electricdave,
You have provided the proof of the primary failure mode these are experiencing!
Their casting is probably cooling too quickly at that end as the break appears at the end where the liquid metal is poured in. You see how jagged that break is? That is the boundary where the two sides of the mold tried to join, and didn't quite fully join before starting to cool and crystallize. I am not a casting expert, but my limited experience would suggest they need need to increase the pool of metal above the part so this section can fully join together, or pour that end as a solid, and then drill the hole out during machining. Probably doing both should yield the properties that they need.
The bad news, inspecting this point of the part via die penetrant is going to be tricky, due to it's location, and it's probable porosity. The flip side is that inspecting for porosity might reveal this condition as a new part. Xray would be more likely to show this error though, but that is a time consuming process.
What we could do is determine if there is a specific steering and suspension angle that we could park/jack the car into that puts static stress on this part and then go carefully inspect for any small cracks in this area when they are being opened by the static stress. If this were an airplane and that was a device controlling a flight control surface, it would be recalled.
You have provided the proof of the primary failure mode these are experiencing!
Their casting is probably cooling too quickly at that end as the break appears at the end where the liquid metal is poured in. You see how jagged that break is? That is the boundary where the two sides of the mold tried to join, and didn't quite fully join before starting to cool and crystallize. I am not a casting expert, but my limited experience would suggest they need need to increase the pool of metal above the part so this section can fully join together, or pour that end as a solid, and then drill the hole out during machining. Probably doing both should yield the properties that they need.
The bad news, inspecting this point of the part via die penetrant is going to be tricky, due to it's location, and it's probable porosity. The flip side is that inspecting for porosity might reveal this condition as a new part. Xray would be more likely to show this error though, but that is a time consuming process.
What we could do is determine if there is a specific steering and suspension angle that we could park/jack the car into that puts static stress on this part and then go carefully inspect for any small cracks in this area when they are being opened by the static stress. If this were an airplane and that was a device controlling a flight control surface, it would be recalled.
