I love this forum and got a lot assistance from people like you with so much kindness and generocity. This communication is not related to immigration, but I would appreicate it if you could spare a little time to help me furnish for better in English. Thank you in advance.
Hi All,
An update from Tom on hopefully final choice of design architecture of blow-out doors was forwarded to you in my last e-mail. The candidated design configuration with ACC Doors and/or Commanded Vent Doors were no longer in consideration. It took a time among all parties to to get to this point.
The Chart below summaries approaches formerly adopted by engineers on analysis of pressure relief doors, along with the method proposed for our application. Following are what I would like to share and receive comments you may have with regard to pressure relief door analysis.
1. Burst Duct Peak Transit Pressure vs. ULT / LIMIT Load.
Of the three analyses shown in the Chart, two took the burst duct pressure as ultimate load, while one applied it as limit load. Whether one should use peak transit pressure as ULT or LIMIT is dictated by how it was understood and characterized with regard to its its impact on structures. If this load delivers a sudden and eventual permanent damage without any economy failure mode in between, it would be appropriate to consider it as ultimate load. As to our structure, the burst duct pressure at the bifur location increases up to 5.689 psig (The triggering pressure ranges from 3.0 psid to 3.5 psid) according to Tom’s latest model, which is higher than the previous design value (3.8 psig). Use of that pressure for ULT case is comparable to that listed in the Chart. So this pressure is recommended as Ultimate Load case.
2. Dynamic Factor
There is no reports in our database as far as I'm concerned documenting relief door analysis with dynamic factors. The popular method was to apply Ult load based on a peak pressure to size the structure. As the relief door experiences high speed blow out under burst duct pressure and has strong impact on the door frame at the stoppers (both AA and BB are using stoppers to arrest the door rotation). Dynamic effect is significant on structural performance and it should not be ignored. AA's earlier designs of relief doors were featured with Lanyards, which differs from our current one as the former is bigger than the latter.
An analysis template for estimation of dynamic factor for the relief door was generated based an energy approach. In the model, it was assumed that the relief door is an impacting component and the door frame is an impacted one. On the impact between the two, the kinetic energy of the door at its highest angular velocity (potential energy is too small to be included compared to kinetic energy) is conservatively considered to be completely transferred to deformation (strain) energy of the door frame. The door frame is simplified as a cantilever beam, with one end being clamped and the other being as an impacted point. The deflection at the impacted end of the beam can be calculated based on energy conservatism theory mentioned above and as a result dynamic load can be obtained from the deflection. Dynamic factor can then be determined by comparison of the load from static model and the one from dynamic analysis. The preliminary analysis indicates the factor is less than 1.85. Given that the dynamic model established is conservative in terms of energy conversion, as some portion of the kinetic energy would be dissipated for heating, sound, rebound of the door,etc, a factor around 1.5 was a reasonably good estimate for the current configuration design of the relief doors.
3. Ls-Dyna Modeling
In addition, use of LS-DYNA for precious dynamic analysis of the pressure relief door would be an option, but not sure if it is worthy of the effort in this misc. and seemingly insignificant type of structures.
4. FEM Modeling
There is also a consideration of use of FEM model to analyze all parts of the Door and Door Frame except Door Hinge Lugs where Smart Tool would be applied for detailed sizing. Meanwhile, FEM modeling would be useful in its transit to Ls-Dyna for dynamic analysis, if necessary.
Any comments and questions please let me know.
Hi All,
An update from Tom on hopefully final choice of design architecture of blow-out doors was forwarded to you in my last e-mail. The candidated design configuration with ACC Doors and/or Commanded Vent Doors were no longer in consideration. It took a time among all parties to to get to this point.
The Chart below summaries approaches formerly adopted by engineers on analysis of pressure relief doors, along with the method proposed for our application. Following are what I would like to share and receive comments you may have with regard to pressure relief door analysis.
1. Burst Duct Peak Transit Pressure vs. ULT / LIMIT Load.
Of the three analyses shown in the Chart, two took the burst duct pressure as ultimate load, while one applied it as limit load. Whether one should use peak transit pressure as ULT or LIMIT is dictated by how it was understood and characterized with regard to its its impact on structures. If this load delivers a sudden and eventual permanent damage without any economy failure mode in between, it would be appropriate to consider it as ultimate load. As to our structure, the burst duct pressure at the bifur location increases up to 5.689 psig (The triggering pressure ranges from 3.0 psid to 3.5 psid) according to Tom’s latest model, which is higher than the previous design value (3.8 psig). Use of that pressure for ULT case is comparable to that listed in the Chart. So this pressure is recommended as Ultimate Load case.
2. Dynamic Factor
There is no reports in our database as far as I'm concerned documenting relief door analysis with dynamic factors. The popular method was to apply Ult load based on a peak pressure to size the structure. As the relief door experiences high speed blow out under burst duct pressure and has strong impact on the door frame at the stoppers (both AA and BB are using stoppers to arrest the door rotation). Dynamic effect is significant on structural performance and it should not be ignored. AA's earlier designs of relief doors were featured with Lanyards, which differs from our current one as the former is bigger than the latter.
An analysis template for estimation of dynamic factor for the relief door was generated based an energy approach. In the model, it was assumed that the relief door is an impacting component and the door frame is an impacted one. On the impact between the two, the kinetic energy of the door at its highest angular velocity (potential energy is too small to be included compared to kinetic energy) is conservatively considered to be completely transferred to deformation (strain) energy of the door frame. The door frame is simplified as a cantilever beam, with one end being clamped and the other being as an impacted point. The deflection at the impacted end of the beam can be calculated based on energy conservatism theory mentioned above and as a result dynamic load can be obtained from the deflection. Dynamic factor can then be determined by comparison of the load from static model and the one from dynamic analysis. The preliminary analysis indicates the factor is less than 1.85. Given that the dynamic model established is conservative in terms of energy conversion, as some portion of the kinetic energy would be dissipated for heating, sound, rebound of the door,etc, a factor around 1.5 was a reasonably good estimate for the current configuration design of the relief doors.
3. Ls-Dyna Modeling
In addition, use of LS-DYNA for precious dynamic analysis of the pressure relief door would be an option, but not sure if it is worthy of the effort in this misc. and seemingly insignificant type of structures.
4. FEM Modeling
There is also a consideration of use of FEM model to analyze all parts of the Door and Door Frame except Door Hinge Lugs where Smart Tool would be applied for detailed sizing. Meanwhile, FEM modeling would be useful in its transit to Ls-Dyna for dynamic analysis, if necessary.
Any comments and questions please let me know.