Mechanical Behaviour of Materials

EVALUATION OF ALTERNATIVE BINDERS FOR THE FILLERS FOR PAINTINGS ON CANVAS: PHYSICAL CHARACTERIZATION AND MECHANICAL BEHAVIOR ANALYSIS ABOUT FILLERS EXAMINED

ABSTRACT
The mechanical behaviour of easel paintings is caused by several conditions related to the intrinsic factors of the materials. This research proposes to choose the fillers suitable for filling some gaps on the basis of the properties of the constituent materials of easel paintings. Therefore, we analysed fillings for easel paintings that are different from traditional fillers made up of Bologna gypsum and rabbit glue. The study examines two issues: the mechanical behaviour (by means of tests: traction, peel and compression) and the aesthetic aspect (by means of the analysis of colour absorption of watercolours and varnish, final varnish and morphological analysis). Since in order to study the mechanical behaviour of these materials there are no standard test methods, we proposed a method to produce the samples and execute the tests. Through a rating process, we selected four kinds of fillers, each on with a different binder with gypsum: Aquazol®500, Balsite®, Tylose®, and Plextol®.

Hydrogen embrittlement is a common, dangerous, and poorly understood cause of failure in many metal alloys. In practice, it
is observed that different types of damage to industrial components have been tied to the presence and localization of hydrogen in metals. Many efforts have been made at understanding the effects of hydrogen on materials, resulting in an abundance of theoretical models and papers. However, a fully developed and practically-applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen embrittlement. The connection of microstructure-based behaviors of materials and effects on the macroscopic measurable characteristics (stress levels, hardness, strength, and impact toughness) is of the utmost importance to achieve a unified model for hydrogen embrittlement. This paper gives an overview of the application of a model for structural integrity analysis of boiler tubes made of
plain carbon steel exposed during operation to a local corrosion process and multiple hydrogen assisted degradation processes: hydrogen embrittlement and high-temperature hydrogen attack. The model is based on the correlation of mechanical properties to scanning electron microscopy fractography analysis of fracture surfaces in the presence of simultaneously active hydrogen embrittlement micromechanisms. The proposed model is practical for use as a predictive maintenance in power plants, as it is based on the use of standard macro-mechanical tests.

Numerical investigation of transient hydrogen-natural gas flow in a steel pipeline. Influence of gaseous hydrogen flow on the structural integrity of precracked pipes. Interaction between transient hydrogen-natural gas flow and hydrogen embrittlement. Failure Assessment Diagram (FAD) of a precracked API 5L X52 steel pipeline. The stress intensity and safety factors analysis during transient hydrogen pressure. Rapid closure valve Failure assessment diagram Semi-elliptical crack Finite element analysis a b s t r a c t We are reporting in this study the hydrogen permeation in the lattice structure of a steel pipeline designed for natural gas transportation by investigating the influence of blending gaseous hydrogen into natural gas flow and resulted internal pressure values on the structural integrity of cracked pipes. The presence of cracks may provoke pipeline failure and hydrogen leakage. The auto-ignition of hydrogen leaks, although been small, leads to a flame difficult to be seen. The latter makes such a phenomenon extremely dangerous as explosions became very likely to happen. In this paper, a reliable method is presented that can be used to predict the acceptable defect in order to reduce risks caused by pipe failure due to hydrogen embrittlement. The presented model takes into account the synergistic effects of transient gas flow conditions in pipelines and hydrogen embrittlement of steel material due to pressurized hydrogen gas permeation. It is found that blending hydrogen gas into natural gas pipelines increases the internal load on the pipeline walls due to overpressure values that may be reached in a transient gas flow regime. Also, the interaction between transient hydrogen gas flow and embrittlement of API 5L X52 steel pipeline was investigated using Failure Assessment Diagram (FAD) and the results have shown that transient flow enhances pipeline failure due to hydrogen permeation. It was shown that hydrogen embrittlement of steel pipelines in contact with the hydrogen environment, together with the transient gas flow and significantly increased transient pressure values, also increases the probability of failure of a cracked pipeline. Such a situation threatens the integrity of high stress pipelines, especially under the real working conditions of hydrogen
gas transportation.

The modern special application requires a very light and very strong materials so that the new researches trend to the development of what called new light alloys. Light alloys and light metals 1-have low density and high strength-toweight ratios. aluminum alloys are lightweight, non-ferrous metals with:  good corrosion resistance, ductility, and strength.  Aluminum is relatively easy to fabricate by forming, machining, or welding.  This metal is a good electrical and thermal conductor.

Bearing in mind the multiple effects of hydrogen in steels, the specific mechanism of hydrogen embrittlement (HE) is active, depending on the experimental conditions and numerous factors which can be grouped as environmental, mechanical and material influences. A large number of contemporary studies and models about hydrogen environment assisted cracking and HE in steels are presented in the form of critical review in this paper. This critical review represent the necessary background for the development of a multiscale structural integrity model based on correlation between simultaneously active HE micro-mechanisms: the hydrogen-enhanced localized plasticity (HELP) and the hydrogen-enhanced decohesion (HEDE) - (HELP+HEDE) and macro-mechanical response of material, unevenly enriched with hydrogen during service of boiler tubes in thermal fossil fuel power plant. Several different experimental methods and techniques were used to determine the boiler tube failure mechanism and afterwards also the viable HE mechanisms in the investigated ferritic-pearlitic low carbon steel, grade 20 - St.20 (equivalent to AISI 1020). That represent a background for the development of a structural integrity model based on the correlation of material macro-mechanical properties to scanning electron microscopy fractography analysis of fracture surfaces of Charpy specimens, in the presence of confirmed and simultaneously active HE micro-mechanisms (HELP+HEDE) in steel. The aim of this paper is to show how to implement what we have learned from theoretical HE models into the field to provide industry with valuable data and practical structural integrity model.

The risk of mechanical instability increases with a fungus infected plane wood thus the
effect causes the death of the plane tree. Experiments with the relaxation holding point
method by a three point bending test showed a non linear time behavior in the plane
wood under mechanical stress. The relaxation curves of the three point bending test have
distributed with a larger deflection a longer stress curve over time. If the selected linear
Maxwell model corresponds to the measured values, the points of the averaged parameters
per deflection are distributed statistically around a total mean. This is not the case with
the viscosity. The mean viscosities show a linear relationship to the deflection. For this
reason, a new nonlinear viscoelastic material model is being developed from the results
of the parameter study. The residual plot for the average viscosities that characterize the
material parameters of a damping element provided a functional relationship between
viscosity and deflection. This means that the parameter of the damping element of a
non linear Maxwell describes a dependency on the deflection. In model development, the
new non linear wood damper element is incorporated into the differential equation of the
Maxwell and is implicitly or explicitly shaped. The results of the parameter study of both
material models are compared with the cod.

Hydrogen embrittlement (HE) in a specific sense meaning can be defined as the hydrogen-caused deterioration of the mechanical properties of most metallic materials and alloys. The coexistence of different HE mechanisms and their simultaneous effects in metallic materials, including steels, is still not well documented, while recognition of the dominant mechanism, one or more, is an extremely challenging and crucial problem. A special structural integrity model was proposed [1] for analysis, prevention, and prediction of HE based on the HELP + HEDE model [2] for HE in steels. The structural integrity model corresponds with the observed coexistence of HE mechanisms (HELP + HEDE model) in metals and transition from HELP dominance to HEDE dominance at a hydrogen concentration above the critical hydrogen concentration [2,3]. The further implementation of methods for evaluation, control, and prevention of hydrogen-assisted mechanical degradation processes and HE in metals requires that the variables relevant to the application be incorporated into the basic concept that define all necessary successive steps (5-step approach) for the industrial application [2]. The global 5-step approach in assessment and prevention of hydrogen assisted mechanical degradation processes and hydrogen embrittlement in metals for the practical industrial application was proposed and consist of the following steps [3]: (1) phenomenology analysis of hydrogen-related degradation (multiscale modeling and simulation of HE phenomena); (2) hydrogen sources and entry into metal/component; (3) structural integrity (SiM) model and (4) predictive maintenance (PdM) model which should provide the basis for future (5) reliable and accurate HE damage prediction of different industrial components.

Aluminium based Metal Matrix Composites (AMCs) are amongst the most sought after materials for aerospace structural applications as they synergize large ductility of Al with higher strength of reinforcements. AMCs typically contain ceramics in the form of fibers, flakes or particles as reinforcements and are marred by lower wettability of filler with the matrix in addition to unfavorable interfacial reactions; thereby leading to tradeoff between strength and ductility from a material designer viewpoint. Hence there exists a pressing need to develop an alternate reinforcement material that obviates the above problems and also result in a light weight AMC. In the current materials research paradigm, High Entropy Alloys (HEAs) have been predicted to possess remarkable functional and structural properties. Moreover in various recent scientific reports, Metallic Glass (MG) reinforcements have been reported to have excellent compatibility with Al matrix and also resulted into enhancement in yield strength of the AMCs. In this paper through thermodynamic modeling using PHSS parameter it is endeavoured to predict metallic glass formation in high entropy regime for Mg-Cu-Zn-Y quaternary system with the aim to harness excellent structural properties of both HEAs and MGs along with Al matrix.

The focus of the present study is to investigate the scuffing phenomenon of EN 31(Pin) against EN 19(Disc) steel under dry
running condition using pin-on-disc machine. Coefficient of friction (COF) and pin wear are experimentally measured for
different combination of loads (10N-70N) and rotational speeds (200 rpm-2000 rpm). The speed and load at which transition to
scuffing occur are also examined. It is observed that the wear resistance increases with sliding velocity for lower load, while at
higher load it increases initially and then becomes stable at higher speed. The COF increases with sliding velocity at lower loads and then becomes steady, while at higher loads, the COF first increases with increase in speed and then decreases considerably. This abrupt decrease in friction coefficient is due to intense heat generation between the disc and the pin and the experiment is stopped due to higher noise and vibration. Archard’s wear model is also used to validate the wear of pin at different loads and speeds. Experimentally measured pin wear shows higher value probably due to decreases in material hardness with increase in interface temperature.

Determining the efficiency and performance of polymer formulations used as consolidants for fragile, multilayered decorative coatings is often a great challenge in conservation. This paper introduces a new application of the standardised double cantilever beam (DCB) test method used in fracture mechanics as an improved means to tackle this problem. The adapted DCB method was employed to determine the independent material property fracture energy, GIc, and the fracture behaviour of brittle, protein-bound (gesso-type) foundation layers on wooden substrates that typically suffer from delamination and flaking. DCB specimens containing the brittle foundation layer between wooden beams were prepared. Once fractured, the specimens were consolidated with different polymer formulations and re-fractured to provide data for direct comparison. The results showed that the method could determine measurable differences in fracture energy, and also supply valuable and detailed information on change...

The characteristics of continuous tempering of quenched W-Mo-V high-speed steel in the temperature range from 180°C to 770°C were determined using dilatometric method. Due to scarcity of available information in the literature, special attention was paid to evaluating the destabilization degree of retained austenite and the mechanism of its transformation during cooling from tempering temperature. The results of tests contributed to a better understanding of the complicated tempering process for this type of high-speed steel.

Laves phase alloys are promising materials for several structural applications, but the extreme brittleness is the predominant shortcoming of a Laves matrix. One potential solution to overcome this shortcoming is to alloy Laves matrix with some soft matrix. A group of Ti-35Zr-5Fe-xMn (x = 0, 2, 4, 6, 8 wt%) alloys was cast with an aim to improve deformation in Laves alloy compositions. The phase and microstructure analyses reveal dual phase matrices, including a β phase and a C14 type Laves phase in the investigated alloys. The mechanical properties such as yield strength, hardness and plastic strain for the investigated alloys are found to be significantly sensitive to volume fraction of the Laves phase. Ti-35Zr-5Fe shows impressive ultimate compressive strength (~1.7 GPa), yield strength (1138 MPa) and large plastic strain (23.2 %). The fracture mechanisms are dependent on the microstructure of the alloys. Additionally, the work-hardening ability of the investigated alloys have also been evaluated based on the analyses of slip band patterns formed around the micro-hardness indentations. Notably, the extreme brittleness is not encountered in all the Ti-35Zr-5Fe-xMn alloys and all exhibit very good compressive elongation including the maximum (32.5 %) in Ti-35Zr-5Fe.

Purpose of the present study is to predict thermal
ratchetting deformation of thin cylindrical shell, in the
framework of unified Chaboche visco-plastic constitutive
model. Strain controlled cyclic characteristics and uniaxial
monotonic loading at different strain rate is analyzed for SS316
L. Thermal ratchet load of 550 ºC is applied cyclically along the
axis of the cylinder to predict the deformation pattern
accounting strain rate dependence of the material operating at
high temperature condition as in Prototype Fast Breeder
Reactor (PFBR). The effect of axial temperature variation is
simulated by cyclically varying the heat transfer properties at
the interacting surfaces of cylindrical shell. To achieve
comparable accuracy and better convergence, semi-implicit
plasticity integration approach is implemented in UMAT code.
Cyclic hardening and strain rate dependence of material is
compared by the experimental results

Laves phase alloys are promising materials for several structural applications, but the extreme brittleness is the predominant shortcoming of a Laves matrix. One potential solution to overcome this shortcoming is to alloy Laves matrix with some soft matrix. A group of Ti-35Zr-5Fe-xMn (x = 0, 2, 4, 6, 8 wt%) alloys was cast with an aim to improve deformation in Laves alloy compositions. The phase and microstructure analyses reveal dual phase matrices, including a β phase and a C14 type Laves phase in the investigated alloys. The mechanical properties such as yield strength, hardness and plastic strain for the investigated alloys are found to be significantly sensitive to volume fraction of the Laves phase. Ti-35Zr-5Fe shows impressive ultimate compressive strength (~1.7 GPa), yield strength (1138 MPa) and large plastic strain (23.2 %). The fracture mechanisms are dependent on the microstructure of the alloys. Additionally, the work-hardening ability of the investigated alloys have al...

ABSTRACT: This research work has investigated the influence of chemical treatment on the mechanical behaviour of animal fibre-reinforced high density polyethylene composites. The animal fibres used for this present study were chicken feather and cow hair fibres procured from local poultries and abattoirs. Prior to the development of the composite materials, the animal fibres were washed and dried, cut into 10 mm and divided into two portions; one portion was treated with 0.25 M NaOH maintained at 60 0C for 1 hour in a water bath, rinsed with distilled water and dried in the oven while the other portion was left untreated. Both portions were then used to reinforce the high density polyethylene polymer at 2, 4, 6, 8 and 10 % fibre loading respectively from which, the flexural and tensile test samples were produced by hot compression moulding. From the test results, it was observed that the chemically treated cow hair and chicken feather fibre reinforced high density polyethylene composites gave the best flexural properties for most fibre loading percentages compared to their untreated animal fibre-reinforced high density polyethylene composites counterparts and the neat high density polyethylene matrix. However, the tensile properties of all the animal fibre-reinforced high density polyethylene composites were not enhanced. Chicken feather and cow hair fibres were chosen for this research work to consider their potential applications as reinforcement for polymeric materials with a view to curtail the environmental pollution they generate by means of their disposal, as they are considered as unusable animal waste.
Keywords: Animal fibres, High density polyethylene, Composite, Chemical treatment, Mechanical behaviour

The effect of extraction by soil retting and chemical treatment on the
mechanical properties of sisal fibre reinforced polyester composites was investigated. The sisal fibre was extracted by soil retting method followed by chemical treatments. Treatments were carried out on the fibre at an elevated temperature of 70°C for 2 hours with 2 molar solutions each of NaOH, KOH, H2O2 and Ethanol. Both treated and untreated fibres were used to develop the sisal fibre reinforced polyester composites in predetermined proportions after which they were tested for mechanical properties. From the results, it was
observed that, KOH treated fibre reinforced polyester composite followed by Ethanol treated fibre samples gave the best results. KOH treatment was observed to enhance the tensile and hardness properties of the polyester composites than other treatments.
Keywords
Soil Retting; Chemical Treatment; Mechanical Properties; Sisal Fibre;
Polyester; Composites.

he properties of polymers can be significantly changed by incorporating nanoparticles, which yields great potential for applications. In the present study, we use nanocomposites of new polyurea elastomers filled with 0.1, 0.5, and 1 wt.% MoS2nanotubes. Using dynamic mechanical analysis (DMA) measurements we show, that the glass transition temperatures Tg of the nanocomposites are increased by small amounts of inorganic nanotubes. In line with results from computer simulations of polymer melts with nanoscopic particles, we explain the observed shift ofTgto be due to a gradual slowing down of polymer chain dynamics in the proximity of nanotubes.

Proteins contain hydrophilic groups, which can bind to water molecules through hydrogen bridges, resulting in water vapour adsorption. An increase in the degree of cross-linking can be a method to improve the cohesiveness force and functional properties of protein-based films. Thus, the objective of this work was to evaluate the effect of chemical treatment of gelatin with formaldehyde and glyoxal on the mechanical properties, water vapour permeability (WVP) and water vapour sorption characteristics of gelatin-based films. Films were produced using gelatin, with and without chemical treatment. The formaldehyde treatments caused a significant increase in the tensile strength and a reduction in the WVP of films. The Guggenheim-Anderson-De Boer and Halsey models could be used to model the sorption isotherms of films. It was observed that an increase in temperature produced a decrease in water sorption, and the chemical modifications did not affect the monolayer moisture content. Copyright © 2007 John Wiley & Sons, Ltd.

The characteristics of the structural states developed during continuous tempering of the W-Mo-V high-speed steel quenched from different temperatures in the range 535°C to 770°C (part I) were determined by subjecting dilatometric specimens to additional heat treating (tempered) up to 690°C followed by cooling to room temperature. The observed differences in the dilatometric effects are discussed in terms of the initial phase composition of steel and the state of austenite at the repeated tempering temperature.

Constant demands for quality improvement of high-speed steels have contributed to the prolonged importance of tests, such as test in structural changes and properties derived from the applied heat treatment. Generally, tools from high-speed steel are treated by multiple tempering after quenching in order to reduce amount of retained austenite and value of internal stresses to the lowest level. A review of literature shows that processes taking place during the first tempering have been studied comprehensively and in great detail while very little attention has been paid to testing structural changes in the succeeding tempering cycles. Having this in mind, the differential dilatometric method has been used to test the influences of quenching temperature (1170-1230°C), tempering temperature (540-605°C), and the number (1 to 5) and tempering time, on the process of destabilization of retained austenite at circumstances of multiple continuous tempering of quenched W-Mo-V high-speed stee...

In this paper, walnut shell particle and coconut fibre are developed. The suitability of walnut particle and coconut fibre as a biocomposite reinforcing material was investigated. 20 wt% of walnut shell particle of size 1.618 m µ-2.685 m µ and 10 wt% of coconut fibre of length 2-3 mm were mixed in epoxy CY 230 resin for preparation of hybrid biocomposite. The tensile properties and flexural test of hybrid biocomposite reinforced with walnut shell particle and coconut fibre were evaluated and analysed. Scanning electro microscopy was employed to characterize the tensile properties and fracture behaviour of biocomposite. The results show that ultimate strength, modulus of elasticity and yield strength of biocomposite material are about 54.3%, 86.4% and 88.3% of pure epoxy resin respectively. The compressive ultimate strength of biocomposite is 44.45 MPa as compared to 55.16 MPa of epoxy resin. This results reveals that the addition of 20 wt% walnut particles and 10 wt% coconut fibres yield better ultimate strength with approximately 80.58% of pure epoxy. The flexural modulus of biocomposite is 1706.15 MPa which is about 86.3% of pure epoxy. The flexural strength of biocomposite is 34.04 MPa which is about 35.7% of pure epoxy.

This study investigated the effects of spin casting method on mechanical behavior of aluminum composite (Al6063/SiC). The composites were cold rolled to 10% deformation before solution heat treating at 520 0 C for 1hour after which it was rapidly cooled in water. Experimental and theoretical density was used to evaluate the porosity of the composite. After cold rolling with 10% deformation and solution heat treating, it was discovered that silicon carbide were well dispersed in aluminum matrix better when compared with the as-cast of both spin and sand casting. The tensile strength and yield strength for spin casting were better when also compared with sand casting.