Fatigue Sensitivity Analysis Technique for Developing Accelerated Durability Test Load Cycles Based on Damage Prediction from CAE Model

Tractors are the self-propelled vehicle which finds its major application in agriculture, haulage and construction equipment. The product development cycle time of a tractor is more as compared to automobiles since it has to undergo rigorous field testing. Bringing more realistic component and system level validation in the test lab will drastically reduce the product development cycle time.

Non-availability of standard usage pattern and customer-correlated proving ground pose a bigger challenge for bringing the field conditions to the lab. As a result, the tractor has to be instrumented with sensors and load-time history needs to be acquired as per real world usage pattern. Raw data from the field cannot be used directly for lab testing since the number of load cycles will be very high. Raw data have to be edited based on damage calculation and fatigue sensitivity analysis technique. One of the major requirements for damage editing is the availability of local strain value at the critical locations. Conventionally component/system has to be instrumented with a strain gauge, to be mounted on the test rig and data has to be acquired in the lab. Measuring strain data with the proto samples will lead to time consuming instrumentation activity.

In this paper, an attempt has been made to predict the damage values of the component / system from the computer aided engineering model. Based on the predicted damage values from the computer aided engineering model and fatigue sensitivity analysis technique an accelerated durability load cycle has been developed. This method has been implemented for developing a test duty cycle for one of the new tractor development programs. The benefits of this exercise include:

• Accelerated durability load cycles developed without any physical part.
• Actual component/system CAE model used for deriving the damage values, hence component/system sensitive accelerated durability load cycles can be developed.