Residual Stresses In Plates Research Articles

Ultrasonic immersion testing of residual stress in plates using collinear Lamb wave mixing technique

Nondestructive estimation of residual stresses has been a major challenge in engineering. Herein, the collinear Lamb wave mixing method is proposed for residual stress measurement in metal plates under immersion ultrasonic testing. Numerical simulations have been conducted to investigate the influences of excitation parameters on the performance of the wave mixing method. The results showed that the receiver position and cycle numbers of primary waves affect the amplitude of the method, and optimal excitation parameters recommended. Ultrasonic immersion experiments are conducted on two types of plate-like specimens using the collinear Lamb wave mixing method. Experimental results showed that the proposed method is effective for measuring the residual stress in metal plates. The immersion ultrasonic testing can significantly reduce the influence of inconsistent coupling conditions between the transmitters and the specimen on experimental results, therefore it is more reliable than conventional contact testing.

Acoustoelasticity to measure residual stresses in plates of 5052 aluminum joined by FSW

Acoustoelasticity to measure residual stresses in plates of 5052 aluminum joined by FSW

Two-dimensional Mapping of Bulk Residual Stress Using Cut Mouth Opening Displacement

BackgroundPrior work described an approach for mapping the two-dimensional spatial distribution of biaxial residual stress in plate-like samples, the approach combining multiple slitting measurements with elastic stress analysis. Objective This paper extends the prior work by applying a new variation of the slitting method that uses measurements of cut mouth opening displacement (CMOD) rather than back-face strain (BFS). MethodsFirst, CMOD slitting is validated using an experiment where: BFS and CMOD are measured simultaneously on the same sample during incremental slitting; two residual stress profiles are computed, one from the BFS data and a second from the CMOD data; and the two residual stress profiles are compared. Following validation, multiple adjacent CMOD slitting measurements are used to construct two-dimensional maps of residual stress in plates cut from quenched aluminum. ResultsThe two residual stress versus depth profiles, each computed separately from BFS or CMOD data, are in agreement, with compression near the plate boundaries (-150 MPa) and tension near the plate center (100 MPa); differences between the two stress profiles have a maximum of 25 MPa and a RMS of 7.2 MPa. Repeated biaxial residual stress mapping measurements show the CMOD technique is repeatable, and complementary contour method measurements show the mappings are valid. Aspects of CMOD and BFS deformations during slitting are also described and show they are generally complementary but that CMOD slitting is favorable in narrow samples.

Electromagnetic ultrasonic measurement for welding residual stress detection - comparison between experiment with numerical simulation

In order to study the feasibility of electromagnetic ultrasonic method on the welding residual stress detection in Q345R plate, experiments and numerical simulations were carried out. The welding residual stress in the plate was firstly measured by electromagnetic acoustic transducer (EMAT). Then, finite element model of welding process was established to predict the residual stress in plate, who’s rationality was verified by blind hole experiment. At last, the average of numerical simulation results at five points along the plate’s thickness direction was compared with the electromagnetic ultrasonic measurement results. The results show that the residual stress measured by EMAT is consistent with those from numerical simulation in direction of the weld. However, in the vertical direction of the weld, the deviation between EMAT results and numerical simulation is relatively large near the weld fusion line. This phenomenon is also found in the junction between the heat affected zone and the base metal.

Distribution of Welding Residual Stress of Mixed Steel U-Rib-Stiffened Plates

To analyze the effects of width and thickness of each composition element of mixed steel U-rib-stiffened plates on the welding residual stress distribution, the distribution of the U-rib and the plate residual stress was calculated using a simplified calculation method. The method involved welding the mixed steel U-rib-stiffened plates for a structure with different sizes and different strength ratios of U-rib to plate. Based on a welding residual stress numerical simulation method validated by the blind hole method test, the distribution law of the mixed steel U-rib stiffened plate was studied. The results showed that the change of plate width has little impact on the welding residual stress and that the ratio of the thicknesses of the plate to U-rib stiffeners, the thickness of the plate, and the thickness of the U-rib has a great influence on the distribution of the welding residual stress. The thickness of plate and steel strength also greatly influenced the distribution width of the residual tensile stress. While analyzing the compression capacity of U-rib-stiffened plates, the simplified distribution of welding residual stress was used.

A parametric study of residual stress in plate

Residual stress is a process-induced stress in a molded part that exists in the body in the absence of external loading or it exists in steel section of the unloaded state. Residual stress is also termed as ‘Locked Stress’. This paper presents to find out this lock stress analytically. The theoretical and analytical inputs are considered in terms of aspect ratio and these results are compared by percentage error. The previous study mentioned many experimental methods by which residual stresses were sorted out. A Plate is a flat surface having thickness small as compared to other two dimensions. Researchers are mainly focused on the treatment of the different plate theories related to Kirchhoff or Reissner/Mindlin. The developed ANSYS finite element model analyzed square and rectangular plate and compared the analytical results in terms of deflection and stress with theoretical results which are obtained from classical theory. Different boundary conditions for different plate size are considered and solved.

Influence of martensitic transformation on welding residual stress in plates and pipes

ABSTRACTMartensitic filler metals with low transformation temperatures can efficiently mitigate harmful tensile welding residual stress. It is vital to clarify the difference in the influence of martensitic transformation for different shapes of welded joints. This article outlines the influence of martensitic transformation in a butt-welded plate and a butt-welded pipe which were designed to have the same dimensions of the cross-section perpendicular to weld line. A clear difference in the influence of martensitic transformation was found in these two joints. Longitudinal tensile stress in weld zone is efficiently reduced in both joints, whereas longitudinal tensile stress is formed in base metal near the weld zone in the pipe. A notably greater influence on transverse stress is found in the pipe than in the plate.

Formation of Residual Stresses in Plates with Functional Holes After Mandrelling

A procedure of simulation of the stress–strain state in the case of mandrelling of the holes is developed on the basis of the finite-element method. We determine the basic regularities of the influence of the relative tension of mandrelling and the diameter of a hole on the formation of local compressive residual stresses in the vicinity of the hole. In particular, it is shown that if the tension of mandrelling increases from 1 to 3 %, then these stresses increase on the cylindrical surface of the hole and become 1.5–2 times higher.

In-situ Curing Strain Monitoring of a Flat Plate Residual Stress Specimen Using a Chopped Stand Mat Glass/Epoxy Composite as Test Material

The curing stresses in a newly proposed bi-axial residual stress testing configuration are studied using a chopped strand mat glass/epoxy specimen. In-situ monitoring of the curing is conducted using dielectric and fibre Bragg grating sensors. It is confirmed that a bi-axial residual stress state can be introduced in the specimens during curing and a quantification of its magnitude is presented. An alternative decomposition method used for converting the dielectric signal into a material state variable is proposed and good agreement with models found in the literature is obtained. From the cure cycles chosen it is suggested that any stress build up in the un-vitrified state is relaxed immediately and only stress build up in the vitrified state contributes to the residual stress state in the specimen.

Analysis of Quenching and Stretching Processes of Aluminum Alloy Thick Plates

7050 aluminum alloy thick plates are usually heat treated and then aged to improve mechanical properties; however, residual stresses in the plates are developed during quenching. In this study, the influences of non-uniform factors on residual stresses in aluminum alloy thick plates during the quenching and stretching processes are studied. The results show strong inhomogeneity of the residual stress distribution in the plates, and the length of influenced area of the stretched plate is discussed.

Different finite element techniques to predict welding residual stresses in aluminum alloy plates

This study is a 3D thermomechanical finite element (FE) analysis of a single-pass and butt-welded work-hardened aluminum (Al) 5456 plates. It aims to validate the use of FE welding simulations to predict residual stress states in assessing the integrity of welded components. The predicted final residual stresses in the plate from the FE simulations are verified through comparison with experimental measurements. Three techniques are used to simulate the welding process. In the first two approaches, welding deposition is applied by using element birth and interaction techniques. In the third approach, the entire weld zone is simultaneously deposited. Results show a value at approximately the yield strength for longitudinal residual stresses of the welded center of the butt-welded Al alloy plates with a thickness of 2 mm. Considering the application of a comprehensive heat source, along with heat loss modeling and the temperature-dependent properties of the material, the approach without deposition predicts a reasonable distribution of residual stresses. However, the element birth and interaction techniques, compared with the no-deposit technique, provide more accurate results in calculating residual stresses. Furthermore, the element interaction technique, compared with the element birth technique, exhibits higher efficiency and flexibility in modeling the deposition of welded metals as well as less modeling cost.

Determination of Residual Stresses in Plate Material by Layer Removal with Machine-integrated Measurement

Structural aircraft components are usually manufactured from rolled plate material. Despite a stress relief treatment residual stress remains in the plates. This can result in distortions of the workpiece after the final manufacturing step, which leads to time-consuming repair processes or even a scrap part. Using an FEM simulation, it is possible to predict distortions caused by residual stress and to avoid them by adjusting the manufacturing process. However, the known methods to determine the residual stress state in plate material are expensive in terms of time and material and require specially trained staff. This paper describes a novel method to measure residual stress in plates with little effort. The method is derived from the well-known Layer-Removal-Method and utilizes a machine tool with a standard probing device. The measuring task is fully automated and can be performed by untrained staff. No special preparation of the specimen is necessary. The paper describes the procedure and the results of residual stress measurement on samples of the material EN AW-7075 T651. The results are in line with values published by other authors.

New Production Technologies in Aerospace Industry - 5th Machining Innovations Conference (MIC 2014) Determination of Residual Stresses in Plate Material by Layer Removal with Machine-integrated Measurement

Structural aircraft components are usually manufactured from rolled plate material. Despite a stress relief treatment residual stress remains in the plates. This can result in distortions of the workpiece after the final manufacturing step, which leads to time-consuming repair processes or even a scrap part. Using an FEM simulation, it is possible to predict distortions caused by residual stress and to avoid them by adjusting the m anufacturing process. However, the known methods to determine the residual stress state in plate material are expensive in terms of time and material and require specially trained staff. This paper describes a novel m ethod to measure residual stress in plates with little effort. The method is derived from the well-known Layer-Removal-Method and utilizes a machine tool with a standard probing device. The measuring task is fully au tomated and can be performed by untrained staff. No special preparation of the specimen is necessary. The paper describes the procedure and the results of residual stress measurement on samples of the material EN AW-7075 T651. The results are in line with values published by other au thors.

Concerning one approach to the reconstruction of heterogeneous residual stress in plate

AbstractIn present paper the inverse problem on the identification of three non‐homogeneous residual stress components in rectangular plate in steady‐state vibration regime is considered. The equation building the iterative process of solving the inverse problem is formulated. An approach to the reconstruction of residual stresses is described on the basis of introduction the Airy prestress function. The technique of leading the inverse problem to a system of linear algebraic equations at each iteration is proposed. Results of conducting a series of computational experiments on the reconstruction are depicted and discussed.

Effects of welding-induced residual stress on ultimate strength of plates and stiffened panels

During the welding of steel-plated structures, geometric distortions and residual stresses are developed. The influence of welding-induced geometric distortions and residual stresses on the compressive ultimate strength in longitudinal direction of plates and stiffened panels were investigated using nonlinear finite element analyses considering a range of plate thicknesses with various levels of residual stresses. The residual stresses in plates and stiffened panels have been modelled carefully and their effects on these structures due to welding-induced imperfections only are studied. The results and insights observed from the current study are presented.

FEA of Residual Stresses in Butt Welded Type Low Carbon Steel Using MMAW Technique

Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Welding is widely employed in diverse structures such as ships, aircraft, marine structures, bridges, ground vehicles, pipelines and pressure vessels. When two dissimilar plates are joined by welding process, a very complex thermal cycle is applied to the weldment, which further causes inhomogeneous plastic deformation and residual stress in and around fusion zone and heat affected zone (HAZ). Presence of residual stresses may be beneficial or harmful for the structural components depending on the nature and magnitude of residual stresses. In this study, a finite element analysis has been carried out to analyze the thermo-mechanical behaviour and effect of residual stress state in butt-welded in low carbon steel plates. A coupled thermal mechanical three dimension finite element model was developed. Finite element method based software SolidWorks Simulation, was then used to evaluate transient temperature and residual stress during butt welding of two plates. Plate thickness of 8 mm were used which are normally joined by multi-pass operation by Manual Metal Arc Welding (MMAW) process. During each pass, attained peak temperature and variation of residual stresses in plates has also been studied. The results obtained by finite element method agree well with those from X-ray diffraction method as published by Murugan et al. for the prediction of residual stresses.

Research of Micromechanism on Residual Stress in Aluminum Alloy Thick Plate

The research of micromechanism of stress evolvement is presented by analyzing fluctuation and change of surface stress in aluminum alloy thick plate with X-ray diffraction(XRD). From the micro view, a model of “rotation looping and shearing grain” was proposed to analyze and discuss the inhomogeneous distribution of micro-stress in location area, due to inhomogeneity of organization in material. The results present that the inhomogeneity of plastic deformation is direct cause lead to residual stress in plate, and complication of micro-stress distribution results from non-uniformity of organization.

Residual Stresses in Composite Plates with Central Filleted Hole

This article deals with the residual stresses in stainless steel fiber-reinforced aluminum composite plates under in-plane loading that have a central filleted hole. In many cases, the residual stresses in the plates increase ability to carry a larger load. The dimensions of the central hole vary from square to circle by increasing fillet radii at the corners. In the study, the effects of the hole dimension, the fillet radius, and the orientation angles on the residual stresses are investigated using the finite element method (FEM) software ANSYS. Results are presented in tabular and graphical forms.

A comparison of brazed residual stress in plate–fin structure made of different stainless steel

In this study, design optimization of brazed residual stress in stainless steel plate–fin structure was investigated theoretically. A sequentially coupling finite element analysis (FEA) program was developed to simulate the brazed residual stress distribution, with an emphasis on the material selection for plate–fin metal and filler metal. The properties of three different stainless steel for plate–fin and three different materials for filler metal were incorporated into nine different FEA models. The results show that large residual stresses are generated in brazed joint due to the yield strength mismatching between base metal and filler metal. It is found that the best models are 304 or 347 stainless steel for base metal and BNi4 for filler metal. The residual stresses in the brazed joint are mainly affected by yield strength mismatching. But the yield strength mismatching has little effect on the residual stresses for the base metal.

Use of neutron and synchrotron X-ray diffraction for evaluation of residual stresses in a 2024-T351 aluminum alloy variable-polarity plasma-arc weld

The residual stress fields associated with variable-polarity plasma-arc (VPPA) welds in 2024-T351 aluminum alloy plates have been measured nondestructively using neutron and synchrotron X-ray diffraction. Neutron diffraction allows in-depth measurements of the full strain tensor to be made in thick components; synchrotron X-rays allow for rapid measurements of strains inside components, although their penetration is less than that of the neutrons and constraints arising from the diffraction geometry generally lead to only two strain components being easily measurable. Hence, a combination of the two techniques, applied as described herein, is ideal for a detailed nondestructive evaluation of residual stresses in plates. The residual stresses in a 12-mm-thick VPPA-welded aluminum 2024-T351 alloy plate have been measured using neutron diffraction. The stresses were then remeasured by a combination of neutron and synchrotron X-ray diffraction after the plate had been reduced in thickness (or, skimmed) to 7 mm by machining both sides of the weld, mimicking the likely manufacturing operation, should such welds be used in aerospace structures. A strong tensile residual stress field was measured in the longitudinal direction, parallel to the weld, in both the as-welded and skimmed specimens. There was only a slight modification of the residual stress state on skimming.