Hole-drilling Method Research Articles

Influence of process parameters on residual stresses in deep-drawing process with FEM and experimental evaluations

This paper presents experimental and simulation study to minimize residual stress in cylindrical deep-drawing process. Eight significant process parameters including initial blank thickness, punch and die shoulder radii, blank–holder force, punch velocity, and coefficients of friction between die–blank, holder–blank, and punch–blank are considered. According to number of parameters, the Taguchi’s method is employed to perform design of experiments. The die is designed and manufactured, and the experiments are carried out using AISI 1006 carbon steel sheet. Hole-drilling method based on ASTM E 837-99 standard is applied to measure the residual stresses in drawn cups. Moreover, the deep-drawing process is simulated wholly using ABAQUS/explicit software and the accuracy of finite-element model is verified using experimental results. Finally, the analysis of variance method is applied to define the most important parameters and obtain an optimum level to minimize the residual stress in cylindrical deep-drawing process.

Modelling of residual stresses in a narrow-gap welding of ultra-thick curved steel mockup

A plane strain model, an axisymmetric model and a lumped-pass three-dimensional (3D) model were employed to simulate the residual stresses in a narrow-gap welding 300 mm-thick curved steel mockup. The lumped-pass 3D model was built with the lumping scheme based on the two-dimensional (2D) temperature field result. The residual stresses on the top surface of the mockup were measured using the hole-drilling method and compared with the simulated stresses. Results show that the plane strain model cannot capture the asymmetric conditions of the curved mockup; the through-thickness transverse stress within the weld zone presents a self-equilibrated distribution, and the through-thickness hoop stress within the weld zone are almost tensile with the peak value occurring at a certain depth (8 mm) beneath the top and bottom surfaces.

Diffraction grating strain gauge method: error analysis and its application for the residual stress measurement in thermal barrier coatings

Diffraction grating strain gauge (DGSG) is an optical strain measurement method. Based on this method, a six-spot diffraction grating strain gauge (S-DGSG) system has been developed with the advantages of high and adjustable sensitivity, compact structure, and non-contact measurement. In this study, this system is applied for the residual stress measurement in thermal barrier coatings (TBCs) combining the hole-drilling method. During the experiment, the specimen’s location is supposed to be reset accurately before and after the hole-drilling, however, it is found that the rigid body displacements from the resetting process could seriously influence the measurement accuracy. In order to understand and eliminate the effects from the rigid body displacements, such as the three-dimensional (3D) rotations and the out-of-plane displacement of the grating, the measurement error of this system is systematically analyzed, and an optimized method is proposed. Moreover, a numerical experiment and a verified tensile test are conducted, and the results verify the applicability of this optimized method successfully. Finally, combining this optimized method, a residual stress measurement experiment is conducted, and the results show that this method can be applied to measure the residual stress in TBCs.

Microstructure, mechanical properties and residual stress of a 2205DSS/Q235 rapidly formed LBW joint

Welding seam (WS) of a 2205DSS/Q235 laser-beam welded (LBW) joint consisted of a martensitic phase and a small amount of residual austenite. The microstructure of the heat-affected zone (HAZ) of the 2205DSS side was ferrite-dominated. The HAZ of the Q235 side consisted of a coarse-grained zone (near the WS) and a fine-grained zone which was a result of the thermal cycling. The WS had the was highest hardness, and the hardness value of the HAZ was slightly higher than that of the respective base metal. The strength of these welding joints was approximately 460 MPa. The residual stress was investigated using a finite element method, hole-drilling method, and X-ray diffraction analysis. The results revealed two high stress regions on either side of the WS. The residual stress of the WS was relieved substantially because of the martensitic transformation at 400 °C.

Hole-Drilling Method for Measuring Residual Stresses

Abstract This book describes the theory and practice of the Hole-Drilling Method for measuring residual stresses in engineering components. Such measurements are important because residual stresses have a character because they exist locked-in within a material, independent of any external load. These stresses are typically created during component manufacture, for example, during welding, casting, or forming. Because of their hidden nature, residual stresses are difficult to measure and consequently are often ignored. However, they directly add to loading stresses and can cause catastrophic failure if not properly included during engineering design. Thus, there is an urgent need to be able to identify and measure residual stresses conveniently and reliably. The Hole-Drilling Method provides an adaptable and well-proven method for measuring residual stresses in a wide range of materials and component types. It is convenient to use and gives reliable results. Because of the hidden nature of residu...

English

The goal of this project is to investigate the Residual Stress in hot rolled aluminium alloys where both experiments and computer simulation will be implemented in order to get highest degree of investigation. This project is a miniature investigation process of real problem faced by AIRBUS, in the field of failure of wings against superfluous residual stresses. The residual stress level achieved from simulation matches to what received from the hole-drilling measurement after quenching process, hence, the necessity of the complex and expensive hole-drilling method can simply be omitted in the real industry resulting huge time saving in mass production units.

The impact of AA7075 cold spray coating on the fatigue life of AZ31B cast alloy

To improve the fatigue resistance of magnesium alloys, AA7075 powder, which has high fatigue strength and high adhesion strength, was successfully coated on as-cast AZ31B substrate. The coating proved to be dense, with a porosity of <4% within an average build-up of 282μm, and showing adhesion strength of 42MPa. Residual stress distribution due to the peening effect of cold spray was measured in the coat and substrate by a hole-drilling method, showing a maximum compressive residual stress of −122MPa. Coated and un-coated samples were then tested in load-control mode under fully-reversed loading conditions. Fatigue strength improvement of 25% at 10millioncycles was observed for the coated samples. Casting defects, such as oxides and porosity in un-coated cast AZ31B was found to be the primary source of crack initiation at multiple locations. In the coated samples, while cracks were still initiated from the substrate's pores near the interface, the coating remained intact and crack propagation was delayed considerably. Delamination of coating was solely observed along the final fracture zone, and was due to a high load and mismatch of coat-substrate properties. The longer lives of the coated samples were attributed to the higher fatigue strength of AA7075 relative to AZ31B and coating's high adhesion strength.

A Displacement Based Analytical Model to Determine Residual Stress Components in a Finite Elastic Thin Plate with Hole-Drilling Method

In order to measure the residual stress components in an elastic thin plate, the hole-drilling strain-gage method has been used. This method enables to determine the relation between the magnitudes and directions of the principal stresses and the strain relaxation about the hole. In the existing analytical models based on stress field, the formulations associated with the hole-drilling method are based on the assumption of an infinite plate, this may cause some errors for a finite plate and it’s difficult to validate these solutions by FE methods. Furthermore, in the composite, the displacement field is continuous but the stress field is not necessarily continuous, the displacement field based method has to be used. In the present paper an analyt-ical model based on a displacement field described by a function with coefficients to determine for a finite round thin plate is presented. The coefficients used in the displacement field are independent on the three residual stress components, and they are determined by minimization of the internal strain energy during the hole-drilling process. Once the coefficients in the dis-placement field are determined, three strains measured in three radial directions are utilized to determine the three residual stress components. The proposed analytical model can be also adapted to infinite plate by assuming that the diameter of the round plate tends to infinite.

The effect of third principal stress in the measurement of residual stresses by hole-drilling method

One of the most popular and widely used technique for measuring residual stresses is the hole-drilling method. By this method, it is possible to evaluate only biaxial residual stresses located in plane parallel to the surface, but some processes produce a triaxial stress state. For this reason, the evaluation of triaxial stress state by the method used for biaxial state was assessed in this paper. A hole-drilling experiment was simulated by the finite element method for two different stress states. The first stress state considered constant residual stresses in all directions. The second one considered constant residual stresses in a plane parallel to the surface and the residual stress in a direction perpendicular to the surface was equal to zero on the surface and increased with depth. Both states were simulated for various ratios of stress in a direction perpendicular to the stresses in plane. The obtained results show that residual stress in a perpendicular direction affects the evaluation of residual stresses in plane. If the residual stress in the perpendicular direction is high compared to stresses in plane, the error produced by the evaluation of triaxial stress state by the method for biaxial stress state can also be high. 1 Introduction

Effect of Residual Stress on the Mechanical Properties of FSW Joints with SUS409L

This study was performed to investigate both the residual stress distribution and the effect of the residual stress formed at the welding region on the mechanical properties of the friction stir welded joints with 409L stainless steel sheets. Residual stress measurement with hole‐drilling method; mechanical property evaluation including tensile test, Charpy impact test, and fatigue test; and microstructure observation were conducted. It has got no residual stresses to speak of at the center region of the stir zone because the stored stresses are released in the process of the dynamic recrystallization, while a small quantity of compressive residual stresses is formed at the surface region of the stir zone because of strong compression reaction by the tool shoulder. A considerable amount of compressive residual stresses is formed at the thermomechanical affected zone because of the synergy between the thermal expansion due to the heat conduction from the stir zone and mechanical compression by the tool. The formation of residual stresses shows a similar tendency between the advancing side and the retreating side. Both the mitigation of residual stress in the stir zone and the formation of compressive residual stress in the thermomechanical affected zone contribute to the improvement of the mechanical properties of the friction stir welded joints.

An experimental and numerical study of forces and residual stresses in AISI 316L stainless steel joints due to conventional and pulse gas tungsten arc welding

This paper aims to present the results of a numerical and experimental study of the temperature field, internal forces and the residual stresses in 2 mm thick autogenous welds of AISI 316L stainless steel produced by continuous and pulse current gas tungsten arc welding. A special experimental device was used to measure the temperature and the internal forces due to the welding. The welds were qualified for internal and external weld imperfections according to ISO 15614-1. FEM software ANSYS® Multyphysics™ was applied in order to solve the thermal and mechanical problems. Normal residual stresses were measured by the hole-drilling strain gauge method in the continuous current weld. The peak value of the longitudinal stress was 80 % of the base metal yield stress. The magnitude of the numerically obtained residual stress values was found to be 16 % to 19 % above the measured one in the longitudinal and transverse direction, respectively. The experimental device used in this study allowed for a real time measurement of forces far from the weld seam. On the basis of the correspondence between the calculated and measured forces the numerical results were verified. Therefore, this device might open up new possibilities for determining thermo-mechanical material data.

On the Effect of Part Orientation on Stress Distribution in AlSi10Mg Specimens Fabricated by Laser Powder Bed Fusion (L-PBF)

The freedom of design of AM products suffers from some limitations in case of powder bed metal processes, because AM part's integrity is affected by the residual stress state that is a consequence of the thermal history during part fabrication. Aim of this work is to evaluate the effect of part orientation on stress distribution. Thus, flat samples of AlSi10Mg alloy built along different orientations are produced by means of laser powder bed fusion (L-PBF) process, also known as Selective Laser Melting (SLM). Then, the semi-destructive hole-drilling method is used to evaluate residual stresses beneath the surfaces of samples. The outcomes of the study can be exploited to define design rules in order to both minimize support structures and optimize the orientation of the part in the building volume.

Determination of residual weld stresses with the incremental hole-drilling method in tubular steel bridge joints

Tubular arch bridges are susceptible to fatigue problems due to stress concentrations, welding imperfections and tensile residual weld stresses. These bridges are composed of circular hollow section profiles welded together in tubular joints. This paper describes the determination of residual weld stresses in T-joints with the incremental hole-drilling method. The residual stress distribution can be used to determine fatigue crack behavior and fatigue lifetime more precisely.The incremental hole-drilling method is used to measure residual welding stresses on two similar T-joints. Experimental residual stress measurements were performed with the aid of the RS-200 milling guide. Strain gauge rosettes are attached to the test surface and with the milling guide, a small hole is drilled through the center of the strain gauge rosette. Strains at incremental depths are measured and the residual stresses are calculated according to ASTM E837-13a.A comparison is made between residual stress distributions obtained with finite element simulation and the experimental measurements. The distributions from finite element simulation show tensile yield stresses close to the weld while the experimental measurements indicate tensile yield stresses only in the axial direction of the primary tube. In all other cases, the residual stresses are tensile within 50% of yield stress or even compressional. However, more measurements on similar test specimens are necessary for a reliable residual stress distribution.Knowledge of the residual stress distribution is essential to accurately estimate the crack development under fatigue loads. In future research, the residual stresses can be used to study the influence of residual weld stresses on the fatigue lifetime and improve the design of steel tubular joints in arch bridges.

Alternative Gas Mixtures in Arc Spraying: A Chance to Improve Coating Properties and Residual Stress States

The highly cavitation erosion-resistant propeller alloys CuAl9Ni5Fe4Mn (Ni-Al-Bronze) and CuMn13Al8Fe3Ni2 (Mn-Al-Bronze) were arc-sprayed using a mixture of nitrogen and 2% of hydrogen as atomizing gas and different traverse speeds. The objective was to identify the influences of the different spraying conditions, such as temperature regime and melting loss, on the resulting residual stress states and coating properties. Residual stresses were measured by the incremental hole-drilling method using ESPI. Temperature measurements were carried out by thermographic imaging. Microstructural, chemical and mechanical analyses were realized to examine adhesive and cohesive properties. Additionally, the cavitation erosion behavior was investigated to analyze cohesive coating properties. The spraying process itself was improved, which was apparent by mainly enhanced deposition efficiency and reduced surface temperatures. The amount of oxides and pores as well as the melting loss of alloying elements were reduced. Moreover, an increased cavitation erosion resistance and thus coating cohesion as well as less residual stresses were identified. The change in atomizing gas diminished the impact of the quenching stresses on the coating properties. In contrast, the adhesive strength, Young’s moduli and partially the hardness were slightly reduced. With regard to materials, Ni-Al-Bronze revealed superior coating properties in comparison with Mn-Al-Bronze.

Effect of plasticity at out-of-plane electronic speckle pattern interferometry diagnostics of axisymmetric stresses by the hole-drilling method

Theoretical, calculated, and experimental results of studies on the registration of the accounting effect of plasticity in the diagnosis of axisymmetric stresses by the hole method and speckle-interferometric detection of the field of normal displacements in its vicinity are presented. Theoretical and computational studies were carried out on a disk model of finite thickness from an ideally elastic–plastic material. The theoretical model considers the formation of elastoplastic deformations in the vicinity of the through hole; the calculated finite element model considers in the vicinity of both through and blind holes of different depths. It was noted that at the blind hole, the most informative are the movements of the axisymmetric bend caused by the violation by the blind hole of symmetry of the disk with respect to its median plane. At the same time, an approximate analytical method has been developed to calculate the stresses that cause only elastic deformations. Experimental studies were carried out on a series of samples in the form of steel disks with axisymmetric stresses near the yield point. These stresses were induced by the hot fit of grinded rings from hardened high-strength steel onto disks made of steel with a low yield strength. Examples are given which show that the stress values determined from normal displacements in the vicinity of the probe holes from the calculated–theoretical and experimental are similar.

Residual stress field analysis of Al/steel butt joint using laser welding–brazing

ABSTRACTThe objective of this study is to analyse residual stress of the Al/steel butt joint using the laser welding–brazing. The welding parameters were a laser power of 1200 W, a welding speed of 600 mm min−1, thickness of 150×150×2 mm and 150×150×1 mm, respectively. The residual stress was measured by the hole-drilling methods. Then, a finite-element model of the welding process was established, and it was verified by experiments. The results show that the calculated results are in conformity with the experimental results. The longitudinal residual stress on the galvanised steel (329 MPa) is larger than that on the aluminium alloy (293 MPa). At the location of the fixture, the longitudinal residual stress is substantially zero.

Effect of Process Parameters on Distortion and Residual Stress of High-Pressure Die-Cast AZ91D Components

This paper presents a study of distortion and residual stress within a high-pressure die-cast AZ91D component, cast under different processing conditions. The influence of process parameters, i.e., die temperature, cooling time, intensification pressure and first-phase injection speeds, was examined. Distortions were measured using the in-house standard analog quality control fixture. Residual stress depth profiles were measured using a prism hole-drilling method. It was found that the most important process parameter affecting the distortion was intensification pressure and the second most important was temperature difference between the two die halves (fixed and moving side). Tensile residual stresses were found very near the surface. Increasing the intensification pressure resulted in an increased level of tensile residual stresses.

Effect of crystallographic orientation on quenching stress during martensitic phase transformation of carbon steel plate

During quenching, the residual stresses are affected by the crystallographic orientation of martensite, because the nonuniform thermal stresses affect the crystallographic orientation of the lath-shaped martensite and induce the anisotropic expansion. To simulate this process, the model of anisotropic transformation induced plasticity (TRIP) was built using the WLR-BM phenomenological theory. The equivalent expansion coefficient was introduced considering the thermal and plastic strains, which simplified the numerical simulation. Furthermore, the quenching residual stresses in carbon steel plates were calculated using the finite element method under ANSYS Workbench simulation environment. To evaluate the simulative results, distributions of residual stresses from the surface to the interior at the center of specimen were measured using the layer-by-layer hole-drilling method. Compared to the measured results, the simulative results considering the anisotropic expansion induced by the crystallographic orientation of martenstic laths were found to be more accurate than those without considering it.

Residual stress in high-strength-steel welded circular tube

To determine the distribution characteristics of the residual stress in a transmission tower welded circular tube section fabricated from 690 MPa high-strength steel (HSS), an experimental study using 30 galvanised and non-galvanised 690 MPa HSS specimens was conducted using the sectioning method and the hole-drilling method. Further, the effects of the residual stress measurement method, hot-dip galvanisation and circular diameter-to-thickness ratio on the residual stress were discussed. Finally, two distribution models for galvanised and non-galvanised specimens, and their simplified forms, were established. Comparison with a model of a welded circular tube section composed of normal-strength steel (NSS) showed that, although the maximum tensile residual stress of 690 MPa HSS is consistent with that of NSS, and although both exhibit the desired material yield strength, the maximum compressive residual stress of the HSS specimen is only 57% of that of the NSS specimen.

Process Parameter Settings and Their Effect on Residual Stresses in WC/W2C Reinforced Iron-Based Arc Sprayed Coatings

Residual stresses have been a major source of concern, as they are an inevitable consequence of manufacturing and fabrication processes. The magnitude of these stresses is often as high as, or at least, comparable to the yield strength of the material. In terms of arc sprayed coatings, the utilization of bore hole drilling methods presents some practical disadvantages as mechanical parameters (Poisson’s ratio, Young’s modulus) need to be identified in order to determine the residual stress distribution. Curvature techniques using Almen strips are cost- and time-effective methods that can be used for analytical quality assurance. Within the scope of this work, a quantitative study of the amount of residual stresses induced in a twin wire arc spraying (TWAS) process for a given combination of process parameters was conducted using the incremental bore hole drilling method, as well as the curvature method including Almen strips. Therefore, the effect of the primary gas pressure, substrate preheating temperature, and handling parameters, such as the spray angle and gun velocity, which influence the coating deposition as well as the heat input into the substrate, are examined. The experiments were carried out by using an iron-based cored wire with cast tungsten carbides as filling. The results of both methods are in an acceptable accordance with each other. Different stress fields were observed depending on the parameter settings.