Research of Materials Science March 2015, Volume 4, Issue 1, PP.15-19
Nitriding Treatment on the Influence of Overrunning Clutch Holder of Residual Stress Guanglin Shi1,a, Lin Zhu1,b, Rugui Wang2,c 1. College of Mechanical Engineering, Guangxi University of Science and Technology, Liuzhou 545006, China 2. College of Mechanical Engineering, Guangxi University, Nanning 530004, China Email: a sgl8913@163.com, b zhulin157@163.com, c rugui@163.com
Abstract In this paper, the overrunning clutch holder as the research object and the X-ray stress analysis methods are used to consider the nitriding treatment on the influence of overrunning clutch holder of residual stress, and have a research on the influence of nitriding treatment on the residual stress of holder along with different depth. From the test results, it can be found that although the nitriding treatment do not have a obvious effect on the distribution state of the parts of the surface residual stress, but the residual stress values of the surface could be improved with nitriding treatment, then the micro cracks could be effectively suppressed to expand to the inside parts, further, the fatigue strength of parts could be enhanced, in the end the service life of parts could be increased. Keywords: Overrunning Clutch Holder; Nitriding Treatment; X Ray; Residual Stress
Introduction Overrunning clutch is an important part of the twin turbine torque converter gearbox, and play a role of transmit load. While the holder is a part which could be easily destroyed, so the nitriding treatments are used to improve its performance. Then the X ray residual stress test equipments are used to have a research on the holder of residual stress and its distribution state along with depth none [1].
1. Test plan and theory 1.1 Test plan As showed in the Fig.1, the overrunning clutch holder is composed of the outer ring and the subject, and its material is 40Cr.On account of phenomenon that the side face and bottom face of the cage could be easily damaged, so the measuring point towards the outer ring is on the end face, and the measuring point towards the subject is on the two side faces and one bottom face.
(a)The outer ring of holder
(b)The subject of holder
(c)The part of the subject of holder
FIG.1 THE STRUCTURE OF THE OVERRUNNING CLUTCH HOLDER
1.2 Theory of X ray residual stress analysis For the general metal materials,its residual stress of two-dimensional plane could be measured according to the X ray method. A typical method for determination of this kind of stress is sin 2 ď š method. As showed in the coordinate - 15 http://www.ivypub.org/rms
system Fig.2, the normal stress of any spatial direction is Eq.1:
121 22 2 32 3
(1)
1 , 2 , …is corresponding to the direction of the direction cosine belongs to the Similarly, the normal strain in the same direction is Eq.2:
121 22 2 32 3
(2)
According to Bragg's law ..,then transform the relationship of the previous formula, the Eq.3 can be get: . Order K
E (2 ) . cot 0 2(1 v) 1800 (sin 2 )
(3)
E (2 ) ,M cot 0 0 2(1 v) 180 (sin 2 )
Then K M
FIG. 2 THE SIMPLE COORDINATE GRAPH OF RESIDUAL STRESS MEASUREMENT
2. The influence of the nitriding treatment on the residual stress value As showed in Fig. 3, the X350A X-ray stress analysis equipment is used to consider the influence of nitriding treatment on the residual stress of holder surface. The residual stress of the part can be divided into radial direction and tangential. In order to have a research on the influence of nitriding treatment on the residual stress of cage along with the different layer, electrochemical polishing technologies are used to have a peeling processing on the part’s surfaces, choose saturated NaCl as the medium for polishing, the polishing voltage is 15V, and the current is 2.5 A. In the consideration that the surface of cage with nitriding treatment is fulfilled with Carbon and nitrogen compounds, which would have a big effect on the shape of the diffraction peak, so the common peak method (such as: Parabolic method and correlation method) which Would interfere with the peak shape of positioning and cause peak shape positioning deviation cannot be used anymore. But this problem can be effectively solved by the limited in correlation method[2].
FIG.3 THE RESIDUAL STRESS MEASUREMENT FOR THE CAGE
In the process of X ray residual stress measurement, the voltage is set as 25KV, and the current is set as 6 mA. The roll fixed method is selected as the method of measurement, and the limited in correlation method is selected as the method to fix peak[3].To have a measure in 20 different areas in the part for several times in order to guarantee the reliability of the measurement data. The distribution state of the surface’s average residual stress is showed in Fig.4 (Choose the radial residual stress of outer ring as the research point). Then solving all the average results of the measurement, which showed in Tab.1 and Tab.2. - 16 http://www.ivypub.org/rms
(a) None nitriding treatment
(b) Nitriding treatment
FIG.4 THE DISTRIBUTION STATE OF THE SURFACE’S AVERAGE RESIDUAL STRESS
It can be found from the Fig.4 that the nitriding treatments do not have an obvious effect on the distribution state of the part surface residual stress. TAB.1 THE RESULT OF RESIDUAL STRESS MEASUREMENT FOR THE OUTER RING OF HOLDER (UNITS: MPA) Depth( m )
None nitriding treatment
Nitriding treatment
radial(A11)
tangential(A12)
radial(A21)
tangential(A22)
0
-501.3
-551.7
-1041.6
-1024.5
30
-607.4
-663.6
-1177.1
-1228.8
60
-437.9
-497.5
-874.8
-908.8
90
-227.1
-297.6
-632.1
-704.5
120
-141.1
-197.5
-481.3
-523.7
TAB.2 THE RESULT OF RESIDUAL STRESS MEASUREMENT FOR THE SUBJECT OF HOLDER (UNITS: MPA) None nitriding treatment Depth ( m )
Side face 1
Side face 2
Bottom face
radial
tangential
radial
Tangentia
radial
Tangentia
(B11)
(B12)
(B21)
l (B22)
(B31)
l (B32)
0
-671.1
-419.2
-691.9
-437.7
-647.1
-419.4
30
-874.1
-699.6
-893.9
-675.7
-896.7
-671.9
60
-703.2
-499.6
-717.1
-497.9
-719.3
-391.7
90
-507.1
-271.4
-509.4
-299.1
-522.73
-267.3
120
-331.3
-107.4
-307.1
-127.1
-309.2
-111.7
Nitriding treatment Depth ( m )
Side face 1
Side face 2
Bottom face
radial
Tangentia
radial
Tangentia
radial
Tangentia
(C11)
l (C12)
(C21)
l (C22)
(C31)
l (C32)
0
-1171.3
-867.2
-1013.7
-737.6
-917.3
-671.3
30
-1389.6
-1056.1
-1208.7
-976.5
-1127.3
-897.3
60
-1119.6
-897.4
-1170.3
-871.9
-1147.2
-702.9
90
-1072.1
-761.3
-981.7
-671.5
-992.7
-567.3
120
-731.2
-479.6
-772.1
-397.9
-719.3
-391.7
Then make out the relationship diagram of residual stress and the deep layer according to the measured data, as show in Fig.5; Fig. 6 and Fig.7It can be found that the residual stress with nitriding treatment is obviously bigger than the - 17 http://www.ivypub.org/rms
residual stress without nitriding treatment, on average, increased by 39.7%.The largest residual compressive stress in subsurface parts 30-40 um. The data can explained that the part have a good fatigue performance, and prevent the occurrence of fatigue cracking. So it can be found that the machining process is appropriate.
FIG.5 THE RESIDUAL STRESS OF THE OUTER RING OF HOLDER ALONG DEPTH
FIG.6 THE RADIAL RESIDUAL STRESS OF THE SUBJECT OF HOLDER ALONG DEPTH
FIG.7 THE TANGENTIAL RESIDUAL STRESS OF THE SUBJECT OF HOLDER ALONG DEPTH
3. Conclusion The X-ray stress analysis methods are used to consider the influence of nitriding treatment on the residual stress of cage surface, and have a research on the influence of nitriding treatment on the residual stress of cage along with the different layer. It can be found that the residual stress with nitriding treatment is obviously bigger than the residual stress without nitriding treatment, on average, increased by 39.7%. So it can be found that the machining process is appropriate.
Acknowledgements These researches were supported by the Guangxi Key Laboratory of Vehicle Parts Advanced Design and Manufacturing (Grant No. 2012KFMS07), and the Guangxi Key Laboratory of Automobile Components and Vehicle technology (Grant No.13-051-38).We gratefully acknowledge the support agencies. Besides, we express our sincere thanks to the editors and the anonymous reviewers for their suggestions for the improvement of the paper.
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