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991.
992.
用稀土钇提高离子镀TiN膜层与基体结合力的研究 总被引:1,自引:2,他引:1
研究了不同含量稀土钇对离子镀TiN膜与基体结合力的影响,结果表明,加入稀土钇后,大大提高TiN膜与基体的结合力,并使膜层内TiN相增加,此外,稀土钇能明显提高镀膜过程中钛料蒸发率,在相同镀膜内,能使TiN膜层加厚。 相似文献
993.
994.
介绍了未确知有理数的概念,分析了未确知有理数与随机数的关系,给出了未确知有理数的加减运算。以齿轮模数的测定研究了未确知有理数在机械工程中的应用。 相似文献
995.
采用细粒度金刚石油石,对氧化锆工程陶瓷进行了超声珩磨与普通珩磨的试验研究。试验结果表明,磨削条件对被加工表面的粗糙度和表面破碎影响较大:1)超声珩磨的表面和普通珩磨表面相比,磨削沟槽不仅宽且底部平坦,网纹较均匀,珩磨沟槽的顶部较平整,并且不存在断续现象。2)普通珩磨的延性域加工临界磨削深度不超过1.5m,而超声珩磨方式下,其延性域临界磨削深度可达到3μm。3)普通珩磨方式下,在磨削速度100~150r/m,磨削深度1.0~1.5μm时,可取得较低粗糙度值;超声珩磨方式下,在磨削速度150~190r/m,磨削深度1.0~1.5μm时,取得较低的粗糙度值,同等条件下比普通珩磨低1~2级。 相似文献
996.
G. J. Feng J. D. Rossi M. T. Gerusky 《Journal of Materials Engineering and Performance》1994,3(1):105-109
An attempt has been made to apply the linear elastic fracture mechanics concept to Beta-C titanium alloy pressure vessels
that exhibited brittle fractures during hydrotesting. Based on the results of stress analysis on the real structures and fracture
surface examinations, a stress-intensity factor,K
IC, was estimated. TheK
IC value of the material in the cracking direction was measured by a surface semi-elliptical crack method. It was found that
theK
IC value of the material is very close to the estimated stress-intensity factorK
I during failure, which places the pressure vessels in a critical condition in that a small variation in flaw size may cause
a catastrophic failure. A compromise must be made betweenK
IC and the required yield strength. In this restricted case, the yield strength of the material should be controlled in the
range of 1150 to 1200 MPa to avoid brittle fracture and the possible occurrence of yield during hydrotesting. Control of microstructure
and other mechanical properties is also discussed in this investigation. 相似文献
997.
Design of a six-axis high precision machine tool and its application in machining aspherical optical mirrors 总被引:4,自引:1,他引:4
Hao-Bo Cheng Zhi-Jing Feng Kai Cheng Ying-Wei Wang 《International Journal of Machine Tools and Manufacture》2005,45(9):1085-1094
The paper presents the design of a six-axis machining system and its application in fabricating large off-axis aspherical mirrors with sub-aperture lapping techniques. The new system is based on computer-controlled optical surfacing (CCOS), which combines the faculties of grinding, polishing, and on-machine profile measuring, has the features of conventional loose abrasive machining with the characteristics of a tool having multiple degrees of freedom moving in planar model. And a novel dual touch-trigger probe profiler is designed, which is composed of a probe, model METRO-MT60 made by HEIDENHAIN Co., is integrated into the system for measuring the shape accuracy of the tested aspherical surface, another probe modeled METRO-MT12 is designed as a calibrating device for minimizing the cosine error caused by assembly inaccuracy. The new CNC machining system with two kinds of moving coordinate systems, dual tool activities and on-machine measuring is presently developed based on the new concept. The general material removal function during machining is analyzed on the basis of the Preston hypothesis. Further, an alignment test of the measuring profiler is carried out using a leveling rule as a specimen. The accuracy of the optical surfaces measured by the dual probe profiler is found to be within 1 μm PV after removing cosine error and error compensating, achieves to the resolving power of the profiler is about 0.2–0.5 μm, so the developed system can be applied to the shape accuracy measuring of aspheric fabrication with micro precision during fine grinding process according to the calibrating results. Finally, the manufacturing experiments are carried out by virtue of an off-axis oblate ellipsoid mirror with rectangular aperture as 770 mm×210 mm and centered 127 mm. The accuracy of the aspherical mirror improved from the initial form error of 17.648 μm rms to the final one of 0.728 μm rms after grinding for 200 h. 相似文献
998.
999.
1000.
对利用原位反应与高剪切液态搅拌复合专利技术制备的Al3Ti-TiB2-SiC/Al-13%Si复合材料的增强相的形成热力学进行了理论计算和分析,并采用差热分析法(DTA)进行了试验验证.研究表明:(1)Al-Ti-B体系加入到Al-13%Si熔体中可发生原位反应,形成增强相,原位反应的开始温度为905.3℃,结束温度为1 061.23℃;(2)Al-Ti-B体系加入到Al-13%Si熔体中,制备颗粒增强Al-13%Si复合材料的增强相为TiB2和Al3Ti,但TiB2形成能力最强. 相似文献