Basic knowledge of mechanics

1. What basic knowledge is needed for machine maintenance?

1, what is a mechanical failure? What are the main aspects of the structure? A: Mechanical failure refers to the deviation of various technical indicators (including economic indicators) of machinery from its normal state.

If some parts or components are damaged, resulting in loss of working ability; Engine power is reduced; The power system is out of balance and the noise increases; The working capacity of the working organization has declined; When the consumption of fuel and lubricating oil increases, and so on. , more than the specified index, belongs to the mechanical failure. Mechanical failure is mainly manifested in the damage of its parts and the destruction of the relationship between parts in its structure.

For example, the parts are broken and deformed, the clearance between mating parts is increased or the interference is reduced, and the fixing and fastening device is loose and ineffective. 2. According to the time classification of faults, what are the two types of faults? Answer: According to the timing of the failure, the failure can be divided into sudden failure and gradual failure.

3. According to the classification of faults, which two types can faults be divided into? A: According to the occurrence of faults, faults can be divided into functional faults and potential faults. 4. According to the different causes of faults, what are the two types of faults? Answer: According to the different causes, faults can be divided into man-made faults and natural faults.

5. What is the probability of failure? Answer: The technical condition of machine tools always deteriorates with the extension of its service time, so the service life of machine tools is always limited. Therefore, the possibility of machine tool failure always increases with the extension of service time, so it can be regarded as a function of time.

However, due to the randomness of machine tool faults, it is difficult to predict the exact time of any kind of faults. Therefore, the failure of machine tools can only be expressed by probability, which is called failure probability.

6. What is the failure rate? A: The relationship between the possible failure of a product at a certain moment and the residual probability at that moment is the concept of failure rate. Failure rate can be defined as the conditional probability that a product does not fail in time t, but may fail in the next unit time.

7. What is the decreasing failure rate? A: The failure rate is decreasing, that is, the failure rate decreases monotonously with time. This failure rate usually reflects the failure of some complex products in the early stage.

This is because there are defects and errors in the design, manufacture, inspection and assembly of products, so there is a high failure rate when they are put into operation. However, with the extension of running time and the continuous elimination of faults, the failure rate gradually decreases, which is more obvious in the initial driving state of cars or some electronic equipment.

8. What is the constant failure rate? A: The constant failure rate is a constant and does not change with time. It is widely used to describe the decay and attenuation process of various physical quantities.

In construction machinery, it can be used to describe sudden failure, because the probability of sudden failure is equal at any time, so its failure rate can be regarded as a constant. At the same time, because sudden failure has nothing to do with the service time of machinery, that is, it has nothing to do with its old and new degree, it may happen at any time, so the failure described by constant failure rate is called random failure or accidental failure.

9. What is the incremental failure rate? Answer: Incremental failure rate refers to the situation that the failure rate increases with the extension of product working time. This is a phenomenon that the parts that make up the machinery gradually lose their functions during use.

The failure rate of progressive failure belongs to this type. Because the incremental failure rate becomes very large in the later period of product service life, it is difficult to eliminate the failure by general methods, so it is also called wear failure.

10. What is the average working time before failure? A: Many products are put into use until each product fails (fails). The effective use time of each product is counted and averaged, which is called the average working time before failure (or failure). 1 1. What is the mean time between failures? Answer: For a repairable product, after its failure, it can be restored to its normal function through repair measures.

The average working time of two adjacent faults is called mean time between failures or mean time between failures. 12. What are the characteristics of the failure rate curve? Answer: The failure rate curve of mechanical products in the whole life cycle is called "bathtub curve".

Judging from the timing of different failures, the failure rate of mechanical equipment is high at the initial stage of use, and this failure rate is declining; At the end of the effective life of mechanical products, the failure rate will continue to increase, which is incremental; In other service periods, the failure rate is constant and its value is very small. The time range corresponding to the failure rate curve is called early failure period, random failure period and loss failure period respectively.

13. What are the effects of technical maintenance and operation factors on the failure rate? Answer: During the use of mechanical equipment, the wear and deformation of parts may cause some imbalance between them; Lubricant will gradually become dirty and deteriorate; Some bolted connections may be loose, etc. The appearance and development of these situations will accelerate the damage of mechanical equipment and lead to the improvement of failure rate.

The task of technical maintenance is to prevent these phenomena and eliminate them in time after they appear. 14, what is mechanical maintainability? What is the maintenance time of machinery? Answer: For repairable products, after failure, they can generally be repaired by maintenance, which can make up for the lack of product reliability.

However, maintenance takes a certain amount of time, which affects the use of the product. Therefore, in order to give full play to the efficiency of the product, when it fails, the shorter the maintenance time, the better.

As far as mechanical products are concerned, their repair time is related to their own structure and is determined by factors such as design and manufacture. It is an inherent attribute, indicating the difficulty of mechanical maintenance, which is called mechanical maintainability. 15. How to consider the smoothness of disassembly and assembly in the design of maintainability structure? A: In mechanical repair, the disassembly work is very heavy. Providing convenient conditions for disassembly can improve work efficiency.

2. What's the situation of the auto mechanic?

Introduction: Self-evaluation is serious and responsible, rigorous and self-disciplined, and has a high sense of social work responsibility.

Modest, calm, practical and independent. Be kind to others and have team spirit.

Job hunting intention Expected job nature: Full-time expected job location: Jiangbei District, Haishu District, Yinzhou District Expected job industry: transportation/logistics automobile (motorcycle) and spare parts Expected job position: sales representative, auto mechanic, trainee/reserve cadre/intern Expected job treatment: 1500 yuan/month. Arrival time: Work experience at any time: 20 10-02-0 1 zhuan 20 10-04- 13 Company name: Ningbo Runda Automobile Co., Ltd. Company nature: private/private company size: 300-500 people Job title: O(∩_∩)O~。

3. What should a mechanic have?

To be a mechanic, you should have the following basic requirements: 1, professional ethics, professional ethics norms (1), and abide by laws, regulations and relevant provisions.

(2) Love your job and have a high sense of responsibility. (3) Strictly implement work procedures, work specifications, process documents and safety operation procedures.

(4) serious and responsible work, unity and cooperation. (5) Take good care of equipment and tools, fixtures, knives and measuring tools.

(6) Dress neatly and conform to regulations; Maintain a clean and orderly working environment and civilized production. 2. Basic knowledge Basic theoretical knowledge (1) cartographic knowledge.

(2) Tolerance and cooperation. (3) Common metal materials and knowledge of heat treatment.

(4) Common sense of nonmetallic materials. Basic knowledge of machining (1) Mechanical transmission knowledge.

(2) Knowledge of common machining equipment (classification and use). (3) Knowledge of common cutting tools for metal cutting.

(4) Processing technology of typical parts (spindle, box, gear, etc.). (5) Understand the lubrication of equipment and the use of cutting fluid.

(6) Knowledge of the use and maintenance of tools, fixtures and measuring tools. Basic knowledge of fitter (1) Marking knowledge.

(2) The fitter's operation knowledge (chisel, file, saw, drill, screw hole, tap thread and set thread). Electrician knowledge (1) Types and uses of common electrical appliances for general equipment.

(2) Basic knowledge of electric drive and control principle. (3) Knowledge of safe electricity use.

Knowledge of safe and civilized production and environmental protection. (1) requirements for on-site civilized production.

(2) knowledge of safe operation and labor protection (3) knowledge of environmental protection. Knowledge of quality management (1) The quality policy of the enterprise.

(2) post quality requirements. (3) post quality assurance measures and responsibilities.

Knowledge of relevant laws and regulations (1) and knowledge of labor law. (2) Relevant knowledge of contract law.

Extended data:

Safety operation specification 1. Before starting work, check whether the electric, hydraulic and pneumatic power supplies are disconnected. Hang a warning sign at the switch that says "maintenance is under way, no starting".

If necessary, the distribution box should be locked or supervised by a special person. If the machine and power supply are not cut off, it is forbidden to work.

2. When disassembling the side parts, such as the box cover of the gearbox, the lower screw should be removed first, and the upper screw should be tightened first when assembling. When removing parts with unbalanced center of gravity, remove the screws far away from the center of gravity first, and then install the screws close to the center of gravity. When disassembling the spring, attention should be paid to prevent the spring from collapsing and hurting people. 3. The disassembled parts should be put together as far as possible and placed safely according to the regulations. Don't throw them about. If there is a rotating mechanism, it should be stuck to prevent rotation.

4. When moving parts by manpower, personnel should be properly equipped. When many people move and carry, they should be under unified command, and their actions should be consistent when working.

When lifting shafts, screws, pipes and girders, they must be shoulder to shoulder. We must be steady, let go, and strive for progress while being steady.

When handling machine tools or lifting large and heavy parts, the safety operation procedures of riggers and porters should be strictly observed. 5. When scraping the guide surface of equipment or machine tool, the bottom of the workpiece should be leveled and the joint surface should be kept level.

When using the jack, the bearing surface should be firmly padded to ensure safety. 6. During scraping operation, the scraped workpiece must be smooth, and it is not allowed to move in series. Calibration tools must be equipped with fixed bracelets or rings.

When two or more people do the same workpiece, be sure to pay attention to the direction of the scraper, and never scratch the human body. During reciprocating grinding, fingers should not extend to the grinding surface, and the running position of the grinding plate should be adapted to its center of gravity, and should not exceed the grinding surface of the workpiece to prevent slipping.

During electric grinding, there must be a special person to guard the electric switch or install the interlock device. 7. When using tools, you should operate correctly according to the safety operation procedures of common tools used by locksmiths.

8. The workplace should be kept clean, and oily sewage should not flow on the ground to prevent slipping and hurting people. 9. When cleaning parts, it is forbidden to smoke, ignite or carry out other open flame operations.

Do not use gasoline to clean parts, scrub equipment or floor. Waste oil should be poured into the designated container and recycled regularly, and it is not allowed to be poured into the sewer.

10. Before the safety protection devices on the mechanical equipment are installed, it is forbidden to test run and hand over the production. 1 1. When overhauling containers containing toxic, flammable and explosive substances, pressure relief, cleaning, replacement or neutralization must be carried out in advance to remove indoor gas, liquid and slag, and ventilation measures must be taken before operation.

12. Observe the "general locksmith" safety operation regulations. The main tasks of the mechanic are mainly divided into the following parts: equipment maintenance, manufacturing and maintenance.

1. Machining parts Some machining that is not suitable or cannot be solved by mechanical methods can be done by locksmiths. Such as: scribing in the process of machining parts, precision machining (such as scraping templates, making molds, etc. ), inspection and maintenance, etc.

Assembly: according to the assembly technical requirements of mechanical equipment, the parts are assembled, and after adjustment, inspection and debugging, they become qualified mechanical equipment. 2, equipment maintenance When the machinery fails in the process of use, it is damaged or the accuracy is reduced after long-term use, which affects the use, it should also be maintained and repaired by the fitter.

3, manufacturing and repairing manufacturing and repairing all kinds of tools, fixtures, measuring tools, molds and various professional equipment. 4. Safety precautions (1) The file is a right-handed tool and should be placed on the right side of the vice. When placed on the vise table, the handle of the file should not be exposed outside the vise table, so as not to knock off the ground and hurt the foot or damage the file.

(2) Files with useless handles or files with cracked handles cannot be used. (3) When filing, the file handle should not touch the workpiece, so as to avoid the accident caused by the file handle falling off.

(4) Don't blow iron filings with your mouth to prevent iron filings from entering your eyes. You can't touch the filed surface with your hands.

(5) The file shall not be used as a crowbar or hammer. 5. Maintenance (1) In order to prevent the file from wearing too fast, do not file the hard skin of the blank or the hardened surface of the workpiece with a file, but use other tools or the indented front end and side teeth first.

(2) When filing, use one side of the falling knife first, and then use the other side after this side is dull. Because used file teeth rust easily.

(3) When filing, make full use of the effective working face of the file to avoid local wear. (4) The file cannot be used as a tool for disassembly, knocking and prying, so as to avoid the file being broken due to fragile materials.

(5) When using plastic files and small files, do not use too much force to prevent the knife from breaking. (6) The file should be waterproof and oil-proof.

Files rust easily when they are wet with water. The file is easy to slip when working after being stained with oil.

(7) In the process of filing, if chips are found embedded in the file lines, they should be removed in time to avoid the chips scratching the machined surface. After the file is used up, follow it with a file brush or copper sheet.