Does the mining machine brush the BIOS piece by piece

1. QB is just a payment method that can speed up the transaction speed in a certain field in a certain period of time, which is no different from the canteen meal ticket in essence. The real world currency is distinguished by the country, while the virtual currency is distinguished by the company that launched the currency. QB needs to rely on strategy and promotion, while real-world currency doesn't need promotion. It's legal tender
QB is equivalent to RMB. Although many point cards are not equivalent to RMB, they are also similar to the exchange rate, such as 1 yuan to 100 points
this is not to sell as much as you want
many services launched by Tencent require QB. RMB can buy any domestic goods and services that can be expressed in currency, but QB can't. QB can only purchase the services and goods launched by Tencent or the services and goods jointly launched by Tencent and other companies (such as rising recharge)
QB needs promotion, and it can't purchase the real goods compulsorily. We need to sell QB in exchange for RMB, which is the same as selling a piece of goods in exchange for RMB
RMB is a compulsory currency, and it is the only monetary unit in China. You can buy anything and services that can be measured by price. It is just a payment method that can speed up the transaction speed in a certain field in a certain period of time, which is no different from the canteen meal ticket in essence.

2. Official website has brush BIOS software, mainly to find and you with the same model of BIOS original file more trouble, you can find online. Find can brush, official website brush BIOS software is basically fool operation, the main attention is to backup your BIOS now. And you look at your current BIOS down or overclocking. If it is down frequency (now the mainstream is basically low frequency), you can not brush it back, which has little effect on your daily game performance.

3. 1. Make U disk and start disk
2. Download the latest BIOS from the main board's official website and unzip it to the root directory of the USB flash disk:
3. Insert the USB flash disk into the computer and restart it. Enter the BIOS and set the USB flash disk boot priority
4. Save the BIOS and exit. After restarting, you will enter the DOS interface (as shown below). Enter dir to view the files in the USB flash disk
5. Input backup to backup the BIOS and generate a bak.rom file in the U disk
6. Input update to start the BIOS brushing (you must not turn off the power ring the BIOS brushing process, otherwise it will fail and the machine will not start)
the prompt "program ended normally" or the cursor is not moving (pay attention to observe and wait) indicates that the BIOS refresh is successful. Finally, restart to see if you can enter the operating system normally.

4. No. Some need DOS, some can read and upgrade directly, some can use automatic upgrade software directly in the system environment, and some need to enter the brush mode. But new motherboards

5. "BIOS refresh" is not strange, because "BIOS refresh" can not only add new functions, but also solve some compatibility problems. But in the process of refreshing, sometimes there are some problems like this and that, which make the refreshing fail. So what causes refresh failure? In fact, if you understand the BIOS refresh process, you will solve these questions. To write the BIOS file to the BIOS chip, it involves: BIOS file, BIOS chip and BIOS refresh program. Therefore, we will make a detailed introction from these three aspects This paper mainly introces the BIOS chip, because if you understand the BIOS chip, you will understand the refresh process)
BIOS can be divided into three types: award BIOS, AMI BIOS and Phoenix BIOS. Each of the three kinds of BIOS has its own characteristics (we won't explain them in detail here), but no matter which type of BIOS, it provides the lowest level and most direct driver for the system hardware. BIOS file is a compressed binary file (take award BIOS as an example, the principle of amibios is consistent with it, and even completely consistent in some places. For example, the starting address of the boot block of the two kinds of BIOS files, 1m file starts from 1e000h, 2m file starts from 3e000h) (Figure 1), which can be roughly divided into three parts. One part is called system BIOS, which is the most basic part of the system. The file name is usually original.tmp. All BIOS have this part (Figure 2), which contains the basic BIOS program Prompt information and instructions, etc; In fact, this part is also a decompressor. After that, the moles are mainly decompressed by this part; At the same time, the addressing space of the file is defined. When we open a BIOS file with modbin program, the temporary file is the system BIOS mole, with the size of 128K (usually, we modify the contents of BIOS, mainly to modify this part). The second part is to extend the BIOS program, which is different from the standard award BIOS function customized by various manufacturers. In fact, almost all manufacturers will add this part of content; Then there are CPU microcode, ACPI and other moles, in which we can add other moles (such as jabber Recovery Wizard); The third part is the boot block, which is also the only mole in the BIOS file that has not been compressed. Because it supports isa graphics card and floppy drive, we can use this part to start the machine and recover when the BIOS is damaged. BIOS files are generally 1m (128KB * 8), 2m (256Kb *), 4m (512k * 8). 1mbit = 8 * 128kbyte (1byte = 8bit)

BIOS chip is actually the carrier of BIOS file. BIOS files are stored in the chip, and the programs in the chip can be erased, read and written through the external interface of the chip. BIOS chip can be understood as a building with multiple units (storage unit of the chip), each unit stores a binary code (0 or 1). The binary BIOS files are stored in the chip one by one in order. BIOS chip can be divided into EPROM, EEPROM, flashrom and so on according to the storage principle and technology. EPROM is a non-volatile memory (Fig. 3) (Fig. 4),

has the feature of no loss after power failure; The memory unit is composed of floating gate FET. The floating gate is charged by high voltage to write the chip, erase the internal data, and eliminate the charge on the floating gate by ultraviolet light to make it uncharged. The working voltage of EPROM is 5V. When writing, a special programmer must be used, and a certain programming voltage must be applied (VPP = 12-24 V, depending on different chip models). EPROM models start with 27 (such as ATMEL 27c020)< The EEPROM is an electrically erasable volatile memory (Fig. 5) (Fig. 6). Its memory cell is also composed of floating gate FET. When writing, the floating gate is charged by the tunneling effect under high voltage; However, the voltage polarity is opposite, so the floating gate is not charged. The working voltage of EEPROM is 5V. When writing, a certain programming voltage (VPP = 12V) needs to be added. The model of eerprom starts with 28 (such as am28f020)

flash ROM is also an electro erasable volatile memory (flash memory chip) (Fig. 7) (Fig. 8), which is also composed of floating gate FET. When writing, the floating gate is charged by hot electron injection; When erasing, the floating gate loses electrons by using the tunneling effect under high voltage. The working and refreshing voltage of flash ROM is 5V, and its models are generally 29, 39 and 49 (such as SST 39sf020). At present, BIOS chips on the motherboard are basically flash ROM. BIOS chip has three basic operations: read, erase and program. To understand the above operation process, first understand the structure of the chip. Chip (memory) external interface (PIN) can be divided into: data line, address line, control line, power line (Figure 9). The address line is used to determine the address of the data, and the data line is used to input and output data. The control line includes CE, OE and we; CE is a chip selection signal. When CE is at low level, the chip is selected (that is, any operation can be performed on the chip. When multiple BIOS chips are used in series, CE can be used to select which chip to operate. For example, in rd2000 al BIOS system, CE is used to switch two BIOS chips. Generally, the motherboard is a single BIOS chip, so CE is always at low level, That is to say, it's always for selection; When OE is low level, data output is allowed, that is, the contents in the chip can be read. When OE is high level, the output is prohibited and the contents cannot be read; When we is low level, we can program (write) the chip. When we is high level, we can't program the chip (we can connect this pin to high level, then the chip can't write. Invincible lock is to raise this pin to high level to protect the chip). For EEPROM, it doesn't need to erase, so it can program directly. For flash ROM, it needs to erase the contents of the chip first, and then it can write new contents. The power line includes VCC, VPP and PR. VCC is 5V power supply, VPP is 12V power supply when 28 series write (29 series this pin is NC, that is, empty pin), PR is 12V power supply of 28 series block BIOS, which is written for boot block. Whether the chip is reading, erasing or programming, all kinds of signals need to cooperate with each other according to a certain time sequence and a certain level, and the control signal time sequence is completed by the programming program. The process of completing this time sequence is also called refresh process (it is also a program code provided by the manufacturer. Although the manufacturer of the same type of chip is different, the refresh process is the same); Different chip, its control timing is also different, so the programming program will also carry on the corresponding control according to the chip model

different chips have different control timing, and the programming program will control according to the chip model. How does the refresh program identify the chip model? In fact, each kind of chip has its own identification, which is chip ID (also known as chip ID card). Because different chips have different IDS, the refresh program reads the chip ID to distinguish different chips, and calls different refresh process codes (control program) according to the chip ID to complete the chip programming

seeing this, we have a general understanding of how the refresh works. Then we continue to learn how the refresh program can write the chip. When we run the refresh program (take AWDFLASH as an example), after the refresh program starts, we directly detect the BIOS ID (this is the ID of the BIOS file); At this time, the BIOS ID and BIOS date are displayed on the top of the program, but the chip type is not displayed (because the refresh program is a BIOS image transferred into memory at this time, there is no operation on the BIOS chip) (Figure 10); At the same time, it prompts you to enter the BIOS file name that will be refreshed soon (here, many netizens ask that the BIOS file extension downloaded is not bin and other rule extensions, such as 123, etc.). In fact, the BIOS file is just a binary file, so no matter what kind of extension, just input it according to the file name and extension of the file). When we enter the path and file name of the BIOS file, press enter, and then the refresh program detects whether the CE pin of the BIOS chip is low. If it is low, the chip is selected, and then detects the ID of the chip, Then, according to the BIOS ID, the model of the corresponding BIOS chip is displayed in the flash type of the program (Figure 11), and the corresponding refresh process code is called (at this time, the BIOS chip can be read and written). If the refresh program can't read the ID of the chip, and the unknown flash is displayed in (flash type), then we can't read and write the BIOS chip.

(the reason may be that the BIOS chip has been damaged, and if the refresh program can't call in the corresponding refresh process code, the system will exit without any prompt, This is mainly because the refresh program version is too high or too low. At this time, you can replace other versions of the refresh program (Figure 12). If the normal system will continue, it will prompt whether to save the original BIOS. If you press save, the system will call in the refresh process code of the corresponding chip according to the BIOS ID detected in the previous step, and check whether the OE pin is low level. If it is low level, the processor will determine the read address of the chip storage unit through a0-a17 address line according to the refresh process of the chip, Then read the data of the specified address from the chip through the data line d0 ~ D7 (read 8-bit binary code at a time), and save it as a file according to the file name you input. If we choose to write instead of saving the file, first of all, the system will compare the ID of the BIOS file we are about to write with the image file in memory (this is the BIOS file ID, which is why we can't modify the ID with ordinary modification tools). If not, the system will prompt the program files part number doesn & # 39; T match with your system (Figure 13). If this prompt appears, we should not force writing; If it is consistent, the processor determines the write address of the chip storage unit through a0-a17 address line according to the chip refresh process, and then writes the updated BIOS file to the chip storage unit through d0-d7 data line. After normal writing, the system will prompt to restart or return to the operating system. We can choose by ourselves, and the refresh process is completed. Now we understand the BIOS chip refresh process, in the future in the refresh process of any error, we can clearly know the problem and the reason

the author's note: Although the control lines CE, OE and we of BIOS chip can be divided into high and low levels, they are all low levels under normal conditions, that is, the chip can be programmed at any time. As we said above, the refresh program detects the control pin of the chip when programming, just to let you understand that the refresh program reads and writes according to the refresh process of the chip. This is why the CIH virus can destroy the contents of the chip. However, we can artificially pull the we pin to the high level, that is, first cut off the connection between the 31 pin (we) and the motherboard, and then weld a 1K resistor between the 31 pin (we) and the 32 pin (VCC), so as to raise the we pin to the high level, without any interference

6. "BIOS refresh" is not strange, because "refresh BIOS" can not only add new functions, but also solve some compatibility problems. But in the process of refreshing, sometimes there are some problems like this and that, which make the refreshing fail. So what causes refresh failure? In fact, if you understand the BIOS refresh process, you will solve these questions. To write the BIOS file to the BIOS chip, it involves: BIOS file, BIOS chip and BIOS refresh program. Therefore, we will make a detailed introction from these three aspects This paper mainly introces the BIOS chip, because if you understand the BIOS chip, you will understand the refresh process)
BIOS can be divided into three types: award BIOS, AMI BIOS and Phoenix BIOS. Each of the three kinds of BIOS has its own characteristics (we won't explain them in detail here), but no matter which type of BIOS, it provides the lowest level and most direct driver for the system hardware. BIOS file is a compressed binary file (take award BIOS as an example, the principle of amibios is consistent with it, and even completely consistent in some places. For example, the starting address of the boot block of the two kinds of BIOS files, 1m file starts from 1e000h, 2m file starts from 3e000h) (Figure 1), which can be roughly divided into three parts. One part is called system BIOS, which is the most basic part of the system. The file name is usually original.tmp. All BIOS have this part (Figure 2), which contains the basic BIOS program Prompt information and instructions, etc; In fact, this part is also a decompressor. After that, the moles are mainly decompressed by this part; At the same time, the addressing space of the file is defined. When we open a BIOS file with modbin program, the temporary file is the system BIOS mole, with the size of 128K (usually, we modify the contents of BIOS, mainly to modify this part). The second part is to extend the BIOS program, which is different from the standard award BIOS function customized by various manufacturers. In fact, almost all manufacturers will add this part of content; Then there are CPU microcode, ACPI and other moles, in which we can add other moles (such as jabber Recovery Wizard); The third part is the boot block, which is also the only mole in the BIOS file that has not been compressed. Because it supports isa graphics card and floppy drive, we can use this part to start the machine and recover when the BIOS is damaged. BIOS files are generally 1m (128KB * 8), 2m (256Kb *), 4m (512k * 8). 1mbit = 8 * 128kbyte (1byte = 8bit)

BIOS chip is actually the carrier of BIOS file. BIOS files are stored in the chip, and the programs in the chip can be erased, read and written through the external interface of the chip. BIOS chip can be understood as a building with multiple units (storage unit of the chip), each unit stores a binary code (0 or 1). The binary BIOS files are stored in the chip one by one in order. BIOS chip can be divided into EPROM, EEPROM, flashrom and so on according to the storage principle and technology. EPROM is a non-volatile memory (Fig. 3) (Fig. 4),

has the feature of no loss after power failure; The memory unit is composed of floating gate FET. The floating gate is charged by high voltage to write the chip, erase the internal data, and eliminate the charge on the floating gate by ultraviolet light to make it uncharged. The working voltage of EPROM is 5V. When writing, a special programmer must be used, and a certain programming voltage must be applied (VPP = 12-24 V, depending on different chip models). EPROM models start with 27 (such as ATMEL 27c020)
EEPROM is an electrically erasable volatile memory (Fig. 5) (Fig. 6). Its memory cell is also composed of floating gate FET. When writing, the floating gate is electrified by the tunneling effect under high voltage; However, the voltage polarity is opposite, so the floating gate is not charged. The working voltage of EEPROM is 5V. When writing, a certain programming voltage (VPP = 12V) needs to be added. The model of eerprom starts with 28 (such as am28f020)

flash ROM is also an electro erasable volatile memory (flash memory chip) (Fig. 7) (Fig. 8), which is also composed of floating gate FET. When writing, the floating gate is charged by hot electron injection; When erasing, the floating gate loses electrons by using the tunneling effect under high voltage. The working and refreshing voltage of flash ROM is 5V, and its models are generally 29, 39 and 49 (such as SST 39sf020). At present, BIOS chips on the motherboard are basically flash ROM. BIOS chip has three basic operations: read, erase and program. To understand the above operation process, first understand the structure of the chip. Chip (memory) external interface (PIN) can be divided into: data line, address line, control line, power line (Figure 9). The address line is used to determine the address of the data, and the data line is used to input and output data. The control line includes CE, OE and we; CE is a chip selection signal. When CE is at low level, the chip is selected (that is, any operation can be performed on the chip. When multiple BIOS chips are used in series, CE can be used to select which chip to operate. For example, in rd2000 al BIOS system, CE is used to switch two BIOS chips. Generally, the motherboard is a single BIOS chip, so CE is always at low level, That is to say, it's always for selection; When OE is low level, data output is allowed, that is, the contents in the chip can be read. When OE is high level, the output is prohibited and the contents cannot be read; When we is low level, we can program (write) the chip. When we is high level, we can't program the chip (we can connect this pin to high level, then the chip can't write. Invincible lock is to raise this pin to high level to protect the chip). For EEPROM, it doesn't need to erase, so it can program directly. For flash ROM, it needs to erase the contents of the chip first, and then it can write new contents. The power line includes VCC, VPP and PR. VCC is 5V power supply, VPP is 12V power supply when 28 series write (29 series this pin is NC, that is, empty pin), PR is 12V power supply of 28 series block BIOS, which is written for boot block. Whether the chip is reading, erasing or programming, all kinds of signals need to cooperate with each other according to a certain time sequence and a certain level, and the control signal time sequence is completed by the programming program. The process of completing this time sequence is also called refresh process (it is also a program code provided by the manufacturer. Although the manufacturer of the same type of chip is different, the refresh process is the same); Different chip, its control timing is also different, so the programming program will also carry on the corresponding control according to the chip model

different chips have different control timing, and the programming program will control according to the chip model. How does the refresh program identify the chip model? In fact, each kind of chip has its own identification, which is chip ID (also known as chip ID card). Because different chips have different IDS, the refresh program reads the chip ID to distinguish different chips, and calls different refresh process codes (control program) according to the chip ID to complete the chip programming

seeing this, we have a general understanding of how the refresh works. Then we continue to learn how the refresh program can write the chip. When we run the refresh program (take AWDFLASH as an example), after the refresh program starts, we directly detect the BIOS ID (this is the ID of the BIOS file); At this time, the BIOS ID and BIOS date are displayed on the top of the program, but the chip type is not displayed (because the refresh program is a BIOS image transferred into memory at this time, there is no operation on the BIOS chip) (Figure 10); At the same time, it prompts you to enter the BIOS file name that will be refreshed soon (here, many netizens ask that the BIOS file extension downloaded is not bin and other rule extensions, such as 123, etc.). In fact, the BIOS file is just a binary file, so no matter what kind of extension, just input it according to the file name and extension of the file). When we enter the path and file name of the BIOS file, press enter, and then the refresh program detects whether the CE pin of the BIOS chip is low. If it is low, the chip is selected, and then detects the ID of the chip, Then, according to the BIOS ID, the model of the corresponding BIOS chip is displayed in the flash type of the program (Figure 11), and the corresponding refresh process code is called (at this time, the BIOS chip can be read and written). If the refresh program can't read the ID of the chip, and the unknown flash is displayed in (flash type), then we can't read and write the BIOS chip.

(the reason may be that the BIOS chip has been damaged, and if the refresh program can't call in the corresponding refresh process code, the system will exit without any prompt, This is mainly because the refresh program version is too high or too low. At this time, you can replace other versions of the refresh program (Figure 12). If the normal system will continue, it will prompt whether to save the original BIOS. If you press save, the system will call in the refresh process code of the corresponding chip according to the BIOS ID detected in the previous step, and check whether the OE pin is low level. If it is low level, the processor will determine the read address of the chip storage unit through a0-a17 address line according to the refresh process of the chip, Then read the data of the specified address from the chip through the data line d0 ~ D7 (read 8-bit binary code at a time), and save it as a file according to the file name you input. If we choose to write instead of saving the file, first of all, the system will compare the ID of the BIOS file we are about to write with the image file in memory (this is the BIOS file ID, which is why we can't modify the ID with ordinary modification tools). If not, the system will prompt the program files part number doesn & # 39; T match with your system (Figure 13). If this prompt appears, we should not force writing; If it is consistent, the processor determines the write address of the chip storage unit through a0-a17 address line according to the chip refresh process, and then writes the updated BIOS file to the chip storage unit through d0-d7 data line. After normal writing, the system will prompt to restart or return to the operating system. We can choose by ourselves, and the refresh process is completed. Now we understand the BIOS chip refresh process, in the future in the refresh process of any error, we can clearly know the problem and the reason! If you have different opinions on BIOS refresh, please come to my home www.biosrepair.com Let's have a talk with the author
the author's note: Although the control lines CE, OE and we of BIOS chip can be divided into high and low levels, they are all low levels under normal conditions, that is, the chip can be programmed at any time. As we said above, the refresh program detects the control pin of the chip when programming, just to let you understand that the refresh program reads and writes according to the refresh process of the chip. This is why the CIH virus can destroy the contents of the chip. However, we can artificially pull the we pin to the high level, that is, first cut off the 31 pin (we) and the motherboard

7. If the object is just put on the belt and is in the acceleration stage, then the friction force is the driving force and the direction is the same as that of the belt
if the belt has been leveled, it is static friction, and the friction can be considered as 0
if the belt has been tilted at a constant speed, as in the acceleration stage, the friction force should be balanced with the gravity force along the belt, and the direction is the same as that of the belt movement

8. Gear is an important basic mechanical component. Gear transmission has a large amount and a wide range, which plays a leading role in mechanical transmission. As the mechanism of gear tribology is very complex, it is still one of the hot topics in mechanical research, and the friction coefficient is the difficulty and focus of long-term research in the future. Jost pointed out that tribological research has great economic benefits, especially for mechanical transmission. The main effects of the friction on the tooth surface of gear transmission are: recing the transmission efficiency, aggravating the tooth failure (wear, pitting, gluing, fracture, etc.), causing system vibration and noise, etc. With the development of gear transmission to high speed, heavy load, precision, high efficiency, low noise and long life, the foundation project is supported by the National Natural Science Foundation of China (50475139), At the same time, engaged in the development of automotive safety technology, the research of tooth surface friction characteristics is of great significance to rece friction loss, increase the bearing capacity of gear teeth and improve the transmission performance of the system. Friction loss is the main factor of power loss in gear transmission, especially in high speed, heavy load and high power transmission system. Under certain working conditions, the influence of tooth surface friction on the fatigue strength of tooth root bending and tooth surface contact can not be ignored; Researchers began to pay attention to the influence of tooth friction in gear finite element analysis. The results show that the friction on the tooth surface accelerates the formation of pitting corrosion, the initiation and propagation of root crack and the fracture of the tooth. At the same time, the tooth surface friction affects the dynamic characteristics of the gear system and is an important source of vibration and noise excitation. The above research shows that the accurate solution of the friction force and friction coefficient of each point on the meshing tooth surface has a positive significance for the research of gear fatigue strength design, failure mechanism analysis, system dynamics and vibration and noise rection. In this paper, the author will focus on the calculation method of tooth surface friction coefficient under complex lubrication. According to the different research methods, the calculation methods of friction factor of the 182 th issue of lubrication and seal can be divided into two categories: one is based on the theory of elastohydrodynamic lubrication, the other is based on the test of tooth friction characteristics. Combined with the author's research results, the impact friction model and the calculation method of friction coefficient are supplemented. In 1965, bodensieck first proposed "oil film thickness coefficient" A: A: (1) where: H... Is the minimum oil film thickness; = ￣／ ＋ ， 、 They are the root mean square values of the roughness of tooth surface 1 and 2 respectively. Akin 16] summarized the results of predecessors and combined with their own research, divided the gear lubrication friction state into three categories: a > 3, complete elastohydrodynamic lubrication state; a > 3, complete elastohydrodynamic lubrication state; 1 a 3, mixed EHL condition; A < 1, boundary lubrication. The calculation methods of tooth surface friction coefficient under the above three lubrication conditions are studied. 1.1 complete EHL the current mature EHL theory and friction coefficient calculation formula are established under steady EHL. The typical calculation method is the line / point contact isothermal full film EHL numerical method of Dawson theory. According to the theory of elastohydrodynamic lubrication, Dowson and Higginson obtained the formula of friction coefficient for the numerical solution of line contact isothermal full film Elastohydrodynamic: 7 / DX (2) in the calculation of gear transmission, the minimum oil film thickness at the instantaneous meshing is a very important evaluation index, and its empirical formula is: H... = 2.65 G0. " 3) The Dowson formula was later confirmed by many tests, and was widely recognized as an important achievement in the ideal Elastohydrodynamic stage, and was widely used in the calculation of high pair transmission. The error of the formula is large in the following cases: (1) the material parameter g is less than 1 000, that is, when the lubricant with low viscosity coefficient is used for the material with low elastic molus; ② When the load coefficient is less than l0, the light load will occur; ③ When the oil supply is insufficient or the shear heat causes the viscosity to drop at high speed. It should be noted that since the rolling friction is almost completely located at the entrance of the parallel oil film, only the load that makes the oil film have the parallel section is considered in the derivation of equation (3), that is, H = H., As shown in Figure 1. Figure 1 Line Contact Elastohydrodynamic Lubrication Model for more general high pair contact, in 1977, harmrock and Dowson carried out a large number of numerical calculations on the Elastohydrodynamic problem of isothermal elliptical contact, and proposed the calculation formulas of pressure distribution, oil film shape and minimum oil film thickness of Point Contact Elastohydrodynamic under various conditions. In 1979, they put forward the lubrication state diagram of isothermal elliptical contact, which laid a foundation for the calculation of EHL film thickness of ideal point contact. The oil film thickness formula proposed by harmrock and Dowson is as follows: Hmm = 3.63 G0 (1-e) (4). The experimental results show that the calculated results of formula (4) are in good agreement with the actual measured values, and it is recommended to be used in the calculation of isothermal Point Contact Elastohydrodynamic Lubrication. 1.2 the concept of hybrid EHL was formally put forward, which can be traced back to the research of Chris tensen. In gear transmission, the friction coefficient of tooth surface changes significantly with the change of speed, load distribution and tooth profile surface shape. Martin found that e to the above factors, the lubrication state of gear teeth oscillates between liquid friction and boundary friction. In fact, mixed elastohydrodynamic lubrication is a widespread contact state in actual gear transmission, which is a combination of liquid lubrication, boundary lubrication and film lubrication. Wu used a simplified friction model of gear pair to study the tooth surface friction characteristics under the combined action of dynamic pressure oil film and boundary contact. Based on the "macro micro" method, Jiang explored the friction and wear phenomenon of tooth surface under mixed lubrication. Based on the theory of mixed elastohydrodynamic lubrication and combined with experimental research, Kelley and lemanski [2 (equation (5)), Martin (equation (6)) have proposed different friction coefficient calculation formulas; Gohar 2 (Eq. (7)) modifies the Evans Johnson formula by adding the influence factor of nonlinear viscosity and viscoelasticity. However, e to the randomness of tooth surface roughness and the time-varying of tooth surface contact state ring rolling and relative sliding, the friction characteristics of gear teeth under mixed lubrication are very complicated, Up to now, there is no perfect physical model and related theory. Vaishya and Houser have carried out in-depth numerical analysis and experimental comparison of the above research results. The results show that Kelley and lemanski's formula including the flash temperature factor of surface finish is in good agreement with the experimental results, which is closer to the actual working condition of gear meshing. Vaishya and Houser also revised the Kelley lemanski formula in the case of low viscosity lubricants, page 3
2006 issue 10 Zhou Chang Jiang et al: calculation method of tooth surface friction coefficient of gear transmission 187 another method for calculating tooth surface friction coefficient under mixed lubrication state is that the comprehensive friction coefficient is determined by the friction coefficient under boundary lubrication state and some liquid friction factors Count. Composition: / = f.q +. q 9) Where: Q and qehd are respectively the load-bearing coefficients of the peak contact and the elastohydrodynamic lubrication oil film, both of which are measured by the corresponding experiments, and they satisfy Q + q a = 1. It is determined by the contact property of the surface asperity and can be measured by experiments. It is not a constant, but a function of the slip to roll ratio of the meshing teeth. 1.3 boundary lubrication boundary lubrication was first proposed by Hardy in 1919 to describe a lubrication state between liquid lubrication and dry friction. Later, with the contribution of F.P. browdon, d.tabor and B.B. pylrhh, the development of boundary lubrication theory is becoming more and more perfect, which is called the important theoretical basis for improving the lubrication performance of gear transmission. In gear transmission, boundary lubrication exists objectively under certain conditions. For example, in the area near the meshing point, the top of the passive gear teeth scrapes along the profile of the driving gear, and the dynamic oil film is basically destroyed, mainly in the form of boundary lubrication. The mechanism of boundary lubrication is complex and it is difficult to test and analyze. So far, there is no unified calculation formula and its application is still in the experience stage. Boundary lubrication has a significant effect on adhesion effect and furrow effect. Tallian studied the pressure and turbulence of Elastohydrodynamic contact on rough surface, and pointed out that the possibility of plastic welding on the working surface in steady state is very small after running in. For the tooth surface of grinding and hobbing and running in, it can be considered that the tooth surface is in elastic peak contact ring the above meshing stage, and its boundary oil film will not break. It is generally considered that the peak point contact is in the state of boundary lubrication, and its friction coefficient is basically constant. The friction coefficient of boundary lubrication measured by experiment is generally: = 0.1 ~ 0.2. Buckingham semi empirical formula is often used to calculate the friction coefficient under boundary lubrication (a < 1): "= 0.05e + 0.ooz/v 10) 2. Research on the calculation method of tooth surface friction coefficient based on the test of tooth surface friction characteristics. The friction coefficient between meshing tooth surfaces is time-varying and strongly nonlinear; Its value depends on many factors, such as tooth surface material, surface finish, tooth shape, load, working temperature, lubrication state, rheological properties of Unsteady Oil Film and types of lubricating oil. Therefore, it is very difficult to establish the analysis model of gear friction characteristics according to the pure elastohydrodynamic lubrication theory, and the solution is also very complex; Too much condition simplification often affects the reliability of the analysis conclusion. As a result, many experimental studies on the friction characteristics of the tooth surface emerge as the times require. 2.1 experimental study on tooth surface friction coefficient of simulated specimen based on the equivalent principle of curvature radius of meshing point (Fig. 2): the instantaneous meshing contact of K point with the distance s from the tooth profile to the node P, the available curvature radii are RL = RL sins + s and R2 = /ƈsint ￣ s, respectively, The friction contact of the equivalent cylinder or disk is simulated by two simulation specimens whose rotational speed is equal to that of the gear. Fig. 2 Simulation Test Research on tooth surface friction of involute gear with equivalent radius of curvature, the friction torque of simulation specimen is directly measured by means of gear friction characteristic test bench, and then the friction force and friction coefficient are calculated. The calculation formula is usually relatively simple, such as formula (11) and formula (12): u = 4.255t/f 2mf / (11) (12). The common testing machines are double disk, four disk, disk ball testing machine, etc. these simulation testing machines play a great role in studying the lubrication mechanism of oil film, friction characteristics and the analysis of tooth surface friction and friction coefficient. But its main shortcomings are as follows: 1) the oil film between the cylinder or disc can not fully reflect the complex rheological and shear characteristics of the oil film between the actual gear teeth; ② It can't really reflect the influence of multi physical field coupling effect of heat, fluid and structure on lubricating oil film; ③ Each pair of cylinder or disk can only simulate one meshing point on the tooth profile, and can not reflect the effect of some tooth shape parameters on the oil film properties; ④ It can not reflect the influence of the alternation of multi lubrication state on the oil film friction characteristics in the actual gear meshing cycle. 2.2 based on power loss and friction

9. If the object is just put on the belt and is in the acceleration stage, then the friction force is the driving force and the direction is the same as that of the belt
if the belt has been leveled, it is static friction, and the friction can be considered as 0
if the belt has been tilted at a constant speed, as in the acceleration stage, the friction force should be balanced with the gravity force along the belt, and the direction is the same as that of the belt movement

10. Increase the positive pressure on the contact surface
increase the pressure by tightening the belt