Évaliation of stress states and mechanical properties of rolled products using electromagnetic and ultrasonic methods

2004 ◽  
Vol 92 (3-4) ◽  
pp. 63-69
Author(s):  
E. Schneider
Keyword(s):  
Mechanical Properties ◽  
Ultrasonic Methods ◽  
Stress States

scholarly journals Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1099
Author(s):  
Qingqing Chen ◽  
Yuhang Zhang ◽  
Tingting Zhao ◽  
Zhiyong Wang ◽  
Zhihua Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Stress ◽  
Failure Criterion ◽  
Mesoscale Model ◽  
Fracture Behaviour ◽  
Descent Method ◽  
Triaxial Stress ◽  
Gradient Descent Method ◽  
Stress States ◽  
Shear Failures

The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states.

Measurements of Residual Stress in the Layers of Thin Film Micro-Gas Sensors

2000 ◽  
Vol 657 ◽  
Author(s):  
Youngman Kim ◽  
Sung-Ho Choo
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Residual Stress ◽  
Gas Sensor ◽  
Gas Sensors ◽  
Micro Gas Sensor ◽  
Thin Film Layer ◽  
Film Layer ◽  
The Difference ◽  
Stress States

ABSTRACTThe mechanical properties of thin film materials are known to be different from those of bulk materials, which are generally overlooked in practice. The difference in mechanical properties can be misleading in the estimation of residual stress states in micro-gas sensors with multi-layer structures during manufacturing and in service.In this study the residual stress of each film layer in a micro-gas sensor was measured according to the five difference sets of film stacking structure used for the sensor. The Pt thin film layer was found to have the highest tensile residual stress, which may affect the reliability of the micro-gas sensor. For the Pt layer the changes in residual stress were measured as a function of processing variables and thermal cycling.

scholarly journals Effect of Plastic Deformation on Elastic and Plastic Recovery in CP-Titanium

2016 ◽  
Vol 716 ◽  
pp. 891-896 ◽  
Author(s):  
Saber Khayatzadeh ◽  
Salah Rahimi ◽  
Paul Blackwell
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Elastic Modulus ◽  
Strain Relaxation ◽  
Sheet Material ◽  
Rolling Direction ◽  
Material Model ◽  
Dimensional Changes ◽  
Load Removal ◽  
Stress States

The springback associated with cold deep drawing of sheet metals leads to undesired dimensional changes in the final products. This is often due to the heterogeneous plastic deformation in different areas of the intended geometry that creates various stress states throughout the part. The major objective of this study is to understand the interconnection between springback, level of plastic deformation, degradation of elastic modulus and strain recovery in a CP-Ti material. The mechanical properties of the sheet material and the dependency of mechanical properties on directionality are investigated by examining samples from three orientations of parallel to the rolling direction (RD), at 45° to RD and perpendicular to RD. The degradation of elastic modulus as a function of level of plastic deformation was explored for 0° and 45° samples by conducting multi-step uniaxial loading-unloading in tension.The experimental results showed that the mechanical properties vary for each direction, with the lowest elastic modulus along RD. A significant degradation was observed in elastic modulus (up to 50% reduction) with increased plastic deformation. This resulted in more strain relaxation compared to that associated with the initial elastic modulus. For stresses below 100MPa, a nonlinear (plastic) recovery was observed, resulting in additional relaxation in the total strain upon load removal in each step of the interrupted tests. This plastic recovery behaviour is observed to be dependent on sample orientation. It is concluded that accurate prediction of springback during sheet metal forming, requires a material model which takes into accounts the directional degradation of elastic modulus and the plastic recovery as a function of plastic deformation.

Effect of Residual Stress on Mechanical Property of Monolithic Bulk Metallic Glass

2010 ◽  
Vol 654-656 ◽  
pp. 1050-1053
Author(s):  
Min Ha Lee ◽  
Joong Hwan Jun ◽  
Jürgen Eckert
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Metallic Glass ◽  
Cold Rolling ◽  
Bulk Metallic Glass ◽  
Metallic Glasses ◽  
Metallic Materials ◽  
Cyclic Compression ◽  
Stress States ◽  
Intrinsic Plasticity

Mechanical treatments such as deep rolling are known to affect the strength and toughness of metallic glass due to the residual stress. It is well known that compressive residual stress states usually enhance the mechanical properties in conventional metallic materials. We present investigations on the change of fracture behavior related with mechanical properties of “brittle” bulk metallic glass by cold rolling at room temperature. Improvement of the intrinsic plasticity is observed not only after constrained cyclic compression but also after cold rolling. Moreover, neither nanocrystallization nor phase separation occurs during deformation. By these findings we provide a unique fundamental basis by considering the introduction of structural inhomogeneity and ductility improvement in metallic glasses. The experimental evidence clearly supports that such an inhomogeneous glassy can be produced by residual stress in well known “brittle” bulk metallic glasses, and does not depend on a specific pinpointed chemical composition.

Changes in Surface Mechanical Properties Through Electrochemical Modifications

2001 ◽  
Vol 697 ◽  
Author(s):  
Martha M. McCann ◽  
Sean G. Corcoran
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Lattice Mismatch ◽  
High Vacuum ◽  
Lessons Learned ◽  
Ultra High Vacuum ◽  
Discrete Control ◽  
Dislocation Densities ◽  
Dislocation Behavior ◽  
Stress States

AbstractThe mechanical response of materials can be dramatically altered by the presence of absorbed species on the surface. An electrochemical environment enables discrete control of the surface, keeping it clean (comparable to ultra-high vacuum) and inducing stable stress states. Applying a potential to the surface alters surface charge, which changes the surface free energy. Oxides are easily added or removed. Utilizing the phenomenon of underpotential deposition (UPD), one monolayer of metal can be added to a surface. The degree of lattice mismatch between the metal and the deposited monolayer will also vary the stress state of the surface. The changes in the mechanical properties of these highly controlled surfaces are measured by in-situ nanoindentation at various potentials. Nanoindentation of single crystals with very low dislocation densities allows careful observation of dislocation behavior with applied load. This enables the identification of dislocation mechanisms by quantifying the changes in mechanical properties under specific environments. Au has been extensively studied in electrochemistry literature; it is well behaved and well characterized. It is a model system that has demonstrated variation in mechanical properties in different electrochemical states. Lessons learned on Gold have also been applied to Zn and Ni systems.

Mechanical Properties of Roller Compacted Concrete under Triaxial Stress State

2013 ◽  
Vol 351-352 ◽  
pp. 497-500
Author(s):  
Huai Liang Wang ◽  
Yu Qing Ren
Keyword(s):  
Mechanical Properties ◽  
Arch Dam ◽  
Direct Shear ◽  
Shear Tests ◽  
High Arch Dam ◽  
Triaxial Stress State ◽  
Arch Dams ◽  
Roller Compacted Concrete ◽  
Combined Loads ◽  
Stress States

Considering the true mechanical states of roller compacted gravity and arch dams, the strength experiments of the roller compacted concrete (RCC) specimens with two graded-aggregates made from a high arch dam are carried out. These specimens are of three kinds: body specimens, layer-treated specimens and layer-untreated specimens and the tests include direct shear and triaxial compressive-compressive-shear, tensile-compressive-shear tests. The shear strength of three kinds of specimens under different stress states is analyzed systematically. By regression of the tests results, respective failure criterions for RCC under different combined loads are proposed.

scholarly journals Measuring the effect of residual stress on the machined subsurface of Inconel 718 by nanoindentation

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245391
Author(s):  
Ling Chen ◽  
Qirui Du ◽  
Miao Yu ◽  
Xin Guo ◽  
Wu Zhao
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Inconel 718 ◽  
Material Model ◽  
Hardened Layer ◽  
Gradient Material ◽  
Material Surface ◽  
Inconel 718 Alloy ◽  
Finite Element Software ◽  
Stress States

Inconel 718 alloy is widely used in aero-engines and high-temperature environments. However, residual stress caused by processing and molding leads to an uneven distribution of internal pressure, which reduces the reliability of service process. Therefore, numerical simulation of the nanoindentation process was applied to evaluate the effect of residual stress on the machined subsurface of Inconel 718. A gradient material model of Inconel 718 was established in ABAQUS finite element software. Mechanical properties based on nanoindentation testing showed an influence of residual stress in combination with indenter geometry. The orthogonal experimental results show that under diverse residual stress states, the indenter’s geometry can affect the pile-up of the material surface after nanoindentation and significantly influence the test results. With increases in piling-up, the error caused by residual stress on the characterization of the mechanical properties of the hardened layer increases. Through the establishment of a numerical model, the influence of residual stress can be predicted within nanoindentation depths of 300 nm.

Micromachining of thin 3C-SiC films for mechanical properties investigation

2010 ◽  
Vol 1246 ◽  
Author(s):  
Jean-Francois Michaud ◽  
Sai Jiao ◽  
Anne-Elisabeth Bazin ◽  
Marc Portail ◽  
Thierry Chassagne ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Film Thickness ◽  
Young’S Modulus ◽  
Inductively Coupled Plasma ◽  
Defect Density ◽  
Young's Modulus ◽  
Cantilever Deflection ◽  
Inductively Coupled ◽  
Stress States ◽  
Sic Films

AbstractIn this work, the mechanical properties of cubic silicon carbide are explored through the analysis of the static and dynamic behavior of 3C-SiC cantilevers. The investigated structures were micro-machined using Inductively Coupled Plasma (ICP) etching of thin 3C-SiC films grown on silicon. The aim was to evaluate the influence of some basic parameters (film orientation, film thickness, defect density) on the mechanical properties of the material.X-Ray Diffraction was used to evaluate the crystalline quality of the epilayers. Scanning Electron Microscopy observations of static cantilever deflection highlight the major difference between the stress states of (100) and (111) oriented layers for which the intrinsic stresses are of opposite signs. The cantilever deflection is highly dependent on the film thickness, as stated for (100) oriented epilayers. The lowest deflection is obtained for the thickest layer. The Young's modulus of 3C-SiC is calculated from the resonance frequency of clamped-free cantilevers, measured by laser Doppler vibrometry. The relatively low and orientation independent value of Young's modulus (~350GPa) found on the samples is probably associated with the high defect density usually observed in very thin 3C-SiC films grown on Si.

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