Variation Of Mechanical Properties Research Articles

Effect of welding processes on mechanical and metallurgical characteristics of carbon steel cylindrical components made by wire arc additive manufacturing (WAAM) technique

In recent decades, Additive Manufacturing (AM) has become a viable alternative to the manufacture of metal parts. Wire arc additive manufacturing (WAAM), a welding-based AM technique is an important research area since it permits the economical manufacture of large-scale parts with relatively high deposition rates. This article compares the effect of heat input on mechanical properties of carbon steel cylindrical components fabricated by Gas Metal Arc Welding (GMAW) and Cold Metal Transferred Arc Welding (CMTAW) processes. Firstly, the influence of heat input on the grain size was analysed. Subsequently, the effect of heat input on the tensile properties, impact toughness and hardness of the cylindrical components were studied along the building direction. The cylindrical component made by CMTAW process showed superior tensile properties and higher impact toughness than GMAW component. Similarly, CMTAW component exhibited higher hardness than GMAW cylindrical component. The variations in mechanical properties are mainly due to the appreciable variations that have occurred in the microstructural features and different grain sizes evolved at different heat input levels. The bottom and top regions of the fractured tensile and impact specimens of the components are characterised by dimple structures revealing the ductile fracture.

Nanovoid formation induces property variation within and across individual silkworm silk threads.

Silk is a unique fiber, having a strength and toughness that exceeds other natural fibers. While inroads have been made in our understanding of silkworm silk structure and function, few studies have measured structure and function at nanoscales. As a consequence, the sources of variation in mechanical properties along single silk fibers remain unresolved at multiple scales. Here we utilized state of the art spectroscopic and microscopic methodologies to show that the silks of species of wild and domesticated silkworms vary in mechanical properties along a single fiber and, what is more, this variation correlates with nanoscale void formations. These results can also explain the strain hardening behaviours observed in the silks where structural features of the proteins could not. We thereupon devised a predictive thermal model and showed that the voids contribute to temperature regulation within the silkworm cocoons.

Tuning compatibility and water uptake by protein charge modification in melt-polymerizable protein-based thermosets

The effects of charge state on water uptake and mechanical properties of thermoset protein-based copolymers were investigated. Superneutralization was shown to reduce the material's mechanical property variation with humidity.

Study of wear performance and mechanical properties of HDPE on addition of CNT fillers

Carbon nanotube (CNT)/High-Density Polyethylene (HDPE) nanocomposite specimens were prepared with varying concentrations of 0, 0.04, 0.12 wt% by using ethanol as solvent followed by sonication and magnetic stirring for homogeneous distribution of CNT throughout the composite. To find variation in different mechanical properties like the modulus of elasticity, yield strength, tensile test was conducted and observed that the addition of nanofillers enhances the modulus of elasticity by 24.4 percent, and Yield Strength by 5.19 percent, with 0.12 percent CNT Toughness was evaluated by Charpy and Izod tests and found that it was improved by adding CNT nanofillers. Toughness improvement by the Izod test was 35 percent and by Charpy test, it was 4.76 percent with 0.12 percent CNT. The pin on the disc wear test exhibits depletion on the wear of nanocomposites. Even compared with the available theoretical model and found maximum 2.43 percent error in results for modulus of elasticity.

Effect of multiple remelting on behaviour of AlSi5Cu3 Aluminium alloy

The present paper investigated the microstructural behaviour and mechanical properties of AlSi5Cu3 alloy after multiple remelting. The AlSi5Cu3 alloy is selected owing to excellent properties, better casting characteristics and numerous applications in diverse sectors. Total three remelting of AlSi5Cu3 alloy is performed and behaviour of alloy is evaluated for as casted and each remelted conditions. The microscopic study and grain size analysis revealed that the number of grains is gradually reduced after second and third remelting due to the presence of porosity and casting uncertainty. The results confirmed that the maximum values of mechanical properties were obtained in the first remelted condition whereas minimum values were detected in the third remelted condition. For the third remelted condition, the hardness is decreased by 8.33%, 11.11% and 2.78% whereas the ultimate tensile strength is reduced by 3.93%, 5.51% and 1.57% compared to as casted, first remelted and second remelted conditions respectively. The results evidenced that minor variation in microstructural behaviour and mechanical properties is observed after multiple remelting.

Variation in fresh and mechanical properties of GGBFS based self-compacting geopolymer concrete in the presence of NCA and RCA

Current work depicts the study of fresh and strength characteristics of Ground Granulated Blast Furnace Slag (GGBFS) based Self-Compacting Geopolymer Concrete (SCGC) with Natural Coarse Aggregate (NCA) and Recycled Coarse Aggregate (RCA) by variation of critical parameters like molarity of sodium hydroxide and ratio in alkali activated solution with their admissible wide range of variations. All the fresh property tests of SCGC like segregation resistance (SR), filling ability (FLA), passing ability (PA), and mechanical properties like unconfined compression test, tensile test were performed to examine the attainment of SCGC with NCA and RCA. The critical parameters: molarity of sodium hydroxide and ratio of alkali activated solution for design of the SCGC mix were 10 M, 12 M, 14 M and 2, 2.5, 3 respectively. Other materials like superplasticizer, extra water quantity in the mix were considered from existing research. Mix designs for the production of SCGC were prepared considering NCA and RCA separately. Source material used in current research was GGBFS. All SCGC mixes with several combination was stable as per EFNARC 2002 guidelines. Mixes with NCA performed better and SCGC mix with 12 M and AAS ratio 2.5 were stood competitive than all other mixes.

Experimental and analytical study on the behavior of hybrid GFRP/steel bars in reinforced concrete deep beams

Abstract The deep beam is one of the essential members of high-rise buildings structures, so the deep beams are used as a transfer girder; in walls water structures, the deep beam behavior is different from the slender beam behavior; the deep beam plane section before does not remain plane after bending. In recent years, the use of FRP as a composite material in reinforced concrete structures has been growing up to cover problems by weight of structure buildings, corrosion, repairing, and construction cost. This paper presents an experimental, analytical study to assign the variation of mechanical properties of reinforced concrete deep beams using vertical and horizontal GFRP stirrups. This paper investigates the mechanical properties of test specimens for deep beams reinforced in shear with GFRP or steel bars as web reinforcement. The deep beams are reinforced with glass fiber reinforced polymer (GFRP) in various ratios as a web reinforcement configuration (0, 0.25%, and 0.40%) rather than traditional steel web reinforcement. All tested specimens have the same span to depth ratio of 0.40 (a/d); the primary and secondary reinforcement is steel bars. The web reinforcement ratio significantly affected deep beams’ load capacity and mechanical behavior. The GFRP enhancement the mechanical behavior of the reinforced concrete deep. Increasing the GFRP web reinforcement ratio enhances the deep beam load capacity. The test results compared with the traditional ACI design method strut-tie model to demonstrate the effect of web reinforcement ratio on deep beam load capacity and strut width. The test results have been verified by ABAQUS 6.13.

Contributions of Porosity and Laser Parameter Drift to Inter-Build Variation of Mechanical Properties in Additively Manufactured 316l Stainless Steel

Contributions of Porosity and Laser Parameter Drift to Inter-Build Variation of Mechanical Properties in Additively Manufactured 316l Stainless Steel

Thermomechanical behavior of polymeric periodic structures

Additive manufacturing (AM) enables the fabrication of periodic structures with regular repeat units and tailorable mechanical properties. Polymer-based AM processes, such as fused filament fabrication (FFF), permit rapid, low-cost fabrication of periodic structures from a wide range of materials. However, the mechanical properties of polymers are strongly affected by temperature, especially near the glass transition temperature (T g ), which has a significant impact on the design and application of the structures. Herein, we utilize a coupled experimental and computational approach to evaluate the mechanical behavior of polymeric periodic structures (PPS) with uniform and spatially varying temperatures that span T g . Individual unit cells (square, auxetic, and honeycomb) are additively manufactured from polylactic acid (PLA) (T g = 54 °C) and experimentally evaluated by dynamic mechanical analysis (DMA) using a tension test fixture and thermal chamber. The unit cells are subjected to sequential tension and compression tests, up to a maximum of +/−20% strain, which are repeated from 40 °C to 65 °C in 5 °C increments. Maximum forces vary by two orders of magnitude when temperature varies across T g , and a hysteresis loop is observed for temperatures 14 °C below T g . This indicates that viscoelasticity has a significant impact on the mechanical properties of the structure below T g and that the structures are capable of dissipating energy. Experimental force-displacement and energy dissipation results agree favorably with results from a multiphysics finite element framework, which utilizes bulk material properties as inputs. The computational framework is then applied to structures comprising tessellated unit cells to evaluate the effects of uniform temperatures and temperature gradients on mechanical properties. The results demonstrate that non-uniform temperature fields can produce spatial variation of mechanical properties, such as Poisson’s ratio, throughout the structure. Insight obtained in this investigation provides guidelines for the design, fabrication, and implementation of PPS operating across a range of temperatures that passively modifies their mechanical properties and energy dissipation characteristics. • Thermomechanical analysis of square, honeycomb, and auxetic periodic structures. • Experimental and computational analysis of 3D printed PLA across glass transition. • Thermal gradients spatially affect array mechanical properties (Poisson’s ratio). • Square unit cell and honeycomb array dissipate highest energy per unit mass. • Applicable to other polymers and structures by updating bulk finite element inputs.

On three-dimensional J-integral for finite deformation problems with continuous and discontinuous spatially mechanical property variations

In welded joints, which are widely used in various applications, the mechanical properties of material change discontinuously due to the effects of temperature history and weld between dissimilar materials. Therefore, it is necessary to develop a method for evaluating fracture mechanics parameter for structure with discontinuous changes in mechanical properties. One of the fracture mechanics parameters to evaluate crack propagation is the J-integral. The objective of this study is to establish an accurate mechanical strength evaluation method for problems with discontinuous changes in mechanical properties. For this purpose, we propose a three-dimensional J-integral which is applicable to large-deformation elastic-plastic problems that allow continuous and discontinuous changes of mechanical properties.

Morphology, thermal stability, electronic structure and mechanical properties of α-AlFeMnSi phases with varying Mn/Fe atomic ratios: Experimental studies and DFT calculations

Separation of Fe-containing intermetallics is an effective method to decrease Fe content in Al-Si alloys. The three-dimensional (3D) morphology and stability of Fe-containing intermetallics are important parameters affecting their separation efficiency. Combined with experiments and first-principles calculations, the variation of 3D morphology, stability, electronic structure and mechanical properties of α-AlFeMnSi are studied with the evolution of Fe/Mn atomic ratio. The experimental results show that the 3D morphology of α-AlFeMnSi transforms from Chinese character to regular polyhedron with the increment of Mn/Fe atomic ratio and all α-AlFeMnSi phases have cubic crystal structure. The calculated mixing enthalpies indicate that all α-AlFeMnSi phases are stable in thermodynamics due to the negative values. The electronic structure and Mulliken population calculations show that the variation of Mn/Fe ratio results in the overall change of chemical bondings of Si-Mn, Si-Fe, Al-Mn and Al-Fe, which leading to the evolution of stability and mechanical properties of α-AlFeMnSi phases. The calculated results of mechanical properties demonstrate that the Young’s modulus and hardness of α-AlFeMnSi phases are improved with the increment of Mn/Fe atomic ratio, which is also validated by nano-indentation measurements. These results provide the componential guidance about designing easy-separable Fe-containing intermetallics and try to explain physical mechanism of property evolution of α-AlFeMnSi phase.

Towards a wickless smooth–Wall aluminium food packaging tray mould tool digital twin - Advanced computational modelling supported by experimental validation

With the objective of eliminating defects in the rims of smooth–walled aluminium trays, potentially causing food spillage and waste, the present study uses computational simulation to identify practical engineering solutions for the problem. The complex tool geometry used for the multi-stage tray manufacture is modelled using an Explicit analysis. The model was validated using experimental data from a local Tool & Die manufacturer. Laboratory testing also assessed the variation in mechanical properties of the aluminium sheet and the changes in thickness that occurred throughout the manufacture of the tray. The validated model was used to study the effects of three manufacturing parameters, namely holding pressure, the initial shape of the aluminium sheet, and the curling diameter of the rim. Optimum levels of each parameter were numerically identified, leading to one practical solution being tested by the manufacturer which has now been successfully adopted into the design of a tool that can produce defect-free trays.

Influence of aluminium and niobium alloying on phase composition, structure and properties of heat- and wear-resistant cast iron of Cr-Mn-Ni-Ti system

The paper presents the data on phase composition and structure forming for the alloys and oxide layers, on distribution of elements among the alloy structural components and oxidation surface through the depth of oxide and sub-oxide layers, on variation of wear resistance, scale resistance, growing stability and mechanical properties of cast iron of Cr-Mn-Ni-Ti-Al-Nb system depending on different aluminium and niobium content and thermal accumulating capacity of a casting mould. Complex carbides (Nb, Ti)C are forming in white cast iron during niobium alloying. Quantitative metallographic analysis of (Nb, Ti)C carbides and (Cr, Fe, Mn)7C3 complex carbides was carried out on the samples with examined composition. The tests for scale resistance were conducted, structure and properties of cast iron were investigated. It was determined that chemical composition and structure of oxide layers depend on distribution of alloying elements among the alloy structural components. It was established that the areas of oxide film surface layer, which were formed on eutectics, contain mainly manganese; its concentration is more than 65 %, while Al is 4 % and Cr is 1 %. Manganese leads to increase of defects amount, such as pores, micro-cracks and vacancies, in oxide film during high-temperature gas oxidation; penetration ability of this film also increases, what has a negative effect on metal resistance to further destruction caused by oxidation. The film becomes porous, its thickness enlarges. Aluminium provides favourable influence on forming of the thin protective spinel-type films (dense substance with good metal adhesion) with minimal amount of defects; diffusion through such oxide film is very difficult. The areas of oxide layer, which were formed on austenite dendrites, contain mainly aluminium; its concentration is more than 24 %, while Mn is 16 % and Cr is 12 %. High aluminium content provides small film thickness. Joint alloying by aluminium and niobium leads to simultaneous increase of heat resistance and wear resistance. Wear resistance increased as a result of enlargement of the part of primary carbides (Nb, Ti)C with high hardness in the structure of cast iron. Composition of oxide films includes aluminium which strengthens their protective properties and rises of the alloy scale resistance. Alloying by niobium leads to secondary hardening during cooling in a casting mould. Dispersion particles of М7С3 carbides are forming in solid state, thereby no structure degradation occurs during testing at increased temperatures, and growing stability rises.

Improving the mechanical reliability of shape memory bulk metallic glass composites by mechanical training

Mechanical reliability of metallic glass composites is an important performance affecting their engineering applications as structural materials. In this work, the reliability of shape memory bulk metallic glass composites was evaluated by coefficient of variation. The coefficient of variation of mechanical properties, especially the plastic strain was reduced more than 34% by 1 cycle mechanical training at 800∼900 MPa or by 10 cycles at 600 MPa. The mechanism of enhanced reliability by proper mechanical training was revealed. These proper training treatments would provide more martensite nuclei, thus reduce the randomness of martensitic transformation and shear bands initiation. This investigation provides a method for improving the mechanical reliability of bulk metallic glass composites for the first time.

Achieving high-strength nanocrystalline WE43 Mg alloy by a combination of cold rotary swaging and aging treatment

In this work, a bulk nanocrystalline WE43 alloy prepared through rotary swaging was subjected to the aging treatment at different temperatures. The mechanical property and microstructure variations during aging were systematically studied. Aging at 175 °C enhanced the alloy to be maximumly with 516 MPa in ultimate tensile strength (UTS), 477 MPa in yield strength (YS) and 8.5% in elongation to failure. The significant strengthening effect resulted from rare-earth elements segregation at grain boundary. During aging at 225 °C, tremendous enhancement was obtained in the initial stage of aging, while the formation of massive precipitates along grain boundary deteriorated the strength as aging time was prolonged.

Stability of SiNx Prepared by Plasma-Enhanced Chemical Vapor Deposition at Low Temperature.

In this paper, the environmental stability of silicon nitride (SiNx) films deposited at 80 °C by plasma-enhanced chemical vapor deposition was studied systematically. X-ray photoelectron spectroscopy and Fourier transform infrared reflection were used to analyze the element content and atomic bond structure of the amorphous SiNx films. Variation of mechanical and optical properties were also evaluated. It is found that SiNx deposited at low temperature is easily oxidized, especially at elevated temperature and moisture. The hardness and elastic modulus did not change significantly with the increase of oxidation. The changes of the surface morphology, transmittance, and fracture extensibility are negligible. Finally, it is determined that SiNx films deposited at low-temperature with proper processing parameters are suitable for thin-film encapsulation of flexible devices.

Metallurgical and Mechanical Properties Variation Along the Thickness of Electron Beam Welded Ferritic Stainless Steel Joints After Postweld Heat Treatment

Metallurgical and Mechanical Properties Variation Along the Thickness of Electron Beam Welded Ferritic Stainless Steel Joints After Postweld Heat Treatment

Statistical constitutive model of steel in randomly pitted structures

Pitting corrosion degrades mechanical properties of steel by inducing thickness reduction and stress concentration on the rough surface of a structural member in ship and marine structures. This paper presents a scheme for ultimate strength assessment of randomly pitted structures to treat such an adverse effect using an equivalent steel of degraded mechanical properties. Tensile tests of steel specimens with/without artificial corrosion pits were carried out to validate their numerical models. Numerical analyses were performed to explore the effects of pitting parameters (angularity, spacing, coalescence, and ratio of diameter, d, to depth, h, of pits) on tensile strength of pitted specimens. Numerous stochastic simulations indicate that random natures of pitting parameters induce a great variation of mechanical properties of a randomly pitted specimen obeying a normal distribution. Meanwhile, tensile strength of randomly pitted specimens is highly depended on equivalent d/h (the ratio of mean diameter to mean depth of all pits) besides degree of volume loss (DOV) of corroded material. A constitutive model of randomly pitted steel was established to be bilinear, whose material parameters were statistically described by the equivalent d/h and DOV. It was verified to be sufficiently precise in predicting the ultimate strength of pitted structures.

Experimental study of effect of number of heating–cooling cycles on mode I and mode II fracture toughness of travertine

Fracture toughness is considered a critical index for measuring the fracture strength of cracked rocks, which is sometimes influenced by the heating–cooling process. This process and its repetition change the physical and mechanical properties of rocks. The façade of buildings bears a larger number of heating–cooling cycles over days and seasons. Accordingly, this study simulated the heating–cooling process and its impact on the mode I and mode II fracture toughness of travertine as a widely used rock in the façade of modern buildings by designing a larger number of low-temperature heating–cooling cycles. Previous researches mostly has been studied the effect of high temperatures on physical and mechanical rock properties but in this study, effect of low temperature in a large number of heating–cooling cycle is investigated. Two types of travertine were considered and studied. The mode I and mode II fracture toughness tests were performed on 160 cracked chevron notched Brazilian disc (CCNBD) specimens after applying 0, 1, 4, 8, 16, 32, 64, and 128 heating–cooling cycles. Mechanical properties were measured, and scanning electron microscope (SEM) images were taken to evaluate and match the results of fracture toughness tests. According to the results, mode I and mode II fracture toughness increased after a heating–cooling cycle and then decreased by increasing the number of cycles. The changes in the fracture toughness were consistent with variations of mechanical properties and SEM images with increasing the number of heating–cooling cycles.

Effect of TEA·H3PO4 and TEA·C18H30O3S on the mechanical properties and hydration characteristics of cement paste

In this study, TEA·H3PO4 (TP) and TEA·C18H30O3S (TDS) have been used as organic admixtures in cementitious materials. Mortar specimens with different TP and TDS dosages were subjected to mechanical, setting time, hydration degree, isothermal calorimeter tests, as well as to XRD, TG, SEM and MIP analyses. Results show that less than 0.10% TP and 0.05% TDS shorten the initial setting time, while more than 0.50% TDS can lead to a retarding effect in mortar specimens. TP is beneficial to increase the early age strength, but a sharp decrease in both compressive and flexural strengths is found when TDS is introduced. The XRD and TG analyses indicate that the introduction of TDS brings more generation of the portlandite (CH), ettringite (AFt), and monosulfate (AFm), whereas TP leads to the reduction of CH content in the cement pastes. Moreover, the SEM observations reveal that the decline in strength may result from the air-entraining effect caused by the incorporation of TDS which increase the amount and size of hydration pores, and the variation of mechanical properties of mortar specimens with TP is closely linked to the size of CH generated in mortar specimens.