Introduction to Reliability Design of Mechanical System

A lot of mechanical parts are subject to failure due to the deterioration. Usually the preventive maintenance is taken to ensure the safety and reliability. Therefore, it is very important to study the gradual reliability design of the mechanical part for improving the gradual reliability of the mechanical system under the condition of considering the preventive maintenance. Beta distribution is employed to describe the randomness of the mechanical part state after the preventive maintenance. The deterioration process of the mechanical part is modeled using the nonstationary Gamma process. The gradual reliability model before the first preventive maintenance is proposed according to the gradual failure principle and using the initial state distribution and the properties of Gamma process. Then, the gradual reliability model between any two times of preventive maintenance is also derived. Subsequently, the sensitivity equations of the proposed gradual reliability model to each parameter are given. The application process and practicality of the proposed approach are described by a numerical example. This work solved the problem where the maintenance has not been well considered in the reliability design of the mechanical part and contributed to the theory and method of improving the safety and reliability operation of the mechanical system.

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The reliability design of mechanical system and its parametric accelerated life testing

Handbook of Materials Failure Analysis with Case Studies from the Chemicals, Concrete and Power Industries ◽

10.1016/b978-0-08-100116-5.00011-9 ◽

2016 ◽

pp. 259-276 ◽

Cited By ~ 3

Author(s):

Seong-woo Woo

Keyword(s):

Mechanical System ◽

Accelerated Life Testing ◽

Life Testing ◽

Reliability Design ◽

Accelerated Life

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Reliability design and case study of mechanical system like a hinge kit system in refrigerator subjected to repetitive stresses

Engineering Failure Analysis ◽

10.1016/j.engfailanal.2019.02.015 ◽

2019 ◽

Vol 99 ◽

pp. 319-329 ◽

Cited By ~ 6

Author(s):

Seongwoo Woo ◽

Dennis L. O'Neal

Keyword(s):

Mechanical System ◽

Reliability Design

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Reliability Design of Mechanical System‐Like Water‐Dispensing System in Refrigerator Subjected to Repetitive Impact Loading

System Reliability ◽

10.5772/intechopen.69255 ◽

2017 ◽

Author(s):

Seong‐woo Woo

Keyword(s):

Mechanical System ◽

Impact Loading ◽

Reliability Design ◽

Repetitive Impact

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Study on Reliability Tests to a Few Samples of Mechanical System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.42.339 ◽

2010 ◽

Vol 42 ◽

pp. 339-342

Author(s):

Shu Yi Guo ◽

Yong Qi Qi

Keyword(s):

Mechanical System ◽

Fatigue Failure ◽

Mechanical Systems ◽

Auxiliary Information ◽

Economic Loss ◽

Test Sample ◽

Small Samples ◽

Reliability Test ◽

Reliability Design ◽

Mechanical Devices

The reliability tests play more and more important role in mechanical systems. A new method named a few samples and combined the probability and the fuzzy mathematics has been set up to explore the unknown system of a few samples with the help of the life samples of the known probabilistic distribution. The method reduced the traditional reliability test samples by some auxiliary information. It converted lots of reliability test into a few samples. This paper introduced two engineering examples to verify the method as an effective way to carry out the reliability tests. It provides the theory basis for the reliability of complicated mechanical systems. The loss caused by fatigue failure is as high as 3%~4% of Gross National Product. Fatigue fracture owned to the cycle load accounts for 95% of the total number of mechanical structure failure. Unfortunately no evidence of failure is observed when fatigue failure reaches its life. This causes human casualties and great economic loss. So the reliability research on complicated mechanical systems has to realize from reliability assessment to the active reliability design. One of the key problems of the active reliability design for complicated mechanical system is to reduce the great waste of the resources used in the probability reliability test. For example, dozens of the high precision gears made of certain material may be run out in the fatigue test which would be running day and night for several months. It has been described many methods about system reliability design in the former research [1-3]. But for many high technological products and important mechanical devices, it is impossible to get the test sample to carry out probability analysis. To exert the advantages of the active reliability design and to realize the green reliability design [4], the only way is to study small samples in the reliability tests and to develop new technique. It is named as a few samples reliability tests method of the complicated mechanical systems.

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Study of the dynamics of ТПА 350 automatic mill working stand elements

Ferrous Metallurgy Bulletin of Scientific Technical and Economic Information ◽

10.32339/0135-5910-2020-8-830-840 ◽

2020 ◽

Vol 76 (8) ◽

pp. 830-840

Author(s):

S. R. Rakhmanov ◽

V. V. Povorotnii

Keyword(s):

Mechanical System ◽

Dynamic Model ◽

Maximum Amplitude ◽

Calculation Scheme ◽

Dynamic Loads ◽

Forced Oscillations ◽

Mass Model ◽

Automatic Mill ◽

Hollow Billet ◽

Oscillation Movement

To form a necessary geometry of a hollow billet to be rolled at a pipe rolling line, stable dynamics of the base equipment of the automatic mill working stand has a practical meaning. Among the forces, acting on its parts and elements, significant by value short-time dynamic loads are the least studied phenomena. These dynamic loads arise during transient interaction of the hollow billet, rollers, mandrel and other mill parts at the forced grip of the hollow billet. Basing of the calculation scheme and dynamic model of the mechanical system of the ТПА 350 automatic mill working stand was accomplished. A mathematical model of dynamics of the system “hollow billet (pipe) – working stand” within accepted calculation scheme and dynamic model of the mechanical system elaborated. Influence of technological load of the rolled hollow billet variation in time was accounted, as well as variation of the mechanical system mass, and rigidity of the ТПА 350 automatic mill working stand. Differential equations of oscillation movement for four-mass model of forked sub-systems of the automatic mill working stand were made up, results of their digital calculation quoted. Dynamic displacement of the stand elements in the inter-roller gap obtained, which enabled to estimate the results of amplitude and frequency characteristics of the branches of the mill rollers setting. It was defined by calculation, that the maximum amplitude of the forced oscillations of elements of the ТПА 350 automatic mill working stand within the inter-roller gap does not exceed 2 mm. It is much higher than the accepted value of adjusting parameters of the deformation center of the ТПА 350 automatic mill. A scheme of comprehensive modernization of the rollers setting in the ТПА 350 automatic mill working stand was proposed. It was shown, that increase of rigidity of rollers setting in the ТПА 350 automatic mill working stand enables to stabilize the amplitude of forced oscillations of the working stand elements within the inter-rollers gap and considerably decrease the induced nonuniform hollow billet wall thickness and increase quality of the rolled pipes at ТПА 350.

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