Dependence Between Aging Treatments and Residual Stresses on Composite Laminate

2006 ◽  
Vol 524-525 ◽  
pp. 813-817 ◽  
Author(s):  
Olivier Sicot ◽  
X.L. Gong ◽  
Xiao Jing Gong ◽  
Abel Cherouat ◽  
Jian Lu
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Composite Structures ◽  
Hole Drilling ◽  
The Finite Element Method ◽  
Hole Drilling Method ◽  
Incremental Hole Drilling ◽  
Drilling Method ◽  
Initial Cycle ◽  
Calibration Coefficients

The objective of this paper is to study the influence of residual stresses due to fabrication conditions on the thermomechanical behavior of carbon/epoxy laminate structures (cross ply). These studied laminates have undergone various cycles of thermal aging. The addition of a post-cure cycle after the end of the initial cycle makes it possible to reduce the residual stresses level. The incremental hole-drilling method is used to measure the residual strain in the laminates. These measured strains and the numerical calibration coefficients obtained by the finite element method allow to calculating the residual stress distribution in composite depth. The obtained results show that heat treatments of composite structures do not lead to an important reduction the initial residual stress due the fabrication conditions.

Study of Residual Stress Distribution by a Combined Method of Moire´ Interferometry and Incremental Hole Drilling, Part I: Theory

1998 ◽  
Vol 65 (4) ◽  
pp. 837-843 ◽  
Author(s):  
Zhu Wu ◽  
Jian Lu ◽  
Bongtae Han
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Plane Surface ◽  
Moiré Interferometry ◽  
Hole Drilling ◽  
Moire Interferometry ◽  
Hole Drilling Method ◽  
Surface Displacements ◽  
Incremental Hole Drilling ◽  
Drilling Method

A new method combining Moire´ interferometry and the incremental hole-drilling method is developed to determine both uniform and nonuniform residual stress distribution in depth. The study is reported in two parts. In this first part, the theoretical development of the moire´ interferometry hole-drilling method is presented. The relationship between the in-plane surface displacements produced by introducing a blind hole and the corresponding residual stresses is established by employing the existing theoretical solution containing a set of undetermined coefficients. The coefficients are calibrated by the three-dimensional finite element method and they are processed nondimensionally for general use. The whole field in-plane surface displacements data Ux and Uy produced by the relaxation of residual stresses are obtained from moire´ interferometry after each increment of hole drilling. The high signal-to-noise ratio provided by moire´ interferometry allows accurate determination of fringe orders near the hole boundary which is essential for enhancing fidelity of residual stress determination. The experimental procedure to determine the signs of residual stresses is described and the accuracy of the method is also discussed.

Influence of Residual Stresses on the Damage of Composite Laminates under Tensile Loading

2015 ◽  
Vol 784 ◽  
pp. 361-368
Author(s):  
Zhong Meng Wen ◽  
Xiao Lu Gong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Composite Laminates ◽  
Tensile Loading ◽  
Hole Drilling ◽  
Acoustic Emission Technique ◽  
Hole Drilling Method ◽  
Incremental Hole Drilling ◽  
Drilling Method

This work investigates the effect of residual stresses on the damage of composite laminate. The incremental hole-drilling method is applied to determine residual stresses in composite laminates [02/θ2]s and then acoustic emission technique is used for the identification of damage appearance during the tensile testing. The samples with different residual stress distribution are prepared through curing and post curing in order to study the role of residual stress on the damage of composite laminates. Besides the experimental method, the theoretical approach is applied to illustrate the role of residual stress on the damage of composite laminates.

scholarly journals The Effect of Fiber Waviness on the Residual Stress State and Its Prediction by the Hole Drilling Method in Fiber Metal Laminates: A Global-Local Finite Element Analysis

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 156
Author(s):  
Steffen Tinkloh ◽  
Tao Wu ◽  
Thomas Tröster ◽  
Thomas Niendorf
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Residual Stresses ◽  
Global Model ◽  
Hole Drilling ◽  
Fiber Waviness ◽  
Hole Drilling Method ◽  
Residual Stress State ◽  
Incremental Hole Drilling ◽  
Drilling Method

In this paper, fiber waviness, as one of the most frequently occurring defects in fiber reinforced composites, is numerically investigated with regard to the formation of residual stresses in fiber metal laminates. Furthermore, the prediction of the residual stress state in the thickness direction by means of the simulated hole drilling method is studied. To this regard, a global-local finite element analysis based on the submodel technique is presented. The submodel technique essentially consists of two governing steps: In the first step, a global model is first utilized to calculate and analyze the residual stress distribution and deformation in the intrinsically joined hybrid structure. Effective cure-dependent thermo–elastic properties predicted by a numerical homogenization procedure were used to simulate the curing-process and analyze the residual stresses state. However, the dimension of the intrinsically manufactured hybrid plate is large compared to the diameter of the drilled hole (2 mm), so that a local model is necessary, which provides only a geometric partial portion of the global model. The local model takes the global stress state into account and is subsequently used to simulate the incremental hole drilling method with a refined mesh discretization. The production-related fiber waviness is modeled by an element-wise orientation approximating a sinus function. In order to validate the global-local modeling approach, a comparison between numerical results and experimental data from literature is presented. The comparison between global residual stress state (global model) and the simulated hole drilling method (local model) is used to assess the applicability and reliability of the hole drilling method in case of fiber waviness. It is found that an in-plane fiber waviness leads to a rather low variance of residual stresses over thickness. In case of an out-of-plane fiber waviness, oscillating residual stress fields occur over the entire thickness along the fiber direction. Moreover, the current limits of the incremental hole drilling method could be pointed out by the presented investigations. It is seen that the simulated results of the incremental hole drilling method are sensitive to waviness, even if the amplitude-wavelength-ratio is small. Without further adjustment of the calibration coefficients the oscillating stress and strain fields lead, in particular fiber waviness in thickness direction, to unreliable predictions. For the experimental application it can be concluded that the specimens have to be carefully examined with regard to fiber waviness.

Use of Full Field of Strains Found By Grating Shearography to Determine Residual Stress

2005 ◽  
Vol 40 (7) ◽  
pp. 621-630 ◽  
Author(s):  
G Montay ◽  
J Bulhak ◽  
Y Surrel ◽  
A Vautrin ◽  
J Lu
Keyword(s):  
Residual Stress ◽  
Strain Field ◽  
Hole Drilling ◽  
The Finite Element Method ◽  
Full Field ◽  
Hole Drilling Method ◽  
Incremental Hole Drilling ◽  
Drilling Method ◽  
Very High Spatial Resolution ◽  
High Level

A new method combining grating shearography and the incremental hole drilling method has been developed to determine the residual stress distribution in depth. Grating shearography is a technique designed to determine directly the strain field with a high level of sensitivity and a very high spatial resolution. The hole drilling method is one of the most popular methods used in mechanical engineering to determine the residual stress locked into a structure. This new optical method enables the strain to be measured while taking into account the entire strain field around the hole. The finite element method is used to calibrate the method. The method was tested on an ultrasonic shot-peened aluminium specimen.

scholarly journals Residual Stresses from Incremental Hole Drilling Using Directly Deposited Thin Film Strain Gauges

2022 ◽  
Author(s):  
S. Heikebrügge ◽  
R. Ottermann ◽  
B. Breidenstein ◽  
M.C. Wurz ◽  
F. Dencker
Keyword(s):  
Thin Film ◽  
Residual Stress ◽  
Strain Gauges ◽  
Hole Drilling ◽  
Depth Profiles ◽  
Hole Drilling Method ◽  
Polymer Foil ◽  
Incremental Hole Drilling ◽  
Drilling Method ◽  
Calibration Coefficients

Abstract Background Commonly, polymer foil-based strain gauges are used for the incremental hole drilling method to obtain residual stress depth profiles. These polymer foil-based strain gauges are prone to errors due to application by glue. For example zero depth setting is thus often erroneous due to necessary removal of polymer foil and glue. This is resulting in wrong use of the calibration coefficients and depth resolution and thus leading to wrong calculations of the obtained residual stress depth profiles. Additionally common polymer foil-based sensors are limited in their application regarding e.g. exposure to high temperatures. Objective This paper aims at a first step into the qualification of directly deposited thin film strain gauges for use with the incremental hole drilling method. With the directly deposited sensors, uncertainties regarding the determination of calibration coefficients and zero depth setting due to the absence of glue can be reduced to a minimum. Additionally, new areas of interest such as the investigation of thermally sprayed metallic layers can be addressed by the sensors due to their higher temperature resilience and their component inherent minimal thickness. Methods For the first time, different layouts of directly deposited thin film strain gauges for residual stress measurements were manufactured on a stainless steel specimen. Strain measurements during incremental hole drilling using a bespoke hole drilling device were conducted. Residual stress depth profiles were calculated using the Integral method of the ASTM E837 standard. Afterwards, strain measurements with conventional polymer foil-based strain gauges during incremental hole drilling were conducted and residual stress depth profiles were calculated accordingly. Finally the obtained profiles were compared regarding characteristic values. Results The residual stress depth profiles obtained from directly deposited strain gauges generally match the ones obtained from conventional polymer foil based strain gauges. With the novel strain gauges, zero depth setting is simplified due to the absence of glue and polymer foil. With the direct deposition, a wide variety of rosette designs is possible, enabling a more detailed evaluation of the strain field around the drilled hole. Conclusions The comparative analysis of the obtained residual stress depth profiles shows the general feasibility of directly deposited strain gauges for residual stress measurements. Detailed investigations on uncertainty sources are still necessary.

Residual Stress Measurements in an Autofrettage Tube Using Hole Drilling Method

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Hamid Jahed ◽  
Mohammad Reza Faritus ◽  
Zeinab Jahed
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Hoop Stress ◽  
Test Method ◽  
Test Material ◽  
Hole Drilling ◽  
Hole Drilling Method ◽  
Ring Sample ◽  
Drilling Method ◽  
American Society

Relieved strains due to drilling hole in a ring sample cut from an autofrettage cylinder are measured. Measured strains are then transformed to residual stresses using calibration constants and mathematical relations of elasticity based on ASTM standard recommendations (American Society for Testing and Materials, ASTM E 837-08, 2008, “Standard Test Method for Determining Residual Stresses by the Hole-Drilling Strain-Gage Method,” American Society for Testing and Materials). The hydraulic autofrettage is pressurizing a closed-end long cylinder beyond its elastic limits and subsequently removing the pressure. In contrast to three-dimensional stress state in the autofrettage tube, the stress measurement in hole drilling method is performed on a traction free surface formed from cutting the ring sample. The process of cutting the ring sample from a long autofrettaged tube is simulated using finite element method (FEM) and the redistribution of the residual stress due to the cut is discussed. Hence, transformation of the hole drilling measurements on the ring slice to the autofrettage residual stresses is revealed. The residual stresses are also predicted by variable material properties (VMP) method (Jahed, H., and Dubey, R. N., 1997, “An Axisymmetric Method of Elastic-Plastic Analysis Capable of Predicting Residual Stress Field,” Trans. ASME J. Pressure Vessel Technol., 119, pp. 264–273) using real loading and unloading behavior of the test material. Prediction results for residual hoop stress agree very well with the measurements. However, radial stress predictions are less than measured values particularly in the middle of the ring. To remove the discrepancy in radial residual stresses, the measured residual hoop stress that shows a self-balanced distribution was taken as the basis for calculating residual radial stresses using field equations of elasticity. The obtained residual stresses were improved a lot and were in good agreement with the VMP solution.

scholarly journals Incremental Hole-Drilling Method Vs. Thin Components: A Simple Correction Approach

2014 ◽  
Vol 996 ◽  
pp. 283-288 ◽  
Author(s):  
Esther Held ◽  
Simone Schuster ◽  
Jens Gibmeier
Keyword(s):  
Residual Stress ◽  
Thin Metal ◽  
Hole Drilling ◽  
Depth Profiles ◽  
Hole Drilling Method ◽  
Incremental Hole Drilling ◽  
Metal Sheets ◽  
Drilling Method ◽  
Measured Strain ◽  
The Impact

The incremental hole-drilling method is a widely used technique to determine residual stress depth profiles in technical components. Its application is limited in respect to the components geometry, for instance the components thickness. In this paper, a direct correction of the measured strain relaxations is proposed to consider the impact of deviant geometries, here the component thickness, on the residual stress evaluation that moreover, allows the application of commercially available evaluation software. The herein proposed approach is based on finite element simulation of the incremental hole drilling. The simulated strain relaxations for thin metal sheets are evaluated with an algorithm as used in commercially available evaluation software (i) for uncorrected data as well as (ii) for strain data corrected by the proposed correction procedure. It is shown that the correction approach leads to a significant improvement of the measurement accuracy. Further, by means of the approach residual stress depth profiles in thin metal sheets can be as usual determined using commercial evaluation software for the incremental hole-drilling method regardless of the algorithm used, i.e. differential or integral.

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