When two different processing methods are selected, the stress nephogram in Y direction on the upper surface of spur bevel gear blank is shown in Figure 1. It can be seen from the figure that the upper surface of the straight bevel gear blank is subjected to a compressive stress of about – 5.9mpa before machining. After machining, the large end and small end of the machined tooth top in the machining area of the upper surface are subject to a tensile stress of about 13.6mpa, the yellow area in the middle of the tooth top is subject to a tensile stress of about 6Mpa, and the light blue area near the tooth top on the side of the tooth groove is subject to a compressive stress of about – 7MPa, The stress at other positions on the side of the alveolar decreases to almost 0. In the process of machining, the unprocessed area on the upper surface of spur bevel gear blank is subjected to a maximum tensile stress of about 13.6mpa at the surrounding edges, and the compressive stress at the center of the unprocessed area has little change compared with that before machining. After the processing of spur bevel gear blank with two processing methods is completed, the stress distribution on the upper surface of spur bevel gear blank is the same, and the bottom of each tooth groove is subjected to a compressive stress of about – 8Mpa.
When two different processing methods are selected, the stress nephogram in Y direction on the bottom surface of spur bevel gear blank is shown in Figure 2. It can be seen from the figure that the bottom surface of spur bevel gear blank is subjected to a compressive stress of about – 5.9mpa before machining. When machining starts, the stress around the whole bottom surface changes from compressive stress to tensile stress. The red area in the figure indicates that the maximum tensile stress on the surrounding boundary of the bottom surface is about 13.6mpa; The center of the gear cutting area corresponding to the lower surface of the spur bevel gear blank is subject to small tensile stress, and the stress is about 6Mpa; In addition to the tensile stress at the boundary around the bottom surface, the stress in the green area in the middle decreases from about – 5.9mpa to about – 3Mpa. When the straight bevel gear blank continues to be processed, the surrounding boundary of the bottom surface is still subject to a tensile stress of about 13.6mpa, and the area of compressive stress before the bottom surface gradually changes to a tensile stress of about 6Mpa with the processing. Finally, the whole bottom surface of spur bevel gear blank is subject to tensile stress, and the tensile stress on the surrounding boundary is large, while the tensile stress in the middle position is the smallest. After being processed by two processing methods, the stress state on the bottom surface of spur bevel gear blank is the same.
Cut the straight bevel gear blank along the length direction. The stress nephogram of the straight bevel gear blank section before machining is shown in Figure 3. The stress of the straight bevel gear blank section during machining is shown in Figure 4. It can be seen from the figure that the stress on the spur bevel gear blank before machining is distributed in layers along the thickness direction of the spur bevel gear blank. After machining, the position where the spur bevel gear blank is close to the upper surface and the original maximum compressive stress is reduced from about – 14MPa to about – 10MPa when it is close to the gear cutting position, and the compressive stress in the uncut area at the corresponding position is reduced from about – 14MPa to about – 12MPa; When the straight bevel gear blank is close to the upper surface, the tensile stress value decreases from about 11mpa to about 9Mpa when it is close to the cutting position, and the tensile stress in the uncut area at the corresponding position basically does not change; In the whole machining process, the stress value of the straight bevel gear blank near the position where the original maximum compressive stress is on the lower surface is reduced from about – 14MPa to about – 12MPa; The position of the spur bevel gear blank close to the lower surface where the original maximum tensile stress is almost unchanged in the whole machining process. After processing, the compressive stress near the bottom of each tooth slot is about – 8Mpa. From this point of view, the stress distribution after processing in two different ways is the same.
After processing in mode 1, the straight bevel gear blank is cut along the width direction, and the stress nephogram in the Y direction of the section is shown in Figure 5. Figure a shows the stress nephogram of the straight bevel gear blank section before machining, and figure B shows the sectional stress nephogram from the top of the tooth. In Figure B, the compressive stress near the top of the tooth is reduced from about – 14MPa to about – 10MPa, and the tensile stress between the top of the tooth and the root of the tooth is reduced from about 11mpa to about 9Mpa; The middle part of the section is subjected to a compressive stress of about – 5MPa; The position of the spur bevel gear blank near the lower surface where the maximum tensile stress and compressive stress were originally subjected to has no obvious change in the stress value after machining, and the stress near the large and small end of the spur bevel gear blank is released. Figure C shows the sectional stress nephogram from the bottom of the cogging. The light blue area near the cogging indicates that it is subjected to a compressive stress of about – 8Mpa, the material inside the spur bevel gear blank near the lower surface is also subjected to a compressive stress of about – 10MPa, and the red part in the middle is subjected to a tensile stress of about 11mpa.
After processing in mode 2, the straight bevel gear blank is cut along the width direction, and the stress nephogram in the Y direction of the section is shown in Figure 6. Comparing Figure 6 with figure 5, the stress distribution of straight tooth section and cogging section in the two figures are basically the same.
From the above analysis, it can be concluded that no matter which processing method is adopted, the stress on the upper and lower surfaces of spur bevel gear blank changes the most, from about – 5.9mpa before processing to tensile stress, the maximum tensile stress can reach about 13.6mpa, and the processed tooth groove bottom is subject to large compressive stress. In the machining process, the internal stress of the material near the cutting area changes more than that away from the cutting area, but the change of the y-direction stress in the whole straight bevel gear blank is small. It can be seen that the change of the y-direction stress in the straight bevel gear blank during the machining process is mainly reflected in the upper and lower surfaces of the straight bevel gear blank.