Improving accuracy of bulk residual stress characterization in ribbed geometries through equivalent bending stiffness

Abstract The monolithic thin-walled parts are widely used in the aeronautic and astronautic field because of its excellent mechanical performance and light weight, but the thin-walled parts are vulnerable to the machining deformation due to its low stiffness and high material removal rate. According to the relative basic theory, the stiffness and internal residual stress of the part are the critical factors affecting the dimensional stability. In this work, the influences of equivalent bending stiffness and residual stress on the dimensional stability of thin-walled parts are studied. Nine typical thin-walled parts in three groups with two materials (7075 aluminum alloy for A1~A3 and B1~B3, and Ti6Al4V titanium alloy for B4~B6) are machined and treated with different processes. Topology optimization technique is used to optimize the structure of parts to enhance the bending stiffness. Corresponding finite element method (FEM) simulations are carried out to further investigate the generation mechanism. The deformations in 312 hours after machining are measured using coordinate measuring machine, and the deformation changes of the parts are obtained and analyzed. Finally, based on topological optimization and stress relief technology, a machining deformation control method for the monolithic thin-walled parts is proposed. Results show that the maximum and average deformations of thin-walled are evidently decreased using the proposed method.

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Effects of TVSR process on the dimensional stability and residual stress of 7075 aluminum alloy parts

REVIEWS ON ADVANCED MATERIALS SCIENCE ◽

10.1515/rams-2021-0048 ◽

2021 ◽

Vol 60 (1) ◽

pp. 631-642

Author(s):

Yan Xu ◽

Zhongjun Shi ◽

Bianhong Li ◽

Zhang Zhang

Keyword(s):

Residual Stress ◽

Aluminum Alloy ◽

Dimensional Stability ◽

Stress Relief ◽

Bending Stiffness ◽

Machining Process ◽

7075 Aluminum Alloy ◽

Maximum Deformation ◽

Equivalent Bending Stiffness ◽

Thin Walled

Abstract Residual stress generated during the blank forming and machining process significantly influences the dimensional stability of the mechanical parts. The equivalent bending stiffness and thermal vibration stress relief (TVSR) are two factors that affect the deformation of thin-walled workpiece. To increase the machining accuracy, on the one hand, increase the equivalent bending stiffness in manufacturing, and on the other hand, usually conduct the stress relief process to reduce the residual stress in manufacturing. In the present study, morphology optimization and TVSR process are conducted on a thin-walled part Specimen B of 7075 aluminum alloy to control the residual stress and machining deformation before finish machining. As a contrast, Specimen A is machined in one step. The deformations vary with time of Specimen A and B are measured. The corresponding finite element model is built to further study the stress and distortion during the machining process. Results showed that (1) deformation decreased with the increase of equivalent bending stiffness, compared with Specimen A, the maximum deformation of Specimen B decreased by 58.28%. (2) The final maximum deformation of Specimen B can be reduced by 38.33% by topology reinforcement to improve the equivalent stiffness and TVSR to reduce the residual stress.

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Microbridge Testing of Silicon Oxide/Silicon Nitride Bilayer Films

MRS Proceedings ◽

10.1557/proc-657-ee8.5 ◽

2000 ◽

Vol 657 ◽

Author(s):

C.-F. Qian ◽

Y.-J. Su ◽

M.-H. Zhao ◽

T.-Y. Zhang

Keyword(s):

Residual Stress ◽

Silicon Nitride ◽

Young’S Modulus ◽

Silicon Oxide ◽

Young's Modulus ◽

Single Layer ◽

Bilayer Films ◽

Silicon Nitride Films ◽

Small Deflection ◽

Equivalent Bending Stiffness

ABSTRACTThe present work further develops the microbridge testing method to characterize mechanical properties of bilayer thin films. A closed-form formula for deflection versus load under small deflection is derived with consideration of the substrate deformation and residual stress in each layer. The analysis shows that the solution for bending a bilayer beam is equivalent to that for bending a single-layer beam with an equivalent bending stiffness, an equivalent residual force and a residual moment. One can estimate the Young's modulus and residual stress in a layer if the corresponding values in the other layer are known. The analytic results are confirmed by finite element calculations. The microbridge tests are conducted on low-temperature-silicon oxide (LTO)/silicon nitride bilayer films as well as on silicon nitride single-layer films. All microbridge specimens are prepared by the microfabricating technique. The tests on the single-layer films provide the material properties of the silicon nitride films. Then, applying the proposed method for bilayer films under small deflection yields the Young's modulus of 37 GPa and the residual stress of -148 MPa for LTO films.

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Direct influence of residual stress on the bending stiffness of cantilever beams

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2011.0662 ◽

2012 ◽

Vol 468 (2145) ◽

pp. 2595-2613 ◽

Cited By ~ 9

Author(s):

M. X. Shi ◽

B. Liu ◽

Z. Q. Zhang ◽

Y. W. Zhang ◽

H. J. Gao

Keyword(s):

Residual Stress ◽

Finite Element ◽

Cantilever Beam ◽

Intermolecular Forces ◽

Bending Stiffness ◽

Direct Influence ◽

Theoretical Predictions ◽

Calculation Results ◽

Geometry Nonlinearity ◽

First Time

Although the cantilever beam has been widely used as a sensor to measure various physical quantities, important issues such as how residual stress affects its bending stiffness and what are the underlying physical origins have not been fully understood. We perform both theoretical analyses and finite-element simulations to demonstrate for the first time that without changing the material tangent stiffness, residual stress within the beam can directly influence the bending stiffness of the beam. This direct influence arises from two origins: geometry nonlinearity and Poisson’s ratio effect. For a cantilever beam with adsorbed macromolecules on its surfaces, we find that longer macromolecular chains have lower normal stiffness and larger intermolecular forces, which makes the effect of the residual stress more pronounced. The excellent agreement between our theoretical predictions and finite-element calculation results validate our analysis. The present work provides an important framework for improving the sensitivity of a cantilever beam as a sensor.

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Investigation on the influence of the equivalent bending stiffness of the thin-walled parts on the machining deformation

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-018-2987-5 ◽

2018 ◽

Vol 101 (5-8) ◽

pp. 1171-1182 ◽

Cited By ~ 3

Author(s):

Bianhong Li ◽

Hanjun Gao ◽

Hongbin Deng ◽

Hai Pan ◽

Baoguo Wang

Keyword(s):

Bending Stiffness ◽

Machining Deformation ◽

Equivalent Bending Stiffness ◽

Thin Walled

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A machining deformation control method of thin-walled part based on enhancing the equivalent bending stiffness

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-020-05585-3 ◽

2020 ◽

Vol 108 (9-10) ◽

pp. 2775-2790

Author(s):

Bianhong Li ◽

Hanjun Gao ◽

Hongbin Deng ◽

Chao Wang

Keyword(s):

Control Method ◽

Bending Stiffness ◽

Deformation Control ◽

Machining Deformation ◽

Equivalent Bending Stiffness ◽

Thin Walled

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Correlation between Flexural Crack and Impedance Signal of Circular Steel Tube Beam

Korean Society of Hazard Mitigation ◽

10.9798/kosham.2020.20.5.225 ◽

2020 ◽

Vol 20 (5) ◽

pp. 225-231

Author(s):

Jong-Won Lee

Keyword(s):

Structural Characteristics ◽

Damage Index ◽

Steel Tube ◽

Bending Stiffness ◽

Structural Safety ◽

Analysis Model ◽

Damage Indices ◽

Circular Steel Tube ◽

Equivalent Bending Stiffness ◽

Cracked Beams

It is necessary to develop a technique that can be used to estimate cracks, which indicates a typical type of damage, using sensors to achieve the structural safety of circular steel-tube structural members widely used in infrastructures. Impedance techniques have been actively investigated to detect local damage, such as cracks. The cracks were estimated by experimentally investigating the relationship between the cracks and impedance signals using a damage index. The aim of this study is to investigate the correlation between the change in impedance signal and the change in the analytically obtained equivalent bending stiffness of cracked beams owing to crack formation and propagation in a circular steel-tube beam. In other words, the impedance signal was measured while gradually inducing cracking in circular steel-tube cantilever beams, two damage indices were obtained, and the results were compared with the analytically obtained equivalent bending stiffness of cracked beams constructed using an energy method. It was found that a close correlation between both the damage index for the impedance signal and equivalent bending stiffness for the crack location and the size of each damage case existed. Based on this correlation, the structural characteristics of the current state of a structure can be evaluated more accurately using the damage estimation results, and the behavior of the structure can be predicted using the analysis model.

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Bending properties of stainless steel dynamic compression plates and limited contact dynamic compression plates

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.1055/s-0038-1632677 ◽

2001 ◽

Vol 14 (02) ◽

pp. 64-68 ◽

Cited By ~ 6

Author(s):

C. M. Hill ◽

T. Kageyama ◽

M. G. Conzemius ◽

G. K. Smith ◽

F. M. Little

Keyword(s):

Stainless Steel ◽

Fracture Healing ◽

Bending Strength ◽

Dynamic Compression ◽

Bending Stiffness ◽

Four Point Bending ◽

Plate Size ◽

Equivalent Bending Stiffness ◽

The Difference ◽

Strength And Stiffness

SummaryThe equivalent bending stiffness and bending strength of the stainless steel DCP and stainless steel LC-DCP were compared. Three plates, of each size, were tested destructively in ‘four point bending’. All of the LC-DCP were significantly less stiff and less strong than the comparable size DCP, with the exception of the 4.5 mm narrow LC-DCP which was significantly stronger and more stiff than the 4.5 mm narrow DCP (p <.01). The design advantages of the LC-DCP are ease and versatility of plate application and improved cortical blood flow which one assumes promotes fracture healing. Also, the lower recorded stiffness of the LC-DCP may be advantageous in that it decreases the stress protection of the plated bone. Since optimal strength and stiffness of bone plates are currently unknown, the clinical relevance of the decreased strength and stiffness of the LC-DCP has yet to be determined.Stainless steel LC-DCP and DCP of various sizes were tested in four point bending to ascertain equivalent bending stiffness and bending strength of each type of plate. The LC-DCP were consistently less stiff and strong than their DCP counterparts (p <.01) with the exception of the 4.5 mm Narrow LC-DCP which was stronger and more stiff than the 4.5 mm Narrow DCP. In general, as plate size increased. the difference between the two plate designs decreased. If it can be shown that there is not any detrimental effect on fracture healing, the design features of the LC-DCP make it a desirable choice for most fracture applications.

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