scholarly journals Process Modeling of Thermoset Composites used for Wind Blade Manufacturing

2021 ◽  
Author(s):  
Sagar P. Shah ◽  
Sagar U. Patil ◽  
Christopher J. Hansen ◽  
Gregory M. Odegard ◽  
Marianna Maiaru
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Wind Energy ◽  
Process Modeling ◽  
Material Characterization ◽  
Virtual Manufacturing ◽  
Stress Generation ◽  
Cure Cycle ◽  
Thermoset Composites

A computational process modeling framework, informed by accurate material characterization, is presented for virtual manufacturing of wind energy thermoset composites. Process modeling simulations of composite microstructures are carried out to predict in-situ matrix property evolution and performance-altering residual stress generation. To achieve this, comprehensive material characterization effort is carried out. A novel material property dataset for a widely-used wind energy thermoset system is generated as a function of the temperature and curing. Informed by these material properties, the ability of the process model to reliably estimate manufacturing-induced residual stresses is highlighted. For a prescribed cure cycle, in-situ elastic modulus evolution, chemical and thermal strains, and random fiber distribution are shown to significantly influence residual stress generation. The results also show that a full process modeling analysis that includes the complete cure cycle (instead of the standard approach of just considering post-processing cool-down) is necessary to accurately predict manufacturing-induced residual stresses.

scholarly journals Effect of Manufacturing on the Transverse Response of Polymer Matrix Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2491
Author(s):  
Sagar P. Shah ◽  
Marianna Maiarù
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Process Modeling ◽  
Polymer Matrix Composites ◽  
Effect Study ◽  
Matrix Composites ◽  
Computationally Efficient ◽  
Thermoset Composites ◽  
Residual Stress State ◽  
Composite Stiffness

The effect of residual stress build-up on the transverse properties of thermoset composites is studied through direct and inverse process modeling approaches. Progressive damage analysis is implemented to characterize composite stiffness and strength of cured composites microstructures. A size effect study is proposed to define the appropriate dimensions of Representative Volume Elements (RVEs). A comparison between periodic (PBCs) and flat (FBCs) boundary conditions during curing is performed on converged RVEs to establish computationally efficient methodologies. Transverse properties are analyzed as a function of the fiber packing through the nearest fiber distance statistical descriptor. A reasonable mechanical equivalence is achieved for RVEs consisting of 40 fibers. It has been found that process-induced residual stresses and fiber packing significantly contribute to the scatter in composites transverse strength. Variation of ±5% in average strength and 18% in standard deviation are observed with respect to ideally cured RVEs that neglect residual stresses. It is established that process modeling is needed to optimize the residual stress state and improve composite performance.

Residual Stresses for In-Situ Deposition of Thin-Film High-Temperature Superconductors

1994 ◽  
Vol 116 (4) ◽  
pp. 249-257 ◽  
Author(s):  
P. E. Phelan ◽  
M. N. Ghasemi Nejhad
Keyword(s):  
Thin Film ◽  
Residual Stress ◽  
Residual Stresses ◽  
High Temperature Superconductors ◽  
Oxygen Stoichiometry ◽  
Chemical Shrinkage ◽  
In Situ Deposition ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Residual stresses are caused by nonuniform thermal expansion and chemical shrinkage taking place during processing. For thin-film high-temperature superconductors, residual stresses result because of the thermal expansion mismatch between the film and substrate, and the introduction of oxygen into the film after in-situ deposition, which makes the unit cell dimensions change (chemical shrinkage) as the oxygen stoichiometry changes. Since both the reliability of the film—especially the bond between the film and substrate—and the film critical temperature are functions of the state of stress, it is important to understand how the residual stresses vary with processing conditions. Here, a three-dimensional residual stress analysis is carried out based on laminate theory, which assumes the lateral dimensions of the entire system to be much larger than its thickness. The normal residual stress components in the film, and the peeling stress at the film/substrate interface, are calculated. The results demonstrate the crucial role that chemical shrinkage plays in the formulation of residual stresses. A large portion of the stresses arises from the initial change of the unit cell dimensions due to changes in the film oxygen stoichiometry. Therefore, the processing temperature, and especially the initial oxygen pressure in the deposition chamber, are the key variables that impact the residual stresses.

The Influence of Chemical Composition on Residual Stresses in NiCoMo Alloy Deposits on 12 Ni Maraging Steel

2013 ◽  
Vol 768-769 ◽  
pp. 449-455 ◽  
Author(s):  
Zoran Bergant ◽  
Janez Grum
Keyword(s):  
Residual Stress ◽  
Chemical Composition ◽  
Residual Stresses ◽  
Base Material ◽  
Stress Generation ◽  
Hole Drilling ◽  
Residual Stress Field ◽  
Hole Drilling Method ◽  
Similar Chemical ◽  
Drilling Method

The in-plane residual stresses in laser cladded specimens, made of 12-nickel precipitation hardening maraging hot-working tool steel 1.2799 (SIST EN 10027-2) are analyzed using the hole drilling method. The CO2 laser was used to deposit the alloy NiCoMo-1 with significantly higher content of nickel and cobalt with austenitic microstructure at room temperature. The Nd:YAG laser was used to deposit the maraging alloy designated NiCoMo-2, with similar chemical composition as the base material. The comparison of residual stress field showed the sign and the magnitude of residual stresses depends on the chemical composition of the clad being deposited. The high tensile residual stresses were found in NiCoMo-1 layers and favorable compressive residual stresses were found in NiCoMo-2 layers. The metallurgical aspects of residual stress generation are discussed.

Process modeling and characterization of thermoset composites for residual stress prediction

2021 ◽  
pp. 1-12
Author(s):  
Sagar P. Shah ◽  
Sagar U. Patil ◽  
Christopher J. Hansen ◽  
Gregory M. Odegard ◽  
Marianna Maiarù
Keyword(s):  
Residual Stress ◽  
Process Modeling ◽  
Thermoset Composites ◽  
Stress Prediction

Modelling of Residual Stresses Induced by Turning of 316L

2009 ◽  
Vol 83-86 ◽  
pp. 230-236 ◽  
Author(s):  
F. Valiorgue ◽  
J. Rech ◽  
H. Hamdi ◽  
P. Gilles ◽  
J.M. Bergheau
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Cutting Parameters ◽  
Stress Generation ◽  
Workpiece Surface ◽  
New Approach ◽  
Residual Stress State ◽  
Cutting Operation ◽  
Experimental Works ◽  
The Impact

Residual stresses are very important for the lifetime of pieces in their mechanisms. These kind of damages are mainly caused by mechanical, thermal, and metallurgical affectations of the machined material. To control these affectations, we need to link the cutting parameters to the residual stress state observed onto the workpiece surface and depth. These connections can be made with analytical works, experimental works or numerical works. In our case, it has been chosen to work with a numerical support in order to observe and understand precisely the phenomenon involved during cutting operation. While this way of study is really popular, we proposed to model the residual stress generation in a original way by keeping aside the chip formation. This new approach presented in a previous paper was simple and only use a 2D model. This first model moves thermo mechanical loadings onto the workpiece surface to recreate the relative motion between the tool and the workpiece. The new 3D model, presented in this paper, is now improved with an original friction law. It underlines the impact of each passage of the tool onto the others. The physical properties are thermo dependant and the flow stress model is based on a Johnson cook behaviour.

scholarly journals On Residual Stresses Development during Nitriding of Steel: Thermochemical and Time Dependence

2010 ◽  
Vol 89-91 ◽  
pp. 256-261 ◽  
Author(s):  
Sebastien Jegou ◽  
Regis Kubler ◽  
Laurent Barrallier
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Time Dependence ◽  
Volume Change ◽  
Stress Generation ◽  
X Rays ◽  
Microstructural Effects

This work deals with the development of residual stresses during nitriding of steels. The main features of a chemico-thermo-echanical model of nitriding are presented. A micro-macroapproach is applied based on volume change computation in agreements with thermochemical modifications. Results are correlated with the characterization of a ternary Fe-C-3w.%Cr alloy nitrided at 550°C for various time. Residual stress-depth analyses are carried out by X-rays diffraction. Residual stress generation is deeply dependant on chemical and thermodynamical evolutions during the treatment, taking advantage on microstructural effects.

scholarly journals Investigation on micro-residual stress distribution near hole using nanoindentation: Effect of drilling speed

2019 ◽  
Vol 52 (9-10) ◽  
pp. 1252-1263 ◽  
Author(s):  
Abhishek Kumar Tiwari ◽  
Amit Kumar ◽  
Navin Kumar ◽  
Chander Prakash
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Process Parameters ◽  
Residual Stress Distribution ◽  
Stress Generation ◽  
Work Piece ◽  
Drilling Speed ◽  
Drilling Operation

Residual stresses are induced in the material during manufacturing operations, which considerably affect the fatigue performance and the lifespan of a mechanical work piece. The nature, magnitude, and distribution of residual stresses decide their beneficial or detrimental effects. Past research efforts concluded that mechanical process parameters influence residual stress nature, distribution, and the magnitude. Nevertheless, how residual stress generation depends on the process parameters, is not well investigated especially in the case of a drilling operation. In fact, the residual stress field is required to be regulated near drilled holes to improve the fatigue strength of structural joints, especially in the aircraft industry. Accordingly, this work attempts to estimate the drilling-induced micro-residual stress distribution near the drilled hole. In addition, the effect of drilling speed on residual stress distribution has also been studied. A nanoindentation technique is used to follow-up precise distribution of micro-residual stresses near the holes drilled at three different drilling speeds of 700, 900, and 1100 r/min. The outcomes indicate the presence of compressive residual stresses near the hole. In addition, an increase in residual stress level is noticed with an increase in the drilling speed up to 900 r/min. A uniform distribution of residual stresses is observed near the hole when drilled at a higher drilling speed of 1100 r/min. These findings may be useful in planning an improved drilling operation to produce beneficial residual stress distribution. This may ultimately improve the fatigue strength and the service life of mechanical components or structures with drilled holes.

Optimization of Tensile Residual Stress on Machined Surface in MQL Turning

2015 ◽  
Vol 713-715 ◽  
pp. 209-212 ◽  
Author(s):  
Xia Ji ◽  
Alexander H. Shih ◽  
Manik Rajora ◽  
Ya Min Shao ◽  
Steven Y. Liang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Minimum Quantity Lubrication ◽  
Optimization Procedure ◽  
Stress Generation ◽  
Tool Geometry ◽  
Machined Surface ◽  
Good Surface ◽  
Optimal Inputs ◽  
Marquardt Algorithm

Producing good surface integrity is one of the main challenges of the machining industry. The increase of the utilization of minimum quantity lubrication (MQL) in order to reduce the amount of lubrication induced a lack of understanding of the physics behind the residual stress generation. Residual stress in the machined surface and subsurface is affected by materials, machining conditions, and tool geometry. These residual stresses could affect the service qualify and component life significantly. Residual stress can be determined by empirical or numerical experiments for selected configurations, even if both are expensive procedures. This paper presents a hybrid neural network that is trained using Simulated Annealing (SA) and Levenberg-Marquardt Algorithm (LM) in order to predict the values of residual stresses in cutting and radial direction after the MQL face turning process accurately. First, SA is used to train the weight and bias values of the ANN after which LM is used to fine tune the values trained by SA. Then, based on the predictions, an optimization procedure, using Genetic Algorithm (GA), is applied in order to find the best cutting conditions. At each generation, GA suggests a population of inputs that are then sent to the trained ANN in order to predict the residual stresses. The objective is to find the optimal inputs that minimize the tensile stress on the machined surface.

Effect of Initial Residual Stress on Stress Relaxation in Cold-Drawn Steel Rods

2010 ◽  
Vol 652 ◽  
pp. 227-232
Author(s):  
Jesus Ruiz-Hervias ◽  
Jose M. Atienza ◽  
Javier R. Santisteban ◽  
Manuel Elices Calafat
Keyword(s):  
Residual Stress ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Cross Section ◽  
Stress Relaxation Behavior ◽  
Relaxation Experiment ◽  
Initial Residual Stress ◽  
Residual Stress State ◽  
Residual Strains

This work shows the effect of the initial residual stress state on the stress relaxation behavior of cold-drawn steel rods. The evolution of residual strains at several locations along the rod diameter was measured in-situ by neutron diffraction during a stress relaxation experiment. It was found that if residual stresses are significant, stress relaxation is not homogeneous in the cross-section of the rods. This also explains the higher stress losses found in the rods with high residual stresses.

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