Higher Fracture Strain Research Articles

Mechanical properties and failure characteristics of cast and extruded Mg97Y2Zn1 alloys with LPSO phase

Mechanical properties and failure characteristics of Mg97Y2Zn1 (at%) alloys, prepared by gravity casting and extrusion processes, are examined experimentally. High tensile and fatigue strengths are obtained for extruded Mg97Y2Zn1 alloys, with the values being approximately twice as high as those for cast Mg97Y2Zn1 alloys. Such high strengths are attributed to the high internal stress arising from the complicated microstructure and severe lattice strain in the α-Mg and long-period stacking order phases. On the other hand, a high fracture strain is obtained for cast Mg97Y2Zn1 alloy, which is affected not only by the lower internal stress, but also severe kink deformation. The failure characteristics, e.g., crack growth characteristics are examined via direct observation during tensile and fatigue tests at micro- and nano-scales. Meandering fatigue crack growth is obtained for the cast Mg97Y2Zn1 alloys. The mean roughness of the fracture surface for cast Mg97Y2Zn1 alloys is more than twice as high as that for commercially available AM60 and AZ91 cast alloys. A coarse fracture surface that was observed in the cast Mg97Y2Zn1 alloys would make severe roughness-induced crack closure, leading to high fatigue strength.

Uncoupling the Impact of Fracture Properties and Composition on Sensory Perception of Emulsion‐Filled Gels

AbstractThe aim of the study is to investigate the effect of fracture properties and composition of emulsion‐filled gels on dynamic texture perception. Twelve emulsion‐filled gels varying in fracture stress (High/Low) and strain (High/Low) were prepared from three binary gel mixtures. Mechanical properties, syneresis, friction properties, microstructure, melting behavior, oral breakdown and texture perception of the gels were determined. Gels varying in composition but exhibiting similar fracture properties were obtained. Serum release, melting in mouth and friction varied between gels differing in composition. Fracture properties and melting of gels impacted oral breakdown. Fracture properties impacted perception of texture attributes at first bite and during chew down. Melting and syneresis impacted chew down perception of gels. We conclude that fracture stress mainly impacted texture perception at first bite, whereas fracture strain impacted perception of chew down texture attributes with high fracture strain gels being perceived creamy. The composition of gels impacted properties such as melting and serum release, which accounted for high variations in perception of moistness and creaminess between samples.Practical ApplicationsFracture properties of food are known to impact the perception of first bite texture attributes. Moreover, they are known to control breakdown of food during oral processing. However, little is known about the impact of fracture properties on perception of chew down texture attributes. The current study highlights the impact of fracture properties on chew down texture perception. It identifies other gel properties depending on gels composition that account for variation in perception between gels. The use of emulsion‐filled gels enabled the investigation of sensory attributes related to fat perception. Such knowledge can be used for food reformulation, for instance formulation of low fat soft solid foods. This study indicates which mechanical properties should be controlled to obtain a desired texture profile of soft solid foods.

A Flexible Ionic Liquid Gelled PVA‐Li2SO4 Polymer Electrolyte for Semi‐Solid‐State Supercapacitors

A novel high‐performance flexible gel polymer electrolyte (FGPE) for supercapacitors is prepared by a freeze‐drying method. In the presence of 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) ionic liquid, Li2SO4 can easily be added into poly(vinyl alcohol) (PVA) aqueous solution over a large concentration range. The resultant FGPE demonstrates considerably high ionic conductivity (37 mS cm−1) and a high fracture strain at 100% elongation at the optimal weight ratio of PVA:BMIMCl:Li2SO4 = 1:3:2.2. The supercapacitor fabricated with the resultant FGPE and activated carbon electrodes shows an electrode‐specific capacitance of 136 F g−1 with a stable operating voltage of 1.5 V, a maximum energy density of 10.6 Wh kg−1, and a power density of 3400 W kg−1. Double supercapacitors in series can efficiently drive a light emitting diode (LED) bulb for over 5 min and the retention of the specific capacitance reaches 90% even after 3000 charge–discharge cycles. The ionic conductivity and charge–discharge behaviors of the resultant FGPE are not affected by bending up to 180°. The flexible supercapacitor device shows only a small capacitance loss of 18% after 1000 cycles of 135° bending.

Deformation mechanism of Ni54Mn25Ga20.9Gd0.1 high-temperature shape memory alloy

Ni54Mn25Ga20.9Gd0.1 polycrystalline high-temperature shape memory alloy displayed high compressive fracture strain of 24.6% and large shape memory effect of 7.5%. However, its deformation mechanism was still unknown. In this paper, the structure revolution characterized by XRD and TEM indicated a new deformation mechanism different before was found. The deformation process of Ni54Mn25Ga20.9Gd0.1 alloy could be divided into four stages, including elastic deformation of non-modulated tetragonal martensite (T), stress-induced T to seven-layered modulated martensite (7 M) transformation, variants reorientation of 7 M, and elastic–plastic deformation of reoriented 7 M. The 7 M formed by compression deformation disappeared completely after heating to the temperature above Af.

Dynamic texture perception, oral processing behaviour and bolus properties of emulsion-filled gels with and without contrasting mechanical properties

Many highly palatable foods are composed of multiple components which can have considerably different mechanical properties leading to contrasting texture sensations. The aim of this study was to better understand the impact of contrasting mechanical properties in semi-solid gels on oral processing behaviour and dynamic texture perception. Four reference emulsion-filled gels without mechanical contrast were prepared using agar (1 or 2 wt%) or gelatine (2.5 or 5.5% wt). Six emulsion-filled gels with contrasting mechanical properties were obtained by combining two different gel layers. Agar reference gels displaying low fracture strain produced boli with many small particles and were perceived as grainy. Gelatine reference gels displaying high fracture strain produced boli with few large particles which melted in mouth and were perceived as creamy. Reference gels with large fracture stress were masticated for long times with a high chewing muscle activity and perceived as firm and grainy. Bolus properties, oral processing behaviour and dynamic sensory perception of the 6 contrasting gels were compared to the 4 reference gels using Principal Component Analysis. The presence of an agar layer in contrasting gels dominated bolus properties which contained many small particles and did not mix readily in mouth. The temporal sensory profiles and sensory trajectories of contrasting gels fell between the temporal sensory profiles and sensory trajectories of the two gel layers which they were composed of. We conclude that distinct features of dynamic texture perception in emulsion-filled gels with mechanical contrast are perceived separately in mouth.

J0450201 CFRP積層板の粘塑性挙動のモデル化

We estimate effects of ply thickness on mechanical properties and damage evolution of CFRP angle-ply laminates under various tensile loading. It should be noted that the laminate thickness is almost the same, but the ply thickness are quite different. Monotonic tensile tests, cyclic loading-unloading tensile tests and stress relaxation tensile tests are performed on [(±θ)_<12>]_s (t-0.05 prepreg×48plies, t-0.05 ply thickness), [(±θ)_4]_s (t-0.15 prepreg×16plies, t-0.15 ply thickness) and [(+θ)_4/(-θ)_4]_s (t-0.15prepreg× 16plies, t-0.6 ply thickness) T700SC/2500 carbon/epoxy laminates with various fiber directions (θ=30, 40, 45, 50 and 67.5°) at 1.0 mm/min crosshead speed. Laminates with thin ply thickness showed high strength and fracture strain. From SEM observation, t-0.6 laminates exhibit brittle fracture, however delamination occurred in each interlaminar interface in thin ply thickness (t-0.05, t-0.15) laminates. In stress relaxation tests, laminates exhibit nonlinear response and then stress relaxation behavior appears. In addition, it is considered that each angle-ply laminate have rate dependence in comparison with monotonic tensile test results at 0.1mm/min crosshead speed. Also damage evolution can be determined by cyclic loading-unloading tensile tests. We use mesoscale damage model to investigate damage evolution in CFRP laminates. From damage observation and damage evolution analysis, it is considered that thin ply thickness laminate can accumulate damage in specimen until high stress state.

Design of a new Ni-free austenitic stainless steel with unique ultrahigh strength-high ductility synergy

A conceptual approach was used to design a new Ni-free austenitic stainless steel with a unique combination of ultrahigh strength and ductility. The concept was based on the alloying of the 0.05C–18Cr–12Mn (wt.%) steel by 0.39%N and heavy warm rolling (84% reduction) at 1173K (900°C) to achieve the yield strength of minimum 1GPa and high tensile strength and elongation due to a proper stability of the austenite as a result of the optimized stacking fault energy (SFE). The yield strength of 1010MPa, tensile strength of 1150MPa and high fracture strain of 70% were measured for the steel designed. Dislocation and solid solution hardening mechanisms are introduced as the main contributors for the ultrahigh yield strength of the steel. The strain hardening is gradual and the hardening rate reaches a high level of ∼2400MPa at a high true strain of 40% due to slow α′-martensitic transformation and mechanical twinning. Consequently, the ductility of the designed steel is excellent.

Mechanical properties of tough hydrogels synthesized with a facile simultaneous radiation polymerization and cross-linking method

Radiation-induced polymerization and cross-linking method has been applied to hydrogel preparations for decades, but less attention has been paid to the mechanical properties of the hydrogels. In this work, we provide a systematic study on the mechanical properties of hydrogels synthesized with the simultaneous radiation polymerization and cross-linking method. The prepared polyacrylamide (PAAm) had very good mechanical properties, namely high compressive strengths (several to more than 10MPa), high tensile strengths (up to 260kPa), high fracture strains (up to 12) and high fracture energies (10–160J/m2). Absorbed dose and monomer concentration were the two important factors affecting the mechanical properties of the gels. The compressive strength and elastic modulus of the gels increased with increasing absorbed dose and monomer concentration, while the tensile strength, fracture strain and fracture energy of the gels decreased with increasing absorbed dose. The gels also showed excellent elastic recovery property, as indicated by the low stress–strain hysteresis ratios in cyclic tensile tests as well as the small loss factors measured with dynamic mechanical analysis (DMA).

Dynamic texture perception and oral processing of semi-solid food gels: Part 1: Comparison between QDA, progressive profiling and TDS

Texture perception of food is a dynamic phenomenon depending on food properties and oral processing. Several sensory techniques enable to measure texture perception over time. The aim of this study was to compare quantitative descriptive analysis (QDA), temporal dominance of sensation (TDS) and progressive profiling in the assessment of dynamic texture of emulsion filled gels varying in fracture stress (low/high), fracture strain (low/high) and oil release (oil droplets bound/unbound to the gel matrix).The QDA results revealed that the variation of mechanical properties led to significant differences in texture properties perceived at first bite (firmness and brittleness). Texture attributes perceived at later stages of mastication showed significant differences between gels depending on the first bite properties e.g. soft gels were perceived as more melting. Progressive profiling showed that creaminess increased over eating time while firmness decreased. TDS results were in agreement with the other methods and additionally conveyed information on the succession of perceived attributes over time. The TDS sensory trajectories demonstrated that for all gels dynamic perception evolved in a similar fashion but samples with a high or low fracture strain differed at the end of oral processing.We conclude that texture perception of semi-solid gels is dynamic and can be measured by either of the three sensory methods. The mechanical properties of the gels influence the perception of texture attributes at first bite and at later stages of mastication. QDA, TDS and progressive profiling gave matching and complementary results in the assessment of dynamic sensory texture.

Nanocomposite glide surfaces for FRP hydraulic cylinders – Evaluation and test

The use of continuous fibre-reinforced plastics (FRP) can significantly reduce the mass of hydraulic cylinders, such that light-weight actuators are becoming increasingly common especially in mobile applications. Currently, metallic inner liners are used as piston glide surfaces, which are commonly subject to failure-critical stresses due to the different mechanical behaviour of FRP laminate and metal structure. Adapted polymeric nanocomposites offer great potential to counteract these deficits, based on their good wear characteristics and chemical resistance as well as their high fracture strain and layer adhesion strength appropriate for the laminate deformation. Given this background, theoretical and experimental studies are being carried out on a nanoparticle-reinforced epoxy gelcoat, which has been adapted for load and for efficient manufacturing, as a piston glide surface layer under combined tribological, mechanical and media load. To evaluate the theoretical projection of the mechanical and hygrothermal load on the nanocomposite layer, the stresses and deformations are calculated using multi-layer composite theory for thick-walled anisotropic cylinder shells, and are then compared with experimental data.

Biaxial tensile tests identify epidermis and hypodermis as the main structural elements of sweet cherry skin.

The skin of developing soft and fleshy fruit is subjected to considerable growth stress, and failure of the skin is associated with impaired barrier properties in water transport and pathogen defence. The objectives were to establish a standardized, biaxial tensile test of the skin of soft and fleshy fruit and to use it to characterize and quantify mechanical properties of the sweet cherry (Prunus avium) fruit skin as a model. A segment of the exocarp (ES) comprising cuticle, epidermis, hypodermis and adhering flesh was mounted in the elastometer such that the in vivo strain was maintained. The ES was pressurized from the inner surface and the pressure and extent of associated bulging were recorded. Pressure : strain responses were almost linear up to the point of fracture, indicating that the modulus of elasticity was nearly constant. Abrading the cuticle decreased the fracture strain but had no effect on the fracture pressure. When pressure was held constant, bulging of the ES continued to increase. Strain relaxation upon releasing the pressure was complete and depended on time. Strains in longitudinal and latitudinal directions on the bulging ES did not differ significantly. Exocarp segments that released their in vivo strain before the test had higher fracture strains and lower moduli of elasticity. The results demonstrate that the cherry skin is isotropic in the tangential plane and exhibits elastic and viscoelastic behaviour. The epidermis and hypodermis, but not the cuticle, represent the structural 'backbone' in a cherry skin. This test is useful in quantifying the mechanical properties of soft and fleshy fruit of a range of species under standardized conditions.

Kinetic grain growth, shape memory and corrosion behavior of two Cu-based shape memory alloys after thermomechanical treatment

Metallurgical and mechanical properties along with shape memory and corrosion behavior of Cu-11.8% Al-3.7% Ni- 1%Mn and Cu-11% Al-5.6% Mn shape memory alloys (SMAs) were comparatively studied. The influence of grain refinement on the properties was studied by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), potentiodynamic polarizations and bend and tensile tests. Static recrystallization and kinetic grain growth show a rapid recrystallization in the first 15 s of annealing at 800 °C followed by grain growths. The minimum grain sizes obtained after 15 s are 90 and 260 μm for Cu-Al-Ni-Mn and Cu-Al-Mn, respectively. Tensile tests show typical three-stage curves for both alloys, and it is seen that alloys exhibit high fracture stress and strain after grain refinement. Microstructural observations show zig-zag morphology of β′1 martensite in the Cu-Al-Ni-Mn and coexistence of β′1 and γ′1 in the Cu-Al-Mn, which were confirmed by differential scanning calorimetry results. The shape memory ratios (η) of the alloys before thermomechanical treatment, and after thermomechanical annealing at 800 °C for different time up to 15 min followed by water quenching, were evaluated. In addition, corrosion behavior of alloys after grain refinement was analyzed by means of potentiodynamic polarization measurements. The results showed that the anodic reactions were dominated by dissolution of copper, and Cu-Al-Ni-Mn alloy exhibits a better corrosion resistance than Cu-Al-Mn alloy.

Intrinsically Stretchable Supercapacitors Composed of Polypyrrole Electrodes and Highly Stretchable Gel Electrolyte

There has been an emerging interest in stretchable power sources compatible with flexible/wearable electronics. Such power sources must be able to withstand large mechanical strains and still maintain function. Here we report a highly stretchable H3PO4-poly(vinyl alcohol) (PVA) polymer electrolyte obtained by optimizing the polymer molecular weight and its weight ratio to H3PO4 in terms of conductivity and mechanical properties. The electrolyte demonstrates a high conductivity of 3.4 × 10(-3) S cm(-1), and a high fracture strain at 410% elongation. It is mechanically robust with a tensile strength of 2 MPa and a Young's modulus of 1 MPa, and displays a small plastic deformation (5%) after 1000 stretching cycles at 100% strain. A stretchable supercapacitor device has been developed based on buckled polypyrrole electrodes and the polymer electrolyte. The device shows only a small capacitance loss of 5.6% at 30% strain, and can retain 81% of the initial capacitance after 1000 cycles of such stretching.

Fabrication and Testing of Planar Stent Mesh Designs Using Carbon-Infiltrated Carbon Nanotubes

This paper explores and demonstrates the potential of using pyrolytic carbon as a material for coronary stents. Stents are commonly fabricated from metal, which has worse biocompatibilty than many polymers and ceramics. Pyrolytic carbon, a ceramic, is currently used in medical implant devices due to its preferable biocompatibility properties. Micropatterned pyrolytic carbon implants can be created by growing carbon nanotubes (CNTs), and then filling the space between with amorphous carbon via chemical vapor deposition (CVD). We prepared multiple samples of two different stent-like flexible mesh designs and smaller cubic structures out of carbon-infiltrated carbon nanotubes (CI-CNT). Tension loads were applied to expand the mesh samples and we recorded the forces at brittle failure. The cubic structures were used for separate compression tests. These data were then used in conjunction with a nonlinear finite element analysis (FEA) model of the stent geometry to determine Young's modulus and maximum fracture strain in tension and compression for each sample. Additionally, images were recorded of the mesh samples before, during, and at failure. These images were used to measure an overall percent elongation for each sample. The highest fracture strain observed was 1.4% and Young's modulus values confirmed that the material was similar to that used in previous carbon-infiltrated carbon nanotube work. The average percent elongation was 86% with a maximum of 145%. This exceeds a typical target of 66%. The material properties found from compression testing show less stiffness than the mesh samples; however, specimen evaluation reveals poorly infiltrated samples.

Melt compounding with graphene to develop functional, high-performance elastomers

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer—ethylene–propylene–diene monomer rubber (EPDM)—using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment.

EVALUATION OF LAYER INTERACTION USING LAYER THICKNESS AND PLASTIC ZONE SIZE OF MULTILAYERED METALLIC SHEETS

Each layer of multilayered metallic sheet (ML sheet) shows a distinctive deformation behavior different from monolithic layer if two kinds of layers having different mechanical property are laminated. The stress gradient of ML sheet is different from that of monolithic material due to layer interaction, and a void characteristic of ductile fracture is found in the brittle layer. The brittle layer has a larger plastic zone and higher fracture strain than the monolithic layer due to the suppression stress of the ductile layer. As a layer becomes thinner, the size of the plastic zone increases. This is because of the high fracture strain. As a characteristic stress–strain behavior of such ML sheet, there is the turning point in which the main influence is turned into the section of the ductility, increases by the increase of plastic zone size from the section of the strength and by the volume fraction increase.

Gas permeability and mechanical properties of PDMS mixed with PMPS nanofibers produced by electrospinning

ABSTRACTPolymethylphenylsilicone (PMPS), a siloxane polymer with a phenyl group, was first successfully electrospun to fabricate different diameters of silicone fibers ranging from 500 nm to 10 μm by considering solubility parameters of 12 different solvents. The resulting PMPS fibers were mixed with polydimethylsiloxane (PDMS) by retaining their original nanofiber structures to produce a polysiloxane-based nanofibrous composite. As for the mechanical properties, the PMPS/PDMS composite presented higher Young’s modulus and higher fracture strain than pure PDMS. The gas permeability test revealed that the PMPS/PDMS composite exhibited higher CO2 permeability than the pure PDMS membrane. Moreover, CO2 permeability gradually increased by raising the compounding ratio of PMPS-fibers in the PMPS/PDMS composite and by decreasing the diameter of PMPS-fibers. The enhancement mechanism observed in both mechanical properties and CO2 permeability was discussed from the viewpoint of the interface between PMPS and PDMS along with the nanofiber network structures.

212 構成層厚の異なるCFRPアングルフライ積層板の力学的特性(0S12-2高分子系複合材料の成形と力学的特性II,0S12高分子系複合材料の成形と力学的特性)

We estimate effects of ply thickness in mechanical properties and damage evolution of CFRP angle-ply laminates under various tensile loading. It should be noted that the laminate thickness is almost the same, but the ply thickness are quite different. Monotonic tensile tests , cyclic loading-unloading tensile tests and stress relaxation tensile tests are performed on [(±)_12]_s(t-O.O5prepregx48plies), [(±)_4]_s(t-O.15prepregxl6plies) and [(+θ_4/(-θ)_4]_s (t-0.15prepregxl6plies) T700SC/2500 carbon/epoxy laminates with various fiber directions (θ=30, 40, 45, 50 and 67.5°) .Ply thickness is expressed as t-0 05, t-0 15 and t-0 6, respectively. Damage evolution can be determined by cyclic loading-unloading tests. We use mesoscale damage model to investigate damage evolution in CFRP laminates. We discuss effect of ply thickness on mechanical property of angle-ply laminates. Laminates have thin ply thickness showed high strength and fracture strain.

The Manufacture of Resorbable Suture Material from Magnesium – Drawing and Stranding of Thin Wires

AbstractWith the aid of multiple wire drawing passes, the magnesium alloys ZEK100, MgCa0.8, and AL36 were reduced to monofilament wires possessing diameters between 0.5 and 0.1 mm. These filaments were subsequently twisted into poly‐filament suture material using stranding. In order to analyze the microstructural constituents and the mechanical‐tribological properties, metallographic specimens were prepared and tensile tests were performed on both monofilament as well as poly‐filament wire strands. Appropriate parameters were ascertained for the wire drawing process with regard to forming rate, temperature, and heat treatment. During the investigations, the alloy ZEK100 exhibited particularly interesting mechanical properties which, owing to its high tensile strengths (up to 550 MPa for monofilament) and fracture strains (up to 30% for poly‐filament), are comparable to those of conventional polymer‐based suture materials. In addition to this, integrating a core (internal, individual wire) into the poly‐filament mesh of wire strands represents an interesting alternative for future research in which structures composed of different materials, and the advantages of combining their properties are brought into particular focus.

Improving the Toughness of Poly (L-lactic acid) by Interpenetrating Network Structure

An interpenetrating polymer network was formed by blending of PLLA and PEG cross-linked β-CD to improve the toughness of PLLA, and the mechanical properties of PLLA composites were studied using tensile test. The PLLA composite samples exhibited a single glass transition and their Tg values decreased with increasing PEG/β-CD content, indicating that PLLA and PEG/β-CD are miscible. The PLLA composite samples aged at room temperature achieved the highest fracture strain (about 235%), about 40 times that of the original PLLA sample, while the Young's modulus was not seriously hampered.