Issue:
Allowables in MMPDS for 4130 bar stock in the normalised condition have no statiscal basis (Table 2.*.*.* g1), nor is a specification minimum stated in the various bar stock AMS and MIL specifications (only F condition is addressed - I'm guessing the reason for this absence is that 4130 bar is more typcially used in higher strength applications).
Possible Solutions:
To comply with 23.613 (and ASTM equivalent), my options appear to be:
A) heat treat the assembly to f condition per ams2759, with quality control/testing to verify tensile properties. Warping is a risk.
B) have the supplier conduct testing above the requirements of the specs (which as noted above, do not stipulate testing for normalised material) to verify properties in MMPDS. We would then deal with S-basis issues from there.
Neither of these two solutions appear very economical, and will undermine the original motivation for a welded assembly.
Questions:
Is my logic correct?
How has this situation been addressed in the past? Is there another solution path I'm missing?
Background
I am working with a mechanical systems installation for a new part 23 aircraft. The installation includes a 4130 weldment, comprising machined bar stock and tube - welding is favoured over machined parts assemblies in this application, for economy of manufacture.
In this application the critical requirement is stiffness not strength, so the entire weld assembly is normalised condition.
Substantiation is by analysis, with first article proof test.
Allowables in MMPDS for 4130 bar stock in the normalised condition have no statiscal basis (Table 2.*.*.* g1), nor is a specification minimum stated in the various bar stock AMS and MIL specifications (only F condition is addressed - I'm guessing the reason for this absence is that 4130 bar is more typcially used in higher strength applications).
Possible Solutions:
To comply with 23.613 (and ASTM equivalent), my options appear to be:
A) heat treat the assembly to f condition per ams2759, with quality control/testing to verify tensile properties. Warping is a risk.
B) have the supplier conduct testing above the requirements of the specs (which as noted above, do not stipulate testing for normalised material) to verify properties in MMPDS. We would then deal with S-basis issues from there.
Neither of these two solutions appear very economical, and will undermine the original motivation for a welded assembly.
Questions:
Is my logic correct?
How has this situation been addressed in the past? Is there another solution path I'm missing?
Background
I am working with a mechanical systems installation for a new part 23 aircraft. The installation includes a 4130 weldment, comprising machined bar stock and tube - welding is favoured over machined parts assemblies in this application, for economy of manufacture.
In this application the critical requirement is stiffness not strength, so the entire weld assembly is normalised condition.
Substantiation is by analysis, with first article proof test.
