Reliability design of the hottest machinery I

Mechanical reliability design (I)

mechanical reliability can generally be divided into structural reliability and mechanism reliability. Structural reliability mainly considers the strength of mechanical structures and the failure caused by fatigue, wear, fracture, etc. due to the influence of load; The reliability of the mechanism mainly considers the failure caused by the strength problem, but the failure caused by the kinematics problem when the mechanism has been operated by Tongling Ambo circuit board Co., Ltd., which specializes in PCB process

mechanical reliability design can be divided into qualitative reliability design and quantitative reliability design. The so-called qualitative reliability design is to apply successful design experience to make the designed products achieve the purpose of reliability on the basis of failure mode impact and hazard analysis. The so-called quantitative reliability design is to design products that meet the specified reliability requirements by establishing the relationship between implicit limit state function or explicit limit state function on the basis of fully mastering the strength distribution and stress distribution of the designed parts and the randomness of various design numbers

"mechanical reliability design method is a commonly used method. It is the most direct and effective method used in any industry to carry out mechanical reliability design at present. Both structural reliability design and mechanism reliability design are commonly used in a large number of ways. Although the reliability quantitative design can design appropriate parts that meet the requirements according to the reliability index, the specific data of material strength distribution and load distribution are still scarce at present, and there are many factors to be considered, which limits its popularization and application, and is generally used in the design of key or important parts

mechanical reliability design due to different products and composition differences, the reliability design methods that can be adopted are:

1 Fault prevention design

mechanical products generally belong to series system To improve the reliability of the whole machine, we should first start with the strict selection and control of parts. For example, standard parts and general parts are preferred; Select reliable parts that have been verified by use analysis; Strictly follow the standard selection and control of purchased parts; Make full use of the results of fault analysis and adopt mature experience or schemes verified by analysis and test

2. Simplified design

under the condition of meeting the predetermined functions, the mechanical design should be as simple as possible, and the number of parts should be reduced as much as possible. The simpler the more reliable is a basic principle of reliability design, and it is the most effective method to reduce faults and improve reliability. However, other parts cannot perform extraordinary functions or work under high stress conditions due to the reduction of parts. Otherwise, simplifying the design will not achieve the purpose of improving reliability

3. Derating design and safety margin design

derating design is a design method to make the service stress of parts lower than its rated stress. Derating design can be achieved by reducing the stress borne by the parts or improving the strength of the parts. Engineering experience has proved that most mechanical parts have low failure rate and high reliability when they work below the rated bearing stress. In order to find the best derating value, a lot of experimental research needs to be done. When the load stress of mechanical parts and the strength of specific parts that are mainly exported to developed countries and bear some stress are uncertain within a certain range, we can improve the average strength (such as by greatly increasing the safety factor) and reduce the average stress, Reduce stress changes (such as through the restriction of service conditions) and strength changes (such as reasonable selection of process methods, strict control of the whole processing process, or elimination of unqualified parts through inspection or test) to improve reliability. For important parts involving safety, limit design method can also be adopted to ensure that they will not fail under the worst limit state