Effect of Mo addition on residual stress and mechanical properties of SiC ceramic/Nb521 alloy joints brazed by using AgCuTi filler

Fiber prestressing during matrix curing can significantly improve the mechanical properties of fiber-reinforced polymer composites. One primary reason behind this improvement is the generated compressive residual stress within the cured matrix, which impedes cracks initiation and propagation. However, the prestressing force might diminish progressively with time due to the creep of the compressed matrix and the relaxation of the tensioned fiber. As a result, the initial compressive residual stress and the acquired improvement in mechanical properties are prone to decline over time. Therefore, it is necessary to evaluate the mechanical properties of the prestressed composites as time proceeds. This study monitors the change in the tensile and flexural properties of unidirectional prestressed glass fiber reinforced epoxy composites over a period of 12 months after manufacturing. The composites were prepared using three different fiber volume fractions 25%, 30%, and 40%. The results of mechanical testing showed that the prestressed composites acquired an initial increase up to 29% in the tensile properties and up to 32% in the flexural properties compared to the non-prestressed counterparts. Throughout the 12 months of study, the initial increase in both tensile and flexural strength showed a progressive reduction. The loss ratio of the initial increase was observed to be inversely proportional to the fiber volume fraction. For the prestressed composites fabricated with 25%, 30%, and 40% fiber volume fraction, the initial increase in tensile and flexural strength dropped by 29%, 25%, and 17%, respectively and by 34%, 26%, and 21%, respectively at the end of the study. Approximately 50% of the total loss took place over the first month after the manufacture, while after the sixth month, the reduction in mechanical properties became insignificant. Tensile modulus started to show a very slight reduction after the fourth/sixth month, while the flexural modulus reduction was observed from the beginning. Although the prestressed composites displayed time-dependent losses, their long-term mechanical properties still outperformed the non-prestressed counterparts.

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Residual Stresses in Intrinsic UD-CFRP-Steel-Laminates - Experimental Determination, Identification of Sources, Effects and Modification Approaches

Materials Science Forum ◽

10.4028/www.scientific.net/msf.825-826.369 ◽

2015 ◽

Vol 825-826 ◽

pp. 369-376 ◽

Cited By ~ 5

Author(s):

Robert Prussak ◽

Daniel Stefaniak ◽

Christian Hühne ◽

Michael Sinapius

Keyword(s):

Mechanical Properties ◽

Residual Stress ◽

Tensile Strength ◽

Epoxy Composite ◽

Thermal Residual Stress ◽

Fiber Metal Laminates ◽

Fiber Metal ◽

Impact Energies ◽

The Impact ◽

Specific Impact

This paper focuses on the reduction of process-related thermal residual stress in fiber metal laminates and its impact on the mechanical properties. Different modifications during fabrication of co-cure bonded steel/carbon epoxy composite hybrid structures were investigated. Specific examinations are conducted on UD-CFRP-Steel specimens, modifying temperature, pressure or using a thermal expansion clamp during manufacturing. The impact of these parameters is then measured on the deflection of asymmetrical specimens or due yield-strength measurements of symmetrical specimens. The tensile strength is recorded to investigate the effect of thermal residual stress on the mechanical properties. Impact tests are performed to determine the influence on resulting damage areas at specific impact energies. The experiments revealed that the investigated modifications during processing of UD-CFRP-Steel specimens can significantly lower the thermal residual stress and thereby improve the tensile strength.

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Study on Welding Deformation and Residual Stress of H-Section Beam Based on Finite Element Method

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.753.305 ◽

2017 ◽

Vol 753 ◽

pp. 305-309 ◽

Cited By ~ 1

Author(s):

Xu Lu

Keyword(s):

Mechanical Properties ◽

Residual Stress ◽

Finite Element ◽

Source Parameters ◽

Welding Process ◽

Steel Structure ◽

Bottom Plate ◽

Welding Deformation ◽

Element Simulation ◽

Main Components

The welding H-section beam has good mechanical properties with its superior structure. So they become the main components of steel structure and have been widely used. In this paper, the welded H-section beam is used as the research object. The finite element simulation model is established. The heat source parameters are determined. The deformation of the steel due to the welding process is studied. The results show that the bottom plate and the bottom plate inward bending is about 2.32mm cause by welding process. The residual stress can reach 400MPa.

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

MRS Proceedings ◽

10.1557/proc-657-ee5.19 ◽

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.

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Influence of Steel Grain Size on Residual Stress in Grinding Processing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.2389 ◽

2010 ◽

Vol 638-642 ◽

pp. 2389-2394 ◽

Cited By ~ 3

Author(s):

Masahide Gotoh ◽

Katsuhiro Seki ◽

M. Shozu ◽

Hajime Hirose ◽

Toshihiko Sasaki

Keyword(s):

Mechanical Properties ◽

Residual Stress ◽

Grain Size ◽

Stress State ◽

Mechanical Grinding ◽

Fine Grained ◽

Residual Stress State ◽

Analysis Methods ◽

Average Grain Size ◽

Fine Grained Steels

The fine-grained rolling steels NFG600 and the conventional usual rolling steels SM490 were processed by sand paper polishing and mechanical grinding to compare the residual stress generated after processing. The average grain size of NFG600 and SM490 is 3 μm and 15μm respectively. Therefore improvement of mechanical properties for such fine-grained steels is expected, it is important to understand the residual stress state of new fine-grained materials with processing. In this study, multi axial stresses of two kinds of specimens after polishing and grinding were measured by three kinds of analysis methods including cos-ψ method. As a result, as for σ33, the stress of NFG was compression, though that of SM490 was tension.

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Effects of residual stress on the mechanical properties of plasma-sprayed thermal barrier coatings

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2013.08.016 ◽

2013 ◽

Vol 110 ◽

pp. 314-327 ◽

Cited By ~ 23

Author(s):

Xiancheng Zhang ◽

Makoto Watanabe ◽

Seiji Kuroda

Keyword(s):

Mechanical Properties ◽

Residual Stress ◽

Thermal Barrier Coatings ◽

Thermal Barrier ◽

Barrier Coatings ◽

Plasma Sprayed

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High-temperature mechanical properties and oxidation resistance of SiCf/SiC ceramic matrix composites with multi-layer environmental barrier coatings for turbine applications

Ceramics International ◽

10.1016/j.ceramint.2021.07.176 ◽

2021 ◽

Author(s):

Qing Hu ◽

Xin Zhou ◽

Yunwei Tu ◽

Xiangrong Lu ◽

Jingqi Huang ◽

...

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Oxidation Resistance ◽

Ceramic Matrix Composites ◽

Ceramic Matrix ◽

Matrix Composites ◽

Barrier Coatings ◽

Environmental Barrier Coatings ◽

High Temperature Mechanical Properties ◽

Sic Ceramic

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Minimization of the Local Residual Stress in 3D Flip Chip Structures by Optimizing the Mechanical Properties of Electroplated Materials and the Alignment Structure of TSVs and Fine Bumps

ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS and NEMS: Volume 1 ◽

10.1115/ipack2011-52063 ◽

2011 ◽

Author(s):

Kohta Nakahira ◽

Hironori Tago ◽

Fumiaki Endo ◽

Ken Suzuki ◽

Hideo Miura

Keyword(s):

Mechanical Properties ◽

Residual Stress ◽

Thermal Deformation ◽

Flip Chip ◽

Flexural Rigidity ◽

Three Dimensional ◽

Strain Gauges ◽

Copper Interconnection ◽

Induced Stress ◽

Alignment Structure

Since the thickness of the stacked silicon chips in 3D integration has been thinned to less than 100 μm, the local thermal deformation of the chips has increased drastically because of the decrease of the flexural rigidity of the thinned chips. The clear periodic thermal deformation and thus, the thermal residual stress distribution appears in the stacked chips due to the periodic alignment of metallic bumps, and they deteriorate the reliability of products. In this paper, the dominant structural factors of the local residual stress in a silicon chip are discussed quantitatively based on the results of a three-dimensional finite element analysis and the measurement of the local residual stress in a chip using stress sensor chips. The piezoresistive strain gauges were embedded in the sensor chips. The length of each gauge was 2 μm, and an unit cell consisted of 4 gauges with different crystallographic directions. This alignment of strain gauges enables to measure the tensor component of three-dimensional stress fields separately. Test flip chip substrates were made by silicon chip on which the area-arrayed tin/copper bumps were electroplated. The width of a bump was fixed at 200 μm, and the bump pitch was varied from 400 μm to 1000 μm. The thickness of the copper layer was about 40 μm and that of tin layer was about 10 μm. This tin layer was used for the rigid joint formation by alloying with copper interconnection formed on a stress sensing chip. The measured amplitude of the residual stress increased from about 30 MPa to 250 MPa depending on the combination of materials such as bump, underfill, and interconnections. It was confirmed that both the material constant of underfill and the alignment structure of fine bumps are the dominant factors of the local deformation and stress of a silicon chip mounted on area-arrayed metallic bumps. It was also confirmed experimentally that both the hound’s-tooth alignment between a TSV (Through Silicon Via) and a bump and control of mechanical properties of electroplated copper thin films used for the TSV and bump is indispensable in order to minimize the packaging-induced stress in the three-dimensionally mounted chips. This test chip is very effective for evaluating the packaging-process induced stress in 3D stacked chips quantitatively.

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