Powder metal gears have a lower density than conventional steel gears due to their intrinsic porosity from the manufacturing process. This also results in a lower elasticity leading to larger deformations and lower contact pressure in a gear contact. By using different modelling tools (namely FEA and available commercial software), the load behavior along the line of action is studied to compare the influence of lower elasticity with standard wrought steel elasticity for FZG-C type gears. A further step is taken analyzing this effect on the mean coefficient of friction through the recalculation of the gear mesh power loss factor. Conclusions observed are differences in load distribution and marginal differences in the gear mesh power loss factor when comparing sintered and wrought steel FZG-C type gears. Sintered steel showed a marginally longer line of action and simultaneously a decrease of the single tooth contact length when compared to wrought steel, while differences in the gear mesh power loss factor proved non-essential due to the spread in previously measured experimental data.

Influence of Shot Peening on Surface Durability of Plasma Case-Hardened Sintered Powder Metal Gears (Influences of Shot Diameter and Shot Hardness)

In order to investigate the influence of shot peening on the surface durability of sintered powder metal gears, the plasma case-hardened sintered powder metal gears shot-peened with different shot diameter and shot hardness were fatigue-tested using a gear testing machine. The hardness, the compressive residual stress and the surface roughness of the gears increased by the shot peening. The pores near the tooth surface of the shot-peened gears were obviously deformed excect for those of the lightest shot-peened gear in this study. The failure mode of the unpeened gear was pitting, and those of the shot-peened gears was mainly spalling. The failure depth agreed almost with the depth where the amplitude A (τyz/HV) of the ratio of orthogonal shear stress to Vickers hardness became peak near the tooth surface. In these experiments the surface durability of the lightest shot-peened gear was highest comparing with those of the other gears. Therefore, it can be proposed that the light shot peening, which does not cause too large surface roughness and the deformed sharp pore, has to be selected in order to improve the surface durability of sintered powder metal gears.

SMC Quality rating

SMC Powder Metallurgy of Galeton, Pennsylvania, has passed the tough qualification tests to win accreditation to ISO/TS16949, a quality management system that satisfies the international auto business. Peter Lake, President of the SRI Quality System Register, said: ”SMC has demonstrated effective implementation of a quality management system that satisfies the tough new auto standard for the manufacture of powder metal gears, sprockets, bearings and structural parts. This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.

1108 粉末焼結歯車の面圧強さに及ぼすショットピーニングの影響

1108 粉末焼結歯車の面圧強さに及ぼすショットピーニングの影響

F-0332 ショットピーニング粉末焼結歯車の面圧強さと動的性能(S36-6 歯車の負荷能力・面圧強度,高周波焼入れ)(S36 伝動装置の基礎と応用)

F-0332 ショットピーニング粉末焼結歯車の面圧強さと動的性能(S36-6 歯車の負荷能力・面圧強度,高周波焼入れ)(S36 伝動装置の基礎と応用)

Relationship between Surface Durability and Hardness of Sintered Powder Material. In Case of Induction-Hardened Sintered Powder Metal Gears and Rollers.

In order to evaluate the surface durability and spalling failure depth of induction-hardened sintered powder metal gears and rollers, the relationship between the surface durability and the hardness was investigated. The failure mode of the gears and rollers was spalling due to subsurface cracks. The spalling failure depth agreed almost with the peak depth of the amplitude A(τ <yz>/H υ) of the ratio of the orthogonal shear stress to Vickers hardness. The surface durability was evaluated using the amplitude A(τ <yz>) of the shear stress and the hardness Hυ at the peak amplitude of A(τ <yz>). In case of the sintered specimens with a same pore distribution, the relationship between A(τ <yz>) and Hυ was represented by one line. In a case of the sintered specimens with differenet pore distribution, it was difficult to evaluate the surface durability using the relationship between A(τ <yz>) and Hυ. It could be understood that the pore distribution played an important role when the sintered material was designed in terms of the surface durability.

Influence of Particle Diameter of Steel Powder on Fatigue Strength of Induction-Hardened Sintered Powder Metal Gears.

In order to elucidate the influences of particle size of steel powder on the surface durability of induction-hardened sintered powder metal gears, the gears with three kinds of particle sizes were fatigue-tested using a power circulating gear testing machine. The three kinds of particle diameters were under 45μm, 75μm∼106μm and 150μm∼250μm, respectively. The surface durability of the gear with the smallest particle size was almost equal to that of the gear with the intermediate particle size. While the surface durability of the gear with the largest particle size was inferior to those of the other gears. The smaller the particle size became, the smaller the pore size became and the lager the pore cluster factor by fractal dimension became. The failure mode of all gears was spalling with pitting. It was understood that the pore size and the pore cluster factor were important parameters to evaluate the surface durability of the sintered powder metal gears.

Powder metal gears: A natural fit in hydraulic pump applications

As manufacturers in industries as diverse as automotive and truck OEMs agricultural, off-road, and material handling equipment continue to seek means of reducing cost without compromising design or performance integrity, the future of powder metal components appears very bright. Indeed, the Metal Powder Industries Federation (MPIF) estimates North American sales alone at over $2 billion, and world wide shipments in excess of one million tonnes. Spanning market boundaries in particular is the growing utilisation of powder metal (P/M) gears in hydraulic pump applications. From low pressure engine lubrication pumps to higher pressure industrial applications P/M gears can satisfy the key design criteria of performance, cost and ease of manufacture.

Fatigue Strength and Dynamic Performance of Induction-Hardened Sintered Powder Metal Gears. Comparison with Steel Gear and Influence of Hardened Depth.

Int this paper, induction-hardened sintered powder metal spur gears were compared with an induction-hardened melted steel spur gear in terms of fatigue strength and dynamic performance, and the influence of hardened depth on the fatigue strength of the sintered gears was also investigated, using a power circulating gear testing machine. The damping characteristic of the sintered gear was superior to that of the steel gear, but the fatigue strength of the sintered gears was inferior to that of the steel gear, since many pores existed in the sintered gears. The failure mode of the sintered gears was pitting with spalling, and that of the steel gear was tooth breakage due to pitting. We consider the origin of pitting of the sintered gears was pores, while the origin of the pitting of the steel gear was defects on the tooth surface. The fatigue strength and the failure mode of the sintered gears were not influenced by hardened depth. During the fatigue processes of both the sintered gears and the steel gear, the changes in dynamic performance were almost the same since the tooth surface deteriorations of both types of gears were similar in shape. Both dynamic performances became worse due to the tooth surface deterioration.

Surface Failure and Durability of Induction-Hardened Sintered Powder Metal Rollers and Gears with Various Hardened Depths

In this report, the effect of hardened depth on failure modes and fatigue strengths of induction-hardened sintered powder metal rollers and spur gears was elucidated, including the effect of relative radius of curvature of the rollers. These experimental results were discussed by an amplitude of ratio of orthogonal shear stress to Vickers hardness. Failure mode of the rollers was spalling due to subsurface origin crack with slight micropits and that of the gears was pitting with spall near the pitch point independent of the hardened depth. The depths of spalling cracks agreed almost with the occurring depths of peak amplitude of the ratio of orthogonal shear stress to Vickers hardness. Surface durability of the test rollers increased as the surface hardness increased and the relative radius of curvature decreased. Surface durability of the test rollers and the test gears was hardly influenced by the hardened depth.

A Study on Surface Durability of Induction-Hardened Sintered Powder Metal Rollers. Influences of Powder Type, Sign of Specific Sliding and Relative Radius of Curvature.

In order to obtain fundamental data about tooth-surface durability and the tooth-surface failure mode of induction-hardened sintered powder metal gears, rollers made of two kinds of powders with diameters of 30 and 60 mm were fatigue-tested with pairs of same-diameters rollers under a sliding-rolling contact condition. The surface failure mode in this experiment was spalling due to subsurface cracking. The depth of the spalling crack agreed with the depth of the maximum amplitude of the ratio of orthogonal shear stress to Vickers hardness. The surface durabilities of the rollers increased as the relative radius of curvature decreased, and they were hardly influenced by the powder type and the sign of specific sliding.

A study on fatigue of induction-hardened sintered powder metal gears. Module 5, standard pressure angle 20.DEG. and contact ratio 1.246.

Induction-hardened stintered powder metal gears having a module of 5, a standard pressure angle of 20° and a contact ratio of 1.246 were fatigue-tested using a power circulating gear testing machine, in order to elucidate the fatigue strength and the relationship between tooth surface failure and dynamic performance during the fatigue process. The fatigue limit for the number of cycles to gear failure of 108 was about 850 MPa by Hertzian stress. The failure mode of these gears was pitting. Pitting occurred at the dedendum flank of the gears in the initial stage of the fatigue process and developed to the addendum flank in the final stage of the fatigue process. The dynamic performance of the gears changed depending upon the tooth surface deterioration due to pitting. The pores existing on or beneath the tooth surface could play an important role in the initiation and propagation of pitting cracks.

A study on surface durability of induction-hardened sintered powder metal rollers. Influences of powder type, sign of specific sliding and relative radius of curvature.

In order to obtain fundamental data about tooth surface durability and the tooth surface failure mode of induction-hardened sintered powder metal gears, rollers made of two kinds of powders with diameters of 30 and 60 mm were fatigue-tested with pairs of the same diameter rollers under a sliding-rolling contact condition. The surface failure mode in this experiment was spalling due to subsurface cracking. The depth of the spalling crack agreed with the depth of the maximum amplitude of the ratio of orthogonal shear stress to Vickers hardness. The surface durabilities of the rollers increased as the relative radius of curvature decreased, and they were hardly influenced by the powder type and the sign of specific sliding.

A study on fatigue and dynamic performance of induction-hardened sintered powder metal gears. (Case of module 2, standard pressure angle 14.5.DEG. and contact ratio 2.172).

A conventional skew gear pair does not change its relative position of gear axes. On the contrary, one of the axes of the gear pair offered in this paper is able to be displaced one-parametrically on the space fixed to the other gear axis. At any relative position of the gear axes, the gears rotate at a constant speed ratio. The displaceable axis gear pair has three backgrounds as follows. (i) The gear pair is potentially a power transmission element. (ii) The motion of these gears can be applied to the generating motion of gear manufacturing. (iii) The gear tooth bearing problem is based on a deflection or displacement of the gear axis in loading. This paper discusses the relative curvature of gear tooth surfaces and the motion of the tooth bearing pattern.2145Three kinds of induction-hardened sintered powder metal gears were fatigue-tested using a power circulating gear testing machine in order to elucidate the fatigue strength and failure mode. The relation between the tooth profile change and the dynamic performance in the fatigue tests of the gears were also investigated. The fatigue strengths of three kinds of gears were almost the same. The failure modes in these gears were tooth breakage at the tooth fillet, tooth breakage due to pitting near the pitch point, and destructive tooth surface failure. Except for one case of the destructive tooth surface failure, the dynamic performace changed slightly during the fatigue test since the tooth profile deterioration was small. The occurrence of the destructive tooth surface failure influenced the dynamic performance of the gear.