Modeling Fatigue Failure in Elastoplastic Materials

Mateusz Stec October 28, 2016

Imagine bending a metallic paper clip back and forth until, after a few repetitions, it breaks entirely. This is one example of fatigue failure, the most common type of structural collapse. In more severe cases, such failure can lead to collapse or malfunction in structures like car exhaust pipes and aircraft jet engines. To better understand and predict fatigue failure in elastoplastic materials, we can use the COMSOL Multiphysics® software to accurately model both the materials and the fatigue process.

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Mateusz Stec August 4, 2016

Damage occurs in bearings, gears, rails, and cams due to a damage mechanism called contact fatigue. This happens in assemblies when two parts in contact experience a time-dependent contact pressure. When the transferred load is too high, and after numerous load cycles, a piece of the surface material can flake off and leave a small crater. This phenomenon is called spalling or pitting. With the COMSOL Multiphysics® software, we can model contact fatigue and predict failure in these components.

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Caty Fairclough May 28, 2015

Simulating fatigue offers valuable insight into how stress can affect the longevity of a structure and its components. This can help identify potential design problems and pave the way for the development of a safer structure. Arriving at this solution, however, often requires running several simulations to test different scenarios. Our Frame Fatigue Life demo app demonstrates how simulation apps can save you time and energy in evaluating the impact of fatigue.

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Bridget Cunningham March 6, 2015

Reciprocating engines are used extensively for power generation in a variety of applications, most notably within the automobile industry. In the design process, it is important to ensure that all of the engine’s parts can withstand high stresses and loads in order to maximize the operational lifetime. Here, we analyze fatigue in an engine’s connecting rods.

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Mateusz Stec December 26, 2014

When simulating fatigue, you are faced with two main challenges. The first is to select a suitable fatigue model for your application and the second is to obtain the material data for the selected model. I recently addressed the first challenge in the blog post “Which Fatigue Model Should I Choose?“. Today, I will address the second challenge and discuss how you can obtain fatigue model parameters.

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Mateusz Stec November 25, 2014

The most frequent question we get regarding the Fatigue Module is “Which fatigue model should I use in my simulations?” There is no straight answer to this question, since fatigue is not based on an exact differential equation, but on engineering observations that lead to different physical models. The applicability of each model can depend on factors such as material and loading type. Today, I will discuss different approaches for fatigue model selection and the applicability of the different models.

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Guest Nagi Elabbasi August 8, 2014

Today, we invite guest blogger Nagi Elabbasi of Veryst Engineering to share the work they performed on simulating wear in COMSOL Multiphysics. Using COMSOL Multiphysics, we implemented a wear model and validated it by simulating a pin-on-disc wear test. We then used the model to predict wear in an automotive disc brake problem. The results we found showed good agreement with published wear data.

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Lexi Carver July 24, 2014

Modular orthopedic devices, common in replacement joints, allow surgeons to tailor the size, material, and design of an implant directly to a patient’s needs. This flexibility and customization is counterbalanced, however, by a need for the implant components to fit together correctly. With parts that are not ideally matched, micro-motions and stresses on mismatched surfaces can cause fretting fatigue and corrosion. Researchers at Continuum Blue Ltd. have assessed changes to femoral implant designs to quantify and prevent this damage.

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Mateusz Stec May 1, 2014

Engineers simulating fatigue in nonlinear materials are faced with two challenges. You must correctly represent the material behavior with a constitutive relation and find a fatigue model that captures the life-controlling mechanism. Both challenges require a thorough material knowledge. Today, we will address these challenges when modeling thermal fatigue in nonlinear materials.

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Mateusz Stec July 22, 2013

Research on fatigue started in the 19th century, initiated following failing railroad axles that caused train accidents. In a rotating axle, stress varies from tension to compression and back to tension in one revolution. The load history is simple because it is uniaxial and proportional. Fatigue can then be evaluated with the S-N curve, also known as the Wöhler curve, which relates stress amplitude to a component’s life. In many applications we deal with multiaxiality and non-proportional loading. In this […]

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Mateusz Stec May 30, 2013

In many applications, loads applied to structures are random in nature. The sampling results of the structural response will differ depending on the data collection time. Although the stress experienced is not always high, the repeated loading and unloading can lead to fatigue. The engineering challenges in these types of applications are defining the stress response to the random load history in the critical points, and predicting fatigue damage. This is simulated with the Cumulative Damage feature in the Fatigue […]

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