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71.
72.
The strength of case-hardened parts under cyclic loading can be determined in an experimental manner, but this can produce
a large amount of costs due to the expenditure of material and testing time. Therefore, a calculation method is developed,
that strongly reduces the number of experiments. The presented model is based on Weibull's weakest-link concept and allows
to compute the survival probability of a case-hardened part which is loaded close to the fatigue limit. The essential quantities
in this model are the distribution of Vicker's hardness of the material, the exponents of the Weibull distribution of the
volume and the surface, the residual stress state, the surface roughness and the surface oxidation depth. By integrating the
survival probabilities of the surface and the volume, the survival probability of the entire specimen or part can be calculated,
which allows to compute the fatigue limit. The necessary parameters have to be determined from reference specimens. The model
is successfully examined by comparing experimental and calculated results of smooth and notched case-hardened specimens under
alternating torsion, rotating bending, repeated tension and tension-compression.
Received 20 August 2001 / Accepted 11 November 2001 相似文献
73.
影响塑料模压制件内应力的因素分析 总被引:1,自引:0,他引:1
主要讨论了造成塑料模压制件内应力的主要因素,包括制件造型设计不合理、模具设计不合理、成型工艺条件不正确等,并针对不同情况给出了相应的解决办法 相似文献
74.
75.
76.
在介绍推进波作用下底泥起动特点的基础上,将上层水体作为粘性流体,底泥作为粘弹性体,推导了推进波作用下泥床面剪应力的表达式,并根据试验结果,给出了推进波作用下底泥起动时的床面剪应力与底泥流变参数的关系。 相似文献
77.
M. Kovac 《Journal of Materials Engineering and Performance》1994,3(1):61-64
This article discusses residual stress measurements by means of electrochemical removal of material layers with residual stresses
and simultaneous measurement of strain on the opposite specimen side with strain gages. Exact measurements are impossible
particularly because of the small bevel gear module. With the method presented, the average residual stresses in the tooth
root plane and underlying layers are measured. Residual stress distribution after each consecutive production phase is plotted
and analyzed. Residual stress measurements enable the engineer to adequately assess each individual production phase and by
that improve the quality of the complete production process. 相似文献
78.
Quantitative x-ray diffraction topography techniques have been used to measure the residual strain magnitude and uniformity
of deposition for Mo and W sputtered films on Si(100) substrates. High sensitivity rocking curve measurements were able to
determine differential strains for films as thin as 2.5 nm; while Bragg angle contour mapping had similar sensitivity and
was also able to assess coating uniformity and stress distribution over areas covering a whole wafer. Measurements of strain
versus film thickness over a range of 2.5 nm to 80 nm showed that a critical thickness exists for maximum residual strain.
Growth beyond this range produces stress relaxation. This non-destructive type of analysis could be employed on a wide range
of film-substrate combinations. 相似文献
79.
Johan M. Thevelein 《Yeast (Chichester, England)》1994,10(13):1753-1790
80.