Test particles according to VDA 19 - Determination of the sensitivity of components to particulate contamination

Targeted contamination of components with standard particles

Standard parts made of aluminum

Continuously more compact components, higher power densities, lower emission values, safety systems, driver assistance systems, and lower fuel consumption are some of the buzzwords in the modern automotive sector. And all of this with decreasing manufacturing costs? An ambitious goal that has nonetheless been impressively implemented and continues to be by international automakers and their suppliers in recent years. In this context, technical cleanliness in accordance with VDA 19 / ISO 16232 is playing an increasingly prominent role.

The miniaturization of vehicle components, often necessary for the implementation of the above-mentioned goals, hints at this need. But how much dirt can a component tolerate? Which particle sizes ultimately lead to impaired function or even failure? While the answer to this question seems obvious at least in the field of vehicle electronics—namely, that the length of an electrically conductive particle should not exceed the smallest conductor track spacing of an electronic component—the solution is often much more complex. For example, if a particle whose length exceeds the gap between two open conductor tracks causes a short circuit, then two particles each half the length of the conductor track spacing are equally capable of impairing the function of the electronic component. Similar considerations apply to the flow of media in fluid-carrying systems. If a particle aligned with the flow in a medium can pass through a constriction significantly smaller than its maximum dimension, then the same particle, when oriented differently, could cause severe damage. And what happens if many particles, which are significantly smaller than a constriction in a hydraulic system, pass through the constriction simultaneously? One of these particles could pass unimpeded, and many particles together could cause damage in this example. These considerations clearly illustrate how complex the question of dirt tolerance in functionally relevant automotive components truly is. Developers and designers are usually tasked with specifying cleanliness requirements for individual components of relevant parts. Often, well-established values are adopted without question. In many cases, the cleanliness requirements from a previous project are even increased, as a safety measure. The requirements created in this way not only cause frustration for suppliers but also significantly increase the manufacturing costs of the components. The potential for savings achievable through the use of realistic cleanliness requirements is particularly substantial.

Determination of particulate limits through damage particle tests

But how can one determine at what level of dirt mass, particle size, or particle dimension a damage potential against the component arises? The second revised edition of Volume 1 of VDA 19, published last year, provides very helpful information for particulate limit determination in Chapter 2. These range from evaluating design measures and simulations to comparisons with similar applications. A very significant and highly realistic approach is offered by the limit determination method described in the aforementioned VDA volume, which uses damage particle tests. In this method, a component is subjected to particles of increasing size and number until it shows initial impairment of function or until the particle load leads to complete failure of the part. The insights gained in this way regarding the robustness of a component against particulate contamination are extremely realistic. Today, users have access to particles that correspond in size to the classes listed in VDA 19 / ISO 16232 for conducting damage particle tests. Thus, a VDA 19-compatible method is available to develop very realistic limits and, consequently, meaningful cleanliness specifications. The company Marhan – Normpartikel has established itself in recent years as a manufacturer of these valuable particles. Here, users receive not only test particles in various sizes and materials but also comprehensive and expert advice on their versatile applications.

Targeted contamination of original components with standard particles

As a leading service provider for standard particle-related applications, Marhan also offers contamination of original components supplied by customers with standard particles. This service is of particular interest for testing technical cleanliness. It provides the user with a defined contaminated original of their components for the first time. This enables the examiner to determine suitable extraction parameters directly from the component in a very realistic manner. The determination of appropriate fluid quantities, ultrasound settings, temperatures, and extraction times was previously only possible through a decay test according to VDA 19. Particles that adhere to unfavorable locations on a component may, under certain circumstances, remain attached even after the sixth extraction cycle during the standard decay curve determination. Consequently, these particles would not be detected during cleanliness testing. This potential error can be minimized or even eliminated by directly determining the extraction parameters from the component. Together with the extraction standard developed by Marhan – Normpartikel, the overarching goal is to increase the comparability of cleanliness test results, thus moving a significant step closer to more reliable assessments.