scholarly journals High rate loading of hybrid joints in a Split Hopkinson Tension Bar

2018 ◽  
Vol 183 ◽  
pp. 02023
Author(s):  
Noah Ledford ◽  
Hanna Paul ◽  
Matti Isakov ◽  
Stefan Hiermaier
Keyword(s):  
High Rate ◽  
Static Properties ◽  
Aerospace Applications ◽  
Hybrid Joint ◽  
Lap Shear ◽  
Hybrid Joints ◽  
Split Hopkinson ◽  
Improved Performance ◽  
High Rate Loading ◽  
Split Hopkinson Tension Bar

Bonded joints are nowadays seen as one of the preferred joining methods in aerospace applications. However, the difficulty in certifying bond strength and the relatively low energy absorption capability of the joint are barriers to widespread adoption. The use of a hybrid joint, that is, the combination of a mechanical and a bonded joint, allows for a fail-safe design and offers improved performance of the joint. The quasi-static properties of hybrid joints have been investigated by a number of researchers. In contrast, the high rate loading regime has been only sparsely investigated. In this work, hybrid joints are tested in quasi-static and high rate loading in order to analyze their loading rate dependence. The hybrid joint studied is a composite-aluminum double lap shear joint with Sikaforce 7752 adhesive and Hi-Lite-315 countersunk titanium bolts. In order to quantitatively analyze the high rate behavior of the hybrid joints and their respective sub-components, additional tests are carried out on simply bonded and simply bolted specimens. The high rate characterization was performed with a Split Hopkinson Tension Bar. The main challenges for these tests are the relatively large specimen size and complex specimen geometry needed to properly characterize the joint behavior, which both are in contradiction with the assumptions of the classical Split Hopkinson Bar-analysis. In this paper we describe an approach to solve these challenges based on an elastic wave analysis of the system.

Modeling of multimaterial hybrid joints under high-rate loading

2020 ◽  
Vol 234 (5) ◽  
pp. 446-453
Author(s):  
Noah Ledford ◽  
Michael May
Keyword(s):  
Experimental Testing ◽  
Element Model ◽  
High Rate ◽  
Testing System ◽  
Bonded Joints ◽  
Loading Rates ◽  
Hybrid Joints ◽  
Split Hopkinson ◽  
Mixed Material ◽  
High Rate Loading

Joint failure plays a key role in determining structural stability and crash or impact response. Characterizing the joints at high loading rates is challenging as oscillations are often overlaid on the measured data, making interpretation of the results more difficult. This paper builds upon the experimental testing three different mixed-material joints using a split-Hopkinson tension bar. The correction proposed in this work is verified using a finite element model of the entire testing system. The modeling efforts also investigate the differences in a specimen only model and a model including the entire testing system. The failure mechanisms of bolted and bonded joints are investigated, where the substrate stress state is found to play a large role in determining the failure mode for bolted joints. This work lays the foundations needed to investigate the mixed-material bolted and bonded joints in detail.

Dynamic Tensile Response of Magnesium Nanocomposites

2014 ◽  
Vol 566 ◽  
pp. 56-60 ◽  
Author(s):  
Y. Chen ◽  
V.P.W. Shim ◽  
Manoj Gupta
Keyword(s):  
Yield Stress ◽  
Rate Sensitivity ◽  
High Rate ◽  
Strain Rates ◽  
Tensile Response ◽  
Az31 Mg Alloy ◽  
Split Hopkinson ◽  
Melt Deposition ◽  
High Rate Loading ◽  
Critical Resolved Shear Stress

AZ31-based magnesium nanocomposites were produced by a disintegrated melt deposition technique, whereby different volume fractions of 50-nm Al2O3 nanoparticles (1.0v%, 1.4v% and 3.0v%) were used as reinforcement and added to AZ31 Mg alloy. A monolithic counterpart was also produced by the same process for comparison. Samples of these materials were subjected to dynamic tension at strain rates up to 1.2 103 s-1, using a split-Hopkinson Bar device. Compared to the quasi-static response, the monolithic and composite materials showed significantly increased yield stress and ductility under dynamic loading. The enhancement in yield stress with strain rate indicates rate sensitivity of the critical resolved shear stress for slip systems under tension. The addition of nanoparticles was found to reduce the grain size of the resulting material and increase the yield stress and ductility simultaneously, for both low and high rate loading.

scholarly journals Investigation of joints from laser powder fusion processed and conventional material grades of 18MAR300 nickel maraging steel

2021 ◽  
Author(s):  
W. Tillmann ◽  
L. Wojarski ◽  
T. Henning
Keyword(s):  
Tensile Strength ◽  
Maraging Steel ◽  
Solid Material ◽  
High Volume ◽  
Heat Treatment Condition ◽  
Hybrid Joint ◽  
Hybrid Joints ◽  
Laser Systems ◽  
Conventional Material ◽  
The Individual

AbstractEven though the buildup rate of laser powder bed fusion processes (LPBF) has steadily increased in recent years by using more and more powerful laser systems, the production of large-volume parts is still extremely cost-intensive. Joining of an additively manufactured complex part to a high-volume part made of conventional material is a promising technology to enhance economics. Today, constructors have to select the most economical joining process with respect to the individual field of application. The aim of this research was to investigate the hybrid joint properties of LBPF and conventionally casted 18MAR300 nickel maraging steel depending on the manufacturing process and the heat treatment condition. Therefore, the microstructure and the strength of the hybrid joints manufactured by LPBF or vacuum brazing were examined and compared to solid material and joints of similar material. It was found that the vacuum-brazed hybrid joints using a 50.8-μm-thick AuNi18 foil provide a high tensile strength of 904 MPa which is sufficient for a broad field of application. Furthermore, the additively manufactured hybrid samples offered with 1998 MPa a tensile strength more than twice as high but showed a considerable impact of buildup failures to the strength in general.

scholarly journals Stress Transfer Mechanism of Flange in Split Hopkinson Tension Bar

2020 ◽  
Vol 10 (21) ◽  
pp. 7601
Author(s):  
Hyunho Shin ◽  
Sanghoon Kim ◽  
Jong-Bong Kim
Keyword(s):  
Stress Transfer ◽  
Transfer Mechanism ◽  
Explicit Finite Element ◽  
Impact Theory ◽  
Quantitative Basis ◽  
Split Hopkinson ◽  
One Step ◽  
The One ◽  
The Impact ◽  
Split Hopkinson Tension Bar

To reveal the stress transfer mechanism of the flange in a split Hopkinson tension bar, explicit finite element analyses of the impact of the hollow striker on the flange were performed across a range of flange lengths. The tensile stress profiles monitored at the strain gauge position of the incident bar are interpreted on a qualitative basis using three types of stress waves: bar (B) waves, flange (F) waves, and a series of reverberation (Rn) waves. When the flange length (Lf) is long (i.e., Lf > Ls, where Ls is the striker length), the B wave and first reverberation wave (R1) are fully separated in the time axis. When the flange length is intermediate (~Db < Lf < Ls, where Db is the bar diameter), the B and F waves are partially superposed; the F wave is delayed, then followed by a series of Rn waves after the superposition period. When the flange length is short (Lf < ~Db), the B and F waves are practically fully superposed and form a pseudo-one-step pulse, indicating the necessity of a short flange length to achieve a neat tensile pulse. The magnitudes and periods of the monitored pulses are consistent with the analysis results using the one-dimensional impact theory, including a recently formulated equation for impact-induced stress when the areas of the striker and bar are different, equations for the reflection/transmission ratios of a stress wave, and an equation for pulse duration time. This observation verifies the flange length-dependent stress transfer mechanism on a quantitative basis.

Simultaneous effects of strain rate and temperature on mechanical response of fabricated Mg–SiC nanocomposite

2019 ◽  
Vol 54 (5) ◽  
pp. 659-668 ◽  
Author(s):  
K Rahmani ◽  
GH Majzoobi ◽  
A Atrian
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
High Rate ◽  
Dynamic Tests ◽  
Hopkinson Pressure Bar ◽  
Compaction Temperature ◽  
Static Tests ◽  
Split Hopkinson ◽  
Pressure Bar

Mg–SiC nanocomposite samples were fabricated using split Hopkinson pressure bar for different SiC volume fractions and under different temperature conditions. The microstructures and mechanical properties of the samples including microhardness and stress–strain curves were captured from quasi-static and dynamic tests carried out using Instron and split Hopkinson pressure bar, respectively. Nanocomposites were produced by hot and high-rate compaction method using split Hopkinson pressure bar. Temperature also significantly affects relative density and can lead to 2.5% increase in density. Adding SiC-reinforcing particles to samples increased their Vickers microhardness from 46 VH to 68 VH (45% increase) depending on the compaction temperature. X-ray diffraction analysis showed that by increasing temperature from 25℃ to 450℃, the Mg crystallite size increases from 37 nm to 72 nm and decreases the lattice strain from 45% to 30%. In quasi-static tests, the ultimate compressive strength for the compaction temperature of 450℃ was improved from 123% for Mg–0 vol.% SiC to 200% for the Mg–10 vol.% SiC samples compared with those of the compaction at room temperature. In dynamic tests, the ultimate strength for Mg–10 vol.% SiC sample compacted at high strain rate increased remarkably by 110% compared with that for Mg–0 vol.% SiC sample compacted at low strain rate.

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