Optimization Of Mechanical Performance Research Articles

Counter-intuitive mechanical performance variation in aged low-temperature interconnections in electronic packaging

Different from the conventional aging induced continuous mechanical performance deterioration in solder joints, a counter-intuitive “decrease-increase-decrease” variation in shear strength with a peak value 12 MPa higher than the initial state was captured in aged low-temperature BGA structure Cu/Sn–58Bi/Cu solder joints. The first decrease in shear strength was dominated by the coarsening of Sn and Bi phases. The following increase in shear strength was rooted in the concurrent Bi subgrain strengthening, solid solution strengthening of Bi element in Sn-rich phase and precipitation strengthening induced by the Bi-rich phase particles. The eventual decrease in shear strength was ascribed to severely deteriorated interface between the solder matrix and intermetallic compound layer being the weaker site in the long time aged solder joint. This aging induced strengthening phenomenon is inspiring in mechanical performance optimization and reliability elevation of SnBi-based solder joints for the coming chiplet and heterogeneous integration packaging.

Mechanical Performance Optimization and Microstructural Mechanism Study of Alkali-Activated Steel Slag–Slag Cementitious Materials

The optimal proportion of alkali-activated steel slag–slag cementitious materials is investigated by considering the combined effects of steel slag content, alkali content, water glass modulus, and water–binder ratio using the Box–Behnken design in response surface methodology. Qualitative and semi-quantitative analyses of X-ray diffraction (XRD) patterns and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) images are conducted. The microstructural mechanism is elucidated based on the chemical composition, surface morphology, and microscale pore (crack) structures of the samples. A microreaction model for the alkali-activated steel slag and slag is proposed. The optimal composition for alkali-activated steel slag–slag cementitious materials is as follows: steel slag content, 38.60%; alkali content, 6.35%; water glass modulus, 1.23; and water–binder ratio, 0.48. The strength values predicted by the response surface model are p1d = 32.66 MPa, p7d = 50.46 MPa, and p28d = 56.87 MPa. XRD analysis confirms that the compressive strength of the sample is not only influenced by the amount of gel formed, but also, to a certain extent, by the CaCO3 crystals present in the steel slag, which act as nucleation sites. The SEM-EDS results confirm that the gel phase within the system comprises a hydrated calcium silicate gel formed through the reaction of volcanic ash and geopolymer gel formed through geo-polymerization. Analysis of the pore (crack) structure reveals that the compressive strength of the specimens is primarily influenced by porosity, with a secondary influence of the pore fractal dimension.

Sustainable Future: Development and Potential of Modern Timber Structures

The increasingly prominent issues of high energy consumption and carbon emissions brought about by traditional construction materials have led to the rapid emergence of modern timber structures as a sustainable alternative. This paper comprehensively analyzes the multiple advantages of timber construction, emphasizing its characteristics such as environmental friendliness, thermal insulation, seismic resistance, flexibility, and durability. The eco-friendliness of timber structures stems from wood being a renewable resource, and the construction process significantly reduces carbon footprint. Wood possesses certain flexibility and shock-absorbing capabilities, enabling it to dissipate energy during earthquakes and enhance the building's seismic resistance. Additionally, the design flexibility of modern timber structures allows their application in diverse complex scenarios to meet various demands. In timber structure design, optimization of mechanical performance remains crucial to ensure stability and safety. Implementing appropriate protective measures can prolong the service life of timber structures and ensure their safety in fire incidents. Numerous successful domestic and international cases demonstrate the feasibility of timber structures in various architectural contexts, highlighting their broad prospects for development. Particularly in China, the abundant potential of timber resources provides substantial opportunities for timber structure development. With advancing technology and accumulated experience, China's timber structure construction is poised to achieve significant breakthroughs. In summary, with its unique advantages, modern timber construction will continue to demonstrate its sustainable development value in areas including environmental friendliness, seismic resilience, and durability. It will play a crucial role in contributing to the sustainable development of future architecture.

Controllable precipitation behavior near grain boundaries enabled by artificial strain concentration in age-hardening aluminum alloys

Regulating the precipitation behavior in the vicinity of grain boundary (GB) is crucial for improving the mechanical property and corrosion resistance of age-hardening aluminum alloy. In this work, we innovatively propose a strain-concentration controlled strategy to realize the controllable fabrication of the thinner precipitate-free zone (PFZ), associated with the finer grain boundary precipitates in Al–Zn–Mg–Cu alloy. Specifically, the primary PFZ with certain solute atoms is introduced by short pre-aging treatment, followed by the subsequent cyclic deformation at room temperature to induce the localized plastic deformation in the primary PFZ. Compared with the traditional aging, the Al–Zn–Mg–Cu alloy treated by the current process manifests superior combination of impact toughness and corrosion properties, as well as the slightly improved unidirectional tensile properties. Furthermore, the atomic-scale mechanism of the unique precipitation behavior near GB is revealed using the molecular dynamics simulation. A large number of dislocations are generated in PFZ, which acts as the favorable precipitation sites and contribute to the secondary precipitates in the primary PFZ. The present work provides a novel design route and an atomic-scale understanding for controlling the precipitation behavior in the vicinity of GB, and it has the potential to direct the optimization of mechanical performance and corrosion resistance in a board spectrum of aging-hardening alloys.

Enhanced strength and ductility of high chromium cast iron/low carbon steel bimetal by heterostructure design

In this study, the heterostructured high chromium cast iron (HCCI)/low carbon steel (LCS) bimetal was designed by optimized heat treatment process. The microstructure, mechanical properties and deformation behavior of bimetal were studied. The bonding zone of HCCI/LCS bimetal is comprised of ferrite and pearlite, while the diffusion zone of HCCI mainly consists of M23C6 and ferrite due to the diffusion of C atoms from the HCCI to the LCS. The shear strength value of the bimetal is 395.2 MPa and no microcracks were observed at the interface. The tensile strength and total elongation of the bimetal are 452.1 MPa and 26.2 %, respectively. The analysis of the deformation behavior shows that the back stresses originate from the cooperative effect between the hard and soft zones, which improves the overall strength and ductility of the bimetal. In the deformed samples, large plastic deformations and stress concentrations were observed in the soft zones due to the dislocation were blocked in the hard zones, which confirmed the typical hetero-deformation induced (HDI) strengthening. The present work sheds light on heterostructure of HCCI/LCS bimetal that can be feasibly employed, and it could guide the optimization of mechanical performance of a wide range of fragile alloys for toughness engineering.

The microstructure and mechanical performance optimization of a new Fe-Ni-based superalloy for Gen IV nuclear reactor: The critical role of Nb alloying strategy

The effects of Nb alloying on microstructural evolution and mechanical performance of a newly developed solid-solution strengthened Fe-Ni-based superalloy, considered as the candidate material for high-temperature components manufacturing in fourth Generation (Gen IV) advanced nuclear reactor, were systematically investigated. The results show that the increase in the Nb content obviously increased the volume fraction and average size of MC carbides, and the MC carbides more preferentially distributed at grain boundaries. The average grain size and low Σ coincident site lattice (CSL) boundary exhibited a gradually decreased trend with increasing Nb content. Meanwhile, the thermal stability (grain size and grain boundary precipitation) of the alloy can be improved notably via Nb alloying. The tensile strength of Nb-alloyed alloys at 750 °C was enhanced significantly compared to that of Nb-free alloy, mainly due to the synergistic effect of solid-solution strengthening and fine grain strengthening. It was impressive that the variation of Nb content had no obvious influence on the yield strength, but gradually decreased the ultimate tensile strength. The detrimental effects of the decrease in Σ3 boundaries and intergranular precipitates were assumed to restrict the strengthening factors. The ductility of Nb-alloyed alloys decreased remarkably due to the changed dominant deformation mechanism from planar slip to wavy slip; however, it showed an increasing trend in high Nb-content alloys due to the occurrence of dynamic recrystallization and grain rotation. The present work establishes Nb alloying as an effective method to optimize the microstructure and mechanical properties of solid-solution strengthened Fe-Ni-based superalloys, and the appropriate Nb content is recommended to be controlled below 0.5 wt% for this alloy.

Optimization of Mechanical Performance of Seismic Isolation Bearings for Continuous Beam Bridges

Optimization of Mechanical Performance of Seismic Isolation Bearings for Continuous Beam Bridges

Optimization of mechanical performance of limestone calcined clay cement: Effects of calcination temperature of nanosized tubular halloysite, gypsum content, and water/binder ratio

Halloysite is a clay mineral that has a nanosized tubular morphology and high pozzolanic activity, and its calcination product can be used as a supplementary cementitious material in limestone calcined clay cement (LC3). In this study, the effects of the calcination temperature of halloysite, gypsum content, and water/binder (W/B) ratio on the mechanical properties and microstructures of LC3 were evaluated. The results demonstrated that halloysite calcined at the temperature of 650°C–850°C exhibited high pozzolanic activity: LC3 prepared using halloysite calcined above 650°C exhibited a shorter setting times and higher compressive strengths than those prepared with halloysite calcined at 550°C. This is attributable to the formation of more additional calcium aluminate silicate hydrate gel, and a larger amount of hemicarboaluminate and monocarboaluminate at higher temperatures than at lower temperatures, which results in more filling of pores in LC3 under the former conditions than the later conditions. The results also indicated that the optimum content of additional gypsum for LC3 was between 0 wt% and 2 wt%, and overdose gypsum did not substantially alter their setting times but decrease their compressive strengths. In contrast, a decrease in the W/B ratios decreased their setting times, total porosity, and increased their compressive strengths. Overall, in this study, LC3 prepared using halloysite calcined at 750°C, with a W/B ratio of 0.40 and without additional gypsum, exhibited the highest compressive strengths, which were 42.6, 51.7, and 57.1 MPa after 3, 7, and 28 days of curing, respectively. These findings deepen the research on the hydration mechanism of LC3 prepared with calcined halloysite and provide basic data for the wide application of this approach.

A novel dual-heterogeneous-structure ultralight steel with high strength and large ductility

A dual-heterogeneous structure with bimodal grain size distributions of both austenite and B2 phase was developed in a novel ultralight steel by a simple rolling and annealing process. Tensile test results show that the steel annealed at 900 °C (denoted as A900) exhibited the superb synergy of a high specific yield strength of 160.3 MPa g cm−3, a high tensile strength of 1300 MPa, a large ductility of 39.3% and a persistently high work hardening rate, which can be mainly attributed to the heterogeneous structures caused multi-level deformation mechanisms. Detailed microstructural analysis of the deformed A900 samples unveils that with an increase of strain, the plastic deformation of individual austenite grains was governed by different factors, i.e., grain size and Schmid factor (SF) at 4.2% and 9% strains and local stress at 25% strain, while the deformation of individual B2 grains was mainly regulated by grain size at 4.2%, grain size and SF at 9% strain and local stress in the late deformation stage, which leads to the consistently high work hardening rate and large elongation. In addition, owing to the hardness difference, a high density of geometrically necessary dislocations was observed near the interfaces of austenite/B2, which also contribute to the consistently high heterogeneous deformation-induced strengthening effect and thus the outstanding mechanical properties. The present work sheds light on the dual-heterogeneous structure of the ultralight steel that can be feasibly employed, and it could guide the optimization of mechanical performance of a wide range of alloys for lightweight engineering.

Examination of steel compatibility with additive manufacturing and repair via laser directed energy deposition

High strength steels are a vital material for aerospace applications but are also prone to damage from fatigue, corrosion, and wear. Additive manufacturing (AM) processes such as laser directed energy deposition (L-DED) offer a means for repairing both the geometry and structure of damaged steels; however, significant variation in tensile properties have been reported following repair. While previous studies have tried to improve performance through postdeposition heat treatment, such practices may not be possible for commercial parts due to risks of distortion and thermal damage to the substrate. Instead, this investigation analyses the role of the intrinsic heat treatment effect on as-deposited tensile properties through a detailed review of both AM and AM repair literature. By assessing a wide variety of high strength steels, the links between conventional heat treatment parameters and steel performance in AM are established, and the role of steel composition understood. This review is supported by additional AM and L-DED repaired samples, with consistent parameters used between steels to ensure similar thermal histories, and eliminate potential discrepancies seen between AM machines. The results demonstrate the effect of intrinsic heat treatment on martensitic and precipitation hardening steels, the role of residual heat and heat extraction through the substrate, and flag potential issues faced by steels at risk of temper embrittlement. Taken together, these findings provide a clear vision for the advancement of AM repair and the optimization of mechanical performance.

Optimization of Mechanical Performance for 3D Printed Kevlar and Carbon Fiber Composites

Kevlar is commercial brand of fibers supporting para-aramids of light weight for major part of composite. It is applicable in robotics and automobile sectors where parts need to possess high tensile strength and excellent fatigue resistance. Carbon fibers are processed by thermal conversion of organic fiber with low Carbon content such as polyacrylonitrile (PAN) which contain around thousands of filaments. In the current work, samples are produced through Mark Two 3D printer and subjected under investigation for improving mechanical performance in evaluating tensile, flexural and impact behavior as per ASTM Standards. The differentiation is presented by finding the error between experiment and simulation results.

Mechanical Performance Optimization in Spray-Based Three-Dimensional-Printed Mortar Using Carbon Fiber

From the perspective of the features of effective vertical and overhanging construction, the spray-based three-dimensional (S-3D) mortar printing technology has promoted the application of 3D printing in construction fields. Carbon fibers were used to optimize the mechanical performance of S-3D printed mortar. The effects of carbon fiber volume (0%, 0.5%, 1.0%, 1.5%, and 2.0%) and length (3 and 5 mm) on the working properties, printing accuracy, mechanical properties, and microstructural properties of the S-3D printed mortar were studied comprehensively. The test results showed that the S-3D printed mortar with the 1.5 vol% and 3 mm length carbon fiber (L3-V1.5 specimen) showed optimal printing accuracy in the single-layer and accumulative thickness tests. The S-3D printed L3-V1.5 mortar had the maximum flexural strength, which increased by 53.06% and 39.96% at 7 and 28 days, respectively, more than those of its cast counterparts. In addition, the S-3D printing process enhanced the interlayer bonding strength, and the ultimate interlayer splitting strength of the S-3D printed L3-V1.5 mortar increased by 2.16% and 3.33% at 7 and 28 days, respectively, more than those of the cast mortar without carbon fibers. The S-3D printing process improved the carbon fiber alignment and compactness and, thus, the mechanical properties of the S-3D printed mortar.

Influence of the graft-copolymerized hydrophilic lignin content on the structure and mechanical properties of gel-spun poly(vinyl alcohol) composite fibers

Lignin is a cost-effective, biobased filler for the fabrication of high-performance poly(vinyl alcohol) (PVA) composite fibers that increases fiber performance and sustainability. However, amorphous and hydrophobic lignin often have poor compatibility with semi-crystalline and hydrophilic PVA matrixes. Moreover, aggregation of the filler at high content could occur to impede the effectiveness of lignin as a reinforcing filler. To address these issues, modified organosolv lignin (OL24) with hydrophilicity was obtained from the graft copolymerization of organosolv lignin and acrylic acid monomers after 24 h of reaction and later used as a reinforcing filler at different ratios of 0%, 5%, 10%, 20% and 30% in PVA to achieve composite fibers with better compatibility between the filler and matrix, and enhanced sustainability. The influence of the graft-copolymerized hydrophilic lignin content on the structure and mechanical performance of gel-spun PVA composite fibers was fundamentally investigated. The results showed that 10% OL24/PVA fiber had outstanding mechanical properties with an average tenacity of 7.8 cN/dtex (tensile strength of 1.02 GPa), average specific modulus of 143.21 cN/dtex (Young’s modulus of 18.62 GPa) and toughness of 20.90 J/g. It was concluded that the higher orientation, larger crystal size and stronger hydrogen bonding in the composite fiber structure contributed to the good fiber mechanical performance. These results offer technical support for the mechanical performance optimization of lignin-reinforced polymeric high-performance fibers.

Hydroelastic analysis of double-segment floating sandwich structures under wave action

This study develops a structure-hydroelasticity coupling theoretical model to predict the dynamic response of double-segment floating sandwich structures, which are consisted of two steel panels and a honeycomb ultrahigh-performance concrete (UHPC) core layer. The meso-configuration of the honeycomb core is parametrized using the representative volume element (RVE) based on the three-dimensional finite element method, and the corresponding parameterized formulas associated with homogenized mechanical properties are developed. According to the homogenized model with meso-configuration parameters, a sixth-order elastic boundary condition on the floating sandwich structures is established. An analytical solution for water wave interaction with double-segment floating sandwich structures is derived, and the structural dynamic response and internal stress are directly calculated. As an example, representative floating segments are designed for smaller shear stress in the core, which relies on the interactivity of the meso- and macroscale characteristics, including sandwich features, honeycomb configurations, distributed segments and wave conditions. The structure-hydroelasticity coupled methodology has potential to achieve the mechanical performance optimization of floating structures.

Optimization of mechanical performance of a Bernoulli gripper based on the force characteristic curve synthesis method

PurposeThe Bernoulli gripper fixedly installed on the manipulator is subject to limitations such as a small-working region and poor anti-interference capacity. This paper aims to propose a novel Bernoulli gripper design that involves the connection of a positive stiffness component such as a spring in series, based on the force characteristic curve synthesis method, to optimize the mechanical performance.Design/methodology/approachThe proposed gripper is designed and manufactured. In the suction procedure, the force characteristic curve of the proposed gripper is theoretically and experimentally investigated. In the hovering detection procedure, a dynamic model of the manipulator-gripper-workpiece system is established, and an apparatus is set up to compare the displacements of the workpiece and the manipulator. The proposed gripper is finally applied in the lifting procedure, showing good impact resistance.FindingsThe optimization of mechanical performance of the proposed gripper is realized. The proposed gripper has the effect of increasing the stiffness of the negative stiffness part of the force characteristic curve and reducing the stiffness of the positive stiffness part, increasing the working region. The stability and the anti-interference ability of the workpiece under high-frequency vibration are improved. Meanwhile, the impact resistance in the lifting procedure is enhanced, compared with the original one.Originality/valueThis research proposes a novel design for the Bernoulli grippers to optimize the mechanical performance. The proposed gripper has advantages of a larger working region, better anti-interference ability and better impact resistance. These findings serve as important theoretical and experimental references for the design of the Bernoulli gripper.

Hierarchical structure design of Strombus gigas shell inspired laminated artificial composites and the mechanical performance optimization strategy

Strombus gigas shell is a natural biocomposite with good strength and extraordinary toughness, inspired by its internal refined hierarchical microstructures, a soft and hard phases composed cross-laminated hierarchical artificial structural composite that reinforced by discontinuous fiber was designed and prepared by 3D printing, and an investigation on the failure behavior and its strengthening and toughing mechanisms was carried out. It shows that the geometric configuration of the crossed-structure will regulate the local stress status in the hard phase and soft interface of the hierarchical structure significantly, and four different failure modes of this structure were proposed. Through the optimal design of the crossed-structure, the internal structure will undergo adaptive adjustment during loading process, then multiple failure forms and energy dissipation modes may burst out together and realize the improved combination of strength and toughness. This result may provide an optimization strategy for the lightweight composites design and additive manufacturing process.

Finite element simulation and optimization of mechanical performance of the magnesium-alloy biliary stent.

A biliary stent is used to expand the bile duct during interventional treatment of biliary stricture. To reduce the complications after stent implantation, it is necessary to understand and improve the comprehensive performance of magnesium alloy biliary stents. In this study, at first, the mechanical performance of magnesium alloy biliary stent in bile ducts with different ellipticitiesis studied, and the influence of the ellipticity of bile duct on the interaction of the stent-bile duct coupling system is better understood. Proposed results show the increment of ellipticity of the bile duct will increase the difficulty of expanding the stent. Second, to improve the mechanical performance and degradation performance of the stent simultaneously, an optimal design method based on a zero-order algorithm is used to reduce the maximum equivalent stress on the stent effectively, to make the stress distribution more uniform, and to expand the bile duct of the lesion more effectively and uniformly. The results of this analysis and optimization are useful to predict the clinical effect of stents and to design and optimize stents for both bile duct and other non-vascular.

Achieving excellent energy storage reliability and endurance via mechanical performance optimization strategy in engineered ceramics with core-shell grain structure

Although dielectric ceramic capacitors possess attractive properties for high-power energy storage, their pronounced electrostriction effect and high brittleness are conducive to easy initiation and propagation of cracks that significantly deteriorate electrical reliability and lifetime of capacitors in practical applications. Herein, a new strategy for designing relaxor ferroelectric ceramics with K0.5Na0.5NbO3-core/SiO2-shell structured grains was proposed to simultaneously reduce the electric-field-induced strain and enhance the mechanical strength of the ceramics. The simulation and experiment declared that the bending strength and compression strength of the core-shell structured ceramic were shown to increase by more than 50% over those of the uncoated sample. Meanwhile, the electric-field-induced strain was reduced by almost half after adding the SiO2 coating. The suppressed electrical deformation and enhanced mechanical strength could alleviate the probability of generation of cracks and prevent their propagation, thus remarkably improving breakdown strength and fatigue endurance of the ceramics. As a result, an ultra-high breakdown strength of 425 kV cm−1 and excellent recoverable energy storage density (Wrec ∼ 4.64 J cm-3) were achieved in the core-shell structured sample. More importantly, the unique structure could enhance the cycling stability of the ceramic (Wrec variation < ±2% after 105 cycles). Thus, mechanical performance optimization via grain structure engineering offers a new paradigm for improving electrical breakdown strength and fatigue endurance of dielectric ceramic capacitors.

Mechanical performance optimization and microstructure analysis of similar thin AA6061-T6 sheets produced by swept friction stir spot welding

Mechanical performance optimization and microstructure analysis of similar thin AA6061-T6 sheets produced by swept friction stir spot welding

Compression strength and fracture mechanism of a hierarchical porous yttria-stabilized zirconia microsphere prepared using electro-spraying associated with phase inversion technique

The compression strength and breakage mechanism of a hierarchical porous sphere in hundred-micron size were investigated in the present work. 3 mol% yttria-stabilized zirconia (YSZ) microspheres were prepared by electro-spraying associated with phase inversion (ES-PI) technique. The characteristic compression strengths of the ES-PI microspheres were measured by quasi-static uniaxial compression test, which increased from 19 MPa to 155 MPa as the sintering temperature increased from 1100 °C to 1400 °C. With the similar porosity, the compression strength of the hierarchical structure microsphere was almost three times higher than that of the hollow microsphere. Further, the breakage mechanism of the ES-PI microspheres was proposed by the honeycomb model of cellular materials, which suggested that the breakage of the ES-PI microsphere initiated from the elastic instability of the walls around the finger-like pores. These findings can help the mechanical performance optimization for ceramic microspheres with lightweight structure.