Metal Plasticity Research Articles

Influence of Denture Cleansers on the Retention Loss of Attachment Systems Retained Implant Overdenture.

This study aimed to evaluate the effects of different denture cleansing solutions (DCSs) on the retention of Locator and Locator R-Tx attachment systems of implant retained overdentures (IRO). Two part acrylic resin blocks were fabricated, upper part contained metal housing and plastic inserts and lower part contained implant analogs and abutments. Eighty pink plastic inserts (40/attachment, 10/solution) were immersed in Corega, Fittydent, sodium hypochlorite, and water for a time simulating upto 1-year of clinical usage. Acrylic blocks were held on a universal testing machine for a pull-out test to record the dislodgement force. Measurements were conducted after 6 months (T1) and 12 months (T2). One-way ANOVA followed by Tukey's HSD test was used to analyze the results (α = 0.05). For both attachments, retention significantly decreased after immersion in different solutions at T2 (P < 0.001). Locator R-Tx attachment in NaOCl showed a significant decrease in retention compared with other solutions at T1. At T2, there was a significant decrease in retention for all DCS compared with water (P < 0.001). Locator R-TX showed higher retention values per solution compared to Locator attachment (P < 0.001). In terms of retention loss %, NaOCl recorded the highest (61.87%) loss, followed by Corega (55.54%) and Fittydent (43.13%), whereas water demonstrated the best retention (16.13%) in both groups. Locator R-TX has better retention with different DCS immersion. The loss of retention varied with different types of DCS and NaOCl recorded the highest retention loss. Therefore, denture cleanser selection must be guided by the type of IRO attachment.

The Correlation of LVI Parameters and CAI Behaviour in Aluminium-Based FML.

An experimental analysis of mechanical behaviour for aluminium-based fibre metal laminates under compression after impact was conducted. Damage initiation and propagation were evaluated for critical state and force thresholds. Parametrization of laminates was done to compare their damage tolerance. Relatively low-energy impact had a marginal effect on fibre metal laminates compressive strength. Aluminium-glass laminate was more damage-resistant than one reinforced with carbon fibres (6% vs. 17% of compressive strength loss); however, aluminium-carbon laminate presented greater energy dissipation ability (around 30%). Significant damage propagation before the critical load was found (up to 100 times the initial damaged area). Damage propagation for assumed load thresholds was minor in comparison to the initial damage size. Metal plastic strain and delaminations are dominant failure modes for compression after impact.

Modification of Polyamide 66 for a Media-Tight Hybrid Composite with Aluminum

Metal-plastic composites are becoming increasingly important in lightweight construction. As a combination, e.g., for transmission housings in automobiles, composites made of die-cast aluminum housings and Polyamide 66 are a promising material. The interface between metal and plastic and the properties of the plastic component play an important role with regard to media tightness against transmission oil. The mechanical properties of the plastic can be matched to aluminum by glass fibers and additives. In the case of fiber-reinforced plastics, the mechanical properties depend on the fiber length and their orientation. These structural properties were investigated using computer tomography and dynamic image analysis. In addition to the mechanical properties, the thermal expansion coefficient was also investigated since a strongly different coefficient of the joining partners leads to stresses in the interface. Polyamide 66 was processed with 30 wt% glass fibers to align the mechanical and thermal expansion properties to those of aluminum. In contrast to the reinforcement additives, an impact modifier to improve the toughness of the composite, and/or a calcium stearate to exert influence on the rheological behavior of the composite, were used. The combination of the glass fibers with calcium stearate in Polyamide 66 led to high stiffnesses (11,500 MPa) and strengths (200 MPa), which were closest to those of aluminum. The coefficient of thermal expansion was found to be 6.6 × 10-6/K for the combination of Polyamide 66 with 30 wt% glass fiber and shows a low expansion exponent compared to neat Polamid 66. It was detected that the use of an impact modifier led to less orientated fibers along the injection direction, which resulted in lower modulus and strength in terms of mechanical properties.

Computational modeling of tension behaviors of metal matrix composites with particle network architecture

Rigid powders as the second phase in the conventional metal matrix composites (MMCs) are usually uniform and random, but recently powders dispersed with some special architectures to form configuration composites would yield a remarkable enhancement in the stiffness, strength and toughness as well. In this work, FE investigation was performed on tension behaviors of MMCs with network architectures to understand their dependences on particle volume fraction, particle size, network thickness and morphology. With the aid of the Gurson’s porous metal plasticity theory, the void nucleation rate acted as an internal state variable to monitor the development of micro-cracks in the metal matrix. The impedance effect of particle network architectures on the propagation of micro-cracks was interpreted in stark contrast to that in uniform MMCs, whereby their particular strengthening and toughening mechanisms were clarified. The present study would be helpful to the guidance in designing advanced MMCs with superior comprehensive properties.

Specimen geometry design for plasticity and fracture characterization of sheet metal under high testing speed and various stress states

To model a vehicle crash event using the finite element (FE) method, accurate material properties of automotive sheet metals at high strain rates and various stress states need to be known. In this paper, a series of specimen geometries were designed for dynamic tensile tests in a servo-hydraulic tensile machine to get rid of the system ringing effect. These specimen geometries, which consist of different Stress triaxialities and Lode angle parameters, were optimized according to a similar physical principle as that used for the Gen. III specimen of Fang and Grams using FE simulations. Oscillation-free forces were obtained during the high-speed tests in the strain rate range of up to 103 s−1 using specimens that have a novel design. The deformation and local strain fields of the specimens were measured using digital image correlation (DIC) techniques. Furthermore, the deformation and fracture behavior of a micro-alloyed steel (H340) were characterized and analyzed. The determination of the model parameters for plasticity, damage/fracture modeling, and the material’s strain-rate dependency could be conducted more accurately based on the improved oscillation-free force measurements, which resulted in an improved prediction of the plasticity and fracture behavior of the investigated steel.

Effect of Heat Input on the Microstructure and Mechanical Properties of Local Dry Underwater Welded Duplex Stainless Steel

Duplex stainless steel welded metals were underwater local dry prepared on S32101 lean duplex stainless steel trapezoidal groove plates with a self-made drain cover employing Supercore 2205P flux-cored filler wire. Different heat inputs were employed to investigate the effects on mechanical characteristics and the microstructure of welded metals. The results demonstrated that as the heat was applied, austenite concentrations in the weld metals increased. It was found that the austenite concentration and the fraction of Σ3-austenite twin-grain boundaries followed the same trends. With increasing heat input, the recrystallized ferrite and austenite grains initially decreased and subsequently increased, whereas the fraction of interphase boundaries between special ferrite and austenite exhibited the reverse trend. With a heat input of 1.4 kJ/mm, the toughness and plasticity of the weld metals were enhanced by an increase in austenite content, Σ3 recrystallized grains, and austenite twin-grain boundaries. The plasticity and tensile strength values of the welded metal changed more when the heat input was raised from 1.0 to 1.2 kJ/mm than when it was raised from 1.2 to 1.4 kJ/mm. Considering energy conservation, it is recommended to adopt 1.2 kJ/mm for welding heat input.

In-situ three-dimensional X-ray investigation on micro ductile fracture mechanism of a high-Mn steel with delayed necking effect

This study investigates the micro ductile fracture mechanism of a high-Mn steel with delayed necking effect (DN-HMn steel) under monotonic tension. A random-oriented micro-grain structure cooperating with intragranular twins in the DN-HMn steel contributes to its high tensile strength of 880 MPa and high uniform elongation of over 55%, accounting for 92.8% of the total elongation. Three-dimensional (3D) visualization of the ductile fracture process is presented, and characteristics of void evolution are identified. It was observed that voids distribute and grow uniformly during deformation, with larger voids forming a double-helix spatial distribution pattern at high strain levels, which fits the principal shear stress trajectory. The number and volume of voids in the DN-HMn steel showed a significant increase, with the porosity increasing from 0.071‰ (initial state) to 1.580‰ (before fracture). Intervoid necking was found to be the mode of void coalescence, which occurred close to the necking strain of the sample. The DN-HMn steel demonstrated a significant volume expansion of 4.58% throughout the elongation process, which breaks the volume conservation law of classical metal plasticity theory. This study opens new perspectives for understanding the ductile fracture mechanism of this steel.

Mechanical metamaterials made of freestanding quasi-BCC nanolattices of gold and copper with ultra-high energy absorption capacity

Nanolattices exhibit attractive mechanical properties such as high strength, high specific strength, and high energy absorption. However, at present, such materials cannot achieve effective fusion of the above properties and scalable production, which hinders their applications in energy conversion and other fields. Herein, we report gold and copper quasi-body centered cubic (quasi-BCC) nanolattices with the diameter of the nanobeams as small as 34 nm. We show that the compressive yield strengths of quasi-BCC nanolattices even exceed those of their bulk counterparts, despite their relative densities below 0.5. Simultaneously, these quasi-BCC nanolattices exhibit ultrahigh energy absorption capacities, i.e., 100 ± 6 MJ m−3 for gold quasi-BCC nanolattice and 110 ± 10 MJ m−3 for copper quasi-BCC nanolattice. Finite element simulations and theoretical calculations reveal that the deformation of quasi-BCC nanolattice is dominated by nanobeam bending. And the anomalous energy absorption capacities substantially stem from the synergy of the naturally high mechanical strength and plasticity of metals, the size reduction-induced mechanical enhancement, and the quasi-BCC nanolattice architecture. Since the sample size can be scaled up to macroscale at high efficiency and affordable cost, the quasi-BCC nanolattices with ultrahigh energy absorption capacity reported in this work may find great potentials in heat transfer, electric conduction, catalysis applications.

A Review of Recent Patents on Metal Precision Plastic Forming Technology

Background: Precision plastic forming technology has become an important development direction of advanced manufacturing technology because of its remarkable characteristics of high yield, high quality, and low consumption. Compared with traditional forming technology, it not only improves the utilization rate of metal materials, but also strengthens the dimensional accuracy of the workpiece. Therefore, the development trend of metal plastic precision forming technology has been paid increasing attention. Objective: To meet the increasing requirement of processing quality and processing efficiency in the metal precision plastic forming technology, metal cold precision plastic forming technology, metal warm precision plastic forming technology, metal thermal precision plastic forming technology and metal composite precision plastic forming technology is being improved continuously. Methods: This paper reviews the current various representative patents related to metal cold precision plastic forming technology, metal warm precision plastic forming technology, metal thermal precision plastic forming technology, and metal composite precision plastic forming technology. Results: Through investigating a large number of patents on metal precision plastic forming, metal cold precision plastic forming technology, metal warm precision plastic forming technology, metal thermal precision plastic forming technology and metal composite precision plastic forming technology are discussed. Conclusion: The optimization of metal precision plastic forming is conducive to increasing processing efficiency and processing quality. More relevant patents will be invented in the future.

Static and Time-Dependent Plasticity of Monolithic Metal–Organic Frameworks

Mechanical properties of monolithic metal–organic frameworks (MOFs), especially static and time-dependent plasticity, are essential to the mechanical stability of their device applications. In this study, the hardness and elastic moduli of monoZIF-8 and monoUiO-66 MOFs were compared and analyzed in terms of formation enthalpy, topological structure, and crystal defects formed during sol–gel synthesis. For the first time, the creep behaviors of monoUiO-66 and monoZIF-8 were investigated using nanoindentation. The stress exponent n values for creep were calculated to be about 9 and 40 for monoUiO-66 and monoZIF-8, respectively, implying grain boundary sliding (GBS, n = 2) between nanocrystals is unlikely to occur. The suspected absence of GBS was also supported by the identical creep behavior of monoZIF-8 and a ZIF-8 single crystal. Small activation volumes V* determined for monoUiO-66 (0.721–0.839 nm3) and monoZIF-8 (1.29–2.54 nm3) correspond to only 2–3 intrinsic pores in the MOF frameworks, indicating that pore collapse is probably the predominant creep mechanism.

Prevalence, Perpetrators, and Factors Associated With Intimate Partner Violence Among Adolescents Living in Urban Slums of Kampala, Uganda.

Intimate partner violence (IPV) poses a public health burden, yet few studies have assessed co-existence of physical, emotional, and sexual IPV among adolescents. We assessed recent IPV victimization and associated factors and described IPV patterns and perpetrators among young people from urban slums in Kampala, Uganda. We conducted a prospective cohort study among 14 to 19-year-old individuals enrolled from March 2019 to March 2020 and followed quarterly for 12 months. We collected data on socio-demographics, sexual behavior, and substance use through interviews. Recent IPV victimization was documented at all visits if a participant reported experiencing physical, emotional, and/or sexual IPV in the past 3 months. Baseline factors associated with recent IPV victimization were determined using multivariable logistic regression. We enrolled 490 adolescents (60.6% female) with median age 18 years (Interquartile range (IQR) 17-18 years), 91.0% had less than secondary level education. Females mainly engaged in sex work (17.5%) and selling fruits/snacks (9.1%) while males commonly earned from sale of metal scrap or plastic waste (28.5%), 41% reported ≥10 life-time sexual partners, 16.1% were high-risk alcohol drinkers and 34.9% used illicit drugs in the past 3 months. Overall, 27.8% reported recent IPV victimization (20.0% females) with emotional IPV being common (17.8%). At baseline, recent IPV victimization was associated with high-risk alcohol consumption (adjusted odds ratio [aOR] 2.57; 95% confidence interval [CI] [1.44, 4.58]), reported paid sex in the past 3 months (aOR 1.82; [1.02, 3.22]) and being separated (aOR 2.47; [1.29, 4.73]). Recent IPV victimization declined from baseline to month 9 and increased at month 12 visits which coincided with the COVID-19 pandemic. IPV victimization is high among young people living in urban slums with emotional IPV being prevalent. IPV interventions are needed and should also address excessive alcohol consumption.

Axisymmetric model for Taylor impact test and estimation of metal plasticity using nonlinear deformation profile

Axisymmetric model for Taylor impact test and estimation of metal plasticity using nonlinear deformation profile

Mechanistically informed artificial neural network model for discovering anisotropic path-dependent plasticity of metals

The plasticity of metals involves various complicated phenomena that have not been fully discovered or explained by existing theories. The data-driven method provides a new avenue that is different from the traditional methodology and extends the existing understanding of the constitutive behavior of metals. This study proposes an artificial neural network (ANN) model informed by mechanistic features to discover anisotropic path-dependent plasticity. The proposed framework imposed physical and numerical constraints of the constitutive law on a neural network with good interpretability and reliability. The modified return-mapping algorithm was combined with the ANN using an automatic differential technique, where a sub-fully connected neural network was employed to predict the elastoplastic tangent stiffness to ensure the stability of the plastic flow. Moreover, a yield function constructed using a fully connected neural network was adopted for anisotropic and path-dependent yields. The influence of the number of hidden layers and neurons on the final accuracy was also investigated. A metamaterial representative volume element was created to produce sufficient stress–strain response data for the learning purpose of the neural network. After proper training, the proposed method successfully revealed its hidden anisotropic yield and hardening behavior. A comparison with the traditional yield function was also performed using finite element simulations.

Enhanced strength and ductility in a powder metallurgy Ti material by the oxygen scavenger of CaB6

• There exists a continuous oxide layer on the irregular HDH Ti powder surface. • CaB 6 addition promotes the improved sintered density and refines the grain size. • The scavenging of O by CaB 6 addition makes a high strength and superior ductility for α-Ti alloy. The challenge of producing a high-ductility titanium (Ti) material using inexpensive high-oxygen hydride-dehydride (HDH) Ti powder is hereby addressed by the incorporation of CaB 6 oxygen-scavenger. The oxygen-scavenging behaviour, microstructure evolution, mechanical behavior and improvement mechanism were systematically investigated. A continuous TiO 2 oxide layer with a thickness of approximately 9.3 nm is presented on the HDH Ti powder surface. The oxide layer will dissolve into Ti matrix during sintering, making the increase of c / a value and leading to the Ti-Ti bonds developing from plastic metal bonds toward brittle covalent bonds. The CaB 6 addition can scavenge O impurity and make a significant increase in tensile ductility for α-Ti matrix. A small addition of 0.2 wt.% CaB 6 provides a superior tensile elongation of 22.2% for Ti material, almost three times as high as that of pure Ti (7.5%). The increase of deformation twining activity and grain refinement are responsible for the improved ductility. Furthermore, the CaB 6 oxygen-scavenger can react with the surface oxide layer to in-situ form rod-like TiB and granular CaTiO 3 reinforcements, refining the coarse near equiaxed grain of α-Ti matrix into fine equiaxed crystals. The multiple mechanisms of grain-boundary strengthening, load-bearing strengthening of TiB and Orowan strengthening of CaTiO 3 nanoparticles work together to increase the tensile strength of Ti/CaB 6 composites. This work offers an effective method to fabricate high-performance Ti material using inexpensive high-oxygen HDH Ti powder.

Finite Element-Based Performance Analysis of Encased Composite Columns under Monotonic Axial Compression Load

This paper presents the results of an investigation into the performance of fully encased composite columns under monotonic axial load using finite element simulation. The damage characteristics and the performance investigation of the specimen were mainly focused on the influence of the compressive strength of concrete and the size of reinforcement. The concrete material was modeled using concrete damage plasticity (CDP), which incorporates the hardening and softening behaviors, and the steel was modeled using metal plasticity. The results obtained from the current study were validated by using previously conducted experimental work and manual calculation based on Eurocode 4. According to the FEA result, damage to the concrete matrix was significantly minimized with the increase in the strength of the concrete. By keeping other parameters constant, an increase in longitudinal reinforcement diameter minimizes the equivalent plastic strain both in structural steel and reinforcement bars. Furthermore, the results showed that the numerical simulation fairly validated the analytical solution.

Seismic performance of precast column-beam joint with artificial plastic hinge

To improve the seismic performance and repairability of precast structures, an artificial plastic hinge (APH) was proposed for precast beam-column joint. The proposed APH was made from a combination of steel and high-strength-concrete (HSC), and the AHP will dissipates energy through metal plastic deformation when the earthquake occurs. To carry out the research, three full-scale beam-column joints were designed and fabricated, including one cast-in-place joint and two precast joints with APH. By using hysteretic loads, the seismic performance of joint was examined. For more systematic research, the finite element models were established and verified, and the parameter analysis was carried out. The findings demonstrate that the proposed joint performs well in terms of ductility and energy dissipation. It is recommended to use 12 mm steel plate thickness in the actual design, and to ensure the number of connecting bolts to avoid connection damage under earthquake. Through design optimization, the damage to the APH will be revealed at the location of the replaceable steel components, so as to achieve rapid repair after the earthquake.

On the acoustic method of control of spatial inhomogeneity of plastic deformation of weakly anisotropic orthotropic materials

In this paper, the possibilities of using non-destructive acoustic control to determine the features of the spatial distribution of local plastic deformations during deformation of flat samples made of AMg61 alloy were investigated. The methodological features of using the acoustic anisotropy parameter to study the patterns of changes in spatial inhomogeneities of the field of local plastic deformations are analyzed. A computational and experimental method for determining the acoustic anisotropy parameter is proposed, which allows to correctly determine not only its magnitude, but also the directions of the local axes of acoustic anisotropy. The sources of errors of the proposed methodology, the limits of its applicability, as well as the requirements for hardware and software for its implementation are analyzed. The results of experimental studies carried out on samples of weakly anisotropic aluminum alloy AMg61 are compared with the representations of autowave mechanics of plasticity of metals. An engineering algorithm for determining the early localization of zones of loss of stability during plastic deformation of samples is proposed. The possibility of creating a methodology for assessing the plasticity resource of a material during its plastic shaping is shown.

Stress-Invariants-Based Anisotropic Yield Functions and Its Application to Sheet Metal Plasticity

The yield criterion, or so-called yield function, plays an important role in the study of the plastic working of a sheet because it governs the plastic deformation properties of the sheet during the plastic-forming process. In this paper, we propose a novel anisotropic yield function useful for describing the plastic behavior of various anisotropic sheets. The proposed yield function includes the anisotropic version of the second stress invariant J2 and the third stress invariant J3. The proposed yield function can explain the anisotropic plastic behavior of various sheets by introducing the parameters α and β and also exhibits both symmetrical and asymmetrical yield surfaces. The parameters included in the proposed model were determined with an optimization algorithm from uniaxial and biaxial experimental data under a proportional loading path. In this study, the validity of the proposed anisotropic yield function was verified by comparing the yield surface shape, normalized uniaxial yield stress value, and Lankford anisotropic coefficient R-value derived from the experimental results. Applications of the proposed anisotropic yield functions to an aluminum sheet showed symmetrical yielding behavior and, to pure titanium sheets, showed asymmetric yielding behavior; thus, it was shown that the yield curve and yield behavior of various types of sheet materials can be predicted reasonably by using the proposed new yield anisotropic function.

Effect of metal supply during forging on loading of drive elements of lever radial forging machine

In order to find the values of the loads acting on the drive elements of the radial forging machine (RFM), the problem for determining of the forging force of bars with different feeds using the method of joint solution of approximate equations of equilibrium and plasticity of metal in the deformation zone is considered. A system of differential equations describing the dynamics of the drive of the lever RFM is compiled, and the solution is implemented. The results obtained allow us to determine the parameters of lever RFM for performing of specific tasks of plastic metal working.

Metal structures as the basis of architectural design

The article is devoted to the role of metal structures in solving the architectural and artistic image of the facility. If earlier metal structures were associated with industrial facilities, facilities of engineering or transportation infrastructure, in modern architecture metal structures create an architectural image in absolutely any type of buildings and facilities. New technologies and changes in the metal itself contribute to the creation of memorable images. Four main techniques for using metal structures have been identified. The first technique is the traditional solution in the form of a load-bearing metal frame in the building structure, when all the metal is hidden. Most high-rise buildings in the world are built according to this scheme. The second technique is open metal structures, which are the main architectural details of facades and the entire architectural and planning solution, such as the Bird's Nest Stadium in Beijing. The third technique is when the metal itself serves more of a decorative function. The metal plasticity and the surface finishes versatility contribute to the creation of memorable images. The fourth technique is metal structures for large-span structures that work for both the interior space of the facility and its exterior perception.