Metal Additive Manufacturing of Pressure Vessel Experimental Models
Navy SBIR 2019.2 - Topic N192-111
NAVSEA - Mr. Dean Putnam -
Opens: May 31, 2019 - Closes: July 1, 2019 (8:00 PM ET)


TITLE: Metal Additive Manufacturing of Pressure Vessel Experimental Models


TECHNOLOGY AREA(S): Materials/Processes


ACQUISITION PROGRAM: PMS397, Columbia Class Program Office, Tactical Submarine Evolution Plan (TSEP).


OBJECTIVE: Develop and demonstrate a metallic additive process for manufacturing pressure vessel models with detailed structural features that have specified property and tolerance levels in support of experimental pressure vessel testing.


DESCRIPTION: The advent of metallic additive manufacturing creates the potential to experimentally test and evaluate unique structural hull forms rapidly and inexpensively. It also allows testing of the structural features of pressure vessels for their impact on stress, strain, and hydrodynamic performance. The current state-of-the-art is to fabricate models out of forgings using a machining process (i.e., wire electrical discharge machining, lathe, or mill) or fabricating a welded model. This is very time-consuming and expensive, with times/costs ranging from 6 months/$800K for machined models to 3 years/$8M for welded models. Often, a structural feature cannot be reproduced in a machined model due to fabrication complexity and is often not explored due to the excessive time and cost. There are also significant risks associated with the fabrication of models to scaled tolerance levels as traditional fabrication methods can unintentionally impart defects that far exceed those that would be expected at full scale. These issues result in reduced testing and evaluation that can result in carrying risk of the adequacy of a structural feature forward to full scale trials at which point the design is very costly to modify. These late design risks have resulted in trial measurements that show features susceptible to cracking or unexpectedly low margins that must be monitored over the life of the vessel, adding to lifecycle costs. Innovative hull forms are often abandoned or not included in early concepts where cost or complexity of model fabrication has impeded design exploration due to the uncertainty in structural performance and the time and cost to assess the design and to validate the structural design tools.


The Navy seeks a metallic additive manufacturing process that reduces the time and cost to fabricate structural models of pressure vessels. Metallic additive manufacturing processes currently have limited material types, are challenged to achieve optimal material properties, and are unable to achieve dimensional tolerance requirements. To achieve these requirements, the Navy is open to new or innovative techniques that combine 3D printing with

established near net shape and selective surface net shape techniques such as Powder Metallurgy – Hot Isostatic Pressing. In particular, the demonstration should include high strength steels of or similar to HY80 and HY100. This process will enable the evaluation of innovative hull forms and structural features earlier in the design cycle and reduce maintenance costs of inspection and repair for the full-scale vessel. Model fabrication time and cost targets are 1 month /$100K for an 18 to 24-inch diameter, ring-stiffened model. The model material will be demonstrated to provide a linear elastic stress-strain response with a constant Poisson’s ratio in the linear portion of the curve and a consistent, predictable yield and ultimate strength under tensile and compressive loading (minimum and maximum allowable strengths should be consistent with plate material specifications e.g. HY80, 80 minimum tensile strength). The model material response, if subjected to loads that would result in catastrophic failure, must be biased where a ductile failure is preferred over brittle failure. The model must demonstrate fabrication tolerance level goals that are close to those of the current traditional machined methods. Machining methods can produce simple structures which have tolerances of +- 5 to 8 thousandths is acceptable for the axisymmetric features, the asymmetric details cannot currently be machined therefore loser tolerances are acceptable 1.25 times the axisymmetric machining tolerances. Surface finish of 125 is acceptable local sealing surfaces require 32, some relaxation is acceptable in localized regions. Simplified strain measurement recommendations need to be provided in support of Government instrumentation and hydrostatic testing inside a Government pressure-testing chamber.


PHASE I: Develop a technical concept for a metallic additive manufacturing process that can feasibly fabricate structural models. Demonstrate acceptability of material properties and dimensional tolerances as discussed in the Description. Develop a strain measurement evaluation process to be used in testing the feasibility of the specific concepts. Identify and develop a concept to manufacture, test, and evaluate a pressure vessel model with a structural feature, which meets or exceeds typical machined tolerance levels with time and cost targets discussed in the Description. Develop a Phase II plan. The Phase I Option, if exercised, will include the initial layout and capabilities description to develop the process in Phase II.


PHASE II: Use the new metallic manufacturing process to manufacture two prototype pressure vessel models (geometry file and tolerances requirements provided by the Government) and support the instrumentation and hydrostatic testing with the Government. Demonstrate manufacturing tolerance as compared to traditional machine methods. Measure properties of the materials used for manufacture of the model and evaluate against requirements provided in the Description. Use cost and time for the prototype to demonstrate the feasibility of meeting the time and cost targets identified in the Description. Support experimental test of the prototypes for demonstration as needed.


PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the process to independently create models that meet the time, cost, and tolerance constraints identified in the Description. Deliver to the Navy (PMS397, PMS450, and SSNX) data gathered regarding tolerance levels obtained and properties of materials used in manufacturing the models to develop a validated procedure to build and test models, and eventually procure and test models for evaluation of structural features in future pressure vessels. The Navy (PMS450 and SSNX) would likely procure future models from the vendor or, if advantageous to the Navy, may procure hardware with supporting procedures to fabricate models in-house. The demonstration products and procedures used may allow for the production of high-quality, high-tolerance pressure vessel applications within industry (oil/gas, chemical, power).



1.   Frazier, William E. "Metal Additive Manufacturing: A Review." Journal of Materials Engineering and Performance, 2014, 23.6, pp. 1917-1928.


2.   Murr, Lawrence E., et al. "Metal Fabrication by Additive Manufacturing Using Laser and Electron Beam Melting Technologies." Journal of Materials Science & Technology 28.1, 2012, pp. 1-14.


3.   Maxey, W. A., et al. "Ductile Fracture Initiation, Propagation, and Arrest in Cylindrical Vessels." Fracture Toughness: Part II. ASTM International, 1972.

4.   Kooistra, L. F., Lange, E. A., and Pickett, A. G. "Full-Size Pressure Vessel Testing and Its Application to Design." Journal of Engineering for Power 86.4, 1964, pp. 419-428.


KEYWORDS: Additive Manufacturing; Pressure Vessels Models; Metal Based Additive Manufacturing; 3D Printing Combined with Near Net Shape and Selective Surface Net Shape Techniques; Powder Metallurgy – Hot Isostatic Pressing, Fabricating a Welded Model; Wire Electrical Discharge Machining



Paul Young






Nathan Klontz






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