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Mechanical Industry Standard of the People's Republic of China
JB/T5664-1991
Heavy Duty Gear
Published on August 14, 1991
Failure Criteria
Implemented on July 1, 1992
Published by the Ministry of Machinery and Electronics Industry of the People's Republic of China
Mechanical Industry Standard of the People's Republic of China
Heavy Duty Gear
Subject Content and Scope of Application
Failure Criteria
JB/T5664-1991
This standard specifies the failure criteria for wear, pitting, spalling, bonding, plastic deformation, fracture and cracking of heavy-duty (used to transmit power) gears with a circumferential speed v≤20m/s.
This standard is mainly used to determine whether the heavy-duty gears that have been in operation and have been damaged have reached the degree of failure, to prevent major accidents in a timely manner, and to prepare spare parts. It can also be used for product reliability assessment. This standard is not suitable for failure criterion of heavy-duty gears with special requirements for reliability, vibration or noise, nor is it suitable for criterion of qualification of heavy-duty gear manufacturing and bench testing. 2
Referenced standards
GB3480
GB3481
GB6404
GB8543
GB10095
Calculation of load-bearing capacity of involute cylindrical gearsTerminology, characteristics and causes of gear tooth damageDetermination method of sound power level of gear unit noiseDetermination of mechanical vibration of gear unit during acceptance testPrecision of involute cylindrical gears
Forms and criteria of failure
Classification of heavy-duty gears
The classification and description of heavy-duty gears are shown in Table 1.
Classification of heavy-duty gears
3.2 Failure due to tooth surface wear
Forms of wear
Normal wear
General equipment
Important equipment
Equipment with high safety requirements
Gear failure only causes the shutdown of a single device, such as open transmission gears, mining crusher gears, etc. Gear failure causes the shutdown of the unit, production line or the entire plant, and equipment damage. For example, ball mills, sintering, chemical engineering, light industrial machinery gears, etc.
Gear failure causes equipment and personal accidents. For example, the tooth surfaces of lifting equipment and passenger elevator gears are inevitably slowly worn in meshing transmission. Abnormal wear
Includes abrasive wear (see Figure 1); transition wear (see Figure 2); corrosive wear (see Figure 3), etc. Approved by the Ministry of Machinery and Electronics Industry on August 14, 1991 and implemented on July 1, 1992
JB/T5664-1991
Abrasive wear
AA is the pitch line area
Due to the external hard particles falling into the agglomerated tooth surface, the tooth surface shows uniform wear streaks b Abrasive wear
Due to the abrasive in the lubricating oil, the teeth show wear streaks Figure 1
Figure 2 Transition wear
JB/T5664- 1991
The carburized layer at the tooth root and tooth top has been worn away, steps appear on the tooth surface, and the tooth thickness is reduced. 3.2.2 Criteria for wear failure
Figure 3 Corrosion wear
Chemical corrosion (indicated by the arrow)
No matter what kind of wear, or wear that occurs simultaneously with several types of wear, if the percentage value M (M=△S/m) of the sum of the wear on both sides of the tooth root △S (mm) and the gear module m. (mm) reaches or exceeds the indicators listed in Table 2, the gear should be judged to have failed. Table 2
Classification of heavy-duty gears
w10m/s
v≥10-20m/s
According to the calculation method of gear bending strength in GB3480 and the various parameters of the gear after wear measured, calculate the bending strength of the gear after wear. If
SF'<[SF min]
, the gear tooth should be judged as failed.
Where: Sp
[SF min]
Safety factor for calculating bending strength of worn gear teeth; the minimum tooth root bending strength safety factor for judging gear failure specified in a standard is shown in Table 3. .·(1)
Classification of heavy-duty gears
JB/T5664-1991
The two judgment methods a and b are equivalent, and method a is preferred. 3.3 Failure of tooth surface pittingWww.bzxZ.net
3.3.1 Form of pitting
Initial pitting Pitting occurs in the early stage of load operation. After running-in, the pitting can converge and no longer develop linearly. III
Expansion pitting The contact stress of the gear always exceeds the contact fatigue limit, the pitting continues to expand, the wear is aggravated, the vibration and noise increase, and finally the gear fails (see Figure 4).
a Tooth surface pitting failure
b Macroscopic fracture morphology of pitting block, the fracture source is at the arrow point Figure 4
3.3.2 Criteria for pitting failure
Ratio of tooth surface pitting area to gear tooth working surface area α, ratio of maximum size of pits with more than 20% pitting to modulus value β, ratio of maximum depth of pits with more than 20% pitting to modulus value Y, Class I heavy-duty gear pitting reaches or exceeds any of the two groups of indicators in the table, Class II and Class III heavy-duty gear pitting reaches or exceeds each group of indicators in the table, the gear should be judged as failed Heavy-duty gear classification
JB/T 5664-1991
Note: ① The pitting pit depth includes microcrack depth and tooth surface wear thickness. <10m/s
② When the pitting pit depth reaches the value in the table and other indicators have not reached the value in the table, the gear file should be established for follow-up observation. ③ The pitting area is measured in accordance with the method of measuring the contact spots on the tooth surface in GB10095. b.
According to the equivalent tooth width b" of the tooth surface without pitting, the tooth surface contact stress α is calculated according to the following simplified formula: T, (i+1)
Wherein: dw
pinion pitch diameter, mm;
T-pinion shaft input working torque, N·mm: transmission ratio, i=large gear teeth number z/small gear teeth number zi: b
-measured equivalent tooth width without pitting, mm. b-
(1-α)s
ratio of the tooth surface pitting area to the working tooth surface area; S-tooth working tooth surface area, mm2:
h-tooth working tooth height, mm;
When ">[], the gear should be judged as failed. [oa]
Allowable contact stress on tooth surface, N/mm
【]=2XHB
or【]=18×HRC
Measured Brinell hardness of the tooth surface of quenched and tempered gear: HB
Measured Rockwell hardness of the tooth surface of a hardened gear: N/mm2.
If one of the two judgment methods a and b is judged as failure, the gear should be judged as failure. 3.4 Tooth surface spalling failure
3.4.1 Form of spalling
v≥10~20m/s
Spalling refers to a kind of gear tooth damage in which the material on the tooth surface peels off in pieces. The shape of the spalling pit is irregular, generally shallow and flat, and larger than the pitting pit (see Figure 5).
a Spalling
JB/T5664-1991
Surface floating, tooth surface 45HRC, arrows indicate spalling pits Figure 5
3.4.2 Criteria for tooth surface spalling failure
The same as the criterion for tooth surface pitting failure.
3.5 Tooth surface bonding failure
3.5.1 Form of bonding
b Macromorphology of hard tooth spalling fracture
A—Fracture source B—Cut-off area
Bonding is a serious adhesive wear phenomenon caused by the metal of the meshing tooth surfaces directly contacting and bonding under a certain pressure, and the metal is torn off the tooth surface with the relative movement of the tooth surface (see Figure 6). a Wear, plastic deformation, bonding
3.5.2 Criteria for bonding failure
b Destructive bonding
If the ratio of the bonding area of the tooth surface to the working tooth surface area and the ratio of the depth of the bonding groove to the module 5 reach or exceed the indicators in Table 6
, the gear should be judged as failed. Classification of heavy-duty gears
I, II
Gear tooth plastic deformation failure
3.6.1 Form of wing deformation
JB/T5664-1991
<10m/s
v≥10~20m/s
Thermal plastic deformation Poor lubrication, excessively high gear working temperature, partial or full tooth plastic deformation (see Figure 7). Indentation
Due to the entry of hard foreign matter into the meshing or eccentric loading, the working tooth surface is partially concave and the non-working tooth surface is convex (see Figure 8). a Thermoplastic deformation-wrinkle
b Thermoplastic deformation
3.6.2 Criteria for plastic deformation failure of gear teeth
JB/T5664-1991
Figure 8 Indentation
If the peak or valley of the tooth surface caused by plastic deformation of gear teeth is higher or lower than the theoretical tooth shape by 20% of the gear module, the gear should be judged as failed. 3.7 Failure of gear teeth due to fracture and cracks
3.7.1 Forms of fracture and cracks
Overload fracture and cracks Gears are subjected to severe overload, impact or foreign objects entering the meshing, causing instantaneous fracture and cracks (see Figure 9). Fracture and cracks due to eccentric load
Fatigue fracture and cracks
Eccentric load causes local overload, and its fracture and cracks are mainly angle fractures (see Figure 10). When the cyclic stress exceeds the bending fatigue limit of the gear, cracks generally appear at the stress concentration point on the tensile side of the tooth root, and continue to expand, causing the gear teeth to fracture or crack (see Figure 11). In addition, there are random tooth fractures that are unrelated to the root fillet section caused by severe wear, pitting, spalling, bonding and manufacturing defects (see Figure 12).
Figure 9 Overload tooth breakage
Crane gear m=8mm, 45 steel quenched and tempered, due to sudden overload, multiple gear teeth broke from the rootFigure 10
Eccentric load tooth breakage
JB/T5664-1991
Bidirectional bending fatigue tooth breakage (example gear) b Fatigue fracture
c Gear rim fatigue fracture
JB/T5664-1991
Random fracture
Fracture source Pitting
b Random fracture
Fracture source Oxide inclusions
C Random fracture
Eccentric load → plastic deformation → pitting → tooth breakage failure
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