Compressive Plastic Deformation Research Articles

Experimental Investigation of Quasi-Static and Dynamic Impact Resistance in Thin Wood Veneer Laminates

The incorporation of sustainability into the design of transport vehicles has become increasingly important in recent years. A low carbon footprint makes wood-based structures attractive to replace other lightweight materials such as aluminum or fiber-reinforced plastics. This paper investigates and compares the static and dynamic impact behavior of thin Beech wood veneer laminates in standardized mechanical tests. The results obtained from Quasi-Static Indentation (QSI) and dynamic Low-Velocity Impact (LVI) tests reveal similarities and differences with regard to load vs. displacement behavior, damage mechanisms, permanent deformation, and energy absorption. While yield strength and damage modes are comparable in both test cases, it is found that the bending stiffness is strain-rate sensitive. Plastic deformation in compression is identified as the governing mechanism for energy absorption. These results can guide the design of sustainable wood-based structures for future transport applications where a thorough understanding of impact and crashworthiness is important.

Pressure Indicator Composite Films via Compressive Deformation of a Translucent Matrix Containing a Contrasting Filler.

A neglected mechanism for pressure-responsive color change is demonstrated using cellulose acetate composites prepared by direct (solvent) immersion annealing (DIA), with different loadings of activated charcoal filler. Namely, compressive plastic deformation of the translucent cellulose acetate leads to a decrease in the optical path length and a concomitant increase in the visibility of the opaque contrasting filler. Composites bearing 1-7 wt% activated charcoal exhibited a linear relationship between applied pressure and resulting pressure mark brightness in the range of 12-56 MPa. Comparison of pressure mark patterns with cross-sectional scanning electron microscopy (SEM) supports the importance of the porous morphology arising from DIA for the tuning of the pressure indicator sensitivity. A simple ball drop test is used to illustrate the robustness and utility of these indicators in optical impact assessment.

Compressive mechanical response and microstructures in low strain rate plastic deformation of stainless steel 316L fabricated by selective laser melting

Characterization of the mechanical properties plays an essential role in the post-processing and evaluation of the functionality of the additively manufactured metallic parts. A number of studies have been focused on the tensile properties of additively manufactured metals. However, the quasi-static compression test of the additively manufactured 316L blocks with different heat-treatment conditions and scanning strategies seems to be overlooked in the literature. This paper aims to provide a comprehensive study of compressive mechanical response in plastic deformation of SS316L fabricated by selective laser melting (SLM). The mechanical response and microstructures in compressive deformation is analyzed for three printing strategies with 0°-, 90°- and 67.5°- scanning and three heat treatment conditions (450 °C for 3 h, 1100 °C for 1 h with furnace cool and 1100 °C for 1 h with water quenching) for selective laser melted (SLMed) stainless steel 316L in comparison with wrought stainless steel 316L in this work. Alteration of mechanical properties, microstructure evolution and compressive deformation mechanism is studied. Melt pool features are not significantly affected by low-temperature heat treatment (450 °C for 3 h) but fully dissolved through high-temperature heat treatment (1100 °C for 1 h). High-temperature heat treatment provides a higher resistance to compressive plastic deformation for SLMed 316L compared with the low-temperature heat-treated and as-built samples where more twinnings are observed. The compressive plastic deformation mechanism of 90°- and 67.5°-scanning samples is similar, which mainly results from twinning-induced plasticity. For 0°-scanning samples, the strong crystallographic texture is the main cause of anisotropic deformation. Modelling and simulation have been conducted to explain the anisotropic deformation mechanism of the 0°-scanning strategy. Simulation results suggest that the morphology difference of laser-scanning tracks and melt pools, which leads to material flow along the laser scanning direction, explains the anisotropic deformation mechanism.

Largely enhanced compressive strength and plastic deformation of Fe-doped all-d-metal heusler alloy Cr2CoV

The structure dynamic stability, magnetic property, strength, and plastic deformation of all-d-metal Heusler alloys Cr2Co1-xFexV (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) have been investigated in this study. It is found that Cr2Co1-xFexV alloys tend to crystalize in the XA-type Heusler phase. The atomic radius becomes the decisive factor in determining the lattice size. With the increase of Fe concentration, the interaction between Cr(B)-Fe atoms increases, resulting in the increase of Curie temperature. The magnetic moments of the Cr2CoV and Cr2FeV are analyzed in conjunction with the theoretical calculations. The ductility and compressive strength of the materials gradually increase with the increase of Fe content. Especially in Cr2FeV alloy, a high compressive strength of up to 3050 MPa and a large ductility of up to 61% are achieved, and no fracture occurs, showing excellent mechanical properties. The electron localization function diagram shows that d-d orbital hybridization is formed and weak in Cr2CoV and Cr2FeV alloys, which helps to form metal bonds. Consequently, the ductility of the all-d-metal Heusler alloys was improved, which increased the fatigue life in practical application.

Effect of Strain Rate on Deformation Behaviors of Ti-12.1Mo -1Fe Metastable Beta Alloy

The addition of expensive elements to β titanium alloys, which are widely used in the aerospace and automobile industries, causes their price to increase. Low-cost, high-strength alloy (Ti-12.1Mo-1.0Fe) was designed in this study and the compressive behaviors of this alloy were evaluated for application to automobile parts, etc. As a result of ambient compression in the quasi-static and dynamic strain rate range (1×10<sup>-4</sup>/s~6×10<sup>3</sup>/s), twinning occurred at all strain rates, and in particular, adiabatic shear bands were observed, which cause cracks and fractures under dynamic strain rate conditions. In addition, when the relationship between these bands and mechanical characteristics was evaluated, an increase of compression strength and Vickers hardness was confirmed to occur, due to the strain rate hardening effect under compression loading. Some twins were formed by the deformation behavior during compression plastic deformation of the Ti-12.1Mo-1.0Fe alloy, and it exhibited excellent compression strength characteristics, showing a very high strain rate hardening effect at a high strain rate.

High compression strength pure tungsten fabricated by plasma arc additive manufacturing

Pure W were fabricated by wire plasma arc additive manufacturing technology (WPAAM) and systematically investigated in terms of the microstructure and mechanical property. The as-fabricated W exhibits large-size columnar grains along the deposition direction, and it has extremely few microcracks, compared with that fabricated by laser powder bed fusion (LPBF). The compression strength and compressive plastic deformation capability of WPAAM W are significantly improved compared to the widely studied LPBF W and the fine grained W fabricated by other processes. In particular, the strength of WPAAM W is comparable to that of ultrafine grained W. A microstructure-based predictive model of compressive strength is developed to understand the strength performance of AM W. The proposed model correlates the manufacturing process, microstructure and mechanical property of additive manufactured W. This study is expected to shed light in the development of additive manufacturing technology of refractory metals.

Uniaxial deformation of nanowires in 16 refractory multi-principal element alloys

Metallic nanowires are widely employed as small-scale structural materials due to their characteristically small volume and high strength compared with their bulk counterparts. Nowadays, the mechanical properties of nanowires in pure metals are well understood with the help of experiments and simulations. However, the deformation of nanowires in metallic alloys remains elusive. In recent years, a new class of alloys called refractory multi-principal element alloys (RMPEAs) emerged. RMPEAs are alloys that form solid solution phases and consist of three or more principal elements, most of which are refractory metals. In this paper, we perform atomistic simulations to investigate the uniaxial deformation of nanowires in 16 body-centered cubic RMPEAs. For each RMPEA, three nanowires consisting of atoms randomly distributed in three different ways are used. The main finding is that dislocation slips on {110} planes and twinning on {112} planes, respectively, control the compressive and tensile plastic deformation of the nanowires. To provide references, we also study the deformation of nanowires in natural and A-atom potential-based artificial pure metals. Results show that the deformation of RMPEA nanowires cannot be predicted by simply extrapolating from those of pure metal nanowires, highlighting the significance of directly simulating RMPEAs using multiple random atomic structures. It is also found that RMPEAs possess a reduced tension-compression asymmetry compared with pure metals, regardless of the underlying plastic deformation mechanism.

Late mechanical properties and energy evolution mechanism of cemented tailings backfill under early damage

Cemented tailings backfill (CTB) is a composite material prepared using cement, tailings and water. During early mining operation, CTB is inevitably subject to failure and damage caused by human or equipment crushing. However, the current literature is silent on the condition of the CTB after early damage. In this study, an analysis method of mechanical properties and failure models of early damaged CTB based on energy evolution was proposed which provided new ideas to reduce the failure and collapse analysis of CTB in mines. The results show that the early damage had significant effects on the late mechanical properties, energy evolution, failure model and microstructure of the CTB. Moderate early damage improved the later loading capacity of CTB. The UCS increased and then decreased in the late CTB at damage ages 3 d and 7 d, whereas it continued to decrease at ages of 14 d and 21 d. The early damage input energy was divided into releasable elastic deformation energy dominated by compression intensive deformation and plastic deformation energy dominated by damage deformation. The total energy after maintenance of the damaged CTB was the sum of the undamaged CTB energy and the early elastic deformation energy and then removed the plastic deformation energy. The late CTB failure model was from shear damage to tensile damage and then to mixed tensile-shear damage, which showed a certain damage effect. Combined with the economic benefits and the late mechanical properties of the damaged CTB, the CTB with a damage age of 7 d was more advantageous.

Analysis of the effects of isothermal aging and Laser Shock Peening on the flow properties, fatigue crack growth, and fracture toughness of Inconel 718

Laser Shock Peening (LSP) is a surface treatment that improves the fatigue life and fatigue strength of components by inducing a shallow layer that is characterized by compressive residual stress and plastic deformation. This study investigates the use of LSP on Inconel 718 (IN718) on the fatigue crack growth (FCG) and fracture toughness (FT) of as-received (AR), solution-treated (SOL), and samples aged for 0.5, 4, and 100 h. Experimental results on aged samples established that the hardness of samples 0.5 and 4 h increased due to the precipitation of γ′ and γ″ phases while in the 100 h sample the hardness decreases due to the presence of coarser γ″ phase and intergranular δ-phase. These microstructural features impacted the plastic flow behavior of the different samples which was adequately described using a two-fitting approach to the Voce equation. While thermal aging accelerated the FCG of aged samples, the plastic flow and residual stress induced by the LSP significantly reduces the effect of thermal aging, by reducing the FCG rate and increasing the FT of the IN718 aged samples. Finally, results from EBSD analysis showed that the LSP-induced plastic strain depends on the microstructural transformations that occurred during the aging treatment.

An Investigation of Compressive Creep Aging Behavior of Al-Cu-Li Alloy Pre-Treated by Compressive Plastic Deformation and Artificial Aging

In this paper, the effects of compressive pre-deformation and successive pre-artificial aging on the compressive creep aging behavior and microstructure evolution of the Al-Cu-Li alloy have been studied. Severe hot deformation mainly occurs near the grain boundaries during the compressive creep initially, which steadily extends to the grain interior. After that, the T1 phases will obtain a low radius-thickness ratio. The secondary T1 phases in pre-deformed samples usually only nucleate on dislocation loops or Shockley incomplete dislocations induced by movable dislocations during creep, which are especially prevalent in low plastic pre-deformation. For all pre-deformed and pre-aged samples, two precipitation situations exist. When pre-deformation is low (3% and 6%), solute atoms (Cu and Li) can be consumed prematurely during pre-aging at 200 °C, with dispersed coherent Li-rich clusters in the matrix. Then, the pre-aged samples with low pre-deformation no longer have the ability to form secondary T1 phases in large quantities during subsequent creep. When dislocation entangles seriously to some extent, a large quantity of stacking faults, together with a "Suzuki atmosphere" containing Cu and Li, can provide the nucleation sites for the secondary T1 phase, even when pre-aged at 200 °C. The sample, pre-deformed by 9% and pre-aged at 200 °C, displays excellent dimensional stability during compressive creep because of the mutual reinforcement of entangled dislocations and pre-formed secondary T1 phases. In order to decrease the total creep strain, increasing the pre-deformation level is more effective than pre-aging.

Dynamic mechanical properties and energy dissipation analysis of frozen sandstone with initial damage

Damaged rock masses on the slopes of open pit coal mines are prone to geological disasters such as landslides under low temperatures and dynamic loads such as blasting impacts. Based on the Low Temperature Split Hopkinson Pressure Bar (LT-SHPB) system, dynamic compressive tests were done on sandstone specimens, which were damaged by uniaxial loading and unloading test. Dynamic stress–strain curves and dynamic mechanical properties of frozen sandstone with initial damage were analyzed as well as the energy dissipation characteristics. The results indicate that both compressive state and plastic deformation state of the dynamic stress-strain curves increase with the increase of the damage value. Dynamic peak stress and dynamic elastic modulus exhibit an evident damage weakening effect while the dynamic peak strain, in contrast, exhibits a damage enhancement effect. In addition, all three dynamic mechanical properties of the damaged frozen sandstone exhibit an impact effect. The dissipation energy ratio and reflection energy ratio of frozen sandstone increase with the increase of initial damage value while the transmission energy ratio decreases. With the increase of initial damage value and strain rate, the energy utilization rate during the sandstone failure process increases, resulting in more small fragments and powders.

Mechanical behaviors of Tou-Kung in historic timber structures subjected to vertical load

This paper investigates the mechanical behaviors of Tou-Kung under the action of vertical loads. A 1/3.52 scaled model of intact Tou-Kung fabricated according to the Building Standards of the Qing Dynasty was carried out on vertical loading test. The failure modes, vertical load–displacement curves, and vertical stiffness analysis are analyzed. The results show that the main failure modes of Tou-Kung are the compressive splitting of Da-Tou and plastic compressive deformation of Qiao’s middle part along the radial direction. The vertical load–displacement curves of intact Tou-Kung can be divided into three stages: elastic, plastic, and hardening. In general, the vertical load and displacement of Tou-Kung increases as the loading progresses. And the vertical stiffness increases first, then decreases, and finally increases. On this basis, numerical simulation is used to investigate the effect of overall tilting on Tou-Kung’s mechanical behaviors. It can be found that the tilting of Tou-Kung significantly changes the load transferring path in Tou-Kung, and the stress distribution of Da-Tou and Qiao gradually changes from symmetry to asymmetry as the tilting angle increases. Furthermore, the stress in the embedded area between the Da-Tou and Qiao is the highest, which is consistent with the test results. The vertical load–displacement curves of all damaged FEMs show the same change trend. However, with the increase of tilting angle, the initial stiffness, ultimate load and ultimate stiffness decrease.

Improvement of hydrogen detection sensitivity of palladium film by in-plane compressive plastic deformation and application to hydrogen gas sensor

The hydrogen energy, which is environmentally friendly and does not emit carbon dioxide, has been attracting attention as an alternative fuel to the fossil fuel. In the shift to a hydrogen energy society, the highly sensitive hydrogen gas sensor has been required for the storage and management of hydrogen gas. In this study, we propose a film deposition method to induce the in-plane plastic deformation in the thin film and apply it to a hydrogen gas sensor, where the palladium film formed by this method is deposited on a thin quartz resonator. It is found that the sensor chip with the plastically deformed palladium film is about 1.5 times more sensitive than the conventional sensor chip and has high-speed response. The developed sensor is a novel device that can be used in an oxygen-free environment without any temperature compensation and constant heating.

Low-velocity impact (LVI) and post-impact fatigue properties of GLARE laminates with holes

The impact peak force and the post-impact maximum permanent displacement of GLARE laminates with double holes are predicted with the goodness of fit above 0.98 within the impact energy range of 5–30J. The normalized post-impact residual fatigue life decreases exponentially with the increase of impact energy and the post-impact maximum permanent displacement. DIC analysis shows that delamination and local deformation promote crack initiation between two holes and simultaneous initiation of multi cracks. The compressive plastic deformation in the dent center hinders the fatigue crack propagation. A multiple fatigue source failure mode is observed with the increase of impact energy.

Enhanced plasticity in laser additive manufactured Nb-reinforced bulk metallic glass composite

The microstructures and mechanical properties of 50 wt% Nb-reinforced Zr-based bulk metallic glass composites, (BMGCs), manufactured via laser directed energy deposition (LDED) with two different laser powers, P , are investigated and compared with those of LDED manufactured monolithic bulk metallic glass (BMG). Results show that both BMGCs have a multi-component microstructure that includes dual-sized Nb particles and devitrification-induced nano crystals at the melt-pool boundaries whereas the monolithic BMG contains only the latter. The nanocrystals at the melt-pool boundaries embrittle the LDED manufactured monolithic BMG, which reflects as a higher yield strength but negligible plastic deformation in uniaxial compression. In contrast, both BMGCs undergo significant plastic deformation as the Nb-reinforcements, besides improving plasticity by arresting propagating shear bands, reduces the enthalpy of relaxation, Δ H rel , of the matrix and decreases the volume fraction of the nanocrystallites, V nc , at the melt-pool boundaries. However, amongst the two, the BMGC manufactured at higher P exhibits much higher shear band plasticity, despite having higher V nc and lower Δ H rel . This is rationalized by analyzing the load transfer characteristics of the Nb-BMG matrix interfaces in the two BMGCs. • LDED manufactured Nb-reinforced Zr-based BMGCs have significantly improved plasticity. • Nb induced plasticity improvement is achieved through limiting the structural relaxation of amorphous matrix. • Higher thermal diffusivity of Nb can minimize the devitrification induced brittle phases and thus enhance plasticity. • Partially dissolving Nb in the amorphous matrix by sufficient laser power can maximize shear band arresting capabilities.

Heat treatment effects on microstructure and mechanical properties of TiZrNbTa high-entropy alloy

Microstructure and mechanical properties of TiZrNbTa high-entropy alloy (HEA) in the as-cast and annealed states are systematically investigated. The yield strength of TiZrNbTa HEA strongly depends on the heat treatment temperatures. With the increase of heat treatment temperature, the yield strength of TiZrNbTa increases first and then decreases. When the heat treatment temperature reaches 600 ℃, the yield strength and uniform strain of TiZrNbTa HEA are 1583 ± 55 MPa and 20.5% ± 1.8%, respectively. Compared with the as-cast state TiZrNbTa, the yield strength of TiZrNbTa HEA after simple heat treatment, i.e., 600 ℃ for 1 h improves by 47%, which is attributed to the spinodal decomposition strengthening. By comparing the contribution of grain boundary strengthening for the TiZrNbTa HEA before and after annealing, the significant decrease in the yield strength of the TiZrNbTa HEA is not caused by grain coarsening after heat treatment at 800 ℃, but by the formation of a vein-like phase in grain boundaries. The Ti(Zr)-rich and Nb(Ta)-rich phases in TiZrNbTa HEA exhibit different performances in large compressive strain conditions. The Ti(Zr)-rich phase exhibits good compressive plastic deformation ability, and the Nb(Ta)-rich phase has a higher strength. The TiZrNbTa HEA after one-step simple heat treatment displays excellent mechanical properties, which significantly improves the possibility of clinical application as a new orthopedic-implant alloy.

Water jet impact damage mechanism and dynamic penetration energy absorption of 2A12 aluminum alloy

This study aims to explore the waterjet cavitation impact (WCI) mechanism of 2A12 aluminum alloy and its dynamic penetration energy absorption after WCI treatment. The effects of WCI process parameters on the residual stress, surface quality, and microstructure of 2A12 aluminum alloy are investigated through experiment and simulation and, a dynamic penetration model of 2A12 aluminum alloy is established with ABAQUS software and finite element simulation is performed. The results show that WCI can greatly enhance the residual compressive stress of the target. Comprehensive evaluation of surface residual stress, surface quality, and plastic deformation layer reveals that a combination of small jet angle with large jet pressure, or large jet angle with medium jet pressure, delivers the best strengthening effect; the residual compressive stress and plastic deformation layer introduced by WCI can effectively increase the defensible performance of 2A12 aluminum alloy, making the projectile residual velocity far lower than before WCI treatment.

Local creep damage effects on subsequent low temperature fatigue crack growth behaviour of thick-walled pressure vessels

The influence of prior creep damage on the subsequent fatigue cracking behaviour of thick-walled pressure vessels has been thoroughly investigated in this study. Creep damage was introduced into fracture mechanics specimens by performing creep tests at 550 °C and stopping them after reaching a desired crack length. Using this experimental methodology, creep damage was successfully introduced ahead of the crack tip in the form of intergranular voids and microcracks. In order to assess the creep damage effects, in the absence of significant plasticity, on the structural integrity of thick-walled pressure vessels the material was uniformly pre-strained under compressive plastic deformation prior to the specimen manufacture, thus hardening the material. Fatigue tests were performed on specimens with and without creep damage and the results were compared with each other. Moreover, metallurgical investigations were conducted to understand the influence of microstructural damages, as a result of creep loading conditions, on the fatigue cracking behaviour of the material. The results from this study show a clear reduction in the fatigue cracking rate in the presence of creep damage local to the crack tip. The findings have been discussed in terms of the effects of static creep loading conditions and microstructural damages on the subsequent fatigue cracking behaviour under cyclic loading conditions.

Microstructure evolution and accelerated magnetocaloric phase formation of LaFe13.1Co0.7Si1.4 alloy by forging deformation at room temperature

In order to improve the preparation process and practical process of magnetic refrigerant, a method of accelerating phase formation by cold compression plastic deformation at room temperature is proposed. To determine the significance of this method, the grain structure, phase composition and magneto-thermal effects of LaFe13.1Co0.7Si1.4 alloy were systematically studied. The results show that with the increase of compression ratio, the number of grains per unit volume increases and the grain size tends to be uniform. Compared with the uncompressed sample, the proportion of magnetothermal phase in the pre-compressed samples increases after annealing under the same conditions. When the deformation is 40%, the ratio of 1:13 phase in pre-deformed sample after 1 day annealing is 72 vol%, which is significantly better than that of the undeformed sample. After annealing for 3 days, the Curie temperature (TC) of 40% pre-deformed LaFe13.1Co0.7Si1.4 samples is 330 K, and the magnetic entropy changes to − 4.70 J/kg K and − 5.42 J/kg K under 2 T and 3 T magnetic fields, respectively. The appropriate Curie temperature and value of ∆SM make it an attractive potential candidate for magnetic refrigeration application at room or even high temperature.

Elastodontic Devices in Orthodontics: An In-Vitro Study on Mechanical Deformation under Loading.

The purpose of the present study was to evaluate the mechanical resistance of elastodontic devices (ED): their maximum compression loads and plastic deformation under loading (percentage). An Instron universal machine (Model 3365, Instron, Industrial Product Group, Grove City, PA, USA) was employed with a 100 N load cell and with Bluehill software for loading analyses. Each device was submitted to a five-cycles test. The following ED were evaluated: A.M.C.O.P. (Micerium, Genova, Italy) in red color, in orange color, and in blue color; HealthyStart (Ortho-Tain, Winnetka, IL, USA), and T4K™ phase 1 (Myofunctional Research Co., Helensvale, Australia). During the five-cycles test, the Ortho-Tain device delivered the greatest compression load (7.56 N), with the lowest percentage of deformation (0.95%). For all devices, a slight plastic deformation of the material was registered, ranging from 0.95% to 1.75%. For the T4K device it was not possible to complete the five-cycles test. For all the analyzed ED, a slight plastic deformation under loading was registered, that in all cases can be considered clinically acceptable. Further studies are needed to test the appliances after clinical usage.