Peak Longitudinal Stress Research Articles

Temporal evolution of ascending aortic aneurysm wall stress predicts all-cause mortality.

Diameter-based risk stratification for elective repair of ascending aortic aneurysm fails to prevent type A dissection in many patients. Aneurysm wall stresses may contribute to risk prediction; however, rates of wall stress change over time are poorly understood. Our objective was to examine aneurysm wall stress changes over 3-5 years and subsequent all-cause mortality. Male veterans with <5.5 cm ascending aortic aneurysms and computed tomography at baseline and 3- to 5-year follow-up underwent three-dimensional aneurysm model construction. Peak circumferential and longitudinal wall stresses at systole were calculated using finite element analysis. Temporal trends were assessed by mixed-effects modelling. Changes in aortic wall stresses, diameter and length over time were evaluated as predictors of subsequent 3-year all-cause mortality by Cox proportional hazards modelling. Sixty-two male veterans were included in the study. Yearly changes in geometric and biomechanical measures were 0.12 mm/year (95% confidence interval, 0.04-0.20) for aortic diameter, 0.41 mm/year (0.12-0.71) for aortic length, 1.19 kPa/year -5.94 to 8.33) for peak circumferential stress, and 0.48 kPa/year (-3.89 to 4.84) for peak longitudinal stress. Yearly change in peak circumferential stress was significantly associated with hazard of death-hazard ratio for peak circumferential stress growth per 10 kPa/year, 1.27 (95% CI, 1.02-1.60; P = 0.037); hazard ratio for peak circumferential stress growth ≥ 32 kPa/year, 8.47 (95% CI, 2.42-30; P < 0.001). In this population of nonsurgical aneurysm patients, large temporal changes in peak circumferential stress, but not aortic diameter or length, was associated with all-cause mortality. Biomechanical stress and stress changes over time may be beneficial as additional risk factors for elective surgery in small aneurysms.

Height and body surface area versus wall stress for stratification of mid-term outcomes in ascending aortic aneurysm

ObjectivesCurrent diameter-based guidelines for ascending thoracic aortic aneurysms (aTAA) do not consistently predict risk of dissection/rupture. ATAA wall stresses may enhance risk stratification independent of diameter. The relation of wall stresses and diameter indexed to height and body surface area (BSA) is unknown. Our objective was to compare aTAA wall stresses with indexed diameters in relation to all-cause mortality at 3.75 years follow-up. MethodsFinite element analyses were performed in a veteran population with aortas ≥ 4.0 cm. Three-dimensional geometries were reconstructed from computed tomography with models accounting for pre-stress geometries. A fiber-embedded hyperelastic material model was applied to obtain wall stress distributions under systolic pressure. Peak wall stresses were compared across guideline thresholds for diameter/BSA and diameter/height. Hazard ratios for all-cause mortality and surgical aneurysm repair were estimated using cause-specific Cox proportional hazards models. ResultsOf 253 veterans, 54 (21 %) had aneurysm repair at 3.75 years. Indexed diameter alone would have prompted repair at baseline in 17/253 (6.7 %) patients, including only 4/230 (1.7 %) with diameter < 5.5 cm. Peak wall stresses did not significantly differ across guideline thresholds for diameter/BSA (circumferential: p = 0.15; longitudinal: p = 0.18), but did differ for diameter/height (circumferential: p = 0.003; longitudinal: p = 0.048). All-cause mortality was independently associated with peak longitudinal stresses (p = 0.04). Peak longitudinal stresses were best predicted by diameter (c-statistic = 0.66), followed by diameter/height (c-statistic = 0.59), and diameter/BSA (c-statistic = 0.55). ConclusionsDiameter/height improved stratification of peak wall stresses compared to diameter/BSA. Peak longitudinal stresses predicted all-cause mortality independent of age and indexed diameter and may aid risk stratification for aTAA adverse events.

Aortic area/height ratio, peak wall stresses, and outcomes in veterans with tricuspid versus bicuspid aortic valve–associated ascending thoracic aortic aneurysms

BackgroundIn ascending thoracic aortic aneurysm risk stratification, aortic area/height ratio is a reasonable alternative to maximum diameter. Biomechanically, aortic dissection may be initiated by wall stress exceeding wall strength. Our objective was to evaluate the association between aortic area/height and peak aneurysm wall stresses in relation to valve morphology and 3-year all-cause mortality. MethodsFinite element analysis was performed on 270 ascending thoracic aortic aneurysms (46 associated with bicuspid and 224 with tricuspid aortic valves) in veterans. Three-dimensional aneurysm geometries were reconstructed from computed tomography and models developed accounting for prestress geometries. Fiber-embedded hyperelastic material model was applied to obtain aneurysm wall stresses during systole. Correlations of aortic area/height ratio and peak wall stresses were compared across valve types. Area/height ratio was evaluated across peak wall stress thresholds obtained from proportional hazards models of 3-year all-cause mortality, with aortic repair treated as a competing risk. ResultsAortic area/height 10 cm2/m or greater coincided with 23/34 (68%) 5.0 to 5.4 cm and 20/24 (83%) 5.5 cm or greater aneurysms. Area/height correlated weakly with peak aneurysm stresses: for tricuspid valves, r = 0.22 circumferentially and r = 0.24 longitudinally; and for bicuspid valves, r = 0.42 circumferentially and r = 0.14 longitudinally. Age and peak longitudinal stress, but not area/height, were independent predictors of all-cause mortality (age: hazard ratio, 2.20 per 9-year increase, P = .013; peak longitudinal stress: hazard ratio, 1.78 per 73-kPa increase, P = .035). ConclusionsArea/height was more predictive of high circumferential stresses in bicuspid than tricuspid valve aneurysms, but similarly less predictive of high longitudinal stresses in both valve types. Peak longitudinal stress, not area/height, independently predicted all-cause mortality. Video Abstract [Display omitted]

A new method for simulating electron beam welding process of niobium sheets with beam oscillation

Oscillating electron beam welding (EBW) is necessary for the fabrication of pure niobium superconducting radiofrequency (SRF) cavities. Due to the negative effects that welding deformation and residual stress have on the performance of the SRF cavities, it is crucial to predict residual stress and welding distortion with high precision for the design of welding tooling and the optimization of welding parameters. However, the stress and distortion simulation of oscillating EBW received little attention in the previous research. In order to accurately predict the welding stress and distortion of niobium cavities with thin walls, a novel heat source with two reverse 2D Gaussian heat sources was used for the first time in the finite element method (FEM) simulation of EBW with beam oscillation. Additionally, a computational fluid dynamics (CFD) simulation of the molten pool was run as a guide for adjusting the parameters of the designed heat source. The FEM simulation with 2D Gaussian heat source was taken as a comparison. An EBW experiment of niobium sheets was performed to verify the simulation. The simulated molten pool of this model has a wider width, which is significantly closer to the actual measurement. Compared with the result estimated by 2D Gaussian heat source. The joint simulated with the designed heat source displays a smoother temperature gradient. The mechanical results suggest that the peak longitudinal stress in the weld center, the peak transverse stress in the weld center, the longitudinal contradiction, and the transverse contradiction estimated by the designed model deviate from the experimental results by only −4.88%, −4.03%, −9.32%, and −5.98%, respectively. The error of the simulation by the proposed method is dramatically smaller than the evaluation by the 2D Gaussian model. The designed heat source and the CFD validation provides a reliable simulation scheme for the oscillating EBW of thin sheets, and the oscillating EBW of thick plates will be simulated using the suggested method with the improvement of the heat source model in the future.

Abstract 15119: Diastolic Peak Wall Stresses in Marfan vs Non-Marfan Ascending Thoracic Aortic Aneurysm: A Propensity Score Analysis

Introduction: Marfan syndrome (MFS) carries a risk of aortic dissection and death. The current aneurysm repair guideline of diameter ≥5cm may neglect up to 15% of MFS patients who dissect at smaller diameters. Since dissection can occur biomechanically when wall stress exceeds tissue strength, patient-specific biomechanics may enhance risk stratification for MFS patients. The goal of this study was to compare aneurysm wall stresses between propensity score-matched MFS and non-MFS aneurysm patients. Methods: The cohort consisted of 5 MFS and 42 non-MFS patients with aortic aneurysm. Preoperative CTA or MR scans were used to create 3D hexahedral meshes. Finite element analysis was performed with MFS and nonMFS material properties to determine peak (99th percentile) diastolic stresses[TE1] . Propensity scores were calculated by logistic regression using age, sex, height, hypertension, diabetes, smoking history, valve type, and sinus diameter. Five pairs were formed by 1:1 optimal matching without replacement. Comparisons used the paired t-test. Results: Diameters were similar at the sinus but lower for MFS at the STJ (3.4±0.5 vs 3.9±0.7cm, p=0.003) and the ascending aorta (3.1±0.5 vs 4.3±0.5cm, p&lt;0.001). Peak circumferential stresses (CS) were similar between MFS and nonMFS aneurysms across all regions. As well, peak longitudinal stresses (LS) were similar between the two cohorts across all regions (Fig 1). Conclusion: Both CS and LS were similar at all regions for MFS vs non-MFS patients. Because LS has been implicated in acute dissection and LS were similar, differences in tissue strength, rather than wall stress, are most likely causes of high dissection rates in MFS due to material weakness from fibrillin mutation.

Association of 3-Year All-Cause Mortality and Peak Wall Stresses of Ascending Thoracic Aortic Aneurysms in Veterans

Risk of aortic dissection in ascending thoracic aortic aneurysms is not sufficiently captured by size-based metrics. From a biomechanical perspective, dissection may be initiated when wall stress exceeds wall strength. Our objective was to assess the association between aneurysm peak wall stresses and 3-year all-cause mortality. Finite element analysis was performed in 273 veterans with chest computed tomography for surveillance of ascending thoracic aortic aneurysms. Three-dimensional geometries were reconstructed and models developed accounting for prestress geometries. A fiber-embedded hyperelastic material model was applied to obtain circumferential and longitudinal wall stresses under systolic pressure. Patients were followed up to 3 years following the scan to assess aneurysm repair and all-cause mortality. Fine-Gray subdistribution hazards were estimated for all-cause mortality based on age, aortic diameter, and peak wall stresses, treating aneurysm repair as a competing risk. When accounting for age, subdistribution hazard of mortality was not significantly increased by peak circumferential stresses (p=0.30) but was significantly increased by peak longitudinal stresses (p=0.008). Aortic diameter did not significantly increase subdistribution hazard of mortality in either model (circumferential model: p=0.38; longitudinal model: p = 0.30). The effect of peak longitudinal stresses on subdistribution hazard of mortality was maximized at a binary threshold of 355kPa, which captured 34 of 212(16%) patients with diameter <5 cm, 11 of 36(31%) at 5.0-5.4 cm, and 11 of 25(44%) at ≥5.5 cm. Aneurysm peak longitudinal stresses stratified by age and diameter were associated with increased hazard of 3-year all-cause mortality in a veteran cohort. Risk prediction may be enhanced by considering peak longitudinal stresses.

Study of Through-Thickness Stress Distribution in Steel Double-V Butt Weld

Through-thickness stress distribution in 32 mm thick ferritic steel plates welded with double-V groove was studied using neutron diffraction and finite element methods. The stress distribution is close to the symmetrical with respect to the weld centerline and not symmetrical with respect to the weld mid-thickness. The peak longitudinal stress (530 MPa) is located in the first half of the weld thickness, where the groove was filled first. The region of maximum compressive transverse stresses (–400 MPa) is located in the second half of the plate thickness. Post weld heat treatment reduces maximum tensile stresses down to ∼200 MPa. The position of maxima and minima of transverse residual stresses obtained by finite element methods are in agreement with the results of measurement by the neutron diffraction method. However, at some locations, the calculated values are approximately 300 MPa higher than the experimental ones.

Wall stress analyses in patients with ≥5 cm versus

ObjectiveCurrent guidelines for elective surgery of ascending thoracic aortic aneurysms (aTAAs) use aneurysm size as primary determinant for risk stratification of adverse events. Biomechanically, dissection may occur when wall stress exceeds wall strength. Determining patient-specific aTAA wall stresses by finite element analysis can potentially predict patient-specific risk of dissection. This study compared peak wall stresses in patients with ≥5.0 cm versus <5.0 cm aTAAs to determine correlation between diameter and wall stress. MethodsPatients with aTAA ≥5.0 cm (n = 47) and <5.0 cm (n = 53) were studied. Patient-specific aneurysm geometries obtained from echocardiogram-gated computed tomography were meshed and prestress geometries determined. Peak wall stresses and stress distributions were determined using LS-DYNA finite element analysis software (LSTC Inc, Livermore, Calif), with user-defined fiber-embedded material models under systolic pressure. ResultsPeak circumferential stresses at systolic pressure were 530 ± 83 kPa for aTAA ≥5.0 cm versus 486 ± 87 kPa for aTAA <5.0 cm (P = .07), whereas peak longitudinal stresses were 331 ± 57 kPa versus 310 ± 54 kPa (P = .08), respectively. For aTAA ≥5.0 cm, correlation between peak circumferential stresses and size was 0.41, whereas correlation between peak longitudinal wall stresses and size was 0.33. However, for aTAA <5.0 cm, correlation between peak circumferential stresses and size was 0.23, whereas correlation between peak longitudinal stresses and size was 0.14. ConclusionsPeak patient-specific aTAA wall stresses overall were larger for ≥5.0 cm than aTAA <5.0 cm. Although some correlation between size and peak wall stresses was found in aTAA ≥5.0 cm, poor correlation existed between size and peak wall stresses in aTAA <5.0 cm. Patient-specific wall stresses are particularly important in determining patient-specific risk of dissection for aTAA <5.0 cm.

Predissection-derived geometric and distensibility indices reveal increased peak longitudinal stress and stiffness in patients sustaining acute type A aortic dissection: Implications for predicting dissection

ObjectiveTo assess ascending aortic distensibility and build geometry and distensibility-based patient-specific stress distribution maps in patients sustaining type A aortic dissection (TAAD) using predissection noninvasive imaging. MethodsReview of charts from patients undergoing surgical repair of TAAD (n = 351) led to the selection of a subset population (n = 7) with 2 or more predissection computed tomography angiography scans and echocardiograms at least 1 year before dissection. Ascending aortic wall biomechanical properties (aortic strain, distensibility, and stiffness) were compared with age- and size-matched nondissected nonaneurysmal controls. Patient-specific aortic strain served as an input in aortic geometry-based simulated 3-dimensional reconstructions to generate longitudinal and circumferential wall stress maps. Inspection of perioperative dissection scans and intraoperative visual examination confirmed primary tear locations. ResultsPredissection echocardiography revealed ascending aortas of patients sustaining TAAD to exhibit decreased aortic wall strain (14.50 ± 1.13% vs 8.49 ± 1.08%; P < .01), decreased distensibility (4.26 ± 0.44 vs 2.39 ± 0.33 10−6 cm2·dyne−1; P < .01), increased stiffness (3.84 ± 0.24 vs 7.48 ± 1.05; P < .001), and increased longitudinal wall stress (246 ± 22 vs 172 ± 37 kPa; P < .01). There was no significant difference in circumferential wall stress. Predissection computed tomography angiography models revealed overlap between regions of increased longitudinal wall stress and primary tear sites. ConclusionsUsing predissection imaging, we identified increased stiffness and longitudinal wall stress in ascending aortas of patients with dissection. Patient-specific imaging-derived biomechanical property maps like these may be instrumental toward designing better prediction models of aortic dissection potential.

The effect of the weld fusion zone shape on residual stress in submerged arc welding

A new multiple-electrode submerged arc welding technique has been developed that imparts improved fracture toughness properties in the heat affected zone, produces a narrower weld bead geometry, and can also be employed with lower heat inputs than conventional SAW. This study examines how the difference in the weld fusion zone profile affects residual stresses for weldments of API X70 steel made using the same consumable, heat input and restraint, varying only the shape of the weld fusion zone. The contour method and neutron diffraction have been employed to map and compare longitudinal and transverse residual stresses. Results show peak longitudinal stresses in the weld are within 50 MPa for both, and this is believed to be because they have the same heat input and hence similar heat affected zone size. By contrast, the peak stress in the transverse direction is 120 MPa lower for the new SAW technique. The reduction in transverse stress is attributed to a narrower fusion zone profile. The new SAW technique opens up the possibility of producing high quality narrower welds with lower heat input which could lead to significant reductions in residual stress.

Residual Stress and Fatigue Strength of Hybrid Laser-MIG-Welded A7N01P-T4

A7N01P-T4 aluminum alloy is widely used in some important welded components of high-speed trains. The hybrid laser-metal inert gas (MIG) welding process was studied to solve problems associated with the MIG welding process, such as low welding efficiency, high residual stress and deformation, and serious loss of strength. A high-speed camera, a voltage and current collection system, and NI DAQ were used to acquire arc profiles, welding voltage, and welding current simultaneously. Thermal cycle tests were carried out. Residual stresses induced by the welding process and fatigue strength of the joint were investigated. Large-size fatigue specimens were used in fatigue tests. The results show that the energy of the hybrid welding process is focused, and the power density of hybrid welding process is intense. The heat input per unit of the hybrid welding process is only half of that of the MIG welding process. Compared with the MIG welded joint, the overall residual stress level of the hybrid-welded joint is lower. The peak longitudinal stress of the hybrid-welded joint is reduced by 20 pct. The fatigue strength of hybrid joints is 14 pct higher than that of MIG-welded joints. Narrow weld and HAZ, weak softening behavior, and low residual stress level are the causes of the improvement of fatigue strength.

Residual Stress Reduction in Single Pass Welds Using Parallel Line Reheating

Current postweld heat treatment (PWHT) methods rely mainly on static thermal sources or line heating using dispersed beams which require significant capital investment and often pose limits on weldment size. In the current study, an alternative PWHT method based on line heating is presented and analyzed. The method, which is intended to perform low temperature stress relief, employs parallel oxyacetylene torches to induce a tensile stress in the vicinity of the weld toe. X-ray diffraction (XRD) measurements taken from bead-on-plate (BOP) welds made using ASTM A572-50 showed a 37% decrease in the peak longitudinal stress after parallel line reheating was performed. A corresponding reduction in the stress gradient on the plate surface was also observed. Welding and reheating were also modeled in sysweld to assess how torch placement affected the longitudinal stress distribution and an optimum offset was identified for the 8-mm plate thickness used. Analysis of the thermomechanical history in the vicinity of the weld toe indicates that a tensile stress is superposed during reheating and is concurrent with the reduction in the peak longitudinal stress.

Analysis of shockless dynamic compression data on solids to multi-megabar pressures: Application to tantalum

Magnetically-driven, planar shockless-compression experiments to multi-megabar pressures were performed on tantalum samples using a stripline target geometry. Free-surface velocity waveforms were measured in 15 cases; nine of these in a dual-sample configuration with two samples of different thicknesses on opposing electrodes, and six in a single-sample configuration with a bare electrode opposite the sample. Details are given on the application of inverse Lagrangian analysis (ILA) to these data, including potential sources of error. The most significant source of systematic error, particularly for single-sample experiments, was found to arise from the pulse-shape dependent free-surface reflected wave interactions with the deviatoric-stress response of tantalum. This could cause local, possibly temporary, unloading of material from a ramp compressed state, and thus multi-value response in wave speed that invalidates the free-surface to in-material velocity mapping step of ILA. By averaging all 15 data sets, a final result for the principal quasi-isentrope of tantalum in stress-strain was obtained to a peak longitudinal stress of 330 GPa with conservative uncertainty bounds of ±4.5% in stress. The result agrees well with a tabular equation of state developed at Los Alamos National Laboratory.

Ramp compression of iron to 273 GPa

Multiple thickness Fe foils were ramp compressed over several nanoseconds to pressure conditions relevant to the Earth's core. Using wave-profile analysis, the sound speed and the stress-density response were determined to a peak longitudinal stress of 273 GPa. The measured stress-density states lie between shock compression and 300-K static data, and are consistent with relatively low temperatures being achieved in these experiments. Phase transitions generally display time-dependent material response and generate a growing shock. We demonstrate for the first time that a low-pressure phase transformation (α-Fe to ε-Fe) can be overdriven by an initial steady shock to avoid both the time-dependent response and the growing shock that has previously limited ramp-wave-loading experiments. In addition, the initial steady shock pre-compresses the Fe and allows different thermodynamic compression paths to be explored.

Using heat sink technology to decrease residual stress in 316L stainless steel welding joint: Finite element simulation

316L type stainless steel is widely used in chemical industries due to its excellent resistance to corrosion. But the welding residual stresses have a great effect on stress corrosion cracking. This paper used finite element method to study the effect of heat sink on residual stress. The effects of contact length and the average heat transfer coefficient on residual stress have been investigated. It is found that the heat sink technology can decrease the residual stress greatly. Compared to the model without heat sink, 20% of the peak longitudinal stress has been reduced. The heat sink decreases the dwell time during cooling from 850 °C to 400 °C, which is helpful to decrease the risk of sensitization of 316L stainless steel. With the contact length increase, the transverse stress is decreased. Further increase of the contact length has no positive effect on reducing the longitudinal stress. With the average heat transfer coefficient increase, the transverse stress is decreased greatly while the longitudinal stress decreases slightly, and some tensile residual stresses have been changed to compressive in some zone.

High‐pressure magnetically driven compression waves in condensed matter.

The Z machine is a fast pulsed‐power machine at Sandia National Laboratories designed to deliver a 100‐ns rise‐time, 26‐MA pulse of electrical current to Z‐pinch experiments for research in radiation effects and inertial confinement fusion. Since 1999, Z has also been used as a current source for magnetically driven, high‐pressure, high‐strain‐rate experiments in condensed matter. In this mode, Z produces simultaneous planar ramp‐wave loading, with rise times in the range of 300–800 ns and peak longitudinal stress in the range of 4–400 GPa, of multiple macroscopic material samples. Control of the current‐pulse shape enables shockless propagation of these ramp waves through samples 1–2 mm thick to measure quasi‐isentropic compression response, as well as shockless acceleration of copper flyer plates to at least 28 km/s for impact experiments to measure ultra‐high‐pressure (∼3000 GPa) shock compression response. This presentation will give background on the relevant physics, describe the experimental technique, and show recent results from both types of experiments. [Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract No. DE‐AC04‐94AL85000.]

Stiff Response of Aluminum under Ultrafast Shockless Compression to 110 GPA

A laser-produced x-ray drive was used to shocklessly compress solid aluminum to a peak longitudinal stress of 110 GPa within 10 ns. Interface velocities versus time for multiple sample thicknesses were measured and converted to stress density (Px-rho) using an iterative Lagrangian analysis. These are the fastest shockless compression Px(rho) results reported to date, and are stiffer than models that have been benchmarked against both static and shock-wave experiments. The present results suggest that at these short time scales there is a higher stress-dependent strength and a stiffer time-dependent inelastic response than had been expected.

Graded-Density Reservoirs for Accessing High Stress Low Temperature Material States

In recently developed laser-driven shockless compression experiments an ablatively driven shock in a primary target is transformed into a ramp compression wave in a secondary target via unloading followed by stagnation across an intermediate vacuum gap. Current limitations on the achievable peak longitudinal stresses are limited by the ability of shaping the temporal profile of the ramp compression pulse. We report on new techniques using graded density reservoirs for shaping the loading profile and extending these techniques to high peak pressures.

Micromechanical aspects of fatigue in a MIG welded aluminium airframe alloy: Part 1. Microstructural characterization

Fusion welding of high strength aluminium alloys is being widely considered within the commercial aircraft industry as an alternative to established mechanical fastening methods. The objective of the present article is to characterise the microstructural features of metal inert gas (MIG) welded plate of the conventional damage tolerant alloy, 2024-T351. Micromechanical aspects of the fatigue performance of this welded material are then addressed in a companion article. The general microstructure of the MIG weld was studied using optical microscopy and scanning electron microscopy, in association with electron back-scattered diffraction mapping. Columnar dendritic structures at the edge of the fusion zone are seen, with fairly uniform equiaxed dendritic grain structure dominating in the weld centre. Local microstructural conditions of the different elements of the weld have been assessed via micro-hardness and differential scanning calorimetry, identifying the balance between aging, overaging, re-solutionising and re-precipitation occurring across the weld region. Residual stress measurements by laboratory X-ray and synchrotron X-ray diffraction are also discussed, showing stress relaxation and redistribution occurring under loads representative of smooth specimen fatigue testing. The fusion zone is seen to present a tensile residual stress field, with peak longitudinal stress occurring towards the interface with the fusion zone.

The determination of the residual strains and stresses in a tungsten inert gas welded sheet of IN718 superalloy using neutron diffraction

The residual stress state in a tungsten inert gas (TIG) welded sheet of IN718, a high-strength nickel-based superalloy, has been characterized using neutron diffraction. The measurements were performed using a time-of-flight diffractometer, which allowed lattice strains from the γ-γ′ {111} and γ-γ′ {311} composite peaks to be compared with the Reitveld-refined spectra. Residual stresses were estimated using plane-specific values of Young's modulus and Poisson's ratio for the {311} and {111} peaks, and the macroscopic material response for the Reitveld-refined data. These values were obtained from a theoretical analysis of existing data after Kröner. The weld considered was an autogenous TIG weld 180mm long placed centrally on to a 2mm × 100mm × 200mm solution heat-treated sheet of IN718. The strain was mapped over the central 140mm of the plate; within this region, the measured strains were almost constant along the length, with the peak bulk longitudinal strain of 1700 × 10-6 detected 4mm from the weld centre, in the heat-affected zone. The corresponding peak longitudinal stress was 270 MPa, and the tensile region 11 mm wide, with the longitudinal residual stresses typically up to 2.5 times greater than those in the transverse direction. It was also found that, while in-weld stresses derived from analysis of single peaks may be incorrect due to textural and compositional effects, those derived from Reitveld refinement of the entire spectrum showed reasonable agreement with those obtained from incremental hole drilling measurements made with the Matthar-Soete method.