This type of specimen, sometimes referred to as "harp" casting, frequently is used for determining hot tearing susceptibility.
Instead of finding the pressure drop under applied strain rate, the critical strain rate that causes hot tearing was estimated.
It is evident that this model predicts that material becomes very intolerable to imposed strain rate and very susceptible to hot tearing as the temperature approaches solidus.
Experiments were performed up to around 707F (375C) for this alloy, and no hot tearing was reported.
The underlying hypothesis is that hot tearing may be avoided if thermal expansion and shrinkage of the mold and casting occur simultaneously.
2, this result does not give a conclusive proof of hot tearing.
75, when the danger of hot tearing is not so great.
So, the simulation would show no danger of hot tearing if this result was used as a prediction.
We have previously shown that the rate of aging of an elastomer can be predicted by combining results of critical tearing energy experiments on oven aged specimens with the measured oxidative induction time determined using DSC (ref.
93 where r is the decrease in tearing energy per second of aging, and T is the absolute temperature.
Figure 4 shows the tearing energy of the CSM tubes taken from the same hoses that the covers were taken from for figure 3 along with some additional hoses, for which the covers were not available.
Power steering hoses removed from high mileage vehicles also show a decrease in their tearing energy as compared to unaged materials.
Thus, the results predicted by the oxidative aging model appear to work well for modeling the decrease in the tearing energy of power steering hose covers from high mileage vehicles.
From table 2 we know that the decrease in tearing energy for tubes removed from high mileage vehicles appears to be significantly less than that done by impulse testing.
The biggest roadblock to using the results of this study to predict the life for hoses is the lack of knowledge of the minimum tearing energy required to prevent a hose from undergoing significant amounts of crack growth.