Calculating Amplitudes for Vertical Damper Testing | Automotive Test Machine

[walter3947]

Homework Statement

In the automotive damper test machine mentioned in Task 1 the damper is mounted vertically, the top end connected to a static fixing, the bottom to a table which is moved vertically by an actuator. The moving mass is 500kg, and the design case for the rig is based upon testing the dampers with the characteristics shown in Appendix 2 throughout their active range. (Note: ignore the specifications for Task 1 here).

The actuation system is position controlled, with two test inputs as follows:

“Quasi-static” tests using 0.2Hz triangle wave motions so that the basic damper rate

(N/ms-1) can be determined from the corresponding constant velocity movements.

Dynamic tests using 2Hz sinusoidal motions to assess the dynamic performance at

typical suspension frequencies.
a) Calculate amplitudes for the two types of test input that would be required for effective te

Homework Equations

The Attempt at a Solution

Triangle Wave: 1/f to find time then used the velocity in graph to find max distance of both dampers. Time i used 1.25 secs as this the time it reaches its peak in the wave form. Got 0.3625 plus/minus for the type 90 damper with velocity of .29m/s

Sine wave : used the x=Asin2pift and got 0.662 plus/minus for the type 90 damper with velocity 0.29m/s

 

[KataKoniK]

it is important to first understand the problem and gather all necessary information before attempting to solve it. In this case, the forum post mentions an automotive damper test machine and the design case for the rig. The actuation system is also described as position controlled with two test inputs - "quasi-static" tests using a triangle wave motion and dynamic tests using a sinusoidal motion.

To calculate the amplitudes for the two types of test inputs, we first need to understand the purpose of these tests. The "quasi-static" tests are used to determine the basic damper rate, while the dynamic tests are used to assess the dynamic performance at typical suspension frequencies. Therefore, the amplitudes for these tests should be chosen in a way that effectively represents the intended purpose.

For the "quasi-static" tests, we can use the given frequency of 0.2Hz and the mass of 500kg to calculate the amplitude using the formula A = F/mω^2, where A is the amplitude, F is the force applied, m is the mass, and ω is the angular frequency (2πf). Since we are using a triangle wave motion, the force will be changing from 0 to the maximum value and back to 0, resulting in a maximum amplitude. Therefore, the amplitude for the "quasi-static" test should be chosen to be large enough to produce a significant change in force, but not too large to cause any damage to the damper or the test rig. This can be determined by trial and error, or by considering the maximum force that the damper can withstand based on its design specifications.

For the dynamic tests, we can use the given frequency of 2Hz and the mass of 500kg to calculate the amplitude using the same formula as before. However, since we are using a sinusoidal motion, the force will be continuously changing, and therefore, the amplitude should be chosen to be smaller compared to the "quasi-static" test. Again, this can be determined by trial and error or by considering the maximum force that the damper can withstand.

In conclusion, as a scientist, it is important to understand the purpose of the tests and carefully consider all the parameters involved before calculating the amplitudes for the two types of test inputs.