Inter-diffusion analysis of joint interface of tungsten–rhenium couple

The diffusive properties of mesophilic methanogenic granular sludge have been studied using diffusion analysis by relaxation time separated pulsed field gradient nuclear magnetic resonance (DARTS PFG NMR) spectroscopy. NMR measurements were performed at 22°C with 10 ml granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Spin-spin relaxation (T2) time measurements indicate that three 1H populations can be distinguished in methanogenic granular sludge beds, corresponding to water in three different environments. The T2 relaxation time measurements clearly differentiate the extragranular water (T2 ≈ 1000 ms) from the water present in the granular matrix (T2 = 40-100 ms) and bacterial cell associated water (T2 = 10-15 ms). Self-diffusion coefficient measurements at 22°C of the different 1H-water populations as the tracer show that methanogenic granular sludge does not contain one unique diffusion coefficient. The observed distribution of self-diffusion coefficients varies between 1.1 × 10−9 m2/s (bacterial cell associated water) and 2.1 × 10−9 m2/s (matrix associated water).

Download Full-text

Influence of surface roughness, friction coefficient, and wrap angle on clinching joint strength and its correlation with belt friction phenomenon

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/13506501211025362 ◽

2021 ◽

pp. 135065012110253

Author(s):

Santosh Kumar ◽

Vimal Edachery ◽

Swamybabu Velpula ◽

Avinash Govindaraju ◽

Sounak K. Choudhury ◽

...

Keyword(s):

Surface Roughness ◽

Friction Coefficient ◽

Joint Strength ◽

Joint Interface ◽

Cross Sectional ◽

Lap Shear ◽

Mathematical Correlation ◽

Mechanical Clinching ◽

Wrap Angle

Clinching is an economical sheet joining technique that does not require any consumables. Besides, after its usage, the joints can be recycled without much difficulty, making clinching one of the most sustainable and eco-friendly manufacturing processes and a topic of high research potential. In this work, the influence of surface roughness on the load-bearing capacity (strength) of joints made by the mechanical clinching method in cross-tensile and lap-shear configuration is explored. Additionally, a correlating mathematical model is established between the joint strength and its surface parameters, namely, friction coefficient and wrap angle, based on the belt friction phenomenon. This correlation also explains the generally observed higher strength in lap-shear configuration compared to cross-tensile in clinching joints. From the mathematical correlation, through friction by increasing the average surface roughness, it is possible to increase the strength of the joint. The quality of the thus produced joint is analyzed by cross-sectional examination and comparison with simulation results. Experimentally, it is shown that an increment of >50% in the joint strength is achieved in lap-shear configuration by modifying the surface roughness and increasing the friction coefficient at the joint interface. Further, the same surface modification does not significantly affect the strength in cross-tensile configuration.

Download Full-text

Transient liquid phase bonding of Cu and Al using metallic particles interlayers

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture ◽

10.1177/0954405420988235 ◽

2021 ◽

pp. 095440542098823

Author(s):

Alireza Zaheri ◽

Mohammadreza Farahani ◽

Alireza Sadeghi ◽

Naser Souri

Keyword(s):

Liquid Phase ◽

Mechanical Test ◽

Transient Liquid Phase ◽

Transient Liquid Phase Bonding ◽

Joint Interface ◽

Test Results ◽

X Ray Diffraction ◽

X Ray ◽

Metallic Particles ◽

Powder Interlayer

The bonding strength, and microstructures of Cu and Al couples using metallic powders as interlayer during transient liquid phase bonding (TLP bonding) were investigated. The interfacial morphologies and microstructures were studied by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. First, to explore the optimum bonding time and temperature, nine samples were bonded without interlayers in a vacuum condition. Mechanical test results indicated that bonding at 560°C in 20 min returns the highest bond strength (84% of Al). This bonding condition was used to join ten samples with powder interlayers. Powders were prepared by mixing different combinations of Cu, Al (+Fe nanoparticles) and Zn. In the bonding zone, different Cu9Al4, CuAl, and CuAl2 intermetallic co-precipitate. The strongest bonding is formed in the sample with the 70Al (+Fe)-30Cu powder interlayer. Powder interlayers present thinner and more uniform intermetallic layers at the joint interface.

Download Full-text

Finite Element Modeling of Residual Stress at Joint Interface of Titanium Alloy and 17-4PH Stainless Steel

Metals ◽

10.3390/met11040629 ◽

2021 ◽

Vol 11 (4) ◽

pp. 629

Author(s):

Nana Kwabena Adomako ◽

Sung Hoon Kim ◽

Ji Hong Yoon ◽

Se-Hwan Lee ◽

Jeoung Han Kim

Keyword(s):

Residual Stress ◽

Finite Element ◽

Stainless Steel ◽

Finite Element Modeling ◽

Equivalent Stress ◽

Stress Gradient ◽

Joint Interface ◽

Element Modeling ◽

Actual Experiment ◽

Maximum Equivalent Stress

Residual stress is a crucial element in determining the integrity of parts and lifetime of additively manufactured structures. In stainless steel and Ti-6Al-4V fabricated joints, residual stress causes cracking and delamination of the brittle intermetallic joint interface. Knowledge of the degree of residual stress at the joint interface is, therefore, important; however, the available information is limited owing to the joint’s brittle nature and its high failure susceptibility. In this study, the residual stress distribution during the deposition of 17-4PH stainless steel on Ti-6Al-4V alloy was predicted using Simufact additive software based on the finite element modeling technique. A sharp stress gradient was revealed at the joint interface, with compressive stress on the Ti-6Al-4V side and tensile stress on the 17-4PH side. This distribution is attributed to the large difference in the coefficients of thermal expansion of the two metals. The 17-4PH side exhibited maximum equivalent stress of 500 MPa, which was twice that of the Ti-6Al-4V side (240 MPa). This showed good correlation with the thermal residual stress calculations of the alloys. The thermal history predicted via simulation at the joint interface was within the temperature range of 368–477 °C and was highly congruent with that obtained in the actual experiment, approximately 300–450 °C. In the actual experiment, joint delamination occurred, ascribable to the residual stress accumulation and multiple additive manufacturing (AM) thermal cycles on the brittle FeTi and Fe2Ti intermetallic joint interface. The build deflected to the side at an angle of 0.708° after the simulation. This study could serve as a valid reference for engineers to understand the residual stress development in 17-4PH and Ti-6Al-4V joints fabricated with AM.

Download Full-text

Effect of Creep on the Residual Stresses in Tube-to-Tubesheet Joints

ASME 2010 Pressure Vessels and Piping Conference: Volume 3 ◽

10.1115/pvp2010-25005 ◽

2010 ◽

Author(s):

Nor Eddine Laghzale ◽

Abdel-Hakim Bouzid

Keyword(s):

Contact Pressure ◽

Analytical Model ◽

Nuclear Power ◽

Structural Integrity ◽

Environmental Safety ◽

Maintenance Cost ◽

Joint Interface ◽

Plant Safety ◽

Material Creep ◽

Nuclear Power Plant Safety

Steam generators are the subject of major concern in nuclear power plant safety. Within these generators, in addition to the structural integrity, the gross tightness barrier, which separates the primary and secondary circuits, is primarily ensured by the presence of a residual contact pressure at the tube-to-tubesheet joint interface. Any leakage is unacceptable, and its consequences are very heavy in terms of the human and environmental safety as well as maintenance cost. Some studies have been conducted to understand the main reasons for such a failure. However, no analytical model able to predict the attenuation of the residual contact pressure under the effect of material creep relaxation behavior. The development of a simple analytical model able to predict the change of the residual contact pressure as a function of time is laid out in this paper. The results from the analytical model are checked and compared with those of finite elements.

Download Full-text

The Interface Microstructure and Shear Strength of Sn2.5Ag0.7Cu0.1RExNi/Cu Solder Joints under Thermal-Cycle Loading

Metals ◽

10.3390/met9050518 ◽

2019 ◽

Vol 9 (5) ◽

pp. 518 ◽

Cited By ~ 1

Author(s):

Congcong Cao ◽

Keke Zhang ◽

Baojin Shi ◽

Huigai Wang ◽

Di Zhao ◽

...

Keyword(s):

Shear Strength ◽

Fracture Mechanism ◽

Thermal Cycle ◽

Solder Joints ◽

Joint Interface ◽

Interface Microstructure ◽

Average Thickness ◽

Thermal Cycles ◽

Initial State ◽

Cycle Loading

The interface microstructure and shear strength of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints under thermal-cycle loading were investigated with scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and physical and chemical tests. The results show that an intermetallic compound (IMC) layer of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints evolved gradually from the scalloped into larger wavy forms with increasing number of thermal cycles. The roughness and average thickness of IMC increased with thermal-cycle loading. However, at longer thermal-cycle loading, the shear strength of the joints was reduced by about 40%. The fracture pathway of solder joints was initiated in the solder seam with ductile fracture mechanism and propagated to the solder seam/IMC layer with ductile-brittle mixed-type fracture mechanism, when the number of thermal cycles increased from 100 to 500 cycles. By adding 0.05 wt.% Ni, the growth of the joint interface IMC could be controlled, and the roughness and average thickness of the interfacial IMC layer reduced. As a result, the shear strength of joints is higher than those without Ni. When compared to joint without Ni, the roughness and average thickness of 0.05 wt.% Ni solder joint interface IMC layer reached the minimum after 500 thermal cycles. The shear strength of that joint was reduced to a minimum of 36.4% of the initial state, to a value of 18.2 MPa.

Download Full-text

Spectral Diffusion Analysis of Intravoxel Incoherent Motion MRI in Cerebral Small Vessel Disease

Journal of Magnetic Resonance Imaging ◽

10.1002/jmri.27149 ◽

2020 ◽

Vol 51 (4) ◽

Author(s):

Sau May Wong ◽

Walter H. Backes ◽

Gerhard S. Drenthen ◽

C. Eleana Zhang ◽

Paulien H.M. Voorter ◽

...

Keyword(s):

Small Vessel Disease ◽

Cerebral Small Vessel Disease ◽

Spectral Diffusion ◽

Small Vessel ◽

Intravoxel Incoherent Motion ◽

Vessel Disease ◽

Diffusion Analysis ◽

Motion Mri

Download Full-text

Comparative Study of Copper Brazing with Ag-Cu-Zn and Ag-Cu-P Filler in Heat Treatment Furnace

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.937.154 ◽

2014 ◽

Vol 937 ◽

pp. 154-157 ◽

Cited By ~ 1

Author(s):

Rong Wang ◽

Ya Juan Jin

Keyword(s):

Heat Treatment ◽

Eutectic Structure ◽

Copper Surface ◽

Joint Interface ◽

Heat Treatment Furnace ◽

Wetting Ability ◽

Treatment Furnace ◽

Brazed Joints ◽

And Diffusion ◽

Better Than

Wetting and spreading ability of Ag-Cu-Zn filler and Ag-Cu-P filler on copper surface under heat treatment furnace was studied. The microstructures of brazed joints of Ag-Cu-Zn and Ag-Cu-P filler under the same parameter were also observed. The microstructure shows that the wetting ability of Ag-Cu-Zn filler on the copper surface is better than Ag-Cu-P and its structure is uniformed and regulated. It is founded that there were obvious dissolution and diffusion between base metal and filler for the copper/Ag-Cu-Zn/copper joint, there were white and black eutectic structure formed in the joint interface.

Download Full-text