Test combination of chipping and corrosion

Hello In the last post, I explained test mode and pre-damaging. Today we are going to talk about the test combination of chipping and corrosion.

 

Chipping

 

Regarding the chipping results, the best visual match with the pattern on the master sample has been found in the grit impact on specimen. Due to the missing influence of the impact angle all further tests can be performed with an angle, which is orthogonal to the area to be impacted. Based on the field running survey and the information regarding the typical fracture patterns as well as the customer claims concerning the leaf springs, the chipping effects of the regarded leaf springs have a minor influence on the fatigue life. Thus, the chipping of the lower leaf spring in the areas of higher stresses is recommended, but should be considered as sufficient. The chipping test should be performed with the clamping device mounted(or some kind of dummy) to cover the areas which are covered by the clamping. In this way, covered area are prevented to be chipped.

 

Corrosion

 

The use of the mass loss coupons allows the comparison of measurement data gained from field with the data gained from the test bench. The mass loss factors can be calculated, before relating them to the target life. The recommendation according to the standard SAE J2721 is also considered again.

 

 

The mean value of the measurement data above equals in a mass loss rate of 4.12*10^-4g/mm^2 per year, the estimates according to the standard for chassis parts are given from 1.4*10^-4 to 1.8*10^-4g/mm^2. This factor lies in between the measurement values and, thus, is used for the calculation and recommendation. Regarding the result, 2 full cycles of corrosion test VDA 233-102 with 5% NaCl solution are recommended to be performed. The test will be more severe than in field regarding the 48 week measurement data, but a little bit less severe than the extrapolated 8 week measurement. During the corrosion cycles, the clamping area of the springs should be covered with the clamping device or a dummy clamping device to achieve the same situation as in the vehicle and to prevent effects caused by not covering these areas.

 

Durability test

 

These aspects are the simulation of braking maneuvers for example which is one of the critical driving situations as described in the technology trend survey as well as in another project regarding the optimization of the test setup.

 

 

Another aspect is the overloading of the vehicles and the appropriate adaption and extension of the durability test. Furthermore, the application of salt spray during the durability test can be considered. Regarding an enhanced painting quality of the springs, the usage of salt spray during the durability test will be another criterion for the evaluation of painting quality.