How can you improve the accuracy of fatigue testing for vehicle materials?

Carga aplicada, tempo de movimentação, atrito e temperatura influencia no resultado. Trabalho em baixa ou alta temperatura, nivel de alinhamento ou tripitações devem ser analisado

Choosing the right test method is one thing... but first you have to make sure you have collected enough and accurate data before you start the analysis of the usual average and maximum loads on your components. Only if you know the exact load applied to your components you can decide if the chosen test method is the right method...

Capturing material behavior at processing temperatures is key to building an accurate FE model for fatigue life prediction. This involves incorporating the material's plastic and elastic properties at processing temperatures and generating true stress-strain curves in addition to strain life plastic and elastic Coffin Mason etc.. However, a critical limitation lies in neglecting processing defects within the model. Every step in the material processing chain introduces these defects, which significantly influence fatigue life. Here's where the challenge arises: accounting for these imperfections in the FE model for a more realistic prediction of fatigue behavior.

The right test method also depends on the type of loading the component will be submitted to. To improve the quality of the results, it is recommended to elaborate a programa starting with the basic requirements (uniaxial, stress-controlled, constant amplitude, high-cycle test under controlled temperature) to understand the material behavior and to progress to more complex tests including other parameters (variable loading, corrosion).

One thing I found useful depending on the type, shape, and size of the material or component you want to test, you need to select the appropriate test method that can simulate the realistic loading and boundary conditions. For example, you can use uniaxial or multiaxial fatigue tests, strain-controlled or stress-controlled tests, constant or variable amplitude tests, or low-cycle or high-cycle fatigue tests. You also need to consider the frequency, waveform, and phase of the applied load, as well as the environmental factors such as temperature, humidity, and corrosion

Uma sugestão para os corpos de prova não devem ser extraído dos canais de alimentação. Todo corpo de prova deve respeitar uma distância aceitável dos canais de alimentação do metal para não levar material com impurezas que dificilmente passar nos testes de impacto e alongamento. Corte horizontal seguindo a direção da entrada do metal

Um laboratório que contenha temperatura controlada, controle de vibrações, e ferramentas aferidas e dentro da validade. Sempre atento as boas praticas, para que os padrões de testes sejam eficazes, constantes e organizados.

Specimen preparation is one of the key points for a well designed fatigue test. The surface of the specimen needs to be mirror polished. Even a minute scratch would yield catastrophic results. During loading the rotating specimen would fail at the region of that crack and not at the theoretical region of highest stress concentration. The ends of the specimen need to be knurled properly in order to facilitate proper gripping in the testing machine otherwise during rotation slipping would occur.

Manter a organização, as devidas demarcações que garantam efetividade no preparo da bancada de testes. Garantir que todo material utilizado estejam dentro dos padrões dos fornecedores. Todo e/ou qualquer material que não se enquadre nos processos de testes. 5s.

A thorough sensibility analysis of the test parameters must be carried out in order to understand which ones really play a significant role in the material behavior. Knowing how one parameter does or does not influence the others will certainly improve the understanding and the acceptance or rejection of the test results.

Correlation of materials stress-strain data with proven accurate CAE results at points of known fatigue areas subjected to given force’s or loads and constraints of system.

It is highly recommended to perform the calculation of measurement uncertainty for the test, indicating the assumed range of variation of the test result (stress, strain, life cycle, etc.).

One thing actually I want to contribute is that : Use of advanced testing equipment , optimizing testing parameter , moreover and important is to considered real world condition.

Bias is one factor that cannot be avoided. The accuracy of test result mainly concerns with human error and bussiness losses. Test result verification or auditor is also needed.

One thing that I have found helpful is to understand the dynamics of the material you are working on. Materials are becoming more complex and understanding the fundamentals such as design of the material, structure, raw materials used and where the material will be used in the automobile are critical. Standards and guidelines are equally important.

Seguir padrões e diretrizes relevantes, como ASTM, ISO, SAE e NACE, é fundamental para melhorar a precisão dos testes de fadiga. Essas organizações estabelecem recomendações e requisitos para garantir a qualidade, segurança e consistência dos testes, abordando aspectos como projeto, execução, análise e relatório. Isso ajuda a garantir que os resultados dos testes sejam confiáveis e comparáveis, facilitando a tomada de decisões no desenvolvimento de produtos e na avaliação de sua durabilidade.

Foster a culture of continuous improvement by seeking feedback, identifying the areas of improvement & optimisation. Robust testing protocol.

This is very important. One should always seek feedback from the knowledgeable professionals who are experienced enough especially those who are associated with R&Ds of different Industries. They have better ideas about specimen preparation, parameter control, identification of endurance limit stress from the S-N curve.

One thing that I have found extremely helpful in quality control and assurance is the aspect of continual improvement . Implementation of a culture of continuous improvement, where feedback from testing is used to refine testing methodologies, optimize parameters, and streamline processes over time, considerably impacts performance

I, as a former racer, double BMW master technician, general gear head, and engineer, think that more real world testing by qualified test drivers on a closed course would give you real world stress in controlled environments. Proper engineering first and real world stress testing before design releases. Many automakers spend millions on R&D/Engineering all the time but find out what really happens in the real world and have to endure the costs of lawsuits and recalls from improper testing.

Algo muito importante também são as escolhas dos colaboradores envolvidos no projeto. Escolhas técnicas , colaboradores que se empenham em realizar as ações com finalidade e concluir o projeto com êxito.