During the shipbuilding manufacturing process, materials are exposed to significant stresses as induced both thermally and mechanically, that alter the intended design and significantly affect the production schedule, labor hours (fitting, welding, rework, etc.), and material structural performance. The type and magnitude of deformation of a given structure depends on many factors such as the material, thickness and quality of components, the process heat input, preheat and inter-pass temperatures, type and size of welds, welding sequence and direction, location, sequence, and degree of fixturing. Numerical simulations using Finite Element Analysis (FEA) have long been used to analyze and estimate welding distortion. Joint level detailed welding analyses are required to capture the physics driving distortion, and they are performed by expert analysts with insight to pedigreed material properties. For large assemblies, however, these analyses can take days or weeks to set up, run, and obtain results, and optimization is not feasible. Traditional approaches for performing welding analysis using FEA are not suitable for very large structures and production environments where hundreds of analyses are needed for each ship.
A project team selected for funding by the National Shipbuilding Research Program (NSRP) proposes the development of a fully customizable fast analysis solver that can be used by shipyard Production Planning and Engineering groups for rapidly predicting weld-induced deformation of very large assemblies/sub-assemblies and optimizing their welding sequences to minimize the efforts. Oak Ridge National Laboratory (ORNL) has recently developed a superfast, high-performance computational (HPC) solver for weld residual stress and distortion simulations of large and complex welded structures. The solver takes full advantages of modern GPU-based HPC hardware and incorporates patented acceleration schemes based on many years of experience in welding simulation at ORNL. The speed gains depend on the size and complexity of the model - the larger the model, the greater the speedup. The speedup factors are in the range of 100 times for simple 3D models to 2200 times for large, multiple pass welded structures. This solver, recognized by the International Institute of Welding in 2021, has been successfully used in predicting distortion on automotive structures and nuclear piping systems.
The project participants will develop a user-friendly and fast FEA solver for shipbuilding applications by leveraging ORNL’s and Hexagon’s prior work for the automotive and nuclear industries. This solver will enable quick computation of complex material modeling that can address ongoing design and manufacturing issues in the industry. The primary use-case for the development of this solver will be weld-sequencing simulation of panel and unit assembly construction. The complex nature of weld sequencing for distortion control will allow the team to understand the current solver time and computational requirements, address existing limitations, train engineers on efficient and accurate use of the tool, and utilize Hexagon’s robust graphical user interface to tackle the optimization of other manufacturing processes in shipbuilding and other industries. The team envisions a solver capable of replacing current analytical tools utilized to simulate welding processes that predict welding-induced stress distributions, and it can be used to improve ship structural designs, predict fatigue life and cracking in high stress areas, and minimize movement of alignment critical structures where hot work is required in the surrounding areas. Other potential applications include the optimization of the thermal straightening process used to correct distortion, prediction of heating paths for thermally forming curved shell plates, optimization of the hybrid laser arc welding process to improve toughness, and dynamic simulation of mechanical systems.