Inertia Dynamometer Brake Thermal Roughness
© Copyright 2011 General Motors Company All Rights Rerved
1 Scope
Note: Nothing in this standard supercedes applicable laws and regulations.
Note: In the event of conflict between the English and domestic language, the English language shall take precedence.
教师如何做课题1.1 Purpo. This standard documents an inertia dynamometer test procedure to asss thermal roughness.
1.2 Foreword. This standard asss brake torque variation as a function of brake operating tempe
rature. This standard creates the environment when the brake pulsation phenomenon sometimes referred to as “hot judder ” may occur. This type of brake pulsation occurs only at elevated brake operating temperatures. The dynamometer test schedules outlined in this procedure were derived from GMW15919 and should be ud as the first tool of physical evaluation during the brake development process. Three evaluation methods are ud to asss thermal roughness. The first method is applicable to all pasnger car and light truck brake corners. The cond method is applicable only to high performance vehicles. The third method is applicable to vehicles in the European or similar markets.
1.3 Applicability. This procedure is applicable to all pasnger car and light truck brake corners.
2 References
Note: Only the latest approved standards are applicable unless otherwi specified. 2.1 External Standards/Specifications. None
2.2 GM Standards/Specifications. GMW14925 GMW15142 GMW14974 GMW15919
黑椒猪排3 Resources
3.1 Facilities. The Milford Proving Ground Brake Systems Laboratory inertia brake dynamometer or equivalent test facility shall be ud.
3.2 Equipment.
金鱼画法3.2.1 An inertia brake dynamometer capable of constant pressure control applies.
3.2.2 A dial indicator and a micrometer with a minimum resolution of 1 μm.
3.2.3 Optional: Non-contact proximity nsors with a minimum resolution of 1 μm and a frequency respon of at least 1000 Hz.
3.2.4 The following measurements shall be made and digitally recorded at 500 Hz.
a. Dynamometer speed in kilometers per hours
(km/h).
b. Braking time in conds (s).
c. Brake apply pressure in kilopascals (kPa).
d. Brake torque in Newton meters (N·m).
e. Brake rotor/drum temperature in degrees
Celsius (°C).
3.2.5 Optional: During a brake apply cycle, the following measurements shall be made and digitally recorded at 1000 Hz.
3.2.5.1 Rotor lateral runout (LRO) micrometers (μm) and Rotor Thickness Variation micrometers (μm) at one to three points along the brake swept area on both the inboard and outboard rotor faces. See Figure A1.
Note: The minimum point is at the specified outer diameter location.
3.2.5.2 Rotor positional marker voltage.
3.3 Test Vehicle/Test Piece. Production reprentative brake corner hardware shall be ud for testing and to produce the tailstock asmbly.
3.4 Test Time. Calendar time: 1 day Test hours: 8 hours Coordination hours:
2 hours
3.5 Test Required Information. Not applicable. 3.6 Personnel/Skills. One technician trained for the operation of an inertia brake dynamometer and to perform the duties described in Section 4 Procedure is required.
4 Procedure
4.1 Preparation.
4.1.1 The rotor thermocouple shall be installed per GMW14974.
4.1.2The pre- and post-test asmbled corner LRO shall not exceed 50 μm. The corner LRO shall be measured on the inboard face of the rotor at a radius 10 mm inside of the rotor outer diameter using a dial indicator or non-contact proximity nsors (or equivalent). The asmbled LRO shall be measured and recorded both pre- and post-test.
4.1.3The initial rotor thickness variation (RTV) shall not exceed 5 μm. The rotor thickness variation (RTV) shall be measured at a radius 10 mm inside of the rotor outer diameter. If a micrometer is ud, make the thickness measurements every 10° around the rotor for a total of 36 measurements.
沙场点兵4.1.4 Optional: Non-contact proximity nsors may be placed on the asmbly to measure rotor thickness variation. The transducers shall be placed as shown in Figure A1.
4.2 Conditions.
4.2.1 Environmental Conditions.Cooling air is provided to the brake. Cooling air temperature shall be between 10 °C and 30 °C. Cooling air humidity control is not required.
4.2.2 Test Conditions.Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc.
4.2.2.1See GMW15142 for loading conditions. The inertia equivalent to the gross vehicle loading condition weight is recommended, however, the equivalent lightly loaded vehicle loading inertia may be added to the test quence, if requested.
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4.3 Instructions.
4.3.1Perform paragraphs 4.3.1 to 4.3.6 of GMW1492
5.
4.3.2Perform brake warm-ups stops until rotor temperature is greater than 100 °C and then perform the Thermal Roughness Schedule for a total of 15 snubs. Allow the rotor to cool to ambient temperature after each 15 snub quence.
4.3.3 Repeat paragraph 4.3.2 four times for a total of five times. This completes the Ba Thermal Roughness Schedule.
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4.3.4For high performance vehicles, perform paragraphs 4.3.1 to 4.3.3 starting with a green friction t. Allow the rotor to return to ambient temperature. 4.3.5Perform brake warm-up stops until rotor temperature is greater than 100 °C, and then perform the High Performance Thermal Roughness Schedule for a total of 15 snubs. Allow the rotor to cool to ambient temperature.
4.3.6Asss the condition of the hardware and repeat paragraph 4.3.5 three additional times for a total of four times. This completes the High Performance Thermal Roughness Schedule.
4.3.7 For European or similar market vehicles with brake systems using low-metallic friction materials, perform the Ba Thermal Roughness Schedule (paragraphs 4.3.1 to 4.3.3) starting with a green friction t. Perform brake warm-up stops until rotor temperature is greater than 100 °C, and then perform the 80% vehicle maximum speed (Vmax) Thermal Roughness Schedule.
4.3.8 Asss the condition of the hardware and repeat the 80% Vmax Thermal Roughness Schedule four additional times for a total of five times. This completes the 80% Vmax Thermal Roughness Schedule.
4.3.9With-U: Test is written for one brake hardware build. Thermal roughness is dependent on previous thermal conditioning history of the hardware, initial rotor thickness variation, and lining wear conditions. As such, it is recommended that the test be repeated for the worn condition with at least 6 microns and no more than 10 microns of first order rotor thickness variation and a half-worn lining condition. The half-worn lining condition can be achieved by machining linings to a 50%-thickness-plus-one-millimeter condition and completing one GMW14925test (without park brake or static apparent friction ctions).
5 Data
5.1 Calculations.Any needed calculations are described in the following data prentation paragraphs.
5.1.1 Data Prentation.
防守战术5.1.1.1 Perform order tracking on torque-time data for each stop to determine the peak-to-peak brake torque variation (BTV) resulting from the first four orders. Using the peak-to-peak torque variation and pha angle of each of the first four orders, reconstruct each stop. Record the peak-to-peak BTV (Newton meters (N·m) and percent (%)), average torque, average apparent friction, initial brake temperature and maximum brake temperature for each thermal roughness snub/stop (e Table B1).
5.1.1.2Plot the average apparent friction, initial brake temperature and maximum brake temperature versus stop condition (e Figure B1).
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5.1.1.3Plot the maximum peak-to-peak BTV percent (%) versus snub number for each thermal roughness stop (e Figure B2).
5.1.1.4Plot the maximum peak-to-peak BTV Newton meter (N·m) versus snub number for each thermal roughness stop (e Figure B3).
5.1.1.5Plot the maximum peak-to-peak BTV percent (%) versus initial brake rotor temperature for each thermal roughness stop (e Figure B4).
5.1.1.6Plot the maximum peak-to-peak BTV Newton meter (N·m) versus initial brake rotor temperature for each thermal roughness stop (e Figure B5).
5.1.1.7Optional: Calculate the maximum in-stop RTV. Perform order tracking on RTV-time data for each stop to determine the maximum order component of the in-stop RTV. Record the maximum in-stop RTV and dominant order component for each thermal roughness stop.
5.1.1.8Optional: Plot the maximum in-stop RTV versus initial brake temperature (IBT) and snub number for each thermal roughness stop.
5.2 Interpretation of Results.Results may be compared to applicable technical specifications or to the results for other brake corners.
5.3 Test Documentation. Publish the test information and results according to GM corporate protocol using the Evaluation Report template and Global Document Management system or its successor.
6 Safety
This standard may involve hazardous materials, operations, and equipment. This standard does not propo to address all the safety problems associated with its u. It is the responsibility of the ur
of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to u.
7 Notes
7.1 Glossary.
80% Vmax Thermal Roughness Schedule: Snubs are made from 80% Vmax initial speed to 80 km/h with a first stop IBT of 100 °C, constant pressure control, 2 km/h cooling air speed, 20 000 kPa/s pressure apply rate, and with 45 s between the start of each brake application. The target pressures for a single quence are 3000, 1500, 5000, 5000, and 3000 kPa, concutively. If vehicle acceleration data is known, tho data should be ud to determine the brake cycle time, and, if it less than 45 s, the cycle time should be lowered accordingly. Ba Thermal Roughness Schedule: Snubs are made from 115 km/h initial speed to 30 km/h with a first stop IBT of 100 °C, 2 km/h cooling air speed, 20 000 kPa/s pressure apply rate, 2000 kPa constant pressure control, with 45 s between the start of each brake application. If vehicle acceleration data is known, tho data should be ud to determine the brake cycle time, and, if it is less than 45 s, the cycle time should be lowered accordingly.
Brake Torque Variation: The difference between the maximum and minimum braking torque during a braking event. The peak-to-peak BTV refers to the difference between the maximum and minimum braking torque during one revolution of a braking event.
Constant Pressure Control: A dynamometer control algorithm that maintains the brake pressure at a constant level during a brake apply.
High Performance Thermal Roughness Schedule:Snubs are made from 160 km/h initial speed to 10 km/h with a first stop IBT of 100 °C, 2 km/h cooling air speed, 20 000 kPa/s pressure apply rate, 5000 kPa constant pressure control, with 45 s between the start of each brake application. If vehicle acceleration data is known, tho data should be ud to determine the brake cycle time, and, if it less than 45 s, the cycle time should be lowered accordingly.
Initial Brake Temperature:The brake rotor temperature at the start of the braking event.
Rotor Thickness Variation:Rotor thickness variation is the difference between the maximum total asmbled lateral runout (d) and the minimum total asmbled lateral runout (ALRO) during one revolution. Total ALRO is the sum of inboard and outboard rotor cheek LRO at each measurement position.
Snub: The braking deceleration of a vehicle from a higher reference speed to a lower reference speed greater than zero.
7.2 Acronyms, Abbreviations, and Symbols. ALRO Asmbled Lateral Runout
BTV Brake Torque Variation
IBT Initial Brake Temperature
LRO Lateral Runout
RTV Rotor Thickness Variation
Vmax Vehicle Maximum Speed
8 Coding System
This standard shall be referenced in other documents, drawings, etc., as follows:
Test to GMW14985
© Copyright 2011 General Motors Company All Rights Rerved
9 Relea and Revisions
This standard was originated in January 2006. It
was first approved by the Chassis Global Brake
Subsystem Leadership Team in May 2006. It was
first published in November 2006.
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© Copyright 2011 General Motors Company All Rights Rerved
Appendix A
Note 1: Outer Diameter OD = R1 - 10 mm, where R1 = Rotor Outer Radius.
Note 2: Center Diameter CD = R1 - (R1 - R2)/2.
Note 3: Inner Diameter ID = R2 + 10 mm, where R2 = Pad Swept Area Inner Radius.
Figure A1: Brake Rotor Dimensions
© Copyright 2011 General Motors Company All Rights Rerved
