Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties ...

https://journals.sagepub.com/doi/pdf/10.1177/0021998318772152

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance:

Modeling metal deposition in heat transfer analyses of additive manufacturing processes

Wire and arc additive manufacturing (WAAM) is an emerging technology which has the potential to significantly reduce material usage and manufacturing time through the production of near net-shape components with high deposition rates. One of the main problems of this process is the residual stresses and distortions of the deposited workpiece. To help understand and optimise the process, finite element (FE) models are commonly used; however, the conventional transient models are not efficient for simulating a large-scale WAAM process. In this paper, the stress evolution during the thermal cycles of the WAAM process was investigated with the help of a transient thermomechanical FE model. It was found that the peak temperatures experienced during the thermal cycles of the WAAM process determine the residual stress of that point. Based on this finding, an efficient “engineering” FE model was developed. Compared to the conventional transient thermomechanical approach, this model can save the computational time by 99 %. This new model produced distortion and residual stress predictions that were nearly identical to the original transient model and the experimental results.

A computationally efficient finite element model of wire and arc additive manufacture

Design and manufacturing of stainless steel bipolar plates for proton exchange membrane fuel cells

Numerical analysis and experimental investigation of welding residual stresses and distortions in a T-joint fillet weld

Simple thermo-elastic–plastic models for welding distortion simulation

The main aim of the work was to investigate a simplified finite element simulation of the out-of-plane distortion caused by fusion butt welding. The thermal transient part of the simulation made use of a finite element analysis of the two-dimensional cross-section of the weld joint and the thermoelastic-plastic treatment was based on analytical algorithms describing transverse and longitudinal deformations, leading to predictions of transverse angular deformation and longitudinal contraction force. These results were then applied to a non-linear elastic finite element model to provide predictions of the final angular and overall deformations of the butt-welded plates. The validity of the simulation was investigated via full-scale tests on 4m x 1.4m x 5 mm steel plates, butt welded using a flux-cored Ar-CO2 metal-inert gas process. Thermography and thermocouple arrays were used to validate the thermal transient computations and out-of-plane deformations were measured using displacement transducers for transient deformations and a laser scanning system to measure the profiles of the whole plates before and after welding. The results of six full-scale tests are given and comparison with the simulations shows that the procedure provides good prediction of the angular and overall out-of-plane deformations. Prediction accuracy requires account to be taken of initial shape, gravity loading, and support conditions.

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Computational prediction of out-of-plane welding distortion and experimental investigation - Awarded Central Electricity Generating Board Prize

The study's aim is to improve the applicability of finite element analysis to the prediction of welding distortions, with particular emphasis on out-of-plane deformations. Robust simulation strategies are established which take account of material properties and joint configurations, but are at the same time computationally efficient. This is achieved by reducing the full transient thermo-elastoplastic analysis to variants of an uncoupled thermal, elasto-plastic and structural treatment. A two-dimensional cross-section thermal model was used to establish thermal transients. The maximum temperatures, experienced at each node during the welding cycle, were then used to link the thermal welding strains to the elasto-plastic and structural response of the welded structures. Three efficient models have been identified that reduce the transient analysis to a simple multi-load-step analysis and these were applied to sample butt-welded plates. The simulation techniques are supported by full-scale welding tests on steel plates. The evolution of angular distortion can be treated simply through non-linear, stepwise, static analyses. This captures important effects of restraint and material properties. The longitudinal bending distortion can then be established via simple elastic-perfectly plastic algorithms, through a fictitious elastic thermal load analysis.

Computationally efficient welding distortion simulation techniques

Prediction and control of thermal distortion is particularly important for the design and manufacture of multiply stiffened welded structures. This study aimed to develop and experimentally validate a comprehensive simulation tool to predict distortion, with particular emphasis on out-of-plane deformation generated in double-sided fillet-welded attachments. Simulation was used to optimise the relative positions of a twin-arc configuration, to give minimum out-of-plane deformation consistent with reasonable production time for single stiffener, double-fillet attachments. The critical buckling load of the structure was approached and exceeded as the arcs were brought closer and simulation allowed the influence of this factor to be determined.

Thermal Distortion of Stiffened Plate due to Fillet Welds Computational and Experimental Investigation

Special solution methods are presented for the prediction of distortion in stiffened plate fabrications, caused by butt welds and fillet welds. These methods involve strategic reduction of the many complex features embodied in full multi-physics welding simulation. In particular, an analytical method is used to replace the thermo-elastic-plastic stage of a typical full computational analysis. The aim is to provide a robust solution strategy that enables clear understanding of the effects of different welding and fabrication procedures. The approach is underpinned by full-scale practical trials, and two case studies relating to typical fabrication questions are included.

Duncan Camilleri

Papers

Simple thermo-elastic–plastic models for welding distortion simulation

Computational prediction of out-of-plane welding distortion and experimental investigation - Awarded Central Electricity Generating Board Prize

Computationally efficient welding distortion simulation techniques

Thermal Distortion of Stiffened Plate due to Fillet Welds Computational and Experimental Investigation

Using computationally efficient, reduced-solution methods to understand welding distortion